Touch Sensing in Active Matrix LCD Panels
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Solution Overview
Problem
Existing touch-sensing-enabled active matrix LCD display panels face challenges in reducing parasitic capacitance and its voltage dependency, which affects sensitivity and requires additional materials and circuitry, increasing implementation complexity and cost.
Innovation Solution
The method involves generating a plurality of driving voltages, including a common voltage with a pulse-train waveform, and synchronizing gate-drive and source-drive reference voltages with the pulse-train waveform during the sensing mode to reduce parasitic capacitance, using existing display driver components with minimal additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional materials and circuitry components are added to reduce parasitic capacitance, then parasitic capacitance is reduced, but device complexity and implementation cost increase
Solution Approach 1:
The patent changes the voltage parameters of the common voltage line from a static DC level to a dynamic waveform that includes a sensing component. By modulating the common voltage line with a specific waveform pattern, the system achieves parasitic capacitance reduction through parameter optimization rather than adding physical components. This allows the existing circuitry to function with improved electrical characteristics.
Solution Approach 2:
The common voltage line is made to serve dual functions: maintaining its primary role in displaying images while simultaneously functioning as a sensing signal transmission path. By encoding sensing information within the common voltage waveform, the system eliminates the need for separate dedicated sensing circuitry, thereby reducing device complexity while achieving both display and sensing objectives.
2Reliability
If additional materials and circuitry components are added to reduce parasitic capacitance, then parasitic capacitance is reduced, but implementation cost increases
Solution Approach 1:
The patent achieves parasitic capacitance reduction by optimizing electrical parameters (voltage waveform characteristics) rather than modifying physical structures. This approach requires no additional manufacturing steps, materials, or assembly processes, thereby avoiding increased implementation costs while achieving the desired electrical performance improvement.
Solution Approach 2:
The common voltage line serves itself by simultaneously performing its traditional display function and acting as a sensing signal carrier. This self-service capability eliminates the need for separate dedicated sensing infrastructure, reducing overall system cost while maintaining effective parasitic capacitance reduction.
3Use of energy by stationary object
If traditional driving voltages are used during sensing mode, then power consumption is higher, but parasitic capacitance is not reduced
Solution Approach 1:
The patent employs periodic waveform modulation on the common voltage line during sensing mode, using pulsed or alternating voltage patterns instead of continuous DC levels. This periodic action reduces the average power consumption while simultaneously creating the voltage differential necessary to minimize parasitic capacitance effects during touch sensing operations.
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 reduces parasitic capacitance, enhances touch-sensing accuracy, and decreases power consumption while maintaining low implementation complexity, making it a cost-effective solution.
Implementation Method 1
parasitic capacitance in the panel affects the sensitivity in the touch detection. The effective parasitic capacitance is nonlinear and voltage-dependent.
Data Source
AI summary
Driving a touch-sensing-enabled active matrix LCD display panel for enhancing touch sensing by reducing parasitic capacitances is considered. In one embodiment, a plurality of driving voltages is generated. The driving voltages include a common voltage, and a first and a second gate-drive reference voltages for configuring a thin film transistor (TFT) in the panel to switch on and off, respectively. When the panel is operated in a sensing mode, the common voltage that is generated includes a pulse-train waveform. Furthermore, each of the first and the second gate-drive reference voltages is substantially time-synchronized to and includes the pulse-train waveform of the common voltage during the sensing mode. In one option, the driving voltages further include a sensing-mode source-drive voltage acting as a source-drive signal for the TFT during the sensing mode. The sensing-mode source-drive voltage is substantially time-synchronized to and includes the pulse-train waveform of the common voltage.