Patent ID: 8077481

Claim:
A primary winding current controlled synchronous rectifying drive circuit, comprising: a current sampling circuit that detects a current signal in a primary winding of a transformer (S) and forwards it to a signal shaping and reset circuit; and a current compensation signal circuit that compensates a magnetizing current in the primary winding of the transformer; wherein the signal shaping and reset circuit converts a sample of the current signal into a voltage signal and shapes it into a pulse signal, and then forwards the current signal to a logic control and power drive circuit that converts the pulse signal into one or more drive signal(s) through logic control, then the drive signal(s) are amplified to drive a corresponding synchronous rectifier; wherein the current sampling circuit comprises a current transducer(ST), which comprises a primary sampling winding (N 1 ) for detecting the current signal in the primary winding of the transformer, a compensation winding (N 2 ), and a secondary output winding (N 4 ); wherein the current compensation signal circuit comprises the inductor (L 1 ); and wherein the inductor (L 1 ) is connected in series with the compensation winding (N 2 ) of the current transducer (ST) and is connected in parallel with any two terminals of a secondary winding (S) of the transformer.