OLED Data Driver Current Measurement Circuit
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Solution Overview
Problem
Organic light-emitting display devices face luminance imbalance and image quality deterioration due to OLED degradation and variations in threshold voltages of driving transistors, leading to inconsistent pixel performance.
Innovation Solution
An organic light-emitting display device with a data driver that includes current measurers with operational amplifiers, feedback capacitors, and correlated double sampling units to precisely measure currents from each pixel, applying differential reference voltages and using initialization switches to compensate for differences in pixel deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current measurement methods are used, then device complexity is reduced, but measurement precision deteriorates due to inability to compensate for pixel deterioration and threshold voltage differences
Solution Approach 1:
The measurement circuit is divided into multiple independent measurement circuits, each dedicated to measuring current from a specific pixel. Each measurement circuit includes its own operational amplifier, feedback capacitor, and reference voltage source, allowing independent and precise measurement of each pixel's current without interference from other pixels.
Solution Approach 2:
Operational amplifiers are introduced as intermediary components between the pixel and the measurement system. These amplifiers convert the current signal from the pixel into a measurable voltage signal while maintaining precision through feedback mechanisms, enabling accurate current measurement without directly increasing the overall device complexity.
2Reliability
If simple measurement structures are used, then device complexity is reduced, but luminance imbalance and image quality deterioration occur due to uncompensated pixel differences
Solution Approach 1:
Feedback capacitors are incorporated into each measurement circuit to store and utilize feedback signals from the operational amplifiers. This feedback mechanism enables the system to continuously monitor and adjust measurements, compensating for pixel deterioration and threshold voltage differences to maintain consistent display quality across all pixels.
Solution Approach 2:
Different reference voltages are applied to different measurement circuits based on the specific characteristics of each pixel. By changing the reference voltage parameter for each measurement circuit, the system can compensate for variations in pixel performance and maintain uniform display luminance across all pixels.
3Measurement precision
If differential reference voltages are applied to compensate for pixel variations, then measurement precision improves, but device complexity increases due to multiple operational amplifiers and feedback components
Solution Approach 1:
The measurement system is segmented into multiple independent measurement circuits, each with its own operational amplifier and feedback capacitor. This segmentation allows each circuit to independently measure and compensate for pixel variations using differential reference voltages, achieving high precision without requiring a single complex centralized measurement system.
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 solution enables precise current measurement and compensation, ensuring uniform display quality by addressing OLED degradation and transistor variations, thereby improving image consistency and precision.
Implementation Method 1
a first operational amplifier including a non-inverted input terminal to which a first reference voltage is applied, and an inverted input terminal connected to a first pixel from among the plurality of pixels
Implementation Method 2
a first feedback capacitor connected between the inverted input terminal and an output terminal of the first operational amplifier
Implementation Method 3
Each of the current measurers may further include a correlated double sampling unit connected to the output terminals of the first and second operational amplifiers
Data Source
AI summary
An organic light-emitting display device includes: pixels; and a data driver including a plurality of current measurers connected to the pixels via at least one data line, each of the current measurers including: a first measurement circuit including: a first operational amplifier including a non-inverted input terminal to which a first reference voltage is applied, and an inverted input terminal connected to a first pixel from among the pixels; and a first feedback capacitor connected between the inverted input terminal and an output terminal of the first operational amplifier; and a second measurement circuit including: a second operational amplifier including a non-inverted input terminal to which a second reference voltage is applied, and an inverted input terminal connected to a second pixel from among the pixels; and a second feedback capacitor connected between the inverted input terminal and an output terminal of the second operational amplifier.