Third Harmonic Rejection-Based PFC Improvement for Single-Stage Flyback Converter

This study introduces a novel method for improving power factor (PF) and minimizing total harmonic distortion (THD) in single-stage critical conduction mode (CRM) flyback power factor correction (PFC) converters. The proposed approach utilizes a third harmonic rejection-based variable on-time control (THR-VOT) technique. By extracting the third harmonic component from the input voltage waveform, the method significantly enhances the sinusoidal nature of the input current, resulting in both a higher PF and a reduction in THD. The effectiveness and practical applicability of the proposed method are validated through theoretical analysis and experimental implementation on a 100 W CRM flyback PFC prototype controlled by an STM32F427 microcontroller. The experimental results reveal significant improvements in energy efficiency, verifying the method’s robustness. This control approach also stands out for its simplicity and cost-efficiency, making it a viable solution for active PFC in single-stage converters.