In a general aspect, a circuit for controlling operation of an ignition circuit including an insulated-gate bipolar transistor (IGBT) device can include a current slope detection circuit configured to detect a slope of a current in a primary winding of an ignition coil included in the ignition circuit and a driver circuit coupled with the current slope detection circuit. The current slope detection circuit can be further configured to, during charging of the ignition coil, if the detected slope is above a first limit, provide a first indication to the driver circuit; and, if the detected slope is below a second limit, provide a second indication to the driver circuit. The driver circuit can be configured to, in response to receiving the first indication or the second indication, modify operation of the ignition circuit.

An ignition transformer includes a primary winding and a secondary winding and are electromagnetically coupled to each other. A battery is connected to a first end of the primary winding. A switch connected to a second end of the primary winding is turned on or off in response to an ignition signal. A saturable reactor includes a saturable core and includes a first winding, and a second winding the first and second windings electromagnetically coupled to each other. A first end of the first winding is connected to a first end of the second winding. A second end of the first winding is connected to the ignition plug. A reset circuit applies a reset voltage to the first and second ends of the second winding. The reset voltage is a voltage to switch a magnetization status of the saturable core between a saturated state and an unsaturated state.

A method for determining a level of spark plug fouling and providing an indication to change the spark plugs of an ignition system is provided. The method includes providing a dwell command on a control wire of an ignition system and generating an indication of a recommendation to change a spark plug of the ignition system based upon a current on the control wire.

A method for determining a level of spark plug fouling and providing an indication to change the spark plugs of an ignition system is provided. The method includes providing a dwell command on a control wire of an ignition system and generating an indication of a recommendation to change a spark plug of the ignition system based upon a current on the control wire.

A drive circuit that operates stably and has a small circuit size. Provided is a switch apparatus including a power semiconductor element connected between a first terminal on a high potential side and a second terminal on a low potential side; a capacitor; a charging section that charges the capacitor for at least a portion of an interval during which the power semiconductor element is OFF; a discharging section that causes the capacitor to gradually discharge, in response to the power semiconductor element becoming ON; and a cutoff section that sets the power semiconductor element to an OFF state, in response to a voltage of the capacitor becoming lower than a threshold voltage.

In one embodiment, an igniter circuit may include a circuit to determine if the current through a load switch exceeds a threshold value, and to responsively disable a second switch that couples DC power to the igniter circuit.

An ignition control device according to one embodiment of the present invention is configured to, based on a pulse signal to be induced in an ignition coil in accordance with rotation of an internal combustion engine, cause a voltage to be supplied to an ignition plug included in the internal combustion engine, to be generated in the ignition coil. The ignition control device includes: a switching element configured to energize the ignition coil; a biasing unit configured to bias control terminals of the switching element so that the switching element is turned on when the pulse signal is induced; a state detecting unit configured to detect a biased state of the switching element; and a control unit configured to set a timing for controlling de-energization of the ignition coil in response to a result of detection performed by the state detecting unit, and to control the switching element to be turned off in accordance with the timing.

A method for determining a level of spark plug fouling and providing an indication to change the spark plugs of an ignition system is provided. The method includes providing a dwell command on a control wire of an ignition system and generating an indication of a recommendation to change a spark plug of the ignition system based upon a current on the control wire.

In one embodiment, an igniter circuit may include a circuit to determine if the current through a load switch exceeds a threshold value, and to responsively disable a second switch that couples DC power to the igniter circuit.

A dual coil ignition system is provided. The dual coil ignition system includes a first inductive ignition coil including a first primary winding and a first secondary winding, and a second inductive ignition coil including a second primary winding and a second secondary winding, the second secondary winding connected in series to the first secondary winding. The dual coil ignition system further includes a diode network including a first diode and a second diode connected between the first secondary winding and the second secondary winding.