Analysis and Experimental Validation of an Interleaved LLC Resonant Converter with Reduced Component Count

This paper presents an interleaved LLC resonant half-bridge DC-DC converter with lesser component count. Unlike most of the conventional interleaved LLC resonant converters, the proposed converter uses only one power transformer having two primary windings and one secondary winding. The primary windings of the transformer are fed in parallel via dual resonant tanks by operating the power switches of half-bridge network with interleaved half-switching cycle. Due to parallel feeding, core magnetization current divides equally between primary windings. Consequently, the effective value of magnetization inductance seen at each primary winding becomes twofold of the measured value. An equivalent circuit of converter is derived to validate this phenomenon. The gain characteristics of the equivalent circuit indicate that the maximum gain of converter occurs at relatively lower switching frequency than the conventional two power transformers-based interleaved LLC converters. Consequently, the proposed converter will have same operational characteristics at half magnetizing inductance. The validity of developed equivalent circuit and operational principle and performance of converter are confirmed by both simulation and experimental results of a 1000-W prototype. The experimental results show that for an input voltage of 400 V, converter has maximum efficiency of 96.24% at output power of 1000 W.