Current Harmonics Analysis and Design for Load-Independent ZVS Single-Switch Resonant DC/DC Converter

This article presents a new design theory named
current harmonics analysis
(CHA) for designing load-independent zero voltage switching (LI-ZVS) single-switch resonant dc/dc converters. Compared to the traditional
V
_DS

shaping analysis
method, the proposed CHA adopts frequency-domain harmonic analysis to eliminate the mathematical iterations and improves ZVS load variation range. The relation between circuit parameters and LI-ZVS characteristics is investigated and discussed. A step-by-step design procedure is developed for the proposed method. Furthermore, the
V
_DS
stress is investigated for better engineer practices and its alleviation method without degradation on ZVS feature is proposed and implemented. At last, to validate the design theory, a prototype with single-switch parallel resonant topology, operating at 20-MHz switching frequency for lithium battery chargers is designed, implemented, and verified experimentally. The measured results show a ZVS operation characteristic with a load variation range of 100 times by employing the proposed CHA method, while achieving a conversion efficiency of 92% in a wide load range. To the best of the authors’ knowledge, it is the widest ZVS load variation range compared to previously reported converters.