Circuit arrangement for supplying a 12 volt lamp from a 24 volt DC source, especially for use in a microfilm reader

摘要

A circuit is described for supplying a 12 volt lamp from a 24 volt DC source, especially for microfilm readers, by means of which the 12 volt lamp can be operated from a 24 volt DC source without any bias resistor which destroys energy and generates heat. As components which are essential to the invention, the circuit contains a power stage to whose output the 12 volt lamp is connected without any intermediate smoothing means, as well as a frequency transmitter which pulses the power stage in such a manner that 24 volt pulses appear at the output of the power stage at such a frequency and at such time intervals that, overall, an r.m.s. voltage of 12 volts DC is available, which is then supplied to the 12 volt lamp.