Study and implementation of asymmetrical half-bridge converter

Compared with conventional hard-switching mode, the soft switching technique causes smaller losses in applications of Switching Power Supply (SPS). The asymmetrical halfbridge converter with synchronous rectification and soft-switching technique uses turn-on and turn-off hours to achieve soft switching mode for reducing losses at high frequency, voltage and current stresses between two power switches. To reduce losses, multiplication of forward voltage and current, and increase efficiency of asymmetrical halfbridge converter, the super fast diodes are replaced with the synchronous rectification technique in secondary side of transformer. In this experiment, the turns ratio of transformer is designed to match duty cycles for devices with asymmetrical and complementary operation. Moreover, operating principle of circuit, analysis of steady-state and transient state, and design consideration are all discussed in this paper. Finally, A 300 W prototype with 400V_DC input and 24V_DC output operating with PWM IC-L6591 is built and tested, and the efficiency at full load is 92.09% which verifies the feasibility of theoretical analysis.