Modeling and Design of Four-Switch Buck–Boost Converter With Combined PWM and Phase-Shift Control Scheme

The four-switch buck–boost (FSBB) converter has the functions of voltage step-up and step-down as well as positive output, which is suitable for the applications with wide input voltage range. With the combined pulsewidth modulation (PWM) and phase-shift control, all the power switches can realize zero-voltage switching with minimized inductor ripple. In this article, a small-signal model of FSBB converter with the combined PWM and phase-shift control is established. The small-signal characteristics of the power stage are analyzed, and the design method of the closed-loop parameters is proposed, ensuring the stability of the converter under all the operation conditions. Finally, a 420-W prototype of the FSBB converter is fabricated and tested in the lab. The experiment results verify the correctness of the small-signal model and the closed-loop parameter design method.