Alternating Row Driving for Amorphous Silicon OLED Displays
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Solution Overview
Problem
Amorphous silicon TFTs in OLED devices face challenges with threshold voltage deterioration, leading to non-uniform current flow and degraded image quality, especially when manufacturing large display devices with complex polysilicon TFT processes.
Innovation Solution
A display apparatus and driving method where alternating rows of pixels receive data voltage and reverse bias voltage in alternating sub-frames, using a matrix arrangement of light emitting devices, driving transistors, and switching transistors to manage current flow and reduce threshold voltage stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon TFTs are used in OLED devices, then large screen manufacturing becomes easier and production processes are simplified, but threshold voltage deterioration occurs leading to non-uniform current flow and degraded image quality
Solution Approach 1:
The display panel is divided into multiple pixel rows, with odd-numbered rows and even-numbered rows receiving different voltages in alternating frames. This segmentation allows different regions to be driven differently, preventing threshold voltage deterioration in amorphous silicon TFTs while maintaining image quality.
Solution Approach 2:
The patent implements periodic voltage application where odd-numbered pixel rows receive data voltages in odd frames and even-numbered pixel rows receive data voltages in even frames. This periodic alternating action prevents continuous current flow through individual TFTs, thereby preventing threshold voltage deterioration while maintaining ease of manufacture with amorphous silicon TFTs.
2Manufacturing precision
If polysilicon TFTs are used in OLED devices, then image quality is improved, but manufacturing processes become complex and production costs increase
Solution Approach 1:
The patent changes the operating parameters of amorphous silicon TFTs by implementing alternating frame driving with different voltages for odd and even pixel rows. This parameter change allows amorphous silicon TFTs to achieve performance comparable to polysilicon TFTs without requiring complex manufacturing processes.
3Productivity
If data voltage is continuously applied to all pixel rows, then complete image display is achieved, but threshold voltage deterioration occurs due to continuous current supply
Solution Approach 1:
The pixel rows are segmented into odd-numbered and even-numbered groups that are driven alternately. In each frame, only one group receives data voltage while the other receives reverse bias voltage, preventing continuous current flow and threshold voltage deterioration while maintaining complete image display through frame-by-frame alternation.
Solution Approach 2:
The patent implements periodic alternation where odd-numbered pixel rows are activated in odd frames and even-numbered pixel rows are activated in even frames. This periodic action ensures that no single row receives continuous current, preventing threshold voltage deterioration while maintaining complete and continuous image display.
Data Source
AI summary
A display apparatus includes a plurality of pixels arranged in a matrix. Each pixel includes a light emitting device, a driving transistor for supplying a driving current to the light emitting device, a first switching transistor coupled with the control terminal of the driving transistor to transmit a data voltage, and a second switching transistor coupled with the control terminal of the driving transistor to transmit a reverse voltage. The first and second switching transistors are alternately coupled with scanning lines driven by one of two scanning drivers, and are alternately turned on at different times. The display apparatus periodically applies the reverse voltage to the driving transistors to turn off the diving transistors and to compensate for variation of the threshold voltage of the driving transistors.