Spark ignition circuits

Claim 1

A spark ignition circuit comprising an output transformer having a primary and a secondary winding, a capacitor, half wave rectifier means for charging the capacitor from the secondary winding of the transformer, during collapse of flux therein the voltage across said capacitor being utilized to provide a spark across a spark gap connected across the capacitor, a transistor having a collector emitter path connected in series with the primary winding of the transformer and a source of d.c. supply, the circuit further including a switching transformer having a saturable core, a first winding on said core, a conductive path through which said first winding is connected in parallel with the primary winding of the output transformer, a second winding on said core to provide base drive for the transistor during the conduction period thereof, the transistor becoming substantially non-conductive when the core of the swItching transformer saturates, the core of the switching transformer being at least partially reset by the voltage induced in the primary winding of the output transformer during collapse of flux therein, said voltage being applied to said first winding through said conductive path, a third winding on said core and a resistor in series with the capacitor and through which the charging current of the capacitor flows, said resistor being connected in parallel with said third winding, the current flow in said third winding acting to assist re-setting of the core of the switching transformer.