UBC Theses and Dissertations

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UBC Theses and Dissertations

Coreless planar magnetic winding structures for power converters : track-width-ratio Cove, Samuel Robert


With the accelerated growth of slim consumer electronics has come the need to reduce the profile of all electronic components. Planar magnetics provide an excellent solution to this problem, where copper strip conductors and flattened planar magnetic cores allow for the height of the components to be severely decreased compared to traditional wire-wound components. Planar magnetics also provide more repeatable characteristics and easier manufacturability. The major design goals for planar windings are low resistance, predictable inductance, and acceptable capacitance. This work investigates the application of a constant ratio between turn widths, called the Track-Width-Ratio (TWR) as a technique to attain these qualities in planar spiral windings. This work introduces the generalized racetrack planar spiral winding, whose low-frequency analysis can be applied to a variety of common winding shapes while accommodating changing track widths. The accompanying dimensional system provides the specification of the novel winding arrangements, including predicting their inductance and resistance. A design example demonstrates an 18% increase in low-frequency performance. The second part investigates the AC resistance from TWR. The proposed technique provides a correction factor based on the most recent models for ac resistance. A winding technique which combines hollow windings with TWR is proposed to increase the quality factor of planar spiral windings at high frequency operation. A design example highlights a change in efficiency from 70% to 90% within a 5W Wireless Power Transfer system. Finally TWR is employed to reduce planar spiral capacitance. Through an inverse TWR winding structure, a significant decrease in capacitance is observed with a moderate reduction in resistance and inductance. A quasi-analytical approach with finite element analysis is employed to determine the winding capacitance. These windings show a 50% decrease in capacitance and a 20% decrease in resistance compared to traditional windings. All results from this work have been confirmed experimentally and highlight the exceptional flexibility which is provided when the turn widths are included in the design of planar spiral windings.

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