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1. (WO2000060730) SYNCHRONOUS RECTIFIER AND METHOD OF OPERATION

Pub. No.:    WO/2000/060730    International Application No.:    PCT/US2000/007613
Publication Date: Fri Oct 13 01:59:59 CEST 2000 International Filing Date: Thu Mar 23 00:59:59 CET 2000
IPC: H02M 3/158
H02M 3/335
H02M 7/217
Applicants: SEMICONDUCTOR COMPONENTS INDUSTRIES, L.L.C.
Inventors: BALL, Alan, Richard
Title: SYNCHRONOUS RECTIFIER AND METHOD OF OPERATION
Abstract:
A synchronous rectifier circuit (10) includes a polarity comparator (14) that generates a signal to a driver circuit (16) for controlling the voltage at the gate of a power MOSFET (60). The power MOSFET (60) is switched to operate in the conduction mode and short out a parasitic diode (62) when the diode is forward biased. The power MOSFET (60) is switched to operate in the nonconduction mode when the parasitic diode (62) is reverse biased. A bias supply circuit (12) uses a capacitor (70) to generate a regulated internal bias that provides power to the polarity comparator (14) and to the driver circuit (16). The internal bias allows the powerMOSFET (60) to provide a current conduction that is substantially isolated from the changes in voltage levels at the terminals (64, 66) of the synchronous recifier circuit (10).