GB1048222A - Improvements in voltage regulators for generators - Google Patents

Abstract

1,048,222. Automatic voltage controls. ROBERT BOSCH G.m.b.H. Jan. 15, 1964 [Jan. 16, 1963], No. 1767/64. Addition to 1, 035, 071. Heading G3R. In a voltage regulator of the type in which a main transistor in series with the field winding of a generator is controlled in dependence upon output voltage variations, there is provided a controllable semi-conductor rectifier for protecting the transistor from overloads which might arise from a short circuit in the field winding. As shown, the output voltage of a generator 13 is maintained constant by a voltage regulator comprising a main transistor 22 in series with the field winding 14 of the generator and a control transistor 23 for controlling transistor 22 in dependence on output voltage as detected by a potentiometer 29 and a Zener diode 30. A controllable rectifier 36, having its anode-cathode path connected in parallel with the emitter-base path of the transistor 22, has its control electrode connected to the positive lead 16 of the generator, and the arrangement is such that this rectifier is rendered conductive when the emitter current of the main transistor exceeds a maximum permissible value; the conducting rectifier 36 then short circuits the emitter-base circuit of transistor 22 which is thus switched to its blocked state so that the emitter current is reduced to a safe value. The main transistor may be a compound transistor, and the control electrode of the controllable rectifier may be associated with a potentiometer. (Fig. 3, not shown).