Design and Fabrication of VHF Tapped Power Inductors Using Nanogranular Magnetic Films

摘要

The design and fabrication of coupled inductors with low profile, low cost, and high power density for tapped-inductor high-step-down dc–dc power converters in the very-high-frequency (30–300 MHz) range are presented. The inductor consists of a multilayer thin-polyimide printed circuit board with nanogranular thin-film magnetic material deposited on both sides and on beveled cuts to form a fully linked closed core. The magnetic material Co–Zr–O has good soft magnetic properties, high resistivity, and high flux density capability. Multilayer Co–Zr–O/ZrO$_2$ thin films are used to improve the performance of the magnetic core. A winding loss model of this coupled inductor is presented. Coupled inductors with turns ratios 2 and 10 for several different converter applications have been designed, fabricated, and measured. Loss in the magnetic material is investigated. Small-signal and large-signal measurements show good performance of the fabricated components with high-frequency, high-field excitation.