Research Of OLED-On-Silicon Microdisplay Driving Technologies

OLED-on-silicon micro-display is a sector of flat-panel display which OLED integrates onto silicon chips. Micro-display is usually less than 1 inch diagonal OLED-on-silicon micro-display perfectly combines the advantage of OLED together with mature CMOS technology, which has attributes of wide viewing angle, fast response time, low power consumption, and wide operation temperature. The driving circuit is fabricated on a silicon wafer. It can be applied to personal entertainment devices and helmet displays for pilots. Nowadays, OLED-on-silicon micro-display is one of research hot-point of panel display. Starting from the pixel circuit of the OLED-on-silicon micro-display, the driving circuit for the OLED and system design is researched in this paper, and the four main points of this paper are sum up as follows:1. Pixel circuit designPixel area of OLED-on-silicon micro-display is much smaller than traditional TFT AMOLED and pixel current are needed from hundreds of pA to tens of nA. How to realize such a small current is the pixel circuit’s keystone and difficulty. To solve this issue, a novel pixel circuit for OLED-on-silicon micro-display is presented in this paper. The proposed pixel circuit is composed of one PMOS, three NMOS, one storage capacitor, one OLED and four signal lines. This circuit is verified by simulation work using Pspice. In this proposed circuit, the current flowing through the OLED is constant, and the pixel circuit is fully controlled by digital signal.2. Time ratio grayscale modulationGrayscale modulation can be realized by time ratio grayscale(TRGS) scheme which different grayscale can be achieved by controlling the light-emitting time. In this paper, one frame is divided into six sub-frames. Sub-frame is either On-state sub-frame or Off-state sub-frame. With the method of progressive scanning, different grayscale(from 0 to 63) can be achieved by controlling the number of “On-state sub-frame” and “Off-state sub-frame”.3. Data progressing module system designAccording to digital integrated circuit design method, system design of data processing module is accomplished using verilog. This module can converter RGB data to the corresponding signal. And the module is verified by simulation work using Modelsim.4. Layout designAbiding by MOSIS/ORBIT 2.0U SCNA Design Rules, layout of unit pixel is designed, while the effect of parasitic resistance and capacitance of the scan lines and data lines for the pixel array is analyzed in the worst case design. The pixel circuit layout design is feasible by simulation.