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.
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