Conventionally, a control apparatus that controls an ignition apparatus of an internal combustion engine and controls ignition of an air-fuel mixture in a combustion chamber is known. For example, in a control apparatus described in PTL 1, a discharge time of a spark plug is measured. Operation of an internal combustion engine is controlled based on the measured discharge time.
In addition, as a related technology for reducing load placed on the spark plug, suppressing needless power consumption, and continuing spark discharge, the present applicants have proposed the following energy input circuit (refer to Japanese Patent Application No. 2013-082958; this technology was unpublished at the time of filing of the Japanese application serving as basis for priority rights of the present application).
The energy input circuit inputs electrical energy from a negative side of a primary coil before a spark discharge (referred to, hereafter, as a main ignition) started by a so-called full-transistor type ignition circuit goes out, and thereby continuously sends a secondary current that is in the same direction as the main ignition. As a result, the energy input circuit enables the spark discharge generated as the main ignition to be continued over an arbitrary period.
Hereafter, the spark discharge that is continued by the energy input circuit, that is, the spark discharge following the main ignition is referred to as continued spark discharge. In addition, the period over which the continued spark discharge continues is referred to as a continued discharge period.
The energy input circuit adjusts the secondary current and maintains the spark discharge by controlling a primary current during the continued discharge period. In addition, as a result of the secondary current during the continued spark discharge being adjusted, the load placed on the spark plug can be reduced, needless power consumption can be suppressed, and spark discharge can be continued.
Furthermore, to enable spark discharge to be stably continued without being affected by individual differences among apparatuses, degradation over time, diversity in discharge environments, and the like, the present applicants have also proposed a configuration in which a feedback circuit is added. The feedback circuit detects the secondary current and provides feedback to the energy input circuit (refer to Japanese Patent Application No. 2013-246091; this technology was unpublished at the time of filing in the Japanese application serving as basis for priority rights of the present application.)