JP2001165817A - Disconnection detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disconnection detection circuit to detect the defective connection with a simple circuit configuration even when defective connection such as disconnection and connection detachment is generated in a power supply path to supply the power to a sensor for the quantity of state of a vehicle. SOLUTION: The power supply path to connect power I/O terminals 13 and 25 to each other to supply the power to the sensor 29 for the quantity of state of the vehicle comprises at least diodes D2 and D3 interposed in series in the power supply path, a transistor TR1 and a resistor R1 to be interposed in parallel to the diodes D2 and D3, and a resistor R2 to be interposed in parallel to the transistor TR1, and defective connection is detected based on the ON-OFF state signal output to be outputted from an output terminal 23 of the transistor TR1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle state quantity sensor such as a vehicle speed sensor or an engine speed sensor for measuring a state quantity such as a speed of a vehicle such as an automobile or an engine speed. The present invention relates to a disconnection detection circuit that can detect a connection failure with a simple circuit configuration even when a connection failure such as disconnection or disconnection occurs in a power supply path for supplying power to a quantity sensor.

[0002]

2. Description of the Related Art Conventionally, as this kind of disconnection detection circuit,
For example, one disclosed in JP-A-5-107292 is known. This disconnection detection circuit includes an input resistor connected between a signal input terminal of a converter such as an A / D converter and one of the power supply common lines, a signal output terminal of the sensor, and one of the power supply common lines. Between the sensor output resistance connected between the two power supply common lines, the sensor power supply side resistance connected between the signal output terminal of the sensor and the other of the power supply common lines, and the sensor power supply side resistance in series. And a series resistor connected in series with the output means for outputting the state displacement amount as a current change, and connected in series with one of the power supply common lines.

[0003] In the disconnection detecting circuit thus configured, the input resistance connected between the signal input terminal of the converter and one of the power supply common lines has two input resistors connecting between the sensor and the converter. When both of the power supply common lines are disconnected or the wire harness is separated, or when the output of the power supply line or sensor to which the input resistance is not connected is disconnected or the wire harness is separated, the signal input to the converter is performed. The terminal is pulled to the potential of one of the power supply lines, and is set as a signal outside the output area of a normal sensor. Also, when the power supply line connected to the input resistor is disconnected or the wire harness is separated, the signal input terminal of the converter is pulled to the potential of the other power supply line, and the signal outside the output area of the normal sensor is output. And Therefore, when an output other than the normal output area of the sensor becomes an input on the converter side, a state such as disconnection or separation of the wire harness occurs, and as a result, it can be determined that the signal is a normal signal. And the occurrence of connection failure such as disconnection or disconnection.

[0004]

However, in the above-mentioned prior art, since a relatively expensive converter such as an A / D converter is employed, the cost of the entire circuit is increased, and the circuit is also expensive. There is an inherent problem to be solved such that the configuration tends to be complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended for use even when a connection failure such as disconnection or disconnection occurs in a power supply path for supplying power to a vehicle state quantity sensor. It is another object of the present invention to provide a disconnection detection circuit capable of detecting a connection failure with a simple circuit configuration.

[0006]

In order to achieve the above object, a disconnection detection circuit according to a first aspect of the present invention includes at least a power supply input / output for supplying power to a vehicle state quantity sensor for measuring a state quantity in a vehicle. A disconnection detection circuit provided in a power supply path connecting terminals, for detecting a connection failure such as disconnection or disconnection in the power supply path, wherein the power supply path includes at least the same power supply path. One or a plurality of diodes inserted in series, a transistor and a first resistor inserted in parallel with the diode, and a second resistor inserted in parallel with the transistor are included. The connection failure is detected based on an on / off state signal output from an output terminal of the transistor.

In the circuit according to the first aspect of the invention, when there is no connection failure such as disconnection or disconnection in the power supply path including the ground line of the vehicle state quantity sensor, one or more power supply input terminals are provided. When a current flows into the diode, a voltage drop occurs between the diode terminals. The voltage drop causes the transistor to conduct and turn on, and an on-state signal is output from the output terminal of the transistor. on the other hand,
If any connection failure occurs in the power supply path, no current flows into one or a plurality of diodes from the power input terminal, so that no voltage drop occurs between the diode terminals. At this time, the transistor is turned off and turned off, and an off-state signal is output from the output terminal of the transistor. Since the on-state signal and the off-state signal described above can be easily identified from the potential difference between the two, a connection failure can be detected based on such a state signal output. Specifically, by associating the presence or absence of a connection failure with the potential of each state signal, it is possible to determine the presence or absence of a connection failure based on the state signal output, for example, in a separately provided detection device or the like.
The disconnection detection circuit can be provided as a single device independently of other devices, or can be provided integrally with the above-described detection device, control device, and the like.

According to the disconnection detecting circuit of the first aspect,
Even if a connection failure such as disconnection or disconnection occurs in the power supply path for supplying power to the vehicle state quantity sensor, the connection failure is achieved with a very simple circuit configuration consisting of a transistor, a diode, and a resistor. Can be detected.

Here, when the disconnection detecting circuit according to the first aspect is put to practical use, it can be easily imagined that there is a demand for downsizing of the circuit. As one of the approaches to circuit design aiming at such miniaturization, it is conceivable to make the components of the circuit as small as possible. To do this,
Work such as optimizing the circuit constant of each element for miniaturization is required. If you mention the guidelines at this time,
For example, when the transistor in this circuit is used in a grounded base configuration, the magnitude of the base current of the transistor depends on the circuit constants of the first and second resistors. Therefore, by setting the circuit constants of the first and second resistors to appropriate values, it becomes possible to make the base current of the transistor a very small value, contributing to the miniaturization of the transistor element which requires the most installation space. As a result,
The present disconnection detection circuit can be reduced in size. It is needless to say that the disconnection detection circuit according to the present invention includes such an application example or another modification example in its technical range.

[0010] The disconnection detecting circuit according to claim 2 is
2. The disconnection detecting circuit according to claim 1, wherein a third resistor is provided between the output terminal of the transistor and ground.

According to the disconnection detecting circuit of the second aspect,
Since the output terminal of the transistor is provided with the third resistor between the output terminal and the ground, the state signal output appearing at the output terminal of the transistor is received as the inter-terminal voltage at the third resistor, and is taken out. be able to.

Further, in the disconnection detecting circuit according to a third aspect of the present invention, in the disconnection detecting circuit according to the second aspect, the output terminal of the transistor includes a combination of a transistor and a resistor instead of the third resistor. Or one or more transistor circuits according to (1).

According to the disconnection detecting circuit of the third aspect,
The output terminal of the transistor is provided with one or more transistor circuits according to a combination of a transistor and a resistor instead of the third resistor, so that the state signal output appearing at the output terminal of the transistor is output from the transistor circuit. And can be taken out after receiving power.

[0014] On the other hand, the disconnection detecting circuit according to claim 4 is
4. The disconnection detection circuit according to claim 1, wherein one of a plurality of diodes inserted in series in the power supply path among the power supply paths is connected between the power supply input / output terminals. 5. Is characterized in that a forward diode is provided.

According to the disconnection detecting circuit of the fourth aspect,
In the preceding stage of the diode inserted in series in the power supply path, a forward diode is provided between the power supply input / output terminals, so that even when a reverse voltage is applied to the power supply input terminal. In addition, the present disconnection detection circuit can be protected from troubles such as burning.

According to a fifth aspect of the present invention, in the disconnection detection circuit according to any one of the first to fourth aspects, the disconnection detection circuit is inserted in series in the power supply path among the power supply paths. After one or more diodes,
A forward diode is provided between the power input / output terminals.

According to the disconnection detecting circuit of the fifth aspect,
Since a diode which is forwardly provided between the power supply input / output terminals is provided at a stage subsequent to the diode inserted in series in the power supply path, there is a case where an excessive positive voltage is applied to the power supply output terminal. However, this disconnection detection circuit can be protected from troubles such as burning.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a disconnection detecting circuit according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a disconnection detection circuit according to the present invention, and FIG. 2 is a circuit diagram showing a modification of the disconnection detection circuit.

In FIG. 1, a disconnection detecting circuit 11 supplies power to a vehicle state quantity sensor 29 such as a vehicle speed sensor or an engine rotation speed sensor for measuring a state quantity such as a speed of a vehicle such as an automobile or an engine rotation speed. For this purpose, the power supply path including the ground line of the vehicle state quantity sensor 29 has a function of detecting a connection failure such as disconnection or disconnection.

Disconnection detecting circuit 11 having such a function
A power input terminal 13 to which a DC power is input; a disconnection detection signal terminal 24 to which a disconnection detection signal is output; a power output terminal 25 to which the input DC power is output;
And a ground terminal 26 for grounding the first housing. The power input terminal 13 and the disconnection detection signal terminal 24 are provided.
The intended purpose of detecting a connection failure in the power supply path is achieved by the cooperative action of the following elements provided between the three terminals of the power supply terminal and the power supply output terminal 25.

A disconnection detecting circuit 11 for achieving such a purpose
Referring to the circuit configuration of FIG.
Between 25, four diodes D1, D2, D3, D4
Are connected in series in the forward direction. The cathode terminal 15 of the diode D1 is connected to a power supply circuit for other devices other than the circuit 11, and power is supplied to the power supply circuit for other devices. Note that the diode D1 has a function of protecting the disconnection detection circuit 11 from troubles such as burning even when a reverse voltage is applied to the power input terminal 13, while the diode D4 has a function of protecting the power output terminal 25. Has a function of protecting the disconnection detection circuit 11 from troubles such as burnout even when an excessive positive voltage is applied to the circuit.

Between the cathode terminal 15 of the diode D1 and the anode terminal 21 of the diode D4, the transistors TR1 and TR3 are connected in parallel with the diodes D2 and D3.
And a resistor R1 are interposed. The transistor TR1 is, for example, a PNP type, and a resistor R2 is inserted in parallel with the transistor TR1 so as to bypass between the emitter terminal 17 and the base terminal 19. A resistor R3 is connected to the collector terminal 23 of the transistor TR1 with the other end grounded, and a disconnection detection signal terminal 24 is connected.

The vehicle state quantity sensor 29 that receives power from the above-described disconnection detection circuit 11 is interposed between the power output terminal 25 and the ground terminal via the relay terminal 27. The state quantity detection signal detected by the vehicle state quantity sensor 29 is sent to the detection device 35 via the relay terminals 31 and 33. Then, in the detection device 35, a state amount detection process based on the state amount detection signal, a disconnection presence / absence determination process based on the disconnection detection signal sent from the disconnection detection signal terminal 24,
Is performed.

In such a disconnection detecting circuit 11, when there is no connection failure such as disconnection or disconnection in the power supply path including the ground wire of the vehicle state quantity sensor 29, the power supply input terminal 13 is connected via the diode D1. And diode D
2 and D3, the current flows into the diodes D2 and D3.
A voltage drop occurs between the three terminals, and the transistor TR1 conducts due to the voltage drop to be turned on, and an on-state signal as a disconnection detection signal received by the resistor R3 is output to the output terminal 23 of the transistor TR1. . on the other hand,
If any connection failure occurs in the power supply path, no current flows from the power input terminal 13 to the diodes D2 and D3.
No voltage drop occurs between the three terminals. At this time, the transistor TR1 is turned off and turned off, and an off-state signal as a disconnection detection signal received by the resistor R3 is output to the output terminal 23 of the transistor TR1. Since the on-state signal and the off-state signal described above can be easily identified from the potential difference between the two, a connection failure can be detected based on such a state signal output. Specifically, by associating the presence or absence of a connection failure with the potential of each state signal, the detection device 35 or the like can determine the presence or absence of a connection failure based on the state signal output. The disconnection detection circuit 11 can be disposed as a single device independently of other devices, or can be disposed integrally with the detection device 35, the control device, and the like.

According to such a disconnection detection circuit, even if a connection failure such as disconnection or disconnection occurs in the power supply path for supplying power to the vehicle state quantity sensor, the transistor, diode, and resistance are used. The connection failure can be detected with a very simple circuit configuration.

Here, when the above-described disconnection detection circuit is put into practical use, it is easy to imagine that there is a demand for downsizing of the circuit. As one of the approaches to circuit design aiming at such miniaturization, it is conceivable to make the components of the circuit as small as possible. For this purpose, it is necessary to perform an operation of optimizing the circuit constant of each element for miniaturization. If the guidelines at this time are mentioned, this circuit 11
Is used in a grounded base mode, and the magnitude of the base current of the transistor TR1 depends on the circuit constants of the resistors R1 and R2. Therefore, by setting the circuit constants of the resistors R1 and R2 to appropriate values, it becomes possible to make the base current of the transistor TR1 a very small value, which can contribute to the miniaturization of the transistor element that takes up the most installation space. As a result, downsizing of the disconnection detection circuit 11 can be realized.

By the way, in the above-described disconnection detection circuit 11, an example in which the state signal of the transistor TR1 is received by the resistor R3 has been described. However, the present invention is not limited to this example. Alternatively, a mode in which power is received by one or a plurality of transistor circuits related to a combination of a transistor and a resistor may be employed.

Such a modification will be described with reference to FIG. 2 focusing on the difference in circuit configuration from FIG. 1. The transistor circuit interposed between the transistor TR1 and the disconnection detection signal terminal 24 is an NPN type. Transistor T
It is configured by combining R2 and three resistors R4, R5, R6. A resistor R4 is inserted between the collector output terminal of the transistor TR1 and the base terminal 41 of the transistor TR2, and a resistor R5 is inserted between the base terminal 41 of the transistor TR2 and the ground terminal. The emitter terminal 43 of the transistor TR2 is grounded. The collector terminal 4 of the transistor TR2
5 is pulled up by being connected to the internal power supply via the resistor R6, and by connecting the collector terminal 45 of the transistor TR2 to the disconnection detection signal terminal 24, the state signal of the transistor TR1 after the polarity conversion is converted to the state signal. It is designed to be taken out.

According to the disconnection detecting circuit 11 according to the modification configured as described above, the state signal output appearing at the output terminal of the transistor TR1 can be taken out after receiving power in the above-described transistor circuit.

The state quantity detection signal detected by the vehicle state quantity sensor 29 according to each of the above-described embodiments is sent to the detection device 35 via the relay terminals 31 and 33. Then, the detection device 35 performs a state amount detection process based on the state amount detection signal and a disconnection presence / absence determination process based on the disconnection detection signal sent from the disconnection detection signal terminal 24. As a result of the disconnection presence / absence determination processing described above, when the detection device 35 determines that there is a disconnection, the state quantities such as the vehicle speed and the engine rotation speed detected in the state quantity detection processing are regarded as invalid. . Therefore, it is possible to prevent an erroneous state quantity detection result from being transmitted to a driver or the like.

The above-described embodiment has been described by way of example in order to facilitate understanding of the present invention.
It is not described to limit the technical scope of the present invention. Therefore, the present invention naturally includes all embodiments belonging to the technical scope and includes any equivalents thereof.

[0033]

As described above, according to the disconnection detecting circuit of the first aspect, a connection failure such as disconnection or disconnection occurs in the power supply path for supplying power to the vehicle state quantity sensor. Even in this case, the connection failure can be detected with a very simple circuit configuration including a transistor, a diode, and a resistor.

Further, according to the disconnection detecting circuit of the second aspect, since the third resistor is provided between the output terminal of the transistor and the ground, the state appears at the output terminal of the transistor. The signal output can be taken out after receiving the power as a terminal-to-terminal voltage at the third resistor.

According to the third aspect of the present invention, one or a plurality of transistor circuits related to a combination of a transistor and a resistor are provided at the output terminal of the transistor instead of the third resistor. Therefore, the state signal output appearing at the output terminal of the transistor can be taken out after receiving power in the transistor circuit.

On the other hand, according to the disconnection detection circuit of the present invention, a diode which is forwardly provided between the power supply input / output terminals is provided at a stage preceding the diode inserted in series in the power supply path. Therefore, even when a reverse voltage is applied to the power input terminal, the present disconnection detection circuit can be protected from troubles such as burning.

According to the disconnection detecting circuit of the fifth aspect, a diode which is forwardly provided between the power supply input / output terminals is provided at a stage subsequent to the diode inserted in series in the power supply path. Therefore, even when an excessively large positive voltage is applied to the power supply output terminal, an extremely excellent effect that the present disconnection detection circuit can be protected from troubles such as burnout can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a disconnection detection circuit according to the present invention.

FIG. 2 is a circuit diagram of a disconnection detection circuit according to a modification of the present invention.

[Explanation of symbols]

 Reference Signs List 11 disconnection detection circuit 13 power supply input terminal 15 cathode terminal of diode D1 17 emitter terminal of transistor TR1 19 base terminal of transistor TR1 21 anode terminal of diode D4 23 collector output terminal of transistor TR1 24 disconnection detection signal terminal 25 power supply output terminal 26 housing Body ground terminal 27 Relay terminal 29 State quantity detection sensor 31, 33 Relay terminal 35 Detecting device 41 Base terminal of transistor TR2 43 Emitter terminal of transistor TR2 45 Collector terminal of transistor TR2

Claims (5)

[Claims] 1. A power supply path connecting at least power supply input / output terminals for supplying power to a vehicle state quantity sensor for measuring a state quantity in a vehicle, wherein the power supply path includes a disconnection or disconnection. A disconnection detection circuit for detecting a connection failure, wherein at least one or a plurality of diodes inserted in series with the power supply path and the diode are inserted in parallel in the power supply path. A transistor and a first resistor; and a second resistor interposed in parallel with the transistor. The connection failure is based on an on / off state signal output from an output terminal of the transistor. A disconnection detection circuit characterized by detecting a disconnection. 2. The disconnection detection circuit according to claim 1, wherein a third resistor is provided between the output terminal of the transistor and the ground, at the output terminal of the transistor. 3. The disconnection detection circuit according to claim 2, wherein one or more transistor circuits related to a combination of a transistor and a resistor are provided at the output terminal of the transistor instead of the third resistor. A disconnection detection circuit characterized in that: 4. The disconnection detection circuit according to claim 1, wherein, in the power supply path, a stage preceding to one or a plurality of diodes inserted in series with the power supply path includes: A disconnection detection circuit, comprising a diode in a forward direction between power supply input / output terminals. 5. The disconnection detection circuit according to claim 1, wherein, in the power supply path, at a stage subsequent to one or a plurality of diodes inserted in series with the power supply path, A disconnection detection circuit, comprising a diode in a forward direction between power supply input / output terminals.