Transistorized ignition systems

Claim 1

A transistorized ignition system for switching the primary winding of an ignition coil of an internal combustion engine, including infra-red operated pulse generating means consisting of an infra-red lamp, a photo-transistor detector and a bladed chopper disc driven in synchronism with the engine revolutions to thereby interrupt the infra-red beam from the lamp in timed relation therewith; means for ensuring that the photo-transistor produces cleanly switched square wave pulses without a trace of oscillation; lensing means associated with the lamp and phototransistor for ensuring that the infra-red radiation beams all converge at a point in the plane of the rotating chopper disc; a transistorized trigger circuit having a plurality of transistors arranged in cascade to be triggered in inverse relation to one another from the output of the photo-transistor; a transistorized power stage arranged to switch in inverse relation to the last stage of the trigger circuit, said power stage being in series with the primary winding of the ignition coil; means for slowing down the fast switch off of the power stage; and means for protecting the power stage against induced positive and negative going transients at the instant of switch off.