LCD Driving Method Using Over-Driving and Black Pixel Voltages
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Solution Overview
Problem
Conventional LCDs suffer from motion image quality issues due to the slow response speed of liquid crystal molecules, leading to image retention and poor display quality when showing motion images, as they retain previous frame brightness, influencing the current frame display.
Innovation Solution
The implementation of a driving method that divides the frame time into three subframes, where over driving, black, and gray pixel data voltages are applied sequentially to generate a pulse-like brightness curve, enhancing the response speed of liquid crystal molecules and reducing image retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LCD uses hold type display method with constant brightness in frame time, then manufacturing is simple, but motion image quality deteriorates due to image retention
Solution Approach 1:
The patent divides the frame time into three subframes and applies different driving voltages (over-driving voltage, black pixel voltage, and gray pixel voltage) to different time segments. This segmentation of time allows the liquid crystal molecules to respond more quickly to changes, reducing image retention effects while maintaining manufacturing simplicity.
Solution Approach 2:
The patent employs periodic over-driving pulses at specific time intervals within each frame cycle. By applying high voltage pulses periodically at the beginning of each subframe, the liquid crystal molecules are stimulated to change orientation more rapidly, creating a pulse-like brightness curve that reduces motion image retention without complicating the manufacturing process.
2Device complexity
If LCD uses conventional single voltage driving, then device complexity is low, but response speed is slow causing image retention
Solution Approach 1:
The patent dynamically adjusts the driving voltage applied to liquid crystal pixels based on the timing within the frame cycle. By switching between different voltage levels (over-driving, black, and gray pixel voltages) at different times, the system optimizes the response speed of liquid crystal molecules without requiring complex additional hardware, thus improving speed while keeping device complexity manageable.
Solution Approach 2:
The patent changes the voltage parameter applied to liquid crystal pixels over time within each frame. By varying the voltage from high (over-driving) to lower levels (black and gray pixel voltages) across three subframes, the liquid crystal response speed is enhanced without permanently increasing device complexity, as the changes are achieved through temporal variation of the driving signal.
3Use of energy by moving object
If LCD displays motion images with slow response, then energy consumption is low, but image retention occurs reducing display quality
Solution Approach 1:
The patent applies over-driving voltage in the first subframe as a preliminary action to prepare the liquid crystal molecules for rapid response. This preliminary high-voltage pulse stimulates the molecules to change orientation more quickly before the actual image content is displayed in subsequent subframes, thereby reducing image retention and improving motion display quality without significantly increasing overall energy consumption.
Solution Approach 2:
The patent applies different voltage levels to different time periods within the frame cycle. By concentrating higher voltage application only during specific subframes (over-driving and black pixel phases) rather than continuously, the system achieves improved local response quality where needed while maintaining lower energy consumption during other periods, thus resolving the contradiction between energy use and display quality.
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
This approach effectively improves motion image display quality by mimicking the impulse-type brightness curve of CRT monitors, reducing human vision retention and enhancing the overall motion image quality of LCDs.
Implementation Method 1
The pixel electrically connected to a scan line and a data line generates a predetermined brightness in a frame time
Implementation Method 2
the response speed of the liquid crystal molecule is smaller than the changing speed of the electric field
Data Source
AI summary
A LCD (Liquid Crystal Display) with improved motion image quality and a driving method therefor. The LCD includes a pixel, a data driving circuit and a scan driving circuit. The data driving circuit generates over driving pixel data and gray pixel data according to pixel data of a Nth frame and pixel data of a (N+1)th frame, and outputs driving voltages, which correspond to the over driving pixel data, black pixel data and the gray pixel data, to the pixel at first, second and third time. The scan driving circuit outputs a scan signal at the first time, second time and third time to enable the pixel to receive the driving voltages corresponding to the over driving pixel data, the black pixel data and the gray pixel data. The driving voltages enables the pixel to generate a brightness curve similar to a pulse curve.