OLED Pixel Circuit Threshold Voltage and Mobility Compensation
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices face challenges in accurately controlling current flow through OLEDs due to variations in threshold voltage and mobility of driving transistors, which affect light emission efficiency and display quality, and are further complicated by capacitance and abnormal element properties on sensing lines.
Innovation Solution
The OLED display device and driving method involve a scan switch, driving switch, sensing switch, and organic light emitting diode configuration that allows for precise detection and compensation of threshold voltage and mobility by applying reference voltages and initialization voltages, and sharing sensing lines among sub-pixels to enhance accuracy and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold voltage and mobility of driving transistor are not compensated, then device complexity is reduced, but current control precision deteriorates
Solution Approach 1:
The pixel circuit is divided into distinct functional modules: sensing switches for detection, storage capacitors for voltage holding, and compensation transistors for threshold correction. This segmentation allows each component to perform its specific function efficiently while maintaining overall current control precision without excessive complexity
Solution Approach 2:
The sensing switches are activated before the main driving transistor to pre-detect and store the threshold voltage and mobility characteristics. By performing this measurement and compensation action in advance, the circuit eliminates the need for complex real-time adjustment mechanisms during normal operation
2Measurement precision
If sensing line capacitance is not considered, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The sensing circuit incorporates feedback mechanisms where the detected voltage at the sensing line is fed back to adjust the compensation stored in capacitors. This feedback loop continuously corrects for capacitance effects, maintaining measurement precision without requiring complex predictive models
Solution Approach 2:
The circuit dynamically adjusts capacitance values by switching between different capacitor configurations based on the detected threshold voltage and mobility parameters. This parameter adaptation allows the system to compensate for sensing line capacitance effects while maintaining relatively simple circuit architecture
3Measurement precision
If mobility detection is not performed, then device complexity is reduced, but current control precision deteriorates
Solution Approach 1:
The sensing switches and storage capacitors serve dual functions: they detect both threshold voltage and mobility characteristics of the driving transistor. This multi-functionality allows comprehensive parameter detection without requiring separate dedicated circuits for each measurement, thereby reducing overall device complexity
Solution Approach 2:
The driving transistor itself is used as part of the sensing mechanism during the compensation phase. By utilizing the transistor's own electrical characteristics during normal operation to detect its parameters, the circuit eliminates the need for external test equipment or separate measurement circuits
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 approach enables accurate control of current flow, improves light emission efficiency, and enhances display quality by compensating for threshold voltage and mobility variations, while minimizing errors caused by capacitance and abnormal element properties.
Implementation Method 1
The current passing through the drain and source electrodes of the driving transistor is applied to an organic light emitting diode and allows the organic light emitting diode to emit light
Data Source
AI summary
An organic light emitting diode display device is disclosed which includes: a scan switch controlled by a scan pulse on a gate line and connected between a data line and a first node; a driving switch which includes a gate electrode connected to the first node, a source electrode connected to a second node, and a drain electrode connected to a first driving voltage line; a sensing switch controlled by a sensing control signal and connected between the second node and a third node on a sensing line; and an organic light emitting diode connected between the second node and a second driving voltage line.