A new low loss power ferrite for 1-10 MHz power conversion

This paper describes the progress that have been made in developing improved power ferrites for high frequency use. This development project has two specific goals (1) develop a ferrite which can be operated at elevated flux densities in the 1-10 MHz range with acceptable loss (2) develop ferrites for 1.0 MHz or lower frequencies use which can be operated at much higher flux level than is possible with the currently available ferrites. We examine the loss mechanisms in ferrites on a more fundamental level than what has been done before. We develop a theory of nonlinear electric conduction in the ferrites which shed new light on the loss phenomena in soft ferrites. The theory is based on quantum mechanical tunneling through the insulating films between the ferrite and show excellent agreement with measured nonlinear conductivity. Based on this, a new loss mechanism "tunneling enabled magnetic loss" is proposed. This loss mechanism is able to account for all the observed loss behavior of the current ferrites as regards the dependence on the flux density, the core size as well as frequency. A new type of layered ferrite has been proposed and different parameters specified in such a structure. We have also devised ways to manufacture this type of ferrites.