IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINE

Current flow to the ignition coil during low-speed operation of the engine, is controlled by an auxiliary control switch which is connected in shunt with the primary of the ignition coil. Serially connected with the primary is a main control switch which is controlled to close until current through the primary has reached a certain value, at which time the main switch opens and the shunt auxiliary switch is closed to permit continued inductive current flow through the coil and thus store ignition energy, the cycle repeating to maintain current flow through the primary at a level to store sufficient energy for the ignition spark which, at the ignition instant, effects opening of the shunt circuit by opening the auxiliary switch while also opening the circuit to the primary, thus providing a high-voltage pulse which provides for sparking of the spark plug. The sensor for current flow through the primary is preferably a resistor which, when the voltage drop thereacross exceeds a predetermined level, controls changeover of a transistor.