PURPOSE: To operate an ignition device accurately and stably by outputting an auxiliary device driving signal with a time width corresponding to the degree of a condition in which the time width of one cycle of an engine becomes not larger than an unchanging time width at the time of a specified speed.

CONSTITUTION: Due to the rise of the primary current (i) of an ignition circuit 7, the trigger circuit 3 of a driving device 1 outputs a trigger signal V3 while a one-shot multi circuit 4 which functions as a timer outputs a reference signal V1 and, while this signal and a search signal V2 which is obtained from the rise of the primary current (i) are being simultaneously outputted, a comparator 5 outputs a driving signal V4 to an auxiliary device 6 which is an over-rotation preventing device, etc. Hence, in a condition that the time width of one cycle of an engine becomes not larger than the time width of unchanging one cycle at the time of the specified speed of the engine, the driving signal V4 of a time width corresponding to the degree of this condition is outputted. Thus, an ignition device can be operated irrespective of the difference of an induced voltage generated by the difference in the types or rating thereof or the dimension of an installing machine, etc.