OLED Driving Apparatus Threshold Voltage Compensation
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Solution Overview
Problem
In organic electro-luminescence display devices, the deterioration of driving transistors leads to a shift in threshold voltage, causing image quality degradation, particularly when insufficient time is given for negative voltage application and increased data voltage is required to compensate, making it difficult to prevent threshold voltage increase effectively.
Innovation Solution
A pixel driving apparatus that includes a display controller to detect the shift in threshold voltage using a sensing line and switching transistors, allowing for compensation during the detection mode and adjusting the data voltage accordingly to maintain image quality during the emission mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If negative voltage is applied to compensate for threshold voltage shift, then threshold voltage stability is improved, but insufficient time for negative voltage application causes compensation to be ineffective
Solution Approach 1:
The patent applies negative voltage to the gate of the driving transistor during the programming period, before the emission period begins. This preliminary application of negative voltage compensates for threshold voltage shift in advance, ensuring the transistor operates correctly during the subsequent emission period without requiring additional time during the emission period itself.
Solution Approach 2:
The patent implements periodic application of negative voltage during each programming period of every frame. By repeatedly applying negative voltage at regular intervals (each frame), the threshold voltage is continuously compensated, maintaining stability over time without requiring prolonged continuous application.
2Illumination intensity
If data voltage is increased to compensate for threshold voltage shift, then image quality is maintained, but threshold voltage increase becomes more difficult to prevent
Solution Approach 1:
The patent applies negative voltage to the gate of the driving transistor during the programming period to preemptively counteract the threshold voltage increase that would otherwise occur. This preliminary anti-action prevents the threshold voltage shift before it affects the emission period, allowing normal data voltage levels to maintain image quality without exacerbating threshold voltage issues.
3Measurement precision
If sensing line and switching transistors are used to detect threshold voltage shift, then detection precision is improved, but device complexity increases
Solution Approach 1:
The sensing line and switching transistors are integrated into the existing pixel driving circuit structure, allowing the same hardware components to serve dual functions: driving the OLED during emission period and sensing threshold voltage during programming period. This multi-functionality improves detection precision without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the sensing function with the existing driving circuitry by using the same data line and transistor structure for both driving and sensing operations at different time periods. This consolidation achieves precise threshold voltage detection while minimizing additional circuit complexity through resource sharing.
Data Source
AI summary
Disclosed is an apparatus that prevents a degradation of image quality due to a deterioration of a driving apparatus in an organic electro-luminescence display device.