Pixel Circuit Timing for Threshold Voltage Compensation
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Solution Overview
Problem
Display devices face insufficient compensation time for transistor threshold voltage variations as resolution and driving frequency increase, affecting pixel performance.
Innovation Solution
A pixel circuit with a specific configuration of transistors and capacitors, including back-gate transistors and a light-emitting element, is used to extend compensation time by adjusting gate signal pulse widths and phases, ensuring adequate voltage compensation and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If resolution and driving frequency of display device are increased, then display quality and performance are improved, but compensation time for transistor threshold voltage becomes insufficient
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks with dedicated transistors: a first transistor for threshold voltage compensation, a second transistor for data signal transmission, a third transistor for initialization, and a fourth transistor for light emission control. This segmentation allows each transistor to perform its function independently and efficiently, ensuring adequate compensation time even at high resolutions and driving frequencies.
Solution Approach 2:
The first transistor performs threshold voltage compensation in advance during a dedicated compensation period before the data signal is transmitted. By completing the compensation action preliminarily, the circuit ensures that threshold voltage variations are accounted for before affecting the light emission, maintaining display quality at high driving frequencies.
2Reliability
If internal compensation technique is used to compensate for transistor threshold voltage, then pixel performance is maintained, but compensation time becomes insufficient at high resolution and frequency
Solution Approach 1:
The compensation mechanism is localized to specific transistors within the pixel circuit. The first transistor is specifically designed for threshold voltage compensation with its gate connected to a scan line and its source/drain connected to the light emitting element, providing targeted compensation at the local pixel level without requiring extended global compensation time.
Solution Approach 2:
The circuit utilizes different voltage levels and timing parameters for different transistors. The scan line provides a first voltage level for compensation, while the data line provides a second voltage level for data transmission. By changing voltage parameters and timing sequences, the circuit achieves reliable compensation within the available time frame at high resolutions and frequencies.
Data Source
AI summary
A pixel circuit includes first to fifth transistors, a capacitor, and a light emitting element. The first transistor is coupled between first and second power lines, and includes a gate electrode coupled to a first node and a back-gate electrode coupled to a second node. The second transistor is coupled between a data line and the first node, and includes a gate electrode coupled to a first scan line. The third transistor is coupled between a third power line and the first node, and includes a gate electrode coupled to a reference scan line. The fourth transistor is coupled between a second node and a fourth power line, and includes a gate electrode coupled to a second scan line. The fifth transistor is coupled between a first power line and the one electrode of the first transistor, and includes a gate electrode coupled to a light-emitting control line.