Self-Canceling Coil Structure for Wireless Power Transfer

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Solution Overview

Problem

Conventional air core inductors in wireless power transfer systems cause significant magnetic interference and power losses due to their magnetic field expansion, which can damage nearby components like NFC tags.

Innovation Solution

A self-canceling coil structure with two circular turns having opposite current directions and a similar center position, along with an auxiliary coil, is used to minimize magnetic interference by canceling out magnetic flux outside the coil, thereby reducing interference and enhancing magnetic field strength within the coil.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If air core inductors are employed to achieve high frequency operation, then efficiency is improved, but magnetic interference to nearby components increases

Engineering Contradiction:

Improvepower lossesVSAvoidmagnetic interference

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The coil structure is divided into two separate turns (first turn 102 and second turn 104) that are concentric and adjacent to each other. Each turn carries current in opposite directions, creating independent magnetic fields that cancel each other outside the coil structure while maintaining the needed inductance for high frequency operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs counteracting magnetic fields by having the first and second turns carry currents in opposite directions. The magnetic field generated by one turn counterbalances the magnetic field of the other turn in the external region, effectively canceling out the harmful magnetic interference while preserving the internal magnetic field needed for power transfer.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Power

If conventional coil structures are used to provide desired inductance, then power transfer capability is maintained, but magnetic flux density extends over longer distances causing interference

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidmagnetic flux extension

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The coil is segmented into two distinct turns with opposite current directions. This segmentation allows the magnetic fields to cancel externally while maintaining the inductance needed for power transfer capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful effect of extended magnetic flux into a beneficial self-canceling mechanism. By deliberately designing adjacent turns with opposite currents, the previously harmful magnetic field extension becomes a controlled feature that cancels itself out, reducing interference while maintaining power transfer.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Quantity of substance

If turns are placed immediately next to each other with currents in the same direction, then inductance is achieved, but magnetic field cancellation does not occur

Engineering Contradiction:

ImproveinductanceVSAvoiduncanceled magnetic field

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

Instead of having currents flow in the same direction through adjacent turns, the patent inverts the current direction in one of the turns. This inversion causes the magnetic fields to cancel externally while maintaining the inductance, solving the problem of uncanceled magnetic fields.

Inventive Principle:

Principle #13The other way round (Inversion)

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 self-canceling coil structure reduces magnetic interference and power losses, improves wireless power transfer efficiency, and maintains effective coupling between coils while minimizing damage to adjacent components.

Implementation Method 1

the first turn 102 and the second turn 104 of the coil structure 100 are implemented as two concentric circles. The currents of these two concentric circles flow in a same direction as shown in FIG. 1.

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Methodology Applied

Scientific EffectMagnetic field cancellation: Magnetic Field

Data Source

PatentUS10505591B2Self-canceling magnetic structures for transferring power and communication signals

Publication Date: 2019.12.10 QUANTEN TECHNOLOGIES LIMITED

AI summary

A system includes a first power transfer coil configured to be magnetically coupled to a second power transfer coil and an auxiliary coil adjacent to the first power transfer coil, wherein at least one of the first power transfer coil and the auxiliary coil comprises a first turn and a second turn circular in shape, and wherein the first turn and the second turn have a similar center position and a current flowing through the first turn and a current flowing through the second turn are in opposite directions.