GB942675A - Improvements relating to automatic voltage regulating systems for vehicle generators - Google Patents

Abstract

942,675. Automatic voltage control systems. R. BOSCH G.m.b.H. June 24, 1960 [June 27, 1959], No. 22122/60. Heading G3R. In an automatic direct voltage regulator for a vehicle lighting system, two power transistors are connected by their emitter-collector paths in series with a field-winding of a generator and a potential divider, comprising two resistors, is connected in parallel with the series arrangement, the junction of the resistors being connected to the base of one of the transistors; the ratio of the values of the resistors corresponds to the ratio of the required emitter-collector voltages of the transistors. As shown, delta-corrected windings 11-13 of an alternator 10 supply a battery 15 through a three-phase rectifier 21, lines 16, 18 and a reverse-current rectifier 18. A field 14 is connected in series with transistors 35, 36 across lines 16,18 and is biased from a transistor 41, connected as a blocking oscillator, so as to maintain the line voltage constant. The voltage at a tapping 61 of a potential divider 62-64 is opposed by the voltage across a Zener diode 43 so that the transistor 41 only becomes conductive when the line voltage exceeds a predetermined value. The increasing collector current passing through a winding 50 of a transformer causes voltages to be induced in windings 45, 46 which are connected so as to cause blocking oscillations to occur. The voltage across a capacitor which is charged through rectifiers 48, 52 from windings 45,46 renders the transistor 35 non-conductive and since the base potential of the transistor 36 is fixed by a potential divider 37, 38 this transistor is also rendered non-conductive. Increase in the effective resistance of transistors 35, 36 causes the current through the field 14 to fall and to reduce the line voltage until the blocking oscillations are stopped when the line voltage falls below the predetermined value. The voltage at the junction of the windings 45,46 is maintained constant by a crystal diode 44 having a non-linear characteristic. In a modification, the junction between transistors 35, 36 is connected to line 16 through a resistor and to the junction of resistors 37, 38 by a diode so as to ensure that the transistor 36 is fully non-conductive when transistor 35 is fully non-conductive. In a further modification, the emitter-collector paths of three transistors are connected in series with the field winding, the base voltages of two of the transistors being'determined by potential dividers. The output current from the alternator 20 is limited by developing across a condenser 32 a direct voltage proportional to load current through a current transformer 24 and rectifiers 30, 31 connected as shown. At a predetermined line current the voltage across the condenser 32 is such that a diode 60 conducts to apply a bias to the transistor 41 through the Zener diode and initiates blocking oscillations.