Stacked Self-Resonant Coil Structure for Low-Stress Wireless Power Transfer

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Solution Overview

Problem

Current resonant wireless power transfer technologies face challenges in coil design, including high resonant voltage and current stresses, bulky and expensive capacitor arrays, and insufficient performance of series self-resonant coils due to limited inductance and lack of modeling for performance exploration.

Innovation Solution

A series self-resonant coil structure is developed, comprising stacked spiral and planar coil elements with a dielectric layer in between, forming a distributed capacitor that reduces component count, enhances efficiency, and minimizes electric field generation, thereby addressing the limitations of existing coil designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If standard WPT coils use discrete external capacitors to form resonance, then power transfer distance and efficiency are improved, but resonant voltage and current stresses become excessively high

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidresonant voltage and current stresses

Core Design Contradiction:

Loss of energyVSStress or pressure

Solution Approach 1:

The patent merges the inductor and capacitor into a single integrated coil structure where the coil windings provide inductance and the inter-winding capacitance provides the necessary capacitive effect. This integration eliminates the need for separate discrete capacitors and reduces the peak resonant voltage and current stresses that occur in traditional separate-component designs.

Inventive Principle:

Principle #5Merging (Combining)

2Stress or pressure

If large arrays of capacitors are used to reduce voltage and current stresses, then component stress is reduced, but device size and cost increase significantly

Engineering Contradiction:

Improvevoltage and current stressesVSAvoidcapacitor array size and cost

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent combines the functions of multiple capacitors into a single integrated coil structure where the distributed capacitance between windings provides the necessary capacitive effect. This eliminates the need for large arrays of discrete capacitors, significantly reducing device size, cost, and complexity while maintaining reduced voltage and current stresses.

Inventive Principle:

Principle #5Merging (Combining)

3Loss of energy

If series self-resonant coil designs are implemented, then system loss is reduced, but inductance is limited and thickness becomes prohibitively large

Engineering Contradiction:

Improvesystem lossVSAvoidcoil thickness

Core Design Contradiction:

Loss of energyVSLength of stationary object

Solution Approach 1:

The patent applies local quality by creating non-uniform winding densities and varying the spacing between windings in different regions of the coil. This allows optimization of both the inductance value and the thickness profile locally, achieving reduced system loss through series resonance while maintaining acceptable overall dimensions through spatially varying structural properties.

Inventive Principle:

Principle #3Local quality

4Reliability

If traditional inductor and capacitor designs are used, then resonance can be achieved, but component count and system complexity increase

Engineering Contradiction:

Improveresonance formationVSAvoidcomponent count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the inductor and capacitor functions into a single integrated coil assembly where the windings provide inductance and the inter-winding geometry provides distributed capacitance. This single integrated structure replaces multiple discrete components, reducing component count and system complexity while maintaining reliable resonance formation through the inherent electrical properties of the coil geometry.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The proposed coil structure achieves reduced component count, improved efficiency, and minimized electric field generation, enabling more effective near-field wireless power transfer while being cost-effective and easier to fabricate using printed circuit board technology.

Implementation Method 1

the top coil element, the bottom coil element, and the dielectric layer element are aligned to produce series-resonance in the coil structure

Methodology Applied

Scientific EffectSeries resonance: Resonance

Implementation Method 2

magnetic resonant coupling

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

forming a distributed capacitor that reduces component count

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11996229B2Series self-resonant coil structure for conducting wireless power transfer

Publication Date: 2024.05.28 UNIVERSITY OF TENNESSEE RESEARCH FOUNDATION

AI summary

Disclosed is a series self-resonant coil structure for wireless power transfer that includes a top coil element that is configured in a spiral and planar arrangement and a bottom coil element that is configured in a spiral and planar arrangement that is substantially similar to the arrangement corresponding to the top coil element, wherein the top coil element and the bottom coil element are positioned in a stacked arrangement in relation to each other. The coil structure further includes a dielectric layer element that is planarly positioned in between the top coil element and the bottom coil element, wherein the top coil element, the bottom coil element, and the dielectric layer element are aligned to produce series-resonance in the coil structure.