Touch Sensing on LCD Panels with Inversion Drive Compensation
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Solution Overview
Problem
Capacitive touch sensing technologies in liquid crystal display (LCD) panels are affected by the inversion drive method, leading to signal offset and deterioration in signal-to-noise ratio (SNR) due to changes in potential distribution around sense electrodes.
Innovation Solution
A semiconductor device with an analog front end and processing circuitry that generates touch sensing data by comparing capacitance detection data from the current touch sensing frame with data from a previous frame, accounting for the liquid crystal display panel's state, thereby reducing the influence of inversion drive on sensing signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inversion drive is performed to avoid burn-in of the LCD panel, then the LCD panel reliability is improved, but the sensing signal quality deteriorates due to potential distribution changes
Solution Approach 1:
The system performs preliminary actions by storing capacitance values from a reference frame before inversion drive occurs, then uses these stored values to compensate for changes detected in subsequent frames. This preliminary storage of baseline data enables the system to maintain accurate touch sensing despite the inversion drive causing potential distribution changes that would otherwise degrade signal quality.
2Reliability
If inversion drive is performed to avoid burn-in of the LCD panel, then the LCD panel reliability is improved, but signal-to-noise ratio of the sensing signal deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring capacitance changes in successive frames and comparing them against stored reference values. When inversion drive causes potential distribution changes that degrade the signal-to-noise ratio, the feedback mechanism detects these changes and uses the stored reference data to compensate, thereby maintaining accurate touch sensing information despite the inversion drive operation.
3Ease of operation
If capacitance detection is performed on sense electrodes in an LCD panel with inversion drive, then touch sensing functionality is achieved, but offset generation in sensing signal occurs
Solution Approach 1:
The system extracts and separates the offset component from the capacitance detection signal by comparing current frame data against stored reference frame data. By taking out the reference capacitance values before inversion drive occurs and using them to subtract or compensate for offset changes in subsequent measurements, the system maintains accurate touch sensing functionality while eliminating the offset generation caused by inversion drive.
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 effectively suppresses the impact of LCD panel state changes on touch sensing, improving the SNR and accuracy of touch sensing data in LCD panels.
Implementation Method 1
analog front end configured to obtain capacitance detection data depending on capacitances of a plurality of sense electrodes
Implementation Method 2
Capacitive sensing is one type of touch sensing technologies
Data Source
AI summary
A semiconductor device includes an analog front end and processing circuitry. The analog front end is configured to obtain capacitance detection data depending on capacitances of a plurality of sense electrodes of a liquid crystal display panel. The processing circuitry is configured to generate touch sensing data associated with a current touch sensing frame, based on capacitance detection data associated with the current touch sensing frame and capacitance detection data associated with a former touch sensing frame selected in response to a state in which the liquid crystal display panel is placed in the current touch sensing frame.