Circuit arrangement for monitoring the operating voltage in the ignition system of a motor vehicle

摘要

In ignition systems for internal combustion engines, faults which are superimposed on the battery voltage and which lead to a brief glitch in the supply voltage of the ignition can, under certain conditions, bring about an ignition spark and thus lead to misfiring. The causes of the faults which lead to such misfiring include, for example, a connection terminal which is not seated tightly on the battery of the vehicle or brief opening of the operating switch. A circuit arrangement is described which performs monitoring of the supply voltage and which in the event of an excessively low voltage switches off a current flowing across the ignition coil in such a way that no ignition spark is produced. The switching off takes place by means of a feedback loop which limits the primary voltage of the ignition coil or the collector voltage of the power transistor to correspondingly small values. So that the feedback loop operates even when there is no supply voltage, it draws its feed voltage from the induced primary current of the ignition coil.