Circuit arrangement for constant monitoring of the capacitance of a vehicle airbag ignition capacitor to ensure that it remains above a threshold capacitance required to trigger the airbag primer fuse

摘要

An analysis circuit (16) is connected to the ignition capacitor (1) for measurement and evaluation of the voltage across it. From the measured voltage the circuit determines the capacitance. Also connected to the capacitor are charging (2, 4, 5) and discharging circuits (6, 7) as well as a controller (8). The capacitor is operated so that it charges and discharges between upper and lower values with the lower value sufficient to trigger the safety mechanism.