Abstract: An ignition system for internal combustion engines comprises means for generating an ignition signal in synchronism with the revolution of an internal combustion engine and an ignition circuit device for interrupting a primary current of an ignition coil in accordance with the ignition signal. The ignition circuit device includes an ignition monitor signal producing circuit for producing an ignition monitor signal which circuit operates to set the ignition monitor signal at the time of starting the energization of the ignition coil and thereafter to reset the ignition monitor signal at a subsequent predetermined timing, whereby the ignition circuit device operates, in accordance with the pulse width and the set and reset conditions of the ignition monitor signal, to decide whether the operation of the ignition circuit device is normal or abnormal, to control to generate a predetermined amount of ignition energy, and to prevent erroneous generation the ignition monitor signal due to a noise or the like.

Abstract: In an ignition control system for the internal combustion engine, a reference angle sensor detects the rotational speed of the internal combustion engine, and detects a point near the top dead center, and generates a reference angle signal. An angle sensor similarly detects the rotational speed of the internal combustion engine, and discriminats the rotational speed for each predetermined angle, and generates an angle signal. A microcomputer includes an output compare register, a free-running counter and a timer control status register, and computes the ignition timing and energization time of the ignition coil in response to a reference angle signal from the reference angle sensor and an angle signal from the angle sensor.

Abstract: Energizing interval of an ignition coil, which is basically determined on the basis of the rotational speed of an engine, is corrected by adding thereto an extension amount which is either a function of the rotational speed of the engine or a given upper limit value at the rotational speed of the engine when accelerating condition is detected. Thus, the ignition coil is supplied with a primary winding current for a desired interval even during acceleration so that sufficient ignition voltage will be produced to properly ignite air/fuel mixture in engine cylinders. The extended energizing interval is then reduced stepwise to provide normal energizing interval during engine operations other than acceleration.