Patent ID: 7778002
Filing Date: 2010-08-17
Classification: F02P,H01F

Abstract:
1. An ignition apparatus comprising: a central core having a longitudinal axis, said core comprising magnetically-permeable material; primary and secondary windings outwardly of said core; a shield outwardly of said primary and secondary windings, said shield comprising magnetically-permeable material wherein said core, said primary and secondary windings and said shield are included in a magnetic circuit, said secondary winding having a high-voltage end configured for connection to a spark plug on which a secondary voltage is produced; and a suppression mechanism operatively coupled to said magnetic circuit configured to suppress ringing in said secondary voltage after a spark event, wherein said suppression mechanism includes a shunt resistor configured to be selectively connected across said primary winding, wherein said suppression mechanism includes a series combination of a silicon controlled rectifier (SCR) and said resistor connected across said primary winding, said SCR having a gate terminal coupled to a common node of a control circuit for selectively causing said SCR to conduct wherein said resistor is shunted across said primary winding, said control circuit including a transistor switch configured to close in response to a trigger signal indicative of when a secondary current arising from a spark event has decreased to a predetermined level, said switch being coupled between said common node and ground, said control circuit further including a parallel combination of an inductor and a pull up resistor connected to said common node, wherein when said switch is closed by said trigger signal, a charging current flows through said inductor, wherein when said switch is reopened, said inductor produces a closure signal on said common node coupled to said gate terminal of said SCR, thereby causing said SCR to conduct and connect said shunt resistor across said primary winding.