JP2012221991A - Power supply circuit, switching power supply for lighting and luminaire - Google Patents

Abstract

A power supply circuit capable of increasing the power supply efficiency is provided.
In the power circuit 30, a drain terminal is connected to a primary side coil 33a of a transformer 33 and the other terminal of the primary side coil 33a, and a source terminal is connected to a ground side power supply terminal via a resistor R7. A switching transistor Q2 connected to the gate terminal of the switching transistor Q2, and a control power supply IC 32 that controls on / off of the switching transistor Q2 at a predetermined oscillation frequency. The control power supply IC 32 receives a voltage generated in the resistor R7, and controls the current flowing through the switching transistor Q2 by controlling the ratio between the on time and the off time of the switching transistor Q2 according to the voltage. The control power IC 32 switches the operation state of the switching transistor Q2 between the clock operation and the constant current operation in accordance with the phase of the AC power supply 200.
[Selection] Figure 1

Description

  The present invention relates to a power supply circuit, a switching power supply device for lighting, and a lighting device.

  LEDs (Light Emitting Diodes) have features such as low power consumption and long life, and are widely used for lighting and various industrial purposes. In recent years, the use of LEDs has been expanded, and LED lighting using LEDs has started to spread as an alternative to fluorescent lamps and incandescent lamps. LEDs are expected to expand to various applied products in the future. An example of such an LED lighting device is described in Patent Documents 1 and 2, for example.

  A general lighting fixture often uses a commercial AC 100V power source, and considering the case where an LED lighting device is used instead of a general lighting fixture such as a fluorescent lamp or an incandescent bulb, the LED lighting device is also common. It is desirable that the commercial AC 100V power supply be used similarly to the lighting fixture.

  In addition, when dimming control of an incandescent bulb is performed, the switching element (for example, triac element) is turned on at a certain phase angle of the AC power supply voltage, so that the power supply to the incandescent bulb can be easily dimmed with a single volume element. A controllable phase control dimmer is used. When the dimming control is performed on the LED lighting device using the AC power source, the phase control dimmer is usually used in the same manner as the dimming control is performed on the incandescent light bulb.

  FIG. 6 shows an example of an internal circuit and an operation waveform of a general phase control dimmer. As shown in FIG. 6A, a general dimmer includes a triac TRI, a capacitor C, an inductor L, and a variable resistor R that performs phase control. Then, by adjusting the variable resistance R, the triac is turned on at a certain phase angle of the input AC voltage. Specifically, as shown in FIG. 6B, only the portion corresponding to the adjusted phase angle (triac ON period c) with respect to the original AC power supply waveform a is the output waveform b of the dimmer. Is output as That is, the output waveform b of the dimmer has a shape in which only a part is cut out as shown by the solid line with respect to the semicircle shown by the dotted line.

  A general dimmer uses a triac as a switching element. Since this type of dimmer assumes a resistive load, a load current is required for firing and holding the triac. That is, it is necessary to pass a certain holding current in the dimmer using the triac. In addition, as described above, since a general dimmer assumes a resistive load, it is designed to operate correctly with an incandescent bulb or a halogen lamp. Since the incandescent lamp becomes a resistive load, the current changes linearly. Therefore, the triac operates stably.

  On the other hand, since the LED has a non-linear load in which a current suddenly flows from the forward voltage, when the LED is used as a light source, the dimmer becomes difficult to obtain a necessary holding current and does not operate correctly. Specifically, the operation becomes unstable, for example, the triac is turned on / off. Therefore, when an LED is used as a light source, it is necessary to draw a current as a holding current in order to stably operate the dimmer. In addition, if the dimmer operates in an unstable manner, such as when the triac is turned on or off, the brightness of the LED lighting device flickers, resulting in a malfunction.

  FIG. 7 is a diagram showing an insulating (flyback) illumination power supply circuit used in a general LED lighting device compatible with a dimmer. Referring to FIG. 7, in the conventional illumination power supply circuit, power is supplied from AC power supply 200 to primary side coil 33 a of transformer 33 via rectifier circuit 20 and smoothing circuit 31. The other terminal of the primary coil 33a is connected to the switching transistor Q2. The switching transistor Q2 is controlled to be turned on / off by the control power supply IC 532 so that power is sent to the secondary coil 33b and current is supplied to the LED (light emitting diode) 550.

  Further, in order to keep the current flowing through the switching transistor Q2 constant, the source terminal of the switching transistor Q2 is connected to the ground power supply via the resistor R7 for detecting the current value. The control power supply IC 532 receives a voltage value generated in the current value detection resistor R 7, and the input voltage value (detected voltage value) is compared with the reference voltage by the control power supply IC 532. Then, the on / off time ratio of the switching transistor Q2 is adjusted by adjusting the duty of the oscillator frequency (oscillator 35).

  FIG. 8 shows an example of specific operation waveforms in the control power supply IC. 8, a represents a voltage waveform obtained by converting the current flowing through the primary coil 33a (see FIG. 7) by the detection resistor R7 (see FIG. 7), and b represents resistance division of the input voltage (resistor 1 and resistor 2). A voltage waveform (voltage waveform of the reference voltage) smoothed by the capacitor C1 (see FIG. 7) and c is a gate drive waveform of the switching transistor Q2 (see FIG. 7).

  As shown in FIG. 8, the voltage waveform a of the current flowing through the primary coil 33a (see FIG. 7) is compared with the reference voltage b by the comparator CMP1 (see FIG. 7), and the oscillator is connected to the flip-flop 36 (see FIG. 7). 35 (see FIG. 7) and the oscillation frequency (clock). The flip-flop 36 outputs a high level according to the rising timing of the clock and turns on the switching transistor Q2 (see FIG. 7). When the current flowing through the primary side coil 33a increases and the voltage waveform a rises and reaches the reference voltage b, a high level is input to the reset terminal of the flip-flop 36, so that the output of the flip-flop 36 becomes a low level. As a result, the switching transistor Q2 is turned off and the current is interrupted.

  Here, since the reference voltage b is linked to the input voltage level, the reference voltage b increases as the input voltage increases. For this reason, the ON period of the switching transistor Q2 becomes longer, and a large amount of current flows. Thereby, since the electric power supplied to the secondary side coil 33b also increases, the electric current which flows into LED550 also increases. Therefore, the illumination is brightly lit. On the contrary, when the input voltage is lowered, the reference voltage b is also lowered, so that the ON period of the switching transistor Q2 is shortened. Thereby, illumination becomes dark.

  FIG. 9 shows an outline of the relationship between the input voltage and the reference voltage b. When the ON period of the triac of the dimmer 210 (see FIG. 7) is long, the average value of the input voltage waveform (the reference voltage b smoothed by the ∝capacitance C1 (see FIG. 7)) becomes high. On the contrary, when the ON period of the triac is small, the average value of the input voltage waveform (∝reference voltage b) is low. For this reason, it becomes possible to adjust the brightness of illumination by a dimmer (adjustment of the ON period of the triac).

  Further, as shown in FIG. 7, the control power IC 532 is supplied with power from a regulator composed of a transistor Q1, a resistor R5, and a Zener diode ZD via a Schottky diode SBD_1. The control power IC 532 is supplied with power from the auxiliary winding coil 33c via the Schottky diode SBD_2 when a current flows through the transformer 33. Thus, the efficiency is improved.

  A current extraction circuit for stably operating the dimmer 210 includes a comparator CMP2, a transistor Q3, and a resistor R6. The comparator CMP2 compares the input voltage divided by the resistors R3 and R4 with the reference voltage Vref. When the input voltage divided by the resistors R3 and R4 is lower than the reference voltage Vref, the transistor CMP3 is turned on by the comparator CMP2. The current adjusted by the resistor R6 is extracted from the power supply via the regulator transistor Q1, thereby operating as a holding current of the dimmer 210.

  FIG. 10 shows an example of specific operation waveforms of the current extraction circuit. The voltage waveform input to the comparator CMP2 (see FIG. 7) is an amplitude value obtained by resistance-dividing (reducing) the input AC voltage waveform with a waveform that is linked to the on period of the triac. This waveform is compared with the reference voltage Vref, and when the input voltage is lower than the reference voltage Vref, a constant current operation for extracting the holding current is performed. Conversely, when the input voltage is higher than the reference voltage Vref, the switching operation for lighting the LED is performed, and the current value also has a substantially sawtooth waveform.

JP 2008-52994 A JP 2006-319172 A

  In the conventional illumination power supply circuit shown in FIG. 7, a holding current for causing the dimmer 210 to operate stably flows through the transistor Q1. In general, the control power supply IC 532 operates at a power supply voltage of about 20V, and about 20V is applied to the source terminal of the transistor Q1, and about 140V of the AC input voltage is applied to the drain terminal. The product of the voltage difference of about 120 V and the flowing current value is the power consumption in the transistor Q1. For this reason, the conventional power supply circuit for illumination has a problem that a large power loss occurs in an LED illumination device that requires high efficiency.

  Further, since a high voltage is applied to the regulator transistor Q1, an element having a high breakdown voltage and high heat dissipation is required. Therefore, there is a problem that the cost increases. In addition, since the power supply circuit becomes larger due to an increase in the board mounting area, there is a problem that it cannot be stored in a lighting device such as a light bulb.

  The present invention has been made in order to solve the above-described problems, and one object of the present invention is to provide a power supply circuit, a lighting switching power supply device, and a lighting device capable of improving the power supply efficiency. Is to provide.

  Another object of the present invention is to provide a power supply circuit, a lighting switching power supply device, and a lighting device capable of reducing the cost and reducing the product size.

  In order to achieve the above object, a power supply circuit according to a first aspect of the present invention includes a primary coil of a transformer connected to a power supply terminal smoothed by rectifying an input AC voltage of an AC power supply, and a primary The drain terminal is connected to the other terminal of the side coil, the source terminal is connected to the ground side power supply terminal via the first resistor for current value detection, and the gate terminal of the switching transistor is connected to the predetermined oscillation. And a power supply controller that controls on / off of the switching transistor at a frequency. The power supply control unit receives a voltage generated in the first resistor for detecting the current value, and controls the ratio between the ON time and the OFF time of the switching transistor in accordance with the voltage, thereby flowing to the switching transistor. It is configured to control the current. The power supply control unit is configured to switch the operation state of the switching transistor between a clock operation and a constant current operation in accordance with the phase of the AC power supply.

  In the power supply circuit according to the first aspect, as described above, the power supply control unit that switches the operation state of the switching transistor between the clock (switching) operation and the constant current (DC) operation in accordance with the phase (cycle) of the AC input power supply. It is set as the structure provided. For this reason, the power supply control unit can draw a holding current for stably operating the dimmer by setting the operation state of the switching transistor to a constant current (DC) operation. On the other hand, power (current) can be supplied to a light source such as an LED by switching the operation state of the switching transistor to a clock (switching) operation by the power supply control unit.

  As described above, in the power supply circuit according to the first aspect, it is possible to realize the holding current drawing for the stable operation of the dimmer and the LED lighting operation by the clock (switching) operation with one switching transistor. That is, the holding current can be drawn using a switching transistor for performing the LED lighting operation. For this reason, there is no need to separately provide a transistor (regulator transistor) for allowing a holding current to flow, so that it is possible to eliminate power loss caused by providing this transistor separately. As a result, the efficiency of the power supply can be increased.

  In the power supply circuit according to the first aspect, as described above, there is no need to separately provide a transistor (regulator transistor) for allowing a holding current to flow, and accordingly, the number of components can be reduced accordingly. In addition, a transistor (regulator transistor) for flowing a holding current requires an expensive element having high withstand voltage and high heat dissipation. Therefore, by eliminating such a transistor, product cost can be reduced. Further, when such a transistor is mounted, the power supply circuit becomes larger due to an increase in the substrate mounting area. Therefore, the size of the product can be reduced by eliminating the need for such a transistor.

  In the power supply circuit according to the first aspect, preferably, the power supply control unit operates the constant current (DC) when the input AC voltage level is low, and the switching transistor operates as a clock (switching) when the input AC voltage level is high. The gate of the switching transistor is switched to operate. If comprised in this way, when the ON period of the triac of a dimmer which the input AC voltage level falls will become short, for example, an electric current can be drawn out as a holding current. Thereby, the dimmer can be operated stably.

  In this case, preferably, a voltage obtained by dividing the input AC voltage level by resistance is compared with a reference voltage, and when the input AC voltage level is low, a predetermined direct current (DC) voltage is applied to the gate terminal of the switching transistor. Has been. With this configuration, the switching transistor can be easily operated at a constant current. The constant current value (= holding current value) can be adjusted by this direct current (DC) voltage.

  In the configuration in which the operation of the switching transistor is switched depending on the level of the input AC voltage level, the power supply control unit includes a first comparator, and the first comparator compares a voltage obtained by resistance-dividing the input AC voltage level with a reference voltage, When the AC voltage level is lower than the reference voltage, a predetermined direct current (DC) voltage can be applied to the gate terminal of the switching transistor.

  Further, in the configuration in which the operation of the switching transistor is switched depending on the level of the input AC voltage level, preferably, a second resistor connected in series to the input power supply line is further provided, and a voltage difference between both ends of the second resistor is detected. When a decrease in the supply current accompanying a decrease in the input AC voltage level is detected and the detected voltage difference is small, a predetermined direct current (DC) voltage is applied to the gate terminal of the switching transistor. Even in such a configuration, the switching transistor can be easily operated at a constant current. The constant current value (= holding current value) can be adjusted by this direct current (DC) voltage.

  In the configuration in which a direct current (DC) voltage is applied to the gate terminal of the switching transistor when the input AC voltage level is low, the power supply control unit preferably includes a second comparator having a capacitor connected in series, and the input AC voltage level The voltage obtained by dividing the resistance is input to the second comparator via the capacitor, and the second comparator switches the direct current (DC) voltage applied to the gate terminal of the switching transistor. If comprised in this way, the timing which the triac of a dimmer turns on can be detected, and the holding current value extracted at this timing can be switched.

  In this case, preferably, a change point at which the input AC voltage increases is detected by the second comparator, and a direct current (DC) voltage applied to the gate terminal of the switching transistor for a predetermined period from when the input AC voltage increases. Is configured to be high. If comprised in this way, since the transition from the holding current value level to the current value level during the switching operation for turning on the LED can be performed in stages, the dimmer can be stabilized.

  An illumination switching power supply according to a second aspect of the present invention is an illumination switching power supply including the power supply circuit according to the first aspect. If comprised in this way, efficiency improvement of the switching power supply device for illumination can be achieved. In addition, cost reduction and product size reduction can be achieved.

  An illumination device according to a third aspect of the present invention is an illumination device including the illumination switching power supply device according to the second aspect. If comprised in this way, a highly efficient and small illuminating device can be obtained at low cost.

  As described above, according to the present invention, it is possible to easily obtain a power supply circuit, a lighting switching power supply device, and a lighting device that can achieve high power efficiency.

  Furthermore, according to the present invention, it is possible to easily obtain a power supply circuit, a lighting switching power supply device, and a lighting device that can reduce costs and reduce the product size.

It is the figure which showed the circuit structure of the LED lighting apparatus provided with the power supply circuit for illumination by 1st Embodiment of this invention. It is the figure which showed the circuit structure of the power supply circuit for illumination by 2nd Embodiment of this invention. It is the figure which showed the circuit structure of the power supply circuit for illumination by 3rd Embodiment of this invention. It is the figure (figure which showed the example of a waveform of a holding current and a switching current) which showed the example of a rough operation waveform at the time of switching of switching operation and constant current operation of the power supply circuit by 3rd Embodiment of this invention. It is the figure which showed the circuit structure of the power supply circuit for illumination by 4th Embodiment of this invention. It is the figure which showed the example of the internal circuit of the general phase control type dimmer, and the example of an operation waveform. It is the figure (figure which showed an example of the conventional power supply circuit for illumination) which showed the power supply circuit for insulation (flyback type) illumination used for the LED lighting apparatus corresponding to a general dimmer. It is the figure which showed the example of schematic operation | movement waveform of the conventional power supply circuit for illumination. It is the figure which showed the example of the operating voltage waveform by the phase angle of a light controller. It is the figure which showed the example of a switching operation | movement schematic of switching operation and constant current operation in the conventional illumination power supply circuit.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a circuit configuration of an LED lighting apparatus including an illumination power supply circuit according to a first embodiment of the present invention. First, with reference to FIG. 1 and FIGS. 7-10, the LED lighting apparatus provided with the power supply circuit for illumination by 1st Embodiment of this invention is demonstrated.

  As shown in FIG. 1, the LED illumination device 5 according to the first embodiment includes an LED illumination switching power supply device 10 and an LED module 50 to which electric power is supplied from the LED illumination switching power supply device 10. The LED illumination switching power supply 10 is an insulating (flyback) switching power supply, and includes a rectifier circuit 20 and an illumination power supply circuit 30.

  The rectifier circuit 20 is connected to the AC power source 200 via the dimmer 210. The rectifier circuit 20 is composed of, for example, a bridge-type full-wave rectifier circuit in which four diodes are combined, and rectifies the input voltage of the illumination power supply circuit 30. The dimmer 210 is a triac dimmer using a triac.

  The illumination power supply circuit (power supply circuit) 30 according to the first embodiment includes a smoothing circuit 31, a control power supply IC (power supply control unit) 32, and a primary side coil 33 a of a transformer 33.

  The smoothing circuit 31 is connected to the input power line 70. The output side of the smoothing circuit 31 is connected to the power supply terminal 34. One terminal of the primary side coil 33 a of the transformer 33 is connected to the power supply terminal 34. For this reason, the input AC voltage from the AC power supply 200 is rectified via the rectifier circuit 20, smoothed by the smoothing circuit 31, and supplied to the primary coil 33 a of the transformer 33. In addition, a free-wheeling diode FRD is connected in reverse parallel to the primary side coil 33a of the transformer 33.

  One end of the resistor R5 is connected between the smoothing circuit 31 and the primary coil 33a. The other end of the resistor R5 is connected to the cathode of the Zener diode ZD. The resistor R5 and the Zener diode ZD constitute a voltage source (regulator). The connection point between the resistor R5 and the Zener diode ZD is connected to the control power supply IC 32 via the Schottky diode SBD_1. Furthermore, the transformer 33 has an auxiliary winding coil 33c, and this auxiliary winding coil 33c is connected to the control power supply IC 32 via a Schottky diode SBD_2.

  As a result, the control power IC 32 is supplied with power from the voltage source (regulator) including the resistor R5 and the Zener diode ZD via the Schottky diode SBD_1. The control power IC 32 is supplied with power from the auxiliary winding coil 33c via the Schottky diode SBD_2 when a current flows through the transformer 33. Thus, the efficiency is improved.

  The other terminal of the primary coil 33a is connected to a switching transistor (switching element) Q2. This switching transistor Q <b> 2 is on / off controlled by the control power supply IC <b> 32 to send electric power to the secondary coil 33 b of the transformer 33 and supply current to the LED module 50.

  The switching transistor Q2 is formed of, for example, a field effect transistor (FET), and the other terminal of the primary side coil 33a is connected to the drain terminal thereof. Further, in order to keep the current flowing through the switching transistor Q2 constant, the source terminal of the switching transistor Q2 is connected to a ground power supply via a current value detection resistor (first resistor) R7. A connection point between the source terminal of the switching transistor Q2 and the resistor R7 is connected to the control power supply IC32, and a voltage value generated in the current value detection resistor R7 is input to the control power supply IC32. The input voltage value (detected voltage value) is compared with a reference voltage by the control power supply IC 32, and the duty of the oscillator frequency (oscillator 35) is adjusted. As a result, the on / off time ratio of the switching transistor Q2 (the ratio between the on time and the off time) is adjusted (controlled), and the current flowing through the switching transistor Q2 is controlled as in the above-described conventional power supply circuit. As a result, the current flowing through the switching transistor Q2 is kept constant.

  The control power supply IC 32 includes an oscillator 35, a switch SW, a flip-flop 36, and comparators CMP1 and CMP2. The oscillator 35 is connected to the set terminal of the flip-flop 36 and inputs a pulse wave (for example, a square pulse wave) to the set terminal of the flip-flop 36. The comparator CMP1 is an example of the “first comparator” in the present invention.

  One input terminal of the switch SW is connected to the DC voltage source 37, and the other input terminal of the switch SW is connected to the output terminal of the flip-flop 36. The output terminal of the switch SW is connected to the gate terminal of the switching transistor Q2.

  The switch SW switches the connection of the gate terminal of the switching transistor Q2 to either the DC voltage source 37 or the flip-flop 36 according to the output signal from the comparator CMP2. When the gate terminal of the switching transistor Q2 is connected to the DC voltage source 37 by the switch SW, a predetermined DC voltage Vdc is applied to the gate terminal of the switching transistor Q2. On the other hand, when the gate terminal of the switching transistor Q2 is connected to the flip-flop 36 by the switch SW, the clock output from the flip-flop 36 is input to the gate terminal of the switching transistor Q2. As described above, the power supply circuit 30 according to the first embodiment is configured such that the gate terminal of the switching transistor Q2 can be switched between the flip-flop output and the direct current (DC) voltage Vdc by the switch SW.

  The input power supply line 70 is connected to resistors R1 and R2 for resistance division (voltage division). A connection point between the resistor R1 and the resistor R2 is connected to an inverting input terminal of the comparator CMP1. A smoothing capacitor C1 is connected between the resistor R1 and the resistor R2. Therefore, the voltage obtained by dividing the input voltage (input AC voltage level) by resistance and smoothing by the capacitor (capacitance) C1 is input to the inverting input terminal of the comparator CMP1 as the reference voltage (reference voltage b in FIG. 8). The The voltage value generated in the current value detection resistor R7 is input to the non-inverting input terminal of the comparator CMP1. That is, the voltage value obtained by converting the current flowing through the primary coil 33a is input to the non-inverting input terminal of the comparator CMP1.

  The comparator CMP1 compares the voltage waveform of the current flowing in the primary side coil 33a with a reference voltage (voltage obtained by dividing the input voltage by resistance and smoothing by the capacitor C1), and the oscillation frequency (from the oscillator 35) to the flip-flop 36 ( The result is input together with the clock.

  When the gate terminal of the switching transistor Q2 is connected to the flip-flop 36, the flip-flop 36 outputs a high level according to the rising timing of the clock from the oscillator 35, and turns on the switching transistor Q2. As shown in FIG. 7, when the current flowing through the primary side coil 33a increases and its voltage value increases and reaches the reference voltage (the voltage value of the current flowing through the primary side coil 33a by the comparator CMP1 is greater than the reference voltage). When it is determined that the level is high, a high level is input from the comparator CMP1 to the reset terminal of the flip-flop 36. As a result, the output of the flip-flop 36 becomes a low level, so that the switching transistor Q2 is turned off and the current is cut off.

  In this way, the gate terminal of the switching transistor Q2 performs a switching operation at a predetermined oscillation frequency by the clock output from the flip-flop 36, and the LED module 50 is turned on by a current detection feedback loop operation similar to the above-described conventional power supply circuit. Make it work.

  As described above, since the reference voltage is linked to the input voltage level, the reference voltage increases as the input voltage increases. For this reason, the ON period of the switching transistor Q2 becomes longer, and a large amount of current flows. Thereby, since the electric power supplied to the secondary side coil 33b also increases, the electric current which flows into the LED module 50 also increases. Therefore, the illumination is brightly lit. On the contrary, since the reference voltage is lowered when the input voltage is lowered, the ON period of the switching transistor Q2 is shortened. Thereby, illumination becomes dark. Therefore, as shown in FIG. 9, the brightness of the illumination can be adjusted by the dimmer 210 (adjustment of the on period of the triac).

  The input power supply line 70 is connected to resistors R3 and R4 for resistance division (voltage division). A connection point between the resistors R3 and R4 is connected to an inverting input terminal of the comparator CMP2. On the other hand, a reference voltage source 38 is connected to the non-inverting input terminal of the comparator CMP2.

  The comparator CMP2 compares the input voltage divided by the resistors R3 and R4 with the reference voltage Vref. When the input voltage divided by the resistors R3 and R4 is higher than the reference voltage Vref, the switch SW is connected to the flip-flop 36 side. As a result, the gate terminal of the switching transistor Q2 performs a switching operation by the clock output from the flip-flop 36, and the LED module 50 is turned on by the above-described current detection feedback loop operation.

  On the other hand, when the input voltage divided by the resistors R3 and R4 is lower than the reference voltage Vref, the comparator CMP2 connects the switch SW to the DC voltage source 37 side. For example, when the divided voltage value of the AC power supply 200 becomes low, such as when the triac of the dimmer 210 is turned off, the switch SW is connected to the DC voltage source 37 side. As a result, the gate terminal of the switching transistor Q2 is biased with a direct current (DC) voltage Vdc, so that a direct current (DC) current in accordance with the gate-source voltage flows between the source and drain of the switching transistor Q2. The switching transistor Q2 operates at a constant current so as to draw the holding current. In this manner, the switching transistor Q2 is operated as a holding current of the dimmer 210 by drawing a current from the power source. The operation waveforms of the holding current and the switching current according to the first embodiment are substantially the same as the operation waveform example shown in FIG.

  In the first embodiment, the extraction current flows to the primary side coil 33a of the transformer 33, but is not transmitted to the secondary side coil 33b of the transformer 33 because of the direct current (DC) operation, and Since the input AC power supply voltage at this time is low, the LED module 50 is not lit during the holding current extraction operation.

  Thus, in the first embodiment, the operation state of the switching transistor Q2 is switched to either the clock (switching) operation or the constant current operation in accordance with the phase of the AC power supply 200. Further, when the input AC voltage level is low, the switching transistor Q2 operates at a constant current, and the holding current is drawn. On the other hand, when the input AC voltage level is high, the switching transistor Q2 operates as a clock, and the LED module 50 is turned on.

  In the power supply circuit 30 according to the first embodiment, the output of the comparator CMP2 is input to the switch SW in the control power supply IC 32, and the switch SW causes the gate terminal of the switching transistor Q2 to be connected to the flip-flop output and the direct current (DC) voltage Vdc. This is different from the above-described conventional power supply circuit (see FIG. 7).

  Further, since the holding current for stable operation of the dimmer 210 can be extracted from the input power supply line 70 via the primary side coil 33a by the switching transistor Q2, the power supply circuit to the control power supply IC 32 is also a conventional power supply. The circuit is changed (see FIG. 7). Specifically, in the first embodiment, as described above, the regulator transistor Q1 and the extraction current setting resistor R6 (see FIG. 7) are eliminated, and the circuit configuration is simplified. In addition, a voltage source (regulator) is configured only by the resistor R5 and the Zener diode ZD in order to initially start the control power supply IC32. The Schottky diode SBD_1 is left to prevent backflow when power is supplied from the auxiliary winding (coil). However, since there is no drawing of the holding current, the regulator transistor Q1 for buffering can be deleted.

  The LED module 50 serving as a light source includes one or more LEDs. For example, the anode side of the LED module 50 is connected to one end of the secondary side coil 33b of the transformer 33 via a Schottky diode SBD_3 for preventing backflow. Moreover, the cathode side of the LED module 50 is connected to the other end of the secondary side coil 33b of the transformer 33, for example.

  In the first embodiment, as described above, the control power supply that switches the operation state of the switching transistor Q2 between the clock (switching) operation and the constant current (DC) operation in accordance with the phase (cycle) of the AC input power supply (AC power supply 200). The IC 32 is provided. Therefore, the control power supply IC 32 can draw a holding current for stably operating the dimmer 210 by setting the operation state of the switching transistor Q2 to a constant current (DC) operation. On the other hand, power (current) can be supplied to the LED module 50 by switching the operation state of the switching transistor Q2 to the clock (switching) operation by the control power supply IC32.

  As described above, in the first embodiment, the holding current extraction operation for stably operating the dimmer 210 with one switching transistor Q2 and the clock operation (lighting switching power supply operation) for lighting the LED module 50 are performed. be able to. That is, the holding current can be drawn using the switching transistor Q2 for performing the LED lighting operation. For this reason, there is no need to separately provide a transistor (regulator transistor) for allowing a holding current to flow, so that it is possible to eliminate power loss caused by providing this transistor separately. As a result, the efficiency of the power supply can be increased.

  In the first embodiment, as described above, there is no need to separately provide a transistor (regulator transistor) for flowing a holding current, and accordingly, the number of components can be reduced accordingly. In addition, a transistor (regulator transistor) for flowing a holding current requires an expensive element having high withstand voltage and high heat dissipation. Therefore, by eliminating such a transistor, product cost can be reduced. Further, when such a transistor is mounted, the power supply circuit becomes larger due to an increase in the substrate mounting area. Therefore, the size of the product can be reduced by eliminating the need for such a transistor.

  In the conventional power supply circuit shown in FIG. 7, when the regulator transistor Q1 is deleted, the current flows through the resistor R5 when the holding current is pulled out. Therefore, the voltage drop fluctuation at the resistor R5. Problems with the operation of the control power supply IC due to the above and power loss at the resistor R5 are problematic.

  In the first embodiment, the switching transistor Q2 operates at a constant current (DC) when the input AC voltage level is low, and the switching transistor Q2 operates as a clock (switching) operation when the input AC voltage level is high. For example, when the ON period of the TRIAC of the dimmer 210 that reduces the input AC voltage level is shortened, the current can be extracted as the holding current. Thereby, the dimmer 210 can be operated stably.

  In the first embodiment, the voltage obtained by dividing the input AC voltage level by resistance is compared with the reference voltage. When the input AC voltage level is low, the DC voltage Vdc is applied to the gate terminal of the switching transistor Q2. Therefore, the switching transistor Q2 can be easily operated at a constant current. Since a direct current (DC) current according to the gate-source voltage of the switching transistor Q2 flows as the holding current, the constant current value (= holding current value) can be adjusted by the direct current (DC) voltage Vdc.

(Second Embodiment)
FIG. 2 is a diagram showing a circuit configuration of an illumination power supply circuit according to the second embodiment of the present invention. Next, an illumination power supply circuit according to a second embodiment of the present invention will be described with reference to FIGS. In FIG. 2, corresponding components are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In the second embodiment, as shown in FIG. 2, the configuration of the power supply circuit part is partially different from the configuration of the first embodiment described above.

  Specifically, the second embodiment is characterized in that the voltage at both ends of the resistor R8 connected in series (series) to the input power supply line 70 is connected to the input of the comparator CMP2 with respect to FIG. Yes. The resistor R8 is an example of the “second resistor” in the present invention.

  More specifically, the resistor R8 is connected in series (series) to the input power line 70, the input side of the resistor R8 is connected to the non-inverting input terminal of the comparator CMP2, and the output side of the resistor R8 is the comparator. It is connected to the inverting input terminal of CMP2. The comparator CMP2 detects a decrease in supply current accompanying a decrease in input AC voltage level by detecting a voltage difference across the resistor R8.

  For example, when the ON period of the triac of the dimmer is shortened and the input AC voltage level is lowered, the brightness of the LED also becomes dark, and the current flowing through the LED also decreases. This decrease in the circuit current is equivalently detected by the voltage difference between both ends of the resistor R8 connected to the input power supply line 70 in series. In terms of maintaining the current flowing in the triac, it can be said that it is a direct and effective means because it can detect the current level and correct the current.

  The comparator CMP2 connects the switch SW to the flip-flop 36 side when the potential difference between both ends of the current detection resistor R8 is large. The gate terminal of the switching transistor Q2 performs a switching operation by a clock output from the flip-flop 36, and turns on the LED by the above-described current detection feedback loop operation.

  On the other hand, when the potential difference of the current detection resistor R8 is small (for example, when the potential difference is approximately 0), the comparator CMP2 connects the switch SW to the DC voltage source 37 side. As a result, the gate terminal of the switching transistor Q2 is biased with a direct current (DC) voltage Vdc, so that a direct current (DC) current in accordance with the gate-source voltage flows between the source and drain of the switching transistor Q2. The switching transistor Q2 operates at a constant current so as to draw the holding current.

  Other configurations of the second embodiment are the same as those of the first embodiment.

  In the second embodiment, as described above, the current detection resistor R8 connected in series to the input power supply line 70 is provided, and the voltage difference between both ends of the current detection resistor R8 is detected, thereby reducing the input AC voltage level. The switching transistor Q2 is easily operated at a constant current by detecting the accompanying decrease in the supply current and applying the direct current (DC) voltage Vdc to the gate terminal of the switching transistor Q2 when the detected voltage difference is small. be able to. Since a direct current (DC) current according to the gate-source voltage of the switching transistor Q2 flows as the holding current, the constant current value (= holding current value) can be adjusted by the direct current (DC) voltage Vdc.

  Other effects of the second embodiment are the same as those of the first embodiment.

(Third embodiment)
FIG. 3 is a diagram showing a circuit configuration of an illumination power supply circuit according to the third embodiment of the present invention. FIG. 4 is a diagram showing a schematic operation waveform example at the time of switching between the switching operation and the constant current operation of the power supply circuit according to the third embodiment of the present invention. Next, an illumination power supply circuit according to a third embodiment of the present invention will be described with reference to FIG. 1, FIG. 3, FIG. 4, and FIG. In addition, in each figure, the same code | symbol is attached | subjected to a corresponding component, and the overlapping description is abbreviate | omitted suitably.

  This third embodiment is largely different from the first embodiment shown in FIG. 1 in that a comparator CMP3 and a switch SW2 are added. The comparator CMP3 is an example of the “second comparator” in the present invention.

  Specifically, as shown in FIG. 3, the connection point between the resistor R3 and the resistor R4 is also connected to the inverting input terminal of the comparator CMP3 via the capacitor C2. On the other hand, the reference voltage source 40 is connected to the non-inverting input terminal of the comparator CMP3. The switch SW1 (SW) has one input terminal connected to the DC voltage source 37 and the other input terminal connected to the output terminal of the switch SW2. The switch SW2 has one input terminal connected to the DC voltage source 39 and the other input terminal connected to the flip-flop 36.

  By switching the switch SW1 and the switch SW2, the gate terminal of the switching transistor Q2 is connected to any one of the DC voltage source 37, the DC voltage source 39, and the flip-flop 36. The switch SW1 is switched by the comparator CMP2, and the switch SW2 is switched by the comparator CMP3.

  In the third embodiment, the voltage waveform obtained by dividing the AC input power supply is time-differentiated by the capacitor (capacitance) C2 and compared with the reference voltage Vref2 by the comparator CMP3, whereby the triac is turned on and the AC voltage rises. It becomes possible to detect the phase portion. Using this detection signal, the switch SW2 can switch the direct current (DC) voltage value connected to the gate terminal of the switching transistor Q2.

  When the on phase of the triac is detected, the switch CMP2 is switched to the DC voltage source 39 side by the comparator CMP3, and the DC voltage Vdc2 is applied to the gate terminal of the switching transistor Q2.

  Here, by setting the direct current (DC) voltage value Vdc2 applied when detecting the ON phase of the triac to be higher than the direct current voltage value Vdc1 (Vdc), a current (current) that is larger than the holding current (holding current value). Value) can be extracted when the triac is on. That is, since a direct current (DC) current according to the gate-source voltage flows between the source and drain of the switching transistor Q2, the holding current is increased by setting the voltage applied to the gate terminal higher than the direct-current voltage value Vdc1. A current value larger than this value can be extracted when the triac is on.

  In general, since the relationship of the holding current value << LED lighting operation current is established, when the triac is turned on and the switching transistor Q2 starts the clock operation, the current flowing through the input power supply line 70 is abruptly changed to adjust the dimmer. Operation may become unstable.

  For this reason, in the third embodiment, the current flowing through the input power supply line 70 is increased stepwise by increasing the holding current when the holding current is switched to the LED lighting operation current (triac is turned on). Yes. For this reason, the dimmer can be operated stably. It should be noted that, by adjusting the value of the capacitor (capacitance) C2, the differential time constant changes, so the onac detection time of the triac can be adjusted.

  FIG. 4 shows a specific operation waveform example. In FIG. 4, a waveform for comparing the input waveform to the comparator CMP2 with respect to the reference voltage Vref2 by the comparator CMP3 after time differentiation of the input waveform to the comparator CMP2 by the capacitor (capacitance) C2 is added.

  When the differential waveform is higher than the reference voltage Vref2, by applying the voltage Vdc2, which is higher than the voltage Vdc1, to the gate terminal of the switching transistor Q2, a constant current operation can be performed by increasing the holding current value. The change in the current value is switched from the first holding current value (A1) (low) → the second holding current value (A2) (high) → the LED lighting switching current (A3) (higher). The fluctuation can be moderated. Thereby, since the load fluctuation to the dimmer can be suppressed, stable operation is possible.

  Note that the time for applying the DC voltage Vdc2 can be adjusted by adjusting the capacitance value of the capacitor C2. If the capacitance C2 value is increased, the falling slope of the differential waveform becomes gentler and the time is extended. Conversely, the time can be shortened by reducing the capacitance C2.

  Other configurations and effects of the third embodiment are the same as those of the first embodiment.

(Fourth embodiment)
FIG. 5 is a diagram showing a circuit configuration of an illumination power supply circuit according to the fourth embodiment of the present invention. Next, an illumination power supply circuit according to a fourth embodiment of the present invention will be described with reference to FIGS. Note that, in FIG. 5, corresponding components are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  As shown in FIG. 5, in the fourth embodiment, the input of the comparator CMP2 is connected to both ends of a resistor R8 connected in series with the input power line 70 in series with the third embodiment (FIG. 3). It features a configuration in which voltage is connected.

  For this reason, in the fourth embodiment, a decrease in the input AC voltage level is detected by the circuit current, and the input AC voltage is divided by the resistors R3 and R4 and time-differentiated by the capacitor (capacitance) C2, and the comparator CMP3 Since the on-phase is detected and the holding current is switched, the fluctuation of the current value is moderated and the fluctuation of the load on the dimmer can be suppressed, so that a stable operation is possible.

  Other configurations and effects of the fourth embodiment are the same as those of the first to third embodiments.

  In addition, it should be thought that embodiment disclosed this time and a modification are illustrations in all the points, and are not restrictive. The scope of the present invention is shown not by the above description of the embodiments and modifications but by the scope of claims for patent, and includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, although the example which used LED (LED module) as a light source of an illuminating device was shown in the said 1st-4th embodiment, this invention is not restricted to this, Light sources other than LED (LED module) are illuminating device. It can also be used as a light source. Moreover, this invention can be used suitably with respect to the light source used as nonlinear load like LED (LED module).

  Note that embodiments obtained by appropriately combining the techniques disclosed above are also included in the technical scope of the present invention.

5 LED lighting device (lighting device)
10 Switching power supply for LED lighting
(Switching power supply for lighting)
20 Rectifier circuit 30 Lighting power circuit (power circuit)
31 Smoothing circuit 32 Control power supply IC (Power supply control unit)
33 Transformer 33a Primary side coil 33b Secondary side coil 33c Auxiliary winding coil 34 Power supply terminal 35 Oscillator 36 Flip-flop 37, 39 DC voltage source 38, 40 Reference voltage source 50 LED module 70 Input power supply line 200 AC power supply 210 Dimming C1 Capacitor C2 Capacitor (capacity)
CMP1 comparator (first comparator)
CMP2 comparator CMP3 comparator (second comparator)
FRD freewheeling diode Q1 regulator transistor Q2 switching transistor R1 resistor R2 resistor R3 resistor R4 resistor R5 resistor R6 resistor R7 resistor (current value detection resistor, first resistor)
R8 resistor, current detection resistor (second resistor)
SBD Schottky diode SW, SW1, SW2 switch ZD Zener diode

Claims (9)

A primary coil of a transformer connected to a smoothed power supply terminal by rectifying an input AC voltage of an AC power supply;
A switching transistor having a drain terminal connected to the other terminal of the primary side coil and a source terminal connected to a ground side power supply terminal via a first resistor for current value detection;
A power supply control unit connected to the gate terminal of the switching transistor and controlling on / off of the switching transistor at a predetermined oscillation frequency;
The power supply control unit receives a voltage generated in the first resistor for detecting a current value, and controls a ratio between an on time and an off time of the switching transistor according to the voltage, whereby the switching transistor The power supply circuit is characterized in that the current flowing through the switching transistor is controlled and the operation state of the switching transistor is switched between a clock operation and a constant current operation in accordance with the phase of the AC power supply. The power control unit
The gate of the switching transistor is switched so that the switching transistor operates at a constant current when the input AC voltage level is low and the switching transistor operates as a clock when the input AC voltage level is high. The power supply circuit described. Compare the voltage obtained by dividing the input AC voltage level with the reference voltage,
The power supply circuit according to claim 2, wherein when the input AC voltage level is low, a predetermined DC voltage is applied to a gate terminal of the switching transistor. The power supply control unit includes a first comparator,
The first comparator compares a voltage obtained by dividing the input AC voltage level with a reference voltage, and applies a predetermined DC voltage to the gate terminal of the switching transistor when the input AC voltage level is lower than the reference voltage. The power supply circuit according to claim 2 or 3. A second resistor connected in series to the input power line;
By detecting a voltage difference between both ends of the second resistor, a decrease in supply current accompanying a decrease in input AC voltage level is detected. When the detected voltage difference is small, a predetermined DC voltage is applied to the gate terminal of the switching transistor. The power supply circuit according to claim 2, wherein the power supply circuit is applied. The power supply control unit includes a second comparator in which capacitors are connected in series,
A voltage obtained by resistance-dividing the input AC voltage level is input to the second comparator via the capacitor,
6. The power supply circuit according to claim 3, wherein a DC voltage applied to a gate terminal of the switching transistor is switched by the second comparator. The second comparator detects a changing point where the input AC voltage increases,
The power supply circuit according to claim 6, wherein the DC voltage applied to the gate terminal of the switching transistor is increased for a predetermined period from when the input AC voltage is increased.   A switching power supply for lighting, comprising the power supply circuit according to claim 1.   An illumination device comprising the illumination switching power supply device according to claim 8.

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