Extended Range ZVS Active-Clamped Current-Fed Full-Bridge Isolated Dc/Dc Converter for Fuel Cell Applications: Analysis, Design and Experimental Results

Abstract

This paper presents analysis and design of zerovoltage switching (ZVS) active-clamped current-fed full-bridge isolated dc/dc converter for fuel cells applications. The designed converter maintains ZVS of all switches from full-load down to very light load condition over wide input voltage variation. Detailed operation, analysis, design, simulation and experimental results for the proposed design are presented. The additional auxiliary active clamping circuit absorbs the turn-off voltage spike limiting the peak voltage across the devices allowing the selection and use of low voltage devices with low on-state resistance. In addition, it also assists in achieving ZVS of semiconductor devices. The converter utilizes the energy stored in the transformer leakage inductance aided by its magnetizing inductance to maintain ZVS. ZVS range depends upon the design, in particular the ratio of leakage and magnetizing inductances of the transformer. Rectifier diodes operate with zero-current switching. An experimental converter prototype rated at 500W has been designed, built and tested in the laboratory to verify the analysis, design and performance for wide variations in input voltage and load.