OLED Sensing Unit for Simultaneous Threshold and Degradation Compensation
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Solution Overview
Problem
Organic light emitting display devices face issues with non-uniform image display due to degradation of organic light emitting diodes and variations in threshold voltages of driving transistors, requiring separate extraction periods that waste time and affect image quality.
Innovation Solution
An organic light emitting display device and driving method that includes a sensing unit to simultaneously extract threshold voltage information and degradation information of driving transistors and organic light emitting diodes by converting pixel current and reference current into voltages, calculating differences, and using digital converters to store and compensate for these values, thereby improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate extraction periods are used to measure threshold voltage and degradation, then measurement accuracy is improved, but sensing time increases and image quality deteriorates
Solution Approach 1:
The patent combines the measurement of threshold voltage and degradation into a single simultaneous sensing process. The sensing unit measures both parameters at the same time using the same pixel circuit and organic light emitting diode, eliminating the need for separate extraction periods. This merging of measurement processes reduces sensing time while maintaining measurement accuracy for both threshold voltage and degradation characteristics.
Solution Approach 2:
The sensing unit is designed with multi-functionality to perform multiple measurement tasks simultaneously. It can extract both threshold voltage information and degradation information from the same pixel during a single sensing period, making the sensing system universal and efficient. This multi-functional approach allows the system to obtain multiple critical parameters without requiring multiple dedicated measurement cycles.
2Loss of time
If sensing unit extracts both threshold voltage and degradation information simultaneously, then sensing period is reduced, but device complexity increases
Solution Approach 1:
The pixel circuit is designed to perform self-measurement of its own characteristics. The organic light emitting diode and driving transistor within each pixel are used to automatically extract both threshold voltage and degradation information during the sensing period. This self-service capability eliminates the need for external complex measurement equipment and reduces overall device complexity while achieving simultaneous multi-parameter extraction.
Solution Approach 2:
The sensing unit acts as an intermediary component that simplifies the measurement process. It includes a conversion unit that converts current signals from the pixel into voltage signals, and a comparison unit that processes these voltages to extract both threshold voltage and degradation information. This intermediary structure makes the simultaneous extraction of multiple parameters manageable and reduces the complexity of the overall system.
3Reliability
If real-time compensation is implemented for transistor and diode degradation, then image quality is improved, but energy consumption increases
Solution Approach 1:
The system performs preliminary extraction of threshold voltage and degradation information during dedicated sensing periods, then uses this pre-obtained data to compensate for aging effects during normal display operation. By preparing the compensation data in advance during sensing periods rather than continuously monitoring and compensating in real-time, the system improves image quality while minimizing additional energy consumption during the actual display function.
Solution Approach 2:
The compensation process operates periodically by alternating between sensing periods for data extraction and driving periods for image display with compensation applied. During sensing periods, the sensing unit extracts degradation information; during driving periods, the compensation is applied using the extracted data. This periodic operation allows real-time image quality maintenance while controlling energy consumption by limiting sensing operations to specific time windows rather than continuous operation.
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 method reduces the sensing period and allows for real-time compensation of transistor and diode degradation, leading to improved image quality and efficiency in organic light emitting display devices.
Implementation Method 1
a conversion unit configured to convert pixel current supplied from a respective one of the pixels into a first voltage, and configured to convert a reference current from a current source into a second voltage
Implementation Method 2
a comparison unit configured to calculate a difference between the first voltage and the second voltage, and configured to output a comparison voltage corresponding to the difference
Implementation Method 3
The sensing unit may further include an analog-digital converter configured to convert the comparison voltage into a digital value, and a memory configured to store the digital value
Data Source
AI summary
An organic light emitting display device includes pixels each including a driving transistor and an organic light emitting diode, and a sensing unit configured to extract threshold voltage information of the driving transistor and degradation information of the organic light emitting diode from each of the pixels, wherein the sensing unit includes a conversion unit configured to convert pixel current supplied from a respective one of the pixels into a first voltage, and configured to convert a reference current from a current source into a second voltage, and a comparison unit configured to calculate a difference between the first voltage and the second voltage, and configured to output a comparison voltage corresponding to the difference.