Magneto-resistance Current Sensor Bridge Circuit for Linear Output
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Solution Overview
Problem
Current sensors using magneto-resistance effect elements suffer from measurement accuracy issues due to non-proportional output of midpoint potential difference with respect to the induced magnetic field, leading to deteriorated measurement precision.
Innovation Solution
A current sensor design incorporating a magnetic detecting bridge circuit with four magneto-resistance effect elements, each with a self-pinned type ferromagnetic fixed layer formed by anti-ferromagnetic coupling of ferromagnetic films, and symmetrical wiring to the power supply, ensuring equal resistance change rates and 180° different magnetization directions, thereby achieving proportional output to the induced magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic detecting bridge circuit with magneto-resistance effect elements is used, then current detection capability is achieved, but measurement precision deteriorates due to non-proportional output of midpoint potential difference
Solution Approach 1:
The bridge circuit is segmented into four independent magneto-resistance effect elements, each responding to magnetic field components. This segmentation allows the system to achieve proportional output by combining the responses of individual elements, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent introduces asymmetric wiring configurations where two pairs of magneto-resistance effect elements have different wiring arrangements. This asymmetry in wiring combined with the symmetric magnetic field response creates a proportional output relationship, improving measurement precision while managing circuit complexity through deliberate asymmetric design.
2Measurement precision
If conventional magneto-resistance effect elements are used, then basic current detection is possible, but measurement accuracy is poor due to denominator terms in the potential difference equation
Solution Approach 1:
The patent changes the resistance parameters of the magneto-resistance effect elements by controlling their magnetization directions. By setting specific magnetization orientations (parallel or antiparallel), the resistance values are optimized to eliminate denominator terms in the potential difference equation, achieving high measurement accuracy while maintaining ease of manufacture through standard fabrication processes.
3Measurement precision
If symmetrical wiring is implemented, then wiring resistance differences are minimized, but device complexity increases
Solution Approach 1:
The patent employs asymmetric wiring configurations for two pairs of magneto-resistance effect elements, where the wiring arrangements are deliberately different. This asymmetric design, combined with the symmetric magnetic field response characteristics, achieves proportional output and minimizes wiring resistance differences while managing the complexity through purposeful asymmetric architecture.
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 ensures high accuracy in current measurement by eliminating denominator terms in the potential difference equation, providing a linear response to the induced magnetic field and minimizing wiring resistance differences.
Implementation Method 1
a magnetic detecting bridge circuit which is constituted of four magneto-resistance effect elements with a resistance value varied by application of an induced magnetic field from a current to be measured
Implementation Method 2
a self-pinned type ferromagnetic fixed layer which is formed by anti-ferromagnetically coupling a first ferromagnetic film and a second ferromagnetic film via an antiparallel coupling film therebetween
Implementation Method 3
has an output between two magneto-resistance effect elements... the output of the midpoint potential difference is varied in proportion to the induced magnetic field
Data Source
AI summary
A current sensor including a magnetic detecting bridge circuit which is constituted of four magneto-resistance effect elements with a resistance value varied by application of an induced magnetic field from a current to be measured, and which has an output between two magneto-resistance effect elements. The four magneto-resistance effect elements have the same resistance change rate, and include a self-pinned type ferromagnetic fixed layer which is formed by anti-ferromagnetically coupling a first ferromagnetic film and a second ferromagnetic film via an antiparallel coupling film therebetween, a nonmagnetic intermediate layer, and a soft magnetic free layer. Magnetization directions of the ferromagnetic fixed layers of the two magneto-resistance effect elements providing the output are different from each other by 180°. The magnetic detecting bridge circuit has wiring symmetrical to a power supply point.