JP7038316B2 - Illuminated optical communication device and communication module - Google Patents

Description

The present invention relates to an illuminated optical communication device and a communication module.

Conventionally, in a luminaire equipped 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 illuminating light has been proposed.

For example, Patent Document 1 proposes a configuration for improving flicker and communication speed when the amount of light is small in a dimming type lighting device provided with an information transmission function.

Patent Document 2 proposes a configuration in which a current flowing through a light source is divided to disperse heat generation, and a constant current is passed through the light source.

Further, Patent Document 3 proposes a power source for illumination light communication in which the brightness of illumination is constant between non-communication and communication in visible light communication using illumination light.

Further, Patent Document 4 discloses a technique for reducing the overshoot generated in the pulsed current flowing through the light source when the illumination light is 100% modulated.

Japanese Patent Application Laid-Open No. 2015-216580 Japanese Unexamined Patent Publication No. 2014-82226 Japanese Unexamined Patent Publication No. 2010-283616 Japanese Unexamined Patent Publication No. 2017-139211

However, according to the prior art, since the current flowing through the light source is intermittently increased or decreased during the communication of visible light communication, the average current flowing through the light source is reduced and the brightness is lowered as compared with the non-communication time. Further, during communication, the smaller the on-duty of the communication signal, the lower the brightness. Patent Document 3 discloses that the brightness of the illumination is constant between the time of communication and the time of non-communication, but the configuration for that purpose is complicated.

Therefore, an object of the present invention is to provide an illuminated optical communication device and a communication module that reduce a decrease in brightness due to intermittent switching during visible light communication by a circuit configuration suitable for miniaturization and cost reduction.

In view of the above problems, the illumination optical communication device of the present invention is connected to a load circuit including a light emitting diode that emits illumination light in series with the load circuit, and is an intermittent switch that is intermittent according to a binary communication signal. And the suppression circuit that is connected in series with the load circuit and the intermittent switch and suppresses the current flowing through itself so as not to exceed the first set value corresponding to the first reference value, and the first reference value is generated. A voltage source for applying a DC voltage to a series circuit including the load circuit, the intermittent switch, and the suppression circuit, and a feedback signal for making the voltage applied to the suppression circuit constant. In parallel with the constant voltage feedback circuit supplied to the source, the first smoothing capacitor connected in parallel to the series circuit including the load circuit, the intermittent switch and the limiting circuit, and the series circuit of the load circuit and the intermittent switch. It includes a second smoothing capacitor connected.

Further, the communication module of the present invention is connected in series with the load circuit, and is connected in parallel with an intermittent switch that is intermittent according to a binary communication signal and a series circuit of the load circuit and the intermittent switch. It is equipped with a smoothing capacitor.

According to the present invention, it is possible to reduce the decrease in brightness due to the intermittent switching of the intermittent switch in visible light communication. Moreover, it is suitable for miniaturization and cost reduction.

FIG. 1 is a circuit diagram showing a configuration example of the illumination optical communication device according to the first embodiment. FIG. 2 is a diagram showing an average current with respect to the on-duty ratio in the first embodiment. FIG. 3 is a diagram showing various signal waveforms for each capacity of the second smoothing capacitor in the first embodiment. FIG. 4A is a diagram showing LED current with respect to the dimming ratio in the first embodiment. FIG. 4B is a diagram showing LED current with respect to the on-duty ratio in the first embodiment. FIG. 5 is a circuit diagram showing a configuration example of the illumination optical communication device according to the second embodiment. FIG. 6 is a circuit diagram of a communication module including another configuration example of the limiter circuit 101 according to the second embodiment. FIG. 7 is a diagram showing various signal waveforms when the on-duty ratio is constant in the illumination optical communication device of the second embodiment. FIG. 8 is a diagram showing various signal waveforms when the dimming ratio is constant in the illumination optical communication device of the second embodiment. FIG. 9A is a diagram showing the relationship between the dimming ratio and the peak value and the average value of the LED current in the second embodiment. FIG. 9B is a diagram showing the relationship between the dimming ratio and the circuit loss of the limiter circuit in the second embodiment. FIG. 9C is a diagram showing the relationship between the on-duty ratio and the peak value and the average value of the LED current in the second embodiment. FIG. 9D is a diagram showing the relationship between the on-duty ratio and the circuit loss of the limiter circuit in the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, all of the embodiments described below show a preferable specific example of the present invention. The numerical values, shapes, materials, components, arrangement positions of the components, connection forms, and the like 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 showing the highest concept of the present invention will be described as arbitrary components constituting the more preferable form.

(Embodiment 1)
Hereinafter, the illumination optical communication device according to the first embodiment will be described.

The illumination optical communication device according to the first embodiment is an example of an illumination light communication device having a visible light communication function added by adding a communication module to a lighting fixture having a dimming function but not a visible light communication function. explain.

Here, the dimming function is a function of changing the brightness of the illumination light based on a user operation or the like. For example, the brightest lighting state is represented by a dimming ratio of 100%, and the darkest extinguishing state is represented by a dimming ratio of 0%. .. The dimming function in each embodiment adjusts the brightness of the illumination light by analog-like adjustment of the amount of current flowing through the light source. In other words, it is not dimmed by digitally interrupting the current.

Further, the visible light communication function means superimposing a binary communication signal on the illumination light by modulating the brightness of the illumination light. In the visible light communication in each embodiment, the communication signal having a modulation factor of 100%, that is, a binary value is made to correspond to two states of turning on and off the illumination light, and the current flowing through the light source is digitally intermittently modulated. do.

[1.1 Configuration of Illuminated Optical Communication Device]
FIG. 1 is a circuit diagram showing a configuration example of the illumination optical communication device according to the first embodiment. The illumination light communication device shown in the figure has a dimming function for changing the brightness of the illumination light and a visible light communication function. This illuminated optical communication device includes a capacitor for replenishing the current reduced by the interruption of the current in the visible light communication, thereby reducing the decrease in brightness. Therefore, the illumination optical communication device of FIG. 1 includes a power supply circuit 52b, a load circuit 53, and a communication module 10.

The power supply circuit 52b is a power supply circuit having a constant voltage feedback function, and includes a rectifying bridge 62, a capacitor 63, a voltage source 64, a first smoothing capacitor 65, a constant voltage feedback circuit 67a, and a suppression circuit 73.

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 suppression circuit 73 includes a transistor 74 which is a MOSFET, a resistance 75 connected to a source, an error amplifier 77, and a first reference source 76.

The communication module 10 includes a signal generation circuit SG, an intermittent switch SW, and a second smoothing capacitor 165.

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

The voltage source 64 is a DC-DC converter and supplies a DC voltage to a series circuit including a load circuit 53, an intermittent switch SW, and a suppression circuit 73.

The suppression circuit 73 is connected in series with the load circuit 53 and the intermittent switch SW, and the first set value of the suppression circuit 73 that suppresses the current flowing through the suppression circuit 73 so as not to exceed the first set value is the first reference source 76. Corresponds to the first reference value generated in. That is, the first set value corresponding to the first reference value can be determined.

The first reference source 76 generates a variable first reference value according to the dimming ratio based on the user operation or the like. The first reference source 76 enables adjustment of the load current, that is, dimming by making the first reference value variable. When the first reference value is variable, the suppression circuit 73 functions as a dimming circuit that adjusts the illumination light to an arbitrary brightness.

The constant voltage feedback circuit 67a outputs a feedback signal for making the voltage applied to the suppression circuit 73 constant to the voltage source 64. This feedback signal indicates an error between the voltage applied to the suppression circuit 73 and the reference voltage of the reference voltage source 72. The voltage source 64 controls the voltage applied to the suppression circuit 73 to be constant based on the feedback signal.

The load circuit 53 is a light source including a plurality of light emitting diodes that emit illumination light. The load circuit 53 has a terminal on the anode side and a terminal on the cathode side. The terminal on the anode side is connected to the output terminal having the higher potential of the voltage source 64, and the terminal on the cathode side is connected to one end of the intermittent switch SW.

The intermittent switch SW is connected in series with the load circuit 53, and interrupts the current supplied from the voltage source 64 to the load circuit 53 according to a binary communication signal from the signal generation circuit SG. By interrupting the intermittent switch SW, the illumination light is modulated, that is, the communication signal is superimposed on the illumination light.

The signal generation circuit SG generates a binary communication signal. The binary communication signal is, for example, an ID signal for identifying an illumination optical communication device, a communication module, or the like, and may be repeatedly generated. The signal generation circuit SG may generate a binary communication signal according to an input signal from an external device.

The second smoothing capacitor 165 is connected in parallel with a series circuit including the load circuit 53 and the intermittent switch SW. The second smoothing capacitor 165 supplements the decrease in the LED current, that is, the current flowing through the load circuit 53 due to the interruption of the intermittent switch SW. That is, the electric charge charged during the off period of the intermittent switch SW is discharged during the on period to increase the current during the on period of the intermittent switch SW. As a result, it is possible to reduce the decrease in brightness due to the intermittentness of the intermittent switch SW.

Next, the communication module 10 will be described. The communication module 10 can be added to an existing lighting fixture having no visible light communication function via terminals T1 to T3. The existing lighting fixture having no visible light communication function has, for example, a configuration in which the communication module 10 of FIG. 1 is deleted and the terminals T2 and T3 are directly connected.

By connecting the communication module 10 to such an existing luminaire, the illuminating optical communication device of FIG. 1 can be obtained.

[1.2 Operation of Illuminated Optical Communication Device]
Next, the simulation result for verifying the operation of the illumination optical communication device in this embodiment will be described.

FIG. 2 is a diagram showing LED current with respect to the on-duty ratio in the first embodiment. Further, FIG. 3 is a diagram showing various signal waveforms for each capacity of the second smoothing capacitor in the first embodiment.

In this simulation, the capacitance C of the second smoothing capacitor 165 is 0 μF, 22 μF, 33 μF, 47 μF, 68 μF, and 82 μF. FIG. 2 shows changes in the LED current when the on-duty ratio is changed for these six ways. FIG. 3 shows various signal waveforms for these six types. Note that FIG. 2 shows the average current of the LED current.

As shown in FIG. 2, when the on-duty ratio is 100%, that is, when the intermittent switch SW is always on, the LED current is 270 mA of direct current. Further, when the capacitance C = 0 μF, that is, when there is no second smoothing capacitor 165, the average current decreases as the on-duty ratio becomes smaller due to the interruption of the intermittent switch SW. The brightness of the illumination light is reduced by this decrease.

On the other hand, it can be seen that the larger the capacitance C of the second smoothing capacitor 165 is, the smaller the decrease in the average current is even in the region where the on-duty ratio is small. That is, if the capacitance C of the second smoothing capacitor 165 is set to an appropriate value, the reduction in brightness due to the intermittent switching of the intermittent switch SW can be sufficiently reduced.

Further, FIG. 3 shows LED current, detection current, capacitor current, and output voltage as various signal waveforms. The LED current is a current flowing through the load circuit 53. The detected current is the sum of the LED current and the capacitor current, and is the current flowing through the suppression circuit 73. The capacitor current is the current flowing through the second smoothing capacitor 165. The output voltage is the voltage of the first smoothing capacitor 65 connected between the output terminals of the power supply circuit 52b.

In FIG. 3, in any of the cases (a) to (f), the on-duty ratio is set to 75%, and the frequency of the communication signal for interrupting the intermittent switch SW is set to 2.4 kHz. When there is no second smoothing capacitor 165 (a), a whiskers-like pulse current is observed in the LED current waveform, but when there is a second smoothing capacitor 165 (b) to (f), a whiskers-like pulse current is observed. The LED current has no whiskers-like pulse current, resulting in a wide overshoot-like waveform. The whiskers-shaped pulse current is also called a spike current.

Further, when the second smoothing capacitor 165 is not present (a), pulsation is observed in the output voltage, but when the second smoothing capacitor 165 is present (b) to (f), the pulsation is small. As the capacity of the second smoothing capacitor 165 is increased, the capacitor current increases and the drop in the off period in the detected current becomes smaller, and eventually becomes a flat direct current as in (e) and (f). In that state, the overshoot of the LED current is also reduced, and the shape of the LED current is almost rectangular. That is, the second smoothing capacitor 165 supplements the current decrease in the off period in which the LED current does not flow, which occurs due to the intermittent operation, in the on period. Further, the constant voltage feedback control system by the voltage source 64 and the constant voltage feedback circuit 67a also operates stably without being affected by the interruption.

Next, the LED current when dimming is performed by making the first reference source 76 of the suppression circuit 73 variable will be described.

FIG. 4A is a diagram showing LED current with respect to the dimming ratio in the first embodiment. Further, FIG. 4B is a diagram showing an LED current with respect to the on-duty ratio in the first embodiment.

FIG. 4A examines the relationship between the dimming ratio and the peak value and the average value of the LED current with the intermittent on-duty ratio fixed at 75%. The LED current on the vertical axis is a relative value with the LED current at a dimming ratio of 100% as 100%. Even if the on-duty ratio is interrupted at 75%, the average current at the dimming ratio of 100% is the value when it is not intermittent (that is, the value when the on-duty ratio is 100%), but the peak value is close to 140%. Has risen to. This characteristic is seen in the load interruption of the suppression circuit 73 having a constant current property, and is related to the responsiveness of the feedback to the error amplifier 77. As a result, the peak value rises in inverse proportion to the on-duty ratio.

FIG. 4B shows the relationship between the on-duty ratio and the peak value and the average value of the LED current assuming that the dimming ratio is fixed at 100%, and the average value of the LED current is maintained even if the LED current is interrupted as described above. However, the peak value is rising. According to the illumination optical communication device of the first embodiment, it is possible to reduce the decrease in the average LED current, that is, the brightness due to the interruption, and to eliminate the whiskers pulse current of the LED current due to the interruption, with a simple configuration. ..

[1.3 Other effects, etc.]
As described above, the illumination optical communication device according to the first embodiment is connected in series to the load circuit 53 including the light emitting diode that emits the illumination light and the load circuit 53, and is intermittently connected according to the binary communication signal. A suppression circuit 73, which is connected in series with the switch SW, the load circuit 53, and the intermittent switch SW, and suppresses the current flowing through the switch SW so as not to exceed the first set value corresponding to the first reference value, and the first reference value. To make the voltage applied to the first reference source 76, the load circuit 53, the intermittent switch SW, and the suppression circuit 73 constant, the voltage source 64 for applying a DC voltage to the series circuit, and the suppression circuit 73. A constant voltage feedback circuit 67 that supplies a feedback signal to the voltage source 64, a first smoothing capacitor 65 connected in parallel to a series circuit including a load circuit 53, an intermittent switch SW, and a suppression circuit 73, a load circuit 53, and an intermittent switch. A series circuit composed of SW and a second smoothing capacitor 165 connected in parallel are provided.

According to this configuration, it is possible to reduce the decrease in brightness due to intermittent use. Moreover, it is suitable for circuit miniaturization and cost reduction. Further, it is possible to eliminate the whisker-shaped pulse current of the LED current associated with the intermittent operation.

Here, the first reference source 76 may generate the first reference value according to the dimming ratio that indicates the brightness of the illumination light.

According to this configuration, it is possible to reduce the decrease in brightness due to intermittentness while maintaining the brightness according to the dimming ratio.

Here, the illumination optical communication device includes a lighting fixture having a load circuit 53, a suppression circuit 73, a first reference source 76, a voltage source 64, a first smoothing capacitor 65, and a constant voltage feedback circuit 67a, an intermittent switch SW, and a second. A communication module 10 having a smoothing capacitor 165 may be provided, and the communication module 10 may be attached to and detached from a lighting fixture.

According to this configuration, the visible light communication function can be added to the existing lighting fixture having no visible light communication function by adding the communication module 10. Moreover, it is possible to reduce the decrease in brightness due to the intermittent, suitable for miniaturization and cost reduction of the circuit, and it is possible to eliminate the whisker-shaped pulse current of the LED current due to the intermittent.

Further, the communication module 10 in the first embodiment is a communication module added to a lighting fixture having no visible light communication function and adding a visible light communication function. The lighting fixture is connected in series with a load circuit 53 including a light emitting diode that emits illumination light, a load circuit 53, and an intermittent switch SW, and does not exceed the first set value corresponding to the first reference value. A suppression circuit 73 that suppresses the flowing current, a first reference source 76 that generates a first reference value, a voltage source 64 that applies a DC voltage to a series circuit including a load circuit 53, an intermittent switch SW, and a suppression circuit 73. A constant voltage feedback circuit 67 that supplies a feedback signal for making the voltage applied to the suppression circuit 73 constant to the voltage source, and a first smoothing capacitor 65 connected between two terminals for output of the voltage source 64. To prepare for. The communication module 10 is connected in series with the load circuit 53, and is connected in parallel with the intermittent switch SW that is intermittent according to the binary communication signal and the series circuit of the load circuit 53 and the intermittent switch SW. And.

According to this configuration, the communication module 10 can be miniaturized and reduced in cost, and can be easily added to the existing lighting equipment. In addition, it is possible to reduce the decrease in brightness due to the interruption and discontinuity of the intermittent switch SW in visible light communication. Further, it is possible to eliminate the whisker-shaped pulse current of the LED current associated with the intermittent operation.

(Embodiment 2)
According to the first embodiment, the whisker-shaped pulse current of the LED current due to the interruption of the intermittent switch SW can be reduced, but as is clear from FIG. 3, there is some overshoot in the LED current. If the capacitance value of the second smoothing capacitor 165 is large enough, this overshoot is almost negligible. However, the larger the capacitance value, the larger the external dimension of the second smoothing capacitor 165. Further, in many cases, it is desired to make the capacitor capacity as small as possible due to restrictions on the shape and dimensions of the actual communication module 10. In the second embodiment, a configuration example is described in which a limiter circuit is mounted on the communication module 10 of the first embodiment to limit the overshoot of the LED current, which becomes more remarkable as the capacitance value of the second smoothing capacitor 165 becomes smaller. do.

[2.1 Configuration of Illuminated Optical Communication Device]
FIG. 5 is a circuit diagram showing a configuration example of the illumination optical communication device according to the second embodiment. Compared to FIG. 1, this illuminated optical communication device has a limiter circuit 101 added in the communication module 10, an intermittent switch SW incorporated in the limiter circuit 101, and a communication signal of the inverter 102 and the inverter 102. It is different from the point that it is input to the gate terminal of the intermittent switch SW via the switch transistor 84. Hereinafter, the differences will be mainly described.

The limiter circuit 101 includes an intermittent switch SW, an operational amplifier 86, a reference source 87, a resistor 88, and a loss detection circuit 99.

A resistor 88 is connected to the source terminal of the MOSFET, which is the intermittent switch SW. The resistor 88 is a detection resistor for detecting the amount of current flowing through the limiter circuit 101 as a voltage value.

A reference source 87 is connected to the positive input end of the operational amplifier 86, and a resistor 88 is connected to the negative input end of the operational amplifier 86.

The switch transistor 84 is connected between the gate terminal of the intermittent switch SW and the negative end of the reference source 87, and is controlled on and off by an inverted signal of the communication signal. During the high level period of the communication signal, the inverting signal is low level, so that the switch transistor 84 is off. When the switch transistor 84 is off, the intermittent switch SW conducts according to the output voltage of the operational amplifier 86. The current flowing through the intermittent switch SW at the time of conduction is limited so as not to exceed the current value corresponding to the second reference value of the reference source 87.

Further, during the period when the communication signal is at a low level, the inverted signal becomes a high level, so that the switch transistor 84 is turned on, the gate voltage of the intermittent switch SW becomes equal to or less than the threshold value, and the LED current is cut off.

In this way, the intermittent switch SW is not a simple on and off operation, but operates so as to limit the current flowing through itself when it is on so as not to exceed the current value corresponding to the second reference value.

The loss detection circuit 99 detects the magnitude of the loss that occurs in the limiter circuit 101. The magnitude of the loss is detected as a voltage drop occurring in the intermittent switch SW and the resistance 88. The magnitude of the detected loss is input to the reference source 87 and reflected in the second reference value. That is, the reference source 87 generates the second reference value so that the loss is the minimum necessary value.

As described above, the illumination optical communication device of FIG. 5 adjusts the second reference value of the reference source 87 when the average current of the LED current is not constant by the dimming function or the visible light communication, and is generated in the limiter circuit 101. The loss can be reduced.

Next, another configuration example of the limiter circuit 101 will be described.

FIG. 6 is a circuit diagram of the communication module 10 including another configuration example of the limiter circuit 101 according to the second embodiment. The communication module 10 in the figure includes a signal generation circuit SG, an inverter 102, a driver 103, a limiter circuit 101, and a second smoothing capacitor 165.

The inverter 102 is an inverting driver that inverts the communication signal from the signal generation circuit SG and outputs it to the limiter circuit 101.

The driver 103 is a non-inverting driver that outputs the communication signal from the signal generation circuit SG to the communication module 10 without inverting it.

The limiter circuit 101 has the same function as the limiter circuit 101 of FIG. 5, except that the reference source 87 and the loss detection circuit 99 are embodied as compared with FIG. Hereinafter, the differences will be mainly described.

The limiter circuit 101 includes an intermittent switch SW, an operational amplifier 86, a resistor 88, a resistor 89, a resistor 90, a resistor 91, a transistor 92, a resistor 93, a capacitor 94, a resistor 95, a diode 96, a resistor 97, a capacitor 193 and a resistor 194. ..

Here, the reference source 87 and the loss detection circuit 99 in FIG. 5 are composed of a voltage dividing and integrating circuit including a resistor 91, a resistor 194, and a capacitor 193 in FIG. Further, the transistor 92 prevents the voltage applied to the limiter circuit 101 from sneaking into the integrating circuit including the resistor 194 and the capacitor 193 while the intermittent switch SW is off. Further, the transistor 92 is turned on during the period when the intermittent switch SW is turned on, and generates a second reference value according to the voltage drop of the limiter circuit 101.

In this way, the limiter circuit 101 is configured as a simple analog circuit.

[2.2 Operation of Illuminated Optical Communication Device]
Next, the simulation result of the operation of the illumination optical communication device of FIG. 6 will be described.

FIG. 7 is a diagram showing various signal waveforms when the on-duty ratio is constant in the illumination optical communication device of the second embodiment. Further, FIG. 8 is a diagram showing various signal waveforms when the dimming ratio is constant in the illumination optical communication device of the second embodiment.

7 and 8 show LED current, output voltage, circuit loss, and circuit voltage waveforms as various signal waveforms. The LED current is the current flowing through the load circuit 53, and the output voltage is the voltage held in the first smoothing capacitor 65. The circuit loss is the loss generated by the limiter circuit 101. The circuit voltage is the voltage applied to the limiter circuit 101.

FIGS. 7A to 7D show various signal waveforms when the on-duty ratio is constant at 75% and the dimming ratio is 100%, 75%, 50%, and 20%. 8 (a) to 8 (d) show various signal waveforms when the dimming ratio is constant at 100% and the on-duty ratio is 90%, 75%, 50%, and 30%.

From the dimming ratio 100% lighting in FIG. 7 (a) to the 20% lighting in (d), the LED current waveform maintains a square wave, and no whiskers-like pulse current or overshoot is found. Further, as the dimming ratio becomes smaller, the pulsation of the output voltage becomes smaller, and the circuit loss of the limiter circuit 101 decreases.

From the on-duty ratio of 90% in FIG. 8 (a) to 30% in (d), the LED current waveform maintains a rectangular wave, and no whiskers-like pulse current or overshoot is found. The pulsation of the output voltage increases as the on-duty ratio decreases, and the loss of the limiter circuit 101 increases.

9A to 9D show the above results graphically, and FIG. 9A is a diagram showing the relationship between the dimming ratio and the peak value and the average value of the LED current. This figure is almost the same result as FIG. 4A of the first embodiment.

FIG. 9B is a diagram showing the relationship between the dimming ratio and the circuit loss of the limiter circuit 101. As shown in the figure, the larger the dimming ratio and the larger the average current, the higher the circuit loss. It is considered that this circuit loss is due to the consumption of overshoot current having a considerably large width. The larger the capacitance value of the second smoothing capacitor 165, the smaller the overshoot of the LED current, so that the circuit loss can be reduced, but it is a trade-off with the shape of the second smoothing capacitor 165, for example, the external dimensions.

FIG. 9C is a diagram showing the relationship between the on-duty ratio and the peak value and the average value of the LED current. The figure is substantially the same as FIG. 4B of the first embodiment.

FIG. 9D is a diagram showing the relationship between the on-duty ratio and the circuit loss of the limiter circuit 101. In the figure, the smaller the actual on-duty ratio, the larger the loss, and the characteristics that are approximately similar to the peak value of the LED current are shown. This is because the average value of the LED current is maintained and the peak value increases as the on-duty ratio becomes smaller.

As described above, in the illumination optical communication device of the second embodiment, the decrease in brightness is reduced even if the LED current is interrupted, and the overshoot of the LED current due to the interruption is suppressed even when the capacity of the second smoothing capacitor 165 is small. It can be made closer to a square wave. It is particularly effective in visible light communication where a highly accurate signal waveform is required. A small capacitor with a small capacity can be used for the second smoothing capacitor 165, which is suitable for miniaturization and cost reduction, can be easily mounted in the communication module 10, and is also suitable for miniaturization of the communication module 10. There is.

[2.3 Other effects, etc.]
As described above, the illumination optical communication device according to the second embodiment includes a limiter circuit 101 which is connected in series with the load circuit 53 and the intermittent switch SW and limits the overshoot current flowing through the load circuit 53.

The capacitance of the second smoothing capacitor 165 can be reduced, in other words, the second smoothing capacitor 165 can be a small capacitive element, and a small capacitor with a small capacitance can be used for the second smoothing capacitor 165. .. In addition, it is possible to suppress the overshoot of the LED current due to the intermittentness and bring it closer to a rectangular wave. It is particularly effective in visible light communication where a highly accurate signal waveform is required.

Here, the limiter circuit 101 is connected in series to the source terminal of the intermittent switch SW, and has a resistor 88 for detecting the magnitude of the source current as a voltage, a voltage detected by the resistor 88, and a second reference value. An operational amplifier 86 that amplifies the error and outputs the amplified signal to the gate terminal of the intermittent switch SW, and a switch that changes the voltage of the gate terminal to a voltage equal to or lower than the threshold of the intermittent switch SW when the communication signal indicates an off period. It may have a transistor 84.

According to this, since the intermittent switch SW has two operations, the communication module 10 can be miniaturized and the cost can be reduced. The two operations are an operation of interrupting the LED current and an operation of limiting the current flowing through the LED current at the time of conduction according to the magnitude of the amplified signal.

Here, the limiter circuit 101 has an integrating circuit that divides and integrates the voltage drop of the limiter circuit 101 when the intermittent switch SW is conducting, and may generate an integrated value by the integrating circuit as a second reference value.

According to this, since the reference source 87 is configured as a simple analog circuit, the limiter circuit 101 and the communication module 10 can be miniaturized and reduced in cost.

Although the dimming function in each embodiment has been described on the premise that the amount of current is adjusted in an analog manner, dimming may be performed by intermittently interrupting the current digitally. However, the frequency of the intermittent dimming that digitally interrupts the current should be one digit or more slower than the frequency of the intermittent by visible light communication.

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.

For example, a part or all of each circuit 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 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, in the present invention, an element such as a switching element (for example, a transistor), a resistance element, or a capacitive element is 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. included. In other words, "connected" in the above embodiment is not limited to the case where two terminals (or nodes) are directly connected, and the two terminals are not limited to the case where the same function can be realized. It also includes the case where (or a node) is connected via an element.

Further, the logical level represented by the high level and the low level or the switching state represented by the on and off is exemplified for the purpose of specifically explaining the present invention, and the exemplified logical level or the switching state is represented. Equivalent results can be obtained with different combinations.

In addition, the division of functional blocks in the block diagram is an example, and multiple functional blocks can be realized as one functional block, one functional block can be divided into multiple, 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 embodiments has been described above based on the embodiment, the present invention is not limited to this embodiment. As long as it does not deviate from the gist of the present invention, a form in which various modifications conceived by those skilled in the art are applied to the present embodiment or a form constructed by combining components in different embodiments is also within the scope of one or a plurality of embodiments. May be included within.

10 Communication module 53 Load circuit 64 Voltage source 65 First smoothing capacitor 67a Constant voltage feedback circuit 73 Suppression circuit 76 First reference source 84 Switch transistor 86 Operational amplifier 88 Resistance 101 Limiter circuit 165 Second smoothing capacitor SW intermittent switch

Claims (7)

A load circuit including a light emitting diode that emits illumination light,
An intermittent switch connected in series with the load circuit and intermittent according to a binary communication signal,
A suppression circuit that is connected in series with the load circuit and the intermittent switch and suppresses the current flowing through itself so as not to exceed the first set value corresponding to the first reference value.
The first reference source that generates the first reference value and
A voltage source that applies a DC voltage to the series circuit including the load circuit, the intermittent switch, and the suppression circuit,
A constant voltage feedback circuit that supplies a feedback signal to the voltage source to keep the voltage applied to the suppression circuit constant, and
A first smoothing capacitor connected in parallel to a series circuit including the load circuit, the intermittent switch and the suppression circuit,
An illumination optical communication device including a series circuit including the load circuit and the intermittent switch and a second smoothing capacitor connected in parallel. The illumination optical communication device according to claim 1, wherein the first reference source generates the first reference value according to a dimming ratio that indicates the brightness of the illumination light. A limiter circuit connected in series with the load circuit and the intermittent switch and limiting the overshoot current flowing through the load circuit is provided .
The first smoothing capacitor is connected in parallel with a series circuit including the load circuit, the intermittent switch, the limiter circuit and the suppression circuit.
The second smoothing capacitor is connected in parallel with a series circuit including the load circuit, the intermittent switch and the limiter circuit.
The illumination optical communication device according to claim 1 or 2. The limiter circuit is
A resistance connected in series to the source terminal of the intermittent switch to detect the magnitude of the source current as a voltage,
An operational amplifier that amplifies the error between the voltage detected by the resistance and the second reference value and outputs the amplified signal to the gate terminal of the intermittent switch .
The illumination optical communication device according to claim 3, further comprising a switch transistor that changes the voltage of the gate terminal to a voltage equal to or lower than the threshold value of the intermittent switch when the communication signal indicates an off period. The limiter circuit is
A resistance connected in series to the source terminal of the intermittent switch to detect the magnitude of the source current as a voltage,
An operational amplifier that amplifies the error between the voltage detected by the resistance and the second reference value and outputs the amplified signal to the gate terminal of the intermittent switch.
It has an integrating circuit that divides and integrates the voltage drop of the limiter circuit when the intermittent switch is conducting.
The illumination optical communication device according to claim 3, wherein the integrated value by the integrating circuit is generated as the second reference value. A lighting fixture having the load circuit, the suppression circuit, the first reference source, the voltage source, the first smoothing capacitor, and the constant voltage feedback circuit.
The intermittent switch and the communication module having the second smoothing capacitor are provided.
The illumination optical communication device according to claim 1 or 2 , wherein the communication module is removable from the lighting equipment. It is a communication module that is added to lighting equipment that does not have a visible light communication function and adds a visible light communication function.
The lighting fixture is
A load circuit including a light emitting diode that emits illumination light,
A suppression circuit that is connected in series with the load circuit and suppresses the current flowing through itself so as not to exceed the first set value corresponding to the first reference value.
The first reference source that generates the first reference value and
A voltage source that applies a DC voltage to the series circuit including the load circuit and the suppression circuit,
A constant voltage feedback circuit that supplies a feedback signal to the voltage source to keep the voltage applied to the suppression circuit constant, and
It is equipped with a first smoothing capacitor connected between the two terminals for the output of the voltage source.
The communication module is
An intermittent switch connected in series with the load circuit and intermittent according to a binary communication signal,
A communication module including the load circuit and a series circuit of the intermittent switch and a second smoothing capacitor connected in parallel.

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