PURPOSE: To prevent a high voltage from being produced when a key switch is opened, by connecting a switching element between the primary portion of an ignition coil and the ground and coupling another switching element and a charge and discharge capacitor between the primary portion of the ignition coil and the ground.
CONSTITUTION: When a power switch 11 is closed, a detection signal from a pickup coil 1 is applied to an output section 6 through an amplifying section 2 and a driving section 3. When output transistors 4, 5 are closed, the power switch 11 is opened. The driving section 3 keeps the output transistors 4, 5 closed by the charged energy of the charge and discharge capacitor 14 of the amplifying section 2 until the capacitor is discharged through an ignition coil 7 and a switching diode 13. After the power switch 11 is opened, primary energy is bypassed through another switching diode 12 to suppress the primary voltage of the ignition coil 7 to reduce its secondary high voltage.
MIZUMOTO MASAO
TOKYO SANYO ELECTRIC CO
NIPPON DENSO CO