DRIVING CIRCUIT OF LIGHT EMITTING DIODE AND LIGHTING APPARATUS USING THE SAME

• US 20110163684A1
• Filed: 02/25/2010
• Published: 07/07/2011
• Est. Priority Date: 01/04/2010
• Status: Abandoned Application

• Current Assignee: Cal-Comp Electronics & Communications Company Limited (Cal-Comp Electronics Public Company Limited)
• Original Assignee: Cal-Comp Electronics & Communications Company Limited (Cal-Comp Electronics Public Company Limited)
• Inventors: Li, Ching-Ju, Wang, Hao-Yuan
• Application Number:
  US12/712,204
• Publication Number:
  US 20110163684A1
• Time in Patent Office: Days
• US Class Current: 315/254
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A driving circuit of light emitting diodes (LEDs) and a lighting apparatus using the same are provided in the application. The driving circuit includes a rectifier unit, an isolation element, a processing unit and a voltage converter circuit. The rectifier unit is coupled to a triac dimmer and outputs a first operation voltage. The processing unit detects a conducting condition of the triac dimmer according to a voltage waveform of the first operation voltage and outputs a pulse width modulation signal to drive the LEDs according to the detected conduction condition, so that flash problems of the LEDs caused by operation voltage variation are prevented.

Claims

1. A driving circuit of light emitting diodes (LEDs) adapted to receive an alternating current (AC) power adjusted by a triac dimmer to drive an LED unit, comprising:

a rectifier unit, for rectifying the AC power to output a first operation voltage;

an isolation element, coupled to the rectifier unit for receiving the first operation voltage to output a second operation voltage;

a processing unit, coupled to the rectifier unit for detecting a conducting condition of the triac dimmer according to a voltage waveform of the first operation voltage, and outputting a pulse width modulation (PWM) signal according to the conducting condition; and

a voltage converter circuit, coupled to the isolation element and the processing unit, converting the second operation voltage into a driving voltage according to the PWM signal, so as to drive the LED unit.

2. The driving circuit of the LEDs as claimed in claim 1, wherein the isolation element is a diode having an anode coupled to the rectifier unit and a cathode coupled to the voltage converter circuit.

3. The driving circuit of the LEDs as claimed in claim 1, wherein the isolation element is a direct current (DC) transformer having one end coupled to the rectifier unit and another end coupled to the voltage converter circuit.

4. The driving circuit of the LEDs as claimed in claim 1, wherein the processing unit comprises:

a comparator, having a positive input terminal coupled to the first operation voltage, and a negative input terminal coupled to a signal source;

a determining unit, coupled to an output terminal of the comparator for determining the conducting condition of the triac dimmer according to an output of the comparator; and

a pulse width modulator, coupled to the determining unit, for outputting the PWM signal, wherein the determining unit adjusts a duty cycle of the PWM signal according to the conducting condition and a look-up table,

wherein the look-up table records a corresponding relationship between the conducting condition of the triac dimmer and the duty cycle of the PWM signal.

5. The driving circuit of the LEDs as claimed in claim 1, wherein the signal source is a triangle wave signal source.

6. The driving circuit of the LEDs as claimed in claim 1, wherein the signal source is a DC reference voltage.

7. The driving circuit of the LEDs as claimed in claim 1, wherein the rectifier unit is a bridge rectifier.

8. The driving circuit of the LEDs as claimed in claim 1, further comprising:

a capacitor, coupled between a common node of the isolation element and the voltage converter circuit and the ground.

9. The driving circuit of the LEDs as claimed in claim 1, wherein the processing unit is an application-specific integrated circuit (ASIC).

10. The driving circuit of the LEDs as claimed in claim 1, wherein the triac dimmer is a tri-electrode AC switch (TRIAC).

11. The driving circuit of the LEDs as claimed in claim 1, wherein the voltage converter circuit is a buck circuit.

12. A lighting apparatus adapted to receive an AC power adjusted by a triac dimmer for lighting, comprising:

an light emitting diode (LED) unit; and

a driving circuit, coupled to the triac dimmer and the LED unit, and comprising;

a rectifier unit, for rectifying the AC power to output a first operation voltage;

an isolation element, coupled to the rectifier unit for receiving the first operation voltage to output a second operation voltage;

a processing unit, coupled to the rectifier unit for detecting a conducting condition of the triac dimmer according to a voltage waveform of the first operation voltage, and outputting a pulse width modulation (PWM) signal according to the conducting condition; and

a voltage converter circuit, coupled to the isolation element and the processing unit for converting the second operation voltage into a driving voltage according to the PWM signal, so as to drive the LED unit.

13. The lighting apparatus as claimed in claim 12, wherein the isolation element is a diode having an anode coupled to the rectifier unit and a cathode coupled to the voltage converter circuit.

14. The lighting apparatus as claimed in claim 12, wherein the isolation element is a direct current (DC) transformer having one end coupled to the rectifier unit and another end coupled to the voltage converter circuit.

15. The lighting apparatus as claimed in claim 12, wherein the processing unit comprises:

a comparator, having a positive input terminal coupled to the first operation voltage, and a negative input terminal coupled to a signal source;

a determining unit, coupled to an output terminal of the comparator for determining the conducting condition of the triac dimmer according to an output of the comparator; and

a pulse width modulator, coupled to the determining unit, for outputting the PWM signal, wherein the determining unit adjusts a duty cycle of the PWM signal according to the conducting condition and a look-up table,

wherein the look-up table records a corresponding relationship between the conducting condition of the triac dimmer and the duty cycle of the PWM signal.

16. The lighting apparatus as claimed in claim 12, wherein the signal source is a triangle wave signal source.

17. The lighting apparatus as claimed in claim 12, wherein the signal source is a DC reference voltage.

18. The lighting apparatus as claimed in claim 12, wherein the rectifier unit is a bridge rectifier.

19. The lighting apparatus as claimed in claim 12, further comprising:

a capacitor, coupled between a common node of the isolation element and the voltage converter circuit and the ground.

20. The lighting apparatus as claimed in claim 12, wherein the processing unit is an application-specific integrated circuit (ASIC).

21. The lighting apparatus as claimed in claim 12, wherein the triac dimmer is a tri-electrode AC switch (TRIAC).

22. The lighting apparatus as claimed in claim 12, wherein the voltage converter circuit is a buck circuit.