JP2013004413A - Lighting device and illuminating fixture using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of reducing variation in brightness of respective light-emitting elements in dimming with low light flux, and of suppressing flicker when a light source part is seen through a video apparatus, and to provide an illuminating fixture using the same.SOLUTION: A lighting device has: a step-down chopper circuit 5 variably controlling an on pulse width of a switching element Q1 to step down a DC voltage; and a current adjustment circuit 50 adjusting an output current of the step-down chopper circuit 5 to variably control a load current flowing in a light source part 10. The current adjustment circuit 50 has: resistances R17 and R18 connected in parallel to the light source part 10 and dividing the output current of the step-down chopper circuit 5; a switching element Q2 connected in series to the resistances R17 and R18; and a controller 50A on-off controlling the switching element Q2. The controller 50A on-off controls the switching element Q2 in a region with deep dimming of the light source part 10.

Description

  The present invention relates to a lighting device for a light emitting element such as a light emitting diode and a lighting fixture using the same.

  2. Description of the Related Art Conventionally, a power supply assembly (lighting device) that supplies power to a light emitting diode (LED) illumination module has been provided. As shown in FIG. 12, the conventional example described in Patent Document 1 includes a series circuit of a diode D100 connected between both ends of a DC power supply 100 and a control switch 101 indicated by a MOSFET. The inductor L100 and the LED lighting module 102 are connected between both ends of the diode D100. The controller 103 generates a dual PWM switching signal that is supplied to the control input of the control switch 101 through the amplifier 104. This dual PWM switching signal is essentially a combination of a high frequency PWM switching signal component supplied to a low frequency pulse burst, ie, a low frequency PWM switching signal component.

  The controller 103 has a current mode pulse width modulator 105, which receives the LED current reference signal, the detection current, and the high frequency sawtooth signal from the current source 106. The current mode pulse width modulator 105 generates a high frequency pulse width modulation switching signal component supplied to one input of the AND gate 107, and the other input of the AND gate 107 receives a low frequency PWM switching signal component. To do. The output from the AND gate 107 is supplied to the gate of the control switch 101 through the amplifier 104.

  Therefore, in the above conventional example, the average current flowing through the LED lighting module 102 can be changed to change the light intensity output from the LED lighting module 102 by changing the low frequency component of the dual PWM switching signal. it can.

JP 2006-511078 gazette

  In the so-called burst dimming method in which dimming is performed so that a load current flows intermittently through the LED module 102 (light source unit) as in the conventional example, dimming can be easily performed to a low luminous flux. However, in this burst dimming method, since the load current flows intermittently, there is a pause period in which the load current does not flow. Therefore, for example, when the light source is viewed through another video device such as a video camera, there is a risk that the flicker that interferes with the frequency specific to the video device may be observed.

  On the other hand, as a dimming method of the light source unit, an amplitude control method in which the peak value of the load current flowing through the light source unit can be considered. In this amplitude control method, since the load current flows continuously to the light source unit, the possibility that the flicker is visually observed when the light source unit is viewed through the video equipment as described above is reduced.

  By the way, the light emitting diodes (light emitting elements) constituting the light source section have variations in forward voltage, and variations of 15% or more occur depending on the type. For this reason, in the amplitude control method, the voltage applied to the light source unit is lowered during dimming with a low luminous flux, and there is a problem in that the brightness of each light emitting diode varies in the light source unit. This problem becomes more prominent as the number of light emitting diodes connected in series increases.

  The present invention has been made in view of the above points, and reduces variations in brightness of each light emitting element during dimming with a low luminous flux, and suppresses flicker when the light source section is viewed through video equipment. An object of the present invention is to provide a lighting device that can be used and a lighting fixture using the same.

  The lighting device of the present invention includes a DC power supply circuit that outputs DC power and a first switching element, and variably controls the on-pulse width of the first switching element to vary the output power of the DC power supply circuit. A chopper circuit that outputs and a current adjustment circuit that variably controls a load current flowing in a light source unit composed of a plurality of light emitting elements by adjusting an output current of the chopper circuit, and the current adjustment circuit includes: An impedance element connected in parallel to shunt the output current of the chopper circuit, a second switching element connected in series with the impedance element, and a controller for controlling on / off of the second switching element; The control unit controls on / off of the second switching element in a region where light control of the light source unit is deep.

  In this lighting device, a capacitor for applying a pulse voltage generated when the second switching element is turned on by charging / discharging to the light source unit is connected in series with the second switching element. It is preferable to be connected to.

  In this lighting device, the current adjustment circuit includes a smoothing capacitor for smoothing the load current, and a switching element connected in series with the smoothing capacitor, and the control unit adjusts the light source unit. It is preferable that the switching element is turned on when the light enters a deep region, and the switching element is turned off when the dimming rate of the light source unit reaches a predetermined value.

  In this lighting device, it is preferable that the control unit sets the switching frequency of the second switching element to be higher than the switching frequency when the switching element is on when the switching element is switched off.

  In this lighting device, it is preferable that the control unit starts on / off control of the second switching element before the brightness of each light emitting element starts to vary.

  A lighting fixture according to the present invention includes any one of the lighting devices described above and a fixture main body that houses the light source unit.

  The present invention has an effect of reducing variation in brightness of each light-emitting element during dimming with a low luminous flux and suppressing flicker when the light source unit is viewed through a video device.

It is the circuit schematic which shows Embodiment 1 of the lighting device which concerns on this invention. It is a circuit detailed drawing in a lighting device same as the above. (A), (b) is an operation | movement waveform diagram in a lighting device same as the above. (A), (b) is a figure which shows the mode of light emission of the light source part in a lighting device same as the above. It is a circuit schematic diagram of the step-down chopper circuit in Embodiment 2 of the lighting device according to the present invention. (A), (b) is an operation | movement waveform diagram in a lighting device same as the above. (A), (b) is a figure which shows the mode of light emission of the light source part in a lighting device same as the above. (A)-(c) is a figure which shows the mode of light emission of the light source part at the time of imaging with a video camera in the lighting device same as the above. It is a circuit schematic diagram of the step-down chopper circuit in Embodiment 3 of the lighting device according to the present invention. (A)-(d) is a circuit schematic diagram which shows the other structure of the pressure | voltage fall chopper circuit in each embodiment of the lighting device which concerns on this invention. It is the schematic which shows embodiment of the lighting fixture which concerns on this invention. It is the circuit schematic of the electric power feeding assembly for LED lighting modules of a prior art example.

(Embodiment 1)
Hereinafter, Embodiment 1 of the lighting device according to the present invention will be described with reference to the drawings. In this embodiment, as shown in FIG. 1, the filter circuit 1, the rectifier circuit 2, the step-up chopper circuit 3, the control power supply circuit 4, the step-down chopper circuit 5, the oscillation circuit 6, and the pulse width setting circuit 7, a dimming circuit 8, and a power cutoff detection circuit 9. Further, the light source section 10 formed by connecting a plurality (32 in the present embodiment) of light emitting diodes (light emitting elements) LD1 in series is connected to the output terminal CN2 of the step-down chopper circuit 5. Note that the light source unit 10 may have a configuration in which a plurality of light emitting diodes LD1 are connected in parallel, or those connected in series are connected in parallel.

  As shown in FIG. 2, the filter circuit 1 includes an input terminal CN1 to which a commercial power source VS1 is connected, a current fuse F1, a surge protection element SPD1, a filter capacitor CF1, and a line filter LF1, and includes a commercial power source VS1. Cut the power noise. The input terminal CN1 is connected to the input terminal of the line filter LF1 through the current fuse F1. A surge protection element SPD1 and a filter capacitor CF1 are connected in parallel to the input terminal of the line filter LF1. The output terminal of the line filter LF1 is connected to the input terminal of a full-wave rectifier DB1 of the rectifier circuit 2 described later.

  As shown in FIG. 2, the rectifier circuit 2 includes a full-wave rectifier DB1 composed of a diode bridge, and a high-frequency bypass capacitor C1 is connected in parallel to the output terminal of the full-wave rectifier DB1. The negative terminal of the output terminal of the full-wave rectifier DB1 is a ground on the circuit board, and is grounded to the chassis potential via a series circuit of the capacitors C2 and C3 at a high frequency.

  As shown in FIG. 2, the step-up chopper circuit 3 includes an inductor L1, a switching element Q3 made of a MOSFET, a diode D1, a smoothing capacitor C4, and a PFC control circuit IC1. The positive terminal of the output terminal of the full-wave rectifier DB1 is connected to the drain terminal of the switching element Q3 and the anode terminal of the diode D1 via the inductor L1. The source terminal of the switching element Q3 is connected to the negative electrode of the output terminal of the full-wave rectifier DB1 via the current detection resistor R1. The cathode terminal of the diode D1 is connected to the positive electrode of the smoothing capacitor C4. The negative electrode of the smoothing capacitor C4 is connected to the negative electrode of the output terminal of the full wave rectifier DB1.

  The smoothing capacitor C4 is a large-capacity capacitor made of an aluminum electrolytic capacitor or the like, and a small-capacitance capacitor C5 for high-frequency bypass is connected in parallel at both ends thereof. The capacitor C5 is made of a film capacitor or the like, and bypasses the high frequency component flowing through the smoothing capacitor C4. The step-up chopper circuit 3 boosts the pulsating voltage output from the full-wave rectifier DB1 by switching on / off of the switching element Q3 at a high frequency, and smoothes it by the smoothing capacitor C4 to generate a DC voltage. (For example, 410V) is output. Therefore, in the present embodiment, the commercial power supply VS1, the filter circuit 1, the rectifier circuit 2, and the boost chopper circuit 3 constitute a DC power supply circuit that outputs DC power.

  The PFC control circuit IC1 is configured by L6562A manufactured by ST Microelectronics. The first pin (INV) of the control circuit IC1 is an inverting input terminal of a built-in error amplifier (not shown), the second pin (COMP) is an output terminal of the error amplifier, and the third pin (MULT) is a built-in multiplication circuit. An input terminal (not shown) and a fourth pin (CS) are chopper current detection terminals. In addition, the control circuit IC1 has a 5th pin (ZCD) as a zero cross detection terminal, a 6th pin (GND) as a ground terminal, a 7th pin (GD) as a gate drive terminal, and a 8th pin (Vcc) as a power supply terminal. It is.

  The voltage across the capacitor C1, which is the input voltage of the step-up chopper circuit 3, is a pulsating voltage obtained by full-wave rectifying the AC power supply voltage of the commercial power supply VS1. This pulsating voltage is divided by the resistors R2 to R4 and the resistor R5 and input to the third pin of the PFC control circuit IC1. As a result, the voltage across the capacitor C1 is detected. The built-in multiplication circuit connected to the third pin is used to control the current waveform of the input current drawn from the commercial power supply VS1 via the full-wave rectifier DB1 so as to be similar to the pulsating voltage waveform.

  The voltage across the smoothing capacitor C4 is divided by the series circuit of the resistors R6 to R9 and the series circuit of the resistor R10 and the variable resistor VR1, and is input to the first pin of the PFC control circuit IC1. As a result, the voltage across the smoothing capacitor C4 is detected. The capacitors C6 and C7 and the resistor R1 connected between the first pin and the second pin are feedback impedances of the built-in error amplifier. The voltage across the current detection resistor R1 is input to the fourth pin of the PFC control circuit IC1 through a noise filter circuit composed of a resistor R12 and a capacitor C8. Thereby, the current flowing through the switching element Q3 is detected. One end of the secondary winding N1 of the inductor L1 is connected to the circuit ground by being connected to the 6th pin of the PFC control circuit IC1, and the other end is input to the 5th pin of the PFC control circuit IC1 through the resistor R13. Has been. Thereby, the energy accumulated in the inductor L1 is detected.

  The 7th pin of the PFC control circuit IC1 is a gate drive terminal. When the terminal is at a high level, a current flows through the resistor R15 via the resistor R14, and the voltage across the resistor R15 increases. Then, when the voltage across the resistor R15 becomes equal to or higher than the threshold voltage between the gate and the source of the switching element Q3, the switching element Q3 is turned on. Further, when the gate drive terminal becomes low level, the charge accumulated between the gate and the source of the switching element Q3 is discharged via the diode D2 and the resistor R16, so that the switching element Q3 is switched off.

  When the current flowing through the switching element Q3 detected by the 4th pin reaches a predetermined peak value, the PFC control circuit IC1 switches the switching element Q3 off. Further, when the energy of the inductor L1 detected by the fifth pin is released, the PFC control circuit IC1 switches the switching element Q3 on again. Further, the PFC control circuit IC1 controls the switching element Q3 so that the ON time of the switching element Q3 becomes long when the pulsating voltage detected at the third pin is high, and turns on the switching element Q3 when the pulsating voltage is low. Control to shorten the time. Further, the PFC control circuit IC1 controls the switching element Q3 so that the ON time of the switching element Q3 is short when the voltage across the smoothing capacitor C4 detected at the first pin is higher than the target value, and when the voltage is lower than the target value. Is controlled so that the ON time of the switching element Q3 becomes longer. Thereby, the PFC control circuit IC1 performs control so that the peak current flowing through the switching element Q3 matches the target value.

  As shown in FIG. 2, the control power supply circuit 4 includes an IPD element IC2 connected to the smoothing capacitor C4 and its peripheral circuits. The IPD element IC2 is a so-called intelligent power device, and is composed of, for example, MIP2E2D manufactured by Panasonic. The IPD element IC2 is a 3-pin IC having a drain terminal, a source terminal, and a control terminal, and includes a switching element made of a power MOSFET and a control circuit for controlling on / off of the switching element. .

  A step-down chopper circuit is configured by the switching element incorporated in the IPD element IC2, the inductor L2, the smoothing capacitor C9, and the diode D3. Further, the Zener diode ZD1, the diode D4, the smoothing capacitor C10, and the capacitor C11 constitute a power supply circuit for the IPD element IC2. The voltage across the smoothing capacitor C9 becomes the power supply voltage VC1 that supplies the power supply voltage for control to the other integrated circuit IC1 and the integrated circuits IC3, IC4, and IC5 described later. Therefore, since the smoothing capacitor C9 is not charged until the IPD element IC2 starts operation, the other integrated circuits IC1, IC3, IC4, and IC5 do not operate.

  Hereinafter, the operation of the control power supply circuit 4 will be described. When the smoothing capacitor C4 is charged by the output voltage of the full-wave rectifier DB1 in the initial stage of turning on the power, current flows through the path of the drain terminal of the IPD element IC2, the control terminal, the smoothing capacitor C10, the inductor L2, and the smoothing capacitor C9. . As a result, the smoothing capacitor C9 is charged with the polarity shown in FIG. 2 and supplies an operating voltage to the IPD element IC2. Then, the IPD element IC2 starts operating, and the on / off of the built-in switching element is started.

  When the switching element of the IPD element IC2 is on, a current flows through the path of the smoothing capacitor C4 → the drain terminal of the IPD element IC2 → the source terminal → the inductor L2 → the smoothing capacitor C9, and the smoothing capacitor C9 is charged. When the switching element is switched off, the energy stored in the inductor L2 is released to the smoothing capacitor C9 via the diode D3. As a result, a circuit composed of the IPD element IC2, the inductor L2, the diode D3, and the smoothing capacitor C9 operates as a step-down chopper circuit. Will occur.

  When the switching element of the IPD element IC2 is off, a regenerative current flows through the diode D3. The voltage across the inductor L2 is the sum of the voltage across the smoothing capacitor C9 and the forward voltage across the diode D3. To be clamped. A voltage obtained by subtracting the sum of the Zener voltage of the Zener diode ZD1 and the forward voltage of the diode D4 from this sum voltage is the voltage across the smoothing capacitor C10. The control circuit built in the IPD element IC2 controls on / off of the switching element so that the voltage across the smoothing capacitor C10 is constant. As a result, the voltage across the smoothing capacitor C9 is controlled to be constant.

  When the power supply voltage VC1 is generated at both ends of the smoothing capacitor C9, the PFC control circuit IC1 starts its operation and the boost chopper circuit 3 operates. Then, when the first timer circuit IC3 and the second timer circuit IC4, which will be described later, also start operation, the on / off control of the switching element Q1 of the step-down chopper circuit 5, which will be described later, is also started. In addition, a dimming operation can be performed by starting the operation of a buffer circuit IC5 described later.

  As shown in FIG. 2, the step-down chopper circuit 5 includes an inductor L3, a switching element Q1 (first switching element) made of a MOSFET, a diode D5, and a smoothing capacitor C12. The step-down chopper circuit 5 charges the smoothing capacitor C12 by stepping down the voltage across the smoothing capacitor C4 by variably controlling the on-pulse width of the switching element Q1. The positive electrode of the smoothing capacitor C4 is connected to the positive electrode of the smoothing capacitor C4. The negative electrode of the smoothing capacitor C12 is connected to the drain terminal of the switching element Q1 and the anode terminal of the diode D5 via the inductor L3. The cathode terminal of the diode D5 is connected to the positive electrode of the smoothing capacitor C12. The source terminal of the switching element Q1 is connected to the negative electrode of the smoothing capacitor C4. Further, a current adjusting circuit 50 described later is connected in parallel to both ends of the smoothing capacitor C12. The voltage across the smoothing capacitor C12 is applied to the light source unit 10 via the output terminal CN2.

  As shown in FIG. 2, the oscillation circuit 6 includes a first timer circuit IC3 and operates as an astable multivibrator by externally attaching a time constant setting resistor R21 and a capacitor C18. As shown in FIG. 2, the pulse width setting circuit 7 includes a second timer circuit IC4, and a monostable multivibrator is provided by externally attaching a time constant setting resistor R23, a variable resistor VR2, and a capacitor C19. Works as. In addition, the light receiving element of the photocoupler PC1 is connected in parallel to the series circuit of the resistor R23 and the variable resistor VR2, and the pulse width of the output signal of the monostable multivibrator is variable according to the optical signal intensity of the photocoupler PC1. I have control.

  Each of the first timer circuit IC3 and the second timer circuit IC4 is a well-known timer IC (so-called “555”), for example, UPD5555 manufactured by Renesas Electronics or its dual version UPD5556, or a compatible product thereof. Consists of. The 1st pin of each of the timer circuits IC3 and IC4 is a ground terminal, and the 8th pin is a power supply terminal. In each of the timer circuits IC3 and IC4, capacitors C14 and C15 connected between the power supply terminal and the ground terminal are both small capacitors for bypassing and remove noise of the power supply voltage VC1.

  The fifth pin of each of the timer circuits IC3 and IC4 is a control terminal, and a reference voltage that is normally 2/3 of the power supply voltage VC1 is applied by a built-in voltage dividing resistor. In each of the timer circuits IC3 and IC4, capacitors C16 and C17 connected between the fifth pin and the first pin are both small capacitors for bypassing, and noise of a reference voltage applied to the fifth pin is reduced. Remove.

  The second pin of each timer circuit IC3, IC4 is a trigger terminal. When this terminal voltage becomes lower than half of the reference voltage of the fifth pin (1/3 of the power supply voltage VC1), the output of the built-in flip-flop is Inverting, pin 3 (output terminal) goes high, and pin 7 (discharge terminal) is open. The 6th pin of each of the timer circuits IC3 and IC4 is a threshold terminal. When this terminal voltage becomes higher than the reference voltage of the 5th pin, the output of the built-in flip-flop is inverted, the 3rd pin (output terminal) becomes low level, and the 7th pin (discharge terminal) is short-circuited with the 1st pin. It will be in the state. The fourth pin of each of the timer circuits IC3 and IC4 is a reset terminal. When this terminal voltage becomes low level, the operation is stopped, and the third pin (output terminal) is fixed at low level.

  In the oscillation circuit 6, the voltage across the capacitor C18 is input to the second pin (trigger terminal) and the sixth pin (threshold terminal) of the first timer circuit IC3, respectively, and compared with the internal reference voltage.

  Hereinafter, the operation of the oscillation circuit 6 will be described. Since the voltage across capacitor C18 is lower than the reference voltage (1/3 of power supply voltage VC1) compared at pin 2 (trigger terminal) at the initial stage of power-on, pin 3 (output terminal) is high. Level 7 and the 7th pin (discharge terminal) is opened. Therefore, the power supply voltage VC1 is applied to the capacitor C18 via the resistors R21 and R22, so that the capacitor C18 is charged.

  Next, when the voltage across the capacitor C18 becomes higher than the reference voltage (2/3 of the power supply voltage VC1) compared at the 6th pin (threshold terminal), the 3rd pin (output terminal) goes to the low level. The pin (discharge terminal) is short-circuited with the first pin (ground terminal). As a result, the capacitor C18 is discharged through the resistor R21.

  When the voltage across the capacitor C18 becomes lower than the reference voltage (1/3 of the power supply voltage VC1) compared at the 2nd pin (trigger terminal), the 3rd pin (output terminal) becomes the high level, and the 7th pin The (discharge terminal) is opened and the capacitor C18 is charged again. Thereafter, the above operation is repeated.

  Here, the time constant determined by the resistors R21, R22 and the capacitor C18 is set such that the oscillation frequency of the binary signal output from the third pin (output terminal) is a high frequency of several tens of kHz. Further, the resistance values of the resistors R21 and R22 are set to satisfy R21 << R22. For this reason, the period during which the capacitor C18 is discharged (the period during which the third pin is at the low level) is extremely shorter than the period during which the capacitor C18 is charged (the period during which the third pin is at the high level). Therefore, a binary signal having a short low-level pulse width is output from the third pin (output terminal) of the first timer circuit IC3 at a high frequency of several tens of kHz. Using this binary signal, the second pin (trigger terminal) of the second timer circuit IC4 is triggered only once per cycle.

  Hereinafter, the operation of the pulse width setting circuit 7 will be described. When a binary signal from the third pin (output terminal) of the first timer circuit IC3 is input to the second pin (trigger terminal) of the second timer circuit IC4, the second timer is output at the falling edge. The second pin of the circuit IC4 becomes high level. As a result, the 7th pin (discharge terminal) of the second timer circuit IC4 is opened, and the capacitor C19 is charged via the series circuit of the resistor R23 and the variable resistor VR2 and the light receiving element of the photocoupler PC1. When the voltage across the capacitor C19 becomes higher than the reference voltage (2/3 of the power supply voltage VC1) compared at the 6th pin (threshold terminal), the 3rd pin (output terminal) becomes low level and the 7th pin ( The discharge terminal is short-circuited with the first pin (ground terminal). As a result, the capacitor C19 is instantaneously discharged.

  Therefore, the high level pulse width of the binary signal output from the third pin (output terminal) of the second timer circuit IC4 charges the capacitor C19 from the ground potential to the reference voltage (2/3 of the power supply voltage VC1). It is determined by the time required to do. The maximum value of the charging time is set to be shorter than the oscillation cycle of the first timer circuit IC3 constituting the oscillation circuit 6. The minimum value of the charging time is set to be longer than the low-level pulse width of the binary signal output from the third pin (output terminal) of the first timer circuit IC3.

  The binary signal output from the third pin (output terminal) of the second timer circuit IC4 is a drive signal for the switching element Q1. That is, when the third pin of the second timer circuit IC4 is at a high level, a current flows through the resistor R25 via the resistor R24, and the voltage across the resistor R25 becomes equal to or higher than the threshold voltage between the gate and the source of the switching element Q1. As a result, the switching element Q1 is switched on. When the third pin of the second timer circuit IC4 is at a low level, the charge accumulated between the gate and the source of the switching element Q1 is discharged via the diode D6 and the resistor R26, so that the switching element Q1 becomes Switch off.

  The dimming circuit 8 gives an optical signal to the light receiving element of the photocoupler PC1 based on the input dimming signal. As shown in FIG. 2, the non-polarizing circuit 80, the insulating circuit 81, And a DC conversion circuit 82. Here, the dimming signal input to the dimming circuit 8 is a PWM signal composed of, for example, a rectangular wave pulse having a frequency of 1 kHz and an amplitude of 10 V and a variable pulse width, and is dimming of an inverter lighting device for a fluorescent lamp. It is widely used as a signal.

  The depolarization circuit 80 includes a full-wave rectifier DB2, and connects the dimming signal line to the input terminal of the full-wave rectifier DB2 so that the dimming signal line operates normally even if the wiring of the dimming signal line is connected in reverse polarity. ing. A series circuit of a resistor R27 and a Zener diode ZD2 is connected between the output terminals of the full-wave rectifier DB2, and a series circuit of a light emitting element of the resistor R28 and the photocoupler PC2 is connected in parallel to both ends of the Zener diode ZD2. Has been.

  The insulation circuit 81 is composed of a photocoupler PC2. Here, a plurality of lighting devices are generally connected in parallel to the dimming signal line and the power supply line. In this case, since the circuit ground of each lighting device is not always at the same potential, it is necessary to insulate the dimming signal line from the circuit ground of each lighting device. The light emitting element of the photocoupler PC2 is connected to the dimming signal line, and the light receiving element is connected in series with the resistor R29, and is connected between the power supply voltage VC1 and the circuit ground of the lighting device.

  When the PWM signal is at a high level, the light-emitting element of the photocoupler PC2 generates an optical signal, and the resistance value of the light-receiving element of the photocoupler PC2 decreases, so that the connection point between the resistor R29 and the light-receiving element of the photocoupler PC2 is reduced. The potential drops. On the other hand, when the PWM signal is at a low level, the light emitting element of the photocoupler PC2 does not generate an optical signal, and the resistance value of the light receiving element of the photocoupler PC2 becomes high. Therefore, the resistance between the resistor R29 and the light receiving element of the photocoupler PC2 The potential at the connection point rises. The voltage change at this connection point is repeated at the frequency of the PWM signal, but is converted into a DC voltage by a DC conversion circuit 82 described later.

  The DC conversion circuit 82 includes an integrated circuit IC5 that includes a first operational amplifier OP1 and a second operational amplifier OP2, and a time constant circuit that includes a resistor R30 and a capacitor C20. As the integrated circuit IC5, for example, UPC358 manufactured by Renesas Electronics Corporation or a compatible product thereof may be used. The first operational amplifier OP1 is used as a buffer amplifier, lowers the voltage at the connection point between the resistor R29 and the light receiving element of the photocoupler PC2, and applies it to the series circuit of the resistor R30 and the capacitor C20.

  Hereinafter, the operation of the dimming circuit 8 will be described. If the period during which the PWM signal is at a low level is long, the period during which the capacitor C20 is charged through the resistor R30 is lengthened, so that the voltage across the capacitor C20 increases. On the other hand, if the period during which the PWM signal is at a high level is long, the period during which the capacitor C20 is discharged through the resistor R30 becomes long, and the voltage across the capacitor C20 decreases. The voltage across the capacitor C20 is output with a low impedance by the second operational amplifier OP2, thereby driving the light emitting element of the photocoupler PC1.

  When the voltage across the capacitor C20 is low, the output voltage of the second operational amplifier OP2 is also low, so that the current flowing to the light emitting element of the photocoupler PC1 via the resistor R31 increases, and the resistance of the light receiving element of the photocoupler PC1. The value decreases. That is, when the period during which the PWM signal is at a high level is lengthened, the on-pulse width of the switching element Q1 set by the pulse width setting circuit 7 is shortened, and the light output of the light source unit 10 is decreased.

  On the other hand, when the voltage across the capacitor C20 is high, the output voltage of the second operational amplifier OP2 also increases, so that the current flowing to the light emitting element of the photocoupler PC1 through the resistor R31 decreases, and the light receiving element of the photocoupler PC1. The resistance value increases. That is, when the period during which the PWM signal is at a low level becomes longer, the on-pulse width of the switching element Q1 set by the pulse width setting circuit 7 becomes longer, and the light output of the light source unit 10 increases. Therefore, if the dimming signal line is disconnected, the light output of the light source unit 10 is maximized.

  As shown in FIG. 2, the power interruption detection circuit 9 includes diodes D7 and D8 each having an anode terminal connected to the input terminal of the full-wave rectifier DB1. The cathode terminals of the diodes D7 and D8 are connected to the base terminal of the switching element Q4, which is an npn transistor, via a parallel circuit of resistors R32 and R33. A time constant circuit composed of a parallel circuit of a capacitor C21 and a resistor R34 is connected between the base terminal and the emitter terminal of the switching element Q4. The emitter terminal of the switching element Q4 is connected to the negative electrode of the output terminal of the full-wave rectifier DB1. The collector terminal of switching element Q4 is connected to the base terminal of switching element Q5, which is an npn transistor. A parallel circuit of a resistor R38 and a capacitor C22 is connected in parallel between the emitter and collector of the switching element Q5. The capacitor C22 is a small-capacitance capacitor for removing noise.

  Hereinafter, the operation of the power interruption detection circuit 9 will be described. When power supply from the commercial power supply VS1 is normal, the capacitor C21 is charged through the diodes D7 and D8 and the resistors R32 and R33, so that the switching element Q4 is maintained in the on state. For this reason, the bias current of the switching element Q5 via the resistor R35 is bypassed to the switching element Q4, and the switching element Q5 maintains the OFF state.

  On the other hand, when the power supply from the commercial power supply VS1 is cut off, the path for charging the capacitor C21 is cut off, so that the charge of the capacitor C21 is discharged through the resistor R34. Here, if the time constant determined by the capacitor C21 and the resistor R34 is appropriately set, when the power supply of the commercial power supply VS1 is cut off for a plurality of cycles, the switching element Q4 is switched off. When the switching element Q4 is switched off, the power supply voltage VC1 that is the voltage across the smoothing capacitor C9 is maintained while the electric charge in the smoothing capacitor C4 remains. For this reason, a current flows through the resistor R34 via the resistor R35, the switching element Q5 is forward biased, and the switching element Q5 is turned on.

  Here, the resistor R37 is connected in series with the resistor R38, and when the switching element Q5 is in the OFF state, the power supply voltage VC1 is divided by the series circuit of the resistors R37 and R38, and the second timer circuit IC4. An enable signal is supplied to the 4th pin (reset terminal). When the switching element Q5 is switched on as described above, the enable signal is bypassed to the switching element Q5, so that the 4th pin (reset terminal) of the second timer circuit IC4 becomes low level, and the second timer circuit IC4 Stops. Thereby, switching element Q1 maintains an OFF state, and operation of a lighting device stops.

  Hereinafter, the current adjustment circuit 50 which is a feature of the present embodiment will be described. As shown in FIGS. 1 and 2, the current adjustment circuit 50 is a control that performs on / off control of the switching element Q2 (second switching element) including a series circuit of a capacitor C13, a resistor R19, and a MOSFET. Part 50A. A resistor R20 is connected in parallel to the capacitor C13, and resistors R17 and R18 are connected in parallel as impedance elements to the series circuit of the capacitor C13 and the resistor R19.

  Hereinafter, the operation of the current adjustment circuit 50 will be mainly described. In the present embodiment, the resistors R17 and R18 each have a resistance value of 27 kΩ and a rated power of 3 W. The resistor R19 has a resistance value of 36Ω and a rated power of 1 W, and the resistor R20 has a resistance value of 68 kΩ. The capacitor C12 is a film capacitor having a capacitance value of 0.47 μF, and the capacitor C13 is a film capacitor having a capacitance value of 1 μF.

  First, when the light source unit 10 is fully lit, the switching element Q2 is in an off state. At this time, the load current flowing through the light source unit 10 is 300 mA, and the load voltage is 98V. Thereafter, when the dimming rate of the light source unit 10 is lowered by the dimming signal, the on-pulse width of the switching element Q1 is shortened, so that the peak value of the load current is gradually lowered, and the light output of the light source unit 10 is changed to the dimming rate. It decreases with.

  After that, when the dimming rate is lowered and the dimming becomes a deep region (low luminous flux), the load voltage of the light source unit 10 decreases, and the brightness of each light emitting diode LD1 starts to vary. For example, as shown in FIG. 4A, when the load current is 30 μA, the brightness of the light emitting diode LD1 indicated by “S2” is darker than that of the light emitting diode LD1 indicated by “S1” in FIG. Therefore, in the present embodiment, the control unit 50A monitors the load current, and before the brightness of each light emitting diode LD1 starts to vary, that is, when the load current reaches about 8 mA, the switching element Q2 is switched to a high frequency (120 Hz to 1 kHz). ) Starts on / off control. As a means for detecting the load current, for example, a current detection resistor may be inserted in series with the light source unit 10 and the load current may be detected based on the voltage across the resistor. Of course, other means may be adopted as long as the load current can be detected.

  When the switching element Q2 is switched on, an inrush current flows to the capacitor C13 via the resistor R19, a pulse voltage of several hundred ns is applied to the capacitor C13 (see FIG. 3B), and the capacitor C13 is charged. . Thereafter, a current of about 6 to 7 mA flows through the resistors R17 and R18. Here, when the resistors R17 and R18 are not provided, the on-pulse width of the switching element Q1 has a lower limit, so that the load current can be controlled only up to about 5 mA, and dimming with a low luminous flux is difficult. On the other hand, in the present embodiment, the load current can be reduced by switching on the switching element Q2 and diverting it to the resistors R17 and R18, so that the load current can be controlled to 50 μA.

  Thereafter, when the switching element Q2 is switched off, the electric charge accumulated in the capacitor C13 is discharged through the resistor R20, and the resistors R17 and R18 are disconnected from the path through which the load current flows. Then, the current that has flowed through the resistors R17 and R18 flows into the light source unit 10, thereby increasing the load current. That is, by switching on / off the switching element Q2 at a high frequency, a pulsed load current can be supplied to the light source unit 10. For this reason, variation in the brightness of each light emitting diode LD1 can be suppressed even during dimming with a low luminous flux. For example, as shown in FIG. 4B, even when the load current is 30 μA, the brightness of each light-emitting diode LD1 is substantially uniform. FIG. 3A shows an operation waveform diagram when the load current is 8 mA to 100 μA, and FIG. 3B shows an operation waveform diagram when the load current is 100 μA or less.

  As described above, in the present embodiment, the current adjustment circuit 50 switches the on / off of the switching element Q2 at a high frequency, thereby adjusting the current that is shunted to the resistors R17 and R18 and comparing the load current with the amplitude control method. Can be adjusted to a low value. For this reason, in this embodiment, the light source unit 10 can be dimmed to a low luminous flux. In addition, by switching on / off of the switching element Q2 at a high frequency and causing a pulsed load current to flow through the light source unit 10, variations in brightness of each light emitting diode LD1 can be suppressed. In the present embodiment, every time the switching element Q2 is turned on, a pulse voltage is applied by charging the capacitor C13. Therefore, the average voltage of the load voltage can be increased, and the brightness of each light emitting diode LD1 is increased. The variation in thickness can be further suppressed.

  Furthermore, in the present embodiment, in a shallow light control region, light control is performed not by a burst light control method in which the step-down chopper circuit 5 is operated intermittently but by an amplitude control method that controls the peak value of the load current. For this reason, since the load current continuously flows through the light source unit 10, flicker when the light source unit 10 is viewed through the video equipment can be suppressed. In the present embodiment, in a deeply dimmed region, the load current is adjusted by switching the switching element Q2 at a high frequency while continuing the oscillation operation of the step-down chopper circuit 5. For this reason, compared with the case where a load current is intermittently supplied to the light source unit 10 at a low frequency as in the burst dimming method, flicker when the light source unit 10 is viewed through the video equipment can be suppressed.

  In this embodiment, the operation power supply of each circuit is secured in the control power supply circuit 4 by the output voltage of the boost chopper circuit 3, and the boost chopper circuit 3 operates stably even when dimming with a low luminous flux. Therefore, there is an advantage that the operating power supply does not become unstable.

(Embodiment 2)
Hereinafter, Embodiment 2 of the lighting device according to the present invention will be described with reference to the drawings. However, since the configuration of this embodiment is the same as that of the first embodiment except for the current adjustment circuit 50, common portions are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 5, the current adjustment circuit 50 of this embodiment includes a circuit in which a parallel circuit of resistors R17 and R18 and a switching element Q2 are connected in series, a switching element Q6 including a resistor R39, an electrolytic capacitor C23, and a MOSFET. Are connected in parallel with each other. Further, the current adjustment circuit 50 is provided with a control unit 50A that controls on / off of the switching elements Q2, Q6.

  In the first embodiment, as shown in FIG. 3A, the load current pulsates during the on / off control of the switching element Q2 in the current adjustment circuit 50. For this reason, there is a risk of flickering when the light source unit 10 is viewed through the video equipment. Here, in this embodiment, flickering when the light source unit 10 is viewed through the video equipment can be avoided by smoothing the load current by the electrolytic capacitor C23 during the on / off control of the switching element Q2.

  However, when the load current is smoothed by the electrolytic capacitor C23, the brightness of each light emitting diode LD1 may vary in the dimming with a low luminous flux as in the amplitude control method. For example, as shown in FIG. 7A, when the load current is 30 μA, the brightness of the light emitting diode LD1 indicated by “S2” is darker than that of the light emitting diode LD1 indicated by “S1” in FIG. Therefore, in the present embodiment, the above problem is solved by switching off the switching element Q6 and disconnecting the electrolytic capacitor C23 from the circuit before the brightness of each light emitting diode LD1 starts to vary.

  Hereinafter, the operation of the current adjustment circuit 50 of the present embodiment will be described. First, when the load current reaches about 8 mA in a deeply dimmed region, the control unit 50A of the current adjustment circuit 50 starts control to turn on / off the switching element Q2 at a high frequency. At this time, the control unit 50A smoothes the load current by the electrolytic capacitor C23 by switching on the switching element Q6 (see FIG. 6A). Thereby, since the pulsation of the load current is suppressed, flicker when the light source unit 10 is viewed through the video equipment can be avoided.

  Thereafter, the dimming rate is further decreased, and before the variation of the brightness of each light-emitting diode LD1 begins, that is, when the load current becomes about 100 μA, the control unit 50A switches the switching element Q6 to OFF to turn off the capacitor C23. Disconnect from the circuit. Thereby, a pulsed load current flows through the light source unit 10 (see FIG. 6B). Therefore, for example, as shown in FIG. 7B, even when the load current is 30 μA, the brightness of each light emitting diode LD1 becomes substantially uniform, and variation in the brightness of each light emitting diode LD1 can be suppressed. .

  By the way, after the switching element Q6 is switched off and the electrolytic capacitor C23 is disconnected from the circuit, a pulsed load current flows through the light source unit 10, so that flicker may occur when the light source unit 10 is viewed through the video equipment. There is. Therefore, in the present embodiment, it is desirable to disconnect the electrolytic capacitor C23 from the circuit and to make the switching frequency of the switching element Q2 higher than the switching frequency when the switching element Q2 is on. In this case, since the load current flowing through the light source unit 10 after the electrolytic capacitor 23 is disconnected from the circuit can be brought close to a direct current level, occurrence of flicker when the light source unit 10 is viewed through the video equipment can be suppressed.

  The inventors of the present application conducted an experiment of imaging the light source unit 10 with a video camera capable of setting the shutter speed between 1/60 and 1/8000 while changing the switching frequency of the switching element Q2. As a result, it has been found that if the switching frequency of the switching element Q2 is set to 1 kHz, flicker does not occur when the light source unit 10 is imaged through a video camera if the shutter speed is 1/1000 or less. For example, as shown in FIG. 8A, when dimming only by the amplitude control method, the brightness of the light emitting diode LD1 indicated by “S2” is darker than that of the light emitting diode LD1 indicated by “S1” in FIG. Become. On the other hand, as shown in FIG. 8B, when the switching frequency of the switching element Q2 is set to 1 kHz in the circuit configuration of the present embodiment, the brightness of each light emitting diode LD1 becomes substantially uniform, and the brightness of each light emitting diode LD1. The variation in thickness can be suppressed. Further, as shown in FIG. 8C, even when the switching frequency of the switching element Q2 is set to 500 Hz in the circuit configuration of the present embodiment, variation in brightness of each light emitting diode LD1 can be suppressed.

  Note that, when the switching frequency of the switching element Q2 is set too high, variations in the brightness of the light emitting diodes LD1 begin to be noticeable, and therefore it is necessary to set the switching frequency appropriately according to the number of light emitting diodes LD1 and the like.

(Embodiment 3)
Hereinafter, Embodiment 3 of the lighting device according to the present invention will be described with reference to the drawings. However, since the configuration of this embodiment is the same as that of the first embodiment except for the current adjustment circuit 50, common portions are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 9, the current adjustment circuit 50 of the present embodiment is obtained by connecting the series circuit of the resistor R39, the electrolytic capacitor C23, and the switching element Q6 in the second embodiment in parallel to the current adjustment circuit 50 of the first embodiment. Composed. The operation of the present embodiment is the same as that of the second embodiment, and the switching element Q6 is switched on / off before and after the brightness variation of each light emitting diode LD1 starts to occur.

  In the present embodiment, in addition to the circuit configuration of the second embodiment, a pulse voltage generated by charging the capacitor C13 can be applied to the light source unit 10 every time the switching element Q2 is turned on as in the first embodiment. . Therefore, the average voltage of the load voltage can be increased, and variations in brightness of each light emitting diode LD1 can be further suppressed.

  Incidentally, in each of the above embodiments, the output voltage of the power supply unit is stepped down by the step-down chopper circuit 5 and applied to the light source unit 10, but it is not necessary to be limited to the step-down chopper circuit 5, and FIG. The step-up chopper circuit as shown in FIG. Further, instead of the step-down chopper circuit 5, a step-up / step-down chopper circuit as shown in FIG. 10 (b), a flyback converter circuit as shown in FIG. 10 (c), and a forward converter as shown in FIG. 10 (d). A circuit may be used. In the circuits shown in FIGS. 10C and 10D, the transformer T1 is used instead of the inductor L3. Each circuit is well known in the art and will not be described in detail here. Regardless of which circuit is used, by connecting the current adjustment circuit 50 between the circuit and the light source unit 10, the same effects as those of the above-described embodiments can be obtained.

  Hereinafter, embodiments of a lighting apparatus according to the present invention will be described with reference to the drawings. In the following description, the vertical direction in FIG. 11 is defined as the vertical direction. In addition, the lighting device A1 in this embodiment uses the lighting device in any one of the above embodiments. As shown in FIG. 11, the present embodiment is a separate lighting type lighting fixture in which a power supply unit and a lighting device A1 are arranged separately from the light source unit 10, and the fixture main body 11 that houses the light source unit 10 is placed on the ceiling 13. Embedded. For this reason, the instrument main body 11 including the light source unit 10 can be made thin, and the lighting device A1 as a separately installed power supply unit can be installed regardless of the place.

  The instrument main body 11 is made of metal such as aluminum die casting, for example, and is formed in a bottomed cylindrical shape having an open lower end. A light source unit 10 including a plurality (three in the drawing) of light emitting diodes LD1 and a substrate 10A on which a series circuit of the respective light emitting diodes LD1 is mounted is disposed on the upper bottom portion inside the instrument body 11. Each light emitting diode LD1 is arranged so that the direction of light irradiation is downward in order to irradiate the external space with light from the lower end of the instrument body 11. In addition, a light diffusing plate 11A for diffusing light from each light emitting diode LD1 is provided in the opening at the lower end of the instrument body 11. On the back surface (upper surface) of the ceiling 13, the lighting device A1 is disposed at a place different from the fixture body 11, and the lead wire 12 is connected between the lighting device A1 and the light source unit 10 via the connector 12A. Wired.

  As described above, in the present embodiment, the same effects as in any one of the above embodiments can be achieved by using the lighting device A1 in any one of the above embodiments. In addition, although this embodiment is a power supply installation type lighting fixture which has arrange | positioned the power supply part and the lighting device A1 separately from the light source part 10, the power supply integrated type type lighting device A1 built in the fixture main body 11 with the light source part 10 was built. You may comprise as a lighting fixture.

  Note that the lighting device A1 of any of the above embodiments does not need to be limited to the lighting fixture as described above. For example, a backlight of a liquid crystal display, a light source of a device such as a copying machine, a scanner, or a projector. It may be used as a lighting device. In each of the above embodiments, the light emitting diode LD1 is used as the light emitting element constituting the light source unit 10. However, the present invention is not limited to this. For example, an organic EL element or a semiconductor laser element may be used as the light emitting element. Good.

1 Filter circuit (DC power supply circuit)
10 Light source 2 Rectifier circuit (DC power supply circuit)
3 Boost chopper circuit (DC power supply circuit)
5 Step-down chopper circuit (chopper circuit)
50 Current adjustment circuit 50A Control unit LD1 Light emitting diode (light emitting element)
R17, R18 Resistance (impedance element)
Q1 First switching element Q2 Second switching element VS1 Commercial power supply (DC power supply circuit)

Claims (6)

  A DC power supply circuit that outputs DC power; a chopper circuit that has a first switching element and variably controls the on-pulse width of the first switching element to variably output the output power of the DC power supply circuit; A current adjusting circuit that adjusts an output current of the chopper circuit to variably control a load current flowing in a light source unit composed of a plurality of light emitting elements, and the current adjusting circuit is connected in parallel to the light source unit and connected to the chopper. An impedance element that shunts the output current of the circuit, a second switching element connected in series with the impedance element, and a control unit that controls on / off of the second switching element, The lighting device is characterized in that on / off of the second switching element is controlled in a region where light control of the light source part is deep.   In the current adjustment circuit, a capacitor for applying a pulse voltage generated when the second switching element is turned on by charging / discharging to the light source unit is connected in series with the second switching element. The lighting device according to claim 1.   The current adjustment circuit includes a smoothing capacitor for smoothing the load current, and a switching element connected in series with the smoothing capacitor, and the control unit is provided in a region where light control of the light source unit is deep. 3. The lighting device according to claim 1, wherein the switching element is switched on and the switching element is switched off when a dimming rate of the light source unit reaches a predetermined value.   The lighting device according to claim 3, wherein when the switching element is switched off, the control unit sets the switching frequency of the second switching element to be higher than the switching frequency when the switching element is on.   5. The control unit according to claim 1, wherein the controller starts on / off control of the second switching element before the brightness of the light emitting elements starts to vary. Lighting device.   A lighting fixture comprising: the lighting device according to any one of claims 1 to 5; and a fixture main body that houses the light source unit.