Title page for ETD etd-07252006-134030

Type of Document Master's Thesis
Author Prasai, Anish
Author's Email Address aprasai@vt.edu
URN etd-07252006-134030
Title Methodologies for Design-Oriented Electromagnetic Modeling of Planar Passive Power Processors
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Odendaal, Willem Gerhardus Committee Chair
Boroyevich, Dushan Committee Member
De La Ree Lopez, Jaime Committee Member
  • core losses
  • electromagnetic radiation
  • multiple windings
  • analytical modeling
  • shield design
  • finite element modeling
  • cross-coupling
  • high frequency
  • planar windings
  • planar core
  • planar transformer
  • electroplating
  • sputtering
  • leakage inductance
  • winding capacitances
  • winding losses
Date of Defense 2006-07-05
Availability unrestricted
The advent and proliferation of planar technologies for power converters are driven in part by the overall trends in analog and digital electronics. These trends coupled with the demands for increasingly higher power quality and tighter regulations raise various design challenges. Because inductors and transformers constitute a rather large part of the overall converter volume, size and performance improvement of these structures can subsequently enhance the capability of power converters to meet these application-driven demands. Increasing the switching frequency has been the traditional approach in reducing converter size and improving performance. However, the increase in switching frequency leads to increased power loss density in windings and core, with subsequent increase in device temperature, parasitics and electromagnetic radiation. An accurate set of reduced-order modeling methodologies is presented in this work in order to predict the high-frequency behavior of inductors and transformers.

Analytical frequency-dependent expressions to predict losses in planar, foil windings and cores are given. The losses in the core and windings raise the temperature of the structure. In order to ensure temperature limitation of the structure is not exceeded, 1-D thermal modeling is undertaken. Based on the losses and temperature limitation, a methodology to optimize performance of magnetics is outlined.

Both numerical and analytical means are employed in the extraction of transformer parasitics and cross-coupling. The results are compared against experimental measurements and are found to be in good accord. A simple near-field electromagnetic shield design is presented in order to mitigate the amount of radiation.

Due to inadequacy of existing winding technology in forming suitable planar windings for PCB application, an alternate winding scheme is proposed which relies on depositing windings directly onto the core.

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