Adaptive Common Voltage Control for LCD Flicker Reduction
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Solution Overview
Problem
Conventional liquid crystal display devices consistently supply a constant common voltage to the common electrode of liquid crystal cells, leading to issues such as flicker and residual images on the screen, particularly in phase-alternating line (PAL) and National Television Systems Committee (NTSC) systems.
Innovation Solution
A liquid crystal display device with a controller that selectively controls the supply of first and second common voltages based on the scan line system, using a first common voltage generator for PAL systems and a second common voltage generator for NTSC systems, with a frame counter or scan line format to determine the appropriate voltage supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant common voltage is supplied to the common electrode, then the device structure is simple, but flicker and residual images occur on the screen
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static constant common voltage supply to a dynamic common voltage supply that changes according to the scan line system. The common voltage generator now adjusts the common voltage based on detected scan line format (PAL/NTSC), making the system adaptive rather than fixed, thereby eliminating flicker and residual images while maintaining reasonable structural complexity.
Solution Approach 2:
The patent implements parameter changes by modifying the common voltage parameter according to the scan line system type. The common voltage generator changes the voltage magnitude or polarity based on whether PAL or NTSC format is detected, allowing the display to adapt to different scanning standards and prevent display artifacts without requiring complete system redesign.
2Device complexity
If a constant common voltage is supplied to the common electrode, then the circuit design is simple, but display quality deteriorates with flicker and residual images
Solution Approach 1:
The patent incorporates feedback by including a scan line format detector that monitors the input signal characteristics and provides feedback to the common voltage generator. This feedback loop enables the system to automatically adjust the common voltage based on the detected PAL or NTSC format, ensuring reliable display quality without manual intervention or complex external circuitry.
Solution Approach 2:
The system applies self-service by enabling the common voltage generator to automatically adjust its output based on the scan line format detection. The detector and voltage generator work together in an autonomous manner, with the system self-regulating to prevent flicker and residual images without requiring external control or complex user configuration.
3Reliability
If different common voltages are supplied for different scan line systems, then display quality improves, but device complexity increases
Solution Approach 1:
The patent implements universality by designing a common voltage generator that serves multiple functions: it generates the common voltage for both PAL and NTSC systems and automatically adapts its output based on the detected scan line format. This multi-functional approach allows a single device to support multiple display standards without requiring separate voltage generation circuits for each system.
Data Source
AI summary
A liquid crystal display device for automatically selecting a common voltage adaptive for a scan line system to supply it to a common electrode of liquid crystal cells is disclosed.In the liquid crystal display device, a controller is selectively controls a supply of a first common voltage or a second common voltage in accordance with a scan line system of an image signal displayed at a liquid crystal display panel. A first common voltage generator supplies the first common voltage in accordance with a control of the controller to the common electrode of the liquid crystal cells. And, a second common voltage generator supplies the second common voltage in accordance with a control of the controller to the common electrode of the liquid crystal cells.