Multi-level active clamp forward converter with reduced voltage stress

A conventional active-clamp forward converter is a favorable candidate in low-to-medium power applications. However, the switches suffer from high voltage stress, i.e., sum of the input voltage and the reset capacitor voltage. Therefore, it is not 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 new multi-level active-clamp forward converter is proposed in this paper. In the proposed converter, the voltage stresses on switches are clamped to either the input voltage or the reset capacitor voltage by simply utilizing one clamping diode and adjusting gate signals. Utilizing low-voltage rated switches, the proposed converter features high efficiency and low cost for high input voltage applications. The operational principle and design consideration of the proposed converter are presented, and verified experimentally.