Magnetic Field Sensor With Switchable Flux Conductor
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Solution Overview
Problem
TMR and GMR sensors used in mobile devices suffer from strong 1/f noise, making it difficult to accurately measure small magnetic fields like the Earth's magnetic field, as the direct application of the spinning current principle used in Hall sensors is not applicable.
Innovation Solution
A magnetic field sensor with a flux conductor assembly and switchable elements that deflect the external magnetic field onto a sensor unit, allowing for periodic reversal of the flux direction, enabling differentiation between noise offset and actual signal through modulation of the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If TMR sensors or GMR sensors are used for mobile devices, then power consumption is reduced compared to Hall sensors, but 1/f noise becomes strongly pronounced making accurate measurement of small magnetic fields difficult
Solution Approach 1:
The patent applies periodic action by repeatedly switching the magnetic flux conductor between different magnetic states (saturated and unsaturated) at a frequency above 1/f noise frequencies. This periodic switching modulates the magnetic flux reaching the sensor, enabling the measurement system to operate at higher frequencies where 1/f noise is reduced, thereby improving measurement accuracy while maintaining low power consumption of TMR/GMR sensors
Solution Approach 2:
The patent introduces a magnetic flux conductor as an intermediary element between the external magnetic field and the TMR/GMR sensor. This flux conductor can be switched between saturated and unsaturated states to modulate the magnetic flux, effectively transferring the magnetic field information to the sensor in a manner that avoids direct 1/f noise contamination while preserving the sensor's low power consumption advantages
2Measurement precision
If the spinning current principle is applied to TMR sensors or GMR sensors, then an attempt is made to suppress 1/f noise, but the direct application is not applicable since reversal of measuring current does not result in inversion of measuring signal
Solution Approach 1:
Instead of reversing the measuring current through the sensor as in conventional spinning current methods, the patent inverts the approach by switching the magnetic flux conductor's state to reverse the direction of magnetic flux reaching the sensor. This inversion of the flux path rather than current direction achieves signal modulation while being compatible with TMR/GMR sensor characteristics that do not respond to current reversal
Solution Approach 2:
The patent replaces the electrical current reversal mechanism with a magnetic flux switching mechanism. Instead of using electrical spinning current to modulate the measurement, it uses magnetic flux conductors that can be switched between saturated and unsaturated states to achieve flux reversal, substituting an electrical control mechanism with a magnetic field-based control mechanism suitable for TMR/GMR sensors
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 solution significantly reduces noise behavior, allowing for accurate measurement of external magnetic fields by computing out 1/f noise contributions through periodic reversal of the deflected flux, improving measurement accuracy in mobile devices.
Implementation Method 1
The flux conductor assembly (110) includes at least one switchable element (101, 102, 103, 104), which is designed to deflect a flux of the external magnetic field (100) onto the sensor unit (107) as a function of a switching state of the at least one switchable element (101, 102, 103, 104)
Implementation Method 2
TMR sensors are based on the tunnel magnetoresistance (TMR), the tunnel current changing as a function of the magnetic orientation of two thin magnetic layers
Implementation Method 3
GMR sensors are based on the giant magnetoresistance (GMR), which occurs in structures which have various magnetic and nonmagnetic thin layers. The electrical resistance is dependent in this case on the mutual orientation of the magnetization of these various layers
Data Source
AI summary
A magnetic field sensor for measuring an external magnetic field, including a sensor unit; and a flux conductor assembly including at least one switchable element, which is designed to deflect a flux of the external magnetic field onto the sensor unit as a function of a switching state of the at least one switchable element, the sensor unit being designed to measure the deflected flux of the external magnetic field; and an evaluation unit, which is designed to ascertain a value of the external magnetic field as a function of the deflected flux of the external magnetic field measured by the sensor unit and the switching state of the at least one switchable element.