Emission Control Line Driver Circuit Stability
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Solution Overview
Problem
The existing emission control line drivers for organic light emitting displays require multiple transistors to manage four clock signals, leading to increased manufacturing costs and reliability issues, particularly with unstable low-level output due to leakage current in PMOS transistors.
Innovation Solution
The proposed emission control line driver uses three clock signals to simplify the circuit structure and stabilize the output voltage of the gate electrode, allowing for controlled emission control signal width and secure output stability by periodically reducing the gate electrode voltage and using a three-transistor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four clock signals are used to drive the emission control line driver stages, then the emission control signals can be generated, but the number of transistors increases and manufacturing cost increases
Solution Approach 1:
The patent changes the clock signal parameter from four signals to three signals, thereby reducing the number of transistors required in each stage while maintaining the ability to generate proper emission control signals. This parameter change directly addresses the contradiction by simplifying the circuit structure without compromising output stability.
Solution Approach 2:
The patent extracts one clock signal from the original four-clock-signal system, eliminating the need for one entire clock signal pathway and its associated transistors. This extraction reduces device complexity while the remaining three clock signals are reconfigured to maintain the necessary emission control functionality.
2Ease of manufacture
If PMOS transistors are used in the emission control line driver, then the circuit can be implemented, but the low level output becomes unstable due to leakage current
Solution Approach 1:
The patent applies periodic action by using clock signals to periodically reset or refresh the transistor states, preventing leakage current from causing unstable low level outputs. The periodic clocking ensures that any leakage effects are corrected regularly, maintaining output stability while allowing the use of PMOS transistors.
Solution Approach 2:
The patent implements feedback mechanisms where the output state is monitored and used to control subsequent transistor operations. This feedback ensures that leakage current effects are compensated for, maintaining stable low level outputs while using PMOS transistors in the circuit implementation.
3Reliability
If multiple transistors are included in the stages, then the emission control signals can be generated, but the manufacturing cost increases
Solution Approach 1:
The patent changes the operational parameters of each transistor stage to achieve the same emission control signal generation with fewer transistors. By optimizing the transistor configuration and clock signal usage, the patent reduces the transistor count per stage while maintaining driving reliability, thereby reducing manufacturing cost.
Solution Approach 2:
The patent makes each transistor stage more universal by designing it to handle multiple functions with fewer components. The stages are configured to perform emission control signal generation, timing control, and signal conditioning using a reduced transistor count, improving ease of manufacture while maintaining reliability.
4Reliability
If the gate electrode voltage is not periodically reduced, then the transistor operation is simple, but the output stability deteriorates due to leakage current
Solution Approach 1:
The patent implements periodic reduction of the gate electrode voltage through clocked control signals. This periodic action resets the gate voltage at regular intervals, preventing leakage current from causing voltage drift and maintaining output stability. The periodic control adds minimal complexity while significantly improving reliability.
Data Source
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AI summary
An emission control line driver is capable of securing the stability of an output and of freely controlling the width of emission control signals. The emission control line driver includes a plurality of stages (321) respectively coupled to emission control lines (E1). Each of the stages includes a plurality of transistors (M1-M14) that are configured to output the emission control signal. The width of the emission control signal may be controlled to correspond to the width of a start signal. Furthermore, a circuit structure of the stages is simplified.