A novel soft-switching full bridge converter

A novel soft-switching full-bridge (SSFB) converter with additional secondary switch and non-dissipative energy recovery snubber is proposed in this paper. With a simple switching scheme for the primary side switches, the proposed SSFB converter regulates the output voltage by adjusting the duty cycle of the secondary switch. Moreover, by utilizing the capacitor-diode-diode (CDD) turn-off snubber circuit, the circulating current of the converter is eliminated and the zero-voltage-switching (ZVS) turn-on and zero-current-switching (ZCS) turn-off for all primary side switches can be obtained over entire load range. As a result, rectifier diodes have no reverse recovery problem and its ringing voltage is clamped. Thanks to these advantages, the converter shows high efficiency, especially at light load condition, which is difficult to achieve with conventional phase shift full-bridge converter. A 3kW prototype circuit is designed and tested to verify the proposed idea.