Experimental Analysis of GaN-Based Half-Bridge LLC Resonant Converter with Enhanced Efficiency through Resonant Tank Optimization

The increasing demand for compact, efficient, and cost-effective power conversion systems across sectors such as renewable energy, industrial automation, and telecommunications has highlighted the need for high-performance DC-DC converters. This paper presents the design, implementation, and experimental validation of a 500 W half-bridge LLC resonant DC-DC converter for 63-75 V input and a regulated 14.5 V output. A key feature of the design is resonant-tank optimization to maintain inductive-region operation and allow soft switching, with experimental evaluation of the soft-switching margin that identifies where ZVS degrades near high-load operation. The incorporation of GaN FETs allows 100 kHz operation with peak efficiency above 90%, and a controlled GaN-versus-MOSFET comparison on the same platform under identical conditions shows a load-dependent efficiency improvement that increases toward higher output power, ranging from approximately 1% to 10%. Practical high-frequency hardware effects, including gate-drive and auxiliary-winding oscillations, are characterized and mitigated using a simple decoupling-and-gate-tuning approach. In addition, an adaptive protection framework is integrated, including configured input over- and under-voltage thresholds and multi-level over-current protection, to provide safe operation. Experimental validation through efficiency measurements and dynamic-load testing confirms stable behaviour over the tested operating range.