Sensor Offset Error Compensation Using Variable Supply Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sensors often suffer from offset errors due to slight mismatches in sensor elements, leading to residual offset errors that conventional techniques, such as the spinning current principle, cannot fully eliminate.
Innovation Solution
The solution involves operating sensors at different input conditions, such as varying supply voltages or magnetic fields, to generate output signals with distinct offset errors, which are then combined using a correction factor to cancel out the offset, thereby producing an offset-free total output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spinning current principle is used to cancel offset, then magnetic field proportional terms are enhanced, but residual offset error remains (about 30 micro-Tesla for Hall plates and about 0.5-1 mT for vertical Hall devices)
Solution Approach 1:
The patent changes the operating parameter from fixed supply voltage to variable supply voltage, operating the sensor at multiple different supply voltages (first supply voltage and second supply voltage) to generate multiple output signals. This parameter change enables the system to capture offset error characteristics at different operating conditions, allowing for more comprehensive offset compensation through correction factors derived from the voltage-dependent offset behavior.
2Measurement precision
If sensor elements are made identical to reduce offset, then manufacturing complexity increases, but offset error cannot be fully eliminated due to inherent mismatches (0.1%-1% resistance variation)
Solution Approach 1:
The patent implements feedback by measuring the actual offset error at different supply voltages and using this information to calculate correction factors. The correction circuitry continuously compensates for offset errors by applying these correction factors to the sensor output, creating a closed-loop system that adapts to manufacturing variations without requiring extremely precise sensor element matching during fabrication.
3Measurement precision
If multiple clock phases are used to extend spinning current principle, then offset cancellation improves, but device complexity increases (more than four sensor elements required)
Solution Approach 1:
The patent makes the sensor elements multi-functional by utilizing them at different supply voltages rather than requiring separate sensor elements for different clock phases. The same sensor elements can operate under multiple supply voltage conditions, generating multiple output signals that are processed to eliminate offset errors, thereby reducing the total number of sensor elements needed while maintaining comprehensive offset cancellation capability.
Data Source
AI summary
Embodiments relate to reducing offset error in sensor systems. In embodiments, the sensitivity and offset of a sensor depend differently on some parameter, e.g. voltage, such that operating the sensor at two different values of the parameter can cancel the offset error. Embodiments can have applicability to stress sensors, Hall plates, vertical Hall devices, magnetoresistive sensors and others. The offset error can be reduced using a correction factor based on a first offset error of the sensor system when operated in a first phase and a second offset error of the sensor system when operated in second first phase. The sensor system can generate an output signal based on first and second output signals generated when operating in the first and second phases, respectively.