GB1040261A - An improved electrical power supply circuit - Google Patents

Abstract

1,040,261. Automatic voltage control. SOLARTRON ELECTRONIC GROUP Ltd. June 17, 1963 [June 21, 1962], No. 2400/62. Heading G3R. A power supply circuit for supplying a stabilized voltage at output terminals 25, 26 comprises input terminals 16, 17 connected to an unstabilized unidirectional voltage source 10-15, a switching transistor 18 and a capacitor 19 connected in series across the terminals 16 and 17, a circuit including a transistor 21 for stabilizing the voltage appearing across the capacitor 19 and a bi-stable control circuit 20 which controls the switching transistor 18. The impedance of transistor 21 is controlled in known manner, by a circuit including a potential divider 22, 23, a reference Zener diode 27 and an amplifier 24, to maintain a constant voltage at terminals 25, 26, and the power dissipation in the transistor 21 is kept below a pre-determined level by the operation of control circuit 20 whose input circuit is connected across the transistor 21 and whose output is applied to the base of transistor 18. The arrangement is such that transistor 18 is switched continually from a fully conducting state, when capacitor 19 charges from the unstabilized input source, to a non-conducting state, when the capacitor 19 discharges into the load, as the voltage across transistor 21 rises and falls within predetermined limits. Thus, neither transistor can be overloaded, since transistor 18 is either non-conducting or fully conducting whilst the voltage across transistor 21 is maintained below a level at which the power dissipation would be excessive. The transistor 18 may be connected in parallel with the input terminals and the transistor 21 in parallel with the load. Valves may replace the transistors in the circuit which may also be arranged to maintain current constant. A detailed circuit arrangement including overload protection is described with reference to the drawing accompanying the complete Specification (not shown).