Display Device Backlight Luminance Optimization via Periodic LED Driving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing local dimming technique for LCDs using passive driving with time division results in a backlight that is not bright enough due to the limited duty ratio of the PWM signal, as each LED driver channel is shared among multiple areas, leading to shorter LED activation times and reduced luminance.
Innovation Solution
A display device with a drive unit that divides the frame period into a partial offset period and a remaining period, where all LEDs are turned on at maximum luminance during the offset period and driven based on input image data during the remaining period, allowing for increased luminance by adjusting the duration of these periods according to screen luminance settings, application usage, or power supply status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LEDs are driven by time division with multiple areas sharing LED driver channels, then the number of LED driver channels is reduced, but the backlight luminance becomes insufficient
Solution Approach 1:
The patent applies preliminary action by turning on all LEDs at maximum luminance during an offset period before the main image display period. This preliminary full-brightness activation ensures that the backlight reaches sufficient luminance levels before regional dimming control is applied, resolving the contradiction between reduced driver channels and adequate luminance output.
Solution Approach 2:
The patent implements periodic action by dividing the frame period into distinct offset period and image display period, with LEDs being driven at full power during the offset period and then controlled according to image data during the remaining period. This periodic switching between full-brightness and dimmed states maintains adequate overall luminance while enabling local dimming functionality with fewer driver channels.
2Adaptability or versatility
If the duty ratio of PWM signal is limited to one-n-th for n time divisions, then the LED driver can be shared among more areas, but the LED activation time is reduced and backlight becomes darker
Solution Approach 1:
The patent compensates for the reduced LED activation time during the image display period by providing a preliminary offset period where all LEDs are activated at maximum luminance. This ensures that even though the duty ratio during image display is limited, the overall LED activation time and cumulative luminance output are sufficient for high-quality local dimming performance.
Solution Approach 2:
The patent changes the temporal distribution of LED activation by introducing an offset period with 100% duty ratio before the image display period. This parameter change in the time-domain distribution of LED activation compensates for the reduced activation time during the actual image display, maintaining adequate overall luminance while enabling finer local dimming control.
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 enables a brighter backlight by optimizing the duration of LED activation periods, achieving luminance levels exceeding traditional passive driving methods, with adjustable offset periods to suit various conditions such as screen brightness, application requirements, and power availability.
Implementation Method 1
light-emitting elements in a backlight divided into a plurality of areas
Data Source
AI summary
A display device includes: light-emitting elements in a backlight divided into a plurality of areas, the light-emitting elements being arranged in such a manner as to correspond to the plurality of areas; and a drive unit configured to drive the light-emitting elements in the plurality of areas by time division based on an input image every prescribed period of time, the drive unit turning on all the light-emitting elements in the plurality of areas in a partial period of the prescribed period of time and driving those light-emitting elements in at least one of the plurality of areas based on the input image in a remaining period of the prescribed period of time.