Pixel Circuit Resistor Line for Low Gray-Level Uniformity
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Solution Overview
Problem
Existing display panels face challenges in achieving uniform brightness at low gray levels due to the feedthrough effect, which causes voltage drops and fluctuations in current through OLEDs, leading to uneven brightness and reduced uniformity.
Innovation Solution
A pixel circuit design incorporating a resistor line between the gate and source of thin-film transistors, with a resistance value ranging from 900 to 1200 kΩ, which slows down the voltage drop during the writing signal line's turned-off stage, stabilizing the voltage difference and maintaining consistent current through OLEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the parasitic capacitance Cgs of the switching TFT is reduced, then the influence of gate voltage decrease on source voltage is reduced, but the structure optimization has encountered a bottleneck
Solution Approach 1:
The patent introduces a resistor line as an intermediary component between the gate and source of the switching TFT. This resistor line has a specific resistance value (900-1200 kΩ) that acts as a mediator to control the voltage drop speed, preventing the feedthrough effect from causing rapid voltage changes while maintaining a simple structure without complex optimizations
2Reliability
If the storage capacitance of the pixel is increased, then the stability of voltage difference Vg−Vs is maintained, but the pixel size is decreasing and design space is limited
Solution Approach 1:
Instead of changing the physical size of the storage capacitor, the patent changes the electrical parameter (resistance) by introducing a resistor line with specific resistance value (900-1200 kΩ). This parameter change allows voltage stability to be achieved through electrical characteristics rather than physical size, accommodating the trend toward smaller pixel areas
3Speed
If the WR RC loading is reduced, then the WR signal drops faster, but the optimization is limited by manufacturing processes and design
Solution Approach 1:
The patent changes the resistance parameter of the introduced resistor line to achieve the desired signal drop speed. By selecting a specific resistance range (900-1200 kΩ), the patent optimizes the WR signal characteristics without being constrained by manufacturing process variations, as the resistor line's characteristics can be precisely controlled during fabrication
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces the feedthrough effect, improving low gray-level uniformity and enhancing the overall quality of the display panel by maintaining stable voltage and current, particularly suitable for high PPI pixel designs.
Implementation Method 1
Feedthrough means that the voltage of the gate of the switching TFT is suddenly reduced as the WR is turned off, to cause the voltage of the source of the TFT to drop due to a parasitic capacitor Cgs inside the TFT, especially between the gate and the source of the TFT
Implementation Method 2
A pixel circuit including a first thin-film transistor, a second thin-film transistor and a resistor line. The resistor line is connected between a first node and a second node. A formula of resistance value of the resistor line is R=ρl/s, where R is a resistance value, ρ is an electrical resistivity and s is a cross-sectional area of the resistor line. Resistance value of the resistor line ranges from 900 to 1200 kΩ
Data Source
AI summary
A pixel circuit, a display panel and a method for improving low gray-level uniformity for a display panel are provided. A feedthrough effect can be effectively reduced by increasing resistance value of a resistor line between a source of a switching thin-film transistor and a gate of a driving thin-film transistor. Low gray-level uniformity of the display panel is improved. Quality of the display panel is enhanced.