Scan Driver Dual-Scan Charging for LCD Display Quality
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Solution Overview
Problem
As display devices increase in size and resolution, the reduced time for activating gate lines in liquid crystal display (LCD) devices leads to lower charging rates of liquid crystal capacitors, resulting in inadequate voltage application and compromised display quality.
Innovation Solution
A scan driver with a shift register and multiple signal applying unit, utilizing sub scan and main scan signals with specific pulse widths and timing to ensure liquid crystal capacitors receive data voltage twice, ensuring full charging even with reduced activation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of gate lines is increased to enhance display resolution, then the display quality is improved, but the time for activating each gate line is reduced, causing the liquid crystal capacitor charging rate to decrease
Solution Approach 1:
The patent applies preliminary action by pre-charging the liquid crystal capacitor before the main scanning operation. Specifically, a sub scan signal is applied to activate the gate line in advance, allowing the liquid crystal capacitor to receive a preliminary data voltage through the source line before the main scanning process ensures full charging. This pre-charging mechanism compensates for the reduced activation time caused by increased gate line count.
2Manufacturing precision
If the driving frequency is raised to reduce afterimage effects, then the display quality is improved, but the time for electrically charging the liquid crystal capacitor is further reduced
Solution Approach 1:
The sub scan signal mechanism performs preliminary charging of the liquid crystal capacitor at a lower frequency stage, so that when the main scanning operates at higher driving frequencies to reduce afterimage effects, the capacitor is already partially charged and requires less time to reach full charge, thus maintaining adequate charging even at high driving frequencies.
Solution Approach 2:
The patent employs periodic action by implementing dual scanning operations - a sub scan at lower frequency and a main scan at higher frequency. The sub scan operates periodically to pre-charge capacitors, while the main scan periodically ensures full charging. This multi-periodic approach allows the system to maintain both high driving frequencies for reducing afterimage effects and sufficient charging time through the lower-frequency sub scan operations.
Data Source
AI summary
A scan driver drives a display device having a plurality of gate lines transferring scan signals, and a plurality of source lines transferring data signals. The scan driver includes a shift register and a multiple signal applying unit. The shift register includes a plurality of cascade-connected stages, each stage having an output terminal electrically connected to a respective one of the plurality of gate lines. The multiple signal applying unit applies a sub scan signal and a main scan signal. The sub scan signal and the main scan signal sequentially activate each of the plurality of gate lines. Therefore, the scan lines receive the scan signal twice, so that the liquid crystal capacitors electrically connected to the gate lines receive the data voltage twice. As a result, even though the time for charging the liquid crystal capacitors may be reduced, the liquid crystal capacitors may be fully charged to enhance display quality.