Reduction of Alternating‐Current Resistance and Heat Generation of Spiral Inductors with Magnetic Sealing Technique

Abstract

As direct current-direct current (DC-DC) converters increase their power density, their inductors require a planar structure with good heat dissipation. Planar inductors use rectangular wires or substrate patterns for their windings. Winding structures can be stacked, in which the structures are on top of each other; spiral, in which the windings are configured in the same plane; or composite structures of both. Here, the authors clarify the alternating-current (AC) resistance of inductors with different winding structures and propose a magnetic sealing technique (MST) that reduces the AC resistance of low-profile spiral inductors. Magnetic field simulation revealed the effect of MST on the AC resistance and inductance. Furthermore, spiral inductors with MST were fabricated, and the AC resistance reduction effect of MST was confirmed with impedance analyzer. The heat-generation reduction effect in an MST inductor was demonstrated in a 1-MHz 100 V/320 V 800-W boost DC-DC converter prototype with GaN devices.