Analytical and experimental demonstration of a high efficiency class EF inverter for VHF power conversion

This paper discusses a high-efficiency class EF (Φ) inverter that utilizes a modified input network instead of the conventional quarter-wavelength input transmission line. An analytical demonstration shows reduced in-line losses, and an experimental comparison of two 15 MHz, 40 W class EF inverters is conducted. The results indicate that the inverter’s overall efficiency reaches 91.8% with the new input network, which is 5 percentage points higher than the conventional class EF inverter under the same conditions. Additionally, experimental waveforms suggest that the new input network provides better drain-to-source voltage waveforms and slightly lower voltage stress compared to the conventional network.