Ignition system for internal combustion engine

Abstract

This invention relates to an ignition system for an internal combustion engine in which an advance characteristic is provided by utilizing a discharge of a capacitor. The ignition system comprises an ignition coil, a semiconductor switch to control a primary current through the ignition coil, a signal coil to generate a signal of one cycle per one revolution of the internal combustion engine, an ignition position control circuit to produce a conducting signal for conducting the semiconductor switch with the signal from the signal coil used as a control signal. The ignition coil is operated by rapidly varying the primary current through the ignition coil by means of the conduction of the semiconductor switch. The ignition position control circuit includes capacitor means, a capacitor charging circuit to charge the capacitor means with one polarity by a constant current flowing from a DC power source through a unilateral element such as a diode or a transistor, a capacitor discharging circuit having a discharge control switch conducting during leading one half cycle of a signal from the signal coil to discharge the capacitor means through the discharge control switch. The ignition control circuit further includes a reference voltage generating circuit to generate a reference voltage of a value lower than the maximum value of the voltage across the capacitor means and a conducting signal generating circuit to generate a conducting signal when the voltage across the capacitor means becomes lower than the reference voltage.