AMOLED compensation circuit patent analysis

OLED, a self-light-emitting diode, has been touted as the next big thing in display technology for its exceptional properties including no need for a backlight, wide viewing angle, quick responding speed and low current consumption. In particular, LG unveiled the world’s first 55-inch flat OLED TV in early 2013 followed by 55-inch curved OLED TV in April. With Samsung joining the fray with its latest 55-inch curved OLED TV, a fierce competition is expected in the OLED TV industry.

In anticipation of the OLED TV market coming into full bloom next year and encroaching the LCD TV market, developing mass production technology for OLED panels will soon emerge as a major issue. Extensive R&D efforts are under way to refine the OLED manufacturing process, namely, TFT backplane, color patterning, encapsulation and driving circuit. Especially, a lot of research has centered on the development of compensation circuit, as threshold voltage and IR-drop reduce the luminance of a driving TFT for an AMOLED display.

Read more: AMOLED panel shipments get boost from premium smartphones

OLED is a current driving circuit whose luminance properties are extremely sensitive to current changes. Driving TFTs for each pixel circuit of an AMOLED display can have different threshold voltages, which undermines the consistency of luminance of the panel.

In addition, when a VDD line passes each pixel circuit, it creates an IR-drop, resulting in a gradual decrease in pixel luminance towards the bottom of the panel that requires compensation.

Displaybank now offers a report examining a number of selected U.S. patents, analyzes patent application trends and patents filed by major companies and pinpoints key patents and new technology patents, offering a wide array of in-depth analyses. These analyses are expected to help keep pace with development trends for an AMOLED pixel driving circuit technology that compensates the threshold voltage and IR-drop as well as key patented technologies.

amoled shipments

Patent Application Trends
The number of U.S. patent applications for AMOLED pixel driving circuit (Vth and IR-drop compensation) technology is generally on the rise, with threshold voltage (Vth) compensation taking the biggest share. Top assignees are Samsung Display, Global OLED Technology, LG Display, Chimei Innolux, and Sharp, in the order of the number of applications.

amoled patent analysis

Key Patent Analysis
Out of 244 U.S. patents, those listed in the top 50 issued patents in terms of the number of forward citations were selected as key patents and subjected to an in-depth analysis: technology development trends, overview of key patents and case analysis.

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