This paper analyzes the problem with a synchronous rectification scheme, that is, when the secondary rectifier switch and the primary active switch are turned on at the same time, the problem of turning on rectifier switch in advance occurs when the switching frequency is greater than the resonant frequency.

This paper proposes that the formula for time domain analysis can be used to calculate the delay of the turn-on time of the rectifier switch relative to the turn-on time of the switch in primary side, so as to confirm the normal opening of the rectifier switch.