IONIC CURRENT DETECTING DEVICE

摘要

PROBLEM TO BE SOLVED: To make compatible both control for an ionic current output voltage to allow it to be processed in a post stage processing device and shortening of decay time for LC resonance relating to an ignition coil. SOLUTION: An ionic current flows to one end of a capacitor 11 from the other end of the capacitor 11 via an ignition secondary coil 1b, an ignition plug 4, an ionic current detecting resistance 15 and a load resistance 14. A voltage expressed in terms of '-ionic current value×detected resistance value' is found in a connecting point between the resistances 15 and 14, and inverted in an inversion circuit 16 to be supplied to a processing circuit 20 as an ionic current output. A resistance value R1 of the resistance 15 and a resistance value R2 of the resistance 14 are selected to satisfy both conditions that the ionic current output does not exceed a power source voltage and that a noise by the ignition coil(LC resonance current) is attenuated quickly to get small.