JPS6319097A - Line abnormality monitor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a line abnormality monitoring device that detects a short circuit in a line and disconnects the short circuit.

(Prior Art) A conventional line abnormality monitoring device of this type known as a short circuit isolator is shown in FIG. 2, for example.

In FIG. 2, 1 is a receiver equipped with a power supply circuit and a reception circuit, and a plurality of terminal loads such as sensors or repeaters are connected between a pair of power supply and signal lines 2a and 2b led out from the receiver 1. 3 are connected in parallel, and the power supply/signal line 2 is also connected in parallel.
a and 2b are connected in parallel with the terminal load 3 and then returned to the receiver 1 side to form a loop line.

Such loop-connected power supply/signal lines 2a, 2
In the middle of line b, line abnormality monitoring devices 4a, 4b, 4c, and 4d, known as short circuit isolators, are provided on the receiver 1 side and for each group of predetermined terminals 3.

FIG. 3 shows the line abnormality monitoring device shown in FIG. 2, which has a switch 5 inserted and connected to the positive side of the power supply/signal line 2a, and also has a switch 5 inserted and connected to the power supply/signal line 2a side, which is the positive side, and a switch 5 on both sides of the inserted and connected switch 5. The line voltage is input to a short circuit detection circuit 6 that detects a line short circuit from a drop in line voltage, and the short circuit detection circuit 6
The output is given to the switch control circuit 7 to control the switch 5 on and off. Furthermore, a resistor 8 is connected in parallel with the switch 5, so that when the receiver 1 turns on the power, the switch 5, which is in an OFF state, can be bypassed and the power supply voltage can be supplied to the track and the track monitoring device located at the subsequent stage. There is.

The operation of the system shown in FIG. 2 equipped with such track abnormality monitoring devices 4a to 4d is as follows.

First, when the receiver 1 is powered on, the track abnormality monitoring device 4
Since each of the switches 5 provided at a to 4d is in an off state, a power supply voltage is supplied to the switch 5 via a resistor 8 connected in parallel. power supply signal line 2a,
If 2b is normal, the detection output of the short circuit detection circuit 6 is 1q.
Therefore, the switch control circuit 7 turns on the switch 5, and power is supplied to the terminal load 3 via the switched ON switch 5 of each of the line abnormality monitoring devices 4a to 4d, and the terminal load causes fire, etc. enters the monitoring state.

On the other hand, in the steady monitoring state, for example, the power supply signal lines 2a, 2
If a short circuit accident occurs at point A in b, the line voltage in section C where the short circuit occurred will drop to approximately zero volts, and the line voltage in sections B and D where no short circuit has occurred will also drop to approximately zero volts, and this line voltage drop. are track abnormality monitoring devices 4a, 4b,
The short circuit detection circuit 6 of 4c and 4d detects the short circuit, and the switch control circuit 7 turns off the switch 5.

Therefore, a short circuit occurs at point A, and the line in section C between the track abnormality monitoring devices 4b and 40 is normal in section B.

It is separated from the D line. Furthermore, when the switches 5 of the track abnormality monitoring devices 4b and 4C are turned off due to the detection of a short circuit at point A,
Section B via the resistors 8 of the track abnormality monitoring devices 4a and 4d.
The power supply voltage is supplied to the line D again, and therefore the switches 5 of the line abnormality monitoring devices 4a and 4d are turned on again and the line B is switched on again.
, D is restored to normal voltage, and the number of terminal loads 3 that stop due to short circuit can be minimized.

(Problem to be Solved by the Invention) However, in such a conventional line abnormality monitoring device, a bypass resistor 8 is connected in parallel with the switch 5 to supply power when the power is turned on. , resistance 8
The power supply voltage supplied to the terminal loads 3 through the terminal varies depending on the number of terminal loads 3, and it is not possible to supply a constant power supply voltage to the loads when the power is turned on.

That is, as shown in FIG. 3, if the composite load impedance of the terminal loads connected to the terminals 11 and 12 on the load side is 7, the composite load impedance Z decreases according to the number of terminal loads connected in parallel, and the terminal loads Since the voltage between 11 and 12 becomes a partial pressure voltage of the resistor 8 and the composite load impedance 7, the terminal voltage becomes high when the terminal load is small, and becomes low when the terminal load is large.

In this way, if the power supply voltage supplied through the resistor 8 of the line abnormality monitoring device differs when the power is turned on depending on the number of terminal loads connected, for example, if the terminal load, such as a sensor or a repeater, is equipped with a microcomputer. In this case, if the supply voltage before switch 5 is turned on is close to the operating voltage of the microcomputer, the voltage transient at the time of power-on causes the power supply voltage to fluctuate near the operating point, causing the microcomputer to run out of control or cause an initial reset. There was a risk of malfunctions such as not starting properly.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and it is possible to supply a normal power supply voltage from power-on to switch-on regardless of the number of connected loads. It is an object of the present invention to provide a line abnormality monitoring device that can maintain a predetermined voltage at which a microcomputer or the like installed in a load will not cause abnormal operation until the time of completion.

In order to achieve this object, the present invention includes a switch means inserted into a line and a line voltage of the line to which this switch means is inserted and connected. A short circuit detection means for detecting a short circuit, a switch control means for turning on the switch means when the detection output of the short circuit detection means is not obtained and turning on the switch means when the detection output is obtained, and a switch means are inserted. A constant voltage supply means is provided for applying a predetermined constant voltage having a higher threshold value and lower than the operating point voltage of the connected load to the connected line.

(Function) According to the configuration of the present invention, a predetermined constant voltage is supplied to the load side by the constant voltage supply means from the time when power is applied to the line until the switch means is turned on, and this constant voltage is supplied to the load side. By keeping the constant voltage applied by the voltage supply means at a voltage below the operating point of the microcomputer installed in the sensor, repeater, etc. as the connected load, the switch means is turned on and a normal power supply voltage is supplied. Until then,
This is to reliably prevent the microcomputer installed in the load from running out of control or from abnormal operation such as failure to initial reset.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

First, to explain the configuration, 15 is a line abnormality detection device of the present invention, and the terminals 9 and 10 are connected to the power supply signal line 2a,
2b connects the power supply side of the receiver, etc., and terminal 1
The load side is connected to 1.12 by power supply/signal lines 2a and 2b.

A switch 5 is inserted and connected to the line between the terminals 9 and 11 to which the power supply/signal line 2a is connected, and as this switch 5, for example, an analog switch using an FET or the like is used. The line voltages on both sides of the line where the switch 5 is inserted and connected are input to the short circuit detection circuit 6, and the short circuit detection circuit 6 sets at least one of the input line voltages below a preset threshold voltage vth for detecting a line short circuit. When this happens, a line short circuit detection output is output to the switch control circuit 7. The switch control circuit 7 outputs a control signal to turn on the switch 5 when the detection output of the short circuit detection circuit 6 is not obtained, and generates a control signal to turn off the switch 5 when the short circuit detection output is obtained.

On the other hand, 18 is a constant voltage supply circuit, which supplies a predetermined constant voltage V1 to the lines on both sides to which the switch 5 is inserted and connected.
supply.

That is, the power supply signal lines 2a and 2b on the terminal 11.12 side
If the operating point voltage of the microcomputer provided in the terminal load connected between is Va, then the constant voltage supply circuit 18
The constant voltage V1 applied to the lines on both sides of the switch 5 by
is the threshold voltage y for short circuit detection in the short circuit detection circuit 6
The voltage is set to a predetermined voltage that is larger than th and smaller than the operating point voltage Va of the terminal load. More specifically, if the operating point voltage Va of the microcomputer installed in the terminal load is Va=5V, the constant voltage VJI applied to the lines on both sides of the switch 5 by the constant voltage supply circuit 18, is determined to be about Va=2 to 3■, and correspondingly, the threshold voltage vth for short circuit detection of the short circuit detection circuit 6
is set to a voltage equal to or lower than Vth=1V, for example.

A constant voltage supply circuit 18 that generates a constant voltage VJL based on the threshold voltage yth for short circuit detection and the operating point voltage Va of a terminal load such as a microcomputer is connected to each of the lines on both sides to which the switch 5 is inserted and connected. A diode D is connected to the signal line from both sides to prevent backflow.
1. D2 and diodes D1 and D
A transistor 20 is connected in series from the connection point of 2 through a resistor R1, and resistors R2 and R3 are connected to the base of the transistor 20.
A divided voltage is applied by the transistor 20.
A diode D3. It is connected to supply the lines on both sides to which the switch 5 is inserted and connected through each of D4.

In such a constant voltage supply circuit 18, if the collector voltage of the transistor 20 is VC, then the transistor 20
The base-emitter voltage vbe of is Vbe-(R3/
(R2+R3))-VC...(1) It becomes. Here, if the forward voltage of the diode D4 is Vf, the forward voltage Vf of the diode D4 is approximately equal to the base-emitter voltage vbe of the transistor 20. Therefore, if Vf=Vbe, the voltage between the terminals 11 and 12 on the load side The voltage v1 applied to is Vm=Vc−Vf −
-・(2). When the collector voltage Vc obtained from the above equation (1) is substituted into the equation (2), the terminal 1 on the load side
The voltage vl applied between 1.12 and 12 is Vm=Vbe-R
2/R3...(3) can be represented.

That is, as is clear from equation (3), the constant voltage vfL output by the constant voltage supply circuit 18 has a constant base-emitter voltage Vbe of 0.6 V, for example, and therefore the base circuit of the transistor 20 Resistors R2 and R provided in
For example, by setting R2=4XR3, a constant voltage output of 2.4V can be obtained.

Note that the above explanation assumes that the legitimate children 9 and 10 are the power supply side, and the terminals 11 and 10 are the power supply side.
Taking the case where the 12 side is the load side as an example, or conversely, if the terminal 11.12 side is the power supply side and the terminal 9. can be applied to

Next, the operation of the embodiment shown in FIG. 1 will be explained.

Now, if power is supplied to the power supply/signal lines 2a and 2b by turning on the power supply circuit provided in the receiver etc., a predetermined power supply voltage is applied to the terminals 9 and 10 of the line abnormality monitoring device 15, and at this time, Since the switch 15 is in the off state, the diode D1 and the resistor R1 of the constant voltage supply circuit 18
A power supply voltage is supplied to the transistor 20 via the transistor 20 . In addition, since the diode D2 is provided as a power blocking diode for the load side, the constant voltage supply circuit 18
There is no direct power supply via.

The transistor 20, which receives power supply through the diode D1 and the resistor R1, becomes conductive due to the base bias generated by the divided voltage of the resistors R2 and R3, and the transistor 20 becomes conductive.
After the collector voltage Vc of 0 passes through the diode D4 and receives a voltage drop by the forward voltage Vf of the diode D4,
A constant voltage VD/ given by the above equation (3) is applied between the terminals 11 and 12 on the load side.

Note that the diode D3 is in a cutoff state because the collector voltage VC side of the transistor 20 is low.

In this way, immediately after the power is turned on, the constant voltage supply circuit 1
Since the constant voltage V1 created in step 8 is applied between the power supply signal lines 2a and 2b on the load side connected to the load terminals 11 and 12, a plurality of terminal loads connected in parallel to the terminal side line, For example, constant voltage supply circuit 1 for sensors, repeaters, etc.
8 is supplied as a power supply voltage, and even if a microcomputer is installed in a sensor or repeater, the constant voltage Vl is lower than the operating point voltage Va of the microcomputer, so the microcomputer stops. It is possible to reliably prevent the microcomputer from running out of control due to fluctuations in the power supply voltage near the operating point, and from malfunctions in which the initial reset is not performed.

Next, when a constant voltage VfL is applied to the load side from the constant voltage supply circuit 18, this constant voltage VfL is applied to the short circuit detection circuit 6 at the same time.
is also input as the line voltage on the load side, and the constant voltage v
1 is the threshold voltage vt for short circuit detection in the short circuit detection circuit 6
Since the voltage is higher than h, the short circuit detection circuit 6 does not detect a short circuit, and therefore the switch drive circuit 7 turns on the switch 5 with a slight delay in response to the constant voltage v output from the constant voltage supply circuit 18. By turning on the switch 5, a normal power supply voltage is supplied to the load side.

Of course, if a short circuit occurs between the power supply signal lines 2a and 2b on the load side connected to the terminals 11.12, the terminals 11.1
2 drops to approximately OV, and the line voltage on the load side to the short circuit detection circuit 6 falls below the threshold voltage vth, causing the short circuit detection circuit 6 to generate a short circuit detection output, and in response to this short circuit detection output, the switch control circuit 7 turns off the switch 5, and disconnects the short-circuited load-side line from the power supply side.

In addition, since this embodiment has been described as a line abnormality monitoring device used for loop wiring, power is supplied to the load side line from both sides, so the short circuit detection circuit 6 and the constant voltage supply circuit 1
Reference numeral 8 has a configuration in which detection and supply is made to both sides of the switch 5. However, the present invention is not limited to a device used for loop wiring, and can also be applied to a case where power is supplied only from one side.

In this case, the track abnormality monitoring device 1 in the embodiment shown in FIG.
5, the input part on the power supply side of the short circuit detection circuit 6, the connection line and diode from the connection point on the anode side of the diode D1, where the diode D3 of the constant voltage supply circuit 18 is provided, to the connection point on the 7 node side of the diode D4. A connection line from the connection point on the cathode side of diode D1, where D2 is provided, to the connection point on the cathode side of diode D4 can be eliminated.

Further, as the switch 5 and the switch control circuit 7 of this embodiment, a latching relay circuit may be used for the switch control circuit 7, and a relay contact of the latching relay circuit may be used as the switch 5. In this case, when the short circuit detection circuit 6 does not detect a short circuit, a set signal is input to close the relay contact, and when a short circuit is detected, a reset signal is input to open the relay contact. By using this latching relay circuit, current consumption can be reduced.

Furthermore, although this embodiment has been described as a power supply/signal line, it may also be a power supply line.

(Effects of the Invention) As described above, according to the present invention, the switch means inserted and connected to the line and the line voltage connected to the switch means are inputted, and the line voltage decreases below a predetermined threshold voltage. short-circuit detection means for detecting a short circuit in a line when a short-circuit detection output is obtained; switch control means for turning on the switch means when a short-circuit detection output is not obtained; and turning off the switch means when a detection output is obtained; Since a constant voltage supply means is provided to apply a predetermined constant voltage smaller than the operating point of the terminal load and larger than the threshold voltage of the short circuit detection means to the line into which the means is inserted, when the power is turned on, the constant voltage is first applied. Since the supply means supplies a predetermined constant voltage lower than the operating point of the terminal load to the line on the load side, even if there is a terminal load or a microcomputer, it will not receive a power supply that exceeds the operating point, so it is difficult to turn on the power. It is possible to reliably prevent the microcomputer from running out of control immediately after.

In addition, since the constant voltage supply circuit supplies a predetermined constant voltage to the load side immediately after the power is turned on and the switch inserted into the power supply line is open, it is different from the conventional switch connected by insertion. Compared to connecting resistors in parallel,
Regardless of the number of terminal loads connected, the power supply voltage to the load side can be maintained at a constant voltage when the switch is open immediately after power is turned on.

Furthermore, since the magnitude of the constant voltage applied to the load side by the constant voltage supply means is set to a voltage larger than the threshold voltage of the short circuit detection means, the short circuit detection means can be detected by supplying constant voltage to the load side immediately after power is turned on. The short circuit detection operation of the terminal is canceled to reliably create a switch-on state, and the normal power supply caused by this switch-on ensures a normal start by initial reset of the microcomputer provided in the terminal load.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram showing an embodiment of the present invention, Fig. 2 is a system configuration diagram using a conventional line abnormality monitoring device, and Fig. 3 is a circuit block diagram showing a conventional device. be. 2a, 2b: Power supply signal line 5: Switch 6: Short circuit detection circuit 7: Switch control circuit 9.10: Power supply side terminal 11.12: Load side terminal 15: Line abnormality monitoring device 18: Constant voltage supply circuit 20 : Transistors D1-D4: Diodes R1-R3: Resistors

Claims (1)

[Claims] a switch means inserted into and connected to a line; a short-circuit detection means for inputting the line voltage to which the switch means is inserted and connected; and detecting a short circuit in the line when the line voltage falls below a predetermined threshold voltage; switch control means for turning on the switch means when a detection output is not obtained from the detection means and turning off the switch means when a detection output is obtained; and a terminal load on the line to which the switch means is inserted and connected. and a constant voltage supply means for applying a predetermined constant voltage that is lower than the operating point voltage of the short-circuit detection means and higher than the threshold voltage of the short-circuit detection means.