Operation of Plasma Display Panel

Operation of Plasma Display PanelPlasma display is a matrix of gas-filled cells put between two parallel glass surfaces. The gaseous medium is usually neon or xenon. Gas discharge occurs between the transparent electrode on the front side of the screen and the address electrodes on its back side. Gas discharge causes ultraviolet radiation, which, in turn, initiates the visible luminescence of luminophor. In color plasma displays each pixel of the screen consists of three identical microscopic enclosures which contain the inert gas (xenon) and have two electrodes, the front and the rear one. After high-frequency voltage is applied to the electrodes, high-frequency capacitance discharge occurs. In the interelectrode space plasma is generated. It emits ultraviolet light that falls on the luminophors in the bottom of each enclosure.The luminophors emit one of the primary colors: red, green or blue. Then the colored light passes through glass and goes to a viewer's eyes. Thus, in plasma technology pixels work like luminous tubes, but they can hardly be used to make panels.The first difficulty is the size of a pixel. A sub-pixel of a plasma display panel has the volume of 200 microns x 200 microns x 100 microns, and it is necessary to put a few million pixels, one by one, to make a panel.Secondly, the front electrode should be as transparent as possible. For this purpose indium and tin oxides are used, as it conducts current and is transparent. Unfortunately, plasma displays can be so large, and the oxide layer may be so thin, that during the flow of high currents a voltage drop across the resistance of the conductors will occur, which will greatly reduce and distort signals. Therefore it is necessary to add chromium intermediate connecting wires, it is a better conductor, but, unfortunately, it is not transparent.Finally, we need to find the right luminophors. They depend on the desired color:These three luminophors give the light with a wavelength between 510 and 525 nm for green, 610 nm for red and 450 nm for blue.The last problem is pixel addressing, since, as we have already seen, it is necessary to change the color intensity independently for each of the three sub-pixels in order to get the desired shade. The 1280x768-pixel plasma display panel has about three million sub-pixels, and, subsequently, about six million electrodes. As you all understand, it is impossible to make six million tracks to control of sub-pixels individually, so the tracks should be multiplexed.The front tracks usually align into solid lines, and the rear one - into columns. Electronics built-in in the plasma panel with the help of a matrix of tracks selects a pixel to be lighted up on the panel. It is completed very fast, so you can't notice anything, just like beam scanning in CRT-monitors.

Category:

Science & Technology

Tags:

• cell
• discharge
• display
• display information
• luminescence
• operating principle