OLED Pixel Circuit Temperature and Degradation Sensing
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Solution Overview
Problem
In organic light emitting diode (OLED) display devices, pixel degradation over time leads to decreased luminance, and existing compensation methods are inadequate as they do not account for temperature variations, resulting in deteriorated image quality.
Innovation Solution
The implementation of a pixel structure that includes temperature-dependent elements, such as temperature-variable resistors or transistors, which allow for simultaneous temperature and degradation sensing, enabling accurate compensation by measuring currents through these elements during dedicated sensing periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If degradation sensing technique is used to measure current through OLED, then pixel degradation compensation is improved, but temperature variations cause luminance changes that deteriorate image quality
Solution Approach 1:
The sensing operation is segmented into two distinct phases: degradation sensing period where OLED current is measured, and temperature sensing period where temperature-dependent element current is measured. This segmentation allows separate measurement of degradation and temperature effects, enabling independent compensation for each factor without mutual interference.
Solution Approach 2:
A temperature-dependent element (such as a temperature-dependent transistor or resistor) is introduced as an intermediary component to sense temperature variations. This element provides a temperature-specific current signal that serves as a mediator between the physical temperature parameter and the compensation control system, enabling temperature compensation.
2Adaptability or versatility
If temperature-dependent elements are added to the pixel structure, then temperature sensing capability is improved, but device complexity increases
Solution Approach 1:
The temperature-dependent element is integrated into the existing pixel circuit structure, sharing common components such as the sensing line and control transistors with the degradation sensing function. This multi-functionality approach allows a single pixel structure to perform both degradation sensing and temperature sensing without requiring completely separate sensing circuits.
Solution Approach 2:
The invention utilizes parameter changes in the temperature-dependent element (such as threshold voltage or resistance changes with temperature) to encode temperature information in the current signal. By exploiting inherent parameter variations of existing components with temperature, additional sensing capability is achieved without adding complex dedicated temperature sensing hardware.
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 allows for precise degradation and temperature compensation, thereby improving the image quality of OLED display devices by accounting for both factors in real-time adjustments.
Implementation Method 1
a temperature-dependent element connected to the second terminal of the fourth transistor, a resistance of the temperature-dependent element being changed depending on a temperature of the pixel
Data Source
AI summary
A pixel of an organic light emitting diode (OLED) display device includes a first transistor having a gate connected to a scan line, a first terminal connected to a data line, and a second terminal, a capacitor having a first electrode connected to the second terminal of the first transistor and a second electrode connected to a first power supply voltage, a second transistor having a gate connected to the first electrode of the capacitor, a first terminal connected to the first power supply voltage, and a second terminal, an OLED having an anode connected to the second terminal of the second transistor and a cathode connected to a second power supply voltage, and a third transistor having a gate connected to a first sensing gate line, a first terminal connected to a sensing line, and a second terminal connected to the anode of the OLED.