OLED Dimming Control for Flicker Noise Reduction
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Solution Overview
Problem
Conventional organic light emitting displays experience flicker noise and horizontal stripe noise during dimming driving due to the increase in emission control signal width, leading to non-uniform light emission and reduced pixel brightness in blank regions.
Innovation Solution
The organic light emitting display incorporates a dimming controller and emission control line driver to control emission control signals such that pixels are turned on and off at least twice in one frame period, ensuring a uniform light-emitting area within the active region, and the emission control signals are synchronized with scan signals to maintain a consistent voltage across light-emitting regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the emission control signal width is increased during dimming driving, then the brightness control is improved, but flicker noise and horizontal stripe noise are generated
Solution Approach 1:
The emission control signals are segmented into multiple sub-periods within one frame period. Instead of using a single continuous emission control signal, the patent divides the emission control into multiple discrete time segments, which prevents the formation of continuous noise patterns and reduces both flicker noise and horizontal stripe noise while maintaining dimming functionality.
2Illumination intensity
If the emission control signal width is increased during dimming driving, then the brightness control is improved, but the light-emitting area becomes non-uniform in the active region
Solution Approach 1:
The patent applies different emission control signal characteristics to different regions of the display panel. By controlling the emission control signals locally in the active region versus the blank region, the light-emitting area is maintained uniformly within the active region while allowing non-uniformity in the blank region, thus resolving the contradiction between brightness control and uniformity.
3Reliability
If the voltage of the first power source ELVDD is increased to correspond to low voltage drop, then the power supply stability is improved, but the brightness of pixels in the active region increases causing horizontal stripe noise
Solution Approach 1:
The patent employs periodic emission control signals with specific timing characteristics that synchronize with the scan signals. By using periodic action at optimized intervals, the power source voltage can be increased for stability without causing continuous brightness variation, as the periodic emission control prevents the accumulation of voltage-related brightness differences that would manifest as horizontal stripe noise.
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 reduces or prevents the generation of horizontal stripes in displayed images, enhancing display quality by maintaining uniform brightness and reducing noise during dimming operations.
Implementation Method 1
the organic light emitting display display images using organic light emitting diodes (OLED) that generate light by recombination of electrons and holes
Data Source
AI summary
An organic light emitting display includes first scan lines, data lines, and first emission control lines at an active region for displaying an image, second scan lines and second emission control lines at a blank region where no image is displayed, pixels coupled to the first scan lines, the data lines, and the first emission control lines in the active region, a dimming controller for controlling brightness of the pixels, and an emission control line driver for supplying emission control signals to the first and second emission control lines corresponding to control of the dimming controller so that a light-emitting area including ones of the pixels is uniform in the active region.