An Improved Single-mode Control Strategy Based on Four-switch Buck-Boost Converter

Based on the needs of power processing unit (PPU) in space propulsion system, this paper analyzes the application of four-switch Buck-Boost converter (FSBB) in this field. In terms of FSBB's control strategies, the traditional single-mode strategy is low efficiency. While the two-mode strategy's control loop is relatively complicated. What's more, near the two modes' switching point, the converter will continuously switch between the Buck and Boost modes, which is not conducive to the stable operation of the system. So this paper proposes an improved single-mode control strategy. By fixing the switches' duty cycle of the Buck unit and controlling the duty cycle of the Boost unit, FSBB is enabled the function of buck-boost only in Boost mode. Also, an 80-160V input and 125-250V output prototype was built in the laboratory to verify the proposed strategy.