Pixel Circuit Compensation for Threshold Shift and Crosstalk
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Solution Overview
Problem
Display devices using Low Temperature Polycrystalline Oxide (LTPO) pixel circuits face issues with threshold voltage shifting in driving transistors due to movable ions, leading to short-term residual images and brightness non-uniformity, as well as parasitic capacitance causing crosstalk and abnormal display effects.
Innovation Solution
A pixel circuit with a driving circuit, a first compensation circuit, and a second compensation circuit, utilizing storage capacitors and switching transistors to compensate for threshold voltage shifts and reduce parasitic capacitance, thereby improving brightness uniformity and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LTPO pixel circuits are used with narrow bezel design, then refresh rate and stability are improved, but threshold voltage shifting occurs due to movable ions causing short-term residual images and brightness non-uniformity
Solution Approach 1:
The first compensation circuit proactively compensates for threshold voltage shifts before they cause visible display defects. By detecting and correcting Vth changes in advance through the storage capacitor that tracks gate electrode voltage variations, the circuit prevents brightness non-uniformity and residual images from occurring, allowing high refresh rates to be maintained without sacrificing display quality
Solution Approach 2:
The compensation circuits implement feedback mechanisms where the storage capacitor continuously monitors the gate electrode voltage of the driving transistor and adjusts compensation signals accordingly. This closed-loop feedback corrects threshold voltage shifts caused by movable ions, ensuring brightness uniformity is maintained even at high refresh rates with narrow bezels
2Power
If driving transistor is used to control driving current, then light emission is achieved, but parasitic capacitance causes crosstalk and abnormal display effects
Solution Approach 1:
The patent extracts and isolates the parasitic capacitance effects into dedicated compensation circuits separated from the main driving transistor. By removing the harmful capacitive coupling between nodes and placing storage capacitors in isolated compensation paths, the circuit eliminates crosstalk while preserving the driving transistor's current control functionality for light emission
Solution Approach 2:
The storage capacitor acts as an intermediary element that mediates between the gate electrode and other circuit nodes. By introducing this intermediate component, the circuit blocks direct parasitic capacitance coupling paths that cause crosstalk, while still allowing the driving transistor to effectively control driving current through the compensated gate voltage
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 minimizes the impact of threshold voltage fluctuations and parasitic capacitance, enhancing display quality by ensuring consistent brightness and reducing abnormal display effects.
Implementation Method 1
the first compensation circuit comprises a first storage capacitor, and a first electrode of the first storage capacitor is electrically connected to the control terminal of the driving circuit
Implementation Method 2
the second compensation circuit includes a second storage capacitor and a first switching transistor, wherein a first electrode of the second storage capacitor is electrically connected to the first terminal of the driving circuit
Data Source
AI summary
A pixel circuit and its driving method, as well as a display device, are disclosed. The pixel circuit includes a driving circuit, a first compensation circuit, and a second compensation circuit. The first compensation circuit includes a first storage capacitor, with a first electrode of the first storage capacitor connected to the control terminal of the driving circuit, and a second electrode of the first storage capacitor connected to the first terminal of the driving circuit. The second compensation circuit includes a second storage capacitor and a first switching transistor. A first electrode of the second storage capacitor is connected to the first terminal of the driving circuit, a first electrode of the first switching transistor is connected to the second storage capacitor, and the gate electrode of the first switching transistor is configured to receive a second compensation control signal.