Touch Sensor Gate Potential Adjustment for TFT Protection
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Solution Overview
Problem
The challenge is to enhance the sensitivity of touch sensors in display devices while maintaining the thickness of liquid crystal modules, as increasing the amplitude of the common drive signal can damage TFT circuits due to exceeding their withstand voltage, limiting the accuracy of multi-touch detection and proximity sensing.
Innovation Solution
A display device with a touch sensor that uses the common electrode for both display and touch functions, where the gate potential of TFT circuits is increased during specific periods, allowing different potential signals to be switched at given timings to optimize the drive signal for touch detection without exceeding the TFT's withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplitude of the common drive signal is increased to improve touch sensor sensitivity, then the detection accuracy of multi-touch and proximity sensing is improved, but the TFT circuits may be damaged due to exceeding their withstand voltage
Solution Approach 1:
The gate potential of the TFT circuits is dynamically adjusted based on the operating mode. During touch sensor detection periods, the gate potential is increased to allow higher common drive signal amplitudes for improved sensitivity. During normal display periods, the gate potential is maintained at standard levels to protect the TFT circuits. This dynamic adjustment resolves the contradiction by adapting the protective measure to the specific operational context.
Solution Approach 2:
The system periodically switches between display mode and touch detection mode. During touch detection periods, the gate potential is temporarily increased to enable high-amplitude drive signals for sensitive touch detection. During display periods, the gate potential returns to normal protective levels. This periodic switching allows the system to achieve high measurement precision during detection while maintaining reliability during normal operation.
2Device complexity
If the common electrode is used for both display and touch functions to maintain module thickness, then the device structure is simplified and thickness is reduced, but the drive signal amplitude must be limited to protect TFT circuits
Solution Approach 1:
The common electrode serves dual functions: it acts as the common electrode for liquid crystal display and as one of the touch sensor electrodes. This multi-functionality simplifies the device structure and maintains thin module thickness. The invention resolves the limitation on drive signal amplitude by dynamically adjusting the gate potential during touch detection periods, enabling the same electrode to support both display and high-sensitivity touch detection functions.
Solution Approach 2:
The gate potential parameter of the TFT circuits is changed based on the operational mode. During touch detection, the gate potential is increased to allow higher drive signal amplitudes. This parameter change enables the multi-functional common electrode to achieve both structural simplicity and high detection precision by adapting the electrical characteristics to the specific function being performed.
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 improves the accuracy of touch sensor detection, enabling multi-touch and proximity sensing while preventing damage to the TFT circuits, thus enhancing the sensitivity and reliability of the touch sensor without increasing the module thickness.
Implementation Method 1
a touch detection electrode provided opposite to the common electrode and forming capacitance between the touch detection electrode and the common electrode
Data Source
AI summary
A display device with a touch sensor is provided and includes a substrate; pixel electrodes on the substrate; thin film transistors (TFTs) coupled to the pixel electrodes; touch sensor electrodes arranged opposite to the pixel electrodes; a gate buffer coupled to the TFTs; a first switch coupled to the gate buffer; first-L and first-H lines coupled to the first switch; a second line coupled to the gate buffer; and a drive control circuit applying a drive signal to the touch sensor electrodes, wherein a signal supplied to the TFTs is one of a pulse wave signal and a signal in which different three potentials are switched at given timings, wherein three potentials include a first potential supplied through the first-L line, a second potential supplied through the second line, and a third potential supplied through first-H line, wherein the first switch switches to couple the gate buffer with first-L line and first-H line in synchronization with the drive signal in which a first and second common potential are repeated, such that the TFT circuits are supplied with the pulse wave signal in which first and third potential are repeated, and wherein the third potential is greater than the first potential and less than the second potential.