| 摘要 |
980,332. Automatic voltage control. STANDARD TELEPHONES & CABLES Ltd. July 14, 1961 [July 16, 1960], No. 25674/61. Heading G3R. [Also in Division H2] In a bridge-controlled voltage regulator the output circuit is protected from overload by disconnecting a control stage of the regulator via a feedback circuit from an indicating branch of the bridge. As shown, a load R L is supplied from an unregulated supply through a regulating transistor T1 controlled through a transistor T2 by a transistor T3 responsive to the output of a voltage responsive bridge network comprising resistors R1 R2, R3 and a transistor T4 the base-emitter bias of which is determined by a comparison between the line voltage and constant voltage from a potential divider connected across a Zener diode GL. On overload, the increase in voltage across a resistor R5, in series with the transistor T1 and the load R L , causes the load voltage to fall to a value which renders the transistor T4 non-conductive so rendering the regulating transistor T1 non-conductive which reduces the voltage across the load R L to a low value. When the fault causing the overload is eliminated the voltage regulator is rendered operative under no-load by energizing the bridge from the unregulated supply through a switch T and a resistor R6. Alternatively, when the output is loaded the voltage is applied through the resistor R5. In a modification, a transistor T5 is arranged to be momentarily connected in circuit until the regulating transistor T1 takes over. The switch-on can also be effected by biasing the base of transistor T3 from the unregulated supply through a switch T. In other embodiments, Figs. 2 and 3, not shown, the connections for the opposite polarity of supply and alternative transistors are set out. |
