Ultra-thin Nanocrystalline Shielding for Inductive Receiver Coils
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Solution Overview
Problem
The use of metal objects, such as batteries, on top of inductive receiver coils for charging purposes leads to deteriorated inductive power transfer due to induced eddy currents, which generate heat and pose safety concerns, and existing thick softmagnetic ferrite layers are not suitable for compact mobile device designs.
Innovation Solution
An ultra-thin softmagnetic metal foil, typically Mumetal with a thickness of 50 micrometers or less, is used between the receiver coil and the metal object, along with radial slits to dissipate eddy currents, providing effective magnetic shielding while maintaining a thin profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick softmagnetic ferrite layer is used between the receiver coil and metal object, then magnetic shielding function is improved, but device thickness increases to at least 1 mm
Solution Approach 1:
The patent changes the material parameter from conventional ferrite to nanocrystalline alloy with vastly superior magnetic permeability (μr≥10,000 versus ferrite's lower permeability). This parameter change enables the shielding layer to be reduced from 1 mm thickness to 50 micrometers or less while maintaining effective magnetic shielding function.
Solution Approach 2:
The patent employs nanocrystalline alloy material comprising 70-80% Fe, 10-15% Si, and 5-10% B, representing a composite material solution that combines multiple elements to achieve both high magnetic permeability and mechanical flexibility. This composite material enables thin-film implementation while maintaining shielding effectiveness.
2Area of stationary object
If metal object is placed on top of receiver coil, then device area is reduced, but eddy currents are induced causing heat generation and safety concerns
Solution Approach 1:
The patent introduces an ultra-thin softmagnetic shielding layer as an intermediary component between the receiver coil and metal object. This intermediary serves dual functions: it shields the metal object from the alternating magnetic field to prevent eddy current generation, while simultaneously guiding magnetic flux to maintain inductive power transfer efficiency. The shielding layer thickness of 50 micrometers or less minimizes its impact on device area.
Solution Approach 2:
The patent segments the shielding function from the structural support function by using a separate ultra-thin softmagnetic layer. This segmentation allows the shielding layer to be optimized for magnetic properties while being thin enough not to significantly increase device area, resolving the contradiction between area reduction and eddy current prevention.
3Object-affected harmful factors
If conventional ferrite material is used for shielding, then magnetic shielding is achieved, but mechanical brittleness requires minimum thickness of 1 mm
Solution Approach 1:
The patent changes the material composition parameter from conventional ferrite to nanocrystalline alloy with specific elemental ratios (70-80% Fe, 10-15% Si, 5-10% B). This parameter change produces a material that is both magnetically superior and mechanically flexible, eliminating the brittleness issue that forced conventional ferrite to be at least 1 mm thick.
Solution Approach 2:
The patent implements the shielding function using a flexible thin film of nanocrystalline alloy with thickness of 50 micrometers or less. This thin film approach replaces the rigid, thick ferrite structures, providing both mechanical flexibility and effective magnetic shielding in a compact form factor suitable for portable devices.
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
This solution significantly reduces eddy current-induced losses and heat generation, allowing for efficient inductive power transfer while maintaining a compact device design, ensuring both effective shielding and safety.
Implementation Method 1
an ultra-thin softmagnetic metal foil disposed in between the receiver coil and the metal object, wherein the ultra-thin softmagnetic metal foil advantageously provides a magnetic shielding layer
Implementation Method 2
the presence of the metal object on top of the receiver coil undesirably deteriorates an inductive power transfer to the receiver coil due to induced eddy currents in the metal object
Implementation Method 3
To dissipate formation of any undesirable eddy currents in the shielding layer, the shielding layer is further provided with eddy current dissipation features
Implementation Method 4
an inductive receiver coil configured for generating current in response to being exposed to an alternating magnetic field generated substantially on a first side of the receiver coil
Data Source
AI summary
An electronic device which is inductively powered or charged has a receiver coil on which a metal object can be placed without causing deterioration of the coil's magnetic field and without generating heat in the metal object. An ultra-thin, flexible, high magnetic permeability metal foil having a thickness of 50 μm or less is provided as a shielding layer between the coil and the object. Radial slits are provided in the shielding layer, which suppress unwanted eddy currents in the layer to reduce power transfer losses and heat generation.