Patent ID: 7932622

Claim:
A power switch circuit for driving an airbag squib module, comprising: a power transistor having a first electrode, a second electrode, and a control electrode, a path between the first electrode, and a second electrode being connected in series with the airbag squib module between a supply potential and a reference potential; a pre-charge capacitance for storing a charge; a charging circuit for charging the pre-charge capacitance, the charging circuit being coupled to the pre-charge capacitance; and a controllable energy-coupling element connected between a first electrode of the pre-charge capacitance, and the control electrode of the power transistor, wherein the charging circuit comprises: a first current source coupled with the pre-charge capacitance and adapted to charge the pre-charge capacitance by providing a first current; a second current source that can be activated and deactivated, the second current source being adapted to discharge the capacitance by sinking a second current if the second current source is activated, wherein the first current source and the second current source are coupled in such a way that magnitudes of the first current and the second current are in a predetermined relationship, wherein the first current source and the second current source are further adapted such that an absolute magnitude of the first current is smaller than an absolute magnitude of the second current.