OLED Sensor Transistor Threshold Voltage Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The organic light emitting display faces reduced lifetime due to changes in the characteristics of driving transistors over time, leading to a decrease in operating current and luminance deviations between compensated and non-compensated subpixels.
Innovation Solution
Incorporating a sensing circuit unit that measures the threshold voltages of driving transistors during vertical blank intervals and supplies compensation data, while turning on sensor transistors of non-selected subpixels to maintain voltages below the threshold voltage during image display intervals, ensuring consistent charging patterns across all subpixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor transistors are turned on during image display interval to measure threshold voltages, then measurement precision is improved, but luminance deviation occurs between compensated and non-compensated subpixels
Solution Approach 1:
The sensor transistor is activated periodically during vertical blank intervals rather than continuously during image display. This timing-based separation allows threshold voltage measurement to occur without interfering with normal display operation, eliminating luminance deviation while maintaining measurement capability
Solution Approach 2:
Threshold voltage measurements are performed in advance during vertical blank intervals before the image display interval begins. This preliminary measurement approach ensures that compensation data is ready before display, preventing any luminance deviation during the actual display period
2Device complexity
If driving transistor characteristics are allowed to change over time, then device complexity is reduced, but reliability decreases due to reduced operating current
Solution Approach 1:
A feedback mechanism is implemented where sensor transistors continuously monitor the threshold voltage of driving transistors during vertical blank intervals. The measured threshold voltage information is used to generate compensation data that adjusts the data signal, creating a closed-loop system that maintains reliable operation despite transistor characteristic changes over time
Solution Approach 2:
The system dynamically changes the data signal parameters based on measured threshold voltage variations. By adjusting the data signal compensation values according to the actual transistor state, the system maintains consistent operating current and display performance even as transistor characteristics drift over time
Data Source
AI summary
In one aspect, there is an organic light emitting display comprising: a display panel including subpixels; a data driver that supplies a data signal to the display panel; a scan driver that supplies a scan signal to the display panel; and a sensing circuit unit that measures the threshold voltages of driving transistors through sensor transistors of the display panel and prepares compensation data, wherein the scan driver turns on the sensor transistor of a selected subpixel to measure the threshold voltage of the driving transistor of the selected subpixel during a vertical blank interval of the display panel, and turns on the sensor transistors of non-selected subpixels to supply voltages below the threshold voltage of organic light emitting diodes to the non-selected subpixels during an image display interval of the display panel.