Current Sensor with Self-Pinned Magnetoresistance Elements
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Solution Overview
Problem
Current sensors face challenges in downsizing and improving measurement accuracy due to the need for a U-shaped conductive body, which restricts downsizing and increases interference from induction magnetic fields.
Innovation Solution
A current sensor design using self-pinned type magnetoresistance effect elements with ferromagnetic fixed layers that can fix magnetization directions arbitrarily without an antiferromagnetic layer, allowing for parallel arrangement and a conductive body extending in one direction to reduce interference and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a U-shaped conductive body is used to draw current through opposite directions for magnetic field detection, then measurement capability is improved, but device size is increased and measurement accuracy is reduced due to interference
Solution Approach 1:
The conductive body is divided into multiple separate conductors (first conductor and second conductor) instead of using a single U-shaped structure. Each conductor carries current in the same direction, and multiple magnetoresistance effect elements are arranged to detect magnetic fields from different conductors. This segmentation allows independent positioning of each conductor and sensor element, reducing overall sensor area while maintaining measurement capability through differential detection of magnetic fields from multiple current paths.
2Measurement precision
If a U-shaped conductive body is used to draw current through opposite directions, then magnetic field detection capability is improved, but induction magnetic field interference is increased
Solution Approach 1:
Instead of trying to eliminate the induction magnetic fields generated by current-carrying conductors, the invention utilizes these fields constructively. Multiple magnetoresistance effect elements are positioned to detect magnetic fields from different conductors, and the detection circuit processes these signals differentially. The induction magnetic fields that would normally be considered interference are converted into useful detection signals, improving measurement capability while allowing conductors to be arranged in space without requiring a U-shape configuration.
3Area of stationary object
If magnetoresistance effect elements are arranged in parallel with arbitrary magnetization directions, then device downsizing is enabled, but traditional antiferromagnetic layer structures increase complexity
Solution Approach 1:
The invention extracts and eliminates the antiferromagnetic layer from the magnetoresistance effect element structure. Instead of using the conventional spin valve structure with antiferromagnetic, ferromagnetic fixed, nonmagnetic, and ferromagnetic free layers, the patent employs a simplified structure with only ferromagnetic fixed layers and ferromagnetic free layers separated by a nonmagnetic intermediate layer. The magnetization directions of the ferromagnetic fixed layers are set arbitrarily (e.g., in-plane or out-of-plane) without requiring antiferromagnetic coupling, thereby simplifying the element structure while enabling flexible arrangement for downsized sensor design.
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 enables the downsizing of current sensors, reduces interference from induction magnetic fields, and improves measurement accuracy and range, allowing for precise and extensive current measurement.
Implementation Method 1
a current sensor that uses a magnetoresistance effect element outputting an output signal owing to an induction magnetic field from a current to be measured
Implementation Method 2
owing to an exchange coupling magnetic field (Hex) occurring between the ferromagnetic fixed layer and the antiferromagnetic layer, the magnetization direction of the ferromagnetic fixed layer is fixed in one direction
Implementation Method 3
the magnetization direction of the free magnetic layer is changed owing to an external magnetic field
Data Source
AI summary
A current sensor includes a substrate, a conductive body being provided above the substrate and extending in one direction, and magnetoresistance effect elements being provided between the substrate and the conductive body and outputting output signals owing to an induction magnetic field from a current to be measured being conducted through the conductive body, wherein each of the magnetoresistance effect elements has a laminated structure including a ferromagnetic fixed layer whose magnetization direction is fixed, a non-magnetic intermediate layer, and a free magnetic layer whose magnetization direction fluctuates with respect to an external magnetic field, the ferromagnetic fixed layer is a self-pinned type formed by antiferromagnetically coupling a first ferromagnetic film and a second ferromagnetic film through an antiparallel coupling film, the Curie temperatures of the first ferromagnetic film and the second ferromagnetic film are approximately equal, and a difference between the magnetization amounts thereof is substantially zero.