Patent ID: 7028676

Claim:
An inductive ignition system comprising: a stator provided with an ignition coil having a primary winding connected to an ignition-current circuit comprising a first current-control switch, and a secondary winding connected to a spark plug; a rotor having a magnet to cyclically produce into the stator, a variable magnetic flux during each revolution to induce into the primary winding voltage signals, each comprising four voltage pulses alternately of opposite polarities, and for the circulation of an ignition current in the primary winding circuit; a first control circuit comprising a current-control resistor connected in series to the current-control switch; a second control switch having a control electrode connected between the current control resistor and the current control switch to trigger the latter by turning ON and OFF the same; a second control circuit being provided to control the minimum rotational speed at which spark the engine; the second control circuit comprising a voltage comparator having an open-collector outlet connected to the control electrode of the second control switch, a reversing inlet of the voltage comparator being connected to a first reference voltage circuit, a non reversing inlet of the voltage comparator being in turn connected to a timing circuit; the timing circuit comprising a timing capacitor to provide the non reversing inlet of the voltage comparator with a second inlet voltage higher than the first reference voltage, at each charging of the timing capacitor, in a time at least equal to a time necessary for rising the current flowing in the current-control resistor at a value for triggering the second control switch, causing the turning OFF of current-control switch upon reaching said minimum rotational speed, to spark the engine.