Source Driving Device Polarity Reversal Control for LCD Ghosting
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Solution Overview
Problem
Existing liquid crystal display technologies face issues with ghosting signals due to residual DC signals caused by long-term dominance of either polarity in alternating voltage methods, leading to abnormal displays and reduced lifespan of liquid crystals.
Innovation Solution
A source driving device with a positive-negative polarity reversal control unit and a polarity signal control unit that reverses polarity in response to a trigger signal, ensuring that the polarity reversal control signal is alternated regularly to prevent DC signal residue and ghosting phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If alternating voltage polarity method is used to drive TFT-LCD, then liquid crystal deterioration is reduced and display lifespan is extended, but residual DC signal accumulates when one polarity is dominant, causing ghosting signals and abnormal display
Solution Approach 1:
The patent implements periodic polarity reversal of the data voltage signal applied to liquid crystal cells. By systematically inverting the polarity of data voltages across different columns at regular intervals (e.g., every frame or half-frame), the patent prevents accumulation of residual DC signals while maintaining the benefits of alternating voltage driving. This periodic action ensures that no single polarity dominates for extended periods, thereby eliminating ghosting signals while preserving display lifespan.
Solution Approach 2:
The patent introduces dynamic polarity control where the polarity of data voltages is not fixed but changes over time based on a control signal. The source driving device dynamically adjusts the polarity state of different column groups, switching between positive and negative polarity configurations. This dynamic approach allows the system to adaptively prevent DC accumulation while maintaining normal display characteristics throughout the operational lifespan.
2Reliability
If polarity is alternated between adjacent liquid crystal cells and successive frame periods, then liquid crystal characteristics are maintained, but complex control circuits are required to manage polarity reversal timing
Solution Approach 1:
The patent combines the polarity reversal control function with the existing source driving circuitry. The polarity inversion is achieved by leveraging the dual-gate structure of the source driver, where control signals can selectively activate different voltage paths. By merging the polarity control functionality into the existing driving architecture rather than adding separate dedicated circuits, the patent reduces overall system complexity while maintaining reliable liquid crystal characteristic control.
Solution Approach 2:
The source driving device is designed with multi-functional capability, where the same circuit structures serve both normal voltage driving and polarity reversal functions. The control circuits can operate in multiple modes (normal driving, polarity reversal, different inversion schemes) using the same hardware resources. This universality reduces the need for dedicated complexity in polarity management while ensuring reliable liquid crystal characteristics through flexible control.
Data Source
AI summary
A source driving device, a polarity reversal control method thereof, and a liquid crystal display device. In the source driving device, a polarity signal control unit is added, and an output terminal of the polarity signal control unit is connected to control terminals of a first channel selection circuit and a second channel selection circuit in a positive-negative polarity reversal control unit, respectively. Polarity reversal condition of the polarity reversal control signal outputted by the polarity signal control unit is controlled using a trigger control signal inputted to a control terminal of the polarity signal control unit.