Hall Sensor Bias Current Splitting for Stable Signal Linearity
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Solution Overview
Problem
Existing magnetic field sensors face challenges in accurately measuring electric currents and object positions due to the decreasing magnetic field flux density with increasing distance from the current-carrying conductor, and the need for precise biasing to maintain sensitivity and linearity.
Innovation Solution
A magnetic field sensor chip with an input terminal for receiving an external bias current, an internal current generator to split the bias current into multiple internal bias currents, a Hall sensor biased by the first internal bias current to generate a sensor signal based on the magnetic field, and an amplifier biased by the second internal bias current to amplify the sensor signal, all integrated on a semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor element is placed in close proximity to the current-carrying conductor to improve measurement sensitivity, then the magnetic field flux density increases, but the device complexity and potential interference increase
Solution Approach 1:
The patent combines the Hall sensor, current generator, amplifier, and offset compensation circuitry into a single integrated sensor element structure. This merging allows the sensor to achieve high measurement sensitivity through close proximity to the conductor while managing complexity through integration rather than separate discrete components.
Solution Approach 2:
The patent introduces a magnetic field shielding layer as an intermediary between the sensor element and the current-carrying conductor. This shielding layer mediates the magnetic field interaction, allowing the sensor to detect the field accurately while reducing direct interference and enabling the sensor to be positioned optimally without excessive complexity.
2Device complexity
If a single bias current is used for both Hall sensor and amplifier to simplify the circuit, then the device complexity decreases, but the operating point stability deteriorates
Solution Approach 1:
The patent segments the bias current into separate current paths for the Hall sensor and the amplifier. The current generator produces a reference current that is divided into a first bias current for the Hall sensor and a second bias current for the amplifier. This segmentation allows independent optimization of each component's operating point, ensuring stability while maintaining circuit simplicity through the unified current generation approach.
Solution Approach 2:
The patent implements offset compensation circuitry that uses feedback to detect and correct operating point drifts. The feedback mechanism continuously monitors the output and adjusts the bias currents accordingly, maintaining stable operating points for both the Hall sensor and amplifier even when using a unified current generation approach.
3Measurement precision
If the Hall sensor operates at a fixed operating point to maintain linearity, then the measurement accuracy improves, but the adaptability to different magnetic field conditions decreases
Solution Approach 1:
The patent employs dynamic biasing where the first bias current for the Hall sensor can be adjusted based on the measured magnetic field conditions. The current generator adapts the bias current levels to maintain the Hall sensor at its optimal linear operating point across varying magnetic field strengths, thereby preserving linearity and accuracy while adapting to different measurement conditions.
4Measurement precision
If the amplifier gain is increased to improve signal output, then the signal-to-noise ratio improves, but the offset components and noise are amplified
Solution Approach 1:
The patent uses offset compensation circuitry that converts the harmful offset components into a correctable signal. The compensation circuitry detects the offset and generates a compensating signal that cancels the offset before amplification. This allows the amplifier to operate at high gain for improved signal output while the offset compensation prevents noise and offset amplification, effectively converting the potential harm into a benefit.
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 enables accurate measurement of electric currents and object positions by maintaining the Hall sensor at a precise operating point and the amplifier in an active region, thereby enhancing sensitivity and linearity while reducing noise and offset components.
Implementation Method 1
a Hall sensor configured to be biased by the first internal bias current and set at a first operating point based on the first internal bias current, wherein the Hall sensor is further configured to generate a sensor signal based on a magnetic field and the first operating point
Data Source
AI summary
A magnetic field sensor chip includes an input terminal configured to receive an external bias current from an external current source; an internal current generator configured to split the external bias current into a plurality of internal bias currents, including a first internal bias current and a second internal bias current; a Hall sensor configured to be biased by the first internal bias current and set at a first operating point based on the first internal bias current, wherein the Hall sensor is further configured to generate a sensor signal based on a magnetic field and the first operating point; and an amplifier configured to be biased by the second internal bias current and set at a second operating point based on the second internal bias current. The amplifier is configured to amplify the sensor signal into an amplified sensor signal based on the second operating point.