Circuit arrangement for driving a solenoid valve, especially for fuel-injection valves

摘要

A solenoid valve is switched in a reciprocating manner between an open position and a closed position, by means of a transistor. A pulse-width modulated squarewave signal from a microcomputer is used as a reference signal. In order to keep the magnet current constant in the event of temperature and hence resistance changes in the magnet winding, a comparator stage is provided in which an amplitude comparison is carried out between the magnet current as the actual value and an analogue voltage which is formed from the squarewave signal and is pulsed in synchronism with the squarewave signal. The output signal of the comparator stage switches the transistor at the frequency of the duty ratio and a very high repetition frequency, as a result of which a temperature-independent mean value of the operating voltage applied to the solenoid valve is achieved. <IMAGE>