JP7081363B2 - Lighting equipment, lighting equipment - Google Patents

Description

The present invention relates to a lighting device that lights a light source and a luminaire using the lighting device.

For lighting fixtures that use LEDs (Light Emitting Diodes) as a light source, regulations regarding harmonics of input current are stipulated. In Japan, the Japanese Industrial Standards set limits for the harmonics of the input current. Therefore, the lighting device has a PFC (Power Factor Direction) circuit which is a power factor improving circuit for suppressing the harmonic of the input current and improving the power factor.

The lighting device controls the brightness of the LED. Since the brightness of the LED depends on the magnitude of the current of the LED, the lighting device has a current control circuit that controls the magnitude of the output current to be constant. In particular, there is a case where the PFC circuit and the current control circuit are realized by one circuit.

Japanese Unexamined Patent Publication No. 2009-21280

Patent Document 1 discloses that zero current detection is performed using the output voltage of the secondary winding of the coil as the timing control for turning on the switching element of the PFC circuit. This is called the current critical mode. In this case, since the coil needs to have a transformer structure, the coil becomes large due to the winding thickness. Further, since the secondary winding hinders the heat dissipation of the main winding, there is a problem that the winding temperature rises. In other words, this hinders the high output of the lighting device.

As another means for detecting zero current, it is conceivable to detect the coil current by using a shunt resistor. In this case, there is a problem that the efficiency of the lighting device is lowered because a loss occurs in the shunt resistance.

Further, a means for detecting zero current by measuring the voltage across the coil is also conceivable. In this case, if the voltage to be measured fluctuates, zero current cannot be detected correctly, and there is a problem that current critical mode control cannot be performed.

The present invention has been made to solve the above-mentioned problems, and provides a lighting device and a lighting fixture capable of control in a current critical mode while suppressing an increase in size of the device and deterioration of heat dissipation. The purpose is.

The lighting device according to the present invention has a rectifying circuit for rectifying AC power, a coil through which a current output from the rectifying circuit flows, and a switching element for changing an increase or decrease in the current flowing through the rectifying circuit. A DC conversion circuit that converts the power output from the rectifying circuit into DC power, a control unit that controls the DC conversion circuit, and a first voltage divider that divides the output voltage of the rectifying circuit. A voltage divider circuit, a second voltage divider circuit that divides the voltage across the switching element, a first voltage divider output from the first voltage divider circuit, and a second voltage divider output from the second voltage divider circuit. It is characterized by being provided with a comparator that compares the voltage of the voltage and outputs the voltage according to the magnitude relationship to the control unit.

Other features of the invention will be clarified below.

According to the lighting device according to the present invention, it is detected that the coil current becomes zero by dividing and comparing the voltage across the switching element and the output voltage of the rectifier circuit. It is possible to control in the current critical mode while suppressing the deterioration of.

It is a figure which shows the structural example of the lighting apparatus and the lighting apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the structural example of the current control circuit. It is a timing chart which shows the operation of a current control circuit. It is a timing chart which shows the operation of a DC conversion circuit. It is a timing chart which shows the timing which changes a switching element from off to on. It is a figure which shows the structural example of the lighting device and the lighting fixture which concerns on Embodiment 2. FIG. It is a timing chart which shows the timing which changes a switching element from off to on. It is a figure which shows the structural example of the lighting apparatus and the lighting apparatus which concerns on Embodiment 3. FIG. It is a timing chart which shows the timing which changes a switching element from off to on. It is a figure which shows the structural example of the lighting apparatus and the lighting apparatus which concerns on Embodiment 4. FIG. It is a timing chart which shows the timing which changes a switching element from off to on.

The lighting device and the lighting fixture according to the embodiment of the present invention will be described with reference to the drawings. The same or corresponding components may be designated by the same reference numerals and the description may be omitted. The present invention is not limited to the embodiments.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a lighting device and a lighting fixture according to the first embodiment. The luminaire 200 is connected to the AC power supply 1. The luminaire 200 includes a lighting device 100, a light source 8 that lights up by receiving the current supply of the lighting device 100, and a dimmer 10 that outputs a dimming signal for turning on, turning off, or dimming the light source 8. ing. The lighting device 100 converts the power supplied from the AC power supply 1 into a direct current that can be input to the light source 8 and outputs the power via the input filter 2 that removes the high frequency component of the AC current output from the AC power supply 1. .. The light source 8 is composed of, for example, a group of LEDs in which a plurality of LEDs are connected in series. One end of the LED group is connected to the positive electrode side DC bus, and the other end of the LED group is connected to the negative electrode side DC bus. Instead of the light source 8 provided with the LED, the light source 8 provided with the organic EL may be used.

The lighting device 100 includes an input filter 2, a rectifier circuit 3 connected to the input filter 2 to rectify AC power, a capacitor 4 connected in parallel to the rectifier circuit 3, a DC conversion circuit 5 which is a PFC circuit, and a current control circuit 7. .. The lighting device 100 includes a DC conversion circuit 5 and a control unit 9 for controlling the current control circuit 7.

The lighting device 100 includes a DC conversion circuit 5, a smoothing capacitor 6 that smoothes the output voltage of the DC conversion circuit 5, and a current control circuit 7 that controls the magnitude of the current output to the light source 8. The DC conversion circuit 5 has a function of suppressing harmonics of the current input from the AC power supply 1 to improve the power factor, and converting the power output from the rectifier circuit 3 into DC power to supply the light source 8. Have.

The input filter 2 arranged between the AC power supply 1 and the rectifier circuit 3 has a coil 2a and a filter capacitor 2b, and reduces high-frequency components superimposed on the current output from the AC power supply 1. The coil 2a is connected in series with the AC power supply 1. One end of the coil 2a is connected to one end of the AC power supply 1, and the other end of the coil 2a is connected to the filter capacitor 2b and the rectifier circuit 3. The other end of the filter capacitor 2b is connected to the AC power supply 1 and the rectifier circuit 3.

The rectifier circuit 3 is arranged between the input filter 2 and the DC conversion circuit 5, and converts the AC power supplied from the AC power supply 1 into DC power. The rectifier circuit 3 is composed of a diode bridge in which four diodes are combined. The configuration of the rectifier circuit 3 is not limited to this, and may be configured by combining MOSFETs that are unidirectional conduction elements.

The capacitor 4 is connected in parallel to the output of the rectifier circuit 3 and smoothes the output voltage of the rectifier circuit 3. One end of the capacitor 4 is connected to the positive electrode side DC bus, and the other end of the capacitor 4 is connected to the negative electrode side DC bus.

The DC conversion circuit 5 is arranged between the rectifier circuit 3 and the current control circuit 7. The DC conversion circuit 5 includes a switching element 5b composed of a MOSFET or the like, a coil 5a, and a diode 5c. By controlling the switching element 5b on and off by the control unit 9, the output voltage of the rectifier circuit 3 is boosted, and the boosted voltage is output to the smoothing capacitor 6. Further, the DC conversion circuit 5 has a function of suppressing harmonics of the input current and improving the power factor. In the first embodiment, an example in which the DC conversion circuit 5 is configured by the step-up chopper circuit will be described. In addition to the step-up chopper circuit, the direct current conversion circuit 5 may be configured by a circuit such as a buck-boost chopper circuit, a flyback circuit, a flyforward circuit, a SEPIC (Single Ended Primary Indicator Controller), a Zeta converter, or a Cuk converter. ..

The coil 5a is arranged between the capacitor 4 and the switching element 5b on the positive electrode side DC bus. The coil 5a can be formed by winding an insulating wire around the core. One end of the coil 5a is connected to one end of the capacitor 4. The other end of the coil 5a is connected to the anode of the diode 5c. A voltage having a different polarity is applied to the coil 5a as the switching element 5b is turned on and off. When the switching element 5b is turned on, the current output from the rectifier circuit 3 to the coil 5a increases.

The drain of the switching element 5b is connected to the coil 5a and the anode of the diode 5c in the positive electrode side DC bus. The source of the switching element 5b is connected to the other end of the capacitor 4 and the other end of the smoothing capacitor 6 in the negative electrode side DC bus. The gate of the switching element 5b is connected to the control unit 9. A control signal output from the control unit 9 is input to the gate of the switching element 5b. By inputting a control signal, on / off control of the switching element 5b is performed.

The diode 5c is arranged between the switching element 5b and the smoothing capacitor 6 on the positive electrode side DC bus. The anode of the diode 5c is connected to the coil 5a and the switching element 5b, and the cathode of the diode 5c is connected to the smoothing capacitor 6.

The smoothing capacitor 6 is arranged between the DC conversion circuit 5 and the current control circuit 7. One end of the smoothing capacitor 6 is connected to the positive electrode side DC bus, and the other end of the smoothing capacitor 6 is connected to the negative electrode side DC bus.

The control unit 9 includes a target value output unit 9a, a voltage detection unit 9b, a calculation unit 9c, and a drive unit 9d in order to control the DC conversion circuit 5.

A dimmer 10 is connected to the target value output unit 9a. The target value output unit 9a determines an output current target value corresponding to the type of dimming signal output from the dimmer 10, and outputs the determined output current target value to the calculation unit 9c. The output current target value is a signal that specifies the current target value that the lighting device 100 outputs to the light source 8.

The voltage detection unit 9b detects the voltage of the smoothing capacitor 6 and outputs the voltage information corresponding to the value of the detected voltage to the calculation unit 9c. As the voltage detection unit 9b, a resistance voltage divider circuit can be exemplified. In the voltage divider circuit, one end of a series resistor in which two or more resistors are connected in series is connected to a DC bus on the positive side, and the other end of the series resistor is connected to a DC bus on the negative side. This is a circuit that divides the voltage applied to the smoothing capacitor 6.

The calculation unit 9c outputs a control signal for controlling the DC conversion circuit 5 based on a predetermined output voltage target value and voltage information input to the voltage detection unit 9b. The current control circuit 7 converts the DC voltage output from the DC conversion circuit 5 into a DC current that can be input to the light source 8 based on the control signal output from the control unit 9.

FIG. 2 is a diagram showing a configuration example of the current control circuit 7. The current control circuit 7 includes a switching element 7a such as a MOSFET, a coil 7b, a diode 7c, and a filter capacitor 7d. The switching element 7a is arranged on the positive electrode side DC bus. The drain of the switching element 7a is connected to one end of the smoothing capacitor 6 shown in FIG. 1 and the cathode of the diode 5c. The source of the switching element 7a is connected to the cathode of the diode 7c and one end of the coil 7b. The gate of the switching element 7a is connected to the drive unit 9d. A control signal output from the control unit 9 is input to the gate of the switching element 7a. The control signal is a signal for on / off control of the switching element 7a.

One end of the coil 7b is connected to the source of the switching element 7a and the cathode of the diode 7c. The other end of the coil 7b is connected to one end of the filter capacitor 7d and one end of the light source 8 shown in FIG. The cathode of the diode 7c is connected to the source of the switching element 7a and one end of the coil 7b. The anode of the diode 7c is connected to the other end of the smoothing capacitor 6 shown in FIG. 1, the other end of the filter capacitor 7d, and the other end of the light source 8 shown in FIG.

The current control circuit 7 shown in FIG. 2 is composed of a step-down chopper circuit, but in addition to the step-down chopper circuit, a circuit such as a buck-boost chopper circuit, a flyback circuit, a flyforward circuit, a STEPIC, a Zeta converter, or a Cuk converter is used. The current control circuit 7 may be configured.

FIG. 3 is a timing chart showing the relationship between the current flowing through the light source 8, the current flowing through the coil 7b, and the gate voltage of the switching element 7a. FIG. 3 shows, in order from the top, the current flowing through the light source 8, the current flowing through the coil 7b, and the gate voltage of the switching element 7a. The horizontal axis represents time.

The switching cycle Tsw is equal to the time from the time when the control signal of the switching element 7a changes from off to on until the control signal of the switching element 7a changes from off to on again. The switching cycle Tsw is set in advance in the calculation unit 9c. The on-time Ton is equal to the time from when the control signal of the switching element 7a changes from off to on until it changes from on to off.

When the control signal of the switching element 7a changes from the off state to the on state, the switching element 7a is turned on, so that a current path is formed through the smoothing capacitor 6, the switching element 7a, the coil 7b, and the filter capacitor 7d. As shown in, the current flowing through the coil 7b increases.

When the control signal of the switching element 7a changes from the on state to the off state, the switching element 7a is turned off, so that a current path passing through the coil 7b, the filter capacitor 7d and the diode 7c is formed, and the coil 7b shown in FIG. 3 has a current path. The flowing current is reduced to zero. When the switching cycle Tsw has elapsed, the control signal of the switching element 7a changes from off to on. As a result, the switching element 7a is turned on again.

At this time, the current flowing through the coil 7b has a triangular wavy waveform, but the current output to the light source 8 is smoothed by the filter capacitor 7d, and the average value of the currents flowing through the coil 7b is output from the current control circuit 7. .. After the current flowing through the coil 7b drops to zero, a resonant current is generated in the parasitic capacitance of the switching element 7a and the resonance circuit formed by the coil 7b, but the description is omitted.

When controlling the current flowing through the light source 8 to dimm the light source 8, the arithmetic unit 9c keeps the switching cycle Tsw that turns on the switching element 7a constant, and changes the on-time Ton according to the target value of the output current. The control method for obtaining a specific output by adjusting the on-time ton in this way is called duty control because the ratio of the on-time ton to the switching cycle Tsw is called duty.

The switching elements 5b and 7a may be made of, for example, a silicon-based semiconductor or a wide bandgap semiconductor such as silicon carbide or a gallium nitride-based material. By using wide bandgap semiconductors for the switching elements 5b and 7a, it is possible to reduce the energization loss of the switching element, and even if the switching frequency, that is, the drive frequency is set to a high frequency, heat dissipation is good. Therefore, the heat dissipation parts of the DC conversion circuit 5 and the current control circuit 7 can be miniaturized or omitted, and the lighting device 100 can be miniaturized and the cost can be reduced.

Next, the operation of the DC conversion circuit 5 will be described in detail.

FIG. 4 is a timing chart showing the relationship between the current flowing through the coil 5a shown in FIG. 1, the drain voltage of the switching element 5b, and the gate voltage of the switching element 5b. In FIG. 4, in order from the top, the current of the AC power supply 1 input to the lighting device 100, the current flowing through the coil 5a, the zero current detection signal output by the zero current detection circuit 11, and the drain voltage of the switching element 5b. , The gate voltage of the switching element 5b is shown. The horizontal axis represents time.

In FIG. 4, for convenience of explanation, the period in which the gate voltage of the switching element 5b is turned on and off is described to be longer than the actual period. The cycle in which the gate voltage of the switching element 5b is turned on and off is equal to the time from the time when the gate voltage of the switching element 5b changes from off to on until the gate voltage of the switching element 5b changes from off to on again.

When the switching element 5b is turned on, a current path of the AC power supply 1, the rectifier circuit 3, the coil 5a and the switching element 5b is formed, and the AC power supply 1 is short-circuited via the coil 5a. Therefore, the current flowing through the coil 5a increases, and energy is stored in the coil 5a.

When the on time set in the calculation unit 9c elapses, the switching element 5b is turned off. As a result, a current path for the coil 5a, the diode 5c and the smoothing capacitor 6 is formed. In this current path, the energy stored in the coil 5a is released and the smoothing capacitor 6 is charged.

When the current flowing through the coil 5a becomes zero, the switching element 5b is turned on again. The switching element 5b can change the increase / decrease of the current flowing through the coil 5a. In this way, the control of turning on the switching element 5b immediately after the current of the coil 5a becomes zero is called a current critical mode.

Due to the series of on / off operations of the switching element 5b, the current flowing through the coil 5a becomes a triangular wave-shaped waveform, and its apex becomes a sinusoidal envelope as shown by a dotted line. At this time, the high frequency component is removed from the current waveform input from the AC power supply 1 by the input filter 2, and the average value of the coil current flowing through the coil 2a is input to form a sine wave shape.

At this time, the voltage detection unit 9b detects the applied voltage of the smoothing capacitor 6, and the control unit 9 performs feedback control so that the detected voltage follows the target value, thereby controlling the on-time of the switching element 5b. Will be done.

When the on-time of the switching element 5b is feedback-controlled, if the on-time changes significantly, the envelope of the apex of the current flowing through the coil 5a does not become a sine wave, and the input current of the AC power supply 1 becomes a sine wave. Can't. Therefore, in the control unit 9, the response time of the feedback control is set so that the loop gain of the feedback control is 1 times (0 dB) or less in 1/2 cycle or more of one cycle of the AC power supply 1. In other words, the response time of the feedback control is set to be 1 time (0 dB) or less at a frequency of 2 times or less the frequency of the AC power supply 1.

Specifically, when the power supply frequency is 50 Hz, the loop gain of the feedback control is 1 times (0 dB) or less at a frequency of 100 Hz or less in a half cycle (half wave) of the power supply frequency, that is, a cycle of 10 msec or more. As a result, the feedback control is set so as not to respond in a cycle shorter than 1/2 of the power supply cycle. Further, within 1/2 cycle of the power supply cycle, the fluctuation of the on-time of the switching element 5b is suppressed, and the envelope of the apex of the current flowing through the coil 5a becomes a sinusoidal waveform.

In the feedback control, the same effect can be obtained by setting the update cycle of the on-time to a cycle corresponding to half of the cycle of the AC power supply 1 or a cycle longer than the cycle corresponding to half of the cycle of the AC power supply 1. be able to.

After detecting the zero current, a slight delay time is provided until the switching element 5b is turned on, and the switching element 5b is turned on near the bottom of the drain voltage vibration during the period when the drain voltage of the switching element 5b is freely oscillating. You can also do it. As a result, it is possible to suppress abrupt fluctuations in the drain voltage and suppress noise caused by switching.

When dimming the light source 8, in order to reduce the input current of the AC power supply 1, the arithmetic unit 9c controls so as to shorten the on-time of the switching element 5b.

Next, the zero current detection circuit 11 and its operation will be described. FIG. 1 shows a zero current detection circuit 11. The zero current detection circuit 11 includes voltage divider resistors 11a, 11b, 11c, 11d, and a comparator 11e. The comparator 11e outputs a zero current detection signal for detecting that the current of the coil 5a has become zero.

One end of the voltage dividing resistor 11a is connected to the capacitor 4, and the other end is connected to the voltage dividing resistor 11b and the input terminal of the comparator 11e. One end of the voltage dividing resistor 11b is connected to the voltage dividing resistor 11a and the input terminal of the comparator 11e, and the other end is connected to the negative electrode side DC bus. That is, the voltage dividing resistors 11a and 11b divide the output voltage VDB of the rectifier circuit 3 into a voltage that can be input to the comparator 11e. The voltage dividing resistors 11a and 11b are examples of the first voltage dividing circuit 11A that divides the output voltage VDB of the rectifier circuit 3.

One end of the voltage dividing resistor 11c is connected to the drain terminal of the switching element 5b, and the other end is connected to the voltage dividing resistor 11d and the input terminal of the comparator 11e. One end of the voltage dividing resistor 11d is connected to the voltage dividing resistor 11c and the input terminal of the comparator 11e, and the other end is connected to the negative electrode side DC bus. That is, the voltage dividing resistors 11c and 11d divide the drain voltage Vds of the switching element 5b into a voltage that can be input to the comparator 11e. The voltage dividing resistors 11c and 11d are examples of the second voltage dividing circuit 11B that divides the drain voltage Vds of the switching element 5b. The second voltage dividing circuit 11B can also be said to be a circuit that divides the voltage across the switching element 5b. The voltage divider ratios in the first voltage divider circuit 11A and the second voltage divider circuit 11B can be made equal.

The comparator 11e compares the output voltage VDB of the rectifying circuit 3 with the drain voltage Vds of the switching element 5b via the voltage dividing resistors 11a and 11b and the voltage dividing resistors 11c and 11d. The drain voltage Vds of the switching element 5b may be simply referred to as Vds, and the output voltage VDB of the rectifier circuit 3 may be simply referred to as VDB. To be precise, the comparator 11e compares the first voltage-separated voltage VDB ⁻ which is a voltage divider of VDB and the second voltage divider voltage Vds ⁻ which is a voltage divider of Vds −, and outputs a signal based on the comparison result to the calculation unit 9c. Output to. Hereinafter, when the voltage dividing ratios in the first voltage dividing circuit 11A and the second voltage dividing circuit 11B are equal and the second voltage dividing voltage Vds ⁻ is larger than the first voltage dividing voltage VDB ⁻ , a high signal is output and the second voltage divider is output. A configuration for outputting a low signal when the voltage voltage Vds ⁻ is smaller than the first voltage divider voltage VDB ⁻ will be described.

FIG. 5 is a timing chart showing the timing of changing the switching element 5b from off to on. In FIG. 5, in order from the top, the current flowing through the coil 5a, the voltage of the coil 5a, the second voltage dividing voltage Vds ⁻ , the zero current detection signal output by the zero current detection circuit 11, and the gate voltage of the switching element 5b. Is shown. The horizontal axis represents time.

t1 is the timing at which the gate voltage of the switching element 5b is changed from on to off. After t1, the diode 5c conducts, so that the output voltage of the DC conversion circuit 5 charged in the smoothing capacitor 6 is applied to the drain of the switching element 5b. After t1, the coil 5a discharges the charged energy to the smoothing capacitor 6, so that the current of the coil 5a decreases. Further, since the second voltage dividing voltage Vds ⁻ is larger than the first voltage dividing voltage VDB ⁻ , a high signal is output as a zero current detection signal.

t2 is the timing when the current of the coil 5a is reduced to zero. When the current of the coil 5a is reduced to zero, a parasitic capacitance of the switching element 5b and a resonance voltage are generated in the resonance circuit formed by the coil 5a. The waveform of the voltage of the coil 5a and the dotted line shown in the waveform display column of the second voltage dividing voltage Vds ⁻ are auxiliary lines indicating the resonance voltage after t2. The resonance voltage of the coil 5a is zero, and the resonance voltage of the second divided voltage Vds ⁻ is a vibration waveform that converges to VDB ⁻ .

t3 is the timing at which the second voltage dividing voltage Vds ⁻ is reduced to the first voltage dividing voltage VDB ⁻ due to the resonance voltage after the current of the coil 5a is reduced to zero. A low signal is output as a zero current detection signal at t3. The arithmetic unit 9c detects that the zero current detection signal has changed from high to low, and determines that the current of the coil 5a has decreased to zero.

The resonance voltage of Vds changes depending on the magnitude of VDB and the instantaneous value of the output voltage Vpfc of the DC conversion circuit 5. However, since the resonance voltage of Vds converges to VDB, by comparing the voltage dividing voltage of Vds and the voltage dividing voltage of VDB, zero current is detected even when the output voltage Vpfc of the VDB or the DC conversion circuit 5 fluctuates. The signal can be changed from high to low. It should be noted that the logic of the zero current detection signal can be reversed from the above-mentioned logic, and control corresponding to the logic can be realized.

t4 is the timing for changing the gate of the switching element 5b from off to on. When Vds drops to near zero, the output of the rectifier circuit 3 is short-circuited via the coil 5a, so that the current of the coil 5a increases after t4, and the coil 5a charges energy. For example, t4 can be a timing at which the vibration of Vds becomes a minimum value. The smaller Vds at the timing when the switching element 5b is turned on, the more abrupt changes in voltage can be suppressed and noise can be reduced. In addition, the change width of the voltage can be reduced and the loss can be reduced. Therefore, it is possible to investigate how long the period of t3-t4 should be to minimize Vds at the timing t4 when the switching element 5b is turned on. Noise and loss can be suppressed by continuing to use the optimum t3-t4 period determined in the investigation.

By using the above-mentioned zero current detection circuit 11, it is possible to eliminate the need for the secondary winding of the coil, which has been conventionally required when controlling by the current discontinuous mode including the current critical mode. As a result, the coil can be miniaturized, the heat dissipation can be improved, the temperature rise of the coil can be suppressed, and the output of the lighting device can be increased. Further, when the secondary winding is provided, the shape of the coil is limited to the transformer, but this configuration does not require the secondary winding, so that the degree of freedom in the shape of the coil 5a is improved. For example, as the coil 5a, an air core coil, a single-sided substrate planar coil, or a drum type coil can be applied.

The comparator 11e compares the first voltage dividing voltage VDB ^- output from the first voltage dividing circuit 11A and the second voltage dividing voltage ^Vds- output from the second voltage dividing circuit 11B, and corresponds to the magnitude relationship. It can be said that the voltage is output to the control unit 9. In the first embodiment, the comparator 11e outputs a zero current detection signal to the control unit 9, and when the second voltage dividing voltage Vds ⁻ becomes lower than the first voltage dividing voltage VDB ⁻ , the zero current detection signal is logically inverted. .. Then, after this logic inversion, the control unit 9 showed an operation of turning on the switching element 5b. If the voltage dividing ratios of the first voltage dividing circuit 11A and the second voltage dividing circuit 11B are different, more complicated processing is required as compared with the case of comparing the magnitude relationship between the first voltage dividing voltage and the second voltage dividing voltage. ..

The configuration described in the first embodiment can also be applied to the lighting device and the luminaire according to the following embodiment. Since the lighting device and the lighting fixture according to the following embodiment have much in common with the first embodiment, the differences between the lighting device and the lighting fixture according to the first embodiment will be mainly described.

Embodiment 2.
FIG. 6 is a diagram showing a configuration example of the lighting device 100A and the lighting fixture 200A according to the second embodiment. The luminaire 200A according to the second embodiment is different from the luminaire 200 according to the first embodiment in that the lighting device 100A is used instead of the lighting device 100. The difference between the lighting device 100A according to the second embodiment and the lighting device 100 according to the first embodiment is that in the lighting device 100A, the zero current detection circuit 11C includes a diode 11f and a voltage source 11g.

The zero current detection circuit 11C includes voltage dividing resistors 11a, 11b, 11c, 11d, a comparator 11e, a diode 11f, and a voltage source 11g which is a DC power supply. The diode 11f and the voltage source 11g constitute the voltage supply unit 11D. The comparator 11e outputs a zero current detection signal for detecting that the current of the coil 5a has become zero.

In the diode 11f, the cathode is connected to the voltage dividing resistors 11a and 11b and the input terminal of the comparator 11e, and the anode is connected to one end of the voltage source 11g. One end of the voltage source 11g is connected to the anode of the diode 11f. The voltage source 11g provides a voltage greater than the forward voltage of the diode 11f.

As described above, the first voltage divider circuit 11A outputs the midpoint voltage of the two resistance elements connected in series as the first voltage divider voltage VDB ⁻ . Therefore, it can be said that the cathode of the diode 11f is connected to the midpoint of the two resistance elements.

The other end of the voltage source 11g is connected to the voltage dividing resistor 11b on the negative electrode side DC bus. The voltage dividing resistors 11a and 11b divide the VDB into the first voltage dividing voltage VDB ⁻ which can be input to the comparator 11e. When the first voltage dividing voltage VDB ⁻ drops below the voltage of the voltage source 11g, the voltage of the voltage source 11g is input to the comparator 11e. In the second embodiment, the voltage of the voltage source 11g is provided to the comparator 11e only when the first voltage dividing voltage VDB ⁻ becomes smaller, and in other cases, the first voltage dividing voltage VDB ⁻ becomes the comparator 11e. It can be said that the OR circuit provided is provided.

As described above, the comparator 11e outputs a zero current detection signal based on the voltage of the voltage source 11g to the arithmetic unit 9c in addition to the divided voltage of VDB and Vds. Here, as an example, when the voltage dividing ratios of the voltage dividing resistors 11a and 11b and the voltage dividing resistors 11c and 11d are the same and the second voltage dividing voltage Vds ⁻ is larger than the first voltage dividing voltage VDB ⁻ , a high signal is output. A configuration for outputting to the control unit 9 and outputting a low signal to the control unit 9 when the second voltage dividing voltage Vds ⁻ is smaller than the first voltage dividing voltage VDB ⁻ will be described.

When the first voltage dividing voltage VDB ⁻ input to the comparator 11e is larger than the voltage of the voltage source 11g, the diode 11f does not conduct. In this case, since the circuit operation of the zero current detection circuit 11C is the same as the circuit operation of the zero current detection circuit 11 in the first embodiment, the description thereof will be omitted.

On the other hand, in the case where the first voltage dividing voltage VDB ⁻ is smaller than the voltage of the voltage source 11g, the circuit operation of the zero current detection circuit 11C will be described with reference to FIG. 7.

FIG. 7 is a timing chart showing the timing of changing the switching element 5b of FIG. 6 from off to on. FIG. 7 shows, in order from the top, the current flowing through the coil 5a, the voltage of the coil 5a, the second voltage dividing voltage Vds ⁻ , the zero current detection signal output by the zero current detection circuit 11C, and the gate voltage of the switching element 5b. The horizontal axis represents time.

t1 is the timing at which the gate voltage of the switching element 5b is changed from on to off. Since the diode 5c conducts during the period from t1, the output voltage of the DC conversion circuit 5 charged in the smoothing capacitor 6 is applied to the drain of the switching element 5b. After t1, the coil 5a discharges the charged energy to the smoothing capacitor 6, so that the coil current decreases. Since the first voltage divider voltage VDB ⁻ is larger than the second voltage divider voltage Vds ⁻ , a high signal is output as a zero current detection signal.

t2 is the timing when the current of the coil 5a is reduced to zero. When the current of the coil 5a is reduced to zero, a resonance voltage is generated in the parasitic capacitance of the switching element 5b and the resonance circuit formed by the coil 5a. The dotted line shown in the display column of the waveform of the voltage of the coil 5a and the waveform of the second voltage dividing voltage Vds ⁻ is an auxiliary line indicating the resonance voltage after t2. Further, the voltage of the coil 5a is zero, and the second voltage dividing voltage Vds ⁻ is a vibration waveform that converges to the first voltage dividing voltage VDB ⁻ .

t3 is the timing at which the second voltage dividing voltage Vds ⁻ drops to the voltage of the voltage source 11 g due to the resonance voltage after the current of the coil 5a is reduced to zero. When the second voltage dividing voltage Vds ⁻ becomes smaller than the voltage of the voltage source 11g, a low signal is output from the zero current detection circuit 11C. The arithmetic unit 9c detects that the zero current detection signal has changed from high to low, and determines that the current of the coil 5a has decreased to zero. In order to generate a timing in which the second voltage dividing voltage Vds ⁻ becomes smaller than the voltage of the voltage source 11g in the process of decreasing the second voltage dividing voltage Vds ⁻ , the voltage source 11g provides the comparator 11e. The voltage needs to be smaller than the maximum value of the second voltage dividing voltage Vds ⁻ .

t4 is the timing at which Vds drops to zero due to the resonance voltage after the current of the coil 5a drops to zero. When Vds drops to zero, the parasitic diode of the switching element 5b conducts, so Vds does not drop below zero.

t5 is the timing for changing the gate of the switching element 5b from off to on. When Vds drops to near zero, the output of the rectifier circuit 3 is short-circuited via the coil 5a, so that the current of the coil 5a increases after t5, and the coil 5a charges energy.

The zero current detection circuit 11 shown in the first embodiment has a configuration that does not use the voltage source 11g. Therefore, when the VDB or the first voltage dividing voltage VDB ⁻ drops to near zero, the second voltage dividing voltage Vds ⁻ may not be lower than the first voltage dividing voltage VDB ⁻ . In this case, the zero current detection signal cannot be changed from high to low, and zero current cannot be detected. On the other hand, the zero current detection circuit 11C shown in the second embodiment uses the voltage source 11g, and even when the first voltage dividing voltage VDB ⁻ drops to near zero, it replaces the first voltage dividing voltage VDB ⁻ . Since the voltage of the voltage source 11g is provided to the comparator 11e, zero current can be detected.

When the switching element 5b is changed from off to on based on zero current detection such as critical mode control, if zero current detection is not possible, the switching operation cannot be restarted after being stopped. As a countermeasure against this, when zero current cannot be detected, there is a method in which the control unit 9 restarts switching after a predetermined time has elapsed. However, this is not preferable because the switching frequency is lowered and the input current waveform is distorted and harmonics are increased.

Therefore, by using the zero current detection circuit 11C according to the second embodiment, it is possible to reliably carry out the control in the current critical mode or the current discontinuous mode other than the critical mode. Moreover, the secondary winding of the coil, which was conventionally required in the critical mode, can be eliminated. As a result, it is possible to suppress the temperature rise of the coil and increase the output of the lighting device by reducing the size of the coil and improving the heat dissipation. Further, when the secondary winding is provided, the shape of the coil 5a is limited to the transformer, but since the present configuration does not require the secondary winding, the degree of freedom in the shape of the coil 5a is improved. Therefore, for example, an air core coil, a single-sided substrate planar coil, or a drum type coil can be applied as the coil 5a. In addition, even when the VDB drops, such as in the vicinity of the power supply voltage zero cross or when the power supply voltage drops momentarily, zero current can be detected more accurately, resulting in loss reduction and heat generation suppression by suppressing harmonics in the lighting device. Is possible.

Although the voltage source 11g is described as an individual component in the second embodiment, the voltage source may be provided by dividing the voltage of the control power supply or the like for operating the comparator 11e, for example. When the first voltage divider voltage VDB ⁻ becomes smaller than a predetermined value, the voltage supply unit 11D replaces the first voltage divider voltage VDB ⁻ with a voltage higher than the first voltage divider voltage VDB ⁻ . This is the circuit provided for 11e. Another circuit that brings about such an action can be adopted as the voltage supply unit 11D.

Embodiment 3.
FIG. 8 is a diagram showing a configuration example of the lighting device 100B and the lighting fixture 200B according to the third embodiment. The difference between the luminaire 200B according to the third embodiment and the luminaire 200 according to the first embodiment is that the luminaire 200B uses the lighting device 100B instead of the lighting device 100. The difference between the lighting device 100B according to the third embodiment and the lighting device 100 according to the first embodiment is that the zero current detection circuit 11E includes the voltage drop diode 11h in the lighting device 100B.

The zero current detection circuit 11E includes voltage dividing diodes 11a, 11b, 11c, 11d, a comparator 11e, and a voltage drop diode 11h. The cathode of the voltage drop diode 11h is connected to the voltage dividing resistors 11a and 11b, and the anode is connected to the voltage dividing resistors 11c and 11d. More specifically, the cathode of the voltage drop diode 11h is connected to the output of the first voltage divider circuit having voltage divider resistors 11a, 11b. The anode of the voltage drop diode 11h is connected to the output of the second voltage divider circuit having voltage divider resistors 11c, 11d. The voltage drop diode 11h lowers the second voltage dividing voltage Vds ⁻ . The comparator 11e outputs a zero current detection signal for detecting that the current of the coil 5a has become zero.

The comparator 11e outputs a signal based on the divided voltage of VDB and Vds to the calculation unit 9c. In this example, the voltage dividing resistors 11a and 11b and the voltage dividing resistors 11c and 11d have the same voltage dividing ratio. Further, when the second voltage divider voltage Vds ⁻ is larger than the first voltage divider voltage VDB ⁻ , the comparator 11e outputs a high signal, and the second voltage divider voltage Vds ⁻ is smaller than the first voltage divider voltage VDB ⁻ . In some cases, the comparator 11e outputs a low signal.

FIG. 9 is a timing chart showing the timing of changing the switching element 5b shown in FIG. 8 from off to on. In FIG. 9, in order from the top, the current flowing through the coil 5a, the voltage of the coil 5a, Vds, the second voltage dividing voltage Vds ⁻ , the zero current detection signal indicating the timing when the current flowing through the coil 5a becomes zero, and the switching element. The gate voltage of 5b is shown. The horizontal axis represents time.

t1 is the timing when the gate voltage of the switching element 5b is changed from on to off, and the output voltage of the DC conversion circuit 5 charged in the smoothing capacitor 6 is applied to the drain of the switching element 5b due to the conduction of the diode 5c. Will be done. After t1, the energy charged in the coil 5a is discharged to the smoothing capacitor 6, so that the current in the coil 5a is reduced. Since Vds is larger than VDB, a high signal is output as a zero current detection signal.

At this time, since Vds is larger than VDB and the voltage dividing ratios due to the voltage dividing resistors 11a, 11b, 11c, and 11d are the same, the voltage drop diode 11h conducts. As a result, the second voltage dividing voltage Vds ⁻ input to the comparator 11e becomes a voltage obtained by adding the forward voltage of the voltage drop diode 11h to the average value of the output voltage of the DC conversion circuit 5 and the VDB.

t2 is the timing when the current of the coil 5a is reduced to zero. When the current of the coil 5a is reduced to zero, a parasitic capacitance of the switching element 5b and a resonance voltage are generated in the resonance circuit formed by the coil 5a. The voltage waveform of the coil 5a and the dotted line shown in the display column of the Vds waveform are auxiliary lines indicating the resonance voltage after t2. The resonance voltage of the coil 5a is zero, and the resonance voltage of Vds is a vibration waveform that converges on VDB.

t3 is the timing at which the second voltage dividing voltage Vds ⁻ drops to the first voltage dividing voltage VDB ⁻ due to the resonance voltage after the current of the coil 5a is reduced to zero. After t3, since the second voltage dividing voltage Vds ⁻ is smaller than the first voltage dividing voltage VDB ⁻ , a low signal is output as a zero current detection signal. The arithmetic unit 9c detects that the zero current detection signal has changed from high to low, and determines that the current of the coil 5a has decreased to zero. When the second voltage dividing diode Vds ⁻ becomes smaller than the first voltage dividing voltage VDB ⁻ , the voltage drop diode 11h becomes non-conducting.

t4 is the timing for changing the gate of the switching element 5b from off to on. When Vds drops to near zero, the output of the rectifier circuit 3 is short-circuited via the coil 5a, so that the current of the coil 5a increases after t5, and the coil 5a charges energy.

By the way, the output voltage of the DC conversion circuit 5 may become an overvoltage. For example, if the normal output voltage is 400V, an overvoltage of 500-600V may occur. In this case, for example, even if an output voltage of 600 V is generated, the second voltage dividing voltage Vds ⁻ must be reduced so that the comparator 11e does not fail due to this. That is, when determining the resistance values of the voltage dividing resistors 11c and 11d, the overvoltage that may occur in the output voltage of the DC conversion circuit 5 is taken into consideration, and the second voltage dividing voltage Vds ⁻ is set within the withstand voltage of the comparator 11e. There is a need. Therefore, the second voltage dividing voltage Vds ⁻ when no overvoltage is generated must be lowered, and as a result, a narrow voltage range is used. Use of a narrow voltage range causes malfunction. On the other hand, the zero current detection circuit 11E according to the third embodiment can suppress the peak value of the second voltage dividing voltage Vds ⁻ by using the voltage drop diode 11h. Then, when an overvoltage does not occur, a wide voltage range can be used, and malfunction can be suppressed.

By using the zero current detection circuit 11E of this configuration, the secondary winding of the coil, which was conventionally required when controlling in the current critical mode or the current discontinuous mode other than the current critical mode, is eliminated. Can be done. As a result, it is possible to suppress the temperature rise of the coil and increase the output of the lighting device by reducing the size of the coil and improving the heat dissipation. Further, when the secondary winding is provided, the shape of the coil is limited to the transformer, but since the present configuration does not require the secondary winding, the degree of freedom in the shape of the coil 5a is improved. As the coil 5a, for example, an air core coil, a single-sided substrate planar coil, or a drum type coil can be applied. In addition, since the voltage dividing voltage input to the comparator 11e can be reduced, an inexpensive comparator 11e having a rough detection resolution can be used, and the cost of the lighting device 100B can be reduced.

Embodiment 4.
FIG. 10 is a diagram showing a configuration example of the lighting device 100C and the lighting fixture 200C according to the fourth embodiment. The difference between the luminaire 200C according to the fourth embodiment and the luminaire 200 according to the first embodiment is that the luminaire 200C uses the luminaire 100C instead of the luminaire 100. The difference between the lighting device 100C and the lighting device 100 according to the first embodiment is that the zero current detection circuit 11F of the lighting device 100C includes an output stop switching element 11i.

The zero current detection circuit 11F includes voltage dividing resistors 11a, 11b, 11c, 11d, a comparator 11e, and an output stop switching element 11i composed of, for example, a MOSFET. The drive unit 9d is connected to the gate of the output stop switching element 11i in addition to the switching element 5b. The drive unit 9d controls the on / off state of the output stop switching element 11i based on the calculation result of the calculation unit 9c.

The drain terminal of the output stop switching element 11i is connected to the output terminal of the comparator 11e and the arithmetic unit 9c. The source terminal of the output stop switching element 11i is connected to the negative electrode side bus voltage. The comparator 11e outputs a zero current detection signal for detecting that the current of the coil 5a has become zero. However, when the output stop switching element 11i is on, the output voltage of the zero current detection circuit 11F is fixed to low. The output stop switching element 11i switches whether or not the output terminal of the comparator 11e is connected to the reference potential. The output stop switching element 11i adds a mask function to the output voltage of the zero current detection circuit 11F.

The comparator 11e outputs a signal based on the divided voltage of VDB and Vds to the calculation unit 9c. In this example, the voltage dividing ratios of the voltage dividing resistors 11a and 11b and the voltage dividing resistors 11c and 11d are the same. Further, a high signal is output when the second voltage dividing voltage Vds ⁻ is larger than the first voltage dividing voltage VDB ⁻ , and a low signal is output when the second voltage dividing voltage Vds ⁻ is smaller than the first voltage dividing voltage VDB ⁻ . The configuration for outputting is described.

FIG. 11 is a timing chart showing the timing of changing the switching element 5b shown in FIG. 10 from off to on. In FIG. 10, in order from the top, the current flowing through the coil 5a, the voltage of the coil 5a, the second voltage dividing voltage Vds ⁻ , the zero current detection signal output by the zero current detection circuit 11C, the drain voltage of the output stop switching element 11i, and switching. The gate voltage of the element 5b is shown. The horizontal axis represents time.

t1 is the timing at which the gate voltage of the switching element 5b is changed from on to off. When the diode 5c conducts, the output voltage of the DC conversion circuit 5 charged in the smoothing capacitor 6 is applied to the drain of the switching element 5b. After t1, the coil 5a discharges the charged energy to the smoothing capacitor 6, so that the current of the coil 5a decreases. Since the second voltage divider voltage Vds ⁻ is larger than the first voltage divider voltage VDB ⁻ , a high signal is output as a zero current detection signal. At this time, the output stop switching element 11i is changed from on to off.

t2 is the timing when the current of the coil 5a is reduced to zero. When the current of the coil 5a is reduced to zero, a parasitic capacitance of the switching element 5b and a resonance voltage are generated in the resonance circuit formed by the coil 5a. The dotted line shown in the display column of the voltage waveform of the coil 5a and the waveform of the second voltage dividing voltage Vds ⁻ is an auxiliary line indicating the resonance voltage after t2. The voltage of the coil 5a is zero, and the second voltage dividing voltage Vds ⁻ is a vibration waveform that converges to the first voltage dividing voltage VDB ⁻ .

t3 is the timing at which the second voltage dividing voltage Vds ⁻ drops to the first voltage dividing voltage VDB ⁻ due to the resonance voltage after the current of the coil 5a is reduced to zero. Since Vds is smaller than VDB at t3, a low signal is output as a zero current detection signal. The arithmetic unit 9c detects that the zero current detection signal has changed from high to low, and determines that the current of the coil 5a has decreased to zero. Further, when the arithmetic unit 9c determines that the current of the coil 5a has decreased to zero, the arithmetic unit 9c outputs a signal for changing the output stop switching element 11i from off to on to the output stop switching element 11i. That is, the control unit 9 turns on the output stop switching element 11i when it receives the first logic inversion of the zero current detection signal.

In the fourth embodiment, after detecting that the current of the coil 5a has decreased to zero at t3, a delay time is provided until the switching element 5b is changed from off to on again. By providing a delay time, the switching frequency can be lowered, so that the switching loss generated in the switching element 5b can be suppressed, and the high frequency loss such as iron loss or copper loss generated in the coil 5a can be reduced. Can be done.

As a means for providing the delay time, there is a method in which the arithmetic unit 9c provides a delay until the signal for switching the switching element 5b from off to on is transmitted after detecting the falling edge or the logic inversion of the zero current detection signal.

t4 and t5 are timings at which the second voltage dividing voltage Vds ⁻ intersects the first voltage dividing voltage VDB ⁻ again due to the resonance voltage after the current of the coil 5a is reduced to zero. At t4, the second voltage divider voltage Vds ⁻ is larger than the first voltage divider voltage VDB ⁻ , so that a high signal is output, and at t5, a low signal is output. When the delay time starts to progress after receiving the first logical inversion of the zero current detection signal at t3, the delay time can be reset when the logical inversion of the zero current detection signal is received again at t4 and t5. In order to prevent such an adverse effect, the output stop switching element 11i is turned on at the timing after t3, and the output of the comparator 11e is fixed to low, so that unnecessary zero current detection during the period in which the delay time is provided is detected. To mask.

t6 is the timing for changing the gate of the switching element 5b from off to on, and the drain voltage of the switching element 5b drops to near zero. Since the output of the rectifier circuit 3 is short-circuited via the coil 5a, the current of the coil 5a increases after t6, and the coil 5a charges energy. The delay time started at t3 continues until, for example, t6.

By using the zero current detection circuit 11F of this configuration, it is possible to eliminate the need for the secondary winding of the coil, which was conventionally required when controlling in the current critical mode or the current discontinuous mode other than the critical mode. can. As a result, it is possible to suppress the temperature rise of the coil and increase the output of the lighting device by reducing the size of the coil and improving the heat dissipation. Further, when the secondary winding is provided, the shape of the coil is limited to the transformer, but since the present configuration does not require the secondary winding, the degree of freedom in the shape of the coil 5a is improved. As the coil 5a, for example, an air core coil, a single-sided substrate planar coil, or a drum type coil can be applied. In addition, by providing a delay time, the switching frequency can be lowered, so that the switching loss generated in the switching element 5b can be suppressed. This reduces high frequency losses such as iron loss and copper loss generated in the coil 5a, and contributes to improving the efficiency of the lighting device 100C.

The output stop switching element 11i is not limited to the MOSFET, and a switching element such as a transistor or a thyristor can be used. Since the MOSFET is capable of high-speed switching, it was adopted in this embodiment.

In the configuration shown in the above embodiment, a configuration in which a voltage dividing resistor is used as a voltage dividing means used in the zero current detection circuit is shown. As the pressure dividing means, a means for connecting a capacitor in series to divide the pressure can also be used. The configuration shown in the above-described embodiment shows an example of the contents of the present invention, and can be combined with embodiments 2, 3 and 4, or can be combined with another known technique. It is also possible to omit or change a part of the configuration without departing from the gist of the present invention.

Further, although the case where the light source 8 is composed of the LED has been described, the light source 8 is not limited to the LED and may be an organic EL (Electroluminescence).

1 AC power supply, 2 input filter, 3 rectifying circuit, 4 capacitor, 5 DC conversion circuit, 6 smoothing capacitor, 7 current control circuit, 8 light source, 9 control unit, 10 dimmer, 11 zero current detection circuit, 2a, 5a , 7b coil, 2b, 7d filter capacitor, 5b, 7a switching element, 5c, 7c, 11f diode, 11g voltage source, 11h voltage drop diode, 11i output stop switching element, 9a target value output unit, 9b voltage detection unit, 9c Calculation unit, 9d drive unit, 11a, 11b, 11c, 11d voltage dividing resistor, 11e comparer, 100, 100A, 100B, 100C lighting device, 200, 200A, 200B, 200C lighting equipment

Claims (11)

A rectifier circuit that rectifies AC power and
It has a coil through which a current output from the rectifier circuit flows and a switching element that changes the increase or decrease of the current flowing through the coil, suppresses harmonics to improve the power factor, and power output from the rectifier circuit. With a DC conversion circuit that converts
The control unit that controls the DC conversion circuit and
The first voltage divider circuit that divides the output voltage of the rectifier circuit and
A second voltage divider circuit that divides the voltage across the switching element,
The voltage of the first voltage divider output from the first voltage divider circuit and the voltage of the second voltage divider output from the second voltage divider circuit are compared, and the voltage corresponding to the magnitude relationship is output to the control unit. A lighting device characterized by being equipped with a comparator. The comparator outputs a zero current detection signal to the control unit, and when the second voltage dividing voltage becomes lower than the first voltage dividing voltage, the zero current detection signal is logically inverted.
The lighting device according to claim 1, wherein the control unit turns on the switching element after the logic inversion occurs. The lighting device according to claim 1 or 2, wherein the voltage dividing ratios in the first voltage dividing circuit and the second voltage dividing circuit are equal. A voltage supply unit that provides a voltage higher than the first voltage dividing voltage to the comparator instead of the first voltage dividing voltage when the first voltage dividing voltage becomes smaller than a predetermined value is provided. The lighting device according to any one of claims 1 to 3, wherein the lighting device is characterized in that. The first voltage divider circuit outputs the midpoint voltage of two resistance elements connected in series as the first voltage divider voltage.
The voltage supply unit has a diode having a cathode connected to the midpoint of the two resistance elements, and a voltage source connected to the anode of the diode and providing a voltage larger than the forward voltage of the diode. The lighting device according to claim 4. The lighting device according to claim 4, wherein the voltage provided by the voltage supply unit to the comparator is smaller than the maximum value of the second voltage dividing voltage. A claim is characterized in that a cathode is connected to the output of the first voltage divider circuit, an anode is connected to the output of the second voltage divider circuit, and a voltage drop diode for lowering the second voltage divider circuit is provided. The lighting device according to any one of 1 to 6. It is equipped with an output stop switching element that switches the presence / absence of connection between the output terminal of the comparator and the reference potential.
The lighting device according to claim 2, wherein the control unit turns on the output stop switching element upon receiving the first logic inversion. The lighting device according to any one of claims 1 to 8.
A luminaire characterized by comprising a light source that receives the current supply of the lighting device. The luminaire according to claim 9, wherein the light source includes an LED. The luminaire according to claim 9, wherein the light source includes an organic EL.

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