A Wide Load Range ZVS Push-Pull DC/DC Converter With Active Clamped

A new active-clamped zero-voltage switching (ZVS) push-pull converter is proposed in this paper. Compared with the conventional push-pull converter, one auxiliary switch Q(3) and a clamping capacitor Ca are added in the primary side of the transformer to recycle the energy stored in the leakage inductors and clamp the voltage spike. Owing to the proposed converter which maintains ZVS of all the three switches from full load to very light-load condition, switching losses are reduced significantly. The voltage across the switch can be clamped at the input voltage plus the clamping capacitor voltage, i.e., V-in+V-Ca, are much less than those of a conventional push-pull converter that enabling the use of low-voltage, low-performance, and low-cost devices. In addition, the proposed topology can eliminate the problems of flux imbalance existing in the conventional one. Detailed operation, analysis, design, comparative study, and experimental results for the proposed converter are presented in this paper. An 800 W prototype was developed in the laboratory to evaluate and demonstrate the validity of the converter.