Backlight Timing Controller for LCD Brightness Uniformity
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Solution Overview
Problem
Liquid crystal display devices with backlights face issues of varying brightness due to changes in blank periods, leading to unequal backlight lifetimes and noticeable flicker, especially when displaying moving images.
Innovation Solution
A timing controller adjusts the on-periods of backlights to maintain equal brightness by detecting changes in blank periods and setting precise turning-on and turning-off timings, using a combination of blank-line detecting, timing calculating, and clock signal processing units to ensure consistent illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the blank period changes due to output repetition rate adjustments, then the image signal transmission timing changes, but the backlight brightness becomes unequal and flicker increases
Solution Approach 1:
The patent implements dynamic adjustment of backlight on-periods based on detected blank period changes. The timing controller continuously monitors the blank period duration and modifies the backlight illumination timing accordingly, transforming the static backlight control into a dynamic system that adapts to varying output repetition rates while maintaining brightness uniformity
Solution Approach 2:
The patent employs feedback control by detecting the actual blank period duration and using this information to adjust the backlight on-periods. The timing controller creates a closed-loop system where the backlight control is continuously refined based on the detected synchronization timing, ensuring brightness uniformity despite changes in output repetition rate
2Loss of energy
If backlights are turned off during blank periods to reduce power consumption, then energy efficiency improves, but brightness uniformity deteriorates due to unequal on-periods
Solution Approach 1:
The patent changes the illumination parameter (on-period duration) of the backlights based on the detected blank period. By dynamically adjusting the on-period length rather than using a fixed pattern, the system maintains equal brightness across all backlights while still achieving power savings during blank periods
3Device complexity
If fixed horizontal line numbers are used for backlight control, then the control timing is simple, but brightness uniformity deteriorates when blank period changes
Solution Approach 1:
The patent transforms the static control approach (fixed horizontal line numbers) into a dynamic one by detecting the actual blank period duration and adjusting the backlight on-periods accordingly. This maintains simplicity in control logic while achieving brightness uniformity through adaptive timing adjustments
Data Source
AI summary
A backlight driving circuit is controlled by a timing controller and executes on/off control of the backlights. The timing controller detects, using a synchronous signal, a change in a blank period which is of one frame period for display of one screen, during which the image signal is not transmitted. Upon detecting the change in the blank period, the timing controller adjusts the on-periods of the backlights in order to make the brightness of the backlights equal to one another. Consequently, the backlights have an equal brightness with one another in spite of the change in the blank period. This makes the lives of the backlights equal to one another. In a case where the plural backlights constitute a backlight unit, a reduction in life of the backlight unit is prevented. Further, it is also possible to prevent the brightness of the backlights from being differentiated even through a long-term use.