Patent ID: 8526202

Claim:
A synchronous rectification circuit for a power converter, comprising: a power switch including a body diode and configured as a synchronous rectifier for coupling to a transformer and an output capacitor; and a switching control circuit configured to provide a control signal in response to a first voltage signal related to a voltage across the power switch and a second voltage signal which is a delayed version of the first voltage signal; wherein the switching control circuit is configured to provide the control signal to the synchronous rectifier without any other-input signal that provides information about an operating state of the power converter; wherein the switching control circuit comprises: first and second inputs, configured for coupling to a positive and a negative terminals of the power switch and sensing a voltage across that power switch; an output terminal, configured for outputting a signal to drive the power switch; a voltage comparing unit, configured to act in response to the first and second inputs, wherein the voltage comparing unit is configured to output a logic signal according to the voltage difference between the sensed voltage drop across the power switch and a reference threshold voltage; and a logic processing circuit, coupled to the voltage comparing unit and configured to provide the first voltage signal and the second voltage signal; where the logic process unit comprises: an input terminal for receiving an input signal; a delay module coupled to the input terminal; an SR flip-flop coupled to the input terminal and the delay module; a NAND logic gate coupled to the input terminal and the SR flip-flop; and a drive circuit coupled to the output of the logic processing unit and the output terminal of the synchronous rectification circuit, wherein the delay module is configured to provide a delay time between the determination of the first voltage signal and the second voltage.