Active snubber forward converter

Abstract

In a forward converter power supply comprising a transformer having a primary winding connected to a primary circuit and a secondary winding connected to a secondary circuit, and a switching transistor in the primary circuit, an active network snubber in the primary circuit for receiving and storing continuing current from the transformer primary winding upon switching of the transistor and for returning current through the transformer primary winding so as to resent the transformer and thereby returning parasitic energy in the transformer caused by leakage inductance and magnetizing current to the energy source. The snubber comprises a capacitor for receiving and storing continuing current from said primary winding upon switching of the transistor, a diode for providing a path for flow of the continuing current from the primary winding to the capacitor and an electronic switch operatively connected to the capacitor to the primary winding and to the switching transistor for returning current from the capacitor to the primary winding upon further switching of the transistor. The capacitor is connected so that the voltage thereon automatically adjusts to reset the transformer upon the further switching of the transistor. The electronic switch and the switching transistor are operatively connected in a manner so as to be always in opposite conducting states.