Abstract: The primary winding of an ignition coil is placed in series with the collor of a switching transistor. In order to protect the transistor against overvoltages, the collector is also connected to a level comparator and the base receives a two-state control signal which is synchronous with the rotation of the engine. One input of the comparator is connected through a divider network to the collector of the transistor and the outer input is connected to a fixed direct-current voltage source. Provision is also made for an error amplifier connected to the output of the comparator, and for a summing circuit which is connected to the control input of the transistor and receives the control signal.