JPS5895461A - Overvoltage protecting circuit - Google Patents

Abstract

PURPOSE:To protect an electronic current supply circuit from an overvoltage, by providing a means, which controls the current supply to terminals, and a means, which detects the overvoltage to control the turn-on/off of the current supply and prevents the reverse current from a subscriber's line to the current supply circuit, between lines of subscribers. CONSTITUTION:In the telephone exchange system, a current is supplied from an exchange (c) to the telephone set of a subscriber terminal (a) through a subscriber's line (b) consisting of lines A and B. In the normal operation, the potential at a point A'' of a current supply circuit 1 is 0-VBB volt, and the potential at a point B'' is 0-VBB/2 volt. When an overvoltage is applied to lines A and B, potentials of lines A' and B' in the exchange are restrained to 200- 400V by the clamp function of a triode discharge tube GL, and the overvoltage is not transmitted to the current supply circuit 1 by diodes 8 and 9 of a reverse current preventing rectifier couple 3. Points A'' and B'' are monitored by an overvoltage detecting circuit 2; and when potential at these points become a positive voltage or a voltage lower than VBB/2, the current supply circuit 1 is controlled to be turned off by the detection output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric power exchange system, and more particularly, to a method for protecting electronic components constituting a current supply circuit from an overvoltage applied to an electronic current supply circuit of a subscriber line exchange. It is related to the circuit that makes noodles.

In time-division telephone exchange systems, etc., as semiconductor technology advances, subscriber line exchanges, which had traditionally been mostly made up of magnetic products, are gradually becoming more computerized, starting with the central control system. Since electronic components mainly used in
Furthermore, increasing dependence is being realized. However, 770 people can directly access the terminal! Trunks and call path switch networks that send out warning signals handle extremely high signal levels, and overvoltages of several hundred volts are applied during lightning strikes or power cross-contamination through subscriber lines. Electromagnetic components were still the mainstay because they did not match well with electronic systems that handle small signals, and this was an obstacle to making switching equipment smaller and more functional.

Figure 1 is a diagram for explaining this prior art, and shows the entire current supply system for supplying DC current for signal superimposition to subscriber terminals. In the figure, 0) indicates the subscriber terminal, 0) indicates the subscriber terminal, and 2) indicates the subscriber line consisting of lines A and B, with M being 11 ponds and Bt-4i ground wire. B) Shows the Hiroshima switching center, with fuses FUSE 1 and FUME 2 connected in series to ASB, and line ASB.
According to the current supply circuit, there are 93 station discharge tubes G and L, a battery Vll, and a relay RLY. )0 Talking current supply A talking current for signal superimposition is supplied from the trunk 10 to the subscriber terminal equipment via the subscriber line (battery line, ground line B). Therefore, if there is an induced lightning strike or power line collision on the subscriber line, the potential of the battery line and the potential of the ground line B are limited to 200 V or less at the peak value by triode discharge tubes G and L installed between the lines. The overcurrent flowing due to the application of overvoltage is limited to 9 tOA or less by cutting off the fuse FUSE1, FU&E2 fil path, thereby preventing destruction of circuit elements forming the communication current supply trunk 10. That's what I do. However, it is almost impossible to directly apply this sophisticated overvoltage and overcurrent protection function to a nine-call current supply trunk that is converted into an electronic circuit because there is a large gap in the breakdown resistance of electronic components and electromagnetic components. . In other words, the breakdown resistance of electromagnetic parts is extremely high and the above-mentioned overvoltage protection method is sufficient, but in the case of electronic parts, sufficient rilla#
In addition to designing to have tt, adding a p circuit function will lead to higher costs and fine wrinkles, which is not economical, and will therefore greatly reduce the breakdown resistance of electronic components. The current situation is that it cannot be taken.

In view of the above-mentioned drawbacks, the present invention aims to protect a current supply circuit from overvoltage applied to the circuit by using an overvoltage detection circuit having a circuit configuration.

The present invention provides a %flL supply circuit that controls the current supply to subscriber terminals on and off, and when the ground line potential, which is approximately at the level of the power supply voltage supplied to the current supply circuit, drops below that level, Alternatively, there is an overvoltage detection circuit that detects when the battery line potential, which is normally at a negative potential, becomes a positive potential, and an overvoltage detection circuit that is inserted in series with the subscriber line and connects the current supply circuit from the subscriber line when overvoltage is applied. The circuit comprises a reverse current blocking circuit for blocking reverse current, and when an overvoltage is applied to the line, the overvoltage detection circuit detects it and uses its output to turn off the current supply circuit. The current supply circuit is protected from overvoltage application. Below, #I2
The present invention will be explained in detail according to FIGS.

FIG. 2 shows a current supply system for supplying direct f&current for superimposing audio and image signals to a subscriber terminal mainly using semiconductor elements, which is a diagram illustrating the principle of the present invention. 1
Figure 1 shows that in the case of "0", DC current for signal superimposition is supplied to the subscriber terminal equipment from the communication current supply trunk 10 of the switching center (C) through the subscriber line (B). It is similar, but the transmission trunk f/L supply trunk 1 shown in the same figure
0 is the current supply circuit 1, the overvoltage detection circuit 2, the diode 8,! It is composed of a backflow prevention flow device pair 5 consisting of.

9. At the entrance of the conversion station (c), triode discharge tubes G and L are connected in the same way as in Fig. 1, so that in the event of an induced lightning strike or power line collision, the batteries 111j inside the exchange station! A' ground 111iB
The wave value of the voltage applied to ' is limited to within 200V.

Next, we will explain the overvoltage msi method in the circuit shown in FIG. Also, the potential at the ground connection point B' of the current supply circuit 1 is in the range of 0 to V-A volts, depending on the resistance of the subscriber terminal connected across the line. However, the voltage of the battery vIIm is normally -48V in the current supply path.

Meanwhile, join! When overvoltage is applied to ASB, the potential of battery w A/ and ground -B' in exchange e9 is suppressed to a crossing value of, for example, 200 to 400 V by the voltage clamping action of shield discharge tubes G and L. .

Now, if a positive overvoltage is applied to one line,
+200 for exchange battery IIIA' and ground 41B'
A positive voltage of ~400 μ is generated. At this time, overvoltage is transmitted to the connection point A' between the current supply circuit 1 and the battery line A', but the diodes in the backflow blocking rectifier pair 3! The reverse current is blocked, and no positive overvoltage is transmitted to the connection point B' between the current supply side w11 and the ground. When a negative overvoltage is applied to the 4 circuits, the diode 8 in the reverse blocking rectifier pair 3 blocks the reverse current and connects the current supply circuit 1 and the battery line A'. No negative overvoltage is transmitted to point A1. That is, the potential fluctuation at the thread removal point A# is in the range of vnm to 0 during normal operation, and is in the range of positive overvoltage to 0 when overvoltage is applied. 9, connection point B
'' is normal operation. At times, vBl/
2 to 0, negative overvoltage when overvoltage is applied ~■B
I! /2 range.

Therefore, the battery line potential is monitored at the connection point by an overvoltage detection circuit 2 provided between both connection points and the current supply circuit 1,
The ground m potential is monitored at the connection point B'', and at least one of the cases in which the battery line potential B' becomes a positive voltage is detected. Supply circuit 1 on/off control input (0N10
FF) is controlled so that the current supply circuit 1 is turned off, current no longer flows through the current supply circuit 1, it is protected from being destroyed by the application of overvoltage, and the failure of the subscriber line is restored. If the overvoltage application condition *b is removed, no overvoltage will occur at the connection points A' and B'',
The output of the overvoltage detection circuit 2 disappears, the current supply circuit recovers its current supply function, and returns to normal operation.
The figure shows an embodiment of the present invention, and specifically shows a second circuit block. 1 is an electronic current supply 1gll1lI, which was developed by Honda alone.
The operation and functions are explained in detail in ``Japanese Publication No. 55-115766'', so the details will be omitted here, but to briefly explain only the functions, a feedback circuit is configured with a transistor circuit, and When viewed from the roadside (A', B'), it has low resistance (220Ω x 2) in terms of DC and high impedance (~50) in terms of current transformation, and is equivalent to the conventional relay RLY. do the work. Note that the circuit consisting of transistors Q, Q, , Q, indicated by the broken line 4 is a drive circuit provided to add an on/off function to the electronic current supply circuit 1.

In the -(2) path, the electronic current supply circuit 1 can be turned off by setting the input of the terminal 0N10FF to the -1- level. Reference numeral 2 denotes an overpressure detection circuit, which mainly includes a comparator 5.6 and an OR gate 7. To the single input of comparator 5, the ground-potential is divided by resistance (dividing ratio = R1) and added from connection point B' by resistor & IL. The potential of line B is
When the voltage of the current supply circuit 1 drops below 1 of the voltage v11m, the comparator 5 detects an overvoltage and outputs Vml R1.
* It is being done. 9. The single power of comparator 6 is grounded, and the battery line potential is resistance-divided (dividing ratio = )Rh0B- and applied to the input from connection point A' by resistor RISR4R6, and the battery line voltage is When it becomes positive, the comparator 6 is configured to output it as overvoltage detection.Then, the detection output of the comparator 5.4 is outputted from the output terminal (OUT) through the OR gate 7, and the electronic tIL flow supply circuit 1 input terminal 0N10FF. Therefore, the overvoltage detection circuit outputs an output when at least one of the comparators 5.6 detects an overvoltage. 3 joins! Silicon diode 8, which is the backflow prevention cost inserted in the temple road ASB? It consists of Note that Vec is the power supply voltage of the drive circuit 4, and the comparator 5.6 and OR
The power supply for gate 7 is omitted.

The example in Figure 1 is a concrete example of the valley block of the original ring diagram in Figure JI2, and its overall operation has already been explained in Figure 2, so we will not explain it here. omitted.

jI4 diagram is the present invention L7? This is the first example of $2.
0, that is, In, which is a variant of the first embodiment shown in the figure.
In figure s, the input of overvoltage detection circuit 2 is connected to reverse blocking rectifier pair 5.
and A″, which is the connection point of electronic current supply 1Ii 1 time w11.
In FIG. 1, the communication current is extracted from point A'B' which is directly connected to the subscriber line at the stage before the reverse switch circuit 103. If the input breakdown voltage of comparator 5.6 can be obtained in both positive and negative directions,
This kind of configuration is also possible. Furthermore, in the fifth example, the backflow blocking rectifier pair 5 was configured with silicon diodes 8.9, but in Figure #14, the backflow blocking rectifier pair 5 was configured with thyristors 108, 109, 110, and 111. The current reverse switch circuit 105 is also used.

That is, under normal conditions, thyristors 108 and 109 are fired, and line B'' → thyristor 109 → line B' → line B
→Subscriber terminal → Edge line → Line A' → Thyristor 1 east →
The current is set to 9 in the path of the melting path A#, but when the current is reversed, the thyristors 110 and 111 are fired, and the m#5
A current is passed in the direction of g'→thyristor 110→line A'...→line B'→thyristor 111→line M1. In this case, the function of the reverse current blocking rectifier pair 3 shown in the JGS diagram can be shared by the above-mentioned talking current reverse switch circuit,
It is possible to reduce the DC-S component generated in the backflow blocking rectifier pair S. As is clear from the above embodiments, the present invention is provided between a pair of subscriber loops to control the current supply to the subscriber terminals. and an overvoltage detection means for detecting overvoltage on the subscriber 1i line and controlling the current supply means on and off according to its detection output; Since it is equipped with a backflow prevention means for blocking backflow current from the line to the current supply circuit, it is possible to reliably protect the electronic current supply circuit installed on the subscriber cord line from overvoltage.

[Brief explanation of drawings]

The first is a conventional overvoltage protection circuit. i
Overall circuit of current supply system - 1 Figure 2 is an overall circuit diagram of a telephone *R supply system comprising the overvoltage detection circuit of the present invention, and Figure 5E physically shows the overvoltage detection circuit of the present invention. Practical circuit diagram No. 4 is an implementation circuit of part 2, which is a modification of the embodiment of part 1. 1...Electronic current supply circuit 2...Overvoltage detection circuit assembly...Backflow blocking rectifier pair 4...Drive circuit 5.6...Comparator 7...OR gate $, 9...Silicon Diode 10...Talking current supply trunk 103...Talking current reverse switch circuit 108-1
11...Thyristor Q, ~Q,...Transistor vmm...Battery Wee...Power supply location...Subscriber terminal G, L...Mi1 Houkikan No. 41!1 Page 1 Continued ■Applicant Nippon Telegraph and Telephone Public Corporation ■Applicant Oki Electric Industry Co., Ltd. 1-7-12 Toranomon, Minato-ku, Tokyo Applicant NEC Corporation 5-33-1 Shiba, Minato-ku, Tokyo No. ■Applicant Fujitsu Ltd. 1015 Kamiodanaka, Nakahara-ku, Kawasaki City

Claims (1)

[Claims] A pair of additions f consisting of a battery wire with a negative potential and a ground wire with a positive potential.
In a communication current supply system that supplies direct current from a switching center to subscriber terminals via an ls path, a current supply circuit provided between the subscriber lines for controlling the supply of communication current to the subscriber terminals; The potential of the 1L source voltage supplied to the supply circuit is lower than that at V2;
. Alternatively, an overvoltage detection circuit is inserted in series with a subscriber line, and is connected to the subscriber line in series with an overvoltage detection circuit that detects that the potential at the edge of the battery, which is at a negative potential, changes to a positive potential, and controls the current supply circuit on and off based on the detected output. Overvoltage protection circuit 0 characterized in that it comprises a reverse current blocking circuit that blocks reverse current from flowing from the subscriber line to the stain current supply circuit when overvoltage application is interrupted.