Touch Sensor Panel Parasitic Capacitance Correction
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Solution Overview
Problem
Touch sensor panels often produce erroneous or distorted readings due to poorly grounded objects, especially when multiple touch events occur, leading to inaccurate detection of touch events.
Innovation Solution
Incorporating reverse driving circuits in the sense lines to calculate object-to-ground capacitance, which is used to estimate new pixel touch output values iteratively, thereby correcting for parasitic capacitance effects and improving accuracy in determining touch events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reverse driving circuits are added to calculate object-to-ground capacitance, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary calculation of object-to-ground capacitance through reverse driving circuits before processing touch event data. This preliminary action enables the system to identify poor grounding conditions in advance and apply appropriate corrections to pixel touch output values, thereby improving measurement precision without requiring complex real-time processing during touch detection
Solution Approach 2:
The patent introduces object-to-ground capacitance as an intermediary parameter that mediates between the raw pixel touch output values and the final corrected touch event detection. By calculating this intermediate capacitance value through reverse driving circuits and using it to correct pixel readings, the system achieves improved accuracy while keeping the overall architecture manageable through a clear intermediate processing step
2Measurement precision
If iterative estimation of pixel touch output values is performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The iterative estimation process implements a feedback mechanism where calculated object-to-ground capacitance values are fed back into the pixel touch output value correction process. The system repeatedly refines pixel values using the capacitance information until convergence is achieved or a maximum iteration count is reached, balancing measurement precision with acceptable processing time through controlled iterative refinement
3Reliability
If object-to-ground capacitance calculation is implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The reverse driving circuits implemented in the sense lines serve multiple functions: they enable normal touch detection operation and simultaneously calculate object-to-ground capacitance for reliability improvement. By making the sense lines multi-functional, the system achieves enhanced reliability through capacitance-based grounding detection without adding entirely separate dedicated circuits, thereby limiting the increase in device complexity
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 touch event detection by compensating for poor grounding conditions, reducing false negatives and improving the reliability of touch input in multi-touch scenarios.
Implementation Method 1
sense lines of the touch sensor panel can include reverse driving circuits to facilitate calculation of an object-to-ground capacitance
Data Source
AI summary
Compensation of pixels included in a touch sensor panel that generate erroneous readings (so called “negative pixels”) due to a poor grounding condition of the object touching the touch sensor panel is disclosed herein. To compensate for the erroneous readings, sense lines of the touch sensor panel can include reverse driving circuits to facilitate calculation of an object-to-ground capacitance. If the calculated object-to-ground capacitance indicates the presence of a poor grounding condition, then the object-to-ground capacitance and detected pixel touch output values are used to estimate new pixel touch output values that are used instead of the detected pixel touch output values to determine touch event(s).