Hall Effect Sensor Circuit with Dual Bias Voltage Segmentation
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Solution Overview
Problem
Hall effect sensors face a compromise in design between low residual offset error and high signal-to-noise ratio due to the need for balancing bias voltage, which results in neither characteristic being particularly good, leading to suboptimal performance in applications requiring low noise and high bandwidth.
Innovation Solution
A magnetic field sensor configuration with two circuit portions, one operating at a higher bias voltage and bandwidth for high frequencies and the other at a lower bias voltage and bandwidth for low frequencies, with signals from each portion being filtered and combined to reduce residual offset error and enhance signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a higher bias voltage is applied to the Hall effect sensor, then the signal-to-noise ratio is improved, but the residual offset error increases due to nonlinear effects
Solution Approach 1:
The sensor output is divided into two frequency bands using filter circuitry: a first output signal contains frequency components below a cutoff frequency (where offset error dominates), and a second output signal contains frequency components above the cutoff frequency (where noise is the main issue). This segmentation allows different processing strategies for different frequency ranges.
Solution Approach 2:
The bias voltage is dynamically adjusted based on frequency content: a first bias voltage is applied during phases when processing low-frequency signals (to minimize offset error), and a second, higher bias voltage is applied when processing high-frequency signals (to maximize signal-to-noise ratio). This parameter change resolves the contradiction by adapting the voltage level to the specific frequency band being processed.
2Measurement precision
If a lower bias voltage is applied to reduce residual offset error, then nonlinear effects are minimized, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The sensor output is divided into two frequency bands using filter circuitry: a first output signal contains frequency components below a cutoff frequency (where offset error dominates), and a second output signal contains frequency components above the cutoff frequency (where noise is the main issue). This segmentation allows different processing strategies for different frequency ranges.
Solution Approach 2:
The bias voltage is dynamically adjusted based on frequency content: a first bias voltage is applied during phases when processing low-frequency signals (to minimize offset error), and a second, higher bias voltage is applied when processing high-frequency signals (to maximize signal-to-noise ratio). This parameter change resolves the contradiction by adapting the voltage level to the specific frequency band being processed.
3Reliability
If a fixed bias voltage optimized for noise is used, then the signal-to-noise ratio is improved, but the residual offset error remains suboptimal
Solution Approach 1:
The bias voltage transitions from a fixed value to a dynamic, time-varying parameter. The control circuitry switches between a first bias voltage (optimized for low offset error) and a second bias voltage (optimized for low noise) based on the operating phase and frequency content of the signal. This dynamic adjustment allows the system to achieve optimal performance in both offset error and noise reduction, rather than being constrained to a fixed compromise.
Solution Approach 2:
The sensor operates in periodic phases where the bias voltage is switched between two values in a periodic manner. During first operating phases, a first bias voltage is applied with corresponding first filter settings; during second operating phases, a second bias voltage is applied with corresponding second filter settings. This periodic switching allows the system to periodically optimize for different performance metrics and combine the results.
4Measurement precision
If spinning current schemes are used to reduce residual offset error, then offset error is minimized, but the device complexity increases due to multiple switching operations
Solution Approach 1:
The bias voltage control circuitry serves multiple functions: it adjusts the bias voltage level based on frequency content, it coordinates with the filter circuitry to match cutoff frequencies with appropriate voltage levels, and it optimizes both offset error and signal-to-noise ratio simultaneously. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby managing complexity while achieving superior 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 approach reduces residual offset error and improves signal-to-noise ratio while maintaining low noise levels, achieving better performance than conventional designs by leveraging the benefits of both high and low bias voltage configurations.
Implementation Method 1
a first magnetic field sensor element configured for a first bias voltage and coupled to first filter circuitry to provide a first signal of a first bandwidth
Implementation Method 2
a second magnetic field sensor element configured for a second bias voltage less than the first bias voltage and coupled to second filter circuitry to provide a second signal of a second bandwidth less than the first bandwidth
Data Source
AI summary
Embodiments relate to Hall effect sensor circuits and devices that provide improved performance, such as reduced residual offset errors and/or improved S/N ratios. In an embodiment, a Hall effect sensor circuit comprises two circuit portions, a first with a higher bandwidth for higher frequencies and having an improved S/N ratio, and a second with a lower bandwidth for lower frequencies and having low residual offset. First and second Hall plates or devices are incorporated in the first and second circuit portions. The first Hall plate can be operated with a larger bias voltage and a larger, high-pass-filtered signal bandwidth, while the second Hall plate can be operated with a smaller bias voltage and a smaller, low-pass-filtered signal bandwidth. Individual output signals from each of the first and second Hall plates can be scaled and combined to provide an overall output signal with the benefits of each circuit portion, including reduced residual offset error and negligible increased noise.