Pixel Circuit Threshold Voltage Correction for Display Uniformity
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Solution Overview
Problem
Conventional pixel circuits with threshold voltage correcting functions are complex, inefficient, and hinder miniaturization and high-resolution displays due to variations in threshold voltage among drive transistors, leading to non-uniformity and decreased yield.
Innovation Solution
A pixel circuit with correcting means that detects and writes the threshold voltage of the drive transistor during the horizontal scanning period, using switching transistors to reset and charge the pixel capacitor to the threshold voltage, thereby canceling the dependency of output current on threshold voltage and carrier mobility, simplifying the circuit configuration and reducing the number of elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional pixel circuits with threshold voltage correcting functions are used, then uniformity of brightness is improved, but device complexity increases and manufacturing yield decreases
Solution Approach 1:
The patent extracts the threshold voltage correction function from a separate complex circuit and integrates it into the existing pixel circuit structure. By using the pixel capacitor and existing transistors in a corrected sequence, the invention eliminates the need for additional dedicated correction circuits, thereby reducing device complexity while maintaining brightness uniformity
Solution Approach 2:
The patent makes the pixel capacitor serve dual functions: holding the video signal voltage and storing the threshold voltage compensation value. The existing transistors in the pixel circuit are made to perform multiple roles including sampling, driving, and threshold correction operations, thereby reducing the need for additional components and simplifying the overall circuit structure
2Stability of the object's composition
If conventional pixel circuits with threshold voltage correcting functions are used, then uniformity of brightness is improved, but productivity decreases due to decreased yield
Solution Approach 1:
By removing the need for complex external correction circuits and additional transistors, the invention reduces the number of fabrication steps and potential failure points in the manufacturing process. The simplified circuit structure with fewer elements directly improves manufacturing yield and productivity while maintaining the brightness correction function
Solution Approach 2:
The patent uses standard, readily available transistor and capacitor structures that are already part of the conventional pixel circuit fabrication process. By avoiding specialized or complex components, the invention maintains compatibility with existing manufacturing processes, thereby improving yield and reducing production costs
3Area of moving object
If the number of circuit elements is reduced for miniaturization, then area is improved, but threshold voltage variations cause non-uniformity
Solution Approach 1:
The patent makes the pixel capacitor serve dual functions: holding the video signal voltage and storing the threshold voltage compensation value. This multi-functional approach allows the circuit to maintain brightness uniformity despite using fewer elements and smaller area, as the same capacitor that is already present in the miniaturized circuit is utilized for correction purposes
Solution Approach 2:
The patent merges the threshold voltage correction function with the existing video signal holding function in the pixel capacitor. By combining these functions into a single component and using the existing transistor network for both sampling and correction, the invention achieves brightness uniformity without increasing the number of elements or occupying additional area
4Reliability
If conventional complex correction circuits are used, then threshold voltage dependency is canceled, but device complexity increases
Solution Approach 1:
The patent extracts the threshold voltage correction function from a separate complex correction circuit and integrates it into the existing pixel circuit operations. By using the pixel capacitor and existing transistors in a corrected sequence, the invention eliminates the need for additional dedicated correction circuits, thereby reducing device complexity while maintaining the cancellation of threshold voltage dependency
Solution Approach 2:
The pixel circuit performs its own threshold voltage correction using its internal components (pixel capacitor and existing transistors) without requiring external correction circuits or additional specialized elements. The circuit corrects its own threshold voltage variations through self-contained operations, simplifying the overall system architecture
Data Source
AI summary
A pixel circuit performs a threshold voltage correcting function. A sampling transistor becomes conductive in response to a control signal supplied from a scan line and samples a video signal supplied from a signal line to a pixel capacitor during a horizontal scanning period. The pixel capacitor applies an input voltage to a gate of a drive transistor in response to the sampled video signal. The drive transistor supplies an output current in accordance with the input voltage to a light-emitting device. A threshold voltage correcting period is provided to be part of the horizontal scanning period, to detect the threshold voltage of the drive transistor, and to write the threshold voltage in the pixel capacitor.