Novel Drivers for High-Resolution OLED Displays
This PhD deals with the design of the driving circuitry for OLED displays, mainly focusing on active matrix OLED (AMOLED) displays. These provide an improved picture quality compared to the previously used LCD technology. Since the OLED pixels are current driven instead of voltage driven, a drive transistor is used to control the current through the OLED, and hence the brightness of the pixel. However, process variations and bias stress can cause the threshold voltage of this transistor to shift, leading to a non-uniform brightness within the display. To obtain a uniform brightness, some compensation circuitry needs to be implemented. Although this compensation can be implemented inside the pixel engine, this would increase the area of the pixels, and thus limit the resolution of the display. Therefore, this research opts to implement the calibration in the (silicon) column drivers of the display. This approach has following advantages: the measurements are much more accurately when performed in silicon, the power consumption can be reduced substantially, higher resolutions are allowed, and the degradation of the display can be analyzed. In this PhD, various backplanes are designed and tested combined with the implementation of the calibration, in order to obtain a high-resolution, uniform display.