Planar inductors of new structure are developed for miniaturized dc-dc converters. A thin air gap is introduced into the sandwich-structured planar inductors between a pair of magnetic plates, in one of which a meander coil is embedded. Due to the thin air gap introduced, the flux density in the magnetic plates becomes uniform, resulting in low iron loss. Planar inductors using NiZn ferrite thin plates were successfully applied to a 10 W-class buck converter operated at 2 MHz. The efficiency was higher than 82% and the effective volume of the inductor was 0.2 cm3(1 cm square and 2 mm thick).
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