Liquid Crystal Display Common Voltage Modulator for Ripple Cancellation
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Solution Overview
Problem
LCDs face image quality degradation due to voltage ripples caused by parasitic capacitors, which distort the common voltage and lead to crosstalk, impairing the display's performance.
Innovation Solution
A common voltage modulator is introduced, using two non-overlapping common voltage lines and a circuit with transistors and capacitors to apply compensating voltages, canceling out ripples and maintaining a stable common voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gray scale voltages are applied rapidly to pixel electrodes, then response speed is improved, but voltage ripples are generated due to parasitic capacitor coupling, degrading image quality
Solution Approach 1:
A common voltage modulator is introduced as an intermediary component between the common voltage source and the common electrode. The modulator detects voltage ripples caused by parasitic capacitor coupling and applies compensating voltages to cancel these ripples, thereby maintaining stable common voltage during rapid gray scale transitions without degrading image quality
Solution Approach 2:
The common voltage modulator implements a feedback mechanism by continuously monitoring the common voltage on the common voltage line and dynamically adjusting the compensating voltage applied to the common electrode. This feedback loop detects ripple voltages and generates corresponding compensation signals to maintain voltage stability during rapid response operations
2Device complexity
If a single common voltage line is used, then device complexity is reduced, but voltage stability deteriorates due to coupling effects from parasitic capacitors
Solution Approach 1:
The single common voltage line is functionally segmented into two separate lines: a first common voltage line for transmitting the common voltage from the source, and a second common voltage line for applying compensating voltages to the common electrode. This segmentation allows independent control of voltage transmission and compensation functions, improving voltage stability while managing device complexity
Solution Approach 2:
The common voltage modulator serves as an intermediary that receives the common voltage from the first common voltage line and processes it to generate compensating voltages applied through the second common voltage line. This intermediary structure enables active ripple compensation without requiring complete redesign of the voltage distribution architecture
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 effectively stabilizes the common voltage, reducing image impairment and ensuring good performance by compensating for voltage distortions caused by parasitic capacitors.
Implementation Method 1
parasitic capacitors are inevitably formed between the scanning lines 131 and the data lines 141... Each parasitic capacitor is capable of interfering with operation of the liquid crystal panel 11... voltage of the common electrode 18 corresponding to the pixel electrode 17 is correspondingly pulled up or pulled down due to a coupling effect of the parasitic capacitor
Data Source
AI summary
An exemplary liquid crystal display includes a common electrode capable of having a predetermined common voltage applied thereto, a first common voltage line connected to the common electrode, a second common voltage line connected to the common electrode, and a common voltage modulator connected to the first and second common voltage lines. The first and second common voltage lines have no overlap and being at opposite sides of the liquid crystal display. The common voltage modulator is configured to receive a distorted common voltage from the common electrode via the first common voltage line, and apply a corresponding compensating voltage to the common electrode via the second common voltage line.