METHOD AND APPARATUS TO PROVIDE SYNCHRONOUS RECTIFYING CIRCUIT FOR FLYBACK POWER CONVERTERS

• Main Authors: CHEN TSO-MIN, YANG TA-YUNG
• Format: Patent
• Language: English
• Published: 29.01.2009
• Subjects: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC,OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWERSUPPLY SYSTEMS; CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS,e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USERAPPLICATIONS; CONTROL OR REGULATION THEREOF; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUTPOWER; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERATION; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE

A synchronous rectifying circuit is provided for flyback power converter. A pulse generator is utilized to generate a pulse signal in response to a leading edge and a trailing edge of a switching signal. The switching signal is used for switching the transformer of the power converter. An isolation device such as pulse transformer or small capacitors is coupled to the pulse generator for transferring the pulse signal through an isolation barrier of a transformer. A synchronous rectifier includes a power switch and a control circuit. The power switch is connected in between the secondary side of the transformer and the output of the power converter for the rectifying operation. The control circuit having a latch is operated to receive the pulse signal for controlling the power switch.