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Modeling of energy dissipation in thin-film electroluminescent indicator

Keywords:

M.K. Samokhvalov – Dr. Sc. (Phys.-Math.), Professor, Head of Department «Electronic Instrumentation Design and Technology», Ulyanovsk State Technical University
E-mail: sam@ulstu.ru
M.O. Takhtenkova – Ph. D. (Eng.), Senior Research Scientist, Research Division, Ulyanovsk Institute of Civil Aviation named after B.P. Bugaev
E-mail: pites@ulstu.ru


Thin-film electroluminescent capacitors raise interest among researchers, developers and users of information displays due to the possibility of formation of a flat solid-state display panels with high resolution. For the design of display devices and improve the effi-ciency of converting electrical energy into light emission it is necessary to study processes of scattering power in thin-film electrolu-minescent capacitor and their dependence on composition of the control circuit and the excitation conditions. In the technical literature the analysis of the scattering energy of the electric field is limited only by the scattering in the phosphor layer of the thin-film electroluminescent structures. But if we consider the processes in the energy consumption indicator devices based on electroluminescent capacitors should also take into account the dissipation of energy due to the nonzero resistance of the external voltage source and control circuit conductors.
Mathematical calculation of active power dissipation, the average electrical power dissipation in thin-film electroluminescent capacitor and series resistor in one period and the efficiency of power consumption in the condenser in the composition of the indicator control circuit was produced on the basis of obtained by the authors of the ratios. The efficiency factor of thin-film electroluminescent capacitor in the composition of the indicator control circuit is defined as the ratio of the active power dissipated in the phosphor to the total power consumption of display devices and control circuit. Mathematical modeling was carried out using the software package MathCAD. Using Microsoft Office Excel created volume surface charts, which are a convenient tool for assessment of possible input parameters of the control circuit to ensure the specified output parameters of the indicator element.
Linear dependence of active power on the frequency pronounced at small values of the resistance of the serial resistor. With the in-crease in the values of the resistor 500−2000 ohms, the dependence becomes nonlinear. At high frequency values and (or) the resis-tance value of the resistor, the illumination may not occur is a negative region on the chart. This is because the relaxation time becomes comparable with the value of the time duration of the excitation pulse voltage, and the phosphor ceases to have enough time to switch to the conducting state when the excitation of the luminescence centers. The value of the coefficient of efficiency of the thin-film capacitor reaches 98,8% with the smallest resistance value 1 Ohm at a frequency of 100 Hz. With the increase of the resistance coefficient decreases (to a value of 7.8% at R = 2 MOhm). Therefore, for the efficient operation of an electroluminescent capacitor in a schema indicator control is necessary to reduce the resistance of the conductors and the internal resistance of the voltage source.
Studies have shown that the three-dimensional surface diagrams are a convenient and clear tool for assessment of possible input pa-rameters of the control circuit, to ensure the specified output parameters of the indicator element, the desired power output and re-sponse time. The results are of importance for the harmonization of the circuit parameters and control modes the display devices based on thin-film electroluminescent capacitor.

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