Improved High Step-Up Z-Source DC–DC Converter With Single Core and ZVT Operation

A previously proposed high step-up dc-dc converter based on Z-source circuit is improved such that conduction losses of the converter and current stress of its power switch are reduced. The improved converter contains only one magnetic core and all of the inductors are coupled. It is shown that using one core allows us to use windings with lower copper resistance that results in reducing resistive losses of the coupled inductors. Also, by rearranging two diodes of the converter, the switch current and its conduction loss are reduced. In addition, a previously proposed auxiliary circuit for zero-voltage-transition operation is employed with a minor modification that makes it possible to use a relatively large snubber capacitor that significantly decreases current-voltage overlap of the main switch at turn-off instant. Improvement in the overall efficiency of the presented structure over the existing high step-up Z-source converter is demonstrated by implementing a 100-W prototype of each converter for 30- to 300-V voltage conversion.