Variable Voltage Gate Driver for OLED Black Grayscale Uniformity
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Solution Overview
Problem
High-resolution electroluminescent display devices face challenges in expressing a black grayscale due to variations in pixel driving characteristics and high-potential power voltage IR drops, leading to non-uniform image quality and decreased contrast ratio.
Innovation Solution
A gate driver and electroluminescent display device with a variable voltage output unit that selectively applies initialization or reference voltages to the anode of the electroluminescent element, reducing the impact of high-potential power voltage and enabling uniform image quality across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of the display device is increased, then the image quality is improved, but the ability to express black grayscale deteriorates
Solution Approach 1:
The patent applies preliminary action by initializing the anode of the electroluminescent element to a reference voltage before the sampling period. This preliminary initialization ensures that the anode starts at a known potential state, preventing unwanted light emission during initialization while maintaining the ability to express black grayscale in high-resolution displays.
Solution Approach 2:
The patent implements dynamics by making the anode voltage variable rather than fixed. The anode voltage is dynamically adjusted to the reference voltage during the sampling period, allowing the display to adapt to different operating conditions and maintain black grayscale expression capability across high-resolution panels.
2Reliability
If the width of the high-potential power voltage line is increased, then the IR drop is reduced, but the device area increases
Solution Approach 1:
The patent applies parameter changes by modifying the voltage level applied to the anode from the conventional high-potential power voltage to a reference voltage that is lower than the operating voltage of the OLED. This parameter change reduces the voltage differential across the power voltage line, thereby reducing IR drop and improving voltage uniformity without requiring increased line width.
3Power
If a high-potential power voltage is applied to the anode, then the OLED operates normally, but the contrast ratio decreases
Solution Approach 1:
The patent changes the voltage parameter applied to the anode from high-potential power voltage to reference voltage during the sampling period. This parameter change ensures that the anode voltage is lower than the OLED operating voltage, preventing current flow and light emission while maintaining the ability to express black grayscale, thereby improving contrast ratio.
4Measurement precision
If the length of the high-potential power voltage line is increased, then the resolution is improved, but the IR drop increases
Solution Approach 1:
The patent applies parameter changes by reducing the voltage level on the power voltage line from high-potential power voltage to reference voltage. This parameter change directly reduces the voltage differential across the line, thereby reducing IR drop and energy loss, allowing high-resolution displays to maintain voltage uniformity even with longer power voltage lines.
Data Source
AI summary
Provided is an electroluminescent display device. The electroluminescent display device includes a display panel including a display area in which an image is displayed and a non-display area in which an image is not displayed. The electroluminescent display device further includes a subpixel including a subpixel circuit disposed in the display area and an electroluminescent element, wherein the subpixel circuit includes a driving transistor. The electroluminescent display device also includes a gate driver disposed in the non-display area, and a variable voltage output unit disposed in the non-display area and configured to supply a variable voltage to the subpixel. The variable voltage output unit selectively outputs an initialization voltage or a reference voltage to an anode of the electroluminescent element. Therefore, the anode of the electroluminescent element can be initialized using the initialization voltage during an initialization period.