Ignition control apparatus

An ignition control apparatus applied to an internal combustion engine that includes a spark plug, the spark plug being caused by an induced voltage to generate a plasma discharge for igniting a combustible mixture within a combustion chamber, the induced voltage being generated by switching on and off by a switching element included in a drive circuit, the ignition control apparatus comprising:

• a processing system, including a processor for executing a process such that the ignition control apparatus is at least configured to perform:
• an in-cylinder pressure acquisition which acquires a pressure within the combustion chamber as an in-cylinder pressure;
• a frequency signal transmission which transmits a frequency signal to the switching element, the frequency signal causing switching on and off to be repetitively performed by the switching element at a predetermined frequency;
• a weak discharge generation which causes the frequency signal transmission to transmit the frequency signal during an intake stroke and control the frequency signal such that a weak discharge, which has a secondary current which is lower than that of the plasma discharge, for igniting the combustible mixture is generated a plurality of times at the spark plug;
• and
• a control of the frequency signal such that a duty ratio, which is a ratio of a switched on time period to a sum of the switched on time period and a switched off time period of the switching element, is changed in accordance with the in-cylinder pressure that is acquired by the in-cylinder pressure acquisition, such that a frequency of generating the weak discharges at the spark plug during a time period in which the frequency signal is being transmitted becomes higher than a predetermined frequency.