OLED Driving TFT Threshold Voltage Sensing Method
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Solution Overview
Problem
The aging of organic light emitting diodes and threshold voltage shifts in drive thin film transistors lead to a decline in OLED display quality, necessitating accurate threshold voltage compensation.
Innovation Solution
A threshold voltage detection method for OLED drive thin film transistors, involving a sub pixel driving circuit with three thin film transistors, a capacitor, and a detection process circuit, using correlated double sampling and analog-to-digital conversion to calculate the threshold voltage based on current and voltage data, with multiple detections for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional voltage signal transmission is used in AMOLED pixel driving circuit, then the circuit structure can be kept simple, but the conversion of voltage signals to current signals becomes complex and threshold voltage detection accuracy deteriorates
Solution Approach 1:
The patent introduces a detection process circuit as an intermediary component between the sub pixel driving circuit and the control system. This dedicated detection circuit includes detection transistors, capacitors, and signal processing units that specifically measure threshold voltage and other electrical characteristics without disrupting the normal pixel driving function, thereby improving measurement precision while keeping the overall system manageable
Solution Approach 2:
The patent replaces traditional voltage signal transmission with a current signal transmission system for pixel driving. By using current-mode operation with dedicated detection transistors and capacitive coupling, the system achieves more accurate threshold voltage detection and compensation compared to conventional voltage-based approaches
2Ease of operation
If threshold voltage compensation is not performed, then the device operation can be simple, but display quality deteriorates due to aging and threshold voltage shift
Solution Approach 1:
The patent implements a feedback mechanism where the detection process circuit continuously monitors the threshold voltage of the drive transistor and other electrical characteristics. The measured data is fed back to the control system, which then adjusts the driving parameters to compensate for threshold voltage shifts caused by aging, thereby maintaining display quality over time
Solution Approach 2:
The patent performs threshold voltage detection and compensation operations during idle periods or between display frames. By conducting measurements and adjustments in advance before they affect display output, the system maintains reliable display quality without requiring complex real-time intervention during active display operation
3Measurement precision
If multiple detection operations are performed to improve accuracy, then threshold voltage detection precision improves, but detection time increases
Solution Approach 1:
The patent performs multiple threshold voltage detection operations at different time points within a periodic cycle. By conducting measurements at multiple phases and combining the results through statistical processing or averaging in the control system, the patent achieves higher detection precision while confining the total detection time within acceptable periodic intervals
Solution Approach 2:
The detection process circuit is designed to operate continuously or near-continuously during idle periods, accumulating measurement data over time. This continuous detection approach allows multiple measurements to be performed without significant interruption to display operation, improving precision while minimizing time loss through efficient utilization of available operational windows
Data Source
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AI summary
A threshold voltage sensing method for an OLED driving thin film transistor. The method comprises: providing two different data voltages by setting a data signal so that a driving thin film transistor forms two different gate-source voltages, and then separately sensing, by means of an external sensing and processing circuit (2), current flowing through the driving thin film transistor under the two different gate-source voltages; and calculating, by a central processing unit (24), a threshold voltage of an OLED driving thin film transistor by means of the two gate-source voltages, two pieces of current data, and a computing formula based on a current formula of the driving thin film transistor. The method can accurately obtain the threshold voltage of the driving thin film transistor of each pixel in an OLED display devic, improve the threshold voltage compensation effect of the OLED driving thin film transistor, and improve OLED display quality.