An ignition apparatus includes an ignition plug, a boost transformer, an ignition power source and a measurement unit. The ignition plug has a center electrode and a ground electrode. The boost transformer supplies the ignition plug with electric power generated in a secondary coil upon supply of AC power from the ignition power source to a primary coil. The measurement unit measures the discharge voltage of the ignition plug. The ignition power source includes a discharge state determining unit that determines the discharge state of the ignition plug based on the measured discharge voltage and a current controlling unit that controls electric current supplied to the primary coil. When a discharge path formed between the center and ground electrodes of the ignition plug is determined by the discharge state determining unit as being in an over-extended state, the current controlling unit reduces the electric current supplied to the primary coil.

In a general aspect, an ignition circuit can include a control circuit configured to receive a command signal from an engine control unit, and a driving circuit coupled with the control circuit. The driving circuit can be configured to be coupled with a resonant circuit that includes a primary winding of an ignition coil. The control circuit and the driving circuit can be configured, in response to a command signal, to drive the resonant circuit at a first frequency to generate a voltage in the ignition coil to initiate a spark in a spark plug; and, in response to the spark being initiated in the spark plug, drive the resonant circuit at a second frequency to maintain the spark in the spark plug for combustion of a fuel mixture. The control circuit can be configured to, after the combustion of the fuel mixture, to disable the driving circuit.

In a general aspect, an ignition circuit can include a control circuit configured to receive a command signal from an engine control unit, and a driving circuit coupled with the control circuit. The driving circuit can be configured to be coupled with a resonant circuit that includes a primary winding of an ignition coil. The control circuit and the driving circuit can be configured, in response to a command signal, to drive the resonant circuit at a first frequency to generate a voltage in the ignition coil to initiate a spark in a spark plug; and, in response to the spark being initiated in the spark plug, drive the resonant circuit at a second frequency to maintain the spark in the spark plug for combustion of a fuel mixture. The control circuit can be configured to, after the combustion of the fuel mixture, to disable the driving circuit.

An internal combustion engine generates a cleaner exhaust. A combustion chamber combusts a fuel and generates combustion products. A fuel inlet channel introduces the fuel into the combustion chamber. An air inlet channel introduces air into the combustion chamber. An outlet channel discharges the combustion products from the combustion chamber. A set of electrodes is arranged inside the internal combustion engine that generate an electric field in contact with the fuel, the air and/or the combustion products when a voltage is applied across the set of electrodes. A sensor is arranged inside the internal combustion engine that measures a combustion condition. A controller adapts the electric field based on the combustion condition. The engine generates exhaust with reduced toxicity and waste product relative to prior combustion engines by energizing a fluid mixture of fuel, air, and combustion products to improve a redox reaction causing a more complete combustion reaction.

Disclosed is an inventive method for controlling a corona ignition device of an internal combustion engine. A corona discharge, which ignites fuel in a combustion chamber of the engine, is generated by applying a voltage to the corona ignition device. An actual value that is characteristic of the nitrogen oxide concentration of the exhaust gas is compared with a setpoint value, and, if the actual value deviates from the setpoint value by more than a specified threshold value and the actual value is greater than the setpoint value, the voltage is reduced after the comparison.