Power Switch For Cars

05 Motorist are generally well aware that car fuses do not blow just like that. None the less, when something appears to be amiss in the electrical circuit, a new fuse is nearly always fitted prior to in- vestigating the possible cause for the malfunction, which then, of course, costs two fuses. The circuits shown here are short circuit proof power switches, or electronic fuses with switch control dimensioned for relatively heavy (lamp) loads in a car. Both circuits are com- posed of a power switch, Ti, and a cur- rent limiter, T 2 . The circuit is fully short- circuit and overload resistant, provided Ti is adequately cooled, and the whole unit is constructed in a sturdy enclos- ure. The circuit in Fig. la has the lower voltage drop of the two, while that in Fig. lb is used when a TO-218 style Type MJE2955T or TIP2955 is not obtainable. It is interesting to note that the plastic TO-218 package is mechanically inter- changeable with the wellknown TO-3 outline, and enables ready mou...