The popularity of highly resonant, loosely coupled, wireless energy transfer systems operating at 6.78 MHz has increased dramatically over the last few years. In this paper we present the zero voltage switching (ZVS) voltage mode class D amplifier topology and evaluate its performance as a suitable A4WP Class-3 compliant amplifier using eGaN FETs and compare the performance with MOSFETs.

Experimental verification has revealed that the ZVS class D amplifier can inherently drive a reflected load impedance range from +20j Ω though -30j Ω and 1.7 Ω through 57 Ω while maintaining A4WP Class-3 compliance, which is a significantly wider range than any other topology explored as of this date. The eGaN FET based amplifier was found to have 30 % lower losses and operate as much as 17°C cooler when delivering 16 W into the load than a MOSFET version.

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