Display Device Equal Sub-field Periods Addressing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In organic EL display devices using the sub-field drive method, the addressing period becomes shorter than desired, leading to insecure light emitting periods, and issues like peak current increase and false contouring occur, affecting display quality and reliability.
Innovation Solution
The display device divides one field into equal sub-field periods, using pulse signals with duty ratios that increase in geometric progression to extend addressing periods and distribute light emitting periods evenly across sub-fields, reducing peak current and suppressing false contouring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sub-field drive method is used to achieve multiple gray level display, then the light emitting periods can be distributed across sub-fields, but the addressing period becomes too short to be secured
Solution Approach 1:
The patent applies periodic action by using multiple sub-fields with different duty ratios in a cyclic manner. Each sub-field has a specific pulse width (1/8, 1/4, 1/2 of the horizontal period) and they are repeated in sequence, allowing the system to achieve 256 gray levels while maintaining adequate addressing time for each sub-field.
2Duration of action of moving object
If the addressing period is extended to allow proper data writing, then the light emitting period becomes insecure
Solution Approach 1:
The patent uses dynamic pulse width modulation where the pulse width varies across different sub-fields. The first sub-field uses 1/8 horizontal period, the second uses 1/4, and the third uses 1/2, allowing flexible allocation of time between addressing and light emitting based on the specific sub-field being active.
3Device complexity
If conventional drive methods are used, then the circuit structure remains simple, but peak current increases and false contouring occurs
Solution Approach 1:
The patent segments the light emitting period into multiple sub-fields with different duty ratios. Instead of using a single long pulse, the display is divided into first, second, and third sub-fields with pulse widths of 1/8, 1/4, and 1/2 horizontal periods respectively, distributing the current demand and preventing false contouring.
Data Source
AI summary
In a display device performing multiple gray level display using a sub-field drive method, an operation rate of a scan driver and a data driver is reduced and power consumption in the circuits are reduced. When 28 levels of gray level display is performed with 8 bits of video data, one field is equally divided by 8 into eight sub-fields to generate a first sub-field SF0 through an eighth sub-field SF7. Each of the sub-fields SF0 through SF7 has an equal length of sub-field period to each other. And a line-sequential addressing is adopted in addressing pixels so that each line of video data is written-in collectively. Addressing operation of the pixels and light emitting operation of the pixels are performed in parallel. Each of addressing periods AP0 through AP7 in each of the sub-fields is approximately equal to the sub-field period, that is a period of one field divided by 8.