Importance

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Abstract

An occupant crash protection device for a vehicle has: a current limiting circuit which receives a supply of a trigger signal generated when it is judged that a significant accident happens, and which controls a squib firing current to have a constant amount; a squib; and a mechanical acceleration switch, the current limiting circuit, the squib, and the acceleration switch being connected in series between terminals of a direct current power source. In the device, the current limiting circuit has: a first n-channel field effect transistor which is connected in series to the squib; a second n-channel field effect transistor which is connected in parallel to the first n-channel field effect transistor and which receives a minute amount of a current obtained by shunting the squib firing current which is to flow through the first n-channel field effect transistor; and bias control means for, in synchronization with the squib firing current, comparing the amount of the current flowing through the second n-channel field effect transistor with a reference amount, and controlling a gate voltage so that the amount of the current flowing through the first n-channel field effect transistor has an amount proportional to the reference amount.

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First Claim