GB1400446A - Spark ignition circuits - Google Patents

Abstract

1400446 Ignition systems JOSEPH LUCAS (INDUSTRIES) Ltd 17 July 1972 [17 July 1971] 33694/71 Heading F1B The invention relates to spark ignition systems of the kind intended to operate from a source of D.C. supply and comprising an output transformer 11 having a secondary winding, a primary winding 12 on the transformer, a transistor 14 having its collector emitter path connected between the primary winding and the source of D.C. supply, circuit means for causing switching of the transistor whereby the primary winding of the transformer is periodically connected to the source of D.C. supply, a capacitor 27 charged through a rectifier 26 by the voltage developed across the secondary winding of the transformer and a barrier gap 28 in series with the capacitor 27 and a sparkplug 29, the barrier gap breaking down when the voltage across the capacitor attains a value determined by the barrier gap. Accoring to the invention the ignition system includes a switching transformer 15 having a saturable core, the switching transformer providing base drive for the transistor 14 during the conduction period thereof and the transistor becoming substantially non-conductive when the core of the switching transformer saturates. In amodification(not shown) a further winding is provided on the switching transformer 15 and is connected in parallel with a resistor in the secondary circuit of the transformer 11.