EMI Filter Resonance Tuning for Power Converter Interference

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Solution Overview

Problem

Existing EMI filters in power converters face interference from energy-storage magnetic components, leading to reduced performance and increased volume and cost, as simply increasing inductance or capacitance does not efficiently address strong electromagnetic interference at specific frequencies.

Innovation Solution

A power conversion apparatus with a two-port network connected between the energy-storage magnetic component and the inductor component, forming a series resonance with a mutual inductance, where the resonant frequency is adjusted to 85%–115% of the frequency needing improved insertion loss, thereby reducing interference and enhancing filtering performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the value of inductances or capacitances in the EMI filter is increased to improve insertion loss and weaken interference, then the filtering performance is improved, but the volume and cost of the EMI filter increase

Engineering Contradiction:

Improvefiltering performanceVSAvoidvolume of EMI filter

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent changes the resonant frequency parameter of the EMI filter to match the interference frequency from energy-storage magnetic components. By adjusting the resonant frequency to coincide with the interference frequency, the filter achieves maximum insertion loss at the problematic frequency without requiring increased inductance or capacitance values, thus avoiding volume and cost increases.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the value of inductances or capacitances in the EMI filter is increased to improve insertion loss, then the filtering performance is improved, but the cost of the EMI filter increases

Engineering Contradiction:

Improvefiltering performanceVSAvoidcost of EMI filter

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent optimizes the resonant frequency parameter rather than increasing component values. By tuning the resonant frequency to match the interference frequency, the existing inductors and capacitors can be used at their designed values, avoiding the need for more expensive, higher-value components and reducing overall filter cost.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the distance between devices or components is reduced to reduce power converter volume, then the power density is increased, but the interference with the EMI filter from energy-storage magnetic components increases

Engineering Contradiction:

Improvepower densityVSAvoidinterference with EMI filter

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful mutual inductance effect into a beneficial resonance mechanism. Instead of treating the coupling between energy-storage magnetic components and the EMI filter inductor as purely harmful interference, the patent deliberately tunes the resonant frequency to match the interference frequency, transforming the mutual inductance into a useful resonance that enhances filtering at the problematic frequency.

Inventive Principle:

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

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 approach effectively reduces interference from energy-storage magnetic components, enhances EMI filter performance, and improves insertion loss at specific frequencies without increasing the volume or cost of the EMI filter.

Implementation Method 1

a series resonance is formed by the two-port network and a mutual inductance which is formed by a coupling between the energy-storage magnetic component and the inductor component

Methodology Applied

Scientific EffectSeries resonance: Resonance

Implementation Method 2

a mutual inductance which is formed by a coupling between the energy-storage magnetic component and the inductor component

Methodology Applied

Scientific EffectMutual inductance: Electromagnetic Induction

Data Source

PatentUS9350231B2Method for improving performance of filter and power conversion apparatus

Publication Date: 2016.05.24 DELTA ELECTRONICS INC(CN)

AI summary

A power conversion apparatus is disclosed in the present application. The power conversion apparatus comprises: a power converter comprising an energy-storage magnetic component, and a filter comprising an inductor component and a two-port network connected the energy-storage magnetic component and the inductor component, wherein a series resonance is formed by the two-port network and a mutual inductance which is formed by a coupling between the energy-storage magnetic component and the inductor component.