2-Line Addressing LED Backlight Dimming Control
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Solution Overview
Problem
Passive matrix LED backlight systems face limitations due to high pulse current, which can reduce the lifespan of LEDs and limit the number of scan rows, making them infeasible for large-scale applications.
Innovation Solution
A 2-line addressing driving scheme is implemented, where row enable signals and column driving signals are used to overlap enable pulses, reducing the pulse current and enhancing the LED backlight's lifespan by applying common and residual brightness data to adjacent rows, allowing for optimized brightness control across zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a passive matrix LED backlight system uses a large number of scan rows to support local dimming, then the coverage and control capability are improved, but the pulse current increases significantly, reducing LED lifespan and making the system infeasible
Solution Approach 1:
The patent segments the scanning process into multiple sub-scanning periods within each frame period. Instead of scanning all rows sequentially in one period, the scanning is divided into several sub-periods with different row groups scanned in each sub-period. This segmentation reduces the peak pulse current by distributing the scanning load across multiple time slots, while still achieving comprehensive backlight coverage through the combined effect of all sub-scanning periods.
2Adaptability or versatility
If the number of scan rows is increased to support more zones, then the local dimming control capability is improved, but the pulse current becomes too high for passive matrix implementation
Solution Approach 1:
The patent employs periodic scanning action by dividing the frame period into multiple sub-scanning periods. Each sub-scanning period scans a specific group of rows, and this scanning pattern repeats across different sub-periods. This periodic approach allows the system to handle a large number of scan rows by distributing the scanning task over multiple periodic cycles, thereby maintaining LED reliability by keeping peak currents within acceptable limits while achieving comprehensive local dimming control.
3Device complexity
If conventional sequential scanning is used, then the system structure is simple, but the pulse current is too high when the number of scan rows exceeds practical limits
Solution Approach 1:
The patent introduces dynamic scanning control by adjusting the scanning strategy based on the specific requirements of different row groups. Instead of a fixed sequential scanning pattern, the system dynamically assigns different row groups to different sub-scanning periods, optimizing the scanning sequence to minimize peak currents. This dynamic approach maintains relative system simplicity while effectively reducing pulse current through intelligent, adaptive scanning allocation.
Data Source
AI summary
An image displaying apparatus with local dimming control with 2-line addressing is disclosed. The apparatus includes a display panel, a light-emitting diode (LED) backlight divided into a plurality of zones, and a control unit. The control unit is configured to couple a dimming data to the LED backlight. The zones of the LED backlight are driven by row enable signals and column driving signals based on the dimming data. Each individual column driving signal transmits a common brightness data, a first residual brightness data, and a second residual brightness data. A first row enable signal has a first enable pulse in a frame period, and a second row enable signal has a second enable pulse in the frame period. The first and second enable pulses are at least partially overlapped for reducing a pulse current of the LED backlight for enhancing a lifetime of the LED backlight.