Permanent Magnet Hybrid Core Inductors for High Saturation Capability

Abstract

Inductor designs with large dc current relative to ac ripple are often saturation-limited, but these designs also often greatly underutilize the core material's flux carrying capabilities. Instead of using the full flux swing range from reverse saturation to forward saturation, these designs typically only use half the range. To use the full range, we propose a permanent magnet (PM) hybrid core in which a PM provides a dc flux offset in the core while being placed outside of the main winding flux path. In this work, we derive first-order theory for analyzing and designing the PM hybrid core. We then demonstrate a working proof-of-concept prototype using off-the-shelf parts. This prototype outperforms a comparable ferrite inductor design by achieving the same energy storage at half the dc resistance, thus demonstrating the potential benefits of the PM hybrid core.