WO2024063156A1

WO2024063156A1 - Squib firing circuit

Info

Publication number: WO2024063156A1
Application number: PCT/JP2023/034434
Authority: WO
Inventors: 賢紀床
Original assignee: ヴィオニアスウェーデンセーフティーシステムズエービー; 賢紀床
Priority date: 2022-09-22
Filing date: 2023-09-22
Publication date: 2024-03-28

Abstract

This squib firing circuit comprises: a plurality of upstream switching elements that are connected in parallel to one end of a squib, and supply power to the squib when in an on-state; and downstream switching elements that are of the same number as the upstream switching elements, and are connected in parallel to the other end of the squib. The sum of the on-resistances of the upstream switching elements and the downstream switching elements is a resistance value that allows the flow of a current of a value satisfying the current at which the squib fires.

Description

squib firing circuit

The present invention relates to a squib firing circuit.

Passenger cars are equipped with airbag devices that deploy airbags to protect occupants in the event of a collision. The airbag system includes an electrical ignition device (squib). When a vehicle control device detects a collision, it sends an electric current to the squib, causing it to fire. When the squib ignites, the gas generating agent in the inflator is ignited and burned, generating gas. The gas generated inflates the airbag to protect the occupants. Patent Document 1 proposes an airbag ignition system that can reliably deploy an airbag in the event of a collision of a vehicle or the like.

Japanese Patent Application Publication No. 2000-280857

In recent years, electrical and electronic circuits have been increasingly converted to ASICs (application specific integrated circuits), including the electrical circuits that supply power to squibs. High-density ASICs have low power durability, and the power supply voltage supplied to the circuit is lower than 5V or 3.3V. For example, 1.75V is used as the power supply voltage. Further, the power resistance of a transistor for driving an external load included in an ASIC is decreasing due to miniaturization of semiconductors, and therefore, the voltage for driving the load is decreasing. In order to make the squib ignition more reliable, it is necessary to supply a higher power supply voltage.

The airbag ignition system disclosed in Patent Document 1 does not consider ASIC implementation and does not operate at a low power supply voltage. The present invention has been made in view of this situation. The object is to provide a squib firing circuit that fires a squib with a low supply voltage electrical circuit.

A squib firing circuit according to an aspect of the present application includes a plurality of upstream switching elements connected in parallel to one end of the squib and supplying power to the squib when in an on state, and the upstream switching elements connected in parallel to the other end of the squib. The device includes the same number of downstream switching elements as the switching elements, and the sum of the on-resistances of the upstream switching element and the downstream switching element has a resistance value that allows a current to flow that satisfies the current that causes the squib to fire.

In the squib firing circuit according to one aspect of the present application, the plurality of upstream switching elements and the plurality of downstream switching elements are included in a single integrated circuit.

In the squib firing circuit according to one aspect of the present application, the upstream switching element and the same number of downstream switching elements as the upstream switching elements are included in a single integrated circuit, and the squib firing circuit includes a plurality of integrated circuits, A plurality of sets of the upstream switching elements included in the integrated circuit and the same number of downstream switching elements as the upstream switching elements are connected in parallel to one of the squibs.

In the squib firing circuit according to one aspect of the present application, the upstream switching element and the downstream switching element are switching transistors.

In the squib firing circuit according to one aspect of the present application, one of the upstream switching elements and one of the downstream switching elements constitute a constant current circuit, and the sum of the currents supplied by the plurality of constant current circuits is equal to the sum of the currents supplied by the plurality of constant current circuits. This is the value that satisfies the current that causes the squib to fire.

In the squib ignition circuit according to one aspect of the present application, it is possible to ignite the squib using an electric circuit with a low power supply voltage.

FIG. 1 is an explanatory diagram showing a configuration example of an airbag system. FIG. 1 is an explanatory diagram showing a configuration example of an airbag system. It is an explanatory diagram showing an example of parallel connection. FIG. 7 is an explanatory diagram showing another example of parallel connection.

Embodiments will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of the configuration of an airbag system. The airbag system 100 includes an airbag ECU (Electronic Control Unit) 10, a squib 3, an on-vehicle battery 4, and an airbag (not shown). The airbag ECU 1 is an electronic circuit that controls deployment of the airbag. The squib 3 is an ignition device that ignites the gas generating agent of the inflator. Since a vehicle is usually equipped with a plurality of airbags, the same number of squibs 3 as airbags are installed in the vehicle.

The airbag ECU 1 includes a boost circuit 11, a power supply circuit 12, a power backup capacitor 13, a system ASIC (Application Specific Integrated Circuit) 14, a high side switch 15, an additional ASIC 16, and a CAN (Controller Area Network) interface 17. , an MCU (micro controller unit) 18, and an on-board sensor 19.

The onboard battery 4 is a secondary battery. The negative terminal of the vehicle battery 4 is connected to the body of the vehicle, and the positive terminal is connected to the ignition switch IG.

The boost circuit 11 boosts the voltage of the vehicle battery 4 connected via the ignition switch IG to a predetermined voltage. The booster circuit 11 supplies charge to the power supply backup capacitor 13 . The power supply circuit 12 steps down the backup power supply voltage of the power supply backup capacitor 13 to a predetermined system voltage when the output voltage of the first booster circuit cannot be maintained due to a drop in the voltage of the vehicle battery 4 or the like.

One end of the power backup capacitor 13 is connected to the output of the booster circuit 11, and the other end is connected to the vehicle ground, which is a reference potential, via the ground of the airbag ECU 1. The power backup capacitor 13 serves to supply power for igniting the squib 3. The power supply backup capacitor 13 stores charges supplied from the booster circuit 11 .

The system ASIC 14 controls the ignition of the squib 3. The high-side switch 15 is disposed between the power supply backup capacitor 13 and the system ASIC 14 and additional ASIC 16. When the high-side switch 15 is turned on, the power stored in the power supply backup capacitor 13 is supplied to the system ASIC 14 and additional ASIC 16.

The additional ASIC 16 controls the ignition of the squib 3 similarly to the system ASIC 14. The CAN interface 17 allows the MCU 18 to communicate with other ECUs via CAN. The MCU 18 controls the system ASIC 14 and the additional ASIC 16, and controls the ignition of the squib 3.

The on-board sensor 19 detects the acceleration of the airbag ECU 1. The acceleration detection result is transmitted to the system ASIC 14 and MCU 18.

The system ASIC 14 includes a first power controller 141, a second power controller 142, a first sensor interface 143, a second sensor interface 144, a deployment controller 145, a switch controller 146, and a squib driver 2.

The first power controller 141 controls the boost circuit 11. The second power controller 142 controls the power supply circuit 12.

The first sensor interface 143 receives signals from a collision detection sensor and a side collision prediction sensor mounted on the vehicle. The collision detection sensor is a front collision detection sensor, a side collision detection sensor, or the like. The front collision detection sensor is, for example, an acceleration sensor mounted on a strong frame in front of the vehicle, and detects a collision based on the magnitude of acceleration. The side collision detection sensor is a sensor that detects a collision on the side of a vehicle. A side collision detection sensor is a pressure sensor mounted inside a vehicle door, and detects a collision based on the pressure generated by the deformation of the door. A collision prediction sensor including a side collision is composed of a sensor installed outside the airbag ECU 1, such as a radar, Lidar (Laser Imaging Detection and Ranging), and a stereo camera, and can also be used in place of a side collision detection sensor. It is possible.

The second sensor interface 144 receives signals from the situation sensing sensor. The situation detection sensor includes a sensor for predicting the physique of the driver, a sensor for detecting the presence or absence of a passenger in the front passenger seat or the rear seat, and the like. For example, the situation detection sensor is a pressure sensor provided on the seat surface or backrest of the seat. A pressure sensor detects the load applied to the seat and backrest, detects the presence or absence of an occupant, and estimates the occupant's weight, physique, or seating posture.

The deployment controller 145 deploys the airbag at the time of a collision based on commands from the MCU 18 and sensor information from the first sensor interface 143 and the second sensor interface 144. The switch controller 146 turns on the high side switch 15 under control from the expansion controller 145. When the high-side switch 15 is turned on, the squib driver 2 supplies the power stored in the power backup capacitor 13 to the squib 3, causing the squib 3 to fire.

FIG. 2 is an explanatory diagram showing an example of the configuration of the airbag system. FIG. 2 shows the configuration of the squib driver 2. As shown in FIG. In FIG. 2, the arrangement of the structure has been changed and descriptions have been added to make it easier to understand the structure of the squib driver 2. Further, in FIG. 2, components unnecessary for understanding the configuration of the squib driver 2 in FIG. 1 are omitted. In FIG. 2, components common to those in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted.

The squib driver 2 includes firing

circuits

21, 22, 23, . . . for each squib 3. Since the configuration of each firing circuit is the same, the firing circuit 21 will be described as a representative. The firing circuit 21 fires the squib 3. The squib 3 ignites the gas generating agent of the inflator. Firing circuit 21 includes an upstream driver interface 211 , an upstream controller 212 , an upstream switching element 213 , a downstream driver interface 214 , a downstream controller 215 , and a downstream switching element 216 .

The upstream driver interface 211 receives commands from the deployment controller 145 and outputs operation commands to the upstream controller 212 and downstream controller 215. The downstream driver interface 214 receives commands from the second sensor interface 144 and the SPI (Serial Peripheral Interface) interface 148 and outputs operation commands to the downstream controller 215.

The upstream controller 212 and the downstream controller 215 operate only when receiving operation commands from the upstream driver interface 211 and the downstream driver interface 214. The upstream controller 212 turns on the upstream switching element 213 (conducting state) and creates a state in which power from the power supply backup capacitor 13 is accepted via the high side switch 15. The upstream switching element 213 can supply current to the upstream terminal of the squib 3. The downstream controller 215 turns on the downstream switching element 216 to ground the downstream terminal of the squib 3. This causes current to flow through the squib 3, causing it to ignite. The airbag deploys when the squib 3 ignites.

It is desirable that the upstream controller 212 and the upstream switching element 213, as well as the downstream controller 215 and the downstream switching element 216, constitute a constant current circuit. This is to prevent a situation where a large amount of current is supplied to one squib 3 and insufficient current is supplied to other squibs 3 when a plurality of squibs 3 are fired.

The upstream switching element 213 and downstream switching element 216 are configured with switching transistors with excellent response. For example, the upstream switching element 213 and downstream switching element 216 are configured with MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors).

The reason why the squib 3 does not fire unless both the upstream driver interface 211 and the downstream driver interface 214 receive an operation command is to deploy only the appropriate airbag according to the situation inside the vehicle when a collision is detected. It is.

In FIG. 2, one firing circuit supplies current to one squib 3. However, depending on the specifications of the squib 3, one firing circuit may not be able to supply sufficient current to the squib 3. For example, the power supply voltage supplied to the ignition circuit is 17.7V, in the ignition circuit, the resistance value (ON resistance) of the upstream switching element and the wiring resistance are 1.25Ω in total, the squib resistance is 9.85Ω, and the resistance of the downstream switching element is 1.25Ω. When the resistance value (on resistance) and wiring resistance are 1.25Ω in total, the current flowing through the squib is 1.43A from equation (1).

I= V/R = 17.7 /(1.25×2 + 9.85) = 1.43…(1)

If the squib 3 reliably fires with a current of 1.43A, no problem will occur, but if a larger current, for example 1.75A, is required, the squib 3 will not fire. That is, the sum of the on-resistances of the one upstream switching element 213 and the one downstream switching element 216 has a resistance value that allows a current to flow that is less than the current that causes the squib 3 to fire. In addition, if the resistance value of the squib 3 is set high, the sum of the resistance values will further increase and will not reach the current that causes the squib 3 to fire. Since the resistance value of the squib 3 is greater than the sum of the on-resistances of the upstream switching element 213 and the downstream switching element 216, the squib 3 has a dominant influence on the firing current. At this time, in order to ignite the squib 3, it is conceivable to increase the power supply voltage. However, there are cases where it is not possible to increase the power supply voltage due to problems with the power resistance of the ASIC that constitutes the ignition circuit. Therefore, a plurality of firing circuits are connected in parallel to one squib 3.

(Embodiment 1)
FIG. 3 is an explanatory diagram showing an example of parallel connection. The example shown in FIG. 3 is an example in which two of the plurality of firing circuits included in one squib driver 2 constituting one system ASIC 14 are connected in parallel to one squib 3. By connecting the firing circuit 21 and the firing circuit 22 to one squib 3, the maximum current that can be passed through the squib 3 is 1.43×2=2.86 (A), which exceeds the required current of 1.75A. , the operation of the squib 3 is guaranteed. At that time, for example, if the current upper limit of the constant current circuit in the

ignition circuits

21 and 22 is set to 1.2A, 1.2A x 2 = 2.4A will be the upper limit of the supply current, and unnecessary energy consumption will be avoided. It can be prevented. In other words, compared to the above example, the reduction is 2.86-2.4=0.46 (A). In other words, the capacity of the power supply backup capacitor 13 is reduced.

(Embodiment 2)
This embodiment relates to a configuration in which a plurality of sets of upstream switching elements included in different system ASICs (integrated circuits) and the same number of downstream switching elements as the upstream switching elements are connected in parallel to one squib. FIG. 4 is an explanatory diagram showing another example of parallel connection. The example shown in FIG. 4 is an example in which a plurality of

system ASICs

14a and 14b are prepared, and each firing circuit of the

squib drivers

2a and 2b of the two

system ASICs

14a and 14b is connected in parallel to one squib 3. be. By connecting the firing circuit 21a and the firing circuit 21b to one squib 3, the maximum current that can be passed through the squib 3 is 1.43×2=2.86 (A), which exceeds the required current of 1.75A. , the operation of the squib 3 is guaranteed.

In Embodiments 1 and 2, even if the squib cannot be reliably ignited with the current supplied by a single ignition circuit, the power supply voltage can be increased by connecting multiple ignition circuits to one squib. It becomes possible to supply a current that reliably ignites the squib without causing the squib to ignite.

In the second embodiment, current is supplied to one squib 3 from the firing circuit 21a and the firing circuit 21b included in

different system ASICs

14a and 14b. Therefore, if there is a lag in the start of operation between the ignition circuit 21a and the ignition circuit 21b, the current flowing to the squib 3 will be halved during the time when the lag occurs. Therefore, it is desirable to allow some time for supplying the current to the squib 3. For example, if the condition for the squib 3 to ignite is to supply a current of 1.75 A for 500 μs or more, the time during which the current can be supplied is designed to be, for example, 600 μs. Specifically, this can be achieved by increasing the capacity of the power supply backup capacitor 13.

The technical features (constituent features) described in each embodiment can be combined with each other, and new technical features can be formed by combining them.
The embodiments disclosed herein are illustrative in all respects and should be considered not to be restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above-mentioned meaning, and it is intended that all changes within the scope and meanings equivalent to the scope of the claims are included.
Further, although the scope of claims uses a format in which claims refer to two or more other claims (multi-claim format), this is not a limitation. It may also be written using a multi-claim format that cites at least one multi-claim.

100: Airbag system 1: Airbag ECU
11: Boost circuit 12: Power supply circuit 13: Power backup capacitor 14: System ASIC
141: First power controller 142: Second power controller 143: First sensor interface 144: Second sensor interface 145: Deployment controller 146: Switch controller 147, 148:

SPI interface

14a, 14b: System ASIC
15: High side switch 16: Additional ASIC
17: CAN interface 18: MCU
19: On-board sensor 2:

Squib driver

21, 22, 23: Firing circuit 211: Upstream driver interface 212: Upstream controller 213: Upstream switching element 214: Downstream driver interface 215: Downstream controller 216: Downstream switching

element

2a, 2b:

Squib Driver

21a, 21b: Ignition circuit 3: Squib 4: Vehicle battery IG: Ignition switch

Claims

a plurality of upstream switching elements connected in parallel to one end of the squib and supplying power to the squib when in an on state;
comprising the same number of downstream switching elements as the upstream switching elements connected in parallel to the other end of the squib,
The sum of the on-resistances of the upstream switching element and the downstream switching element has a resistance value that allows a current to flow that satisfies the current for firing the squib.
The squib firing circuit of claim 1, wherein a plurality of said upstream switching elements and a plurality of said downstream switching elements are included in a single integrated circuit.
the upstream switching element and the same number of downstream switching elements as the upstream switching elements are included in a single integrated circuit;
comprising a plurality of the integrated circuits,
The squib firing circuit according to claim 1, wherein a plurality of sets of the upstream switching elements included in the different integrated circuits and the same number of downstream switching elements as the upstream switching elements are connected in parallel to one of the squibs.
The squib firing circuit according to any one of claims 1 to 3, wherein the upstream switching element and the downstream switching element are switching transistors.
One of the upstream switching elements and one of the downstream switching elements are elements that constitute a constant current circuit,
The squib firing circuit according to any one of claims 1 to 3, wherein the sum of the currents supplied by the plurality of constant current circuits is a value that satisfies the current that causes the squib to fire.