Air-Core Inductors

Posted on by John Russell
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Project Overview

Today's power converters are large and inefficient because they are based on decades-old technologies and rely on expensive, bulky, and failure-prone components. Within the next 20 years, 80% of the electricity used in the U.S. will flow through these devices, so there is a critical need to improve their size and efficiency. MIT is teaming with Georgia Institute of Technology, Dartmouth College, and the University of Pennsylvania (UPenn) to create more efficient power circuits for energy-efficient light-emitting diodes (LEDs) through advances in 3 related areas. First, the team is using semiconductors made of high-performing gallium nitride grown on a low-cost silicon base (GaN-on-Si). These GaN-on-Si semiconductors conduct electricity more efficiently than traditional silicon semiconductors. Second, the team is developing new magnetic materials and structures to reduce the size and increase the efficiency of an important LED power component, the inductor. This advancement is important because magnetics are the largest and most expensive part of a circuit. Finally, the team is creating an entirely new circuit design to optimize the performance of the new semiconductors and magnetic devices it is using. This project is funded by the ARPA-e ADEPT program.

Microfabricated Air-Core Inductors

Air-core magnetics offer the advantage of avoiding the high losses most ferromagnetic materials contribute at very high frequencies. Although some air-core designs have high winding losses and produce external magnetic fields that are a liability for electromagnetic interference and induced power losses in nearby materials, toroidal configurations can be self shielding and can be designed for low losses. We are working towards two approaches: 1. Microfabricated air-core inductors on low-loss substrates; and 2. Silicon-embedded inductors. The collage shows various 3-D microfabricated inductors with inductances ranging from 0.05 to 0.7 uH. The inductor designs are compatible with flip-chip bonding technologies for integrated PowerSoc. In collaboration with MIT, Dartmouth college, and UPenn, we are currently evaluating these inductors in high-voltage high-frequency circuits.


Collaborations: MIT, Dartmouth College, University of Pennsylvania

Sponsor: ARPA-e

Inductor in Silicon

Publications

  1. X. Yu, M. Kim, F. Herrault, C.-H. Ji, J. Kim, and M.G. Allen, "Silicon-embedding approaches to 3-D toroidal inductor fabrication," Journal of Microelectromechanical Systems, in press.
  2. M. Araghchini, J. Chen, V. Doan-Nguyen, D.V. Harburg, D. Jin, J. Kim, M. Kim, S. Lim, B. Lu, D. Piedra, J. Qiu, J. Ranson, M. Sun, X. Yu, H. Yun, M.G. Allen, J.A. del Alamo, G. DesGroseilliers, F. Herrault, J.H. Lang, C.G. Levey, C.B. Murray, D. Otten, T. Palacios, D.J. Perreault, and C.R. Sullivan, "A technology overview of the powerchip development program," Transactions on Power Electronics,v 28, n 9, p 4182-4201, Sept. 2013. (PDF)
  3. J.K. Kim, F. Herrault, X. Yu, M. Kim, R.H. Shafer, and M.G. Allen, "Microfabrication of air core inductors with metal-encapsulated polymer vias," Journal of Micromechanics and Microengineering, v 23, n 3, p 035006 (7 pp.), March 2013. (PDF)
  4. J.K. Kim, F. Herrault, X. Yu, and M.G. Allen, "Microfabrication of air-core toroidal inductor with very high aspect ratio metal-encapsulated polymer vias," PowerMEMS 2012, p 30-33, Dec. 2012. (PDF)
  5. X. Yu, M. Araghchini, F. Herrault, J.K. Kim. J.H. Lang, and M.G. Allen, "Fabrication, modeling and performance analysis of silicon-embedded 3-D toroidal inductors," PowerMEMS 2012, p 58-61, Dec. 2012. (PDF)
  6. M. Araghchini, M. Kim, X. Yu, F. Herrault, M.G. Allen, and J.H. Lang, "Modeling and measured verification of loss in MEMS toroidal inductors," IEEE Energy Conversion Congress and Exposition (ECCE), p 3293-3300, Sept. 2012. (PDF)
  7. D.V. Harburg, X. Yu, F. Herrault, C.G. Levey, M.G. Allen, and C.R. Sullivan, "Micro-fabricated thin-film inductors for on-chip power conversion," 2012 7th International Conference on Integrated Power Electronics Systems (CIPS), p. 6ff, March 2012. (PDF)
  8. X. Yu, M.S. Kim, F. Herrault, C.-H. Ji, J.K. Kim, and M.G. Allen, "Silicon-embedded 3D toroidal air-core inductor with through-wafer interconnect for on-chip integration," IEEE International Conference on Micro Electro Mechanical Systems (MEMS), p 325-328, Jan. 2012. (PDF)
  9. Y.-K. Yoon, J.-W. Park, and M.G. Allen, "Polymer-core conductor approaches for RF MEMS," Journal of Microelectromechanical Systems, v. 14, n. 5, Oct, 2005. (PDF)