Analysis and design of resonant rectifier for high-frequency dc-dc converters

This paper presents an analysis and a novel design method of the resonant rectifier for dc-dc power converters operating in MHz frequency range. Compared to the conventional rectifier circuits such as a half-wave rectifier and a full-bridge one, the resonant rectifier features zero or low dv/dt at the turn-on and turn-off instant of the diode in the rectifier. Therefore, it significantly reduces undesirable oscillation of parasitic inductance and capacitance caused by high dv/dt and thereby provides benefits of lower noise and loss for MHz-frequency switching. In this work, we analyze the resonant rectifier where the inductor resonates with the junction capacitance of the diode, whereas most prior works use a large inductor as a dc current source. In addition, we propose the design scheme based on the analysis that the rectifier operates as an impedance inverter. The impedance inversion of the rectifier enables zero voltage switching (ZVS) and narrow-band frequency modulation of the converter for wide load ranges. Experimental results from a GaN-based prototype verify the feasibility and the effectiveness of the proposed design.

I. Introduction

There has been a continuous effort to increase the switching frequency of power converters. Various resonant converters have been studied to lower switching loss even at high switching frequency [1], [2]. The configuration of the resonant dc-dc converters considered in this paper is shown in Fig. 1: It consists of an inverter, resonant tank, and a rectifier stage. By the resonant operation, ZVS turn on of the inverter switch is achieved. Conventionally, for high-frequency ac-dc rectification, a half-wave rectifier or a full-bridge rectifier is generally used [1], [3]. However, the conventional rectifiers suffer from undesirable ringing attributed to parasitic inductance and the junction capacitance of the rectifier diode. This parasitic oscillation causes voltage spike at switching instants and increases switching loss and noise [4]. Furthermore, these problems deteriorate as the frequency increases to several MHz.