Future of Bidirectional On-Board Charging: A comparative Analysis of CLLC and DAB topologies

Abstract:
Modern electric vehicles rely on on-board chargers (OBC) to provide fast and efficient charging when connected to the grid. Classical OBC implementations use a dual-stage conversion featuring a PFC rectifier plus a dc-dc converter. Dc-dc converters are often implemented using a resonant LLC structure which provides efficient power conversion. However, modern needs for bidirectional conversion have fostered the transition to bidirectional CLLC structures. In this context, the dual active bridge topology arises as a high performance and versatile implementation. While both topologies have benefits and drawbacks, it is far from trivial to establish a comparison between both topologies. This paper provides a comparative analysis considering efficiency and power density as figures of merit. The selected topology has been designed and experimentally verified, providing relevant engineering insights.