Novel S-Link Enabling Ultra-Compact and Ultra-Efficient Three-Phase and Single-Phase Operable On-Board EV Chargers

On-Board Chargers (OBCs) comprising an ac-dc front-end and a subsequent isolated dc-dc converter stage represent a crucial component of Electric Vehicles (EVs), and must be able to charge the EV battery from both, a three-phase mains and a single-phase mains. Further, a lightweight and compact realization of the OBC is key in mobile applications. This requirement for high gravimetric and volumetric power density is often hindered by the large (electrolytic) dc-link capacitor required to buffer the power pulsation at twice the mains frequency in single-phase operation, which can be omitted by employing an active Power Pulsation Buffer (PPB) circuit allowing to minimize the overall capacitor volume. This paper proposes a novel Smart-dc-Link (S-Link) concept which improves the OBC performance by utilizing the active PPB circuitry also in three-phase operation. There, the S-Link facilitates a six-pulse dc-link voltage variation enabling a substantial switching loss reduction in the ac-dc converter front-end, while advantageously the dc output voltage can be kept constant.