Composite Coupled Inductor Core for Low Electromagnetic Interference
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Solution Overview
Problem
Existing coupled inductors face issues with electromagnetic interference due to fringing magnetic flux and capacitive coupling, which are problematic in applications requiring low electromagnetic interference such as automotive, industrial control, and medical applications.
Innovation Solution
The development of coupled inductors with a composite magnetic core comprising a coupling magnetic structure embedded in a leakage magnetic structure, utilizing materials with varying permeability to minimize fringing magnetic flux and capacitive coupling, and incorporating a metal shield to further reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a magnetic core with gap is used to provide energy storage and prevent magnetic saturation, then leakage inductance is increased, but electromagnetic interference increases due to fringing magnetic flux
Solution Approach 1:
The magnetic core is segmented into multiple magnetic paths: a first magnetic path through the gap for energy storage and a second magnetic path through the shielding structure for flux containment. This segmentation allows the gap to provide leakage inductance while the shielding structure captures fringing flux, resolving the contradiction between energy storage and EMI reduction.
Solution Approach 2:
A shielding structure acts as an intermediary element that intercepts fringing magnetic flux from the gap before it can radiate outward. The shielding structure includes a first portion and a second portion that create a controlled magnetic path, mediating between the energy storage function of the gap and the EMI reduction requirement.
2Volume of moving object
If windings are positioned close to the magnetic core for compact design, then device size is reduced, but capacitive coupling between windings increases
Solution Approach 1:
A non-magnetic spacer serves as an intermediary element positioned between adjacent windings. This spacer maintains electrical isolation and reduces capacitive coupling while allowing the windings to remain close to the magnetic core for compact design. The spacer is non-magnetic to avoid interfering with the magnetic flux paths.
Solution Approach 2:
The spacer is strategically positioned only in regions where capacitive coupling is problematic, such as between adjacent windings on the same leg of the magnetic core. This localized application maintains compact overall dimensions while addressing the specific capacitive coupling issue where it occurs.
3Loss of energy
If leakage magnetic flux path is extended for better energy storage, then leakage inductance is increased, but fringing magnetic flux and electromagnetic interference worsen
Solution Approach 1:
The shielding structure converts the harmful fringing magnetic flux into a beneficial contained magnetic path. The first portion and second portion of the shielding structure guide the leakage flux through a controlled path that provides the desired leakage inductance while preventing the flux from radiating as electromagnetic interference.
Solution Approach 2:
The magnetic core assembly combines magnetic material (for flux conduction) with non-magnetic materials (gap region and spacer). This composite structure creates distinct magnetic paths: one through the magnetic material for controlled flux flow and another through the non-magnetic gap region for energy storage, while the shielding portions contain the flux and prevent fringing.
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 minimizes electromagnetic interference by reducing fringing magnetic flux and capacitive coupling, enhancing compatibility in applications requiring low electromagnetic interference.
Implementation Method 1
the coupling magnetic structure magnetically couples together a plurality of windings
Implementation Method 2
the leakage magnetic structure provides a magnetic flux path for leakage magnetic flux
Implementation Method 3
utilizing materials with varying permeability to minimize fringing magnetic flux
Data Source
AI summary
A coupled inductor for low electromagnetic interference includes a plurality of windings and a composite magnetic core including a coupling magnetic structure formed of a first magnetic material and a leakage magnetic structure formed of a second magnetic material having a distributed gap. The coupling magnetic structure magnetically couples together the plurality of windings, and the leakage magnetic structure provides leakage magnetic flux paths for the plurality of windings.