Powering small AMOLED display in portable GSM systems

Abstract

Passive Matrix OLEDs are now popular in many applications such as mobile phones, mainly for the sub display in clam shell or in automotive for dashboard. Compared to LCD-TFT, OLED technology has great advantage of wider viewing angle, higher contras ratio, very quick response time and elimination of the backlight power consumption. However the main limitation of Passive Matrix is the display size, making this technology not suitable for display larger than 1.5″. Active Matrix OLED technology is an emerging technology that will change the display world situation. It can associate PM technology advantages, easily overcomes this limitation and is now ready for mass production. However, AMOLED display raises new challenges for engineers. In fact the AMOLED driver requires a positive and negative power supply from a Li-Ion battery. Therefore a dual DC/DC converter made up of a boost plus an inverter is required to deliver regulated voltage with high signal integrity. Actually to avoid any color shift and flicker on the display the DC/DC converter must combine challenging features such as high accuracy and excellent dynamic parameters. Also key features for portable application are taking into account including preserving battery life time, parts count and very low profile solution. This paper reviews the challenge of powering AMOLED display for portable application and after discussing the various constraints requirements gives an efficient solution to the system designer.