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

Fig. 1. Topology of proposed DCDC converter.
  Fast charging technology is a key feature that could attract customers to purchase an elec-trical vehicle instead of a gasoline-driven car. For the charging stations, solid-state-transformer (SST) based charging station have drawn increasing attention which requires a high efficiency high power density DC/DC stage to provide universal charging for all EVs no matter their battery voltage is 400V or 800V. A two-stages DC/DC converter consisting of a three phase CLLC converter and four phase interleaving buck converters could meet the wide output voltage range as shown in Fig. 1.
  For the three phase CLLC DC/DC converter, it can run at high switching frequency so that the resonant inductors and transformers of three phases can be integrated into one six-leg core and built with PCB windings with the benefits from SiC devices as shown in the structure 1 of Fig.2. However, the core loss on the plate is still large due to the flux on the plate is not evenly distributed. A novel core structure based on the six-leg integrated transformer will be proposed to reduce the core loss of core plate by adopting additional legs without sacrificing the footprint of core as shown in the structure 2 of Fig. 2. Detailed analysis of the new core structure and comparison will be shown in the final paper. The peak efficiency of the proposed converter can be expected to 98.59% and its power density is up to 180W/in3. The detailed experiment results will be provided in the full paper.
Structure Comparison.
Fig. 2. Structure Comparison.

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