Ignition apparatus for internal combustion engine

An ignition apparatus for an internal combustion engine, the ignition apparatus comprising:

• a main ignition circuit configured to perform an energization control of a primary coil of an ignition coil, thereby causing a spark discharge in an ignition plug;
• an energy input circuit configured to selectively input electrical energy to the primary coil during the spark discharge started by operation of the main ignition circuit, thereby applying a secondary electric current in the same direction to a secondary coil of the ignition coil, the energy input circuit also configured to keep the secondary electric current at a secondary electric current command value, thereby continuing the spark discharge started by operation of the main ignition circuit;
• and
• an engine control unit (ECU) configured to:
• determine, when the secondary electric current drops below a predetermined threshold value during a determination period, that blow-off has occurred, the determination period being a predetermined time period ΔT from the start of the spark discharge by the main ignition circuit;
• and control electrical energy to be inputted by the energy input circuit to the primary coil during the spark discharge started by operation of the main ignition circuit in a next cycle when it is determined, based on a determination result of the engine control unit (ECU), that blow-off has occurred during the spark discharge by the main ignition circuit.