The Design Of The Pixel Driving Circuit For OLED-on-Silicon

OLED display which is likely to replace LCD to become the mainstream next-generation display technology, has advantages of active solid-state lighting, ultra-thin, high brightness, short response time, wide working temperature range, wide angle, energy-saving, environmental protection as well as flexible bending.Building OLED on silicon exploits the advantages of mature CMOS technology to integrate high density, complex circuits on a single chip to provide a system-on-chip solution for display systems. OLED-on-silicon would be well suited for portable applications such as viewfinders and head mounted displays.Because single crystal silicon has larger carrier mobility than a-Si and p-Si and OLED pixel area is very small, traditional pixel driver can not drive OLED directly with normal width-to-length ratio. To fit the OLED pixel, the MOS will have a very large size. It is the problem of single pixel driving circuit using standard CMOS process. In this work, the problem of small output current using CMOS process is discussed.First, the simulation software HSPICE does not have the model of OLED, so people use the model of diode to simulate OLED. In this paper, the model of diode level1 is chosen. Through several tries, a group of parameters are gained. The validity of the model of OLED based on level1 diode model is proved.For different kinds of input signal (voltage signal and current signal), two different thoughts is proposed to solve the problem of small output current using CMOS process. For the voltage input signal, OLED is paralleled to gain the small output current and the body effect is used to reduce the consumption.And then a voltage programmed pixel driving circuit is proposed. The largest output voltage is 4.9V. For the current input signal, the theory of current mirror is used. Then a current programmed pixel driving circuit is proposed. The small output current is 90.1pA.