OLED Data Driver Negative Bias Stress Transistor Degradation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting diode (OLED) display devices face issues with the positive-shifted threshold voltage and deterioration of driving transistors, which existing compensation circuits are unable to effectively address, leading to reduced performance and lifespan.
Innovation Solution
A data driver is developed that includes a digital-to-analog conversion unit for generating both positive and negative polarity analog signals, which are output to the transistors supplying current to the OLEDs, along with a timing controller to manage these signals, effectively delaying the deterioration of the driving transistors by applying adaptive negative bias stress during black image representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional driving transistor is used to supply current to the OLED, then the display device can operate, but the transistor threshold voltage shifts positively and deteriorates over time
Solution Approach 1:
The patent applies preliminary anti-action by introducing negative bias stress during black image display periods to counteract the positive threshold voltage shift that occurs during normal operation. The data driver controller detects black image periods and applies a negative voltage signal to the driving transistor, which prevents the accumulation of positive charge traps and delays threshold voltage degradation before it affects display performance.
Solution Approach 2:
The patent implements periodic action by alternating between normal driving mode during image display and compensation mode during black image periods. The data driver controller periodically switches the transistor operation between applying normal drive signals and applying negative bias stress signals, creating a cyclic compensation mechanism that maintains transistor performance over extended operation periods.
2Measurement precision
If existing compensation circuits are used, then basic voltage compensation is provided, but they cannot effectively compensate for positive threshold voltage shift and transistor deterioration
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage signal characteristics based on the displayed image content. The data driver controller changes the voltage polarity and magnitude depending on whether a black image is being displayed, transitioning from standard drive voltages to negative bias stress voltages. This parameter modulation enables effective compensation that adapts to operational conditions, significantly improving threshold voltage stability compared to fixed compensation circuits.
Data Source
AI summary
A data driver and a display device using the same are disclosed. The data driver includes a digital to analog conversion unit for converting a digital signal into either a positive polarity analog signal or a negative polarity analog signal, and an output circuit unit for outputting either the positive polarity analog signal or the negative polarity analog signal, as an output signal, to a transistor that supplies a current to an organic light emitting diode (OLED).