Display Apparatus Driving Transistor Threshold Correction Circuit
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Solution Overview
Problem
In organic EL display apparatuses, the long-term deterioration of I-V characteristics and secular changes in threshold voltage and mobility of driving transistors lead to non-uniform emission light luminance across pixels, affecting display quality due to incomplete or excessive threshold value correction processes.
Innovation Solution
A display apparatus with a power supply scanning circuit and signal outputting circuit that selectively supply different reference potentials to the gate electrode of the driving transistor, ensuring a non-conducting state during threshold correction and stable image signal writing by changing the reference potentials from Vofs1 to Vofs2 and then to Vofs3, preventing current leaks and maintaining uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If threshold value correction process is implemented to compensate for I-V characteristic deterioration, then uniformity of emission light luminance is improved, but the process becomes incomplete or excessive leading to non-uniform luminance
Solution Approach 1:
The patent applies preliminary action by establishing a non-conducting state for the driving transistor before the threshold value correction process. The power supply potential is switched to a second potential (lower than the first potential) to ensure the transistor is completely turned off, preventing any current flow during the correction process. This preliminary preparation ensures the correction process is both complete and controlled, avoiding both incomplete correction and excessive correction that would lead to non-uniform luminance.
2Ease of manufacture
If the same reference potential is used throughout the threshold correction process, then the process is simple, but current leaks occur causing non-uniform luminance
Solution Approach 1:
The patent applies dynamics by changing the reference potential dynamically during different stages of the threshold value correction process. The power supply scanning circuit switches between a first potential (for normal operation) and a second potential (for threshold correction). The signal outputting circuit also dynamically switches reference potentials from Vofs1 to Vofs2 and then to Vofs3. This dynamic potential switching prevents current leaks during correction while maintaining simplicity in the overall control architecture.
3Productivity
If the driving transistor remains in conducting state during threshold correction, then image signal writing is continuous, but current leaks cause non-uniform luminance
Solution Approach 1:
The patent applies preliminary action by switching the power supply potential to the second potential (lower than the first) before the threshold value correction process begins. This ensures the driving transistor is completely turned off in advance, preventing any current flow during the correction process. The transistor is switched back to the first potential after correction, resuming normal operation. This preliminary preparation maintains productivity by minimizing disruption to image signal writing while ensuring luminance uniformity during correction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures a desired threshold value correction process, improving display quality by preventing current leaks and maintaining uniform emission light luminance across pixels, thus enhancing the overall picture quality.
Implementation Method 1
an organic EL element which utilizes a phenomenon that an organic thin film emits light when an electric field is applied thereto
Implementation Method 2
a holding capacitor connected at a first one of electrodes thereof to the gate electrode of the driving transistor and at a second one of electrodes thereof to the second electrode of the driving transistor
Data Source
AI summary
Disclosed herein is a display apparatus, including: a pixel array section having a plurality of pixels each including an electro-optical element, a writing transistor, a driving transistor, and a holding capacitor; a power supply scanning circuit; and a signal outputting circuit; wherein the power supply scanning circuit is operable to supply a second power supply potential to initialize the potential of a second electrode of the driving transistor and then change over the potential of a power supply line to a first power supply potential; and the signal outputting circuit is operable to output, when the writing transistor is in a conducting state, a first reference potential, supply, midway while a threshold value correction process is carried out, a second reference potential, output a third reference potential within a period within which the writing transistor remains in the conducting state, and output a image signal after the threshold correction process ends.