OLED Brightness Compensation Circuit for Defect Detection
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Solution Overview
Problem
OLED display devices suffer from brightness defects, such as bright spots, due to negatively shifted threshold voltages of driving transistors caused by process deviations and foreign substances, leading to undesired patterns and stains during low gray level display.
Innovation Solution
An OLED display device and driving method that compare threshold voltages of adjacent pixels to detect bright-defected pixels, generate a compensation gray value, and apply it to the affected pixels to prevent brightness deterioration, using a brightness compensation circuit with a comparator, bright spot detector, and compensation value generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If process manufacturing is performed without additional compensation measures, then manufacturing simplicity is maintained, but brightness uniformity deteriorates due to threshold voltage shifts
Solution Approach 1:
The patent applies preliminary action by sensing the threshold voltage of the driving transistor during the fabrication process (before final assembly) and pre-calculating compensation values that are stored in a lookup table. This allows the brightness compensation to be performed automatically during operation without adding complex real-time control circuits, thus improving brightness uniformity while maintaining device simplicity.
Solution Approach 2:
The patent implements feedback by measuring the actual threshold voltage of each driving transistor through sensing circuits, comparing it against reference values, and using the deviation information to adjust the driving current compensation. This closed-loop feedback mechanism ensures brightness uniformity across pixels despite process variations, while the feedback data is stored for later use rather than requiring continuous complex processing.
2Measurement precision
If threshold voltage sensing and compensation is implemented, then brightness defect detection capability is improved, but device complexity increases due to additional sensing and compensation circuits
Solution Approach 1:
The patent merges the threshold voltage sensing function with the existing fabrication process monitoring systems. The sensing circuits are integrated into the pixel structure itself, and the compensation values are combined with the standard driving signals through multiplexing techniques. This consolidation improves detection capability without proportionally increasing overall device complexity.
Solution Approach 2:
The patent performs threshold voltage sensing and compensation value calculation during the fabrication process itself, storing the results in lookup tables within the display device. This preliminary action eliminates the need for complex real-time sensing circuits during operation, as the compensation data is already prepared and stored for automatic retrieval and application during display operation.
3Manufacturing precision
If compensation gray values are applied to bright-defected pixels, then brightness uniformity is improved, but processing time increases due to additional compensation calculations
Solution Approach 1:
The patent calculates all compensation gray values during the fabrication process and stores them in lookup tables before the display device is put into operation. During actual display operation, the system simply retrieves the pre-calculated compensation values based on the sensed threshold voltage, eliminating the need for time-consuming real-time calculations and thus improving brightness uniformity without significant time loss.
Solution Approach 2:
The patent uses lookup tables that store pre-calculated compensation values as copies of the required correction data. Instead of performing complex compensation calculations in real-time, the system retrieves stored copy values that represent the necessary adjustments, significantly reducing processing time while maintaining compensation accuracy.
Data Source
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AI summary
An OLED display device (100) is disclosed which includes: a display panel (102) configured with pixels which each include an organic light emitting diode (OLED) and a driving transistor (DT) applying a driving current to the organic light emitting diode (OLED); a gate driver (106) connected to the pixels through gate lines (GL); a data driver (104) configured to apply a sensing voltage to the pixels through data lines (DL) in a sensing mode and enable a sensing current to flow through each of the driving transistors (DT); a sensing driver (110) configured to sense threshold voltages opposite the driving currents which flow through the driving transistors (DT); and a brightness compensation circuit (200) configured to derive negatively shifted degrees of threshold voltages of the driving transistors (DT) from the sensed threshold voltages, detect a bright-defected pixel on the basis of the negatively shifted degrees, and generate a compensation gray value for the bright-defected pixel.