4T1C Display Pixel Circuit for Threshold Compensation
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Solution Overview
Problem
Existing display device pixels face issues with luminance errors due to changes in threshold voltage of driving transistors, necessitating additional transistors for threshold voltage compensation, which increases complexity and reduces resolution.
Innovation Solution
A pixel configuration with a 4T1C structure, including specific transistors and a capacitor, performs threshold voltage compensation in a source follower manner, allowing for a simple configuration suitable for high-resolution displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional transistors are added to perform threshold voltage compensation, then luminance error is reduced, but device complexity increases
Solution Approach 1:
The patent combines the threshold voltage compensation function with the data writing function by using the same transistor (first transistor) for both purposes. During the initialization period, the transistor performs threshold voltage compensation by transferring reference voltage to the first node. During the data writing period, the same transistor transfers data voltage to the first node. This merging eliminates the need for separate compensation transistors while maintaining luminance accuracy.
Solution Approach 2:
The first transistor is designed to perform multiple functions: threshold voltage compensation during initialization and data writing during the data writing period. The transistor's gate receives different voltages (reference voltage or data voltage) depending on the operational period, enabling it to serve universal purposes and reduce overall device complexity.
2Reliability
If additional transistors and capacitors are included in the pixel, then threshold voltage compensation is achieved, but resolution is reduced
Solution Approach 1:
The patent merges threshold voltage compensation and data writing operations into a single transistor structure. By using the first transistor for both compensation (during initialization) and data writing (during data writing period), the pixel achieves threshold voltage compensation without adding extra transistors that would reduce display resolution.
Solution Approach 2:
The patent employs periodic action by dividing the operation into distinct time periods: initialization period for threshold voltage compensation and data writing period for data input. The first transistor alternates between these functions based on the operational period, enabling compensation without permanent structural additions that would compromise resolution.
Data Source
AI summary
A pixel of a display device includes a first transistor including a gate connected to a first node, a first terminal receiving a first power supply voltage and a second terminal connected to a second node, a capacitor disposed between a third node and the second node, a second transistor including a gate receiving a write signal, a first terminal connected to a data line and a second terminal connected to the third node, a third transistor including a gate receiving the write signal, a first terminal receiving a reference voltage and a second terminal connected to the first node, a fourth transistor including a gate receiving an emission signal, a first terminal connected to the first node and a second terminal connected to the third node, and a light-emitting element including an anode connected to the second node and a cathode receiving a second power supply voltage.