Power Converter Filter Circuit Resonance Noise Suppression

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Solution Overview

Problem

High-frequency switching noise in power converter apparatuses is amplified by resonance phenomena due to parasitic inductance between bypass capacitors, leading to malfunction and inefficiency, especially as next-generation power devices operate at higher frequencies.

Innovation Solution

A power converter apparatus with a filter circuit comprising first and second bypass capacitors and inductors, where the inductance is set to ensure a resonance frequency lower than multiple times the switching frequency, preventing resonance matching with the switching frequency and thus reducing switching noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If bypass capacitors are connected with small inductance to operate in high frequency region, then switching noise is reduced, but resonance phenomenon occurs due to parasitic inductance between capacitors

Engineering Contradiction:

Improveswitching frequencyVSAvoidswitching noise amplification

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an inductor as an intermediary element connected between the first and second bypass capacitors. This inductor acts as a mediator that controls the interaction between the capacitors, preventing direct resonance while allowing both to function as noise filters. The inductor's impedance blocks the resonant current path that would otherwise form between the capacitors through the low-inductance connections.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters of the filter circuit by carefully selecting the inductance value of the inserted inductor. By adjusting this parameter, the resonance frequency of the LC circuit is controlled to be lower than the switching frequency, thereby preventing resonance amplification of switching noise while maintaining effective noise filtering across the operating frequency range.

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If multiple bypass capacitors are used to filter different frequency components, then noise suppression is improved, but circuit complexity increases

Engineering Contradiction:

Improvehigh-frequency noiseVSAvoidfilter circuit structure

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent combines multiple noise filtering functions into a single integrated circuit structure. The first and second bypass capacitors, along with the inserted inductor, form a unified filter circuit that simultaneously handles both high-frequency and low-frequency noise components. This merged structure eliminates the need for separate filter circuits for different frequency ranges, reducing overall circuit complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The filter circuit designed in the patent serves multiple functions: the first bypass capacitor filters high-frequency noise, the second bypass capacitor filters low-frequency noise, and the inserted inductor prevents resonance while also contributing to the filtering action. This multi-functional design allows a single circuit to handle various noise suppression tasks that would otherwise require separate dedicated circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 simplifies the circuit, effectively reduces switching noise, and operates with higher efficiency than prior art, suppressing overcurrent and ripple while maintaining a smaller radiator for the switching device.

Implementation Method 1

the filter circuit converts the AC voltage from the switching circuit into a DC voltage by low-pass filtering the AC voltage

Methodology Applied

Scientific EffectLow-pass filtering: Filter (electronic)

Implementation Method 2

The first bypass capacitor bypasses noise of a first frequency component of the AC voltage from the switching circuit, and the second bypass capacitor bypasses noise of a second frequency component

Methodology Applied

Scientific EffectCapacitive bypassing: Capacitance

Implementation Method 3

The inductance (L) of the inductor is set so that a resonance frequency (fr) of the filter circuit is lower than multiple times the switching frequency (fSW) by insertion of the inductor

Methodology Applied

Scientific EffectResonance frequency control: Resonance

Data Source

PatentUS11606021B2Power converter apparatus provided with low-pass filter circuit for reducing switching frequency components

Publication Date: 2023.03.14 OMRON CORP

AI summary

A power converter apparatus includes a switching circuit generating an AC voltage by switching a DC voltage at a predetermined switching frequency, and a filter circuit converting the AC voltage from the switching circuit into the DC voltage by low-pass filtering the AC voltage. The filter circuit includes first and second bypass capacitors, and an inductor. The first bypass capacitor bypasses noise of a first frequency component of the AC voltage from the switching circuit, and the second bypass capacitor bypasses noise of a second frequency component of the AC voltage from the switching circuit, which is lower than the first frequency component. The inductor is between the first and second bypass capacitors, and the inductance thereof is set so that a resonance frequency of the filter circuit is lower than multiple times the switching frequency by insertion of the inductor, thereby reducing the switching noise flowing to the load.