Parallel Hall Quad Sensor Circuit for High-Bandwidth Low-Offset Sensing
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Solution Overview
Problem
Magnetic field sensors face challenges in achieving high bandwidth with minimal offset drift over temperature and stress due to inherent limitations in Hall effect sensor technology, which restricts their ability to accurately sense rapid magnetic field fluctuations.
Innovation Solution
The use of multiple Hall quad elements in parallel connected to a chopper stabilized amplifier reduces the time constant and offset, allowing for higher bandwidth sensing by chopping at higher frequencies and eliminating stress-induced offsets, thereby achieving a bandwidth of up to 1 MHz with minimal offset drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional Hall effect sensors are used, then the sensor can detect magnetic fields, but the bandwidth is limited and offset drift occurs over temperature and stress
Solution Approach 1:
The sensor divides the sensing function into multiple independent Hall-type elements (at least two) that operate in parallel. Each element contributes to the overall signal while the parallel configuration reduces the effective time constant, enabling higher bandwidth operation without excessive offset drift
Solution Approach 2:
The patent changes the electrical parameters of the sensing system by connecting multiple Hall elements in parallel, which reduces the equivalent resistance and time constant. This parameter modification allows the sensor to achieve 1 MHz bandwidth while the chopper stabilized amplifier actively compensates for offset drift through periodic signal modulation and filtering
2Speed
If the bandwidth is increased to 1 MHz, then the sensor can detect faster magnetic field fluctuations, but the offset drift over temperature and stress increases
Solution Approach 1:
The chopper stabilized amplifier provides active feedback control by periodically modulating the input signal and using feedback to cancel offset voltages. This feedback mechanism continuously compensates for temperature and stress-induced offset drift, allowing high bandwidth operation with maintained measurement precision
Solution Approach 2:
The chopper stabilized amplifier employs periodic chopping action to modulate the DC offset to a higher frequency where it can be filtered out. This periodic modulation and filtering approach separates the offset drift component from the AC signal, enabling high bandwidth while maintaining low offset drift
3Speed
If multiple Hall quad elements are used in parallel, then the bandwidth increases to 1 MHz, but the device complexity increases
Solution Approach 1:
The patent combines multiple Hall-type elements into a unified parallel configuration that functions as a single sensing unit. The merged structure shares common biasing and readout circuitry through the chopper stabilized amplifier, reducing the overall complexity compared to using multiple independent sensors while achieving the desired bandwidth performance
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 enables higher bandwidth sensing with reduced offset drift over temperature and stress, allowing for more accurate detection of rapid magnetic field fluctuations, improving the performance of magnetic field sensors in applications such as gear tooth sensing.
Implementation Method 1
Magnetic field sensors generally include a magnetic field sensing element... Various types of magnetic field sensing elements are known, including Hall effect elements
Implementation Method 2
a chopper stabilized amplifier and a plurality of Hall-type elements in parallel and connected to the chopper stabilized amplifier
Data Source
AI summary
In one aspect, a magnetic field sensor includes a chopper stabilized amplifier and a plurality of Hall-type elements in parallel and connected to the chopper stabilized amplifier. In another aspect, a magnetic field sensor includes a chopper stabilized amplifier and a plurality of Hall quad elements in parallel and connected to the chopper stabilized amplifier. In a further aspect, a current sensor has a bandwidth of 1 MHz and includes a chopper stabilized amplifier and a plurality of Hall quad elements, fabricated in silicon, in parallel and connected to the chopper stabilized amplifier.