A contactless erroneous ignition prevention type ignition system for internal combustion engines, in which the energization of the ignition coil is held regardless of an input signal for a predetermined time period after starting the energization. At a first predetermined time after the output signal of a rotational signal generator corresponding to the rotational speed of the internal combustion engine exceeds a reference level, the energization of the ignition coil is started, and the energization of the ignition coil is maintained regardless of the output signal of the rotational signal generator until a second predetermined time. The charging timing of a capacitor of a frequency-voltage converter circuit for controlling the dwell angle of the ignition coil is controlled according to the first and second predetermined times.

A pick-up provides a square wave signal whose period corresponds to 720.degree. /N where N is the number of engine cylinders for a four stroke, two cycle internal combustion engine. An integrator is reset by both positive-going and negative-going edges of said square wave signal to produce a sawtooth waveform having a period equal to 360.degree. /N. A blanking circuit which is coupled with the pick-up blanks the sawtooth waveform of said integrator during alternate half cycles of the square wave. The blanked sawtooth waveform is supplied to one input of a comparator and a desired timing signal to the other input of said comparator. The comparator provides an engine timing signal when a predetermined relationship between the blanked sawtooth signal and the desired timing signal is attained. In this way, the engine timing signal is given once per cycle of said blanked sawtooth waveform with the timing thereof relative to said square wave being determined by the desired timing signal. The preferred embodiment discloses a four cylinder engine configuration with electronic spark timing control.

A solid state ignition system for an internal combustion engine is controlled by a spark advance means in relation to one or more parameters affecting spark quality. Supply battery voltage is monitored by the spark advance means whereby the latter generates control signals that regulate primary ignition current so that the latter attains a predetermined level before primary ignition current is interrupted.

A spark ignited internal combustion engine includes a spark coil in which current is turned on and off to generate spark events. A triangular wave voltage generator and comparator combine to retard the spark events from spark timing signals, the voltage ramping in one direction toward a reference in response to a spark timing signal and ramping in the other direction when the comparator senses that the voltage equals the reference, at which time a spark event is initiated. An RF clamp clamps the input to the comparator to prevent initiation of a spark event from each spark event to the following spark timing event. A minimum burn timer may be initiated by the comparator to prevent current flow in the spark coil for a minimum predetermined time after the initiation of a spark event; and the RF clamp may include a timer to delay its initiation sufficiently to allow latching of the minimum burn timer.

Changes in the magnetic field around a Wiegand wire created by a magnetic rotor coupled to a shaft of the engine induce a signal in a sensing coil. The signal is applied to an input switch which forms part of a control circuit. The output of the control circuit is connected to an interrupter switch connected in series with an ignition coil such that a spark is created at the secondary of the ignition coil when the interrupter switch opens. The control circuit maintains the interrupter switch in the nonconductive state for a predetermined percentage of the ignition cycle at low engine speeds and for a lesser percentage at high engine speeds so that enough energy can build in the ignition coil prior to the next interruption at the higher speeds.