Push-Pull Class \Phi } RF Power Amplifier

• Published in: IEEE transactions on power electronics 2020-10, Vol.35 (10), p.10515-10531
• Main Authors: Gu, Lei, Zulauf, Grayson, Zhang, Zhemin, Chakraborty, Sombuddha, Rivas-Davila, Juan
• Format: Article
• Language: English
• Subjects: Harmonic analysis; Impedance; Inductors; power amplifiers; radiofrequency amplifiers; soft switching; Stress; Switches; switching converters; Tuning; zero current switching; Zero voltage switching
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2020.2981312

The Class \Phi _\text{2}/EF_{\text{2}} amplifier is an attractive topology for high-voltage and high-frequency power conversion because of the high efficiency, reduced device voltage stress, simplicity of gate driving, and load-independent ZVS operation. Due to many degrees of freedom for tuning, previous studies can only solve the single-ended \Phi _\text{2} circuit using numerical methods. This work focuses on improving the design and operating characteristics of a push-pull \Phi _\text{2} amplifier with a T network connected between the switch nodes, or a PPT \Phi _\text{2} amplifier. The PPT \Phi _\text{2} amplifier has less circulating energy and achieves higher cutoff frequency f_{T} than other \Phi _\text{2}/EF_{2} circuits. We, then, present a series-stacked input configuration to reduce the switch voltage stress and improve the efficiency and power density. A compact 6.78-MHz, 100-V, 300-W prototype converter is demonstrated that uses low-cost Si devices and achieves 96% peak total efficiency and maintains above 94.5% drain efficiency across a wide range of voltage and power. Together with the advances in wide-bandgap semiconductors and magnetic materials, the PPT \Phi _\text{2} circuit opens more possibilities for the state-of-the-art performance of solid-state RF amplifiers in high-frequency, high-power applications, including wireless charging for electric vehicles, plasma RF drives, and nuclear magnetic resonance spectroscopy.