T01.1 - High-Frequency DC-Transformer Design for High Power Density Phase-Modular On-Board Chargers

This work presents the design, implementation, and experimental validation of a high-power-density, bidirectional DC-transformer (DCX) for a phase-modular on-board charger (OBC) supporting grid-to-vehicle (G2V) and vehicleto- everything (V2X) operation. Three identical isolated DCX modules, each using 650V GaN transistors and operating above 600 kHz, are paralleled to deliver 11kW over a 250−450V battery range. An integrated planar high-frequency transformer with flux-canceling techniques reduces core volume and losses by ∼12% compared to a standard design. To suppress circulating currents from voltage or timing mismatches, a three-phase Current Equalizing Transformer (CET) is introduced, providing high differential-mode impedance while remaining transparent to zero-sequence currents. Main application and design aspects are presented, together with preliminary single-DCX experimental results demonstrating ZVS, high efficiency across the voltage range, and validating design choices.