Display Pixel Circuit Compensation for Threshold Voltage Variation
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Solution Overview
Problem
Variations in threshold voltage of drive transistors in display devices lead to fluctuations in drain current and luminosity, degrading image quality, especially in high-definition or large-scale pixel regions due to wire resistance effects.
Innovation Solution
A display device circuit structure incorporating multiple switching elements and a storage capacitor, with specific voltage application timing and power supply line configurations to compensate for threshold voltage variations and minimize wire resistance impacts, ensuring uniform luminosity across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple switching elements and storage capacitors are added to compensate for threshold voltage variations, then luminosity uniformity is improved, but device complexity increases
Solution Approach 1:
The pixel circuit is segmented into multiple functional blocks: a drive transistor for current control, a first switching element for gate control, a second switching element for data signal input, a third switching element for reference signal input, a storage capacitor for voltage storage, and a light emitting element for display. Each segment performs a specific function in the threshold voltage compensation process, allowing the complex compensation mechanism to be organized into manageable, functionally-separated components.
Solution Approach 2:
The compensation mechanism performs preliminary action by applying reference signals and storing compensation voltages in the storage capacitor before the actual display operation. The third switching element applies a reference signal to the storage capacitor during a compensation phase, and the storage capacitor holds this compensation voltage ready to offset threshold voltage variations during subsequent display operations, ensuring uniform luminosity before the actual imaging begins.
2Measurement precision
If more power supply lines with different voltages are used, then threshold voltage compensation accuracy is improved, but device complexity increases
Solution Approach 1:
The power supply system demonstrates multi-functionality by using a third power supply line that can serve dual purposes: it provides a third voltage for compensation operations and works in conjunction with the first and second power supply lines to enable various switching states. The fourth switching element controls connections to this third power supply line, allowing the same voltage source to be used for both compensation phase operations and display phase operations, reducing the need for entirely separate voltage sources.
Solution Approach 2:
The storage capacitor acts as an intermediary between the reference signal and the drive transistor gate. Instead of directly applying complex multi-voltage compensation signals to the transistor, the storage capacitor mediates by storing a compensated voltage that is then applied to the gate. This intermediary component simplifies the power supply requirements by converting complex voltage manipulation into a simpler charge storage and release mechanism.
Data Source
AI summary
A display device including a pixel, a drive transistor including a first and a second terminal and a gate, a first switching element controlling a connection between the second terminal and the gate, a storage capacitor of a second terminal connected to the gate, a second switching element controlling a connection between the storage capacitor and a first signal line, a third switching element arranged in parallel with the second switching element and controlling a connection between the storage capacitor and a second signal line, a fourth switching element controlling a connection between the drive transistor and a first power supply line, a light emitting element connected with the drive transistor and a second power supply line, a fifth switching element controlling a connection between the drive transistor and the light emitting element, a sixth switching element controlling a connection between the drive transistor and a third power supply line.