OLED Display Timing Control for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting diode (OLED) displays experience luminance imbalance due to voltage drops in power lines, leading to image distortion and uniformity issues.
Innovation Solution
A display device and driving method that divide the display unit into upper, center, and bottom portions, adjusting the light emission and blank periods of sub-frames to minimize voltage drops by varying the scan start times and data voltage application, ensuring consistent voltage across all pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the power line is extended to supply power to all pixels in the display unit, then the display area is increased, but voltage drop occurs causing luminance imbalance
Solution Approach 1:
The display unit is divided into multiple scan line groups (first group, second group, third group, etc.) corresponding to different voltage compensation regions. Each group is assigned a specific scan start time and light emission period to compensate for voltage drops in different areas of the extended power line.
Solution Approach 2:
Different scan start times and light emission periods are applied to different scan line groups based on their position in the display unit. Groups closer to the power line source receive different timing parameters than groups farther away, compensating for the cumulative voltage drop effect in each local region.
2Illumination intensity
If the light emission period is extended to improve image quality, then luminance is enhanced, but voltage drop increases causing greater luminance imbalance
Solution Approach 1:
The light emission period is made dynamic and variable across different scan line groups rather than being uniform. Each group's light emission period is adjusted based on its position to compensate for voltage drop, allowing the system to maintain luminance uniformity while still providing adequate brightness across the entire display.
3Device complexity
If scan start times are synchronized across all groups, then control is simplified, but luminance imbalance occurs due to voltage drop
Solution Approach 1:
The scan start time parameter is changed for different scan line groups to compensate for voltage drop effects. By adjusting this temporal parameter across groups, the system maintains luminance uniformity without requiring complex hardware modifications or power line redesign.
4Reliability
If voltage is increased to compensate for power loss, then current consumption increases, but luminance imbalance is reduced
Solution Approach 1:
The system uses periodic blank periods between light emission periods to allow voltage recovery and reduce cumulative voltage drop. This periodic timing structure enables the display to maintain luminance uniformity while managing power consumption through controlled intervals of high and low current draw.
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
Effectively reduces luminance imbalance and image distortion by optimizing the timing of light emission and blank periods, maintaining uniformity and reducing current consumption.
Implementation Method 1
an OLED emitting light with predetermined luminance corresponding to a data current supplied from a pixel circuit
Data Source
AI summary
A display device includes a display unit including pixels, each of which emits light according to data voltages, respectively; and a timing controller which divides an area of the display unit into an upper, center and bottom portions, divides one frame time into light emission sub-frames of a light emission period and a blank sub-frame of a blank period in which is supplied a black data signal, divides the upper, center and the bottom portions into groups, differentiates a scan start time of a light emission sub-frame and a scan start time of the blank sub-frame of each group, and increases the light emission period and decreases the blank period in proportional to an increase ratio of the light emission period as a group is closer to a middle of the center portion.