The Drive circuit and the constant current control circuit null of the occupant crash protection which possesses constant current control

摘要

PROBLEM TO BE SOLVED: To supply a constant current to a squib without providing a current detecting resistance in a current supply course toward the squib to develop an air bag. ;SOLUTION: Forth Tr15 is provided in series to a squib, and Sense Tr19 to compose a current mirror circuit with the Forth Tr15 is connected in parallel. Constant current is supplied from a constant current source 20 to the Sense Tr19. A computation amplification circuit 21 controls the gate voltages of the Forth Te15 and of the Sense Tr19 so that the source voltage of the Forth Tr15 an that of the Sense Tr19 may be equal. Thus, in the case where an igniting power transistor 13 has been turned on, the constant current corresponding to the current mirror ratio of the current mirror circuit is supplied from the Forth Tr15 to the squib 11.;COPYRIGHT: (C)1998,JPO