Floating Power Supply Scanning Line for OLED Flicker Reduction
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Solution Overview
Problem
In active matrix image display apparatuses using organic EL devices, providing a pause in the emission period leads to image quality deterioration due to changes in the gate-source voltage of the driving transistor, causing leak currents and resulting in shading, cross-talk, and other image quality issues.
Innovation Solution
The image display apparatus includes a scanning line driving circuit that sets the scanning line for power supply to a floating state during the pause, preventing a leak current by maintaining the source voltage of the driving transistor at a higher voltage and ensuring the inter-terminal voltage of the holding capacity is set to a voltage equal to or higher than the threshold voltage of the driving transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a pause is provided halfway through the emission period to reduce flicker, then the repetition frequency of emission is increased, but image quality deteriorates due to gate-source voltage changes and leak currents
Solution Approach 1:
The patent changes the voltage parameter of the scanning line from a fixed low voltage to a floating state during the pause period. This parameter change prevents the gate-source voltage of the driving transistor from dropping, thereby eliminating leak current and maintaining image quality while still achieving flicker reduction through the pause mechanism
Solution Approach 2:
The patent prepares for the pause period by maintaining the scanning line at a floating state before the pause begins. This beforehand cushioning ensures that when the pause occurs, the gate-source voltage is already protected from dropping, preventing leak current and image quality deterioration in advance
2Illumination intensity
If the scanning line is set to a fixed voltage during pause, then light emission stops, but leak current occurs and gate voltage changes causing image quality deterioration
Solution Approach 1:
The patent changes the scanning line voltage parameter from a fixed low voltage to a floating state during the pause. This parameter change maintains the source voltage at a higher level, preventing gate voltage changes and leak current, thereby ensuring image quality stability while still controlling light emission
Data Source
AI summary
The present invention retains a scanning line for power supply in a floating state in a pause provided halfway through a period of emission.