Sensor Arrangement with Digital Current Mirror Feedback
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Solution Overview
Problem
Current sensor arrangements with multiple current biased sensor elements face challenges in maintaining consistent sensitivity due to non-linear errors, residual offset, offset drift, and sensitivity mismatch, which degrade performance over time and with temperature variations.
Innovation Solution
The solution involves generating base currents for each sensor element by mirroring a common input current and adjusting them using digitally controllable adjustment current sources, allowing for continuous equalization and minimizing drift effects through a feedback loop, enabling individual optimum bias current settings and accounting for static mismatches and drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If matched currents are provided for all sensor elements to overcome bias current mismatch, then sensitivity matching is improved, but device area increases and drift remains unaccounted for
Solution Approach 1:
The patent implements a feedback mechanism where the actual bias currents of individual sensor elements are measured and compared to a reference value. Based on the measured deviations, adjustment currents are generated and applied to the current mirror structures to compensate for mismatches. This closed-loop feedback system continuously maintains current matching without requiring oversized current mirrors, thereby achieving precise sensitivity matching with compact device area.
2Measurement precision
If current mirror area is enlarged to improve current matching, then bias current mismatch is reduced, but the system cannot account for time and temperature related drift
Solution Approach 1:
The system continuously measures the actual bias currents and compares them against a reference, generating adjustment signals that compensate for both initial mismatches and subsequent drift due to temperature and time variations. This dynamic feedback approach enables the system to maintain accurate current matching under varying operating conditions without requiring excessively large current mirrors.
Solution Approach 2:
The patent transitions from static current matching (fixed during operation) to dynamic current matching (continuously adjusted during operation). The bias currents are actively regulated through feedback control, allowing the system to adapt to changing environmental conditions and maintain precision throughout the operational lifetime.
3Measurement precision
If one-time calibration is performed to improve current matching, then initial sensitivity is improved, but drift over time and temperature cannot be compensated
Solution Approach 1:
Instead of relying on one-time calibration, the system implements continuous feedback control that actively monitors and adjusts bias currents throughout operation. The measured current deviations are continuously corrected through adjustment currents applied to the current mirrors, ensuring that sensitivity is maintained at the calibrated level despite temperature variations, aging, and other time-dependent effects.
Solution Approach 2:
The calibration process is transformed from a discrete one-time event into a continuous ongoing process. The feedback loop operates continuously during normal sensor operation, constantly making small adjustments to maintain optimal bias conditions, thereby extending the effective operational stability indefinitely rather than degrading over time.
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 sensor performance by minimizing the impact of bias current mismatches and drift, allowing for continuous adjustment during operation, and reducing the need for large current mirrors, while being compatible with existing techniques like current spinning and automatic gain control.
Implementation Method 1
respective base currents for the plurality of current biased sensor elements are generated by mirroring a common input current
Implementation Method 2
The measured Hall voltage for a Hall element is directly proportional to the magnetic field to be measured and to a bias current of the Hall element
Data Source
AI summary
A sensor arrangement has a current mirror structure that is configured to provide respective base currents at each of a plurality of output current paths based on an input current. For each of the output current paths, a respective adjustment current source is provided that is digitally controllable and is connected to the respective output current path for adjusting the base current of said output current path. For each of the output current paths, a current biased sensor element is coupled in said output current path. The sensor arrangement further has a selection element for selectively connecting one of the output current paths to an evaluation block based on a selection signal. The evaluation block is configured to generate a sensing value corresponding to a resulting current in the connected output current path, to compare the sensing value with an average value, and to update the average value based on the sensing value. A digital control is adapted for generating the selection signal and for digitally adjusting the respective adjustment current source of the connected output current path based on the comparison result.