JP6837213B2 - Illumination optical communication device and communication module - Google Patents

Description

The present invention relates to an illumination optical communication device and a communication module that perform visible light communication by modulating the illumination light.

Conventionally, in a lighting fixture provided with a light emitting diode (LED, Light Emitted Diode) as a light source, visible light communication in which a signal is transmitted by modulating the intensity of the illumination light has been proposed. Since such an illumination optical communication device transmits a signal by modulating the illumination light itself, it does not require a special device such as an infrared communication device. In addition, since power saving can be realized by using a light emitting diode as a light source for lighting, its use in a ubiquitous information system in an underground mall or the like is being considered.

FIG. 164A is a diagram showing a configuration of an illumination optical communication device disclosed in Patent Document 2. In this circuit, a resistor R3 for current detection, a load circuit 53 including three light emitting diodes, an inductor L1 and a switch element Q1 are connected in series between both ends of the DC power supply 51, and the switch element Q1 is controlled. On / off is controlled by the circuit 54. Further, a smoothing capacitor C3 and a rectifier diode D2 are connected between both ends of the series circuit of the load circuit 53 and the inductor L1, and the inductor L1 and the switch element Q1 form a DC-DC converter. A feedback signal is input to the control circuit 54 from the constant current feedback circuit 55, and the output current of the DC-DC converter is controlled to be substantially constant. The DC-DC converter is a constant current feedback type power supply that is controlled to supply a constant current. Further, a communication signal S1 is input to the control circuit 54, and the load current I1 is modulated by turning on / off the switch element Q1 at a high frequency during a period when the communication signal is high.

FIG. 164B is a diagram showing a circuit portion including a specific example of the constant current feedback circuit 55 of FIG. 164A. The constant current feedback circuit 55 compares the voltage drop of the resistor R3 through which the load current I1 flows with the height of the reference source E1 by the error amplifier A1, amplifies the deviation, and outputs the deviation to the control circuit 54. Further, the series circuit of the resistor R4 and the capacitor C2 connected between the inverting input terminal and the output terminal of the error amplifier A1 constitutes a phase compensation circuit for ensuring the stability of the feedback system. In such a phase compensation circuit, a compensation circuit including an integrating element is generally used to adjust the gain and the phase in the one-round transfer function, and is known as PI control or PID control in classical information theory. For example, FIG. 164C is a diagram showing an illumination optical communication device including an average current detection circuit disclosed in Patent Document 1. It can be said that the integrating circuit 56 (consisting of the resistor R5 and the capacitor C3) connected between both ends of the resistor R3 for current detection uses the above-mentioned PI control as the output averaging means.

Further, Patent Document 3 discloses that in visible light communication using illumination light, the brightness of illumination is made constant in both the non-communication time in which a carrier signal for communication is not exchanged and the communication time in which a carrier signal is exchanged. At the same time, it discloses a power source for illumination optical communication that is low in cost and has high light source utilization efficiency and power efficiency.

Further, the illumination optical communication device of Patent Document 4 includes a DC-DC converter having a step-up mode and a step-down mode, a constant current clamp switch, and a constant current clamp control circuit, and the on-duty of the constant current clamp switch is stored in advance. It discloses that the current limit is started when the maximum value (or the minimum value) is reached, and the limit is stopped when the current limit is smaller than the maximum value (or larger than the minimum value).

Further, Patent Document 5 discloses a dimming type lighting device in which flicker becomes inconspicuous even when the amount of light is small and the data transmission speed is improved.

Japanese Unexamined Patent Publication No. 2006-120910 Japanese Unexamined Patent Publication No. 2012-69505 Japanese Unexamined Patent Publication No. 2010-283616 Japanese Unexamined Patent Publication No. 2011-130557 Japanese Unexamined Patent Publication No. 2015-216580

FIG. 165 is a diagram schematically showing waveforms of an intermittent signal, an output voltage at the time of modulation, and a load current (LED current) in a circuit configuration of 100% modulation using a constant current feedback type power supply. Here, 100% modulation means to modulate the illumination light in two states, a lighting state and an extinguishing state. The intermittent signal is a modulated signal that controls the on and off of the switch. The output voltage is the output voltage of the constant current feedback type power supply. The LED current is the current flowing through the LED.

In the figure, when the intermittent signal (modulated signal) is low, the switch is turned off and the LED is turned off. The longer this off period, the greater the output voltage across the smoothing capacitor 65. At the moment when the intermittent signal (modulated signal) becomes high, a large overshoot occurs in the LED current. That is, at the moment when the intermittent signal (modulation signal) becomes high, the output voltage is high, so the peak value of the LED current is high, and the LED current is also lowered as the output voltage is lowered.

As described above, there is a problem that the overshoot of the LED current increases as the switch is interrupted. Generally, an optical communication receiving device reads a change in an optical signal, and when an overshoot is large, it becomes a main cause of malfunction (for example, reception error). As described above, when 100% modulation is performed using a constant current type power supply, there is a problem that the receiving device may malfunction.

An object of the present invention is to provide an illuminated optical communication device and a communication module that are less likely to cause a reception error of the receiving device even when 100% modulated optical communication is performed using a constant current feedback type power supply.

In order to achieve the above object, one form of the illumination optical communication device according to the present invention includes a light source that emits illumination light, a power supply circuit that supplies a current to the light source to make the current constant, and the light source. A switch that is connected in series with the light source to interrupt the current flowing through the light source, a signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light, the light source, and the light source. It is connected in series with the switch and includes a current suppression circuit that suppresses the current flowing through the light source so as not to exceed a variable current set value.

Further, one form of the communication module according to the present invention is a communication module that is detachable from the lighting device and modulates the illumination light, and modulates the illumination light with a switch connected in series with the light source of the illumination device. A signal generation circuit that generates a binary communication signal that controls the on and off of the switch, and the light source and the switch are connected in series so that the light source does not exceed a variable current set value. It is provided with a current suppression circuit that suppresses the flowing current.

According to the illumination optical communication device and the communication module according to the present invention, there is an effect that a reception error of the receiving device is unlikely to occur even when 100% modulated optical communication is performed using a constant current feedback type power supply.

FIG. 1A is a circuit diagram showing a configuration of an illumination optical communication device according to the first embodiment. FIG. 1B is a circuit diagram showing a configuration of a lighting device to which a communication module is not added according to the first embodiment. FIG. 2 is a circuit diagram showing a first modification of the current suppression circuit in FIG. 1A. FIG. 3 is a circuit diagram showing a second modification of the current suppression circuit in FIG. 1A. FIG. 4 is a circuit diagram showing a third modification of the current suppression circuit in FIG. 1A. FIG. 5 is a diagram showing a first simulation result for the circuit example of FIG. FIG. 6 is a diagram showing a second simulation result for the circuit example of FIG. FIG. 7 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 8 is a diagram showing a fourth simulation result for the circuit example of FIG. FIG. 9 is a diagram showing a fifth simulation result for the circuit example of FIG. FIG. 10 is a diagram showing a sixth simulation result for the circuit example of FIG. FIG. 11 is a diagram showing a seventh simulation result for the circuit example of FIG. FIG. 12 is a diagram showing an eighth simulation result for the circuit example of FIG. FIG. 13 is a diagram showing a ninth simulation result for the circuit example of FIG. FIG. 14 is a diagram showing a tenth simulation result for the circuit example of FIG. FIG. 15 is an explanatory diagram showing a modulation method of a communication signal. FIG. 16 is a diagram showing examples (1) to (4) of communication signals. FIG. 17 is a diagram showing a simulation result (No. 1) of the case (1) of FIG. FIG. 18 is a diagram showing a simulation result (No. 2) of the case (1) of FIG. FIG. 19 is a diagram showing a simulation result (No. 1) of the case (2) of FIG. FIG. 20 is a diagram showing a simulation result (No. 2) of the case (2) of FIG. FIG. 21 is a diagram showing a simulation result (No. 1) of the case (3) of FIG. FIG. 22 is a diagram showing a simulation result (No. 2) of the case (3) of FIG. FIG. 23 is a diagram showing a simulation result (No. 1) of the case (4) of FIG. FIG. 24 is a diagram showing a simulation result (No. 2) of the case (4) of FIG. FIG. 25A is a diagram showing the relationship between the current set value and the LED current (mean value and fluctuation value) as the simulation result of the case (1) of FIG. FIG. 25B is a diagram showing the relationship between the current set value and the ripple rate of the LED current as the simulation result of the case (1) of FIG. FIG. 25C is a diagram showing the relationship between the current set value and the circuit loss as the simulation result of the case (1) of FIG. FIG. 26A is a diagram showing the relationship between the current set value and the LED current (mean value and fluctuation value) as the simulation result of the case (2) of FIG. FIG. 26B is a diagram showing the relationship between the current set value and the ripple rate of the LED current as the simulation result of the case (2) of FIG. FIG. 26C is a diagram showing the relationship between the current set value and the circuit loss as the simulation result of the case (2) of FIG. FIG. 27A is a diagram showing the relationship between the current set value and the LED current (mean value and fluctuation value) as the simulation result of the case (3) of FIG. FIG. 27B is a diagram showing the relationship between the current set value and the ripple rate of the LED current as the simulation result of the case (3) of FIG. FIG. 27C is a diagram showing the relationship between the current set value and the circuit loss as the simulation result of the case (3) of FIG. FIG. 28A is a diagram showing the relationship between the current set value and the LED current (mean value and fluctuation value) as the simulation result of the case (4) of FIG. FIG. 28B is a diagram showing the relationship between the current set value and the ripple rate of the LED current as the simulation result of the case (4) of FIG. FIG. 28C is a diagram showing the relationship between the current set value and the circuit loss as the simulation result of the case (4) of FIG. FIG. 29A is an explanatory diagram showing an intermittent LED current waveform. FIG. 29B is a diagram showing a current set value according to the on-duty ratio. FIG. 30A is a circuit diagram showing a modified example of the illumination optical communication device according to the first embodiment. FIG. 30B is a waveform diagram showing threshold control of switching current in the power supply circuit of FIG. 30A. FIG. 31A is a diagram showing a first configuration example of the current suppression circuit according to the second embodiment. FIG. 31B is a diagram showing a second configuration example of the current suppression circuit according to the second embodiment. FIG. 32A is a diagram showing the relationship between the on-duty ratio and the LED current as a simulation result of the circuit in which the diode of FIG. 31A is removed. FIG. 32B is a diagram showing the relationship between the on-duty ratio and the LED current ripple rate as a simulation result of the circuit in which the diode of FIG. 31A is removed. FIG. 33A is a diagram showing the relationship between the on-duty ratio and the LED current as the simulation result of FIG. 31A. FIG. 33B is a diagram showing the relationship between the on-duty ratio and the LED current ripple rate as the simulation result of FIG. 31A. FIG. 34 is a diagram showing the relationship between the on-duty ratio and the circuit loss as the simulation result of FIG. 31A. FIG. 35A is a diagram showing a configuration example of the current suppression circuit according to the third embodiment. FIG. 35B is a diagram showing a first configuration example of the current suppression circuit according to the fourth embodiment. FIG. 35C is a diagram showing a second configuration example of the current suppression circuit according to the fourth embodiment. FIG. 35D is a diagram showing a third configuration example of the current suppression circuit according to the fourth embodiment. FIG. 35E is a diagram showing a configuration example of the current suppression circuit according to the fifth embodiment. FIG. 35F is a diagram showing a configuration example of the current suppression circuit according to the sixth embodiment. FIG. 36 is a diagram showing the relationship between the on-duty ratio and the LED current as the simulation result of FIG. 35A in the third embodiment. FIG. 37 is a diagram showing the relationship between the on-duty ratio and the ripple rate of the LED current as the simulation result of FIG. 35A in the third embodiment. FIG. 38 is a diagram showing the relationship between the on-duty ratio and the circuit loss as the simulation result of FIG. 35A in the third embodiment. FIG. 39 is a diagram showing the relationship between the on-duty ratio and the LED current as the simulation result of FIG. 35B in the fourth embodiment. FIG. 40 is a diagram showing the relationship between the on-duty ratio and the ripple rate of the LED current as the simulation result of FIG. 35B in the fourth embodiment. FIG. 41 is a diagram showing the relationship between the on-duty ratio and the circuit loss as the simulation result of FIG. 35B in the fourth embodiment. FIG. 42 is a diagram showing the relationship between the on-duty ratio and the LED current as the simulation result of FIG. 35E in the fifth embodiment. FIG. 43 is a diagram showing the relationship between the on-duty ratio and the ripple rate of the LED current as the simulation result of FIG. 35E in the fifth embodiment. FIG. 44 is a diagram showing the relationship between the on-duty ratio and the circuit loss as the simulation result of FIG. 35E in the fifth embodiment. FIG. 45 is a diagram showing a comparative reference example in which the current suppression circuit is removed from FIG. 1A. FIG. 46 is a diagram showing LED current and output voltage waveforms when the on-duty ratios are 60%, 75%, 90%, and 100% as a simulation result of the circuit for comparison reference in FIG. 45. FIG. 47 is a diagram showing LED current and output voltage waveforms when the on-duty ratio is 75% and the smoothing capacitances are 10 μF, 20 μF, and 30 μm as a simulation result of the circuit for comparison reference in FIG. 45. FIG. 48A is a diagram showing the relationship between the on-duty ratio and the LED current as a simulation result of the circuit for comparison reference in FIG. 45. FIG. 48B is a diagram showing the relationship between the on-duty ratio and the ripple rate of the LED current as a simulation result of the circuit for comparison reference in FIG. 45. FIG. 49A is a diagram showing the relationship between the on-duty ratio and the output voltage as a simulation result of the circuit for comparison reference in FIG. 45. FIG. 49B is a diagram showing the relationship between the on-duty ratio and the ripple rate of the output voltage as a simulation result of the circuit for comparison reference of FIG. 45. FIG. 50A is a circuit diagram showing a configuration example of the illumination optical communication device according to the seventh embodiment. FIG. 50B is a diagram showing a truth table showing the operating states of the communication signals, switches, and transistors of the signal generation circuit in FIG. 50A. FIG. 51 is a diagram showing a first simulation result for the circuit example of FIG. 50A. FIG. 52 is a diagram showing a second simulation result for the circuit example of FIG. 50A. FIG. 53 is a diagram showing a third simulation result for the circuit example of FIG. 50A. FIG. 54 is a diagram showing a fourth simulation result for the circuit example of FIG. 50A. FIG. 55 is a diagram showing a configuration example of the communication module according to the eighth embodiment. FIG. 56 is a diagram showing simulation results for the circuit example of FIG. 55. FIG. 57A is a diagram showing a configuration example of the communication module according to the ninth embodiment. FIG. 57B is a diagram showing a truth table showing the communication signals from the signal generation circuit in FIG. 57A and the operating states of the two valves and the transistors. FIG. 57C is a diagram showing a modified example of the communication module according to the ninth embodiment. FIG. 57D is a diagram showing a truth table showing the communication signals from the signal generation circuit in FIG. 57C and the operating states of the two valves and the transistor 2. FIG. 57E is a diagram showing another modification of the communication module according to the ninth embodiment. FIG. 57F is a diagram showing a truth table showing the communication signals from the signal generation circuit in FIG. 57E and the operating states of the two valves, the transistor and the bipolar transistor. FIG. 57G is a diagram showing a configuration example of the communication module 10 including a modification of the combined control circuit of FIG. 57A. FIG. 58 is a diagram showing a first simulation result for the circuit example of FIG. 57C. FIG. 59 is a diagram showing a second simulation result for the circuit example of FIG. 57C. FIG. 60 is a diagram showing a third simulation result for the circuit example of FIG. 57C. FIG. 61 is a diagram showing a first simulation result for the circuit example of FIG. 57E. FIG. 62 is a diagram showing a second simulation result for the circuit example of FIG. 57E. FIG. 63 is a diagram showing a third simulation result for the circuit example of FIG. 57E. FIG. 64 is a circuit diagram showing a modified example of the illumination optical communication device according to the seventh embodiment. FIG. 65 is a block diagram of the illumination optical communication device according to the tenth embodiment. FIG. 66 is a diagram showing another example of the current suppression circuit according to the tenth embodiment. FIG. 67 is a diagram showing another example of the current suppression circuit according to the tenth embodiment. FIG. 68 is a diagram showing another example of the current suppression circuit according to the tenth embodiment. FIG. 69 is a diagram showing an operation example of the illumination optical communication device according to the tenth embodiment. FIG. 70 is a diagram showing a schematic configuration of an illumination optical communication device according to a tenth embodiment. FIG. 71 is a diagram showing a schematic configuration of an illumination optical communication device according to a comparative example of the tenth embodiment. FIG. 72 is a diagram showing a first control example of the current set value according to the tenth embodiment. FIG. 73 is a diagram showing a second control example of the current set value according to the tenth embodiment. FIG. 74 is a diagram showing a third control example of the current set value according to the tenth embodiment. FIG. 75 is a diagram showing a modified example of the third control example of the current set value according to the tenth embodiment. FIG. 76 is a diagram showing a fourth control example of the current set value according to the tenth embodiment. FIG. 77 is a diagram showing a usage example of the illumination optical communication device according to the tenth embodiment. FIG. 78 is a diagram showing an example of the appearance of the illumination optical communication device according to the tenth embodiment. FIG. 79 is a diagram showing another usage example of the illumination optical communication device according to the tenth embodiment. FIG. 80 is a circuit diagram showing a modified example of the illumination optical communication device according to the eleventh embodiment. FIG. 81 is a circuit diagram showing a fourth modification of the current suppression circuit. FIG. 82 is a circuit diagram showing a fifth modification of the current suppression circuit. FIG. 83 is a block diagram showing a configuration example of a control circuit and a signal generation circuit. FIG. 84A is a flowchart showing a processing example of the control circuit. FIG. 84B is an explanatory diagram of a shift register in the control circuit. FIG. 84C is a flowchart showing a correction example of step S45 of FIG. 84B. FIG. 85 is a circuit diagram showing a configuration example of the illumination optical communication device according to the twelfth embodiment. FIG. 86 is a diagram showing a circuit example of the DC-DC converter according to the twelfth embodiment. FIG. 87 is a time chart of the potential of each part of the illumination optical communication device according to the twelfth embodiment. FIG. 88 is a circuit diagram showing a configuration example of the illumination optical communication device according to the thirteenth embodiment. FIG. 89 is a circuit diagram showing a configuration example of the illumination optical communication device in the comparative reference example. FIG. 90 is a time chart of the potential of each part of the illumination optical communication device in the comparative reference example. FIG. 91 is a circuit diagram showing a modified example of the illumination optical communication device according to the twelfth or thirteenth embodiment. FIG. 92 is a waveform diagram showing threshold control of the switching current in the power supply circuit of FIG. 91. FIG. 93A is a circuit diagram showing the configuration of the illumination optical communication device according to the fourteenth embodiment. FIG. 93B is a circuit diagram showing a more detailed configuration example of the current suppression circuit. FIG. 94A is a diagram showing the first simulation result. FIG. 94B is a diagram showing the second simulation result. FIG. 95 is a diagram schematically showing the relationship between two communication signals having different on-duty ratios and the LED current. FIG. 96 is a diagram showing the relationship between the on-duty ratio and the LED current when the current set value is fixed. FIG. 97A is a diagram showing a third simulation result. FIG. 97B is a diagram showing a fourth simulation result. FIG. 98 is a diagram showing the LED current, the output voltage, the SW voltage, and the voltage of the current suppression circuit in FIG. 93A. FIG. 99A is a circuit diagram showing the configuration of the illumination optical communication device according to the fifteenth embodiment. FIG. 99B is a circuit diagram showing a configuration of an illumination optical communication device to which a communication module is not added according to the fifteenth embodiment. FIG. 99C is a circuit diagram showing a specific configuration example of the communication module and the second current suppression circuit according to the fifteenth embodiment. FIG. 100 is a diagram showing simulation results for the circuit examples of FIGS. 99A and 99C. FIG. 101 is a diagram showing a current set value according to the on-duty ratio. FIG. 102 is a circuit diagram showing the configuration of the illumination optical communication device according to the sixteenth embodiment. FIG. 103 is a circuit diagram showing the configuration of the illumination optical communication device according to the seventeenth embodiment. FIG. 104 is a diagram showing a first simulation result for the circuit example of FIG. 102. FIG. 105 is a diagram showing a second simulation result for the circuit example of FIG. 102. FIG. 106 is a diagram showing a third simulation result for the circuit example of FIG. 102. FIG. 107 is a diagram showing a first simulation result for the circuit example of FIG. 103. FIG. 108 is a diagram showing a second simulation result for the circuit example of FIG. 103. FIG. 109 is a diagram showing a third simulation result for the circuit example of FIG. 103. FIG. 110 is a circuit diagram showing the configuration of the illumination optical communication device according to the eighteenth embodiment. FIG. 111 is a circuit diagram showing another configuration of the illumination optical communication device according to the eighteenth embodiment. FIG. 112A is a circuit diagram showing a current suppression circuit including a first modification of the reference source according to the eighteenth embodiment. FIG. 112B is a circuit diagram showing a current suppression circuit including a second modification of the reference source according to the eighteenth embodiment. FIG. 113 is a block diagram of the illumination optical communication device according to the nineteenth embodiment. FIG. 114 is a diagram showing the configuration of the lighting unit according to the nineteenth embodiment. FIG. 115 is a diagram showing a modulation operation by the illumination optical communication device according to the nineteenth embodiment. FIG. 116 is a diagram showing a dimming operation by the illumination optical communication device according to the nineteenth embodiment. FIG. 117 is a diagram for explaining a problem when the modulation operation and the dimming operation are combined. FIG. 118 is a flowchart of the operation of the illumination optical communication device according to the nineteenth embodiment. FIG. 119 is a diagram showing a first operation example of the illumination optical communication device according to the nineteenth embodiment. FIG. 120 is a diagram showing a second operation example of the illumination optical communication device according to the nineteenth embodiment. FIG. 121 is a block diagram of the receiving device according to the nineteenth embodiment. FIG. 122 is a flowchart of the operation by the receiving device according to the nineteenth embodiment. FIG. 123 is a block diagram of the illumination optical communication device according to the twentieth embodiment. FIG. 124 is a diagram showing an operation example of the illumination optical communication device according to the twentieth embodiment. FIG. 125 is a block diagram of a modified example of the illumination optical communication device according to the twentieth embodiment. FIG. 126 is a diagram showing a usage example of the illumination optical communication device according to the 20th embodiment. FIG. 127 is a block diagram showing a configuration example of the illumination optical communication device according to the twenty-first embodiment. FIG. 128 is a waveform diagram showing a first operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 129A is a waveform diagram showing a second operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 129B is a waveform diagram showing a second operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 130 is a waveform diagram showing a third operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 131 is a waveform diagram showing a first operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 132 is a waveform diagram showing a second operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 133 is a waveform diagram showing a third operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 134 is a waveform diagram showing a fourth operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 135 is a waveform diagram showing a fifth operation example of the illumination optical communication device according to the twenty-first embodiment. FIG. 136 is a diagram showing a configuration example of a modulation circuit that is a premise of the 22nd embodiment. FIG. 137 is a diagram showing a configuration example of the modulation circuit and a configuration example of the overpower detection circuit according to the 22nd embodiment. FIG. 138 is a waveform diagram of each part during normal operation in the 22nd embodiment. FIG. 139 is a waveform diagram of each part during overpower operation in the 22nd embodiment. FIG. 140 is a diagram showing main circuit loss and overpower detection levels in six models having different LED loads. FIG. 141 is a diagram showing a configuration example of the modulation circuit according to the 23rd embodiment. FIG. 142 is a waveform diagram of each part during normal operation in the 23rd embodiment. FIG. 143 is a waveform diagram of each part during overpower operation in the 22nd embodiment. FIG. 144 is a diagram showing main circuit loss and overpower detection level in 6 models having different LED loads. FIG. 145 is a diagram showing a configuration example of the modulation circuit according to the 24th embodiment. FIG. 146 is a diagram showing a configuration example of the modulation circuit according to the 25th embodiment. FIG. 147 is a diagram showing a configuration example of the modulation circuit according to the 26th embodiment. FIG. 148 is a diagram showing a configuration example of the modulation circuit according to the 27th embodiment. FIG. 149 is a diagram showing a configuration example of the modulation circuit according to the 28th embodiment. FIG. 150 is a waveform diagram (normal time) of each of the explanatory parts in the normal operation in the 22nd embodiment. FIG. 151 is a diagram showing the results of simulating the rising waveforms of the gate voltage and the LED current at the rising edge of the inverted communication signal. FIG. 152 is a diagram showing a result of simulating the falling waveforms of the gate voltage and the LED current at the falling edge of the inverting communication signal. FIG. 153 is a diagram showing signal waveforms of each part when a rise delay time is involved. FIG. 154 is a diagram showing a configuration example of a modulation circuit including the delay circuit according to the 28th embodiment. FIG. 155 is a diagram showing signal waveforms of each part of FIG. 154. FIG. 156 is a diagram showing main circuit loss with respect to LED current in a plurality of models having different load capacities. FIG. 157 is a diagram showing main circuit loss with respect to load power in a plurality of models having different load capacities. FIG. 158 is a diagram showing optimum resistance values for LED currents in a plurality of models having different load capacities. FIG. 159 is a diagram showing an optimum reference resistance for load power in a plurality of models having different load capacities. FIG. 160 is a circuit diagram for explaining the gate capacitance. FIG. 161 is a diagram for explaining the influence of the gate capacitance. FIG. 162 is a diagram showing a configuration example of a modulation circuit including the delay circuit according to the 29th embodiment. FIG. 163 is a diagram showing signal waveforms of each part of FIG. 162. FIG. 164A is a diagram showing a configuration of an illumination optical communication device disclosed in Patent Document 2. FIG. 164B is a diagram showing a circuit portion including a specific example of the constant current feedback circuit of FIG. 164A. FIG. 164C is a diagram showing an illumination optical communication device including an average current detection circuit disclosed in Patent Document 1. FIG. 165 is a diagram schematically showing waveforms of an intermittent signal, an output voltage at the time of modulation, and a load current (LED current) in a circuit configuration of 100% modulation using a constant current feedback type power supply.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, all the embodiments described below show a preferable specific example of the present invention. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps and the order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present invention will be described as arbitrary components constituting the more preferable form. In addition, each figure is a schematic view and does not necessarily represent strict dimensions and numerical values.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
[1.1 Configuration of Illuminated Optical Communication Device]
First, the configuration of the illumination optical communication device of the first embodiment will be described.

FIG. 1A is a circuit diagram showing a configuration of an illumination optical communication device according to the first embodiment. This illumination optical communication device includes a power supply circuit 52a having a function of making the output a constant current, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and a communication module 10. The communication module 10 includes an intermittent switch SW, a signal generation circuit SG, and a current suppression circuit 1.

The power supply circuit 52a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

The power supply circuit 52a full-wave rectifies a commercial power supply (for example, AC 100V) with a rectifying bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected between both ends of the output of the DC-DC converter 64. Further, a load circuit 53, a current suppression circuit 1, and a series circuit of the intermittent switch SW are connected in parallel with the smoothing capacitor 65.

The power supply circuit 52a has a function of directly or indirectly detecting the current flowing through the load circuit 53 and controlling the current values to be constant. This function is provided in FIG. 1A by a detection resistor 66 for directly detecting the current of the load circuit 53 and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and an amplifier 69. A resistor 71 for gain adjustment and a capacitor 70 for phase compensation connected between the negative input terminals of the above are provided. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 with the amplifier 69, amplifies the difference, and feeds it back to the control unit of the DC-DC converter 64. That is, the DC-DC converter 64 is subjected to negative feedback control so that the voltage drop of the detection resistor 66 and the reference voltage match. Further, the gain is set by the voltage division ratio between the resistor 71 connected between the inverting input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 is integrated for phase compensation. Acts as an element.

The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52a and smoothes the output of the power supply circuit 52a.

The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52a, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

The intermittent switch SW is added in series with the load circuit 53, and interrupts the current supplied from the power supply circuit 52a to the load circuit 53.

The signal generation circuit SG generates a binary communication signal that controls the on / off of the intermittent switch SW in order to modulate the illumination light. The communication signal is input to the control terminal of the intermittent switch SW, and turns the intermittent switch SW on and off. The signal generation circuit SG may repeatedly generate an ID signal indicating an ID unique to the illumination optical communication device as a communication signal, or generate a communication signal in response to a transmission signal input from an external device. May be good.

[1.2 Configuration of current suppression circuit 1]
Next, a configuration example of the current suppression circuit 1 will be described.

The current suppression circuit 1 is added in series with the load circuit 53 and the intermittent switch SW to suppress the magnitude of the current flowing through the load circuit 53. For example, the current suppression circuit 1 is connected in series with the load circuit 53 as a light source and the intermittent switch SW, and the current flowing through the load circuit 53 is set according to the reference value so as not to exceed the current set value corresponding to the reference value. It may be suppressed. By doing so, it is possible to reduce the overshoot generated in the current flowing through the load circuit 53, which is the light source, at the moment when the intermittent switch SW is turned on, so that the reception error in the receiving device can be reduced.

The current suppression circuit 1 is composed of a transistor 2 which is a MOSFET, a resistor 3 connected to a source, an amplifier 5, a reference source 4, and a control circuit 6.

The reference source 4 outputs a reference value to the positive input terminal of the amplifier 5. The reference value defines an upper limit (current set value) of the current flowing through the load circuit 53 which is a light source. For example, the reference value is proportional to the current set value. Further, the reference source 4 may output a reference value as a fixed value, or may output a variable reference value according to an arrangement pattern (for example, a bit pattern) of a communication signal generated by the signal generation circuit SG. ..

The transistor 2 is connected in series with the load circuit 53, which is a light source, and the intermittent switch SW, and suppresses the current flowing through the load circuit 53 based on the reference value.

The resistor 3 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor 3 is connected to the negative input terminal of the amplifier 5.

In the amplifier 5, the reference source 4 is connected to the positive input terminal, and the source of the transistor 2 is connected to the negative input terminal. The amplifier 5 amplifies the difference between the reference value and the current value detected by the resistor 3, and outputs the amplified signal to the gate of the transistor 2.

The control circuit 6 controls to change the reference value of the reference source 4 according to the arrangement pattern of the communication signal in order to output a variable reference value from the reference source 4. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal, and when the calculated partial on-duty ratio is the first ratio, sets the reference value as the first value and partially When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The "partial on-duty ratio" is, for example, the ratio of the on-duty period to the total period of the latest off-duty period and the on-duty period immediately before the off-duty period. Alternatively, the "partial on-duty ratio" may be replaced by the moving average of the most recent n bits of the communication signal. In this way, overshoot suppression can be made more appropriate when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio.

[1.3 Modification example of current suppression circuit 1]
Next, first to third modification examples of the current suppression circuit 1 will be described.

The current suppression circuit 1 in FIG. 1A is not limited to this configuration, and may be configured as shown in FIGS. 2 to 4.

FIG. 2 is a circuit diagram showing a first modification of the current suppression circuit 1 in FIG. 1A. The current suppression circuit 1 shown in FIG. 2 includes bipolar transistors 11 and 12, a reference source 4, a resistor 14, and a control circuit 6. Bipolar transistors 11 and 12 form a current mirror circuit. The current flowing through the bipolar transistor 12 is determined by the reference source 4 and the resistor 14. The bipolar transistor 11 can pass a current within a range not exceeding a current (that is, a current set value) that is twice the mirror ratio of this current. The control circuit 6 changes the reference source 4 or the resistor 14 according to the signal arrangement of the communication signal output from the signal generation circuit SG.

FIG. 3 is a circuit diagram showing a second modification of the current suppression circuit in FIG. 1A. The current suppression circuit 1 shown in FIG. 3 includes a bipolar transistor 21, an emitter resistor 22r, a bias resistor 23, a Zener diode 24, and a control circuit 6.

The bipolar transistor 21 is connected in series with the load circuit 53, and suppresses the current flowing through the load circuit 53 according to the base voltage (reference value) of the bipolar transistor 21.

The emitter resistor 22r is a resistor for detecting the magnitude of the current flowing through the load circuit 53 (that is, the current flowing through the emitter resistor 22r).

The bias resistor 23 is a resistor for biasing the base voltage of the bipolar transistor 21.

The Zener diode 24 outputs a reference value to the base of the bipolar transistor 21.

The control circuit 6 changes the reference value of the Zener diode 24 according to the signal arrangement of the communication signal.

FIG. 4 is a circuit diagram showing a third modification of the current suppression circuit in FIG. 1A. The current suppression circuit 1 shown in FIG. 4 includes a three-terminal regulator 25a, a detection resistor 26, and a control circuit 6.

In the three-terminal regulator 25a, the input terminal IN and the output terminal OUT are connected in series with the load circuit 53, and the current flowing between the input terminal IN and the output terminal OUT is supplied according to the voltage input to the adjustment terminal ADJ. Suppress.

The detection resistor 26 is a resistor for detecting the magnitude of the current flowing through the load circuit 53 (that is, the current flowing through the detection resistor 26). Further, the detection resistor 26 is a variable resistor, and the resistance value thereof is a reference value. The terminal on the intermittent switch SW side of the detection resistor 26 is connected to the adjustment terminal ADJ of the three-terminal regulator 25a.

The control circuit 6 changes the resistance value of the detection resistor 26 according to the signal arrangement of the communication signal.

In this way, even with the modification of the current suppression circuit 1, when the magnitude of the overshoot depends on the partial on-duty ratio (or the partial signal arrangement), the suppression of the overshoot is made more appropriate. Can be done.

In FIGS. 1A, 2 to 4, when the reference source 4 outputs a fixed reference value, the current suppression circuit 1 does not have to include the control circuit 6.

[1.4 Operation of Illuminated Optical Communication Device]
The operation of the illumination optical communication device configured as described above will be described using simulation results.

5 to 14 show the results of simulating the current suppression circuit 1 of FIG.

FIG. 5 is a diagram showing a first simulation result for the circuit example of FIG. In FIG. 5, the capacitance value of the smoothing capacitor 65 is set to 20 uF, and the frequency and on-duty ratio of the communication signal from the signal generation circuit SG are set to 2.4 kHz and 75%. Under this setting, FIG. 5 shows the LED current and the voltage waveform applied to the current suppression circuit 1 when the current setting value of the current suppression circuit 1 is changed in four ways. There are four current setting values: 423 mA, 373 mA, 332 mA, and 318 mA. Incidentally, the operating frequency of the DC-DC converter is set to 65 kHz, and the average value of the load current (LED current) when not intermittent is set to 240 mA.

When the current set value of the current suppression circuit 1 is set to 423 mA in FIG. 5, a large overshoot occurs in the LED current waveform, the applied voltage is extremely low, and the current suppression circuit 1 substantially functions. Not.

When the current set value of the current suppression circuit 1 is gradually lowered to 373 mA, 332 mA, and 318 mA, the overshoot portion of the LED current is cut, and when the current set value is 318 mA, the overshoot of the LED current waveform disappears. It is a square wave. Along with this, the applied voltage of the current suppression circuit 1 gradually increases, and when the current set value is lowered, the current suppression circuit 1 starts to work, and at the current set value of 318 mA, the current of the current suppression circuit 1 in the entire on-period region. It can be seen that suppression is working effectively.

FIG. 6 is a diagram showing a second simulation result for the circuit example of FIG. FIG. 6 shows the LED current and the voltage waveform applied to the current suppression circuit 1 when the current set value of the current suppression circuit 1 is gradually lowered from 318 mA to 309 mA, 299 mA, and 289 mA in the simulation of FIG. Shown. As the current set value decreases, the peak value of the LED current decreases, but the waveform of the rectangular wave without overshoot is maintained. Further, the applied voltage waveform rises sharply as the current set value decreases.

The above results are shown in diagrams in FIGS. 7 and 8. FIG. 7 is a diagram showing a third simulation result for the circuit example of FIG. FIG. 7 shows the relationship between the current set value of the current suppression circuit 1 and the LED current. With the current set value of 318 mA as the boundary, if the set value is large, the average value of the LED current is maintained constant, but the fluctuation range (overshoot) is large, and if the set value is small, the fluctuation range of the LED current (overshoot) is large. ) Disappears, but the average value decreases. FIG. 8 is a diagram showing a fourth simulation result for the circuit example of FIG. FIG. 8 shows the relationship between the current set value of the current suppression circuit 1 and the circuit loss (that is, the power consumption of the current suppression circuit 1) generated in the current suppression circuit 1. It can be seen that, with the current set value of 318 mA as a boundary, the loss is suppressed to a small value when the set value is large, and the loss increases sharply when the set value is small. From these results, under the simulation conditions of FIG. 5 with respect to the circuit example of FIG. 2, if the current set value of the current suppression circuit 1 is set to 318 mA, the overshoot of the LED current is suppressed and the average value is not intermittent. The value of the case is maintained, and the circuit loss of the current suppression circuit 1 can be suppressed to a low value.

FIG. 9 is a diagram showing a fifth simulation result for the circuit example of FIG. In FIG. 9, in the circuit example of FIG. 2, the current set value of the current suppression circuit 1 is set to 318 mA, which is the optimum value under the above conditions (FIGS. 5 and 6), and the current is modulated from the signal generator SG. The voltage waveform applied to the LED current and the current suppression circuit 1 when the on-duty ratio of the signal is changed in three ways is shown. There are three on-duty ratios: 70%, 75%, and 80%. Other conditions are the same (capacity value 20uF of smoothing capacitor 65, modulation signal frequency 2.4kHz from signal generation circuit SG, operating frequency 65kHz of DC-DC converter, average load current (LED current) when not intermittent). Value 240mA).

At an on-duty ratio of 75%, no overshoot is observed in the LED current waveform, and the applied voltage of the current suppression circuit 1 is also low (this can be said to be the optimum condition).

When the on-duty ratio is 80%, the overshoot is not completely removed from the LED current waveform, causing a slope in the latter half of the on period, and the applied voltage is extremely low, which is substantially during this period. It can be seen that the current suppression circuit 1 is not functioning.

Further, when the on-duty ratio is 70%, the overshoot of the LED current waveform is completely removed to form a rectangular wave, but the applied voltage becomes high and the loss becomes large.

The relationship between the on-duty ratio of the modulated signal from the signal generator and the LED current is shown in FIG. FIG. 10 is a diagram showing a sixth simulation result for the circuit example of FIG. When the current set value of the current suppression circuit 1 is 318 mA, the average value of the LED current is maintained constant when the on-duty ratio is large, with the on-duty ratio of 75% as the boundary, but the fluctuation range (overshoot). ) Is large and the on-duty ratio is small, the fluctuation range (overshoot) of the LED current disappears, but the average value decreases.

FIG. 11 is a diagram showing a seventh simulation result for the circuit example of FIG. FIG. 11 is a diagram showing the overshoot of the LED current by the ripple rate. FIG. 12 is a diagram showing an eighth simulation result for the circuit example of FIG. FIG. 12 shows the relationship between the on-duty ratio and the circuit loss of the current suppression circuit 1. From these results, it can be inferred that the optimum current setting value of the current suppression circuit 1 depends on the on-duty ratio of the communication signal from the signal generator SG.

FIG. 13 shows the result of obtaining the optimum current set value of the current suppression circuit 1 according to the on-duty ratio of the modulated signal from the signal generator SG. FIG. 13 is a diagram showing a ninth simulation result for the circuit example of FIG. In FIG. 13, if the current set value is changed as shown in the figure according to the on-duty ratio on the horizontal axis, the fluctuation value (overshoot) of the LED current is suppressed, and the average value becomes a value when it is not intermittent. Can be maintained. The circuit loss of the current suppression circuit 1 in that case is shown in FIG. FIG. 14 is a diagram showing a tenth simulation result for the circuit example of FIG. In FIG. 14, it can be seen that the circuit loss is within a low value at the on-duty ratio of 50% to 90%.

FIG. 15 is an explanatory diagram showing a modulation method of a communication signal. FIG. 15 shows an example of a modulated signal form used in an illumination optical communication device. The figure conforms to the 1-4 PPM transmission method specified in JEITA-CP1223. For example, a 4PPM signal of 2-bit data "00" is modulated to "1000" in a one-symbol period consisting of four slots. That is, a pulse appears in one of the four slots. In visible light communication, an inverted 4PPM signal is often used in order to light up 3 slots out of 4 slots to secure a lighting time. The communication signal in the figure is a signal modulated into an inverted 4PPM signal. In this case, the high level of the communication signal turns on the intermittent switch SW and turns on the load circuit 53 which is a light source. Further, the low level of the communication signal turns off the intermittent switch SW and turns off the load circuit 53 which is a light source. For example, one slot is 104.167 usc (= 1 / 9.6 kHz), and four slots (416 usec) form one symbol (here, one symbol is two bits). The 1-4 PPM signal is composed of two values of logical values 0 and 1, and is a data array in which a logical value 1 stands in one slot out of four slots. The communication signal generated by the signal generation circuit SG is an inverted 4PPM signal in which this logical value is inverted. The inverted 4PPM signal modulates the data depending on where the negative pulse stands in the 4 slots, and the on-duty ratio is 75% as far as the 4 slots of one symbol are seen. However, it can be seen that the pattern of the signal arrangement is diverse and the partial on-duty ratio is also diverse if the symbol delimiters are ignored. FIG. 16 shows an example thereof.

FIG. 16 is a diagram showing examples (1) to (4) of communication signals. Of the data for the four symbols in the figure, a circle is added to the off period and on period immediately before the rise of the communication signal from the low level to the high level. Looking at the partial data circled, the partial on-duty ratio is, for example, in the period (the latest one cycle) in which the latest off period and the on period immediately before the off period are combined. It can be defined as the ratio of the on-period. In the case (1) of FIG. 16, the frequency of the most recent cycle is 1.2 kHz, and the partial on-duty ratio is 75%. In case (2), it is 4.8 kHz, 50%, in case (3), it is 3.2 kHz, 66.7%, and in case (4), it is 2.4 kHz, 75%. That is, in the first embodiment, it is disclosed that the optimum current setting value of the current suppression circuit 1 is changed according to the on-duty ratio, but in an application in which the partial on-duty ratio changes from moment to moment. , It may correspond dynamically.

Further, as a simulation result of the circuit example shown in FIG. 2, the tendency of the LED current waveform and the waveform of the voltage applied to the current suppression circuit 1 in the four cases shown in the cases (1) to (4) of FIG. The results of the investigation are shown in FIGS. 17 to 24.

FIG. 17 is a diagram showing the simulation result (No. 1) of the case (2) of FIG. 16 (1.2 kHz, partial on-duty ratio 75%). Further, FIG. 18 is a diagram showing a simulation result (No. 2) of the case (1) of FIG.

In FIG. 17, when the current set value of the current suppression circuit 1 is 676 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 318 mA, the overshoot of the LED current disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 3 V.

FIG. 18 shows the result when the current set value is further lowered with respect to FIG. The LED current maintains a square wave, but the current value gradually decreases. Further, when the current set value is further lowered, the voltage applied to the current suppression circuit 1 rises sharply, and the current set value exceeds 20 V at 289 mA.

FIG. 19 is a diagram showing the simulation result (No. 1) of the case (2) of FIG. 16 (4.8 kHz, on-duty ratio 50%). Further, FIG. 20 is a diagram showing a simulation result (No. 2) of the case (2) of FIG.

In FIG. 19, when the current set value of the current suppression circuit 1 is 558 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 475 mA, the overshoot of the LED current disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.2 V.

FIG. 20 shows the result when the current set value is further lowered with respect to FIG. The LED current maintains a square wave, but the current value gradually decreases. Further, the voltage applied to the current suppression circuit 1 rises sharply, and the current set value exceeds 30 V at 407 mA.

FIG. 21 is a diagram showing the simulation result (No. 1) of the case (3) of FIG. 16 (3.2 kHz, on-duty ratio 66.7%). Further, FIG. 22 is a diagram showing a simulation result (No. 2) of the case (3) of FIG.

In FIG. 21, when the current set value of the current suppression circuit 1 is 463 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 357 mA, the overshoot of the LED current disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.4 V. FIG. 22 shows the result when the current set value is further lowered. The LED current maintains a square wave, but the current value gradually decreases. Further, the voltage applied to the current suppression circuit 1 rises sharply, and the current set value exceeds 22 V at 320 mA.

FIG. 23 is a diagram showing the simulation result (No. 1) of the case (4) of FIG. 16 (2.4 kHz, on-duty ratio 75%). Further, FIG. 24 is a diagram showing a simulation result (No. 2) of the case (4) of FIG.

In FIG. 23, when the current set value of the current suppression circuit 1 is 429 mA, the current suppression circuit 1 cannot suppress the overshoot current. When the current set value is lowered to 318 mA, the overshoot of the LED current disappears, and the applied voltage of the current suppression circuit 1 rises to a peak of about 1.4 V. FIG. 24 shows the result when the current set value is further lowered. The LED current maintains a square wave, but the current value gradually decreases. Further, the voltage applied to the current suppression circuit 1 rises sharply, and the current set value exceeds 20 V at 289 mA.

25A to 25C, FIGS. 26A to 26C, 27A to 27C, and 28A to 28C are diagrams of the results described with reference to FIGS. 17 to 24.

25A, 26A, 27A, and 28A show the current set value and the LED current (mean value and fluctuation value) as the simulation results of the cases (1), (2), (3), and (4) of FIG. It is a figure which shows the relationship with.

25B, 26B, 27B, and 28B show the relationship between the current set value and the ripple rate of the LED current as the simulation results of the cases (1), (2), (3), and (4) of FIG. It is a figure which shows.

25C, 26C, 27C, and 28C are diagrams showing the relationship between the current set value and the circuit loss as the simulation results of the cases (1), (2), (3), and (4) of FIG. is there.

These figures show the relationship between (A) the current set value and the average value and the fluctuation value of the LED current, (B) the current set value and the LED current ripple rate, and (C) the current set value and the loss of the current suppression circuit 1. ing. From these results, the optimum current setting value of the current suppression circuit 1 is about 475 mA when the on-duty ratio is 50%, about 357 mA when the on-duty ratio is 66.7%, and 75% when the on-duty ratio is 75%. Is found to be about 318 mA.

Next, the optimum current set value of the current suppression circuit 1 will be described according to the partial on-duty ratio of the communication signal from the signal generator SG. The power supply circuit 52a, which is the premise of the illumination optical communication device in the present embodiment, has a constant current feedback function as described above. A typical example is a constant current feedback circuit 67 using an amplifier as shown in FIG. Usually, a phase compensation circuit is added to ensure the stability of the feedback system. In such a phase compensation circuit, a compensation circuit including an integrating element is used to adjust the gain and the phase in the one-round transfer function, and is known as PI control or PID control. In other words, such a phase compensation circuit can be said to be a means for controlling the average value of outputs to be constant. With this in mind, FIG. 29A is an explanatory diagram showing an ideal waveform of the intermittent LED current. Looking at the intermittent waveform of the LED current shown in FIG. 29A, the average value Iave of this waveform is represented by the following equation (1).

Iave = Iop x ONd (1)

Here, Iop is the peak value of the LED current. ONd is an on-duty ratio and is represented by 100 × Ton / T (%).

The average value Iave is controlled by the constant current feedback function so as to be the same as the average current when there is no interruption, and is controlled to be a constant value even if the on-duty ratio changes. That is, as the on-duty ratio becomes smaller, the peak value Iop increases so that the Iave becomes a constant value. If this peak value Iop is set as the current set value of the current suppression circuit 1, the LED current waveform becomes a square wave and overshoot can be removed, and the loss of the current suppression circuit 1 can also be suppressed, that is, a so-called optimum value can be obtained ( (2) See equation).

Optimal current set value = Iave / ONd (2)

Here, Iave is the average LED current when no interruption is applied.

FIG. 29B shows the optimum current setting value for each partial on-duty ratio obtained by using the equation (2) under the condition that the average LED current is 240 mA when the LED is not intermittent. It can be seen that it is in good agreement with the optimum current setting value for each partial on-duty ratio shown in the previous studies.

According to this, the brightness of the illumination light when the overshoot of the LED current is suppressed and the illumination light is not modulated and the brightness of the illumination light when the illumination light is modulated can be seen by a person. The above can be almost the same.

[1.5 Configuration example of communication module 10]
Next, the configuration of the detachable communication module 10 will be described.

FIG. 1B is a circuit diagram showing a configuration of a lighting device to which the communication module 10 is not added according to the first embodiment. That is, FIG. 1B shows a configuration in which the communication module 10 is deleted and the short line S10 is added in the illumination optical communication device of FIG. 1A. The illumination optical communication device of FIG. 1A represents an illumination device having a visible light communication function. FIG. 1B represents a lighting device having no visible light communication function.

The communication module 10 or the short wire S10 is connected to the terminals T1 and T2 in FIGS. 1A and 1B. The terminals T1 and T2 may be terminal blocks or connectors, and the portions of the wiring in the existing lighting device in which the wiring material corresponding to the short wire S10 in FIG. 1B is cut may be referred to as terminals T1 and T2.

According to the configurations shown in FIGS. 1A and 1B, the power supply circuit and the LED light source mounted on the existing lighting fixture having no optical communication function are used as they are, and a simple circuit part (that is, the communication module 10) is retrofitted. An optical communication function can be added by adding with.

[1.6 Modification example of illumination optical communication device]
Next, a modified example of the illumination optical communication device will be described.

FIG. 30A is a circuit diagram showing a modified example of the illumination optical communication device according to the first embodiment. The illumination optical communication device shown in the figure has a different circuit configuration inside the power supply circuit 52a as compared with FIG. 1A. Hereinafter, the differences will be mainly described.

In the power supply circuit 52a of FIG. 1A, the constant current feedback circuit 67 performs feedback control to make the average value of the output current constant, whereas in the power supply circuit 52a of FIG. 30A, the switching current threshold control is performed. It is configured to do.

The power supply circuit 52a of FIG. 30A includes a rectifying bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that configure the DC-DC converter 64 as a back converter.

The control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and the circuits around the switch element 81, and the threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current via the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. The operation of such a DC-DC converter 64 will be described with reference to FIG. 30B.

FIG. 30B is a waveform diagram showing threshold control of the switching current in the power supply circuit 52a of FIG. 30A. However, FIG. 30B shows the case where the terminals T1 and T2 are short-circuited in FIG. 30A, or the communication module 10 is connected to the terminals T1 and T2, and the intermittent switch SW is maintained in the ON state. The waveform is shown.

In FIG. 30B, the set signal S is a signal input from the signal source 83 to the set input terminal S of the flip-flop 84. The positive input signal is a signal input to the positive input terminal of the comparator 85, and indicates the voltage drop of the resistor 82, that is, the magnitude of the current flowing through the switch element 81. The reset signal R is a signal input to the reset input terminal of the flip-flop 84. The output signal Q is a signal output from the output terminal Q of the flip-flop 84. The output signal Q becomes a gate signal of the switch element 81 via the driver 90 and the resistor 91. The switching current is a current flowing through the switch element 81, and is detected as a voltage drop of the resistor 82.

The set signal is generated by the signal source 83 and periodically goes high. When the set signal S becomes high, the output signal Q of the RS flip-flop 84 becomes high. The output signal Q is input to the gate of the switch element 81 (MOSFET) via the driver circuit 90 and the gate resistor 91. The switch element 81 is turned on when the output signal Q becomes high.

The magnitude of the switching current (current flowing through the switch element 81) is detected as a voltage drop of the resistor 82, input to the positive input terminal of the comparator 85, and compared with the reference voltage Vref applied to the negative input terminal of the comparator 85. To. When the voltage drop reaches the reference voltage Vref, the output of the comparator 85 becomes high, is converted into a pulse by a differentiating circuit composed of a capacitor 87 and a resistor 88, and is input to the reset input terminal of the RS flip-flop 84. At this point, the output signal Q of the flip-flop 84 becomes low, and the switch element 81 turns off. Detecting the magnitude of the current flowing through the switch element 81 as the switching current is a substitute for detecting the magnitude of the current flowing through the load circuit 53.

Such threshold control of the switching current substitutes the constant current feedback control of FIG. 1A, and works to make the average of the output currents constant. As a result, also in FIG. 30A, similarly to FIG. 1A, if the current suppression circuit 1 is not provided, the problem of overshoot described in the problem column occurs. However, in the configuration of FIG. 30A, the overshoot can be reduced by providing the current suppression circuit 1 as in FIG. 1A.

The power supply circuit 52a may be one that performs constant current feedback control in FIG. 1A or one that performs switching current threshold control in FIG. 30A. Further, since the current suppression circuit 1 has a function of reducing overshoot, it is effective if it is a power supply circuit that can cause overshoot by turning on and off the intermittent switch SW.

(Embodiment 2)
In the second embodiment, a configuration in which the reference value (and thus the current set value) is made variable in an analog circuit in the current suppression circuit 1 will be described. In the first embodiment, the reference value is changed according to the on-duty ratio, but in the second embodiment, the reference value is changed according to the voltage applied to the current suppression circuit 1 immediately before the intermittent switch SW is turned on. The point to make is different. That is, the voltage applied to the current suppression circuit 1 is used instead of the on-duty ratio. The LED current overshoot increases as the on-duty ratio increases. Further, as shown in FIG. 51, the overshoot of the LED current increases as the output voltage (corresponding to the voltage applied to the current suppression circuit 1) increases. Therefore, in the second embodiment, the voltage applied to the current suppression circuit 1 is used as a substitute for the on-duty ratio.

The illumination optical communication device of the second embodiment has substantially the same configuration as that of FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, the differences will be mainly described.

A configuration example of the current suppression circuit 1 according to the second embodiment is shown in FIGS. 31A and 31B.

The current suppression circuit 1 shown in FIG. 31A is composed of a transistor 2 which is a MOSFET 2, a resistor 3 connected to a source, a constant voltage source 4a, voltage dividing resistors R1 and R2, a capacitor C1, and a diode D. To. Further, the current suppression circuit 1 shown in FIG. 31B includes bipolar transistors 11 and 12, a constant voltage source 13, voltage dividing resistors R1 and R2, a noise prevention capacitor C1, and a current limiting resistor 14. It is composed of a diode D.

In FIG. 31A, the voltage of the constant voltage source 4 is divided by the resistors R1 and R2, and is connected to the gate terminal of the transistor 2 and the point via the resistor 3 via the capacitor C1. Further, the diode D is connected from the drain terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2. Further, in FIG. 31B, the bipolar transistors 11 and 12 form a current mirror, the voltage of the constant voltage source 13 is divided by the resistors R1 and R2, and the collector terminal and the base terminal are short-circuited via the resistors C1 and the resistor 14. A reference current is passed through the bipolar transistor 12. Further, the diode D is connected from the collector terminal of the bipolar transistor 11 toward the voltage dividing points of the resistors R1 and R2. These configurations do not directly control the reference source when obtaining the optimum current set value of the current suppression circuit 1 according to the on-duty ratio of the modulated signal from the signal generator SG, but the current set value. The voltage applied to the current suppression circuit 1 generated when is inappropriate is used to feed back to the voltage dividing point of the reference source.

The resistors R1 and R2 and the diode D of FIGS. 31A and 31B correspond to the control circuit 6 of FIG. 1A for changing the reference value.

The operation of FIG. 31A in the second embodiment of the present invention will be described with reference to simulation results. The main setting conditions in the simulation are: the capacitance value of the smoothing capacitor is 20uF, the modulation signal frequency from the signal generation circuit is 2.4kHz, the operating frequency of the DC-DC converter is 65kHz, and the load current (LED current) when not intermittent. The average value is set to 240 mA.

The simulation results are shown in FIGS. 32A, 32B, 33A, 33B and 34. 32A and 32B show simulation results when the diode D as a feedback circuit is first removed in order to see the effect of the feedback by the diode D shown in FIGS. 31A and 31B. Fluctuations in LED current because the current suppression circuit 1 is set to function at an on-duty ratio of 90% or less when the on-duty ratio of the modulated signal from the signal generator SG is in the range of 50% to 90%. The value (overshoot) is removed over the entire on-duty ratio region (see FIG. 32B), but the average value of the LED current decreases as the on-duty ratio decreases. Further, as shown in FIG. 34, the current suppression circuit 1 loss becomes significantly larger as the on-duty ratio becomes smaller (see the diagram without a diode). 33A and 33B are the results when the feedback circuit by the diode D is added. When the on-duty ratio is 50% to 90%, the fluctuation value (overshoot) of the LED current is suppressed to a small value, and the average value is maintained at the value when it is not intermittent. Further, as shown in FIG. 34 (with a diode), it can be seen that the loss of the current suppression circuit 1 is significantly reduced as compared with the case without the feedback circuit by the diode D.

(Embodiment 3)
Also in the third embodiment, the configuration in which the reference value (and thus the current set value) is made variable in the analog circuit in the current suppression circuit 1 will be described as in the second embodiment.

The illumination optical communication device of the third embodiment has substantially the same configuration as that of FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, the differences will be mainly described.

FIG. 35A is a diagram showing a configuration example of the current suppression circuit 1 according to the third embodiment. The current suppression circuit 1 shown in FIG. 35A includes a bipolar transistor 2, a resistor 3 connected to an emitter, a reference source 4, voltage dividing resistors R1 and R2, a capacitor C1, and an amplifier as a voltage follower circuit. It is composed of 5, a base resistor Rb, a diode D, and a resistor R3.

In FIG. 35A, the constant voltage source 4a is divided by the resistors R1 and R2, and is connected to the positive input terminal of the voltage follower using the amplifier 5 via the capacitor C1. The output terminal of the amplifier 5 is connected to its negative input terminal and is also connected to the base terminal of the transistor 2 via the base resistor Rb, and supplies a drive voltage to the point via the base terminal and the resistor 3. Further, the diode D is connected from the collector terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2. In this configuration, when the optimum current set value of the current suppression circuit 1 is obtained according to the on-duty ratio of the modulated signal from the signal generator, the reference source is not directly controlled, and the current set value is not set. The applied voltage of the current suppression circuit 1 generated in an appropriate case is used to feed back to the voltage dividing point of the reference source, and the difference from FIGS. 31A and 31B showing the second embodiment is that the amplifier 5 is used. It is the addition of the voltage follower that was there.

The resistors R1, R2, R3 and diode D in FIG. 35A correspond to the control circuit 6 that changes the reference value in FIG. 1A.

36 to 38 are diagrams showing simulation results for verifying the operation of the current suppression circuit 1 of FIG. 35A. The main setting conditions for the simulation are a capacitance value of the smoothing capacitor 65 of 20 uF, a modulation signal frequency from the signal generation circuit SG of 2.4 kHz, an operating frequency of the DC-DC converter of 65 kHz, and a load current (LED current) when not intermittent. ) Is set to 240 mA. FIG. 36 shows the peak value, the average value, and the fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at the value when it is not intermittent. FIG. 37 shows the fluctuation value (overshoot) of the LED current as a ripple rate, and it can be seen that the overshoot is also removed from this. FIG. 38 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is kept low with respect to changes in the on-duty ratio.

(Embodiment 4)
Also in the fourth embodiment, the configuration in which the reference value (and thus the current set value) is made variable in the analog circuit in the current suppression circuit 1 will be described as in the second embodiment.

The illumination optical communication device of the fourth embodiment has substantially the same configuration as that of FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, the differences will be mainly described.

FIG. 35B is a diagram showing a first configuration example of the current suppression circuit 1 according to the fourth embodiment. The current suppression circuit 1 shown in FIG. 35B includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a constant voltage source 4a, voltage dividing resistors R1 and R2, a capacitor C1, an amplifier 5, and a diode. It is composed of D and a resistor R3.

In FIG. 35B, the constant voltage source 4a is divided by the resistors R1 and R2 and connected to the positive input terminal of the amplifier 5 via the capacitor C1. The negative input terminal of the amplifier 5 is connected to the connection point between the transistor 2 and the resistor 3, the output terminal of the amplifier 5 is connected to the gate terminal of the transistor 2, and the drive voltage is connected between the gate terminal and the point via the resistor 3. Is supplied. Further, the diode D is connected from the drain terminal of the transistor 2 toward the voltage dividing point by the resistors R1 and R2 via the adjusting resistor R3. In these configurations, when the optimum current setting value of the current suppression circuit 1 is obtained according to the on-duty ratio of the modulated signal from the signal generator, the reference source is not directly controlled, but the current setting value is used. The applied voltage of the current suppression circuit 1 generated in an inappropriate case is used to feed back to the voltage dividing point of the reference voltage, and the difference from FIG. 31A in the second embodiment is that the amplifier 5 is added. is there.

39 to 41 are diagrams showing simulation results for verifying the operation of FIG. 35B. The main setting conditions for the simulation are 20 uF for the capacitance value of the smoothing capacitor, 2.4 kHz for the modulated signal frequency from the signal generation circuit, 65 kHz for the operating frequency of the DC-DC converter, and the load current (LED current) when not intermittent. The average value is set to 240 mA. The simulation results are shown in FIGS. 39 to 41. FIG. 39 shows the peak value, the average value, and the fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at the value when it is not intermittent. FIG. 40 shows the fluctuation value (overshoot) of the LED current by the ripple rate, and it can be seen that the overshoot is almost eliminated from this as well. FIG. 41 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is kept low with respect to changes in the on-duty ratio.

In FIGS. 39 to 41, the LED current ripple is slightly larger than that of the simulation results of the third embodiment (FIGS. 36 to 38), and some unstable operation is observed.

An example for achieving more stable operation according to the third and fourth embodiments is shown in FIGS. 35C and 35D. FIG. 35C is a diagram showing a second configuration example of the current suppression circuit according to the fourth embodiment. FIG. 35C shows an amplifier 5a having a voltage follower and a diode Da added between the voltage dividing points of the resistors R1 and R2 and the positive input terminal of the amplifier 5, and is added to the filter circuit formed by the capacitors C1 and the resistor R4. An impedance conversion circuit is added so that the resistors R1, R2, R3, etc. are not affected.

FIG. 35D is a diagram showing a third configuration example of the current suppression circuit according to the fourth embodiment. In FIG. 35D, a ripple filter formed by a transistor Tr, a resistor R5, and a capacitor C3 is added between the voltage dividing points of the resistors R1 and R2 and the positive input terminal of the amplifier 5, and the pulsating voltage of the positive input terminal of the amplifier 5 is suppressed. It was done.

(Embodiment 5)
Also in the fifth embodiment, the configuration in which the reference value (and thus the current set value) is made variable in the analog circuit in the current suppression circuit 1 will be described as in the second embodiment.

The illumination optical communication device of the fifth embodiment has substantially the same configuration as that of FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, the differences will be mainly described.

FIG. 35E is a diagram showing a configuration example of the current suppression circuit according to the fifth embodiment. The current suppression circuit 1 shown in FIG. 35E includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4, voltage dividing resistors R1 and R2, a capacitor C1, an amplifier 5, and the amplifier. It is composed of a resistor Rg, a capacitor Cp, a resistor Rp, a diode D, and a resistor R3 provided between the output terminal and the positive input terminal of No. 5.

In FIG. 35E, the reference source 4 is divided by resistors R1 and R2 and connected to the positive input terminal of the amplifier 5 via the capacitor C1. The negative input terminal of the amplifier 5 is connected to the connection point between the transistor 2 and the resistor 3, the output terminal of the amplifier 5 is connected to the gate terminal of the transistor 2, and between the gate terminal and the point via the resistor 3. The drive voltage is supplied. Further, the diode D is connected from the drain terminal of the MOSFET toward the voltage dividing point by the resistors R1 and R2 via the adjusting resistor R3. Further, a resistor Rg for gain adjustment is connected between the output terminal and the negative input terminal of the operational amplifier, and a phase compensation circuit composed of a capacitor Cp and a resistor Rp is added in parallel with the resistor Rg.

42 to 44 are diagrams showing simulation results for verifying the operation of the current suppression circuit 1 of FIG. 35E. The main setting conditions for the simulation are 20 uF for the capacitance value of the smoothing capacitor, 2.4 kHz for the modulated signal frequency from the signal generation circuit, 65 kHz for the operating frequency of the DC-DC converter, and the load current (LED current) when not intermittent. The average value is set to 240 mA. FIG. 42 shows the peak value, the average value, and the fluctuation value of the LED current when the on-duty ratio of the intermittent switch SW is changed in the range of 50% to 90%. The fluctuation value (overshoot) of the LED current is almost eliminated, and the average value is maintained at the value when it is not intermittent. FIG. 43 shows the fluctuation value (overshoot) of the LED current as a ripple rate, and it can be seen that the overshoot is almost eliminated from this as well. FIG. 44 shows the relationship between the on-duty ratio and the current suppression circuit 1 loss. The circuit loss is kept low with respect to changes in the on-duty ratio.

In FIGS. 42 to 44, the LED current ripple rate is improved and more stable operation is obtained as compared with the simulation results of the fourth embodiment (FIGS. 39 to 41).

(Embodiment 6)
The current suppression circuit 1 of the second to fifth embodiments has a configuration in which the reference value (and thus the current set value) is variable in an analog circuit, whereas in the sixth embodiment, the reference value (as a result, the current setting value) is digital. As a result, the current suppression circuit 1 that makes the current set value variable will be described.

The illumination optical communication device of the fifth embodiment has substantially the same configuration as that of FIG. 1A, but the configuration of the current suppression circuit 1 is different. Hereinafter, the differences will be mainly described.

FIG. 35F is a diagram showing a configuration example of the current suppression circuit according to the sixth embodiment. The current suppression circuit 1 shown in FIG. 35F includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4, a microcomputer (that is, a CPU 7c), and voltage dividing resistors R1, R6, R7, and R8. It is composed of switches S01 to S03 for switching the voltage dividing ratio, an amplifier 5, and a resistor R3.

In FIG. 35F, the voltage applied to the current suppression circuit 1 (transistor 2 and resistor 3) is input to the microcomputer (CPU 7c) via the resistor R3. The constant voltage source 4a is connected to the positive input terminal of the amplifier 5 via the resistor R1, and the voltage dividing resistors R6 to R8 and the changeover switches S01 to S03 are connected between the connection point and the negative end of the reference voltage. .. The microcomputer calculates an appropriate reference voltage value according to the voltage between the current suppression circuits 1, or selects from a correspondence table constructed in advance to switch the changeover switches S01 to S03. These configurations can be said to be a method in which a part of the above-described embodiments 3 to 5 is digitized.

The resistors R1 and R3, diodes D, R6 to R8, switches S01 to S03, and CPU7c in FIG. 35F correspond to the control circuit 6 for changing the reference value in FIG. 1A.

(Comparison reference example)
Subsequently, in order to confirm the effect of the current suppression circuit 1 in each embodiment, a comparative reference example without the current suppression circuit 1 will be described.

FIG. 45 is a diagram showing an illumination optical communication device as a comparative reference example in which the current suppression circuit 1 is deleted from FIG. 1A. The illumination optical communication device of the figure is different from FIG. 1A in that it does not have the current suppression circuit 1 and that the load circuit 53, which is a light source, and the intermittent switch SW are directly connected. Since the illumination optical communication device of the comparative reference example does not include the current suppression circuit 1, it does not have a function of suppressing the current flowing through the light source so as not to exceed the current set value.

The results of simulating the comparative reference example shown in FIG. 45 will be described with reference to FIGS. 46 to 49B.

FIG. 46 is a diagram showing LED current and output voltage waveforms when the on-duty ratios are 60%, 75%, 90%, and 100% as a simulation result of the circuit for comparison reference in FIG. 45. In this simulation, the capacitance of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal that drives the intermittent switch SW is 2.4 kHz. As shown in the figure, it can be seen that the smaller the on-duty ratio, the larger the overshoot of the LED current. In addition, the voltage waveform also fluctuates, but it is not as violent as the fluctuation of the current, suggesting that the operating resistance of the LED load is low.

FIG. 47 is a simulation result of the LED current waveform and the output voltage waveform when the frequency of the modulated signal is 2.4 kHz, the ON-Duty is 75%, and the capacitance of the output smoothing capacitor is changed by 10 to 30 uF. It can be seen that the smaller the smoothing capacitor capacity, the larger the overshoot of the LED current. 48A, 48B, 49A, and 49B are schematic representations of the above simulation results. Even if the horizontal axis ON-Duty changes, the average value of the LED current does not change, and the constant current feedback control (averaging control) is functioning, but the peak value increases as the ON-Duty decreases. The fluctuation range in the figure represents the magnitude of the overshoot of the LED current, and is also indicated by the ripple rate. For example, comparing FIGS. 10 to 14 of the first embodiment with FIGS. 48A, 48B, 49A, and 49B of the comparative reference example, the overshoot of the LED current is well reduced in the embodiment. I understand.

As described above, the illumination light communication device according to the first to sixth embodiments has a light source 53 that emits illumination light, a switch SW that is connected in series with the light source and interrupts the current flowing through the light source, and the illumination light. A signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch SW for modulation is connected in series with the light source and the switch so as not to exceed a variable current set value. It includes a current suppression circuit 1 that suppresses the current flowing through the light source.

According to this, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the intermittent switch SW is turned from off to on can be reduced, thereby reducing the reception error in the receiving device. ..

Here, the current suppression circuit 1 is connected in series with a reference source 4 that outputs a variable reference value corresponding to the current set value, the light source, and the switch, and sets the current flowing through the light source to the reference value. Based on this, the transistor 2 to be suppressed and the partial on-duty ratio of the communication signal are calculated, and when the calculated partial on-duty ratio is the first ratio, the reference value is set to the first value, and the portion When the on-duty ratio is a second ratio larger than the first ratio, the control circuit 6 for setting the reference value to a second value smaller than the first value is provided, and the second value is set. The corresponding current set value may be smaller than the current set value corresponding to the first value.

According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, the suppression of the overshoot can be made appropriate.

Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

Here, the control circuit 6 may change the reference value so as to satisfy the following equation.

I1 = (Iave / ONd) x 100

Here, I1 is the current set value, Iave is the average current flowing through the light source when the illumination light is not modulated by the interruption of the switch, and ONd is the partial on-duty ratio of the communication signal. The unit is%).

According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is almost the same as the brightness of the illumination light when the illumination light is modulated. Can be.

Here, the control circuit 6 may change the reference value so as to satisfy the following equation.

(Iave / ONd) × 100 ≦ I1 <Ip

Here, Iave is the average current flowing through the light source when the illumination light is not modulated by the intermittent operation of the switch, ONd is the partial on-duty ratio of the communication signal, and I1 is the current set value. Yes, Ip is the peak value of the current flowing through the light source when the current suppression circuit does not suppress it.

Here, the current suppression circuit 1 is connected in series with a reference source 4 that outputs a variable reference value corresponding to the current set value, the light source, and the switch, and uses the current flowing through itself and the light source as the reference. The reference source 4 includes a transistor 2 that suppresses based on a value, the reference source 4 is a constant voltage source 4a that generates a constant voltage, two resistors (R1, R2) that divide the constant voltage, and the current suppression circuit 1. A diode (D) that feeds back the voltage applied to the two resistors to the connection point between the two resistors, and a capacitance element (C1) that holds the potential of the connection point as the reference value, and the potential of the connection point. May have a configuration indicating the reference value.

According to this, since the overshoot generated in the current flowing through the light source is reduced at the moment when the switch is turned on, it is possible to reduce the reception error in the receiving device. This is because when the power supply circuit of the illumination optical communication device is a current feedback type, the size of the overshoot depends on the partial on-duty ratio, and the output voltage gradually increases during the off period. There is. Due to the feedback of the diode, the reference value also rises according to the output voltage that gradually rises during the off period, so that the overshoot can be appropriately reduced.

Here, the transistor 2 is a field effect transistor, and the current suppression circuit 1 is connected to the source of the transistor 2, a source resistor connected in series with the transistor 2 and the switch SW, an output terminal, and a minus. It has an amplifier 5 having an input terminal and a positive input terminal, the output terminal is connected to the gate of the transistor 2, the negative input terminal is connected to a connection point between the transistor 2 and the source resistor, and the positive is connected. The input terminal may be connected to the connection point between the two resistors and the capacitance element.

Here, the transistor 2 is a bipolar transistor, and the current suppression circuit 1 has an emitter resistance connected to the emitter of the transistor 2 and connected in series with the transistor and the switch, and an output terminal, a negative input terminal, and the like. It has an amplifier 5 having a positive input terminal, the output terminal is connected to the base of the transistor, the negative input terminal is connected to a connection point between the transistor and the emitter resistor and the capacitance element, and the positive input terminal is connected. May be connected to the connection point between the two resistors.

Here, the current suppression circuit 1 may include a gain adjustment circuit added to the amplifier 5 and a phase compensation circuit added to the amplifier 5.

Here, the current suppression circuit 1 may further include a voltage follower circuit inserted between the connection point between the two resistors and the positive input terminal.

Here, the control circuit 6 may include a detection unit that detects a voltage applied to the current suppression circuit 1 and a CPU that determines the reference value according to the detected voltage.

Here, the illumination optical communication device has a power supply circuit 52a that supplies a current to the light source, the switch, and the current suppression circuit 1 connected in series, and the power supply circuit 52a calculates an average value of the supplied currents. Feedback control may be performed to make it constant.

Here, the power supply circuit 52a includes a DC-DC converter 64 having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and responds to the difference between the detected value and a predetermined value. The on and off of the switch element 81 may be controlled.

The communication module according to the first to sixth embodiments is a communication module 10 that modulates the illumination light and can be attached to and detached from the illumination device, and has a switch SW connected in series with the light source of the illumination device and the illumination. A signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch to modulate light is connected in series with the light source and the switch so as not to exceed a variable current set value. A current suppression circuit 1 that suppresses the current flowing through the light source is provided.

According to this, the communication module can be added to the existing luminaire. That is, the existing lighting equipment can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than when a new optical communication lighting equipment is installed. Further, since the overshoot generated in the current flowing through the light source at the moment when the switch is turned on is reduced, the reception error in the receiving device can be reduced.

(Embodiment 7)
In the seventh embodiment, even when 100% modulated optical communication is performed using a constant current feedback type power supply, a reception error of the receiving device is unlikely to occur, and an illuminated optical communication device and a communication module suitable for cost reduction are provided. provide.

One form of the illumination light communication device according to the present embodiment is an illumination light communication device that modulates the illumination light according to a communication signal, and includes a light source that emits the illumination light, a transistor connected in series with the light source, and the like. It includes a signal generation circuit that generates the binary communication signal, and a combined control circuit that causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. The combined control circuit is also a modification of the current suppression circuit already described.

Further, one form of the communication module according to the present embodiment is a communication module that is detachable from the lighting device and modulates the illumination light, and has a binary value with a transistor connected in series with the light source of the lighting device. It includes a signal generation circuit that generates the communication signal, and a combined control circuit that causes the transistor to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

According to the illumination optical communication device and the communication module according to the present embodiment, there is an effect that a reception error of the receiving device is unlikely to occur even when 100% modulated optical communication is performed using a constant current feedback type power supply. .. Moreover, since the transistor is also used as a switch element that performs the modulation operation and a current suppression element that performs the suppression operation, it is possible to suppress an increase in circuit elements and is suitable for cost reduction. ..

[7.1 Configuration of Illuminated Optical Communication Device]
First, the configuration of the illumination optical communication device according to the seventh embodiment will be described.

FIG. 50A is a circuit diagram showing a configuration example of the illumination optical communication device according to the seventh embodiment. This illumination optical communication device includes a power supply circuit 52a having a function of making the output a constant current, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and a communication module 10. The communication module 10 includes a transistor 2 and a combined control circuit 1b.

The power supply circuit 52a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

The power supply circuit 52a full-wave rectifies a commercial power supply (for example, AC 100V) with a rectifying bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected between both ends of the output of the DC-DC converter 64. Further, a load circuit 53, a combined control circuit 1b, and a series circuit of the transistor 2 are connected in parallel with the smoothing capacitor 65.

The power supply circuit 52a has a function of directly or indirectly detecting the current flowing through the load circuit 53 and controlling the current values to be constant. This function is based on the detection resistor 66 and the constant current feedback circuit 67 for directly detecting the current of the load circuit 53 in FIG. 50A. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and an amplifier 69. A resistor 71 for gain adjustment and a capacitor 70 for phase compensation connected between the negative input terminals of the above are provided. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 with the amplifier 69, amplifies the difference, and feeds it back to the control unit of the DC-DC converter 64. That is, the DC-DC converter 64 is subjected to negative feedback control so that the voltage drop of the detection resistor 66 and the reference voltage match. Further, the gain is set by the voltage division ratio between the resistor 71 connected between the inverting input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 is integrated for phase compensation. Acts as an element.

The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52a and smoothes the output of the power supply circuit 52a.

The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52a, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

The transistor 2 is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect).
Transistor), which is connected in series with the load circuit 53. The transistor 2 is used for the modulation operation of the illumination light and the suppression operation of the current flowing through the light source (that is, the load circuit 53). Here, the modulation operation is the modulation of the illumination light, by interrupting the current supplied from the power supply circuit 52a to the load circuit 53 in the transistor 2. Further, the suppression operation means suppressing the current flowing through the light source and the transistor 2 so as not to exceed the current set value.

The combined control circuit 1b causes the transistor 2 to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source. Therefore, the combined control circuit 1b includes a signal generation circuit SG, a switch SW, a reference source 4, a control circuit 6, a resistor R5, a resistor R6, and an amplifier 7.

The signal generation circuit SG generates a binary communication signal that controls the on and off of the transistor 2 in order to modulate the illumination light. The communication signal is not directly input to the gate of the transistor 2, but is indirectly input to the control terminal of the transistor 2 via the switch SW and the amplifier 7, and indirectly turns on and off the transistor 2. The modulation method of this communication signal may be the same as that of FIG. 15 already described.

The switch SW is, for example, a switching transistor, and a binary communication signal from the signal generation circuit SG is input to its gate or base, and is turned on and off according to the communication signal. The switch SW and the signal generation circuit SG in the combined control circuit 1b function as a modulation control circuit that controls the modulation operation of the illumination light. The switch SW may be a switching element such as a thyristor.

Further, the modulation operation of the illumination light will be described with reference to FIG. 50B. FIG. 50B is a diagram showing a truth table showing the communication signals of the signal generation circuit SG in FIG. 50A, the switch SW, and the operating state of the transistor 2. “SG” indicates the logical value (high level or low level) of the communication signal, “SW” indicates the state of the switch SW (on or off), and “2” indicates the state of the transistor 2 (on or off). Here, it is assumed that the communication signal is the inverted 4PPM signal of FIG.

When the communication signal is L (low level), the switch SW is on, the transistor 2 is off, no current flows through the light source, and the light is turned off.

When the communication signal is H (high level), the switch SW is off, the transistor 2 is on, and a current flows through the light source to light it. In this way, the illumination light is modulated by turning on and off the transistor 2 by the binary communication signal.

Next, the operation of suppressing the current flowing through the light source will be described. The notation of "* ON" in FIG. 50B has the following meaning. That is, the transistor 2 is not always in a completely on state, but is dynamically turned in a completely on or incompletely on state according to an error between the positive input terminal and the negative input terminal of the amplifier 7. The degree of incomplete turning (that is, the magnitude of the source-drain resistance of the transistor 2) is determined according to the above error. As a result, the current flowing through the transistor 2 (that is, the current flowing through the light source) is suppressed so as not to exceed the current set value. This current set value is determined according to the reference value input to the positive input terminal of the amplifier 7.

This suppression operation is performed by the circuit portion of the combined control circuit 1b excluding the signal generation circuit SG and the switch SW. That is, the reference source 4, the control circuit 6, the resistor R5, the resistor R6, and the amplifier 7 in the combined control circuit 1b function as a current suppression circuit that causes the transistor 2 to perform a suppression operation.

The reference source 4 outputs a reference value to the positive input terminal of the amplifier 7. The reference value defines an upper limit (current set value) of the current flowing through the load circuit 53 which is a light source. For example, the reference value is proportional to the current set value. Further, the reference source 4 may output a reference value as a fixed value, or may output a variable reference value according to an arrangement pattern (for example, a bit pattern) of a communication signal generated by the signal generation circuit SG. ..

The resistor R3 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor R3 is connected to the negative input terminal of the amplifier 5.

In the amplifier 7, the reference source 4 is connected to the positive input terminal via the voltage dividing resistors R5 and R6, and the source of the transistor 2 is connected to the negative input terminal. The amplifier 7 determines the level of the gate signal or the base signal to the transistor 2 so that the current flowing through the light source does not exceed the current set value when the communication signal is instructed to turn on or off. Specifically, the amplifier 7 amplifies the difference between the reference value and the current value detected by the resistor R3, and outputs the amplified signal to the gate of the transistor 2.

The control circuit 6 controls to change the reference value of the reference source 4 according to the arrangement pattern of the communication signal in order to output a variable reference value from the reference source 4. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal, and when the calculated partial on-duty ratio is the first ratio, sets the reference value as the first value and partially When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The "partial on-duty ratio" is, for example, the ratio of the on-duty period to the total period of the latest off-duty period and the on-duty period immediately before the off-duty period. Alternatively, the "partial on-duty ratio" may be replaced by the moving average of the most recent n bits of the communication signal. In this way, overshoot suppression can be made more appropriate when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio.

In FIG. 50A, when the reference source 4 outputs a fixed reference value, the combined control circuit 1b does not have to include the control circuit 6.

[7.2 Operation of Illuminated Optical Communication Device]
The operation of the illumination optical communication device configured as described above will be described using simulation results.

51 to 54 show the results of simulating the combined control circuit 1b of FIG. 50A.

FIG. 51 is a diagram showing a first simulation result for the circuit example of FIG. 50A. FIG. 51 shows LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, and 100%. In this simulation, the capacitance of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal (that is, the communication signal) that drives the switch SW is 2.4 kHz. As shown in the figure, it can be seen that the overshoot of the LED current is suppressed regardless of the on-duty ratio. In addition, the voltage waveform also fluctuates, but it is not as violent as the current fluctuation, suggesting that the operating resistance of the LED load is low.

FIG. 52 shows the result of obtaining the optimum current set value of the combined control circuit 1b according to the on-duty ratio of the modulated signal from the signal generator SG. FIG. 52 is a diagram showing a second simulation result for the circuit example of FIG. 50A. Also in this simulation, the capacitance of the smoothing capacitor 65 is set to 20 uF, and the frequency of the modulated signal for driving the switch SW is set to 2.4 kHz. In FIG. 52, if the current set value is changed as shown in the figure according to the on-duty ratio on the horizontal axis, the fluctuation value of the LED current due to overshoot is suppressed, and the average value is the case where the transistor 2 is not interrupted. Can be maintained at a value. The fluctuation width in the figure represents the overshoot of the modulated rectangular wavy LED current waveform. Since the average value of the LED current is substantially constant regardless of the on-duty, the brightness of the illumination light is also maintained to be substantially constant regardless of the on-duty. Further, since the fluctuation range is small, the overshoot of the LED current waveform is suppressed and the wave becomes a substantially rectangular wave, so that a reception error of the receiving device can be prevented. Although some fluctuation is seen at 100% on-duty (no modulation), it is due to the high frequency ripple existing in the original waveform without modulation.

FIG. 53 is a diagram showing a third simulation result for the circuit example of FIG. 50A. Also in this simulation, the capacitance of the smoothing capacitor 65 is set to 20 uF, and the frequency of the modulated signal for driving the switch SW is set to 2.4 kHz. In FIG. 53, the peak value and the average value of the output voltage take substantially the same value according to the on-duty ratio on the horizontal axis, and the fluctuation range is small and falls within the range.

Further, the circuit loss of the combined control circuit 1b is shown in FIG. 54. FIG. 54 is a diagram showing a fourth simulation result for the circuit example of FIG. 50A. The simulation conditions are the same as those in FIGS. 52 and 53. The vertical axis shows the circuit loss in the combined control circuit 1b. In FIG. 54, it can be seen that the circuit loss at the on-duty ratio of 50% to 90%, that is, during the modulation operation, is within a low value.

[7.3 Configuration example of communication module 10]
Next, the detachable communication module 10 will be described.

In FIG. 50A, the communication module 10 is connected to one end of the load circuit 53 and one end of the power supply circuit 52a via terminals T1 and T2. Terminals T1 and T2 may be terminal blocks or connectors. In this way, the communication module 10 can be attached to and detached from the terminals T1 and T2.

A short wire can be connected to the terminals T1 and T2 instead of the communication module 10. In FIG. 50A, a device in which a short wire is connected to terminals T1 and T2 instead of the communication module 10 functions as a lighting device having no visible light communication function.

According to the configuration as shown in FIG. 50A, the power supply circuit and the LED light source mounted on the existing lighting fixture having no optical communication function are used as they are, and a simple circuit part (that is, the communication module 10) is added later. This makes it possible to add an optical communication function.

As described above, the dual-purpose control circuit 1b in the illumination optical communication device of the seventh embodiment controls the transistor 2 to simultaneously perform the illumination light modulation operation and the current suppression operation of the light source.

According to this, since the overshoot that occurs at the rising edge of the current waveform is suppressed by the suppression operation, there is an effect that a reception error of the receiving device is unlikely to occur. Further, since the transistor 2 is also used as the switch element that performs the above-mentioned modulation operation and the current suppression element that performs the suppression operation, it is possible to suppress an increase in the number of circuit elements.

The combined control circuit 1b causes the transistor 2 to execute a modulation operation by generating a gate signal or a base signal input to the gate or base of the transistor 2 according to the communication signal, and the communication signal is turned on or off. The level of the gate signal or base signal may be determined so that the current flowing through the light source does not exceed the current set value when instructing the lighting of.

Further, the combined control circuit 1b includes a current detection circuit (that is, a resistor R3) that detects the magnitude of the current flowing through the light source, a reference source 4 that outputs a reference value corresponding to the current set value, and the magnitude of the current. An amplifier 7 having two input terminals to which the reference value is input, amplifying an error between the two input terminals, and outputting the amplified signal as a gate signal or a base signal, and at least two input terminals. It may be provided with a switch circuit (for example, a switch SW) that is coupled to one side and makes the error substantially zero when the communication signal indicates that the light is turned off. Here, setting the error to substantially 0 means a value at which the error lowers the output of the amplifier 7. To make the error substantially 0, for example, the negative input terminal and the positive input terminal may have the same potential, and the negative input terminal may have a higher potential than the positive input terminal.

Further, the above-mentioned switch circuit has a switch transistor (for example, a switch SW), and the switch transistor becomes the reference value of the two input terminals by conducting the communication signal when the communication signal is instructed to turn off. The level of the corresponding input terminal may be substantially set to the ground level. Here, the substantially ground level means a level at which the above error is substantially zero, in other words, a level at which the output of the amplifier 7 is substantially at a low level. For example, the substantially grounding level may be the grounding level (that is, 0V), or may be the same level or lower than the negative input terminal even if it is not the grounding level.

Here, one end of the switch transistor (for example, the switch SW) is connected to the input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor is a wiring having a substantially ground potential. It may be connected to (see FIG. 50A).

Here, the dual-purpose control circuit 1b further includes a resistance element (for example, a resistor 17) connected between an input terminal corresponding to a reference value and the wiring having a substantially ground potential, and a switch transistor (for example, a valve). One end of B2) may be connected to the input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor may be connected to the reference source (see FIG. 57C).

(Embodiment 8)
In the seventh embodiment, a circuit example of the dual-purpose control circuit 1b in which the switch SW is connected to the positive input terminal of the amplifier 7 is shown. On the other hand, in the eighth embodiment, a circuit example of the dual-purpose control circuit 1b in which the switch SW is connected to the negative input terminal of the amplifier 7 will be described.

The configuration of the illumination optical communication device in the eighth embodiment is the same except for the communication module 10 of FIG. 50A. Hereinafter, the differences will be mainly described.

FIG. 55 is a diagram showing a configuration example of the communication module 10 having the combined control circuit 1b according to the eighth embodiment. The figure is mainly different from FIG. 50A in that the switch SW is connected to the negative input terminal and the resistor R8 is added. The differences will be mainly described below.

The switch SW has an input terminal (that is, a negative input terminal) corresponding to the magnitude of the current detected by the resistor R3 of the two input terminals of the amplifier 7, and a wiring having a substantially reference value level (that is, that is). It is connected to the positive side wiring of the reference source 4). The operating states of the communication signal, the switch SW, and the transistor 2 of the signal generation circuit SG of FIG. 55 are the same as the truth table shown in FIG. 50B.

The resistor R8 is a resistor for limiting the current flowing from the reference source 4 to the ground wire (wiring connected to the terminal T2) via the resistor R8 and the resistor R3 when the switch SW is on.

The switch SW of FIG. 55 conducts when the communication signal is instructed to turn off, so that the level of the negative input terminal corresponding to the magnitude of the current among the two input terminals is substantially set to a reference value. Make it a level. Here, the level of the reference value is substantially set to a level at which the above error is substantially set to 0, in other words, a level at which the output of the amplifier 7 is set to a low level. For example, the level of the reference value may be substantially the same level as the reference value, or may be a level higher than the positive input terminal.

As described above, the combined control circuit 1b of FIG. 55 substantially sets the negative input terminal corresponding to the magnitude of the current flowing through the light source to the level of the reference value when the communication signal is instructing to turn off. Turn off transistor 2. Further, the combined control circuit 1b turns on the transistor 2 when the communication signal indicates lighting.

As a result, the combined control circuit 1b can cause the transistor 2 to perform a modulation operation.

The operation of the illumination optical communication device according to the eighth embodiment configured as described above will be described with reference to the simulation results.

FIG. 56 is a diagram showing a first simulation result for the circuit example of FIG. 55. FIG. 56 shows LED current and output voltage waveforms when the on-duty ratio is 60%, 75%, 90%, 100%. In this simulation, the capacitance of the smoothing capacitor 65 is 20 uF, and the frequency of the modulation signal (that is, the communication signal) that drives the switch SW is 2.4 kHz. The figure shows a result similar to that of FIG. 51, and it can be seen that the overshoot of the LED current is suppressed regardless of the on-duty ratio. In addition, the voltage waveform also fluctuates, but it is not as violent as the fluctuation of the current, suggesting that the operating resistance of the LED load is low.

As described above, the dual-purpose control circuit 1b in the illumination optical communication device of the eighth embodiment controls the transistor 2 to perform the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

The switch circuit (that is, the switch SW which is a switching transistor) conducts when the communication signal is instructed to turn off, so that the level of the input terminal corresponding to the magnitude of the current among the two input terminals is substantially adjusted. The level of the reference value is set.

According to this, the dual-purpose control circuit 1b turns off the transistor 2 when the communication signal indicates that the light is turned off. As a result, the combined control circuit 1b can cause the transistor 2 to perform a modulation operation.

Further, one end of the switch transistor (switch SW in FIG. 55 or valve B2 in FIG. 57A) is connected to an input terminal corresponding to the magnitude of the current among the two input terminals, and the other end of the switch transistor is connected. , It may be connected to a wiring having substantially a reference value level.

(Embodiment 9)
In the ninth embodiment, some configuration examples of the combined control circuit 1b will be described.

The configuration of the illumination optical communication device according to the ninth embodiment is the same except for the communication module 10 of FIG. 50A. Hereinafter, the differences will be mainly described.

FIG. 57A is a diagram showing a configuration example of a communication module including the combined control circuit 1b according to the ninth embodiment.

The communication module 10 of FIG. 57A includes a transistor 2 and a combined control circuit 1b. The combined control circuit 1b includes a signal generation circuit SG, a valve B1, a valve B2, a resistor R3, a resistor R8, an amplifier 7, a resistor 9a, a resistor 11r, a capacitor 12c, an amplifier 13a, a resistor 14, a capacitor 15 and an inverter 16.

The circuit portion of the combined control circuit 1b having the signal generation circuit SG, the valve B1, the valve B2, and the inverter 16 functions as a modulation control circuit for causing the transistor 2 to perform a modulation operation.

Since the signal generation circuit SG has already been described, it will be omitted.

The valve B1 may be, for example, a switching element such as a switching transistor or a thyristor, and is opened or closed, that is, in a non-conducting or conductive state according to a control signal input to the control terminal. A communication signal from the signal generation circuit SG is input to the control terminal of the valve B1.

The valve B2 may be the same element as the valve B1. An inverted communication signal is input from the signal generation circuit SG to the control terminal of the valve B2 via the inverter 16. The bulb B2 has a negative input terminal corresponding to the magnitude of the current flowing through the light source of the two input terminals of the amplifier 7, and a wiring having a substantially reference value level (that is, a positive side wiring of the constant voltage source 4a). ) And is connected.

Here, the operating states of the valve B1, the valve B2, and the transistor 2 will be described with reference to FIG. 57B. FIG. 57B is a diagram showing a truth table showing the communication signals from the signal generation circuit SG in FIG. 57A and the operating states of the valves B1, B2 and the transistor 2. "SG" is the logical value (high level or low level) of the communication signal, "B1" is the state of valve B1 (on or off), "B2" is the state of valve B2 (on or off), and "2". Indicates the state (on or off) of the transistor 2. When the communication signal is L (low level), the bulb B1, the bulb B2, and the transistor 2 are off, on, and off, respectively, and no current flows through the light source and the light is turned off. That is, the valve B2 conducts when the communication signal is instructed to turn off, so that the level of the negative input terminal corresponding to the magnitude of the current among the two input terminals is substantially set to the level of the reference value. To. As a result, the output signal of the amplifier 7 becomes low level and the transistor 2 is turned off.

When the communication signal is H (high level), the bulb B1, the bulb B2, and the transistor 2 are on, off, and on, respectively, and a current flows through the light source to light the light source.

As a result, the illumination light is modulated by turning on and off the transistor 2 according to the binary communication signal.

Further, the circuit portion of the combined control circuit 1b excluding the partial signal generation circuit SG, the bulb B1, the bulb B2, and the inverter 16 functions as a current suppression circuit that suppresses the current flowing through the light source in the transistor 2.

The resistor R3 is a resistor for detecting the magnitude of the current flowing through the transistor 2, that is, the current flowing through the load circuit 53 which is a light source.

The resistor R8 is a resistor for limiting the current flowing from the constant voltage source 4a to the ground wire through the resistor R8 and the resistor R3 when the valve B2 is on.

The resistors 9a and 11r are circuits that function as variable reference sources. That is, the resistors 9a and 11r detect the magnitude of the voltage applied to the combined control circuit 1b when the valve B1 is on. That is, the voltage at the connection point between the valve B1 and the resistor 11r indicates the magnitude of the voltage applied to the combined control circuit 1b, and the positive input of the amplifier 7 via the amplifier 13a (here, the amplifier 13a functions as a buffer). It is input to the terminal as a reference value. The voltage applied to the combined control circuit 1b changes depending on the on-duty, for example, the output voltage of FIG. 51 or FIG. 56. In FIG. 57A, the voltage applied to the combined control circuit 1b is input to the positive input terminal of the amplifier 7 as a variable reference value. With this variable reference value, the current set value indicating the upper limit of the current flowing through the transistor 2 can be set to an appropriate value according to the output voltage and the on-duty.

The constant voltage source 4a generates a constant voltage equal to or higher than the reference value.

The resistor 11r and the capacitor 12c function as a filter, and the amplifier 13a functions as a buffer for impedance matching. The resistor 14 and the capacitor 15 function as a noise cut filter.

As described above, in the combined control circuit 1b of FIG. 57A, the valve B2 (for example, the switch transistor) has a large current flowing through the light source when the communication signal is instructed to turn off (when the communication signal is L). The transistor is turned off by making the corresponding negative input terminal substantially at the reference level. As a result, the combined control circuit 1b can cause the transistor 2 to perform a modulation operation.

Next, a modification of the combined control circuit 1b will be described.

FIG. 57C is a diagram showing a modified example of the communication module including the combined control circuit 1b according to the ninth embodiment. Further, FIG. 57D is a diagram showing a truth table showing the communication signals from the signal generation circuit SG in FIG. 57C, the states of the valves B1, B2, and the transistor 2.

In the combined control circuit 1b of FIG. 57C, the connection position of the valve B2 is different from that of FIG. 57A, the resistor 17 is added, and the constant voltage source 4a, the inverter 16 and the resistor R8 are deleted. It's different. The differences will be mainly described below.

The valve B2 is connected to the positive input terminal corresponding to the reference value of the two input terminals of the amplifier 7 and the output terminal of the amplifier 13a, and when the communication signal is instructing to turn off (the communication signal is L). When) is off, the level of the positive input terminal corresponding to the reference value of the two input terminals is substantially set to the ground level via the resistor 17. That is, when the communication signal is instructed to turn off (when the communication signal is L), the error between the two input terminals becomes substantially zero, and the transistor 2 is turned off.

On the other hand, when the communication signal indicates lighting (when the communication signal is H), the transistor 2 conducts and functions as a current suppression element, as in FIG. 57A.

Next, another modification of the combined control circuit 1b will be described.

FIG. 57E is a diagram showing another modification of the communication module including the combined control circuit 1b according to the ninth embodiment. FIG. 57F is a diagram showing a truth table showing the states of the communication signal from the signal generation circuit SG in FIG. 57E, the valves B1 and B2, the transistor 22, and the bipolar transistor 20.

FIG. 57E is different from FIG. 57A in that it includes bipolar transistors 20, 21, transistors 22, buffers 23b, buffers 24b, and resistors 26 instead of the resistors R3, R8, transistors 2, and amplifier 7. The differences will be mainly described below.

The bipolar transistors 20 and 21 constitute a current mirror circuit and perform the same function as the transistor 2 of FIG. 57A or FIG. 57B. That is, when the communication signal is instructed to turn off (when the communication signal is L), the transistor 22 is turned off, and the base signal of the transistor 21 on the mirror side of the current mirror becomes substantially 0V (or 0A). The bipolar transistor 20 is turned off. At this time, the valves B1 and B2 are open (off) so that unnecessary current does not flow. When the communication signal indicates lighting (communication signal is H), the valves B1 and B2 are closed (on), and the transistor 22 is also on. At this time, the reference value from the output terminal of the amplifier 13a is supplied as a base signal to the base of the bipolar transistor 20 via the valve B2 and the resistor 25. As a result, the bipolar transistor 20 suppresses the current flowing through the bipolar transistor 20 so as not to exceed the current set value corresponding to the reference value.

Next, the results of simulating the combined control circuit 1b of FIG. 57C will be described with reference to FIGS. 58 to 60.

FIG. 58 is a diagram showing a first simulation result for the circuit example of FIG. 57C. FIG. 58 shows a peak value, an average value, and a fluctuation value (that is, the same as the LED current) of the current (that is, the same as the LED current) flowing through the combined control circuit 1b according to the on-duty ratio of the modulated signal (that is, the communication signal) from the signal generator SG. That is, the fluctuation range) is shown. In this simulation, the capacitance of the smoothing capacitor 65 is 20 uF, the frequency of the modulated signal is 2.4 kHz, and the on-duty ratio is changed from 50% to 90%. The peak value of the LED current is substantially equal to the current set value corresponding to the reference value shown in FIG. 52, indicating that the overshoot is suppressed. The average value of the LED current is almost constant regardless of the on-duty ratio, that is, the brightness is apparently constant for humans. The fluctuation value of the LED current is almost 0, and the overshoot is almost eliminated.

FIG. 59 is a diagram showing a second simulation result for the circuit example of FIG. 57C. FIG. 59 shows the ripple rate (volatility) of the LED current when the on-duty ratio is changed. The simulation conditions are the same as in FIG. 58. As shown in the figure, the ripple rate is smaller than 2%. The ripple rate described here is defined as follows by dividing the fluctuation of the rectangular wave-shaped LED current that flows during the period when the transistor 2 is on by the average current value.

Ripple rate = (current peak value-current bottom value) / (2 x average current value)

FIG. 60 is a diagram showing a third simulation result for the circuit example of FIG. 57C. FIG. 60 shows the circuit loss (that is, power consumption) of the combined control circuit 1b when the on-duty ratio is changed. The simulation conditions are the same as in FIG. 58. As shown in the figure, the circuit loss is suppressed to be lower than 0.5 W. This is an effect of suppressing the occurrence of extra power loss in the combined control circuit 1b by controlling the current flowing through the transistor 2 to a substantially target current set value.

Subsequently, the results of simulating the combined control circuit 1b of FIG. 57E will be described with reference to FIGS. 61 to 63.

FIG. 61 is a diagram showing a first simulation result for the circuit example of FIG. 57E. FIG. 61 shows the peak value, the average value, and the fluctuation value (that is, the fluctuation width) of the current (that is, the same as the LED current) flowing through the combined control circuit 1b according to the on-duty ratio of the modulated signal from the signal generator SG. Shown. In this simulation, the capacitance of the smoothing capacitor 65 is 20 uF, the frequency of the modulated signal is 2.4 kHz, and the on-duty ratio is changed from 50% to 100%. The peak value of the LED current is substantially equal to the current set value corresponding to the reference value shown in FIG. 52, indicating that the overshoot is suppressed. The average value of the LED current is almost constant regardless of the on-duty ratio, that is, the brightness is apparently constant for humans. The fluctuation value of the LED current is almost 0, and the overshoot is almost eliminated.

FIG. 62 is a diagram showing a second simulation result for the circuit example of FIG. 57E. FIG. 62 shows the ripple rate (volatility) of the LED current when the on-duty ratio is changed. The simulation conditions are the same as in FIG. 61. As shown in the figure, the ripple rate is 1.5% or less. The ripple rate described here is also the same as in the case of FIG. 59.

FIG. 63 is a diagram showing a third simulation result for the circuit example of FIG. 57E. FIG. 60 shows the circuit loss (that is, power consumption) of the combined control circuit 1b when the on-duty ratio is changed. The simulation conditions are the same as in FIG. 61. As shown in the figure, the circuit loss is suppressed to be lower than 0.7 W. This is an effect of suppressing the occurrence of extra power loss in the combined control circuit 1b by controlling the current flowing through the transistor 2 to a substantially target current set value.

Next, a modified example of the combined control circuit 1b shown in FIG. 57A will be described.

FIG. 57G is a diagram showing a configuration example of the communication module 10 including a modification of the combined control circuit 1b of FIG. 57A. The combined control circuit 1b of FIG. 57G has a configuration suitable for practical use, which also serves as simplification, based on FIG. 57A. FIG. 57G differs from FIG. 57A in the following points. That is, the impedance matching circuit (amplifier 13a, resistor 11r, capacitor 12c) is omitted, the valve element B1 is replaced with a MOSFET, and a gate resistor Rg1 and a gate protection resistor Rg2 are added.

Further, in order to prevent the applied voltage during the period when the transistor 2 is off (the voltage applied to the combined control circuit 1b gradually increases during the off period) from wrapping around to the positive input terminal of the amplifier 7, a signal is generated. A delay circuit Dy that delays the rise of the signal of the circuit SG is provided, and its output is connected to the gate resistance Rg1 of the MOSFET (B1).

Further, in FIG. 57G, the valve B2 in FIG. 57A is omitted, the output terminal of the inverter 16 is connected to the negative input terminal of the amplifier 7 via the resistor 10, and the gain is obtained between the output terminal and the negative input terminal of the amplifier 7. By connecting the adjustment resistor Rf and the capacitor Cf as an integrating element, the transient characteristics associated with the on / off of the transistor 2 can be adjusted. In particular, since the rising time of the modulated rectangular wave-shaped LED current waveform of the capacitor Cf can be changed by changing its capacitance value, it is convenient to make an appropriate adjustment according to the reception sensitivity of the receiving device.

The capacitor Co provided between the terminals T1 and T2 suppresses parasitic vibration that may occur when the transistor 2 is turned off, and is effective in reducing noise and preventing malfunction.

(Modification example)
Next, a modified example of the illumination optical communication device will be described.

FIG. 64 is a circuit diagram showing a modified example of the illumination optical communication device according to the seventh embodiment. The illumination optical communication device shown in the figure has a different circuit configuration inside the power supply circuit 52a as compared with FIG. 50A. Hereinafter, the differences will be mainly described.

In the power supply circuit 52a of FIG. 50A, the constant current feedback circuit 67 performs feedback control to make the average value of the output current constant, whereas in the power supply circuit 52a of FIG. 64, the threshold value control of the switching current is performed. Is configured to do.

The power supply circuit 52a of FIG. 64 includes a rectifying bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that configure the DC-DC converter 64 as a back converter.

The control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and the circuits around the switch element 81, and the threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current via the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. The operation of such a DC-DC converter 64 has already been described with reference to the waveform diagram of FIG. 30B.

The switching current threshold control in FIGS. 64 and 30B substitutes for the constant current feedback control of FIG. 50A, and works to make the average of the output currents constant. As a result, in FIG. 64 as in FIG. 50A, if there is no combined control circuit 1b, the problem of overshoot occurs. However, in the configuration of FIG. 64, overshoot can be reduced by providing the combined control circuit 1b as in FIG. 50A.

As described above, the illumination light communication device according to the seventh to ninth embodiments is an illumination light communication device that modulates the illumination light according to a communication signal, and is a light source that emits illumination light and a transistor connected in series with the light source. 2. The signal generation circuit SG that generates the binary communication signal, and the combined control circuit 1b that causes the transistor 2 to perform both the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

According to this, since the transistor 2 is also used as the switch element that performs the above-mentioned modulation operation and the current suppression element that performs the above-mentioned suppression operation, it is possible to suppress an increase in the number of circuit elements. In the suppression operation, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the transistor 2 is turned from off to on is reduced, and thus the reception error in the receiving device can be reduced.

Here, the combined control circuit 1b causes the transistor 2 to execute the modulation operation by generating a gate signal or a base signal input to the gate or base of the transistor 2 according to the communication signal, and the communication signal. The level of the gate signal or the base signal may be determined so that the current flowing through the light source does not exceed the current set value in the suppression operation when is instructing to turn on or off.

According to this configuration, the transistor can suppress the current flowing through the light source depending on the level of the gate signal or the base signal.

Here, the combined control circuit 1b includes a current detection circuit R3 that detects the magnitude of the current flowing through the light source, a reference source 4 that outputs a reference value corresponding to the current set value, and the magnitude of the current and the reference. An amplifier 7 having two input terminals into which a value is input, amplifying an error between the two input terminals, and outputting the amplified signal as the gate signal or the base signal, and the two input terminals. It may be provided with a switch circuit which is coupled to at least one of them and makes the error substantially zero when the communication signal indicates that the light is turned off.

According to this configuration, the modulation operation is enabled by making the error between the two input terminals substantially zero when the communication signal is instructed to turn off.

Here, the switch circuit has a switch transistor, and the switch transistor corresponds to the reference value of the two input terminals by conducting the switch transistor when the communication signal is instructed to turn off. The level of the input terminal may be substantially set to the ground level.

According to this configuration, when the communication signal is instructed to turn off, the modulation operation can be performed by setting the input terminal corresponding to the reference value to a substantially ground level.

Here, one end of the switch transistor is connected to an input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor is connected to a wiring having a substantially ground potential. May be good.

Here, the dual-purpose control circuit 1b further includes a resistance element 17 connected between an input terminal corresponding to the reference value and a wiring having a substantially ground potential, and one end of the switch transistor is described as described above. It may be connected to the input terminal corresponding to the reference value of the two input terminals, and the other end of the switch transistor may be connected to the reference source.

Here, the switch circuit has a switch transistor, and the switch transistor conducts when the communication signal is instructed to turn off, so that the magnitude of the current among the two input terminals is increased. The level of the corresponding input terminal may be substantially set to the level of the reference value.

According to this configuration, when the communication signal is instructed to turn off, the modulation operation can be performed by setting the input terminal corresponding to the magnitude of the current to substantially the level of the reference value.

Here, one end of the switch transistor is connected to an input terminal corresponding to the magnitude of the current among the two input terminals, and the other end of the switch transistor is a wiring having a substantially reference value level. You may connect to.

Here, the combined control circuit 1b further includes a feedback capacitor Cf connected between the output terminal of the amplifier and the input terminal corresponding to the magnitude of the current among the two input terminals, and the feedback capacitor. The feedback resistor element Rf connected in parallel with the above may be provided.

According to this configuration, the gain can be adjusted by the feedback resistance element Rf, and the capacitor Cf as an integrating element is provided, so that the transient characteristics associated with the on / off of the transistor 2 can be adjusted. In particular, since the feedback capacitor Cf can define the rise time of the modulated rectangular wave-shaped LED current waveform according to its capacitance value, it is convenient to make an appropriate adjustment according to the reception sensitivity of the receiving device.

Here, the dual-purpose control circuit 1b may further include a capacitor element Co connected between the terminal on the power supply line side of the transistor and the ground line.

According to this configuration, parasitic noise that may occur due to the off operation of the transistor can be suppressed, which is effective in reducing noise and preventing malfunction.

Here, the switch circuit is connected to the input terminal to which the reference value is input among the two input terminals, and the switch element B1 that turns on and off according to the communication signal and the two input terminals. An inverter that outputs a resistance element R10 connected to an input terminal corresponding to the magnitude of the current and an inverted signal obtained by inverting the communication signal to the input terminal corresponding to the magnitude of the current via the resistance element. The combined control circuit 1b may further include a delay circuit Dy inserted into a signal line for transmitting the communication signal from the signal generation circuit to the switch element.

According to this configuration, a delay circuit for delaying the communication signal or the inverting signal of the signal generation circuit SG is provided, and the delayed communication signal is output to the control terminal of the switch element B1. As a result, it is possible to reliably prevent the voltage applied to the dual-purpose control circuit 1b during the period when the transistor 2 is off (this voltage rises to division during the off period) from wrapping around to the positive input terminal of the amplifier, which is a reference. It is possible to prevent garbled prices.

Here, the reference source may output the variable reference value according to the on-duty ratio of the communication signal or the voltage applied to the combined control circuit 1b.

According to this configuration, since the reference value can be dynamically optimized, the current suppression operation can also be optimized.

Here, the illumination optical communication device has a power supply circuit that supplies a current to the light source and the transistor connected in series, and the power supply circuit performs feedback control for making the average value of the supplied current constant. You may go.

Here, the power supply circuit includes a DC-DC converter 64, which is a back converter having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switching element, and is the difference between the detected value and a predetermined value. The on and off of the switching element may be controlled according to the above.

According to this configuration, overshoot can be effectively reduced even when a DC-DC converter that controls the threshold value of the switching current is provided as a power supply circuit.

Further, the communication module according to each embodiment is a communication module that modulates the illumination light and can be attached to and detached from the illumination device, and includes a transistor connected in series with the light source of the illumination device and the binary communication signal. A signal generation circuit for generating the above light source and a combined control circuit 1b for causing the transistor to perform the modulation operation of the illumination light and the suppression operation of the current flowing through the light source.

According to this, the communication module can be added to the existing luminaire. That is, the existing lighting equipment can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than when a new optical communication lighting equipment is installed. Further, since the overshoot generated in the current flowing through the light source at the moment when the switch is turned on is reduced, the reception error in the receiving device can be reduced. Further, since the transistor has the functions of both a switch element that performs a modulation operation and a current suppression element that performs a suppression operation, it is possible to suppress an increase in circuit elements.

(Embodiment 10)
In the tenth embodiment, an illumination optical communication device or a communication module capable of reducing reception errors in visible light communication and realizing stable circuit operation is provided.

The illumination light communication device according to the tenth embodiment includes a light source that emits illumination light, a switch that is connected in series with the light source and interrupts the current flowing through the light source, and the switch is turned on to modulate the illumination light. A modulation signal generator that generates a modulation signal that controls off and off, a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed the current set value, and the current. A control unit for changing a set value is provided, and the light source, the switch, and the current suppression circuit are connected in series in this order. Further, the current suppression circuit is connected to the ground potential.

Further, the communication module according to the tenth embodiment is a communication module that is detachable from the lighting device and modulates the illumination light, and is connected in series with the light source included in the lighting device to interrupt the current flowing through the light source. The switch, the modulation signal generator that generates a modulation signal that controls the on and off of the switch to modulate the illumination light, and the light source and the switch are connected in series so as not to exceed the current set value. A current suppression circuit that suppresses the current flowing through the light source is provided, and the light source, the switch, and the current suppression circuit are connected in series in this order. Further, the current suppression circuit is connected to the ground potential.

Embodiment 10 According to the illumination optical communication device and the communication module, reception errors in visible light communication can be reduced and stable circuit operation can be realized.

[10.1 Configuration of Illuminated Optical Communication Device]
First, the configuration of the illumination optical communication device according to the tenth embodiment will be described. FIG. 65 is a block diagram showing the configuration of the illumination optical communication device 100 according to the tenth embodiment.

The illumination light communication device 100 shown in FIG. 65 functions as a visible light communication transmitter that transmits a signal by modulating the intensity of the illumination light. The illumination optical communication device 100 includes a light source 101, a power supply circuit 102, a communication module 103, and a dimming control unit 104.

The light source 101 includes one or more light emitting elements (for example, LEDs) and emits illumination light.

The power supply circuit 102 supplies electric power to the light source 101. The power supply circuit 102 includes a power supply 111, a DC-DC converter 112, a capacitor 113, a detection resistor 114, and a constant current feedback circuit 115.

The power supply 111 outputs a DC voltage to the DC-DC converter 112. The DC-DC converter 112 converts the DC voltage supplied from the power supply 111 into a desired voltage V0, and outputs the voltage V0 to the light source 101. The capacitor 113 is connected between the output terminals of the DC-DC converter 112.

The detection resistor 114 is used to detect the current flowing through the light source 101. The constant current feedback circuit 115 controls the output voltage V0 of the DC-DC converter 112 so that the current flowing through the detection resistor 114, that is, the current flowing through the light source 101 is constant.

Further, the DC-DC converter 112 controls the output voltage V0 based on the dimming signal S3 output from the dimming control unit 104.

The communication module 103 can be attached to and detached from the lighting device including the light source 101 and the power supply circuit 102. When the communication module 103 is not attached to the lighting device, the cathode of the light source 101 and the GND terminal of the power supply circuit 102 are short-circuited. That is, by attaching the communication module 103 to a lighting device that does not support visible light communication, the visible light communication function can be realized by the lighting device.

The communication module 103 includes a modulation switch 121, a current suppression circuit 122, a modulation signal generation unit 123, an external synchronization signal input unit 124, a control unit 125, a control power supply 126, a voltage detection circuit 127, and a drive circuit 128. And.

The modulation signal generation unit 123 generates a modulation signal based on a communication signal transmitted by visible light communication. The modulation signal generation unit 123 may repeatedly generate a modulation signal indicating an ID unique to the illumination optical communication device 100, or may generate a modulation signal according to a communication signal input from an external device. Good.

The external synchronization signal input unit 124 supplies the modulation signal generated by the modulation signal generation unit 123 to the control unit 125.

The control unit 125 is composed of a microcomputer (for example, a CPU), generates a binary modulation signal S1 based on the modulation signal supplied from the external synchronization signal input unit 124, and transmits the generated modulation signal S1 via the drive circuit 128. Is supplied to the control terminal (gate terminal) of the modulation switch 121.

The control power supply 126 generates a power supply voltage of the control unit 125 from the voltage V0 output from the power supply circuit 102, and supplies the generated power supply voltage to the control unit 125. The voltage detection circuit 127 detects the output voltage V0 of the power supply circuit 102.

The modulation switch 121 is connected in series with the light source 101 to interrupt the current supplied from the power supply circuit 102 to the light source 101. The modulation switch 121 is, for example, a transistor (for example, MOSFET).

The current suppression circuit 122 is connected in series with the light source 101 and the modulation switch 121 to suppress the current flowing through the light source 101. Specifically, the current suppression circuit 122 suppresses (clips) the current flowing through the light source 101 so as not to exceed the current set value Is.

The current suppression circuit 122 includes a transistor 131 which is a MOSFET, a current setting circuit 132, an amplifier 133, and a current detection circuit 134 which is a resistor connected to the source of the transistor 131.

The current setting circuit 132 outputs a reference value to the positive input terminal of the amplifier 133. The reference value defines the upper limit of the current flowing through the light source 101 (current set value Is). For example, the reference value is proportional to the current set value. Further, the current setting circuit 132 outputs a variable reference value according to the current command value S2 generated by the control unit 125. The current setting circuit 132 may output a reference value as a fixed value.

The transistor 131 is connected in series with the light source 101 and the modulation switch 121, and suppresses (clips) the current flowing through the light source 101 based on the reference value.

The current detection circuit 134 is a source resistor for detecting the magnitude of the current flowing through the light source 101. The terminal on the transistor 131 side of the current detection circuit 134 is connected to the negative input terminal of the amplifier 133.

The positive input terminal of the amplifier 133 is connected to the current setting circuit 132, and the negative input terminal of the amplifier 133 is connected to the source terminal of the transistor 131. The amplifier 133 amplifies the difference between the reference value output from the current setting circuit 132 and the current value detected by the current detection circuit 134, and outputs the amplified signal to the gate of the transistor 131.

The circuit configuration shown in FIG. 65 is an example, and the illumination optical communication device 100 does not need to include all the components shown in FIG. 65. For example, the illumination optical communication device 100 does not have to include at least one of the dimming control unit 104 and the voltage detection circuit 127.

Further, the configuration of the power supply circuit 102 is also an example, and the configuration is not limited to this configuration. For example, the power supply circuit 102 may not include the detection resistor 114 and the constant current feedback circuit 115. Further, the DC-DC converter 112 may perform constant current control. For example, the DC-DC converter 112 may perform switching current threshold control. Alternatively, the power supply circuit 102 may perform constant voltage control instead of constant current control. For example, the power supply circuit 102 may include a constant voltage feedback circuit instead of the detection resistor 114 and the constant current feedback circuit 115, or the DC-DC converter 112 may perform constant voltage control.

Further, the configuration of the current suppression circuit 122 is also an example, and is not limited to this as long as the configuration can suppress (clip) the current flowing through the light source 101. For example, instead of the current suppression circuit 122, the current suppression circuits 122A, 122B or 122C shown in FIGS. 66 to 68 may be used. The terminal T1 shown in FIGS. 66 to 68 is connected to the modulation switch 121, and the terminal T2 is connected to the GND terminal of the power supply circuit 102.

The current suppression circuit 122A shown in FIG. 66 includes bipolar transistors 141 and 142, a current setting circuit 132A which is a variable voltage source, and a resistor 143. Bipolar transistors 141 and 142 form a current mirror circuit. The current flowing through the bipolar transistor 142 is determined by the voltage output from the current setting circuit 132A and the resistance value of the resistor 143. The bipolar transistor 141 can carry a current within a range not exceeding a current (that is, a current set value Is) that is twice the mirror ratio of this current. The current setting circuit 132A changes the output voltage according to the current command value S2 output from the control unit 125.

The current suppression circuit 122B shown in FIG. 67 includes a bipolar transistor 151, an emitter resistor 152, a bias resistor 153, and a current setting circuit 132B which is a Zener diode.

The bipolar transistor 151 is connected in series with the light source 101 and the modulation switch 121. The current flowing through the light source 101 is suppressed according to the base voltage (reference value) of the bipolar transistor 151.

The emitter resistor 152 is a resistor for detecting the magnitude of the current flowing through the light source 101 (that is, the current flowing through the emitter resistor 152).

The bias resistor 153 is a resistor for biasing the base voltage of the bipolar transistor 151.

The current setting circuit 132B outputs a reference value corresponding to the current command value S2 output from the control unit 125 to the base of the bipolar transistor 151.

The current suppression circuit 122C shown in FIG. 68 includes a three-terminal regulator 161 and a current setting circuit 132C which is a detection resistor.

In the three-terminal regulator 161, the input terminal IN and the output terminal OUT are connected in series with the light source 101 and the modulation switch 121, and the input terminal IN and the output terminal OUT are separated from each other according to the voltage input to the adjustment terminal ADJ. Suppress the flowing current.

The current setting circuit 132C is a resistor for detecting the magnitude of the current flowing through the light source 101 (that is, the current flowing through the current setting circuit 132C). Further, the current setting circuit 132C is a variable resistor, and its resistance value is changed according to the current command value S2 output from the control unit 125. Further, the current setting circuit 132C is connected between the output terminal OUT of the three-terminal regulator 161 and the terminal T2, and the terminal T2 is connected to the adjustment terminal ADJ of the three-terminal regulator 161.

[10.2 Basic operation]
Hereinafter, the basic operation of the illumination optical communication device 100 will be described. FIG. 69 is a diagram showing the basic operation of the illumination optical communication device 100. As shown in FIG. 69, the modulation switch 121 is turned on / off according to the modulation signal S1. The modulation method used here conforms to, for example, the 1-4 PPM transmission method specified in JEITA-CP1223. Specifically, 2-bit data is converted into 4-slot pulses. Of these four slots, three are always high level (on) and one slot is low level (off).

Further, in the example of FIG. 69, the current command value S2 is constant, and the current set value Is is constant.

Here, when modulation for visible light communication is performed, immediately after the modulation switch 121 is turned on, as shown by the dotted line in FIG. 69, the LED current, which is the current flowing through the light source 101, momentarily increases. A shoot occurs. Due to the occurrence of this overshoot, there is a problem that the visible light receiver may not be able to receive the signal correctly.

On the other hand, in the illumination optical communication device 100 according to the tenth embodiment, the maximum value of the LED current is limited to the current set value Is by providing the current suppression circuit 122. As a result, the occurrence of overshoot is suppressed as shown in FIG. 69. As a result, reception errors in visible light communication can be reduced.

The constant current feedback circuit 115 shown in FIG. 65 also has a function of making the LED current constant, but the constant current control by the constant current feedback circuit 115 is a control having a relatively large time constant. That is, this constant current control is a control that makes the average current constant in a predetermined period, and it is not possible to suppress an overshoot that occurs momentarily as shown in FIG. 69.

Further, in the tenth embodiment, as shown in FIG. 70, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order between the power supply terminal and the GND terminal of the power supply circuit 102. On the other hand, as a connection form of the light source 101, the modulation switch 121 and the current suppression circuit 122, the light source 101, the current suppression circuit 122 and the modulation switch 121 may be connected in this order as in the illumination optical communication device 100A shown in FIG. 71. Conceivable.

However, in the connection form of FIG. 71, there is a problem that the operation becomes unstable because the current suppression circuit 122 is not connected to the GND terminal of the power supply circuit 102. Specifically, when the modulation switch 121 is off, the GND (V1) of the current suppression circuit 122 is in a floating state, so that the potential fluctuation of the GND becomes large. On the other hand, in the tenth embodiment, by using the connection form shown in FIG. 70, the current suppression circuit 122 is always connected to the GND terminal, so that stable operation can be improved regardless of the state of the modulation switch 121.

In particular, when the variable current set value Is is used, the minute current cannot be controlled with high accuracy in the connection form shown in FIG. 71, and it is difficult to control the current set value Is with high accuracy. On the other hand, by using the connection form shown in FIG. 70, the minute current can be controlled with high accuracy, so that the current set value Is can be controlled with high accuracy. Further, in the tenth embodiment, the GND of the control unit 125 (the GND of the control power supply 126), which is a microcomputer that generates the current command value S2, and the GND of the current suppression circuit 122 are shared, so that the current set value Is Can be controlled with higher precision.

The signal generation circuit 129 shown in FIGS. 70 and 71 is a circuit that generates a binary modulation signal S1 that controls on and off of the modulation switch 121 in order to modulate the illumination light, and is the modulation shown in FIG. 65. It includes a signal generation unit 123, an external synchronization signal input unit 124, a control unit 125, and a drive circuit 128.

In the above description, as the modulation method, a 100% modulation method that completely cuts off the LED current during the off period is used, but a method in which the LED current is lower than the on period during the off period may be used. However, in the 100% modulation method, the above-mentioned overshoot becomes particularly remarkable. Therefore, the method of the tenth embodiment is particularly effective when the 100% modulation method is used.

As described above, the illumination light communication device 100 according to the tenth embodiment modulates the illumination light with the light source 101 that emits the illumination light, the modulation switch 121 that is connected in series with the light source 101 and interrupts the current flowing through the light source 101, and the illumination light. The modulation signal generation unit 123 that generates the modulation signal S1 that controls the on / off of the modulation switch 121 is connected in series with the light source 101 and the modulation switch 121, and the light source 101 is connected so as not to exceed the current set value Is. A current suppression circuit 122 that suppresses the flowing current and a control unit 125 that changes the current set value Is are provided, and the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

As a result, the occurrence of overshoot can be suppressed by the current suppression circuit 122, so that reception errors in visible light communication can be reduced. Further, by connecting the light source 101, the modulation switch 121, and the current suppression circuit 122 in series in this order, the GND potential is supplied to the current suppression circuit 122 regardless of the state of the modulation switch 121. Therefore, stable circuit operation can be realized.

Further, the illumination optical communication device 100 can set an appropriate current set value Is for each state by changing the current set value Is. Further, by supplying the GND potential to the current suppression circuit 122 regardless of the state of the modulation switch 121, it is possible to stably control the current set value Is, which requires highly accurate control.

Further, the communication module 103 according to the tenth embodiment is a communication module 103 that modulates the illumination light and can be attached to and detached from the illumination device. The intermittent modulation switch 121, the modulation signal generation unit 123 that generates the modulation signal S1 that controls the on / off of the modulation switch 121 to modulate the illumination light, and the light source 101 and the modulation switch 121 are connected in series to generate a current. A current suppression circuit 122 that suppresses the current flowing through the light source 101 so as not to exceed the set value Is is provided, and the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

As a result, the occurrence of overshoot can be suppressed by the current suppression circuit 122, so that reception errors in visible light communication can be reduced. Further, by connecting the light source 101, the modulation switch 121, and the current suppression circuit 122 in series in this order, the GND potential is supplied to the current suppression circuit 122 regardless of the state of the modulation switch 121. Therefore, stable circuit operation can be realized.

[10.3 Current setting value first control example]
Hereinafter, a control example of the current set value Is will be described. Although a plurality of methods for controlling the current set value Is will be described below, only one of the following methods may be used, or a plurality of methods may be used in combination.

FIG. 72 is a diagram showing a first control example of the current set value Is. In the first control example, the control unit 125 changes the current command value S2 (current set value Is) according to the length of the off period (low period of the modulation signal S1) of the modulation switch 121. Specifically, the control unit 125 sets the current set value Is higher as the off period is longer. That is, the control unit 125 sets the current set value Is to the first value when the off period is the first length, and sets the current when the off period is the second length longer than the first length. Set the value Is to a second value higher than the first value. For example, when 4PPM is used, when the period corresponding to 1 slot is T0 and the period corresponding to 2 slots is T1, the control unit 125 is longer than T0 and shorter than the threshold value shorter than T1. The current set value Is is set to the first value, and when the off period is longer than the above threshold value, the current set value Is is set to a second value higher than the first value.

Alternatively, the control unit 125 may calculate the partial on-duty ratio of the modulation signal S1 and change the current command value S2 (current set value Is) according to the calculated partial on-duty ratio. .. Specifically, the control unit 125 sets the current set value Is lower as the partial on-duty ratio becomes higher. That is, the control unit 125 may set the current set value Is so as to be inversely proportional to the partial on-duty ratio. In other words, the control unit 125 sets the current set value Is to the first value when the partial on-duty ratio is the first ratio, and the partial on-duty ratio is larger than the first ratio. When the ratio is 2, the current set value Is is set to a second value smaller than the first value.

Here, the "partial on-duty ratio" is the ratio of the on (high) period of the modulated signal S1 in a predetermined period. For example, the "partial on-duty ratio" is the ratio of the on-duty period to the combined period of the most recent off-duty period and the on-duty period immediately before the off-duty period. Alternatively, the "partial on-duty ratio" may be the moving average of the most recent n bits of the modulated signal S1.

Here, the magnitude of the overshoot depends on the length of the off period (partial on-duty ratio). Therefore, overshoot can be suppressed more appropriately by changing the current set value Is according to the length of the off period (partial on-duty ratio).

Further, when the length of the off period (partial on-duty ratio) is variable, the average luminance value decreases as the off period is longer. Therefore, in order to keep the average luminance value constant, the off period If is long, it is necessary to increase the brightness value during the on period. By controlling the current set value Is described above, the current set value Is can be appropriately changed even when the brightness value is controlled.

[2nd control example of 10.4 current set value]
FIG. 73 is a diagram showing a second control example of the current set value Is. In the second control example, the control unit 125 changes the current command value S2 (current set value Is) according to the dimming signal S3. For example, the dimming signal S3 is generated by the dimming control unit 104 when a dimming (change of brightness) operation is performed by the user. The power supply circuit 102 changes the current flowing through the light source 101 by changing the output voltage V0 according to the dimming signal S3. As a result, the brightness of the illumination light is changed.

FIG. 73 shows an example when the dimming operation is performed. The control unit 125 lowers the current command value S2 (current set value Is) when dimming is instructed by the dimming signal S3. That is, the control unit 125 sets the current set value Is according to the dimming level of the light source 101. Specifically, the control unit 125 sets the current set value Is higher as the dimming level is higher (brighter). That is, the control unit 125 sets the current set value Is to the first value when the dimming level is the first level, and sets the current when the dimming level is the second level higher than the first level. Set the value Is to a second value higher than the first value.

By controlling the current set value Is in this way, the current set value Is can be appropriately changed according to the dimming level.

Further, as shown in FIG. 73, the control unit 125 gradually reduces the current command value S2 from the timing when the dimming is instructed by the dimming signal S3. As a result, the current command value S2 can be reduced following a change in the dimming level (brightness), so that an increase in loss due to a sudden decrease in the current command value S2 can be suppressed.

[3rd control example of 10.5 current set value]
FIG. 74 is a diagram showing a third control example of the current set value Is. In the third control example, the control unit 125 receives a current command value S2 (current set value) according to the LED current detection value S4, which is the detection result of the LED current (current flowing through the light source 101) detected by the current detection circuit 134. Is) is changed. Specifically, the control unit 125 sets the current set value Is lower as the LED current becomes smaller. That is, the control unit 125 sets the current set value Is to the first value when the LED current is the first current value, and the current when the LED current is a second current value smaller than the first current value. The set value Is is set to a second value lower than the first value.

Thereby, for example, when the dimming level is changed as shown in FIG. 74, the current set value Is can be appropriately changed according to the dimming level. Further, as described with reference to FIG. 72, even when the luminance value (LED current) is changed according to the length of the off period (partial on-duty ratio), the current set value Is can be appropriately changed. As a result, it is possible to suppress an increase in loss during dimming and the like.

Further, as shown in FIG. 74, the timing for detecting the LED current is preferably the timing at which the overshoot does not occur and the current value is stable. For example, as shown in FIG. 75, the current detection circuit 134 detects the LED current at a timing after a predetermined delay time Td has elapsed from the rising edge of the modulation signal S1 (timing when the modulation switch 121 is turned on). To do. As a result, the LED current can be detected with high accuracy.

In FIG. 65, the current detection circuit 134 in the current suppression circuit 122 is also diverted to detect the LED current, but a current detection circuit is provided separately from the current detection circuit 134 in the current suppression circuit 122. The detection result by the current detection circuit may be used for the above control.

[10.6 Example of Fourth Control of Current Set Value]
FIG. 76 is a diagram showing a fourth control example of the current set value Is. In the fourth control example, the control unit 125 changes the current command value S2 (current set value Is) according to the LED voltage detection value S5, which is the detection result of the voltage V0 detected by the voltage detection circuit 127. Here, the voltage V0 is the voltage applied to the light source 101. Specifically, the control unit 125 sets the current set value Is lower as the voltage V0 becomes smaller. That is, the control unit 125 sets the current set value Is to the first value when the voltage V0 is the first voltage value, and when the voltage V0 is the second voltage value smaller than the first voltage value, the current. The set value Is is set to a second value lower than the first value.

Here, the voltage V0 changes in the same tendency as the LED current. Therefore, the same effect as that of the third control example can be realized by the above control.

The timing of voltage detection may be controlled in the same manner as in the case of LED current detection. That is, as in the case of FIG. 75, the voltage detection circuit 127 detects the voltage V0 at the timing after the predetermined delay time Td elapses from the rising edge of the modulation signal S1 (the timing when the modulation switch 121 is turned on). You may.

[10.7 Example of using an illuminated optical communication device]
Hereinafter, an example of using the illumination optical communication device 100 will be described. FIG. 77 is a diagram showing a usage example of the illumination optical communication device 100. For example, as shown in FIG. 77, the illumination optical communication device 100 is an RGB floodlight. When the user photographs the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone, the visible light receiver receives the visible light signal.

FIG. 78 is a diagram showing the appearance of the illumination optical communication device 100, which is an RGB floodlight.

FIG. 79 is a diagram showing another usage example of the illumination optical communication device 100. For example, as shown in FIG. 79, the illumination optical communication device 100 is an RGB spotlight. When the user photographs the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone, the visible light receiver receives the visible light signal.

(Embodiment 11)
The control circuit 6 in the current suppression circuit 1 shown in FIG. 1A or the like can be configured as an analog circuit or a digital circuit. In the eleventh embodiment, an example in which the control circuit 6 is configured as a digital circuit will be described.

One embodiment of the illumination light communication device according to the eleventh embodiment includes a light source that emits illumination light, a switch that is connected in series with the light source and interrupts the current flowing through the light source, and the illumination light for modulating the illumination light. A signal generation circuit that generates a binary communication signal that controls on and off of the switch is connected in series with the light source and the switch, and flows through the light source so as not to exceed the current set value corresponding to the reference value. The current suppression circuit includes a current suppression circuit that suppresses the current, and the current suppression circuit is connected in series with the reference source that outputs the reference value, the light source, and the switch, and the current flowing through the light source is based on the reference value. The control circuit includes a transistor for suppressing and a control circuit having a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting, and the control circuit is based on the n bit data. The partial on-duty ratio of the communication signal is calculated, and the reference value is determined according to the calculated partial on-duty ratio.

[11.1 Configuration of Illuminated Optical Communication Device]
The overall configuration of the illumination optical communication device according to the eleventh embodiment may be the same as that of the illumination optical communication device shown in FIG. 1A, or may be the same as that of the illumination light communication device shown in FIG. 80.

FIG. 80 is a circuit diagram showing a modified example of the illumination optical communication device according to the eleventh embodiment. In FIG. 80, the internal configuration of the communication module 10 is different from that in FIG. 64, but the power supply circuit 52a is the same. The communication module of FIG. 80 is as described above in FIG. 1A. Further, the power supply circuit 52a is as described above in FIG. 64.

[11.2 Modification example of current suppression circuit 1]
Next, first to third modification examples of the current suppression circuit 1 will be described.

The current suppression circuit 1 in FIG. 1A or FIG. 80 is not limited to this configuration, and may be configured as in the first to third modifications shown in FIGS. It may be configured as 82.

FIG. 81 is a circuit diagram showing a fourth modification of the current suppression circuit 1 in FIG. 1A or FIG. 80. The current suppression circuit 1 shown in FIG. 81 includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4, and a control circuit 6. The reference source 4 includes a constant voltage source 4a, voltage dividing resistors R1, R6, R7, R8, and switch elements S01 to S03 for switching the voltage dividing ratio.

The control circuit 6 switches the switch elements S01 to S03 by calculating an appropriate reference voltage value according to the signal arrangement of the communication signal or selecting an appropriate reference voltage value from a pre-constructed correspondence table. You may. The larger the number of resistors and switch elements in the voltage divider circuit, the finer the reference voltage can be switched.

FIG. 82 is a circuit diagram showing a fifth modification of the current suppression circuit 1 in FIG. 1A or FIG. 80. The current suppression circuit 1 of FIG. 82 includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 4, and a control circuit 6. The reference source 4 includes a constant voltage source 4a, voltage dividing resistors R11, R12, R13, R14, and switch elements S01 and S02 for switching the voltage dividing ratio.

The positive potential side of the reference source 4 is connected to the positive input terminal of the error amplifier via the resistor R11. A series circuit of resistors R12, R13, and R14 is provided between the connection point and the negative potential side of the reference voltage, and switch elements S01 and S02 that short-circuit one or two of these are connected. To.

The control circuit 6 of FIG. 82 may be the same as that of FIG. 81.

[11.3. Configuration example of control circuit 6]
Next, the configuration of the control circuit 6 that controls to change the reference value of the reference source 4 according to the signal arrangement of the communication signal will be described in more detail with reference to FIGS. 83 and 84A to 84C. That is, the control circuit 6 has a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting, and the communication signal is partially turned on based on the n bit data. A configuration example in which the duty ratio is calculated and the reference value is determined according to the calculated partial on-duty ratio will be described.

FIG. 83 is a block diagram showing a configuration example of the control circuit 6 and the signal generation circuit SG in FIG. 1A or FIG. 80. In the figure, the control circuit 6 includes a shift register 6a, a calculation unit 6b, a correction unit 6c, a conversion unit 6d, and a reference value setting unit 6e.

The shift register 6a holds n (n is an integer of 2 or more) bit data of the communication signal generated by the signal generation circuit SG while shifting.

The calculation unit 6b calculates a partial on-duty ratio of the communication signal based on the n-bit data held in the shift register 6a. The partial on-duty ratio is, for example, (i) the period obtained by combining the latest off period (the period in which bit 0 is continuous) and the on period immediately before the off period (the period in which bit 1 is continuous). The ratio of the on-period may be used. Alternatively, the "partial on-duty ratio" may be substituted by (ii) the moving average value of the latest n bits of the communication signal, or may be the moving average value of a predetermined number of bits in the n bits.

When the calculation unit 6b obtains the moving average value as a partial on-duty ratio, the calculation unit 6b may simply obtain the addition average for the n bits of the shift register 6a.

The correction unit 6c corrects the partial on-duty ratio calculated by the calculation unit 6b. If the calculation methods such as (i) and (ii) are different, the calculation result will be different, so the correction unit 6c will correct the calculation.

The conversion unit 6d converts the corrected partial on-duty ratio to the corresponding appropriate reference value. That is, the conversion unit 6d determines an appropriate reference value according to the corrected partial on-duty ratio.

The reference value setting unit 6e sets the determined reference value in the reference source 4. That is, the reference value setting unit 6e controls the reference source 4 so that the reference source 4 outputs the determined reference value.

Next, a configuration example of the signal generation circuit SG will be described.

In FIG. 83, the signal generation circuit SG includes a signal source 6f, a discrimination unit 6g, a standby control unit 6h, and a drive unit 6i.

The signal source 6f generates a communication signal. For example, the signal source 6f may repeatedly generate a communication signal including the ID of the illumination optical communication device, or may generate a communication signal including the ID of the illumination optical communication device and modulated information from the outside. Good.

The discriminating unit 6g determines whether or not the latest bit output from the signal source 6f is "1". If the bit immediately preceding the latest bit is 0, the latest bit output from the signal source 6f causes a rising edge in the current waveform of the load circuit 53, which is the light source. If the bit immediately before the latest bit is 1, the continuation state of the load circuit 53, which is the light source, continues in the section of the latest bit output from the signal source 6f.

When the determination unit 6g determines that the latest bit is "1", the standby control unit 6h controls the switch SW by the latest bit, that is, the operation of outputting the latest bit to the gate of the switch SW. Wait until the ready signal is received from 6. This standby completes the setting of the reference value according to the partial on-duty ratio immediately before the rising edge in the current suppression circuit 1 before the rising edge occurs in the current waveform of the load circuit 53 which is the light source. This is to make it.

The drive unit 6i outputs the latest bit “1” to the gate of the switch SW at the timing when the ready signal is received from the control circuit 6.

In addition, instead of determining whether or not the latest bit output from the signal source 6f is "1", the discriminating unit 6g determines whether or not the latest 2 bits output from the signal source 6f is "01". That is, it may be determined whether or not the latest bit is 1 and the bit immediately before it is 0. In this way, the discriminating unit 6g determines whether or not a rising edge is generated in the current waveform of the load circuit 53, which is a light source, by the latest bit output from the signal source 6f.

Subsequently, an operation example of the control circuit 6 will be described in more detail.

FIG. 84A is a flowchart showing a processing example of the control circuit in FIG. 1A. In FIG. 84A, at the start of visible light communication in the illumination optical communication device (for example, when the power of the illumination light communication device is turned on), the control circuit 6 first initializes (for example, resets) the shift register 6a (S40). , The initial value of the reference value is set in the reference source 4 (S41). This initial value may be, for example, a reference value corresponding to an average on-duty ratio of 75% of the communication signal.

When the signal source 6f of the signal generation circuit SG inputs 1 bit of the communication signal serially generated to the shift register 6a (S42), the control circuit 6 determines whether or not the input 1 bit is 1. S43).

When it is determined that the input 1 bit is 1, the control circuit 6 obtains the average value of the n-bit data held by the shift register 6a as a partial on-duty ratio (S44). This average value is a moving average value obtained by shifting the n bits of the communication signal, which is serial data, for each loop processing (S42 to S47) of FIG. 84A. Further, the control circuit 6 corrects the moving average value (S45), obtains a reference value from the correction result, sets the reference value in the reference source 4 (S46), and outputs a ready signal to the signal generation circuit SG (S46). S47). By the output of this ready signal, one bit input in step S42 is output to the gate of the switch SW. In step S46, the current set value and the reference value of the current suppression circuit 1 are obtained from the corrected moving average value by using the relational expression (2) described later, or by using a numerical table in advance. You may prepare it. This numerical table may be, for example, a table in which the corrected moving average value and the reference value are associated with each other.

Next, a configuration example of the shift register 6a will be described. FIG. 84B is an explanatory diagram showing a configuration example of the shift register 6a in the control circuit 6. FIG. 84B illustrates an 8-bit shift register 6a. The shift register 6a has a serial-in terminal for inputting 1-bit data, a parallel-out terminal for outputting 8-bit data, and a serial-out terminal for outputting 1-bit data. In the retained 8-bit data, they are referred to as bits b1, b2, ..., B8 in order from the serial-in terminal side. Bit b1 is the latest bit output from the signal source 6f. At the timing when the latest bit is input to bit b1 from the serial-in terminal, bit b2 is input to the gate of the switch SW. The bit b1 is output to the gate of the switch SW at the timing when the ready signal in step S47 of FIG. 84A is output.

Next, a specific example of the correction in step S45 of FIG. 84A will be described.

FIG. 84C is a flowchart showing a correction example of step S45 of FIG. 84A. When the moving average value is obtained in step S44, the latest bit b1 of the shift register 6a is 1, as determined in step S43. In FIG. 84C, in the control circuit 6, if the bit b2 immediately before the latest bit b1 is 0 (S11: yes), the moving average value is multiplied by the coefficient k1 (S12), and the bit b3 immediately before the bit b2 is set. If it is 0 (S13: yes), the coefficient k1 is multiplied again (S14). That is, when the first bit b1 from the end of the shift register 6a is 1 and the second and subsequent bits b2 are 0 consecutive bits or more, the control circuit 6 sets the moving average value to a coefficient k1 smaller than 1. , Is raised to the same number as the number of consecutive 0 bits. Here, the coefficient k1 may be, for example, 0.9.

Next, in the case of no in step S11, the control circuit 6 multiplies the moving average value by the coefficient k2 (S16) if the bit b3 is 1 (S15: yes), and further, if the bit b4 is 1 (S17). : Yes), multiply by the coefficient k2 again (S18). That is, in the control circuit 6, when the 1st bit b1 from the end of the shift register 6a is 1 and 1 bit or more is continuous after the 2nd bit b2 or the 3rd bit b3, the moving average value is 1. The larger coefficient k2 is raised to the power of the same number of bits as 1 consecutive bits after bits b2 or b3. Here, the coefficient k2 may be, for example, 1.03.

With such a correction, the moving average value in all the assumed data sequences can be kept in the range of about 0.5 to 0.9. The above correction method is just one example, and it is necessary to select it according to the required dynamics. In particular, the coefficient to be multiplied varies depending on the data transmission type used, the power supply circuit conditions, and the like, so it is necessary to examine the validity under actual conditions.

With such a configuration, it is possible to more appropriately suppress the overshoot generated in the current flowing through the load circuit 53.

[11.4 Operation of Illuminated Optical Communication Device]
As for the operation of the illumination optical communication device configured as described above, for example, the simulation results shown in FIGS. 5 to 14 are applicable. It operates in the same manner as in the first embodiment.

As described above, the illumination light communication device according to the eleventh embodiment modulates the illumination light, the light source 53 that emits the illumination light, the switch SW that is connected in series with the light source and interrupts the current flowing through the light source, and the illumination light. Therefore, the signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch is connected in series with the light source and the switch SW so as not to exceed the current set value corresponding to the reference value. The current suppression circuit 1 includes a current suppression circuit 1 that suppresses the current flowing through the light source, and the current suppression circuit 1 is connected in series with the reference source 4 that outputs the reference value, the light source, and the switch, and flows through the light source. A control circuit 6 having a transistor 2 that suppresses a current based on the reference value and a shift register 6a that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting is provided. The control circuit 6 calculates a partial on-duty ratio of the communication signal based on the n-bit data, and determines the reference value according to the calculated partial on-duty ratio.

According to this, it is possible to reduce the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned on, and thereby reduce the reception error in the receiving device. Moreover, since the partial on-duty ratio is calculated using the shift register and the reference value is determined according to the calculated partial on-duty ratio, the reference value is set to an appropriate value more dynamically. be able to.

Here, the control circuit 6 sets the reference value to the first value when the partial on-duty ratio is the first ratio, and the partial on-duty ratio is larger than the first ratio. When the ratio is 2, the reference value is set to a second value smaller than the first value, and the current set value corresponding to the second value is smaller than the current set value corresponding to the first value. You may.

According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, the suppression of the overshoot can be made appropriate.

Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

Here, the control circuit may change the reference value so as to satisfy the following equation.

I1 = (Iave / ONd) x 100

Here, I1 is the current set value, Iave is the average current flowing through the light source when the illumination light is not modulated by the interruption of the switch, and ONd is the partial on-duty ratio of the communication signal. The unit is%).

According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is almost the same as the brightness of the illumination light when the illumination light is modulated. Can be.

Here, the control circuit may change the reference value so as to satisfy the following equation.

(Iave / ONd) × 100 ≦ I1 <Ip

Here, Iave is the average current flowing through the light source when the illumination light is not modulated by the intermittent operation of the switch, ONd is the partial on-duty ratio of the communication signal, and I1 is the current set value. Yes, Ip is the peak value of the current flowing through the light source when the current suppression circuit does not suppress it.

Here, the control circuit 6 calculates a moving average value as a partial on-duty ratio with respect to data having a predetermined number of bits from the end of the shift register 6a, and the n-bit data held in the shift register. The moving average value may be corrected based on the bit pattern of, and a reference value corresponding to the corrected moving average value may be determined.

According to this, the overshoot generated in the current flowing through the light source at the moment when the switch is turned on is reduced, so that the reception error in the receiving device can be reduced. This is because when the power supply circuit of the illumination optical communication device is a current feedback type, the size of the overshoot depends on the partial on-duty ratio, and the output voltage gradually increases during the off period. There is. Due to the feedback of the diode, the reference value also rises according to the output voltage that gradually rises during the off period, so that the overshoot can be appropriately reduced.

Here, in the correction of the moving average value, the control circuit 6 moves the moving average value when the first bit from the end of the shift register is 1 and the second and subsequent bits are 0 consecutive bits or more. A coefficient smaller than 1 may be multiplied by the average value by the same number as the number of consecutive 0 bits.

Here, in the correction of the moving average value, the control circuit 6 has 1 in the first bit from the end of the shift register 6a, and 1 in which the second bit or the third and subsequent bits are continuous by 1 bit or more. In some cases, the moving average value may be multiplied by a coefficient larger than 1 by the same number as the number of consecutive 1 bits.

Here, instead of calculating the moving average value as a partial on-duty ratio, the control circuit 6 averages the communication signal whose N (N is an integer of 2 or more) value pulse position-modulated. The on-duty ratio (1- (1 / N)) × 100 (%) may be used.

Here, the communication signal is pulse-position-modulated with an N (N is an integer of 4 or more) value, and the number of bits of the shift register 6a and the number of bits subject to the moving average value are N bits or more. May be good.

Here, the reference source 4 includes a constant voltage source 4a that generates a fixed voltage, a plurality of resistance elements (for example, some of R1, R6 to R7, and R11 to R14) that divide the constant voltage source, and the resistance. The control circuit 6 includes one or more switch elements (for example, some of S01 to S03) connected in series or in parallel with the element, and the control circuit 6 turns on the one or more switch elements according to the corrected value. Off may be controlled.

Here, the illumination optical communication device has a power supply circuit 52a that supplies a current to the light source, the switch, and the current suppression circuit connected in series, and the power supply circuit 52a keeps an average value of the supplied currents constant. You may perform feedback control to make it.

Here, the power supply circuit 52a includes a DC-DC converter 64 having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and responds to the difference between the detected value and a predetermined value. The on and off of the switch element 81 may be controlled.

Further, the communication module according to the eleventh embodiment is a communication module 10 that modulates the illumination light and can be attached to and detached from the illumination device. A signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch for modulation, and a current suppression circuit that is connected in series with the light source and the switch SW to suppress the current flowing through the light source. The current suppression circuit 1 includes a reference source 4, which outputs the reference value, and a transistor 2 which is connected in series with the light source and the switch and suppresses the current flowing through the light source based on the reference value. The control circuit 6 includes a control circuit 6 having a shift register 6a that shifts and holds the head n (n is an integer of 2 or more) bit data of the communication signal, and the control circuit 6 is based on the n-bit data. The partial on-duty ratio of the communication signal is calculated, and the reference value is determined according to the calculated partial on-duty ratio.

According to this, the communication module can be added to the existing luminaire. That is, the existing lighting equipment can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than when a new optical communication lighting equipment is installed. Further, since the overshoot generated in the current flowing through the light source at the moment when the switch is turned on is reduced, the reception error in the receiving device can be reduced.

(Embodiment 12)
In the twelfth embodiment, an illumination optical communication device and a communication module that prevent malfunction of the overvoltage protection circuit at the time of turning on the power will be described even in the case of 100% modulated optical communication.

Generally, the output voltage of the power supply circuit becomes high in the no-load state. Further, the power supply circuit often includes an overvoltage protection circuit that stops operation when the output voltage exceeds the overvoltage protection level. When 100% modulation is performed by visible light communication, the switch element is turned off (that is, no load state) until the modulation operation starts in the startup time until the output voltage or output current of the power supply circuit rises when the power is turned on. , The output voltage may rise and exceed the overvoltage protection level, causing the power supply circuit to stop. That is, there is a possibility that the overvoltage protection circuit malfunctions due to the no-load state and the power supply is stopped.

For example, when a communication module for visible light communication is retrofitted to an existing lighting fixture, an overvoltage protection circuit in a power supply circuit may operate. Further, when designing a power supply circuit, there is a problem that it becomes difficult to design a margin of an overvoltage protection circuit.

Therefore, one form of the illumination optical communication device according to the twelfth embodiment is an illumination optical communication device that modulates the two states of turning on and off the illumination light so as to correspond to a binary communication signal, and provides an overvoltage protection circuit. A power supply circuit, a light source connected to the power supply circuit to emit the illumination light, a first switch element connected in series with the light source, a signal generation circuit for generating the binary communication signal, and after the power is turned on. The bias that supplies the bias voltage that turns on the first switch element to the control terminal of the first switch element during the period until the signal generation circuit starts the operation of generating the communication signal. It includes a circuit and a second switch element connected to a control terminal of the first switch element and turned on and off according to the communication signal. The bias circuit is also a modification of the current suppression circuit already described.

Further, one form of the communication module according to the twelfth embodiment is a communication module that is detachable from the lighting device by modulating the two states of turning on and off the illumination light emitted by the lighting device so as to correspond to a binary communication signal. A light source that is connected in series with the light source of the lighting device and emits the illumination light, a first switch element that is connected in series with the light source, a signal generation circuit that generates the binary communication signal, and a power supply. A bias circuit that supplies a bias voltage that turns on the first switch element to the control terminal of the first switch element after the signal is turned on and until the signal generation circuit starts the operation of generating the communication signal. It is a second switch element connected to the control terminal of the first switch element, and includes a second switch element that turns on and off according to the communication signal after the signal generation circuit starts operation.

According to the illumination optical communication device and the communication module according to the present embodiment, it is possible to prevent the overvoltage protection circuit from malfunctioning when the power is turned on.

[12.1 Configuration example of illumination optical communication device]
First, an example of the circuit configuration of the illumination optical communication device according to the twelfth embodiment will be described.

FIG. 85 is a circuit diagram showing a configuration example of the illumination optical communication device according to the twelfth embodiment. This illumination optical communication device includes a power supply circuit 51a having a function of making the output a constant current, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and a communication module 10.

The power supply circuit 51a includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64, a detection resistor 66, and a constant current feedback circuit 67. The constant current feedback circuit 67 includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

The power supply circuit 51a full-wave rectifies a commercial power supply (for example, AC 100V) with a rectifying bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected between both ends of the output of the DC-DC converter 64. That is, the smoothing capacitor 65 is connected between the power supply line and the ground line of the power supply circuit 51a. The load circuit 53 and the first switch element 2a are connected in series between the power supply line and the ground line of the power supply circuit 51a.

The power supply circuit 51a has a function of directly or indirectly detecting the current flowing through the load circuit 53 and controlling the current values to be constant. This function is provided in FIG. 85 by a detection resistor 66 and a constant current feedback circuit 67 for directly detecting the current in the load circuit 53. The constant current feedback circuit 67 includes an amplifier 69, a reference voltage source 72 connected to the positive input terminal of the amplifier 69, an input resistor 68 connected to the negative input terminal of the amplifier 69, an output terminal of the amplifier 69, and an amplifier 69. A resistor 71 for gain adjustment and a capacitor 70 for phase compensation connected between the negative input terminals of the above are provided. The constant current feedback circuit 67 compares the voltage drop of the detection resistor 66 with the voltage of the reference voltage source 72 with the amplifier 69, amplifies the difference, and feeds it back to the control unit of the DC-DC converter 64. That is, the DC-DC converter 64 is subjected to negative feedback control so that the voltage drop of the detection resistor 66 and the reference voltage match. Further, the gain is set by the voltage division ratio between the resistor 71 connected between the negative input terminal and the output terminal of the amplifier 69 and the input resistor 68, and the capacitor 70 provided in parallel with the resistor 71 is integrated for phase compensation. Acts as an element.

The smoothing capacitor 65 is connected between the power supply line and the ground line of the power supply circuit 51a to smooth the output of the power supply circuit 51a.

The load circuit 53 includes a plurality of light emitting diodes connected in series. The plurality of light emitting diodes are light sources that emit illumination light. This illumination light is modulated by a binary communication signal.

The communication module 10 includes a bias circuit 1c, a first switch element 2a, a second switch element 3a, an inverter 5a, and a signal generation circuit SG.

The first switch element 2a is connected in series with the load circuit 53, which is a light source, and 100% modulates the illumination light emitted by the light source by turning it on and off. The 100% modulation referred to here means that the illumination light is modulated in two states, a lighting state and an extinguishing state. The first switch element 2a in FIG. 85 is a normally-off type switch transistor. That is, when a voltage equal to or higher than the threshold value is not applied between the source and the gate of the first switch element 2a, the state is turned off. One end of the first switch element 2a is connected to the load circuit 53. The other end of the first switch element 2a is connected to the ground wire. The control terminal of the first switch element 2a is connected to the second switch element 3a, and the bias voltage from the bias circuit 1c is input.

The bias circuit 1c sets a bias voltage for turning on the first switch element 2a during the period after the power of the illumination optical communication device is turned on and before the signal generation circuit SG starts the operation of generating the communication signal. It is supplied to the control terminal of the first switch element 2a. This bias voltage prevents the power supply circuit 51a from being in a no-load state during the period, and prevents the output voltage of the power supply circuit 51a from rising and exceeding the overvoltage protection level.

The second switch element 3a is turned on and off according to the communication signal. Specifically, the second switch element 3a is a normal-off type transistor. One end of the second switch element 3a is connected to the control terminal of the first switch element 2a. The other end of the second switch element 3a is connected to the ground wire. The control terminal of the second switch element 3a is connected to the signal generation circuit SG via the inverter 5a, and the inverted communication signal is input.

As a result, when the communication signal is low level, the second switch element 3a is on and the control terminal of the first switch element 2a is low level. As a result, the first switch element 2a is off.

Further, when the communication signal is at a high level, the second switch element 3a is off, and the control terminal of the first switch element 2a maintains the bias voltage level. As a result, the first switch element 2a is on.

Further, in the above period after the power is turned on, since the output level of the inverter 5a is low, the second switch element 3a is off, and the control terminal of the first switch element 2a becomes the level of the bias voltage. Since the bias voltage rises as the output voltage rises from the power-on, the first switch element 2a is turned on before the operation of the signal generation circuit SG starts. As a result, the first switch element 2a is on during the above period when the power is turned on.

As described above, although the first switch element 2a is a normally-off type switch due to the bias voltage, it apparently behaves as a normal-on during the above period, so that the no-load state at the time of turning on the power is eliminated. As a result, it is possible to prevent the overvoltage protection circuit from malfunctioning when the power is turned on. In addition, the margin of the overvoltage protection level and the degree of freedom in designing the margin can be increased.

The signal generation circuit SG generates a binary communication signal. This communication signal may be, for example, an inverted 4PPM signal defined by JEITA-CP1223.

[12.2 Bias circuit 1c configuration example]
As shown in FIG. 85, the bias circuit 1c includes a first resistance element 6r, a second resistance element 7r, a capacitor 8, and a resistor 4r.

The first resistance element 6r and the second resistance element 7r are connected in series between the power supply line and the ground line of the power supply circuit 51a. The connection point between the first resistance element 6r and the second resistance element 7r is electrically coupled to the control terminal of the first switch element 2a, that is, is connected via the input resistor 4r. The bias voltage can be easily generated as a voltage dividing value of a voltage dividing circuit including the first resistance element 6r and the second resistance element 7r.

Further, power is supplied from the power supply line of the power supply circuit 51a to the signal generation circuit SG and the inverter 5a via the connection point between the first resistance element 6r and the second resistance element 7r. That is, the connection point between the first resistance element 6r and the second resistance element 7r is such that the signal generation circuit SG and the capacitor 8 that supplies the power supply voltage to the inverter 5a are connected in parallel to the second resistance element 7r. (Signal generation circuit SG and power supply voltage of inverter 5a) are stabilized. In this way, the voltage dividing value of the voltage dividing circuit including the first resistance element 6r and the second resistance element 7r can be used as the power supply voltage of the signal generation circuit SG and the inverter 5a.

[12.3 DC-DC converter configuration example]
Next, a configuration example of the power supply circuit 51a having an overvoltage protection circuit will be described.

FIG. 86 is a diagram showing a circuit example of a DC-DC converter 64 having an overvoltage protection circuit 64a according to the twelfth embodiment. The DC-DC converter 64 in the figure has input terminals i1, i2, output terminals o1, o2, feedback input terminals FB, transformer TR1, switch SW1, diode D1, capacitor C1, buffer b1, error amplifier A1, resistors R1, and R2. , A triangular wave generation circuit GN, and an overvoltage protection circuit 64a.

The input terminals i1 and i2 are connected to both ends of the two output terminals of the rectifying bridge 62 and the capacitor 63 of FIG. 85, and a rectified and smoothed DC voltage is applied.

The output terminals o1 and o2 are connected to both ends of the smoothing capacitor 65 of FIG. 85. The output terminal o1 is connected to the power line, and the output terminal o2 is connected to the ground line.

The feedback input terminal FB is connected to the constant current feedback circuit 67 of FIG. 85, and a feedback signal from the amplifier 69 is input. This feedback signal indicates the magnitude of the output current of the power supply circuit 51a.

The DC-DC converter 64 is a so-called flyback converter, in which electrical energy is transmitted to the secondary side by the switching operation of the switch SW1 connected in series with the primary winding of the transformer TR1, and the diode D1 and the capacitor C1. A DC voltage is output between the output terminals o1 and o2.

The switch SW1 performs a switching operation in response to the triangular wave signal generated by the triangular wave generation circuit GN and the feedback signal. That is, the switch SW1 is in the off state when the level of the triangular wave signal generated by the triangular wave generation circuit GN does not reach the level of the feedback signal, and the switch SW1 is turned on when the level of the triangular wave signal exceeds the level of the feedback signal. It is in a state. For example, when the triangular wave signal repeats the same triangular wave at a constant frequency, the output signal of the error amplifier A1 (comparator) is a PWM-modulated pulse signal whose pulse width is determined according to the level of the feedback signal of the positive input terminal of the error amplifier A1. become.

In the overvoltage protection circuit 64a, the error amplifier A2 (comparator) compares the output voltage of the output terminal o1 with the overvoltage protection level defined by the constant voltage source Vr. The output signal of the error amplifier A2 is inverted from the low level to the high level when the output voltage of the output terminal o1 exceeds the overvoltage protection level. The latch circuit La latches and outputs a high level when the output signal of the error amplifier A2 is inverted. The AND circuit G1 forcibly lowers the input signal of the buffer b1 to the low level by killing the pulse signal of the error amplifier A1 when the latch circuit La outputs the high level. When the input signal of the buffer b1 is forcibly lowered to the low level, the output signal of the buffer b1 is also forcibly lowered to the low level, and as a result, the switching operation of the switch SW1 is stopped while the switch SW1 is off.

In this way, the overvoltage protection circuit 64a stops the power supply operation of the power supply circuit 51a when the output voltage of the power supply circuit 51a becomes overvoltage, that is, when the overvoltage protection level is exceeded.

[12.4 operation]
The operation of the illumination optical communication device according to the twelfth embodiment configured as described above will be described.

FIG. 87 is a time chart of the potential of each part of the illumination optical communication device according to the twelfth embodiment. In the figure, the converter oscillation output (a) shows the time course of the potential of the output terminal of the error amplifier A1 or the control terminal of the switch SW1 in FIG. 86. (B) The modulation control power supply voltage indicates the time passage of the power supply voltage supplied to the signal generation circuit SG from the connection point between the first resistance element 6r and the second resistance element 7r in FIG. 85, and the first switch element. The time lapse of the bias voltage input to the control terminal of 2a is shown. (C) The modulated signal output indicates the time history of the output signal of the signal generation circuit SG, that is, the communication signal. (D) The LED current indicates the time course of the current flowing through the light source, that is, the load circuit 53. (E) The modulated output voltage indicates the time course of the output voltage of the power supply circuit 51a. L1 in the figure indicates the modulation control operation level, that is, the level of the power supply voltage at which the signal generation circuit SG starts operation. L2 indicates the overvoltage protection level of the overvoltage protection circuit 64a, and corresponds to the reference level of the constant voltage source Vr in FIG.

The time T1 in the figure indicates the timing of turning on the power of the power supply circuit 51a. From time T1, (a) the converter oscillation output starts to output effectively, and (e) the output voltage with modulation starts to rise.

At time T2, (d) LED current begins to flow. That is, the period from time T2 to T3 is the period during which the first switch element 2a is turned on by the bias voltage, and is the period after the power is turned on until the signal generation circuit SG starts the operation of generating the communication signal. The period. At time T2, (e) the output voltage with modulation drops slightly because the LED current starts to flow. (E) As the output voltage with modulation decreases, (b) the modulation control voltage also decreases slightly.

During the period from time T2 to T3, since the first switch element 2a is turned on by the bias voltage, the no-load state is eliminated and the LED current flows. Therefore, (e) the output voltage with modulation exceeds the overvoltage protection level L2. That is, the malfunction of the overvoltage protection circuit 64a is prevented.

At time T3, (b) the modulation control voltage exceeds the modulation control operation level, so (c) the modulation signal output is enabled and (d) the LED current is switched.

After time T3, the illumination optical communication device is in a steady operating state.

As described above, the illumination optical communication device of the twelfth embodiment is an illumination optical communication device that modulates the two states of turning on and off the illumination light to correspond to a binary communication signal, and is an overvoltage protection circuit. The power supply circuit 51a having the above, the load circuit 53 which is a light source connected to the power supply circuit 51a and emitting the illumination light, the first switch element 2a connected in series with the light source, and the binary communication signal are generated. The signal generation circuit SG and the bias voltage for turning on the first switch element 2a during the period after the power is turned on until the signal generation circuit starts the operation of generating the communication signal. It includes a bias circuit 1c supplied to the control terminal of the first switch element 2a, and a second switch element 3a connected to the control terminal of the first switch element 2a and turned on and off according to the communication signal.

According to this configuration, the first switch element 2a behaves as a normalization even if it is a normally-off type switch due to the bias voltage, so that the no-load state at the time of turning on the power is eliminated. As a result, it is possible to prevent the overvoltage protection circuit from malfunctioning when the power is turned on. In addition, the margin of the overvoltage protection level and the degree of freedom in designing the margin can be increased.

Here, the overvoltage protection circuit 64a may stop the power supply operation when the output voltage becomes overvoltage.

According to this configuration, it is possible to prevent the overvoltage protection circuit from malfunctioning and stopping the power supply circuit when the power is turned on.

Here, the first switch element 2a is a normal off type switch transistor, the bias circuit 1c includes a first resistance element 6r, and one end of the first resistance element 6r is a power supply line of the power supply circuit 51a. The other end of the first resistance element 6r is directly or indirectly connected to the control terminal of the first switch element 2a, and one end of the second switch element is connected to the first switch element 2a. The other end of the second switch element may be connected to the ground wire.

According to this configuration, a bias voltage is supplied to the control terminal of the first switch element 2a from the other end of the resistance element. The bias circuit 1c that supplies the bias voltage can be configured by a simple resistance element. The first switch element 2a behaves as if it is apparently normal due to the bias voltage.

Here, the first switch element 2a is a normally-off type switch transistor, and the bias circuit 1c is a first resistance element 6r and a first resistance element 6r connected in series between a power supply line and a ground line of the power supply circuit. The connection point between the first resistance element 6r and the second resistance element 7r, including the two resistance element 7r, is electrically coupled to the control terminal of the first switch element 2a, and is connected to the power supply line of the power supply circuit. Electricity may be supplied to the signal generation circuit via the connection point between the first resistance element 6r and the second resistance element 7r.

According to this configuration, the first switch element 2a behaves as if it is apparently normal due to the bias voltage. Further, the bias circuit 1c can be configured by a simple voltage dividing circuit including a first resistance element and a second resistance element. Further, the bias voltage can be easily generated as a voltage dividing value of the voltage dividing circuit.

Here, the bias circuit 1c includes a capacitance element 8 connected in parallel to the second resistance element, and is a connection point between the first resistance element 6r and the second resistance element 7r from the power supply line of the power supply circuit. The signal generation circuit may be supplied with power via the above.

According to this configuration, the voltage dividing value of the voltage dividing circuit including the first resistance element and the second resistance element can be used as the power supply voltage of the signal generation circuit.

Further, the communication module according to the twelfth embodiment is a communication module that can be attached to and detached from the lighting device by modulating the two states of turning on and off the illumination light emitted by the lighting device so as to correspond to a binary communication signal. The load circuit 53, which is a light source connected in series with the light source of the lighting device and emits the illumination light, the first switch element 2a connected in series with the light source, and the signal generation circuit SG for generating the binary communication signal. A bias voltage that turns on the first switch element 2a is supplied to the control terminal of the first switch element 2a after the power is turned on and until the signal generation circuit starts the operation of generating the communication signal. A second switch element 3a connected to the control terminal of the first switch element 2a and the bias circuit 1c, which is turned on and off according to the communication signal after the signal generation circuit SG starts operation. It includes a switch element 3a.

According to this configuration, the communication module can be added to the existing luminaire. That is, the existing lighting equipment can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than when a new optical communication lighting equipment is installed. In addition, it is possible to prevent malfunction of the overvoltage protection circuit when the power of the existing lighting equipment equipped with the communication module is turned on.

(Embodiment 13)
Subsequently, the illumination optical communication device according to the thirteenth embodiment will be described. In the twelfth embodiment, an example in which the first switch element 2a is a normally-off type switch transistor has been described. On the other hand, in the thirteenth embodiment, an example in which the first switch element is a normalion type switch transistor will be described.

FIG. 88 is a circuit diagram showing a configuration example of the illumination optical communication device according to the thirteenth embodiment. In the figure, the circuit configuration of the communication module 10 is different from that in FIG. 85. Hereinafter, the differences will be mainly described.

Compared with FIG. 85, the communication module 10 of FIG. 88 is different in that it includes the first switch element 2b instead of the first switch element 2a and that the circuit configuration of the bias circuit 1c is different.

The first switch element 2b is not a normalization type switch transistor but a normalization type switch transistor.

The bias circuit 1c supplies a bias voltage that becomes a forward bias to the control terminal of the first switch element 2b when the second switch element 3a is off after the power is turned on, and is the first when the second switch element 3a is on after the power is turned on. It is configured to supply a bias voltage that becomes a reverse bias to the control terminal of the switch element 2b. Specifically, the bias circuit 1c includes a first resistance element 6r, a second resistance element 7r, a capacitor 8, a third resistance element 9, a fourth resistance element 9a, and a diode 11d.

The first resistance element 6r and the second resistance element 7r are connected in series between the power supply line and the ground line of the power supply circuit 51a.

The third resistance element 9 and the fourth resistance element 9a are connected in series. The third resistance element 9 and the fourth resistance element 9a connected in series are electrically coupled between the power supply line of the power supply circuit and the connection point between the first resistance element 6r and the second resistance element 7r. To. Here, the case of being electrically coupled includes the case of being directly connected and the case of being indirectly connected. For example, one end of the fourth resistance element 9a in FIG. 88 is indirectly connected to the connection point between the first resistance element 6r and the second resistance element 7r via the diode 11d.

One end of the first switch element 2b is connected to the power supply line, and the other end of the first switch element 2b is electrically coupled to the connection point between the first resistance element 6r and the second resistance element 7r. The control terminal of the first switch element 2b is connected to the connection point between the third resistance element 9 and the fourth resistance element 9a.

One end of the second switch element 3a is connected to the control terminal of the first switch element 2b, and the other end of the second switch element 3a is connected to the ground wire.

As described above, the bias circuit 1c includes a two-stage voltage dividing circuit including a voltage dividing circuit including the first and second resistance elements 6r and 7r and a voltage dividing circuit including the third and fourth resistance elements 9 and 9a. When the second switch element 3a is on, the bias voltage becomes reverse bias, so the first switch element 2b is turned off. Since the second switch element 3a is off in the period after the power is turned on until the signal generation circuit SG starts the operation of generating the communication signal, the first switch element 2b is turned on and the no-load state is set. It will be resolved.

The power supply voltage of the signal generation circuit SG is supplied from the power supply line of the power supply circuit 51a to the signal generation circuit SG via the connection point between the first resistance element 6r and the second resistance element 7r. Therefore, the bias circuit 1c includes a capacitor 8 connected in parallel to the second resistance element in order to stabilize the power supply voltage supplied to the signal generation circuit SG.

As described above, the illumination optical communication device of the thirteenth embodiment is an illumination optical communication device that modulates the two states of turning on and off the illumination light to correspond to a binary communication signal, and is an overvoltage protection circuit. The power supply circuit 51a having the above, the load circuit 53 which is a light source connected to the power supply circuit 51a and emitting the illumination light, the first switch element 2b connected in series with the light source, and the binary communication signal are generated. The signal generation circuit SG and the bias voltage for turning on the first switch element 2b during the period after the power is turned on until the signal generation circuit starts the operation of generating the communication signal. It includes a bias circuit 1c supplied to the control terminal of the first switch element 2b, and a second switch element 3a connected to the control terminal of the first switch element 2b and turned on and off according to the communication signal.

Here, the first switch element 2b is a normalion type switch transistor, and the second switch element is connected between the control terminal of the first switch element 2b and the ground wire, and the bias circuit 1c Supply a bias voltage that becomes a forward bias to the control terminal of the first switch element 2b when the second switch element is off after the power is turned on, and the first switch when the second switch element is on after the power is turned on. A bias voltage that becomes a reverse bias may be supplied to the control terminal of the element 2b.

According to this configuration, since the normalion type switch transistor is used, the no-load state at the time of turning on the power is eliminated, and the malfunction of the overvoltage protection circuit can be prevented.

Here, the bias circuit 1c is a third resistance element 9 connected in series with a first resistance element 6r and a second resistance element 7r connected in series between the power supply line and the ground line of the power supply circuit. The third resistance element 9 and the fourth resistance element 9a include a fourth resistance element 9a and a connection point between the power supply line of the power supply circuit and the first resistance element 6r and the second resistance element 7r. One end of the first switch element 2b is connected to the power supply line, and the other end of the first switch element 2b is electrically connected to the first resistance element 6r and the second resistance. It is electrically coupled to the connection point with the element 7r, and the control terminal of the first switch element 2b is connected to the connection point between the third resistance element 9 and the fourth resistance element 9a, and the second switch element One end of 3a may be connected to the control terminal of the first switch element 2b, and the other end of the second switch element 3a may be connected to the ground wire.

According to this configuration, the bias circuit 1c includes a two-stage voltage divider circuit composed of first and second resistance elements and a voltage divider circuit consisting of third and fourth resistance elements. When the second switch element is on, the bias voltage becomes reverse bias, so the first switch element 2b is turned off.

Here, the bias circuit 1c includes a capacitance element 8 connected in parallel to the second resistance element, and is a connection point between the first resistance element 6r and the second resistance element 7r from the power supply line of the power supply circuit. The signal generation circuit may be supplied with power via the above.

According to this configuration, the voltage dividing value of the voltage dividing circuit including the first resistance element and the second resistance element can be used as the power supply voltage of the signal generation circuit.

(Comparison reference example)
Subsequently, an illumination optical communication device not provided with the bias circuit 1c will be described as a comparative reference example in comparison with the twelfth embodiment.

FIG. 89 is a circuit diagram showing a configuration example of the illumination optical communication device in the comparative reference example. The figure is different from FIG. 85 or FIG. 88 in that the communication module 10 does not include the bias circuit 1c. That is, the communication module 10 includes a first switch element 73, a buffer 74, a signal generation circuit SG, and a capacitor 76c. The communication module 10 has a function of modulating the illumination light 100% by the communication signal, but does not have the function of the bias circuit 1c. Therefore, the power supply circuit 51a has no load during the rising period when the power is turned on. The above condition may occur, and the overvoltage protection circuit may malfunction.

FIG. 90 is a time chart of the potential of each part of the illumination optical communication device in the comparative reference example of FIG. 89. Here, it is assumed that the DC-DC converter 64 of FIG. 89 is shown in FIG. 86.

In FIG. 90, (a), (b), and (c) show the time course of the voltage and current of each part when the overvoltage protection circuit 64a is not malfunctioning. (A) The error amplifier oscillation output shows the time course of the voltage of the output terminal of the error amplifier A1 or the control terminal of the switch SW1 in FIG. 86. (B) The LED current indicates the time course of the current flowing through the light source, that is, the load circuit 53. (C) The normal output voltage indicates the time course of the output voltage of the power supply circuit 51a when the overvoltage protection circuit 64a is not malfunctioning.

The power is turned on at time T1, (a) the converter oscillation output starts to output effectively, and (b) LED current starts to flow at time T2. At time T2, (c) the normal output voltage has not reached the overvoltage protection level, and (b) the LED current starts to flow and the no-load state is eliminated. That is, the no-load state is in the period from the time T1 to the time T2, but the no-load state is canceled in the period from the time T2 to the time T3. (C) Since the no-load state is eliminated in the state where the normal output voltage has not reached the overvoltage protection level, the overvoltage protection circuit 64a does not malfunction.

On the other hand, FIGS. 90 (d), (e), and (f) show the time course of the potential of each part when the overvoltage protection circuit 64a malfunctions. (D) The output voltage at no load indicates the time course of the output voltage of the power supply circuit 51a when the overvoltage protection circuit malfunctions. (E) The output of the latch circuit La shows the time course of the output voltage of the latch circuit La of FIG. 86 when the overvoltage protection circuit malfunctions. (F) The oscillating output at the time of latch indicates the time course of the voltage of the output terminal of the error amplifier A1 or the control terminal of the switch SW1 when the overvoltage protection circuit malfunctions. In FIGS. 90 (d), (e), and (f), the signal generation circuit SG rises slowly, and at time T3, the signal generation circuit SG does not start operation, that is, the LED current does not flow in a no-load state. It has become. Therefore, (d) the output voltage at no-load exceeds the overvoltage protection level L1 at time T3, (e) the output of the latch circuit La becomes a high level, and (f) the oscillation output at latch stops. That is, at time T3, the overvoltage protection circuit 64a malfunctions and the power supply is stopped.

As described above, if the period after the power is turned on and the period until the signal generation circuit SG starts the operation of generating the communication signal is a no-load state, the overvoltage protection circuit 64a may malfunction.

(Modification example)
Next, a modified example of the illumination optical communication device will be described.

FIG. 91 is a circuit diagram showing a modified example of the illumination optical communication device according to the twelfth or thirteenth embodiment. The illumination optical communication device of the figure has a different circuit configuration inside the power supply circuit 51a as compared with FIG. 85 or FIG. 88. Hereinafter, the differences will be mainly described.

In the power supply circuit 51a of FIG. 85 or FIG. 88, the constant current feedback circuit 67 performs feedback control to make the average value of the output current constant, whereas in the power supply circuit 51a of FIG. 91, the switching current is measured. It is configured to perform feedback control.

The power supply circuit 51a of FIG. 91 includes a rectifying bridge 62, a capacitor 63, and a DC-DC converter 64. The DC-DC converter 64 includes an inductor 80, a switch element 81, a diode 66d, a resistor 82, a signal source 83, a flip flop 84, a comparator 85, a constant voltage source 86, a capacitor 87, a resistor 88, a diode 89, a driver 90, and a gate resistor. 91 is provided.

The inductor 80, the switch element 81, and the diode 66d are basic circuit elements that configure the DC-DC converter 64 as a back converter.

The control for turning on and off the switch element 81 is performed by the signal source 83, the flip-flop 84, the comparator 85, and the circuits around the switch element 81, and the threshold control of the switching current of the switch element 81 is performed. That is, the switching current is also a current via the load circuit 53 (light emitting diode), and an alternative function of constant current feedback can be obtained by threshold control. The operation of such a DC-DC converter 64 will be described with reference to FIG. 856.

FIG. 92 is a waveform diagram showing threshold control of the switching current in the power supply circuit 51a of FIG. 91. However, FIG. 92 shows the waveform when the terminals T1 and T2 are short-circuited in FIG. 91, or when the communication module 10 is connected to the terminals T1 and T2 and the transistor 2 is maintained in the ON state. Is shown.

In FIG. 92, the set signal S is a signal input from the signal source 83 to the set input terminal S of the flip-flop 84. The positive input signal is a signal input to the positive input terminal of the comparator 85, and indicates the voltage drop of the resistor 82, that is, the magnitude of the current flowing through the switch element 81. The reset signal R is a signal input to the reset input terminal of the flip-flop 84. The output signal Q is a signal output from the output terminal Q of the flip-flop 84. The output signal Q becomes a gate signal of the switch element 81 via the driver 90 and the resistor 91. The switching current is a current flowing through the switch element 81, and is detected as a voltage drop of the resistor 82.

The set signal is generated by the signal source 83 and periodically goes high. When the set signal S becomes high, the output signal Q of the RS flip-flop 84 becomes high. The output signal Q is input to the gate of the switch element 81 (MOSFET) via the driver circuit 90 and the gate resistor 91. The switch element 81 is turned on when the output signal Q becomes high.

The magnitude of the switching current (current flowing through the switch element 81) is detected as a voltage drop of the resistor 82, input to the positive input terminal of the comparator 85, and compared with the reference voltage Vref applied to the negative input terminal of the comparator 85. To. When the voltage drop reaches the reference voltage Vref, the output of the comparator 85 becomes high, is converted into a pulse by a differentiating circuit composed of a capacitor 87 and a resistor 88, and is input to the reset input terminal of the RS flip-flop 84. At this point, the output signal Q of the flip-flop 84 becomes low, and the switch element 81 turns off. Detecting the magnitude of the current flowing through the switch element 81 as the switching current is a substitute for detecting the magnitude of the current flowing through the load circuit 53.

Such threshold control of the switching current substitutes the constant current feedback control of FIGS. 85 and 88, and works to make the average of the output currents constant.

The power supply circuit 51a may perform constant current feedback control in FIGS. 85 and 88, or may perform switching current threshold control in FIG. 91.

The power supply circuit 51a in FIG. 91 may include an overvoltage protection circuit 64a. In that case, the power supply circuit 51a of FIG. 91 includes the overvoltage protection circuit 64a shown in FIG. 86, and the non-inverting input terminal of the AND circuit G1 is connected to the output terminal Q of the flip-flop 84.

As shown in FIGS. 85 and 88, the power supply circuit 51a may perform feedback control for keeping the average value of the supplied currents constant.

Further, as shown in FIG. 91, the power supply circuit 51a includes a back converter (that is, a DC-DC converter 64) having an inductor 80 and a switch element 81, detects the magnitude of the current flowing through the switch element 81, and detects the detected value. The on and off of the switch element 81 may be controlled according to the difference between the value and the predetermined value.

When the first switch element 2a or 2b is a voltage-driven type, the bias voltage may be a bias voltage having a biased voltage value, or the first switch element 2a or 2b may be a current-driven type. For example, it may be a bias current having a biased current value.

(Embodiment 14)
In the 14th to 18th embodiments, the configuration in which the power supply circuit of the illumination optical communication device includes a constant voltage feedback circuit instead of the constant current feedback circuit will be described.

When a constant voltage feedback type power supply is provided instead of the constant current feedback type power supply (for example, FIG. 50C and FIG. 1 of Patent Document 3), a large overshoot is unlikely to occur in the LED current, and the above-mentioned overshoot problem is solved. It is thought that it can be reduced. However, in the case of providing a constant voltage feedback type power supply, if 100% modulated visible light communication is performed, there arises a problem that the brightness of the illumination light is lowered because the average current is lowered due to the interruption and discontinuity of the switch.

In the present embodiment, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, the illumination light suppresses the decrease in brightness due to the interruption and discontinuity of the switch and is less likely to cause a reception error of the receiving device. The communication device and the communication module will be described.

One form of the illumination light communication device according to the present embodiment is to modulate the illumination light with a light source that emits illumination light, a switch that is connected in series with the light source and interrupts the current flowing through the light source. The light source is connected in series with the light source and the switch to generate a binary communication signal for controlling the on and off of the switch, and the light source is connected so as not to exceed the current set value corresponding to the reference value. The average value of the voltage applied to the current suppression circuit that suppresses the flowing current, the DC power supply circuit that applies a DC voltage to the light source, switch, and current suppression circuit connected in series, and the current suppression circuit is constant. It includes a constant voltage feedback circuit that controls the DC power supply circuit.

Further, one form of the communication module according to the present embodiment is a communication module that is detachable from the lighting device and modulates the illumination light, and is a switch connected in series with the light source of the lighting device and the illumination light. A signal generation circuit that generates a binary communication signal that controls the on and off of the switch to modulate the switch, and a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source. The first, second, and third terminals for attaching and detaching to the lighting device are provided, and the first terminal is connected to one end of the series circuit including the switch and the current suppression circuit on the switch side. The second terminal is connected to the connection point between the switch and the current suppression circuit in the series circuit, and the third terminal is connected to the other end of the series circuit on the current suppression circuit side.

According to the illumination optical communication device and the communication module according to the present embodiment, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, the decrease in brightness due to the interruption and discontinuity of the switch is suppressed, and the brightness is suppressed. , There is an effect that it is difficult to cause a reception error of the receiving device.

[14.1 Configuration of Illuminated Optical Communication Device]
First, the configuration of the illumination optical communication device of the 14th embodiment will be described.

FIG. 93A is a circuit diagram showing the configuration of the illumination optical communication device according to the fourteenth embodiment. This illumination optical communication device includes a power supply circuit 52b having a function of making the output a constant voltage, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, a switch SW, a signal generation circuit SG, and a current suppression circuit 73. And.

The power supply circuit 52b includes a rectifier bridge 62, a capacitor 63, a DC-DC converter 64 which is a DC power supply circuit, and a constant voltage feedback circuit 67a. The constant voltage feedback circuit 67a includes an input resistor 68, an amplifier 69, a capacitor 70, a resistor 71, and a reference voltage source 72.

The power supply circuit 52b full-wave rectifies a commercial power supply (for example, AC 100V) with a rectifying bridge 62, smoothes it with a capacitor 63, and then converts it into a desired DC voltage with a DC-DC converter 64. A smoothing capacitor 65 is connected between both ends of the output of the DC-DC converter 64. Further, a load circuit 53, a current suppression circuit 73, and a series circuit of the switch SW are connected in parallel with the smoothing capacitor 65.

The power supply circuit 52b feeds the voltage applied across the current suppression circuit 73 to the DC-DC converter 64 of the power supply circuit 52b via the constant voltage feedback circuit 67a, and supplies the voltage applied to the current suppression circuit 73. It forms a kind of constant voltage power supply that controls constantly.

The smoothing capacitor 65 is connected between the outputs of the power supply circuit 52b and smoothes the output of the power supply circuit 52b.

The load circuit 53 includes a plurality of light emitting diodes connected in series between the outputs of the power supply circuit 52b, and the output of the power supply circuit is supplied. The plurality of light emitting diodes are light sources that emit illumination light.

The switch SW is added in series with the load circuit 53, and interrupts the current supplied from the power supply circuit 52b to the load circuit 53.

The signal generation circuit SG generates a binary communication signal that controls the on and off of the switch SW in order to modulate the illumination light. The communication signal is input to the control terminal of the switch SW to turn the switch SW on and off. The signal generation circuit SG may repeatedly generate a communication signal indicating an ID unique to the illumination optical communication device, or may generate a communication signal in response to a transmission signal input from an external device.

[Structure of 14.2 Current Suppression Circuit 73]
Next, a configuration example of the current suppression circuit 73 will be described.

The current suppression circuit 73 is added in series with the load circuit 53 and the switch SW to suppress the magnitude of the current flowing through the load circuit 53. For example, the current suppression circuit 73 is connected in series with the load circuit 53 as a light source and the switch SW, and suppresses the current flowing through the load circuit 53 according to the reference value so as not to exceed the current set value corresponding to the reference value. You may try to do it. In this way, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Further, since the overshoot generated in the current flowing through the load circuit 53, which is a light source, can be reduced at the moment when the switch SW is turned on, it is possible to reduce the reception error in the receiving device.

The current suppression circuit 73 includes a transistor 74 which is a MOSFET, a resistor 75 connected to a source, an error amplifier 77, a reference source 76, and a control circuit 6.

The reference source 76 outputs a reference value to the positive input terminal of the error amplifier 77. The reference value defines an upper limit (current set value) of the current flowing through the load circuit 53 which is a light source. For example, the reference value is proportional to the current set value. Further, the reference source 76 may output the reference value as a fixed value, or may output a variable reference value according to the arrangement pattern (for example, bit pattern) of the communication signal generated by the signal generation circuit SG. ..

The transistor 74 is connected in series with the load circuit 53, which is a light source, and the switch SW, and suppresses the current flowing through the load circuit 53 based on the reference value.

The resistor 75 is a source resistor for detecting the magnitude of the current flowing through the load circuit 53. The source side terminal of the resistor 75 is connected to the negative input terminal of the error amplifier 77.

In the error amplifier 77, the reference source 76 is connected to the positive input terminal, and the source of the transistor 74 is connected to the negative input terminal. The error amplifier 77 amplifies the difference between the reference value and the current value detected by the resistor 75, and outputs the amplified signal to the gate of the transistor 74.

The control circuit 6 controls to change the reference value of the reference source 76 according to the arrangement pattern of the communication signal in order to output a variable reference value from the reference source 76. For example, the control circuit 6 calculates a partial on-duty ratio of the communication signal, and when the calculated partial on-duty ratio is the first ratio, sets the reference value as the first value and partially When the on-duty ratio is a second ratio larger than the first ratio, the reference value is set to a second value smaller than the first value. At this time, the control circuit 6 may change the reference value so as to be inversely proportional to the partial on-duty ratio of the communication signal. The "partial on-duty ratio" is, for example, the ratio of the on-duty period to the total period of the latest off-duty period and the on-duty period immediately before the off-duty period. Alternatively, the "partial on-duty ratio" may be replaced by the moving average of the most recent n bits of the communication signal. In this way, overshoot suppression can be made more appropriate when the magnitude of the overshoot generated in the current flowing through the load circuit 53 depends on the partial on-duty ratio.

[14.3 Modification example of current suppression circuit 73]
Next, first to third modification examples of the current suppression circuit 73 will be described.

The current suppression circuit 73 in FIG. 93A is not limited to this configuration. .. For example, the internal configuration of the current suppression circuit 73 may be the same as the first to third modifications of the current suppression circuit 1 shown in FIGS. 2 to 4.

Further, as shown in FIG. 93B, the illumination optical communication device of FIG. 93A may have a detachable communication module 10 including a portion including the current suppression circuit 73.

The communication module 10 includes a current suppression circuit 73, a switch SW, and a capacitor 65. The communication module 10 shown in FIG. 1A does not include the capacitor 65, whereas the communication module 10 shown in FIG. 93B contains the capacitor 65. The capacitor 65 is a relatively large-capacity capacitor that smoothes the output voltage from the DC-DC converter 64. The communication module 10 can include an internal power supply circuit that generates a power supply voltage of the communication module 10 itself from the voltage across the capacitor 65. The internal power supply circuit may be, for example, the same as the control power supply 126 of FIG. 65, and may be a three-terminal regulator. As a result, even when the switch SW is off, the power supply voltage inside the communication module 10 can be continuously and stably supplied, and it becomes easy to secure the necessary power.

The other communication module 10 such as FIGS. 1A and 30A may also have a configuration including a capacitor 65 and an internal power supply circuit as shown in FIG. 93B.

[14.4 Operation of Illuminated Optical Communication Device]
The operation of the illumination optical communication device configured as described above will be described using simulation results.

94A, 94B, 97A, and 97B show simulation results in which the current suppression circuit 1 of FIG. 2 is used instead of the current suppression circuit 73 in FIG. 93A. FIG. 94A is a diagram showing a first simulation result in which the current suppression circuit 1 of FIG. 2 is used instead of the current suppression circuit 73 in FIG. 93A. In FIG. 94A, the capacitance value of 65 of the smoothing capacitor is set to 20uF, the frequency of the communication signal (modulation signal) from the signal generation circuit SG is set to 2.4 kHz, and the on-duty ratio of the switch SW is set to 60% and 75%. The LED current and output voltage waveforms are shown when the values are changed to 90% and 100%. Incidentally, the operating frequency of the DC-DC converter 64 is set to 65 kHz, and the average value of the load current (LED current) when not intermittent is set to 240 mA. In the case of each on-duty ratio, the LED current waveform changes the clamp current value (peak value) while maintaining a square wave, but the average value of the LED current is constant regardless of the on-duty ratio value ( The voltage source of the current suppression circuit 73 is variable so as to be 240 mA). The smaller the on-duty ratio of the output voltage, the larger the pulsating component.

FIG. 94B is a diagram showing a second simulation result in which the current suppression circuit 1 of FIG. 2 is used instead of the current suppression circuit 73 in FIG. 93A. As shown in FIG. 94B, the voltage applied to the current suppression circuit 73 tends to have a higher peak value as the on-duty ratio becomes smaller. Due to this tendency, the brightness of the LED, which is the load circuit 53, can be kept substantially constant regardless of whether the on-duty ratio is large or small.

The relationship between the on-duty ratio and the brightness of the LED will be described with reference to FIGS. 95 and 96, which show comparative examples. FIG. 95 is a schematic diagram showing the relationship between two communication signals having different on-duty ratios and the LED current. However, FIG. 95 shows a case where the current suppression circuit 73 does not exist, or a case where the current setting value of the current suppression circuit 73 is fixed.

The communication signal (1) shows a case where the on-duty ratio is relatively large, and the communication signal (2) shows a case where the on-duty ratio is relatively small. In any of the communication signals (1) and (2), the average value (level II) of the LED current when the switch SW is intermittent is smaller than the average value (level I) when the switch SW is not intermittent. The level II of the communication signal (2) having a small on-duty ratio is smaller than the level II of the communication signal (1). That is, the value of the average current in the case of intermittent is lower than the value of the current in the case of non-intermittent in proportion to the off-duty ratio. This indicates that if the current set value is not controlled by the current suppression circuit 73, the brightness may change if the LED load is interrupted for optical communication.

FIG. 96 is a diagram showing the relationship between the on-duty ratio and the LED current in the case where the current set value is fixed or the case where the current suppression circuit 73 does not exist. From the figure, even if the on-duty ratio on the horizontal axis changes, the peak value of the LED current (level I in FIG. 95) does not change, and the average value (level II in FIG. 95) has a small on-duty ratio. It has dropped so much. That is, the smaller the on-duty ratio, the darker the illumination light. That is, the brightness is lowered due to visible light communication.

With respect to FIGS. 95 and 96, in the illumination optical communication device according to the fourteenth embodiment as shown in FIG. 94A, the peak value of the LED current (that is, the current set value) increases as the on-duty ratio becomes smaller. As a result, the average value of the LED current can be made constant regardless of whether the on-duty ratio is small or large, and the illumination light can be used regardless of whether the switch SW is intermittent or not, and regardless of the on-duty ratio. The brightness can be kept constant.

FIG. 97A is a diagram showing a third simulation result in which the current suppression circuit 1 of FIG. 2 is used instead of the current suppression circuit 73 in FIG. 93A. FIG. 97A shows the optimum current setting value of the current suppression circuit 73 for each on-duty ratio. F By changing the current set value for each on-duty ratio as shown in the figure, the average value of the LED current can be made constant to the value when it is not intermittent. That is, the decrease in brightness due to the switch SW is suppressed. Further, as shown in FIG. 97B, the loss of the current suppression circuit 73 (that is, the power consumption of the current suppression circuit 73 itself) can be maintained at a low value.

FIG. 98 is a diagram showing the LED current, the output voltage, the SW voltage, and the voltage of the current suppression circuit in FIG. 93A. FIG. F is an explanatory diagram for calculating the optimum current setting value of the current suppression circuit 73 according to the on-duty ratio of the modulated signal from the signal generation circuit SG. The power supply circuit 52b, which is the premise of the illumination optical communication device of the fourteenth embodiment, is a constant voltage power supply and has a constant voltage feedback function as described above. As a typical example, a constant voltage feedback circuit 67a using an error amplifier as shown in FIG. 93A is provided. Usually, a phase compensation circuit is added to ensure the stability of the feedback system. In such a phase compensation circuit, a compensation circuit including an integrating element is used to adjust the gain and the phase in the one-round transfer function, and is known as PI control or PID control. In other words, such a phase compensation circuit can be said to be a means for controlling the average value of the voltages applied to the current suppression circuit 73 to be constant.

With this in mind, looking at the various waveforms shown in FIG. 98, the LED current that flows when the switch SW is turned on is first maintained in a rectangular wave shape by the current suppression circuit 73. Since the load current is cut off during the period when the switch SW is off, the output voltage rises and this voltage is applied to the switch SW. Next, during the period when the switch SW is on, the LED current flows, so that the output voltage drops and this voltage is applied to the load circuit 53 and the current suppression circuit 73, which are light sources. Since the current of the load circuit 53 is a square wave, the fluctuation amount ΔVo of the output voltage is applied to the current suppression circuit 73, and the average value Wave of this voltage waveform is constant by the constant voltage feedback circuit 67a (in the case shown in FIG. 98, it is about about. It is controlled to 1V). That is, if the reference voltage source 72 of the constant voltage feedback circuit 67a is appropriately set in consideration of the current value of the load circuit 53, the capacitance value of the smoothing capacitor 65, the variable range of the on-duty ratio, etc., the LED current waveform can be obtained. The loss of the current suppression circuit 73 can be suppressed to a substantially desired range while maintaining a rectangular wave. Further, by changing the peak cut value Iop of the LED current to the value represented by the equation (1) according to the on-duty ratio, the average value of the LED current is constant regardless of the value of the on-duty ratio. Can be maintained at a value.

Optimal current setting value = Iop = 100 × Iave / ONd (%) (1)

Here, Iop is the peak cut value of the LED current, that is, the optimum current setting value of the current suppression circuit 73. Iave is the average LED current value when there is no interruption. ONd is the on-duty ratio (%) of the switch SW.

The relationship between the partial on-duty ratio of the communication signal and the optimum current set value is as shown in FIG. 29B. FIG. 29B shows the result of obtaining the optimum current setting value for each on-duty ratio using the equation (1). In the figure, the on-duty ratio ONd and the current set value are inversely proportional to each other.

As described above, according to the illumination light communication device according to the fourteenth embodiment, the overshoot of the LED current can be suppressed, the malfunction of the receiving device can be reduced, and the illumination light when the illumination light is not modulated. It is possible to make the brightness of the illumination light and the brightness of the illumination light when the illumination light is modulated almost the same in human appearance.

(Embodiment 15)
The illumination optical communication device of the fifteenth embodiment will be described with reference to FIGS. 99A to 99C.

FIG. 99A is a circuit diagram showing the configuration of the illumination optical communication device according to the fifteenth embodiment. The figure is different from FIG. 93A in that the first current suppression circuit 73a and the second current suppression circuit 73b are provided instead of the current suppression circuit 73. Another difference is that the switch SW, the signal generation circuit SG, and the second current suppression circuit 73b are detachable as the communication module 10 at the portions T1 to T3 of the first to third terminals. Hereinafter, the differences will be mainly described.

The first current suppression circuit 73a is connected in series with the load circuit 53, which is a light source, and the switch SW, and suppresses the current flowing through itself so as not to exceed the first current set value corresponding to the first reference value. Specifically, the first current suppression circuit 73a is composed of a transistor 74 which is a MOSFET, a resistor 75 connected to a source, an error amplifier 77, and a reference source 76. The reference source 76 outputs the first reference value to the positive input terminal of the error amplifier 77. The first reference value defines the first current set value among the currents flowing through the load circuit 53 which is a light source. For example, the first reference value is proportional to the first current set value. The reference source 76 outputs the first reference value as a fixed value.

The second current suppression circuit 73b is connected in parallel with the first current suppression circuit 73a, and suppresses the current flowing through itself so as not to exceed the second current set value corresponding to the second reference value.

FIG. 99C is a circuit diagram showing a specific configuration example of the communication module 10 and the second current suppression circuit 73b according to the fifteenth embodiment. The second current suppression circuit 73b in the figure has the same configuration as the current suppression circuit 73 shown in FIG. 93A, and operates in the same manner. The output of the reference source 76 in the figure is called the second reference value. The upper limit of the current flowing through the second current suppression circuit 73b according to the second reference value is called the second current set value. Further, it can be said that the communication module 10 that can be attached to and detached from the first to third terminal portions has a configuration suitable for adding an illumination optical communication function by retrofitting to an existing LED lighting fixture. FIG. 99B is a circuit diagram showing a configuration of an illumination optical communication device to which the communication module 10 is not added according to the fifteenth embodiment. As shown in the figure, when the illumination optical communication device (ordinary lighting device) does not include the communication module 10, a short wire S10 connecting the first and second terminals T1 and T2 may be provided.

The operations of FIGS. 99A and 99C will be described with reference to simulation results. FIG. 100 is a diagram showing simulation results for the circuit examples of FIGS. 99A and 99C. The main setting conditions for the simulation are a capacitance value of the smoothing capacitor 65 of 20 uF, a modulation signal frequency from the signal generation circuit SG of 2.4 kHz, an operating frequency of the DC-DC converter 64 of 65 kHz, and a load when the switch SW is not interrupted. The average value of the current (LED current) is set to 240 mA.

As shown in FIG. 100, the first current set value based on the first reference value of the reference source 76a of the first current suppression circuit 73a is set to the current value (240 mA) when the switch element SW is not interrupted (in the same figure). Existing current value). The second current set value based on the second reference value of the second current suppression circuit 73b is increased as shown in the "additional current value" in the figure as the on-duty ratio of the switch SW becomes smaller. The ideal set value in the figure is the sum of the first current set value and the second current set value. As a result, the average current value of the LED load can be kept constant regardless of the on-duty ratio.

Next, FIG. 101 calculates the optimum second current setting value of the added second current suppression circuit 73b according to the on-duty ratio of the modulated signal from the signal generation circuit SG in the fifteenth embodiment. It is explanatory drawing for this. See also the explanatory diagram showing the waveform of the intermittent LED current shown in FIG. 29A. As already described with reference to FIG. 98, the first and second current setting values of the first current suppression circuit 73a and the second current suppression circuit 73b each set the peak cut value (Iop) of the LED current. In the fifteenth embodiment, since the first set current value is set as a fixed value in the first current suppression circuit 73a to the LED current of 240 mA when the current is not interrupted, the second current suppression circuit 73b added. 2 It is optimal to set the current set value (additional current set value) to the value represented by the following equation (2).

Iop2 = Iave × [100 / ONd (%) -1] (2)

Here, Iop2 is the current peak cut value of the second current suppression circuit 73b, that is, the optimum additional current setting value. Iave is the average LED current value when there is no interruption. ONd is the on-duty ratio (%) of the switch SW.

FIG. 101 is a diagram showing a current set value according to the on-duty ratio. The figure shows the result of obtaining the optimum current setting value for each on-duty ratio using the equation (2). The total current set value in the figure shows the sum of the first current set value and the second current set value. The additional current set value indicates the second current set value. In this example, the first current set value is a fixed value of 240 mA, and the second current set value is a variable value of 0 to 240 mA.

As described above, the current flowing through the switch SW is suppressed by the first current suppression circuit 73a and the current suppression circuit 73b so as not to exceed the sum of the first current set value and the second current set value. By fixing the first current set value and making the second current set value variable, the circuit operation system can be improved, and it is more appropriate to suppress the decrease in the brightness of the illumination light due to the interruption of the switch SW. Can be improved. Further, the overshoot generated in the LED current can be reduced, and the malfunction of the receiving device can be reduced. Further, by making the second current suppression circuit 73b removable as a part of the communication module 10, it can be easily added to the existing lighting device.

The communication module 10 of FIGS. 99A and 99C does not include the switch SW and the signal generation circuit SG, and may be only the circuit portion of the current suppression circuit 73b and the second and third terminals T2 and T3. In this case, in FIG. 99B, a switch SW and a signal generation circuit SG are provided instead of the short wire S10, and the switch SW is connected between the first and second terminals.

(Embodiment 16)
The illumination optical communication device of the 16th embodiment will be described with reference to FIG. 102. Here, the symbols of the circuit parts common to those in FIG. 93A are matched, and the added / changed circuit parts will be mainly described. In the 16th embodiment, by providing the constant current feedback circuit 167 instead of the control circuit 6 of FIG. 93A, the value of the reference source is changed according to the on-duty ratio described in the 14th embodiment. The configuration will be described.

FIG. 102 is a circuit diagram showing the configuration of the illumination optical communication device according to the sixteenth embodiment. FIG. 102 shows a resistor 66 for newly detecting the LED current and a constant current feedback circuit instead of the control circuit 6 that changes the reference source 76 of the current suppression circuit 73, as compared with the fourth embodiment (FIG. 93A). A feedback system is configured by adding 167 and a level shifter 78. The constant current feedback circuit 167 is connected to the negative input terminal of the error amplifier 169 via the input resistor 168, and the constant voltage source 72c is connected to the positive terminal of the error amplifier 169. Further, a gain adjusting resistor 71r and a phase compensation capacitor 170 are connected between the output terminal of the error amplifier 169 and the negative input terminal of the error amplifier 169.

The constant current feedback circuit 167 controls the voltage of the positive input terminal of the error amplifier 77 of the current suppression circuit 73 so that the voltage drop of the resistor 66 for detecting the LED current and the value of the constant voltage source 72c match. The level shifter 78 is required when the operation reference point of the current suppression circuit 73 and the operation reference point of the constant current feedback circuit 167 are different.

104 to 106 show simulation results for verifying the operation of the 16th embodiment (FIG. 102). The main setting conditions for the simulation are a capacitance value of the smoothing capacitor 65 of 20 uF, a modulation signal frequency from the signal generation circuit SG of 2.4 kHz, an operating frequency of the DC-DC converter 64 of 65 kHz, and a load when the switch SW is not interrupted. The average value of the current (LED current) is set to 240 mA.

FIG. 104 is a diagram showing a third simulation result for the circuit example of FIG. 102. FIG. 104 shows the mean value, peak value (peak cut value), and fluctuation value (change in peak value) of the LED current with the horizontal axis as the on-duty ratio, and shows the LED current regardless of the on-duty ratio. The average value is kept constant. In addition, the fluctuation range is small, and it can be seen that the LED current maintains a rectangular wave.

FIG. 105 is a diagram showing a second simulation result for the circuit example of FIG. 102. FIG. 105 shows the fluctuation range by the ripple rate, and although some fluctuations are observed, these include high frequency ripples.

FIG. 106 is a diagram showing a third simulation result for the circuit example of FIG. 102. FIG. 106 shows the circuit loss generated in the current suppression circuit 73 with the horizontal axis as the on-duty ratio. It can be seen that the loss is kept low regardless of the on-duty ratio.

According to the illumination optical communication device of the 16th embodiment shown in FIG. 102, when optical communication is performed intermittently with the switch SW, the average value of the LED current is kept constant regardless of the on-duty ratio of the switch SW. Since it can be maintained, it is possible to prevent changes in brightness and flicker as lighting during communication. Further, since the current suppression circuit 73 is connected, the LED current waveform maintains a rectangular wave, and overshoot, which causes a malfunction on the receiving side, is also suppressed. Further, since the applied voltage of the current suppression circuit 73 is controlled to a desired average value by the constant voltage feedback circuit 67a, it is possible to reduce the circuit loss in the current suppression circuit 73.

(Embodiment 17)
The illumination optical communication device of the 17th embodiment will be described with reference to FIG. 103. Here, the figure is matched with the symbols of the circuit parts common to those in FIG. 99, and the added / changed circuit parts will be mainly described. In the 17th embodiment, a specific configuration for varying the value of the second reference value according to the on-duty ratio described in the 15th embodiment will be described.

FIG. 103 shows a resistor 66 for newly detecting the LED current and a constant current feedback circuit 167 as a method of varying the reference source 76 of the second current suppression circuit 73b in the fifteenth embodiment (FIGS. 99A and 99C). , Level shifter 78 is added to form a feedback system. The constant current feedback circuit 167 is connected to the negative input terminal of the error amplifier 169 via the input resistor 168, and the constant voltage source 72c is connected to the positive terminal of the error amplifier 169. Further, a gain adjusting resistor 71r and a phase compensation capacitor 170 are connected between the output terminal of the error amplifier 169 and the negative input terminal of the error amplifier 169.

The constant current feedback circuit 167 controls the voltage of the positive input terminal of the error amplifier 77 of the second current suppression circuit 73b so that the voltage drop of the LED current detection resistor 66 and the value of the constant voltage source 72c match. The level shifter 78 is required when the operation reference point of the second current suppression circuit 73b and the operation reference point of the constant current feedback circuit 167 are different.

107 to 109 show simulation results for verifying the operation of the 17th embodiment (FIG. 103). The main setting conditions for the simulation are a capacitance value of the smoothing capacitor 65 of 20 uF, a modulation signal frequency from the signal generation circuit SG of 2.4 kHz, an operating frequency of the DC-DC converter 64 of 65 kHz, and a load when the switch SW is not interrupted. The average value of the current (LED current) is set to 240 mA.

FIG. 107 is a diagram showing a first simulation result for the circuit example of FIG. 103. FIG. 107 shows the mean value, peak value (peak cut value), and fluctuation value (change in peak value) of the LED current with the horizontal axis as the on-duty ratio, and shows the LED current regardless of the on-duty ratio. The average value is kept constant. In addition, the fluctuation range is small, and it can be seen that the LED current maintains a rectangular wave.

FIG. 108 is a diagram showing a second simulation result for the circuit example of FIG. 103. FIG. 108 shows the fluctuation range by the ripple rate, and although some fluctuations are observed, these include high frequency ripples.

FIG. 109 is a diagram showing a third simulation result for the circuit example of FIG. 103. FIG. 109 shows the circuit loss generated in the first current suppression circuit 73a and the second current suppression circuit 73b with the horizontal axis as the on-duty ratio. It can be seen that the loss is kept low regardless of the on-duty ratio.

According to the 17th embodiment shown in FIG. 103, when optical communication is performed intermittently with the switch SW, the average value of the LED current can be maintained constant regardless of the on-duty ratio of the switch SW. Therefore, it is possible to prevent changes in brightness and flicker as lighting during communication. Further, since the first current suppression circuit 73a and the second current suppression circuit 73b are connected, the LED current waveform maintains a square wave, and overshoot, which causes a malfunction on the receiving side, is also suppressed. Further, the voltage applied to the first current suppression circuit 73a and the second current suppression circuit 73b is controlled to a desired average value by the constant voltage feedback circuit 67a, so that the first current suppression circuit 73a and the second current suppression circuit 73a and the second current suppression are suppressed. It is also possible to reduce the circuit loss in the circuit 73b.

In addition, if the circuit portion of the second current suppression circuit 73b, the constant current feedback circuit 167, the level shifter 78, and the switch SW in FIG. 103 is a communication module to be retrofitted to the existing LED lighting fixture, the illumination optical communication function can be easily added. It has the features that can be done. The communication module may be a circuit portion of the second current suppression circuit 73b, the constant current feedback circuit 167, and the level shifter 78 of FIG. 103, which does not include the switch SW.

(Embodiment 18)
The illumination optical communication device according to the eighteenth embodiment is shown in FIGS. 110 and 111. The basic main circuit configuration of these figures is the same as that of FIGS. 93A and 99A, and the same symbols are added. 110 and 111 are different from FIGS. 93A and 99A in that the control circuit 6 has a specific configuration example and the signal generation circuit SG has a specific configuration example as a block diagram. Hereinafter, the differences will be mainly described.

The control circuit 6 and the signal generation circuit SG in FIGS. 110 and 111 are the same as the control circuit 6 and the signal generation circuit SG in FIG. 83, and are as described above.

Here, a circuit example of the reference source 76 for switching the reference value or the second reference value is shown in FIGS. 112A and 112B.

FIG. 112A is a circuit diagram showing a current suppression circuit including a first modification of the reference source 76 in the eighteenth embodiment. The current suppression circuit 73 shown in FIG. 112A includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 76, and a control circuit 6. The reference source 76 includes a constant voltage source 4a, voltage dividing resistors R1, R6, R7, R8, and switch elements S01 to S03 for switching the voltage dividing ratio.

The control circuit 6 switches the switch elements S01 to S03 by calculating an appropriate reference voltage value according to the signal arrangement of the communication signal or selecting an appropriate reference voltage value from a pre-constructed correspondence table. You may. The larger the number of resistors and switch elements in the voltage divider circuit, the finer the reference voltage can be switched.

Further, FIG. 112B is a circuit diagram showing a current suppression circuit including a second modification of the reference source 76 in the eighteenth embodiment. The current suppression circuit 73 of FIG. 112B includes a transistor 2 which is a MOSFET, a resistor 3 connected to a source, a reference source 76, and a control circuit 6. The reference source 76 includes a constant voltage source 4a, voltage dividing resistors R11, R12, R13, R14, and switch elements S01 and S02 for switching the voltage dividing ratio.

The positive potential side of the constant voltage source 4a is connected to the positive input terminal of the error amplifier 5 via the resistor R11. A series circuit of resistors R12, R13, and R14 is provided between the connection point and the negative potential side of the constant voltage source 4a, and switch elements S01 and S02 that short-circuit one or two of these are connected. It is composed.

The larger the number of resistors and changeover switches in the voltage dividing circuit in FIGS. 112A and 112B, the finer the reference voltage can be changed.

The operation example of the control circuit 6 shown in FIGS. 110 and 111 has already been described with reference to the flowchart shown in FIG. 84A, the explanatory diagram of the shift register 6a shown in FIG. 84B, and the flowchart of the correction example shown in FIG. 84C. That's right.

As described above, according to the eighteenth embodiment, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned from off to on is reduced, thereby causing a reception error in the receiving device. Can be reduced. Moreover, since the partial on-duty ratio is calculated using the shift register and the reference value is determined according to the calculated partial on-duty ratio, the reference value is set to an appropriate value more dynamically. be able to.

As described above, the illumination light communication device according to the 14th to 18th embodiments is connected to a light source that emits illumination light, a switch SW that is connected in series with the light source and interrupts the current flowing through the light source, and modulates the illumination light. The signal generation circuit SG that generates a binary communication signal that controls the on / off of the switch SW is connected in series with the light source and the switch SW, and does not exceed the current set value corresponding to the reference value. As described above, the current suppression circuit 73 that suppresses the current flowing through the light source, the DC-DC converter 64 that applies a DC voltage to the light source, the switch, and the current suppression circuit connected in series, and the current suppression circuit are applied. A constant voltage feedback circuit 67a that controls the DC power supply circuit so that the average value of the voltage becomes constant is provided.

According to this, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Moreover, the overshoot generated in the current flowing through the light source (that is, the load circuit 53) at the moment when the switch SW is turned on can be reduced, thereby reducing the reception error in the receiving device.

Here, the current suppression circuit 73 includes a reference source 76 that outputs the reference value, and a transistor 74 that is connected in series with the light source and the switch SW and suppresses the current flowing through the light source based on the reference value. , The partial on-duty ratio of the communication signal is measured, and when the partial on-duty ratio is the first ratio, the reference value is set to the first value, and the partial on-duty ratio is the first. A control circuit 6 for setting the reference value to a second value smaller than the first value when the second ratio is larger than the ratio of 1 is provided, and the current set value corresponding to the second value is the above. It may be smaller than the current set value corresponding to the first value.

According to this, when the magnitude of the overshoot depends on the partial on-duty ratio, the suppression of the overshoot can be made appropriate.

Here, the control circuit 6 may change the reference value so that the current set value is inversely proportional to the partial on-duty ratio.

Here, the control circuit 6 may change the reference value so as to satisfy the following equation.

I1 = (Iave / ONd) x 100

Here, I1 is the current set value, Iave is the average current flowing through the light source when the illumination light is not modulated by the interruption of the switch, and ONd is the partial on-duty ratio of the communication signal. The unit is%).

According to this, the brightness of the illumination light when the overshoot is suppressed and the illumination light is not modulated is almost the same as the brightness of the illumination light when the illumination light is modulated. Can be.

Here, the control circuit 6 has a detection unit 168 that detects the magnitude of the current flowing through the light source, and the magnitude of the current detected by the detection unit so as to keep the average value of the currents flowing through the light source constant. A constant current feedback circuit 167 that performs feedback control for changing the reference value may be provided accordingly.

Further, the illumination light communication device according to the 14th to 18th embodiments modulates the illumination light, the light source 53 that emits the illumination light, the switch SW that is connected in series with the light source and interrupts the current flowing through the light source, and the illumination light. Therefore, the signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch is connected in series with the light source and the switch, and exceeds the first current set value corresponding to the first reference value. The first current suppression circuit 73 that suppresses the current flowing through itself is connected in parallel with the first current suppression circuit so as not to exceed the second current set value corresponding to the second reference value. The output voltage of the DC power supply circuit is constant, the second current suppression circuit 73b that suppresses the current flowing through the DC-DC converter 64 that applies a DC voltage to the light source, switch, and first current suppression circuit that are connected in series. A constant voltage feedback circuit 67a that controls the DC power supply circuit is provided.

According to this, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Moreover, the current flowing through the switch is suppressed by the first current suppression circuit and the second current suppression circuit so as not to exceed the sum of the first current set value and the second current set value. By fixing the first current set value and making the second current set value variable, the circuit operation system can be improved, the overshoot caused by the LED current can be reduced, and the malfunction of the receiving device can be reduced. Can be done.

Here, the second current suppression circuit may change the second reference value so as to satisfy the following equation.

I2 = (Iave / ONd) x 100

Here, I2 is the second current set value, Iave is the average current flowing through the light source when the illumination light is not modulated by the interruption of the switch, and ONd is the partial on-duty of the communication signal. The ratio (unit is%).

Here, the second current suppression circuit has a detection unit that detects the magnitude of the current flowing through the light source and a current detected by the detection unit so as to keep the average value of the currents flowing through the light source constant. A constant current feedback circuit 167 that performs feedback control that changes the reference value according to the size may be provided.

Here, the control circuit 6 has a shift register 6a that holds the head n (n is an integer of 2 or more) bit data of the communication signal while shifting, and data of a predetermined number of bits from the end of the shift register 6a. The moving average value is calculated as a partial on-duty ratio, the moving average value is corrected based on the bit pattern of the n-bit data held in the shift register, and the reference corresponding to the corrected value. The value may be determined.

Here, the second current suppression circuit includes a control circuit 6 having a shift register 6a that shifts and holds the head n (n is an integer of 2 or more) bit data of the communication signal. The moving average value is calculated as a partial on-duty ratio with respect to the data of a predetermined number of bits from the end of the shift register 6a, and the moving average is calculated based on the bit pattern of the n-bit data held in the shift register. The value may be corrected and a reference value corresponding to the corrected value may be determined.

Here, in the correction of the moving average value, the control circuit 6 sets the moving average value to 1 when the first bit from the end of the shift register is 1 and the second and subsequent bits are 0. Smaller coefficients may be raised to the power of the same number of consecutive 0 bits.

Here, in the correction of the moving average value, the control circuit performs the moving average when the first bit from the beginning of the n-bit data is 1 and the second bit or the third and subsequent bits are 1. The value may be multiplied by a coefficient greater than 1 by the same number as the number of consecutive 1 bits.

Here, the control circuit, as a partial on-duty ratio, instead of calculating the moving average value, N (N is an integer of 2 or more) value pulse position-modulated average on of the communication signal. -The duty ratio (1- (1 / N)) x 100 (%) may be used.

Here, the communication signal is N-value pulse position-modulated, and the number of bits of the shift register and the number of bits of the moving average may be at least N bits.

Here, the reference source includes a constant voltage source that generates a fixed voltage, a plurality of resistance elements that divide the constant voltage source, and one or more changeover switches connected in series or in parallel with the resistance elements. The control circuit may control the on and off of the one or more changeover switches according to the corrected value.

Here, the second current suppression circuit may be configured to be detachably attached to the illumination optical communication device.

The communication module according to the 14th to 18th embodiments is a communication module 10 that modulates the illumination light and can be attached to and detached from the illumination device, and is a switch SW connected in series with the light source of the illumination device and the illumination. A signal generation circuit SG that generates a binary communication signal that controls the on and off of the switch to modulate the light, and a current suppression that is connected in series with the light source and the switch to suppress the current flowing through the light source. A circuit 73 and first, second and third terminals T1 to T3 for being attached to and detached from the lighting device are provided, and the first terminal T1 is a switch side of a series circuit including the switch and the current suppression circuit. The second terminal T2 is connected to a connection point between the switch and the current suppression circuit in the series circuit, and the third terminal T3 is on the current suppression circuit side of the series circuit. Connected to the other end.

According to this, the communication module can be added to the existing luminaire. That is, the existing lighting equipment can be used as it is, and the optical communication function can be easily added, and the optical communication function can be realized at a lower cost than when a new optical communication lighting equipment is installed. Further, even when 100% modulated optical communication is performed using a constant voltage feedback type power supply, it is possible to suppress a decrease in brightness due to intermittent switching. Moreover, since the overshoot generated in the current flowing through the light source at the moment when the switch is turned on is reduced, the reception error in the receiving device can be reduced.

(Embodiment 19)
In general, when trying to realize visible light communication in a lighting device that adjusts dimming by PWM (pulse width modulation), the color balance may be lost due to the mixture of PWM control and modulation for visible light communication. is there.

Therefore, in the nineteenth embodiment, an illumination optical communication device capable of suppressing the loss of color balance will be described.

The illumination optical communication device according to one aspect of the present embodiment includes a plurality of illumination units that emit light of different colors, a dimming control unit that controls the dimming level of each of the plurality of illumination units, and the plurality of illumination units. Each of the plurality of illumination units emits the light, including a modulation control unit that superimposes a signal on the light emitted by the plurality of illumination units by modulation that temporally switches between light emission and non-emission of each of the illumination units. A light source, a switch connected in series with the light source and interrupting the current flowing through the light source, and a power supply circuit for supplying power to the light source are provided, and the dimming control unit is provided for each of the plurality of illumination units. On the other hand, by controlling the power supply circuit, when the dimming level is higher than the reference level, amplitude dimming for controlling the intensity of the light emitted by the lighting unit is performed, and the dimming level is higher than the reference level. If it is low and the modulation is not performed, PWM dimming is performed to control the on-duty, which is the ratio of the light emission time in the repeating cycle of light emission and non-light emission of the illumination unit, and the modulation control unit performs the modulation. When the dimming level is higher than the reference level, modulation is performed by controlling the switch, and when the dimming level is lower than the reference level, ( 1) The PWM dimming by the power supply circuit is not performed, and (2) By controlling the switch, the modulation and the PWM dimming are performed at the same time, and the light emission start timing is synchronized with other lighting units. The first control for performing modulation is performed so as to be performed.

Further, the receiving device according to one aspect of the present embodiment includes a light receiving unit that receives a plurality of lights of different colors, in which signals are superimposed by modulation that switches between light emission and non-light emission in a timely manner, and (1) the above. When the ratio of the brightness of each of the plurality of lights received by the light receiving unit to each of the brightnesses of the other lights is larger than a predetermined value, the signals are demodulated using the plurality of lights. (2) When one of the plurality of the ratios is smaller than the predetermined value, the signal is demodulated by using light other than the light whose ratio is smaller than the predetermined value among the plurality of lights. It is equipped with a demodulation unit.

According to the illumination optical communication device and the receiving device according to the present embodiment, it is possible to suppress the color balance from being lost.

[19.1 Configuration of Illuminated Optical Communication Device]
First, the configuration of the illumination optical communication device according to the nineteenth embodiment will be described. FIG. 113 is a block diagram showing the configuration of the illumination optical communication device 100 according to the nineteenth embodiment.

The illumination light communication device 100 shown in FIG. 113 functions as a visible light communication transmitter that transmits a signal by modulating the intensity of the illumination light. Further, the illumination optical communication device 100 is, for example, an RGB floodlight that projects color light. The illumination optical communication device 100 includes illumination units 201R, 201G and 201B, a dimming control unit 202, and a modulation control unit 203.

The illumination unit 201R emits red light, the illumination unit 201G emits green light, and the illumination unit 201B emits blue light.

The dimming control unit 202 controls the dimming level (brightness) of each of the illumination units 201R, 201G and 201B. Specifically, the dimming control unit 202 controls the dimming levels of the illumination units 201R, 201G, and 201B according to the hue and brightness of the projected light, and the dimming signals S1R, S2R, and so on. Generate S3R.

The modulation control unit 203 superimposes a communication signal (visible light signal) on the light emitted by the illumination units 201R, 201G and 201B by modulation that temporally switches between light emission and non-emission of the illumination units 201R, 201G and 201B. Specifically, the modulation control unit 203 generates binary modulation signals S2R, S2G and S2B based on the communication signal transmitted by visible light communication. The modulation signal generation unit 123 may repeatedly generate the modulation signals S2R, S2G and S2B indicating the ID unique to the illumination optical communication device 100, or the modulation signal according to the communication signal input from the external device. S2R, S2G and S2B may be generated.

In the following, the modulation for superimposing the visible light signal (communication signal) on the illumination light is simply referred to as "modulation", and the modulation using PWM for dimming is referred to as "PWM dimming". The details of PWM dimming will be described later.

Further, here, an example in which the illumination optical communication device 100 has an illumination unit of three colors of RGB will be described, but the color emitted by the illumination unit and the number of illumination units are not limited to this, for example, the illumination optical communication device 100. May have lighting units of four or more colors.

[19.2 Configuration of Lighting Unit]
Hereinafter, the configurations of the lighting units 201R, 201G and 201B will be described. Since the configurations of the illumination units 201R, 201G and 201B are the same, only the configuration of the illumination unit 201R will be described below.

FIG. 114 is a diagram showing the configuration of the illumination unit 201R. As shown in FIG. 114, the illumination unit 201R includes a light source 101, a power supply circuit 102, a dimming signal receiving unit 104, a modulation switch 121, a current suppression circuit 122, a control power supply 126, and a drive circuit 128. ..

The light source 101 includes one or more light emitting elements (for example, LEDs) and emits illumination light.

The dimming signal receiving unit 104 receives the dimming signal S1R generated by the dimming control unit 202.

The power supply circuit 102 supplies electric power to the light source 101. The power supply circuit 102 includes a power supply 111, a DC-DC converter 112, a capacitor 113, a detection resistor 114, and a constant current feedback circuit 115.

The power supply 111 outputs a DC voltage to the DC-DC converter 112. The DC-DC converter 112 converts the DC voltage supplied from the power supply 111 into a desired voltage V0, and outputs the voltage V0 to the light source 101. The capacitor 113 is connected between the output terminals of the DC-DC converter 112.

The detection resistor 114 is used to detect the current flowing through the light source 101. The constant current feedback circuit 115 controls the output voltage V0 of the DC-DC converter 112 so that the current flowing through the detection resistor 114, that is, the current flowing through the light source 101 is constant.

Further, the DC-DC converter 112 controls the output voltage V0 based on the dimming signal S1R received by the dimming signal receiving unit 104. Specifically, the DC-DC converter 112 controls on-duty, which is the ratio of the amplitude dimming that controls the intensity of the light emitted by the light source 101 and the light emission time in the repeating cycle of light emission and non-light emission of the light source 101. PWM dimming is performed.

The control power supply 126 generates a power supply voltage of the current suppression circuit 122 or the like from the voltage V0 output from the power supply circuit 102, and supplies the generated power supply voltage to the current suppression circuit 122 or the like. Further, the control power supply 126 includes a PWM detection circuit 127a that detects that PWM dimming is performed based on the voltage V0.

The modulation switch 121 is connected in series with the light source 101 to interrupt the current supplied from the power supply circuit 102 to the light source 101. The modulation switch 121 is, for example, a transistor (for example, MOSFET).

The drive circuit 128 generates a signal to be supplied to the control terminal (gate) of the modulation switch 121 based on the modulation signal S2R generated by the modulation control unit 203.

The current suppression circuit 122 is connected in series with the light source 101 and the modulation switch 121 to suppress the current flowing through the light source 101. Specifically, the current suppression circuit 122 suppresses (clips) the current flowing through the light source 101 so as not to exceed the current set value Is.

The current suppression circuit 122 includes a transistor 131 which is a MOSFET, a current setting circuit 132, an amplifier 133, and a current detection circuit 134 which is a resistor connected to the source of the transistor 131.

The current setting circuit 132 outputs a reference value to the positive input terminal of the amplifier 133. The reference value defines the upper limit of the current flowing through the light source 101 (current set value Is). For example, the reference value is proportional to the current set value. Further, the current setting circuit 132 outputs a variable reference value. The current setting circuit 132 may output a reference value as a fixed value.

The transistor 131 is connected in series with the light source 101 and the modulation switch 121, and suppresses (clips) the current flowing through the light source 101 based on the reference value.

The current detection circuit 134 is a source resistor for detecting the magnitude of the current flowing through the light source 101. The terminal on the transistor 131 side of the current detection circuit 134 is connected to the negative input terminal of the amplifier 133.

The positive input terminal of the amplifier 133 is connected to the current setting circuit 132, and the negative input terminal of the amplifier 133 is connected to the source terminal of the transistor 131. The amplifier 133 amplifies the difference between the reference value output from the current setting circuit 132 and the current value detected by the current detection circuit 134, and outputs the amplified signal to the gate of the transistor 131.

The circuit configuration shown in FIG. 114 is an example, and the illumination unit 201R does not need to include all the components shown in FIG. 114. For example, the illumination unit 201R may not include at least one of the current suppression circuit 122 and the control power supply 126.

Further, the configuration of the power supply circuit 102 is also an example, and the configuration is not limited to this configuration. For example, the power supply circuit 102 may not include the detection resistor 114 and the constant current feedback circuit 115. Further, the DC-DC converter 112 may perform constant current control. For example, the DC-DC converter 112 may perform switching current threshold control. Alternatively, the power supply circuit 102 may perform constant voltage control instead of constant current control. For example, the power supply circuit 102 may include a constant voltage feedback circuit instead of the detection resistor 114 and the constant current feedback circuit 115, or the DC-DC converter 112 may perform constant voltage control.

Further, the configuration of the current suppression circuit 122 is also an example, and is not limited to this as long as the configuration can suppress (clip) the current flowing through the light source 101.

[19.3 Modulation Operation]
Hereinafter, the modulation operation will be described by the illumination optical communication device 100. FIG. 115 is a diagram for explaining the modulation operation by the illumination optical communication device 100. As shown in FIG. 115, the modulation switch 121 is turned on / off according to the modulation signal S2R. The modulation method used here conforms to, for example, the 1-4 PPM transmission method specified in JEITA-CP1223. Specifically, 2-bit data is converted into 4-slot pulses. Of these four slots, three are always high level (on) and one slot is low level (off).

Further, in the example of FIG. 115, the current set value Is is constant.

Here, when modulation for visible light communication is performed, immediately after the modulation switch 121 is turned on, as shown by the dotted line in FIG. 115, the LED current, which is the current flowing through the light source 101, momentarily increases. A shoot occurs. Due to the occurrence of this overshoot, there is a problem that the visible light receiver may not be able to receive the signal correctly.

On the other hand, in the illumination optical communication device 100 according to the nineteenth embodiment, the maximum value of the LED current is limited to the current set value Is by providing the current suppression circuit 122. As a result, the occurrence of overshoot is suppressed as shown in FIG. 115. As a result, reception errors in visible light communication can be reduced.

The constant current feedback circuit 115 shown in FIG. 114 also has a function of making the LED current constant, but the constant current control by the constant current feedback circuit 115 is a control having a relatively large time constant. That is, this constant current control is a control that makes the average current constant in a predetermined period, and it is not possible to suppress an overshoot that occurs momentarily as shown in FIG. 115.

Further, in the nineteenth embodiment, as shown in FIG. 114, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order between the power supply terminal and the GND terminal of the power supply circuit 102. On the other hand, as a connection form of the light source 101, the modulation switch 121, and the current suppression circuit 122, it is conceivable that the light source 101, the current suppression circuit 122, and the modulation switch 121 are connected in this order.

However, in such a connection form, since the current suppression circuit 122 is not connected to the GND terminal of the power supply circuit 102, there is a problem that the operation becomes unstable. Specifically, when the modulation switch 121 is off, the GND of the current suppression circuit 122 is in a floating state, so that the potential fluctuation of the GND becomes large. On the other hand, in the nineteenth embodiment, by using the connection form shown in FIG. 114, the current suppression circuit 122 is always connected to the GND terminal, so that stable operation can be improved regardless of the state of the modulation switch 121.

In the above description, as the modulation method, a 100% modulation method that completely cuts off the LED current during the off period is used, but a method in which the LED current is lower than the on period during the off period may be used.

Further, in FIG. 114, an example in which the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order has been described, but the order in which the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series is this. Not limited to.

[19.4 dimming operation]
Hereinafter, the dimming operation will be described by the illumination optical communication device 100. FIG. 116 is a diagram for explaining a dimming operation by the illumination optical communication device 100.

As shown in FIG. 116, the dimming control unit 202 controls the intensity of the light emitted by the illumination unit 201R when the dimming level is higher than the reference level (dimming levels 5 to 3 in FIG. 116). Dimming. Specifically, the voltage or current output by the power supply circuit 102 is controlled according to the dimming signal S1R, so that the current value of the LED current flowing through the light source 101 is controlled. More specifically, the lower the dimming level, the smaller the LED current value is controlled.

Further, when the dimming level is lower than the reference level (dimming levels 5 to 3 in FIG. 116), the dimming control unit 202 is the ratio of the light emitting time in the repeating cycle of light emission and non-light emission of the illumination unit 201R. PWM dimming to control on-duty. Specifically, the on-duty of the voltage or current output by the power supply circuit 102 is controlled according to the dimming signal S1R. More specifically, the lower the dimming level, the smaller the on-duty is controlled.

[19.5 tasks]
Here, when the modulation operation and the dimming operation are simply combined, the following problems occur when the modulation operation and the dimming operation are not considered to each other. As shown in FIG. 117, when PWM dimming and modulation are performed at the same time, the switch is turned off individually by each control, so that the average brightness is reduced. As a result, when only one color (red light in FIG. 117) is PWM dimmed as shown in FIG. 117, there is a problem that the hue shifts. Further, when the rising edge is detected in the receiving device, there is a problem that the rising edge of the red light is deviated from the rising edge of the other colors in FIG. 117, so that the red light is detected as noise and the reception accuracy is lowered. ..

[19.6 overall operation]
FIG. 118 is a flowchart of operation by the illumination optical communication device 100. The processing shown in FIG. 118 is sequentially performed for each color. Further, it is repeated when the dimming level is changed or at a predetermined time interval.

When modulation is not performed (No in S101), the dimming control unit 202 performs normal dimming control as shown in FIG. 116. Specifically, when the dimming control unit 202 does not perform PMW modulation, that is, when the dimming level is higher than the reference level (No in S102), the dimming control unit 202 performs normal amplitude dimming (S103) and performs PMW modulation. When performing, that is, when the dimming level is lower than the reference level (Yes in S102), normal PWM dimming is performed (S104).

On the other hand, when modulation is performed and PWM dimming is not performed (Yes in S101 and No in S105), the dimming control unit 202 performs amplitude dimming, and the modulation control unit 203 as shown in FIG. 115. Normal modulation is performed (S106). In this case, the modulation signals S2R, S2G and S2B supplied to the illumination units 201R, 201G and 201B are the same signal, and the light emission and non-emission of the illumination units 201R, 201G and 201B are switched at the same timing. ..

Further, the dimming control unit 202 may use the same amplitude dimming method depending on whether modulation is performed or not, or may use different methods. For example, the dimming control unit 202 may perform amplitude dimming so that the average brightness (average value of the LED current) is the same when the modulation is performed and when the modulation is not performed. Specifically, when 4PPM is used, the brightness value is reduced to 75%. Therefore, when modulation is performed, the brightness value (LED current) may be increased so as to offset this decrease. In other words, when the specified dimming level is the same, the current value of the LED current when modulation is performed (current value in the on section) may be higher than the current value of the LED current when modulation is not performed.

On the other hand, when modulation is performed and PWM dimming is performed (Yes in S101 and Yes in S105), in the illumination optical communication device 100, the dimming level of the target color is the dimming level of all other colors. It is determined whether it is sufficiently lower (S107). Specifically, the illumination optical communication device 100 calculates the ratio of the dimming level of the target color (for example, red) to each of the dimming levels (green and blue) of other colors. When all the calculated ratios are lower than the predetermined values, the illumination optical communication device 100 determines that the dimming level of the target color is sufficiently lower than the dimming level of all the other colors. The illumination optical communication device 100 calculates the difference between the dimming level of the target color (for example, red) and the dimming level of other colors (green and blue), and all the calculated differences are predetermined. If it is larger than the value, it may be determined that the dimming level of the target color is sufficiently lower than the dimming level of all other colors.

When the above conditions are not satisfied, that is, when at least one of the calculated ratios is higher than a predetermined value (No in S107), the dimming control unit 202 does not perform PWM dimming, and the modulation control unit 203 performs PWM dimming. (S108). The details of this process will be described later.

When the above conditions are satisfied, that is, when all the calculated ratios are lower than the predetermined values (Yes in S107), the modulation control unit 203 does not perform modulation, and the dimming control unit 202 performs modulation on-duty. The PWM dimming in consideration is performed (S109). The details of this process will be described later.

[19.7 first operation example]
Hereinafter, the details of the first operation example (S108 in FIG. 118) in which the dimming control unit 202 does not perform PWM dimming and the modulation control unit 203 performs modulation in consideration of PWM will be described. FIG. 119 is a diagram for explaining this first operation example.

The example shown in FIG. 119 is an example in which only the dimming level of the illumination unit 201R is lower than the reference level. The relative intensity (R) of red light is 0.1, the relative intensity (G) of green light is 1.0, and the relative intensity (B) of blue light is 0.2. Here, the relative intensity is the ratio of the signal intensity of each signal to the highest signal intensity when the highest signal intensity among the signal intensities of light of a plurality of colors is 1.0.

As shown in FIG. 119, the modulation control unit 203 controls the illumination unit 201R so that the light emission start timing of the illumination unit 201R is the same as the light emission start timing of the illumination units 201G and 201B. In other words, the modulation control unit 203 sets the modulation (S106 in FIG. 118) and the light emission start timing when the modulation is performed, the dimming level is lower than the reference level, and the dimming level is higher than the reference level. The illumination unit 201R is controlled so that they are the same.

Further, the modulation control unit 203 sets the on-duty in consideration of PWM dimming. Specifically, on-duty when modulation is performed and the dimming level is higher than the reference level (S106 in FIG. 118), and PWM performed when modulation is not performed and the dimming level is lower than the reference level. When dimming is performed (S104 in FIG. 118), dimming is performed so that the product with the on-duty and the on-duty are equal. For example, when modulation by 4PPM is performed, the on-duty when modulation is performed is 75%. Therefore, when the on-duty when PWM dimming is performed is 50%, the modulation control unit 203 performs modulation so that the on-duty becomes 32.25%.

Here, when the on-duty becomes equal to or higher than a predetermined threshold value (for example, 75%), the off section (dark section) is too small, and the receiving device may not be able to receive the signal correctly. Therefore, in the nineteenth embodiment, the on-duty is controlled so as not to exceed a predetermined threshold value. That is, in such a case, the adjustment is performed by amplitude dimming instead of changing the on-duty.

As described above, in the illumination optical communication device 100 according to the nineteenth embodiment, the dimming levels of the plurality of illumination units 201R, 201G and 201B and the plurality of illumination units 201R, 201G and 201B, respectively, which emit light of different colors. A signal is superimposed on the light emitted by the plurality of illumination units 201R, 201G and 201B by the dimming control unit 202 that controls the light emission and the modulation that temporally switches the light emission and non-emission of each of the plurality of illumination units 201R, 201G and 201B. It includes a modulation control unit 203. Each of the plurality of illumination units 201R, 201G, and 201B is connected to a light source 101 that emits light in series, a modulation switch 121 that interrupts the current flowing through the light source 101, and a power supply circuit that supplies electric power to the light source 101. It includes 102. The dimming control unit 202 controls the power supply circuit 102 for each of the plurality of lighting units 201R, 201G, and 201B to determine the intensity of light emitted by the lighting unit when the dimming level is higher than the reference level. When controlled amplitude dimming is performed (S103 and S106 in FIG. 118) and the dimming level is lower than the reference level and no modulation is performed, the ratio of the light emission time in the repeating cycle of light emission and non-light emission of the illumination unit is used. PWM dimming is performed to control a certain on-duty (S104 in FIG. 118). When modulation is performed, the modulation control unit 203 controls the modulation switch 121 when the dimming level is higher than the reference level for each of the plurality of illumination units 201R, 201G and 201B (S106 in FIG. 118). When modulation is performed and the dimming level is lower than the reference level, (1) PWM dimming by the power supply circuit 102 is not performed (the PWM modulation function is stopped), and (2) modulation is performed by controlling the modulation switch 121. The first control (first operation) in which PWM dimming is performed at the same time and modulation is performed so that the light emission start timing is synchronized with the other lighting unit (so that the rising edge of the modulation signal is synchronized with the other lighting unit). Example) (S108 in FIG. 118).

As a result, the illumination optical communication device 100 can suppress the phase shift (rising timing, etc.) of the signals of each color when PWM dimming and modulation are performed at the same time, and is on-duty with PWM dimming added. Modulation can be performed. As a result, it is possible to prevent the color balance from being lost.

Further, when PWM dimming and modulation are performed at the same time, all the controls can be performed by the modulation control unit 203, so that it is possible to suppress the processing from becoming complicated.

[19.8 Second operation example]
Hereinafter, the details of the second operation example (S109 in FIG. 118) in which the modulation control unit 203 does not perform modulation and the dimming control unit 202 performs PWM dimming in consideration of the on-duty of modulation will be described. FIG. 120 is a diagram for explaining this second operation example.

The example shown in FIG. 120 is an example in which only the dimming level of the illumination unit 201R is lower than the reference level. Further, the relative intensity (R) of red light is 0.1, the relative intensity (G) of green light is 1.0, and the relative intensity (B) of blue light is 1.0. That is, the dimming level of red light is sufficiently lower than the dimming level of all other colors.

As shown in FIG. 120, no modulation is performed and only PWM dimming is performed. Further, as PWM dimming, control is performed in consideration of on-duty at the time of modulation. Specifically, the dimming control unit 202 is on-duty when modulation is performed and the dimming level is higher than the reference level (S106 in FIG. 118), and the dimming control unit 202 is not modulated and the dimming level is the reference level. PWM dimming is performed on the illumination unit 201R so that the product of the on-duty and the on-duty when the PWM dimming performed in the lower case is performed (S104 in FIG. 118) and the on-duty are equal.

For example, when modulation by 4PPM is performed, the on-duty when modulation is performed is 75%. Therefore, when the on-duty when PWM dimming is performed is 50%, the dimming control unit 202 performs modulation so that the on-duty becomes 32.25%.

Further, unlike the first operation example, in the second operation example, the rise of the red light does not coincide with the rise of the light of another color.

In this case, when modulation is performed using light of all colors in the receiving device, the red light is recognized as noise and the receiving accuracy is lowered. On the other hand, when the intensity of only one color is low, it is easy for the receiving device to discriminate the color having the low intensity. Therefore, since the receiving device can demodulate the signal only from the signals of other colors without using the signal of the color having low intensity, it is possible to suppress the deterioration of the receiving accuracy in the receiving device.

Further, as a method of realizing the function of the illumination optical communication device 100, there is a method of attaching a communication module for realizing the expansion of the visible light communication function to the illumination device that does not support visible light communication. For example, a lighting device that does not support visible light communication includes a light source 101 and a power supply circuit 102 shown in FIG. 114. Further, when the communication module is not attached to the lighting device, the cathode of the light source 101 and the GND terminal of the power supply circuit 102 are short-circuited.

Further, the communication module includes a modulation switch 121, a current suppression circuit 122, a control power supply 126, a drive circuit 128 and the like shown in FIG. 114, and a dimming control unit 202 and a modulation control unit 203 and the like shown in FIG. 113. The lighting device has a normal dimming control function. Therefore, the communication module may include all the functions of the dimming control unit 202 to replace the dimming control function of the lighting device, or the function of the dimming control unit 202 extended in the nineteenth embodiment. Only included in the communication module, the extended function may be added to the dimming control function of the luminaire. Specifically, the expanded functions include a function for controlling not to perform PWM dimming in step S108, a function for controlling to perform PWM dimming in consideration of modulation on-duty in step S109, and the like. Is.

Here, when such a retrofitted communication module is used, as shown in FIG. 114, a control power supply 126 that generates a power supply for the communication module from the output voltage V0 of the power supply circuit 102 is used. However, when PWM control is performed, the voltage V0 fluctuates, so that it becomes difficult for the control power supply 126 to stably generate a power supply for the communication module. Therefore, by controlling so that modulation is not performed when PWM dimming is performed as in the second operation example, the operation of the communication module can be stopped when PWM dimming is performed. Because it can be done, stable operation can be realized.

For example, when the PWM detection circuit 127a shown in FIG. 114 detects the PWM control of the power supply circuit 102, the function (modulation function) of the communication module can be stopped.

In this way, when modulation is performed, the dimming level is lower than the reference level, and the ratio of the dimming level of the target lighting unit to each of the dimming levels of the other lighting units is predetermined. When it is larger than the value (No in S107 of FIG. 118), the modulation control unit 203 performs the first control (first operation example) on the target illumination unit (S108).

When modulation is performed and the dimming level is lower than the reference level and the above ratio is smaller than a predetermined value (Yes in S107), the dimming control unit 202 controls the power supply circuit 102. As a result, the first on-duty when the modulation is performed and the dimming level is higher than the reference level, and the PWM dimming which is performed when the modulation is not performed and the dimming level is lower than the reference level are performed. In this case, PWM dimming having the same on-duty as the product of the second on-duty is performed on the target illumination unit, and the modulation control unit 203 performs a second control in which the target illumination unit is not modulated by the modulation switch 121. (Second operation example) is performed (S109).

As a result, the illumination optical communication device 100 can perform PWM control on duty in consideration of modulation when PWM dimming and modulation are performed at the same time. As a result, it is possible to prevent the color balance from being lost.

Further, when PWM dimming and modulation are performed at the same time, all the controls can be performed by the dimming control unit 202, so that it is possible to suppress the processing from becoming complicated.

Further, when the PWM control is performed, the modulation operation can be stopped, so that stable operation can be realized, for example, when a retrofitted communication module is used.

[19.9 modified example]
In the above description, an example in which the illumination optical communication device 100 selectively performs the first operation example and the second operation example has been described, but the illumination optical communication device 100 has the first operation example and the second operation example. It may have a function of performing only one of the operation examples. That is, when the illumination optical communication device 100 is modulated and PWM dimming is performed (Yes in S105 of FIG. 118), the first operation example (S108) and the second operation example (S109) You may always do one.

[19.10 Receiver]
Hereinafter, a receiving device that receives a visible light signal transmitted by the above-mentioned illumination optical communication device 100 will be described. FIG. 121 is a block diagram of the receiving device 300 according to the nineteenth embodiment. As shown in FIG. 121, the receiving device 300 includes a light receiving unit 301 and a demodulating unit 302.

The light receiving unit 301 receives the illumination light emitted by the illumination light communication device 100. Further, the light receiving unit 301 includes a red light receiving element that receives red light, a green light receiving element that receives green light, and a blue light receiving element that receives blue light, and a light receiving signal based on the light received by each light receiving element. Generate S3R, S3G and S3B.

The demodulation unit 302 demodulates the signals superimposed on the illumination light from the received light signals S3R, S3G, and S3B.

FIG. 122 is a flowchart showing the operation of the receiving device 300. First, the demodulation unit 302 determines whether the strength of one of the received light signals S3R, S3G, and S3B is sufficiently lower than the strength of the other two signals (S201). Specifically, the demodulation unit 302 calculates the ratio of the signal strength of the received signal of the target color to each of the signal strengths of the received signals of other colors. The demodulation unit 302 determines that the signal strength of the target color is sufficiently lower than the signal strength of all the other colors when all the calculated ratios are lower than the predetermined values. The demodulation unit 302 calculates the difference between the signal strength of the target color and the signal strength of each of the other colors, and when all the calculated differences are larger than a predetermined value, the signal of the target color. It may be determined that the intensity is sufficiently lower than the signal intensity of all other colors.

When the above conditions are not satisfied, that is, when at least one of the calculated ratios is higher than a predetermined value (No in S201), the demodulation unit 302 is visible using all of the received light signals S3R, S3G, and S3B. Demodulate the optical signal (S202). That is, the demodulation unit 302 performs a normal demodulation process.

On the other hand, when the above conditions are satisfied, that is, when all the calculated ratios are lower than the predetermined values (No in S201), the demodulation unit 302 has sufficient signal strength among the received light signals S3R, S3G and S3B. The visible light signal is demodulated using a light receiving signal other than the light receiving signal of the color determined to be low (S203). For example, when the signal strength of the received light signal S3R is low, the demodulation unit 302 demodulates the visible light signal from the received light signals S3G and S3B.

By the above operation, the receiving device 300 can stably demodulate the visible light signal from the illumination light emitted by the second operation in the above-mentioned illumination light communication device 100.

In the above description, the light receiving unit 301 includes a plurality of light receiving elements that receive light of each color, but the light receiving unit 301 may include a single light receiving element that receives light including all colors. .. In this case, the demodulation unit 302 may remove a signal component having a strength lower than the threshold value from the signal obtained by the light receiving unit 301, and perform demodulation processing using the signal obtained thereby. In this case as well, the demodulation unit 302 may perform the demodulation process using only the modulated signal with high signal strength without using the unmodulated signal with low signal strength. it can.

As described above, the receiving device 300 according to the nineteenth embodiment has a light receiving unit 301 that receives a plurality of lights of different colors, in which signals are superimposed by modulation that switches between light emission and non-light emission in a timely manner, and (1). When the ratio of each brightness of the plurality of lights received by the light receiving unit 301 to each of the brightnesses of the other lights is larger than a predetermined value, the signal is demodulated using the plurality of lights, and (2). ) When one of the plurality of ratios is smaller than a predetermined value, the demodulation unit 302 is provided to demodulate the signal by using light other than the light whose ratio is smaller than the predetermined value among the plurality of lights.

As a result, the receiving device 300 excludes unmodulated low-intensity color light from the illumination light emitted by the second operation of the illumination light communication device 100 described above, and obtains a visible light signal from the remaining light. Can be demodulated. Therefore, the receiving device 300 can stably demodulate the visible light signal.

[19.11 Example of use of illumination optical communication device]
Hereinafter, an example of using the illumination optical communication device 100 will be described. There are an example of using the illumination optical communication device 100 as the RGB floodlight shown in FIGS. 77 and 78, an example of using the illumination light communication device as the RGB spotlight shown in FIG. 79, and the like.

(Embodiment 20)
In this embodiment, a modified example of the above-described 10th embodiment will be described.

In visible light communication, the amount of change in the required illumination light differs depending on the installation of the illumination light communication device. For example, when the illumination light communication device is installed outdoors during the daytime, the reception device may not be able to correctly detect the illumination light emitted from the illumination light communication device because the surroundings are bright. In the present embodiment, an illumination optical communication device capable of reducing reception errors in visible light communication due to the influence of ambient light and suppressing an increase in power consumption will be described.

First, the configuration of the illumination optical communication device according to the present embodiment will be described. FIG. 123 is a block diagram showing the configuration of the illumination optical communication device 100B according to the present embodiment. The illumination optical communication device 100B shown in FIG. 123 is different from the illumination optical communication device 100 shown in FIG. 65 in that the communication module 103B is provided instead of the communication module 103. The communication module 103B is different from the communication module 103 of FIG. 65 in that it further includes a mode switching unit 171 and an illuminance sensor 172. Further, functions have been added to the external synchronization signal input unit 124 and the control unit 125.

The illumination optical communication device 100B is, for example, a signboard illumination device used for route guidance and the like.

The illuminance sensor 172 detects the illuminance (brightness) around the illumination optical communication device 100B.

The mode switching unit 171 selects one of the normal mode (first operation mode) and the outdoor mode (second operation mode) based on the detection result of the illuminance sensor 172, and a mode switching signal indicating the selected operation mode. Generate S6. This mode switching signal S6 is sent to the control unit 125 via the external synchronization signal input unit 124.

Specifically, when the illuminance around the illumination optical communication device 100B is lower than a predetermined threshold value, the mode switching unit 171 selects the normal mode, and the illuminance around the illumination optical communication device 100B is predetermined. If above the threshold, select outdoor mode. That is, when the illumination optical communication device 100B is installed indoors, the normal mode is selected. Further, when the illumination optical communication device 100B is installed indoors and the surroundings are dark (for example, at night or on a cloudy day), the normal mode is selected. Further, when the illumination optical communication device 100B is installed indoors and the surroundings are bright (for example, during the daytime on a sunny day), the outdoor mode is selected.

The mode switching unit 171 may use the amount of ambient light (light intensity or illuminance) having the same frequency as the modulated illumination light as the ambient illuminance.

The control unit 125 switches the on-duty of the modulation signal S1 and the like according to the operation mode indicated by the mode switching signal S6.

Next, the operation of the illumination optical communication device 100B will be described. FIG. 124 is a diagram showing the operation of the illumination optical communication device 100B in the normal mode and the outdoor mode.

As shown in FIG. 124, the operation in the normal mode is the same as the operation of the tenth embodiment described above.

In the outdoor mode, the control unit 125 lowers the on-duty of the modulation signal S1, that is, the on-duty of the modulation switch 121 from the normal mode, and raises the current command value S2 from the normal mode. For example, when 4PPM is used, the on-duty in the normal mode is 75% and the on-duty in the outdoor mode is 25%.

Here, the modulation method used in the 20th embodiment is, for example, 4PPM, which is a modulation method having a constant on-duty regardless of the logical value of the communication signal.

When the on-duty is changed, the constant current feedback operation in the power supply circuit 102 controls the average current per unit time to be constant. As a result, the current value in the on section in the outdoor mode becomes higher than the current value in the on section in the normal mode. The control unit 125 raises the current set value Is so as to follow the increase in the current value.

When the power supply circuit 102 does not have the constant current control function, the output current or output voltage of the power supply circuit 102 may be controlled based on the instruction from the control unit 125. For example, in the outdoor mode and the normal mode, the product of the on-duty and the current value is controlled to be substantially equal. That is, in the outdoor mode and the normal mode, the product of the on-duty and the current set value Is is controlled to be substantially equal.

As described above, in the outdoor mode, the illuminance of the illumination light is increased by setting the current value in the on section higher than in the normal mode. As a result, the visible light signal can be correctly detected by the receiving device even in the daytime outdoors. Further, in the outdoor mode, the on-duty is set lower than in the normal mode. As a result, an increase in current consumption can be suppressed. Further, since the power supply circuit does not need to support high output, for example, it is possible to easily add a visible light communication function using the communication module 103B attached later.

As described above, the illumination light communication device 100B according to the 20th embodiment is connected to the light source 101 that emits illumination light, the modulation switch 121 that is connected in series with the light source 101 and interrupts the current flowing through the light source 101, and the modulation switch 121. It is provided with a control unit 125 that superimposes a signal on the illumination light by modulating the illumination light by controlling on and off and controls the current value flowing through the light source 101. In the normal mode (first operation mode), the control unit 125 sets the on-duty, which is the ratio of the time during which the modulation switch 121 is turned on in the cycle of turning the modulation switch 121 on and off, to the first ratio. The current value of the current flowing through the light source 101 is set to the first current value while the modulation switch 121 is on, and the on-duty is set to be lower than the first ratio in the outdoor mode (second operation mode). The current value is set to a second current value higher than the first current value.

As a result, the illumination optical communication device 100B can reduce reception errors in visible light communication due to the influence of ambient light, and can suppress an increase in power consumption of the entire illumination optical communication device 100B in the outdoor mode.

Further, the illumination optical communication device 100B further includes an illuminance sensor 172 that detects the illuminance around the illumination optical communication device 100B. The control unit 125 operates in the normal mode when the illuminance detected by the illuminance sensor 172 is lower than a predetermined threshold value, and operates in the outdoor mode when the illuminance detected by the illuminance sensor 172 is higher than the threshold value.

As a result, the illumination optical communication device 100B can select an appropriate operation mode according to the ambient illuminance.

Further, the illumination optical communication device 100B further includes a current suppression circuit 122 which is connected in series with the light source 101 and the modulation switch 121 and suppresses the current flowing through the light source 101 so as not to exceed the current set value Is. The control unit 125 sets the current set value Is higher in the outdoor mode than in the normal mode.

As a result, the illumination optical communication device 100B can appropriately control the current value according to the operation mode.

Further, the communication module 103B according to the 20th embodiment is a communication module 103B that is detachable from the lighting device and modulates the illumination light, and is connected in series with the light source 101 included in the lighting device to transmit the current flowing through the light source 101. It includes an intermittent modulation switch 121 and a control unit 125 that superimposes a signal on the illumination light by modulating the illumination light by controlling the on and off of the modulation switch 121 and controls the current value flowing through the light source 101. .. In the normal mode (first operation mode), the control unit 125 sets the on-duty, which is the ratio of the time during which the modulation switch 121 is turned on in the cycle of turning the modulation switch 121 on and off, to the first ratio. The current value of the current flowing through the light source 101 is set to the first current value while the modulation switch 121 is on, and the on-duty is set to be lower than the first ratio in the outdoor mode (second operation mode). The current value is set to a second current value higher than the first current value.

In the above description, an example in which the mode switching unit 171 switches the operation mode according to the ambient illuminance has been described, but the operation mode is switched according to the time as in the illumination optical communication device 100C shown in FIG. 125. May be good. The illumination optical communication device 100C shown in FIG. 125 is different from the illumination optical communication device 100B shown in FIG. 123 in that the communication module 103C includes a timer 173 for detecting the time instead of the illuminance sensor 172.

The control unit 125 operates in the normal mode when the time detected by the timer 173 is within the predetermined set period, and operates in the outdoor mode when the time detected by the timer 173 is outside the set period. .. For example, the set period is a bright time zone during the day.

As a result, the operation mode can be switched with a simpler configuration than when the illuminance sensor 172 is used.

The above setting period may be set by the user. Further, the operation mode may be switched based on a user's operation or an instruction from an external device. Further, these plurality of controls may be combined. For example, when the user sets indoor and outdoor, the normal mode is always selected when the indoor setting is made, and when the outdoor setting is made, the illuminance sensor 172 or the timer 173 The operation mode may be switched based on the detection result.

In the 20th embodiment, similarly to the 10th embodiment, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order, but the light source 101, the modulation switch 121, and the current are connected in this order. The order of series connection of the suppression circuit 122 is not limited to this.

Hereinafter, a usage example of the illumination optical communication device 100B (100C) will be described. FIG. 126 is a diagram showing a usage example of the illumination optical communication device 100B. For example, as shown in FIG. 126, the illumination optical communication device 100B is a signboard illumination device used for route guidance and the like. When the user photographs the light emitted by the illumination light communication device 100B with a visible light receiver such as a smartphone, the visible light receiver receives the visible light signal.

(Embodiment 21)
In the 21st embodiment, the illumination optical communication device and the communication module that suppress the deterioration of the reception error rate due to the ripple even when the power supply current has ripples will be described.
Further, an illumination optical communication device and a communication module that suppress an increase in power loss due to current suppression of the current suppression circuit even when the power supply current has ripples will be described.

In general, the output current of a power supply circuit often has a ripple frequency that is twice the commercial power frequency. Moreover, the magnitude (fluctuation width) of the ripple is not constant and changes according to the magnitude of the load.

The ripple of the power supply current of the illumination optical communication device appears in the fluctuation of the brightness of the illumination light. There is a problem that fluctuations in brightness can cause reception errors in visible light communication. Further, since the above-mentioned current suppression circuit suppresses the current flowing through the light source so as not to exceed the current set value, there is a problem that the power loss due to the current suppression may increase if there is a ripple in the power supply current.

Therefore, the illumination optical communication device according to the 21st embodiment is, for example, the illumination optical communication device according to the 1st embodiment, which includes a current detection unit that detects a current flowing through the light source, and the current suppression circuit is a current suppression circuit. A reference source that outputs a variable reference value corresponding to the current set value, a transistor that is connected in series with the light source and the switch and suppresses the current flowing through the light source based on the reference value, and the current detector. It is provided with a control circuit that determines the reference value according to the current value detected in the above, and the reference value is determined according to a value determined by the minimum value and the maximum value of the ripple of the current value detected by the current detection unit. Will be done. The value determined by the minimum value and the maximum value may be, for example, a minimum value, a maximum value, an average value, or the like. The reference value is determined so that the current set value is a value determined by the minimum value and the maximum value.

Next, the configuration of the illumination optical communication device according to the 21st embodiment will be described.

FIG. 127 is a block diagram showing a configuration example of the illumination optical communication device according to the present embodiment. The illumination optical communication device shown in FIG. 127 includes a control circuit 6k instead of the control circuit 6 and a signal generation circuit SGa instead of the signal generation circuit SG, as compared with the illumination optical communication device shown in FIG. 1A or FIG. 30A. The point is different. Hereinafter, the differences will be mainly described.

The control circuit 6k determines the reference value according to the current value detected by the current detector. The current detector is, for example, a detection resistor 66. The power supply current is detected by the potential of the terminal on the current suppression circuit 1 side of the detection resistor 66. The control circuit 6k detects the maximum and minimum values of ripple in a certain period of the power supply current from the current value detected by the current detector, and the current set value of the current suppression circuit 1 is determined by the minimum and maximum values ( For example, the reference value is determined so as to be the minimum value.

The signal generation circuit SGa may be equivalent to the signal generation circuit SG in the first operation example to the third operation example described later. Further, in the fourth operation example to the eighth operation example described later, the signal generation circuit SGa further generates a PWM signal having a frequency five times or more that of the communication signal, and superimposes the PWM signal on the OFF period of the communication signal. ..

Hereinafter, operation examples of the first operation example to the eighth operation example in the twenty-first embodiment will be described.

(First operation example)
Next, a first operation example in the 21st embodiment will be described.

FIG. 128 is a waveform diagram showing a first operation example of the illumination optical communication device according to the twenty-first embodiment. The upper part of the figure shows the detected current value detected by the current detector and the control circuit 6k. The detected current value has a ripple frequency that is twice the commercial power frequency, for example. The lower part of the figure shows the LED current (current flowing through the load circuit 53). In this example, the control circuit 6k controls to change the reference value of the reference source 4 according to the minimum value of the ripple current in order to output a variable reference value from the reference source 4. Specifically, the control circuit 6k determines a reference value so that the current set value of the current suppression circuit 1 becomes the minimum ripple value. In the current suppression circuit 1, the current flowing through the light source (load circuit 53 which is an LED) is suppressed so as not to exceed the current set value (here, the minimum ripple value).

According to the first operation example as shown in the lower part of FIG. 128, the fluctuation portion of the LED current shown by the thin solid line and the broken line, that is, the portion exceeding the current set value (here, the minimum ripple value) is suppressed. In this way, the LED current can be shaped into a collection of square waves having the same amplitude over the entire section in which the illumination light is modulated by the communication signal. As a result, even if there is a ripple in the power supply current, it is possible to suppress fluctuations in the illumination light and suppress the occurrence of reception errors in the receiving device.

(Second operation example)
Next, a second operation example according to the 21st embodiment will be described.

FIG. 129A is a waveform diagram showing a second operation example of the illumination optical communication device according to the twenty-first embodiment. The lower part of the figure shows the LED current (current flowing through the load circuit 53). In this example, the control circuit 6k determines the reference value so that the predetermined value is larger than the minimum value of the ripple current and smaller than the maximum value.

According to the second operation example, the portion of the LED current shown by the thin solid line and the broken line, that is, the portion exceeding the current set value (here, a predetermined value) is suppressed. In both FIGS. 128 and 129A, the portion of the LED current shown by the thin solid line and the broken line is suppressed by the current suppression circuit 1 and causes a power loss. FIG. 129A can reduce the power loss due to the suppression of the current suppression circuit 1 as compared with FIG. 128. Further, even if there is a ripple in the power supply current, it is possible to suppress fluctuations in the illumination light and suppress the occurrence of reception errors in the receiving device.

FIG. 129B is a waveform diagram showing a second operation example of the illumination optical communication device according to the twenty-first embodiment. In the figure, the predetermined value of FIG. 129A is specifically used as the average value of the ripple current.

The predetermined value in FIG. 129A is not limited to the average value. In FIG. 129A, the time width of the portion where the LED current becomes a square wave (the portion corresponding to the thin solid line and the broken line) may be equal to or larger than the width including the portion meaningful as the transmission data of the illumination optical communication (for example, the communication ID).

(Third operation example)
FIG. 130 is a waveform diagram showing a third operation example of the illumination optical communication device according to the twenty-first embodiment. The figure shows a detected current value, a current set value or a reference value, and an LED current. The current set value is set to the same value as the detected current value. That is, the control circuit 6k sets the reference value so that the current set value fluctuates in the same cycle as the detected current value.

In the LED current in the figure, although the peak of the square wave fluctuates according to the detected current value, only the overshoot of each square wave (each pulse) is suppressed as shown in the enlarged view in the broken line frame. Therefore, the power loss in the current suppression circuit 1 can be minimized, and the square wave can be formed over the entire section in which the illumination light is modulated by the communication signal, so that it is possible to reduce the occurrence of a reception error in the receiving device.

(Fourth operation example)
FIG. 131 is a waveform diagram showing a fourth operation example of the illumination optical communication device according to the twenty-first embodiment. In the figure, the current set value is the same value that fluctuates in the same cycle as the detected current value, which is the same as the third operation example.

The signal generation circuit SGa generates a PWM signal having a frequency five times or more that of the communication signal, and superimposes the PWM signal on the low level section of the communication signal.

The on section in the figure corresponds to the high level section of the communication signal, and the transistor 2 is in the on state. The off section in the figure corresponds to the low level section of the communication signal, and the PWM signal is superimposed. All the off sections in the figure are not the transistors 2 in the off state but the sections in which high-speed switching is performed by the PWM signal.

In the enlarged view of the broken line portion in the figure, Ion indicates the LED current (here, the same value as the current set value) in the on section. If_max indicates the maximum value of the LED current in the off section. If_ave indicates the average value of the LED current values in the off section, and is represented by (Off_max) × (on-duty ratio of PWM signal). If_min indicates the minimum value (here, 0) of the LED current value in the off section.

The average value If_ave is set to be (immediately preceding Ion)-(minimum ripple value), in other words, (current set value)-(minimum ripple value). That is, the difference between Ion and If_ave is set to be constant for any square wave. As a result, the difference in brightness between the on section and the off section of the communication signal is kept constant.

As described above, the control circuit 6k controls to change the reference value of the reference source 4 so that the current set value becomes the same value as the detected current value, as in the third operation example.

The signal generation circuit SGa generates a PWM signal so that the current average value If_ave = (immediately before Ion)-(minimum ripple value) in the off section in order to make the difference in brightness between the on section and the off section constant. , The PWM signal is superimposed on the off section of the communication signal.

As a result, overshoot can be suppressed from the rectangular wave in the on section of the communication signal, and the power loss in the current suppression circuit 1 can be minimized. Even if the LED current (I_on) increases due to ripple, the increase in power loss in the current suppression circuit 1 is suppressed. Since the difference in brightness between the on section and the off section of the communication signal is constant, it is possible to reduce the occurrence of reception errors in the receiving device.

(Fifth operation example)
FIG. 132 is a waveform diagram showing a fifth operation example of the illumination optical communication device according to the twenty-first embodiment. The fifth operation example shown in the figure is different from the fourth operation example in that when the LED current (or current set value) is equal to or less than the threshold value, the modulation depth due to the communication signal is suppressed. The differences will be mainly described below. The modulation depth is referred to here as Ion-Off_ave, or the difference in brightness between the on-section and the off-section of the illumination light.

The signal generation circuit SGa changes the modulation depth between the section A and the section B in the figure, in other words, suppresses the modulation depth in the section B. The section A is a section in which the current set value (or LED current) exceeds the threshold value. The section B is a section in which the current set value (or LED current) is equal to or less than the threshold value.

In the section A, the signal generation circuit SGa generates a PWM signal so that the current average value If_ave = (immediately preceding Ion) − (lowest ripple value) in the off section. Further, in the section B, the signal generation circuit SGa generates a PWM signal so that the current average value If_ave = (immediately preceding Ion)-(minimum ripple value) -α1 in the off section, that is, the modulation depth is suppressed by α1. To do. α1 may satisfy 0 <α1 <(minimum ripple value).

According to the fifth operation example, by suppressing the current change amount by suppressing the modulation depth in the section B, the power loss can be reduced as compared with the fourth operation example.

(6th operation example)
FIG. 133 is a waveform diagram showing a sixth operation example of the illumination optical communication device according to the twenty-first embodiment. The figure is different from the fifth operation example shown in FIG. 132 in that neither modulation by a communication signal nor high-speed switching is performed in the section B. Hereinafter, the differences will be mainly described.

In the section B, the signal generation circuit SG does not generate a communication signal or a PWM signal for high-speed switching. In other words, the modulation depth is suppressed to 0 (zero).

In this case, the section A may be longer than or equal to the time including a meaningful portion (for example, communication ID) as the transmission data of the illumination optical communication.

According to the sixth operation example, the loss due to the current suppression circuit 1 can be further suppressed while suppressing the occurrence of a reception error in the receiving device.

(7th operation example)
FIG. 134 is a waveform diagram showing a seventh operation example of the illumination optical communication device according to the twenty-first embodiment. The figure is different from the fifth operation example shown in FIG. 132 in that the section in which the modulation depth is suppressed is not the section B but the section A. Hereinafter, the differences will be mainly described.

In the section A, the signal generation circuit SGa generates a PWM signal so that the current average value If_ave = (immediately preceding Ion) − (minimum ripple value) −α1 in the off section. Further, in the section B, the signal generation circuit SGa generates a PWM signal so that the current average value If_ave = (immediately preceding Ion) − (lowest ripple value) in the off section.

According to the seventh operation example, by suppressing the modulation depth in the section A in which the current change is larger than that in the section B, the loss due to the current suppression circuit 1 can be further suppressed as compared with the fifth operation example.

(8th operation example)
FIG. 135 is a waveform diagram showing an eighth operation example of the illumination optical communication device according to the twenty-first embodiment. The figure is different from the sixth operation example shown in FIG. 134 in that neither modulation by the communication signal nor high-speed switching is performed in the section A. Hereinafter, the differences will be mainly described.

In section A, the signal generation circuit SG does not generate a communication signal or a PWM signal for high-speed switching. In other words, the modulation depth is suppressed to 0 (zero).

In this case, the section B may be longer than or equal to the time including a meaningful portion (for example, communication ID) as the transmission data of the illumination optical communication.

According to the eighth operation example, it is possible to further suppress the loss due to the current suppression circuit 1 while suppressing the occurrence of a reception error in the receiving device.

(Embodiment 22)
In the 22nd embodiment, when the reference power supply of the current suppression circuit 1 or the combined control circuit 1b constituting the illumination optical communication device becomes an inappropriate value and there is a risk of causing an excessive power loss, the situation can be promptly dealt with by a simple method. The highly reliable illumination optical communication device that detects and shifts to the protection mode will be described.

FIG. 136 is a diagram showing a configuration example of the modulation circuit 70b which is the premise of the 22nd embodiment. The modulation circuit 70b is, for example, a specific example of the combined control circuit 1b shown in FIG. 50A of the seventh embodiment, and is a part of an illumination optical communication device or a communication module 10. FIG. 136 shows an example in which the optimum current setting value is indirectly obtained by returning the voltage applied to the modulation circuit 70b to the reference power source only during the period when the modulation circuit 70b is energized. In FIG. 136, the MOSFET n71 and the source resistor n72 form a constant current main circuit, and the voltage drop of the source resistor n72 is input to the negative terminal of the operational amplifier n73 via the resistor n76. A parallel circuit of the capacitor n80 and the resistor n81 is connected to the positive terminal of the operational amplifier n73, and an electric charge is accumulated in the capacitor n80 via the resistor n82 and the MOSFET n83. The communication signal (for example, ID signal) is input to the negative terminal of the operational amplifier n73 via the inverter n86 and the resistor n77, and the MOSFET n71 is interrupted and the MOSFET n83 is turned on and off via the resistor n84. As a result, both the MOSFET n71 and the MOSFET n83 are turned ON during the period when the communication signal is ON, and the capacitor n80 is charged by the voltage drop of the MOSFET n71 and the resistor n72 that occurs during the energization period of the modulation circuit 70b. The resistor n78 and the resistor n85 are gate resistors, the resistor n81 is a discharge resistor, and the capacitor n79 is a speed-up capacitor.

In the method of generating the reference power supply as shown in FIG. 136 by utilizing its own voltage drop, an extreme increase in circuit loss due to a small constant current set value as shown in FIG. 8 is unlikely to occur. Since the average value of the LED current is controlled to be almost constant by the LED power supply, a large loss of the modulation circuit 70b means that the voltage drop is large, but the reference power supply rises when the voltage drop is large. This is because the feedback that reduces the voltage drop works. Further, as shown in FIG. 12, it is unlikely that the loss will increase when the ON-duty is extremely small. This is because the target communication signal is 4PPM, the average ON-Duty is 75%, and even if there is a local fluctuation, it is transient, so that the average power loss is not significantly affected.

However, in an extreme case, when the circuit part for generating the reference potential is cut off in the capacitor n80 or the capacitor n80 or the resistor n81 is short-circuited, the loss of the constant current main circuit increases and overheats. The situation is conceivable.

In order to solve such a situation, the illumination optical communication device according to the 22nd embodiment includes the light source and a detection circuit for detecting whether or not the current flowing through the current suppression circuit exceeds a predetermined amount, and the current is present. When it is detected that the amount exceeds the fixed amount, the current suppression circuit is controlled so as to suppress the current.

Further, the illumination optical communication device according to the 22nd embodiment includes a power supply circuit, a smoothing circuit, a load circuit, an intermittent switch, a modulation circuit 70b provided in series with the load circuit and the intermittent switch, and both ends of the modulation circuit 70b. It is composed of a feedback circuit that generates a constant current value using voltage, and is provided in parallel with the modulation circuit 70b to detect a voltage drop during the period when the intermittent switch is ON, and the detection circuit. A configuration may be provided in which a protection circuit for determining the output of the above and shifting to the protection mode is provided. The above detection circuit may be an overpower detection circuit or an overvoltage detection circuit.

The detection circuit in this illumination optical communication device includes a voltage dividing resistor that divides the voltage applied during the period when the intermittent switch is OFF, a means for clamping the voltage dividing voltage, and an integral that is charged through these voltage dividing resistors. A discharge circuit consisting of a capacitor, a diode that discharges the charge of the integrating capacitor to the modulation circuit 70b including the intermittent switch while the intermittent switch is ON, and a discharge resistor, and a comparator and a threshold for discriminating the voltage value of the integrating capacitor. It is preferably composed of a voltage source.

In the detection circuit, it is also preferable to charge the control power supply or the capacitor instead of the voltage dividing resistor and the clamping means.

It is also preferable that the detection circuit in this illumination optical communication device has a second charging path with respect to the integrating capacitor, and the second charging path is configured by providing a Zener die auto in the discharging circuit.

The detection circuit in this illumination optical communication device has an integrating capacitor of a second charging path configured by providing a Zener diode in the discharge circuit, is connected to the potential of the first integrating capacitor by a wired OR, and has a second. It is also preferable that the integrating capacitor << is set to the first integrating capacitor.

When the output (comparator output) of the detection circuit in this illumination optical communication device becomes High, it is also preferable to have a latch circuit that holds that state and a short-circuit switch that short-circuits the modulation circuit 70b at the output of the latch circuit.

Next, the illumination optical communication device of the 22nd embodiment will be described with reference to FIG. 137. As shown in FIGS. 1 and 50A, this illumination optical communication device is intermittent with a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, and a load circuit 53 which is an LED. Assuming that the modulation circuit 70b has a function and is composed of a constant current circuit, an overpower detection circuit 90a is provided in parallel with the modulation circuit 70b.

The overpower detection circuit 90a is composed of a P-type MOSFET n90, its gate protection resistor n91, an N-type MOSFET n92 provided between the gate terminal of the P-type MOSFET n90 and the circuit ground, its gate protection resistor n93, and its gate resistance n94. The integrator circuit including the diode n95, the resistor n96, the capacitor n97 and its discharge resistor n98 provided between the drain terminal of the P-type MOSFET n90 and the circuit ground, and the potential of the capacitor n97 reach a predetermined value. It is composed of a comparator n100 and a threshold power supply n99 thereof for determining the result. The switch circuit is driven by a communication signal, the P-type MOSFET n90 is turned on during the period when the communication signal is high, and the drain voltage is applied to the anode side of the diode n95 while the intermittent switch (MOSFET n71) for modulation is energized. .. The applied voltage charges the capacitor n97 via the resistor n96, and when this potential becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistance.

Since the average value of the current flowing through the main circuit (MOSFET n71 and resistor n72) of the modulation circuit 70b is substantially constant due to the constant current control function of the power supply circuit 52a, the voltage drop during energization of this main circuit is proportional to the power loss. .. Therefore, detecting a state in which this voltage drop is excessive means detecting overpower.

FIG. 138 shows the waveforms of each part during normal operation. During the period when the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. As a result, the voltage drop that occurs across the MOSFET n71 and the resistor n72 during the energization period is as shown in (c). The product of the LED current (b) and the voltage drop (c) is the power loss shown in (d). These are integrated by the resistor n96 and the capacitor n97, and a detection potential of substantially DC is generated in the capacitor n97, but the threshold value of the reference power supply n99 is not reached, and the comparator output maintains Low.

FIG. 139 shows the waveforms of each part when a normal reference power supply is not generated at the operational amplifier plus terminal of the modulation circuit 70b for some reason and the loss of the modulation circuit 70b becomes excessive. While the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows, but the voltage waveform generated across the MOSFET n71 and the resistor n72 during the energization period is (c). As shown by, the value is larger than the normal value. Therefore, as shown in (d), the power loss of the constant current main circuit becomes large, the detection voltage generated in the capacitor n97 also rises and exceeds the threshold value of the reference power supply n99, and the comparator output becomes High.

FIG. 140 is a diagram showing main circuit loss and overpower detection levels in six models having different LED loads. This is the result of measuring the loss of the modulation circuit 70b for each model when normal modulation is performed by the communication signal using six types of LED loads having different load capacities. In either case, the resistor n81 is adjusted to set the optimum operating point at which the circuit loss is minimized within the range in which the LED current waveform can generally maintain a rectangular wave. The magnitude of the main circuit loss is proportional to the LED current value. When the resistance value is gradually lowered from the value of the resistor n81, which is the optimum operating point for each model, the main circuit loss increases and the detection voltage (capacitor n97) eventually rises to reach the threshold value of the reference power supply n99. Then, the output of the comparator n100 becomes High, and the operation shifts to the power protection operation. In this embodiment, the power protection operating point is a substantially constant value regardless of the model.

(Embodiment 23)
The illumination optical communication device of the 23rd embodiment will be described with reference to FIG. 141. As shown in FIGS. 1 and 50A, this illumination optical communication device also has a power supply circuit 52a having a function of making the output constant current, a smoothing capacitor (smoothing circuit) 65, and a load circuit 53 which is an LED. Assuming that the modulation circuit 70b has a function and is composed of a constant current circuit, an overpower detection circuit 90b is provided in parallel with the modulation circuit 70b.

The overpower detection circuit 90b includes an integrator circuit composed of a resistor n101, a resistor n103, and a capacitor n97, a Zener diode n102 that clamps the potential at the connection point between the resistors n101 and n103 to a constant value, and a MOSFET n71 and a resistor of the modulation circuit 70b. It is composed of a discharge circuit including a diode n105 and a resistor n104 for discharging the electric charge of the capacitor via n72, a comparator n100 for determining that the potential of the capacitor n97 has reached a predetermined value, and a threshold power supply n99 thereof. There is. When the potential of the capacitor n97 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistance.

In this embodiment, the charging circuit for charging the capacitor n97 is mainly the applied voltage during the period when the MOSFET n71 of the modulation circuit 70b is OFF. This applied voltage greatly differs depending on the target LED load and its power supply characteristics, but the difference depending on the model can be eliminated by the clamping action of the Zener diode n102. That is, the difference in charging voltage can be ignored by clamping the voltage of the model having the smallest applied voltage among the plurality of target models.

The electric charge charged in the capacitor n97 is discharged via the diode n105 and the resistor n104 via the MOSFET n71 and the resistor n72 of the modulation circuit 70b during the ON period, and the discharge amount is a voltage drop during the ON period. Dependent. If this voltage drop is large, the charge of the capacitor n97 is difficult to discharge, and if the charge amount is constant, the potential of the capacitor n97 rises. If the voltage drop is large, the power loss is also large, so that overpower can be detected.

FIG. 142 shows the waveforms of each part during normal operation. During the period when the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows. As a result, the voltage drop that occurs across the MOSFET n71 and the resistor n72 during the energization period is as shown in (c). The product of the LED current (b) and the voltage drop (c) is the power loss shown in (d). Since the capacitor n97 is charged with the clamped charging voltage, the charging curve is the same every cycle as shown in (e), but the discharge curve depends on the waveform of (c) or (d). That is, it is difficult to discharge when the voltage drop of the main circuit is large, and it is easy to discharge when the voltage drop of the main circuit is small. During normal operation, these charging and discharging are balanced, the potential of the capacitor n97 does not reach the threshold value of the reference power supply n99, and the comparator output maintains Low.

FIG. 143 shows the waveforms of each part when a normal reference power supply is not generated at the operational amplifier plus terminal of the modulation circuit 70b for some reason and the loss of the modulation circuit 70b becomes excessive. While the inverted communication signal (a) is High, the MOSFET n71 constituting the constant current main circuit is turned on and the LED current (b) flows, but the voltage waveform generated across the MOSFET n71 and the resistor n72 during the energization period is (c). As shown by, the value is larger than the normal value. Therefore, as shown in (d), the power loss of the constant current main circuit becomes large, and it becomes difficult to discharge the capacitor n97. As a result, the potential of the capacitor n97 rises and exceeds the threshold value of the reference power supply n99, and the comparator output becomes High. Become.

FIG. 144 is a result of measuring the loss of the modulation circuit 70b when normal modulation is performed by the communication signal using six types of LED loads having different load capacities for each model. In either case, the resistor n81 is adjusted to set the optimum operating point at which the circuit loss is minimized within the range in which the LED current waveform can generally maintain a rectangular wave. The magnitude of the main circuit loss is proportional to the LED current value. When the resistance value is gradually lowered from the value of the resistor n81, which is the optimum operating point for each model, the main circuit loss increases and the detection voltage (capacitor n97) eventually rises to reach the threshold value of the reference power supply n99. Then, the output of the comparator n100 becomes High, and the operation shifts to the power protection operation. According to this embodiment, the power protection operating point differs depending on the model, and a value substantially proportional to the main circuit loss during normal operation can be obtained.

This characteristic is effective when the same modulator is used for a plurality of models. That is, since the power protection operating point is determined according to the main circuit loss during normal operation, it is possible to alleviate the inconvenience that the detection margin becomes small or large in a specific model.

(Embodiment 24)
The illumination optical communication device of the 24th embodiment will be described with reference to FIGS. 145 and 145. As shown in FIGS. 1 and 50A, this illumination optical communication device also has a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of a modulation circuit 70b composed of a constant current circuit, an overpower detection circuit 90c is provided in parallel with the modulation circuit 70b.

The overpower detection circuit 90c constitutes an integrator circuit so as to charge the capacitor n97 from the control power supply via the resistor n101, and discharges the electric charge of the capacitor through the MOSFET n71 and the resistor n72 of the modulation circuit 70b. It is composed of a discharge circuit including a resistor n104, a comparator n100 for determining that the potential of the capacitor n97 has reached a predetermined value, and a threshold power supply n99 thereof. When the potential of the capacitor n97 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistance.

In this embodiment, since the capacitor n97 is charged from the control power supply voltage via the resistor n101, the circuit configuration can be simplified. The main operations and features are the same as those in the second embodiment. Compared with the second embodiment, the charging power is generated even during discharging, so that the control circuit power increases to some extent.

(Embodiment 25)
The illumination optical communication device of the 25th embodiment will be described with reference to FIG. 146. As shown in FIGS. 1 and 50A, this illumination optical communication device also has a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of a modulation circuit 70b composed of a constant current circuit, an overpower detection circuit 90d is provided in parallel with the modulation circuit 70b.

The overpower detection circuit 90d is almost the same as FIG. 141 showing the 23rd embodiment, but is configured by replacing the diode n105 of the discharge circuit in FIG. 141 with a Zener diode n106. The charge / discharge operation is the same, but an overvoltage protection function can be added in addition to the overpower protection with almost the same configuration. The main purpose of overpower protection is to prevent overheating of the device, and since the thermal time constant is relatively large, instantaneousness is not required for the detection response time, but when an overvoltage is applied to the MOSFETn71 of the modulation circuit 70b, the breakdown voltage becomes Prompt detection protection is required before reaching. Since the discharge time constant of the capacitor n97 in the present invention is set to a value sufficiently smaller than the charge time constant, if a Zener diode having an appropriate value is used for the discharge circuit, the capacitor n97 is charged in excess of the Zener voltage. Since the time constant is small, responsiveness to overvoltage can be obtained.

(Embodiment 26)
The illumination optical communication device of the 26th embodiment will be described with reference to FIG. 147. As shown in FIGS. 1 and 50A, this illumination optical communication device also has a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of a modulation circuit 70b composed of a constant current circuit, an overpower detection circuit 90e is provided in parallel with the modulation circuit 70b.

The overpower detection circuit 90e is configured by combining the 23rd embodiment and the 26th embodiment. The first integrating circuit that charges the capacitor n97 via the resistor n101 and the resistor n103, the Zener diode n102 that clamps the connection point potential between the resistor n101 and the resistor n102, and the capacitor n108 are charged via the resistor n104 and the Zener diode n106. It is composed of a second integrating circuit, a diode n107 connected from the capacitor n97 toward the capacitor n108, a comparator n100 for determining that the potential of the capacitor n108 has reached a predetermined value, and a threshold power supply n99 thereof. There is. When the potential of the capacitor n108 becomes equal to or higher than the threshold value of the reference power supply n99, the output of the comparator n100 becomes High. The resistor n98 is a discharge resistance. Further, the time constant of the second integrator circuit is set to be sufficiently smaller than the time constant of the first integrator circuit.

The operation of the first integrator circuit is the same as that of the 23rd embodiment. The discharge circuit of the capacitor n97 is composed of a diode n107, a Zener diode n106, and a resistor n104, which is also the same as in the case of the 23rd embodiment. Therefore, the charging path of the second integrating circuit is shared with the discharging path of the capacitor n97.

By setting the capacitance value of the capacitor n108 to be very small, the time constant of the second integrating circuit can also be made very small, so that the responsiveness as overvoltage protection is remarkably improved.

(Embodiment 27)
The illumination optical communication device of the 27th embodiment will be described with reference to FIG. 148. As shown in FIGS. 1 and 50A, this illumination optical communication device also has a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. Assuming a modulation circuit 70b composed of a constant current circuit, an overpower detection circuit 90 is provided in parallel with the modulation circuit 70b, and the output thereof is held by the holding circuit 110 and both ends of the modulation circuit 70b are short-circuited. It is configured to drive the MOSFET 111 of. The overpower detection circuit 90 is any of the overpower detection circuits 90a to 90e.

In the state where the output of the overpower detection circuits 90a to 90e is High, if a situation occurs in which normal modulation operation cannot be performed for some reason, the modulation circuit should be quickly short-circuited so that the modulation circuit does not intervene. For example, the function as an optical communication device disappears, but the function as a main lighting is maintained.

Such measures minimize the influence of the modulation circuit on the LED power supply, and can contribute to improving the reliability of the system.

(Embodiment 28)
In the 28th embodiment, in the current suppression circuit 1 or the combined control circuit 1b constituting the illumination optical communication device, appropriate power loss feedback control can be performed regardless of the characteristics of the elements used, and an MT capable of supporting a plurality of models. An inexpensive and highly reliable illumination optical communication device that also contributes to the conversion will be described.

FIG. 149 is a diagram showing a configuration example of the modulation circuit 70b which is the premise of the 28th embodiment. The modulation circuit 70b is, for example, a specific example of the combined control circuit 1b shown in FIG. 50A of the seventh embodiment, and is a part of an illumination optical communication device or a communication module 10. FIG. 149 shows an example in which the optimum current setting value is indirectly obtained by returning the voltage applied to the modulation circuit 70b to the reference power source only during the period when the modulation circuit 70b is energized. In FIG. 149, the MOSFET n71 and the source resistor n72 form a constant current main circuit, and the voltage drop of the source resistor n72 is input to the negative terminal of the operational amplifier n73 via the resistor n76. A parallel circuit of the capacitor n80 and the resistor n81 is connected to the positive terminal of the operational amplifier n73, and an electric charge is accumulated in the capacitor n80 via the resistor n82 and the MOSFET n83. The communication signal is input to the negative terminal of the operational amplifier n73 via the inverter n86 and the resistor n77, interrupts the MOSFET n71, and turns on and off the MOSFET n83 via the resistor n84. As a result, both the MOSFET n71 and the MOSFET n83 are turned ON during the period when the communication signal is ON, and the capacitor n80 is charged by the voltage drop of the MOSFET n71 and the resistor n72 that occurs during the energization period of the modulation circuit 70b. The resistor n78 and the resistor n85 are gate resistors, the resistor n81 is a discharge resistor, and the capacitor n79 is a speed-up capacitor.

The circuit operation of FIG. 149 will be described with reference to the operation waveform shown in FIG. 150. The inverted communication signal is input to the negative terminal of the operational amplifier n73 via the resistor n77. By setting the negative input terminal potential to be higher than the potential of the positive terminal during the period when the inverted communication signal is High, the output of the operational amplifier n73 becomes Low and the MOSFET n71 is turned OFF. Further, if the positive terminal of the operational amplifier n73 is set to be higher during the period when the communication signal is Low, the fishing of the operational amplifier n73 becomes High, the MOSFET n71 is turned ON, and the LED current flows. These situations are as shown in FIGS. 150 (a) to (c). The voltage drop generated in the resistor n72 by the LED current is divided by the resistor n76 and the resistor n77 and applied to the negative terminal of the operational amplifier n73, and the output of the operational amplifier n73 is such that the negative terminal potential is substantially equal to the positive terminal. Is controlled.

The gate voltage of the MOSFET n71 at this time is approximately the value obtained by adding the voltage drop of the resistor n72 to the gate threshold value Vth.

FIG. 150D shows a voltage waveform applied to the constant current main circuit (MOSFET n71 and resistor n72) during the modulation operation. Since the MOSFET n71 is turned off during the period when the inverting communication signal is High, the voltage value is roughly obtained by subtracting the cutoff voltage of the LED load from the output voltage of the LED power supply. Further, since the MOSFET n71 is turned on and the constant current operation is performed during the period when the inverting communication signal is Low, the MOSFET n71 operates in the amplification region and is accompanied by a voltage drop, and the voltage drop of the resistor n72 is also added. Only the voltage drop is illustrated in FIG. 150 (e), and since the LED current is flowing during this period, these are also diagrams of power loss.

The MOSFET n71 is turned on and off by the inverting communication signal, and the MOSFET n83 is also turned on and off. Since the inverting communication signal is inverted (that is, non-inverting communication signal) by the inverter n86 and applied to the gate terminal of the MOSFET n83 via the resistor n84, the ON-OFF operation opposite to that of the MOSFET n71 is performed. That is, since the inverting communication signal is turned ON during the Low period, the capacitor n80 is charged via the resistor n82 by the voltage drop shown in FIG. 150 (e). As a result, a reference potential as shown by the broken line in FIG. 150 (e) is generated, and the current value of the modulation circuit 70b is set at this potential. The reference potential can be adjusted by the resistance n82 and the resistance n81, and the power loss feedback function is fulfilled by an appropriate setting. That is, if the voltage drop of the modulation circuit 70b increases for some reason, the charge amount of the capacitor n80 also increases, the gate voltage of the MOSFET n71 rises, the current easily flows, and the voltage drop of the modulation circuit 70b is reduced.

These are switching operations using an operational amplifier, and greatly depend on the characteristics of the operational amplifier. FIG. 151 shows the result of simulating the rising waveforms of the gate voltage and the LED current of the MOSFET n71 at the falling edge of the inverted communication signal. The waveform of the falling edge of the inverted communication signal and the waveform of the rising edge of the LED current are shown in the upper part of FIG. 151. The waveform of the rising edge of the gate voltage is shown in the lower part of FIG. 151.

Further, FIG. 152 shows the result of simulating the falling waveforms of the gate voltage and the LED current of the MOSFET n71 at the rising edge of the inverted communication signal. The waveform of the rising edge of the inverted communication signal and the waveform of the falling edge of the LED current are shown in the upper part of FIG. 152. The waveform of the falling edge of the gate voltage is shown in the lower part of FIG. 152.

As described above, when the inverting communication signal is inverted from High to Low, the output of the operational amplifier, that is, the gate voltage of the MOSFET n71 becomes High, but its rising edge has a slope. The degree of inclination largely depends on the output characteristics of the operational amplifier and is presented as a slew rate characteristic. Further, the capacitance component existing around the operational amplifier n73 is also affected, and the capacitor capacitance provided between the output end and the negative input end, the gate capacitance (Ciss) of the MOSFET, and the like are particularly affected.

By using an operational amplifier with a large slew rate and a MOSFET with a small gate capacitance and reducing the capacitance of the capacitor connected to the operational amplifier output such as the capacitor n79 as much as possible, the rise and fall gradients of the gate voltage can be steep. ..

In FIG. 151, the gate voltage of the MOSFET n71 rises with an inclination from the time when the inverting communication signal falls, and when the voltage reaches the gate threshold value (Vth) of the MOSFET n71, the LED current starts to flow. The gate voltage rises to the value obtained by adding the voltage drop generated in the resistor n72 by the LED current, and the LED current also becomes flat.

The time from the falling point of the inverting communication signal until the LED current reaches 10% of the flat portion is defined as the rising delay time.

In FIG. 152, the gate voltage of the MOSFET n71 drops with an inclination from the rising edge of the inverting communication signal, and when the voltage reaches the gate threshold value (Vth) of the MOSFET n71, the LED current is cut off. The time from the rising edge of the inverting communication signal until the LED current reaches 90% of the flat portion is defined as the falling delay time. Comparing the rise and fall delay times, it can be seen that the rise delay time is significantly larger.

FIG. 153 shows a modulation operation waveform when a rising delay time is involved. Since the gate voltage of the MOSFET n71 is intermittent (b) with an inclination in response to the inverting communication signal (a), a delay occurs in the rise of the LED current waveform (c).

As a result, a delay also occurs in the falling edge of the main circuit applied voltage (d), so that a voltage other than the voltage drop is superimposed on the waveform (e) that the inverted communication signal wants to capture as a voltage drop during the Low period. As a result, the reference potential generated in the capacitor n80 becomes level 2 (dashed line display) higher than the originally expected level 1 (dashed line display), and there is a problem that the expected power loss feedback function cannot be obtained.

In order to solve this problem, the current suppression circuit of the illumination optical communication device according to the 28th embodiment sets a variable reference value corresponding to the current set value according to the current value flowing through the switch and the current suppression circuit. A reference source that is dynamically generated and a delay circuit that delays the generated reference value by a predetermined time length are provided, and the current suppression circuit causes a current flowing through the light source based on the delayed reference value. Suppress.

Further, the illumination optical communication device according to the 28th embodiment includes a power supply circuit, a smoothing circuit, a load circuit, an intermittent switch, a modulation circuit 70b provided in series with the load circuit and the intermittent switch for modulation, and the modulation circuit 70b. In addition to being composed of a feedback circuit that generates a constant current value using the voltage across the above, a delay means is provided in the feedback circuit to delay the ON timing of the feedback switch that operates in the opposite direction to the intermittent switch. It may be.

It is also preferable that the feedback circuit in this illumination optical communication device includes voltage clamping means.

It is preferable that the delay time set by the delay means of the feedback circuit in this illumination optical communication device is at least sufficiently larger than the rise delay time of the modulation intermittent switch.

The delay time set by the delay means of the feedback circuit in this illumination optical communication device is preferably larger than the rise delay time of the modulation intermittent switch and smaller than the minimum pulse width included in the communication signal.

It is also preferable that the feedback switch in this illumination optical communication device has at least a capacitor element between its control terminal and the circuit ground.

The illumination optical communication device of the 28th embodiment will be described with reference to FIG. 154. As shown in FIGS. 1A and 50A, this illumination optical communication device has a power supply circuit 52a having a function of constantizing the output, a smoothing capacitor (smoothing circuit) 65, a load circuit 53, and an intermittent function. On the premise of a modulation circuit composed of a constant current circuit, the configuration of the modulation circuit is improved. Specifically, the gate drive circuit of the second switch (feedback switch: MOSFETn83) that turns on and off in synchronization with the constant current switch (modulation intermittent switch: MOSFETn71) that also has the function of intermittently responding to the inverting communication signal. It is configured by adding a delay circuit that delays the ON timing.

The added delay circuit includes an inverter n86 that inverts (that is, non-inverting) the inverting communication signal, an integrator circuit consisting of a resistor n90 and a capacitor n89, a extraction circuit consisting of a diode n92 and a resistor n93, and a buffer element n88 for waveform shaping. Consists of. After the inverted communication signal is inverted by the inverter n86, the rising edge is blunted by the above integrating circuit, and the rising edge delay time is generated by using the input threshold value of the buffer element n88. When the inverting communication signal is switched to High, the electric charge of the capacitor n89 is quickly discharged via the extraction circuit.

The operation of FIG. 154 showing the 28th embodiment will be described with reference to FIG. 155. In response to the inverting communication signal (a), the gate voltage of the modulation intermittent switch MOSFETn71 is intermittent with a slope ((b)), so that the rising edge of the LED current waveform (c) is delayed. As a result, the rising edge of the main circuit applied voltage ((d)) is also delayed, but the rising edge of the gate voltage of the feedback switch MOSFETn83 is also delayed by the delay circuit of the present invention ((e)). The voltage component other than the voltage drop is removed, and as shown in (f), the reference potential can be generated in the capacitor n80 only by the voltage drop. The obtained reference potential is close to the originally expected level 1 (indicated by a broken line), and an appropriate power loss feedback function can be obtained.

In the modulation circuit 70c of FIG. 154, a Zener diode z94 is added between the drain terminal of the MOSFET n83 and the circuit ground. Its main purpose is to reduce the withstand voltage of the feedback switch MOSFETn83. The feedback circuit targets only the voltage drop during the period when the modulation intermittent switch MOSFET n71 is ON, and does not require the voltage applied during the period when the MOSFET n71 is OFF.

Therefore, clamping the voltage with the Zener diode z94 does not adversely affect the feedback performance. Rather, by using a element having a low withstand voltage and a small capacitance as the MOSFET n83, the parasitic capacitance can be reduced, so that more accurate feedback performance can be obtained.

The main effect according to the 28th embodiment is the so-called MT effect in which an optical communication function can be added to a plurality of LED lighting fixtures by using one modulator. Compared to the case where each modulator corresponding to a plurality of LED lighting fixtures is required, in addition to the cost effect by reducing the number of products, a great effect can be expected to promote the spread of visible light communication.

FIGS. 156 to 159 show various characteristics when a gate voltage rise delay circuit of the MOSFET n83 based on the present invention is added to a plurality of models having different LED currents and load capacities. FIG. 156 shows the results of actual measurement of the relationship between the LED current and the constant current main circuit loss of three types of LED lighting fixtures having different LED current ratings. It can be seen that the main circuit loss increases substantially in proportion to the value of the LED current, and it hardly depends on the delay time of the gate voltage rise of the MOSFET n83. FIG. 157 is the result of actually measuring the relationship between the LED load power and the constant current main circuit loss, and is almost independent of the delay time of the gate voltage rise of the MOSFET n83. Comparing with the result of FIG. 156, it becomes clearer that the constant current main circuit loss depends on the LED current rather than the load power. In these results, the resistance n81 (reference resistance) provided in parallel with the capacitor n80 is adjusted each time, and the constant current main circuit power loss at the point where the LED current waveform becomes a substantially square wave (optimal resistance value) is measured. ing.

FIG. 158 is a result of actually measuring the relationship between the LED current and the optimum resistance value (resistance 81) of three types of LED lighting fixtures having different LED current ratings. As the delay time for the rise of the gate voltage of the MOSFET n83 is increased, the optimum resistance value of the resistor n81 is shifted to the larger one in all three models. If the delay time is lengthened, the period for capturing the voltage drop of the modulation circuit 70b becomes shorter, and the voltage formed in the capacitor n80 decreases accordingly, so that the constant current main circuit loss increases (the LED current waveform has a square wave). Maintain). Since the optimum adjustment point can be found by increasing the value of the reference resistor n81, the optimum adjustment resistance value of the resistor n81 increases with the delay time. The rise delay time of the modulation intermittent switch (MOSFET n71) in this case was approximately 5 ussec. Further, it is considered that the large difference between the optimum resistance value without delay and the optimum resistance value with delay is due to the fact that the voltage other than the main circuit voltage drop was also taken in the case without delay. FIG. 159 is a result of actually measuring the relationship between the LED load power (load capacity) and the optimum resistance value (resistance n81) in the above three types of LED lighting fixtures. Similar to the case of FIG. 158, as the delay time for the rise of the gate voltage of the MOSFET 83 is increased, the optimum resistance value of the resistor n81 is shifted to the larger one in all three models. The reason is the same as in the case of FIG. 158.

Considering the results of FIGS. 158 and 159 from the viewpoint of so-called MT conversion in which an optical communication function can be added to a plurality of LED luminaires by using one modulator, the optimum resistance value is fixed to one, so that the current is present. It is desirable that the three resistance values (resistance 81) in different or different load powers are close to each other. Therefore, it can be seen that it is preferable to have a delay than to have no delay, and in the range of 9 to 24 usc, the larger the delay time is, the more preferable it is. When the delay time is 50 ussec, the line diagram when the delay time is 24 ussec is translated, and even if the delay time is made longer than necessary, the optimum resistance value will only increase, and the three optimums will be used. The resistance value does not approach. Moreover, when the optimum resistance value becomes large, it becomes necessary to pay attention to the input bias current characteristic of the operational amplifier n73. In the present invention, the voltage drop due to the current flowing through the modulation circuit 70b is fed back to the positive terminal of the operational amplifier to obtain the reference potential, but when the optimum resistance value becomes large, the above input bias current cannot be ignored. That is, ideally, the reference potential generated in the capacitor n80 should be generated by the current that feeds back the voltage drop of the modulation circuit 70b, but there is a current flowing into the input plus terminal from the internal circuit of the operational amplifier n73. Then, the ideal feedback control is hindered. As a result, it is necessary to use an operational amplifier having a small input bias current, which is generally expensive. Based on this point, it can be said that the delay time of the MOSFET n83 is preferably 24 usec rather than 50 usec.

According to JEITA-CP1223, which is a standard for visible light communication, one slot of the 1-4 PPM transmission method is 104.167 ussec. Therefore, if the gate voltage rise delay time of the MOSFET 83 is increased to 104 ussec, the voltage drop for one slot will be reduced. It cannot be captured at all. Therefore, the delay time needs to be less than that. The delay time of 50 usc used for the actual measurement of FIGS. 156 to 159 is about 50% of the above-mentioned one slot period. From these results, the gate voltage rise delay time of the MOSFET n83 is set to a range larger than the rise delay time of the modulation intermittent switch (MOSFET n71) and smaller than the shortest pulse width included in the communication signal, and further, the MOSFET n83 It can be said that the gate voltage rise delay time is most preferably set in a range of twice or more the rise delay time of the modulation intermittent switch (MOSFET n71) and 1/2 or less of the shortest pulse width included in the communication signal.

(Embodiment 29)
FIG. 160 shows that only the feedback circuit portion of FIG. 154 is extracted, and that the feedback switch MOSFET n83 naturally has a gate capacitance Ciss. How this gate capacitance affects the reference potential generated in the capacitor n80 will be described with reference to FIG. 161. Since the falling edge of the inverting communication signal is inverted by the inverter n86, it becomes a rising waveform as shown in FIG. 161 (a). The capacitor n89 is charged via the resistor n90 to obtain an integrated waveform as shown in (b). When this voltage reaches the input threshold value Vth of the buffer element n88, the output is delayed by the delay time T as shown in (c) and is supplied to the gate terminal of the MOSFET n83 via the resistor n84. As described above, since the MOSFET n83 has a gate capacitance Ciss, as shown in (d), a current having a differential waveform passes through the gate capacitance when the gate voltage rises. As a result, as shown in (e), the potential of the capacitor n80 rises, causing pulsation at the reference potential of the modulation circuit 70b. Originally, the reference potential of the capacitor n80 is preferably generated by a current that feeds back the voltage drop of the modulation circuit 70b, but the current from the gate circuit of the MOSFET n83 wraps around.

Embodiment 29 of the present invention has been made in view of the above problems, and FIG. 162 shows a specific circuit configuration. The delay circuit of the 29th embodiment is composed of an inverter n86 into which an inverting communication signal is input, a resistor n90 and a capacitor n89 forming an integrating circuit via a diode n92, and a drawing circuit including a transistor n96 and a resistor n85. .. FIG. 163 is an operation explanatory view thereof, in which the capacitor n89 is charged via the resistor n90 and the diode n92 at the falling edge of the inverting communication signal, that is, the rising voltage (a) of the inverter n86 output. The integrated voltage waveform of the capacitor n89 is applied to the gate terminal of the MOSFET n83 as it is, but the voltage of the capacitor n89 has an integrated waveform as shown in (b), and the rising slope of the voltage is gentle. Therefore, the current through the gate capacitance Ciss of the MOSFET n83 is also weak as shown in (d), and the influence on the reference potential generated in the capacitor n80 can be reduced. The MOSFET n83 is turned on with a delay time T when the gate voltage reaches the gate threshold value Vth. Although the fall of the communication signal is not shown, when the output of the inverter n86 becomes Low, a current flows into the inverter n86 via the resistor n90 due to the voltage of the capacitor n89.

Since this current becomes the base current of the transistor n96, the transistor n96 is turned on and the electric charge of the capacitor n89 disappears at the low resistance n85. These form a drawing circuit of the capacitor n89 and quickly turn off the MOSFET 83.

According to the 29th embodiment, the MOSFET n83 gate voltage rise delay time of the feedback circuit can be set, and the current flowing from the gate circuit to the capacitor n80 where the reference potential of the modulation circuit 70b is generated can be suppressed. It enables more accurate feedback control. This contributes to further increasing the possibility of so-called MT, in which an optical communication function can be added to a plurality of LED lighting fixtures by using one modulator.

Although the illumination optical communication device and the communication module according to the present invention have been described above based on the embodiments, the present invention is not limited to the embodiments. As long as the gist of the present invention is not deviated, various modifications that can be conceived by those skilled in the art are applied to the present embodiment, and other embodiments constructed by arbitrarily combining some components in the embodiments and modifications are also available. , Included within the scope of the present invention.

Although the illumination optical communication device according to a plurality of embodiments has been described above, the present invention is not limited to these embodiments.

For example, a part or all of each processing unit included in the illumination optical communication device according to the above embodiment may be realized as an LSI which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them.

Further, the integrated circuit is not limited to the LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection and settings of circuit cells inside the LSI may be used.

That is, in each of the above-described embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

Further, the circuit configuration shown in the circuit diagram is an example, and the present invention is not limited to the circuit configuration. That is, similarly to the above circuit configuration, the present invention also includes a circuit capable of realizing the characteristic functions of the present invention. For example, the present invention also includes an element in which elements such as a switching element (transistor), a resistance element, or a capacitive element are connected in series or in parallel to a certain element within a range in which the same function as the above circuit configuration can be realized. Is done. In other words, "connected" in the above embodiment is not limited to the case where two terminals (nodes) are directly connected, and the two terminals (nodes) are not limited to the case where the same function can be realized. The node) is also included in the case where it is connected via an element.

Further, the logical level represented by high / low or the switching state represented by on / off is exemplified for the purpose of specifically explaining the present invention, and different combinations of the exemplified logical level or switching state are given. Therefore, it is possible to obtain the same result.

Further, the division of the functional block in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, one functional block can be divided into a plurality of functional blocks, and some functions can be transferred to other functional blocks. You may. Further, the functions of a plurality of functional blocks having similar functions may be processed by a single hardware or software in parallel or in a time division manner.

Although the illumination optical communication device according to one or more aspects has been described above based on the embodiment, the present invention is not limited to this embodiment. As long as the gist of the present invention is not deviated, various modifications that can be considered by those skilled in the art are applied to the present embodiment, and a form constructed by combining components in different embodiments is also within the scope of one or more embodiments. May be included within.

1 Current suppression circuit 1c Bias circuit 2 Transistor (switch)
2a, 2b 1st switch element 3a 2nd switch element 4 Reference source 6, 6k Control circuit 6a Shift register 10 Communication module 53 Load circuit (light source)
52a Power supply circuit 64a Overvoltage protection circuit 90, 90a to 90e Overpower detection circuit (detection circuit)
101 Light source 121 Modulation switch (switch)
172 Illuminance sensor 173 Timer 201R, 201G, 201B Illumination unit 202 Dimming control unit 203 Modulation control unit SG signal generation circuit

Claims (16)

A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and turns off and on the light source by interrupting the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch in order to modulate the illumination light in two states of on and off.
An illumination optical communication device that is connected in series with the light source and the switch, and includes a current suppression circuit that suppresses a current flowing through the light source so as not to exceed a variable current set value. A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
It is provided with a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
The current suppression circuit
A reference source that outputs a variable reference value corresponding to the current set value, and
A transistor connected in series with the light source and the switch and suppressing the current flowing through the light source based on the reference value.
The partial on-duty ratio of the communication signal is calculated, and when the calculated partial on-duty ratio is the first ratio, the reference value is set to the first value, and the partial on-duty ratio is the said. A control circuit for setting the reference value to a second value smaller than the first value when the second ratio is larger than the first ratio is provided.
An illumination optical communication device in which the current set value corresponding to the second value is smaller than the current set value corresponding to the first value. The illumination optical communication device according to claim 1 or 2, wherein the power supply circuit performs feedback control for making the average value of the supplied currents constant. The switch is a transistor
The illumination light communication device according to any one of claims 1 to 3, wherein the current suppression circuit makes the transistor also perform a modulation operation of the illumination light and an suppression operation of a current flowing through the light source. The light source, the switch, and the current suppression circuit are connected in series in this order.
The illumination optical communication device according to any one of claims 1 to 3, wherein the current suppression circuit is connected to a ground potential. A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
It is provided with a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
The current suppression circuit
A reference source that outputs a variable reference value corresponding to the current set value, and
A transistor connected in series with the light source and the switch and suppressing the current flowing through the light source based on the reference value.
A control circuit having a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting is provided.
The control circuit is an illumination optical communication device that calculates a partial on-duty ratio of the communication signal based on the n-bit data and determines the reference value according to the calculated partial on-duty ratio. Multiple lighting units that emit light of different colors,
A dimming control unit that controls the dimming level of each of the plurality of lighting units,
It is provided with a modulation control unit that superimposes a signal on the light emitted by the plurality of illumination units by modulation that temporally switches between light emission and non-emission of each of the plurality of illumination units.
Each of the plurality of lighting units
A light source that emits illumination light and
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A power supply circuit that supplies a current to the light source to make the current constant.
It is provided with a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
The dimming control unit controls the power supply circuit for each of the plurality of lighting units.
When the dimming level is higher than the reference level, amplitude dimming is performed to control the intensity of the light emitted by the lighting unit.
When the dimming level is lower than the reference level and the modulation is not performed, PWM dimming is performed to control on-duty, which is the ratio of the light emission time in the repeating cycle of light emission and non-light emission of the illumination unit.
When the modulation control unit performs the modulation, the modulation control unit may perform the modulation with respect to each of the plurality of illumination units.
When the dimming level is higher than the reference level, modulation is performed by controlling the switch.
When the dimming level is lower than the reference level, (1) the PWM dimming by the power supply circuit is not performed, and (2) the modulation and the PWM dimming are performed at the same time by controlling the switch. In addition, an illumination optical communication device that performs the first control of performing modulation so that the light emission start timing is synchronized with other illumination units. Illumination optical communication device
A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
A current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
A control unit that superimposes a signal on the illumination light by modulating the illumination light by controlling the on and off of the switch and controls the current value flowing through the light source is provided.
The control unit
In the first operation mode, the on-duty, which is the ratio of the time that the switch is turned on in the cycle of repeating the on and off of the switch, is set to the first ratio, and the light source is used during the period when the switch is turned on. Set the current value of the current flowing through to the first current value,
In the second operation mode, the on-duty is set to a second ratio lower than the first ratio, the current value is set to a second current value higher than the first current value, and the current value is set to a second current value.
The illumination optical communication device further
It is equipped with either an illuminance sensor that detects the illuminance around the illumination optical communication device and a timer that detects the time.
The control unit performs any of the operations (i) and (ii). (I) When the illuminance detected by the illuminance sensor is lower than a predetermined threshold value, the control unit operates in the first operation mode. If illuminance said detected by the illuminance sensor is higher than the threshold value, when operating in the second operation mode (ii) the time detected by the timer is within a predetermined time period, the first operation operating mode, when the time detected by the timer is outside the period, illuminating light communication device operating in the second operation mode. Illumination optical communication device
A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
It is provided with a current suppression circuit which is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
The illumination optical communication device modulates the two states of the illumination light on and off so as to correspond to a binary communication signal.
The power supply circuit has an overvoltage protection circuit that stops the power supply operation when the output voltage becomes overvoltage.
The illumination optical communication device is
The first switch element, which is the switch,
A bias voltage that turns on the first switch element is applied to the control terminal of the first switch element during the period after the power is turned on until the signal generation circuit starts the operation of generating the communication signal. Bias circuit to supply and
An illumination optical communication device including a second switch element connected to a control terminal of the first switch element and turned on and off according to the communication signal. A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
A current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
A current detection unit for detecting a current flowing through the light source is provided.
The current suppression circuit
A reference source that outputs a variable reference value corresponding to the current set value, and
A transistor connected in series with the light source and the switch and suppressing the current flowing through the light source based on the reference value.
A control circuit for determining the reference value according to the current value detected by the current detection unit is provided.
The reference value is an illumination optical communication device determined according to a value determined by a minimum value and a maximum value of ripple of a current value detected by the current detection unit. A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
A current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
A detection circuit for detecting whether or not the current flowing through the light source and the current suppression circuit exceeds a predetermined amount is provided.
An illumination optical communication device that controls the current suppression circuit so as to suppress the current when it detects that the current exceeds a predetermined amount. A light source that emits illumination light and
A power supply circuit that supplies a current to the light source to make the current constant.
A switch that is connected in series with the light source and interrupts the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
A current suppression circuit, which is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value, is provided.
The current suppression circuit
A reference source that dynamically generates a variable reference value corresponding to the current set value according to the current value flowing through the switch and the current suppression circuit.
It is provided with a delay circuit that delays the generated reference value by a predetermined time length.
The current suppression circuit is an illumination optical communication device that suppresses a current flowing through the light source based on the delayed reference value. A communication module that can be attached to and detached from a lighting device and modulates the lighting light.
A switch that is connected in series with the light source of the lighting device and turns off and on the light source by interrupting the current flowing through the light source.
A signal generation circuit that generates a binary communication signal that controls on and off of the switch in order to modulate the illumination light in two states of on and off.
A communication module including the light source and a current suppression circuit connected in series with the switch and suppressing a current flowing through the light source so as not to exceed a variable current set value. The switch is a transistor
The communication module according to claim 13, wherein the current suppression circuit makes the transistor also perform a modulation operation of the illumination light and a suppression operation of a current flowing through the light source. The light source, the switch, and the current suppression circuit are connected in series in this order.
The communication module according to claim 13 or 14, wherein the current suppression circuit is connected to a ground potential. A communication module that can be attached to and detached from a lighting device and modulates the lighting light.
A switch connected in series with the light source of the lighting device,
A signal generation circuit that generates a binary communication signal that controls on and off of the switch to modulate the illumination light.
It is provided with a current suppression circuit that is connected in series with the light source and the switch and suppresses the current flowing through the light source so as not to exceed a variable current set value.
The current suppression circuit
A reference source that outputs a variable reference value corresponding to the current set value, and
A transistor connected in series with the light source and the switch and suppressing the current flowing through the light source based on the reference value.
A control circuit having a shift register that holds n (n is an integer of 2 or more) bit data of the communication signal while shifting is provided.
The control circuit is a communication module that calculates a partial on-duty ratio of the communication signal based on the n-bit data and determines the reference value according to the calculated partial on-duty ratio.