OLED Current Sensor with Level Shifter for Pixel Measurement
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Solution Overview
Problem
In organic light-emitting display apparatuses, variations in thin film transistor characteristics during manufacturing and degradation over time lead to inaccurate color display, necessitating precise detection of current characteristics to ensure proper operation.
Innovation Solution
An organic light-emitting display apparatus is designed with a sensor system that includes a current sensor, level shifter, and analog-to-digital converter to detect and accurately measure the current characteristics of pixels by integrating currents from active and inactive pixels, generating shift voltages, and outputting digital values based on these measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current characteristics are not accurately detected, then manufacturing process is simple, but color display accuracy deteriorates
Solution Approach 1:
The sensor system is divided into three functional modules: current sensor (with first and second integrators), level shifter, and ADC. Each module performs a specific function in the current detection chain, allowing complex measurement tasks to be broken down into manageable segments that can be independently optimized and implemented.
Solution Approach 2:
The patent transforms the current measurement problem from direct current comparison into a multi-dimensional process: converting currents to voltages through integration, shifting voltage levels to a common reference, and then digitizing the difference. This dimensional transformation enables accurate measurement while managing system complexity through modular functional blocks.
2Measurement precision
If TFT characteristics vary due to manufacturing variations, then manufacturing is easier, but display color accuracy deteriorates
Solution Approach 1:
The patent uses a second pixel as a reference copy to measure noise characteristics. By detecting the current characteristics of this reference pixel (which should be identical to other pixels but is in an inactive state), the system captures the noise component that can then be subtracted from active pixel measurements, enabling accurate detection despite manufacturing variations.
Solution Approach 2:
The system implements a feedback mechanism where the detected current characteristics and noise components are used to correct and compensate for variations in pixel performance. The measured data feeds back into the display system to adjust for manufacturing variations and maintain color accuracy.
3Measurement precision
If noise is not compensated, then system operation is simpler, but measurement accuracy deteriorates
Solution Approach 1:
The patent converts the harmful noise component into a useful measurement by deliberately measuring it through the second integrator connected to an inactive pixel. The noise detected in the reference pixel is then subtracted from active pixel measurements, transforming the previously harmful noise into a correctable parameter that improves overall measurement accuracy.
Solution Approach 2:
The system performs preliminary noise measurement using the second integrator and reference pixel before processing active pixel data. By capturing the noise characteristics in advance through the reference measurement, the system can pre-calculate compensation values that are then applied to subsequent measurements, improving accuracy without adding complexity to the main measurement path.
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 allows for the accurate detection of current characteristics, enabling improved color display and correction of image data, thereby enhancing the overall performance and reliability of the organic light-emitting display apparatus.
Implementation Method 1
the current sensor includes a first integrator configured to integrate the first current to output the first voltage, and a second integrator configured to integrate the second current to output the second voltage
Implementation Method 2
a level shifter configured to receive the first and second voltages and to generate first and second shift voltages respectively corresponding to the first and second voltages, an intermediate voltage of the first and second voltages being equal to a conversion reference voltage
Implementation Method 3
an analog-to-digital converter (ADC) configured to receive the first and second shift voltages and to output a digital value corresponding to a difference between the first and second shift voltages based on the conversion reference voltage
Implementation Method 4
each of the first and second pixels includes a pixel circuit including a first node, and an organic light-emitting device (OLED) connected to the pixel circuit, and the pixel circuit includes a driving transistor configured to output a driving current to the OLED via the first node
Data Source
AI summary
An organic light-emitting display apparatus including a display including pixels arranged in an array, a sensor for detecting respective current characteristics of the pixels, a current sensor for receiving a first current from a first pixel of the pixels, for outputting a first voltage corresponding to the first current, for receiving a second current from a second pixel of the pixels, and for outputting a second voltage corresponding to the second current, a level shifter for receiving the first and second voltages and for generating first and second shift voltages respectively corresponding to the first and second voltages, an intermediate voltage of the first and second voltages being equal to a conversion reference voltage, and an analog-to-digital converter for receiving the first and second shift voltages and for outputting a digital value corresponding to a difference between the first and second shift voltages based on the conversion reference voltage.