Compensation Capacitor for Self-Capacitance Touch Sensor Accuracy
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Solution Overview
Problem
Current touch sensors, particularly capacitive touch screens, face challenges in accurately detecting the presence and location of touches or proximity inputs due to variations in capacitance measurements, which can lead to inaccuracies in determining the position of objects within the touch-sensitive area.
Innovation Solution
The implementation of a touch sensor array with an array of electrodes on substrates, utilizing a self-capacitance measurement method that includes a compensation capacitor to accurately measure changes in capacitance, allowing for precise detection of touch or proximity inputs by compensating for capacitance differences between measurement and sample-and-hold capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-capacitance measurement is used to detect touch inputs, then touch detection capability is enabled, but measurement accuracy deteriorates due to capacitance variations
Solution Approach 1:
The patent introduces a compensation capacitor as an intermediary element that mediates between the measurement capacitor and the sample-and-hold capacitor. This compensation capacitor is configured to compensate for the capacitance of the measurement capacitor, thereby eliminating the mismatch between these two capacitors and improving measurement accuracy without requiring them to be exactly matched.
Solution Approach 2:
The patent changes the capacitance parameter of the compensation capacitor to match and compensate for the measurement capacitor's capacitance. By adjusting the compensation capacitor's value to equal the measurement capacitor's value (Cc = Cx), the system transforms the measurement equation to eliminate the capacitance ratio term, making the measurement independent of the exact capacitance values and improving reliability.
2Measurement precision
If capacitance matching between measurement and sample-and-hold capacitors is严格要求d, then measurement accuracy improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The compensation capacitor serves as a mediator that eliminates the need for direct matching between the measurement capacitor and sample-and-hold capacitor. By introducing this intermediate element, the patent removes the stringent matching requirements while maintaining measurement accuracy, thereby reducing device complexity and manufacturing difficulty.
Solution Approach 2:
The patent extracts the capacitance mismatch problem from the direct relationship between measurement and sample-and-hold capacitors by introducing a separate compensation capacitor. This separation allows the measurement system to function accurately without requiring the original two capacitors to be precisely matched, simplifying the overall design.
3Adaptability or versatility
If capacitance variations are present in the measurement system, then system robustness is maintained, but measurement accuracy deteriorates
Solution Approach 1:
The patent changes the measurement approach by introducing a compensation capacitor whose value is specifically set to match the measurement capacitor's value. This parameter change transforms the measurement equation to eliminate the capacitance ratio term (Cx/CSH), making the measurement accurate even when capacitance variations occur in the system, thereby maintaining both robustness and precision.
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 solution enhances the accuracy of touch detection and location determination by stabilizing capacitance measurements, reducing errors and improving the overall performance of capacitive touch sensors.
Implementation Method 1
a compensation capacitor Cc coupled in parallel to the measurement capacitance Cx... substantially compensating the capacitance difference between the measurement capacitance Cx and the sample-and-hold capacitor CSH
Data Source
AI summary
In one embodiment, a method includes dividing a first amount of charge between a measurement capacitance and a sample-and-hold capacitor resulting in a voltage at the measurement capacitance being a first voltage. The division of the first amount of charge is based at least in part on a configuration of a compensation capacitor relative to the measurement capacitance and the sample-and-hold capacitor. The configuration being determined based at least in part on an output without the compensation capacitor. The method also includes determining a first difference between the first voltage at the capacitance and a reference voltage; and determining whether a touch input to the touch sensor has occurred based at least in part on the first difference.