OLED Pixel Circuit Threshold Hysteresis Compensation
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Solution Overview
Problem
Existing OLED pixel circuits experience low brightness after switching from low-grayscale to high-grayscale images due to threshold voltage hysteresis effects, leading to display non-uniformity.
Innovation Solution
The pixel circuit incorporates a driving transistor, light emission control module, initialization modules, threshold compensation, data writing, and storage modules to reset and stabilize the gate voltage, enabling a large current flow through the driving transistor before high-grayscale image display, compensating for threshold voltage hysteresis and improving responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pixel circuit displays low-grayscale images, then power consumption is reduced, but brightness drops when switching to high-grayscale images due to threshold voltage hysteresis
Solution Approach 1:
The patent applies preliminary action by introducing a pre-charge phase before the main image display. During this pre-charge phase, the driving transistor is activated to charge the storage capacitor, ensuring the gate voltage reaches the required level before the light emitting device needs to emit light. This preliminary action compensates for the threshold voltage hysteresis effect and ensures consistent brightness when switching from low-grayscale to high-grayscale images.
Solution Approach 2:
The patent changes the voltage parameter by introducing a pre-charge voltage level that is different from both the low-grayscale and high-grayscale operating levels. The pre-charge voltage is specifically set to compensate for the threshold voltage shift that occurs during grayscale transitions, thereby maintaining stable brightness across different grayscale levels while managing power consumption.
2Manufacturing precision
If threshold voltage compensation is implemented, then display uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the pre-charge circuit to serve multiple functions: it compensates for threshold voltage hysteresis, ensures proper gate voltage charging, and maintains display uniformity across different grayscale levels. By making this single circuit module multi-functional, the patent improves display uniformity without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the pre-charge function with the existing driving transistor and storage capacitor structure. Instead of adding a completely separate compensation circuit, the pre-charge phase is integrated into the existing pixel circuit operation sequence, combining the voltage charging function with the image display function. This merging approach improves display uniformity while minimizing the increase in device complexity.
Data Source
AI summary
The disclosure discloses a pixel circuit, a method for driving the same, a display panel and a display device, which utilize a first initialization module, a data writing module, a threshold compensation module. Besides, since the pixel circuit is further provided with a second initialization module and the second initialization module is configured to enable a signal of a first voltage terminal to flow through the driving transistor before a light emitting device emits light, after the pixel circuit displays a low-grayscale image and before the pixel circuit displays a high-grayscale image, a large current is enabled to flow through the driving transistor to compensate for a threshold voltage hysteresis effect of the driving transistor, thereby improving the problem that the brightness of a first frame is low after an existing pixel circuit has switched from displaying a low-grayscale image to displaying a high-grayscale image.