PRIMARY DRIVE SYNCHRONOUS HIGH-SPEED SWITCHING RECTIFYING CIRCUIT FOR LLC HALF-BRIDGE POWER CONVERTER FOR DRIVING LED

• US 20110187280A1
• Filed: 01/29/2010
• Published: 08/04/2011
• Est. Priority Date: 01/29/2010
• Status: Abandoned Application

• Current Assignee: Averd Labs Co., Ltd.
• Original Assignee: Averd Labs Co., Ltd.
• Inventors: CHUNG, IL HWI
• Application Number:
  US12/696,255
• Publication Number:
  US 20110187280A1
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H05B 41/36 Controlling
• 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: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Disclosed herein is a secondary rectifier for an LLC half-bridge power converter for driving an LED, which provides a power converter with efficiency and stability higher than a conventional power converter using a rectifying diode. The LLC half-bridge power converter does not employ a fast recovery diode or a Schottky diode for secondary rectification and uses FETs as rectifying elements to achieve high efficiency, high stability and low cost and small volume.

Claims

1. A primary drive synchronous high-speed switching rectifier circuit for an LLC half-bridge power converter for driving an LED, which comprises an output unit 100 receiving a 50% duty cycle pulse signal according to frequency control of a controller and generating pulse signals (having positive voltage periods and negative voltage periods) through a first transformer T1 and first and second switching FETs Q1 and Q2, a resonator 200 LLC-resonating the pulse signals of the output unit 100 according to an inductor L1, a primary coil of a third transformer T3 and a resonating condenser C5, and a secondary rectifier 300 rectifying pulse signals output from two secondary coils of the third transformer T3 of the resonator 200 through rectifying elements, smoothening the pulse signals and outputting DC power to a load,

wherein third and fourth FETs Q3 and Q4 are used as the rectifying elements of the secondary rectifier 300 to full-wave-rectify the pulse signals, and the LLC half-bridge power converter further comprises a rectifier controller 400 that is configured to delay an input pulse by delay time set in consideration of element delay, rise time and fall time and generate a control pulse signal having off time between pulses according to alternate combination of a delayed pulse and the input pulse to control the third and fourth FETs Q3 and Q4 of the secondary rectifier 300.

2. The primary drive synchronous high-speed switching rectifier circuit for an LLC half-bridge power converter for driving an LED according to claim 1, wherein the rectifier controller 400 comprises:

an input pulse detector 410 receiving the 50% duty cycle pulse signal through a primary coil and detecting the pulse signal through two secondary coils in phase with the first transformer T1;

a delay unit 430 comparing the pulse signal detected by the input pulse detector 410 with a reference signal of a delay time setting unit 420 and delaying rise time and fall time of the pulse signal;

a rectifier control pulse generator 440 alternately performing an AND operation on a pulse delayed by the delay unit 430 and negative and positive pulses detected by the input pulse detector 410 to generate a rectifier control pulse signal having off time between pulses; and

a rectifier on/off time controller 450 performing an AND operation on a first rectifier pulse input to the fourth rectifying FET Q4 of the secondary rectifier 300 and a second rectifier pulse input to the third rectifying FET Q3 of the secondary rectifier 300, buffering the AND operation resultant signals and alternately applying the buffered signals as gate control signals of the third and fourth rectifying FETs Q3 and Q4 to control on/off time of the rectifier pulse signal generated by the rectifier control pulse generator 440.