New modulation technique for hybrid softswitching and low duty ratio operation of active-clamped current-fed full-bridge isolated dc/dc converter

A new modulation technique for soft-switching active-clamped current-fed full-bridge isolated dc/dc converter is propsoed. Hybrid soft-switching of semiconductor devices, i.e. zero current switching (ZCS) of top switches and zero voltage switching (ZVS) of bottom switches of full-bridge (H-bridge) as well as auxiliary switch is achieved. Active-clamp circuit absorbs the turn-off voltage spike limiting the peak voltage across the semiconductor devices permitting the use of low voltage low on-state resistance devices as well as assists in achieving ZVS/ZCS of semiconductor devices. Rectifier diodes on secondary commutate with ZCS. Detailed steady state operation, analysis and design of the converter for the proposed modulation have been presented. An experimental converter prototype rated at 200W has been developed and tested in the laboratory to demonstrate the accuracy of analysis and operation employing the proposed new modulation, and check the converter performance. Use of low voltage Infineon OptiMOS and SiC schottky diodes achieve better performance and efficiency.