Design and implementation of zero-voltage-switching flyback converter with synchronous rectifier

A design consideration and circuit implementation of a zero-voltage-switching (ZVS) flyback converter with synchronous rectifier are presented. To reduce the voltage spike due to the transformer leakage inductance when the main switch is turned off at the flyback converter, one auxiliary switch and one clamp capacitor are used in the adopted converter. The resonant circuit, consisting of leakage inductance and output capacitance of switch, is used to achieve ZVS operation for all switches during the transition between the main switch and the auxiliary switch. The synchronous switch is used on the transformer secondary side to reduce the conduction losses further and to increase the circuit efficiency. The operating principle and system analysis of the adopted converter are discussed in detail. The design example of the adopted power converter is presented. Finally experimental results based on a 5 V/20 A prototype circuit are provided to demonstrate the system performance.