Shunt-Based Current Sensor with Reference Resistor for Resistance Drift Compensation

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Solution Overview

Problem

Shunt-based current sensors face accuracy degradation due to changes in the resistance value of the shunt resistor over time, requiring accurate determination of the resistance value to maintain measurement accuracy.

Innovation Solution

The proposed shunt-based current sensor includes a reference resistor connected in series with the shunt resistor, a current excitation circuit generating an AC excitation current, and at least two voltage measurement circuits. The signal processing circuit operates in either a load current redundancy detection mode or a shunt resistance measurement mode to accurately measure the shunt resistance value and load current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a shunt resistor is used to measure battery current, then the current measurement function is provided, but the measurement accuracy degrades over time due to resistance value changes

Engineering Contradiction:

Improvecurrent measurement accuracyVSAvoidmeasurement stability over time

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The signal processing circuit continuously monitors the resistance value of the shunt resistor and automatically adjusts measurement calculations based on the actual resistance, creating a feedback mechanism that compensates for resistance drift and maintains measurement accuracy over time

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically changes the measurement parameters by determining the actual resistance value of the shunt resistor at different times and using this information to correct current measurements, rather than relying on a fixed nominal resistance value

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a highly accurate reference excitation current is applied to the shunt resistor, then the shunt resistance value can be determined accurately, but the cost increases due to requirements for high-precision reference components

Engineering Contradiction:

Improveshunt resistance measurement accuracyVSAvoidcost of high-precision reference components

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent uses ordinary, low-cost reference excitation current sources instead of high-precision reference components, accepting that the reference current may not be perfectly stable but compensating through measurement algorithms that determine resistance ratios rather than relying on absolute precision

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The system introduces a reference resistor as an intermediary element with known resistance, using it to create a comparable measurement circuit that allows determination of the shunt resistance through ratio calculations, thereby eliminating the need for highly accurate reference current sources

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If at least two voltage measurement circuits are provided to measure voltage across the shunt resistor, then redundant detection of load current is achieved, but the device complexity increases

Engineering Contradiction:

Improveredundant detection capabilityVSAvoidnumber of voltage measurement circuits

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The multiple voltage measurement circuits serve dual functions: they perform redundant measurement of the shunt voltage for reliability, and simultaneously enable determination of the shunt resistance value by comparing measurements, thereby achieving multiple objectives with the same added components

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 enables redundant detection of the load current and accurate measurement of the shunt resistance value, thereby improving the overall accuracy and reliability of the current measurement while minimizing costs associated with high-precision reference components.

Implementation Method 1

a current excitation circuit configured to generate an AC excitation current and supply the AC excitation current to the shunt resistor and the reference resistor

Methodology Applied

Scientific EffectAC excitation current generation:

Implementation Method 2

at least two voltage measurement circuits configured to measure a voltage across the shunt resistor

Methodology Applied

Scientific EffectVoltage measurement: Ohm's Law

Data Source

PatentUS20250102545A1Shunt-based current sensor

Publication Date: 2025.03.27 DENSO CORP

AI summary

A shunt-based current sensor executes redundancy detection of a load current flowing through a load by using a shunt resistor. The shunt-based current sensor includes a reference resistor, a current excitation circuit, at least two voltage measurement circuits and a signal processing circuit. The reference resistor is connected to the shunt resistor in series. The current excitation circuit generates an AC excitation current and supply the AC excitation current to the shunt resistor and the reference resistor. At least two voltage measurement circuits measure a voltage across the shunt resistor. A signal processing circuit executes signal processing based on respective measurement voltages of the at least two voltage measurement circuits, and is operated in the load current redundancy detection mode or a shunt resistance measurement mode.