Three-Switch Active-Clamp Forward Converter with Low Switch Voltage Stress

A conventional active-clamp forward (ACF) converter is a favorable candidate in low-to-medium power applications because of its simple structure and zero-voltage switching (ZVS) capability. However, high voltage stress on switches, i.e., sum of the input voltage and the reset capacitor voltage, does not make it suitable for high input voltage applications such as a front-end converter of which the input voltage is about 400-V_dc. To solve this problem, a three-switch ACF (TS-ACF) converter, which employs two main switches and one auxiliary switch with low voltage stress, is proposed. In addition, one of the main switches always ensure ZVS regardless of load conditions. Therefore, the proposed converter can be promising for high input voltage applications with high efficiency.