Fine grained ferrite for low profile transformer

A Mn-Zn ferrite with fine grain size and low core loss at 0.5 to 2 MHz was developed, and a conductor-embedded-type planar transformer was made using the developed ferrite. The Bm/spl middot/f value in the loss level of 400 kW m/sup -3/ of the developed ferrite at f=1 MHz is 2.2 times larger than that of the commercial ferrite. The efficiency and the output power of the conductor-embedded-type planar transformer were 91% and 1.8 W, respectively.