High-Efficiency Class E, , and Inverters

This paper investigates the new Class EF₂ inverter and the already known Class E and E/F₃ inverters. The purpose of this paper is to find the answer to the question: what should be added to a classic Class E inverter to improve its performance with minimum expenditure? Class EF₂ and E/F₃ inverters meet this requirement through operating under zero-voltage switching and zero-voltage slope switching conditions (as in Class E) with improved transistor waveforms (as in Class F and 1/F). Selected results of a numerical analysis of Class E, EF₂ and E/F₃ inverters are shown and discussed. The analysis is aimed at maximizing the power output capabilities of these inverters for soft-switching conditions and fixed voltage and current stresses on their transistors as constraints. Measurement results of the Class EF₂ and E inverters are given to verify the validity of the presented theory. The measured output power of the inverters was 526 and 366 W with the total efficiency of 97.1% and 96.6% at 1 MHz, respectively