OLED Driving TFT Drain Voltage Compensation
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in achieving uniform picture quality due to variations in mobility and threshold voltage of driving TFTs, leading to sensing errors and defects, particularly in the external compensation method where current measurement is inaccurate due to changes in drain-source voltage.
Innovation Solution
The method involves sensing the characteristics of driving TFTs by varying the drain voltage based on changes in anode voltage of the organic light emitting diode, maintaining a constant drain-source voltage, and using feedback compensation to accurately measure and compensate for pixel characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the applied-voltage-based voltage measuring method is used to sense pixel characteristics, then the measuring time is shortened, but the measurement precision deteriorates due to varying drain-source voltage causing incorrect current measurement
Solution Approach 1:
The patent changes the drain voltage parameter from a fixed value to a variable value that is dynamically adjusted based on the anode voltage of the OLED. By making the drain voltage track the anode voltage changes, the drain-source voltage remains constant during measurement, eliminating the measurement error while maintaining the speed benefits of the voltage measuring method
Solution Approach 2:
The patent implements a feedback mechanism where the drain voltage is adjusted according to the measured anode voltage. The system continuously monitors the anode voltage and modifies the drain voltage accordingly to maintain a constant drain-source voltage difference, ensuring accurate current measurement throughout the sensing process
2Device complexity
If the drain voltage is fixed during sensing, then the circuit control is simplified, but the measurement precision deteriorates because current changes according to drain-source voltage variation
Solution Approach 1:
The patent transforms the drain voltage from a fixed parameter to a dynamically adjustable parameter. By changing the drain voltage in response to anode voltage variations, the system maintains constant drain-source voltage, ensuring accurate current measurement without requiring overly complex control circuits
3Reliability
If external compensation is performed using traditional methods, then pixel characteristic variations can be compensated, but sensing errors occur due to inaccurate current measurement from varying drain-source voltage
Solution Approach 1:
The patent modifies the drain voltage parameter dynamically during the external compensation process. By adjusting the drain voltage to track anode voltage changes, the system maintains constant drain-source voltage, eliminating sensing errors and improving both measurement precision and compensation reliability
Solution Approach 2:
The patent employs feedback control where the drain voltage is continuously adjusted based on real-time anode voltage measurements. This feedback mechanism ensures that the drain-source voltage remains constant throughout the sensing process, providing accurate pixel characteristic data for reliable external compensation
Data Source
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AI summary
A method of compensating driving TFTs in an organic light emitting display device is discussed. According to an embodiment, the method includes applying a varied drain voltage to a drain of a specific driving TFT in one of a plurality of pixels; and compensating the specific driving TFT by the varied drain voltage, so as to maintain a constant drain-source voltage at the specific driving TFT.