JPH0645902A - Electronic switch - Google Patents

Abstract

PURPOSE:To detect a short-circuit state or the disconnected state of a load by an electronic switch. CONSTITUTION:A current detecting resistor 14 is connected to an output switching transistor(TR) 13 and a disconnected state is detected by AND operation between the output of the TR 13 and a sensor circuit 12. In addition, a short-circuit detecting circuit 21 is connected to one end of the resistor 14. At the time of generating abnormality such as disconnection or a short-circuit, an abnormality detecting signal is informed through an OR circuit 22 and the abnormal state is outputted through a cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic switch, and more particularly to an electronic switch characterized by a self-diagnosis function.

[0002]

2. Description of the Related Art A conventional electronic switch has a pair of power supply terminals and a control terminal for output, and opens and closes a switching element inside the electronic switch according to the switch output, thereby opening and closing a load connected to the outside. Is configured to. However, the electronic switch may be connected to the load and the power supply by a long cable of about several hundred meters as shown in FIG. 3, for example.

[0003]

When the electronic switch is connected to the load and the power source by such a long cable, the control output line is short-circuited or disconnected with the power source as shown in the figure. There is also a possibility. In such a case, there is a drawback in that it is not possible to easily discriminate the abnormality of the electronic switch, the disconnection or the short circuit abnormality on the power supply side. In order to confirm such an abnormality, it is necessary to check each part of the control output line while turning on and off the electronic switch, which has a drawback that it takes a long time to find the disconnection.

The present invention has been made in view of the above conventional problems, and it is possible to easily detect a disconnection of a control output line or a short circuit to a power supply side or the like based on an output current. This is a technical issue.

[0005]

SUMMARY OF THE INVENTION The present invention is an electronic switch having a pair of power supply terminals, a sensor circuit, and a load switching switching element driven based on the output of the sensor circuit. Current detecting means for detecting the current flowing through the switch, disconnection detecting means for detecting that the current value obtained from the current detecting means is below a predetermined value when the output of the sensor circuit is in the on state, and excessive current flowing through the switching element. It is characterized by comprising: a short circuit detecting means for detecting; and a wire disconnecting detecting means and an alarm output means for outputting an alarm signal when a wire disconnection or a short circuit is detected by the short circuit detecting means.

[0006]

According to the present invention having such a feature, the switching element is driven when the sensor circuit of the electronic switch is in the ON state. At this time, if a normal current flows through the load, the disconnection detecting means or the short circuit detecting means does not operate. However, if the wire breaks, almost no load current flows, and in the short circuit, a large current flows. Therefore, these abnormal states are detected by the disconnection detection means or the short circuit detection means. When such disconnection or short circuit is detected, the alarm output means operates to output an abnormal state to the outside.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a connection state of an electronic switch, a load and a power source according to this embodiment, and FIG. 2 is a circuit diagram showing an internal configuration of the electronic switch. As shown in these figures, the electronic switch 1, the load 2 and the power source 3 are connected by a long cable 4. This cable 4 is the power line 4
a, 4b, an output line 4c, and an alarm output line 4d. An alarm notification relay 5 or an indicator lamp for notifying an abnormal signal is connected between the alarm output line 4d and the power source near the load and the power source.

As shown in FIG. 2, the electronic switch 1 has a constant voltage circuit 11 between terminals 1a and 1b to stabilize the power supply voltage and supply it to each part in the electronic switch.
The electronic switch 1 also has a sensor circuit 12 such as a high-frequency oscillation type proximity switch, and the switch output is output via a switching transistor 13. The emitter of the switching transistor 13 is grounded via a resistor 14 which is a current detecting means, and the collector is connected to the terminal 1c as an open collector output. The output line 4c of the cable 4 described above is provided at the terminal 1c.
Are connected. In addition, the output of the sensor circuit 12 causes the operation display lamp 16 to light up via the operation display unit 15.

Now, one end of the current detecting resistor 14 is connected to the input end of the amplifier 17. The amplifier 17 amplifies a voltage corresponding to a minute current value at the time of disconnection, and its output is given to the comparator 18. Comparator 1
A reference numeral 8 outputs a comparison signal when the load current value of the switching transistor 13 becomes an input voltage corresponding to, for example, 1 mA or less, and the output is given to the AND circuit 19. The AND circuit 19 takes a logical product of the output of the sensor circuit 12 and the output, and the output thereof is given to the OR circuit 20. Here, the amplifier 17, the comparator 18, and the AND circuit 19 constitute a disconnection detecting means for detecting the presence / absence of a disconnection when an output is obtained from the sensor circuit 12. Further, one end of the current detection resistor 14 is also given to the short circuit detection circuit 21. The short circuit detection circuit 21 is a short circuit detection means for detecting a short circuit state when an overcurrent, for example, a load current corresponding to a current value of 200 mA or more flows.
This detection output is given to the OR circuit 20 and also to the sensor circuit 12 to prohibit its output. The OR circuit 20 obtains an abnormal signal by the logical sum of the OR circuit 20 at the time of detecting the disconnection or the short circuit, and the output thereof is given to the alarm output transistor 23 through the light emitting diode 22 for the abnormality display. . The transistor 23 has an emitter grounded and a collector connected to the alarm output cable 4d through a terminal 1d. OR circuit 2 here
0, the light emitting diode 22 and the output transistor 23 are
An alarm output means for outputting an alarm signal when a disconnection or a short circuit is detected is configured.

When the electronic switch 1 is in a normal state, the constant voltage circuit 11 stabilizes the supplied power supply voltage and supplies a constant voltage to each part. Then, the sensor circuit 12 outputs a switching signal according to the presence or absence of an object or the like, thereby controlling the transistor 13 to be turned on / off. Along with this, the light emitting diode 1 for operation display is displayed via the operation display unit 15.
6 lights up. The load 2 is driven via the cable 4 by the output of the switching transistor 13.

On the other hand, even if the sensor circuit 12 is turned on, if any part of the cable 4c is disconnected, or if the load 2 is disconnected, no load current flows. Therefore, since the voltage drop of the resistor 14 does not occur, the terminal voltage of the resistor 14 becomes almost zero level. Therefore, the comparator 18
And the comparison signal is given to the AND circuit 19. In this case, since the AND condition is satisfied by the AND circuit 19, the abnormality display light emitting diode 22 is turned on via the OR circuit 20. Further, the alarm output transistor 23 is turned on, and the alarm output means 5 on the load side is driven via the cable 4d. Load 2
Is short-circuited or the cables 4a and 4c are short-circuited, an excessive current flows through the switching transistor 13. Therefore, the short-circuit detection circuit 21 detects the short-circuit state, and the output of the sensor circuit 12 is prohibited. At the same time, a short circuit detection signal is given to the OR circuit 20, and the logical sum output thereof turns on the light emitting diode 22 for displaying an abnormality. Similarly, since the transistor 23 is also turned on, the load-side alarm notification relay 5 can be driven.

[0012]

As described above in detail, according to the present invention, even when the electronic switch is connected to the load and the power source by a long cable, it is very easy to detect a short circuit or disconnection abnormality of the output line. be able to. Therefore, it is possible to prevent erroneous wiring of the control output line and forgetting of the wiring, and it is possible to easily recover the abnormal state.

[Brief description of drawings]

FIG. 1 is a diagram showing a connection state of an electronic switch, a load and a power source according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an electronic switch of this embodiment.

FIG. 3 is a diagram showing a connection state of a conventional electronic switch, a load, and a power supply.

[Explanation of symbols]

 1 Electronic Switch 2 Load 4 Cable 5 Alarm Notification Relay 12 Sensor Circuit 13 Switching Transistor 14 Current Detection Resistor 16, 22 Light Emitting Diode 18 Comparator 19 AND Circuit 20 OR Circuit 21 Short Circuit Detection Circuit 23 Transistor

Claims (1)

[Claims] 1. An electronic switch having a pair of power supply terminals, a sensor circuit, and a switching element for switching a load that is driven based on the output of the sensor circuit, wherein a current for detecting a current flowing through the switching element. A detection unit, a disconnection detection unit that detects that the current value obtained from the current detection unit when the output of the sensor circuit is in the ON state is less than a predetermined value, and a short circuit detection that detects an excessive current flowing in the switching element. An electronic switch comprising: means, and an alarm output means for outputting an alarm signal when a disconnection or a short circuit is detected by the disconnection detection means and the short circuit detection means.