Composite Magnetic Core Structure for Common-Mode EMI Filtering
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Solution Overview
Problem
Existing magnetic elements used in electronic devices face challenges in controlling volume and cost while maintaining effective common-mode impedance and filtering performance, particularly due to issues with winding stress on internal magnets and the lack of magnetic material in external shells, which affects their filtering function and miniaturization.
Innovation Solution
A composite magnetic core with an internal magnet made from nanocrystalline or amorphous materials and an external magnetic shell made from ferrite or alloy magnetic powder, which protects the internal magnet from winding stress and enhances common-mode impedance, allowing for improved filtering and reduced size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil is directly wound on the outer surface of the internal magnet formed by winding strip material, then the filtering function can be implemented, but the pulling stress generated during winding will destroy the internal magnet and affect the filtering function
Solution Approach 1:
The patent introduces an external magnetic shell as an intermediary component between the internal magnet and the winding coil. This shell protects the internal magnet from direct pulling stress during the winding process while still allowing the magnetic field to pass through for filtering functionality. The external magnetic shell acts as a mediator that transfers the mechanical load away from the fragile internal magnet structure.
2Strength
If the external magnetic shell is made of non-magnetic material to protect the internal magnet, then the protective function is achieved, but the shell cannot participate in the filtering function and increases volume and cost
Solution Approach 1:
The patent makes the external magnetic shell serve dual functions: it provides mechanical protection to the internal magnet while simultaneously participating in the electromagnetic filtering process. By using magnetic material for the external shell, it becomes both a protective structure and a functional filtering component, eliminating the need for separate protective and filtering elements.
Solution Approach 2:
The patent employs composite magnetic material structure consisting of an internal magnet made from nanocrystalline or amorphous materials and an external magnetic shell made from ferrite or alloy magnetic powder. This composite structure combines the high permeability and low loss characteristics of nanocrystalline materials with the protective and filtering capabilities of ferrite, achieving both mechanical strength and electromagnetic functionality.
3Reliability
If the external magnetic shell occupies space in the composite magnetic core but has no filtering function, then the internal magnet is protected, but the volume and costs of the magnetic element are increased
Solution Approach 1:
The external magnetic shell is designed to perform multiple functions simultaneously: mechanical protection of the internal magnet, electromagnetic filtering, and structural support. This multi-functionality eliminates the need for additional components and reduces overall manufacturing complexity and cost.
Solution Approach 2:
The patent merges the protective function and the filtering function into a single external magnetic shell component. By combining these functions that were previously performed by separate components, the design reduces part count, simplifies assembly, and lowers manufacturing costs while maintaining protection and filtering performance.
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 effectively increases common-mode impedance and filtering performance, widening the frequency range of electromagnetic filtering from 150 kHz to 300 MHz, while minimizing the volume and cost of the magnetic element, thus addressing the limitations of conventional technologies.
Implementation Method 1
the external magnetic shell is configured to protect the internal magnet from pulling force in a process of winding the winding
Implementation Method 2
the external magnetic shell is configured to increase common-mode impedance of the magnetic element
Implementation Method 3
A magnetic element is used in an electronic device, has a filtering function, can filter an electromagnetic interference signal
Data Source
AI summary
Embodiments of this application provide a magnetic element and an electronic device. The magnetic element is used in an electronic device. The magnetic element includes a composite magnetic core and a winding. The composite magnetic core includes an external magnetic shell and an internal magnet. The internal magnet is formed by a wound strip material. The external magnetic shell partially or entirely covers a periphery of the internal magnet. The external magnetic shell is fixedly connected to the internal magnet. The winding is on an outer surface of the external magnetic shell. The external magnetic shell is configured to protect the internal magnet from pulling force in a winding process of the winding. The external magnetic shell is configured to increase common-mode impedance of the magnetic element and improve a filtering effect of the magnetic element.