| 摘要 |
PROBLEM TO BE SOLVED: To decrease capacity of a backup power source to reduce its size for achieving low price without lowering performance of an air bag ignition circuit based on the backup power source. SOLUTION: A backup capacitor to supply an ignition current to a squib through an ignition transistor, and a separate backup capacitor to supply a voltage to be applied to a gate of the ignition transistor are provided. A reverse current preventive diode is provided on the opposite side of the gate to the separate backup capacitor, so charges of the separate capacitor extracted to lower its potential are prevented when the ignition current is supplied from the backup capacitor to lower the potential of the capacitor.
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