Power transfer using portable surfaces in capacitively coupled power transfer technology

Abstract

Capacitively coupled power transfer (CCPT) uses electrostatic mechanism to deliver power from a stationary transmitter to a mobile receiver. The authors study various aspects of this technology including physical limitations that are encountered to increase power transfer. They characterise the impact of input voltage, dielectric area, and permittivity of the dielectric material in realisation of CCPT system. It is observed that the peak voltage and VA ratings of the capacitors are affected by the choice of the aforementioned parameters. Air as a dielectric medium leads to low power density. A high permittivity material instead of air dielectric can be used to improve power density. This strategy will make the CCPT technology non-contactless, because a physical contact exists between the transmitter and receiver. However, this contact is different from an ohmic contact. A high power density CCPT system is realised using ceramic dielectric surfaces. Issues encountered in system realization are discussed including automatic resonant frequency tracking. Detailed mathematical models under resonance and off-resonance operation are proposed. The models are validated using simulations and experimental results. A low cost multilayer ceramic capacitor (MLCC) based high power-density transfer surface is realised. Results show that 35 W can be easily transferred using a set of 12 mm2 capacitive surfaces and 32 V source.