JPH11328569A - Abnormality detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality detector capable of exactly discriminating whether a disconnection abnormality is occurring or an abnormality is occurring in a load driving circuit. SOLUTION: A control signal is transmitted to a signal line 53 by outputting a PWM signal to a switching element 16 for output by a control circuit 18 of a signal output circuit 10. Since a switching element 34 for input of a signal input circuit 30 is turned on normally, the output signal of a potential detecting circuit 17 shows nearly power supply potential B when a switching element 16 for output is off. When the disconnection abnormality of a power line 52 and a grounding cable 55 of the signal input circuit 30 occurs, the switching element 34 for input is turned off. Thus, the output signal of the potential detecting circuit 17 shows a ground potential when the switching element 16 for output is off. When the abnormality of the load driving circuit provided in the signal input circuit 30 occurs, a switching element 41 for alarming the abnormality is turned on and power is supplied to a resistor 40. Thus, the output signal of the potential detecting circuit 17 shows nearly B/2 when the switching element 16 for output is off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission device for transmitting a signal from a signal output circuit to a signal input circuit.

[0002]

2. Description of the Related Art JP-A-8-249585 discloses an abnormality detecting device for detecting a power supply line, a ground line, and a disconnection (defective grounding) of a signal line in a signal transmission device for transmitting a signal from a signal output circuit to a signal input circuit. Is known. This conventional abnormality detection device includes a signal output circuit 210, a signal input circuit 230, and a signal line 253, as shown in FIG. Signal output circuit 2
10 has a power terminal 211, a signal output terminal 212, and a ground terminal 213. The signal input circuit 230 has a power supply terminal 231, a signal input terminal 232, and a ground terminal 233. A power supply voltage is supplied to a power supply terminal 211 of the signal output circuit 210 and a power supply terminal 231 of the signal input circuit 230 from a power supply + B via power supply lines 251 and 252, respectively. A signal line 253 is connected between the signal output terminal 212 of the signal output terminal 210 and the signal input terminal 232 of the signal input circuit 230. The ground terminal 213 of the signal output circuit 210 and the ground terminal 233 of the signal input circuit 230
Are grounded via ground lines 254 and 255, respectively.

The signal output terminal 212 of the signal output circuit 210
A resistor 214 is connected between the output terminal and the ground terminal 213, and a series circuit of the resistor 215 and an output switching element 216 such as a transistor is connected.
The signal output terminal 212 is connected via a resistor 217 to an inverting input terminal of a signal line potential detection circuit (comparator) 218. Voltage dividing resistors 219 and 220 are connected between the power supply terminal 211 and the ground terminal 212, and the voltage dividing resistors 219 and 220 are connected.
The connection point between and is connected to the non-inverting input terminal of the signal line potential detection circuit 218. Signal line potential detection circuit 21
The output terminal 8 is a control circuit (CPU) as control means.
221. Further, the control circuit 221 outputs a predetermined PWM signal (pulse width modulation signal) to the control terminal of the output switching element 216 via the resistor 222.

A series circuit of an input switching element 234 such as a transistor, a resistor 235 and a resistor 236 is connected between a power supply terminal 231 and a signal input terminal 232 of the signal input circuit 230. Voltage dividing resistors 237 and 238 are connected between the power supply terminal 231 and the ground terminal 233, and a connection point between the voltage dividing resistors 237 and 238 is a resistor 239.
Is connected to the control terminal of the input switching element 234 via the. An abnormality alarm switching element 240 such as a transistor is connected between the connection point between the resistors 235 and 236 and the ground terminal 233. Resistance 235
The connection point between the resistor 236 and the resistor 236 is connected to a load drive circuit (not shown) such as an actuator drive circuit provided in the signal input circuit 230 via a connection line 241. Further, the signal input circuit 230 is provided with a load abnormality detecting circuit for detecting an abnormality of the load driving circuit (for example, disconnection or short circuit of the load or the driving element), and an output terminal of the load abnormality detecting circuit is connected to a connection line. 242 is connected to a control terminal of the abnormality alarm switching element 240.

[0005] This conventional abnormality detection device operates as follows. The control circuit 221 outputs a predetermined PWM signal to the control terminal of the output switching element 216 to turn on and off the output switching element 216, and
The control signal is transmitted to the signal input circuit 230 through the control signal 3.
A power supply line 252 and a ground line 255 on the signal input circuit 230 side;
When no disconnection abnormality such as disconnection or contact failure occurs in the signal line 253, the potential at the connection point between the voltage dividing resistors 237 and 238 is at a predetermined potential, and the input switching element 234 is provided.
Is on. Therefore, the potential of the connection point between the resistors 235 and 236 changes according to the control signal transmitted via the signal line 253. The load driving circuit uses the resistor 23
The load is driven by detecting a change in the potential at the connection point between the resistor 5 and the resistor 236. In the normal state, the output switching element 21
6 is off, the potential of the signal output terminal 212 becomes a predetermined high potential, so that the output signal of the signal line potential detection circuit 218 becomes low level, and when the output switching element 216 is on, the output signal of the signal output terminal 212 becomes Since the potential becomes a predetermined low potential, the output signal of the signal line potential detection circuit 218 becomes a high level. When the output switching element 216 is turned off, the control circuit 221 controls the signal line potential detection circuit 218
It is determined that the power supply line 231, the ground line 233, the signal line 253, and the like do not have any disconnection abnormality such as disconnection or poor contact. on the other hand,
When a disconnection abnormality occurs in the signal line 253, the signal output terminal 2
12 becomes the ground potential, and the signal line potential detection circuit 21
8 is an output signal of the output switching element 216,
High level regardless of off. When a disconnection abnormality occurs in the power supply line 252 or the ground line 255 on the signal input circuit 230 side, the input switching element 234 is turned off. Accordingly, the potential of the signal output terminal 212 of the signal output circuit 210 becomes the ground potential, and the output signal of the signal line potential detection circuit 218 becomes a high level regardless of whether the output switching element 216 is on or off. Control circuit 22
When detecting that the output signal of the signal line potential detection circuit 218 is at a high level when the output switching element 214 is turned off, a disconnection abnormality occurs in the power supply line 252, the ground line 255, the signal line 253, and the like. Judge that there is.

[0006]

However, in the above-described conventional abnormality detection device, the load abnormality detection circuit provided in the signal input circuit 230 turns on the abnormality alarm switching element 240 when the abnormality of the load drive circuit is detected. To When the abnormality warning switching element 240 is turned on,
Since the connection point between the resistor 235 and the resistor 236 is grounded,
The potential of the signal output terminal 212 goes low, and the output signal of the signal line potential detection circuit 218 goes high regardless of whether the output switching element 216 is on or off. Therefore, the control circuit 221 includes the power line 252 and the ground line 25.
5. It is possible to detect that a disconnection abnormality such as the signal line 253 has occurred and an abnormality has occurred in the load drive circuit. However, it is possible to detect whether a disconnection abnormality has occurred or an abnormality has occurred in the load drive circuit. Cannot be determined.
Therefore, the processing operation for eliminating the abnormality could not be performed accurately. The present invention has been made in order to solve such a problem, and an abnormality detection that can accurately determine whether a disconnection abnormality has occurred or an abnormality has occurred in a load drive circuit. It is an object to provide a device.

[0007]

In order to solve the above-mentioned problems, the present invention is directed to a signal output circuit disposed between a power supply line and a ground line, and a power supply line and a ground line. A signal input circuit disposed between the signal input circuit and a signal line for transmitting a signal from the signal output circuit to the signal input circuit, wherein the signal output circuit includes one of a power supply line and a ground line and a signal line. A first switching element connected between the power supply line and the ground line, and a second switching element connected between the other of the power supply line and the ground line and the signal line; A series circuit of a third switching element and a resistor connected between the one and the signal line, and a disconnection abnormality detection unit that turns off the second switching element when one of the power supply line and the ground line is disconnected, The third switching element when the load drive circuit is abnormal; An abnormality detecting device having a on-load abnormality detecting means. By using the abnormality detection device according to the first aspect, it is possible to accurately determine whether a disconnection abnormality has occurred or an abnormality has occurred in the load drive circuit. According to a second aspect of the present invention, there is provided the abnormality detecting device according to the first aspect, further comprising an abnormality determining unit configured to determine a normal state, a disconnection abnormality, and a load drive circuit abnormality based on the potential of the signal line. . By using the abnormality detection device according to the second aspect, the abnormality can be detected with a simple circuit. According to a third aspect of the present invention, in the abnormality detection device according to the first or second aspect, the disconnection abnormality detection means includes a voltage dividing circuit connected between a power supply line and a ground line, The first switching element is turned off based on the output of the voltage dividing circuit. If the abnormality detecting device according to claim 3 is used,
Disconnection abnormality of the power supply line or the ground line can be easily detected.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of the abnormality detection device of the present invention. The abnormality detection device according to the present embodiment includes a signal output circuit 10, a signal input circuit 30, a signal line 53, and the like. The signal output circuit 10 has a power supply terminal 11, a signal output terminal 12, and a ground terminal 13. The signal input circuit 30 has a power supply terminal 31, a signal input terminal 32, and a ground terminal 33. The power supply terminal 11 of the signal output circuit 10 and the power supply terminal 31 of the signal input circuit 30
A power supply voltage is supplied from a power supply + B via power supply lines 51 and 52, respectively. Signal output terminal 1 of signal output circuit 10
A signal line 53 is connected between the signal input terminal 2 and the signal input terminal 32 of the signal input circuit 30. The ground terminal 13 of the signal output circuit 10 and the ground terminal 33 of the signal input circuit 30 are grounded via ground lines 54 and 55, respectively.

A resistor 14 is connected between the signal output terminal 12 and the ground terminal 13 of the signal output circuit 10, and a series circuit of a resistor 15 and an output switching element 16 such as a transistor is connected. . Signal output terminal 1
A potential detection circuit 17 is connected to 2, and the potential detected by the potential detection circuit 17 is supplied to a control circuit 18. The potential detection circuit 17 includes, for example, a voltage detection circuit and an A / D
It is composed of a conversion circuit and the like. The control circuit 18 outputs a predetermined PWM signal (pulse width modulation signal) to the control terminal of the output switching element 16 via the resistor 19.

A series circuit of an input switching element 34 such as a transistor, a resistor 35, and a resistor 36 is connected between a power supply terminal 31 and a signal input terminal 32 of the signal input circuit 30. Voltage dividing resistors 37 and 38 are connected between the power supply terminal 31 and the ground terminal 33, and the voltage dividing resistors 37 and 3
The connection point 8 is connected to the control terminal of the input switching element 34 via the resistor 39. A resistor 40 is connected between the connection point between the resistors 35 and 36 and the ground terminal 33.
And a series circuit of an abnormal alarm switching element 41 such as a transistor. The connection point between the resistors 35 and 36 is connected to a load drive circuit such as an actuator drive circuit provided in the signal input circuit 30 via a connection line 42. A load abnormality detection circuit for detecting abnormality of the load drive circuit is provided in the signal input circuit 30, and an output terminal of the load abnormality detection circuit controls the abnormality alarm switching element 40 through a connection line 43. Connected to terminal. Note that resistors 14, 15, 35, 36, 4
The resistance value of 0 is the potential at the connection point between the resistor 14 and the resistor 15 when the output switching element 16 is on and off when the abnormality alarm switching element 41 is off, and when the abnormality alarm switching element 41 is on. The potential is set so that the potential at the connection point between the resistor 14 and the resistor 15 when the output switching element 16 is turned on and off can be distinguished and determined.

Next, the operation of the first embodiment will be described. FIG. 2 shows the connection state between the resistors 14 and 15, that is, the state of the potential of the signal output terminal 12 in the normal state, the disconnection abnormality state, and the load drive circuit abnormality state. Control circuit 18
Outputs a PWM signal having a predetermined duty ratio to the control terminal of the output switching element 16 to turn on and off the output switching element 16, and transmits a control signal to the signal input circuit 30 via the signal line 53. . Signal input circuit 30
If there is no disconnection abnormality such as disconnection or poor contact in the power supply line 52, the ground line 55, and the signal line 53 on the side, the potential of the connection point between the voltage dividing resistors 37 and 38 is at a predetermined potential, Switching element 34 is on. For this reason, the potential at the connection point between the resistor 35 and the resistor 36 changes according to the control signal transmitted via the signal line 53. Signal input circuit 3
The load drive circuit provided in 0 detects a change in the potential of the connection point between the resistor 35 and the resistor 36 and drives the load. In this case, when the output switching element 16 is off, the resistors 35, 36, and 14 are connected in series between the power supply + B and the ground, as shown in FIG.
In the present embodiment, the resistors 35 and 36 are set so that the potential at the connection point between the resistors 14 and 15 at this time, that is, the potential detected by the potential detection circuit 17 becomes the first value close to the power supply voltage B. , 14 are set. When the output switching element 16 is on, the resistor 15 is connected in parallel with the resistor 14 as shown in FIG. In the present embodiment, the resistor 35 and the resistor 35 are connected so that the potential at the connection point between the resistor 14 and the resistor 15 at this time becomes a second value close to the ground potential.
Resistance values of 36, 14, and 15 are set. The control circuit 18 controls PW to turn off the output switching element 16.
After outputting the M signal, the output signal of the potential detection circuit 17 is input. If the output signal of the potential detection circuit 17 is within a predetermined range including a predetermined value, for example, the power supply voltage B, the power supply line 52 of the input circuit 30 side It is determined that there is no disconnection abnormality such as disconnection or poor contact in the ground line 55, the signal line 53, or the like.

On the other hand, when a disconnection abnormality occurs in the signal line 53, the potential of the signal output terminal 12 of the signal output circuit 10 becomes the ground potential. Further, when a disconnection abnormality occurs in the power supply line 52 or the ground line 55 on the signal input circuit 30 side, the input switching element 34 is turned off, and the potential of the signal output terminal 12 of the signal output circuit 10 becomes the ground potential. Control circuit 1
8 is a PWM for turning off the output switching element 16
After outputting the signal, the output signal of the potential detection circuit 17 is input, and if the output signal of the potential detection circuit 17 is within a predetermined range including a predetermined value, for example, 0, the power supply line 52 or the ground line on the signal input circuit 30 side 55, it is determined that a disconnection abnormality has occurred in the signal line 53 and the like.

The load abnormality detection circuit provided in the signal input circuit 30 turns on the abnormality alarm switching element 41 when detecting an abnormality in the load drive circuit. When the abnormality alarm switching element 41 is turned on, the resistor 40 is connected between the connection point between the resistors 35 and 36 and the ground terminal 33. In this case, when the output switching element 16 is off, as shown in FIG. 4, the resistors 35, 36, and 14 are connected in series between the power supply + B and the ground, and the resistors 36, 14 Is connected in parallel to the series circuit of. In the present embodiment, the resistance values of the resistors 35, 36, 14, and 40 are set such that the potential at the connection point between the resistor 36 and the resistor 14 at this time becomes a third value close to B / 2. I have. When the output switching element 16 is on, as shown in FIG.
5 is connected. In the present embodiment, the resistor 36 at this time is
The resistance values of the resistors 35, 36, 14, 40, and 15 are set such that the potential at the connection point between the resistor 35 and the resistor 14 has a fourth value close to the ground potential. The control circuit 18 outputs the PWM signal for turning off the output switching element 16 and then inputs the output signal of the potential detection circuit 17
Is within a predetermined range including a predetermined value, for example, B / 2, it is determined that an abnormality has occurred in the load drive circuit provided in the input circuit 30. When detecting an abnormality, the control circuit 18 outputs an alarm according to the type of the abnormality from an abnormality output unit such as a display unit, an indicator lamp, and an audio output unit. Note that the resistors 14, 15, 35, 36 and the like can be omitted.

Next, a second embodiment of the present invention is shown in FIG. In the second embodiment, the types and connection states of the output switching element, the input switching element, and the abnormality alarm switching element in the first embodiment are changed. In the present embodiment, the signal output circuit 1
10 and the power supply terminal 131 of the signal input circuit 130 are connected to the power supply lines 151 and 1 from the power supply + B, respectively.
A power supply voltage is supplied via 52. Signal output circuit 11
A signal line 153 is connected between the 0 signal output terminal 112 and the signal input terminal 132 of the signal input circuit 130. The ground terminal 113 of the signal output circuit 110 and the ground terminal 133 of the signal input circuit 130 are connected to a ground line 154, respectively.
And 155 are grounded.

A resistor 14 is connected between a power supply terminal 111 and a signal output terminal 112 of the signal output circuit 110, and an output switching element 115 and a resistor 116 are connected.
Are connected in series. A series circuit of a resistor 117 and a resistor 118 is connected between the signal output terminal 112 and the ground terminal 113, and a connection point between the resistor 117 and the resistor 118 is connected to a potential detection circuit 119. The control circuit 120 outputs a PWM signal having a predetermined duty ratio to the resistor 1
The signal is output to the control terminal of the output switching element 115 via the switch 21.

The signal input terminal 132 of the signal input circuit 130
A resistor 134 and a resistor 13
5. A series circuit of the input switching elements 136 is connected. Voltage dividing resistors 137 and 138 are connected between the power supply terminal 131 and the ground terminal 133.
A connection point between 37 and 138 is connected to a control terminal of the input switching element 136 via a resistor 139. The connection point between the resistor 134 and the resistor 135 and the power terminal 13
1, a series circuit of the abnormality alarm switching element 140 and the resistor 141 is connected. A connection point between the resistor 134 and the resistor 135 is connected to a load drive circuit such as an actuator drive circuit provided in the signal input circuit 130 via a connection line 142. The output terminal of the load abnormality detection circuit is connected to the control terminal of the abnormality alarm switching element 140 via the connection line 143. The resistors 114, 116, 117, 118, 134, 1
The resistance values of the output switching elements 11 and 35 in the off state of the abnormality alarm switching element 140
5, the potential at the connection point between the resistor 117 and the resistor 118 at the time of on and off, and the potential at the connection point between the resistor 117 and the resistor 118 when the output switching element 115 is on and off when the abnormality alarm switching element 140 is on. The potential is set to a value that can be distinguished from the potential.

Next, the operation of the second embodiment will be described. FIG. 6 shows the state of the potential at the connection point between the resistor 117 and the resistor 118 in a normal state, a disconnection abnormality, and a load drive circuit abnormality. The control circuit 120 outputs a PWM signal to a control terminal of the output switching element 115 to turn on and off the output switching element 115, and
The control signal is transmitted to the signal input circuit 130 via the control signal 3.
A power supply line 152 and a ground line 155 on the signal input circuit 130 side;
When no disconnection abnormality such as disconnection or contact failure occurs in the signal line 153 or the like, the potential at the connection point between the voltage dividing resistors 137 and 138 is at a predetermined potential and the input switching element 13
6 is on. In this case, when the output switching element 115 is off, as shown in FIG. 7, a resistor 114, a resistor 134, and a resistor 135 are connected between the power supply + B and the ground.
Are connected in series, and the resistors 134 and 135
Is connected in parallel with the series circuit of the resistors 117 and 118. In the present embodiment, the resistor 117 at this time is used.
The resistors 114, 134, 135, 117, and 117 are connected so that the potential at the connection point between the resistor 114 and the resistor 118, that is, the potential detected by the potential detection circuit 119 becomes a fifth value close to the ground potential.
A resistance value of 118 is set. When the output switching element 115 is on, as shown in FIG.
14, a resistor 116 is connected in parallel. In this embodiment, the resistor 114 and the resistor 114 are connected so that the potential at the connection point between the resistor 117 and the resistor 118 at this time becomes a sixth value close to the power supply voltage B.
The resistance values of 134, 135, 117, 118 and 116 are set. The control circuit 120 outputs a PWM signal for turning off the output switching element 115, and then inputs an output signal of the potential detection circuit 119, and
Is within a predetermined range including a predetermined value, for example, 0, the power supply line 152 and the ground line 155 on the input circuit 130 side.
It is determined that no disconnection abnormality such as disconnection or poor contact has occurred in the signal line 153 or the like.

On the other hand, when a disconnection abnormality occurs in the signal line 153, the potential of the signal output terminal 112 of the signal output circuit 110 becomes the power supply potential. Further, when a disconnection abnormality occurs in the power supply line 152 or the ground line 155 on the signal input circuit 130 side, the input switching element 136 is turned off, and the potential of the signal output terminal 112 of the signal output circuit 10 becomes the power supply potential. The control circuit 120 includes the output switching element 11
Potential detection circuit 1 after outputting a PWM signal to turn off
19, and if the output signal of the potential detection circuit 119 is within a predetermined range including a predetermined value, for example, the power supply voltage B, the power supply line 152 and the ground line 15 on the signal input circuit 130 side.
5. It is determined that a disconnection abnormality has occurred in the signal line 153 or the like.

The load abnormality detection circuit provided in the signal input circuit 130 turns on the abnormality alarm switching element 140 when detecting an abnormality in the load drive circuit. When the abnormality alarm switching element 140 is turned on, the resistance 1
The resistor 141 is connected between the power supply terminal 131 and the connection point between the resistor 34 and the resistor 135. In this case, when the output switching element 115 is off, as shown in FIG. 8, a series circuit of the resistors 114, 134 and 135 is connected between the power supply + B and the ground, and the resistor 134 and the resistor 13 are connected.
The series circuit of the resistors 117 and 118 is connected in parallel to the series circuit of No. 5, and the resistor 141 is connected in parallel to the series circuit of the resistors 114 and 134. In the present embodiment, the resistance of the resistor 114 and the resistance of the resistance
The resistance values of 134, 135, 117, 118, and 141 are set. When the output switching element 115 is turned on, as shown in FIG.
16 are connected. In the present embodiment, the resistance 1 at this time is
Eighth when the potential at the connection point between the resistor 17 and the resistor 118 is close to B / 2
Resistances 114, 134, 135, 11
7, 118, 141 and 116 are set. The control circuit 120 includes an output switching element 115
Potential detection circuit 11 after outputting a PWM signal for turning off
9 is input, and if the output signal of the potential detection circuit 119 is within a predetermined range including a predetermined value, for example, B / 2, an abnormality occurs in the load driving circuit provided in the input circuit 130. Judge that there is. When detecting an abnormality, the control circuit 120 outputs an alarm corresponding to the type of the abnormality from an abnormality output unit such as a display unit, an indicator lamp, and an audio output unit.
The resistors 114, 116, 117, 118, 134,
135 and the like can be omitted.

As described above, in the abnormality detection device of the present invention, since the resistor is connected in series with the abnormality alarm switching element, the disconnection abnormality of the power supply line, the ground line, the signal line, etc. of the signal input circuit and the signal input circuit internal Since the abnormality of the load drive circuit can be distinguished and determined, processing at the time of abnormality can be performed accurately.

The present invention can be implemented by hardware or software.
The configuration of the signal output circuit and the signal input circuit are shown in FIGS.
Is not limited to the configuration shown in FIG. Further, the control signal is transmitted via the signal line by outputting the PWM signal to the output switching element, but the transmission method of the control signal is not limited to this. In addition, the potential at the potential detection point in the normal state and the abnormal state can be variously changed as long as the disconnection abnormality and the abnormality of the load drive circuit can be determined.

[0022]

As described above, by using the abnormality detection device according to the first aspect, it is possible to accurately determine whether a disconnection abnormality or a load drive circuit abnormality has occurred. it can. Further, if the abnormality detection device according to claim 2 is used, the abnormality can be detected with a simple circuit. Further, if the abnormality detecting device according to claim 3 is used,
Disconnection abnormality of the power supply line or the ground line can be easily detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of an abnormality detection device according to the present invention.

FIG. 2 is a diagram illustrating a potential at a potential detection point according to the first embodiment.

FIG. 3 is a diagram showing connection states of resistors in a normal state and an abnormal state.

FIG. 4 is a diagram showing connection states of resistors in a normal state and an abnormal state.

FIG. 5 is a diagram showing a second embodiment of the abnormality detection device of the present invention.

FIG. 6 is a diagram illustrating a potential at a potential detection point according to the second embodiment.

FIG. 7 is a diagram showing connection states of resistors in a normal state and an abnormal state.

FIG. 8 is a diagram illustrating a connection state of a resistor in a normal state and an abnormal state.

FIG. 9 is a diagram showing a conventional abnormality detection device.

[Explanation of symbols]

 10, 110, 210 Signal output circuit 16, 115, 216 Output switching element 17, 119 Potential detection circuit 30, 130, 230 Signal input circuit 34, 135, 234 Input switching element 41, 140, 240 Abnormal alarm switching element 51, 52, 151, 152, 251, 252 Power supply line 53, 153, 253 Signal line 54, 55, 154, 155, 254, 255 Ground line 40, 141 Resistance

Claims (3)

[Claims] A signal output circuit disposed between a power supply line and a ground line; a signal input circuit disposed between a power supply line and a ground line; and a signal input circuit disposed between the signal output circuit and the signal input circuit. A signal line for transmitting a signal to the signal line, and the signal output circuit includes a first line connected between one of the power supply line and the ground line and the signal line.
Wherein the signal input circuit includes a second switching element connected between the other of the power supply line and the ground line and the signal line, and a second switching element connected between the power supply line and the ground line and the signal line. A series circuit of a third switching element and a resistor connected to the power supply circuit, a disconnection abnormality detecting means for turning off the second switching element when one of the power supply line and the ground line is abnormal, and An abnormality detection device having load abnormality detection means for turning on a third switching element. 2. The abnormality detection device according to claim 1, further comprising an abnormality determination unit configured to determine normality, disconnection abnormality, and load drive circuit abnormality based on the potential of the signal line. 3. The disconnection abnormality detecting means has a voltage dividing circuit connected between a power supply line and a ground line, and turns off the first switching element based on an output of the voltage dividing circuit. 3. The abnormality detection device according to 1 or 2.