JPH09288137A - Judgment apparatus for disconnection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a judgment apparatus by which the disconnection of a resistance is judged precisely. SOLUTION: A voltage which is applied across both terminals of a squib resistance is changed over from a low voltage to a high voltage while a transistor is turned on and off. The disconnection of the squib resistance is judged when the change amount ΔV (=V2 -V1 ) of the output voltage, of an operational amplifier, changed according to a change in the voltage due to its changeover is not a value, in a region F0 , which is larger than a first predetermined threshold value and when an output voltage V2 on the side of the high voltage is larger than a threshold value Vth4 which is by a prescribed value smaller than the power-supply voltage Vmax of the operational amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disconnection determination device, and more particularly, to a disconnection determination device for determining resistance disconnection.

[0002]

2. Description of the Related Art Conventionally, an air bag device control circuit has been proposed as a disconnection determination device. This airbag device control circuit includes an ignition device for the airbag system (hereinafter,
An operational amplifier is provided which amplifies a voltage applied to a filament (hereinafter referred to as a squib resistance) provided for expanding an airbag in a squib) to a predetermined amplification factor and outputs the amplified voltage. Then, the airbag device control circuit switches the voltage applied to the squib resistor from the low voltage to the high voltage, and the change amount of the output voltage of the operational amplifier changed according to the change of the voltage applied to the squib resistor by this switching, The disconnection of the squib resistance is determined by comparing with a predetermined threshold value for determining disconnection.
When the amount of change is smaller than a predetermined threshold value for short circuit determination, it is determined that the squib resistance is short circuited. Therefore, the airbag device control circuit determines that the squib resistor is normally connected if the change amount is equal to or less than the disconnection determination threshold value and greater than or equal to the short circuit determination threshold value.

By the way, the resistance value of the squib resistor changes according to the connection state of the squib resistor. That is, the resistance value becomes large when the squib resistance is about to break due to deterioration over time, and becomes small when water adheres. In this way, when the resistance value of the squib resistance changes,
In response to this, the output voltage of the operational amplifier also changes as shown in FIG. That is, if the maximum value of the resistance value that can be determined as the short-circuited state of the squib resistor connection is R ₁ and the minimum value of the resistance value that can be determined as the disconnected state of the squib resistance is R ₂ , the squib resistance is 0 (completely short-circuited state). ) From R ₁ , R
As the output voltage increases to ₂ , the output voltage also increases. Note that, in FIG. 8, the output voltage of the operational amplifier when a low voltage is applied to the squib resistor is shown with a symbol V ₁ , and the output voltage of the operational amplifier when a high voltage is applied to the squib resistor is V ₂ The symbol is attached.

[0004]

[Problems to be Solved by the Invention]
The output voltage of the pump is the power supply voltage V_maxCan't cross
Therefore, as shown in FIG. 8, the squib resistance is R₁Greater than
Ki R_XOutput voltage V_TwoIs V_maxIs constant
The squib resistance is R_XGreater than R_YWhen the above is reached
Force voltage V₁Is V_maxIs constant. That is, squib resistance
Output voltage V of the operational amplifier regardless of the value of_Two, V₁But
Area E where each is constant_max1(Resistance is R _XAbove), E
_max2(Resistance is R_YThere is).

As described above, when the output voltage of the operational amplifier becomes constant, the change amount ΔV (= V ₂ of the output voltage of the operational amplifier).
-V ₁ ) has a squib resistance of R as shown in FIG.
It increases beyond the threshold value (V _th1 ) for judging the disconnection until it becomes _X, and when the value of the squib resistance becomes R _X or more, the change amount Δ
V decreases, and when the value of the squib resistance becomes R _Y or more, the change amount ΔV becomes 0. Therefore, there is a region E ₂ (having a resistance value of R ₃ or more) in which the amount of change ΔV, which should be calculated if it is originally larger than the threshold value for disconnection determination, is calculated to be less than or equal to the threshold value for disconnection determination.

The present invention has been made in view of the above facts, and an object of the present invention is to provide a disconnection judging device capable of accurately judging a disconnection of a resistance.

[0007]

In order to achieve the above object, the invention according to claim 1 includes an operational amplifier for amplifying and outputting a voltage across a resistor, and an applying means for applying a voltage to the resistor and the operational amplifier. A change means for changing the voltage applied to the resistor, and an absolute value of a change amount of the output voltage of the operational amplifier changed according to the change of the voltage in a region larger than a predetermined first threshold value. A first determination process for determining whether the value is a value, and a value that is less than the maximum value of the output voltage on the high voltage side corresponding to the region and is equal to or more than the minimum value of the output voltage on the high voltage side corresponding to the region. A second determination process, which is predetermined as a second threshold value and determines whether the output voltage on the high voltage side is higher than the second threshold value, is the negative determination result and the other determination result. If the processing result is positive, It comprises a determination unit and disconnection of the anti, the.

According to a second aspect of the present invention, an operational amplifier for amplifying and outputting a voltage across the resistor, an applying means for applying a voltage to the resistor and the operational amplifier, and a voltage applied to the resistor are changed. A changing means and a first judging process for judging whether the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is a value in a region larger than a predetermined first threshold value; And a value that is equal to or lower than the maximum value of the output voltage on the low voltage side corresponding to the region and is equal to or higher than the minimum value of the output voltage on the low voltage side corresponding to the region, as a second threshold value. The second determination process of determining whether the output voltage on the voltage side is greater than a second threshold value, wherein the resistance is determined when one of the processing results is a negative determination and the other processing result is an affirmative determination. The judgment means for judging the disconnection of Eteiru.

According to a third aspect of the present invention, an operational amplifier that amplifies and outputs a voltage across a resistor, an applying unit that applies a voltage to the resistor and the operational amplifier, and a voltage applied to the resistor are changed. The changing means and the high voltage side corresponding to the area within the area where the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is larger than a first threshold value set in advance. Of less than the maximum value of the output voltage and above the minimum value of the output voltage on the high voltage side corresponding to the region is predetermined as the second threshold value, and the output voltage on the high voltage side is the second threshold value. And a determination means for determining that the resistance is broken when the resistance is larger than the threshold value.

According to a fourth aspect of the present invention, an operational amplifier that amplifies and outputs a voltage across the resistor, an applying unit that applies a voltage to the resistor and the operational amplifier, and a voltage applied to the resistor are changed. The changing means and a low value corresponding to the region in which the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is a value larger than a predetermined first threshold value. A value equal to or lower than the maximum value of the output voltage on the voltage side and equal to or higher than the minimum value of the output voltage on the low voltage side corresponding to the region is predetermined as a second threshold value, and the output voltage on the low voltage side is If it is larger than the threshold value of 2, it is determined that the resistance is broken.

Here, the applying means according to the invention of claim 1 applies a voltage to the resistor and the operational amplifier. The operational amplifier amplifies and outputs the voltage across the resistor. The changing means changes the voltage applied to the resistor. In addition, the changing means increases the voltage applied to the resistor,
Alternatively, it may change so as to become smaller.

When the voltage applied to the resistance is changed by the changing means in this way, the judging means judges that one of the first judgment processing and the second judgment processing has a negative judgment and the other judgment result. When the processing result is affirmative, it is determined that the resistance is broken.

That is, the determination means executes, for example, the first determination processing, and when the processing result of the first determination processing is a negative determination, it executes the second determination processing and the second determination processing. When the processing result of (1) is affirmative, it is determined that the resistance is broken. Further, the determination means executes the second determination processing, and when the processing result of the second determination processing is a negative determination, executes the first determination processing and the processing result of the first determination processing is positive. In the case of the judgment, it is judged that the resistance is broken. In addition, the determination means may determine that the resistance is broken when the result of one of the first determination processing and the second determination means executed first is a positive determination.

Here, the first judgment processing determines whether the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is a value in a region larger than a predetermined first threshold value. to decide. That is, in the first determination process, when the voltage applied to the resistance is changed to be large,
It is judged whether the amount of change (positive value) of the output voltage of the operational amplifier is larger than the first threshold value, and if the voltage applied to the resistor is changed to be small, the change of the output voltage of the operational amplifier It is determined whether the quantity (negative value) is smaller than the negative value of the first threshold value. That is, the first determination process determines whether or not the absolute value is larger than a predetermined first threshold value, and if the determination is affirmative, the absolute value is determined to be a value within the region. To do. The first threshold value is a predetermined value with which it can be determined that the resistance is broken.

As described above, since it can be determined that the resistance is broken in the region, in the second determination process, the output voltage is less than the maximum value of the high voltage side corresponding to the region and the high voltage side corresponding to the region. A value equal to or higher than the minimum value of the above output voltage is determined in advance as the second threshold value. That is, if the output voltage on the voltage side is larger than the second threshold value, it can be determined that the resistance is broken. Therefore, the second determination process is
It is determined whether the output voltage on the high voltage side output from the operational amplifier after the voltage is changed by the changing means to be larger or smaller is larger than the second threshold value.

Here, since the output voltage from the operational amplifier cannot be larger than the voltage (power supply voltage) applied by the applying means described above, the maximum value of the output voltage on the high voltage side corresponding to the above region is the power supply. Corresponds to the voltage.

Further, since the operational amplifier has an offset that changes depending on temperature, the minimum value of the output voltage on the high voltage side corresponding to the above area changes. The range of the minimum value that changes in this way is predetermined, and the maximum value of the range is hereinafter referred to as the maximum limit value.

Therefore, it is more preferable that the second threshold value is lower than the power supply voltage of the operational amplifier and equal to or higher than the maximum limit value.

Here, assuming that the maximum resistance value when the resistance connection is in the normal state is the first resistance value, and the resistance value is larger than the first resistance value, the output voltage on the high voltage side is the normal value. It is larger than the case of the state. When the resistance value when the output voltage on the high voltage side matches the power supply voltage is the second resistance value, the output voltage on the low voltage side increases when the resistance value is larger than the second resistance value. Since the output voltage on the high voltage side is constant at the power supply voltage, the absolute value becomes small. Therefore, when the resistance value becomes larger than the second resistance value, the absolute value may become equal to or smaller than the first threshold value. Therefore, even if the processing result of the first determination processing is a negative determination, the resistance may be disconnected.

Further, the second threshold value is less than the maximum value of the output voltage on the high voltage side corresponding to the above region and is more than the minimum value of the output voltage on the high voltage side corresponding to the region,
The output voltage may be less than or equal to the second threshold value even if the resistance is broken. Therefore, even if the processing result of the second determination processing is negative, the resistance may be broken.

As described above, the resistance may be broken even if the processing results of the first judgment processing and the second judgment processing are negative judgments. Therefore, the first judgment processing and the second judgment processing are performed. It is not possible to accurately determine the disconnection of the resistance with only one of them.

On the other hand, when the resistance is broken, the output voltage on the high voltage side is larger than the second threshold value even if the processing result of the first determination processing is negative, and the output voltage on the high voltage side is Even if the output voltage is less than or equal to the second threshold value, the absolute value is greater than the first threshold value. Therefore, when the resistance is broken, even if one of the processing results of the first determination processing and the second determination processing is a negative determination, the other is a positive determination.

Therefore, according to the present invention, when one of the first determination process and the second determination process has a negative determination and the other has a positive determination result, it is determined that the resistance is broken. Therefore, the disconnection of the resistance can be accurately determined without omission.

Next, the invention according to claim 2 will be described. Since the applying means, the operational amplifier, and the changing means according to the invention of claim 2 are the same as those of the invention of claim 1, the description thereof will be omitted.

On the other hand, the judging means judges that the resistance is broken when either one of the first judgment processing and the second judgment processing has a negative judgment and the other processing result has a positive judgment. .

Here, the first judgment processing is the same as that of the invention described in claim 1. On the other hand, the second determination processing according to the invention of claim 2 is less than or equal to the maximum value of the output voltage on the low voltage side corresponding to the region and greater than or equal to the minimum value of the output voltage on the low voltage side corresponding to the region. A value is predetermined as a second threshold value and it is determined whether the output voltage on the low voltage side is larger than the second threshold value. That is, the second determination processing determines whether the output voltage on the low voltage side output from the operational amplifier due to the change of the voltage by the changing means is larger than the second threshold value.

The second threshold value according to the second aspect of the present invention is equal to or less than the maximum value of the output voltage on the low voltage side corresponding to the above-mentioned region and corresponding to the region, considering the above-mentioned offset. More preferably, it is equal to or higher than the maximum limit value of the minimum value of the output voltage on the low voltage side.

Further, even if either the processing result of the first judgment processing or the processing result of the second judgment processing of the invention of claim 2 is a negative judgment, it is the same as the invention of claim 1. , The resistance may be broken. However, if the resistance is broken, even if one of the processing results of the first determination processing and the processing result of the second determination processing is a negative determination, the other is a positive determination.

Therefore, according to the invention of claim 2, the resistance is disconnected when the result of one of the first determination process and the second determination process is a negative determination and the other process result is a positive determination. To determine. Therefore, the disconnection of the resistance can be accurately determined without omission.

Since the applying means, the operational amplifier, and the changing means according to the invention described in claims 3 and 4 are the same as those in the invention described in claim 1, the description thereof will be omitted.

Further, in the judging means according to the third aspect of the present invention, the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is larger than the predetermined first threshold value. And, a value that is less than the maximum value of the output voltage on the high voltage side corresponding to the region and is equal to or more than the minimum value of the output voltage on the high voltage side corresponding to the region is predetermined as the second threshold value, When the output voltage on the high voltage side is larger than the second threshold value, it is determined that the resistance is broken. The first threshold value and the second threshold value are the same as in the first aspect of the invention.

According to a fourth aspect of the present invention, in the determining means, the absolute value of the change amount of the output voltage of the operational amplifier changed according to the change of the voltage is a value within a predetermined first threshold value. And a value equal to or lower than the maximum value of the output voltage on the low voltage side corresponding to the region and equal to or higher than the minimum value of the output voltage on the low voltage side corresponding to the region is predetermined as the second threshold value, When the output voltage on the low voltage side is larger than the second threshold value, it is determined that the resistance is broken. The first threshold value and the second threshold value are the same as the invention according to claim 2.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the airbag device control circuit according to the disconnection determination device of the present embodiment is connected to both terminals 14A and 14B of a squib resistor 14 provided in the squib 12. Squib resistance 1
4A is connected to the non-inverting input terminal 16A of the operational amplifier 16 via the resistor R1, and the other terminal 14B of the squib resistor 14 is connected to the inverting input terminal 16B of the operational amplifier 16 via the resistor R2. It is connected.
The output terminal 16C of the operational amplifier 16 is connected to the inverting input terminal 16B of the operational amplifier 16 via the resistor R3. The output terminal 16C of the operational amplifier 16 is a CPU
It is also connected to 18 input terminals 18A. Further, the operational amplifier 16 is connected to a power supply circuit 20 which applies a power supply voltage V _max to the operational amplifier 16.

The non-inverting input terminal 1 of the operational amplifier 16
One terminal of the resistor R4 is connected between 6A and the resistor R1, and the other terminal of the resistor R4 is grounded. Furthermore,
One terminal of the resistor R5 is connected between the terminal 14B of the squib resistor 14 and the resistor R2, and the other terminal of the resistor R5 is grounded.

The collector C of the transistor Tr1 is connected to the terminal 14A of the squib resistor 14 via the resistor R6 and the diode D1, and the emitter E of the transistor Tr1 is connected to the power supply circuit 20 for applying the voltage V _CC. Has been done. A resistor R7 is connected between the emitter E and the collector C of the transistor Tr1. A resistor R8 is connected between the emitter E and the base B of the transistor Tr1, and the base B of the transistor Tr1 has a resistor R.
9 is connected to the output terminal 18B of the CPU 18.

A display device 22 provided on an instrument panel or the like is connected to the output terminal 18C of the CPU 18. The display device 22 includes a disconnection lamp for indicating that the squib resistor 14 (not shown) is disconnected and a short-circuit lamp for indicating that the squib resistor 14 (not shown) is short-circuited. .

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. In this embodiment, step 10
At 0, the transistor Tr1 is turned off by turning off the current from the output terminal 18B. As a result, a low voltage is applied between both terminals 14A and 14B of the squib resistor 14.

Thus, both terminals 14 of the squib resistor 14 are
When a low voltage is applied between A and 14B, an output voltage obtained by multiplying the low voltage by a predetermined amplification degree is input to the input terminal 18A from the output terminal 16C of the operational amplifier 16.

Therefore, in step 102, the output voltage of the operational amplifier 16 input to the input terminal 18A is taken in, and the voltage taken in in step 104 is stored as V ₁ .

Next, at step 106, the transistor Tr1 is turned on by supplying a predetermined current from the output terminal 18B. Thereby, a high voltage is applied between both terminals 14A and 14B of the squib resistor 14.

Thus, both terminals 14 of the squib resistor 14 are
When a high voltage is applied between A and 14B, an output voltage obtained by multiplying the high voltage by a predetermined amplification degree G is input to the input terminal 18A from the output terminal 16C of the operational amplifier 16.

Therefore, in step 108, the output voltage of the operational amplifier 16 input to the input terminal 18A is fetched, and the voltage fetched in step 110 is stored as V ₂ .

Then, in step 112, it is judged whether the connection of the squib resistor 14 is in the state of disconnection, short circuit or normal.

Next, step 112 will be described in detail with reference to FIG. In step 120 of FIG. 3, it is determined whether the voltage V ₂ is larger than the threshold value V _th4 (see FIG. 4).

Here, the threshold value V _th4 will be described. As shown in FIG. 4, the threshold value V _th4 is an area E in which the difference ΔV between the output voltage V ₂ and the output voltage V ₁ is equal to or less than the threshold value V _th1 (the threshold value V for the disconnection determination described above). ₀ can take a minimum value or a value of the output voltage V ₂ corresponding to the maximum value less than a and the region E ₀ of the output voltage V ₂ corresponding.

Here, the output voltage of the operational amplifier 16 is
Power supply voltage V of amplifier 16_maxCan't cross
And area E₀Output voltage V corresponding to_TwoThe maximum value of
Pressure V _maxCorresponding to

Further, the maximum value of the resistance value of the squib resistor 12 in a normal connection is R _2, and when the resistance value of the squib resistor 12 is R ₂ , a high voltage is applied and the operational amplifier 1
Assuming that the voltage V ₄ is output from 6, the minimum value of the output voltage V ₂ corresponding to the area E ₀ is the voltage V ₄ .

[0048] Thus, the output voltage of the operational amplifier 16, if it exceeds a value less than the output voltage V ₄ or more and the supply voltage V _{ma x,} it can be determined that the disconnection of the squib resistor 14.

By the way, since the operational amplifier 16 has an offset that changes depending on the temperature, the value of the voltage V ₄ changes. The range of the value of the voltage V ₄ is predetermined, and the maximum value of the range is the voltage V _4max .

Therefore, the threshold V _th4 is equal to the voltage V _4max.
It is more preferable that the value is not less than the above and less than the power supply voltage V _max .

Therefore, in this embodiment, a value smaller than the power supply voltage V _max of the operational amplifier 16 by a predetermined value is set as the threshold value V _th4 .

When the output voltage V ₂ is larger than the threshold value V _th4 , it can be determined that the squib resistor 14 is broken, and
In step 122, the disconnection lamp is turned on (disconnection processing), and this routine ends.

On the other hand, when the output voltage V ₂ is less than or equal to the threshold value V _th4 , in step 124, the output voltage change amount ΔV (= V) which changes according to the change in the voltage between both terminals of the squib resistor 14. _2- V ₁ ) is calculated, and in step 126 it is determined whether or not the amount of change ΔV is less than or equal to the threshold value V _th1 .

Here, the reason why it is further judged whether the variation ΔV is the threshold value V _th1 or less when the output voltage V ₂ is the threshold value V _th4 or less will be described. That is, as described above,
Since the threshold value V _th4 is a value smaller than the power supply voltage V _max of the operational amplifier 16 by a predetermined value, even if the output voltage V ₂ is equal to or lower than the threshold value V _th4 , the voltage is equal to or higher than the voltage V ₄ and is equal to the threshold value V th.
If the value is less than _th4 , it should be judged that the squib resistor 14 is disconnected. This area (included in the area E ₀ ) is designated as E ₁ .

However, the output voltage V ₂ is equal to the threshold V
Since it is equal to or less than _th4 , the determination in step 120 becomes a negative determination and the process cannot proceed to step 122.

On the other hand, even if the output voltage V ₂ is the threshold value V _th4 or less, it is at least the voltage V ₄ or more and the threshold value V
If the value is less than _th4 , the variation ΔV is greater than the threshold value V _th1 .

Therefore, when the determination in step 120 is negative, it is further determined whether or not the variation ΔV is less than or equal to the threshold value V _th1 to determine whether the output voltage V ₂ is the value in the region E _1. Whether or not the squib resistor 14 is disconnected is determined.

Therefore, if the change amount ΔV is larger than the threshold value V _th1 , it can be determined that the squib resistor 14 is broken, so the routine proceeds to step 122. On the other hand, when the change amount ΔV is equal to or less than the threshold value V _th1 , it can be determined that the squib resistor 14 is not broken, that is, the connection of the squib resistor 14 is in the normal state or the short-circuited state.

Therefore, when the change amount ΔV is less than or equal to the threshold value V _th1 , it is determined in step 128 whether the change amount ΔV is smaller than the threshold value V _th2 . If the amount of change ΔV is smaller than the threshold value V _th2 , it can be determined that the squib resistor 14 is short-circuited. Therefore, in step 130, the short-circuit lamp is turned on (short-circuit processing), and this routine ends.

If it is determined in step 128 that the amount of change ΔV is greater than or equal to the threshold value V _th2 , the squib resistance 1
Since it can be determined that the connection of No. 4 is in the normal state, the lamp is not turned on and this routine is ended.

As described above, according to the present embodiment, even if the input voltage of the operational amplifier is a value obtained by multiplying the input voltage by the amplification degree, which is larger than the power supply voltage of the operational amplifier, the input voltage is predetermined from the power supply voltage of the operational amplifier. A small value is used as a threshold value, and if the output voltage of the operational amplifier when a high voltage is applied exceeds the threshold value, it is determined that the squib resistance is disconnected. You can

Further, even when the output voltage of the operational amplifier when a high voltage is applied is equal to or lower than the threshold value (V _th4 ), the squib resistance of the squib resistance is increased when the change amount is larger than the threshold value (V _th1 ). Since the disconnection is determined, the disconnection of the squib resistance can be determined without exception.

In the first embodiment described above, the output
Voltage V_TwoIs the threshold V_th4The variation ΔV is
Threshold V_th1Although it is judged whether it is larger, the present invention is
The amount of change ΔV is not limited to this, and the threshold value V
_th1If the judgment is positive, the judgment is made
When it is judged that the quib resistor 14 is disconnected, the change amount ΔV
Threshold V_th1Output voltage V_TwoGashi
Threshold V_th4It is judged whether it is larger or not, and the judgment is positive.
If the squib resistance 14 is broken,
May be. Further, the change amount ΔV is the threshold value V_th1Below,
And output voltage V _TwoIs the threshold V_th4Greater than
Also, it may be determined that the squib resistor 14 is disconnected.
Yes.

Next, a second embodiment of the present invention will be described. Since the configuration of this embodiment is the same as the configuration of the first embodiment described above, the description thereof will be omitted.

Next, the operation of this embodiment will be described. The operation of this embodiment is the same as step 120 of the above-described first embodiment.
Since only (FIG. 3) is different, different parts will be described, the same parts will be denoted by the same reference numerals, and description thereof will be omitted.

In step 132 according to this embodiment, as shown in FIG. 6, the output voltage V ₁ is the threshold value V _th3 (see FIG. 4).
Determine if it is greater than.

Here, the threshold value V _th3 will be described. The threshold V _th4, as shown in FIG. 4, the minimum value over the value of the output voltages V ₁ corresponding to the maximum value or less and the region E ₀ of the output voltages V ₁ corresponding to the region E ₀ Can be taken.

When the resistance value of the squib resistor 14 is R ₂ , a low voltage is applied to the squib resistor 14 and the operational amplifier 1
When the voltage output from the 6 and V _3, also changes the value of the voltage V ₃ by Ohesetto described above. The range of the value of the voltage V ₃ is predetermined, and the maximum value of the range is the voltage V _3max.
And

Therefore, the threshold V _th3 is equal to the voltage V _3max
It is more preferable that the value is not less than the minimum value of the output voltage V ₁ corresponding to the region E ₀ .

[0070] Therefore, in this embodiment, it is set to a threshold V _th3 a predetermined value greater than the reliably determine possible and voltage V _{3m ax} disconnection of the squib resistor 14.

On the other hand, also in this embodiment, when the output voltage V ₁ is less than or equal to the threshold value V _th3 , the steps 124 and 12 are performed.
The process 6 is performed for the following reason.

That is, as described above, since the threshold value V _th3 is a value larger than the voltage V _3max by the predetermined value, even if the output voltage V ₁ is the threshold value V _th3 or less, at least the voltage V ₃ or more and If the value is less than the threshold value V _th3 , it should be judged that the squib resistor 14 is disconnected. However, since the output voltage V ₁ is below the threshold value V _th3 ,
The determination in step 120 becomes a negative determination in step 12
I can't go to 2.

On the other hand, even if the output voltage V ₁ is the threshold value V _th3 or less, it is at least the voltage V ₃ or more and the threshold value V th.
If the value is less than _th3 , the variation ΔV is greater than the threshold value V _th1 .

Therefore, if the determination in step 120 is negative, it is further determined whether the change amount ΔV is equal to or less than the threshold value V _th1 to determine whether the output voltage V ₁ is the value in the region E _1. Whether or not the squib resistor 14 is disconnected is determined.

In the second embodiment described above, when the output voltage V ₁ is less than or equal to the threshold value V _th3, it is determined whether or not the change amount ΔV is greater than the threshold value V _th1. The change amount ΔV is not limited to the threshold value V
If it is larger than _th1 , the squib resistor 14 is judged to be disconnected if the judgment is affirmative, and the output voltage V ₁ is equal to the threshold V even if the variation ΔV is equal to or _smaller than the threshold V _{th1. It} may be determined whether or not it is larger than _th3 , and if the determination is affirmative, it may be determined that the squib resistor 14 is disconnected. Further, when the change amount ΔV is less than or equal to the threshold value V _th1 ,
When the change amount ΔV is larger than the threshold value V _th1 ,
It may be determined that the squib resistor 14 is disconnected.

Next, a third embodiment of the present invention will be described. Since the configuration of this embodiment is the same as the configuration of the first embodiment described above, the description thereof will be omitted.

Next, the operation of this embodiment will be described. The operation of this embodiment is the same as step 120 of the above-described first embodiment.
Since only (FIG. 3) is different, different parts will be described, the same parts will be denoted by the same reference numerals, and description thereof will be omitted.

In step 140 according to this embodiment, as shown in FIG. 7, the change amount ΔV (= V ₂ −V ₁ ) of the output voltage between both terminals of the squib resistor 14 is calculated, and step 142 is executed.
Then, it is determined whether or not the change amount ΔV is less than or equal to the threshold value V _th1 .

If the amount of change ΔV is larger than the threshold value V _th1 , it can be determined that the squib resistor 14 is broken, so that the process proceeds to step 122. On the other hand, the change amount ΔV is the threshold value V
_{If th1} or less, in step 144, output voltage V ₁
Is greater than the threshold value V _th5 (see FIG. 4).

Here, the threshold value V _th5 will be described. When the process proceeds to step 144, the change amount ΔV is equal to the threshold value V _th1.
Although determined as below, there is a region E ₃ (included in the region E ₀ ) that should be determined to be a disconnection of the squib resistor 14. That is, as described above, since the output voltage of the operational amplifier 16 cannot exceed the power supply voltage Vmax, the change amount ΔV of the output voltage of the operational amplifier 16 is equal to the threshold value V _th1.
There is a case in which the threshold voltage V _th1 again increases and then decreases, and then again coincides with the threshold value V _th1 . Even in the region E ₂ where the output voltage V ₁ is larger than the output voltage of the operational amplifier 16 at this time, it should be judged that the squib resistor 14 is disconnected.
Since V is equal to or lower than the threshold value V _th1, it is determined that the connection state of the squib resistor 14 is normal.

[0081] Therefore, the variation ΔV in the output voltage of the operational amplifier 16, and decreased after increased exceeds the threshold value V _th1, the low voltage side of the operational amplifier 16 corresponding to a time consistent with the threshold value V _th1 again Output voltage is set to a threshold value V _th5 .

Therefore, when the output voltage V ₁ is larger than the threshold value V _th5 , the output voltage V ₁ is a value within the region E ₂ and the squib resistor 14 can be determined to be disconnected. Therefore, the process proceeds to step 122. If the output voltage V ₁ is less than or equal to the threshold value V _th5 , the process proceeds to step 128.

In the third embodiment described above, the change
The amount ΔV is the threshold value V_th1Output voltage V in the following cases₁Gashi
Threshold V_th5Although it is judged whether it is larger, the present invention is
The output voltage V is not limited to this.₁Is the threshold V
_th5If the judgment is positive, the judgment is made
It is determined that the quib resistor 14 is disconnected, and the output voltage V ₁
Is the threshold V_th5Even in the following cases, the change amount ΔV
Threshold V_th1It is judged whether it is larger, and the judgment is a positive judgment.
Even if it is determined that the squib resistor 14 is broken
Good.

In the first to third embodiments described above, the state in which the low voltage is applied between the terminals 14A and 14B of the squib resistor 14 is switched to the state in which the high voltage is applied, that is, the squib resistor. 14 terminals 14A, 14
Although the voltage between B is changed so as to be large, the present invention is not limited to this, and a low voltage is applied from a state in which a high voltage is applied between both terminals 14A and 14B of the squib resistor 14. The state may be switched to the above state, that is, the voltage between both terminals 14A and 14B of the squib resistor 14 may be changed to be small.

[0085]

As described above, the present invention has the effect of improving the reliability of the determination result because the disconnection of the resistance can be accurately determined without omission.

[Brief description of drawings]

FIG. 1 is an electric circuit showing an airbag device control circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a main routine according to the first embodiment.

FIG. 3 is a flowchart showing a subroutine of step 112 of the main routine.

FIG. 4 is a graph showing a relationship between a resistance value of a squib resistor and an output voltage of an operational amplifier.

FIG. 5 is a graph showing the relationship between the resistance value of a squib resistor and the amount of change in the output voltage of an operational amplifier.

FIG. 6 is a flowchart showing a subroutine of step 112 according to the second embodiment of the present invention.

FIG. 7 is a flowchart showing another subroutine of step 112 according to the third embodiment of the present invention.

FIG. 8 is a graph showing the relationship between the resistance value of a squib resistor and the output voltage of an operational amplifier.

[Explanation of symbols]

 14 squib resistance 16 operational amplifier 18 CPU 20 power supply circuit Tr1 transistor

Claims (4)

[Claims] 1. An operational amplifier that amplifies and outputs a voltage across a resistor, an applying unit that applies a voltage to the resistor and the operational amplifier, a changing unit that changes the voltage applied to the resistor, and the voltage. A first determination process of determining whether the absolute value of the amount of change in the output voltage of the operational amplifier that has changed in accordance with the change of is within a range larger than a predetermined first threshold value;
A value that is less than the maximum value of the output voltage on the high voltage side corresponding to the region and is equal to or more than the minimum value of the output voltage on the high voltage side corresponding to the region is set in advance as the second threshold value. A second determination process for determining whether the output voltage is greater than a second threshold value, the resistance disconnection when one of the processing results is a negative determination and the other processing result is an affirmative determination. A disconnection determination device comprising: determination means for determining 2. An operational amplifier that amplifies and outputs a voltage across a resistor, an applying unit that applies a voltage to the resistor and the operational amplifier, a changing unit that changes the voltage applied to the resistor, and the voltage. A first determination process of determining whether the absolute value of the amount of change in the output voltage of the operational amplifier that has changed in accordance with the change of is within a range larger than a predetermined first threshold value;
A value that is equal to or lower than the maximum value of the output voltage on the low voltage side corresponding to the region and is equal to or higher than the minimum value of the output voltage on the low voltage side corresponding to the region is set in advance as the second threshold value. A second determination process for determining whether the output voltage is greater than a second threshold value, the resistance disconnection when one of the processing results is a negative determination and the other processing result is an affirmative determination. A disconnection determination device comprising: determination means for determining 3. An operational amplifier for amplifying and outputting a voltage across a resistor, an applying unit for applying a voltage to the resistor and the operational amplifier, a changing unit for changing a voltage applied to the resistor, and the voltage. Within a region in which the absolute value of the amount of change in the output voltage of the operational amplifier that has changed in accordance with the change is larger than a predetermined first threshold value, and the maximum of the output voltage on the high voltage side corresponding to the region. A value that is less than the above value and is equal to or higher than the minimum value of the output voltage on the high voltage side corresponding to the region is predetermined as the second threshold value, and the output voltage on the high voltage side is greater than the second threshold value. 2. A disconnection determination device comprising: a determination unit that determines that the resistance is disconnected. 4. An operational amplifier that amplifies and outputs a voltage across a resistor, an applying unit that applies a voltage to the resistor and the operational amplifier, a changing unit that changes a voltage applied to the resistor, and the voltage. Of the output voltage of the operational amplifier, which has changed in accordance with the change of the absolute value, is larger than a first threshold value set in advance, and the output voltage on the low voltage side corresponding to the area. Of less than or equal to the maximum value of the low voltage side and above the minimum value of the output voltage of the low voltage side corresponding to the region is predetermined as a second threshold value, and the output voltage of the low voltage side is lower than the second threshold value. A disconnection determination device comprising: a determination unit that determines that the resistance has a disconnection when it is large.