Emission Driver Stabilization Block for OLED Voltage Drop
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Solution Overview
Problem
Existing emission drivers in organic light emitting display devices face instability issues with emission control signals, leading to unintended pixel emission and white block image displays, especially under high-temperature and high-illuminance conditions, due to prolonged high voltage differences affecting transistor performance.
Innovation Solution
The emission driver incorporates a stabilization block with a first capacitor connected between the second power source and the fifth node, which limits voltage drop by dividing the DC voltage of the second power source, reducing the bias of the drain-source voltage of the first transistor and maintaining stable gate-on and gate-off voltages, thereby preventing transistor characteristic changes and ensuring stable emission control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional emission driver is used without voltage stabilization, then the device complexity is reduced, but the emission control signal becomes unstable under high-temperature and high-illuminance conditions, causing unintended pixel emission
Solution Approach 1:
A stabilization block is introduced as an intermediary component between the input block and output block. This block includes a first capacitor connected between the second power source and fifth node, and a second capacitor connected between the fifth node and sixth node. The stabilization block mediates voltage fluctuations by dividing the DC voltage of the second power source, thereby preventing emission control signal instability without requiring complete redesign of the emission driver architecture.
Solution Approach 2:
The invention changes the voltage parameter by introducing capacitance ratios between capacitors to control voltage division. The bias of the drain-source voltage of the first transistor is determined based on a capacitance ratio between the first capacitor and the second capacitor. This parameter change allows the system to maintain stable gate-on and gate-off voltages under varying environmental conditions without increasing overall device complexity significantly.
2Power
If high voltage differences are applied to transistors for prolonged periods, then the power driving capability is improved, but the transistor characteristics change due to prolonged high voltage stress, especially in harsh environments
Solution Approach 1:
The stabilization block provides beforehand cushioning by pre-dividing the DC voltage of the second power source through the capacitor network. The first capacitor connected between the second power source and fifth node, along with the second capacitor connected between the fifth node and sixth node, creates a voltage division effect that cushions the transistor from excessive voltage stress before it can cause characteristic changes. This protective mechanism is always in place during operation.
Solution Approach 2:
The invention modifies the voltage parameter applied to the transistor by using the capacitance ratio to control the voltage division. The bias of the drain-source voltage of the first transistor is determined based on a capacitance ratio between the first capacitor and the second capacitor, changing the effective voltage parameter to maintain transistor characteristics while preserving power driving capability.
3Reliability
If the DC voltage of the second power source is not divided, then the circuit design is simplified, but the bias of the drain-source voltage of the first transistor increases, causing unstable gate-on and gate-off voltages
Solution Approach 1:
The stabilization block acts as an intermediary voltage division circuit between the power source and the transistor gates. The first capacitor and second capacitor form a capacitor divider that mediates the voltage transmission, providing stable gate-on and gate-off voltages without requiring complex active voltage regulation circuits. This passive voltage division approach maintains reliability while limiting overall device complexity.
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 solution stabilizes the emission control signal output, preventing unintended pixel emission and enhancing the reliability of the organic light emitting display device even in harsh environmental conditions, by reducing the bias of the drain-source voltage and maintaining transistor performance.
Implementation Method 1
a first capacitor connected between the second power source and the fifth node
Implementation Method 2
a second capacitor connected between the fifth node and the sixth node
Data Source
AI summary
An emission driver according to example embodiments includes a plurality of stages each having an input block; an output block; a first signal processing block controlling a voltage of a first node; a second signal processing block controlling a voltage of a fourth node in response to the signal supplied to a third input terminal and a voltage of a fifth node; a third signal processing block controlling the voltage of the fourth node; a fourth signal processing block controlling the voltage of the third node; and a stabilization block electrically connected between the input block and the output block to limit a voltage drop between the first node and the third node. The stabilization block may limit a voltage drop between a second node and the fourth node by lowering a voltage of a second power source to the fifth node.