Internal combustion engine ignition device

In an internal combustion engine with a spark plug having electrodes between which an arc is formed for igniting an air-fuel mixture in a cylinder, an engine ignition device comprising:

• means for providing direct current voltages;
• a first transformer having a primary winding and a secondary circuit having first and second secondary windings wound in mutual phase-opposition forming a first transformer secondary circuit output;
• said first transformer secondary circuit output including two electronic switches respectively connected in series between said voltages from said direct current voltage means, each switch being controlled by a respective one of said first and second secondary circuits of said first transformer;
• a high voltage generator for selectively supplying the spark plug for triggering an ignition arc, said high voltage generator including a resonant circuit supplied by said first transformer secondary circuit output at a resonant frequency of said resonant circuit for supplying the spark plug with a resonance-amplified voltage suitable for causing an ignition arc between the electrodes of the spark plug;
• said high voltage generator further including a second transformer having primary and secondary circuits and being connected between said first transformer and the spark plug;
• said resonant circuit being connected between said second transformer and the spark plug and being formed by a series inductance in said secondary circuit of said second transformer and a parallel capacitance on the spark plug;
• measuring means for detecting a current in said primary circuit of said second transformer;
• and
• an oscillator for supplying said primary circuit of said first transformer the frequency of said oscillator being controlled according to the detected current in said primary winding of said second transformer.