Especially in the tech sector, if you want to know where you are going, it’s good to know where you came from. In this week’s summer school lesson plan is a quick history of the evolution of organic light emitting diode (OLED) display driver integrated circuits (DDIC) technology.
OLED displays are becoming commonplace, particularly in smart phones, favored by design engineers for its ability to deliver dynamic colors and high contrast ratio for great readability even in sunlight. Further, these displays are responsible and flexible/bendable. More and more, buyers will find suppliers of these and related technologies on their bill of materials (BOM).
Let’s take a look at the development timeline for this fast emerging technology.
2000 - 2005
In the early and mid-2000s, OLED display entered the market first with a two-inch range PM OLED sub display of a feature phone, in which the OLED DDIC employed a low-resolution passive current driving method. In the passive current driving method, the core technologies of DDIC included output current matching, controllability and high current consumption control. This was a period of time when -- despite several advantages of an OLED panel -- its high drive current and voltage caused PM OLED and DDIC to face technical challenges to enter the 3-inch or larger main panel market. Therefore, the industry began to address these issues in order to become more competitive with LCD displays.
2006 to 2010
From roughly 2006 to 2010, OLED displays entered the feature phone main display market with the development of the qVGA AMOLED display, which marked the first real competition for LCD. At this point, the OLED DDIC adopted an active voltage driving method, which enables the source output voltage and the controllability of panel voltage noise to improve OLED image quality.
This first- generation core technology was also the first to benefit from lower cost mass production capability. This first-generation core technology marked an evolution in several DDIC characteristics. For instance, at that time existing OLED pixels used a current driving method, but newer-generation DDIC was required to adopt a voltage driving method to achieve higher resolution and realize lower power consumption.
This in turn led to a significantly reduced “non-uniformity” of the pixel circuitry, which converts voltage into current and results in much better noise sensitivity, as compared to an LCD display of an equivalent resolution. To realize completely OLED’s advantages in faster response time, higher contrast ratio and excellent color reproducibility and naturalness, the DDIC was required to perform several times greater output accuracy and noise controllability than an LCD DDIC.
To achieve this, it was inevitable that the OLED DDIC would grow in complexity and size. However, the industry addressed this seeming disadvantage by successfully developing lower-cost mass production techniques for AMOLED DDICs used in mobile phones and Portable Multimedia Player (PMP). This development enabled the first-generation core technology to become truly competitive with LCD and positioned it well for opportunities to expand the OLED market.
2011 to 2014
With the proliferation of smartphones from the mid-2010s, high-resolution displays were adopted in earnest and the consumption of video content increased. This brought to consumers a widespread recognition of the advantages of OLED displays, including lower power consumption as compared to the first OLED displays.
In addition, the OLED industry made significant strides in solving the screen aging and burn-in issues that led to short product lifetimes. This period marked the second-generation core technology for OLED, which enabled complex functions such as significantly more sophisticated pixel optical compensation capabilities in high resolution (e.g., true HD) formats and low power consumption that did not impair image quality. This led to high-density Static Random Access Memory (SRAM) and diverse compensation functions that could be realized using process technologies of 55nm and below – an important step leading to further cost reductions and development of flexible OLED screens.
2015 and beyond
Beginning in 2015, OLED moved beyond existing LCD by virtue of its own unique characteristics – such as the first bendable type display to extend around the edge of a mobile phone, a true technology milestone. In the coming years, innovations in OLED displays, large and small, will help bring about the changes associated with “Industry 4.0” and its impact on various cultural aspects of society, as will be seen with foldable, rollable, wearable and transparent displays that can be deployed inside and outside. These devices will interact with people on a “touch and see” basis in a “seamless” manner that will appear as part of the “natural environment.”
To keep pace with this forecast development, DDIC technology will enable these natural looking displays without shape or size constraints by integrating Ultra-High Resolution from HD, FHD, QHD to mobile 4K, Ultra-High PPI (Pixel Per Inch) from 250ppi, 350ppi, 500ppi, 750ppi to 1500ppi, ultra-high-speed scan rate from 60Hz, 75Hz, 90Hz to 120Hz, High Dynamic Range (HDR), distortion and optical compensation technology, lower power consumption, lifelike VR driving technology (>90Hz& >1000PPI) and user interface (touch & see).
Looking to the future
The industry will build upon the first and second core technologies in several aspects, such as: improved output voltage accuracy, enhanced noise controllability to remove flicker, and compensation for the growing number of source channels and improved luminous efficiency of OLED. More specific to the second-generation core technology, pixel non-uniformity compensation and aging compensation will need to adopt more complex operations in order to accomplish more sophisticated functions.
These advances in the first and second-generation core technologies mean that the forthcoming third generation core technology will incorporate larger memory and higher order processes from 40nm, to 28nm and under 20nm. This progression in manufacturing will minimize power consumption arising from more complex DDIC operations such as: pixel compensation and comprehension distortion compensation, higher speed operations and integrated modules sensor functions for enhanced “touch and see” interactive features. Figure below represents this progression of OLED display technologies.
Paul Kim, vice president of marketing, Standard Products Group, MagnaChip Semiconductor Corp., co-authored this article. Kim became vice president of marketing, Standard Products Group in December 2015. He joined MagnaChip in August 2011 and served as vice president of Display Design, Display Solutions Division. Prior to joining MagnaChip, Kim served as principal engineer of SOC & Display Driver IC Design Group of Samsung Electronics, where he worked from 1994 to 2010. Kim holds B.S degree in Electrical Engineering from Inha University, Korea.