Abstract: An ignition system for an internal combustion engine comprises a voltage boosting means which generates a high DC voltage by boosting a low DC voltage, a capacitor which charges the high DC voltage from the voltage boosting means, and ignition coil means having a secondary winding to which the high DC voltage is applied from the boosting means, wherein a high capacitive energy charged within the capacitor is supplied into one of spark plugs located within a corresponding engine cylinder in which a spark discharge has started and subsequently the output energy from the boosting means is supplied into that spark plug via the secondary winding of the ignition coil. Consequently, the ignition energy can sufficiently be supplied immediately after an ignition start to which a combustion characteristic is closely related and the complete combustion of air-fuel mixture can be achieved over the whole range of engine revolutional speed.

Abstract: There is provided an engine ignition device which generates a high voltage in the secondary windings of the ignition coil through switching on and off of the electric current flowing in the primary windings by means of an ignition circuit. The generated high voltage is impressed on the ignition plugs to initiate ignition, and, at the same time, the high voltage is boosted by a DC-DC converter connected to the secondary windings and is supplied continuously to the ignition plugs, to prolong the discharge duration. There is further provided a DC-DC converter controlling circuit to control the DC-DC converter to initiate ignition synchronous with the ignition signal output and also to reduce the operating time of the DC-DC converter as the engine increases its speed.