Abstract: A current-interrupting type ignition device having an ignition coil having a primary winding, a secondary winding and an auxiliary winding disposed in the primary circuit, the number of turns of the auxiliary winding being less than that of the primary one. The auxiliary winding is energized in such a manner that electromagnetic flux passes in a direction opposite to that of the primary winding when energized. In this arrangement current flows through the auxiliary winding via a transistor and a diode when the primary current flowing through the primary winding is interrupted, thereby adding a voltage induced across the secondary winding by the transferring effect upon the energization of the auxiliary winding to the corresponding high voltage induced across the secondary winding upon the interruption of the current flow through the primary winding.

Abstract: The output signal induced in an electromagnetic pickup and having a frequency corresponding to the rotational speed of an internal combustion engine is applied to the input of an input transistor. The output of the input transistor is connected to the input of a power transistor having its output connected in series with the primary winding of an ignition coil to turn the power transistor on and off in accordance with the output signal of the electromagnetic pickup and thereby switch on and off the current flowing in the primary winding. A DC bias voltage corresponding to the output signal of the electromagnetic pickup is applied to the input of the input transistor to change its operating level. This change in the operating level changes the ratio between the "on" and "off" periods of the power transistor, namely, the ratio between the "on" and "off" periods of the primary winding of the ignition coil.