GB946214A - Improvements in or relating to electric power supply arrangements - Google Patents

Abstract

946,214. Automatic voltage control. GENERAL ELECTRIC CO. Ltd., and J. W. McPHERSON. Sept. 29, 1961 [Nov. 7, 1960; Dec. 22, 1960], Nos. 38231/60 and 44147/60. Heading G3R. A direct voltage stabilizer circuit 1 is supplied with a normal input and a standby input, e.g. of lower voltage, from a transformer 6 having a primary winding 5 connected to an alternating current source 4. The normal and standby inputs are derived from first and second secondary windings 7, 8 of the transformer and are respectively connected to the circuit 1 over rectifiers 9, 14 filters 10, 15 and switching transistors 11,16. The circuit 1 maintains a supply line 2 at a stabilized negative potential relative to an earth line 3 and comprises a series transistor 12 the conductance of which is controlled in known manner by an error sensing amplifier 3. In normal operation transistor 11 is biased into conduction and transistor 16 is cut-off by a bi-stable circuit 17 under the control of a voltage sensing network 18 connected across the filter 10; the transistor 12 then compensates for normal input voltage variations to maintain the output voltage constant. If, however, the input voltage increases to such a value that it would no longer be possible to stabilize the output voltage without damaging transistor 12, the signal supplied by the sensing network 18 changes the bi-stable circuit 17 from its first condition to its second condition whereby transistor 11 is cut-off and transistor 16 is rendered conductive so that the standby input of lower voltage is applied to the circuit 1 which can thereby operate to maintain the output voltage at the desired level. If the normal input voltage falls to a value within the normal range the network 18 and the bi-stable circuit 17 operates to restore the normal input to the circuit 1. The standby input may be of higher voltage than the normal input and only be used when the voltage of the normal input falls to a low value at which it would no longer be possible to maintain the output voltage at the required stabilized potential. Specification 946, 212 is referred to.