Yoshiteru Watanabe

Design considerations for a CCFL and its surroundings

— A TFT-LCD module includes a backlight unit, which normally uses one or more thin cold-cathode fluorescent lamps (CCFLs). Since a CCFL is driven at high frequency and high voltage, there is a leakage current. In recent years, TFT-LCD modules have been getting thinner, with a wider screen size and a narrower frame; consequently, the leakage current has come to have a significant influence on the design of the LCD module and the dc/ac inverter unit that generates the high-voltage ac to drive the CCFL. It is actually impossible to probe the inside of a working CCFL because of the high voltage, high frequency, and low electric discharge current. This fact adds to the difficulty of the analysis and the design. This paper proposes an electrical model of a CCFL and a simulation method using the model, making it possible to analyze the inside of the CCFL and to provide some important parameters that are required for the basic design of the LCD module and the dc/ac inverter, before the construction and measurement of actual samples.

The application of an electric probe for measuring local concentrations of slurry.

An electric conductivity method was applied to the measurements of local concentrations of spherical particles in slurry.A probe, equipped with two ringlet electrodes on its surface, was utilized for measuring the resistivity of water and slurry.An AC source was used to supply current to the electrode circuit and this was effective in eliminating the accumulation of scales and bubbles which gave rise to instability on the electrode surface.Since the resistivity increment due to solids was expressed as the relative resistivity divided by that of water, the effects of water resistivity fluctuation and position relative to the pipe wall were eliminated.Probe calibration carried out both in fluidized tests and in flow tests through a vertical downward pipe showed dependence on particle size.The data obtained by the two methods indicated different tendencies; the fluidized tests were plotted as straight lines and the flow tests were plotted as curved lines on log-log representations.Since the discharge concentration calculated using the calibration curves from the fluidized tests showed lower values in the high concentration region, the calibration curves obtained from the flow tests were used for concentration measurement.The curves were well represented by a modified version of Maxwells equation including compensated terms for particle size and concentration.The accuracy of the calculated discharge concentration in a non-conductive horizontal pipe and in a conductive vertical pipe was 7.1% in the worst case.Although the application of this method was limited to particles with narrow size distributions, a consistent picture of solid concentration profiles could be presented.