Coupled-inductor-based high-gain converter utilising magnetising inductance to achieve soft-switching with low voltage stress on devices

Abstract

This work proposes a soft-switched quadratic quadrupler boost converter with high voltage step up gain and low voltage stress on devices. With this converter topology, high voltage gain is achieved at low duty ratio operation of MOSFETs and few number of turns in coupled inductor. Operation at low duty ratio keeps boost converter gain in linear region and smaller number of turns in coupled inductor reduces the lossy part of the winding. Further, the magnetising inductance of coupled inductor is utilised to achieve zero voltage switching of MOSFETs to minimise the switching loss. In addition, secondary side diodes are operating under zero current switching conditions using resonance between leakage inductance and the capacitors of voltage quadrupler circuit. This greatly reduces the reverse recovery losses of the secondary side diodes. A detailed analysis of converter dynamics is discussed in one of the subsections to find out small-signal transfer functions with respect to variations in input voltage and duty ratio variation of MOSFETs. A 250 W prototype of the proposed converter is built and tested in laboratory with a maximum efficiency of ∼93% at 175 W output power.