Simulated airbag squib interface
An electronic circuit connects to an airbag crash controller in a way which is functionally identical to an airbag squib. Based on a squib fire signal from the controller, the circuit provides an activation signal indicating airbag deployment and also allows communication with an airbag crash controller by creating an open circuit that is detected by the airbag crash controller as an airbag fault. Each functional part of the circuit includes an isolator to protect the airbag crash controller.
1 . A simulated airbag squib comprising:
a first airbag crash controller squib initiation line;
a second airbag crash controller squib initiation line;
a selected resistive load connected across the first line and the second line so as to simulate an airbag squib;
an electrical switch connected between the resistive load and said second line, so that when the switch is open a resistance between the first line and the second line due to said selected resistive load is substantially greater than a nominal resistance of the airbag squib;
a fault indicating circuit having a first isolator which has an input side and an output side, the fault indicating circuit having a first current loop which includes the output side of the first isolator and supplies voltage from the fault indicating circuit to the electronic switch, and the fault indicating circuit having a second current loop which includes the input side of the first isolator and so the second current loop is electrically isolated from the first current loop;
a control signal source in current controlling relation to the second current loop;
a second circuit having a second isolator which has an input side and an output side, wherein the second isolator input side is connected in parallel to the selected resistive load and the second isolator output side is connected to a signal output line; and
a field effect transistor having a gate, a drain, and a source, wherein the gate is connected to the control signal source, and the drain and the source form a part of the second current loop.
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5 . The simulated airbag squib of claim 1 further comprising a zener diode connected in parallel with the selected resistive load.
6 . The simulated airbag squib of claim 1 further comprising a capacitor connected in parallel with the selected resistive load.
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9 . The simulated airbag squib of claim 1 wherein the first isolator is an isolation transformer and wherein the first current loop includes a first half of the isolation transformer and a rectifying diode, and the second current loop includes a second half of the isolation transformer, and further comprising an AC amplifier connected to the second current loop, wherein the control signal source is an AC signal which is in current controlling relation to the AC amplifier.
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