JP2001318115A - Detection circuit for short circuit of signal line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus by which a short circuit can be diagnosed simply and at low costs by a method wherein a pattern for short-circuit detection is formed on a circuit board of a multistage development structure. SOLUTION: A pattern line which is always maintained at a constant voltage is arranged and installed between patterns of a plurality of signal lines which are arranged in parallel so as to be adjacent. When the potential of the pattern line is generated in any signal line from among the plurality of signal lines, the detection circuit for the short circuit of a signal line judges that the signal line in which the potential of the pattern line is generated is short-circuited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal line short-circuit detecting circuit for detecting a short circuit between signal lines, and is particularly suitable for an occupant protection device that performs multi-stage deployment.

[0002]

2. Description of the Related Art A conventional signal line short-circuit detection circuit of this type will be described below using an occupant protection device such as an airbag unit shown in FIG. That is, 1 is an in-vehicle battery, 2 is an ignition switch, 3 is a booster circuit which is supplied with a voltage from the battery 1 and boosts and outputs the supplied voltage, and 4 is a backup capacitor which is charged by the output of the booster circuit 3. Is done. A switching transistor 5 has a drain connected to the non-ground side terminal of the backup capacitor 4, that is, an output terminal of the booster circuit 3, and a source connected to one end of the primer 6. An output port of the microcomputer 12 described later is connected to the base via the OR gate 7, and when a high-level ignition signal and a diagnostic signal are supplied from the output port, the microcomputer is turned on only while the signal is being supplied. .
Note that the pulse width of the diagnostic signal is set to be about 1/100 of the pulse width of the ignition signal, and is insufficient for driving the primer 6 to ignite.

[0003] Reference numeral 8 denotes a first diagnostic high-resistance element, one end of which is A
Is connected to an output terminal of a constant voltage circuit (not shown) that is a power supply of the microcomputer 12 and has a constant voltage (+ V).
And the other end B is connected to a connection line between the source of the switching transistor 5 and the primer 6. A mechanical acceleration switch 9 is connected between the other end C of the primer 6 and ground (ground), and a second high-resistance element 10 for diagnosis is connected in parallel. Reference numeral 11 denotes a comparison circuit which inputs voltages generated at both terminals B and C of the primer 6 and obtains a difference between the voltages to supply the difference to a diagnosis means 14 of a microcomputer 12 described later.

[0004] Reference numeral 12 denotes a microcomputer, which comprises diagnosis means 14 and collision determination means 13, and each of the means 13, 14 is operated by a dedicated program. That is, the diagnosing means 14 inputs the output signal from the comparison circuit 11 and the voltages generated at both ends B and C of the primer 6 and diagnoses the switching transistor 5, the primer 6 and the mechanical acceleration switch 9. The diagnosis will be described in detail later).

The collision judging means 13 receives an acceleration signal output from the acceleration sensor 15 and judges whether or not the collision is a serious collision based on the magnitude of the acceleration signal, a state of a temporal change, and the like. OR gate 7
A high-level ignition signal is supplied to the switching transistor 5 through the switch to turn on the primer 6.

Next, the operation of the above configuration will be described. (When the collision determination means 13 is operating) After the ignition switch 2 is turned on, the microcomputer 1
Numeral 2 indicates that the diagnosing means 14 inputs the output voltage from the comparison circuit 11 and inputs the voltages generated at both terminals B and C of the primer 6, and diagnoses the primer 6 based on those voltages.
That is, the terminal B side is not grounded or the power line (+
V), whether there is a ground fault,
When the dedicated program of the collision judging means 13 is executed after judging whether or not the C is short-circuited, and the collision judging means 13 of the microcomputer 12 does not judge a serious collision based on the acceleration signal from the acceleration sensor 15 ,
The switching transistor 5 is turned off.

However, the microcomputer 12
When the collision determining means 13 determines that the collision is a serious collision, the switching transistor 5 is turned on by supplying a low-level trigger pulse to the switching transistor 5, and the electric power charged in the backup capacitor 4 is transferred to the detonator 6, the mechanical acceleration. The air flows into the switch 9 in series, whereby the airbag (not shown) is deployed.

(When the diagnostic means 14 is operating) Failure diagnosis of the primer 6 (a) The diagnostic means 14 of the microcomputer 12 inputs the respective voltages of the terminals B and C of the primer 6 and Are both equal to or greater than the specified value, the primer 6 determines that one terminal B is short-circuited to the power line of the constant voltage power supply (+ V), and if the value is within the specified value, it is short-circuited. Judge that there is no. (B) Diagnostic means 14 of microcomputer 12
When it is determined that the voltage at one terminal B of the primer 6 is equal to or higher than a specified value and the voltage at the other terminal C is equal to or lower than the specified value, it is determined that the primer 6 is disconnected. (C) Diagnostic means 1 of microcomputer 12
4 determines, based on the voltages generated at both terminals B and C of the primer 6 that both of the voltages are lower than the specified value, the primer 6 has one of the terminals B or C grounded. Is determined to be.

[0009]

However, in the above-mentioned occupant protection device, one having a structure in which one primer is ignited to deploy one airbag is used. Diagnosis of short-circuit, ground fault, etc. of the primer of the configuration can be easily performed as described above, but a plurality of primers are sequentially ignited to deploy one airbag.
When a circuit configuration using the above-described method is employed in a so-called multi-stage structure, there is a problem that the circuit configuration is complicated as shown in FIG.

Next, the structure of the multi-stage development will be specifically described. In FIG. 3, two portions surrounded by a broken line Y are connected in parallel to form a multi-stage development.
That is, in FIG. 4, each of the portions surrounded by broken lines Z and W corresponds to the portion surrounded by broken line Y connected in parallel. In this configuration, for example, the portion surrounded by broken lines Z and W is one IC. In such a case, an ignition signal may be output from an output port adjacent to or close to the output port due to the circuit configuration inside the IC. In this case, if a circuit pattern is formed by adopting the recent high-density mounting technology of the substrate, the thickness of the pattern wiring must be reduced and the interval must be reduced.

[0011] Therefore, a short circuit due to migration is likely to occur between circuit patterns.
The signal lines on the positive potential side of both the primers 6a and 6b are M and N
May short out at each other. That is, the signal lines on one non-power-supply terminal side of the two diagnostic high-resistance elements 8a and 8b that are not in electrical contact are brought into contact with each other to be connected in parallel, and both primers 6a and 6b are connected in parallel. Although connected, the primer 6 supplied to the diagnostic means 14 ′
Since the voltages at the terminals M and N of the terminals a and 6b do not change in a range where it can be assumed that the terminals have changed, the potential difference does not change.
6b cannot be determined to be short-circuited on the positive potential side.

[0012] Further, other fault diagnosis will also be specifically described. (1) When the short-circuit between the terminals of the primer 6a occurs, the output of the first comparison circuit 11a becomes low level, and the diagnostic high-resistance element 8a and the primer 6a The voltage at the connection line N point with the high-resistance diagnostic element 8
The power supply voltage (+ V) is divided by the a, 10 and the primer 6a to a value obtained by dividing the power supply voltage (+ V) by the diagnostic high-resistance elements 8a, 10. The same applies to the primer 6b. (2) In the disconnection between the terminals of the primer 6a, the output of the first comparison circuit 11a becomes a high level, and the voltage at the connection line N point between the high-resistance element 8a for diagnosis and the primer 6a becomes the power supply voltage (+ V). The voltage at the connection line L between the diagnostic high-resistance element 10 and the primer 6a becomes the ground level. The same applies to the primer 6b. (3) A ground fault at the point L on the negative potential side of the primer 6a or a short circuit between the terminals of the mechanical acceleration switch 9 causes the negative potential L of the primer 6a to fall.
The potential of the point becomes the ground level. The same applies to the primer 6b. (4) The ground fault at the point N on the positive potential side of the primer 6a, the potential at the point N on the positive potential side and the potential at the point L on the negative potential side of the primer 6a become the ground level.

In FIG. 4, since the components are basically the same as or equivalent to the components shown in FIG. 3, the same reference numerals (subscripts are different) are assigned to those parts. ing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an apparatus which can easily and inexpensively diagnose a short circuit by providing a short circuit detecting pattern on a circuit board having a multi-stage structure. The purpose is to provide.

[0015]

According to a first aspect of the present invention, a pattern line, which is always kept at a constant voltage, is arranged between a plurality of signal line patterns arranged close to and parallel to each other. A signal line short-circuit detection circuit that determines that a signal line where a potential of the pattern line is generated is short-circuited when a potential is generated in any of the plurality of signal lines.

According to a second aspect of the present invention, there is provided a signal line short-circuit detecting circuit according to the first aspect, wherein the potential of the pattern line is connected to a power supply or a ground.

According to a third aspect of the present invention, a pattern line held at a predetermined potential is disposed between patterns of signal lines which are arranged in parallel and close to each other and are connected to different loads, and one of the signal lines is provided. A signal line short-circuit detection circuit that determines that a signal line where the potential of the pattern line is generated is short-circuited when the potential of the pattern line is generated.

A fourth invention relates to a signal line short-circuit detection circuit, wherein the load in the third invention is a primer of a passenger protection device.

According to a fifth aspect of the present invention, there are provided a plurality of loads, one ends of which are commonly connected, the other ends of which are connected to different circuits, and which are arranged in parallel and close to each other and connected to a signal line; A constant current circuit for supplying a constant current in series; and supplying the constant current to any one of the signal lines connected to the power supply side for the operation of the constant current circuit. The presence or absence of a change in the potential of
A signal line short-circuit detection circuit including a diagnostic circuit for determining whether or not the plurality of signal lines are short-circuited.

[0020]

Next, an embodiment of the present invention will be described. Embodiment 1 FIG. Before describing the configuration of the first embodiment according to the present invention, the configuration of an occupant protection device that performs multi-stage deployment will be described with reference to FIG. 1. In FIG. 1, the same components as those described in the conventional example of FIG. Or, equivalent parts are denoted by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described below.

That is, the different part is between the signal lines on the positive potential side of the primers 6a and 6b, in other words, the circuit pattern 21 between the primer 6a and the diagnostic high-resistance element 8a, and the primer 6b
A circuit pattern electrically connected to the ground and electrically connected to both the circuit pattern 21 and the circuit pattern 22 between the circuit pattern 22 and the circuit pattern 22 between the high-resistance element 8b for diagnosis. 20 (see the circuit pattern connected to the IC in FIG. 2A). In addition,
2A indicates a portion surrounded by the microcomputer 12 'and broken lines Z and W in FIG.

Accordingly, when the circuit pattern 21 between the primer 6a and the diagnostic high-resistance element 8a contacts or is connected to the circuit pattern 20 due to, for example, migration, the primer 6a and the diagnostic high-resistance element 8a Is at the ground level, the potential at the N point between them becomes ground level.
4 'is determined to be abnormal by reading this voltage level. Similarly, when the circuit pattern 22 between the primer 6b and the diagnostic high-resistance element 8b comes into contact with or is connected to the circuit pattern 20, the M point between the primer 6b and the diagnostic high-resistance element 8b is similarly determined. Since the potential is at the ground level, the diagnosis unit 14 'determines that there is an abnormality.

In the first embodiment, the circuit pattern 21 between the primer 6a and the diagnostic high resistance element 8a and the circuit pattern 2 between the primer 6b and the diagnostic high resistance element 8b
2 and the circuit pattern 2
The circuit pattern 20 that does not come into contact with both the circuit pattern 1 and the circuit pattern 22 is provided. However, as shown by a symbol IC ′ in FIG. 2B, the circuit pattern 21 between the primer 6a and the high-resistance element 8a for diagnosis is provided. Is connected to a power supply (+ V) between the primer 6b and the circuit pattern 22 between the diagnostic high-resistance element 8b,
In addition, a circuit pattern 20 that does not contact both the circuit pattern 21 and the circuit pattern 22 may be provided, and a circuit pattern that is easier to create may be selected.

[0024]

As described above, according to the present invention, a short circuit between circuit patterns can be detected with a simple configuration and at low cost. Further, by applying the present invention to the occupant protection device, the quality of the occupant protection device can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an occupant protection device according to a first embodiment of the present invention.

FIG. 2 is a circuit pattern diagram showing a main part in the present invention.

FIG. 3 is a circuit block diagram of a conventional occupant protection device.

FIG. 4 is a circuit block diagram of a conventional multistage occupant protection device.

[Explanation of symbols]

 Reference Signs List 1 vehicle-mounted battery 2 ignition switch 3 booster circuit 4 backup capacitor 5a, 5b switching transistor 6a, 6b detonator 7a, 7b OR gate 8a, 8b, 10 high-resistance element for diagnosis 9 mechanical acceleration switch 11a, 11b comparison circuit 12 'microcomputer 13 'Collision judgment means 14' Diagnosis means 15 Acceleration sensor 20,21,22 Circuit pattern

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kunihiro Kaneko 5-24-15 Minamidai, Nakano-ku, Tokyo Inside Calso Nic Kansei Corporation (72) Inventor Takayuki Kishi 5-24-15 Minamidai, Nakano-ku, Tokyo Calso Inside Nick Kansei Corporation (72) Inventor Ryuichi Asada 5-24-15 Minamidai, Nakano-ku, Tokyo Calso Inside Nickcal Kansei Corporation (72) Inventor Mineyuki Oishi 5-24-15 Minamidai, Nakano-ku, Tokyo Calso Nick Kansei F term in reference (reference) 2G014 AA03 AB59 AC09 AC18 3D054 AA01 EE14 EE30 EE39 EE49 FF16

Claims (5)

[Claims] 1. A pattern line which is always kept at a constant voltage is arranged between patterns of a plurality of signal lines arranged close to and parallel to each other, and the potential of the pattern line is set to one of the plurality of signal lines. A signal line short-circuit detection circuit that determines that the signal line in which the potential of the pattern line has occurred is short-circuited when the signal line has occurred. 2. The signal line short-circuit detection circuit according to claim 1, wherein the potential of the pattern line is connected to a power supply or a ground. 3. A pattern line held at a predetermined potential is arranged between patterns of signal lines that are arranged in parallel and close to each other and are connected to different loads, and the pattern line is connected to any of the signal lines. A signal line short-circuit detection circuit that, when a potential is generated, determines that the signal line where the potential of the pattern line has been short-circuited. 4. The signal line short-circuit detection circuit according to claim 3, wherein said load is a primer of an occupant protection device. 5. A plurality of loads, one end of which is connected in common, the other end of which is connected to different circuits, and which are arranged in parallel and close to each other and connected to a signal line, and a constant current connected in series to the plurality of loads. And supplying a constant current to one of the signal lines connected to the power supply side for the operation of the constant current circuit, and then changing the potential of the other signal line. A signal line short-circuit detection circuit, comprising: a diagnosis circuit that detects the presence or absence of the signal line and determines whether the plurality of signal lines are short-circuited.