Liquid Crystal Display Driving Circuit Pre-Charging Control
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Solution Overview
Problem
High refresh rate liquid crystal display devices face image quality deterioration due to short writing times for pixel electrodes, as the potential of the pixel electrode does not reach the desired level within the short input period of the video signal.
Innovation Solution
A liquid crystal display device that includes a plurality of pixels with a pixel electrode and a thin film transistor, where a reference video signal voltage and a correction video signal voltage are output in a predetermined order, with the correction voltage adjusting based on the gradation values of adjacent pixels to ensure efficient pre-charging and optimal image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a liquid crystal display device is driven at a high refresh rate, then the refresh rate is improved, but the writing time to pixel electrode shortens causing image quality deterioration
Solution Approach 1:
The patent applies preliminary action by performing pre-charging of the pixel electrode before the actual video signal writing. A pre-charge transistor is activated during a pre-charge period to charge the pixel electrode to an initial potential, ensuring that when the video signal is subsequently written during the shortened writing time at high refresh rates, the pixel electrode can reach the desired potential level within the limited time available.
2Manufacturing precision
If pre-charging is performed to ensure pixel electrode potential reaches desired level, then image quality is improved, but the complexity of driving circuit increases
Solution Approach 1:
The patent segments the driving function into distinct components: a pre-charge transistor separate from the main switching transistor, and a pre-charge period separate from the video signal writing period. This segmentation allows the pre-charging function to be independently controlled and optimized without interfering with the main video signal writing operation, thereby improving image quality while managing circuit complexity through functional separation.
Solution Approach 2:
The patent employs dynamic control of the pre-charge transistor activation timing. The pre-charge period is dynamically adjusted based on the refresh rate, and the pre-charge transistor is activated only when needed during the horizontal period. This dynamic approach allows the circuit to adapt to different operating conditions, maintaining image quality across various refresh rates while avoiding unnecessary circuit complexity in static configurations.
Data Source
AI summary
A data line driving section (6) outputs a video signal voltage for each pixel to a data line (DL) for each predetermined period in order. In outputting a video signal voltage for a pixel, the data line driving section (6) outputs a gradation signal voltage having a voltage corresponding to a gradation value of the pixel as the video signal voltage during a second part of the predetermined period, and outputs a correction gradation signal voltage different from the gradation signal voltage as the video signal voltage during a first part of the predetermined period. A control section (4) changes a relationship between the correction gradation signal voltage and the gradation signal voltage based on a combination of the gradation value of the pixel and a gradation value of a pixel preceding the pixel.