Ignition device

An ignition device, comprising:

• an ignition plug, which is arranged in an internal combustion engine, and includes a first electrode, a second electrode, and a dielectric body arranged between the first electrode and the second electrode;
• an AC power supply configured to generate an AC voltage to be applied between the first electrode and the second electrode;
• a thermal plasma detection circuit configured to detect whether thermal plasma has occurred between the first electrode and the second electrode, and when the thermal plasma is detected, output a thermal plasma occurrence signal;
• and
• an application time period determination circuit configured to determine an application time period for the AC voltage during one cycle of the internal combustion engine in advance before the application, and when the thermal plasma occurrence signal is received while the AC voltage is being applied based on the application time period, change the application time period so as to shorten the application time period,
• wherein, when the thermal plasma occurrence signal is received, the application time period determination circuit determines the application time period to be obtained after the changing so that a time period after a time point at which the thermal plasma is detected by the thermal plasma detection circuit until the application of the AC voltage is to be stopped becomes equal to or longer than a time period corresponding to half a cycle of the AC voltage.

An ignition device, comprising:

• an ignition plug, which is arranged in an internal combustion engine, and includes a first electrode, a second electrode, and a dielectric body arranged between the first electrode and the second electrode;
• an AC power supply configured to generate an AC voltage to be applied between the first electrode and the second electrode;
• a thermal plasma detection circuit configured to detect whether thermal plasma has occurred between the first electrode and the second electrode, and when the thermal plasma is detected, output a thermal plasma occurrence signal;
• an application time period determination circuit configured to determine an application time period for the AC voltage during one cycle of the internal combustion engine in advance before the application, and when the thermal plasma occurrence signal is received while the AC voltage is being applied based on the application time period, change the application time period so as to shorten the application time period;
• and
• a thermal plasma retention detection circuit configured to detect whether the thermal plasma is retained during half a cycle of the AC voltage after the thermal plasma is detected by the thermal plasma detection circuit, and output a thermal plasma retention signal when the thermal plasma is retained,
• wherein, when the thermal plasma occurrence signal is received and the thermal plasma retention signal is received as well, the application time period determination circuit changes the application time period so as to shorten the application time period.