Display Sub-Pixel Emission Signal Control for Mura Reduction
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Solution Overview
Problem
Display devices often experience luminance non-uniformity, known as mura, due to structural and operational issues in pixel circuits, leading to inefficiencies in image display.
Innovation Solution
A display device and method that include a sub-pixel with specific transistors and capacitors, where the first emission signal has an active level in a portion of each frame period and is toggled between active and inactive levels in subsequent periods, reducing off-time and minimizing mura caused by voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first emission signal maintains active level throughout the entire frame period, then the light emitting element can continuously emit light ensuring uniform luminance, but the power consumption increases and the off-time cannot be reduced
Solution Approach 1:
The first emission signal is configured to have an active level during specific sub-periods (first and third sub-periods) and an inactive level during other sub-periods (second and fourth sub-periods) within each frame period. This periodic switching allows the light emitting element to emit light only during required periods while reducing power consumption during inactive periods, thereby resolving the contradiction between maintaining luminance uniformity and reducing power consumption
2Loss of energy
If the off-time of the first emission signal is extended to reduce power consumption, then the power efficiency improves, but the mura phenomenon worsens due to voltage drops
Solution Approach 1:
The first emission signal is activated during the first sub-period before the data writing operation in the second sub-period. This preliminary activation ensures that the light emitting element is already powered and ready to emit light immediately when needed, preventing voltage drops and mura phenomenon while still allowing the signal to be deactivated during the third sub-period to save power, thus resolving the contradiction between power efficiency and luminance uniformity
3Reliability
If the first emission signal is continuously active to maintain voltage levels, then the mura phenomenon is reduced, but the off-time cannot be decreased and power consumption increases
Solution Approach 1:
The first emission signal dynamically switches between active and inactive levels based on the operational requirements of different sub-periods. The signal is active during the first sub-period for preliminary power supply, inactive during the second sub-period for power saving, active during the third sub-period for light emission, and inactive during the fourth sub-period for power saving. This dynamic control reduces the total off-time compared to continuous operation while maintaining luminance uniformity, resolving the contradiction between reducing off-time and maintaining luminance uniformity
Data Source
AI summary
A display device includes a display panel including a sub-pixel, and a display panel driver for driving the display panel. The sub-pixel includes a driving transistor, a storage capacitor connected to a control electrode of the driving transistor, a write transistor writing a data voltage to the storage capacitor in response to a write gate signal, a first emission transistor providing a first power voltage to a first electrode of the driving transistor in response to a first emission signal, a hold capacitor including a first electrode receiving the first power voltage and a second electrode connected to a second electrode of the driving transistor, and a light emitting element emitting light. The first emission signal has an active level in a first portion of each of first periods of one frame, and has the active level in each of second periods respectively subsequent to the first periods.