PURPOSE: To provide a compact ignition system and improve ignition property even in low speed by providing two semiconductor switching elements for short- circuiting half- wave outputs of both polarities of a capacitor charging coil and two break controlling circuits for breaking the short-circuited current flowing to said elements.

CONSTITUTION: When the half-wave output of a charging coil 1 begins to be generated in the direction of broken line, current flows through a circuit of the coil 1→resistance 7b→base emitter of transistor 8b→diode 9b→earth to make current flow between the collector and emitter of Tr 8b and shortcircuit the half-wave outputs. As the shortcircuited current is increased, the voltage drop between the collector and emitter of Tr 8b is increased and voltage at a connecting point b is raised. When said voltage reaches a set value, a thyristor 6b conducts to shortcircuit the base and emitter of Tr 8b so that the current between the collector and emitter is abruptly shut off. Thus, large inductance voltage is generated in the coil 1 to charge a capacitor 13b as charge charged to a capacitor 13a is transferred so that the capacitor 13b is rapidly discharged through a circuit 16a by an ignition signal from a sensor 2 to provide ignition through a coil 16b.