Half-bridge power converter for driving LED by series-resonant connection of inductor, inductor and capacitor

• US 8,138,688 B2
• Filed: 01/22/2010
• Issued: 03/20/2012
• Est. Priority Date: 01/22/2010
• Status: Expired due to Fees

• Current Assignee: Averd Labs Co., Ltd.
• Original Assignee: Averd Labs Co., Ltd.
• Inventors: Chung, Il Hwi
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): A, Minh D
• Application Number:
  US12/692,427
• Publication Number:
  US 20110181205A1
• Time in Patent Office: 788 Days
• Field of Search: 315/219, 315/200.R, 315/209.R, 315/185.R, 315/227.R, 315/291, 315/307
• US Class Current: 315/307
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Disclosed herein is an LLC half-bridge power converter for driving an LED, which uses a CMOS timer IC having 50% duty cycle and a usable frequency range of 50 KHz through 1 MHz as a controller. In the LLC half-bridge power converter for driving an LED, the output of a rectifier is detected to operate an opto-coupler according to a soft-start set value and the opto-coupler is controlled to be turned off when the output of the rectifier exceeds a set rated voltage. The capacitance of a frequency varying condenser of the controller is varied by the opto-coupler to change the frequency of the controller so as to rapidly stabilize the output level and maintain a desired output level.

Claims

1. An LLC half-bridge power converter for driving an LED, which is configured to generate an output pulse signal from an external input power DC through an output unit (110) according to frequency control of a controller (100), resonate the output pulse signal of the output unit (110) through an LLC resonator (120), rectify the output pulse signal through a rectifier (130) at the secondary side of the LLC resonator (120) to output a DC voltage to a load, detect the output of the rectifier (130) through a feedback unit (140) and feed back the output of the rectifier (130) to the controller (100),

wherein the controller 100 is a CMOS timer IC that has 50% duty and a usable frequency range of 50 KHz through 1 MHz and receives a feedback signal based on a soft-start set value set to the feedback unit (140) to vary the output frequency thereof according to a capacitance variation of a frequency varying condenser (C3) to control the final output level of the rectifier (130), and the feedback unit (140) is configured to detect the output of the rectifier (130) and operates an opto-coupler according to the soft-start set value, control the opto-coupler to be tuned off when the output of the rectifier (130) exceeds a set rated voltage and vary the capacitance of the frequency varying condenser (C3) of the controller (100) according to the opto-coupler.

2. The LLC half-bridge power converter for driving an LED according to claim 1, wherein the feedback unit (140) comprises:

a soft-start setting unit (141) setting a time constant of the output of the rectifier (130) according to a resistor (R8) and a condenser (C9) and generating a soft-start voltage through a resistor (R9);

a level detector (142) dividing the output of the rectifier (130) through voltage-dividing resistors (R10) and (R11), detecting whether the divided voltages exceed a set level through a level detecting element (IC20) and bypassing the output of the soft-start setting unit (141) when the divided voltages exceed the set level through a PNP transistor (Q3);

the opto-coupler (OPT) for a feedback signal, which receives the output of the soft-start setting unit (141) controlled by the level detector (132) through an anode to control a light-emitting element and generates a feedback signal according to an NPN light-receiving element; and

a controller frequency varying unit (143) dividing the external input power through voltage-dividing resistors (R1 and R3), applying a bias voltage to a second terminal of the frequency varying condenser (C3) of the controller (100) and controlling the bias of the second terminal of the frequency varying condenser (C3) according to the light-receiving element of the opto-coupler (OPT).

3. The LLC half-bridge power converter for driving an LED according to claim 2, further comprising a protecting circuit (144) that receives the output pulse signal of the output unit (110) through reverse diodes (D3 and D2) and controls a base of the light-receiving element of the opto-coupler (OPT) according to a reverse diode (D1) based on set values of a condenser (C7) and resistors (R6 and R7).