Scan Driver Leakage Control Circuit for Oxide Semiconductor Stability
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Solution Overview
Problem
Oxide semiconductor transistors used in display devices are sensitive to light, leading to unstable element characteristics and threshold voltage shifts, which affects the reliability of scan and sensing signals in display devices.
Innovation Solution
A scan driver with a leakage control circuit is implemented, using oxide semiconductor transistors to control voltage nodes and minimize current leakage by supplying a control voltage to the transistors, ensuring stable output of scan and sensing signals despite transistor degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor transistors are used in display devices, then mobility is higher than amorphous silicon transistors and large area application is easier, but element characteristics become unstable and threshold voltage shifts occur due to light sensitivity
Solution Approach 1:
The leakage control circuit proactively compensates for threshold voltage shifts by controlling the voltage of nodes connected to oxide semiconductor transistors before the shifts can significantly impact signal integrity. This preliminary action prevents the harmful effects of light-induced degradation rather than reacting to them after occurrence.
Solution Approach 2:
The leakage control circuit continuously monitors and adjusts voltages at critical nodes based on the actual state of oxide semiconductor transistors. This feedback mechanism ensures that voltage levels are maintained within optimal ranges despite threshold voltage shifts caused by light exposure, thereby maintaining signal reliability.
2Ease of manufacture
If oxide semiconductor transistors are used, then lower temperature processing enables large area application, but the oxide semiconductor layer is degraded by light exposure causing threshold voltage shifts
Solution Approach 1:
The invention converts the harmful effect of light exposure causing threshold voltage shifts into a manageable parameter by designing leakage control circuits that specifically address this issue. The circuits use additional control signals to compensate for the degradation, effectively turning the light sensitivity problem into a controlled variable that can be managed through electrical means.
Solution Approach 2:
The leakage control circuit acts as an intermediary between the oxide semiconductor transistors and the scan/sensing signals. It introduces additional control nodes and circuits that mediate the interaction between the degraded transistors and the signal paths, ensuring that threshold voltage shifts do not directly impact signal integrity.
3Device complexity
If conventional scan drivers are used without leakage control, then device complexity is lower, but current leakage occurs and scan signal reliability deteriorates over time
Solution Approach 1:
The scan driver is segmented into functional blocks including leakage control circuits, input circuits, and output circuits. Each block has a specific function, with the leakage control circuits dedicated to maintaining voltage levels and preventing current leakage. This segmentation allows the system to achieve high reliability through specialized sub-circuits while keeping the overall architecture manageable.
Data Source
AI summary
An nth (where n is a natural number) stage is included in a scan driver of a display. The nth stage includes: a first input circuit for controlling a voltage of a first node in response to a carry signal of a previous stage; a second input circuit for controlling the voltage of the first node in response to a carry signal of a next stage; a first control circuit for controlling a voltage of an output terminal in response to the carry signal of the next stage; an output circuit for outputting an nth scan signal and an nth carry signal in response to the voltage of the first node and a voltage of a second node; and a leakage control circuit for supplying a control voltage to the first input circuit and the second input circuit in response to one of the nth scan signal and the nth carry signal.