GMR Current Sensor with Stacked Magnetoresistive Elements
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Solution Overview
Problem
Current current sensors face challenges in miniaturization and detection sensitivity, particularly with the use of giant magnetoresistive elements, which are prone to noise from external magnetic fields, and struggle with linearity and high-frequency response.
Innovation Solution
The design employs a current sensor configuration with first and second magnetoresistive elements having stacked structures with pinned layers, nonmagnetic intermediate layers, and free layers that change magnetization direction, positioned in the same layer level to enhance detection precision and stability, utilizing a bias magnetic field to stabilize the anisotropic field and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GMR elements are used to detect current magnetic field, then detection sensitivity and response characteristics are improved, but the sensor becomes prone to noise from external magnetic fields and stability deteriorates
Solution Approach 1:
The sensor divides the detection function into multiple GMR elements (first and second GMR elements) with different magnetization orientations. Each element responds to magnetic fields differently based on its pinned layer orientation, allowing the system to segment the detection task and process signals differentially to reject common-mode noise while preserving the desired measurement signal.
Solution Approach 2:
The invention employs asymmetric magnetization configurations where the first GMR element has its pinned layer magnetization oriented in one direction while the second GMR element has its pinned layer magnetization oriented in a different direction (e.g., perpendicular or at an angle). This asymmetric arrangement creates differential responses to external magnetic fields, enabling noise rejection through signal processing while maintaining high detection sensitivity.
2Volume of moving object
If miniaturization is pursued to create compact sensor configuration, then device size is reduced, but detection precision and stability deteriorate due to increased susceptibility to external noise
Solution Approach 1:
The invention transitions from planar arrangements to three-dimensional stacked configurations of GMR elements. By stacking GMR elements vertically with different magnetization orientations in the thickness direction, the sensor achieves compact footprint while maintaining multiple detection channels. This dimensional transition allows compact miniaturization without sacrificing detection precision, as the vertical stacking enables differential measurement capabilities within a small volume.
3Device complexity
If single GMR element configuration is used, then device complexity is reduced, but linearity and high frequency response characteristics are insufficient
Solution Approach 1:
The sensor segments the detection function across multiple GMR elements with different magnetization orientations. This segmentation enables the system to capture different components of the magnetic field signal, improving linearity through differential measurement and enhancing high-frequency response by capturing transient field changes that a single element might miss. The segmented approach maintains manageable complexity through systematic arrangement and signal processing.
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 allows for precise detection of induced magnetic fields with improved stability and sensitivity, reducing the impact of external noise and enhancing measurement accuracy even for weak currents.
Implementation Method 1
a giant magnetoresistive element (hereinafter, referred to as a GMR element) exhibiting a giant magnetoresistive effect is arranged in the current magnetic field by the control current so as to detect the gradient of the current magnetic field
Implementation Method 2
a pinned layer whose magnetization direction is pinned in a predetermined direction, a nonmagnetic intermediate layer, and a free layer whose magnetization direction changes according to the induced magnetic field
Implementation Method 3
the free layer exhibiting an anisotropic field in a direction different from the magnetization direction of the pinned layer
Data Source
AI summary
Provided is a current sensor capable of detecting an induced magnetic field by a current to be detected with higher precision. The first and second modules are provided on facing surfaces of integrated substrates, respectively, with spacers in between. Each of the first and second modules includes an element substrate, and an MR element layer. On each of the MR elements layers, provided is an MR element having a stacked structure including a pinned layer, a nonmagnetic intermediate layer, and a free layer whose magnetization direction changes according to the induced magnetic field and which exhibits an anisotropic field in a direction different from that of the magnetization of the pinned layer. The stacked structures of the MR elements are provided in a same layer level.