Feeding Line Potential Control for OLED Degradation
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Solution Overview
Problem
Active matrix organic EL display apparatus suffer from light-emitting element degradation due to reverse bias voltage during non-emission periods and current leaks caused by sampling transistors, leading to image shading and crosstalk.
Innovation Solution
A display apparatus with a pixel array and driver that switches feeding lines between high, low, and intermediate potentials to prevent reverse biasing of light-emitting elements and current leaks, using a power supply scanner to correct threshold voltage variations and maintain the light-emitting elements in a non-reversely biased state during non-emission periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse bias voltage is applied to light-emitting elements during non-emission periods, then the sampling transistor can be turned off to prevent current leaks, but the light-emitting elements suffer degradation
Solution Approach 1:
The patent applies a three-level potential switching scheme to the feeding line: high potential during emission periods, intermediate potential during non-emission periods, and low potential during threshold voltage correction periods. The intermediate potential is specifically designed to be higher than the cathode potential, preventing reverse biasing of the light-emitting element while still allowing the sampling transistor to be turned off and preventing current leaks.
2Manufacturing precision
If low potential is applied to feeding lines during non-emission periods, then threshold voltage correction can be performed, but light-emitting elements are reverse biased causing degradation
Solution Approach 1:
The patent implements periodic switching of the feeding line potential between different levels based on the operational phase: high potential during emission periods for normal operation, intermediate potential during non-emission periods to prevent reverse biasing, and low potential during threshold voltage correction periods. This periodic action allows both threshold voltage correction and prevention of light-emitting element degradation to be achieved at different times.
3Stability of the object's composition
If sampling transistor is kept conductive to prevent current leaks, then signal retention is improved, but power consumption increases and threshold voltage variations worsen
Solution Approach 1:
The patent performs threshold voltage correction during non-emission periods when the sampling transistor is turned off. By correcting threshold voltage variations in advance during periods when the pixel is not displaying, the system maintains signal stability without requiring the sampling transistor to remain conductive, thus reducing power consumption while preventing current leaks.
Data Source
AI summary
Disclosed herein is a display apparatus including a pixel array and a driver, the pixel array including rows of scanning lines, rows of feeding lines, columns of signal lines, and a matrix of pixels disposed at the crossings of the scanning lines and the signal lines, the driver including a write scanner for supplying a control signal successively to the scanning lines, a power supply scanner for switching each of the feeding lines between a high potential, a low potential, and an intermediate potential between the high potential and the low potential, and a signal selector for supplying a video signal, which alternately switches between a signal potential and a reference potential, to each of the signal lines.