Plasma ignition system for an internal combustion engine

Abstract

An N cylinder internal combustion engine plasma ignition system comprises a DC-DC converter for boosting low DC voltage to high DC voltage. Each of N ignition energy charging circuits includes a first capacitor connected between the DC-DC converter and ground via first and second diodes. The capacitor is charged by the DC-DC converter. Each of N reverse blocked thyristors connected to a junction of the first diode and first capacitor selectively grounds an electrode of the corresponding first capacitor to discharge ignition energy stored in the first capacitor. For each cylinder a transformer connected between the first capacitor and a spark plug boosts and feeds the discharged energy to the plug. One end of the transformer primary winding is grounded via a second capacitor to generate a damped oscillation when the corresponding thyristor grounds the first capacitor. An ignition trigger signal generator sequentially triggers the corresponding thyristor in a predetermined ignition order whenever the engine revolves through a predetermined angle and supplies a pulse to the DC-DC converter in synchronization with the ignition trigger signal. Derivation of the high DC voltage is halted for a period of time according to the pulsewidth. Each of N core-less inductors connected in series with the secondary winding of a transformer restricts an abrupt large current flow from the corresponding spark plug, to extend the discharge duration of each spark plug and ignite the air-fuel fixture stably without misfire.