Lossless Snubber Cell for a Soft-Switched Bidirectional Buck–Boost Converter

Hyung-Ik Joo,Sang-Kyoo Han

doi:10.1109/access.2020.3022397

Hyung-Ik Joo, Sang-Kyoo Han

Open Access

https://doi.org/10.1109/access.2020.3022397

Copy DOI

Abstract

In this paper, we propose a lossless snubber cell for a soft-switched bidirectional buck-boost converter (BBC). The proposed snubber cell provides all switches with soft-switching conditions in both the bidirectional power flows of the BBC. In addition, the cell also achieves a relatively low circulating current for the snubber operation over a wide load range. In particular, the reverse recovery problem of the synchronous rectifier can be eliminated with the aid of the snubber inductor. Accordingly, the snubber cell enables high-frequency switching of approximately 60 kHz for all power switches and achieves high efficiency and high power density. Moreover, the proposed snubber cell does not have any auxiliary switch; therefore, complex auxiliary circuits or driving algorithms for the auxiliary switch are not required. Therefore, the proposed snubber cell has a simple structure with high reliability. To confirm the validity of the proposed lossless snubber cell, we provide detailed analyses, design guidelines, and experimental results using a 3-kW laboratory prototype.

Highlights

Battery-fed bidirectional dc-dc converters have been widely used in various applications such as wind power, photovoltaic systems, fuel cells, energy storage systems, and electric vehicles [1]–[6]
The proposed snubber cell does not require any auxiliary switch, and it can help all the switches of a buck–boost converter (BBC) to operate under softswitching conditions, such as zero voltage switching (ZVS) and zero current switching (ZCS), over a wide load range
EXPERIMENTAL RESULTS The prototype of the BBC equipped with the proposed snubber cell was implemented using a two-phase interleaved BBC

Summary

INTRODUCTION

Battery-fed bidirectional dc-dc converters have been widely used in various applications such as wind power, photovoltaic systems, fuel cells, energy storage systems, and electric vehicles [1]–[6]. Han: Lossless Snubber Cell for a Soft-Switched Bidirectional BBC Because of these losses, high efficiency is difficult to achieve, and power density decreases due to the limitations of increasing the switching frequency. The most effective way of increasing the efficiency in high-frequency power converters is to decrease or eliminate the switching losses of the transistors using soft-switching techniques These problems can be overcome using either the SiC field-effect transistor (FET) or the GaN FET, which are the wide bandgap (WBG) devices currently in the spotlight. The proposed snubber cell does not require any auxiliary switch, and it can help all the switches of a BBC to operate under softswitching conditions, such as zero voltage switching (ZVS) and zero current switching (ZCS), over a wide load range.

PROPOSED CIRCUIT AND OPERATION ANALYSIS

CHARGING MODE

TURN RATIO OF THE COUPLED INDUCTOR

CLAMP CAPACITOR Cc

EXPERIMENTAL RESULTS