Method of determining charging capacitance of capacitor

摘要

The present invention provides a method of determining a charging capacitance of a capacitor in an air bag system using a bus system. The method is a method of determining a charging capacitance of a capacitor in which a charging capacitance of a capacitor required for activating an air bag system normally is obtained from the following formula (I). C = 2 �¢ E / V 2 (In the formula, C represents a capacitor charging capacitance, V represents a charging voltage, and E represents the minimum ignition energy required for making the heat generating portion of the igniter generate heat to ignite a priming, which is obtained by the following formula (II): E = I min 2 × R max + r 1 + r 2 × T + w × 10
I min : the minimum ignition current value (A)
R max : the maximum resistance value of the heat generating portion (©)
r 1 : an ON resistance value of the switching circuit (the maximum ON resistance value at 150°C) (©)
r 2 : a resistance value of the other elements (©)
T: a time period in which a current flows in the heat generating portion (sec)
w: a power consumed by the whole integrated circuit when the switching circuit is OFF).