JP2013225807A - Signal transmission circuit, power unit and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal transmission circuit, a power unit and a lighting device that implement desired signal resolution while suppressing power consumption.SOLUTION: A signal transmission circuit 30 comprises: a photo coupler 21; a current amplification section 40; a current-voltage conversion section 50 and the like. The current amplification section 40 includes transistors 221, 231, resistances 222, 232 and the like, and amplifies a current flowing through a phototransistor 212. The current-voltage conversion section 50 includes a resistance 24, and converts the current amplified by the current amplification section 40 to a voltage. The current-voltage conversion section 50 transmits (outputs) the conversion voltage to a microcomputer 14 on an output side of the phototransistor 212.

Description

  The present invention relates to a signal transmission circuit that outputs a signal input to a photocoupler to a signal determination unit, a power supply unit including the signal transmission circuit, and a lighting device including the power supply unit.

  A photocoupler is used to electrically insulate a circuit in a circuit composed of a plurality of circuit elements (for example, a power supply circuit). For example, a switching power supply device that can electrically insulate an output side circuit from a control circuit by using a photocoupler in a feedback circuit that feeds back an output voltage to a control circuit is disclosed (see Patent Document 1). ).

JP 2003-174769 A

  In the photocoupler used in the power supply device of Patent Document 1, the signal input to the LED on the input side is once converted into light, and the converted light is transmitted to the phototransistor on the output side, and the signal is output from the output side of the photocoupler. Is output.

  FIG. 13 is a circuit diagram showing an example of a circuit including a conventional photocoupler 303, and FIG. 14 is a time chart showing an example of an input waveform and an output waveform of the conventional photocoupler 303. As shown in FIG. 13, the photocoupler 303 includes an input-side LED 304 and an output-side phototransistor 305 that is electrically insulated from the LED 304. One end of an input resistor 301 is connected to the LED 304, and the other end of the input resistor 301 is a signal input end Vin. One end of the output resistor 302 is connected to the phototransistor 305, and the power supply VCC is connected to the other end of the output resistor 302. A connection node between the phototransistor 305 and the output resistor 302 is a signal output terminal Vout.

  As shown in FIG. 14, when the signal (rectangular pulse signal) applied to the input terminal Vin falls at time t1, the current flowing through the LED 304 becomes 0, and the phototransistor 305 is turned from the on state to the off state. And the voltage at the output terminal Vout rises.

  However, since the collector-emitter capacitance (hereinafter also referred to as output capacitance) of the phototransistor 305 is generally a relatively large value, it takes a long time to charge the output capacitance via the output resistor 302. . For this reason, as shown in FIG. 14, the rise time Δt1 of the signal at the output terminal Vout becomes longer. For example, when the output resistance 302 is 100Ω, the rise time Δt1 is about 10 to 20 μs, when the output resistance 302 is 1 kΩ, the rise time Δt1 is about 30 to 100 μs, and when the output resistance 302 is 10 kΩ, the rise time Δt1. Is about 100 to 300 μs.

  When the frequency of a signal (for example, a rectangular wave pulse) input to the photocoupler 303 is 1 kHz, for example, the resolution of the duty ratio of the signal is within 5% (for example, the duty ratio is 5%, In order to correctly recognize a 95% signal), it is necessary to correctly recognize a signal having a pulse width of 20 μs or less, which is 5% of 1 kHz.

  That is, in the circuit of the photocoupler 303 as shown in FIG. 13, since the rise time of the signal at the output terminal is long, it is necessary to reduce the output resistance in order to shorten the rise time. Power consumption at the output resistance increases, which is not realistic. On the other hand, if the output resistance is set to a large value in order to suppress power consumption, the rise time of the output end becomes long and a desired signal resolution cannot be obtained.

  Further, in the circuit of the photocoupler 303 as shown in FIG. 13, when the current If flowing through the LED 304 is reduced, the current transfer ratio (CTR: Current Transfer Ratio) which is the ratio of the current Ic flowing through the phototransistor 305 to the current If flowing through the LED 304 ) Becomes smaller, the voltage level of the output terminal Vout does not drop to the low level (GND level). Further, when the current If is decreased, not only the CTR is decreased, but also Ic is further decreased because Ic = CTR × If. For this reason, the current If flowing through the LED 304 cannot be reduced, and the output power of a circuit that outputs a signal to the photocoupler 303 (for example, a circuit that outputs a dimming signal) increases.

  The present invention has been made in view of such circumstances, and a signal transmission circuit capable of obtaining a desired signal resolution while suppressing power consumption, a power supply unit including the signal transmission circuit, and an illumination device including the power supply unit The purpose is to provide.

  A signal transmission circuit according to the present invention includes a photocoupler, and in the signal transmission circuit that transmits a signal input to the photocoupler to a signal determination unit, a current amplification unit that amplifies a current flowing through a phototransistor of the photocoupler; And a first current-voltage converter that converts the current amplified by the current amplifier into a voltage.

  The present invention includes a current amplifying unit that amplifies the current flowing through the phototransistor of the photocoupler, and a first current-voltage converting unit that converts the current amplified by the current amplifying unit into a voltage. Then, the voltage converted by the first current-voltage conversion unit is transmitted to the signal determination unit. The signal determination unit is a circuit that receives a signal output from the signal transmission circuit, for example. As a signal discrimination | determination part, it has a function which discriminate | determines signals, such as a microcomputer (microcomputer), for example. Rather than directly connecting an output resistor to the phototransistor, a current amplifier that amplifies the current flowing through the phototransistor on the output side of the phototransistor, and a first current-voltage converter that converts the current amplified by the current amplifier into a voltage , The current flowing through the phototransistor can be reduced, the output signal rising speed can be increased, and a desired signal resolution can be obtained. In addition, since the transition time of the output signal (output voltage) can be shortened, the output resistance can be increased (for example, 1 kΩ, 10 kΩ, etc.), and power consumption at the output resistance can be reduced. . In addition, since the current amplifying unit is provided, the current flowing through the LED of the photocoupler can be reduced (the input resistance of the photocoupler can be increased), and the voltage level of the output terminal Vout is low level (GND level). The problem of not decreasing to the ground level) can also be solved. In addition, since the current flowing through the LED of the photocoupler can be reduced, the output power of an external circuit that outputs a signal to the photocoupler (for example, a circuit that outputs a dimming signal) can be reduced. Many photocouplers can be driven by one external circuit.

  A signal transmission circuit according to the present invention includes a photocoupler, and in the signal transmission circuit that transmits a signal input to the photocoupler to a signal determination unit, a second current that converts a current flowing through a phototransistor of the photocoupler into a voltage is second. A current-voltage conversion unit and a voltage amplification unit that amplifies the voltage converted by the second current-voltage conversion unit.

  The present invention includes a second current-voltage conversion unit that converts a current flowing through the phototransistor into a voltage, and a voltage amplification unit that amplifies the voltage converted by the second current-voltage conversion unit. Then, the voltage amplified by the voltage amplification unit is transmitted to the signal determination unit. The signal determination unit is a circuit that receives a signal output from the signal transmission circuit, for example. As a signal discrimination | determination part, it has a function which discriminate | determines signals, such as a microcomputer (microcomputer), for example. Rather than connecting the output resistor directly to the phototransistor, a second current-voltage converter that converts the current flowing through the phototransistor into a voltage and a voltage amplifier that amplifies the voltage converted by the second current-voltage converter As a result, the current flowing through the phototransistor can be reduced, the output signal rising speed can be increased, and a desired signal resolution can be obtained. In addition, since the transition time of the output signal (output voltage) can be shortened, the output resistance can be increased (for example, 1 kΩ, 10 kΩ, etc.), and power consumption at the output resistance can be reduced. . In addition, since a voltage amplification unit that amplifies the voltage converted by the current-voltage conversion unit is provided, the current flowing to the LED of the photocoupler can be reduced (the input resistance of the photocoupler can be increased), and the output The problem that the voltage level of the terminal Vout does not decrease to the low level (GND level, ground level) can also be solved. In addition, since the current flowing through the LED of the photocoupler can be reduced, the output power of an external circuit that outputs a signal to the photocoupler (for example, a circuit that outputs a dimming signal) can be reduced. Many photocouplers can be driven by one external circuit.

  In the signal transmission circuit according to the present invention, the current amplification unit includes a first transistor connected in series to the phototransistor, and a base or gate connected to a connection node between the phototransistor and the first transistor. The first current-voltage conversion unit has a resistor connected in series to the second transistor.

  In the present invention, the current amplifying unit includes a first transistor connected in series to the phototransistor, and a second transistor having a base or gate connected to a connection node between the phototransistor and the first transistor. Have. The first current-voltage converter has a resistor connected in series to the second transistor. Each of the first transistor and the second transistor may be an NPN transistor, a PNP transistor, an N-channel FET, or a P-channel FET. In the case of an NPN type transistor, the collector of the first transistor is connected to the phototransistor, the base of the second transistor is connected to the connection node between the phototransistor and the first transistor, and the collector of the second transistor A resistor is connected to In the case of a PNP type transistor, the collector of the first transistor is connected to the phototransistor, the base of the second transistor is connected to the connection node between the phototransistor and the first transistor, and the second transistor A resistor is connected to the collector. In the case of an N-channel FET, the drain of the first transistor is connected to the phototransistor, the gate of the second transistor is connected to the connection node between the phototransistor and the first transistor, A resistor is connected to the drain. In the case of a P-channel FET, the drain of the first transistor is connected to the phototransistor, and the gate of the second transistor is connected to the connection node between the phototransistor and the first transistor. A resistor is connected to the drain.

  When the first and second transistors are NPN type or N-channel FET, the base or gate is connected to the connection node between the first transistor connected in series with the phototransistor and the phototransistor and the first transistor. With the second transistor, when the phototransistor is on, the collector voltage of the phototransistor is the power supply voltage VCC (for example, 5 V), and the emitter voltage of the phototransistor is As a result, the voltage becomes about 0.7 V, and as a result, the voltage between the collector and the emitter of the phototransistor becomes about 4.3 V. When the phototransistor is turned off, the emitter voltage of the phototransistor is at the ground level (for example, 0 V), so that the voltage between the collector and the emitter of the phototransistor is about 5.0 V, and the phototransistor is turned on. When transitioning to the off state, the voltage between the collector and the emitter of the phototransistor rises only about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained.

  In the case where the first and second transistors are PNP type or P-channel FET, a base or gate is connected to a connection node between the first transistor connected in series with the phototransistor and the phototransistor and the first transistor. By providing the second transistor connected, when the phototransistor is on, the voltage of the emitter of the phototransistor is at a ground level (eg, 0 V), and the voltage of the collector of the phototransistor is By being in the ON state, the power supply voltage VCC (5 V) −0.7 V = about 4.3 V, and as a result, the voltage between the collector and the emitter of the phototransistor is about 4.3 V (power supply voltage VCC (5 V) −0). .7V). When the phototransistor is turned off, the collector voltage of the phototransistor becomes the power supply voltage VCC (5 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor Rises only about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained.

  Also, the output capacity of the second transistor connected in series with the resistor as the first current-voltage converter (for example, the capacity between the collector and the base) is about 2 to 3 orders of magnitude smaller than the output capacity of the phototransistor. The time required for charging the output capacitance when the second transistor transitions from the on state to the off state is short, the rise time of the output signal can be increased, and a desired signal resolution can be obtained. Further, since the current flowing through the output resistance can be amplified by the first and second transistors, the output resistance can be increased (for example, 1 kΩ, 10 kΩ, etc.), and the power consumption at the output resistance can be reduced. Can be reduced.

  The signal transmission circuit according to the present invention is characterized in that a resistor is connected in series to each of the first and second transistors.

  In the present invention, resistors (referred to as first and second resistors, respectively) are connected in series to the first transistor and the second transistor, respectively. When the resistance value of the first resistor is increased, the bias voltage for the second transistor can be increased, so that the current amplification factor of the current amplification unit can be increased. A desired current gain can be obtained by appropriately setting the values of the first and second resistors. In addition, since the current amplification factor can be varied, even when the current flowing through the LED of the photocoupler is reduced, even if the current transfer rate (CTR) is reduced, a sufficient current can flow through the output resistance. The problem that the voltage level of the output terminal Vout does not decrease to the low level (GND level, ground level) can be prevented. In addition, since the current flowing through the LED of the photocoupler can be reduced, the output power of an external device that outputs a signal to the photocoupler (for example, a dimmer that outputs a dimming signal) can be reduced. It is possible to drive many photocouplers with one external device.

  In the signal transmission circuit according to the present invention, the current amplifying unit includes a resistance element connected in series to the phototransistor, and a transistor having a base or a gate connected to a connection node between the phototransistor and the resistance element. The first current-voltage conversion unit includes a resistor connected in series to the transistor.

  In the present invention, the current amplifying unit includes a resistance element connected in series to the phototransistor, and a transistor having a base or a gate connected to a connection node between the phototransistor and the resistance element. In addition, the first current-voltage converter has a resistor connected in series to the transistor. The transistor may be an NPN-type transistor, a PNP-type transistor, an N-channel FET, or a P-channel FET. In the case of an NPN transistor, a base is connected to a connection node between a phototransistor and a resistance element, and a collector is connected to a resistor. In the case of a PNP transistor, the base is connected to the connection node between the phototransistor and the resistance element, and the collector is connected to the resistor. In the case of an N-channel FET or P-channel FET, the gate is connected to the connection node between the phototransistor and the resistance element, and the drain is connected to the resistor.

  When the transistor of the current amplifying unit is an NPN type or N-channel FET, a transistor having a base or a gate connected to a connection node between the phototransistor and the resistance element is provided. Is the power supply voltage VCC (for example, 5 V), and the emitter voltage of the phototransistor becomes approximately 0.7 V when the transistor as the second element is turned on. The voltage between the emitters is about 4.3V. When the phototransistor is turned off, the voltage at the emitter of the phototransistor becomes the ground level (for example, 0 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor The voltage rises only about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained. In addition, since the resistance element is connected in series to the phototransistor, the circuit configuration is simplified and a low price can be realized as compared with the case where the transistor is connected in series to the phototransistor.

  Further, when the transistor of the current amplifying unit is a PNP type or P-channel FET, the phototransistor is provided with a transistor having a base or a gate connected to a connection node between the phototransistor and the resistance element. The collector voltage of the phototransistor is at the ground level (for example, 0 V), and the voltage of the collector of the phototransistor is changed to the power supply voltage VCC (5 V) −0.7 V = approximately by turning on the transistor as the second element. As a result, the voltage between the collector and the emitter of the phototransistor is about 4.3 V (power supply voltage VCC (5 V) −0.7 V). When the phototransistor is turned off, the collector voltage of the phototransistor becomes the power supply voltage VCC (5 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor Rises only about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained. In addition, since the resistance element is connected in series to the phototransistor, the circuit configuration is simplified and a low price can be realized as compared with the case where the transistor is connected in series to the phototransistor.

  In addition, the output capacitance (for example, the capacitance between the collector and the emitter) of the transistor connected in series with the resistor that is the first current-voltage converter is about two to three orders of magnitude smaller than the output capacitance of the phototransistor. The time required for charging the output capacitance when transitioning from the on state to the off state is short, the rise time of the output signal can be increased, and a desired signal resolution can be obtained.

  In the signal transmission circuit according to the present invention, the second current-voltage conversion unit includes a resistance element connected in series to the phototransistor, and the voltage amplification unit includes a reference voltage source, the phototransistor, and the resistance element. And an operational amplifier in which another input terminal is connected to the reference voltage source.

  In the present invention, the second current-voltage converter has a resistance element connected in series to the phototransistor. The voltage amplifying unit includes a reference voltage source, and an operational amplifier in which one input terminal is connected to a connection node between the phototransistor and the resistance element, and another input terminal is connected to the reference voltage source. For example, the collector of the phototransistor is connected to the power supply voltage VCC, the resistance element of the second current-voltage converter is connected to the emitter of the phototransistor, and one input terminal (for example, non-inverting input terminal) of the operational amplifier is connected to the phototransistor. To the connection node between the emitter and the resistance element. The other end of the plurality of voltage dividing resistors is connected to the power supply voltage VCC, and the other input terminal (for example, the inverting input terminal) of the operational amplifier is connected to a connection node between the voltage dividing resistors. That is, a voltage obtained by dividing the power supply voltage VCC with a voltage dividing resistor is applied as the reference voltage of the reference voltage source to the other input terminal (for example, the inverting input terminal) of the operational amplifier. Note that the reference voltage source is not limited to the configuration in which the power supply voltage is divided by the voltage dividing resistor, and may be a configuration in which the reference voltage source is directly connected to the other input terminal of the operational amplifier.

  Since the operational amplifier operates even when the potential difference at the input terminal is about 0.1 V, for example, when the phototransistor is on, the collector voltage of the phototransistor becomes the power supply voltage VCC (for example, 5 V), and the emitter of the phototransistor The voltage can be about 0.1V. As a result, the voltage between the collector and the emitter of the phototransistor is about 4.9V. When the phototransistor is turned off, the voltage at the emitter of the phototransistor becomes the ground level (for example, 0 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor The voltage rises only about 0.1V. For this reason, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the transition time of the output voltage can be further increased, and a desired signal resolution can be obtained.

  The signal transmission circuit according to the present invention is characterized in that the second current-voltage converter has a diode connected in parallel with the resistance element.

  In the present invention, the second current-voltage converter has a diode connected in parallel with the resistance element. By providing the diode, for example, the voltage of the emitter of the phototransistor can be clipped (limited) by a voltage about the forward voltage of the diode, and when the phototransistor is turned off, the voltage of the emitter of the phototransistor Can be prevented from rising to the power supply voltage.

  In the signal transmission circuit according to the present invention, the reference voltage source includes a power supply voltage source and a plurality of voltage dividing resistors connected in series to the power supply voltage source, and a connection node between the voltage dividing resistors is The other input terminal of the operational amplifier is connected.

  In the present invention, since the reference voltage can be generated using the voltage dividing resistor, the operational amplifier can be operated with a desired reference voltage by appropriately setting the resistance value of the voltage dividing resistor.

  In the signal transmission circuit according to the present invention, the second current-voltage conversion unit includes a diode connected in series to the phototransistor, and the voltage amplification unit is based on a connection node between the phototransistor and the diode. The transistor includes a transistor connected to a gate and a resistor connected in series to the transistor.

  In the present invention, the second current-voltage converter has a diode connected in series with the phototransistor. The voltage amplification unit includes a transistor having a base or a gate connected to a connection node between the phototransistor and the diode, and a resistor connected in series to the transistor. More specifically, when there are a plurality of diodes connected in series to the phototransistor (a plurality of diodes connected in series), the base or gate of the transistor is connected to the connection node between the phototransistor and the diode via a resistor. Connecting. The transistor may be an NPN-type transistor, a PNP-type transistor, an N-channel FET, or a P-channel FET. In the case of an NPN transistor, a base is connected to a connection node between a phototransistor and a diode, and a collector is connected to a resistor. In the case of a PNP transistor, a base is connected to a connection node between a phototransistor and a diode, and a collector is connected to a resistor. In the case of an N-channel FET or P-channel FET, the gate is connected to the connection node between the phototransistor and the diode, and the drain is connected to the resistor.

  When the transistor of the voltage amplification unit is an NPN type or an N-channel FET, a transistor having a base or a gate connected to a connection node between the phototransistor and the diode is provided, so that when the phototransistor is on, the collector of the phototransistor The voltage becomes the power supply voltage VCC (for example, 5 V), and the emitter voltage of the phototransistor becomes about 1.4 V when the diode is turned on. As a result, the voltage between the collector and the emitter of the phototransistor is about 3. 6V. When the phototransistor is turned off, the voltage at the emitter of the phototransistor becomes the ground level (for example, 0 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor The voltage rises only about 1.4V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained. Further, since the diode is connected in series with the phototransistor, the circuit configuration is simplified and a low price can be realized as compared with the case where the transistor is connected in series with the phototransistor.

  In addition, when the transistor of the voltage amplification unit is a PNP type or P-channel FET, a transistor having a base or a gate connected to a connection node between the phototransistor and the diode as the first element is provided so that the phototransistor is turned on. In this state, the emitter voltage of the phototransistor is at the ground level (for example, 0 V), and the collector voltage of the phototransistor is turned on by turning on the transistor as the second element, so that the power supply voltage VCC (5 V) − As a result, the voltage between the collector and the emitter of the phototransistor is about 3.6 V (power supply voltage VCC (5 V) −1.4 V). When the phototransistor is turned off, the collector voltage of the phototransistor becomes the power supply voltage VCC (5 V). Therefore, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor Only rises about 1.4V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor is shortened, the output voltage transition time can be increased, and a desired signal resolution can be obtained. Further, since the diode is connected in series with the phototransistor, the circuit configuration is simplified and a low price can be realized as compared with the case where the transistor is connected in series with the phototransistor.

  In the voltage amplification unit, the output capacitance of the transistor connected in series with the resistor (for example, the capacitance between the collector and the emitter) is about two to three orders of magnitude smaller than the output capacitance of the phototransistor. The time required for charging the output capacitance when transitioning to the off state is short, the rise time of the output signal can be increased, and a desired signal resolution can be obtained.

  A power supply unit according to the present invention includes a signal transmission circuit according to any one of the above-described inventions, and a power control unit that controls power supplied to the light source based on a dimming signal output from the signal transmission circuit. It is characterized by that.

  The present invention includes a signal transmission circuit and a power control unit that controls power supplied to the light source based on a dimming signal output from the signal transmission circuit. Thereby, it is possible to realize a power supply unit capable of obtaining a desired resolution by increasing the resolution of the dimming signal while suppressing power consumption.

  In the power supply unit according to the present invention, the signal transmission circuit receives a PWM signal from an external dimmer, and controls the power supplied to the light source to 10% or less according to the duty ratio of the PWM signal. And

  In the present invention, the signal transmission circuit receives the PWM signal from the external dimmer, and controls the power supplied to the light source to 10% or less according to the duty ratio of the received PWM signal. Thereby, the output of the light source can be controlled with a resolution of 10% or less.

  An illumination device according to the present invention includes a light source and the power supply unit according to the above-described invention.

  In this invention, a light source and a power supply unit are provided. Thereby, it is possible to realize an illuminating device capable of obtaining a desired resolution by increasing the resolution of the dimming signal while suppressing power consumption.

  According to the present invention, a desired signal resolution can be obtained by increasing the speed of rising of an output signal. In addition, the input resistance of the photocoupler can be increased. Furthermore, power consumption can be suppressed.

It is a block diagram which shows an example of a structure of the illuminating device of this Embodiment. It is a circuit diagram which shows the 1st example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 1st example of the signal transmission circuit of this Embodiment. It is a time chart which shows an example of the input waveform and output waveform of the photocoupler of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 2nd example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 2nd example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 3rd example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 3rd example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 4th example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 5th example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 6th example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows the 7th example of the signal transmission circuit of this Embodiment. It is a circuit diagram which shows an example of the circuit provided with the conventional photocoupler. It is a time chart which shows an example of the input waveform and output waveform of the conventional photocoupler.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is a block diagram illustrating an example of the configuration of the illumination device 100 according to the present embodiment. As shown in FIG. 1, the lighting device 100 includes a power supply unit 80, a light source 90, and the like.

  The light source 90 includes, for example, one LED module or a plurality of LED modules connected in series. The light source 90 may include one group of LEDs in which a plurality of LEDs are connected in series, or may have a configuration in which a plurality of groups of LEDs are connected in parallel. The light source 90 is not limited to the LED module, and may be another light source such as EL (Electro-Luminescence).

  The power supply unit 80 removes noise from the AC power supply and prevents noise generated in the power supply unit 80 from propagating to the outside through the power supply line, and rectification that rectifies the AC voltage from the AC power supply. The circuit 11 boosts the voltage after rectification, and has a PFC (Power Factor Control) booster circuit 12 for improving the power factor, a PWM control circuit, and outputs a required voltage to be supplied to the light source 90. DC converter 13, signal transmission circuit 30 for receiving a dimming signal for dimming light source 90 from the outside (for example, dimmer, remote control, etc.), current detection unit 15 for detecting a current flowing through light source 90, and power supply unit 80 And a microcomputer 14 for controlling power (current) supplied to the light source 90. The DC-DC converter 13 and the microcomputer 14 function as a power control unit that controls the power supplied to the light source 90.

  The microcomputer 14 as a signal determination unit acquires the dimming signal (output signal) transmitted (output) by the signal transmission circuit 30 and outputs a PWM signal corresponding to the acquired dimming signal to the DC-DC converter 13. . The signal determination unit is, for example, a circuit that receives the dimming signal output from the signal transmission circuit 30 and discriminates the received dimming signal.

  The dimming signal is, for example, a rectangular pulse waveform having a frequency of 1 kHz, and the light source 90 can be dimmed according to the duty ratio of the dimming signal. For example, when the duty ratio of the dimming signal is changed in the range of 10% to 90%, the dimming level can be changed in the range of 100% to 10%, and the duty ratio of the dimming signal is 95%. In this case, the light source 90 can be turned off.

  2 and 3 are circuit diagrams showing a first example of the signal transmission circuit 30 according to the present embodiment. The signal transmission circuit 30 shown in FIG. 2 has the same configuration as the signal transmission circuit 30 shown in FIG. 3 and has an equivalent circuit configuration, but the signal transmission circuit 30 in FIG. It can be considered to include a current amplifying unit 40 that amplifies the flowing current, a current-voltage converting unit 50 that converts the current amplified by the current amplifying unit 40 into a voltage, and the like. On the other hand, the signal transmission circuit 30 in FIG. 3 includes a current-voltage conversion unit 60 that converts a current flowing through the phototransistor 212 of the photocoupler 21 into a voltage, a voltage amplification unit 70 that amplifies the voltage converted by the current-voltage conversion unit 60, and the like. Can be seen as having

  First, FIG. 2 will be described. As shown in FIG. 2, a dimming signal divided by a resistor 201 and a resistor 208 or a voltage divided by a resistor 202 and a resistor 208 by a diode bridge composed of four diodes 204, 205, 206, and 207. The adjusted light signal is input to the LED 211 of the photocoupler 21. By providing the diode bridge, the dimming signal can be input to the LED 211 even if the polarity of the dimming signal is reversed to positive or negative. Further, the photocoupler 21 is protected by connecting a surge absorber 203 between the input ends.

  The signal transmission circuit 30 includes a current amplification unit 40 that amplifies the current flowing through the phototransistor 212 of the photocoupler 21, and a current-voltage conversion unit 50 as a first current-voltage conversion unit that converts the current amplified by the current amplification unit 40 into a voltage. Etc. Then, the voltage converted by the current-voltage converter 50 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current amplification unit 40 includes transistors 221 and 231 and resistors 222 and 232. The current-voltage conversion unit 50 includes a resistor 24. The resistor 24 corresponds to an output resistor on the output side of the phototransistor 212. The current-voltage conversion unit 50 is not limited to a resistor, and may be a diode, a Zener diode, or the like.

  Rather than directly connecting an output resistor to the phototransistor 212, a current amplifier 40 that amplifies the current flowing through the phototransistor 212 on the output side of the phototransistor 212, and a current that converts the current amplified by the current amplifier 40 into a voltage By providing the voltage conversion unit 50, the current flowing through the phototransistor 212 can be reduced, the rise of the output signal (output voltage) of the output terminal Vout can be speeded up, and a desired signal resolution can be obtained.

  In addition, since the transition time of the output signal (output voltage) can be shortened, the output resistance (resistor 24) can be set to a large value (for example, 1 kΩ, 10 kΩ, etc.), and power consumption at the output resistance is reduced. can do.

  Further, since the current amplifying unit 40 is provided, the current flowing through the LED of the photocoupler can be reduced (the input resistance of the photocoupler can be increased), and the voltage level of the output terminal Vout is low (GND). The problem that the level does not drop to the ground level) can also be solved. In addition, since the current flowing through the LED of the photocoupler can be reduced, the output power of an external circuit that outputs a signal to the photocoupler (for example, a circuit that outputs a dimming signal) can be reduced. Many photocouplers can be driven by one external circuit. Hereinafter, the GND level and the ground level are synonymous.

  Hereinafter, the configuration of FIG. 2 will be described in detail. A power supply voltage VCC (for example, 5 V) is connected to the collector 4 of the phototransistor 212, and the collector of the transistor 221 of the current amplification unit 40 is connected to the emitter 3 of the phototransistor 212. A resistor 222 is connected to the emitter of the transistor 221, and the other end of the resistor 222 is connected to the ground level.

  The power supply voltage VCC is connected to a resistor 24 as a current-voltage converter 50, and the resistor 24 is connected to the collector of the transistor 231 of the current amplifier 40. A resistor 232 is connected to the emitter of the transistor 231, and the other end of the resistor 232 is connected to the ground level. In the configuration of FIG. 2, the resistors 222 and 232 can be omitted.

  The base of the transistor 231 is connected to the base of the transistor 221, and the base of the transistor 231 is connected to a connection node between the emitter 3 of the phototransistor 212 and the collector of the transistor 221. An output terminal Vout is provided at the collector of the transistor 231. 2, the base of the transistor 231 may be directly connected to the connection node between the emitter 3 of the phototransistor 212 and the collector of the transistor 221, or the transistor 231 may be connected via a resistor or an element such as a transistor. May be connected to a connection node between the emitter 3 of the phototransistor 212 and the collector of the transistor 221.

  By including a transistor 221 connected in series with the phototransistor 212 and a transistor 231 having a base connected to a connection node between the phototransistor 212 and the transistor 221, the collector of the phototransistor 212 is turned on when the phototransistor 212 is on. 4 is a power supply voltage VCC (for example, 5 V), and the voltage of the emitter 3 of the phototransistor 212 becomes about 0.7 V when the first transistor 221 is turned on. The voltage between the collector and the emitter is about 4.3V. When the dimming signal becomes low level and the rectangular pulse waveform applied to the LED 211 falls to 0V, the phototransistor 212 is turned off, and the emitter voltage of the phototransistor 212 is set to the ground level (for example, 0V), the voltage between the collector and the emitter of the phototransistor 212 is about 5.0V. That is, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 increases only by about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. .

  The desired signal resolution is, for example, a resolution that can correctly recognize a state in which the duty ratio of the dimming signal is 5% or 95%. If the frequency of the dimming signal is 1 kHz, 1 kHz This means that the pulse waveform having a time width of 20 μs, which is 5%, can be correctly recognized. That is, a desired resolution can be obtained when the rise time of the output signal (output voltage) from the output terminal Vout is within 20 μs.

  Next, FIG. 3 will be described. A signal transmission circuit 30 shown in FIG. 3 includes a current-voltage conversion unit 60 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit that amplifies the voltage converted by the current-voltage conversion unit 60 70 etc. Then, the voltage amplified by the voltage amplifier 70 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current-voltage conversion unit 60 includes a transistor 221, a resistor 222, and the like. The voltage amplifier 70 includes a transistor 231, a resistor 232, a resistor 24, and the like.

  Rather than directly connecting an output resistor to the phototransistor 212, a current-voltage converter 60 that converts the current flowing through the phototransistor 212 into a voltage, and a voltage amplifier 70 that amplifies the voltage converted by the current-voltage converter 60 are provided. By providing, the current flowing through the phototransistor 212 can be reduced, the rising speed of the output signal (output voltage) of the output terminal Vout can be increased, and a desired signal resolution can be obtained.

  In addition, since the transition time of the output signal (output voltage) can be shortened, the output resistance (resistor 24) can be set to a large value (for example, 1 kΩ, 10 kΩ, etc.), and power consumption at the output resistance is reduced. can do.

  In addition, since the voltage amplification unit 70 that amplifies the voltage converted by the current-voltage conversion unit 60 is provided, the current flowing through the LED 211 of the photocoupler 21 can be reduced (the input resistance of the photocoupler 21 can be increased). Furthermore, the problem that the voltage level of the output terminal Vout does not decrease to the low level (GND level) can also be solved. In addition, since the current flowing through the LED 211 of the photocoupler 21 can be reduced, the output power of an external circuit that outputs a signal to the photocoupler 21 (for example, a circuit that outputs a dimming signal) can be reduced. Many photocouplers can be driven by one external circuit.

  Hereinafter, the configuration of FIG. 3 will be described in detail. A power supply voltage VCC (for example, 5 V) is connected to the collector 4 of the phototransistor 212, and the collector of the transistor 221 of the current-voltage converter 60 is connected to the emitter 3 of the phototransistor 212. A resistor 222 is connected to the emitter of the transistor 221, and the other end of the resistor 222 is connected to the ground level.

  In the voltage amplifying unit 70, the resistor 24 is connected to the power supply voltage VCC, and the collector of the transistor 231 is connected to the resistor 24. A resistor 232 is connected to the emitter of the transistor 231, and the other end of the resistor 232 is connected to the ground level. Note that the resistors 222 and 232 can also be omitted in the configuration of FIG.

  The base of the transistor 231 is connected to the base of the transistor 221 of the current-voltage converter 60, and the base of the transistor 231 is connected to a connection node between the emitter 3 of the phototransistor 212 and the collector of the transistor 221. An output terminal Vout is provided at the collector of the transistor 231.

  By including a transistor 221 connected in series with the phototransistor 212 and a transistor 231 having a base connected to a connection node between the phototransistor 212 and the transistor 221, the collector of the phototransistor 212 is turned on when the phototransistor 212 is on. 4 is a power supply voltage VCC (for example, 5 V), and the voltage of the emitter 3 of the phototransistor 212 becomes about 0.7 V when the first transistor 221 is turned on. The voltage between the collector and the emitter is about 4.3V. When the dimming signal becomes low level and the rectangular pulse waveform applied to the LED 211 falls to 0V, the phototransistor 212 is turned off, and the emitter voltage of the phototransistor 212 is set to the ground level (for example, 0V), the voltage between the collector and the emitter of the phototransistor 212 is about 5.0V. That is, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 increases only by about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. .

  FIG. 4 is a time chart showing an example of an input waveform and an output waveform of the photocoupler of the signal transmission circuit 30 of the present embodiment. As shown in FIG. 4, when the signal (rectangular pulse signal) applied to the input terminal Vin falls at time t2, the current flowing through the LED 211 becomes 0, and the phototransistor 212 is turned from the on state to the off state. And the voltage at the output terminal Vout rises.

  In the conventional configuration illustrated in FIG. 13, when the phototransistor transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor rises by about 5V. It took a long time (for example, about 100 μs) to charge the battery. In this embodiment, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 needs to increase only by about 0.7V. For this reason, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time Δt2 of the output voltage at the output terminal Vout is shortened (for example, about 10 μs), and the rise of the output signal is accelerated. Can be

  As described above, the response speed (rise time) of the output signal can be increased. For example, when the duty ratio of the dimming signal becomes 95% or more, the function of turning off the light source 90 is illuminated. For example, a lighting device equipped with a human sensor can be turned off when a person is not near the lighting device, and power consumption of the lighting device can be reduced. A lighting device having a function can be realized.

  Further, as shown in FIGS. 2 and 3, resistors 222 and 232 can be connected in series to the transistor 221 and the transistor 231, respectively. In this case, if the resistance value of the resistor 222 is increased, the bias voltage for the transistor 231 can be increased, so that the current amplification factor can be increased. That is, a desired current gain can be obtained by appropriately setting the resistance values of the resistors 222 and 232.

  In addition, since the current amplification factor can be varied, even when the current flowing through the LED 211 of the photocoupler 21 is reduced, even if the current transfer rate (CTR) of the photocoupler 21 is reduced, the output side of the phototransistor 212 is reduced. A sufficient current can flow through the resistor 24, and the problem that the voltage level of the output terminal Vout does not decrease to a low level (GND level) can be prevented. Further, since the current flowing through the LED 211 of the photocoupler 21 can be reduced, the output power of an external device that outputs a signal to the photocoupler (for example, a dimmer that outputs a dimming signal) can be reduced. It is possible to drive many photocouplers with one external device.

  2 and 3, the transistors 221 and 231 are NPN transistors, but the transistors are not limited to NPN transistors. For example, N-channel FETs can be used as the transistors 221 and 231. When an N-channel FET is used, the power supply voltage VCC (for example, 5 V) is connected to the collector 4 of the phototransistor 212, and the drain of the N-channel FET 221 is connected to the emitter 3 of the phototransistor 212. . A resistor 222 is connected to the source of the N-channel FET 221, and the other end of the resistor 222 is connected to the ground level.

  A resistor 24 is connected to the power supply voltage VCC, and the drain of the N-channel FET 231 is connected to the resistor 24. A resistor 232 is connected to the source of the N-channel FET 231 and the other end of the resistor 232 is connected to the ground level.

  The gate of the N channel FET 231 is connected to the gate of the N channel FET 221, and the gate of the N channel FET 231 is connected to a connection node between the emitter 3 of the phototransistor 212 and the drain of the N channel FET 221. An output terminal Vout is provided at the drain of the N-channel FET 231. Since the operation when the N-channel FET is used is the same as that of the NPN transistor, the description thereof is omitted.

  Further, a PNP transistor can be used instead of the transistors 221 and 231 described above. 5 and 6 are circuit diagrams showing a second example of the signal transmission circuit 31 of the present embodiment. The signal transmission circuit 31 shown in FIG. 5 has the same configuration as the signal transmission circuit 31 shown in FIG. 6 and has an equivalent circuit configuration, but the signal transmission circuit 31 in FIG. 5 is connected to the phototransistor 212 of the photocoupler 21. It can be considered to include a current amplifying unit 41 that amplifies the flowing current, a current-voltage converting unit 51 that converts the current amplified by the current amplifying unit 41 into a voltage, and the like. On the other hand, the signal transmission circuit 31 in FIG. 6 includes a current-voltage conversion unit 61 that converts the current flowing through the phototransistor 212 of the photocoupler 21 into a voltage, a voltage amplification unit 71 that amplifies the voltage converted by the current-voltage conversion unit 61, and the like. Can be seen as having

  First, FIG. 5 will be described. The signal transmission circuit 31 includes a current amplifying unit 41 that amplifies the current flowing through the phototransistor 212 of the photocoupler 21 and a current-voltage converting unit 51 as a first current-voltage converting unit that converts the current amplified by the current amplifying unit 41 into a voltage. Etc. The voltage converted by the current-voltage converter 51 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current amplifying unit 41 includes transistors 227 and 235 that are PNP transistors and resistors 226 and 236. In addition, the current-voltage conversion unit 51 includes a resistor 24. The resistor 24 corresponds to an output resistor on the output side of the phototransistor 212. The current-voltage conversion unit 51 is not limited to a resistor, and may be a diode, a Zener diode, or the like.

  In the configuration of FIG. 5 as well, as in the configuration of FIG. 2, the rising speed of the output signal (output voltage) at the output terminal Vout can be increased to obtain a desired signal resolution, and power consumption at the output resistance can be achieved. Can be reduced. Further, the input resistance of the photocoupler 21 can be increased, and further, the problem that the voltage level of the output terminal Vout does not decrease to the low level (GND level) can be solved. In addition, many photocouplers can be driven by one external circuit.

  Hereinafter, the configuration of FIG. 5 will be described in detail. One end of the resistor 226 is connected to the power supply voltage VCC (for example, 5 V), and the emitter of the transistor 227 is connected to the other end of the resistor 226. The collector of the transistor 227 is connected to the collector 4 of the phototransistor 212, and the emitter 3 of the phototransistor 212 is connected to the ground level.

  Further, one end of a resistor 236 is connected to the power supply voltage VCC, and the emitter of the transistor 235 is connected to the other end of the resistor 236. The collector of the transistor 235 is connected to one end of the resistor 24 as the current-voltage conversion unit 51, and the other end of the resistor 24 is connected to the ground level. The base of the transistor 227 is connected to the base of the transistor 227, and the base of the transistor 235 is connected to a connection node between the collector of the phototransistor 212 and the collector of the transistor 227. An output terminal Vout is provided at the collector of the transistor 235.

  By including a transistor 227 connected in series with the phototransistor 212 and a transistor 235 having a base connected to a connection node between the phototransistor 212 and the transistor 227, the transistor 227 is turned on when the phototransistor 212 is on. As a result, the voltage of the collector 4 of the phototransistor 212 becomes approximately 4.3 V, and the voltage of the emitter 3 of the phototransistor 212 is at the ground level (0 V). Is about 4.3 V (power supply voltage VCC (5 V) −0.7 V). When the dimming signal becomes low level and the rectangular pulse waveform applied to the LED 211 falls to 0V, the phototransistor 212 is turned off, and the collector voltage of the phototransistor 212 is set to the power supply voltage VCC (for example, 5V). That is, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 increases only by about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. .

  Next, FIG. 6 will be described. The signal transmission circuit 31 shown in FIG. 6 includes a current-voltage converter 61 as a second current-voltage converter that converts the current flowing through the phototransistor 212 into a voltage, and a voltage amplifier that amplifies the voltage converted by the current-voltage converter 61. 71 etc. are provided. Then, the voltage amplified by the voltage amplifier 71 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current-voltage conversion unit 61 includes a transistor 227 that is a PNP transistor, a resistor 226, and the like. The voltage amplifying unit 71 includes a transistor 235 that is a PNP transistor, a resistor 236, a resistor 24, and the like.

  In the configuration of FIG. 6, as in the configuration of FIG. 3, the rising speed of the output signal (output voltage) of the output terminal Vout can be increased to obtain a desired signal resolution, and the power consumption at the output resistor is achieved. Can be reduced. Further, the input resistance of the photocoupler 21 can be increased, and further, the problem that the voltage level of the output terminal Vout does not decrease to the low level (GND level) can be solved. In addition, many photocouplers can be driven by one external circuit. The configuration in FIG. 6 is equivalent to the configuration in FIG.

  In the example of FIGS. 5 and 6, the PNP transistor is used, but the transistor is not limited to the PNP transistor. For example, a P-channel FET can be used. When a P-channel FET is used, the base, collector, and emitter of the transistor may be read as the gate, drain, and source, respectively. The operation when using a P-channel FET is the same as that of a PNP transistor.

  2, 3, 5, and 6, the output capacitance of the transistors 231 and 235 connected in series to the resistor 24 (for example, the capacitance between the collector and the emitter) is larger than the output capacitance of the phototransistor 212. Since it is about two to three digits smaller, the time required for charging the output capacitance when the transistors 231 and 235 transition from the on state to the off state is short, the rise time of the output signal can be increased, and the desired signal can be increased. Resolution can be obtained. Further, since the current flowing through the resistor 24 can be amplified by the transistors 221, 227 and the transistors 231, 235, the resistor 24 can have a large value (for example, 1 kΩ, 10 kΩ, etc.), and the power at the resistor 24 can be increased. Consumption can be reduced.

  7 and 8 are circuit diagrams showing a third example of the signal transmission circuit 32 of the present embodiment. The signal transmission circuit 32 shown in FIG. 7 has the same configuration as the signal transmission circuit 32 shown in FIG. 8 and has an equivalent circuit configuration, but the signal transmission circuit 32 in FIG. 7 is connected to the phototransistor 212 of the photocoupler 21. It can be considered to include a current amplifying unit 42 that amplifies the flowing current, a current-voltage converting unit 50 that converts the current amplified by the current amplifying unit 42 into a voltage, and the like. On the other hand, the signal transmission circuit 32 in FIG. 8 includes a current-voltage conversion unit 62 that converts a current flowing through the phototransistor 212 of the photocoupler 21 into a voltage, a voltage amplification unit 70 that amplifies the voltage converted by the current-voltage conversion unit 62, and the like. Can be seen as having

  First, FIG. 7 will be described. The signal transmission circuit 32 in FIG. 7 includes a current amplification unit 42 that amplifies the current flowing through the phototransistor 212 of the photocoupler 21, a current-voltage conversion unit 50 that converts the current amplified by the current amplification unit 42 into a voltage, and the like. Then, the voltage converted by the current-voltage converter 50 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current amplifying unit 42 includes a transistor 231 and resistors 223 and 232. The current-voltage conversion unit 50 includes a resistor 24. The resistor 24 corresponds to an output resistor on the output side of the phototransistor 212. The current-voltage conversion unit 50 is not limited to a resistor, and may be a diode, a Zener diode, or the like. A difference from the first example of FIG. 2 is that a resistor (resistive element) 223 is used instead of the transistor 221. Note that the resistor 222 of FIG. 2 is not provided.

  Rather than directly connecting an output resistor to the phototransistor 212, a current amplifying unit 42 that amplifies the current flowing through the phototransistor 212 on the output side of the phototransistor 212, and a current that converts the current amplified by the current amplifying unit 42 into a voltage By providing the voltage conversion unit 50, the current flowing through the phototransistor 212 can be reduced, the rise of the output signal (output voltage) of the output terminal Vout can be speeded up, and a desired signal resolution can be obtained.

  In addition, since the transition time of the output signal (output voltage) can be shortened, the output resistance (resistor 24) can be set to a large value (for example, 1 kΩ, 10 kΩ, etc.), and power consumption at the output resistance is reduced. can do.

  Further, since the current amplifying unit 42 is provided, the current flowing through the LED of the photocoupler can be reduced (the input resistance of the photocoupler can be increased), and the voltage level of the output terminal Vout is low (GND). The problem that the level does not decrease to the level) can also be solved. In addition, since the current flowing through the LED of the photocoupler can be reduced, the output power of an external circuit that outputs a signal to the photocoupler (for example, a circuit that outputs a dimming signal) can be reduced. Many photocouplers can be driven by one external circuit.

  As shown in FIG. 7, a power supply voltage VCC (for example, 5 V) is connected to the collector 4 of the phototransistor 212, and one end of a resistor 223 is connected to the emitter 3 of the phototransistor 212. The other end of the resistor 223 is connected to the ground level.

  One end of a resistor 24 serving as a current-voltage converter 50 is connected to the power supply voltage VCC, and the collector of a transistor 231 is connected to the other end of the resistor 24. One end of a resistor 232 is connected to the emitter of the transistor 231 and the other end of the resistor 232 is connected to the ground level.

  The base of the transistor 231 is connected to the connection node between the emitter 3 of the phototransistor 212 and the resistor 223. An output terminal Vout is provided at the collector of the transistor 231. As shown in FIG. 7, the base of the transistor 231 may be directly connected to the connection node between the emitter 3 of the phototransistor 212 and the resistor 223, or the base of the transistor 231 may be connected via an element such as a resistor or a transistor. May be connected to a connection node between the emitter 3 of the phototransistor 212 and the resistor 223.

  By providing the transistor 231 whose base is connected to the connection node between the phototransistor 212 and the resistor 223, when the phototransistor 212 is on, the collector voltage of the phototransistor 212 is the power supply voltage VCC (for example, 5V). When the transistor 231 is turned on, the voltage of the emitter of the phototransistor 212 becomes about 0.7 V, and as a result, the voltage between the collector and the emitter of the phototransistor 212 becomes about 4.3 V. When the phototransistor 212 is turned off, the voltage at the emitter of the phototransistor 212 is at the ground level (0V), and the voltage between the collector and the emitter of the phototransistor 212 is approximately 5.0V. At the transition from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 rises only by about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. . In addition, since the resistor 223 is connected in series to the phototransistor 212, the circuit configuration is simplified and low cost can be realized as compared with the case where a transistor is connected in series to the phototransistor.

  Next, FIG. 8 will be described. The signal transmission circuit 32 in FIG. 8 includes a current-voltage conversion unit 62 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit 70 that amplifies the voltage converted by the current-voltage conversion unit 62. Prepare. Then, the voltage amplified by the voltage amplifier 70 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current-voltage conversion unit 62 includes a resistor 223. The voltage amplification unit 70 includes a transistor 231, a resistor 232, a resistor 24, and the like, similarly to the configuration of FIG.

  Rather than connecting an output resistor directly to the phototransistor 212, a current-voltage converter 62 that converts the current flowing through the phototransistor 212 into a voltage, and a voltage amplifier 70 that amplifies the voltage converted by the current-voltage converter 62 are provided. By providing, the current flowing through the phototransistor 212 can be reduced, the rising speed of the output signal (output voltage) of the output terminal Vout can be increased, and a desired signal resolution can be obtained.

  In the third example of FIGS. 7 and 8, an NPN transistor is used. However, an N-channel FET can be used instead of the NPN transistor. When an N-channel FET is used, the base, collector, and emitter of the transistor may be read as the gate, drain, and source, respectively.

  Further, instead of the NPN transistor in FIGS. 7 and 8, a PNP transistor can be used. In the case of using a PNP transistor, the transistor 227 and the resistor 226 having the structure illustrated in FIG. 5 may be replaced with resistors.

  When a PNP transistor is used, the voltage of the collector 4 of the phototransistor 212 is approximately 4.3 V when the phototransistor 212 is on, as in the configuration of FIG. 5 or FIG. Therefore, the voltage between the collector and the emitter of the phototransistor 212 is about 4.3 V (power supply voltage VCC (5 V) −0.7 V). When the dimming signal becomes low level and the rectangular pulse waveform applied to the LED 211 falls to 0V, the phototransistor 212 is turned off, and the collector voltage of the phototransistor 212 is set to the power supply voltage VCC (for example, 5V). That is, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 increases only by about 0.7V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. . In addition, a P-channel FET can be used instead of the PNP transistor. Note that the emitter voltage of the phototransistor 212 is at the ground level (0 V).

  7 and 8 also, the output capacitance of the transistor 231 connected in series with the resistor 24 (for example, the capacitance between the collector and the emitter) is about two to three orders of magnitude smaller than the output capacitance of the phototransistor 212. The time required for charging the output capacitance when the transistor 231 transitions from the on state to the off state is short, the rise time of the output signal can be increased, and a desired signal resolution can be obtained.

  FIG. 9 is a circuit diagram showing a fourth example of the signal transmission circuit 33 of the present embodiment. The signal transmission circuit 33 in FIG. 9 includes a current-voltage conversion unit 62 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit 73 that amplifies the voltage converted by the current-voltage conversion unit 62. Prepare. Then, the voltage amplified by the voltage amplifier 73 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212.

  The current-voltage conversion unit 62 includes a resistor 223. The voltage amplifying unit 73 has one input terminal connected to the resistors 24 and 233 serving as the reference voltage source and a connection node between the phototransistor 212 and the resistor 223, and the resistor 24 serving as the reference voltage source and the resistor An operational amplifier 234 having another input terminal connected to a connection node with 233 is included. The resistors 24 and 233 are voltage dividing resistors that divide the power supply voltage VCC.

  As shown in FIG. 9, the collector 4 of the phototransistor 212 is connected to the power supply voltage VCC, one end of the resistor 223 is connected to the emitter 3 of the phototransistor 212, and the other end of the resistor 223 is connected to the ground level. The other end of the resistor 24 which is a voltage dividing resistor is connected to the power supply voltage VCC, and one end of the resistor 233 is connected to one end of the resistor 24. The other end of the resistor 233 is connected to the ground level.

  Then, one input terminal (for example, non-inverting input terminal) of the operational amplifier 234 is connected to a connection node between the emitter of the phototransistor 212 and the resistor 223. The other input terminal (for example, the inverting input terminal) of the operational amplifier 234 is connected to a connection node between the resistor 24 and the resistor 233. That is, a voltage (for example, a reference voltage) obtained by dividing the power supply voltage VCC by the resistor 24 and the resistor 233 is applied to the other input terminal (for example, the inverting input terminal) of the operational amplifier 234. The output terminal of the operational amplifier 234 is Vout. Note that the reference voltage source is not limited to a configuration in which the power supply voltage VCC is divided by a voltage dividing resistor, and may be a configuration in which the reference voltage source is directly connected to the other input terminal of the operational amplifier 234.

  The voltage applied to the non-inverting input terminal of the operational amplifier 234 becomes larger (higher) according to the current flowing through the phototransistor 212. Further, the voltage applied to the inverting input terminal of the operational amplifier 234 becomes larger (higher) according to the current flowing through the resistor 24. That is, the threshold value of the output current of the photocoupler 21 for switching the output terminal Vout of the operational amplifier 234 to Hi / Low can be determined by appropriately setting the resistance values of the resistor 24 and the resistors 233 and 223.

  Since the operational amplifier 234 operates even when the potential difference at the input terminal is about 0.1 V, for example, when the phototransistor 212 is on, the voltage at the collector 4 of the phototransistor 212 becomes the power supply voltage VCC (for example, 5 V), The voltage of the emitter 3 of the transistor 212 can be about 0.1V, and as a result, the voltage between the collector and the emitter of the phototransistor 212 is about 4.9V. When the phototransistor 212 is turned off, the voltage of the emitter of the phototransistor 212 is at the ground level (for example, 0 V). Therefore, when the phototransistor 212 transitions from the on state to the off state, the collector of the phototransistor 212 -The voltage between emitters rises only about 0.1V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be further increased, and a desired signal resolution can be obtained. it can.

  FIG. 10 is a circuit diagram showing a fifth example of the signal transmission circuit 34 of the present embodiment. The signal transmission circuit 34 in FIG. 10 includes a current-voltage conversion unit 64 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit 73 that amplifies the voltage converted by the current-voltage conversion unit 64. Prepare. Then, the voltage amplified by the voltage amplifier 73 is transmitted (output) to the microcomputer 14 on the output side of the phototransistor 212. A difference from the example of FIG. 9 is that a diode 224 is connected to both ends of the resistor 223. By providing the diode 224, the voltage of the emitter 3 of the phototransistor 212 can be clipped (limited) by a voltage approximately equal to the forward voltage of the diode, and the output current increases when the phototransistor 212 is on ( For example, it is possible to prevent the emitter 3 voltage of the phototransistor 212 from significantly increasing in a low temperature state where the CTR of the photocoupler increases.

  FIG. 11 is a circuit diagram showing a sixth example of the signal transmission circuit 35 of the present embodiment. The signal transmission circuit 35 in FIG. 11 includes a current-voltage conversion unit 65 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit 73 that amplifies the voltage converted by the current-voltage conversion unit 64. Prepare. The difference from the example of FIG. 10 is that the resistor 223 is not provided. In the example of FIG. 11, since the resistor 223 is not necessary, the cost can be reduced.

  FIG. 12 is a circuit diagram showing a seventh example of the signal transmission circuit 36 of the present embodiment. The signal transmission circuit 36 of FIG. 12 includes a current-voltage conversion unit 66 as a second current-voltage conversion unit that converts a current flowing through the phototransistor 212 into a voltage, and a voltage amplification unit 76 that amplifies the voltage converted by the current-voltage conversion unit 66. Prepare. The current-voltage conversion unit 66 includes diodes 224 and 225, and the voltage amplification unit 76 includes resistors 24 and 237 and a transistor 231.

  As shown in FIG. 12, a power supply voltage VCC (for example, 5 V) is connected to the collector 4 of the phototransistor 212, and the emitter 3 of the phototransistor 212 is connected to two of the diodes 224 and 225 connected in series. The anode of the diode 224 is connected. The cathode of diode 225 is connected to ground level.

  One end of the resistor 24 is connected to the power supply voltage VCC, and the collector of the transistor 231 is connected to the other end of the resistor 24. The emitter of transistor 231 is connected to ground level.

  A resistor 237 is connected between the base of the transistor 231 and the connection node between the emitter 3 of the phototransistor 212 and the anode of the diode 224. As a result, the voltage between the base and the emitter of the transistor 231 becomes about 0.7V. An output terminal Vout is provided at the collector of the transistor 231. As shown in FIG. 12, the base of the transistor 231 may be connected to a connection node between the emitter 3 of the phototransistor 212 and the diode 224 via a resistor 237, or other elements other than the resistor 237, for example, The base of the transistor 231 may be connected to a connection node between the emitter 3 of the phototransistor 212 and the diode 224 through an element such as a transistor. Alternatively, when the number of diodes is not two as in the example of FIG. 12 but one, for example, a voltage of about 0.7 V is applied between the base and emitter of the transistor 231. The base of the transistor 231 can be directly connected to the connection node between the emitter 3 and the diode of the phototransistor 212.

  By providing the transistor 231 having the base connected to the connection node between the phototransistor 212 and the diode 224 via the resistor 237, the voltage of the collector 4 of the phototransistor 212 is the power supply voltage VCC (for example, when the phototransistor 212 is on) 5V), and the voltage of the emitter 3 of the phototransistor 212 becomes about 1.4V when the diodes 224 and 225 are turned on. As a result, the voltage between the collector and the emitter of the phototransistor 212 is about 3.V. 6V. When the phototransistor 212 is turned off, the voltage at the emitter of the phototransistor 212 becomes the ground level (0 V). Therefore, when the phototransistor 212 transitions from the on state to the off state, the collector-emitter of the phototransistor 212 The voltage between them rises only about 1.4V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. . In addition, since a diode is connected in series to the phototransistor 212, the circuit configuration is simplified and a low price can be realized as compared with the case where a transistor is connected in series to the phototransistor.

  In the seventh example of FIG. 12, an NPN transistor is used, but an N-channel FET may be used instead of the NPN transistor. When an N-channel FET is used, the base, collector, and emitter of the transistor may be read as the gate, drain, and source, respectively.

  Further, a PNP transistor can be used instead of the NPN transistor in FIG. In the case of using a PNP transistor, the transistors 227 and the resistor 226 having the structure illustrated in FIG. 5 may be replaced with the diodes 224 and 225.

  When a PNP type transistor is used, the voltage of the emitter 3 of the phototransistor 212 is at the ground level (0 V) when the phototransistor 212 is on, as in the configuration of FIG. When the transistor 231 is turned on, the voltage becomes about 3.6 V (power supply voltage VCC (5 V) −1.4 V). As a result, the voltage between the collector and the emitter of the phototransistor 212 becomes about 3.6 V. . When the dimming signal becomes low level and the rectangular pulse waveform applied to the LED 211 falls to 0V, the phototransistor 212 is turned off, and the collector voltage of the phototransistor 212 is set to the power supply voltage VCC (for example, 5V). That is, when the phototransistor 212 transitions from the on state to the off state, the voltage between the collector and the emitter of the phototransistor 212 increases only by about 1.4V. Therefore, the time for charging the output capacitance between the collector and the emitter of the phototransistor 212 is shortened, the transition time of the output voltage at the output terminal Vout can be increased, and a desired signal resolution can be obtained. . In addition, a P-channel FET can be used instead of the PNP transistor.

  As described above, according to the present embodiment, it is possible to achieve a high-speed rise of the output signal and obtain a desired signal resolution. In addition, the input resistance of the photocoupler can be increased. Furthermore, power consumption can be suppressed.

  The power supply unit 80 also controls the power (current) supplied to the light source 90 based on the signal transmission circuits 30, 31, 32, 33, 34, 35, and 36 and the dimming signal output from the signal transmission circuit. A DC-DC converter 13 and a microcomputer 14 are provided as a control unit (current control unit). As a result, it is possible to realize a power supply unit and an illuminating device that can obtain desired resolution by increasing the resolution of the dimming signal while suppressing power consumption.

  The signal transmission circuits 30, 31, 32, 33, 34, 35, and 36 receive the PWM signal from the external dimmer, and the power supplied to the light source 90 is 10% or less according to the duty ratio of the received PWM signal. To control. Thereby, the output of the light source can be controlled with a resolution of 10% or less.

  In the above-described embodiment, the dimming signal is transmitted (output) by the signal transmission circuit, but the signal to be transmitted (output) is not limited to the dimming signal, and uses a photocoupler. The present embodiment is applied to any signal as long as state control is performed according to the duty ratio of a signal having a rectangular pulse waveform having a frequency exceeding about 1 kHz. be able to.

13 DC-DC converter 14 Microcomputer 21 Photocoupler 211 LED
212 Phototransistor 24 Resistor 30, 31, 32, 33, 34, 35, 36 Signal transmission circuit 221, 227, 231, 235 Transistor 222, 223, 226, 232, 233, 236, 237 Resistor 224, 225 Diode 234 Operational amplifier 40, 41, 42 Current amplification unit 50, 51, 60, 61, 62, 64, 65, 66 Current-voltage conversion unit 70, 71, 73, 76 Voltage amplification unit 80 Power supply unit 90 Light source

Claims (12)

In a signal transmission circuit including a photocoupler and transmitting a signal input to the photocoupler to a signal determination unit,
A current amplifying unit for amplifying the current flowing through the phototransistor of the photocoupler;
A signal transmission circuit comprising: a first current-voltage conversion unit that converts the current amplified by the current amplification unit into a voltage. In a signal transmission circuit including a photocoupler and transmitting a signal input to the photocoupler to a signal determination unit,
A second current-voltage converter for converting a current flowing through the phototransistor of the photocoupler into a voltage;
A signal transmission circuit comprising: a voltage amplification unit that amplifies the voltage converted by the second current-voltage conversion unit. The current amplifier is
A first transistor connected in series to the phototransistor;
A second transistor having a base or a gate connected to a connection node between the phototransistor and the first transistor;
The first current-voltage converter is
The signal transmission circuit according to claim 1, further comprising a resistor connected in series to the second transistor.   4. The signal transmission circuit according to claim 3, wherein a resistor is connected in series to each of the first and second transistors. The current amplifier is
A resistance element connected in series to the phototransistor;
A transistor having a base or a gate connected to a connection node between the phototransistor and the resistance element;
The first current-voltage converter is
The signal transmission circuit according to claim 1, further comprising a resistor connected in series with the transistor. The second current-voltage converter is
Having a resistance element connected in series to the phototransistor;
The voltage amplifier is
A reference voltage source;
3. The operational amplifier having one input terminal connected to a connection node between the phototransistor and the resistance element and having another input terminal connected to the reference voltage source. Signal transmission circuit. The second current-voltage converter is
The signal transmission circuit according to claim 6, further comprising a diode connected in parallel with the resistance element. The reference voltage source is
A power supply voltage source;
A plurality of voltage dividing resistors connected in series to the power supply voltage source;
8. The signal transmission circuit according to claim 6, wherein another input terminal of the operational amplifier is connected to a connection node between the voltage dividing resistors. The second current-voltage converter is
A diode connected in series with the phototransistor;
The voltage amplifier is
A transistor having a base or gate connected to a connection node between the phototransistor and the diode;
The signal transmission circuit according to claim 2, further comprising: a resistor connected in series to the transistor.   A signal transmission circuit according to any one of claims 1 to 9, and a power control unit that controls power supplied to the light source based on a dimming signal output from the signal transmission circuit. A featured power supply unit. The signal transmission circuit is
11. The power supply unit according to claim 10, wherein the power supply unit receives a PWM signal from an external dimmer and controls power supplied to the light source to 10% or less in accordance with a duty ratio of the PWM signal.   An illumination apparatus comprising: a light source; and the power supply unit according to claim 10 or 11.

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