A Three Phase CLLC Converter with Improved Planar Integrated Transformer for Fast Charger Applications

Increased attention is being paid to the solid-state-transformer (SST) based charging station which favors a high efficiency high density DC/DC stage. A two stage DC/DC converter with planer magnetics which consists of a three phase CLLC converter and four phase interleaving buck converters is proposed to achieve a wide output voltage range from 200 V to 800 V. In this paper, the detailed analysis of integrated transformer of three phase CLLC converter is discussed. A novel core structure is proposed to replace the 6-leg planar transformer core which can reduce core loss by 28%. A 12.5 kW prototype with over 98.59 % peak efficiency and 180 W/in3 power density is built to verify the feasibility of the proposed core structure.