JP2013030373A - Dc lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC lighting device that prevents a flicker even upon fluctuations in a low frequency voltage/low frequency current generated in a longer period than a high frequency voltage/high frequency current generated by an inverter circuit.SOLUTION: A DC lighting device 2 includes: an input smoothing circuit 10 for converting an alternating current from a commercial power supply and outputting a direct current; an inverter circuit 11 for stepping down the direct current and outputting a pulsating direct current; an output smoothing circuit 12 for smoothing the pulsating direct current output from the inverter circuit 11; and an LED module 5 supplied with the direct current smoothed by the output smoothing circuit 12. The DC lighting device 2 further has a voltage fluctuation absorption circuit (ripple filter circuit 20) subsequent to the output smoothing circuit 12.

Description

  The present invention relates to a DC lighting device in which flickering of a light source does not occur with respect to fluctuations in input voltage.

  Conventionally, dimmers that change the brightness of light sources such as LEDs are dimmed by PWM input (control signal), dimmed by DC voltage input (control signal), and phase control input (power control) of commercial power supply There is a dimming method. In this dimming method of the phase control input of the commercial power supply, the dimmer cannot accurately detect the phase unless a current is constantly passed through the lighting circuit. For this reason, a DC lighting device including an input smoothing circuit (input filter circuit), an inverter circuit, an output smoothing circuit, and the like is known as a dimmer (see, for example, Patent Document 1).

  In this DC lighting device, a triac is used as a light control element. However, the phase control waveform may be disturbed due to a malfunction that the triac extinguishes where the triac must be ignited, and is stable. Dimming control is not possible. In order to solve this problem, a direct current lighting device in which the capacitor of the input smoothing circuit has a small capacity has been developed. However, in this DC lighting device, since the dimming control is proportional to the input waveform, if the input voltage fluctuates, the brightness also fluctuates and feels flickering.

  In order to eliminate this flicker, an LED lighting device in which a capacitor provided in the output smoothing circuit has a large capacity is known (for example, see Patent Document 2). In this LED lighting device, the high-frequency voltage and high-frequency current generated by the inverter circuit are changed to direct current with almost no fluctuation by the output smoothing circuit to reduce the flicker of the LED.

JP 2004-327152 A JP 2010-287430 A

  However, in this LED lighting device, although the high-frequency voltage and high-frequency current generated by the inverter circuit can be changed to a direct current with almost no fluctuation by the output rectifying and smoothing circuit, flickering of the LED can be reduced, but it is generated by the inverter circuit. The fluctuation of the low frequency voltage / low frequency current that occurs in a period longer than the cycle of the high frequency voltage / high frequency current cannot be removed, and a slight flicker (flicker) occurs in the LED at long intervals. There was a case to be worried about.

  Accordingly, the present invention provides a direct current lighting device that does not flicker even when a fluctuation of a high frequency voltage / current generated in a period longer than the cycle of the low frequency voltage / low frequency current generated by the inverter circuit occurs. It is for the purpose.

  In order to achieve this object, the present invention provides an input smoothing circuit that outputs alternating current from a commercial power supply as direct current, an inverter circuit that steps down the direct current and outputs it as pulsating direct current, and outputs from the inverter circuit A direct current lighting device comprising: an output smoothing circuit for smoothing a pulsating direct current; and an LED module to which the direct current smoothed by the output smoothing circuit is supplied; The voltage fluctuation absorbing circuit is provided.

  According to this configuration, fluctuations in the high-frequency voltage and high-frequency current that occur in a period longer than the cycle of the low-frequency voltage and low-frequency current generated by the inverter circuit occur, and the input voltage to the LED module that is the light source Even if the fluctuation is about to occur, the fluctuation of the input voltage to the LED module is absorbed by the voltage fluctuation absorption circuit to prevent the flickering of the LED module, and the LED module can be used comfortably.

It is a circuit diagram which shows the direct current lighting device (LED lighting circuit) which concerns on this invention. It is a principal part enlarged view of FIG. It is explanatory drawing of the high frequency voltage generate | occur | produced by the inverter circuit of FIG. It is explanatory drawing of the voltage smoothing effect | action by the output smoothing circuit of FIG. It is explanatory drawing of the voltage and electric current fluctuation | variation of an output smoothing circuit when there is no ripple filter circuit of FIG. It is explanatory drawing of the voltage and electric current fluctuation | variation of the output smoothing circuit of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Constitution]
FIG. 1 shows a DC lighting device which is an LED lighting device (LED lighting circuit) according to the present invention. In FIG. 1, reference numeral 1 denotes a commercial power source having electric wires 1 a and 1 b, and 2 denotes a DC lighting device used by being connected to the commercial power source 1.

This DC lighting device 2 includes a dimmer 3, a lighting device (lighting circuit) 4, and an LED module 5 including a plurality of LEDs 5a.
<Dimmer 3>
The dimmer 3 includes a triac (dimming element) 6 whose input side is connected to one electric wire 1 a of the commercial power source 1, a coil 7 connected in series to the triac 6, and the triac 6 and the coil 7. A phase control circuit 8 connected in parallel is provided. The phase control circuit 8 inputs a control signal to the triac 6 so as to turn the triac 6 on and off.
<Lighting device 4>
The lighting device 4 has an input terminal 4a connected to the coil 7 and an input terminal 4b connected to the electric wire 1b. Further, the lighting device 4 has an output terminal 4 c connected to the anode side of the LED module 5 and an output terminal 4 d connected to the cathode side of the LED module 5.

  The lighting device 4 includes an input filter circuit 9, an input smoothing circuit 10, an inverter circuit 11, and an output smoothing circuit 12, and a ripple filter circuit (ripple filter) 20 provided at the subsequent stage of the output smoothing circuit 12. ing.

The ripple filter circuit 20 is provided to absorb ripples based on a low frequency voltage and a low frequency current that cannot be smoothed by the output smoothing circuit 12.
(Input filter circuit 9)
The input filter circuit 9 includes a resistor R1, a capacitor C1, and a line filter LF. The line filter LF has magnetically coupled coils L1 and L1 ′. The resistor R1 has one end connected to the input terminal 4a and the other end connected to the coil L1 of the line filter LF. One end of the capacitor C1 is connected between the other end of the resistor R1 and the coil L1, and the other end is connected between the input terminal 4b and the coil L1 ′.

Such an input filter circuit 9 prevents the damped vibration generated in the power supply loop of the commercial power source 1 -the dimmer 3 -the lighting device 4 and the like, and prevents external noise.
(Input smoothing circuit 10)
The input smoothing circuit 10 includes a rectifier circuit (full-wave rectifier circuit) RC1 that forms a bridge circuit with diodes and converts alternating current into direct current including pulsating current. Coils L 1 and L 1 ′ of the input filter circuit 9 are connected to the input side of the rectifier circuit RC 1, and alternating current from the commercial power source 1 is input via the input filter circuit 9.

  Thereby, the rectifier circuit RC1 performs full-wave rectification of the AC voltage supplied from the commercial power supply 1 via the dimmer 3 and the line filter LF. A positive side wiring 13 is connected to the positive output side of the rectifier circuit RC1, and a negative side (ground side) wiring 14 is connected to the negative output side of the rectifier circuit RC1. The plus side wiring 13 is connected to the plus side output terminal 4 c of the lighting device 4. Further, the minus side wiring 14 is connected to the output terminal 4d through the resistor R2, the transistor Q1, and the inductor L2.

Further, the input smoothing circuit 10 includes a capacitor C2 that smoothes the AC voltage rectified by the rectifying circuit RC1. The capacitor C2 is connected to the plus side wiring 13 and the minus side wiring 14 of the rectifier circuit RC1.
(Inverter circuit 11)
The inverter circuit 11 uses a general step-down chopper circuit that converts a DC voltage from the input smoothing circuit 10 into a predetermined DC voltage.

  The inverter circuit 11 includes a diode D1, a transistor (switching element) Q1, a resistor R2, and an inductor L2.

  The resistor R2, the transistor Q1, and the inductor L2 are interposed in the middle of the minus side wiring 14, and are arranged in this order from the rectifier circuit RC1 to the output terminal 4d side.

  The diode D1 has an anode side connected to the transistor Q1 and a cathode side connected to the plus side wiring 13. Reference numerals 14 a and 14 b are part of the minus side wiring 14. The wiring 14a connects the diode D1 and the transistor Q1, and the wiring 14b connects the output terminal 4d and the middle of the wiring 14a via the inductor L2.

  Further, the inverter circuit 11 includes a control circuit (control IC) IC1 that controls ON / OFF of the transistor Q1. The control circuit IC1 turns on the transistor Q1 by inputting a control signal to the base of the transistor Q1 via the resistor R3.

Further, the control circuit IC1 detects a current flowing between the resistor R2 and the transistor Q1 via the wiring 15. When a current of a predetermined value or more flows, the control circuit IC1 interrupts the output of the control signal and supplies the current to the base of the transistor Q1. The control signal input is stopped.
(Output smoothing circuit 12)
The output smoothing circuit 12 has a capacitor C3. One end of the capacitor C3 is connected to the plus side wiring 13 between the cathode side of the diode D1 and the output terminal 4c, and the other end is connected to the wiring 14b between the other end of the inductor L2 and the output terminal 4d. The capacitor C3 is a large-capacity capacitor having a three-digit capacity compared to a small-capacitance capacitor having a single-digit capacity. For example, a normal small-capacitance capacitor is, for example, 1 to 2 μF, whereas a large-capacitance capacitor of 100 μF or more or 400 μF or more is used for the capacitor C3. That is, a capacitor having a large capacity several hundred times that of the small-capacitance capacitor is used for the capacitor C3. If the capacitor C3 is between 100 μF and 400 μm, and the capacitor C3 is 400 μm or more, commercial flicker (flicker) is not recognized at all.
(Ripple filter circuit 20)
As shown in FIGS. 1 and 2, the ripple filter circuit (voltage fluctuation absorbing circuit) 20 has a collector-emitter interposed in the middle of the plus side wiring 13 and a base that is a part of the minus side wiring 14. 14b has a transistor Q2 connected via a capacitor C4. The ripple filter circuit 20 includes a resistor R4 interposed between the base and collector of the transistor Q2, and a capacitor C4 interposed between the base of the transistor Q2 and the wiring 14b.

Here, assuming that the connection point of the output smoothing circuit 12 to the plus side wiring 13 of the capacitor C3 is Pa and the connection point of the capacitor C3 to the wiring 14b (a part of the minus side wiring 14) is Pb, the transistor Q2 is a collector. The side is connected to the connection point Pa and the emitter side is connected to the output terminal 4c. The capacitor C4 is located between the connection point Pb and the output terminal 4d and connected to the wiring 14b.
[Action]
Next, the operation of this configuration will be described.

  When an AC voltage with a half-cycle sinusoidal waveform (AC voltage with a frequency of 50 Hz or 60 Hz) is input from the commercial power supply 1 to the dimmer 3, an alternating voltage that is cut-controlled by the voltage waveform interval from the dimmer 3 is supplied. Is output. In this case, the alternating current has a waveform with a sharp angle at the rising and falling portions on the positive side. The AC voltage and AC current are input to the lighting device 4 from the input terminals 4a and 4b.

  The AC voltage and AC current are input to the input filter circuit 9. The AC voltage from the input filter circuit 9 is input to the input smoothing circuit 10. This AC voltage is full-wave rectified by the rectifier circuit RC1 of the input smoothing circuit 10 and smoothed by the capacitor C2, and then output from the input smoothing circuit 10 as a DC voltage having a pulsating current. Then, the DC voltage having the pulsating current is applied to the inverter circuit 11.

  The DC voltage including the pulsating current from the input smoothing circuit 10 is applied to the capacitor C3 and the LED module 5, and is applied to the transistor Q1 through the capacitor C3, the ripple filter circuit 20, and the LED module 5.

  On the other hand, the control circuit IC1 of the inverter circuit 11 inputs, for example, a control signal having a frequency of about 100 kHz to the base of the transistor Q1. At this time, the control circuit IC1 inputs a control signal to the base of the transistor Q1 every predetermined half cycle, and turns on the transistor Q1 for a predetermined period every predetermined half cycle.

  When the transistor Q1 is ON, a current Io-Q flows between the collector and emitter of the transistor Q2 in FIGS. 1 and 2, the LED module 5, the inductor L2, the transistor Q1, and the resistor R2.

  The current flowing between the transistor Q1 and the resistor R2 is detected by the control circuit IC1 via the wiring 15. When the current Io-Q flowing through the inductor L2 becomes equal to or higher than a predetermined value, the control circuit IC1 goes to the transistor Q1. Is stopped and the transistor Q1 is turned off.

  When the transistor Q1 is OFF, a current Io-D flows between the collector and emitter of the transistor Q2, the LED module 5, the inductor L2, and the diode D1 due to the voltage accumulated in the capacitor C3.

  Such ON / OFF control of the transistor Q1 by the control circuit IC1 is repeatedly performed. Moreover, as described above, when the transistor Q1 is ON, the current Io-Q flows between the collector and emitter of the transistor Q2, the LED module 5, the inductor L2, the transistor Q1, and the resistor R2, and the transistor Q1 is turned OFF. Current Io-D flows between the collector and emitter of the transistor Q2, LED module 5, inductor L2, and diode D1.

  Thus, when the control circuit IC1 of the inverter circuit 11 turns the transistor Q1 on and off at a high frequency (for example, 100 kHz) to generate a high frequency voltage, the high frequency current accompanying the high frequency voltage is large in the output smoothing circuit 12. The voltage is smoothed by the capacitor C3 having a capacitance and becomes a voltage indicated by Vc3 in FIG. This voltage waveform is output between the output terminals 4c and 4d through the ripple circuit 20 as the DC output voltage Vout of FIGS. At this time, the output smoothing circuit 12 outputs the DC output current Iout of FIG.

  Accordingly, since the ripple filter circuit 20 absorbs fluctuations in the pulsating voltage waveform, flickering (flickering) of the LED module 5 with respect to fluctuations in the input of the commercial power supply as shown in FIG. 6 is not recognized.

  However, when the ripple filter circuit 20 of FIG. 1 is not provided, when Vc3 = Vout and the DC output voltage Vout changes as shown in FIG. 5, the DC output current Iout also changes as shown in FIG. The operation of the ripple filter circuit 20 of FIG. 1 will be described next.

Here, if the output current of the output smoothing circuit 12 is Ic, the collector current of the transistor Q2 in the ripple filter circuit 20 is Ic, which is the output current of the output smoothing circuit 12, as shown in FIG. Also,
Ib: Base current of the transistor Q2 Ic: Collector current of the transistor Q2 hFE: When the amplification factor of the transistor Q2 is assumed, the collector current Ic of the transistor Q2 is
Ic = Ib × hFE
It becomes.

  Therefore, when the output voltage / output current of the output smoothing circuit 12 fluctuates at an interval longer than the cycle of the high-frequency voltage / high-frequency current generated by the control circuit IC1, the output voltage / output current is transferred to the transistor Q2 via the resistor R4. The transistor Q2 is controlled so that the collector current Ic is constant. As a result, even if the voltage of the high-frequency voltage / high-frequency current generated by the control circuit IC1 fluctuates at an interval longer than the cycle of the high-frequency voltage / high-frequency current generated by the control circuit IC1, the output terminals 4c and 4d are not changed. No DC output voltage Vout is output.

  As described above, the DC lighting device 2 according to the embodiment of the present invention has the input smoothing circuit 10 that outputs an alternating current from a commercial power supply as a direct current and outputs the direct current with a pulsating current by stepping down the direct current. An inverter circuit 11, an output smoothing circuit 12 that smoothes the pulsating direct current output from the inverter circuit 11, and an LED module 5 that is supplied with the direct current smoothed by the output smoothing circuit 12. Further, the DC lighting device 2 is provided with a voltage fluctuation absorbing circuit (ripple filter circuit 20) of a commercial power source in the subsequent stage of the output smoothing circuit 12. In the above-described embodiment, the ripple filter circuit 20 using the transistor Q2 is used as the voltage fluctuation absorption circuit of the commercial power supply. However, the ripple filter circuit 20 using the transistor Q2 is not necessarily replaced with the voltage fluctuation absorption circuit of the commercial power supply. do not have to. For example, the voltage fluctuation absorbing circuit of the commercial power supply may be a ripple filter circuit using a MOS • FET. If the DC voltage / DC current smoothed by the output smoothing circuit 12 can absorb the fluctuation when it fluctuates at a low frequency, the ripple filter circuit 20 using the transistor Q2 as the voltage fluctuation absorbing circuit of the commercial power supply, A circuit other than a ripple filter circuit using a MOS • FET may be used.

  According to this configuration, fluctuations in the low-frequency voltage / low-frequency current generated in a period longer than the cycle of the high-frequency voltage / high-frequency current generated by the inverter circuit 11 occur, and the input to the LED module 5 as the light source occurs. Even if the voltage fluctuation is about to occur, the fluctuation of the input voltage to the LED module 5 is absorbed by the voltage fluctuation absorption circuit to prevent the LED module 5 from flickering, and the LED module 5 can be used comfortably.

  Further, the output smoothing circuit 12 may include a smoothing large-capacity capacitor C3 provided in parallel with the LED module 5. According to this configuration, when the output smoothing circuit 12 smoothes the high-frequency voltage by the inverter 11 into a DC voltage, the smoothness of the DC voltage is improved as compared with the case where the capacity of the capacitor C3 is small. The LED module 5 can be used comfortably by preventing the flickering of the LED module 5 more reliably than when the capacity is small. Therefore, by providing a voltage fluctuation absorbing circuit (ripple filter circuit 20) of a commercial power supply in the subsequent stage of the output smoothing circuit 12 having a large-capacitance capacitor C3, the high-frequency DC voltage when the output smoothing circuit 12 smoothes the high-frequency voltage. It is possible to reliably prevent flicker based on ripples and flicker based on fluctuations in low frequency voltage / low frequency current that occur in a period longer than the cycle of the high frequency voltage / high frequency current generated by the inverter circuit 11.

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... DC lighting device 5 ... LED module 10 ... Input smoothing circuit 11 ... Inverter circuit 12 ... Output smoothing circuit 20 ... Ripple filter circuit (ripple filter)

Claims (3)

An input smoothing circuit that outputs alternating current from a commercial power supply as direct current, an inverter circuit that steps down the direct current and outputs it as direct current with pulsating current, and an output that smoothes direct current with pulsating current output from the inverter circuit A direct current lighting device comprising a smoothing circuit and an LED module to which direct current smoothed by the output smoothing circuit is supplied,
A direct current lighting device, wherein a voltage fluctuation absorption circuit of a commercial power source is provided after the output smoothing circuit.   2. The direct current lighting device according to claim 1, wherein the output smoothing circuit includes a large capacity capacitor for smoothing provided in parallel with the LED module.   3. The DC lighting device according to claim 1, wherein the voltage fluctuation absorption circuit is a ripple filter provided at a subsequent stage of the output smoothing circuit.