Power switch circuit for driving an airbag squib module
First Claim
1. 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.
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Accused Products
Abstract
A power switch circuit for driving an airbag squib module has a power transistor, a pre-charge capacitance for storing a charge, a charging circuit and a controllable energy-coupling element. The power transistor has a first electrode, a second electrode and a control electrode. A path between the first electrode and the second electrode is connected in series with the airbag squib module between a supply potential and a reference potential. The charging circuit charges the pre-charge capacitance and the charging circuit is therefore coupled with the pre-charged capacitance. The controllable energy coupling element is connected between a first electrode of the pre-charge capacitance and the control electrode of the power transistor. The power switch exhibits a high degree of stability, allows a fast switching of the power transistor and further has an advantageous transient response.
19 Citations
42 Claims
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1. A power switch circuit for driving an airbag squib module, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A power switch circuit for driving an airbag squib module, comprising:
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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 is adapted to provide a current to charge the pre-charge capacitance in a first mode of operation, and wherein the charging circuit comprises a current source adapted to provide a current to discharge the pre-charge capacitance in a second mode of operation, wherein an absolute magnitude of the current provided to discharge the pre-charge capacitance is larger than an absolute magnitude of the current provided to charge the pre-charge capacitance. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
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36. A power switch circuit for driving an airbag squib module, comprising:
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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 is further adapted to provide a current to charge the pre-charge capacitance alternatively in a first manner in a voltage limited mode of operation, wherein the charging current is primarily limited by an output impedance of a voltage providing circuit, or in a second, different manner in a current-controlled mode, wherein the charging current is provided by a current source, wherein an output impedance of the current source is greater than the output impedance of the voltage providing circuit; wherein the voltage-limited mode of operation is used in a standby mode, and wherein the current-controlled mode is used in a firing mode, wherein the standby mode and the firing mode are different modes of operation, wherein the voltage-limited mode is used in the standby mode in which the controllable energy-coupling element is open, and wherein the current-controlled mode is used in the firing mode, in which the controllable energy-coupling element connects the control electrode of the power transistor to the pre-charge capacitance. - View Dependent Claims (37, 38)
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39. A power switch circuit for driving an airbag squib module, comprising:
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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 is adapted to provide a current to charge the pre-charge capacitance in a first mode of operation, and wherein the charging circuit comprises a current source adapted to provide a substantially voltage-independent current to discharge the pre-charge capacitance in a second mode of operation, and wherein the current source adapted to provide a current to discharge the pre-charge capacitance in the second mode of operation is adapted to sink a current from the pre-charge capacitance to a reference potential.
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40. A power switch circuit for driving an airbag squib module, comprising:
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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 is adapted to provide a current to charge the pre-charge capacitance in a first mode of operation, and wherein the charging circuit comprises a current source adapted to provide a substantially voltage-independent current to discharge the pre-charge capacitance in a second mode of operation, and wherein the current source adapted to provide a current to discharge the pre-charge capacitance in the second mode of operation comprises a field effect transistor, a drain-source path of which is circuited between the pre-charge capacitance and a reference potential to discharge the pre-charge capacitance.
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41. A power switch circuit for driving an airbag squib module, comprising:
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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 is adapted to provide a current to charge the pre-charge capacitance in a first mode of operation, and wherein the charging circuit comprises a current source adapted to provide a current to discharge the pre-charge capacitance in a second mode of operation;wherein the power switch circuit further comprises a control logic adapted to control the operation of the power switch circuit, wherein the control logic is adapted to control the charging circuit to operate in the first mode of operation to provide a current charging the pre-charge capacitance in a standby mode, to operate in the second mode of operation to provide a current discharging the pre-charge capacitance for a predetermined period of time after a transition from the standby mode to a firing mode, and to operate in the first mode of operation to provide a current charging the pre-charge capacitance after the predetermined period of time has elapsed, wherein the control logic is further adapted to switch the energy coupling element to a conductive state in the firing mode and to a non-conductive state in the standby mode, wherein the energy coupling element is adapted to provide charge or energy from the pre-charge capacitance to the control electrode of the power transistor in the conductive state.
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42. A power switch circuit for driving an airbag squib module, comprising:
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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 is further adapted to provide a current to charge the pre-charge capacitance alternatively in a voltage limited mode of operation, wherein the charging current is primarily limited by an output impedance of a voltage providing circuit, or in a current-controlled mode, wherein the charging current is provided by a current source, wherein the voltage-limited mode of operation is used in a standby mode, and wherein the current-controlled mode is used in a firing mode; wherein the power switch circuit comprises a voltage-providing circuit; wherein the power switch circuit comprises a multiplexer configured to select a first path during the standby mode, such that the pre-charge capacitance is charged to a desired voltage, wherein a current is only limited by a parasitic output impedance of the voltage-providing circuit, and to select a second path when switching to the firing mode, such that a current loading the pre-charge capacitance is reduced in the firing mode when compared to the standby mode.
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Specification