Emission Driver Circuit for OLED Afterimage Reduction
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Solution Overview
Problem
Display devices face challenges in minimizing afterimage visibility when driven at multiple frequencies, particularly due to hysteresis phenomena affecting the driving characteristics of light-emitting diodes, especially in organic light-emitting display devices.
Innovation Solution
The implementation of a display device architecture that includes a driving transistor set to an on-biased state using a supply voltage, with a specific emission driver configuration that controls the emission transistors to minimize afterimage visibility by managing the emission signals across different frequency operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the display device is driven at multiple frequencies to reduce power consumption, then energy efficiency is improved, but afterimage visibility increases due to hysteresis phenomena
Solution Approach 1:
The emission driver supplies an emission signal at a third voltage level (intermediate between first and second levels) during a holding period before the actual emission period. This preliminary action maintains the driving transistor in an on-biased state, preventing hysteresis effects that cause afterimage visibility when switching between different driving frequencies, thereby enabling power savings without compromising image quality
Solution Approach 2:
The emission driver dynamically changes the voltage level supplied to the emission line across three distinct levels: first level (high voltage to turn on both emission transistors), second level (low voltage to turn off both emission transistors), and third level (intermediate voltage to turn on only the first emission transistor). This parameter change enables precise control of the driving transistor's bias state, eliminating afterimage effects while maintaining energy efficiency at multiple driving frequencies
2Object-affected harmful factors
If the driving transistor is kept in an on-biased state to minimize afterimage visibility, then afterimage visibility is reduced, but power consumption increases
Solution Approach 1:
The emission driver operates in periodic cycles with distinct phases: a data programming period where the emission signal is at the second voltage level (both emission transistors off, saving power), followed by a holding period where the emission signal transitions to the third voltage level (first emission transistor on, maintaining on-biased state to prevent afterimage). This periodic action between different voltage levels achieves both power savings and afterimage elimination
Solution Approach 2:
The frame period is segmented into two functional periods: data programming period and holding period. During the data programming period, power is conserved by keeping both emission transistors off. During the holding period, only the first emission transistor is activated to maintain the driving transistor in an on-biased state. This temporal segmentation allows the system to achieve low power consumption while minimizing afterimage visibility
Data Source
AI summary
Provided herein is a display device including a plurality of pixels, wherein each pixel of the plurality of pixels includes: a driving transistor including a first electrode, a second electrode, and a first gate electrode; a first emission transistor including a third electrode coupled to the first electrode of the driving transistor, a fourth electrode, and a second gate electrode; and a second emission transistor including a fifth electrode coupled to the second electrode of the driving transistor, a sixth electrode, and a third gate electrode, wherein both the second gate electrode and the third gate electrode are coupled to an emission line, and wherein the first emission transistor is turned-on but the second emission transistor is turned-off, based on an emission signal supplied from the emission line.