Transistor ignition system having ballast resistor shunt to maintain constant current through the ignition transformer

Claim 1

IN AN IGNITION SYSTEM ADAPTED TO BE ENERGIZED FROM A VOLTAGE SOURCE WHICH IS SUBJECT TO VARIATION IN OUTPUT VOLTAGE, SAID VOLTAGE SOURCE HAVING A PAIR OF OUTPUT TERMINALS, A TRANSISTOR HAVING AN EMITTER, A COLLECTOR AND A BASEAN IGNITION TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A BALLAST RESISTOR, MEANS CONNECTING SAID BALLAST RESISTOR, THE EMITTER TO COLLECTOR PATH OF SAID TRANSISTOR AND THE PRIMARY WINDING OF SAID IGNITION TRANSFORMER IN SERIES BETWEEN SAID OUTPUT TERMINALS, A SWITCHING MEANS, MEANS FOR CONNECTING THE BASE OF SAID TRANSISTOR TO A TERMINAL OF SAID SOURCE THROUGH SAID SWITCHING MEANS, AND MEANS FOR MAINTAINING THE MAXIMUM CURRENT FLOW THROUGH SAID PRIMARY WINDING SUBSTANTIALLY CONSTANT REGARDLESS OF THE VOLTAGE OF SAID SOURCE OVER A PREDETERMINED RANGE OF VOLTAGE VARIATION THEREOF AND FOR APPLYING SUBSTANTIALLY THE TOTAL VOLTAGE OF SAID SOURCE ACROSS SAID PRIMARY WINDING DURING THE CURRENT BUILDUP THERETHROUGH, COMPRISING A VARIABLE CONDUCTIVITY SHUNTING MEANS CONNECTED ACROSS SAID BALLAST RESISTOR, MEANS TO SENSE THE VOLTAGE APPEARING ACROSS SAID BALLAST RESISTOR, AND MEANS TO SO VARY THE CONDUCTIVITY OF SAID SHUNTING MEANS IN RESPONSE TO THE VOLTAGE APPEARING ACROSS SAID BALLAST RESISTOR AS TO KEEP THE MAXIMUM CURRENT FLOW THROUGH SAID PRIMARY WINDING CONSTANT OVER A PREDETERMINED RANGE OF VARIATION OF SAID SOURCE.