Power supply circuit for driving LED lamp and power supply method, and primary-side control circuit of flyback transformer

Patent metadata

Field	Value
Publication number	US-9356522-B2
Application number	US-201314403782-A
Country	US
Kind code	B2
Filing date	May 31, 2013
Priority date	May 31, 2012
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

The present invention discloses a power supply circuit for driving an LED lamp and a power supply method. The power supply circuit is constituted by an AC-DC converter by adopting DCM-DCM. Also, the power supply circuit adopts a valley fill circuit to reduce rippling of output current and adopts the DCM-DCM to stabilize a link voltage, thereby realizing a power factor correction circuit having two-stage structures. Thus, an input voltage of the flyback converter may be improved, and a high reverse voltage may be applied.

First claim

The invention claimed is:

1. A power circuit for driving an LED lamp, comprising:
a rectification circuit that outputs a rectified voltage;
a boost inductor that outputs a boost current corresponding to the rectified voltage;
a flyback transformer that outputs an output current corresponding to an input current of a primary side from a secondary side;
a switching circuit that is switched by a pulse type signal to control a of the input current of the primary side of the flyback transformer;
a valley fill circuit that provides the input current to the primary side of the flyback transformer by energy accumulated in the valley fill circuit when a boost switching circuit forms a path for increasing the boost current and accumulates the energy in the valley fill circuit by using the boost current when the boost switching circuit forms a path for accumulating the energy in the valley fill; and
the boost switching circuit that includes a first diode and a second diode connected with the boost inductor, provides the path for increasing the boost current through the second diode to the boost inductor in correspondence with turn-on of the switching circuit and provides the path for accumulating the energy in the valley fill circuit through the first diode, a first capacitor of the valley fill circuit, and a second capacitor of the valley fill circuit in correspondence with turn-off of the switching circuit,
wherein the first diode is turned off when the valley fill circuit accumulates the energy higher than a peak voltage of the rectified voltage.

2. The power circuit for driving an LED lamp according to claim 1 , wherein the rectification circuit and the boost inductor operate in a first discontinuous conduction mode for first power factor correction, and the valley fill circuit operates in a second discontinuous conduction mode for second power factor correction for an input voltage applied to the primary side of the flyback transformer.

3. The power circuit for driving an LED lamp according to claim 1 , wherein the valley fill circuit provides an output capacitor for the boost inductor and provides an input capacitor for the flyback transformer.

4. The power circuit for driving an LED lamp according to claim 1 , wherein the valley fill circuit includes the first capacitor and the second capacitor for forming a link voltage, and the first capacitor and the second capacitor are equivalently connected in parallel with each other in order to provide the input current to the primary side of the flyback transformer or are equivalently connected in series with each other in order to accumulate the energy by using the boost current of the boost inductor, according to paths formed by the boost switching circuit.

5. The power circuit for driving an LED lamp according to claim 4 , wherein the valley fill circuit provides the first capacitor and the second capacitor equivalently connected in parallel with each other when the boost switching circuit forms the path for increasing the boost current, and provides the first capacitor and the second capacitor equivalently connected in series with each other when the boost switching circuit forms a path for accumulating the energy.

6. The power circuit for driving an LED lamp according to claim 1 , wherein the valley fill circuit includes the first capacitor and the second capacitor arranged in parallel with each other, a third diode connected from the second capacitor to the first capacitor in a forward direction, a fourth diode connected from the first capacitor to the primary side of the flyback transformer in a forward direction, and a fifth diode connected from a ground to the second capacitor in a forward direction.

7. The power circuit for driving an LED lamp according to claim 6 , wherein the first capacitor and the second capacitor are equivalently connected in parallel with each other when the third diode is turned off, and are equivalently connected in series with each other through the third diode when the third diode is turned on, and turn-on and turn-off of the third diode are performed according to paths formed by the boost switching circuit.

8. The power circuit for driving an LED lamp according to claim 1 , wherein the second diode provides the path for increasing the boost current in between the boost inductor and the switching circuit in correspondence with turn-on of the switching circuit, and the first diode provides the path for accumulating the energy in the valley fill circuit by using the boost current of the boost inductor in correspondence with turn-off of the switching circuit.

9. A power circuit comprising:
a boost power factor correction converter that performs first power factor correction for a rectified voltage in a first discontinuous conduction mode and includes a boost inductor that provides a boost current for forming a link voltage; and
a flyback DC-DC converter that performs second power factor correction for the link voltage formed by the boost current in a second discontinuous conduction mode,
wherein the flyback DC-DC converter comprises:
a flyback transformer that induces an input current of a primary side and outputs an output current from a secondary side;
a switching circuit that is switched by a pulse type signal to control a flow of the input current of the primary side of the flyback transformer;
a valley fill circuit that provides the input current to the flyback transformer by energy accumulated in the valley fill circuit when a boost switching circuit forms a path for increasing the boost current of the boost inductor and accumulates the energy in the valley fill circuit by using the boost current when the boost switching circuit forms a path for accumulating the energy in the valley fill circuit; and
the boost switching circuit that includes a first diode and a second diode connected with the boost inductor, provides the path for increasing the boost current through the second diode to the boost inductor in correspondence with turn-on of the switching circuit and provides the path for accumulating the energy in the valley fill circuit through the first diode, a first capacitor of the valley fill circuit, and a second capacitor of the valley fill circuit in correspondence with turn-off of the switching circuit,
wherein the first diode is turned off when the valley fill circuit accumulates the energy higher than a peak voltage of the rectified voltage.

10. The power circuit according to claim 9 , wherein the valley fill circuit provides an output capacitor for the boost current and provides an input capacitor for the flyback transformer.

11. The power circuit according to claim 9 , wherein the valley fill circuit includes the first capacitor and the second capacitor for forming the link voltage, and the first capacitor and the second capacitor are equivalently connected in parallel with each other in order to provide the input current in the primary side of the flyback transformer or are equivalently connected in series with each other in order to accumulate the energy by using the boost current, according to paths formed by the boost switching circuit.

12. The power circuit according to claim 11 , wherein the valley fill circuit provides the first capacitor and the second capacitor equivalently connected in parallel with each other when the boost switching circuit forms the path for increasing the boost current and provides the first capacitor and the second capacitor equivalently connected in series with each other when the boost switching circuit forms the path for accumulating the energy.

13. The power circuit according to claim 9 , wherein the valley fill circuit includes the

Assignees

• Silicon Works Co Ltd

Inventors

• Hong Ju Pyo
• Kim Jun Ho

Classifications

• H05B45/355

  Power factor correction [PFC]; Reactive power compensation · CPC title

• H05B45/382

  with galvanic isolation between input and output · CPC title

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M1/4258

  using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage (H02M1/4241 takes precedence) · CPC title

• H02M1/42

  Circuits or arrangements for compensating for or adjusting power factor in converters or inverters · CPC title