Ignition system with safety circuit

Claim 1

In an ignition system for an i.c. engine with a magnetic system for generating ignition energy, an ignition coil, a spark plug connected to the secondary winding of the coil, the primary winding of the coil being connected to an ignition switch switchable by triggering, a detector connected to establish a reference time for every spark, a micro-computer with a static memory, a timer, an oscillator, a comparator in which timer pulses and a reference code from the timer and memory respectively are brought into coincidence in order to supply a trigger pulse via output circuits to the said ignition switch, and a reset input on said micro-computer for receiving reset pulses from a pulse generator, the improvement wherein the pulse generator comprises an RC-circuit connected to be chargeable by said output circuits of the micro-computer and to discharge between the trigger pulses to a residual voltage in dependence of the r.p.m. of the engine, and further comprising a sensing circuit coupled between the RC-circuit and said reset input for generating said reset pulse proceeding from a residual voltage which falls below a predetermined reference value for the residual voltage.