The present invention provides a self-driving circuit for DC/DC converter of a low voltage, high current, and high power density. The converter comprises a transformer, output rectification portion SR1 and voltage clamping. The first configuration of the self-driving circuit consists of resisters Ra1, Ra2, capacitors Ca1, Ca2, transistors Qa1, Qa2; and the second configuration consists of Da, small power MOS transistor SRa, an auxiliary winding Nsa, a delay driving circuit and a isolating differential circuit. The self-driving circuit of the present invention may reduce the cross-conductive loss, and increase the converting efficiency.