Forward-Flyback Integrated Converter With Voltage Clamping and Soft Switching

Recently, telecommunication, information and communication technology equipment, and cloud-based applications have gained more attention. The aforementioned applications all require an isolated step-down converter to convert power from the high-voltage dc bus. In this article, a novel isolated converter is proposed to fulfill the requirements of high-efficiency power conversion. The proposed converter is constructed with two coupled inductors connected in series with opposite polarity, two main switches and dc blocking capacitor on the primary side, and two output diodes on the secondary side. It can achieve soft switching for main switches and output diodes, while output current is shared between diodes without additional inductor on the secondary side for high efficiency. Finally, an experimental prototype is built to verify the theoretical analysis, with an input voltage of 400 V, an output voltage range of 36-48 V, and a rated power of 360 W. The highest efficiency reached is 96.6%.