Active Matrix Substrate Common Electrode Feedback Control
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Solution Overview
Problem
In FFS mode liquid crystal display devices, the electric potential of the common electrode fluctuates due to parasitic capacitance and signal delay caused by the use of transparent conductive materials with low conductivity, leading to unstable driving voltage and a greenish display image.
Innovation Solution
An active matrix substrate with a display region and a picture-frame region, where the common electrode is formed of transparent conductive material and connected to input and output electrodes through a feedback circuit, allowing for independent control of electric potential across the common electrode to maintain a stable target waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent conductive material is used for the common electrode, then transparency is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent applies feedback control by introducing a feedback circuit that includes an output electrode connected to the common electrode and a feedback circuitry that receives a feedback signal from the output electrode and adjusts the drive signal accordingly. This feedback mechanism compensates for the low conductivity of transparent conductive materials by dynamically adjusting the driving voltage to maintain stable electric potential distribution across the common electrode, thereby resolving the contradiction between transparency and electrical conductivity.
2Illumination intensity
If the common electrode is formed with low conductivity material, then transparency is improved, but signal delay increases
Solution Approach 1:
The feedback circuitry continuously monitors the electric potential at the output electrode and adjusts the drive signal to compensate for signal delay caused by low conductivity. This active compensation reduces the effective signal delay by pre-adjusting the timing and amplitude of the driving voltage, allowing the transparent conductive material to maintain both transparency and acceptable signal response.
Solution Approach 2:
The patent changes the electrical parameters of the system by dynamically adjusting the drive signal characteristics (amplitude, timing, and waveform) based on feedback from the output electrode. This parameter adjustment optimizes the electric potential distribution across the common electrode, compensating for the inherent slow response of transparent conductive materials and reducing signal delay effects.
3Device complexity
If parasitic capacitance exists between common electrode and signal lines, then device integration is improved, but electric potential stability deteriorates
Solution Approach 1:
The feedback circuitry detects potential fluctuations caused by parasitic capacitance coupling between the common electrode and signal lines, and actively compensates by adjusting the drive signal. This feedback mechanism stabilizes the electric potential despite the presence of parasitic capacitance, allowing tight integration of electrodes and signal lines on the same substrate without sacrificing potential stability.
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
The solution stabilizes the electric potential of the common electrode, thereby stabilizing the driving voltage and reducing the occurrence of the greenish mode in liquid crystal display devices.
Implementation Method 1
a common electrode overlapping the scanning signal lines and the data signal lines and formed of a transparent conductive material
Implementation Method 2
a parasitic capacitance between the common electrode and scanning signal lines and data signal lines for driving the pixel electrodes
Data Source
AI summary
A lower input electrode is electrically connected to a lower end portion of a common electrode. An upper input electrode and an output electrode are electrically connected to an upper end portion of the common electrode. The lower input electrode, the upper input electrode, and the output electrode are electrically connected to one another through only the common electrode.