Absorptive Common-Mode Noise Filter for Broadband EMI Suppression

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Solution Overview

Problem

Existing common-mode noise filters face challenges in achieving broadband suppression of electromagnetic interference (EMI) and radio frequency interference (RFI) due to limitations in absorption rate and size, particularly at high frequencies, and can sometimes exacerbate interference issues by reflecting noise back to radiators.

Innovation Solution

A common-mode noise filter design incorporating a first and second transmission structure with capacitive and lossy elements, allowing for multiple frequency band resonance and enhanced absorption capabilities, thereby converting electromagnetic noise into heat to prevent interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If common-mode reflection circuits are used to suppress common-mode noise, then common-mode noise suppression is improved at gigahertz frequency, but the reflected noise may couple to noise radiators and worsen EMI and RFI

Engineering Contradiction:

Improvecommon-mode noise suppressionVSAvoidEMI and RFI

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional approach by using absorption instead of reflection. The common-mode noise filter converts common-mode noise energy into heat through lossy elements, preventing the noise from being reflected back to radiators and causing EMI/RFI issues.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent converts the harmful common-mode noise energy into beneficial heat energy through lossy elements. The noise energy is absorbed and dissipated as heat, transforming a harmful factor into a harmless form that does not radiate interference.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If multiple stages of resonance circuits are added to achieve high absorption rate, then common-mode noise absorption is improved, but device size and circuit complexity increase

Engineering Contradiction:

Improvecommon-mode noise absorption rateVSAvoidcircuit complexity and size

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments the common-mode noise suppression function into multiple parallel resonance circuits, each targeting different frequency bands. This allows broadband suppression without requiring multiple sequential stages, reducing overall circuit complexity and size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a multi-functional filter that can suppress common-mode noise across broad frequency bands simultaneously. The parallel resonance circuits with different resonant frequencies work together to provide universal suppression coverage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If conventional common-mode filters are designed for broadband suppression, then frequency coverage is improved, but absorption rate decreases and filter size increases

Engineering Contradiction:

Improvebroadband suppression coverageVSAvoidabsorption rate

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent divides the broadband suppression task into multiple frequency-specific resonance circuits connected in parallel. Each circuit targets a specific frequency band with high absorption, and together they provide comprehensive broadband coverage without sacrificing absorption rate.

Inventive Principle:

Principle #1Segmentation

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 filter effectively suppresses common-mode noise across a broader frequency band, achieving high absorption rates and minimizing interference by converting noise into heat, thus addressing the limitations of existing filters and preventing the worsening of EMI and RFI.

Implementation Method 1

The filter is able to suppress the common-mode noise in broad frequency band by means of absorption, instead of reflection. The electromagnetic noise will be converted into heat through the proposed filter

Methodology Applied

Scientific EffectElectromagnetic energy absorption and conversion to heat: Absorption (EM radiation)

Implementation Method 2

The first common-mode noise suppression circuit is connected between the first node and a reference potential, and comprises a capacitive element and a lossy element... The common-mode noise filter can generate resonances at multiple frequency bands

Methodology Applied

Scientific EffectElectrical resonance: Resonance

Data Source

PatentUS11509278B2Common-mode noise filter

Publication Date: 2022.11.22 EMPASS TECH INC

AI summary

A common-mode noise filter is provided, and comprises a first transmission structure and a second transmission structure. At least one first transmission unit is connected between a first signal input end and a first signal output end of the first transmission structure in series. At least one second transmission unit is connected between a second signal input end and a second signal output end of the second transmission structure in series. Two first capacitors are connected between the first signal input end and the second signal input end in series, and connected at a first node together. A first common-mode noise suppression unit is connected between the first node and a reference potential, and comprises a second capacitor and a first lossy element connected to the second capacitor in series or parallel. The first common-mode noise suppression unit can absorb a common-mode noise via the first lossy element.