OLED Pixel Circuit Internal Compensation for Transistor Variations
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Solution Overview
Problem
Existing 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, leading to difficulties in detecting deterioration and compensating for these changes, which results in errors in compensation data and increased memory requirements.
Innovation Solution
The method involves detecting the threshold voltage of the driving transistor and minimizing its mobility component using a pixel structure, allowing internal compensation and reducing the need for separate memory to store mobility values, while using internal clocks with different phases to prevent data communication errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external compensation methods are used to sense and compensate the properties of the driving transistor and the threshold voltage of the organic light emitting diode, then the accuracy of current control is improved, but the number of memories required increases significantly
Solution Approach 1:
The patent extracts and eliminates the need for separate memory components by implementing a memoryless compensation scheme. The compensation is achieved through real-time sensing and direct feedback control, removing the requirement for storing transistor properties in external memories while maintaining accurate current control.
Solution Approach 2:
The system performs self-compensation by using the organic light emitting diode itself as the sensing element. The OLED's own electrical characteristics are utilized to detect its state and trigger compensation actions, eliminating the need for external sensing circuits and associated memory storage.
2Measurement precision
If sensed data is transferred to a timing controller for compensation, then the deterioration degree of the organic light emitting diode can be compensated, but data skewing occurs and communication errors are generated
Solution Approach 1:
The patent implements preliminary compensation actions by pre-calculating and storing compensation values in lookup tables within the display driver integrated circuit. When OLED deterioration is detected, the pre-prepared compensation data is immediately applied without requiring real-time calculation or data transfer, preventing communication errors.
Solution Approach 2:
The patent introduces an intermediary compensation lookup table that mediates between the sensed OLED state and the required compensation current. This intermediary structure allows direct mapping from sensed parameters to compensation values without requiring data transfer to external controllers, eliminating data skewing issues.
3Reliability
If delay control methods are used to manage data timing, then data communication errors can be reduced, but real-time variations during normal operation cannot be sensed
Solution Approach 1:
The patent implements continuous sensing and compensation during normal display operation. The sensing circuit operates continuously alongside the display function, allowing real-time detection of OLED deterioration and immediate application of compensation without interrupting or delaying the display output.
Solution Approach 2:
The patent merges the sensing function with the normal display driving function. The same pixel circuit and driving transistor used for display also perform sensing operations, combining two functions into one system without requiring separate timing control or causing operational delays.
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 detection and compensation of OLED properties, reduces memory usage, and minimizes data communication errors, ensuring precise control of current flow and improved image uniformity.
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
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AI summary
An organic light emitting diode display device is disclosed which includes pixels (122) each configured with an organic light emitting diode and a driving switch (DR) used to control a current flowing through the organic light emitting diode. The organic light emitting diode display device compensates a deterioration property of the organic light emitting diode after properties of the driving switch (DR) is compensated. As such, the deterioration property of the organic light emitting diode can be maximally reflected to a sensing data. In accordance therewith, the deterioration property of the organic light emitting diode can be accurately compensated.