JPH05103414A - Cutoff command circuit with oscillation preventing function - Google Patents

Abstract

PURPOSE:To fully eliminate the erroneous transmission of final cutoff command even though an abnormal state occurs in a power supply circuit of IC for outputting cutoff commands. CONSTITUTION:When anomaly occurs in a power supply circuit 1, an IC3 for breaking command output operates normally for a certain time period by the electric charge stored in a capacitor 5. Also, discharge of this electric charge to other circuit can be prevented by a diode 6, so that a power supply monitor circuit 2 operates before the IC3 for breaking command out oscillates abnormally, and an output signal indicating the normal power supply is set to OFF. By doing this, an erroneous breaking command output of IC3 for breaking command output is input to a logic element 4 after the output signal from the power supply monitor circuit 2 becomes OFF, so that the logic element 4 will not transmit mistakenly a final breaking command output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a breaking command circuit mainly used for a protective relay that detects a fault current of a high speed DC circuit breaker and issues a breaking command.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional shutoff command circuit. In the figure, a power supply circuit 1 that generates positive and negative voltages supplies drive power for a cutoff command output IC3. A control current from a current sensor such as a Hall element is input to the input portion 3a of the cutoff command output IC 3, and the input value is input to the cutoff command output I.
C3 makes a determination and outputs a cutoff command output from the output unit 3b.

In such a circuit, when the power supply circuit 1 is rising or when the power supply circuit 1 becomes abnormal and the positive and negative voltages become unbalanced, the cut-off command output IC 3 oscillates abnormally and the cut-off command output is erroneous. I had a call. In order to prevent the final cutoff command from being erroneously transmitted due to the erroneous transmission, the power supply monitoring circuit 2 is provided so that the generated voltage of the power supply circuit 1 is determined to be normal,
A power supply normality judgment output indicating that is transmitted. That is, a logical product of the power supply normality judgment output of the power supply monitoring circuit 2 and the shutoff command output of the shutoff command output IC 3 is obtained by the logic element 4 and the final shutoff command output is transmitted.

[0004]

In the cutoff command circuit as described above, when the power supply becomes unbalanced and abnormal, for example, the operating time of the power supply monitoring circuit 2, that is, the power supply normality judgment output which has been ON until then. The time until the switch is turned off may be longer than the oscillation time of the cutoff command output IC3, that is, the time until the erroneous transmission of the cutoff command output. At this time, since the logic element 4 takes the logical product of the power supply normality judgment output and the cutoff command output as described above, there is a problem that the final cutoff command is erroneously transmitted.

The present invention has been made in order to solve the above problems, and the final cutoff command is erroneous even when there is an abnormality such as a temporary imbalance in the power supply of the cutoff command output IC. The purpose of the present invention is to provide a shutoff command circuit that does not send a signal.

[0006]

A cutoff command circuit with an oscillation preventing function according to the present invention is a power supply circuit for driving the cutoff command output IC, which is connected to a cutoff command output IC through a diode for preventing current backflow. A capacitor connected between the connection between the shutoff command output IC and the backflow prevention diode and the ground, a power supply monitoring circuit for monitoring the power supply circuit,
A logic element is provided which outputs a final cutoff command by performing a logical product of the cutoff command output of the cutoff command output IC and the output indicating that the power supply of the power supply monitoring circuit is normal.

[0007]

When the abnormality occurs in the power supply circuit that supplies the power for driving the cutoff command output IC, the cutoff command output IC is backed up for a certain period of time by the electric charge accumulated in the capacitor, so that abnormal oscillation is prevented. Has been operated normally. Further, since the diode prevents the electric charge from being discharged to the power supply monitoring circuit or the like, the power supply monitoring circuit operates during that time and the output signal indicating that the power supply is normal is turned off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cut-off command circuit with an oscillation preventing function according to an embodiment of the present invention. The power supply circuit 1 for generating positive and negative voltages is provided with the cut-off command output IC 3 via the diodes 6, 6.
The power supply for driving is supplied to. Furthermore, I for disconnection command output
Capacitors 5 and 5 are connected to power supply terminals 3c and 3d of C3, respectively. These capacitors 5 and 5 are for disconnection command output I
It has the capacity to back up the power source of C3 temporarily, for example, for about 30 msec. Further, diodes 6, 6 are connected in a direction to prevent discharge from these capacitors 5, 5 to other circuits, especially a power supply monitoring circuit 2 described later.

When a current output from a current sensor such as a hall element is input to the input section 3a of the cutoff command output IC3, the cutoff command output IC3 judges the input value and outputs the cutoff command from the output section 3b. Is output to the logic element 4. The power supply monitoring circuit 2 determines whether or not the voltage generated by the power supply circuit 1 is normal, and if it is normal, the power supply normality determination output for the logic element 4 is turned on. The power supply monitoring circuit 2 generally uses a comparator type circuit, and it takes about 5 to 15 msec at maximum until the power supply normality judgment output is turned off after the power supply abnormality occurs. The logic element 4 is an IC for outputting a shutoff command
The cutoff command output from the power supply monitoring circuit 2 and the power supply normality judgment output from the power supply monitoring circuit 2 are logically ANDed to output the final cutoff command output.

Here, for example, when the power supply circuit 1 fails and the power supply becomes unbalanced, the cutoff command output IC3 is backed up by the capacitors 5 and 5, so that the cutoff command output IC3 abnormally oscillates and accidentally cuts off. Send the command output temporarily (for example, about 30ms
can be prevented during ec). During this time, the power supply monitoring circuit 2 determines that the voltage generated by the power supply circuit 1 is abnormal,
As described above, the power supply normality judgment output is turned off within a maximum of about 5 to 15 msec, for example. Therefore, since the erroneous cutoff command output from the cutoff command output IC 3 is input to the logic circuit 4 after the power supply normality judgment output is turned off, the final cutoff command output is erroneously transmitted from the logic circuit 4. There is no such thing.

[0011]

EFFECT OF THE INVENTION When an abnormality occurs in the power supply circuit supplying the power source for driving the cutoff command output IC, the cutoff command output I is generated by the charge stored in the capacitor.
Since C is backed up for a certain period of time, abnormal oscillation is prevented and it operates normally. Also, since the charge is blocked by the diode, it is not discharged to the power supply monitoring circuit, etc.
During that time, the power supply monitoring circuit operates to turn off the output signal indicating that the power supply is normal. Therefore, an erroneous shutoff command output from the shutoff command output IC is input to the logic element after the output signal from the power supply monitoring circuit indicating that the power source input to the logic element is normal is turned off. Will not accidentally send the final shutoff command output.

[Brief description of drawings]

FIG. 1 is a cutoff command circuit with an oscillation preventing function according to an embodiment of the present invention.

FIG. 2 is a conventional cutoff command circuit.

[Explanation of symbols]

 1 Power Supply Circuit 2 Power Supply Monitoring Circuit 3 Cutoff Command Output IC 4 Logic Element 5 Capacitor 6 Diode

Claims (1)

[Claims] 1. A cutoff command output IC connected to the cutoff command output IC via a diode for preventing current backflow.
A power supply circuit for driving, a capacitor connected between the connection between the cutoff command output IC and the backflow prevention diode and ground, a power supply monitoring circuit for monitoring the power supply circuit, a cutoff command for the cutoff command output IC A cutoff command circuit with an oscillation prevention function, comprising: a logical element that outputs a final cutoff command by taking a logical product of the output and the output indicating that the power supply of the power supply monitoring circuit is normal.