Constant voltage regulator for road vehicle - has switching transistor circuit to limit voltage disturbance effects to on board microprocessor controller

A circuit is used to supply the starter of a road vehicle, is designed to avoid voltage disturbances in a microprocessor based ignition control system. The constant voltage regulator circuit (1) is coupled to the battery over a diode (D1) and has an input power transistor (Tr1) coupled to a first stage control transistor (Tr2). The arrangement ensures a small emitter-base current over a resistor (R2) and the control transistor for large changes in battery voltage. A non linear voltage divider provides voltage control and is formed by a Zener diode (D3) and a second control transistor (Tr3). Diodes (D6,D7) and resistors (R4,R5) provide a reference for the second control transistor.