A Three-phase CLLC Resonant Converter with Integrated Planar Magnetics for 22-kW On-board Chargers

In response to the growing demand for higher power and reduced volume, 22-kW on-board chargers incorporating integrated planar magnetics are increasingly gaining traction. Among the preferred solutions for the high-power DC-DC conversion stage are three-phase CLLC converters, valued for their inherent isolation capabilities and exceptional efficiency. Despite their advantages, several challenges persist under this evolving paradigm. The first challenge pertains to integrating the resonant inductance directly into the transformer to achieve higher power density. This integration is critical for optimizing space and performance. Secondly, the elevated power levels introduce significant current stress, necessitating innovative approaches to manage and mitigate this stress effectively. This paper delves into the integration of planar inductors and transformers, focusing specifically on winding structures designed to minimize winding losses. Through comprehensive analysis and development, we present a novel three-phase planar transformer with built-in resonant inductance. This transformative design is tested and validated within a 22 kW CLLC resonant converter. The empirical results demonstrate the converter's impressive capabilities, achieving a power density of 30.7kW/L and a peak efficiency of 98.2%. These findings underscore the efficacy of planar devices and transformers in enhancing performance metrics.