Planar Permanent Magnet Biased Inductor with Improved Current Density Distribution

This paper presents a new type of planar inductor, biased with permanent magnets and presenting increased energy density for DC applications. The proposed design utilizes standard planar ferrite EI cores with no airgaps. The equivalent reluctance of an airgap is achieved by saturating a localized portion of the core. Due to the absence of physical airgaps, the fringing flux and its detrimental effects, on the winding's current density distribution, are minimized. The proposed inductor topology is analyzed using 2D FEA simulations. The physically implemented prototype is compared against a common non-biased inductor, with the same core and windings and using physical airgaps. Empirical laboratory measurements show that the proposed planar biased prototype achieves equivalent inductance, higher saturation current, and lower energy losses compared with the nonbiased reference.