OCB Liquid Crystal Display Voltage Control for Startup Gradation Reversal
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Solution Overview
Problem
OCB mode liquid crystal display devices experience reversal of gradation when the power is turned on due to an initial lack of heat from the backlight and electronic parts, leading to an increased black display voltage that exceeds the optimal level, causing display issues.
Innovation Solution
Incorporating a temperature-sensing unit and a control unit that adjusts the black display voltage based on the sensed temperature and a predetermined correction amount or table to ensure it remains below the optimal level, even at startup, by compensating for temperature differences and using a memory to store correction data for optimal voltage settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature compensation is performed using a temperature sensor on the printed wiring board, then the black display voltage can be corrected for temperature changes, but the sensed temperature is higher than the actual panel temperature due to heat from backlight and electronic parts
Solution Approach 1:
A temperature difference correction value is introduced as an intermediary parameter. The control unit adds this correction value to the temperature sensor output to compensate for the heat interference from backlight and electronic parts, thereby obtaining a more accurate panel temperature for black display voltage control
Solution Approach 2:
The system dynamically adjusts the temperature difference correction value based on operational conditions (backlight on/off state, power mode). By changing the correction parameter according to different thermal states, the system compensates for temperature measurement errors and maintains reliable black display quality
2Device complexity
If the black display voltage is set based on sensed temperature without correction, then the voltage setting is simple, but reversal of gradation occurs at startup when temperature difference is large
Solution Approach 1:
The temperature difference correction value is pre-calculated and stored based on different operational conditions. Before setting the black display voltage, the system preliminarily corrects the sensed temperature by adding this pre-prepared correction value, preventing reversal of gradation at startup without requiring complex real-time calculations
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
Prevents reversal of gradation and maintains good display quality by ensuring the black display voltage does not exceed the optimal level at startup, thereby maintaining contrast and image quality regardless of the environment.
Implementation Method 1
the influence of birefringence of light traveling through the liquid crystal layer can be optically compensated in accordance with the alignment of liquid crystal molecules
Implementation Method 2
a temperature sensor, and corrects the black display voltage V(T) according to a temperature Tr sensed by the sensor
Data Source
AI summary
The OCB mode liquid crystal display device applies a black display voltage V(Tr) with temperature characteristic requirements expressed by:V(T)=<Vs(T), and V(Tr−ΔT)=V(T)=<Vs(Tr),where T represents a panel temperature of the liquid crystal panel, Tr represents a sensed temperature, ΔT represents a temperature difference between the panel temperature and the sensed temperature, and Vs(T) represents an optimal black display voltage.