The Design Optimization of the High-Frequency Planar Transformers for Electric Vehicle Chargers

Electric vehicle chargers can be divided into high-voltage DC (HVDC) system for charging power battery and low-voltage DC (LVDC) system for supplying low-voltage battery. Since the next generation EVs is getting smarter, they calls for chargers with higher power rating, higher power density and reduced loss which poses challenges for the LVDC systems design. In this paper, LLC resonant DC/DC converter is selected for HVDC system and two-stage converter with a Buck/Boost converter and an SRC converter is used for LVDC system. Circuit parameter design and high frequency (HF) planar transformer design are conducted for the aforementioned two kinds of converters respectively. For HVDC system, a transformer integrating resonant inductance and magnetizing inductance on a core is designed, and for LVDC system, a quarter-turn transformer is designed. The rationality and high efficiency of the two high HF planar transformer designs are verified by simulation and experiment results.