Emission Driver Stages with Series Two Transistor Structure
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Solution Overview
Problem
Existing OLED display devices with oxide transistors or n-type metal oxide semiconductor (NMOS) transistors require an emission driver that enhances operation reliability, particularly in charging and discharging circuits to manage carry and emission control nodes effectively.
Innovation Solution
The emission driver incorporates multiple stages with specific charging and discharging circuits, including carry node charging and discharging circuits, emission node charging and discharging circuits, and an output circuit with capacitors for bootstrapping operations, utilizing a series two transistor (STT) structure to manage gate voltages and reduce drain-source voltage stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional emission drivers are used with oxide transistors or NMOS transistors, then the display device can operate, but the operation reliability is insufficient
Solution Approach 1:
The emission driver is divided into multiple stages, with each stage containing dedicated charging and discharging circuits for carry control nodes and emission control nodes. This segmentation allows independent optimization of each circuit's function, improving reliability while maintaining manageable complexity through modular design
Solution Approach 2:
The patent introduces intermediate control nodes (carry control nodes and emission control nodes) that mediate between the clock signals and the final output signals. These intermediate nodes with their dedicated charging/discharging circuits provide precise voltage control, enhancing operation reliability by isolating and managing voltage transitions systematically
2Reliability
If charging and discharging circuits are added to manage control nodes, then operation reliability improves, but device complexity increases
Solution Approach 1:
The charging and discharging circuits are merged into integrated circuit blocks that work together as a unified system. The carry node charging circuit, carry node discharging circuit, emission node charging circuit, and emission node discharging circuit are designed to operate in coordinated sequences, reducing overall system complexity while maintaining the reliability benefits of dedicated voltage control
Solution Approach 2:
The charging and discharging circuits operate in periodic cycles synchronized with the clock signals. Each circuit charges or discharges control nodes at specific intervals during clock cycles, allowing the complex voltage management functionality to be implemented through time-division multiplexing rather than requiring all circuits to be active simultaneously
3Stability of the object's composition
If bootstrapping operation is performed on control nodes, then signal output stability improves, but transistor stress increases
Solution Approach 1:
The bootstrapping operation is performed preliminarily on the control nodes before the final signal output is generated. By pre-charging or pre-discharging the control nodes to appropriate voltage levels, the circuit prepares the conditions for stable signal output while distributing the voltage stress across multiple transistor switches that operate in sequence rather than requiring a single high-stress switching event
Data Source
AI summary
An emission driver includes stages. At least one of the stages has a carry control node outputting a carry signal and an emission control node outputting an emission signal that are separated. Further, a second low gate voltage may be used that may be lower that a first low gate voltage. Further, transistors between each of the carry and emission control nodes and a second low voltage line transferring the second low gate voltage may have a series two transistor structure. Further, a transistor outputting the second low gate voltage as the carry signal may be repeatedly turned on and off in response to an inverted low clock signal. Accordingly, operation reliability of the emission driver of the display device may be improved.