Variable Switching Frequency CCM for Boost PFC Converter with Permanent Magnet-Biased Ferrite Inductor

The demand for high efficiency and power quality in power electronics has made power factor correction (PFC) essential, particularly in single-phase AC–DC conversion. Among several topologies and control schemes, continuous conduction mode (CCM)-boost PFC converters are widely used due to their simplicity, especially in applications above 1 kW. A key component in this system is a boost inductor that must maintain high inductance at a large DC bias. Powder core materials, such as Kool Mu and MPP, are typically used due to their soft saturation and thermal stability, although they exhibit higher core losses than ferrite cores. Ferrite cores, while advantageous in terms of low core loss, suffer from hard saturation and limited DC bias characteristics. Permanent magnet-biased ferrite (PMF) inductors are introduced to address this problem. The saturation current of the inductor can be increased by shifting the B-H curve of the ferrite core. This paper presents a comparative analysis of powder core and PMF inductors of identical size in a 1.4-kW single-phase CCM boost PFC converter. Simulation and experimental results demonstrate that the PMF inductor retains higher inductance at peak current, enabling variable switching frequency control that reduces switching losses and EMI. The results demonstrate the potential of PMF inductors in high-efficiency single-phase PFC systems.