modelling and analysis of Planar Magnetics devices

Maeve Duffy, Prof. W. G. Hurley

Planar magnetics is a relatively new concept which describes the development of microfabrication technologies to produce miniaturised inductors and transformers. As a recent development, the design of miniaturised structures lacks in the formulation and standardisation which has been established for conventional magnetic design. Furthermore, since miniaturisation is achieved through high frequency operation of devices, a number of additional high frequency effects contribute to complication the design procedure. In this thesis, new models for the impedance of planar spiral structures are presented in terms of frequency dependent components of inductance, resistance and capacitance. Solutions are derived directly from Maxwell’s Equations for electromagnetic field distributions under high frequency conditions.
Three different structures are investigated: planar windings in air, planar windings on a magnetic substrate and a planar sandwich structure. In all cases, filamentary formulas are derived to describe the impedance to elementary currents flowing within the finite sections of planar turns, and total impedance is predicted by integrating over total current flowing. Non-uniform current densities are applied to describe the variation in impedance over the section of the turns. In the cases of planar windings with magnetic material included, previous models are improved by accounting for the conductivity of the materials in addition to their permeability values. In this way, the contribution of eddy current losses induced in the volume of the materials are incorporated in the models. Solutions are provided for regions of both infinite and finite extent.
The accuracy of the new models proposed is verified by comparing predicted impedance values with those predicted by simulation in a Finite Element Analysis (F.E.A.) system. Individual models for inductance, resistance and capacitance are also combined in a complete circuit model to predict the frequency response of prototype planar structures fabricated in thick film technology. The results are verified over a frequency range from dc to the first position of resonance.

Start date: 1st of September 1992. This project has been completed.

Project Publications

Journals
J. Lu, H. Jia, A. Arias, W.G. Hurley, Z.J. Shen, “Modeling, Design, and Characterization of Multi-turn Bondwire Inductors with Ferrite Epoxy Glob Cores for Power Supply System-on-Chip or System-in-Package Applications”, IEEE Trans. on Power Electronics, vol.  25, no. 8, pp. 2010-2017, August 2010.
W. G. Hurley, M. C. Duffy, S. O'Reilly, S. C. O'Mathúna, "Impedance Formulas for Planar Magnetic Structures with Spiral Windings", IEEE Trans. on Industrial Electronics, vol. 46, no. 2, pp. 271-278, April 1999.
S. O'Reilly, S. C. O'Mathúna, M. C. Duffy, W. G. Hurley, "A Comparative Analysis of Interconnection Technologies for Integrated Multilayer Inductors", Microelectronics International: Journal of the International Society for Hybrid Microelectronics, vol. 15, no. 1, pp. 6-10, January 1998.
W. G. Hurley, M. C. Duffy, "Calculation of Self and Mutual Impedances in Planar Sandwich Structures", IEEE Trans. on Magnetics, vol. 33, no. 3, pp. 2282-2290, May 1997.
W. G. Hurley, M. C. Duffy, "Calculation of Self and Mutual Impedances in Planar Magnetic Structures", IEEE Trans. on Magnetics, vol. 31, no. 4, pp. 2416-2422, July 1995.

Conferences
W. G. Hurley, M. C. Duffy, S. O'Reilly, S. C. O’Mathúna, "Impedance Formulas for Planar Magnetic Structures with Spiral Windings", IEEE Power Electronics Specialists Conference, PESC'97, St. Louis, MO, pp. 627–633, June 1997.
S. O'Reilly, S. C. O’Mathúna, M. C. Duffy, W. G. Hurley, "A Comparative Analysis of Interconnection Technologies for Integrated Multilayer Inductors", 11th European Microelectronics Conference, Venice, Italy, pp. 427–435, May 1997.
M. C. Duffy, W. G. Hurley, "High Frequency Effects in Planar Magnetics: Inclusive of Skin Effect", IEEE Power Electronics Specialists Conference, PESC'95, Atlanta GA, pp. 645–650, June 1995.
M. C. Duffy, W. G. Hurley, "High Frequency Effects in Planar Magnetic Structures", 29th Universities Power Engineering Conference, UPEC’94, University College Galway, vol. 1, pp. 244–247, September 1994.
M. C. Duffy, W. G. Hurley, "Inductance Calculations for Planar Magnetics", 28th Universities Power Engineering Conference, UPEC’93, Staffordshire University, vol. 1, pp. 34–37, September 1993.

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