Light Emitting Diode (LED) Driving Device

• US 20090146575A1
• Filed: 12/05/2007
• Published: 06/11/2009
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Leadtrend Technology Corporation
• Original Assignee: Leadtrend Technology Corporation
• Inventors: Chu, Yi-Shan, Chao, Hsing-Kuo
• Granted Patent: US 7,772,782 B2
• Time in Patent Office: Days
• US Class Current: 315/247
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/392 wherein the LEDs are placed as freewheeling diodes at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light emitting diode (LED) driving device includes a power factor correction (PFC) circuit, a bridge switch circuit, a resonant circuit, a transformer and a feedback circuit. The PFC circuit adjusts an output signal thereof based on a feedback signal. The bridge switch circuit transforms the output signal of the PFC circuit into a pulse signal. The resonant circuit resonates and outputs a sinusoidal signal to a primary-side of the transformer based on the pulse signal. The feedback circuit outputs the feedback signal to the PFC circuit in response to a primary-side current of the transformer. Therefore, an output current of the LED driving device is adjusted through modulating the feedback circuit.

Claims

1. A light emitting diode (LED) driving device comprising:

a power factor correction (PFC) circuit, for adjusting an output signal according to a feedback signal;

a bridge switch circuit, coupled to the PFC circuit, for transforming the output signal from the PFC circuit into a pulse signal;

a resonant circuit, coupled to the bridge switch circuit, for outputting a sinusoidal signal according to the pulse signal;

a transformer, a first end of a primary-side of the transformer coupled to the resonant circuit, for receiving the sinusoidal signal; and

a feedback circuit, coupled to a second end of the primary-side of the transformer, for outputting the feedback signal corresponding to a primary-side current of the transformer.

2. The LED driving device of claim 1, wherein the bridge switch circuit is a half-bridge switch circuit, comprising a pair of switch elements in series, the pair of switch elements coupled between an output end of the PFC circuit and a ground end, and a joint point of the pair of switch elements coupled to the resonant circuit.

3. The LED driving device of claim 2, wherein the pair of switch elements are driven by a pair of complementary control signals.

4. The LED driving device of claim 2 further comprising:

a signal generator, coupled to control ends of the pair of switch elements, for controlling the pair of switch elements.

5. The LED driving device of claim 4, wherein the signal generator generates the pair of complementary control signals to control the pair of switch elements.

6. The LED driving device of claim 5, wherein the pair of complementary control signals has a duty cycle of 50%.

7. The LED driving device of claim 1 further comprising:

a signal generator, coupled to the bridge switch circuit, for driving the bridge switch circuit.

8. The LED driving device of claim 1, wherein the resonant circuit comprises:

a capacitor, having one end coupled to the bridge switch circuit, for receiving the pulse signal; and

an inductor, coupled between another end of the capacitor and the first end of the primary-side of the transformer, for outputting the sinusoidal signal.

9. The LED driving device of claim 1, wherein the feedback circuit comprises:

a resistor, coupled between the second end of the primary-side of the transformer and a ground end, wherein the primary-side current flows through the resistor to form an alternating-current voltage across the resistor; and

a rectifier element, rectifying the alternating-current voltage across the resistor to generate the feedback signal.

10. The LED driving device of claim 9, wherein the feedback circuit further comprises a filtering element, for filtering the feedback signal to provide a filtered feedback signal to the PFC circuit.

11. The LED driving device of claim 9, wherein the secondary-side of the transformer is coupled to a first LED module, and the resistance of the resistor corresponds to the brightness of the first LED module.

12. The LED driving device of claim 11, wherein the secondary-side of the transformer is further coupled to a second LED module, the second LED module is reversely coupled to the first LED module in parallel, and the resistance of the resistor corresponds to the brightness of the second LED module.

13. The LED driving device of claim 1, wherein the secondary-side of the transformer is coupled to a first LED module, and the transformer drives the first LED module according to the primary-side current.

14. The LED driving device of claim 13, wherein the secondary-side of the transformer is further coupled to a second LED module, the second LED module is reversely coupled to the first LED module in parallel, and the transformer drives the first LED module and the second LED module by turns according to the primary-side current with an alternating current.