Wide Range Dual Switch Forward-Flyback Converter with Symmetrical RCD Clamp

This paper proposes a wide range dual switch forward-flyback with current-doubler rectifier (CDR) converter which adopts staggered clamp structure with two symmetrical RCD type circuit. It overcomes the shortcoming that duty ratio cannot be more than 50% of conventional dual switch forward converters. Compared with the conventional single switch active-clamp forward-flyback converter with CDR, it maintains the advantages of wide voltage input and high efficiency, moreover, reduces the voltage stress of main switch to half of the former in a relative low cost and simple structure. The improved symmetrical RCD clamp structure are also recommended to be used in dual switch forward converter for high and wide range voltage input application, which is a kind of slight dissipative type clamp circuit for it enhances the magnetic reset efficiency greatly compared with conventional RCD clamp circuit. The principle of operation and characteristics of the novel converter are verified on a 200 V-400 V input and 9.5 V/15 A output experimental prototype