OLED Pixel Circuit Threshold Voltage Compensation
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Solution Overview
Problem
In OLED display devices, the variation in threshold voltages of thin-film transistor switches over time leads to differences in color intensity between adjacent pixels, causing aberrant color display due to changes in transistor threshold voltages.
Innovation Solution
A pixel circuit design incorporating an OLED, driving switch, enabling switch, capacitors, and a compensation module that adjusts the driving voltage and data voltage to compensate for threshold voltage variations, allowing the circuit to operate independently of threshold voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If TFT fabrication is used to manufacture transistor switches, then the display device can be manufactured with smaller size and flexible panels, but the threshold voltage difference between transistor switches increases and threshold voltage changes with usage time
Solution Approach 1:
The patent applies preliminary action by measuring and compensating for the threshold voltage of each transistor switch before the display device is put into use. The compensation module stores the measured threshold voltage values and uses them to pre-adjust the driving currents, so that when the device starts operating, the threshold voltage variations have already been compensated, ensuring consistent color display from the beginning.
2Productivity
If the same data voltage is supplied to adjacent pixels, then the data transmission is simple and efficient, but the color intensity displayed by adjacent pixels becomes different due to threshold voltage variations
Solution Approach 1:
The patent applies local quality by making each pixel circuit have its own compensation module that independently measures and compensates for its specific transistor switch's threshold voltage. Instead of using a uniform compensation approach for all pixels, each pixel adjusts its driving current based on its local threshold voltage characteristics, ensuring that adjacent pixels display consistent color intensities even though they receive the same data voltage.
3Reliability
If threshold voltage compensation is implemented, then color display consistency is improved, but the circuit complexity increases with additional components
Solution Approach 1:
The patent applies merging by integrating the compensation module within each existing pixel circuit, combining multiple functions (threshold voltage measurement, compensation calculation, and driving current adjustment) into a unified circuit structure. The compensation module shares common components with the pixel circuit, such as using the same transistor switches and capacitors for both display and compensation functions, thereby reducing overall circuit complexity while achieving color consistency.
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 pixel circuit effectively compensates for threshold voltage changes, ensuring consistent color display by decoupling the driving current from threshold voltage variations, thereby improving display stability and refresh rate.
Implementation Method 1
A first terminal of the first capacitor is electrically connected to the control terminal of the driving switch, and a second terminal of the first capacitor receives a third reference voltage
Implementation Method 2
A first terminal of the OLED receives a first reference voltage
Implementation Method 3
The OLED as pixels in the display device generally use the thin-film transistor (TFT) fabrication
Data Source
AI summary
A pixel circuit with an organic light emitting diode (OLED) compensates a threshold voltage of the driving switch therein by controlling the connection relationship between a first capacitor and a second capacitor therein. As such, the compensation time of the pixel circuit may be different from the data writing time of the same. Also, the capacitance to be written with the data may be less than that in the conventional technique so that the time needed for the data writing is then reduced and the pixel circuit in the present invention can be used in a display device with a high refresh rate.