Pixel Circuit With Series Capacitors for High-PPI Threshold Compensation
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Solution Overview
Problem
Display devices with high PPI (Pixels Per Inch) face challenges due to narrow pixel pitch and limited transistor count, leading to restrictions on signal application and visible artifacts from threshold voltage variations.
Innovation Solution
A pixel circuit design utilizing a minimal number of transistors, including a first transistor connected to a data line, a second transistor receiving a compensation gate signal, and a third transistor for driving an emission element, with capacitors connected in series to pre-charge and store threshold voltages, compensating for variations and enabling high PPI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel pitch is narrowed to achieve high PPI, then the display resolution is improved, but the number of transistors that can be accommodated in each pixel circuit is reduced
Solution Approach 1:
The patent combines multiple transistors into a dual-gate transistor structure where a single transistor body performs the functions of what would traditionally require multiple separate transistors. This merging reduces the total transistor count while maintaining the necessary circuit functionality for high-resolution displays.
Solution Approach 2:
The dual-gate transistor serves multiple functions simultaneously - it acts as both a switching element and a compensation element, and can operate in different modes depending on gate control. This multi-functionality allows fewer transistors to perform the work of more traditional single-function transistors.
2Area of stationary object
If the number of transistors per pixel circuit is reduced, then the pixel area is decreased for high PPI, but the ability to compensate for threshold voltage variations is degraded
Solution Approach 1:
The dual-gate transistor provides dynamic control through its two gates, allowing the transistor characteristics to be adjusted in real-time. This dynamic capability enables threshold voltage compensation by adjusting the back gate voltage to counteract threshold variations, maintaining reliability with fewer transistors.
Solution Approach 2:
The patent utilizes parameter changes in the dual-gate transistor by varying the back gate voltage to compensate for threshold voltage variations. This parameter adjustment mechanism allows the same transistor to adapt its characteristics, providing compensation functionality without requiring additional transistors.
3Ease of manufacture
If a minimal number of transistors is used in the pixel circuit, then the manufacturing cost is reduced, but the circuit functionality for data writing and compensation is restricted
Solution Approach 1:
The patent segments the control functions by assigning specific roles to different gates of the dual-gate transistor - one gate handles data writing while the other handles compensation. This functional segmentation within a single transistor structure maintains versatility while reducing component count and manufacturing complexity.
Data Source
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AI summary
A pixel circuit includes a first transistor including a first gate electrode connected to a first node, a first electrode receiving a first power supply voltage, a second electrode connected to a second node, and a second gate electrode connected to a third node, a second transistor configured to connect a data line and the first node in response to a data write gate signal, a third transistor configured to provide a reference voltage to the third node in response to a compensation gate signal, a first capacitor including a first electrode connected to the first node and a second electrode connected to the second node, a second capacitor including a first electrode connected to the second node and a second electrode 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.