Differential Current Detection Circuit With Wire-Based EMI Cancellation

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Solution Overview

Problem

Conventional current detection circuits require additional components and circuit area to effectively cancel out electromagnetic noise interference, increasing manufacturing costs and complexity.

Innovation Solution

A detection circuit design that includes a differential amplifier with additional detection wires connected in parallel to cancel out induced voltages from electromagnetic noise, reducing the need for extra components and circuit area while maintaining accurate current detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If two current detection circuits with shunt resistors and differential amplifiers are provided to cancel electromagnetic noise, then measurement precision is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvecurrent detection accuracyVSAvoidcircuit configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the noise cancellation function into a single detection circuit by using a twisted pair configuration for the detection wires. Instead of requiring two separate detection circuits, the twisted pair structure allows both signal detection and electromagnetic noise rejection to be achieved in one circuit, thereby reducing device complexity while maintaining measurement precision

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent converts the harmful effect of electromagnetic noise into a beneficial cancellation mechanism through the twisted pair configuration. The twisting causes induced voltages from electromagnetic noise to be equal in magnitude but opposite in polarity, which automatically cancel each other out at the differential amplifier input, transforming noise interference into a self-cancelling effect

Inventive Principle:

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

2Measurement precision

Engineering Contradiction:

Improvecurrent detection accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent reduces manufacturing cost by merging multiple functions into a single detection circuit. The twisted pair configuration eliminates the need for duplicate shunt resistors and differential amplifiers, significantly reducing component count and assembly complexity while maintaining noise rejection capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The twisted pair structure provides cost-effective noise rejection by utilizing the physical twisting of wires rather than requiring additional expensive components. The geometric configuration itself creates the noise cancellation effect, eliminating the need for duplicate expensive differential amplifier circuits

Inventive Principle:

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

3Measurement precision

If two current detection circuits with shunt resistors and differential amplifiers are provided to cancel electromagnetic noise, then measurement precision is improved, but circuit area increases

Engineering Contradiction:

Improvecurrent detection accuracyVSAvoidcircuit area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent reduces circuit area by combining noise cancellation functionality into the existing detection circuit path. The twisted pair wires occupy minimal space compared to the additional components (shunt resistors, differential amplifiers) that would be required for a second detection circuit, achieving compact design while maintaining measurement precision

Inventive Principle:

Principle #5Merging (Combining)

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 solution effectively reduces electromagnetic noise interference without increasing component count or circuit area, enabling accurate current detection while minimizing manufacturing costs.

Implementation Method 1

The first detection wire and the second detection wire are arranged in the electric circuit so as to, by induced voltages generated due to external electromagnetic noise, cancel out induced voltages generated on the plus-side detection wire and the minus-side detection wire due to the electromagnetic noise

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250012833A1Detection circuit

Publication Date: 2025.01.09 MITSUBISHI ELECTRIC CORP

AI summary

A detection circuit includes: a differential; a plus-side detection wire connected between a plus input terminal of the differential amplifier and a detector; a minus-side detection wire connected between a minus input terminal of the differential amplifier and the detector; a first detection wire connected in parallel to the plus-side detection wire between the detector and the plus input terminal of the differential amplifier; and a second detection wire connected in parallel to the minus-side detection wire between the detector and the minus input terminal of the differential amplifier. The first detection wire and the second detection wire are arranged in the electric circuit so as to, by induced voltages generated due to electromagnetic noise, cancel out induced voltages generated on the plus-side detection wire and the minus-side detection wire due to the electromagnetic noise.