Adaptive Charge-Compensation-Based Variable On-Time Control to Improve Input Current Distortion for CRM Boost PFC Converter

For boost power factor correction (PFC) converters operating in critical conduction mode (CRM), charge compensation strategies are utilized to improve input current distortion. However, since massive calculations are required under complex working conditions, it is difficult to achieve accurate charge compensation with limited real-time computing resources. To solve this issue, this paper proposes an adaptive charge-compensation-based variable on-time (ACVOT) control strategy. The ACVOT controller calculates the required switching on-time by adding a fundamental value and an extended on-time. The fundamental value is adjusted by the loop compensator in each half-line cycle to provide a basic bias. The extended on-time is calculated based on partial charge compensation equation in each switching cycle to reduce the distortion. Compared with conventional digital variable on-time (VOT) control, the proposed strategy improves the input current total harmonics distortion (THD) and reduces the LUT/register resources by 54%/43% in FPGA realization. To verify the effectiveness of the proposed strategy, a 200 W prototype is built using the GaN HEMT transistor, where the THD is reduced to 1.4% at full load.