A novel asymmetrical dual switch forward converter employing resonant reset technique for soft switching

To overcome the duty ratio limitation issue existing in dual switch forward converter (DSFC) and improve efficiency, a novel resonant reset asymmetrical DSFC was proposed, which, compared with the former resonant reset DSFCs, maintains the advantage of lowering voltage stress on each switch, at the same time, possesses the merits as duty ratio can exceed 50% and conventional PWM operation capability. In addition, ZVS transition for all switches under all conditions is achieved while the auxiliary circuit is comparatively simple and cost effective: no modification was made on the original transformer component. Therefore, the proposed topology can achieve high power density, lower manufacturing costs and has strong capability for high line and wide range input industrial applications where high efficiency requirement is tense. The detail operation principles, as well as the design considerations, were presented. A prototype aiming at telecom system of 200 V-400 V input, 48 V output, whose highest conversion efficiency is 95.7%, was built to verify the validity and applicability of this topology.