Concepts and Matching Power Semiconductor Devices for Compact On-Board Chargers

The growing popularity of electric vehicles has led to more demanding requirements for on-board chargers (OBCs) in terms of size and efficiency as well as functionalities, e.g. world-wide compatibility and bi-directionality. The state-of-the-art solution of OBCs is a phase-modular design which comprises a large number of components and is thus inherently limited in the achievable power density. The next generation of OBCs are therefore true three-phase topologies like the B6/B8 topology featuring 1200V-rated SiC MOSFETs which can be merged into a unified topology for single- and three-phase compatibility. Further power density improvements demand a transition towards multi-level topologies with 600V-rated GaN HEMTs which allow to break the performance barriers of classic 2-level topologies. This is derived for the PFC and the DC/DC stages based on fundamental scaling laws as well as Pareto optimizations of the employed passive components. As an outlook for further power density increases, on the one hand the concept of the non-isolated OBC, and, on the other hand, the single-stage power conversion enabled by monolithic bi-directional GaN HEMTs are described.