Highly Efficient Capacitive Galvanic Isolation for EV Charging Stations

Abstract

This paper proposes an isolated Switched Capacitor (SC) power converter which provides galvanic isolation through Capacitive Power Transfer (CPT). The combination of these two technologies might answer for electrical and power requirements in different electrical mobility application fields, such as battery charging. Accordingly, due to the low conversion losses the combination of these two technologies can provide, compact, cost effective and highly efficient power converters can be derived, thus potentially answering the scalability requirements for the Electric Vehicles (EV) market. To assess the operation of the proposed circuital solution, a Full Bridge (FB) CPT isolated interfacing converter prototype has been designed and built. Since GaN switches were used for the primary bridge, by taking advantage of their low input capacitance and gate charge, a 500 kHz switching frequency was set, thus deriving a compact power converter. The prototype has been designed for applications up to 12 kW (600 V, 20 A), and tested close to 3 kW (up to 400 V or 15 A) for the purpose of this work to demonstrate its functionality. The measurements assessed a conversion efficiency above 90% with a peak of almost 95%.