A Series-Input Forward Converter with Shared RCD Cell for High-Reliability and Wide Input Voltage Range Applications

An interleaved forward converter, adopting the series-input series-rectifier structure with a shared RCD reset branch, is proposed in this paper. Only one RCD branch is shared by two forward cells as a common transformer reset circuit. The duty ratio of each forward cell can exceed 50%, as a result, the effective duty ratio of the two cells can be more than 100%, which makes the proposed converter suitable for wide-voltage-range application. Compared with the conventional RCD reset single switch forward converter, it maintains the merits of low voltage stress on the main switches, high efficiency because only part of the magnetizing power is dissipated by the reset resistor, and the voltage across the reset capacitor is lower as well. All these features make the proposed converter promising for wide-input-voltage applications with high reliability, high efficiency and a simple structure. Operation principles and characteristics are given in detail and verified with a 200W prototype.