GB1174641A - Improvements in Voltage Regulators - Google Patents

Abstract

1,174,641. Protective arrangements. ROBERT BOSCH G.m.b.H. 26 Jan., 1967 [26 Jan., 1966], No. 3911/67. Heading H2K. [Also in Division G3] An electrical supply system, e.g. for a motor vehicle, comprises a generator 10 connected to a battery 16 over output lines 14, 15 by way of a rectifier 13 and having a separate rectifier 17 for its field winding 12; a voltage regulator 21 including a transistor 22 which is connected, over normally-open relay contacts 28, in series with the field winding 12 and which controls the field current in dependence upon output voltage variations as detected by a circuit including a voltage divider 46, 47, 48, a reference Zener diode 43 and a control transistor 23; and a protective circuit 24 including a relay coil 29 which is connected over a switch 32 to the output lines 14, 15 and which is shunted by a thyristor 26 the control electrode of which is associated with a further output voltage sensing circuit including a voltage divider 58, 59, 60, a Zener diode 57 and a transistor 25. In normal operation the relay coil 29 is energized so that the contacts 28 are in the closed position as shown and the output voltage is maintained constant at a predetermined value by the action of regulator 21 in known manner. However, if, because of a fault in the regulator, the output voltage should become excessive, e.g. at least 5% higher than the rated value, the Zener diode 57 conducts to render transistor 25 conductive, whereby a signal is applied to the control electrode of thyristor 26 which itself conducts to short-circuit the relay coil 29; the contacts 28 then move to de-energize the field winding 12, so that the generator output falls almost to zero, an indicating light 36 then being energized from the battery 16 over a resistor 35, the contacts 28, the transistor 22 and a resistor 27. The thyristor 26 may be replaced by a transistor (Fig. 2, not shown).