LCD Common Voltage Control for Residual Image Reduction
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Solution Overview
Problem
Liquid crystal display (LCD) devices experience deteriorated display quality due to long-term driving patterns affecting transmittance and residual images that persist even after the display is turned off and on again.
Innovation Solution
A display device and driving method that apply a first common voltage for a predetermined period after power is turned on, followed by a second common voltage higher than the first, with a gradual increase, and include a flag signal generator to manage voltage changes based on driving periods and residual image evaluation to minimize flicker and residual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common voltage is applied to the common electrode continuously, then the display device operates normally, but residual images remain and display quality deteriorates
Solution Approach 1:
The patent applies periodic voltage inversion to the common electrode, switching between first and second common voltages at predetermined intervals. This periodic action prevents residual images by continuously changing the electric field configuration, eliminating the static pattern that causes afterimages while maintaining normal display operation.
Solution Approach 2:
The patent changes the voltage parameter of the common electrode by applying different voltage levels (first common voltage and second common voltage) at different time periods. This parameter change resolves the residual image issue by varying the electric field strength and distribution, preventing the formation of persistent visual patterns.
2Object-generated harmful factors
If the common voltage is changed to reduce residual images, then residual images are minimized, but flicker occurs at certain gray scale values
Solution Approach 1:
The patent dynamically adjusts the common voltage based on the display period and gray scale conditions. The system transitions from a static voltage approach to a dynamic one, where the common voltage changes adaptively based on real-time display conditions, thereby reducing residual images while minimizing flicker through condition-based voltage selection.
Solution Approach 2:
The patent implements a feedback mechanism that monitors the display period and gray scale values to determine the appropriate common voltage to apply. This feedback control ensures that voltage changes are made only when necessary to reduce residual images, while maintaining stable voltages during conditions that would cause flicker, thus resolving both issues simultaneously.
3Object-generated harmful factors
If the polarity of data voltage is inverted frequently (dot inversion or line inversion), then residual images are reduced, but transmittance is affected and display quality deteriorates
Solution Approach 1:
The patent applies local quality by inverting the common voltage only in specific regions or at specific pixels where residual images are detected, rather than inverting the polarity of data voltages across the entire display. This localized approach reduces residual images while maintaining stable transmittance characteristics in areas where inversion is not applied.
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
The solution effectively reduces flicker at optimal gray scale values and minimizes residual images, improving display quality by dynamically adjusting common voltages based on driving periods and image signal consistency.
Implementation Method 1
An image is generated based on an electric field applied to the liquid crystal layer. This field is generated based on a voltage applied to field generating electrodes (e.g., a pixel electrode and a common electrode) on the display panels. When the field is applied, the alignment direction of liquid crystal molecules in the liquid crystal layer is controlled.
Data Source
AI summary
A display device includes a liquid crystal display and a power supply to apply a common voltage to a common electrode of the display. The power supply applies a first common voltage to the common electrode for a first period after power is turned on, and applies a second common voltage higher than the first common voltage to the common electrode until the power is turned off after the first period.