Capacitor-Based Voltage Control for OLED Driver Circuit Simplification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active matrix type display devices with electroluminescent elements face challenges in achieving high display quality for intermediate gradations and low power consumption, due to complex driver circuits and increased heat generation.
Innovation Solution
A display device structure with a capacitor to hold voltage between electrodes, allowing a voltage higher than the threshold voltage of the light emitting element to be applied, enabling efficient light emission and gradation control without relying on the threshold voltage, and using transistors as switching elements to simplify the driver circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a current value proportional to gradation is inputted to each pixel to control light emission luminance, then luminescence can be controlled, but the driver circuit structure becomes complicated requiring many current sources
Solution Approach 1:
The patent changes the control parameter from current value to voltage value. By applying a voltage higher than the threshold voltage to the light emitting element and utilizing the capacitor's potential change, the system achieves luminance control through voltage rather than current, thereby simplifying the driver circuit structure while maintaining luminance control capability
Solution Approach 2:
The patent extracts the threshold voltage component from the control mechanism. By separating the threshold voltage (held by the capacitor) from the variable voltage component (applied to control luminance), the system eliminates the need for complex current sources and achieves simplified voltage-based control
2Ease of operation
If a voltage higher than threshold voltage is applied to control current value, then power consumption increases and heat generation increases
Solution Approach 1:
The light emitting element serves itself by utilizing its own threshold voltage characteristic. The capacitor holds the threshold voltage, and the element automatically operates in the appropriate region without requiring excessive external voltage, thereby reducing power consumption and heat generation while maintaining control capability
3Productivity
If intermediate gradation video signal is inputted, then display quality of intermediate gradation deteriorates due to incomplete signal input
Solution Approach 1:
The capacitor performs preliminary action by holding the threshold voltage in advance. This pre-established voltage foundation ensures that when intermediate gradation signals are applied, the light emitting element receives the complete and accurate voltage signal needed for proper luminance control, preventing signal incompleteness and maintaining high display quality
4Ease of operation
If TFT is operated in saturation region to control current value, then power consumption increases and heat generation increases
Solution Approach 1:
The patent changes the operating parameter from current control (requiring saturation region operation) to voltage control. By applying voltage higher than threshold voltage and utilizing the capacitor's potential change, the TFT can operate in a lower power consumption region, thereby reducing heat generation while maintaining current control capability for the light emitting element
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 allows for high-quality display of intermediate gradations with reduced power consumption and simplified driver circuits, maintaining proper gradation even when threshold voltages vary or light emitting elements deteriorate.
Implementation Method 1
a capacitor for holding a voltage between a pair of electrodes
Implementation Method 2
a light emitting element having a pair of electrodes... when a voltage which is equal to or higher than a threshold voltage Vth of the light emitting element is applied to the one electrode of the light emitting element
Data Source
AI summary
It is an object to provide a display device having a simple structure of a driver circuit for inputting a video signal to a pixel, high display quality of the intermediate gradation and low power consumption, and a driving method thereof.Each of a plurality of pixels has a light emitting element and a capacitor. One electrode of the light emitting element is connected to the other electrode of the capacitor and one electrode of the light emitting element is applied to a voltage which is equal to or higher than a threshold voltage of the light emitting element and a potential of one electrode of the capacitor is changed. Therefore, a potential of one electrode of the light emitting element is changed and the light emitting element emits light.