Disclosed is a synchronous forward converter having a reverse current suppressor connected to the gate of a freewheel switch. The reverse current suppressor is configured to receive a control input signal generated by an internal circuitry of a power supply system where the forward converter locates, such as an enable signal, to detect the power-off of the forward converter, and in response thereto turn off the freewheel switch during the interruption of the input power of the forward converter. Alternatively, the reverse current suppressor is configured to detect the decay of the input voltage across the input bulk capacitor located on the primary side of a transformer of the forward converter, and turn off the freewheel switch when the voltage across the secondary side of the transformer is decayed to be smaller than the output voltage of the forward converter.
