Patent ID: 7499294

Claim:
A self-excitation synchronous rectification driver, applying to a power supply that comprises a main transformer having a power driver unit at the primary side and a rectification unit at the secondary side with said rectification unit having a first rectifier switch and a second rectifier switch both controlled by said self-excitation synchronous rectification driver, comprising the following components: a self-excitation coil and a self-excitation driver, wherein the turn-on/turn-off of said second rectifier switch makes said self-excitation coil charge/discharge and trigger said self-excitation driver to turn on or turn off said first rectifier switch; a synchronous-signal source outputting a synchronous signal to synchronize said rectification unit with said power driver unit; a pulse transformer receiving said synchronous signal and coupled to a positive/negative edge detector, wherein said positive/negative edge detector detects the positive edge and negative edge of said synchronous signal; and a latch unit having a period-limiting circuit, coupled to said positive/negative edge detector, outputting a high-level signal or low-level signal according to the positive edge or negative edge of said synchronous signal to control the turn-on/turn-off of said second rectifier switch, wherein when there is none said synchronous signal, said latch unit receives a time constant generated by said period-limiting circuit to control the period of triggering the turn-on/turn-off of said second rectifier switch.