In the July 2002 issue of Power Electronics Technology, author Michael W. Horgan, Magnetics Division of Spang & Co., Butler, Pa., discusses two different core types: distributed air gapped Molypermalloy Powder (MPP) toroids and gapped ferrite toroids.
Low-voltage/high-current requirements for microprocessors are driving the demand for low-height, high-power inductors used in compact power supplies. To meet this need, power inductors must provide up to 100 µH at a few amperes. Critical to achieving these extremely low height requirements is selection of the shape and type of soft magnetic core material used in these inductors.
Washer-shaped toroidal cores provide the required low height. One of the core materials available in the washer shape is distributed air-gapped MPP toroids with finished core heights down to 0.7 mm. The other low-height core material available for self-shielding power inductors is the gapped ferrite. In this article, Horgan compares the performance differences between these two core materials, with a goal of achieving finished component heights (including the coil) down to 1 mm.