Four switch buck-boost converter has been widely used because of its bi-directional and wide step-up and step-down voltage conversion capabilities. With the quadrangle current modulation (QCM) method [1], the converter can achieve zero voltage switching, but the existing QCM approaches impede the wide adoption of FSBB due to their implementation complexity.[2] A simplified control method has been proposed in this paper, which can be fully implemented in digital controllers without zero current detection. Meanwhile, to aid the compensator design, a small signal model was proposed under QCM operation. The proposed small signal model shows a good agreement with the simulation results in the frequency domain. A SiC MOSFET-based 50kW, 900V input, and 500V-1000V output FSBB converter were built to verify the proposed control scheme and the small-signal model.
