OLED Pixel Circuit Reducing Temperature Luminance Sensitivity
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Solution Overview
Problem
Designing a satisfactory OLED display for electronic devices is challenging due to variations in transistor threshold voltages caused by PVT variations, leading to inconsistent light production across display pixels.
Innovation Solution
The implementation of gate driver circuitry and specific pixel configurations, including drive transistors, light-emitting diodes, capacitors, and additional transistors, to extend the threshold voltage sampling time and reduce temperature luminance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the threshold voltage sampling time is extended to reduce temperature luminance sensitivity, then the thermal uniformity improves, but the display refresh rate decreases
Solution Approach 1:
The sampling period is divided into two distinct phases: a first period during the data programming phase where the data loading transistor is active, and a second extended period after the data programming phase where the data loading transistor is inactive. This segmentation allows threshold voltage sampling to continue beyond the traditional data programming window, extending sampling time without compromising refresh rate
Solution Approach 2:
The gate driver circuitry is configured to automatically extend the sampling period into the emission phase without requiring additional control logic in the pixel circuit. The extension is initiated by the gate driver's timing control, which prepares the sampling operation to continue into the next phase, ensuring thermal uniformity is improved before the refresh cycle completes
2Temperature
If additional transistors and capacitors are added to extend sampling time, then temperature luminance sensitivity is reduced, but device complexity increases
Solution Approach 1:
The gate driver circuitry performs multiple functions: it drives the gate line signals for pixel activation, controls the timing of data programming, and extends the threshold voltage sampling period into the emission phase. By making the gate driver universal and multi-functional, no additional dedicated circuitry is needed in the pixel, avoiding increased device complexity
Solution Approach 2:
The pixel circuit utilizes existing components (drive transistor, storage capacitor, data loading transistor) that already serve their primary functions, while the gate driver circuitry self-configures to extend sampling timing. The system serves itself by using the natural timing transitions between phases to enable extended sampling without requiring separate control mechanisms
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 effectively minimizes temperature luminance sensitivity and improves thermal uniformity by extending the threshold voltage sampling period, thereby reducing variations in light output across display pixels.
Implementation Method 1
Each display pixel may include at least an organic light-emitting diode (OLED) that emits light
Implementation Method 2
OLED displays have an array of display pixels based on light-emitting diodes
Data Source
AI summary
A display may include an array of pixels. Each pixel in the array includes an organic light-emitting diode coupled to a drive transistor, a data loading transistor, a first capacitor for storing data charge, and a second capacitor. During a data programming phase, the data loading transistor may be activated to load in a data value onto the first capacitor. After the data programming phase, the second capacitor may be configured to receive a lower voltage, which extends a threshold voltage sampling time for the pixel. Configured and operated in this way, the temperature luminance sensitivity of the display can be reduced.