Two-Switch Buck-Boost PFC Converter with Three-Mode Variable On-Time Control Strategy

In this paper, a two-switch buck-boost power factor correction (PFC) converter with three modes is proposed, which can improve the stability during mode switching due to the buck-boost transition mode. The converter operates in critical conduction mode (CRM) with variable on-time control (VOTC), achieving high power factor (PF) over a wide input range. The working principle of the three modes is analyzed, and the calculation of the control strategy is simplified by linear fitting method. The accuracy of the analysis results was tested by building a 100W experimental prototype.