A Simple Seamless Switching Strategy for Four-Switch Buck-Boost Converter

The four-switch Buck-Boost circuit is well-suited for wide-range voltage regulation due to its unique structure. In conventional two-mode control strategy, mode transition occurs frequently when the output voltage is close to the input voltage, and its implementation is hindered by the duty cycle constraints of switching components. To address these issues, a seamless switching strategy is proposed in this article. This strategy utilizes single carrier dual modulation combined with double closed-loop control to achieve seamless three-mode switching between Buck, Buck-Boost, and Boost operating modes. The proposed strategy can effectively stabilize the output voltage when the input voltage changes and allow for smooth voltage tracking when the reference voltage changes. Besides, the single carrier dual modulation strategy is easy to implement in DSP. Finally, the simulation model was built in PLECS, and the feasibility of the seamless switching strategy were verified.