LCD Panel Driving Segments Frame for Overdrive and Backlight Control
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Solution Overview
Problem
Liquid crystal display (LCD) panels experience smearing and flicker due to frame time differences between scanning lines, leading to reduced image definition and increased power consumption, especially in portable devices.
Innovation Solution
A display panel driving and scanning method that divides the frame period into three time periods: the first for calculating and applying an overdriving signal, the second for displaying the current frame, and the third for turning on the backlight, allowing for quicker pixel charging and reduced backlight usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the backlight source is kept on all the time to ensure continuous display, then the display continuity is maintained, but the power consumption increases
Solution Approach 1:
The backlight source is controlled to operate periodically rather than continuously. It is turned on during display time periods and turned off during scanning time periods, creating a rhythmic on-off pattern that reduces overall power consumption while maintaining perceived display continuity through persistence of vision
Solution Approach 2:
Pixel charging is performed in advance during scanning time periods when the backlight is off. This preliminary charging of pixel electrodes ensures that when the backlight turns on, the pixels are already charged and ready for immediate display, eliminating the need for continuous backlight operation
2Object-affected harmful factors
If the liquid crystal response time is reduced to shorten the smearing effect, then the smearing is reduced, but the power consumption increases and the usage lifetime decreases
Solution Approach 1:
Overdriving signals are applied in advance during the first time period to pre-charge pixels and accelerate liquid crystal response before the actual display period. This preliminary action reduces the response time needed during active display, thereby reducing smearing without requiring continuously high power consumption
Solution Approach 2:
The system uses periodic overdriving signals during scanning periods to accelerate liquid crystal response. By applying these enhanced signals periodically rather than continuously, the system reduces smearing during display while maintaining lower average power consumption
3Duration of action of stationary object
If the scanning speed is increased to reduce flicker, then the flicker is reduced, but the image definition deteriorates due to smearing
Solution Approach 1:
Pixels are charged in advance during the scanning period before the display period begins. This preliminary charging ensures that when the backlight turns on, pixels are already fully charged and ready for immediate display, allowing for faster effective display timing without sacrificing image definition
Solution Approach 2:
The frame period is segmented into distinct scanning time periods and display time periods. During scanning periods, overdriving signals are applied to charge pixels rapidly without backlight illumination. During display periods, the backlight is on and pixels are displayed without smearing. This temporal segmentation allows both fast scanning and high image definition
Data Source
AI summary
A display panel driving and scanning system includes a timing controller to divide one frame period into first to third time periods. In the first time period, an image processing device calculates an overdriving signal for a current frame based on the current frame and a previous frame. In the second time period, the image processing device outputs the current frame, and a source driver charges the capacitors of the pixels in the liquid crystal display panel based on the current frame. In the third time period, the timing controller drives a backlight driving circuit to turn on a backlight source of the liquid crystal display panel for displaying the current frame.