Optimizing a Full-Bridge Capacitor-Clamped LLC Resonant Converter for EV Charging Considering the Effect of Leakage Inductance of the Auxiliary Transformer

The design of conventional LLC converters for Electric Vehicle (EV) battery charging applications is challenging due to the wide range of output voltage, current, and power levels required during different battery charging states. A novel circuit topology, known as the phase-shifted full-bridge clamped LLC resonant converter, has recently been proposed. It operates in a previously unexplored capacitive (instead of inductive) region of the conventional LLC converter while maintaining Zero-Voltage-Switching for all power switches. This new operating region offers new characteristics that can improve the system’s efficiency and power density performance. The study furthers the existing study of this new topology by exploring the impact of the leakage inductance of the auxiliary transformer on the converter's characteristics and proposing an optimization approach to achieve a smaller phase-shift angle range, thus realizing an even higher efficiency. The simulation and experimental results demonstrate the characteristics of specific charging points, providing valuable insights for the development of efficient and reliable EV charging systems.