Bridge Magnetic Sensor Dummy Resistor Structure
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Solution Overview
Problem
Magnetic field sensors face challenges with offset issues and sensitivity changes due to temperature and stress, which affect the accuracy of Hall element measurements, particularly in current biasing methods that compromise sensitivity at varying temperatures.
Innovation Solution
A bridge sensor design incorporating a dummy resistor structure with regulators to maintain a quasi-constant voltage and current, ensuring the dummy common mode voltage matches the sensor structure's common mode voltage, thereby stabilizing resistivity and sensitivity across temperature and stress changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current biasing is used to improve offset, then sensitivity is reduced at low to medium-high temperatures
Solution Approach 1:
The patent implements dynamic biasing by switching between voltage biasing and current biasing modes based on temperature conditions. The system dynamically adjusts the biasing method to optimize performance across different temperature ranges, using voltage biasing at lower temperatures for maximum sensitivity and current biasing at higher temperatures for offset control.
Solution Approach 2:
The patent changes the biasing parameter (voltage vs. current) based on temperature. By monitoring temperature and adjusting the biasing mode accordingly, the system adapts to maintain optimal sensitivity and offset characteristics across the operating temperature range.
2Reliability
If voltage biasing is used to maximize sensitivity, then offset increases
Solution Approach 1:
The system dynamically selects between voltage biasing and current biasing based on temperature. At lower temperatures where sensitivity is critical, voltage biasing is applied to maximize sensitivity. At higher temperatures, the system switches to current biasing to control offset, thus dynamically optimizing the trade-off between sensitivity and offset.
Solution Approach 2:
The biasing parameter is changed from voltage to current based on temperature conditions. This parameter change allows the system to achieve high sensitivity when using voltage biasing at low temperatures while controlling offset when using current biasing at high temperatures.
3Measurement precision
If current biasing is optimized for maximum temperature, then sensitivity is sub-optimal at lower temperatures
Solution Approach 1:
The patent implements a dynamic temperature-compensated biasing system that automatically adjusts the biasing mode based on the operating temperature. When the temperature drops below the optimized maximum temperature, the system switches to voltage biasing to maintain optimal sensitivity. When the temperature is at or above the optimized point, it uses current biasing for optimal offset control.
Solution Approach 2:
The system changes the biasing parameter from current to voltage when temperature decreases below the optimized maximum temperature. This parameter change ensures that sensitivity remains optimal across the full temperature range rather than being optimized for a single temperature point.
4Adaptability or versatility
If Hall plate resistance varies with temperature and stress, then drift increases and dynamic response is affected
Solution Approach 1:
The patent incorporates temperature and stress sensing elements that provide feedback about the operating conditions to the biasing circuitry. This feedback mechanism allows the system to detect changes in Hall plate resistance due to temperature and stress, and automatically adjust the biasing mode to compensate for these changes, thereby reducing drift and maintaining stable dynamic response.
Solution Approach 2:
The patent introduces intermediary sensing elements that measure temperature and stress conditions. These intermediaries provide information about environmental effects on the Hall plate resistance, enabling the biasing circuitry to compensate for resistance variations and maintain stable operation across different temperature and stress conditions.
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 approach improves noise performance and minimizes residual offsets, maintaining sensitivity and accuracy across different temperatures and stress conditions, while reducing current consumption and enhancing stability.
Implementation Method 1
Hall elements for measuring a magnetic field are well known, and are used inter alia in current sensors, or in angular position sensors, where a magnetic field (e.g. generated by a permanent magnet) is measured at several locations of the sensor device, and is converted into an angular position
Data Source
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AI summary
A bridge sensor (100) comprising at least one dummy resistor structure (110), at least one magnetic sensor structure (120), a first and a second regulator (130, 140), the dummy resistor structure and the sensor structure being bridge structures. The first regulator (130) is adapted to apply a predefined bias voltage between bias contacts of the at least one dummy resistor structure (110) and a related current at one of bias contacts of the at least one sensor structure (120). The second regulator (140) is adapted to regulate a dummy common mode voltage of the at least one dummy resistor structure (110) such that the dummy common mode voltage of the at least one dummy resistor structure (110) is the same as the common mode voltage of the at least one sensor structure (120).