A novel two-switch active clamp forward converter for high input voltage applications

A novel two-switch active clamp forward converter suitable for high input voltage applications is proposed. It consists of two main switches, one auxiliary switch, one clamping capacitor, and two clamping diodes. The main advantage of the proposed converter, compared to the conventional active forward converters, is that circuit complexity is reduced and the voltage stress of the main switches is effectively clamped to either the input voltage or the clamping capacitor voltage by two clamping diodes without limiting the maximum duty ratio. Also, the clamping circuit does not include additional active switches, so a low cost can be achieved without degrading the efficiency. Therefore, the proposed converter can feature high efficiency and low cost for high input voltage applications. The operational principles, features, and design considerations of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results from a prototype with 200 W, 375 V input, and 12 V output.