Magnetic Field Sensor Sensitivity Stabilization via Piezoresistive Feedback
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Solution Overview
Problem
Magnetic field sensors experience sensitivity changes due to temperature variations and manufacturing-induced strains, leading to undesirable performance fluctuations.
Innovation Solution
A magnetic field sensor with a feedback circuit and gain-adjustment mechanism that includes piezoresistors and a current conductor to monitor and adjust sensitivity in response to temperature and strain changes, maintaining invariant sensitivity across temperature excursions and manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If temperature compensation is implemented using traditional methods, then temperature stability improves, but device complexity increases
Solution Approach 1:
The patent combines the temperature sensing function and strain compensation function into a single integrated feedback circuit that uses piezoresistors embedded in the substrate. This merged approach allows the circuit to simultaneously measure temperature-induced strain and compensate for sensitivity changes, achieving temperature compensation without requiring separate sensing and compensation circuits, thereby reducing overall device complexity.
Solution Approach 2:
The patent introduces piezoresistors as intermediary elements that are embedded in the substrate to sense temperature-induced strain. These piezoresistors act as mediators between the temperature changes and the feedback control mechanism, converting thermal effects into electrical signals that can be processed by the feedback circuit to adjust the magnetic field sensor's sensitivity accordingly.
2Stability of the object's composition
If sensitivity adjustment circuitry is added, then sensitivity stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the sensitivity adjustment functionality with the existing substrate structure by embedding piezoresistors directly into the substrate during manufacturing. This integration allows the sensitivity adjustment circuitry to be formed as part of the substrate fabrication process rather than as a separate assembly step, simplifying the overall manufacturing process while maintaining sensitivity stability.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support for the magnetic field sensor, acts as a platform for embedding piezoresistors, and functions as part of the feedback control system. This multi-functional design eliminates the need for separate components for each function, reducing manufacturing steps and improving ease of production while achieving sensitivity stability.
3Stability of the object's composition
If piezoresistors are embedded in the substrate, then sensitivity compensation improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates piezoresistors into the substrate during the substrate fabrication process itself, before the magnetic field sensor is assembled. This preliminary action ensures that the piezoresistors are precisely positioned relative to the sensor elements without requiring high-precision post-fabrication alignment, as the positioning is established during the standard substrate manufacturing process.
Solution Approach 2:
By combining the piezoresistor fabrication with the substrate manufacturing process, the patent eliminates the need for separate precision alignment steps. The piezoresistors are formed as integral parts of the substrate structure using the same fabrication techniques and equipment already employed for substrate production, thereby maintaining manufacturing precision without adding complexity.
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 effectively stabilizes the sensitivity of magnetic field sensors, ensuring consistent performance by dynamically adjusting the gain in response to temperature and strain conditions.
Implementation Method 1
The first piezoresistor has a node at which a first piezoelectric output signal is generated. The first piezoelectric output signal is responsive to a strain of the substrate in a first direction.
Implementation Method 2
The current conductor is for generating a second magnetic field.
Implementation Method 3
A magnetic field sensing element can be characterized by a variety of performance characteristics, one of which is a sensitivity, which can be expressed in terms of an output signal amplitude versus a magnetic field to which the magnetic field sensing element is exposed.
Data Source
AI summary
Magnetic field sensors have a magnetic field sensing element and also a feedback circuit to provide a gain-adjustment signal to affect a sensitivity associated with the magnetic field sensing element. In some arrangements, the feedback circuit can include piezoresistors to sense a strain of a substrate over which the magnetic field sensor is disposed. With these arrangements, the feedback circuit can generate the gain-adjustment signal in accordance with the sensed strain. In other arrangements, the feedback circuit can generate pulsed magnetic fields proximate to the magnetic field sensing element in order to directly measure the sensitivity of the magnetic field sensing element. With these arrangements, the feedback circuit can generate the gain-adjustment signal in accordance with the sensed sensitivity.