JP2013251176A - Led drive circuit and led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED drive circuit which can restrain flickers in LED lighting even when the output voltage ON period of a phase controlled dimmer is shortened.SOLUTION: The LED drive circuit comprises: a rectification circuit which can be connected to an AC power supply via a phase controlled dimmer; a switching element; an LED current control circuit which, by detecting a phase angle of the output voltage of the rectification circuit, controls the switching element according to the detected phase angle, thereby controlling a current flowing to an LED load; a power supply voltage generation circuit which generates a power supply voltage for the LED current control circuit on the basis of the output voltage of the rectification circuit; a power storage element; a charge control circuit which supplies electric charges to the power storage element; and a switch circuit which, when the voltage generated by the power supply voltage generation circuit drops below a designated voltage, switches a supply source for the power supply voltage to the LED current control circuit from the power supply voltage generation circuit to the power storage element.

Description

  The present invention relates to an LED driving circuit.

  LEDs (Light Emitting Diodes) have features such as low current consumption and long life, and their uses are spreading not only to display devices but also to lighting fixtures. In addition, in LED lighting fixtures, in order to obtain desired illuminance, a plurality of LEDs are often used.

  A general lighting fixture often uses a commercial AC power source, and considering the case of using an LED lighting fixture instead of a general lighting fixture such as an incandescent bulb, the LED lighting fixture is also a general lighting fixture. Similarly, a configuration using a commercial AC power supply is desirable.

  In addition, when dimming control of an incandescent bulb is performed, power is supplied to the incandescent bulb by turning on a switching element (typically a thyristor element or a triac element) at a phase angle with an AC power supply voltage. A phase control dimmer (generally called an incandescent lycon) that can easily control the dimming is used.

JP-A-3-32356 JP 2011-200117 A

  Also in the LED lighting device, it is required to perform light control using the phase control dimmer.

  Here, FIG. 9 shows a conventional example of an LED lighting system capable of dimming control of an LED lighting device using a commercial AC power source. The output voltage V1 of the commercial AC power supply 1 is converted into a waveform in which a part of a sine wave is cut by the phase control dimmer 2 as shown in the upper part of FIG. 11A, for example, and then the diode bridge DB1 for full-wave rectification. Is input.

  A voltage having a waveform as shown in the lower part of FIG. 11A by full-wave rectification, for example, is input as a power supply voltage to the LED current control circuit 9 via the filter composed of the coil L1 and the capacitor C1 and the starting circuit 11, and It is also input to the phase angle detection circuit 6 and supplied to the anode of the LED array 12.

  When activated, the LED current control circuit 9 drives the switching element 8 based on the detection result of the phase angle, and causes the LED array 12 to flow and light up.

  Here, the power supply voltage generation circuit 10 includes the secondary winding N2 of the transformer T1, and generates a power supply voltage suitable for the LED current control circuit 9 based on the power generated in the secondary winding N2. A technique similar to such a method of generating a power supply voltage is disclosed in Patent Document 1, for example.

  When the LED current flows as described above, power is generated in the secondary winding N2 of the transformer T1, and the output voltage V4 of the power supply voltage generation circuit 10 generated based on the power is input to the switching circuit 3, and the switching circuit 3, the power supply from the starting circuit 11 is cut, and the output voltage V4 is applied to the LED current control circuit 9 as a power supply voltage.

  FIG. 10 shows a conventional example of an insulated LED lighting system. The output voltage V1 of the commercial AC power supply 1 is phase-controlled by the phase control dimmer 2 and then full-wave rectified by the diode bridge DB1. The full-wave rectified voltage is input as a power source to the LED current control circuit 9 via the filter composed of the coil L1 and the capacitor C1 and the starting circuit 11, and is also input to the phase angle detection circuit 6 for insulation. It is also supplied to the primary side of the transformer T2.

  When activated, the LED current control circuit 9 drives the switching element 8 based on the detection result of the phase angle, transmits power from the primary side to the secondary side via the transformer T2, and causes the LED array 12 to flow and light up. .

  When the primary current flows, power is generated in the auxiliary winding 14 of the transformer T2, and the output voltage V4 of the power supply voltage generation circuit 13 generated based on the power is input to the switching circuit 3, and the switching circuit 3 starts the starting circuit. 11 is cut off, and the output voltage V4 is applied to the LED current control circuit 9 as a power supply voltage.

  In the conventional example shown in FIGS. 9 and 10, when the luminance of the LED array 12 is low, the output voltage V2 of the phase control dimmer 2 has a large phase angle as shown in FIG. 11B, for example. That is, since the ON period has a short waveform, the output voltage V4 of the power supply voltage generation circuits 10 and 13 decreases, and the power supply voltage of the LED current control circuit 9 decreases. When the power supply voltage decreases, the LED current control circuit 9 cannot operate normally, and flickering may occur in the lighting of the LED array 12.

  Here, Patent Document 2 discloses a first rectifying / smoothing circuit connected to the first secondary winding of the transformer to supply a direct current to the LED module, and the second secondary winding of the transformer. A second rectifying / smoothing circuit connected to the circuit, an arithmetic circuit for adjusting a magnitude of a current supplied to the LED module by being supplied with power by the second rectifying / smoothing circuit, and the arithmetic operation from the second rectifying / smoothing circuit. A switching power supply device including a power supply circuit that supplies power from a first rectifying and smoothing circuit to the arithmetic circuit so as to compensate for the shortage of power supply to the circuit is disclosed.

  However, in Patent Document 2, there is a problem that power supply to the arithmetic circuit is insufficient if the ON period of the output voltage of the phase control dimmer is close to zero.

  In view of the above problems, an object of the present invention is to provide an LED driving circuit capable of suppressing occurrence of flickering in LED lighting even when the ON period of the output voltage of the phase control dimmer is shortened. To do.

In order to achieve the above object, the LED drive circuit of the present invention includes:
A rectifier circuit connectable to an AC power source via a phase control dimmer;
A switching element;
An LED current control circuit that detects a phase angle of the output voltage of the rectifier circuit, controls the switching element according to the detected phase angle, and controls a current flowing through the LED load;
A power supply voltage generation circuit that generates a power supply voltage for the LED current control circuit based on an output voltage of the rectifier circuit;
A storage element;
A charge control circuit for supplying a charge to the storage element;
Switching the supply of power supply voltage to the LED current control circuit from supply from the power supply voltage generation circuit to supply from the storage element when the voltage generated by the power supply voltage generation circuit is lower than a predetermined voltage Circuit,
It is set as the structure provided with.

  According to such a configuration, when the ON period of the output voltage of the phase control dimmer is shortened (that is, when the phase angle is large), the voltage generated by the power supply voltage generation circuit is lower than a predetermined voltage, The switching circuit switches the supply of the power supply voltage to the LED current control circuit from the supply from the power supply voltage generation circuit to the supply from the storage element. Therefore, since the power supply voltage of the LED current control circuit is stabilized and the LED current control circuit operates normally, it is possible to suppress the occurrence of flickering in the LED load that is lit at low brightness.

  In the above structure, the power storage element may be a battery or a capacitor.

In any of the above configurations,
A regulator for converting the output voltage of the power storage element into the predetermined voltage;
A power supply voltage may be supplied to the LED current control circuit by applying an output voltage of the storage element to the LED current control circuit via the regulator.

  In the above configuration, the output voltage of the regulator may be set variably.

In any of the above configurations,
A transformer having a primary winding and a secondary winding;
The power supply voltage generation circuit may generate the power supply voltage by smoothing a voltage generated in the secondary winding by a current flowing through the primary winding by switching of the switching element.

  In any one of the configurations described above, the power supply voltage generation circuit may be a startup circuit that starts the LED current control circuit when the AC power supply is turned on.

In any of the above configurations,
An LED driving circuit that includes a transformer having a primary winding, a secondary winding, and an auxiliary winding, and drives the LED load by transmitting power from the primary winding to the secondary winding. And
The power supply voltage generation circuit may generate the power supply voltage by smoothing a voltage generated in the auxiliary winding by a current flowing through the primary winding by switching of the switching element.

  Moreover, the LED lighting device of the present invention has a configuration including the LED drive circuit having any one of the above configurations and an LED load connected to the output side of the LED drive circuit.

  According to the present invention, even when the ON period of the output voltage of the phase control dimmer is shortened, occurrence of flickering in the lighting of the LED can be suppressed.

It is a figure which shows the structure of the LED lighting system which concerns on 1st Embodiment of this invention. It is a figure which shows the example of 1 structure of the starting circuit and switching circuit which concern on 1st Embodiment of this invention. It is a figure which shows the signal waveform example of each part in the LED drive circuit which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the LED lighting system which concerns on 2nd Embodiment of this invention. It is a figure which shows the example of 1 structure of the starting circuit and switching circuit which concern on 2nd Embodiment of this invention. It is a figure which shows the example of a waveform of the output voltage of the starting circuit which concerns on 2nd Embodiment of this invention. It is a figure which shows the example of a waveform of the output voltage of the starting circuit which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the LED lighting system which concerns on 3rd Embodiment of this invention. It is a figure which shows the signal waveform example of each part of the LED drive circuit which concerns on 3rd Embodiment of this invention. It is a figure which shows the structure of the prior art example of an LED illumination system. It is a figure which shows the structure of the other example of a conventional LED lighting system. It is a figure which shows the example of a waveform of the output voltage of a phase control type | mold dimmer in case a phase angle is small, and the output voltage of a diode bridge. It is a figure which shows the example of a waveform of the output voltage of a phase control dimmer in case a phase angle is large, and the output voltage of a diode bridge.

<First Embodiment>
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the LED illumination system according to the first embodiment of the present invention. The LED lighting system shown in FIG. 1 includes a phase control dimmer 2 connected to a commercial AC power source 1, an LED drive circuit 100 connected to the output side of the phase control dimmer 2, and an LED drive circuit 100. And an LED array 12 (LED load) in which a plurality of LEDs are connected in series.

  In addition, as an LED illuminating device comprised from the LED drive circuit 100 and the LED array 12, an LED bulb, a ceiling light, a straight tube type light etc. can be mentioned, for example.

  The LED driving circuit 100 includes a diode bridge DB1, a filter composed of a coil L1 and a capacitor C1, a freewheeling diode D1, a capacitor C3, a transformer T1, a power supply voltage generation circuit 10, a starting circuit 21, and a switching circuit 22. The LED current control circuit 28 and the regulator 29 are provided.

  The phase control dimmer 2 turns on a triac (not shown) at a power supply phase angle depending on the resistance value, for example, by changing the resistance value of a semi-fixed resistor (not shown). As a result, a voltage V2 having a waveform obtained by cutting out a sine wave of the AC voltage V1 of the commercial AC power supply 1 at a certain phase angle is output from the phase control dimmer 2. Usually, the semi-fixed resistor is a rotary knob or a slide type, and the phase angle is adjusted by changing the rotation angle of the knob or changing the slide position, thereby enabling LED dimming.

  The diode bridge DB1 (rectifier circuit) performs full-wave rectification on the voltage input from the phase control dimmer 2, and outputs the full-wave rectified voltage V2 'to a filter including the coil L1 and the capacitor C1. The filter serves to smooth the voltage V2 'subjected to full-wave rectification, to prevent internal switching noise from leaking to the input side, and to prevent noise from the input side.

  The output of the filter is connected to the cathode of the freewheeling diode D1, one end of the capacitor C3, and the anode of the LED array 12. The other end of the capacitor C3 and the cathode of the LED array 12 are commonly connected to one end of the primary winding n1 of the transformer T1. The other end of the primary winding n1 is commonly connected to the anode of the freewheeling diode D1 and the switching element 25.

  The LED current control circuit 28 includes a phase angle detection circuit 23, a control circuit 24, and a switching element 25. The output of the filter is also connected to the input terminal of the phase angle detection circuit 23. The phase angle detection circuit 23 detects the phase angle by the phase control dimmer 2 based on the output of the filter. The control circuit 24 controls the drive of the switching element 25 based on the phase angle detection result, and controls the current flowing through the LED array 12.

  The output of the filter is also connected to the input terminal of the starting circuit 21. The starting circuit 21 generates a power supply voltage for starting the LED current control circuit 28 based on the output of the filter.

  The power supply voltage generation circuit 10 includes a secondary winding n2 of the transformer T1, a diode D2, and a capacitor C2. By smoothing the voltage generated in the secondary winding n2 by the diode D2 and the capacitor C2, an output voltage V4 which is a power supply voltage for the LED current control circuit 28 is generated.

  The LED current control circuit 28 also includes a storage element 27 and a charge control circuit 26 that performs control for charging the storage element 27. The regulator 29 converts the output voltage of the power storage element 27 into a constant voltage and outputs it. The power storage element 27 may be formed of a battery or a large capacity capacitor element. The regulator 29 may be a linear regulator or a switching regulator.

  The switching circuit 22 is a circuit that switches application of the output voltage of the starter circuit 21, the output voltage of the power supply voltage generation circuit 10, and the output voltage of the regulator 29 to the LED current control circuit 28.

  A configuration example of the starter circuit 21 and the switching circuit 22 is shown in FIG. 2 includes a resistor R21 having one end connected to the output of the filter, a Zener diode Z21 having the other end connected to the cathode and the anode grounded, and a base having the resistor R21 and the Zener. The transistor Tr21 is connected to the connection point of the diode Z21, the collector is connected to one end of the resistor R21 on the filter side, and the emitter is connected to the power input terminal of the LED current control circuit 28.

  The switching circuit 22 includes a transistor Tr21 and a diode D22 whose anode is connected to the output of the regulator 29 and whose cathode is connected to the power input terminal of the LED current control circuit 28.

  Next, the operation of the LED driving circuit 100 shown in FIGS. 1 and 2 will be described.

  When the commercial AC power source 1 is turned on, the phase controlled by the phase control dimmer 2, full-wave rectified by the diode bridge DB 1, and smoothed by the filter is input to the starting circuit 21. Then, the transistor Tr21 is turned on, and a voltage that is lowered by the base-emitter voltage from the Zener voltage of the Zener diode Z21 is applied to the power input terminal of the LED current control circuit 28.

  Thereby, the phase angle detection circuit 23, the control circuit 24, the switching element 25, and the charge control circuit 26 start operation. The phase angle detection circuit 23 detects the phase angle by the phase control dimmer 2, that is, the ON period of the output voltage of the phase control dimmer 2 based on the output of the filter, and sends the detection result to the control circuit 24. .

  The control circuit 24 drives and controls the switching element 25 based on the phase angle detection result, and current starts to flow through the LED array 12. At this time, a voltage is generated in the secondary winding n2 due to the current flowing in the primary winding n1 of the transformer T1. The voltage generated in the secondary winding n2 is smoothed by the diode D2 and the capacitor C2, and is output to the switching circuit 22 as the output voltage V4.

  When the output voltage V4 equal to or higher than the start-up voltage is output to the switching circuit 22, the emitter potential of the transistor Tr21 rises and the transistor Tr21 is turned off. As a result, the power supply voltage applied to the LED current control circuit 28 is switched from the starting voltage to the output voltage V4. Based on this power supply voltage, the charge control circuit 26 supplies electric charge to the electric storage element 27 and accumulates it.

  Here, FIG. 3 shows examples of waveforms of the output voltage of the diode bridge DB1, the LED current, the current flowing through the secondary winding n2, and the output voltage V4 by comparing the phase angle. As described above, when the phase angle is increased by setting in the phase control dimmer 2, that is, when the ON period is shortened (right side in FIG. 3), the output voltage V4 decreases.

  The output voltage of the storage element 27 is input to the switching circuit 22 via the regulator 29. When the output voltage V4 becomes higher than the output voltage of the regulator 29, the diode D22 is off, and the output voltage V4 is applied to the LED current control circuit 28.

  On the other hand, when the output voltage V4 becomes lower than the output voltage of the regulator 29, the diode D22 is turned on, so that the output voltage V4 switches to the LED current control circuit 28 via the diode D22. Applied.

  As a result, when the phase angle of the output voltage of the phase control dimmer 2 is large, that is, when the ON period is short, the lowered output voltage V4 becomes lower than the output voltage of the regulator 29, so that the diode D22 is turned on. The output voltage of the storage element 27 is applied to the LED current control circuit 28 via the regulator 29. Therefore, since the power supply voltage of the LED current control circuit 28 is stabilized and the LED current control circuit 28 operates normally, it is possible to suppress the occurrence of flickering in the lighting of the LED array 12 with low luminance.

  Note that the output voltage of the regulator 29 may be variably set, and the switching threshold with the output voltage V4 may be adjusted. According to this, even when the power supply voltage at which the LED current control circuit 28 can operate stably varies, it is possible to cope with it. The variable setting of the regulator 29 may be performed by a switch, a volume or the like. Further, it may be set by the end user, or may be initially set in the product production process.

Second Embodiment
Next, the configuration of the LED illumination system according to the second embodiment of the present invention is shown in FIG.

  The LED drive circuit 200 that is a part of the LED illumination system shown in FIG. 4 is different from the first embodiment in that the coil L31 is used instead of the transformer T1 and the power supply voltage generation circuit 10 is not provided. Yes. The switching circuit 31 is a circuit that switches application of the output voltage of the starting circuit 21 and the output voltage of the regulator 29 to the LED current control circuit 28.

  One structural example of the starting circuit 21 and the switching circuit 31 is shown in FIG. The configuration of the starter circuit 21 is the same as that shown in FIG. 2, but the switching circuit 31 is composed of only the diode D31.

  When the phase angle by the phase control dimmer 2 is small, that is, the ON period is long, the output voltage V3 of the filter composed of the coil L1 and the capacitor C1 shown in FIG. 4 becomes large. Although this output voltage V3 is input to the starter circuit 21, it becomes higher than the Zener voltage Vz of the Zener diode Z21 (FIG. 5), and in this case, a voltage dropped from the Zener voltage Vz by the base-emitter voltage Vbe of the transistor Tr21. It becomes the output voltage V5 of the starting circuit 21 (see FIG. 6A). Since the output voltage V5 is higher than the output voltage of the regulator 29, the diode D31 is turned off and the output voltage V5 is applied to the LED current control circuit 28 as a power supply voltage.

  When the phase angle by the phase control dimmer 2 is increased, that is, when the ON period is shortened, the output voltage V3 of the filter becomes smaller than the zener voltage Vz. In this case, the voltage dropped from the output voltage V3 by the base-emitter voltage Vbe becomes the output voltage V5 of the starting circuit 21, and the lower the output voltage V3, the lower the output voltage V5 (see FIG. 6B).

  In this case, since the output voltage V5 is lower than the output voltage of the regulator 29, the diode D31 is turned on and switched from the output voltage V5, and the output voltage of the regulator 29 is applied to the LED current control circuit 28 via the diode D31. Is done.

  Therefore, since the power supply voltage of the LED current control circuit 28 is stabilized and the LED current control circuit 28 operates normally, it is possible to suppress the occurrence of flickering in the lighting of the LED array 12 with low luminance.

<Third Embodiment>
FIG. 7 shows the configuration of an insulated LED lighting system according to the third embodiment of the present invention. The LED drive circuit 300 which is a part of the LED illumination system shown in FIG. 7 is provided with an insulating transformer T2 as a difference from the first embodiment shown in FIG. By transmitting power to the secondary winding n4, a current is passed through the LED array 12 to light it.

  Further, as a difference from the first embodiment, a voltage obtained by smoothing the voltage generated in the auxiliary winding n5 of the transformer T2 by the diode D2 and the capacitor C2 is output as the output voltage V4 of the power supply voltage generation circuit 13. .

  The switching circuit 22 is a circuit that switches application of the output voltage of the starter circuit 21, the output voltage V <b> 4 of the power supply voltage generation circuit 13, and the output voltage of the regulator 29 to the LED current control circuit 28. In addition, what is necessary is just to set it as the structure similar to FIG. 2 as an example of 1 structure of the starting circuit 21 and the switching circuit 22. FIG.

  The operation of the LED driving circuit 300 will be described. When the commercial AC power supply 1 is turned on, the output voltage V3 of the filter composed of the coil L1 and the capacitor C1 is input to the starting circuit 21, and the output voltage of the starting circuit 21 is the LED current control circuit. 28 is applied as a power supply voltage. Thereby, the phase angle detection circuit 23, the control circuit 24, the switching element 25, and the charge control circuit 26 start operation.

  When the primary current flows through the primary winding n3 of the transformer T2 by driving the switching element 25, a voltage is generated in the auxiliary winding n5, and an output voltage V4 based on the generated voltage is generated. Then, the starting circuit 21 is disconnected by the switching circuit 22 and the output voltage V4 is applied to the LED current control circuit 28 as a power supply voltage. Based on this power supply voltage, the charge control circuit 26 supplies electric charge to the electric storage element 27 and accumulates it.

  Here, FIG. 8 shows examples of waveforms of the output voltage, the primary current, the secondary current, the current flowing through the auxiliary winding n5, and the output voltage V4 of the diode bridge DB1 by comparison between the phase angles. As described above, when the phase angle is increased by the operation of the phase control dimmer 2, that is, when the ON period is shortened (right side in FIG. 8), the output voltage V4 decreases.

  The output voltage of the storage element 27 is input to the switching circuit 22 via the regulator 29. When the output voltage V 4 becomes higher than the output voltage of the regulator 29, the output voltage V 4 is applied to the LED current control circuit 28 by the switching circuit 22.

  On the other hand, when the output voltage V4 becomes lower than the output voltage of the regulator 29, the output voltage V4 is switched by the switching circuit 22 and the output voltage of the regulator 29 is applied to the LED current control circuit 28 via the switching circuit 22. .

  As a result, when the phase angle of the output voltage of the phase control dimmer 2 is large, that is, when the ON period is short, the reduced output voltage V4 becomes lower than the output voltage of the regulator 29. A voltage is applied to the LED current control circuit 28 via the regulator 29. Therefore, since the power supply voltage of the LED current control circuit 28 is stabilized and the LED current control circuit 28 operates normally, it is possible to suppress the occurrence of flickering in the lighting of the LED array 12 with low luminance.

  As mentioned above, although embodiment of this invention was described, if it is in the range of the meaning of this invention, embodiment may be variously deformed.

DESCRIPTION OF SYMBOLS 1 Commercial alternating current power supply 2 Phase control type dimmer 10 Power supply voltage generation circuit 12 LED array 21 Starting circuit 22, 31 Switching circuit 23 Phase angle detection circuit 24 Control circuit 25 Switching element 26 Charging control circuit 27 Power storage element 28 LED current control circuit 29 Regulator 100, 200, 300 LED drive circuit DB1 Diode bridge L1 Coil C1 Capacitor T1, T2 Transformer n1, n3 Primary winding n2, n4 Secondary winding n5 Auxiliary winding D2 Diode C2 Capacitor Z21 Zener diode Tr21 Transistor R21 Resistance D22, D31 Diode

Claims (9)

A rectifier circuit connectable to an AC power source via a phase control dimmer;
A switching element;
An LED current control circuit that detects a phase angle of the output voltage of the rectifier circuit, controls the switching element according to the detected phase angle, and controls a current flowing through the LED load;
A power supply voltage generation circuit that generates a power supply voltage for the LED current control circuit based on an output voltage of the rectifier circuit;
A storage element;
A charge control circuit for supplying a charge to the storage element;
Switching the supply of power supply voltage to the LED current control circuit from supply from the power supply voltage generation circuit to supply from the storage element when the voltage generated by the power supply voltage generation circuit is lower than a predetermined voltage Circuit,
An LED driving circuit comprising:   The LED drive circuit according to claim 1, wherein the power storage element is formed of a battery.   The LED drive circuit according to claim 1, wherein the power storage element is configured by a capacitive element. A regulator for converting the output voltage of the power storage element into the predetermined voltage;
4. The power supply voltage is supplied to the LED current control circuit by applying an output voltage of the storage element to the LED current control circuit via the regulator. 5. 2. The LED drive circuit according to item 1.   The LED drive circuit according to claim 4, wherein an output voltage of the regulator is variably set. A transformer having a primary winding and a secondary winding;
The power supply voltage generation circuit generates the power supply voltage by smoothing a voltage generated in the secondary winding by a current flowing through the primary winding by switching of the switching element. The LED drive circuit of any one of Claim 5.   6. The LED drive circuit according to claim 1, wherein the power supply voltage generation circuit is a starter circuit that starts the LED current control circuit when the AC power supply is turned on. . An LED driving circuit that includes a transformer having a primary winding, a secondary winding, and an auxiliary winding, and drives the LED load by transmitting power from the primary winding to the secondary winding. And
The power supply voltage generation circuit generates the power supply voltage by smoothing a voltage generated in the auxiliary winding by a current flowing through the primary winding by switching of the switching element. 6. The LED driving circuit according to any one of items 5.   An LED lighting device comprising: the LED drive circuit according to claim 1; and an LED load connected to an output side of the LED drive circuit.

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