Evaluation of magnetic materials for very high frequency power applications

This paper investigates the loss characteristics of several commercial rf magnetic materials forpower conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor Q_L as a function of inductor current at rf frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of different commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The results of this paper are thus useful for design of magnetic components for very high frequency applications.