Synchronous Rectifier Circuit Capable of Preventing Flow-Through Current

摘要

A synchronous rectifier circuit (DC-DC converter) (1) includes a CR integration circuit (23) and a discharge circuit (24). The CR integration circuit (23) outputs a voltage that varies at delayed timing as compared with a voltage induced in a secondary-side main winding (10B). The discharge circuit (24) discharges a gate voltage of a rectifier transistor (Q2) as a result of conduction of a discharge transistor (Q3) in response to the output voltage from the CR integration circuit (23). According to such a configuration, the rectifier transistor (Q2) is turned off earlier than the timing of switching of polarity of voltages induced in the secondary-side main winding (10B) and a secondary-side auxiliary winding (10C) in response to turn-on of a primary-side transistor (Q1).