Patent ID: 7630217

Claim:
A synchronous rectification forward converter, comprising: a transformer provided with 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; output terminals; a smoothing capacitor connected across the output terminals; a rectification switch element having main terminals and a gate terminal, one of said main terminals being connected in series to one end of the secondary winding of the transformer, the gate terminal being connected to the other end of said secondary winding by a drive current supply path for receiving a control voltage from said secondary winding, thereby turning the rectification switch element ON and OFF in synchronism with ON and OFF of the main switch element; a commutation switch element for being turned OFF in synchronism with ON of the main switch element and for being turned ON to form a discharge path for an excitation energy of the choke coil in synchronism with OFF of the main switch element; an output voltage detection circuit for indirectly detecting an output voltage between the output terminals with use of an induced voltage of the tertiary winding of the transformer; a switching control circuit for controlling a switching of the main switch element; a rectification switch control element for forcedly turning OFF the rectification switch element by controlling a voltage of a control terminal of the rectification switch element; and a rectification switch element driver circuit for controlling the rectification switch control element at a timing when the main switch element is turned OFF in accordance with the control of the switching control circuit.