Synchronous rectifier circuit capable of preventing flow-through current

摘要

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