A Constant Frequency ZVS Modulation Scheme for Four-Switch Buck–Boost Converter With Wide Input and Output Voltage Ranges and Reduced Inductor Current

Abstract

The pseudo continuous current mode (PCCM) four-switch buck-boost (FSBB) converter with negative valley inductor current is suitable for applications where zero-voltage-switching (ZVS) and voltage step-up and step-down are required. To improve its efficiency, many ZVS modulation schemes have been proposed to minimize the root mean square (RMS) inductor current. However, when both input and output voltage ranges are wide, the three-dimensional (3D) look-up table (LUT) with huge data quantity or the switching frequency with wide variation range is typically required in previous schemes. In this paper, a ZVS modulation scheme with constant switching frequency and simple real-time calculation is proposed. Only with a 2D LUT in a small range of input and output voltage, RMS inductor current can be minimized. Moreover, the switching frequency is constant with the proposed scheme. In addition, ZVS conditions, which are accurate and simple, are derived to facilitate the minimization of RMS inductor current. A 1500W FSBB prototype with input and output voltage ranges of 200-400V is built to verify the proposed modulation scheme and derived ZVS conditions.