JP3517864B2 - Driver circuit for occupant protection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an occupant protection device for protecting an occupant in the event of a vehicle collision.

[0002]

2. Description of the Related Art Vehicles are equipped with an occupant protection device such as an airbag device for protecting an occupant in a collision and a seat belt with a pretensioner. These occupant protection devices deploy the bag by the pressure of the generated gas or wind up the slack of the seat belt.
A squib for igniting the gas generating agent is provided for each occupant protection device.

Conventionally, as a circuit for diagnosing the squib, a circuit for diagnosing the squib by flowing a current from a battery to the squib through a resistor connected in parallel with an ignition transistor and monitoring the voltage across the squib. Exists (see Japanese Patent Laid-Open No. 8-183420).

[0004]

However, when the above-mentioned circuit is mounted on a printed circuit board, there is a problem that the board mounting area becomes large due to the large number of components.

An object of the present invention is to control the current control means I
(EN) Provided is a drive circuit for an occupant protection device, which has a small board mounting area by being incorporated in C.

[0006]

Means for Solving the Problems Protecting an occupant according to claim 1.
The drive circuit of the device is a battery for diagnosis of the squib.
The diagnostic current supplied by the squib.
Of the squibOpen short detectionDo Squi
BuOpen short detection circuitOf occupant protection device with
In the dynamic circuit, the squibOpen short detection circuit
The squibAcrossForming a series circuit with the squibOh
In this series circuit, apply a predetermined constant current to one end of the squib.
By supplying and grounding the other end through a resistorSu
Diagnostic current to quibSupplyDoTake controlDiagnostic current control hand
Equipped with stepsThis diagnostic current control means is a
Ignition transistor for controlling the current supplied to Eve
It is provided inside the control IC,This diagnostic current control means
To squibBoth squibs when supplying diagnostic current
Based on the potential difference at the edgesSquibOpen short detection
It is characterized by performing.

According to the drive circuit of the occupant protection system of the first aspect, the squib is diagnosed by causing the current limited by the diagnostic current control means provided inside the ignition transistor control IC to flow to the squib. As described above, since the diagnostic current control means provided inside the ignition transistor control IC supplies a current to the squib to diagnose the squib, it is not necessary to provide the diagnostic current control means on the substrate, and the board mounting area can be reduced. .

According to a second aspect of the present invention, there is provided a drive circuit for an occupant protection device, wherein the diagnostic current control means of the drive circuit for the occupant protection device according to the first aspect includes a transistor.

According to the drive circuit of the occupant protection device of the present invention, since the diagnostic current control means built in the ignition transistor control IC is provided with the transistor, the number of terminals required for squib diagnosis is increased. Can be reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A drive circuit of an occupant protection system according to a first embodiment of the present invention, that is, a squib open short detection circuit will be described below with reference to FIG.

In this squib open short detection circuit, a safing sensor 10, a first ignition transistor 11, a squib 12 and a second ignition transistor 13 are connected in series between a power source + B and GND, and safing is performed. Sensor 10, first ignition transistor 1
Resistors 14, 15 and 16 for squib open short detection are connected in parallel to the first and second ignition transistors 13, respectively.

Further, the potential difference V1 between the squib ends 17 and 18 is
The voltage applied to the squib 12 and the voltage VB of the power source + B are input to the microcomputer 19. A control signal from an ignition transistor control IC (Integrated Circuit) 20 is input to the gates of the first ignition transistor 11 and the second ignition transistor 13.

Since the resistors 14, 15 and 16 (current control means) described above are built in the ignition transistor control IC 20, the ignition transistor control IC 2
0 is provided with terminals 21, 22, and 23.

In this squib open-short detection circuit, a current is made to flow from the power source B + to the squib 12 through the resistors 14, 15 and 16, and the microcomputer 19 detects the potential difference V1 between the squib ends 17 and 18 and the voltage VB at the power source + B. By monitoring and calculating the resistance value R1 of the squib 12, open-short detection of the squib 12 (equivalently resistance) is performed. The resistance value R1 of the squib 12 is calculated by the following mathematical formula 1.
In Equation 1, the resistance value of the resistor 14 is R14, the resistance value of the resistor 15 is R15, and the resistance value of the resistor 16 is R16.

[0015]

[Equation 1]

In this squib open short detection circuit, since the resistors 14, 15 and 16 are built in the ignition transistor control IC 20, the board mounting area of this circuit can be made small and the manufacturing cost can be reduced. it can.

Next, a drive circuit of an occupant protection system according to a second embodiment of the present invention will be described with reference to FIG. In the description of the second embodiment, the same configuration as that of the drive circuit of the occupant protection device according to the first embodiment is the same as that used in the description of the first embodiment. Reference numerals are given and detailed description is omitted.

The drive circuit of this occupant protection device, that is, the squib open short detection circuit, includes resistors 14 and 1 of the squib open short detection circuit according to the first embodiment.
In place of 5, 16, a constant current source 30 is provided in series between the power source + B and the squib 12, and a constant current discharge resistor 31 is provided between the squib 12 and GND (constant current source 30, constant current). The discharge resistance 31 constitutes current control means).

Since the constant current source 30 and the constant current discharging resistor 31 described above are incorporated in the ignition transistor control IC 20, the ignition transistor control IC is used.
The terminal 20 is provided with terminals 32 and 33.

In this squib open-short detection circuit, a constant current is supplied to the squib 12 by the constant current source 30, the potential difference V2 between the squib ends 17 and 18 is monitored by the microcomputer 19, and the resistance value R2 of the squib 12 is calculated. As a result, the open short circuit of the squib 12 (equivalently resistance) is detected. The resistance value R2 of the squib 12 is calculated by R2 = V2 / I1.

In this squib open short detection circuit, a constant current source 30 and a constant current discharging resistor 31 are provided.
Since it is built in the ignition transistor control IC 20,
The circuit board mounting area of this circuit can be reduced, and the manufacturing cost can be reduced. Further, since the number of parts can be reduced, the reliability of board mounting is improved.

Further, since the constant current source 30 and the constant current discharging resistor 31 are built in the ignition transistor control IC 20, the number of terminals provided in the ignition transistor control IC 20 for squib diagnosis is set to the first embodiment. The number can be reduced as compared with the case of the squib open short detection circuit according to the above. In other words, the number of terminals required for the squib open short detection circuit according to the first embodiment can be reduced to two.

Further, the potential difference V2 between the squib ends 17 and 18 is
Is monitored by the microcomputer 19, the squib open-short detection circuit according to the first embodiment, that is, the potential difference V1 between the squib ends 17 and 18 and the voltage VB of the power supply + B is determined by the microcomputer 1.
The number of required microcomputer ports can be reduced as compared with the case of monitoring by 9 in the above. Therefore, the software of the microcomputer can be downsized, and the time for detecting an open short circuit can be shortened.

Next, a drive circuit of an occupant protection system according to a third embodiment of the present invention will be described with reference to FIG. In the description of the third embodiment, the same configuration as that of the drive circuit of the occupant protection device according to the first embodiment is the same as that used in the description of the first embodiment. Reference numerals are given and detailed description is omitted.

The drive circuit of this occupant protection device, that is, the squib open short detection circuit is the resistor 14, 1 of the squib open short detection circuit according to the first embodiment.
5 and 16, a constant current driving transistor 40 is provided in series between the power source + B and the squib 12, and a constant current setting resistor 41 is provided between the squib 12 and GND. Further, a constant current control amplifier 42 is provided, the inverting input terminal of the constant current control amplifier 42 is connected to the connection point of the squib 12 and the constant current setting resistor 41, and the output end of the constant current control amplifier 42 is Transistor 4 for constant current drive
It is connected to the 0 gate. The non-inverting input terminal of the constant current control amplifier 42 has a constant current setting voltage 43 (V
4) is supplied.

Here, the constant current driving transistor 4 described above is used.
0, the constant current setting resistor 41, the constant current control amplifier 42, and the constant current setting voltage 43 are the ignition transistor control IC 20.
The ignition transistor control IC 20 is provided with terminals 44 and 45 because it is built in the.

In this squib open-short detection circuit, a constant current is supplied to the squib 12 by setting the potential of the squib end 18 to V4 by the constant current driving transistor 40 and the constant current control amplifier 42. Then, the potential difference V3 between the squib ends 17 and 18 is set to the microcomputer 1
9 is monitored and the resistance value R3 of the squib 12 is calculated to detect the open short circuit of the squib 12 (equivalently resistance). The resistance value R3 of the squib 12 is obtained by R3 = V3 / V4 × R41. In this calculation formula, the resistance value of the resistor 41 is R41.

In this squib open short detection circuit, the constant current drive transistor 40, the constant current setting resistor 41, the constant current control amplifier 42, and the constant current setting voltage 43 are built in the ignition transistor control IC 20. The circuit board mounting area can be reduced, and the manufacturing cost can be reduced. Further, since the number of parts can be reduced, the reliability of board mounting is improved.

Further, since the constant current driving transistor 40, the constant current setting resistor 41, the constant current control amplifier 42 and the constant current setting voltage 43 are built in the ignition transistor control IC 20, the ignition transistor is used for squib diagnosis. The number of terminals provided in the control IC 20 can be reduced as compared with the case of the squib open short detection circuit according to the first embodiment. In other words, the number of terminals required for the squib open short detection circuit according to the first embodiment can be reduced to two.

Further, the potential difference V3 between the squib ends 17 and 18 is V3.
Is monitored by the microcomputer 19, the required number of microcomputer ports can be reduced as compared with the case of the squib open short detection circuit according to the first embodiment. Therefore, the software of the microcomputer can be downsized, and the time for detecting an open short circuit can be shortened.

Further, since the squib open short detection circuit according to this embodiment is provided with the constant current setting voltage 43, the squib open short detection circuit is more accurate than the squib open short detection circuit according to the first embodiment. Can be flushed to 12.

Next, a drive circuit of an occupant protection system according to a fourth embodiment of the present invention will be described with reference to FIG. In the description of the fourth embodiment, the same configuration as that of the drive circuit of the occupant protection device according to the first embodiment is the same as that used in the description of the first embodiment. Reference numerals are given and detailed description is omitted.

The drive circuit of this occupant protection system is an application of the squib open short detection circuit according to the second embodiment to detect open shorts of three squibs. That is, reference numerals 11a, 11b, 11c
Are the squibs 12a, 12b, 12 respectively.
c is a first ignition transistor, and is denoted by reference numerals 13a, 13
b and 13c are squibs 12a and 1 respectively.
2b and 12c are second ignition transistors.

Reference numerals 50a, 50b and 50c are constant current application switch transistors of the squibs 12a, 12b and 12c, respectively. Further, reference numeral 30 is a constant current source I2, and reference numeral 31 is a constant current discharging resistor. Here, since the constant current source 30, the constant current discharging resistor 31, and the constant current application switch transistors 50a, 50b, 50c described above are built in the ignition transistor control IC 20, the ignition transistor control IC 20 has a terminal 32. , 33a, 33b,
33c is provided.

The open short circuit of the squibs 12a, 12b and 12c is detected by the constant current application switch transistor 5
By turning on any one of 0a, 50b and 50c, any one of the squibs 12a, 12b and 12c is selected. The calculation of the resistance value of each squib 12a, 12b, 12c is performed in the same manner as in the case of the second embodiment.

In this squib open short detection circuit, a constant current source 30, a constant current discharging resistor 31, and constant current application switch transistors 50a, 50b, 50c.
The ignition transistor control IC 20 has four terminals because it is built in the ignition transistor control IC 20, but the number of terminals can be reduced as compared with the conventional squib open short detection circuit.

Next, a drive circuit of an occupant protection system according to a fifth embodiment of the present invention will be described with reference to FIG. In the description of the fifth embodiment, the same configuration as that of the drive circuit of the occupant protection device according to the first embodiment is the same as that used in the description of the first embodiment. Reference numerals are given and detailed description is omitted.

The drive circuit of this occupant protection system is an application of the squib open short detection circuit according to the third embodiment to perform open short detection for three squibs. That is, reference numerals 11a, 11b, 11
Those indicated by c are squibs 12a, 12b, 12 respectively.
c is a first ignition transistor, and is denoted by reference numerals 13a, 13
b and 13c are squibs 12a and 12 respectively.
b and 12c are second ignition transistors.

Reference numerals 51a, 51b and 51c are constant current application switch transistors of the squibs 12a, 12b and 12c, respectively. Further, this squib open short detection circuit has squibs 12a, 12
A constant current driving transistor 40 for supplying a constant current to b and 12c, a constant current setting resistor 41, a constant current control amplifier 42, and a constant current setting voltage 43 are provided.

Here, the constant current driving transistor 4 described above is used.
0, the constant current setting resistor 41, the constant current control amplifier 42, and the constant current setting voltage 43 are the ignition transistor control IC 20.
The ignition transistor control IC 20 is provided with terminals 44, 45a, 45b, and 45c because it is built in.

The open-short detection of the squibs 12a, 12b, 12c is performed by the constant current application switch transistor 5
By turning on any of 1a, 51b, 51c, any of squibs 12a, 12b, 12c is selected and performed. The calculation of the resistance value of each squib 12a, 12b, 12c is performed in the same manner as in the third embodiment.

In this squib open short detection circuit, a constant current driving transistor 40, a constant current setting resistor 41, a constant current control amplifier 42 and a constant current setting voltage 4 are used.
Since 3 is built in the ignition transistor control IC 20, four terminals are provided in the ignition transistor control IC 20, but the number of terminals can be reduced as compared with the case of the conventional squib open short detection circuit.

[0043]

According to the invention described in claim 1, since the current control means is built in the ignition transistor control IC, the board mounting area can be reduced and the manufacturing cost can be reduced.

According to the second aspect of the present invention, since the current control means built in the ignition transistor control IC is provided with the transistor, the number of terminals required for squib diagnosis can be reduced. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a drive circuit of an occupant protection system according to a first embodiment.

FIG. 2 is a circuit diagram of a drive circuit of an occupant protection system according to a second embodiment.

FIG. 3 is a circuit diagram of a drive circuit of an occupant protection system according to a third embodiment.

FIG. 4 is a circuit diagram of a drive circuit of an occupant protection system according to a fourth embodiment.

FIG. 5 is a circuit diagram of a drive circuit of an occupant protection system according to a fifth embodiment.

[Explanation of symbols]

10 ... Safing sensor, 11 ... 1st ignition transistor, 12 ... Squib, 13 ... 2nd ignition transistor, 1
4, 15, 16 ... Resistor, 19 ... Microcomputer,
20 ... Ignition transistor control IC, 30 ... Constant current source, 3
1 ... Constant current discharge resistance, 40 ... Constant current drive transistor, 41 ... Constant current setting resistor, 42 ... Constant current control amplifier, 43 ... Constant current setting voltage.

Continuation of the front page (56) Reference JP-A-7-156743 (JP, A) JP-A-8-50164 (JP, A) JP-A-4-252759 (JP, A) JP-A-6-171456 (JP , A) Actual Kaihei 4-35957 (JP, U) Japanese Patent Publication 6-73363 (JP, B2) Japanese Patent Publication 60-1654 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB) (Name) B60R 21/16-21/32

Claims (2)

(57) [Claims] 1. A by passing a diagnostic current supplied from the battery for the diagnosis of the squib in the squib, the squib O performing open short detection of said squib
In the driving circuit of the occupant protection device having a Pung short detection circuit, the squib open short detection circuit forms the squib in series circuit across the squib, the
Supply a predetermined constant current to one end of the squib in a series circuit
Diagnostic comprising a current control means, the diagnostic current control means for controlling to supply the diagnosis current in the scan <br/> Kuibu by grounding through the resistor and the other end as well as the subject to the squib when the vehicle collision
Ignition transistor control IC for controlling supplied current
This diagnostic current control means is installed inside the machine and applies diagnostic current to the squib.
A drive circuit for an occupant protection device, characterized in that the open short circuit of the squib is detected based on a potential difference between both ends of the squib when supplied . 2. The drive circuit for an occupant protection system according to claim 1, wherein the diagnostic current control means comprises a transistor.