Touch Display Panel Floating Common Electrode Coupling Reduction
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Solution Overview
Problem
Conventional self-capacitive touch display panels suffer from reduced accuracy in touch sensing due to coupling capacitances and large electrode blocks, which hinder precise operations like fingerprint identification.
Innovation Solution
The touch display panel employs a pixel structure with a pixel electrode, a first switching element, and a common electrode, where the common electrode is floating during touch mode, reducing coupling capacitances and allowing for finer touch sensing, and incorporates multiple scanning patterns for efficient touch and fingerprint identification functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional self-capacitive touch display panels use large electrode blocks for touch sensing, then the touch sensing area is sufficient, but the measurement precision and resolution are reduced
Solution Approach 1:
The patent segments the large electrode block into multiple smaller sensing electrodes arranged in a matrix pattern. Each small sensing electrode can be independently controlled and sensed, allowing the system to achieve high resolution touch detection while maintaining sufficient total sensing area. This segmentation enables precise localization of touch points and supports fingerprint identification functionality.
2Reliability
If metal wires and wiring circuits are used to connect electrode blocks to driving chip, then the electrical connection is established, but coupling capacitances are induced and signal quality deteriorates
Solution Approach 1:
The patent introduces a driving chip with integrated signal processing capabilities as an intermediary between the sensing electrodes and the control system. The driving chip includes compensation circuits that actively cancel coupling capacitance effects, thereby maintaining signal integrity despite the presence of metal wire connections. This intermediary processing prevents signal distortion and noise from degrading touch sensing accuracy.
3Stability of the object's composition
If the common electrode is connected to a constant voltage source, then the display function is stable, but the touch sensing signal quality is reduced due to coupling effects
Solution Approach 1:
The patent implements a dynamic voltage control scheme where the common electrode voltage is adjusted based on the operating mode. During fingerprint identification, the common electrode voltage is modulated or floated rather than held constant, which reduces coupling capacitance effects and improves signal quality. The system dynamically switches between display mode (constant voltage) and touch sensing mode (modulated voltage) to optimize both display stability and touch sensing 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 approach enhances the signal-to-noise ratio and resolution of touch sensing, enabling both normal touch and fingerprint identification functions with reduced coupling effects, improving accuracy and operational efficiency.
Implementation Method 1
a pixel electrode, a first switching element connected between the pixel electrode and a data line, and a common electrode corresponding to the pixel electrode
Implementation Method 2
the common electrode is floating during touch mode, reducing coupling capacitances and allowing for finer touch sensing
Data Source
AI summary
A touch display panel capable of operating in a display mode and a touch mode. In the touch mode, a data line transmits a data voltage signal to a pixel electrode of the touch display panel, and a corresponding common electrode is at a constant voltage level. In the touch mode, the data line transmits a touch driving signal to the pixel electrode and then receives a touch sensing signal from the pixel electrode, and the corresponding common electrode is floating.