JP2520112B2 - Track abnormality monitoring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a line abnormality monitoring device which detects a short circuit in a line and disconnects the short circuit portion.

(Prior Art) As a line abnormality monitoring device of this type conventionally known as a short circuit isolator, for example, there is one shown in FIG.

In FIG. 2, reference numeral 1 denotes a receiver including a power supply circuit and a reception circuit, and a plurality of terminal loads such as a sensor or a repeater are provided between the pair of power source / signal lines 2a and 2b drawn from the receiver 1. 3 are connected in parallel, and signal lines 2a and 2 that also serve as power sources
b is connected to the terminal load 3 in parallel and then returned to the receiver 1 side to form a loop line.

Such a loop-connected signal line 2a, 2b that also serves as a power source
In the middle of the process, line abnormality monitoring devices 4a, 4b, 4c, 4d known as short circuit isolators are provided for each group of the receiver 1 side and the predetermined terminal 3.

FIG. 3 shows the line abnormality monitoring device of FIG. 2 taken out, and has a switch 5 to be inserted and connected to the plus-side power source / signal line 2a side. The voltage of the line is input to the short circuit detection circuit 6 which detects a short circuit of the line from the drop of the line voltage, and the short circuit detection circuit 6
Is output to the switch control circuit 7 to control the switch 5 to turn on and off. Further, a resistor 8 is connected in parallel with the switch 5 so that when the power is turned on by the receiver 1, the switch 5 in the off state is bypassed so that the power supply voltage can be supplied to the line and the line monitoring and monitoring device located in the subsequent stage. There is.

The operation of the system of FIG. 2 provided with such line abnormality monitoring devices 4a to 4d is as follows.

First, when the power of the receiver 1 is turned on, the line abnormality monitoring device
Since each of the switches 5 provided in 4a to 4d is in the off state, the power supply voltage is supplied through the resistor 8 connected in parallel to the switch 5. If the power supply / signal lines 2a and 2b are normal, the detection output of the short circuit detection circuit 6 cannot be obtained, so the switch control circuit 7 turns on the switch 5 to turn on the line abnormality monitoring devices 4a to 4d. Power is supplied to the terminal load 3 via the switched switch 5, and the terminal load enters a monitoring state such as a fire.

On the other hand, in the steady monitoring state, for example, the signal lines 2a and 2b that also serve as power sources
If there is a short circuit accident at point A, the line voltage in section C where the short circuit occurs will decrease to approximately zero volts, and the line voltage in sections B and D where no short circuit will occur will also decrease to approximately zero volts.
This line voltage drop is detected by the short circuit detection circuit 6 of the line abnormality monitoring devices 4a, 4b, 4c, 4d, and the switch control circuit 7 turns off the switch 5.

For this reason, a short circuit occurs at point A and the line abnormality monitoring device 4b
The track of section C between 4c is separated from the tracks of normal sections B and D. In addition, the line abnormality monitoring device 4b, 4
When the switch 5 of c is turned off, the line abnormality monitoring devices 4a, 4d
The power supply voltage is again supplied to the lines of the sections B and D via the resistor 8 of, and therefore the switch 5 of the line abnormality monitoring devices 4a and 4d is turned on again and the line voltages of the sections B and D are restored to normal voltages. However, the number of terminal loads 3 that stop due to a short circuit can be minimized.

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

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

In this way, when the power supply voltage supplied through the resistor 8 of the line abnormality monitoring device at power-on differs depending on the number of connected terminal loads, for example, a sensor or a repeater serving as a terminal load is equipped with a microcomputer. If the supply voltage before the switch 5 is turned on is near the operating voltage of the microcomputer, the transient voltage at power-on causes the power supply voltage to fluctuate near the operating point, causing the microcomputer to run away or to perform an initial reset. There is a risk of abnormal operation such as not being properly applied.

(Means for Solving Problems) The present invention has been made in view of such conventional problems, and a normal power supply voltage is supplied by switching on after power-on regardless of the number of load connections. It is an object of the present invention to provide a line abnormality monitoring device capable of keeping a predetermined voltage at which a microcomputer or the like provided in a load does not cause an abnormal operation until the time when it is possible.

In order to achieve this object, in the present invention, a receiver and a plurality of terminal loads are connected in a loop through a signal line that also serves as a power source, and a plurality of terminal loads are connected in parallel to a loop line, and one or a plurality of terminal loads are connected. In a line abnormality monitoring device that disconnects the line on the short-circuit side from the line on the power supply side when a line short circuit is detected for each terminal, switch means inserted and connected to the signal line for both power supply and line voltage to which the switch means is inserted and connected. Is input and the line voltage drops below a predetermined threshold voltage, short-circuit detection means for detecting a short circuit in the line, and when the detection output of the short-circuit detection means is not obtained, the switch means is turned on and the detection output is The switch control means for turning off the switch means when obtained, and the terminal on the line between the power source side and the terminal load side, which is provided in parallel with the switch means and to which the switch means is inserted and connected. It is obtained by a constant voltage supply means for applying a predetermined constant voltage higher than the threshold voltage of and a short circuit detecting means below the operating point voltage of the microcomputer of the load visceral as the supply voltage to the terminal load.

(Operation) According to such a 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 the power supply to the line is turned on until the switch means is turned on. By setting the constant voltage applied by the voltage supply means as the connected load to a voltage below the operating point of the microcomputer provided in the sensor, repeater, etc., until the switch means is turned on and the normal power supply voltage is supplied. During
It is intended to reliably prevent an abnormal operation such as a runaway of a microcomputer provided in the load or an initial reset not being applied.

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

First, explaining the configuration, 15 is a line abnormality detection device of the present invention, the power source side of the receiver or the like is connected to the terminals 9 and 10 by the power source / signal line 2a and 2b, and the terminals 11 and 12 also serve as a power source signal. The load side is connected by the lines 2a and 2b.

A switch 5 is inserted and connected to the line between the terminals 9 and 11 to which the power source / signal line 2a is connected. As the switch 5, for example, an analog switch using a FET or the like is used. The line voltages on both sides of the line to which 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 to a preset threshold voltage Vth or less for detecting a line short circuit. When
The detection output of the line short circuit is output to the switch control circuit 7.
The switch control circuit 7 outputs a control signal for turning on the switch 5 when the detection output of the short circuit detection circuit 6 is not obtained, and generates a control signal for turning 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 Vl to the lines on both sides where the switch 5 is inserted and connected.

That is, when the operating point voltage of the microcomputer provided in the terminal load connected between the power source / signal lines 2a and 2b on the terminals 11 and 12 side is Va, the constant voltage supply circuit 18 causes the lines on both sides of the switch 5 to operate. The applied constant voltage Vl is set to a predetermined voltage higher than the threshold voltage Vth for detecting a short circuit in the short circuit detection circuit 6 and smaller than the operating point voltage Va of the terminal load. Further specifically, if the operating point voltage Va of the microcomputer provided in the terminal load is Va = 5V, the constant voltage Vl applied to the lines on both sides of the switch 5 by the constant voltage supply circuit 18 is Vl = 2 to 3V is set, and correspondingly, the threshold voltage Vth for detecting a short circuit of the short circuit detection circuit 6 is set to, for example, Vth = 1V or less.

The constant voltage supply circuit 18 for generating the constant voltage Vl based on the threshold voltage Vth for detecting a short circuit and the operating point voltage Va of the terminal load such as a microcomputer is connected to each of the lines on both sides where the switch 5 is inserted and connected. Connect the signal lines from the lines on both sides via diodes D1 and D2 for backflow prevention, and connect the transistor 20 in series via the resistor R1 from the connection point of the diodes D1 and D2 to the base of the transistor 20. The divided voltage by the resistors R2 and R3 is applied to, and the collector voltage of the transistor 20 is supplied to the lines on both sides where the switch 5 is inserted and connected through the diodes D3 and D4 for backflow prevention. Connected.

In such a constant voltage supply circuit 18, a transistor
Assuming that the collector voltage of 20 is Vc, the base-emitter voltage Vbe of the transistor 20 is Vbe = {R3 / (R2 + R3)}. Vc (1). Assuming that 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, so Vf = Vbe
Is the voltage Vl applied between the terminals 11 and 12 on the load side.
Becomes Vl = Vc-Vf (2). Substituting the collector voltage Vc obtained from the equation (1) into the equation (2), the voltage Vl applied between the terminals 11 and 12 on the load side is Vl = Vbe · R2 / R3 ( 3) can be represented.

That is, as is apparent from the equation (3), the constant voltage Vl output by the constant voltage supply circuit 18 has a constant value of the base-emitter voltage Vbe of, for example, 0.6 V. It is uniquely determined by the values of the resistors R2 and R3 provided. For example, if R2 = 4 × R3 is set, Vl = 2.4V
The constant voltage output of can be obtained.

In the above description, the terminals 9 and 10 are set to the power supply side, and the terminals 11 and 12 are set to the load side.
Even when the 2 side is the power source side and the terminals 9 and 10 side is the load side, the predetermined constant voltage Vl can be applied to the load side line in exactly the same manner.

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

Now, if power is supplied to the power / signal lines 2a, 2b by turning on the power supply circuit provided in the receiver or the like, a predetermined power supply voltage is applied to the terminals 9, 10 of the line abnormality monitoring device 15,
At this time, since the switch 15 is in the off state, the power supply voltage is supplied to the transistor 20 via the diode D1 and the resistor R1 of the constant voltage supply circuit 18. Since the diode D2 is provided on the load side as a diode for blocking power supply, direct power supply via the constant voltage supply circuit 18 is not performed.

The transistor 20 which is supplied with power via the diode D1 and the resistor R1 is rendered conductive by receiving the base bias due to the divided voltage of the resistors R2 and R3, and the collector voltage Vc of the transistor 20 which is rendered conductive passes through the diode D4 and becomes equal to that of the diode D4. After receiving a voltage drop of forward voltage Vf, load terminals 11 and 12
The constant voltage Vl given by the equation (3) is applied between them.

The diode D3 is connected to the collector voltage Vc of the transistor 20.
Since the side is low, it is in the cutoff state.

In this way, immediately after the power is turned on, the constant voltage supply circuit
Since the constant voltage Vl generated in 18 is applied between the load side power source / signal lines 2a and 2b connected to the load terminals 11 and 12, a plurality of terminal loads connected in parallel to the terminal side line,
For example, a constant voltage Vl from the constant voltage supply circuit 18 is supplied as a power supply voltage to a sensor or a repeater, and the constant voltage Vl is lower than the operating point voltage Va of the microcomputer even if the sensor or the repeater is provided with a microcomputer. Since the microcomputer is at a low voltage, the microcomputer is in a stopped state, and it is possible to reliably prevent runaway of the microcomputer due to fluctuations in the power supply voltage near the operating point or abnormal operation without initial reset.

Next, when the constant voltage Vl is applied from the constant voltage supply circuit 18 to the load side, this constant voltage Vl is simultaneously input to the short circuit detection circuit 6 as the line voltage on the load side, and the constant voltage Vl is detected as a short circuit. Since it is higher than the threshold voltage Vth for detecting a short circuit in the circuit 6, the short circuit detection circuit 6 does not detect a short circuit. Therefore, the switch drive circuit 7 delays the output of the constant voltage Vl by the constant voltage supply circuit 18 by a slight time. Then, the switch 5 is turned on, and when the switch 5 is turned on, a normal power supply voltage is supplied to the load side.

Of course, when a short circuit occurs between the load side power supply / signal lines 2a and 2b connected to the terminals 11 and 12, the voltage between the terminals 11 and 12 drops to about OV, and the load side line for the short circuit detection circuit 6 is detected. When the voltage falls below the threshold voltage Vth, the short-circuit detection circuit 6 produces 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 the short-circuited load side line is fed from the power supply side. It comes to separate.

In this embodiment, since the line abnormality monitoring device used for the loop wiring has been described, since the power is supplied to the load side line from both sides, the short circuit detection circuit 6 and the constant voltage supply circuit.
The switch 18 is configured to detect and supply to both sides of the switch 5. However, the present invention is not limited to the device used for the loop wiring, and can be applied to the case where power is supplied from only one side.

In this case, the line abnormality monitoring device in the embodiment of FIG.
In FIG. 15, the input line on the power supply side of the short-circuit detection circuit 6, the connection line from the connection point on the anode side of the diode D1 provided with the diode D3 of the constant voltage supply circuit to the connection point on the anode side of the diode D4, and the diode D2. The connection line from the cathode side connection point of the diode D1 to the cathode side connection point of the 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, the set signal is input to close the relay contact when the short circuit detection circuit 6 does not detect the short circuit, and the reset signal is input to open the relay contact when the short circuit is detected. By using this latching relay circuit, current consumption can be reduced.

Further, although the present embodiment has been described as a power source / signal line,
It may be a power 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 inserted and connected to the switch means are input, and the line voltage is reduced to a predetermined threshold voltage or less. A short-circuit detecting means for detecting a short circuit of the line when, and a switch control means for turning on the switch means when the short-circuit detection output is not obtained and turning off the switch means when the detection output is obtained, and a switch. Since the line into which the means is inserted is provided with a constant voltage supply means for applying 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, when the power is turned on, first the constant voltage is supplied. 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 the terminal load has a microcomputer, Since the power supply exceeding the score is not received, it is possible to reliably prevent the runaway of the microcomputer immediately after the power is turned on.

In addition, since the constant voltage supply circuit supplies a predetermined constant voltage to the load side immediately after the power is turned on when the switch inserted and connected to the power supply line is open, the switch connected and inserted as in the conventional Compared to the case where resistors are connected in parallel, the power supply voltage to the load side can be maintained at a constant voltage with the switch opened immediately after power is turned on, regardless of the number of connected terminal loads.

Further, since the magnitude of the constant voltage to the load side by the constant voltage supply means is set to a voltage larger than the threshold voltage in the short circuit detection means, the short circuit detection means is provided by supplying the constant voltage to the load side immediately after the power is turned on. The short-circuit detection operation is released to surely create a switch-on state, and normal power supply by this switch-on can ensure a normal start by initial reset of the microcomputer provided in the terminal load.

[Brief description of drawings]

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 the conventional device. 2a, 2b: Signal line for both power supply 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 to D4: Diodes R1 to R3: Resistors

Claims (1)

(57) [Claims] 1. A receiver and a plurality of terminal loads are connected in a loop form via a signal line that also serves as a power source, the plurality of terminal loads are connected in parallel to the loop line, and the line is provided for each one or a plurality of terminals. In a line abnormality monitoring device that disconnects the line on the short-circuit side from the line on the power supply side when a short circuit is detected, switch means inserted and connected to the signal line for both power supply and the line voltage to which the switch means is inserted and connected are input. When the line voltage drops below a predetermined threshold voltage, short-circuit detection means for detecting a short circuit in the line, and when the detection output of the short-circuit detection means is not obtained, the switch means is turned on and the detection output is obtained. A switch control means for turning off the switch means when the switch means is turned on, and a wire provided between the power source side and the terminal load side in parallel with the switch means and in which the switch means is inserted and connected. A constant voltage supply means for applying a predetermined constant voltage lower than the operating point voltage of the microcomputer incorporating the terminal load and higher than the threshold voltage of the short-circuit detection means to the terminal load as a power supply voltage. Characteristic track abnormality monitoring device.