Wireless electric vehicle charging via capacitive power transfer through a conformal bumper

Wireless power transfer (WPT) is emerging as a practical means for electric vehicle (EV) charging. Of the three main approaches to WPT, resonant inductive, inductive, and capacitive coupling, capacitive power transfer (CPT) is proposed herein to charge an EV at a kilowatt scale power level. CPT implementation replaces copper coils and ferrous core focusing/shield materials of inductive approaches with foil surfaces making CPT cost effective and structurally simple to implement, while maintaining efficient power transfer capability. This paper addresses each facet of kilowatt scale CPT system development, namely achieving high coupling capacitance between the vehicle and charging station and the associated drive power electronics. High capacitive coupling is achieved through a conformal (flexible and compressive) foam transmitter bumper that molds and contours itself to the vehicle to minimize air gap during charging. An experimental docking station to charge a Corbin Sparrow EV 156V battery pack was built and measured throughput power is demonstrated at >1kW with a coupling capacitance of 10nF operating at 540kHz.