LCD Drive Control Circuit Reducing Power and Afterimages
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Solution Overview
Problem
Liquid crystal display devices face challenges in reducing power consumption while maintaining a high refresh rate, leading to the occurrence of afterimages due to the alignment characteristics of liquid crystals, which are not kept up with during frequent pausing periods.
Innovation Solution
Implementing a driving method where scan signal lines are scanned during at least two driving frames within a first driving period and not scanned during longer pausing periods, ensuring pixels are refreshed and liquid crystal capacitance reaches necessary levels for display, while all scan signal lines are in a non-scanning state to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a pausing period is provided between scanning periods to reduce power consumption, then power consumption is reduced, but the drive frequency of each pixel decreases causing afterimages
Solution Approach 1:
The scanning period is divided into multiple frames (first frame, second frame, third frame, etc.), and the pausing period is also divided into multiple frames. By segmenting the scanning into multiple frames within one period, the liquid crystal capacitance can be fully charged in each frame, ensuring display quality while allowing for pausing periods to reduce power consumption.
Solution Approach 2:
The invention implements periodic scanning with periodic pausing. Scanning periods are alternated with pausing periods in a cyclic manner, where scanning periods refresh the display and pausing periods reduce power consumption. This periodic action allows the system to balance between power savings and display quality maintenance.
2Loss of energy
If a larger number of pausing frames is used to significantly reduce power consumption, then power consumption is significantly reduced, but the screen is updated fewer times per unit of time
Solution Approach 1:
The invention dynamically adjusts the relationship between scanning periods and pausing periods. By making the pausing period longer than the scanning period, the system optimizes power consumption while ensuring that each scanning period contains multiple frames sufficient to charge the liquid crystal capacitance fully, thereby maintaining acceptable refresh rates.
Solution Approach 2:
The invention changes the parameter of frame duration and the number of frames per period. By increasing the number of frames in the scanning period and making each frame duration appropriate, the system ensures that the liquid crystal capacitance reaches necessary levels even with extended pausing periods, thus maintaining refresh quality while reducing power consumption.
3Use of energy by moving object
If the liquid crystal capacitance does not reach necessary levels due to frequent pausing, then power consumption is reduced, but afterimages occur
Solution Approach 1:
The invention performs preliminary charging of the liquid crystal capacitance during each frame of the scanning period. By ensuring that the capacitance is fully charged before the pausing period begins, the system prevents afterimages from occurring while still allowing power savings during the pausing period when no charging is needed.
Solution Approach 2:
The invention maintains continuous useful action by ensuring that during each scanning period, multiple frames are used to continuously charge the liquid crystal capacitance until it reaches the necessary level. This continuous charging action throughout the scanning period ensures display accuracy is maintained even when pausing periods are used to reduce power consumption.
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 reduces power consumption and minimizes afterimages by ensuring the liquid crystal capacitance reaches necessary levels within the driving period, enabling high-quality display without the persistence of afterimages.
Implementation Method 1
Liquid crystals have such a characteristic as dielectric anisotropy. The liquid crystal dielectric constant ∈ varies, depending on an alignment direction of liquid crystal molecules.
Implementation Method 2
A liquid crystal capacitance Clc is stored between the pixel electrode and a counter electrode.
Implementation Method 3
it takes a certain length of time for the liquid crystal molecules to be aligned in the direction corresponding to a voltage Vlcd
Data Source
AI summary
According to a liquid crystal display device (1), a gate driver is controlled to (a) scan all of scan signal lines during at least two driving frames contained in a first driving period and (b) not scan any of the scan signal lines during pausing frames in a pausing period which is (i) secured between the first driving period and a second driving period by which the first driving period is followed and (ii) is longer than each of the first and second driving periods.