Study of the PWM Operation of the Tungsten Halogen Automotive Lamps

L. Makai, G. Hárs, G. Varga, and T. Torma (Hungary)

Keywords

Computer simulation, Pulse Width Modulation, Halogen automotive lamps, thermalelectric coupling

Abstract

The PWM (Pulse Width Modulation) operation of the automotive halogen lamps will be forced by the automobile manufactures with the introduction of the increased voltage batteries. Increasing the battery voltage could cause decrease in material cost (thinner wires needed) but the commercial automotive halogen lamps can not to operate at higher voltage. In order to contain this problem the lamps will be operated with a special type of square signal called PWM signal. This operation could cause a decrease in lamp life time due to the increased thermal and mechanical stresses of the incandescent filament, so the transient and steady state thermal behavior of the filament needs to be examined. In this article 3D computer models of the incandescent filament will be shown, in which the dependence of the filament temperature on the duty factor and frequency were examined in time, during the heat up process of the incandescent filament. The outputs of the model enable life-time evaluation, and the Fourier analysis of the periodic temperature and current density signals make it possible to determine the harmonics which could cause resonance, by so causing premature failure. The results of this investigation could help to find the optimal point of operation of the lamp.

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