Floating Scanning Line for OLED Threshold Voltage Correction
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Solution Overview
Problem
In high-resolution and high-frequency active matrix image display apparatuses using organic EL devices, it is challenging to correctly set the inter-terminal voltage of the holding capacity to the threshold voltage of the driving transistor within the limited time available, leading to potential failure in correcting fluctuations in threshold voltage, which can result in image quality deterioration.
Innovation Solution
The image display apparatus and its driving method involve setting the inter-terminal voltage of the holding capacity to a voltage equal to or higher than the threshold voltage of the driving transistor by discharging it via the driving transistor in multiple periods with pauses, and setting the scanning line to a floating state during the entire or partial period of these pauses to prevent power supply and subsequent voltage rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inter-terminal voltage of the holding capacity is discharged via the driving transistor in multiple periods to correct threshold voltage fluctuations, then the correction reliability is improved, but the time required for correction increases
Solution Approach 1:
The patent applies periodic action by discharging the inter-terminal voltage of the holding capacity in multiple periods through the driving transistor. This periodic discharge process allows the voltage to gradually approach the threshold voltage over several cycles, improving correction reliability while managing the time constraint by utilizing the natural periodic operation of the display apparatus
Solution Approach 2:
The patent implements preliminary action by setting the scanning line to a floating state during pause periods before the actual discharge operation. This preliminary preparation prevents unintended voltage changes and ensures that the discharge process starts from a known state, improving the overall reliability of the threshold voltage correction
2Stability of the object's composition
If the scanning line is set to floating state during pause periods, then the voltage stability is improved, but the control complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the inherent capability of the scanning line to be set to a floating state without requiring additional active control mechanisms. The scanning line naturally maintains its voltage level when not actively driven, and the patent leverages this natural behavior for pause periods, achieving voltage stability without adding complex control circuitry
Solution Approach 2:
The scanning line serves multiple functions: it acts as an active signal line during normal operation and as a floating voltage reference during pause periods. This multi-functionality allows the same line to provide both operational signaling and voltage stabilization without requiring separate dedicated circuits, thereby avoiding increased control complexity
Data Source
AI summary
The present invention sets a scanning line to which a driving signal for power supply is output to a floating state in an entire period of pauses of threshold voltage correction processing or a partial period thereof.