An Unbalanced Capacitor Voltage Buck Converter With Wide Soft Switching Range

DC–DC converters using soft switching technology have gained popularity in several industrial applications. Nevertheless, a wider soft switching range and a simpler structure are the holy grail for these converters. In this article, an innovative unbalanced dc-link capacitor voltage buck converter with a broad soft switching range has been proposed. The converter uses an auxiliary switch and a small inductor to create an auxiliary network that enables zero voltage switching (ZVS) for the buck switch. The auxiliary switch turns on under zero current switching, whereas the main buck switch operates under ZVS with reduced dv/dt. Unbalanced voltage of a series-connected dc-link capacitor is intended to boost the soft switching range of the buck converter for a broad range of loads by lowering the resonant voltage to less than half the input voltage. LTspice simulations of the converter operating with a power load of 1 kW and a switching frequency of 100 kHz have been demonstrated and the efficiency of the topology based on silicon carbide MOSFET has been discussed. Compared with the traditional hard switching buck converter, the proposed converter reduces total losses by 50% and improves the light-load efficiency to 91.3% from 88.5% and the full-load efficiency to 97.5% from 94.5%. Finally, a 1 kW prototype has been designed and tested to validate the theoretical ideas including the closed-loop control strategy for the converter.

I. Introduction

Buck converter is one of the most well-known dc–dc converters, which is frequently used to produce step-down dc voltage or schedule power flow. This type of converter has been found in widespread applications, including renewable energy storage systems, general industries, electric vehicles, and distributed generation systems [1], [2]. Lightweight, small size, minimal losses, and high reliability are the desired characteristics for dc–dc buck converters. High switching frequency converter topology is a recommended candidate to improve the power density due to the reduced size of passive components and smaller ripple currents [3]. However, high switching frequency exhibits higher switching losses, and high dv/dt and di/dt result in excessive electromagnetic interference as well as switching off voltage spikes and switching on current spikes [4], [5].