Low Device Count Three-Port DC-DC Converter Integrating Onboard Charger and Auxiliary Power Module for Light Electric Vehicles

Increasing the power rating of onboard chargers (OBCs) and auxiliary power modules (APMs) is constrained by cost and size. Integrating OBC with APM mitigates these challenges. This paper proposes a converter integrating OBC and APM using minimum active switches. The proposed integrated power converter (IPC) comprises two transformers and three bridge converters connected to DC-link of front-end rectifier, high voltage (HV) traction battery, and low voltage (LV) auxiliary battery. During OBC operation, simultaneous power transfer to HV and LV batteries leads to current cancellation, reducing RMS current in one of the bridge legs common for both power flow paths. Current cancellation and converter power loss depend upon IPC design parameters, which are turns ratio and leakage inductances of two transformers. This paper introduces three design approaches and compares IPC performance with these approaches analytically and experimentally. Additionally, a control strategy is suggested to ensure desired power flow across different power paths. A laboratory-developed prototype integrating 1 kW OBC and 350 W APM for a light electric vehicle is fabricated to validate IPC performance with three design approaches. In addition to reduced device count, proposed IPC achieves 0.7 % improvement in efficiency compared to its non-integrated version with similar circuit configuration.