Research on two-stage isolated on-board charger and control technology

A two-stage isolated on-board charger (OBC) is proposed for electric vehicles. The OBC adopts two-stage topology including three-phase power factor correction (PFC) converter and full-bridge LLC resonant converter. The OBC can charge the high voltage battery and achieve power factor correction function. Compared with the conventional control circuit, the pre-stage PFC circuit adopts current inner loop composite controller, the composite controller is composed of a repetitive controller and a proportional and integral (PI) controller connected in parallel, which can reduce the total harmonic distortion (THD) of the input AC current. The rear-stage adopts full-bridge LLC resonant converter operates with zero-voltage switching in the full output voltage range. The main parameters of the pre-stage PFC circuit and the rear-stage circuit were designed, the OBC has an input AC voltage range between 187-253 V, and the output DC voltage range between 280-420 V. Simulation and experimental results confirm the correctness of the theoretical analysis.