Simulated airbag squib interface

• US 20050267662A1
• Filed: 05/26/2004
• Published: 12/01/2005
• Est. Priority Date: 05/26/2004
• Status: Active Grant

• Current Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Fisher, John, Monroe, Tex
• Granted Patent: US 7,107,133 B2
• Time in Patent Office: Days
• US Class Current: 701/45
• CPC Class Codes: B60R 2021/01075 between the airbag control unit and pyrotechnic fuses or equivalent actuators
• CPC Class Codes: B60R 21/0173 Diagnostic or recording means therefor

Abstract

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.

Claims

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 first line or said second line, so that when the switch is open the resistance between the first line and the second line is substantially greater than the selected resistance;

a first circuit having a first isolator which has an input side and an output side, the first circuit having a first current loop which includes the output side of the first isolator and which is in voltage supplying relationship to the electronic switch, and the first circuit having a second current loop which includes the input side of the first isolator and so is electrically isolated from the first current loop;

a control signal source in current controlling relation to the second current loop; and

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 resistive load and the second isolator output side is connected to a signal output line.

2. The simulated airbag squib of claim 1 wherein the first isolator is a photovoltaic isolator.

3. The simulated airbag squib of claim 2 wherein the electrical switch is a field effect transistor having a gate, and wherein the photovoltaic isolator comprises a light-emitting diode in the second current loop and a series connected photodiode array connected to the field effect transistor gate.

4. The simulated airbag squib of claim 1 further comprising 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.

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.

7. The simulated airbag squib of claim 1 wherein the second isolator is an optical isolator having a light-emitting diode forming the input side, and an output side formed by a phototransistor in light receiving relation to the light-emitting diode.

8. The simulated airbag squib of claim 7 wherein the phototransistor has a collector connected to a voltage source and an emitter connected to ground, and the output signal line is connected to the collector, so that when the voltage source is switched to ground, the output signal line goes low.

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.

10. An electronic circuit comprising:

an airbag crash controller, having a first squib initiation line, and a second squib initiation line;

a simulated airbag squib, having a squib simulative resistive load connected between the first squib initiation line and the second squib initiation line;

a squib activation detection circuit having a first part connected in parallel to the resistive load, and a second part electrically isolated from the first part and in signal receiving relation to the first part; and

an airbag crash controller fault indicating circuit connected in series with the resistive load, the fault indicating circuit having a first part containing a switch to alternatively connect or isolate the resistive load from the airbag crash controller, and the fault indicating circuit having a second part electrically isolated from the first part, and in signal and power transmitting relation to the first part.

11. The electronic circuit of claim 10 wherein the second part of the squib activation detection circuit is isolated from the first part of the squib activation detection circuit by a photo isolator.

12. The electronic circuit of claim 11 wherein the photo isolator has a light-emitting diode forming an input side of the first part, and the second part forms an output side having a phototransistor with a base in light receiving relation to the light-emitting diode, the phototransistor having a collector connected to a voltage source and an emitter connected to a ground, and having an output signal line connected to the collector, so that when the voltage source is switched to ground the output signal line goes low.

13. The electronic circuit of claim 10 further comprising a field effect transistor having a gate, a drain and a source, wherein the gate is connected to a control signal source, and wherein the drain and the source forming the second part the fault indicating circuit.

14. The electronic circuit of claim 10 wherein the squib activation detection circuit includes a zener diode connected in parallel with the resistive load.

15. The electronic circuit of claim 10 wherein the squib activation detection circuit includes a capacitor connected in parallel with the resistive load.

16. The electronic circuit of claim 10 wherein the switch is a field effect transistor having a gate, and wherein the isolation of the first part of the fault communication circuit from the second part is by an optical isolator having a light-emitting diode forming part of the second part and a series connected photodiode array forming part of the first part, the series connected photodiode array being connected to the gate of the field effect transistor.

17. The electronic circuit of claim 10 wherein the isolation of the first part of the fault communication circuit from the second part is by an isolation transformer, the isolation transformer having a first half connected to a rectifying diode which is connected to the switch, and wherein the isolation transformer has a second half which is connected to an AC amplifier.

18. The electronic circuit of claim 17 wherein the electronic switch is a transistor having a gate, a drain and a source and wherein the drain and the source form a path of resistance substantially lower than the squib simulative resistive load when the transistor is turned on, and wherein the gate is connected through the diode to the first half of the isolation transformer.

19. An electronic circuit comprising:

an airbag crash controller;

a first squib initiation line connected to the crash controller;

a second squib initiation line connected to the crash controller;

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 first line or said second line, so that when the switch is open the resistance between the first line and the second line increases so the airbag crash controller detects a fault;

a first circuit having a first isolator which has an input side and an output side, the first circuit having a first current loop which includes the output side of the first isolator and which is in voltage supplying relationship to the electronic switch, and the first circuit having a second current loop which includes the input side of the first isolator and is electrically isolated from the first current loop;

a control signal source in current controlling relation to the second current loop; and

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 resistive load and the second isolator output side is connected to a signal output line.

20. The simulated airbag squib of claim 19 wherein the electrical switch is a first field effect transistor having a gate, and wherein the first isolator is a photovoltaic isolator that comprises:

a light-emitting diode in the second current loop and in the first current loop a series connected photodiode array connected to the field effect transistor gate; and

a second 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.

21. The simulated airbag squib of claim 19 wherein the second isolator is an optical isolator having a light-emitting diode forming the input side, and an output side formed by a phototransistor in light receiving relation to the light-emitting diode the phototransistor having a collector connected to a voltage source and an emitter connected to ground, and the output signal line is connected to the collector, so that when the voltage source is switched to ground, the output signal line goes low.

22. The simulated airbag squib of claim 19 wherein the first current loop includes a first half of an 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.