Design of A 27.12MHz Ultra-Compact High-Performance Capacitive Wireless Power Transfer System Using Stacked Inverter Architecture

This paper presents an ultra-compact high-performance capacitive wireless power transfer (WPT) system. The compactness of the system is achieved by operating the system at 27.12 MHz, which enables the use of small on-board air-core magnetics and shrinks the system overall size. However, the power level of single inverter operating at this frequency is limited. To enable the power scaled-up of the system, a stacked inverter architecture using multiple of 27.12 MHz inverter module is employed which achieves excellent power sharing against mismatches. This paper also presents a detailed topology comparison for the inverter module and design methodology for the capacitive WPT system that guarantees high performance by ensuring zero-voltage-switching of the inverter using air-core magnetics magnetizing inductance, and by solely using air-core magnetics leakage inductance forming the matching network inductor on the primary side. A prototype 27.12 MHz 12-cm air-gap capacitive WPT system is designed, built and tested, which transfers 500W without any discrete inductor on the primary-side and using discrete secondary-side inductor with only 25% of the size of the inductor used in the conventional 6.78MHz prototype.