Magnetic Sensor With Conversion Unit for Horizontal Field Detection
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Solution Overview
Problem
Magnetic sensors face reduced detection accuracy due to horizontal magnetic field components passing through magnetic shields, causing offsetting and fluctuations in midpoint potential.
Innovation Solution
A magnetic sensor design incorporating a magnetic field conversion unit, a magnetic field detection unit with a Wheatstone bridge circuit, and a magnetic shield, where the magnetic field conversion unit has a longer dimension orthogonal to the input and output directions, and the magnetic shield overlaps the conversion and detection units to shield external fields, utilizing magnetoresistive units with antiparallel magnetization fixed layers to stabilize output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a magnetic shield is provided to shield horizontal magnetic field components, then the harmful effect of horizontal magnetic fields is reduced, but the magnetic shield cannot completely shield the horizontal magnetic field component, causing offsetting and fluctuation in the midpoint potential
Solution Approach 1:
A magnetic field conversion unit is introduced as an intermediary between the magnet and the magnetic field detection unit. This conversion unit converts the horizontal magnetic field component generated by the magnet into a magnetic field component in the vertical direction (perpendicular to the substrate surface), which can then be detected by the magnetoresistive effect element. The magnetic shield remains in place to block direct horizontal field interference, while the conversion unit provides an indirect detection path that is not affected by the shield's limitations.
Solution Approach 2:
The invention changes the parameter being detected by converting the magnetic field component direction. Instead of directly detecting the horizontal magnetic field component (which is partially blocked by the shield), the system converts it into a vertical magnetic field component that can be fully detected by the magnetoresistive effect element. This parameter transformation allows the system to overcome the incomplete shielding effect and achieve stable detection without offsetting or midpoint potential fluctuation.
2Reliability
If the magnetic field conversion unit has a longer dimension in the third direction orthogonal to both input and output directions, then the conversion efficiency is improved, but the device area increases
Solution Approach 1:
The magnetic field conversion unit utilizes the third dimension (vertical direction perpendicular to both input and output directions) to achieve its function. By extending the conversion unit in this orthogonal dimension, the system improves magnetic field conversion efficiency and output stability without requiring additional area in the plane of the substrate. This dimensional approach allows the system to achieve reliable performance while minimizing the device footprint.
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 design effectively suppresses fluctuations in midpoint potential and enhances detection accuracy by stabilizing the output across varying magnetic field conditions.
Implementation Method 1
a magnetoresistive effect element (GMR element, TMR element, or the like) in which resistance changes in accordance with changes in an external magnetic field
Implementation Method 2
This soft magnetic material converts the vertical magnetic field component generated by the magnet into a magnetic field component in a direction parallel to the substrate surface
Data Source
AI summary
A magnetic sensor includes a magnetic field conversion unit that outputs an output magnetic field, a magnetic field detection unit that the output magnetic field can be applied, and a magnetic shield that shields external magnetic fields. The length of the magnetic field conversion unit in the third direction is greater than the length in the second direction. The magnetic shield overlaps the magnetic field conversion unit and the magnetic field detection unit. The magnetic field detection unit includes a Wheatstone bridge circuit in which a first bridge circuit including first and second magnetic field detection units and a second bridge circuit including third and fourth magnetic field detection units are connected in parallel. The first through fourth magnetic field detection units include two magnetoresistive units, and two of the magnetoresistive units have magnetoresistive effect elements that include magnetization fixed layers whose magnetization directions differ from each other.