Magnetoresistance Sensor Reset Circuit for Hysteresis Uncertainty

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Solution Overview

Problem

Magnetoresistance elements in magnetic field sensors suffer from hysteresis characteristics that lead to uncertainty in sensing magnetic fields, particularly when exposed to large or transient magnetic fields, resulting in reduced accuracy and linearity.

Innovation Solution

An electronic circuit with a primary magnetoresistance element and a secondary magnetic field sensing element, where a reset conductor generates a reset magnetic field to temporarily force the primary magnetoresistance element into a saturation region of its hysteresis characteristic, allowing deterministic operation on a known portion of the hysteresis curve.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a magnetoresistance element is used to sense magnetic fields, then sensitivity is improved, but hysteresis characteristic causes uncertainty in measurement

Engineering Contradiction:

Improvemagnetic field sensing accuracyVSAvoidmeasurement uncertainty due to hysteresis

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by using a reset conductor to periodically force the magnetoresistance element into a known saturation state before normal sensing operations. This reset action occurs in advance to eliminate hysteresis uncertainty, ensuring the element starts from a deterministic point on its hysteresis curve. The reset conductor generates a reset magnetic field that temporarily saturates the magnetoresistance element, establishing a known initial state for subsequent measurements.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If a closed loop configuration is used to eliminate hysteresis effects, then measurement accuracy is improved, but the system cannot handle large magnetic fields that cause saturation

Engineering Contradiction:

Improvemagnetic field sensing accuracyVSAvoidability to handle large magnetic fields

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by implementing a hybrid configuration that can adapt between open-loop and closed-loop modes. The system dynamically switches configurations based on magnetic field magnitude: using open-loop with periodic reset for large fields that cause saturation, and closed-loop feedback for smaller fields where hysteresis can be compensated. This dynamic adaptability allows the system to handle both large and small magnetic fields effectively.

Inventive Principle:

Principle #15Dynamics

3Reliability

If periodic reset is applied to eliminate hysteresis uncertainty, then measurement reliability is improved, but additional circuit components are required

Engineering Contradiction:

Improvemeasurement consistencyVSAvoidcircuit component count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing the reset conductor to serve multiple functions: it acts as a reset mechanism to eliminate hysteresis uncertainty, and can also function as part of the sensing circuitry. The reset conductor is disposed proximate to the magnetoresistance element and can be integrated into the existing sensor structure, reducing the need for completely separate reset components and minimizing overall device complexity while maintaining measurement reliability.

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 approach reduces the uncertainty in sensed magnetic fields by ensuring the magnetoresistance element operates on a specific linear region of its hysteresis characteristic, enhancing sensitivity and linearity of magnetic field sensing.

Implementation Method 1

a reset conductor disposed proximate to the magnetoresistance element... configured to generate a reset current... In response to the reset current, the reset conductor is configured to generate a reset magnetic field

Methodology Applied

Scientific EffectMagnetic field generation: Magnetic Field

Implementation Method 2

magnetoresistance elements change resistance in proportion to a magnetic field... a primary magnetoresistance element for providing a first output signal proportional to a magnetic field

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

a secondary magnetic field sensing element for providing a second output signal proportional to a magnetic field... sensing a magnetic field with a secondary magnetic field sensing element

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Data Source

PatentUS8063634B2Electronic circuit and method for resetting a magnetoresistance element

Publication Date: 2011.11.22 ALLEGRO MICROSYSTEMS LLC

AI summary

An electronic circuit includes a primary magnetoresistance element for providing a first output signal proportional to a magnetic field. The primary magnetoresistance element has a primary maximum response axis. The primary magnetoresistance element also has a hysteresis characteristic. The electronic circuit also includes a reset conductor disposed proximate to the magnetoresistance element. The electronic circuit also includes a secondary magnetic field sensing element for providing a second output signal proportional to a magnetic field. The secondary magnetic field sensing element has a secondary maximum response axis, which, in some embodiments, is substantially perpendicular to the primary maximum response axis. In operation, the primary magnetoresistance is reset in accordance with an excessive magnetic field sensed by the secondary magnetic field sensing element.