Patent ID: 7173835

Claim:
A circuit for synchronous rectifying of a power converter, comprising: a transformer, having a primary winding and a secondary winding, wherein said secondary winding of said transformer includes a first terminal and a second terminal, wherein a switching voltage is produced across said second terminal and said first terminal of said secondary winding of said transformer as said transformer is being switched; a saturable inductor, coupled from said transformer to a third terminal; a first transistor, coupled from said transformer to a ground terminal; a second transistor, coupled from said third terminal to said ground terminal; an inductor, coupled from said third terminal to an output terminal of said power converter; a current-sensing device, generating a current signal in response to an inductor current of said inductor; and a control circuit, operating to receive said switching voltage and said current signal for generating a first control signal and a second control signal for driving said first transistor and said second transistor, respectively; wherein said first transistor is switched on in response to said switching voltage, and said second transistor is switched off in response to said current signal; wherein said saturable inductor provides a delay time to inhibit a current flow from said transformer to said second transistor when said switching voltage is being generated.