Capacitive Wireless Power Transfer System Applied to Low-Power Mobile Device Charging

Wireless Power Transfer (WPT) technologies are most popularly based on inductive coupling (IPT), using magnetic fields as transfer interface. Recently, studies have been published on capacitive coupling (CPT), through electric fields. CPT has small power density, due to low coupling capacitance, however, it also features reduced EMI shielding requirements, coupling through metal barriers, simpler coupling structure, lightweight and lower cost. This paper presents a mobile device charging application for the capacitive WPT technology. Using LC resonance, the system achieves 90% simulated efficiency with 5.7pF coupling capacitance. The power level for this application is 5W. 