Capacitive Sensor Temperature Drift Mitigation via Channel Alternation
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Solution Overview
Problem
Capacitive sensing systems in touch devices and touchscreens face challenges due to unwanted background capacitance and temperature drift, which affect the accuracy of sensing input objects, particularly in foldable devices where temperature changes can impact compensation circuitry.
Innovation Solution
A system and method that utilize a plurality of sensor electrodes and a processing system to drive these electrodes with sensing and compensation signals, determining differential capacitance and mitigating temperature drift by alternating the application of compensation signals between channels, effectively canceling out the equivalent capacitance and temperature drift of the compensation circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If compensation circuits are used to counter background capacitance, then sensing accuracy is improved, but temperature drift increases
Solution Approach 1:
The patent divides the sensor array into multiple channels (first channel, second channel, etc.) and applies different compensation strategies to each. By segmenting the sensing system, the patent can independently manage background capacitance compensation while mitigating temperature drift effects through differential measurement between channels.
Solution Approach 2:
The patent changes the operational parameters of the sensor electrodes by alternating between sensing mode and compensation mode. During compensation mode, compensation signals are applied to cancel background capacitance. During sensing mode, the electrodes measure differential capacitance. This parameter switching allows the system to achieve both accurate background compensation and temperature drift mitigation.
2Object-generated harmful factors
If compensation signals are applied to sensor electrodes, then background capacitance is reduced, but temperature drift of compensation circuitry affects sensing accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the processing system continuously monitors the sensor electrodes and adjusts compensation signals accordingly. The system measures the actual capacitance changes and uses this feedback to refine the compensation, thereby maintaining sensing accuracy while reducing background capacitance effects.
Solution Approach 2:
The patent creates a copy of the compensation signal and applies it alternately to different channels. By copying and switching the compensation signals between channels, the system can measure the differential effect and eliminate the temperature drift component of the compensation circuitry itself.
3Reliability
If multiple sensor electrodes are used for differential measurement, then temperature drift is mitigated, but device complexity increases
Solution Approach 1:
The patent designs the sensor electrodes to serve multiple functions: they act as both sensing elements for detecting input objects and as compensation elements for canceling background capacitance and temperature drift. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent employs periodic action by alternating the application of compensation signals between different channels in a systematic sequence. The processing system periodically switches between channels, applying compensation signals to different electrode sets in alternating periods. This periodic switching enables temperature drift mitigation through differential measurement while using a manageable sensor electrode configuration.
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 enhances the accuracy of capacitive sensing by minimizing the impact of temperature drift and background capacitance, improving the reliability of detecting input objects and determining fold angles in foldable devices, while reducing errors and interference.
Implementation Method 1
determine a first differential capacitance between the first channel and the second channel
Implementation Method 2
drive the first channel with a first compensation signal and the second channel with a second compensation signal
Data Source
AI summary
A system and method for mitigating background capacitance and for mitigating the effect of temperature drift in compensation circuitry is provided. The system includes a plurality of sensor electrodes including a first sensor electrode and a second sensor electrode. The first sensor electrode is coupled to a first channel and the second sensor electrode is coupled to a second channel. The system includes a processing system configured to drive the plurality of sensor electrodes with a sensing signal; drive the first channel with a first compensation signal and the second channel with a second compensation signal; determine a first differential capacitance between the first channel and the second channel; drive the first channel with the second compensation signal and the second channel with the first compensation signal; determine a second differential capacitance between the first channel and the second channel; and mitigate temperature drift using the first differential capacitance and the second differential capacitance.