GB957576A - Voltage regulators - Google Patents

Abstract

957,576. Automatic voltage control. JOSEPH LUCAS (INDUSTRIES) Ltd. April 3, 1963 [April 11, 1962],No. 13942/62. Heading G3R. A voltage regulator for a generator 8 supplying a D.C. load 9 includes a first transistor 15 having its emitter connected one output terminal 6 through a resistor 16 andto the other output terminal 7 through a Zener diode 17, and a second transistor 18 of opposite conductivity type to transistor 15 and having its emitter connected to a field winding 19 of the generator 8, its collector connected to terminal 6 over a diode 10, and its base connected to the collector of transistor 15. When the output voltage is low, the potential divider constituted by diode 10 and a resistor 11 maintains the collector voltage of transistor 18 negative with respect to the emitter voltage of transistor 15 which is thereby rendered conductive so that transistor 18 is also held on so that current flows in the winding 19. When the output voltage reaches a certain value as determined by the adjustable setting on a resistance chain 12, 13, 14, the Zener diode 17 breaks down and the emitter voltage of transistor 15 is held constant; any further rise in the collector voltage of transistor 18 results in the switching-off of the transistor 15, with consequential switching-off of the transistor 18, whereby the field current of the generator is controlled to maintain a constant output voltage. It is stated that the diode 10 serves to provide positive feedback between the transistors 15 and 18 whilst maintaining the change in collector voltage of the transistor 18 reasonably small, so that the change from the conductive to non-conductive state is rapid. The transistors 15 and 18, or these transistors and the diode 10, may be constituted by a single semi-conductor crystal (Figs. 2 and 3, not shown). Temperature compensation can be effected by using a temperature sensitive resistor in the resistance chain 12, 13, 14.