A Non-Ecap Wide Range Bidirectional OBC With Multifunction Circuit

The rapid growth of Electric Vehicles (EVs) with larger battery capacities and integrated Vehicle-to-Everything (V2X) applications is accelerating the demand for high-power Bidirectional On-Board Chargers (BOBCs). Conventional BOBC architectures, typically based on Frequency Controlled (FC) CLLLC converters with large Electrolytic Capacitor (E-cap or Ecap), face three critical limitations: 1) low power density and short lifetime of E-cap; 2) complex resonant tank design requiring dual resonant networks for bidirectionality in addition to low inductance ratio for voltage regulation purposes, and 3) high MOSFET turn-off current at the CLLLC stage that elevates switching losses, voltage overshoot, and reliability risks. While active Power Decoupling (PD) concepts have been proposed to mitigate E-cap issues, these solutions often require high capacitance, are only partially utilized in 3-phase mode, and still face reliability challenges in the isolated stage. This paper introduces a novel BOBC architecture featuring a Multi-function Circuit (MC) placed between the AFE and isolated stage. The MC simultaneously performs power decoupling and charging current regulation, enabling the isolated converter to operate purely as a DC transformer (DCX) for galvanic isolation. This MC-DCX approach eliminates bulky E-cap, reduces semiconductor stress, simplifies resonant tank design, improves system reliability, and enhances scalability to both 400V and 800V platforms. A detailed comparison at 22 kW shows lower switching losses, reduced resonant capacitor stress, and improved reliability versus conventional CLLLC designs. The proposed BOBC, integrated with an Auxiliary Power Module (APM) into a compact Integrated Dual Charging Module (IDCM), supports universal grid with 11 kW 1-phase and 22 kW 3-phase charging. Experimental validation confirms the feasibility of the concept. This paper is among the first to provide a systematic comparison of MC-DCX with FC-LLC at the 22 kW level, offering valuable guidance for academic and industrial as BOBCs transition toward higher voltage, higher power, and wider operating ranges.