A 4.21-kW Ultrathin 1.2-mm Stackable Capacitive Coupler for High-Efficiency MHz Capacitive Power Transfer

This paper presents a 1.2-mm-thick ultra-thin stacked capacitive coupler (SCC) that provides a lightweight and compact isolated power conversion interface for space constrained MHz high-power applications. Unlike conventional four-plate and six-plate capacitive couplers in capacitive power transfer (CPT) systems that rely on horizontally distributed electrodes, the proposed SCC introduces a vertically stacked multi-layer structure with independently insulated copper-foil plates, which suppresses nonadjacent cross-coupling effectively and significantly enhances the mutual capacitance. Its four-capacitor equivalent model is derived, and comprehensive voltage-stress and safety analyses are performed to guide plate arrangement and design at MHz frequencies. A 1-MHz SCC prototype achieves 4.21-kW peak power, 95.29% peak dc–dc efficiency, 99.87% peak ac–ac efficiency, and a power density of 83.16 kW/m² for the active capacitive coupling area, demonstrating excellent compactness and energy transfer capability. High frequency voltage and thermal endurance tests and FEM simulations further validate the SCC's reliability. Owing to its ultra-thin profile, high-voltage endurance, simple fabrication, and high power density, the proposed SCC serves as a promising modular power supply solution for compact power modular, transportation electrification and data center power supply.