EPD Paper, April 2007

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Display Technologies

General

Liquid Crystal Displays (LCD)

Flexible Displays

Electrophroetic Displays (EPD)

Some current characterization for electrophoretic suspension fluid.
Addressing. With a display thickness of 50micrometer and an average dielectric constant of 5.0, the capacitance per element would be ~0.055 pF.
EPD driver information and pixel level model
Section 3. To compensate for the leakage current, the storage capacitor must be very large; here, the capacitance is 34 pF. A polysilicon TFT is preferable to an amorphous silicon TFT for the switching transistor, because the large capacitor must be charged during the short pixel selection period.
EPD driven to produce greyscale
I. ...we have reported the world's first active-matrix EPD at an international electron device meeting (IEDM 2000)[12]. Since then, a few displays combining TFTs and microencapsulated electrophoretic materials have also been introduced [13]-[16].
I. Microencapsulated electrophoretic material in this EPD was driven by poly-Si TFTs fabricated with a low temperature process...
Good description of E-Ink displays and driver information

Colloidal suspension physics

Greyscale properties

Reflective Cholesteric Displays (ChLCDs)

Electro-wetting displays

Organic Light Emitting Diode (OLED)

Display Power

LCD greyscale single pixel power consumption formula
Addresses independant scaling of three color LED backlights based on image histogram
3.1: Whenever there is a screen change, the processor generates new data for the changing screen pixels and stores them into the framebuffer. This implies a higher energy consumption with increased temportal changes in the screen. Meanwhile, to maintain a screen on the LCD, the LCDC must sequentially read screen data from the frame-buffer and refresh the LCD pixels even when there is no screen change.
3.1: The display itself consists of several parts: LCD power circuitry, a front light, and an LCD. The LCDs used in the systems we studied are color active thin film transistor (TFT) LCDs. In such LCDs, each pixel has three comonents: R, G and B, signifying red, green and blue, respectively. Liquid crystals for each component are independently oriented by two polarizers, which are connected to a storage capacitor. The capacitor is in turn charged and discharged through a TFT to accommodate screen changes. Moreover, the capacitor must be refreshed at a high rate to maintain an appropriate voltage across the polarizers so that the corresponding liquid crystals remain properly oriented.
Backlight power: 200mW
Panel and Driver power: 20mW


Active Matrix (Thin Film Transistor, TFT)


Display Drivers

TFT characterization
LCD total pixel capacitance 5 pF
Roll-to-Roll manufacturing
Grayscale through pulse-width modulation

Image Quality


Last printed: 1.25

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