Patent ID: 7480158

Claim:
A synchronous rectifying forward converter comprising: a transformer including a primary winding, a secondary winding, and a tertiary winding; a main switch element connected in series to the primary winding of the transformer; a choke coil connected in series to the secondary winding of the transformer; a smoothing capacitor connected in parallel between output terminals; a rectifying switch element that is connected in series to the secondary winding of the transformer and that is turned ON/OFF in synchronization with turning ON/OFF of the main switch element; a commutating switch element that is turned OFF/ON in synchronization with turning ON/OFF of the main switch element and that forms a path to emit excitation energy of the choke coil by being turned ON; and a switching control circuit to apply a drive signal to the main switch element, further comprising a synchronous rectifier element driving circuit that transmits only ON timing and OFF timing as trigger pulses in the drive signal of the main switch element output from the switching control circuit from the primary side to the secondary side via pulse transformers, and that regenerates a drive signal to drive at least one of the rectifying switch element and the commutating switch element in accordance with turning ON/OFF of the main switch element on the basis of the trigger pulses; a pulse separation circuit for separating the ON-timing trigger pulse and the OFF-timing trigger pulse output from the pulse transformers, and the polarity of the ON timing pulse and the OFF timing pulse being the same.