LCD Over-Driving Controller for Backlight Dimming Brightness
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Solution Overview
Problem
Liquid crystal display (LCD) devices with dimming backlight systems suffer from brightness deterioration due to repeated turning on and off of light sources, leading to reduced picture quality.
Innovation Solution
An LCD device with a timing controller, gray scale modulator, backlight dimming controller, and over-driving controller that modulates and compensates red, green, and blue data by comparing current and previous frames, adjusting the dimming signal to prevent brightness loss and improve picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the backlight unit is repeatedly turned on and off for dimming, then power consumption is reduced and display control is improved, but brightness deterioration occurs and picture quality degrades
Solution Approach 1:
The patent applies preliminary action by pre-charging the liquid crystal capacitor to a voltage higher than the normal driving voltage before the backlight turns on. This over-driving approach compensates for the brightness loss that occurs during backlight dimming, ensuring that the liquid crystal molecules are already aligned to a程度 that maintains picture quality even when the backlight is dimmed or turned off. The gray scale modulator calculates the required over-drive voltage based on the dimming duty cycle and applies it in advance.
Solution Approach 2:
The patent changes the voltage parameter applied to the liquid crystal capacitor dynamically based on the backlight dimming state. When the backlight is dimmed or turned off, the gray scale modulator increases the voltage applied to the liquid crystal capacitor beyond the normal driving voltage. This parameter change compensates for the reduced light output, maintaining the optical properties and picture quality despite the lowered illumination intensity.
2Use of energy by moving object
If the backlight unit is dimmed to save power, then energy efficiency is improved, but brightness uniformity deteriorates and blurring occurs
Solution Approach 1:
The patent uses preliminary action by preparing the liquid crystal state in advance before the backlight transitions to a dimmed state. The gray scale modulator calculates the appropriate over-drive voltage based on the intended dimming duty cycle and applies it before the backlight turns off or dims. This ensures that the liquid crystal molecules are pre-aligned to compensate for the upcoming brightness reduction, maintaining uniformity and preventing blurring during the transition and dimmed state.
Solution Approach 2:
The patent implements feedback by continuously monitoring the backlight dimming state and adjusting the gray scale voltage accordingly. The gray scale modulator receives information about the dimming duty cycle from the backlight controller and dynamically adjusts the over-drive voltage applied to the liquid crystal capacitor. This closed-loop feedback ensures that the liquid crystal optical properties remain synchronized with the backlight state, maintaining brightness uniformity and preventing display artifacts.
3Illumination intensity
If the liquid crystal capacitor is charged to higher voltage for over-driving, then picture quality is maintained during dimming, but the complexity of the driving system increases
Solution Approach 1:
The patent applies universality by designing the gray scale modulator to perform multiple functions: normal gray scale modulation during full backlight operation and over-drive voltage calculation during dimmed operation. The same hardware circuitry adapts its behavior based on the backlight dimming state, eliminating the need for separate circuits for normal and dimmed modes. This multi-functional approach maintains picture quality during dimming while avoiding the complexity of additional dedicated hardware.
Data Source
AI summary
An LCD device adapted to improve its picture quality in spite of the brightness variation includes: a gray scale modulator modulating R, G, and B data; a backlight dimming controller generating a back dimming signal that is inversely proportional to the modulated R, G, and B data generated in the gray scale modulator; and an over driving controller selectively overshoot-compensating the R, G, and B data from the gray scale modulator in every gray scale level through the comparison of the R, G, and B data of current frame and the R, G, and B data of previous frame, wherein, the modulated R, G, and B data each include maximum gray scale levels lower than those of the overshoot compensated R, G, and B data.