Light load oscillation problem analysis and suppression of two-switch buck-boost converter

The Two-Switch Buck-Boost converter (TSBB) has the advantages of low switching loss and wide voltage regulation range. It is widely used in various fields such as renewable energy system. TSBB will work in DCM state under light load. At this time, using three mode control method will cause oscillation problem. In this paper, the gain of TSBB in DCM state is derived. The output oscillation problem caused by the failure of gain realization with three-mode control method in DCM state is analysed. Finally, a control mode suitable for DCM state is proposed, which can achieve any required gain and solve the output oscillation problem. A 800-W prototype using TSBB+LLC-DCX topology is built to verify the proposed analysis and control method.