OLED Pixel Circuit Threshold Voltage Compensation
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Solution Overview
Problem
Conventional OLED display devices face issues with luminance degradation and resolution due to variations in the threshold voltage of the driver transistor, which affect the display's ability to maintain consistent grayscale and luminance levels.
Innovation Solution
The OLED display device incorporates a specific pixel structure with a switching transistor, a driver transistor, an emission control transistor, first through third transistors, and capacitors, which includes initializing a node connected to the driver transistor's gate electrode, sensing the threshold voltage, and controlling the data voltage to maintain consistent current flow through the OLED, thereby reducing the impact of threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the driver transistor remains turned on for a long time to maintain OLED emission, then the OLED can display grayscale continuously, but the threshold voltage of the driver transistor varies causing luminance degradation and resolution loss
Solution Approach 1:
The patent applies preliminary action by initializing the gate electrode voltage to a predetermined level before the OLED emission period begins. This initialization ensures that the driver transistor starts with a known, stable threshold voltage state, preventing the voltage variation that occurs during prolonged operation. The gate electrode is reset to an initial voltage level that compensates for expected threshold shifts, thereby maintaining display quality throughout the emission duration.
2Device complexity
If a simple pixel structure is used, then the device complexity is low, but the ability to compensate for threshold voltage variations is insufficient
Solution Approach 1:
The patent implements multi-functionality by enabling the gate electrode to serve dual purposes: it acts as both the control terminal for the driver transistor and as a storage element that maintains the initialization voltage throughout the emission period. This eliminates the need for separate initialization circuits while achieving both threshold voltage compensation and grayscale consistency, thereby improving reliability without proportionally increasing device complexity.
Data Source
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AI summary
An organic light emitting diode (OLED) display device and a method of driving the same are provided. A time point at which each of transistors is turned on is controlled without using an additional transistor so that a node (N2) connected to a source electrode of a driver transistor (Tdr) can be floated, and a node (N1) connected to a gate electrode of the driver transistor (Tdr) can be initialized to an initialization voltage level. Thus, initialization characteristics can be improved to enhance degradation of response characteristics and luminance, and a threshold voltage of the driver transistor (Tdr) and occurrence of a ripple at a high-potential voltage terminal can be compensated.