A ZVS (zero voltage switching) control circuit for use in a flyback power converter includes a primary side controller circuit, a secondary side controller circuit, and a pulse transformer. In one switching cycle, a synchronous rectifier transistor is turned ON twice to generate a circulation current at the primary side winding, and after the synchronous rectifier transistor is turned OFF, the power transistor is turned ON for zero voltage switching. A synchronous signal coupled between the primary side and the secondary side is employed to synchronize the power transistor and the synchronous transistor. The synchronous signal also triggers an SR-ZVS pulse to turn ON the synchronous rectifier transistor for achieving the zero voltage switching when the power transistor is turned ON.