Plasma ignition system for internal combustion engine

Abstract

A plasma ignition system for an internal combustion engine which varies a discharge time of a plasma ignition energy charged capacitor according to the engine operating condition, e.g., the current engine speed. The plasma ignition system comprises: (a) a plurality of plasma ignition plugs, each provided within the corresponding engine cylinder; (b) a DC-DC converter which produces and outputs a high DC voltage; (c) a plurality of first capacitors each for charging and discharging the high DC voltage from the DC-DC converter; (d) a plurality of switching circuits each connected to the corresponding first capacitor for defining the discharge time interval of the corresponding first capacitor in response to a trigger signal inputted thereto at a predetermined ignition timing; (e) a trigger signal generator which generates and outputs the trigger signal to each corresponding switching circuit, the width of the trigger signal being varied so as to become narrower when the engine rotates at a speed higher than a predetermined value; and (f) a plurality of transformers each connected to the corresponding capacitor which receives the high DC voltage from the corresponding first capacitor through the corresponding switching circuit at the primary winding thereof and boosts the high oscillation voltage generated at the primary winding thereof according to the winding ratio between the secondary and primary windings thereof so as to apply the boosted voltage to the corresponding plasma ignition plug.