GB1174621A - Voltage Regulator - Google Patents

Abstract

1,174,621. Protective arrangements. ROBERT BOSCH G.m.b.H. 18 Jan., 1967 [19 Jan., 1966], No. 2655/67. Heading H2K. [Also in Division G3] An electrical supply system, e.g. for a motor vehicle, comprises a generator 10 connected to a battery 15 by way of a rectifier 12 and output leads 13, 14; a voltage regulator 16 including a switching transistor 18 which is connected together with a fuse 23 in series with the generator field winding 24 and which is controlled by way of a further transistor 19, in dependence upon output voltage variations as detected by a sensing circuit 35-39; and a protective circuit 17 including a relay coil 27 which is connected across the output leads 13, 14 in series with the collector-emitter path of a transistor 43, the normally open contacts 26 of the relay being connected in parallel with the field winding 24 and the base of the transistor 43 being connected over a Zener diode 45 to a voltage divider 50, 51, 52 also connected across the output leads 13, 14. In normal operation the arrangement is such that relay 27 is not energized, and the output voltage is maintained constant at a predetermined value by the action of regulator 16 in known manner. However, should an excessive voltage, e.g. 105-110% of predetermined rated output voltage, arise on the leads 13, 14, for example because of a collector to emitter short-circuit in the transistor 18 of regulator 16, the Zener diode 45 conducts to render transistor 43 conductive, thereby energizing relay coil 27 so that contacts 26 close; the current flowing through transistor 18 then rises momentarily to a value above the rating of fuse 23 which thus burns out, whereby the excitation current drops to zero and the generator 10 runs without load. A temperature dependent resistor may replace the transistor 43.