Abstract: A frequency converter including a single-ended blocking frequency converter for generating a plurality of output voltages. Additional secondary circuits are provided so as to obtain an inexpensive circuit and the additional secondary circuits are provided in addition to a blocking frequency converter secondary circuit and each contain a rectifier diode 13, a switch 12, 12a which are controlled by controller 16, 21 which are arranged in the series branch and each contain a free-wheeling diode 17 in a shunt arm and also contain a LC element 16, 16 which is connected to the free-wheeling diode 17. The frequency converter circuit can be used to feed equipment of electrical communication transmission systems.

Abstract: The invention relates to a power supply unit for data viewing devices, which, from a main alternating voltage produces at least one d.c. voltage for the operation of the data viewing device, where the power supply unit is in the form of a switching power supply unit and contains an oscillator which produces signals which determine the switching frequency of the switching power supply unit and where the data viewing device contains a pulse generator which, in order to produce an image on a screen, produces timing pulses of a given repetition frequency and a given duration.More particularly, the control stage for a switching power supply unit of a data viewing device having a display screen includes a free-running oscillator whose frequency is synchronized by timing pulses from a pulse generator. These pulses are of a predetermined repetition frequency and a given duration. The oscillator is preferably an astable multivibrator.

Abstract: A single pulse blocking converter for generating of a constant output voltage has a switching transistor and a transformer wherein a feedback effect of the transformer supplies the base current of the switching transistor by way of the collector-emitter path of a driving transistor. The driving transistor is controlled by means of a control transistor in dependence upon a measured voltage which is in proportion to the output voltage of the blocking converter. The circuit is particularly characterized in that an auxiliary circuit is provided with a transistor which, during the transition of the switching transistor from the conductive into the blocked condition, applies a blocking voltage to the control path of the switching transistor and in that, by means of a periodic resetting of the auxiliary circuit by the pulses from a pulse generator, the blocking voltage is switched off and a new switching period is initiated for the switching transistor.