OLED Pixel Driving Circuit Leakage Current Compensation
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Solution Overview
Problem
Luminance deviations between pixels in OLED display devices due to voltage differences caused by leakage currents and driving TFT characteristic deviations, leading to image quality issues and reduced lifespan.
Innovation Solution
An OLED display device with a pixel driving circuit that compensates for driving TFT characteristic deviations and high-potential voltage drops, using a method that controls anode voltages to minimize leakage currents by setting adjacent pixels to a non-emission state during the sampling and programming periods, thereby maintaining consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common single layer is used for hole injection and hole transporting layers in all pixels, then device structure is simplified, but voltage difference between adjacent pixel anodes causes leakage current and data voltage deviation
Solution Approach 1:
The patent segments the previously common single layer into separate hole injection layer and hole transporting layer structures, or introduces isolation structures between adjacent pixels to prevent electrical interaction through the common layer, thereby eliminating leakage current while maintaining structural simplicity
Solution Approach 2:
The patent introduces an isolation layer or isolation structure as an intermediary between adjacent pixel anodes to prevent direct electrical connection through the common organic layer, blocking leakage current while allowing the common layer structure to be maintained for manufacturing simplicity
2Device complexity
If driving TFT operates without compensation, then device complexity is reduced, but luminance deviation between pixels occurs due to TFT threshold voltage variation and mobility differences
Solution Approach 1:
The patent implements compensation circuits that use feedback mechanisms to detect and correct variations in driving TFT threshold voltages and mobility, adjusting drive currents to maintain uniform luminance across all pixels despite manufacturing variations
Solution Approach 2:
The patent changes operating parameters such as TFT channel width, layer thickness, or material composition to optimize TFT characteristics and reduce threshold voltage variation and mobility differences between pixels, thereby improving luminance uniformity
3Illumination intensity
If high-potential voltage VDD is applied to drive OLED, then luminance output is improved, but voltage drop occurs causing current variation and luminance deviation
Solution Approach 1:
The patent employs compensation circuits with feedback mechanisms that monitor voltage drops across the high-potential voltage line and adjust driving currents accordingly to maintain uniform luminance despite voltage variations
Solution Approach 2:
The patent performs preliminary compensation by pre-calibrating or pre-adjusting driving currents to account for expected voltage drops, or by designing the circuit to compensate for voltage drop before it significantly affects luminance uniformity
Data Source
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AI summary
Provided is an OLED display device including a circuit that controls a voltage of an Nth row unit pixel and a voltage of anodes of pixel lines adjacent to the Nth row unit pixel in order to minimize a voltage difference between the Nth row unit pixel and the pixel lines adjacent to the Nth row unit pixel to suppress a decrease in luminance of the Nth row unit pixel caused by a leakage current introduced to the Nth row unit pixel. The circuit is configured to set the voltage of the anodes of pixel lines adjacent to the Nth row unit pixel to be equal to or lower than a voltage of an anode of the Nth row unit pixel when the Nth row unit pixel is in a sampling period or a programming period during a driving timing of an OLED display device.. Accordingly, it is possible to minimize flow of an unintended leakage current toward a low-potential anode via a common single layer caused by a voltage difference in anode between a pixel including a high-potential anode and a pixel including the low-potential anode.