Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
In Active Matrix Organic Light Emitting Diode (AMOLED) displays, the non-uniformity of Thin Film Transistors (TFTs) due to Excimer Laser Annealing and doping processes leads to a shift in threshold voltage, causing non-uniform brightness across pixels.
Innovation Solution
A pixel driving circuit with a driving sub-circuit, light-emitting control sub-circuits, driving control sub-circuit, and reset sub-circuit, utilizing transistors and storage capacitors to generate and control driving current independently of threshold voltage shifts, ensuring consistent brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If basic 2T1C pixel driving circuit is used, then device complexity is reduced, but manufacturing precision deteriorates due to TFT non-uniformity and threshold voltage shift
Solution Approach 1:
The pixel driving circuit is segmented into multiple functional sub-circuits: a basic 2T1C driving circuit and an additional compensation circuit. The compensation circuit is divided into a first compensation circuit connected to the gate of the driving transistor and a second compensation circuit connected to the light-emitting element. This segmentation allows independent compensation of threshold voltage shifts without fundamentally changing the basic circuit structure, thereby maintaining simplicity while improving manufacturing precision.
2Manufacturing precision
If threshold voltage compensation is implemented, then manufacturing precision is improved, but device complexity increases due to additional circuit components
Solution Approach 1:
The compensation circuits are merged with the existing basic 2T1C driving circuit structure. The first compensation circuit merges with the gate control path, and the second compensation circuit merges with the light-emitting element connection. This merging approach enables threshold voltage compensation functionality while sharing common components and signal paths with the basic circuit, thereby reducing the overall complexity increase compared to fully separate compensation circuits.
3Productivity
If threshold voltage shift occurs, then manufacturing precision deteriorates, but productivity is maintained in basic 2T1C circuit
Solution Approach 1:
The compensation circuits perform preliminary action by pre-compensating for threshold voltage shifts before the light-emitting element is driven. The first compensation circuit adjusts the gate voltage of the driving transistor in advance to counteract expected threshold voltage variations. This preliminary compensation ensures that subsequent light emission maintains uniform brightness across all pixels, thereby improving manufacturing precision without interfering with the normal driving productivity of the basic 2T1C circuit.
Data Source
AI summary
The present disclosure provides a pixel driving circuit and a method for driving the same, a pixel unit, and a display panel. The pixel circuit includes: a driving sub-circuit, configured to generate driving current based on a data signal and a first voltage; a first light-emitting control sub-circuit configured to receive a first control signal and the first voltage, and provide the first voltage to the driving sub-circuit under control of the first control signal; a second light-emitting control sub-circuit configured to receive a second control signal and provide driving current generated by the driving sub-circuit to an output terminal of the pixel driving circuit under control of the second control signal; a driving control sub-circuit configured to receive the second control signal and the data signal and provide the data signal to the driving sub-circuit under control of the second control signal; and a reset sub-circuit configured to receive a reset signal and a second voltage, and reset the driving sub-circuit using the second voltage under control of the reset signal.