Princeton University

School of Engineering & Applied Science

High-Frequency Magnetics for On-Chip Power Conversion and Wireless Power Transfer

Charles Sullivan, Dartmouth College
B205 Engineering Quadrangle
Friday, January 11, 2019 - 11:00am


Magnetic components are essential for most power electronic circuits, but they are often the largest and heaviest components in a power converter, and are responsible for much of the power loss. Increases in switching frequency enabled by wide-band-gap semiconductors and advanced circuit designs can, in principle, reduce the size of magnetics, but high-frequency loss effects make this hard to realize in practice.  This talk will provide a brief survey of the challenges and potential solutions in this field and highlight two emerging technologies: high-power-density magnetics fabricated with MEMS-like processes on a silicon wafer, and high-quality-factor self-resonant structures for wireless power transfer.

Using nano-granular Cr-Zr-O magnetic material, we have demonstrated high efficiency inductors on silicon at power levels up to 25 W. The material’s uniaxial anisotropy and geometries that utilize it effectively will be described.  Although these have been successful, we have demonstrated the ability to deposit material with radial anisotropy, which enables superior geometries.

Wireless power transfer efficiency and range is constrained by the quality factor Q of the resonant transmit and receive coils used.  A new self-resonant structure has been demonstrated that not only avoids the need for separate coils and capacitors, but increases Q by a factor of six compared to similar conventional coils, to enable higher efficiency and range.




Charles R. Sullivan ‘87 is Professor of Engineering at Thayer School of Engineering at Dartmouth and a Fellow of the IEEE. He received a B.S. degree in from Princeton University in 1987 and a Ph.D. from the University of California, Berkeley in 1996. He has published over 190 technical papers and holds 42 US patents.  His research expertise includes modeling and optimization of magnetic components for high-frequency power conversion; thin-film magnetic materials and devices; and electromagnetic modeling of capacitors.  His techniques for modeling and optimization of high-frequency power magnetics are widely used by designers and researchers.


This seminar is supported with funds from the Korhammer Lecture Series