Pixel Circuit Initialization Layout for Black Voltage Suppression
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Solution Overview
Problem
Display devices face challenges in reducing back voltage corresponding to black gradation and preventing bright spot defects due to current leakage in pixels.
Innovation Solution
The display device incorporates a pixel circuit with a driving transistor and switching transistors, including a first and second initialization operation controlled by the same gate signal, which initializes the gate and source/drain electrodes of the driving transistor to bypass accumulated charge, reducing black voltage and preventing current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single initialization operation is performed in conventional display devices, then the manufacturing process remains simple, but black voltage cannot be effectively reduced and bright spot defects occur due to charge accumulation
Solution Approach 1:
The initialization operation is divided into two distinct sections: a first initialization section that initializes the gate electrode, and a second initialization section that initializes the source/drain electrodes. This segmentation allows each initialization operation to target specific charge accumulation problems, effectively reducing black voltage and preventing bright spot defects while maintaining manufacturing feasibility
Solution Approach 2:
The first initialization operation is performed in advance during the first initialization section before the light emitting operation begins. This preliminary initialization of the gate electrode prevents charge accumulation that would otherwise cause black voltage issues during subsequent operations, thereby improving image quality proactively
2Device complexity
If the same gate signal controls both initialization operations, then the control circuit remains simple, but precise timing control becomes difficult
Solution Approach 1:
The same gate signal is utilized in a periodic manner to control both the first and second initialization operations at different time intervals. The gate signal activates the first switching transistor during the first initialization section, then activates the second switching transistor during the second initialization section. This periodic reuse of the gate signal simplifies the control circuit while the sequential timing ensures precise initialization of different electrodes
Data Source
AI summary
A display device includes: a pixel circuit and a light emitting element electrically connected to the pixel circuit, a gate driver outputting a gate signal, and a data driver outputting a data voltage. The pixel circuit includes a driving transistor including a first end of a first area, a second area electrically connected to a power voltage line configured to receive a driving voltage, a first channel area, and a portion of a first gate electrode overlapping the first channel area, a first switching transistor including a portion of a first upper active pattern on the first gate electrode and configured to receive an initialization voltage, and a portion of a first upper gate line configured to receive a first gate signal and overlapping the first upper active pattern, and a connection pattern on the first upper gate line and connecting the first upper active pattern and the first area.