T HIS paper explores opportunities and challenges in power conversion in the VHF frequency range of 30-300 MHz. The scaling of magnetic component size with frequency is investigated, and it is shown that substantial miniaturization is possible with increased frequencies even considering material and heat transfer limitations. Likewise, dramatic frequency increases are possible with existing and emerging semiconductor devices, but necessitate circuit designs that either compensate for or utilize device parasitics. We outline the characteristics of topologies and control methods that can meet the requirements of VHF power conversion, and present supporting examples from power converters operating at frequencies of up to 110 MHz.

This paper presents a new switched-mode resonant inverter, which we term the 8 2 inverter, that is well suited to operation at very high frequencies and to rapid on/off control. Features of this inverter topology include low semiconductor voltage stress, small passive energy storage requirements, fast dynamic response, and good design flexibility. The structure and operation of the proposed topology are described, and a design procedure is introduced. Experimental results demonstrating the new topology are also presented. A prototype 8 2 inverter is described that switches at 30 MHz and provides over 500 W of radio frequency power at a drain efficiency above 92%. It is expected that the 8 2 inverter will find use as a building block in high-performance dc-dc converters among other applications. Index Terms-Class E inverter, class-F power amplifier, class 8 inverter, harmonic peaking, radio frequency inverter, very high frequency, VHF power converter.

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This document describes several aspects relating to the design of dc-dc converters operating at frequencies in the VHF range (30-300 MHz). Design considerations are treated in the context of a dc-dc converter operating at a switching frequency of 100 MHz. Gate drive, rectifier and control designs are explored in detail, and experimental measurements of the complete converter are presented that verify the design approach. The gate drive, a self-oscillating multi-resonant circuit, dramatically reduces the gating power while ensuring fast onoff transitions of the semiconductor switch. The rectifier is a resonant topology that absorbs diode parasitic capacitance and is designed to appear resistive at the switching frequency. The small sizes of the energy storage elements (inductors and capacitors) in this circuit permit rapid start-up and shutdown and a correspondingly high control bandwidth. These characteristics are exploited in a high bandwidth hysteretic control scheme that modulates the converter on and off at frequencies as high as 200 kHz.

Abstract-This paper investigates the loss characteristics of rf magnetic materials for power conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor QL as a function of inductor current at rf frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of several commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The use of the method and data are demonstrated in the design of a magnetic-core inductor, which is applied in a 30 MHz inverter. The results of this paper are thus useful for design of magnetic components for very high frequency (VHF) applications.