Compact Magnetoresistive Current Sensor for High-Precision Detection
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Solution Overview
Problem
Current current sensors face challenges in accurately detecting small signal currents in communication devices due to adverse influences on the communication system, limited frequency bands, and size constraints, with existing methods like transformers and photocouplers being inadequate for direct current detection and prone to signal deterioration over time.
Innovation Solution
A compact current sensor design featuring strip-shaped magnetoresistive elements and thin film coils, where the magnetoresistive elements are positioned closer to the thin film coils to enhance the current magnetic field application, allowing for high-sensitivity and high-precision current detection while maintaining a compact configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional GMR element is provided adjacent to a line to be measured in an in-plane direction, then the device configuration is simple, but it is difficult to detect weak current and miniaturization is disadvantaged
Solution Approach 1:
The patent transitions from in-plane arrangement to vertical stacking by positioning the magnetoresistive element above the conductor at a predetermined distance. This dimensional change allows the magnetic field to penetrate through the insulating film vertically, enabling both compact device footprint and effective detection of weak currents through enhanced magnetic coupling in the vertical direction.
Solution Approach 2:
The patent implements a nested structure where the magnetoresistive element is positioned above the conductor with the insulating film between them, creating a layered configuration. The coil is then positioned to apply magnetic fields through this nested arrangement, allowing multiple functional layers to occupy minimal horizontal space while maintaining effective detection and actuation distances.
2Measurement precision
If resistors are connected in series to measure current, then current detection is achieved, but a load different from communication system is applied and adverse influence is exerted
Solution Approach 1:
The patent replaces the electrical measurement method (series resistors causing voltage drops) with a magnetic field-based detection method. The magnetoresistive element detects the magnetic field generated by the current flowing in the conductor, enabling current measurement without introducing additional electrical loads or voltage drops that would adversely affect the communication system.
Solution Approach 2:
The patent introduces the magnetic field as an intermediary between the current-carrying conductor and the detection element. The magnetoresistive element responds to the magnetic field generated by the signal current, allowing indirect measurement that isolates the detection process from the electrical circuit, thereby avoiding adverse influences on the communication system.
3Adaptability or versatility
If a transformer is used to measure signal current, then alternate current detection is achieved, but direct current cannot be transmitted and frequency band is limited
Solution Approach 1:
The patent changes the detection mechanism from electromagnetic induction (transformer) to magnetoresistive effect, which responds to static and dynamic magnetic fields equally. This parameter change in the detection principle enables the system to detect both direct current (DC) and alternate current (AC) without frequency band limitations, significantly improving adaptability to different current types.
4Reliability
If photocoupler is used for current detection, then frequency characteristics are excellent, but size reduction is difficult and signal deterioration occurs over time
Solution Approach 1:
The patent replaces the optical detection method (photocoupler) with a magnetic field-based magnetoresistive detection method. This substitution maintains excellent frequency characteristics because the magnetoresistive element responds rapidly to magnetic field changes, while simultaneously enabling significant size reduction as the magnetoresistive element and associated coil structure occupy much less space than photocoupler components.
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
The design enables precise measurement of weak currents with improved sensitivity and noise reduction, maintaining a low resistance value and increasing the absolute resistance change, thus enhancing detection precision and reducing heat generation and external noise interference.
Implementation Method 1
a first thin film coil which includes a plurality of winding body portions extending in the first direction in correspondence with the element patterns in the first magnetoresistive element, winds at a second level different from the first level, and applies a first current magnetic field to each of the element patterns in the first magnetoresistive element when a current to be detected is supplied
Implementation Method 2
a first magnetoresistive element including a plurality of strip-shaped element patterns which extend in a first direction at a first level and are disposed so as to be adjacent to each other in a second direction orthogonal to the first direction
Data Source
AI summary
The present invention provides a compact current sensor capable of measuring a current to be detected with high precision. A current sensor includes: a first magnetoresistive element including a plurality of element patterns which extend in an X axis direction at a first level, are disposed so as to be adjacent to each other in a Y axis direction orthogonal to the X axis direction, and are connected in parallel with each other; and a thin film coil which includes a plurality of winding body portions extending in the X axis direction in correspondence with the element patterns and winds at a second level different from the first level, and applies a current magnetic field to each of the element patterns when a current to be detected is supplied. Therefore, the absolute value of the resistance change amount in the magnetoresistive element increases. While realizing a compact configuration, the current to be detected, flowing in the thin film coil can be measured with high precision.