Common Mode Choke Coil Optimized Spacing for Impedance and Frequency

Solution Overview

Problem

Existing common mode choke coils face challenges in achieving both high common mode impedance and high cut-off frequency, as increasing impedance typically results in low cut-off frequencies, and decreasing distances between spiral conductors increases stray capacitance, making it difficult to achieve both performance metrics simultaneously.

Innovation Solution

A common mode choke coil design with a multilayer body featuring a first and second coil, where the distance between specific spiral conductors is minimized to enhance coupling, while maintaining larger distances between other conductors to reduce stray capacitance, thereby achieving high impedance and frequency performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the distance between spiral conductors is decreased to increase common mode impedance, then common mode impedance is improved, but cut-off frequency decreases due to increased stray capacitance

Engineering Contradiction:

Improvecommon mode impedanceVSAvoidcut-off frequency

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent applies local quality by differentiating the spacing between spiral conductors at different locations. Specifically, the distance between adjacent spiral conductors is made smaller at the inner peripheral end portion compared to the outer peripheral end portion. This localized variation in spacing allows the inner region to contribute more to common mode impedance while the outer region maintains larger spacing to reduce stray capacitance, thereby resolving the contradiction between impedance and cut-off frequency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by creating an asymmetric spacing pattern between spiral conductors. The distance between conductors is intentionally made non-uniform, with the inner peripheral end having smaller spacing and the outer peripheral end having larger spacing. This asymmetric configuration optimizes the balance between common mode impedance (enhanced by smaller inner spacing) and stray capacitance (reduced by larger outer spacing), enabling both high impedance and high cut-off frequency.

Inventive Principle:

Principle #4Asymmetry

2Ease of manufacture

If uniform spacing between all spiral conductors is used, then manufacturing is simplified, but performance optimization is limited

Engineering Contradiction:

Improvespacing uniformityVSAvoidcommon mode impedance and cut-off frequency performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by differentiating the spacing between spiral conductors at different locations. Specifically, the distance between adjacent spiral conductors is made smaller at the inner peripheral end portion compared to the outer peripheral end portion. This localized variation in spacing allows the inner region to contribute more to common mode impedance while the outer region maintains larger spacing to reduce stray capacitance, thereby resolving the contradiction between impedance and cut-off frequency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by creating an asymmetric spacing pattern between spiral conductors. The distance between conductors is intentionally made non-uniform, with the inner peripheral end having smaller spacing and the outer peripheral end having larger spacing. This asymmetric configuration optimizes the balance between common mode impedance (enhanced by smaller inner spacing) and stray capacitance (reduced by larger outer spacing), enabling both high impedance and high cut-off frequency.

Inventive Principle:

Principle #4Asymmetry

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 design effectively increases common mode impedance and cut-off frequency by optimizing the spacing between spiral conductors, allowing for improved noise rejection in high-frequency applications.

Implementation Method 1

a first coil and a second coil disposed inside the multilayer body... The first coil includes at least a first spiral conductor, a second spiral conductor, and a third spiral conductor that are connected to one another in a stacking direction of the multilayer body through via conductors

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11264159B2Common mode choke coil

Publication Date: 2022.03.01 MURATA MFG CO LTD

AI summary

A common mode choke coil includes a multilayer body obtained by stacking insulating layers, first and second coils inside the multilayer body, and first to fourth outer electrodes on outer surfaces of the multilayer body. The first and second outer electrodes are respectively connected to first and second ends of the first coil. The third and fourth outer electrodes are respectively connected to first and second ends of the second coil. The first coil includes first to third spiral conductors connected to one another through via conductors. The second coil includes fourth to sixth spiral conductors connected to one another through via conductors. The first spiral conductor is adjacent to the second and fourth spiral conductors. The fourth spiral conductor is adjacent to the first and fifth spiral conductors. The distance between the first and fourth spiral conductors is smaller than the distances between other spiral conductors.