A Novel Design for a 22kW Transformer for a 3 Phase Full Bridge LLC EV Onboard Charger for Smaller Size, Lower Cost and Improved Performance

Abstract:
As power levels increase, powertrain system engineers are already moving to a three-phase full bridge LLC topology but this in turn brings challenges for heat dissipation and symmetrical operation of the transformer. These challenges have limited the performance of existing magnetic integrations. A novel transformer construction for symmetrical operation is presented that also reduces the size and cost compared to the multi transformer approach. This paper introduces the concept and presents the finite element modelling (FEM) and SPICE results used to optimize the design. Finally, the concept is validated through prototyping and evaluation in a 22kW on-board charger (OBC).