Series-Connected Driving Transistors for OLED Current Measurement
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Solution Overview
Problem
In display technology, the variability in threshold voltages of driving transistors in OLED panels leads to non-uniform light emission, as the same data voltage does not consistently produce the same driving current due to differences in transistor characteristics, affecting display uniformity.
Innovation Solution
An array substrate with pixel units and sensing lines, where at least two driving transistors have their outputting terminals connected in series through switching elements, allowing for efficient measurement of driving current by connecting one transistor to a sensing line through a second switching element, reducing the number of switching elements connected directly to the sensing line and thus minimizing equivalent capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple driving transistors are connected in series with switching elements to enable current measurement, then measurement capability is improved, but the number of switching elements increases which increases equivalent capacitance and slows down charging speed
Solution Approach 1:
The patent extracts the measurement function from the normal display circuit by introducing a separate sensing line that connects to the output terminal of the driving transistor through a switching element. This allows current measurement without requiring multiple switching elements in series during normal operation, thus maintaining fast charging speed while enabling measurement capability when needed.
Solution Approach 2:
The patent uses switching elements that can dynamically change the circuit configuration between measurement mode and normal display mode. During measurement, the switching element connects the sensing line to the driving transistor output; during normal operation, the switching element disconnects them. This dynamic switching allows the system to achieve both measurement capability and fast charging speed by optimizing the circuit topology for the current operational requirement.
2Adaptability or versatility
If multiple switching elements are connected to the sensing line for measuring multiple transistors, then measurement versatility is improved, but equivalent capacitance increases which reduces refresh frequency
Solution Approach 1:
The patent implements a universal sensing line that can measure multiple driving transistors by time-division multiplexing. Instead of having separate sensing circuits for each transistor, a single sensing line with controllable switching elements can sequentially connect to different driving transistor output terminals. This multi-functional approach allows one sensing line to serve multiple measurement purposes while maintaining low equivalent capacitance, thus preserving high refresh frequency.
Solution Approach 2:
The patent employs periodic switching of the switching elements to sequentially connect different driving transistors to the sensing line for measurement. Each transistor is measured in a time-division manner during the display refresh cycle. This periodic action allows multiple measurements to be performed with a single sensing line, achieving measurement versatility without increasing the number of simultaneously active switching elements, thereby maintaining high refresh frequency.
Data Source
AI summary
The embodiments of the present disclosure provide an array substrate, a display panel, a display apparatus and a current measuring method. The array substrate may include: a plurality of pixel units and sensing lines. Each of the pixel units may include a driving transistor, and the sensing line is configured to transmit an output of the driving transistor to a sensing device. At least two of the plurality of driving transistors may have their outputting terminals connected in series. Outputting terminals of adjacent driving transistors of the at least two of the driving transistors may be connected through a first switching element. At least one of the driving transistor of the at least two of the driving transistors may have an outputting terminal connected to the sensing line through a second switching element.