Abstract: An internal combustion ignition system includes a switching transistor, an ignition transformer, a ballast resistor and a current sensing resistor. The primary winding of the transformer, and these two resistors are in series with the collector emitter path of the switching transistor across a supply. A sensing transistor has its base-emitter across the current sensing resistor and its collector connected to control a by-pass transistor with its collector-emitter across the ballast resistor. The transistor is on whenever the current in the sensing resistor is below a set level, thereby allowing a rapid current build up when the switching transistor is switched on.