Current limit controller for an air bag deployment system

摘要

An air bag deployment system (10) generates the proper current to activate a squib (74) and deploy an air bag. A separate capacitor (48) powers circuitry in a drive limit controller (54) for providing a variable voltage drive to a MOS device (68) to regulate squib (74) firing current. A switch circuit (38) supplies gate current to a transistor (46) such that an electrical connecting path allows a capacitor (22) to charge a capacitor (48). During squib (74) firing and air bag deployment, the switch circuit (38) provides electrical isolation between the decaying voltage stored on the capacitor (22) that powers the squib (74) current and the capacitor (48) that provides current regulation to the squib (74) from the drive limit controller (54).