High frequency resonant SEPIC converter with wide input and output voltage ranges

Abstract

This document presents a resonant SEPIC converter and control method suitable for high frequency (HF) and very high frequency (VHF) dc-dc power conversion. The proposed design features high efficiency over a wide input and output voltage range, up-and-down voltage conversion, small size, and excellent transient performance. In addition, a resonant gate drive scheme is presented which provides rapid startup and low-loss at HF and VHF frequencies. The converter regulates the output using an on-off control scheme modulating at a fixed frequency. This control method enables fast transient response and efficient light load operation while providing controlled spectral characteristics of the input and output waveforms. An experimental prototype has been built and evaluated. The prototype converter, built with two commercial vertical MOSFETs, operates at a fixed switching frequency of 20 MHz, with an input voltage range of 3.6 V to 7.2 V, an output voltage range of 3 V to 9 V and an output power rating of up to 3 W. The converter achieves higher than 80% efficiency across the entire input voltage range at nominal output voltage, and maintains good efficiency across the whole operating range.