Regulated power supply with current regulating circuit

Abstract

A power supply which includes terminals for connection to an electric power source, a storage capacitance, an electrical charging circuit and an operative arrangement for connecting the storage capacitance in series with the charging circuit across the terminals. The power supply has a charging circuit which includes a first resistor, a second resistor, a third resistor and a rectifier, constituted by at least one diode, in series. A control stage includes a first transistor, which has a collector-emitter path and a base-emitter path. The transistor is operatively connected so that the base-emitter path is connected in parallel with the first resistor. A fourth resistor is provided, the fourth resistor being connected in series with the collector-emitter path of the transistor and the third resistor. In one embodiment, the charging current carrying stage includes a plurality of additional transistors, connected in Darlington configuration, which are controlled by the first transistor which is operatively arranged to be controlled by a signal which corresponds to the D.C. voltage output and is produced by a D.C. voltage sensing circuit and responds to the unfiltered output from the rectifier. An optical coupler is connected between the D.C. output voltage sensing circuit, which may be a Schmidt trigger, and the control stage. A field-effect transistor, preferably a MOSFET, can replace the plurality of transistors in the Darlington configuration.