Backlight Brightness Control via PWM Duty Ratio Segmentation
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Solution Overview
Problem
LCD devices face increased power consumption due to limited adjustment steps in backlight brightness control, which is insufficient for maintaining desired picture contrast, especially in dark environments, leading to improper backlight brightness control.
Innovation Solution
Implementing a backlight brightness controller that varies the backlight brightness in the middle of each frame period by adjusting the duty ratio of the PWM signal in multiple sub-frame periods, effectively increasing the number of adjustment steps without increasing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of adjustment steps of backlight brightness is increased to provide desired picture contrast, then the picture contrast is improved, but the circuit size increases
Solution Approach 1:
The frame period is divided into multiple sub-frame periods, and the backlight brightness is controlled differently in each sub-frame period. This segmentation allows the system to achieve finer brightness control (more adjustment steps) by varying the duty ratio across sub-frames, without requiring a more complex circuit architecture. The segmentation of time enables increased precision without increasing spatial complexity.
Solution Approach 2:
The backlight brightness is controlled in a periodic manner by dividing each frame period into multiple sub-frame periods with different duty ratios. This periodic control approach allows the system to achieve multiple brightness adjustment steps through temporal modulation rather than through increased circuit complexity. The PWM signal is updated periodically at each sub-frame boundary to achieve the desired brightness levels.
2Adaptability or versatility
If the maximum backlight brightness is increased in bright environments, then the adaptability to environment is improved, but the number of adjustment steps for dark environments is reduced
Solution Approach 1:
The system dynamically adjusts the backlight brightness control strategy based on environment light intensity. In bright environments, the maximum backlight brightness is increased to match the ambient light, while in dark environments, the system uses sub-frame period division to provide finer brightness adjustment steps. This dynamic adaptation allows the system to optimize both environment adaptability and brightness control precision for each condition.
Solution Approach 2:
The system changes the control parameters (duty ratio values and sub-frame period divisions) based on environment light intensity. When the environment is bright, the maximum brightness parameter is increased. When the environment is dark, the system increases the number of sub-frame periods to provide more adjustment steps within a reduced brightness range, thereby maintaining control precision across different environmental conditions.
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
This approach allows for more precise control of backlight brightness, enhancing picture contrast and reducing power consumption while maintaining reduced circuit complexity.
Implementation Method 1
a PWM signal whose duty ratio is variable in 256 steps is generated by a brightness control circuit, and the backlight drive circuit is configured to drive the backlight in brightness in accordance with the duty ratio of the generated PWM signal
Data Source
AI summary
A display device is provided with a display panel, a backlight which illuminates the display panel, and a backlight brightness controller controlling a brightness of the backlight so that the brightness of the backlight is variable in the middle of each frame period.