Abstract: An ignition system for an internal combustion engine includes two power transistors respectively connected to opposite ends of the primary winding of an ignition coil to interrupt the primary currents which flow from a power source through the mid-tap of the primary winding. The two power transistors have emitters connected in common and a resistor is connected to the junction of this common connection to detect respective primary currents with the single resistor. A single current control circuit is provided to control the two power transistors in response to the detected respective primary currents.

Abstract: In a method of computing and controlling the fuel injection quantity of a fuel injection system and the ignition timing of an ignition system of an international combustion engine by a microcomputer in accordance with operating conditions of the engine, a discrimination signal indicative of the presence or absence of misfiring is generated in accordance with an electric signal from the ignition system so that when misfiring occurs, even if fuel injection quantity data has already been computed, data for reducing the fuel injection quantity to zero is generated in response to the discrimination signal to stop fuel injection.

Abstract: A contactless ignition system for internal combustion engines of the type including an ignition coil with two primary windings whose primary currents are alternately switched on and off by two power transistors, further includes two Zener diodes each having a breakdown voltage of 300 to 400 volts and connected in series with one of the power transistors and one of the ignition coil primary windings to function as a reverse current blocking diode. By virtue of two series circuits each including the Zener diode, a diode connected in inverse parallel with one of the power transistors and the primary winding, each of the Zener diodes serves both the reverse current blocking function and the overvoltage protection function. The Zener diodes may be replaced with diodes of the avalance type.

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.

Abstract: A contactless ignition system for an internal combustion engine responds to alternating current ignition signals produced in timed relationship with the engine. A primary winding of an ignition coil and a collector-emitter path of a switching transistor are connected across a direct current power source. A trigger circuit responds each cycle of the alternating current ignition signals for operating the switching transistor conductive and nonconductive in timed relationship with the engine to carry an ignition spark. A primary current limiting circuit, responsive to the voltage potential at the direct current power source, controls the amount of the base current for the switching transistor in accordance with the increased voltage of the power source, to thereby limit the primary current flowing through the primary winding to a predetermined magnitude.