Common Mode Filter Asymmetric Coil Symmetry

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Solution Overview

Problem

Existing common mode filters face issues with symmetry between conductor lines, leading to imbalanced inductance and resistance due to differences in the number of turns and lead-out pattern lengths, which affect high-frequency characteristics.

Innovation Solution

A common mode filter design with alternating conductor layers and lead-out patterns, where the second coil pattern has a larger diameter than the first, and the lead-out patterns extend in opposite directions to cancel out differences in resistance and reduce stray capacitance, ensuring symmetry and improved high-frequency performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the number of turns is made substantially the same between the pair of lines, then inductance balance is improved, but the lead-out pattern extends in a long distance causing inductance imbalance

Engineering Contradiction:

Improveinductance balanceVSAvoidlead-out pattern length

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The patent applies asymmetry by intentionally making the second coil pattern larger in diameter than the first coil pattern. This asymmetric design compensates for the difference in lead-out pattern lengths, allowing the overall inductance to be balanced between the pair of lines despite the asymmetric lead-out extensions.

Inventive Principle:

Principle #4Asymmetry

2Stability of the object's composition

If the lead-out pattern extends in opposite directions, then symmetry between conductor lines is improved, but resistance difference occurs due to different lengths

Engineering Contradiction:

Improvesymmetry between conductor linesVSAvoidresistance balance

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent changes the parameter of coil pattern diameter to compensate for resistance differences. By making the second coil pattern larger than the first, the resistance difference caused by asymmetric lead-out pattern lengths is compensated, maintaining overall electrical balance.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the coil patterns are made with different diameters, then lead-out pattern symmetry is improved, but the number of turns difference causes inductance imbalance

Engineering Contradiction:

Improvelead-out pattern symmetryVSAvoidinductance balance

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent carefully controls the parameters of coil patterns (diameter, number of turns, winding pitch) to achieve a balance where the effects of different diameters and different turn numbers compensate each other, resulting in balanced inductance between the pair of lines.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20230253141A1Common mode filter

Publication Date: 2023.08.10 TDK CORP

AI summary

Disclosed herein is a common mode filter that includes: a first conductor layer including a first coil pattern, a first connection pattern, and a first lead-out pattern connecting the first coil pattern and the first connection pattern; and a second conductor layer including a second coil pattern, a second connection pattern, and a second lead-out pattern connecting the second coil pattern and the second connection pattern. The extending direction of the first section of the first lead-out pattern and an extending direction of the second section of the second lead-out pattern are opposed to each other. The first section is longer than the second section. The second coil pattern is larger in diameter than the first coil pattern.