PURPOSE: To contrive decrease of the number of parts items, miniaturization of a noncontact type ignition device and reduction of manufacturing cost by forming a primary coil current limiting circuit of the device in an open loop and also to reduce a thermal burden, applied to a power semiconductor, by improving temperature characteristic of a primary coil current.
CONSTITUTION: When an electrification signal of a primary coil current is input from a control unit 5 to an input electrode of a power semiconductor (Darlington transistor, power MOS.FET, etc.) 3, the primary coil current, flowing in an ignition coil, is amplified. A low resistance element 9, serving as a circuit element of a primary coil current limiting circuit 6, is connected between an earth side electrode of the power semiconductor 3 and the earth. A Zener diode 8, serving as a constant voltage source, is connected between an input electrode of the power semiconductor 3 and the earth to constitute the open loop-shaped primary coil current limiting circuit 6. Temperature characteristic of a primary coil current value of the ignition coil 1 is set so as to be placed in a positive side at the time of high temperature.
SUGIURA NOBORU
URUSHIBARA NORIMI
