An Improved Single‐Stage Boost–Flyback PFC Converter Based on Magnetic Control

ABSTRACT Single‐stage boost–flyback power factor correction (PFC) converter often encounters challenges such as high voltage of the intermediate capacitor, low power factor (PF), and high total harmonic distortion (THD) of input current, especially when input voltage is high. To address the aforementioned challenges, an improved single‐stage boost–flyback PFC converter based on a magnetic control strategy is proposed in this paper by utilizing bias windings on two outer legs of the magnetic core, enabling modulation of inductance through the manipulation of inductor permeability by controlling bias current with different input voltages. To achieve unity PF and low intermediate capacitor voltage, continuous magnetic control (CMC) for the boost–flyback PFC converter is presented. For easier implementation of magnetic control with a smaller magnetic core, segment magnetic control (SMC) is proposed to further narrow the inductance range based on the CMC method. The paper researched the operational principle, control strategy, design considerations, and operational characteristics of the proposed converter. To verify the feasibility of the proposed magnetic control method, a 60 W boost–flyback converter experimental prototype with the SMC strategy is built and tested. The experimental results show that compared to the traditional boost–flyback PFC converter, the proposed SMC for the boost–flyback PFC converter can increase PF, decrease THD, and lower the intermediate capacitor voltage.