GB962987A - Improvements in or relating to vehicle lighting systems incorporating a generator and a voltage regulator - Google Patents

Abstract

962, 987. Automatic voltage control. ROBERT BOSCH G.m.b.H. Nov. 11, 1960 [Nov. 23, 1959], No. 38738/60. Heading G3R. [Also in Division H1] A voltage regulator for the generator 10 of a vehicle lighting system comprises a power transistor 40 which is connected to the generator field winding 14 and which is controlled by a second transistor 41 having its base connected over a Zener diode 43 to a potential divider bridge 45 connected across the output leads 16, 18 of the generator, the potential divider containing a temperature sensitive resistor 48 thermally associated with a rectifier 52 in one output lead. When the generator 10 is driven the voltage between the leads 16, 18 builds up to a value Ug, e.g. 28 V, and a current J L flows to charge a battery 15. Should the generator voltage tend to increase above the value Ug the voltage Us effective at the tapping point 51 of the bridge 45 becomes greater than the breakdown voltage of the Zener diode 43 which thus conducts a control current J S from the base of transistor 41, whereby transistor 41 becomes conductive and initiates a control action, through the intermediary of a transformer 57 and condenser 61, to block transistor 40 so that the field current, and hence the output voltage of the generator, is reduced. Should the current increase beyond the admissible maximum value, e.g. by the switching in of an additional device 64, the temperature of the rectifier 52 carrying the increased load current will rise and the resistance of the associated resistor 48 will also rise, causing a rectifier 51 in the diagonal of the bridge 45 to conduct whereby the Zener diode 43 will also become conductive so that the regulating action becomes effective before Ug reaches its normal operating value of 28 V. The system is thus protected against a temperature rise which would cause the rectifier 52 to lose its rectifying action.