Magnetic Field Sensor With Segmented Back-Bias Magnets

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Solution Overview

Problem

Existing magnetic field measuring devices face challenges in accurately detecting the z-component of magnetic fields due to background field distortions and temperature-related deviations, leading to significant offset voltages and reduced sensitivity.

Innovation Solution

A magnetic field measuring device is designed with two spaced-apart magnets and a ferromagnetic encoder, where the magnets' axes are orthogonal to the semiconductor body's surface, allowing for modulation of magnetic field lines to deflect them in the z-direction, thereby reducing background field interference and enhancing sensitivity by minimizing measurable z-component without the encoder.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single magnet is used in the magnetic field measuring device, then the structure is simple, but the background field distortions are significant and temperature-related deviations cause large offset voltages

Engineering Contradiction:

Improvemagnet arrangementVSAvoidz-component detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The single magnet is divided into two separate magnets positioned on opposite sides of the semiconductor body. This segmentation allows the background field distortions to cancel each other out while maintaining measurement precision for the z-component of magnetic fields.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The two magnets are positioned asymmetrically relative to the semiconductor body, with their axes oriented in opposite directions. This asymmetric arrangement creates a balanced configuration that minimizes background field effects and reduces temperature-related offset voltages.

Inventive Principle:

Principle #4Asymmetry

2Strength

If magnets are positioned close to the semiconductor body, then the magnetic field strength is high, but background field interference and pre-induction values increase

Engineering Contradiction:

Improvemagnetic field strengthVSAvoidbackground field interference

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The harmful background field component is extracted and canceled by introducing a second magnet with opposite polarity. The two magnets work together to eliminate the unwanted z-component background field while maintaining the necessary magnetic field strength for measurement.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The magnetic field components that would normally cause background interference are converted into beneficial cancellation effects. By strategically positioning two magnets with opposite polarities, the background field interference is transformed into a cancellation mechanism that improves measurement precision.

Inventive Principle:

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

3Stability of the object's composition

If the magnetization direction is parallel to the surface, then the magnetic field lines remain in the x-y plane, but the z-component detection capability is reduced

Engineering Contradiction:

Improvemagnetic field line orientationVSAvoidz-component detection sensitivity

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The magnetic field orientation is changed from being confined to the x-y plane to having a significant z-component. By orienting the magnetization direction perpendicular to the surface, the magnetic field lines are deflected into the z-direction, enabling effective detection of the z-component of magnetic fields.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 significantly reduces background field distortions, improves matching between magnetic field sensors, and increases sensitivity by minimizing pre-induction values from 50 mT to below 1 mT, enhancing the detection of z-component magnetic fields.

Implementation Method 1

A Hall voltage is generated by bringing a ferromagnetic plate closer in the Hall sensor

Methodology Applied

Scientific EffectHall effect: Hall Effect

Implementation Method 2

The magnets in an arrangement of this type can also be called 'back-bias' magnets. For this purpose, the magnetic field of both magnets must be modulated by means of a ferromagnetic body, an encoder, such that the magnetic field lines of the magnets are deflected from the quiescent state in the x-y plane at least partially in the z-direction.

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS11585676B2Magnetic field measuring device

Publication Date: 2023.02.21 TDK MICRONAS GMBH

AI summary

A magnetic field measuring device having a semiconductor body with a first surface running in an x-y plane, with a first and second magnetic field sensor disposed on the surface, and an axis of symmetry, which runs perpendicular to the first surface in the z-direction and to which the magnetic field sensors are positioned in a mirrored fashion, first and second magnets, which are spaced apart from one another and in each case have an axis and a polar surface running perpendicular to the axis and facing the semiconductor body. The magnetic polarity changes along the axes on a surface, whereby the axes run in the direction of the axis of symmetry, whereby the axis of symmetry runs between the axes of the magnets, whereby the surfaces of the magnets in each case are spaced apart in the z-direction to the first surface of the semiconductor body.