LCD Backlight Driving Circuit Sub-Block Segmentation Flicker Reduction
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Solution Overview
Problem
Existing liquid crystal display (LCD) driving methods, such as local dimming, suffer from flicker issues due to luminance differences between frames or blocks, particularly when dealing with multimedia content like movies, and require a large number of driving circuits, which limits the use of multiple driving blocks and fails to prevent flicker effectively.
Innovation Solution
A method of driving a light source for LCDs that involves calculating gradation data by dividing image blocks into sub-blocks, determining the duty ratio of driving signals for each block based on gradation data, and excluding non-image data like subtitles to enhance display quality without increasing the number of driving circuits, allowing for accurate luminance control and reduced flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If local dimming driving method is used to control luminance, then power consumption is minimized and contrast ratio is improved, but flicker is generated due to luminance differences between frames or blocks
Solution Approach 1:
The patent divides the image block into multiple sub-blocks (e.g., 4 sub-blocks) and calculates gradation data for each sub-block separately. This segmentation allows more precise control of luminance in different regions, enabling the system to maintain uniform luminance across the display while reducing flicker caused by block-based dimming. The driving circuit is divided into multiple driving blocks corresponding to these sub-blocks, each controllable independently.
Solution Approach 2:
The patent applies different driving strategies to different regions of the display. By calculating gradation data for each sub-block and determining duty ratios based on local luminance requirements, the system achieves local quality control. This allows subtitles or specific regions to be handled differently from the main image content, preventing flicker in subtitle regions while maintaining overall luminance control.
2Reliability
If number of driving blocks is increased to reduce flicker, then display quality improves, but number of driving circuits increases which limits scalability
Solution Approach 1:
The patent segments the image block into sub-blocks and uses a single driving circuit to control multiple driving blocks. The driving circuit calculates gradation data for each sub-block and determines appropriate duty ratios, then drives the corresponding driving blocks with PWM signals. This segmentation approach allows one driving circuit to manage multiple blocks effectively, reducing flicker without proportionally increasing circuit complexity.
Solution Approach 2:
The driving circuit is designed with multi-functionality to handle multiple driving blocks. It can calculate gradation data for different sub-blocks, determine duty ratios based on local luminance requirements, and generate PWM signals for multiple blocks sequentially. This universal design allows a single driving circuit to perform what would traditionally require multiple dedicated circuits, maintaining scalability while improving flicker reduction.
3Illumination intensity
If global dimming or boosting method is used to adjust luminance, then entire screen luminance is controlled, but flicker is generated due to luminance difference between frames
Solution Approach 1:
The patent segments the display into multiple driving blocks with independent PWM control. Instead of applying uniform global dimming or boosting, each driving block can be independently controlled based on local gradation data. This segmentation allows the system to maintain consistent luminance across frames by adjusting individual blocks, thereby reducing flicker while preserving overall luminance control capability.
Solution Approach 2:
The patent implements dynamic luminance control where duty ratios are adjusted in real-time based on calculated gradation data for each sub-block. The driving circuit dynamically determines PWM duty cycles that optimize luminance for each region, allowing adaptive response to changing image content. This dynamic approach prevents flicker by continuously adjusting luminance levels to maintain uniformity across the display.
Data Source
AI summary
A method of driving a light source including a light source module which provides a liquid crystal display panel with light and is driven through a dimming method according to a plurality of driving blocks, the method including; calculating gradation data of an image block of the liquid crystal display panel from an external image signal by dividing the image block into a plurality of sub-blocks, determining a duty ratio of a driving signal which drives an individual driving block of the plurality of driving blocks, the individual driving block corresponding to the image block based on the gradation data, and driving the individual driving block in accordance with the duty ratio.