Abstract: In response to the demands for high efficiency of spaceborne synthetic aperture radar power converter, after comparing the topologies of various power supplies suitable for the spaceborne, a topology scheme of synchronous rectifier forward converter is proposed in this paper, which adopts a novel gate charge retention voltage-driven synchronous rectifier topology to solve the freewheeling driving problem in transformer dead time. Circuit principle, radiation-hardened method, main components, parameter calculation methods are described in detail. A prototype with 50 V~70 V input and 5 V/6 A output is manufactured according to the proposed scheme. The characteristics of high efficiency, radiation-hardened and the accuracy of solution have been proven by experimental results. New forward converter can meet the requirements of the spaceborne power supply.