Driving Halogen Lamps

Halogen lamps are preferable to incandescents in many applications due to their increased brightness and longevity. Halogen bulbs are used in many varied applications, such as: - automotive headlamps - police vehicle-top flashers - ambulance, tow truck, fire engine-top flashers - machine vision - Fiber Optic illumination - large scale lighting Displays - medical and analytical equipment - school bus flashers Halogen Lamps vs. Incandescent A typical incandescent lamp is a glass bulb filled with an inert gas (such as krypton or argon) with a tungsten filament in the center. The filament glows as a potential difference is applied across the terminals of the bulb, giving off light and heat. However, the tungsten molecules are evaporating from the filament to cause this glow; the convection currents of the fill gas carry these molecules to the cooler inner surface of the bulb wall where they are deposited. This decreases bulb output and life in two ways: first, the effective filament diameter is decreased, which increases the resistance of the bulb, and second, the glass is "blackened" by these deposits. This mechanism limits the wattage that a conventional lamp CAN be used at if a satisfactory lifetime is to be achieved. short circuit and turn off the power FET in time (10┬Ás typical shutdown time) to prevent damage. This overcurrent shut- down CAN be delayed such that the initial inrush current doesn't cause a false triggering of this protection feature. This CAN easily be accomplished by adding an RC network to the threshold pin of the MIC5013 such that the initial trip point is very high, but decays with time to a reasonable value (figure 1).
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Driving Halogen Lamps application circuits
Driving Halogen Lamps application circuits



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