GB882994A - Improvements relating to direct voltage stabilisers - Google Patents

Abstract

882,994. Automatic voltage control systems. ELECTRIC & MUSICAL INDUSTRIES Ltd. Jan. 31, 1958 [Jan. 31, 1957], No. 3368/57. Class 38 (4). [Also in Group XL (c)] The D.C. voltage applied to a load is stabilized by connecting a capacitor across the load and charging it intermittently from a D.C. source through a switching transistor or discharging it through a shunt transistor, the "on/off" ratio being controlled in accordance with deviations in output voltage. The load 12 and capacitor 13 are supplied from a rectifier 3 through parallelled transistors 6, 7. The load voltage is detected by an emitter-coupled pair of transistors 31, 32. The base potential of transistor 31 (and hence the emitter potential of both transistors) is stabilized by a Zener diode 35, and the base potential of transistor 32 is proportional to load voltage so that with transistors 6, 7 conducting and the load voltage increasing, the collector potential of transistor 32 becomes less negative causing the transistor 24 to be cut off. Transistor 24 is cross-coupled with a transistor 23 to form a bi-stable pair, hence transistor 23 now conducts causing the two-stage emitter-follower amplifier 17, 16 to cut off and so cut off the switching transistors 6, 7. The resulting fall in load voltage reverses the above and the cycle repeats. Transistors 6, 7 and 16 are arranged to bottom when conducting to reduce power losses. Reference has been directed by the Comptroller to Specification 853,340.