Organic EL Display Power Supply Floating to Reduce Electrical Stress
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Solution Overview
Problem
Organic EL display apparatuses face challenges in maintaining screen uniformity and preventing electrical stress-induced defects due to time degradation and manufacturing variations, particularly during the no-light emission period when a reversed bias is applied, leading to potential defects and image quality deterioration.
Innovation Solution
The display apparatus employs a configuration with a signal writing transistor, a signal storage capacitor, and a device driving transistor, where the power-supply electric potential is changed to control transitions between light emission and no-light emission periods, and during the no-light emission period, the power-supply line is floated to minimize reversed bias, reducing electrical stress by ensuring no reversed bias is applied to the electro optical device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the power-supply electric potential is changed to apply reversed bias during the no-light emission period, then the electro optical device can be controlled to stop emitting light, but electrical stress is generated in the electro optical device leading to potential defects and image quality deterioration
Solution Approach 1:
The patent applies dynamics by making the power-supply electric potential adjustable and time-variable. The power-supply potential is dynamically changed between a first potential during the light emission period and a second potential during the no-light emission period, allowing the system to adapt to different operational states while minimizing electrical stress on the electro optical device
Solution Approach 2:
The patent changes the electrical parameter (power-supply electric potential) to control the operational state of the electro optical device. By varying the potential level between two defined states, the device can transition between light emission and no-light emission periods without generating harmful electrical stress
2Ease of operation
If the power-supply electric potential is changed to apply reversed bias during the no-light emission period, then the electro optical device can be controlled to stop emitting light, but screen uniformity deteriorates due to time degradation and manufacturing variations
Solution Approach 1:
The power-supply electric potential is dynamically adjusted between two defined levels to control the light emission state. This dynamic control allows precise management of the electro optical device operation while compensating for manufacturing variations and time degradation effects
Solution Approach 2:
The patent applies preliminary anti-action by pre-defining two specific power-supply electric potentials that prevent harmful effects. The first potential enables light emission while the second potential stops emission without causing reversed bias damage, thereby preventing screen uniformity deterioration before it can occur
3Stability of the object's composition
If the power-supply electric potential is continuously asserted during the no-light emission period, then the electro optical device remains in a stable electrical state, but the duration of reversed bias application increases causing electrical stress and potential defects
Solution Approach 1:
The patent applies periodic action by alternating the power-supply electric potential between two states corresponding to the light emission period and no-light emission period. This periodic switching controls the operational cycles of the electro optical device, ensuring it receives power only when needed and remains stable during non-emission periods without excessive reversed bias exposure
Solution Approach 2:
The patent maintains continuity of useful action by ensuring the electro optical device receives continuous power supply during the light emission period and controlled potential during the no-light emission period. This continuous controlled供电 prevents electrical stress accumulation while maintaining device stability throughout the operational cycle
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 effectively reduces electrical stress on the organic EL device, preventing defects and maintaining image quality by minimizing the duration of reversed bias application, thus sustaining the device's performance and ensuring consistent luminance.
Implementation Method 1
An organic EL display apparatus employs pixel circuits each including an organic EL device serving as a light emitting device. An organic EL device is a device generating light by itself, an image generated by the light exhibits a high degree of recognizability... since an organic EL device is a device generating light by itself... making use of a phenomenon in which light is generated when an electric field is applied to an organic thin film of the organic EL device
Data Source
AI summary
Disclosed herein is a display apparatus including a pixel matrix section including pixel circuits laid out to form a pixel matrix to serve as pixel circuits each having an electro optical device, a signal writing transistor, a signal storage capacitor, and a device driving transistor, and a power-supply section configured to change a power-supply electric potential appearing on a power-supply line for providing a driving current flowing to the device driving transistor from one level to another in order to control transitions from a light emission period of the electro optical device to a no-light emission period of the electro optical device and vice versa, and stopping an operation to assert the power-supply electric potential on the power-supply line during a portion of the no-light emission period of the electro optical device.