Display Device Flickering Reduction via Voltage Control
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Solution Overview
Problem
Organic electroluminescence (EL) display devices suffer from image quality degradation due to flickering, which is caused by differences in brightness between light emission and non-light emission periods, leading to a decrease in displayed image quality.
Innovation Solution
A display device and driving method that include specific configurations of transistors and capacitors, allowing for precise control of voltages during initialization, light emission, and black insertion periods to reduce flickering, featuring a drive transistor, selection transistor, initialization transistor, reset transistor, light emitting control transistor, storage capacitor, and additional capacitor to manage voltage levels effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used to control light emission, then the display device can function, but flickering occurs due to brightness differences between light emission and non-light emission periods
Solution Approach 1:
The patent applies preliminary action by initializing the drive transistor and setting voltage levels during the non-light emission period before the light emission period begins. The initialization transistor resets the gate voltage of the drive transistor, and the reset transistor adjusts the source voltage, ensuring that the transistor is properly prepared for the upcoming light emission phase. This preliminary preparation prevents flickering by eliminating residual charges and establishing consistent starting conditions for each light emission cycle.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting voltage levels at different nodes during transitions between light emission and non-light emission periods. Specifically, the gate voltage (Vg), source voltage (Vs), and drain voltage (Vd) of the drive transistor are controlled to change appropriately during initialization, light emission, and black insertion periods. By changing these electrical parameters in a controlled manner, the patent eliminates brightness fluctuations and achieves stable display without flickering.
2Ease of manufacture
If voltage control is simplified, then the circuit is easier to manufacture, but precise voltage adjustment during transitions cannot be achieved
Solution Approach 1:
The patent applies segmentation by dividing the voltage control function into multiple independent transistor components: an initialization transistor (IST) for gate voltage control, a reset transistor (RST) for source voltage control, and a light emitting control transistor (BCT) for drain voltage control. Each transistor is controlled by separate control signals, allowing independent optimization of each voltage control stage. This segmentation enables precise voltage adjustment during transitions while maintaining clear manufacturing specifications for each component.
3Reliability
If multiple transistors and capacitors are added for precise voltage control, then flickering is reduced, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing transistors that perform multiple roles during different time periods. For example, the drive transistor serves as both the light emission control element and a storage element during the non-light emission period. The initialization transistor not only initializes the gate but also works in conjunction with the storage capacitor to maintain voltage levels. This multi-functional design reduces the need for completely separate circuits for each function, thereby limiting the increase in overall device complexity while achieving flicker elimination.
Solution Approach 2:
The patent employs nesting by integrating the initialization and reset functions within the existing pixel circuit architecture. The initialization transistor and reset transistor are nested within the pixel circuit alongside the drive transistor and storage capacitor, sharing common nodes and control mechanisms. This nested arrangement allows the additional functionality to be incorporated without requiring completely separate circuit blocks, thus limiting the increase in device complexity while achieving the desired display stability.
Data Source
AI summary
A display device includes a drive transistor having a first electrode connected to a first node, a second electrode connected to a second node, and a third electrode connected to a third node, a first switch having one terminal connected to the first node, a second switch having one terminal connected to the first node, a third switch controlled by a first control signal and having one terminal connected to the second node, a fourth switch controlled by the first control signal together with the third switch, and having one terminal connected to a power supply line and another terminal connected to the third node, a capacitor element having one terminal connected to the first node and another terminal connected to the second node, and a light emitting element including a pixel electrode connected to the second node, and a first common electrode.