JP2017121020A - Illumination light communication device and communication module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination light communication device and a communication module that can reduce reception errors in visible light communication, and superpose a plurality of signals on illumination light while restraining increase in a circuit scale.SOLUTION: An illumination light communication device 100 comprises: a light source 101 for emitting illumination light; a modulation signal generation unit 123 for generating a first modulation signal and a second modulation signal higher in frequency than the first modulation signal for modulating the illumination light; a modulation switch 121 connected in series with the light source 101 for intermittently letting current flow through the light source 101 on the basis of the first modulation signal; a current limiting circuit 122 connected in series with the light source 101 and the modulation switch 121 for limiting current flowing through the light source 101 so as not to exceed a current setting value Is; and a control unit 125 for superposing the second modulation signal on the illumination light by changing the current setting value Is on the basis of the second modulation signal.SELECTED DRAWING: Figure 17

Description

  The present invention relates to an illumination light communication device and a communication module.

  Conventionally, visible light communication has been proposed in which a signal is transmitted by modulating the intensity of illumination light in a luminaire including a light emitting diode (LED) as a light source (see, for example, Patent Document 1). In such an illumination light communication device, a signal is transmitted by modulating the illumination light itself, so that a special device such as an infrared communication device is not required. In addition, since a power saving can be realized by using a light emitting diode as a light source for illumination, use in a ubiquitous information system in an underground shopping area is being studied.

JP 2012-0669505 A

  In such an illumination light communication device, it is desired that a reception error in visible light communication can be reduced and a plurality of signals can be superimposed on the illumination light while suppressing an increase in circuit scale.

  Therefore, an object of the present invention is to provide an illumination light communication apparatus or a communication module that can reduce a reception error in visible light communication and can superimpose a plurality of signals on illumination light while suppressing an increase in circuit scale. .

  An illumination light communication apparatus according to an aspect of the present invention includes a light source that emits illumination light, a first modulation signal for modulating the illumination light, and a second modulation signal having a frequency higher than that of the first modulation signal. A modulation signal generating unit to be generated; a switch connected in series with the light source; and a switch for intermittently passing a current flowing through the light source based on the first modulation signal; and connected in series with the light source and the switch and not exceeding a current set value As described above, a current suppression circuit that suppresses the current flowing through the light source and a control unit that superimposes the second modulation signal on the illumination light by changing the current setting value based on the second modulation signal.

  A communication module according to an aspect of the present invention is a communication module that modulates illumination light and is detachable from an illumination device, the first modulation signal for modulating the illumination light, and the first modulation. A modulation signal generating unit that generates a second modulation signal having a frequency higher than that of the signal, a switch that is connected in series with a light source included in the illumination device, and that interrupts a current flowing through the light source based on the modulation signal, the light source, and A current suppression circuit connected in series with a switch and suppressing a current flowing through the light source so as not to exceed a current set value; and changing the current set value based on the second modulation signal to the illumination light And a control unit that superimposes two modulation signals.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to reduce the reception error in visible light communication, the illumination light communication apparatus or communication module which can superimpose a some signal on illumination light is suppressed, suppressing the increase in a circuit scale.

FIG. 1 is a block diagram of the illumination light communication apparatus according to the first embodiment. FIG. 2 is a diagram illustrating another example of the current suppression circuit according to the first embodiment. FIG. 3 is a diagram illustrating another example of the current suppression circuit according to the first embodiment. FIG. 4 is a diagram illustrating another example of the current suppression circuit according to the first embodiment. FIG. 5 is a diagram illustrating an operation example of the illumination light communication apparatus according to the first embodiment. FIG. 6 is a diagram illustrating a schematic configuration of the illumination light communication apparatus according to the first embodiment. FIG. 7 is a diagram illustrating a schematic configuration of an illumination light communication apparatus according to a comparative example of the first embodiment. FIG. 8 is a diagram illustrating a first control example of the current set value according to the first embodiment. FIG. 9 is a diagram illustrating a second control example of the current set value according to the first embodiment. FIG. 10 is a diagram illustrating a third control example of the current set value according to the first embodiment. FIG. 11 is a diagram illustrating a modification of the third control example of the current set value according to the first embodiment. FIG. 12 is a diagram illustrating a fourth control example of the current set value according to the first embodiment. FIG. 13 is a diagram illustrating a usage example of the illumination light communication apparatus according to the first embodiment. FIG. 14 is a diagram illustrating an example of the appearance of the illumination light communication apparatus according to Embodiment 1. FIG. 15 is a diagram illustrating another example of use of the illumination light communication apparatus according to Embodiment 1. FIG. 16 is a diagram illustrating an operation example of the illumination light communication apparatus according to the second embodiment. FIG. 17 is an enlarged view of FIG.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Each figure is a schematic diagram and is not necessarily illustrated exactly.

  It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

  Each figure is a mimetic diagram and is not necessarily illustrated strictly. In each figure, substantially the same configuration is denoted by the same reference numeral, and redundant description may be omitted or simplified.

(Embodiment 1)
[1. Configuration of illumination light communication apparatus]
First, the configuration of the illumination light communication apparatus according to the present embodiment will be described. FIG. 1 is a block diagram showing a configuration of illumination light communication apparatus 100 according to the present embodiment.

  The illumination light communication apparatus 100 illustrated in FIG. 1 functions as a visible light communication transmitter that transmits a signal by modulating the intensity of illumination light. The illumination light communication apparatus 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 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 for detecting a 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.

  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 a lighting device including the light source 101 and the power supply circuit 102. In a state where 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 an illumination device that does not support visible light communication, the visible light communication function can be realized by the illumination 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. With.

  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 light communication apparatus 100, or may generate a modulation signal in accordance with a communication signal input from an external apparatus. 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 configured by 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 sends the generated modulation signal S1 via the drive circuit 128. 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 V 0 of the power supply circuit 102.

  The modulation switch 121 is connected in series with the light source 101, and interrupts 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, a MOSFET).

  The current suppression circuit 122 is connected in series with the light source 101 and the modulation switch 121 and suppresses 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 that is a MOSFET, a current setting circuit 132, an amplifier 133, and a current detection circuit 134 that is a resistor connected to the source of the transistor 131.

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

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

  The current detection circuit 134 is a source resistance 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 illustrated in FIG. 1 is an example, and the illumination light communication apparatus 100 does not have to include all the components illustrated in FIG. For example, the illumination light communication apparatus 100 may not include at least one of the dimming control unit 104 and the voltage detection circuit 127.

  The configuration of the power supply circuit 102 is also an example, and the present invention 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.

  The configuration of the current suppression circuit 122 is also an example, and the configuration is not limited to this as long as the current flowing through the light source 101 can be suppressed (clipped). For example, instead of the current suppression circuit 122, a current suppression circuit 122A, 122B, or 122C shown in FIGS. 2 to 4 may be used. 2 to 4 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. 2 includes bipolar transistors 141 and 142, a current setting circuit 132A that is a variable voltage source, and a resistor 143. Bipolar transistors 141 and 142 constitute 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 pass a current within a range that does not exceed 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 illustrated in FIG. 3 includes a bipolar transistor 151, an emitter resistor 152, a bias resistor 153, and a current setting circuit 132B that 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 illustrated in FIG. 4 includes a three-terminal regulator 161 and a current setting circuit 132C that is a detection resistor.

  In the three-terminal regulator 161, an input terminal IN and an 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 connected between the input terminal IN and the output terminal OUT according to the voltage input to the adjustment terminal ADJ. Suppresses 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). 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. 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.

[2.1. basic action]
Hereinafter, the basic operation of the illumination light communication apparatus 100 will be described. FIG. 5 is a diagram illustrating a basic operation of the illumination light communication apparatus 100. As shown in FIG. 5, the modulation switch 121 is turned on / off according to the modulation signal S1. The modulation method used here conforms to, for example, the 1-4PPM transmission method defined in JEITA-CP1223. Specifically, 2-bit data is converted into a 4-slot pulse. At all times, three of these four slots are high level (on) and one slot is low level (off).

  In the example of FIG. 5, the current command value S2 is constant, and the current set value Is is constant.

  Here, when the modulation for visible light communication is performed, immediately after the modulation switch 121 is turned on, as indicated by the dotted line in FIG. A shoot occurs. Due to the occurrence of this overshoot, there is a problem that a signal cannot be received correctly in the visible light receiver.

  On the other hand, in illumination light communication apparatus 100 according to the present embodiment, by providing current suppression circuit 122, the maximum value of LED current is limited to current setting value Is. Thereby, the occurrence of overshoot is suppressed as shown in FIG. Thereby, the reception error in visible light communication can be reduced.

  The constant current feedback circuit 115 shown in FIG. 1 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 with a relatively large time constant. That is, this constant current control is a control that keeps the average current constant during a predetermined period, and it is not possible to suppress an instantaneous overshoot as shown in FIG.

  Further, in the present embodiment, as shown in FIG. 6, 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 light communication device 100A illustrated in FIG. Conceivable.

  However, the connection configuration of FIG. 7 has a problem that the operation is 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 in the OFF state, GND (V1) of the current suppression circuit 122 is in a floating state (floating), so that the potential fluctuation of GND increases. On the other hand, in the present embodiment, since the current suppression circuit 122 is always connected to the GND terminal by using the connection form shown in FIG. 6, 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 of FIG. 7, and it is difficult to control the current set value Is with high accuracy. On the other hand, since the minute current can be controlled with high accuracy by using the connection form shown in FIG. 6, the current set value Is can be controlled with high accuracy. Furthermore, in the present embodiment, since the GND of the control unit 125 (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, the current set value Is Can be controlled with higher accuracy.

  The signal generation circuit 129 shown in FIGS. 6 and 7 is a circuit that generates a binary modulation signal S1 for controlling the on / off of the modulation switch 121 in order to modulate the illumination light. The signal generation circuit 129 shown in FIG. A signal generation unit 123, an external synchronization signal input unit 124, a control unit 125, and a drive circuit 128 are included.

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

  As described above, the illumination light communication apparatus 100 according to the present embodiment includes the light source 101 that emits illumination light, the modulation switch 121 that is connected in series with the light source 101, and that interrupts the current flowing through the light source 101, and modulates the illumination light. For this purpose, the modulation signal generator 123 for generating the modulation signal S1 for controlling the on / off of the modulation switch 121, and the light source 101 and the modulation switch 121 are connected in series, and the light source 101 is set so as not to exceed the current set value Is. The light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

  Thereby, since generation | occurrence | production of an overshoot can be suppressed by the current suppression circuit 122, the reception error in visible light communication can be reduced. Further, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order, so that 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.

  Moreover, the illumination light communication apparatus 100 may further include a control unit 125 that changes the current setting value Is.

  Thereby, the current setting value Is suitable for each state can be set by changing the current setting value Is. Furthermore, 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 that requires high-precision control.

  In addition, the communication module 103 according to the present embodiment is a communication module 103 that modulates illumination light, which can be attached to and detached from the illumination device, and is connected in series with the light source 101 included in the illumination device, and a current flowing through the light source 101 is obtained. The modulation switch 121 that is intermittently connected, 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, the light source 101 and the modulation switch 121 are connected in series, and A current suppression circuit 122 that suppresses the current flowing through the light source 101 so as not to exceed the set value Is, and the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order.

  Thereby, since generation | occurrence | production of an overshoot can be suppressed by the current suppression circuit 122, the reception error in visible light communication can be reduced. Further, the light source 101, the modulation switch 121, and the current suppression circuit 122 are connected in series in this order, so that 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.

[2.2. First Control Example of Current Set Value]
Hereinafter, a control example of the current set value Is will be described. In the following, a plurality of methods for controlling the current set value Is will be described, but only one of the following methods may be used, or a plurality of methods may be used in combination.

  FIG. 8 is a diagram illustrating 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 of the modulation switch 121 (low period of the modulation signal S1). 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 setting value Is to the first value when the off period is the first length, and sets the current setting when the off period is the second length longer than the first length. The value Is is set to a second value that is higher than the first value. For example, in the case of using 4PPM, when the period corresponding to 1 slot is T0 and the period corresponding to 2 slots is T1, the control unit 125 is shorter than the threshold longer than T0 and shorter than T1, When the current set value Is is set to the first value and the off period is longer than the threshold, the current set value Is is set to a second value higher than the first value.

  Alternatively, the control unit 125 may calculate a 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 is 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 setting 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 a ratio of the on (high) period of the modulation signal S1 in a predetermined period. For example, the “partial on-duty ratio” is a ratio of the on-period to a period obtained by combining the latest off-period and the on-period immediately before the off-period. Alternatively, the “partial on-duty ratio” may be the nearest n-bit moving average value of the modulation signal S1.

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

  In addition, when the length of the off period (partial on-duty ratio) is variable, the longer the off period, the lower the average luminance value. Therefore, in order to make the average luminance value constant, the off period When is long, it is necessary to increase the luminance value in the on period. By controlling the current set value Is described above, the current set value Is can be appropriately changed even when such brightness value control is performed.

[2.3. Second Control Example of Current Set Value]
FIG. 9 is a diagram illustrating 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 setting 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 (brightness change) 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. Thereby, the brightness of the illumination light is changed.

  FIG. 9 shows an example when a dimming operation is performed. The control unit 125 decreases the current command value S2 (current setting 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 setting value Is to the first value when the dimming level is the first level, and sets the current setting when the dimming level is the second level higher than the first level. The value Is is set to a second value that is higher than the first value.

  By controlling the current set value Is as described above, the current set value Is can be appropriately changed according to the dimming level.

  As shown in FIG. 9, the control unit 125 gradually decreases the current command value S2 from the timing when dimming is instructed by the dimming signal S3. As a result, the current command value S2 can be decreased following the change in the light control level (brightness), and therefore an increase in loss due to the sudden decrease in the current command value S2 can be suppressed.

[2.4. Third example of current setting value]
FIG. 10 is a diagram illustrating a third control example of the current set value Is. In the third control example, the control unit 125 determines the current command value S2 (current setting value) according to the LED current detection value S4 that 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 is smaller. That is, the control unit 125 sets the current setting value Is to the first value when the LED current is the first current value, and the current when the LED current is the 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. 10, the current set value Is can be appropriately changed according to the dimming level. Further, as will be described with reference to FIG. 8, even when the luminance value (LED current) is changed in accordance with the length of the off period (partial on-duty ratio), the current set value Is can be changed appropriately. Thereby, the increase in loss at the time of light control etc. can be suppressed.

  Also, as shown in FIG. 10, the timing for detecting the LED current is preferably a timing at which no overshoot occurs and the current value is stable. For example, as shown in FIG. 11, 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. Thereby, the LED current can be detected with high accuracy.

  In FIG. 1, the current detection circuit 134 in the current suppression circuit 122 is also used for LED current detection. However, 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 control.

[2.5. Fourth example of current setting value]
FIG. 12 is a diagram illustrating 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 setting value Is) according to the LED voltage detection value S5 that is the detection result of the voltage V0 detected by the voltage detection circuit 127. Here, the voltage V 0 is a voltage applied to the light source 101. Specifically, the control unit 125 sets the current set value Is lower as the voltage V0 is 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 the current when the voltage V0 is the second voltage value smaller than the first voltage value. The set value Is is set to a second value lower than the first value.

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

  Note that the voltage detection timing may be controlled in the same manner as the LED current detection. That is, as in FIG. 11, the voltage detection circuit 127 detects the voltage V0 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). May be.

[3. Example of use of illumination light communication device]
Hereinafter, usage examples of the illumination light communication apparatus 100 will be described. FIG. 13 is a diagram illustrating a usage example of the illumination light communication apparatus 100. For example, as shown in FIG. 13, the illumination light communication apparatus 100 is an RGB projector. The visible light receiver receives a visible light signal when the user captures the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone.

  FIG. 14 is a diagram illustrating an appearance of the illumination light communication apparatus 100 that is an RGB projector.

  FIG. 15 is a diagram illustrating another example of use of the illumination light communication apparatus 100. For example, as shown in FIG. 15, the illumination light communication apparatus 100 is an RGB spotlight. The visible light receiver receives a visible light signal when the user captures the light emitted by the illumination light communication device 100 with a visible light receiver such as a smartphone.

(Embodiment 2)
In the present embodiment, a modification of the first embodiment will be described. In addition, the whole structure of the illumination light communication apparatus 100 which concerns on Embodiment 2 is the same as that of FIG. However, a function is added to the control unit 125 (signal generation circuit 129) with respect to the first embodiment.

  Specifically, in this embodiment, in addition to 100% modulation by the modulation switch 121, high-frequency modulation is performed to change the current setting value Is of the current suppression circuit 122. Thereby, the illumination light communication apparatus 100 can transmit two types of visible light signals.

  FIG. 16 is a diagram illustrating an operation of the illumination light communication apparatus 100 according to the present embodiment. FIG. 17 is an enlarged view of one ON period of the modulation switch 121 shown in FIG.

  In the present embodiment, for example, the modulation signal generator 123 generates two types of modulation signals (first modulation signal and second modulation signal) based on two types of communication signals (first communication signal and second communication signal). Generate. The control unit 125 generates the modulation signal S1 based on the first modulation signal as in the first embodiment. Furthermore, the control unit 125 performs high frequency modulation on the current command value S2 based on the second modulation signal.

  For example, the frequency of the modulation signal S1 is about 10 kHz, and the frequency of the current command value S2 is about 1 MHz. The specific frequency is not limited to this, and for example, the frequency of the current command value S2 may be about 1 MHz to 100 MHz.

  Further, as shown in FIGS. 16 and 17, the control unit 125 performs high-frequency modulation of the current command value S2 only in a period in which overshoot occurs, that is, in a period in which the current is suppressed by the current suppression circuit 122. Do. For example, the control unit 125 performs high-frequency modulation only during a predetermined period T1 from the rising edge of the modulation signal S1 (timing when the modulation switch 121 is turned on).

  Here, when the current command value S2 (current set value Is) is changed during the period in which the current is suppressed by the current suppression circuit 122, the LED current increases or decreases following the change. That is, since the brightness of light emitted from the light source 101 is changed, transmission of a visible light communication signal can be realized.

  The control unit 125 may always perform high frequency modulation of the current command value S2, or may perform high frequency modulation of the current command value S2 in a period including at least the period T1. Alternatively, the control unit 125 may perform high-frequency modulation of the current command value S2 only during a part of the period included in the period T1.

  Thus, in this embodiment, two types of communication signals can be transmitted. Thereby, for example, when a receiver exists at a position away from the illumination light communication apparatus 100, the receiver receives only the first communication signal having a large amplitude (change in brightness), and the receiver When approaching the illumination light communication apparatus 100, the receiver can receive both the first communication signal and the second communication signal. Thereby, for example, when the user gets closer to the object, it is possible to realize a use environment in which more detailed information about the object is provided to the user.

  Alternatively, a receiver that can receive only 100% modulation receives only the first communication signal, and a receiver that supports both 100% modulation and high frequency modulation has both the first communication signal and the second communication signal. May be received. As a result, a receiver that supports both 100% modulation and high frequency modulation can acquire more detailed information.

  Note that the information transmitted by 100% modulation and the information transmitted by high frequency modulation may be the same information. That is, the information indicated by the first communication signal and the information indicated by the second communication signal may be the same information. In this case, for example, a receiver that supports only 100% modulation can receive a signal of 100% modulation, and a receiver that supports high frequency modulation can receive a signal of high frequency modulation. Therefore, communication signals can be received by a plurality of types of receivers.

  Different modulation schemes may be used for 100% modulation and high frequency modulation. For example, a 4PPM system may be used as a 100% modulation system, and another system may be used for high frequency modulation. Thereby, communication signals can be received by more types of receivers.

  Further, the modulation method of high frequency modulation may be switched periodically. For example, different modulation schemes may be used alternately for each on period. As a result, the number of modulation schemes of the signal to be transmitted can be further increased, so that more types of receivers can receive communication signals. Also, the modulation method used for high frequency modulation may be 3 or more.

  As described above, the illumination light communication apparatus 100 according to the present embodiment has a light source 101 that emits illumination light, the first modulation signal S1 for modulating the illumination light, and a frequency higher than that of the first modulation signal S1. A modulation signal generator 123 that generates a second modulation signal; a modulation switch 121 that is connected in series with the light source 101 and that intermittently passes the current flowing through the light source 101 based on the first modulation signal S1, and the light source 101 and the modulation switch 121; A current suppression circuit 122 that is connected in series and suppresses the current flowing through the light source 101 so as not to exceed the current setting value Is, and the second modulation signal to the illumination light by changing the current setting value Is based on the second modulation signal. The control part 125 which superimposes is provided.

  Thereby, since generation | occurrence | production of an overshoot can be suppressed by the current suppression circuit 122, the reception error in visible light communication can be reduced. Furthermore, by modulating the current set value Is, the illumination light can be modulated in a period in which overshoot is suppressed. Furthermore, since the current suppression circuit 122 can be used not only for suppressing the occurrence of overshoot but also for modulating the illumination light, a plurality of signals can be used as illumination light while suppressing an increase in circuit scale and cost. Can be superimposed.

  Further, the control unit 125 may change the current setting value Is based on the second dimming signal only during a predetermined time T1 from the timing when the modulation switch 121 is turned on.

  Thereby, since it is possible to suppress the current setting value Is from being unnecessarily modulated, power saving or the like can be realized.

  Further, the modulation signal generation unit 123 generates the first modulation signal S1 from the first communication signal using the first modulation method, and generates the first modulation signal S1 from the second communication signal using a second modulation method different from the first modulation method. Two modulated signals may be generated.

  As a result, a signal can be received by a receiver that supports at least one of the first modulation method and the second modulation method, and therefore, signals can be received by more types of receivers.

  Further, the light source 101, the modulation switch 121, and the current suppression circuit 122 may be connected in series in this order.

  As a result, 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.

  In the second embodiment, as in the first embodiment, the 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. However, the light source 101, the modulation switch 121, and the current are connected. The order of the series connection of the suppression circuit 122 is not limited to this.

  In addition, the communication module 103 according to the present embodiment is a communication module 103 that modulates illumination light, which can be attached to and detached from the illumination device, and includes a first modulation signal S1 and a first modulation for modulating the illumination light. A modulation signal generator 123 that generates a second modulation signal having a frequency higher than that of the signal S1, and a modulation switch that is connected in series with the light source 101 included in the lighting device and intermittently flows a current flowing through the light source 101 based on the first modulation signal S1. 121, a current suppression circuit 122 connected in series with the light source 101 and the modulation switch 121 and suppressing the current flowing through the light source 101 so as not to exceed the current set value Is, and the current set value Is changed based on the second modulation signal Thus, a control unit 125 that superimposes the second modulation signal on the illumination light is provided.

  The illumination light communication apparatus according to the embodiment of the present invention has been described above, but the present invention is not limited to this embodiment.

  For example, some or all of the processing units included in the illumination light communication apparatus according to the above embodiment may be realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  Further, the circuit integration is not limited to 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 manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  That is, in each of the above 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.

  The circuit configuration shown in the circuit diagram is an example, and the present invention is not limited to the circuit configuration. That is, like the above circuit configuration, a circuit that can realize a characteristic function of the present invention is also included in the present invention. For example, the present invention includes a device in which a device such as a switching device (transistor), a resistor, or a capacitor is connected in series or in parallel to a certain device within a range in which a function similar to the above circuit configuration can be realized. It is. In other words, the term “connected” in the above embodiment is not limited to the case where two terminals (nodes) are directly connected, and the two terminals ( Node) is connected through an element.

  In addition, the logic level represented by high / low or the switching state represented by on / off is exemplified to specifically describe the present invention, and different combinations of the illustrated logic level or switching state. Therefore, it is possible to obtain an equivalent result.

  In addition, division of functional blocks in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, a single functional block can be divided into a plurality of functions, or some functions can be transferred to other functional blocks. May be. In addition, functions of a plurality of functional blocks having similar functions may be processed in parallel or time-division by a single hardware or software.

  As mentioned above, although the illumination light communication apparatus which concerns on one or several aspects was demonstrated based on embodiment, this invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, various modifications conceived by those skilled in the art have been made in this embodiment, and forms constructed by combining components in different embodiments are also within the scope of one or more aspects. May be included.

DESCRIPTION OF SYMBOLS 100 Illumination light communication apparatus 101 Light source 103 Communication module 121 Modulation switch (switch)
122 current suppression circuit 123 modulation signal generation unit 125 control unit

Claims (5)

A light source that emits illumination light;
A modulation signal generating unit for generating a first modulation signal for modulating the illumination light and a second modulation signal having a frequency higher than that of the first modulation signal;
A switch that is connected in series with the light source and that interrupts the current flowing through the light source based on the first modulation signal;
A current suppression circuit that is connected in series with the light source and the switch and suppresses a current flowing through the light source so as not to exceed a current setting value;
An illumination light communication apparatus comprising: a control unit that superimposes the second modulation signal on the illumination light by changing the current setting value based on the second modulation signal. The illumination light communication apparatus according to claim 1, wherein the control unit changes the current setting value based on the second modulation signal only during a predetermined time from a timing when the switch is turned on. The modulation signal generation unit generates the first modulation signal using a first modulation method, and generates the second modulation signal using a second modulation method different from the first modulation method. 2. The illumination light communication apparatus according to 2. The illumination light communication apparatus according to claim 1, wherein the light source, the switch, and the current suppression circuit are connected in series in this order. A communication module that modulates illumination light, detachable from an illumination device,
A modulation signal generator for modulating the illumination light and generating a first modulation signal and a second modulation signal having a frequency higher than that of the first modulation signal;
A switch connected in series with the light source provided in the illumination device, and interrupts the current flowing through the light source based on the modulation signal;
A current suppression circuit that is connected in series with the light source and the switch and suppresses a current flowing through the light source so as not to exceed a current setting value;
A communication module comprising: a control unit that superimposes the second modulation signal on the illumination light by changing the current setting value based on the second modulation signal.

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