OLED Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
OLED display devices face challenges in accurately controlling the current flowing through OLEDs, leading to short service life and severe parameter variations, which complicates the control of brightness and stability of the pixel driving circuit.
Innovation Solution
A method is introduced that involves a compensation structure using a detecting capacitor and a storage capacitor, where the detecting capacitor is charged at different voltages during two detecting periods, and the threshold voltage of the driving transistor is calculated to establish a threshold-voltage compensation table for stabilizing the pixel driving circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compensation structure is provided to compensate the pixel driving circuit, then the parameter variations and service life are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the detecting capacitor with existing pixel circuit components by connecting its first plate to the anode of the OLED and second plate to ground, merging the detection function into the existing circuit structure rather than adding completely separate compensation components
Solution Approach 2:
The detecting capacitor serves multiple functions: it detects the threshold voltage of the driving transistor, enables calculation of voltage-time characteristics, and provides data for establishing the compensation table, making a single component perform multiple measurement and compensation functions
2Measurement precision
If the detecting capacitor is charged to different voltages during two detecting periods, then the detection accuracy of threshold voltage is improved, but the measurement time and productivity are reduced
Solution Approach 1:
The patent uses periodic charging actions at two different voltages during two distinct detecting periods, where the capacitor is charged sequentially at different voltage levels and the corresponding time values are recorded, enabling accurate threshold voltage detection through repeated periodic measurements
Solution Approach 2:
The patent changes the charging voltage parameter of the detecting capacitor between the two detecting periods (first charging voltage and second charging voltage), and records the corresponding time values, using parameter variation to enable accurate calculation of the threshold voltage through comparison
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
This method allows the driving transistor to operate stably in a saturation region, improves the detection speed of the threshold voltage, and simplifies the compensation process, reducing costs and avoiding the impact of voltage-current conversion factors on accuracy.
Implementation Method 1
A detecting capacitor is provided for each pixel. A first plate of the detecting capacitor is connected to the anode of the OLED, and a second plate of the detecting capacitor is connected to ground. The detecting capacitor is charged during a first detecting period, to a first charging voltage via the driving transistor
Data Source
AI summary
Disclosed is a method for compensating a pixel driving circuit of an OLED display panel. In the compensation method, a driving transistor is enabled to operate stably in a saturation region for twice, and a threshold voltage of the driving transistor is calculated based on a collected charging voltage and charging time. A pixel driving circuit is compensated by establishing a threshold-voltage compensation table. The compensation method is easy to operate and can significantly improve a detecting speed of a threshold voltage. Moreover, an effect of a voltage-current conversion factor on detecting accuracy of a threshold voltage can be avoided.