Toroidal Common-Mode Choke Layout for High Inductance and Low Capacitance
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Solution Overview
Problem
Common mode chokes face challenges in maximizing inductance while minimizing space and reducing parasitic capacitance, particularly in the design of toroidal cores with coils and conductors, which affects their ability to effectively suppress electromagnetic compatibility (EMC) interference.
Innovation Solution
The design incorporates a toroidal core with cylindrical or angular openings, featuring inner and outer conductors that are electrically connected via a lead frame connecting element, which is spaced from a circuit carrier to minimize parasitic capacitance, and uses insulating bodies to isolate conductors, allowing for compact and cost-effective construction of coils with high inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inner conductors are arranged to fully fill the cross-sectional area of the toroidal core, then the inductance is maximized, but the space for other components is reduced
Solution Approach 1:
The toroidal core is divided into multiple discrete inner conductors (at least two) that are arranged side-by-side to fill the cross-sectional area. This segmentation allows the conductors to be positioned optimally for maximizing inductance while maintaining compact dimensions, resolving the contradiction between achieving high inductance and minimizing space occupation.
2Volume of moving object
If the connecting element is placed close to the circuit carrier for compact design, then the device size is reduced, but parasitic capacitance increases
Solution Approach 1:
An insulating body is introduced as an intermediary element between the connecting element and the circuit carrier. This mediator maintains electrical isolation and minimizes parasitic capacitance while allowing the connecting element to be positioned in a location that optimizes the overall device compactness, thus resolving the contradiction between device size and parasitic capacitance.
3Loss of energy
If the inner conductors are arranged in a compact configuration to maximize inductance, then the inductance per unit volume is increased, but the manufacturing complexity increases
Solution Approach 1:
The inner conductors are designed with uniform cross-sectional areas and are arranged in a regular, homogeneous pattern within the toroidal core. This homogeneous configuration maximizes the inductance per unit volume while simplifying the manufacturing process, as uniform components are easier to produce and assemble compared to irregular configurations.
4Object-affected harmful factors
If the outer conductor is designed to carry current around the toroidal core, then the electromagnetic compatibility suppression is improved, but the device complexity increases
Solution Approach 1:
The outer conductor is merged with the toroidal core structure to form an integrated assembly. The outer conductor is positioned to surround the toroidal core and carries the return current in a configuration that maximizes electromagnetic compatibility suppression. This merging reduces the number of separate components and simplifies the overall device structure while maintaining effective EMC suppression.
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 configuration enhances the impedance of the common mode choke, effectively cancels out EMC interference by maximizing inductance in a compact form factor while minimizing parasitic capacitance, thus improving EMC suppression efficiency.
Implementation Method 1
a magnetic flux passing through the coils captures the toroidal core
Implementation Method 2
a toroidal core, in particular a ferrite core, which is magnetically permeable
Implementation Method 3
The coil current in the two coils is preferably conducted in opposite directions, so that EMC interference in the toroidal core magnetically cancels each other out
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a common-mode choke (1). The common-mode choke (1) has a toroidal core (5) and at least one coil and one further coil. The coil and the further coil are each arranged in the region of the toroidal core (5) in such a way that a magnetic flux passing through the coils encompasses the toroidal core (5). According to the invention, the toroidal core (5) of the common-mode choke (1) of the aforementioned kind surrounds an opening (4) which is, in particular cylindrical or polygonal, in particular cuboidal. The coils each have at least one or only one electrical inner conductor (2, 3) for each coil turn. The inner conductor (2, 3) is arranged in the opening (4), wherein the inner conductors (2, 3) which are arranged in the opening together form - in particular in cross section - a shape which corresponds to the opening (4), and in this way together fill the opening (4). The coils each have at least two, or only two, coil turns. The coil turn comprises an inner conductor (2, 3) and an outer conductor (8, 9) which are electrically connected to one another. The outer conductor (8, 9) is designed to conduct the coil current away from the inner conductor (2, 3) and around the toroidal core (5).