Accurate ZVS Analysis for Magnetic Design and Efficiency Improvement of Full-Bridge LLC Resonant Converter

This letter proposes a comprehensive zero-voltage switching analysis (ZVSA) to illustrate the commutation mechanism of full-bridge (FB) MOSFETs in resonant converters. Inherent contradiction between two conventional ZVSA techniques is discussed with specific consideration of a full-bridge LLC (FBLLC) resonant converter. An analytical approach is proposed to determine the accurate zero-voltage switching (ZVS) criterion for both zero-and finite-phase overlap operations of an FB network. Impact of the proposed ZVSA on power losses of FBLLC is explained analytically. Experimental results are presented not only to validate the proposed ZVSA, but also to validate its effect on FBLLC. Low load efficiency is improved by 6% with the proposed approach.