A Novel Hybrid Operational Mode Wide Range Input ZVS Front-end Dc-Dc Converter Aiming at Optimized Overall Performance

A novel wide range input front-end dc-dc converter featuring in optimized overall input range efficiency is presented in this paper. This proposed converter combines the two kinds of dual switch ZVS forward-flyback topologies together, while the DC Gain for these two kinds of forward-flyback topologies is different and that of secondary full-bridge rectifier is doubled than current-doubler rectifier. Therefore the proposed converter has an extended duty cycle under high-line condition which results the improved high-line efficiency while maintaining the low-line conversion ratio. By the assistance of a micro controller unit and the supporting shifting circuits, the proposed converter can automatically shifts its internal topology configuration on-line to be the most efficient according to the input region which the current voltage falls into. Moreover, the ZVS feature for the primary switches is enabled by a high efficiency saturable reactor. The detail operation principles, as well as the design considerations, were presented. A prototype suitable for server system of 200V-400V input, 48V/5A output, whose high-line efficiency is improved by 2% compared with the conventional wide range input converter, was developed to verify the validity and applicability of this converter.