Comparing the Class E and Φ2 Inverter Topologies for 13.56MHz Resonant Capacitive Power Transfer

Abstract

The class E and Φ2 inverter topologies are compared in the context of a load-independent 13.56MHz resonant capacitive power transfer (RCPT) system intended for electric vehicle charging. In addition to efficiency and power capacity, radiofrequency emissions are evaluated based on the harmonic content of the voltages presented to the transmit resonator. Both inverters deliver over 1kW to the transmit resonator while maintaining system-level load independence. While the class E implementation is more efficient, the class Φ2 inverter offers solid performance and a significantly reduced second harmonic, making it desirable from an electromagnetic compatibility standpoint.