Pixel Circuit With Alternating OLED Emission for Frame Luminance Stability
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Solution Overview
Problem
Electroluminescent display apparatuses experience luminance deviations when the gray level of image data changes from black to white, leading to lower luminance in the first frame compared to subsequent frames maintaining the white gray level due to charge delay in the light emitting device.
Innovation Solution
A pixel circuit design incorporating two light emitting devices and emission transistors that alternate operation between odd and even frames, along with scan transistors for anode voltage initialization, ensures consistent anode voltage initialization across frames, reducing luminance deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light emitting device is used per pixel, then the device complexity is low, but luminance deviation occurs when gray level changes from black to white
Solution Approach 1:
The pixel circuit is divided into two sub-pixels, each with its own light emitting device and emission transistor. The emission transistors operate alternately in odd and even frames, segmenting the charging process to prevent charge delay accumulation and ensure consistent luminance across frame transitions.
Solution Approach 2:
The emission transistors are configured to operate periodically, with the first emission transistor active in odd frames and the second emission transistor active in even frames. This periodic alternation ensures that each light emitting device receives regular voltage initialization, eliminating luminance deviation at frame boundaries.
2Productivity
If the gray level is changed from black to white in the first frame, then the image data displays correctly, but charge delay occurs in the light emitting device causing lower luminance
Solution Approach 1:
The emission transistors are designed to initialize the anode voltage of the light emitting devices in advance during alternating frames. This preliminary voltage initialization ensures that when a gray level change occurs, the light emitting device is already prepared with the correct voltage level, preventing charge delay and immediate luminance output.
3Reliability
If two light emitting devices are used per pixel, then luminance consistency is improved, but the device complexity increases
Solution Approach 1:
The two light emitting devices share common circuit elements including the driving transistor, data line connection, and control logic. The emission transistors are controlled by a unified emission signal that alternates between frames, merging the operation of both sub-pixels into a coordinated system that achieves luminance consistency without duplicating the entire pixel circuit.
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
The solution achieves consistent luminance across frames by equalizing anode voltage initialization, minimizing luminance deviation to zero, thereby maintaining uniform brightness levels.
Implementation Method 1
a light emitting device which emits light with brightness corresponding to the driving current
Data Source
AI summary
A pixel circuit and an electroluminescent display apparatus are discussed. The pixel circuit can include a driving transistor having a gate electrode connected to a gate node and a source electrode connected to a source node, and configured to generate a driving current. The pixel circuit can further include a first light emitting device having a first anode electrode, a second light emitting device having a second anode electrode, a first emission transistor connecting the source node to the first anode electrode in an odd frame and disconnecting the source node from the first anode electrode during an even frame in response to a first emission signal, and a second emission transistor connecting the source node to the second anode electrode in the even frame and disconnecting the source node from the second anode electrode during the odd frame in response to a second emission signal.