GaN in Switched-Mode Power Amplifiers

Abstract

Radio-frequency (rf) power is important to a wide range of applications, including radio transmitters, plasma generation, medical imagers (e.g., MRI), power converters, and wireless power transfer (WPT) among myriad other applications. Advances in power semiconductor devices, magnetics, and circuit design are opening the door to much more efficient generation and delivery of power at radio frequencies. This chapter presents an overview of switched-mode power amplifiers – or radio-frequency inverters – encompassing their design, control, and construction. We focus on the high-frequency (HF, 3–30 MHz) and very-high-frequency (VHF, 30–300 MHz) ranges. We explore key aspects of rf power conversion, including power circuit architecture and design, selection and efficient drive of power devices at rf, and control methods for modulating power and managing load variations. We also address circuit construction, including the design and application of passive components at radio frequencies. Magnetics for power applications at HF and VHF pose a special challenge when compactness and high efficiency are desired. We explore the design of air-core and magnetic-core magnetics for this frequency range, including winding design, core material evaluation and selection, and application of magnetic cores.