JPH077840A - Detecting device for disconnection of controller - Google Patents

Abstract

PURPOSE:To accurately detect the disconnection of a controller which performs data links between communication units through a common signal line, power supply line, and ground line so as to prevent the erroneous actuation of the communication units. CONSTITUTION:A current route is formed of a diode 16, resistor 4, signal line 20, resistor 19, and N-type transistor 21 in parallel with a ground line 10 between communication units A1 and B1. The gate, source, and drain of the transistor 22 are respectively connected to the signal line of the resistor 4, ground line 10, and a power supply line 30 through a power supply pull-up resistor 7. When the ground line 10 is disconnected at a point Z1, an electric current flows toward the signal line 20 from the ground line 10 through the current route and a potential difference is generated at the resistor 4. Therefore, the potential at the connecting point 100 of the drain of the transistor 22 with the resistor 7 changes and the disconnection is detected. A power supply breaker 101 is actuated by the detecting output of the disconnection and the erroneous actuation of the communication units is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a disconnection detecting device for a control device and a control device for surely preventing malfunctions when the occurrence of disconnection is detected using the device.

[0002]

2. Description of the Related Art Recently, there has been a great demand for a control device which transmits and receives signals between a plurality of units arranged at mutually separated portions. Such a control device, for example, in a vehicle or the like, connects a central control unit and a sensor or a drive unit installed in each part of the vehicle with a common signal line, and transmits and receives a measurement signal and a drive command by communication to perform various controls. Used to perform FIG. 4 shows a configuration example of this type of control device. The control device is composed of a plurality of communication units A, B, C and D connected in parallel by a common power line 30, ground line 10 and signal line 20. Each communication unit has a receiving circuit 33, 77, 9
1, 97 and the transmission circuits 44, 88, 92, 96, and the output circuits 11, 55, 93, 95 and the input circuits 23, 6 in which the reception circuits and the transmission circuits are provided in the communication unit, respectively.
Data linking is performed by sending and receiving data by 6, 90 and 94. Further, power is supplied to each communication unit by the power supply line 30 and the ground line 10 in common, and the tolerance against power supply fluctuation is improved.

FIG. 5 shows the details of the input units 23 and 66 and the output units 11 and 55 of the communication unit A and the communication unit B out of the plurality of communication units in the control device. . The input circuit 23 is
After the noise removal is performed by the differentiation circuit including the resistor 2 and the capacitor 1, the signal shaping is performed by the comparator having the reference voltage 8 as the trigger point. The output circuit 11 outputs a signal by an output buffer including an N-type transistor 17 and a P-type transistor 18, a surge absorbing circuit including a pull-up diode 15 and a pull-down diode 16, and a noise absorbing circuit including a resistor 4 and a capacitor 3. Is configured. The configuration of the communication unit B is the same as that of the communication unit A. Further, the communication unit A and the communication unit B are connected by the power supply line 30, the ground line 10 and the signal line 20 so that power is commonly supplied and communication is performed by the common signal line.

[0004]

However, in such a conventional control device, the ground line 10 has the Z line.
In the case of disconnection at the part of, the power supply to the communication unit A is as follows: power line 30 → transmission circuit 44 → diode 16 → resistor 4 → signal line 20 → resistor 19 → N-type transistor 2
The operation of the output circuit 11 is enabled by the system of 1 → GND line 10. However,
The power supply voltage supplied to this output circuit is divided by the impedance of the transmission circuit 44 (about 1 kΩ) and the impedance of the resistors 4 and 19 (1 kΩ). Furthermore, when the voltage breakdown of the diode 16 is included,
Since only about 2 or less is applied and the N-type transistor 21 of the output circuit 55 of the communication unit B operates only at the timing of "ON", the operation of the output circuit becomes very unstable, and accordingly, The control device may malfunction.

As a countermeasure, the ground line has conventionally been duplicated. However, the increase in the number of terminals of the control device connector and the increase in the number of wirings cause problems such as cost increase and wiring difficulty. Moreover, even if the ground lines are duplicated, if the disconnection occurs in a duplicated manner, the problem that the operation of the output circuit is still unstable remains. Therefore, the present invention is not a method of reducing the occurrence of disconnection by arranging a plurality of ground lines and avoiding the instability of the output circuit operation due to the disconnection, and the control due to the instability of the output circuit by detecting the disconnection. An object of the present invention is to provide a control device that surely prevents malfunction of the device.

[0006]

In order to achieve the above object, the invention described in claim 1 is a plurality of communication systems which are connected to each other by a signal line and are supplied with power from a common power line and ground line. A control unit configured to be grounded through the signal line when the ground line is disconnected in one communication unit, in the communication unit, the direction from the ground line in the communication unit to the signal line direction. A current path having a forward direction, voltage drop means provided in the current path, and current detection means for detecting generation of forward current in the current path based on a potential difference generated in the voltage drop means. The disconnection detecting device is configured to detect the disconnection of the ground line due to the generation of the forward current. Further, in addition to the above, the invention according to claim 4 is provided with a power cutoff means for cutting off the power supply line to the communication unit when the disconnection detection device detects a disconnection of the ground line.

[0007]

According to the first aspect of the present invention, in one communication unit, when the ground line is broken, the communication unit is grounded via the signal line to newly form a power supply path. When the power is supplied from the power supply path, the disconnection of the ground line is detected by the potential difference generated in the voltage drop means provided in the current path at the same time when the current is generated in the power supply path. Further, according to the fourth aspect, when the disconnection of the ground line is detected, the power supply to the communication unit is shut off by the power shutoff means, so that the malfunction of the control device due to the disconnection of the ground line is prevented.

[0008]

1 is a circuit diagram showing a first embodiment of the present invention. Since the communication unit A1 and the communication unit B1 have the same configuration, the description will be given on the communication unit A1 side. The communication unit A1 includes a transmission circuit 44 and a reception circuit 3
3, an output circuit 11, and an input circuit 23. An input circuit 23 is composed of a differentiating circuit composed of a resistor 2 and a capacitor 1, and a comparator 9 having a reference voltage 8 as a trigger point.
The input circuit performs noise removal and signal shaping on the signal input from the signal line 20, and then the receiving circuit 3
Send to 3.

The output circuit 11 is composed of an output buffer circuit including an N-type transistor 17 and a P-type transistor 18, a surge absorbing circuit including a pull-up diode 15 and a pull-down diode 16, and an integrating circuit including a resistor 4 and a capacitor 3. To be done. With this circuit, the signal transmitted from the transmission circuit 44 is sent to the signal line 20 after surge absorption and noise removal.

The configuration of the communication unit B1 is also the communication unit A.
It is the same as that of 1. And between the two communication units, the power supply line 30, the ground line 10, and the signal line 20 described above are provided.
Are connected to each other and are commonly supplied with power, and communication is performed by a common signal line. Further, the signal line side potential of the resistor 4 is used as an input to the gate electrode, the source electrode is connected to the ground line 10A, and the drain electrode is connected to the power supply line 30 via the power supply pull-up resistor 7
Two are provided.

With the above configuration, the diode 16, the resistor 4, the signal line 20, the resistor 19 and the N-type transistor 21 connected in series between the two communication units A1 and B1 to be connected to the ground line 10 are used. Parallel current paths are formed. However, normally, when there is no break in the ground line 10A of the communication unit A1, since the ground line 10A and the ground line 10B have the same potential, no current flows in this current path.

In the communication unit A1, when a disconnection occurs at the Z1 portion of the ground line 10A, the ground line 1
The potential of 0 A floats, and the current flows through the current path. Then, this current causes a potential difference between both ends of the resistor 4 and the resistor 19 in the current path. The resistor 4 provided in the current path constitutes a voltage drop means.
The N-type transistor 22 constitutes a current detecting means, and the connection point 10 between the drain and the power supply pull-up resistor 7
The potential of 0 is used as the detection output of the current detection means. Further, the signal extracted as this detection output is passed through a filter circuit including a resistor 6 and a capacitor 5.

In the state where the ground wire is not broken,
As shown in FIG. 2A, the potential Vg of the gate electrode of the N-type transistor 22 is the same as the potential of the signal line 20,
Between the potential Vc of the power supply line 30 and the potential 0 of the ground line 10, a full swing is performed according to the operation of the output circuit of the communication unit A1. During the period T1 where the output of the output circuit 11 is high potential, the potential of the gate electrode is Vg = Vc, and during the period T2 where the output of the output circuit 11 is low potential, Vg = 0.

Further, since the potential Vs of the source electrode is the same as the potential 0 of the ground line 10A, the potential difference Vg of the gate electrode with respect to the source electrode during the period in which no disconnection occurs.
The change of s is Vc ≧ Vgs ≧ 0. Further, this Vgs is the same as the above with respect to the operation of the output circuits of other communication units.

Here, when a disconnection occurs in the Z1 portion of the ground line 10A in the communication unit A1, the communication unit A1 keeps the ground line 10A in the period T2 in which the N-type transistor 21 in the communication unit B1 is "ON". The floating of the potential of causes the communication unit A1 to be grounded through the current path. As a result, a current is generated in the current path. Then, due to this current, the potential on the signal line side of the resistor 19 in the current path rises to Vt.

The potential Vg of the gate electrode of the N-type transistor 22 connected to the signal line 20 also becomes Vt as shown by the solid line in FIG. And ground line 10A
The potential Vs of the source electrode connected to the voltage rises to Vy as shown by the broken line in FIG. The potential difference Vgs between the source electrode and the gate electrode is approximately the resistance 4
It is the same as the potential difference V1 generated at both ends of. V1 becomes Vc × R4 / (R44 + R4 + R19). However, R4 is the resistance value of the resistor 4, R44 is the resistance value of the transmission circuit, and R19 is the resistance value of the resistor 19. Moreover, this potential difference makes the potential of the gate electrode negative with respect to the potential of the source electrode, as shown in FIG. Therefore, V1 is calculated as described above, and the threshold value Vth of the N-type transistor 22 is set to 0>Vth> V1.

When there is no break, as described above, Vgs ≧
0 and Vgs ≧ Vth. Therefore,
The drain electrode of the N-type transistor 22 is always kept "ON" regardless of the operation of the output circuit, and the detection output of the drain electrode side connection point 100 is at "L" potential. Here, when the ground line 10A is broken, the N-type transistor 21 in the communication unit B1 shown in FIG.
A current is generated in the current circuit grounded by the N-type transistor 21 during the period T2 in which is "ON". As a result, a potential difference of V1 is generated across the resistor 4. The potential difference Vgs between the source and gate electrodes is similar to that. That is, Vgs = V1.

Since Vgs <Vth, the detection output of the connection point 100 by the N-type transistor 22 changes from the "L" potential to the "H" potential. This "H" potential becomes a disconnection detection signal indicating that a current in the signal line direction has been generated in the current path. This signal is passed through a filter circuit including a resistor 6 and a capacitor 5 to mask erroneous detection due to a surge applied from the signal line 20. Further, the power supply breaker 101 provided on the communication unit A1 side is activated by a signal from the output of the filter circuit to cut off the power supply.

This embodiment is configured as described above, and a resistor is provided in the current path in the direction from the ground line to the signal line, and the voltage drop due to the current flowing in the current path at the time of disconnection is detected by this resistance. Therefore, the occurrence of disconnection is accurately detected. Further, since the power supply is cut off when the disconnection is detected, it is possible to avoid the unstable circuit operation even if the ground line is disconnected. Further, N-type transistors, resistors and the like added for detecting disconnection are easily formed on the LSI chip as a part of the output circuit.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. Since the communication unit A2 and the communication unit B2 have the same configuration, the description will be given on the communication unit A2 side. The communication unit A2 includes the transmitting circuit 44, the receiving circuit 33, the output circuit 11, and the input circuit 23, as in the previous embodiment. As in the previous embodiment, a diode 16, a resistor 4 and a signal line 2 which are connected in series between both communication units A2 and B2.
0, the resistor 19 and the N-type transistor 21 form a current path in parallel with the ground line 10.

The signal line side potential of the resistor 4 is used as an input to the emitter electrode, and the base electrode is connected to the ground line 10A.
The collector electrode is connected to the power supply line 3 via the power supply pull-up resistor 7.
An NPN transistor 122 connected to 0 is provided. Further, the signal taken out from the connection point 200 between the drain and the power supply pull-up resistor 7 is passed through the filter circuit composed of the resistor 6 and the capacitor 5, and the power breaker 1
It is designed to enter 01.

In the communication unit A2, when a disconnection occurs at the Z2 portion of the ground line 10A, the ground line 1
The potential of 0 A floats, and the current flows in the above current path. Then, due to this current, the resistance 4 in the current path
And a potential difference is generated across the resistor 19.

In the state where the ground wire is not broken,
As shown in FIG. 2A, the potential V of the emitter electrode
e is the potential V of the power supply line 30 as well as the potential of the signal line 20.
Between c and the potential 0 of the ground wire 10 is almost full swing according to the operation of the output circuit of the communication unit A2. In the period T1 in which the output of the output circuit 11 is high potential,
The potential of the emitter electrode is Ve = Vc. Then, the period T when the output of the output circuit 11 is low potential
At 2, Ve = 0.

Since the potential Vb of the base electrode is the same as the potential 0 of the ground line 10, the change in the potential difference Vbe of the emitter electrode with respect to the base electrode during the period when no disconnection occurs is Vc ≧ Veb ≧ 0. Further, this Veb is the same as the above with respect to the operation of the output circuit of another communication unit.

When a disconnection occurs in the Z2 portion of the ground line 10A in the communication unit A2, the communication unit A2 is connected to the ground line 10A during the period T2 in which the N transistor 21 in the communication unit B2 is "ON". Due to the floating potential, the communication unit A2 is grounded through the above-mentioned current path. As a result, a current is generated in the current path. Then, due to this current, the potential on the signal line side of the resistor 19 in the current circuit rises to Vt.

The potential Ve of the emitter electrode of the NPN transistor 122 connected to the signal line 20 also becomes Vt as shown by the solid line in FIG. The potential Vb of the base electrode connected to the ground line 10A is shown in FIG.
As shown by the broken line in (b) of FIG. However, the potential difference Veb between the base electrode and the emitter electrode is
Is approximately the same as the potential difference V1 generated across the resistor 4. This potential difference makes the potential of the emitter electrode negative with respect to the potential of the base electrode, as shown in FIG.

When there is no disconnection, as described above, Veb ≧
It is 0. As a result, the collector electrode of the NPN transistor 122 is always "O" regardless of the operation of the output circuit.
The detection output of the connection point 200 is "
H "potential. Here, when disconnection occurs in the ground line 10A, N in the communication unit B2 shown in FIG.
During the period T2 in which the type transistor 21 is "ON", a current is generated in the current circuit grounded by the N-type transistor 21.

As a result, V1 is generated across the resistor 4. The potential difference Veb between the base and emitter electrodes is similar to that. That is, Veb = V1. Connection point 20 by NPN transistor 122
The detection output of 0 changes from the “H” potential to the “L” potential. This "L" potential becomes the disconnection detection signal. This signal is passed through a filter circuit including a resistor 6 and a capacitor 5 to mask erroneous detection due to a surge applied from the signal line 20. Further, the power supply breaker 101 provided on the communication unit A2 side is activated by a signal from the output of the filter circuit to cut off the power supply.

This embodiment is constructed as described above, and a resistor is provided in the current path in the direction of the signal line from the ground line so that the voltage drop in the resistor based on the current flowing in the current path at the time of disconnection is detected by the NPN transistor. Therefore, the same effect as that of the first embodiment can be obtained.

[0030]

As described above, according to the present invention, the voltage drop means is provided in the current path whose forward direction is the direction from the ground line to the forward direction current in the current path based on the potential difference generated in the voltage drop means. Since the current detecting means for detecting the occurrence is provided, it is possible to accurately detect the disconnection of the ground line. Furthermore, by providing a circuit breaker that shuts off the power supply when a disconnection is detected, it is possible to prevent malfunction of the control device and reduce the number of harnesses and miniaturize connectors compared to the method that was conventionally supported by duplication. The effect that becomes possible is obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a time chart explaining the operation in the embodiment.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

FIG. 5 is a detailed circuit diagram of a conventional example.

[Explanation of symbols]

 4 resistance 9 comparator 10 ground line 10A ground line in communication unit A 10B ground line in communication unit B 11, 55, 93, 95 output circuit 20 signal line 21 N-type transistor 22 N-type transistor 23, 66, 90, 94 input circuit 30 power line 33, 77, 91, 97 receiving circuit 44, 88, 92, 96 transmitting circuit 101 power breaker 122 NPN type transistor

Claims (4)

[Claims] 1. A plurality of communication units which are connected to each other by a signal line and are supplied with power from a common power line and a ground line, and when the ground line is disconnected in one communication unit, the signal line is connected via the signal line. In a control device configured to be grounded, in the communication unit, a current path in which the signal line direction is a forward direction from a ground line in the communication unit,
A voltage drop means provided in the current path, and a current detection means for detecting generation of a forward current in the current path based on a potential difference generated in the voltage drop means, the generation of the forward current causes the A disconnection detecting device for a control device, which is configured to detect disconnection of a ground line. 2. The voltage drop means is formed of a first resistance, and the current detection means uses the signal line side potential of the first resistance as a gate input, the source is the ground line, and the drain is the first. N connected to the power supply line through a resistor 2
2. The disconnection detection device for a control device according to claim 1, wherein the disconnection detection device is formed of a type transistor, and uses a potential at a connection point between the drain and the second resistor as a detection output. 3. The voltage drop means is formed of a first resistor, and the current detection means has a base on the ground line, an emitter on the signal line side of the first resistor, and a collector on the second line. The disconnection detection device for a control device according to claim 1, wherein the disconnection detection device is configured by an NPN transistor connected to the power supply line via a resistor, and a potential at a connection point between the collector and the second resistor is used as a detection output. . 4. A plurality of communication units which are connected to each other by signal lines and which are supplied with power from a common power line and ground line. When a ground line is broken in one communication unit, the communication lines are connected via the signal lines. In a control device configured to be grounded, in the communication unit, a current path in which the signal line direction is a forward direction from a ground line in the communication unit,
A voltage drop means provided in the current path, and a current detection means for detecting generation of a forward current in the current path based on a potential difference generated in the voltage drop means, the generation of the forward current causes the A control device comprising: a disconnection detecting device for detecting disconnection of the ground line; and a power supply disconnecting means for disconnecting the power supply line to the communication unit when the disconnection detection device detects the disconnection of the ground line. .