GB950503A - Improvements in or relating to direct current to direct current convertors - Google Patents

Abstract

950,503. Converting. GENERAL ELECTRIC CO. Ltd. Dec. 4, 1962 [Dec. 5, 1961], No. 43492/61. Heading H2F. [Also in Divisions G3 and H3] In a D.C. to D.C. converter, a semi-conductor controlled rectifier 3, a winding 4 of a saturating current transformer 5, a rectifier 6 and the primary winding 7 of a pulse transformer 8 are connected in series across input terminals 1, 2; the output current for a load 16 is derived from a capacitor 14 which is connected to a secondary winding 11 of the transformer 8 over a rectifier 12, and an oscillator 18 produces a continuous train of firing pulses which are applied to the gate of the S.C.R. 3, by way of a control circuit 19 which includes the emitter/collector path of a transistor 23 and the winding 25 of a transformer 21, the base of transistor 23 being connected to a potentiometer 15 in parallel with the capacitor 14. The arrangement is such that transistor 23 is conducting when the voltage across capacitor 14 is below a desired value, whereby control pulses are supplied continuously to the controlled rectifier 3; each time the rectifier 3 fires it is rendered quiescent shortly afterwards by a circuit including transformer 5 and capacitor 10 (see Division H3), so that current pulses supplied to winding 7 of transformer 8 result in a signal in winding 11, which signal is rectified and smoothed, so providing an increased charge on capacitor 14; when this charge is such that the output voltage has the desired value, the collector/emitter path of transistor 23 is rendered non-conducting and firing pulses no longer reach the controlled rectifier 3. The output voltage of the converter is thus maintained at a desired value. A second control circuit 29, similar to the circuit 19, may be provided, this second circuit being arranged to operate in dependence upon load current, as sensed by the voltage drop across a resistor 30, whereby firing pulses are prevented from reaching the controlled rectifier 3 if the load current exceeds a predetermined value.