GB1176861A - Improvements in Voltage Regulators. - Google Patents

Abstract

1,176,861. Automatic voltage control. ROBERT BOSCH G.m.b.H. Jan. 20, 1967 [Jan. 21, 1966], No.3112/67. Heading G3R. An electrical supply system, e.g. for a motor vehicle, comprises an alternator 10 which is connected over a rectifier 12 and output leads 13, 14 to a battery 15 and a load 17; controllable rectifiers 22, 23 connected in series with the generator field winding 18 so that the latter can be supplied with pulsating excitation current derived from the A. C. output of the alternator; a first voltage divider 36, 37 having its tapping point 35 connected over a diode 38 and respective balancing resistors 39, 40 to the control electrodes of the rectifiers 22, 23; and a transistor 19 having its collector-emitter path connected in parallel with the resistor 37 and having its base connected over a Zener diode 27 to the tapping point 29 of a second voltage divider 32, 33, 34 connected across the output leads 13, 14. In operation, so long as the output voltage is below a predetermined value both Zener diode 27 and transistor 19 are non- conductive, and the rectifiers 22, 23 are rendered conductive by virtue of the positive potential at the tap 35 so that excitation current flows in the field 18. At the predetermined value of output voltage Zener diode 27 conducts to render transistor 19 conductive, whereby the potential at tap 35 becomes negative, so that the rectifiers 22, 23 cannot fire; thus the average value of the field current is controlled in a manner such that the output voltage is maintained constant at the predetermined value. A further transistor 45 is rendered conductive, should the excitation current become excessive for any reason, to short-circuit the control electrodes of rectifiers 22, 23 and thus prevent their firing, whereby the alternator 10 and the rectifiers 22, 23 are protected against overload.