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

The pseudo-continuous conduction mode 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 (3-D) look-up table (LUT) with huge data quantity or the switching frequency with wide variation range is typically required in previous schemes. In this article, a ZVS modulation scheme with constant switching frequency and simple real-time calculation is proposed. Only with a 2-D 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 1500 W FSBB prototype with input and output voltage ranges of 200-400 V is built to verify the proposed modulation scheme and derived ZVS conditions.

Automated summary

This article proposes a zero-voltage switching modulation scheme with constant switching frequency and simple real-time calculation to minimize the rms inductor current. By using a 2-D look-up table within a small range of input and output voltage, the proposed scheme achieves minimized inductor current. The derived zero-voltage switching conditions are accurate and simple, providing additional assistance in minimizing the rms inductor current.