Segmented Amorphous Ribbon Shield for Wireless Charger Eddy Currents
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Solution Overview
Problem
Conventional magnetic field shield sheets for wireless chargers face challenges such as increased eddy currents, heat generation, and reduced power transmission efficiency due to their thickness and material limitations, which hinder the miniaturization of portable devices and affect charging speed.
Innovation Solution
A magnetic field shield sheet comprising at least one layer of amorphous ribbon separated into fine pieces, with a protective film and double-sided tape used to fill gaps and isolate the pieces, reducing eddy currents and maintaining original thickness through a flake treatment and laminating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a ferrite sheet is processed thinly to reduce thickness, then the thickness is reduced, but the sheet becomes easily broken and weak in impact resistance
Solution Approach 1:
The patent uses a composite structure consisting of multiple thin ferrite sheets (first and second ferrite sheets) bonded together with adhesive layers. This composite approach maintains the thin overall profile while distributing mechanical stress across multiple layers, preventing the brittleness and breakage issues of single thin sheets. The adhesive layers provide flexibility and impact resistance that individual thin ferrite sheets lack.
Solution Approach 2:
The magnetic field shielding function is divided into multiple separate ferrite sheets rather than using a single thick sheet. The first ferrite sheet is positioned between the primary coil and secondary coil, while the second ferrite sheet is positioned between the secondary coil and battery, creating segmented shielding zones that are each thin and flexible but collectively provide robust protection.
2Power
If a magnetic sheet is used to strengthen coupling between coils, then power transmission efficiency is improved, but eddy currents increase and heat generation occurs
Solution Approach 1:
The magnetic sheet is segmented into multiple thin ferrite sheets separated by adhesive layers. This segmentation interrupts the continuous magnetic path that would otherwise support large eddy currents, reducing eddy current losses while maintaining sufficient magnetic coupling for power transmission. Each thin sheet creates smaller eddy current loops with higher resistance.
Solution Approach 2:
Different regions of the magnetic shielding structure have different properties: the ferrite sheets provide magnetic permeability for coupling enhancement in coil-proximal regions, while the adhesive layers provide electrical insulation to break eddy current paths. The first adhesive layer is positioned where eddy current suppression is critical, while the second adhesive layer provides additional insulation near the battery.
3Length of stationary object
If the thickness of the power reception portion is reduced to match thinner electronic devices, then device thinness is achieved, but magnetic field shielding effectiveness is reduced
Solution Approach 1:
Multiple thin ferrite sheets bonded with adhesive layers create a composite magnetic shielding structure that achieves effective shielding in a reduced total thickness. The cumulative magnetic permeability of multiple sheets provides shielding effectiveness comparable to or better than a single thick sheet, while the total thickness remains minimal for thin electronic devices.
Solution Approach 2:
Instead of increasing thickness in one dimension to improve shielding, the patent uses multiple layers arranged in the thickness dimension with adhesive spacers, creating a multi-dimensional shielding approach. The adhesive layers add spacing and insulation in the thickness direction, allowing effective shielding without excessive overall thickness.
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 solution significantly reduces eddy current losses, increases the quality factor of the secondary coil, and enhances power transmission efficiency while maintaining a thin profile, thus improving the overall performance and efficiency of wireless charging.
Implementation Method 1
significantly reduces eddy current losses
Implementation Method 2
blocks an effect of an alternating-current magnetic field generated when a charger function for a portable mobile terminal device is implemented in a non-contact wireless manner
Implementation Method 3
a protective film and double-sided tape used to fill gaps and isolate the pieces
Data Source
AI summary
Provided are a magnetic field shield sheet for a wireless charger, a method of manufacturing the sheet, and a receiver for the wireless charger by using the sheet. The sheet includes at least one layer thin magnetic sheet made of an amorphous ribbon separated into a plurality of fine pieces; a protective film that is adhered on one surface of the thin magnetic sheet via a first adhesive layer provided on one side of the protective film; and a double-sided tape that is adhered on the other surface of the thin magnetic sheet via a second adhesive layer provided on one side of the double-sided adhesive tape, wherein gaps among the plurality of fine pieces are filled by some parts of the first and second adhesive layers, to thereby isolate the plurality of fine pieces.