Power supply circuit

Abstract

To provide a power supply circuit capable of suppressing wasteful power consumption when turning off a light source.SOLUTION: Wherein the power supply circuit includes a control circuit that generates a control voltage according to an on-duty ratio of an input pulse width modulation dimming signal, a power factor improvement circuit that generates output power to be output from input power that is input, and a power supply circuit that generates drive power according to the control voltage from the output power, the control circuit causes the drive circuit to turn off the light source when the on-duty ratio is 100%, and the stopping circuit stops a circuit to be stopped included in at least one of the control circuit and the power factor correction circuit when the on-duty ratio is 100%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply circuit. [Background technology]

[0002] Patent Document 1 discloses a lighting device. In this lighting device, a power factor correction circuit boosts the voltage and improves the power factor. Furthermore, a lighting circuit reduces the boosted voltage to light a light source unit. Furthermore, a control unit converts a dimming command value into a target output current, and increases the current flowing in the light source unit if the current flowing in the light source unit is smaller than the target output current, and decreases the current flowing in the light source unit if the current flowing in the light source unit is larger than the target output current (paragraphs 0011, 0021, 0022, and 0023). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-132615 Summary of the Invention [Problem to be solved by the invention]

[0004] In the lighting device disclosed in Patent Document 1, the power factor correction circuit and the control circuit consume power even when the light source is turned off, which results in unnecessary power consumption by the lighting device.

[0005] In view of this problem, an aspect of the present disclosure provides a power supply circuit that can suppress unnecessary power consumption when, for example, a light source is turned off. [Means for solving the problem]

[0006] A power supply circuit according to one embodiment of the present disclosure includes a control circuit that generates a control voltage corresponding to an on-duty ratio of an input pulse-width modulation dimming signal, a power factor correction circuit that generates output power from the input power, a drive circuit that generates drive power from the output power corresponding to the control voltage and drives a light source with the drive power, and a stop circuit, wherein the control circuit causes the drive circuit to turn off the light source when the on-duty ratio is 100%, and the stop circuit stops a stopped circuit included in at least one of the control circuit and the power factor correction circuit when the on-duty ratio is 100%. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram of a lighting system according to a first embodiment. [Figure 2] FIG. 10 is a block diagram of a lighting system according to a second embodiment. [Figure 3] FIG. 10 is a block diagram of a lighting system according to a third embodiment. [Figure 4] FIG. 10 is a block diagram of a power factor correction (PFC) circuit, a control circuit, a dimming circuit, and an auxiliary power supply circuit provided in a lighting system of a fourth embodiment. [Figure 5] FIG. 10 is a block diagram of a PFC circuit, a control circuit, a dimming circuit, and an auxiliary power supply circuit provided in a lighting system of a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0009] 1. First embodiment 1.1 Lighting system FIG. 1 is a block diagram of a lighting system according to a first embodiment.

[0010] The lighting system 1 of the first embodiment shown in FIG. 1 includes an AC power supply 11, a dimmer 12, a power supply circuit 13, and a light source 14.

[0011] The AC power supply 11 supplies AC power 301. The AC power supply 11 is a commercial power supply. The AC power supply 11 may be a power supply other than a commercial power supply.

[0012] The dimmer 12 transmits a pulse-width modulated (PWM) dimming signal 302. The on-duty ratio of the transmitted PWM dimming signal 302 indicates the intensity of light that should be emitted by the light source 14. An on-duty ratio of 100% indicates that the light source 14 should be turned off.

[0013] The power supply circuit 13 generates drive power 303 from the supplied AC power 301 and supplies the generated drive power 303 to the light source 14. The power supply circuit 13 generates drive power 303 according to the on-duty ratio of the PWM dimming signal 302. For example, the power supply circuit 13 reduces the drive power 303 as the on-duty ratio of the PWM dimming signal 302 increases. When the on-duty ratio of the PWM dimming signal 302 is 100%, the power supply circuit 13 sets the drive power 303 to 0.

[0014] The light source 14 emits light having an intensity according to the supplied driving power 303. When the driving power 303 is 0, the light source 14 is turned off. The light source 14 is a plurality of light-emitting diodes (LEDs) electrically connected in series. The light source 14 may be a light source other than a plurality of LEDs electrically connected in series.

[0015] As a result, the power supply circuit 13 causes the light source 14 to emit light having an intensity according to the on-duty ratio of the PWM dimming signal 302. When the on-duty ratio of the PWM dimming signal 302 is 100%, the power supply circuit 13 turns off the light source 14.

[0016] 1.2 Power supply circuit 1 , the power supply circuit 13 includes a rectifier circuit 21, a power factor correction (PFC) circuit 22, a drive circuit 23, a stop circuit 24, a control circuit 25, a first supply line 26, and a second supply line 27. The stop circuit 24 includes a dimming circuit 31, an auxiliary power supply circuit 32, and a signal line 33. The auxiliary power supply circuit 32 includes a voltage change circuit 41.

[0017] The rectifier circuit 21 is electrically connected to the AC power supply 11. As a result, AC power 301 supplied to the power supply circuit 13 is input to the rectifier circuit 21. The rectifier circuit 21 rectifies the input AC power 301 to generate a pulsating current close to DC, and outputs the generated pulsating current. The rectifier circuit 21 is a full-wave rectifier circuit. The full-wave rectifier circuit is a bridge rectifier circuit, a full-wave voltage doubler rectifier circuit, or the like. The rectifier circuit 21 may be a single-wave rectifier circuit. The rectifier circuit 21 includes a rectifier element and a smoothing capacitor. The rectifier element is a diode. The rectifier element may be an element other than a diode.

[0018] The PFC circuit 22 is electrically connected to the rectifier circuit 21. As a result, input power 304 consisting of an output pulsating current is input to the PFC circuit 22. The PFC circuit 22 generates output power 305 from the input input power 304 and outputs the generated output power 305. The PFC circuit 22 reduces the phase difference between the voltage and current of the AC power 301. The PFC circuit 22 suppresses harmonics generated by a smoothing capacitor provided in the rectifier circuit 21. As a result, the PFC circuit 22 improves the power factor of the power supply circuit 13, bringing the power factor of the power supply circuit 13 closer to 1. The PFC circuit 22 is a partial switching type or switching type PFC circuit. As a result, the PFC circuit 22 consumes power.

[0019] The drive circuit 23 is electrically connected to the PFC circuit 22. As a result, the output power 305 is input to the drive circuit 23. The drive circuit 23 generates drive power 303 from the input output power 305, and drives the light source 14 with the generated drive power 303.

[0020] The dimming circuit 31 is electrically connected to the dimmer 12. As a result, the transmitted PWM dimming signal 302 is input to the dimming circuit 31. The dimming circuit 31 outputs the input PWM dimming signal 302. The dimming circuit 31 generates a control signal 306 and outputs the generated control signal 306. The output control signal 306 is input to the control circuit 25 and the voltage change circuit 41. Therefore, the dimming circuit 31 serves as an input circuit that inputs the control signal 306 to the control circuit 25 and the voltage change circuit 41. When the on-duty ratio of the PWM dimming signal 302 is not 100%, the dimming circuit 31 sets the control signal 306 to a first state. When the on-duty ratio of the PWM dimming signal 302 is 100%, the dimming circuit 31 sets the control signal 306 to a second state. The first state is, for example, a state in which the control signal 306 has a potential different from ground potential and is an on signal. The first state of the control signal 306 indicates that the light source 14 is turned on. The second state is, for example, a state in which the control signal 306 has the same potential as the ground potential and the control signal 306 is an off signal. The second state of the control signal 306 indicates that the light source 14 is turned off.

[0021] The control circuit 25 is electrically connected to the dimming circuit 31. As a result, the output PWM dimming signal 302 is input to the control circuit 25. The control circuit 25 is electrically connected to the dimming circuit 31 via a signal line 33. As a result, the output control signal 306 is input to the control circuit 25 via the signal line 33. The control circuit 25 generates a first control voltage 307 and outputs the generated first control voltage 307. When the input control signal 306 is in a first state, the control circuit 25 sets the voltage value of the first control voltage 307 to a voltage value corresponding to the on-duty ratio of the input PWM dimming signal 302. When the input control signal 306 is in a second state, the control circuit 25 sets the voltage value of the first control voltage 307 to a first specific voltage value. The voltage value of the first control voltage 307 being the first specific voltage value instructs the light source 14 to be turned off. When the voltage value of the first control voltage 307 is not the first particular voltage value, the voltage value of the first control voltage 307 dictates the intensity of light that the light source 14 should emit.

[0022] The drive circuit 23 is electrically connected to the control circuit 25 via a first supply line 26. As a result, the drive circuit 23 is supplied with the output first control voltage 307 via the first supply line 26. The drive circuit 23 generates drive power 303 according to the supplied first control voltage 307. When the voltage value of the first control voltage 307 is not the first specific voltage value, the drive circuit 23 sets the drive power 303 to a drive power that causes the light source 14 to emit light with an intensity according to the voltage value of the first control voltage 307. When the voltage value of the first control voltage 307 is the first specific voltage value, the drive circuit 23 sets the drive power 303 to 0.

[0023] As a result, when the on-duty ratio of the PWM dimming signal 302 is not 100%, the control circuit 25 causes the drive circuit 23 to make the light source 14 emit light having an intensity according to the on-duty ratio of the PWM dimming signal 302. When the on-duty ratio of the PWM dimming signal 302 is 100%, the control circuit 25 causes the drive circuit 23 to turn off the light source 14.

[0024] The voltage change circuit 41 is electrically connected to the dimming circuit 31 via a signal line 33. As a result, the output control signal 306 is input to the voltage change circuit 41 via the signal line 33. The voltage change circuit 41 generates a second control voltage 308 and outputs the generated second control voltage 308. When the input control signal 306 is in a first state, the voltage change circuit 41 increases the voltage value of the second control voltage 308 above a second specific voltage value. When the voltage value of the second control voltage 308 is higher than the second specific voltage value, the voltage change circuit 41 instructs the PFC circuit 22 to operate. When the input control signal 306 is in a second state, the voltage change circuit 41 increases the voltage value of the second control voltage 308 below the second specific voltage value. When the voltage value of the second control voltage 308 is below the second specific voltage value, the voltage change circuit 41 instructs the PFC circuit 22 to stop.

[0025] The PFC circuit 22 is electrically connected to the voltage change circuit 41 via the second supply line 27. As a result, the PFC circuit 22 is supplied with the second control voltage 308 output via the second supply line 27. The PFC circuit 22 operates when the voltage value of the supplied second control voltage 308 is higher than a second specific voltage value. The PFC circuit 22 stops operating when the voltage value of the supplied second control voltage 308 is equal to or lower than the second specific voltage value. When the voltage value of the second control voltage 308 is equal to or lower than the second specific voltage value, only a portion of the circuits in the PFC circuit 22 may stop operating. For example, only a circuit, such as a microcontroller, that controls the output current while monitoring the output current may stop operating.

[0026] As a result, when the on-duty ratio of the PWM dimming signal 302 is 100%, the voltage change circuit 41 changes the voltage value of the second control voltage 308 to a second specific voltage value or less. As a result, when the on-duty ratio of the PWM dimming signal 302 is 100%, the stopping circuit 24 stops the PFC circuit 22. As a result, the PFC circuit 22 becomes a stopped circuit that is stopped when the on-duty ratio of the PWM dimming signal 302 is 100%.

[0027] As a result, the PFC circuit 22, which does not need to operate when the light source 14 is turned off, stops when the light source 14 is turned off. This makes it possible to prevent the PFC circuit 22 from wasting power when the light source 14 is turned off.

[0028] When the PFC circuit 22 is operated again after being stopped, the operation of the drive circuit 23 and the dimming circuit 31 are started in this order after the operation of the PFC circuit 22 has stabilized.

[0029] The voltage value of the second control voltage 308 when the PFC circuit 22 is stopped may be 0 V or a voltage value higher than 0 V. For example, if the circuit to be stopped includes a microcontroller, the voltage value of the second control voltage 308 when the PFC circuit 22 is stopped may be a voltage value at which the microcontroller does not operate.

[0030] 2. Second embodiment The following describes the differences between the second embodiment and the first embodiment. For points that are not described, the second embodiment also employs the same configuration as that employed in the first embodiment.

[0031] FIG. 2 is a block diagram of a lighting system according to the second embodiment.

[0032] In the second embodiment, as shown in FIG. 2, the stop circuit 24 includes a first regulator integrated circuit (IC) 34 and a second regulator IC 35.

[0033] The dimming circuit 31 inputs a voltage 309 to the first regulator IC34. A current flows through the first regulator IC34 both when the on-duty ratio of the PWM dimming signal 302 is not 100% and the light source 14 is turned on and when the on-duty ratio of the PWM dimming signal 302 is 100% and the light source 14 is turned off. The first regulator IC34 generates a constant voltage 310 from the input voltage 309 and inputs the generated constant voltage 310 to the auxiliary power supply circuit 32, both when the on-duty ratio of the PWM dimming signal 302 is not 100% and the light source 14 is turned on and when the on-duty ratio of the PWM dimming signal 302 is 100% and the light source 14 is turned off.

[0034] The second regulator IC35 is inserted into a conductive path 61 between the auxiliary power supply circuit 32 and the control circuit 25, which is included in the second supply line 27 that serves as a power supply path. This allows the auxiliary power supply circuit 32 to supply a second control voltage 308 to the second regulator IC35 via the conductive path 61. The second regulator IC35 can supply a constant voltage 311 to the control circuit 25 via the conductive path 61.

[0035] A second control voltage 308 is input to the second regulator IC35. When the voltage value of the second control voltage 308 is higher than a second specific voltage value, a current flows through the second regulator IC35. When the voltage value of the second control voltage 308 is equal to or lower than the second specific voltage value, no current flows through the second regulator IC35. When the voltage value of the second control voltage 308 is higher than the second specific voltage value, the second regulator IC35 generates a constant voltage 311 from the second control voltage 308 and inputs the generated constant voltage 311 to the control circuit 25. When the voltage value of the second control voltage 308 is equal to or lower than the second specific voltage value, the second regulator IC35 does not generate the constant voltage 311. The second regulator IC35 is a step-down regulator. The generated constant voltage 311 has a voltage value lower than the voltage value of the input second control voltage 308. The drive circuit 23 operates when the constant voltage 311 is input. The drive circuit 23 stops when the constant voltage 311 is not input. As a result, the control circuit 25 operates when the control signal 306 is in the first state and the voltage value of the second control voltage 308 is higher than the second specific voltage value. The drive circuit 23 stops when the control signal 306 is in the second state and the voltage value of the second control voltage 308 is equal to or lower than the second specific voltage value. When the control signal 306 is in the second state and the voltage value of the second control voltage 308 is equal to or lower than the second specific voltage value, only a portion of the drive circuit 23 may stop.

[0036] As a result, when the on-duty ratio of the PWM dimming signal 302 is 100%, the stop circuit 24 stops the control circuit 25 in addition to the PFC circuit 22. As a result, the PFC circuit 22 becomes a stopped circuit that is stopped when the on-duty ratio of the PWM dimming signal 302 is 100%.

[0037] As a result, the control circuit 25, which does not need to operate when the light source 14 is turned off, stops when the light source 14 is turned off. This makes it possible to prevent the control circuit 25 from wasting power when the light source 14 is turned off.

[0038] 3 Third embodiment The following describes the differences between the third embodiment and the second embodiment. For points that are not described, the third embodiment also employs the same configuration as that employed in the second embodiment.

[0039] FIG. 3 is a block diagram of a lighting system according to the third embodiment.

[0040] In the third embodiment, as shown in FIG. 3, an auxiliary power supply circuit 32 includes a power supply path 51 and a switch 52.

[0041] The auxiliary power supply circuit 32 generates a second control voltage 308 and supplies the generated second control voltage 308 to the PFC circuit 22 via the power supply path 51. The switch 52 is provided in the power supply path 51. The dimming circuit 31 inputs a control signal 306 to the switch 52. When the input control signal 306 is in a first state, the switch 52 turns on to close the power supply path 51. When the input control signal 306 is in a second state, the switch 52 turns off to open the power supply path 51. As a result, when the on-duty ratio of the PWM dimming signal 302 is not 100%, the switch 52 turns on to close the power supply path 51. When the on-duty ratio of the PWM dimming signal 302 is 100%, the switch 52 turns off to open the power supply path 51. As a result, when the on-duty ratio of the PWM dimming signal 302 is not 100%, the auxiliary power supply circuit 32 supplies the second control voltage 308 to the PFC circuit 22 and the second regulator IC 35. When the on-duty ratio of the PWM dimming signal 302 is 100%, the auxiliary power supply circuit 32 does not supply the second control voltage 308 to the PFC circuit 22 and the second regulator IC 35. When the second control voltage 308 is supplied to the PFC circuit 22 and the second regulator IC 35, the PFC circuit 22 and the control circuit 25 operate. When the second control voltage 308 is not supplied to the PFC circuit 22 and the second regulator IC 35, the PFC circuit 22 and the control circuit 25 stop operating.

[0042] As a result, when the on-duty ratio of the PWM dimming signal 302 is 100%, the stop circuit 24 stops the PFC circuit 22 and the control circuit 25. As a result, the PFC circuit 22 and the PFC circuit 25 become stopped circuits that are stopped when the on-duty ratio of the PWM dimming signal 302 is 100%.

[0043] As a result, when the on-duty ratio of the PWM dimming signal 302 is 100% and the light source 14 is turned off, the PFC circuit 22 and the control circuit 25 are stopped. As a result, the PFC circuit 22 and the control circuit 25, which do not need to operate when the light source 14 is turned off, are stopped. The PFC circuit 22 and the control circuit 25, which do not need to operate when the light source 14 is turned off, are stopped when the light source 14 is turned off. As a result, it is possible to prevent the PFC circuit 22 and the control circuit 25 from wasting power when the light source 14 is turned off.

[0044] By stopping the PFC circuit 22 and the control circuit 25 with the switch 52, it is possible to prevent the PFC circuit 22 and the control circuit 25 from wasting power with a simple circuit.

[0045] 4 Fourth embodiment The following describes the differences between the fourth embodiment and the first embodiment. For points that are not described, the fourth embodiment also employs the same configuration as that employed in the first embodiment.

[0046] FIG. 4 is a block diagram of a PFC circuit, a control circuit, a dimming circuit, and an auxiliary power supply circuit provided in a lighting system of the fourth embodiment.

[0047] As shown in FIG. 4, the dimming circuit 31 includes an N-channel metal oxide semiconductor field effect transistor (MOSFET) 61.

[0048] The drain of the N-channel MOSFET 61 is electrically connected to the signal line 33. The source of the N-channel MOSFET 61 is electrically connected to ground. When the on-duty ratio of the PWM modulation signal 102 is not 100%, the dimming circuit 31 applies a voltage lower than the threshold voltage between the gate and source of the N-channel MOSFET 61 to turn off the N-channel MOSFET 61 and prevent conduction between the source of the N-channel MOSFET 61 and the drain of the N-channel MOSFET 61. When the on-duty ratio of the PWM modulation signal 102 is 100%, the dimming circuit 31 applies a voltage higher than the threshold voltage to the gate of the N-channel MOSFET 61 to turn on the N-channel MOSFET 61 and prevent conduction between the source of the N-channel MOSFET 61 and the drain of the N-channel MOSFET 61. As a result, when the on-duty ratio of the PWM dimming signal 302 is not 100%, the dimming circuit 31 sets the control signal 306 to a first state having a potential different from ground potential. When the on-duty ratio of the PWM dimming signal 302 is 100%, the dimming circuit 31 sets the control signal 306 to a second state having the same potential as the ground potential. The N-channel MOSFET 61 may be replaced with a switching element other than an N-channel MOSFET.

[0049] 4, the auxiliary power supply circuit 32 includes a constant voltage output unit 71 and a voltage changing circuit 41. The voltage changing circuit 41 includes a constant voltage circuit 81.

[0050] The constant voltage output unit 71 outputs a constant voltage.

[0051] The voltage changing circuit 41 generates the second control voltage 308 from the output constant voltage. When the control signal 306 is in the first state, the voltage changing circuit 41 sets the voltage value of the second control voltage 308 to a constant voltage value higher than a second specific voltage value. When the control signal 306 is in the second state, the voltage changing circuit 41 sets the voltage value of the second control voltage 308 to a value equal to or lower than the second specific voltage value.

[0052] As shown in FIG. 4, the constant voltage circuit 81 includes a resistor 91, a Zener diode 92, a diode 93, an NPN transistor 94, and a resistor 95.

[0053] One terminal of the resistor 91 is electrically connected to the output terminal of the constant voltage circuit 81. The cathode of the Zener diode 92 is electrically connected to the other terminal of the resistor 91. The anode of the Zener diode 92 is electrically connected to ground. The anode of the diode 93 is electrically connected to the other terminal of the resistor 91 and the cathode of the Zener diode 92. The cathode of the diode 93 is electrically connected to the signal line 33. The base of the NPN transistor 94 is electrically connected to the other terminal of the resistor 91 and the cathode of the Zener diode 92. The collector of the NPN transistor 94 is electrically connected to the output terminal of the constant voltage circuit 81. One terminal of the resistor 95 is electrically connected to the emitter of the NPN transistor 94. The other terminal of the resistor 95 is connected to ground. The second supply line 27 is electrically connected to the emitter of the NPN transistor 94 and one terminal of the resistor 95.

[0054] As a result, the constant voltage output by the constant voltage output unit 71 is input to one terminal of the resistor 91 and the collector of the NPN transistor 94.

[0055] When the on-duty ratio of the PWM modulation signal 102 is not 100%, the N-channel MOSFET 61 is turned off, and the source of the N-channel MOSFET 61 is not electrically connected to the drain of the N-channel MOSFET 61, no current flows through the diode 93, and the Zener voltage of the Zener diode 92 is applied to the other terminal of the resistor 91, the cathode of the Zener diode 92, and the base of the NPN transistor 94. This turns on the NPN transistor 94, causing the emitter of the NPN transistor 94 to be electrically connected to the collector of the NPN transistor 94, and current flows between the collector and emitter of the NPN transistor 94 and through the resistor 95. As a result, the voltage value of the second control voltage 308 supplied via the second supply line 27 becomes higher than the second specific voltage value, and current is supplied to the PFC circuit 22. This causes the PFC circuit 22 to operate.

[0056] When the on-duty ratio of the PWM modulation signal 102 is 100%, the N-channel MOSFET 61 is turned off, and the source of the N-channel MOSFET 61 is electrically connected to the drain of the N-channel MOSFET 61, a current flows through the diode 93, and a voltage close to the forward voltage of the diode 93 is applied to the other terminal of the resistor 91, the cathode of the Zener diode 92, and the base of the NPN transistor 94. This turns the NPN transistor 94 off, the emitter of the NPN transistor 94 is not electrically connected to the collector of the NPN transistor 94, and no current flows between the collector and emitter of the NPN transistor 94 or through the resistor 95. As a result, the voltage value of the second control voltage 308 supplied via the second supply line 27 becomes equal to or lower than the second specific voltage value, and no current is supplied to the PFC circuit 22. This causes the PFC circuit 22 to stop operating.

[0057] 5 Fifth embodiment The following describes the differences between the fifth embodiment and the first embodiment. For points that are not described, the fifth embodiment also employs the same configuration as that employed in the first embodiment.

[0058] FIG. 5 is a block diagram of a PFC circuit, a control circuit, a dimming circuit, and an auxiliary power supply circuit provided in a lighting system of a fifth embodiment.

[0059] As shown in FIG. 5, the dimming circuit 31 includes an N-channel MOSFET 111.

[0060] The drain of the N-channel MOSFET 111 is electrically connected to the signal line 33. The source of the N-channel MOSFET 111 is electrically connected to ground. When the on-duty ratio of the PWM modulation signal 102 is not 100%, the dimming circuit 31 applies a voltage lower than the threshold voltage between the gate and source of the N-channel MOSFET 111 to turn off the N-channel MOSFET 111 and prevent conduction between the source and drain of the N-channel MOSFET 111. When the on-duty ratio of the PWM modulation signal 102 is 100%, the dimming circuit 31 applies a voltage higher than the threshold voltage between the gate and source of the N-channel MOSFET 111 to turn on the N-channel MOSFET 111 and prevent conduction between the source and drain of the N-channel MOSFET 111. As a result, when the on-duty ratio of the PWM dimming signal 302 is 100%, the dimming circuit 31 sets the control signal 306 to a first state having a potential different from ground potential, and outputs an on signal. When the on-duty ratio of the PWM dimming signal 302 is 100%, the dimming circuit 31 sets the control signal 306 to a second state having the same potential as the ground potential, and outputs an off signal. The N-channel MOSFET 111 may be replaced with a switching element other than an N-channel MOSFET.

[0061] As shown in FIG. 5, the auxiliary power supply circuit 32 includes a DC source 121, a resistor 122, a diode 123, a diode 124, a resistor 125, a capacitor 126, an N-channel MOSFET 127, a third resistor 128, a first resistor 129, a second resistor 130, and an IC 132.

[0062] The negative electrode of the DC source 121 is electrically connected to ground. One terminal of the resistor 122 is electrically connected to the positive electrode of the DC source 121. The other terminal of the resistor 122 is electrically connected to the anode of the diode 123 and the anode of the diode 124. The cathode of the diode 123 is electrically connected to the signal line 33. The cathode of the diode 124 is electrically connected to the gate of the N-channel MOSFET 127. One terminal of the resistor 125 and one terminal of the capacitor 126 are electrically connected to the cathode of the diode 124 and the gate of the N-channel MOSFET 127. The other terminal of the resistor 125 and the other terminal of the capacitor 126 are electrically connected to the source of the N-channel MOSFET 127.

[0063] As a result, when the on-duty ratio of the PWM modulation signal 102 is not 100%, the drain of the N-channel MOSFET 111 is not electrically connected to the source of the N-channel MOSFET 111, and the control signal 306 is in the first state, a positive potential is applied to the gate of the N-channel MOSFET 127 from the DC source 121 via the resistor 122 and the diode 124. This turns on the N-channel MOSFET 127, and the source of the N-channel MOSFET 127 is electrically connected to the drain of the N-channel MOSFET 127. When the on-duty ratio of the PWM modulation signal 102 is 100%, the drain of the N-channel MOSFET 111 is electrically connected to the source of the N-channel MOSFET 111, and the control signal 306 is in the second state, a potential lower than the above-mentioned positive potential is applied to the gate of the N-channel MOSFET 127. This turns off the N-channel MOSFET 127, and the source of the N-channel MOSFET 127 is not electrically connected to the drain of the N-channel MOSFET 127. Therefore, the N-channel MOSFET 127 switches between on and off depending on the state of the control signal 306. The N-channel MOSFET 127 may be replaced with a switching element other than an N-channel MOSFET.

[0064] One terminal of the first resistor 129 is electrically connected to the first terminal 132a of the IC 132. One terminal of the second resistor 130 is electrically connected to the other terminal of the first resistor 129. The other terminal of the second resistor 130 is electrically connected to the second terminal 132b of the IC 132. As a result, the first resistor 129 and the second resistor 130 are electrically connected in series to form a voltage divider circuit. The IC 132 outputs a voltage between the first terminal 132a of the IC 132 and the second terminal 132b of the IC 132. The voltage divider circuit formed by the first resistor 129 and the second resistor 130 divides the voltage output between the first terminal 132a of the IC 132 and the second terminal 132b of the IC 132, and generates a voltage obtained by the voltage division at the connection point between the other terminal of the first resistor 129 and one terminal of the second resistor 130.

[0065] One terminal of the third resistor 128 is electrically connected to the connection point. The drain of the N-channel MOSFET 127 is electrically connected to the other terminal of the third resistor 128. The source of the N-channel MOSFET 127 is electrically connected to the other terminal of the second resistor 130. As a result, the third resistor 128 and the N-channel MOSFET 127 are electrically connected in series to form a series circuit. The series circuit is electrically connected in parallel to the second resistor 130. When the source of the N-channel MOSFET 127 is conductive with the drain of the N-channel MOSFET 127, a current flows between the third resistor 128 and the drain-source of the N-channel MOSFET 127, and therefore the resistance value of the parallel circuit formed by the second resistor 130 and the series circuit being electrically connected in parallel is reduced. When the source of the N-channel MOSFET 127 is not electrically connected to the drain of the N-channel MOSFET 127, no current flows between the third resistor 128 and the drain-source of the N-channel MOSFET 127, and therefore the resistance value of the parallel circuit formed by electrically connecting the second resistor 130 and the series circuit in parallel increases.

[0066] Therefore, when the on-duty ratio of the PWM modulation signal 102 is not 100%, the drain of the N-channel MOSFET 111 is not electrically connected to the source of the N-channel MOSFET 111, and the control signal 306 is in a first state, the voltage at the connection point becomes a first voltage. When the on-duty ratio of the PWM modulation signal 102 is 100%, the drain of the N-channel MOSFET 111 is electrically connected to the source of the N-channel MOSFET 111, and the control signal 306 is in a second state, the voltage at the connection point becomes a second voltage different from the first voltage.

[0067] The IC132 includes a built-in adjustment circuit that adjusts the second control voltage 308 in response to the voltage applied to the feedback terminal 132c of the IC132. The feedback terminal 132c of the IC132 is electrically connected to the connection point. As a result, the adjustment circuit built into the IC132 adjusts the second control voltage 308 in response to the voltage at the connection point. When the voltage at the connection point is a first voltage, the IC132 increases the voltage value of the second control voltage 308 above a second specific voltage value. When the voltage at the connection point is a second voltage, the IC132 decreases the voltage value of the second control voltage 308 below the second specific voltage value. As a result, when the control signal 306 is in a first state, the IC132 increases the voltage value of the second control voltage 308 above the second specific voltage value. When the control signal 306 is in a second state, the IC132 decreases the voltage value of the second control voltage 308 below the second specific voltage value. Therefore, when the control signal 306 is in the first state, the PFC circuit 22 operates, and when the control signal 306 is in the second state, the PFC circuit 22 stops.

[0068] By turning on / off the N-channel MOSFET 127 to stop the PFC circuit 22 and the control circuit 25, it is possible to prevent the PFC circuit 22 and the control circuit 25 from wasting power with a simple circuit.

[0069] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0070] 1. Lighting system 11 AC power supply 12 Dimmer 13 Power circuit 14 Light source 21 Rectifier circuit 22 Power factor correction (PFC) circuit 23 Drive circuit 24 Stop circuit 31 Dimming circuit 32 Auxiliary power circuit 33 Signal line 34 First regulator integrated circuit (IC) 35 Second regulator IC 41 Voltage change circuit 51 Power supply path 52 Switch 61 N-channel metal oxide semiconductor field effect transistor (MOSFET) 71 Constant voltage output section 81 Constant voltage circuit 91 Resistance 92 Zener diode 93 Diode 94 NPN transistor 95 Resistance 111 N-channel MOSFET 121 DC source 122 Resistance 123 Diode 124 Diode 125 Resistance 126 Capacitor 127 N-channel MOSFET 128 The Third Resistance 129 First Resistance 130 The Second Resistance 131 IC 301 AC power 302 Pulse Width Modulation (PWM) Dimming Signal 302 PWM dimming signal 303 Driving Power 304 Input Power 305 Output Power 306 Control Signal 307 First Control Voltage 308 Second Control Voltage 309 Voltage 310 Constant Voltage 311 Constant Voltage

Claims

1. a control circuit that generates a control voltage according to an on-duty ratio of an input pulse width modulation dimming signal; a power factor correction circuit that generates output power from input power; a drive circuit that generates drive power corresponding to the control voltage from the output power and drives a light source with the drive power; a stop circuit; the control circuit causes the drive circuit to turn off the light source when the on-duty ratio is 100%; The stopping circuit stops a circuit to be stopped that is included in at least one of the control circuit and the power factor correction circuit when the on-duty ratio is 100%. power circuit.

2. the circuit to be disabled includes at least a part of the power factor correction circuit; the control voltage is a first control voltage; the stop circuit includes a voltage change circuit that generates a second control voltage and changes a voltage value of the second control voltage to a specific voltage value or less when the on-duty ratio is 100%; At least a part of the power factor correction circuit stops when the voltage value of the second control voltage is changed to or below the specific voltage value.

2. The power supply circuit according to claim 1.

3. the stop circuit includes an input circuit that inputs a control signal to the voltage change circuit; the input circuit sets the control signal to a first state when the on-duty ratio is not 100%, and sets the control signal to a second state when the on-duty ratio is 100%; The voltage change circuit increases the voltage value of the second control voltage above the specific voltage value when the control signal is in the first state, and decreases the voltage value of the second control voltage below the specific voltage value when the control signal is in the second state.

3. The power supply circuit according to claim 2.

4. The voltage change circuit includes a constant voltage circuit that sets the voltage value of the second control voltage to a constant voltage value higher than the specific voltage value when the control signal is in the first state, and sets the voltage value of the second control voltage to a constant voltage value lower than or equal to the specific voltage value when the control signal is in the second state.

4. The power supply circuit according to claim 3.

5. the stop circuit includes an auxiliary power supply circuit; The auxiliary power supply circuit includes: a voltage dividing circuit having a first resistor and a second resistor, the first resistor and the second resistor being connected in series; a series circuit including a third resistor and a switching element, the series circuit being connected in parallel to the second resistor and the third resistor and the switching element being connected in series; an adjustment circuit that adjusts the second control voltage in accordance with a voltage at a connection point between the first resistor and the second resistor; 4. The power supply circuit according to claim 3, wherein the switching element switches between on and off depending on the state of the control signal.

6. the stopped circuit includes at least a part of the control circuit; At least a part of the circuit of the control circuit stops when the voltage value of the second control voltage is changed to be equal to or lower than the specific voltage value.

3. The power supply circuit according to claim 2.

7. the stopped circuit includes at least a part of the control circuit; the stop circuit includes an input circuit that inputs a control signal to the control circuit; the input circuit sets the control signal to a first state when the on-duty ratio is not 100%, and sets the control signal to a second state when the on-duty ratio is 100%; At least a part of the control circuit operates when the control signal is in the first state and stops when the control signal is in the second state.

3. The power supply circuit according to claim 2.

8. the circuit to be disabled includes at least a part of the power factor correction circuit; the control voltage is a first control voltage; the stop circuit includes a power supply path, an auxiliary power supply circuit that generates a second control voltage and supplies the second control voltage to the power factor correction circuit via the power supply path, and a switch provided in the power supply path; The switch is turned off when the on-duty ratio is 100%; At least a part of the power factor correction circuit operates when the second control voltage is supplied to the power factor correction circuit, and stops when the second control voltage is not supplied to the power factor correction circuit.

2. The power supply circuit according to claim 1.

9. the stop circuit includes an input circuit that inputs a control signal to the switch; the input circuit sets the control signal to a first state when the on-duty ratio is not 100%, and sets the control signal to a second state when the on-duty ratio is 100%; The switch is turned on when the control signal is in the first state, and turned off when the control signal is in the second state.

9. The power supply circuit according to claim 8.

10. the stopped circuit includes at least a part of the control circuit; the power supply path includes a conductive path between the auxiliary power supply circuit and the control circuit.

9. The power supply circuit according to claim 8.

11. a regulator that generates a constant voltage having a voltage value lower than a voltage value of the second control voltage from the second control voltage and supplies the constant voltage to the control circuit; The auxiliary power supply circuit supplies the second control voltage to the regulator through the conductive path. The power supply circuit according to claim 10.

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