OLED Pixel Circuit Brightness Compensation via Feedback Control
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Solution Overview
Problem
Thin film transistors (TFTs) in organic light emitting diode (OLED) displays deteriorate over time, leading to non-uniform brightness and decreased light emission due to variations in voltage and current applied to pixel electrodes, especially at higher data voltages.
Innovation Solution
Incorporating a detecting transistor and a controller to monitor the electric signal or pixel current applied to the pixel electrode, comparing it to a predetermined reference level, and adjusting the data voltage or pixel voltage accordingly to maintain consistent brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If TFTs are driven at higher data voltages to improve brightness, then light emission intensity increases, but TFT deterioration accelerates and voltage application becomes unreliable
Solution Approach 1:
The patent implements a feedback mechanism where a detection transistor continuously monitors the actual voltage applied to the pixel electrode and feeds this information back to a compensation transistor. The compensation transistor adjusts the data voltage in real-time to compensate for TFT deterioration, ensuring reliable voltage application even at higher brightness levels.
Solution Approach 2:
The patent dynamically changes the data voltage parameter based on detected TFT characteristics. By measuring the actual voltage and adjusting the compensation voltage accordingly, the system adapts the operating parameters to maintain reliability while achieving desired brightness levels.
2Duration of action of stationary object
If TFTs operate for extended periods to maintain display functionality, then display duration increases, but TFT deterioration causes non-uniform brightness and voltage deviations
Solution Approach 1:
The feedback loop continuously monitors voltage application during extended operation and compensates for deterioration effects. This allows the display to maintain uniform brightness over long periods by dynamically adjusting for TFT degradation.
Solution Approach 2:
The patent applies preliminary compensation by detecting TFT characteristics early in the operation and preemptively adjusting voltage levels. This prevents brightness non-uniformity from developing during extended operation.
3Illumination intensity
If a detection mechanism is added to monitor voltage and compensate for deterioration, then brightness uniformity improves, but device complexity increases
Solution Approach 1:
The patent merges the detection and compensation functions into the existing pixel circuit structure. The detection transistor and compensation transistor are integrated with the driving transistor and pixel electrode, combining multiple functions within a unified circuit architecture rather than adding separate external components.
Solution Approach 2:
The detection transistor serves multiple functions: monitoring voltage, detecting TFT deterioration, and providing feedback for compensation. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity.
Data Source
AI summary
A display device with improved brightness and a method of controlling the display device are presented. The display device includes a driving transistor, a pixel electrode electrically connected to the driving transistor, a detecting transistor detecting a magnitude of an electric signal transferred from the driving transistor to the pixel electrode, and a controller. The controller regulates a data voltage applied to the pixel electrode based on a difference between the detected electric signal and a predetermined reference level. The display device achieves improved homogeneity of brightness by compensating for any deterioration of TFTs.