Noise reduction circuitry, load system and power conversion device

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Solution Overview

Problem

When the voltage of the power source of the noise canceller is lower than the DC link voltage of the power converter, there is a disadvantage in the flow of a compensation current.

Innovation Solution

A noise reduction circuitry that injects a compensation current into a power line or earth, with a direct-current power source voltage set to be less than ⅔ of the DC link voltage, and uses a noise detection unit to detect and amplify common mode noise current or voltage, reducing impedance and ensuring sufficient compensation current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the voltage of the direct-current power source is set lower than the DC link voltage of the power converter, then elements with low voltage resistance can be used in the noise canceller, but the compensation current flow is insufficient

Engineering Contradiction:

Improveuse of low voltage resistance elementsVSAvoidcompensation current flow

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the voltage parameter of the direct-current power source to be less than 2/3 of the peak DC link voltage, and adjusts the impedance parameter of the path to be less than 1/3 of the impedance on the power source side. These parameter changes enable the noise canceller to operate reliably with lower voltage resistance elements while maintaining sufficient compensation current flow.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the voltage of the direct-current power source is set lower than the DC link voltage, then the noise canceller can operate with lower voltage requirements, but the compensation current does not flow sufficiently

Engineering Contradiction:

Improvepower source voltage requirementVSAvoidcompensation current flow

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent optimizes the voltage parameter by setting it to less than 2/3 of the peak DC link voltage, and simultaneously optimizes the impedance parameter of the path to be less than 1/3 of the power source side impedance. This dual parameter optimization ensures sufficient compensation current flow while maintaining low voltage requirements for the noise canceller operation.

Inventive Principle:

Principle #35Parameter changes

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

Suppresses the insufficient flow of compensation current and effectively reduces common mode noise by amplifying detected noise current, allowing the use of high-speed transistors and operational amplifiers even with lower voltage resistance.

Implementation Method 1

a noise canceller that injects a compensation current into a power line or an earth to reduce a common mode noise current flowing to an alternating-current power source

Methodology Applied

Scientific EffectCommon mode noise cancellation:

Implementation Method 2

a direct-current power source that supplies power to the noise canceller, and a voltage Vcc of the direct-current power source is less than 2⁄3 of a peak value of a DC link voltage

Methodology Applied

Scientific EffectDirect-current power supply: Battery (electricity)

Implementation Method 3

when the compensated common mode noise current whose positive direction is a direction of flow from the alternating-current power source side to the first connection point

Methodology Applied

Scientific EffectElectrical noise detection:

Data Source

PatentUS12567795B2Noise reduction circuitry, load system and power conversion device

Publication Date: 2026.03.03 DAIKIN INDUSTRIES LTD

AI summary

[Problem] To suppress the disadvantage that occurs with regard to the flow of a compensation current when a voltage of a power source of a noise canceller is lower than a DC link voltage of a power converter.[Solving means] A noise reduction circuitry includes a noise canceller that injects a compensation current into a power line or an earth to reduce a common mode noise current flowing to an alternating-current power source from a power converter including a switching element connected to the alternating-current power source through the power line and the earth, and a direct-current power source that supplies power to the noise canceller, and a voltage Vcc of the direct-current power source is less than ⅔ of a peak value of a DC link voltage of the power converter, and when a connection point between the power line and a path connecting the power line and the earth via the noise canceller is a first connection point, and a connection point between the path and the earth is a second connection point, when the compensated common mode noise current whose positive direction is a direction of flow from the alternating-current power source side to the first connection point and flowing through the power line on a side closer to the alternating-current power source than the first connection point is Ig(t), when the compensation current whose positive direction is a direction of flow from the alternating-current power source side to the first connection point and flowing through the path is Io(t), when an impedance of the path is Z1, when an impedance on a side closer to the alternating-current power source than the first connection point and the second connection point is Z2, and when V(t)=2*(Z1*Io(t)−Z2*Ig(t)), the voltage Vcc is set to be a maximum value of a quasi-peak value of V(t) or √2 times or more an effective value of V(t).