JPH03139090A - Overvoltage protecting circuit of subscriber's circuit - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a subscriber's circuit by providing a diode on a speech power source line, and setting its polarity to the polarity for obstructing a current at the time when a higher voltage than a regular speech power source is generated from a power source supply part of the outside. CONSTITUTION:When each power source is supplied from a power source supply part 14 and each subscriber's circuit 13 is operating, when a package is inserted into the power source supply part 14, a voltage of a telephone power source VBB rises suddenly by a making current to a capacitor 12 of its package. A voltage of its raised power source VBB rises suddenly. The voltage of its raised power source VBB appears in a speech power source line 102 of an active subscriber's circuit package 10, but since passing of a current is obstructed by a diode 11, a large current does not flow to a subscriber's circuit 13. Accordingly, a protective diode in a subscriber's circuit is not broken down and a regular operation can be executed.

Description

[Detailed Description of the Invention] [Summary] Concerning an overvoltage protection circuit for a subscriber circuit in a time-division exchange, a simple configuration prevents damage to the circuit due to a voltage rise in the telephone power supply that occurs when a subscriber circuit package is actively inserted. The purpose is to provide an overvoltage protection circuit for subscriber circuits that can protect multiple subscriber circuits of a time-sharing exchange, one power line for circuits that supplies power to each subscriber circuit, one power line for telephone calls, and one earth line. A subscriber circuit package is provided in which each line is provided with a terminal for connection to an external power supply, and a bypass capacitor is connected between the telephone power supply line and the ground air line, and a diode is connected to the telephone power supply line. The polarity is □ to block the current when a voltage higher than the source is generated for normal calls from the external power supply, and the polarity is □ to block the current when a voltage higher than the source is generated from the external power supply. Constructed to prevent electrical current.

[Field of Industrial Application] The present invention relates to an overvoltage protection circuit for a subscriber circuit of a time division exchange.

The subscriber circuits of time-division exchanges are configured such that multiple circuits are installed in one package, and if a failure occurs in the subscriber circuit while the exchange is in operation, the package must be removed and another normal circuit installed. When replacing a package or adding a subscriber circuit, the subscriber circuit package must be inserted and operated while the exchange is in operation. When inserting a new circuit into a device that is driven by a power supply in this way (this is called active insertion), a charging current flows through the inserted circuit, temporarily fluctuating the power supply voltage, causing a
There is a problem with destroying the circuit.

A solution is desired.

[Conventional technology] FIG. 3 is a configuration diagram of conventional example 1.

In FIG. 3, 30 is a power supply unit provided in the bank panel of the exchange, 31 to 33 are power lines provided in the subscriber circuit pancase, 31 is a circuit power supply (Vcc: +5V, for example) line, and 32 33 represents the telephone power line (VBB: for example -48■), 34 represents the subscriber circuit (BS) provided corresponding to the subscriber line 11 and 12.
(represented by H-LSI).

The subscriber circuit 34 receives power supplies Vcc, VBB, and GND and has a function of supplying two call currents (Ba
ttery feed: B) and loop monitoring function (Su
pervision: S ) and hybrid function (
Hybrid:H) executes each function (represented by BSH).

A plurality of (eight, for example) subscriber circuits 34 are provided in one package, and each line 31 to 33 is connected to each of the subscriber circuits in multiple ways. Also.

Subscriber line 1 to which subscriber circuit 34 is connected! Diodes DI and D2 for preventing electrostatic damage are provided in L and 12,
A capacitor C2 is connected to the subscriber circuit 34.

In the configuration shown in FIG. 3, when the exchange is in operation, the subscriber circuit 34 of the subscriber circuit package connected to the power supply section 3o
In , capacitor C2 is charged to about -44V when no call current is flowing (when the subscriber is not using the telephone).

When another subscriber circuit package with the same configuration is inserted into this frame in the power-on state (active insertion), an inrush current is generated in the bypass capacitor C1 of that package, causing a transient VBB of the power supply section. Rise.

The waveform diagram of VBB at that time is shown in FIG. 5. As shown in FIG. 0, the rise in the telephone power supply VBB at this time reaches several tens of volts (V).

Then, in other adjacent subscriber circuit packages that had been driven by the same power supply unit 30, the charging voltage (-
44V), the voltage across both ends becomes smaller due to the voltage rise of VBB, and the charge stored in the capacitor C2 is discharged.

This discharge current flows through the destruction prevention diode at the terminal of the subscriber circuit BSH-LSI, passes through the route of VBB → diode D2 → capacitor C2 → diode D1 → C, and its current value I! As shown in FIG. 5, the current is several amperes, which destroys the diodes DI and D2 of the subscriber circuit 34 (BSH-LSH), rendering the entire circuit unusable.

In order to prevent this, a configuration of conventional example 2 shown in FIG. 4 has been proposed.

In the 41st ffl, Vc c, G, VBB# and B
11-1-LSI each represents the same thing as in Figure 3.

TRI and TR2 are transistors, RL is a relay rj! l
,rj! 2 represents a contact point of relay RL, and R1-R3 represent resistances.

When the package shown in FIG. 4 is inserted into the exchange, transistors TR2 and TRI are turned on and relay RL is driven. As a result, after a predetermined time determined by the delay time characteristics of relay RL, relay contacts rffil and rI1
2 is turned on. Therefore, the charging current generated when the package is inserted is between the power supply VBB and the subscriber circuit BSH-LS.
The current flows according to the characteristics of an RC filter consisting of a resistor R3 connected in series between G and I, and a capacitor C1 connected between G and G. Then, the sudden rush current is suppressed within the time determined by the time constant of the circuit.

The contacts of relay RL are driven after the delay time (several milliseconds) of the relay, so that resistor R3 and resistor R2 are short-circuited, respectively, and the resistance is removed from the ground air line and the power supply VBB line,
Relay RL then maintains the open drive state in which power is supplied.

[Problem to be solved by the invention B1 According to the conventional example 2 shown in FIG. 4 above, a relay is used and its delay time is used to prevent a large inrush current. Due to the constant driving, chattering tends to occur, and when chattering occurs in FIG. 4, there is a problem in that the rush current cannot be sufficiently suppressed. Furthermore, it is difficult to precisely adjust the delay time of the relay, and a complicated circuit configuration is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an overvoltage protection circuit for a subscriber circuit, which can prevent the circuit from being destroyed due to the voltage rise of the power source for telephone calls that occurs when a subscriber circuit package is actively inserted.

[Means to solve the problem 1 FIG. 1 is a diagram showing the principle configuration of the present invention.

In FIG. 1, reference numeral 10 indicates a subscriber circuit package 100, a circuit power line, 101 a ground air line, 102 a communication power line, 11 a diode provided according to the present invention, 12 a bypass capacitor, and 13 a plurality of represents the installed subscriber circuit.

The present invention provides a diode in the communication power line of the subscriber circuit package to prevent the subscriber circuit in the package from being destroyed when the communication power supply on the power supply side rises.

[Function] Each power supply is supplied from the power supply section 14 to each subscriber circuit 1.
3 is in operation, when another package (not shown) is inserted into the power supply section 14, the voltage of the telephone power supply VBB increases rapidly due to the current applied to the capacitor 12 of that package. The increased voltage of the power supply VBB appears on the communication power line 102 of the active subscriber circuit package IO, but since the diode 11 prevents the current from passing, no large current flows through the subscriber circuit 13.

Therefore, the protection diodes in the subscriber circuit 13 are not destroyed and can perform normal operation.

[Example] FIG. 2 is a configuration diagram of the embodiment.

In FIG. 2, 20a and 20b are subscriber line terminals connected to subscriber terminals, and 21 is a subscriber capacitor C2, 2.
2 is a subscriber circuit (BSH-LSI), 23 is a diode Di and a bypass capacitor C1 added according to the present invention.
represents an overvoltage protection circuit consisting of Although only one subscriber circuit 22 is shown in FIG. 2, a total of eight subscriber circuits are actually mounted on the subscriber circuit puff cage. Further, the circuit including transistors and resistors shown on the left side of the subscriber circuit 22 has the same structure as the conventional circuit, and realizes the ability to supply a call flow to the subscriber terminal.

When the subscriber circuit package shown in FIG. 2 is connected to a power supply and is operating, if another subscriber circuit package is inserted into an adjacent position, the voltage of the two-call power supply VBB increases due to an inrush current. Then, the increased call volume is
BB is supplied to the subscriber circuit of FIG. This results in
The subscriber circuit 22 in FIG. 2 has a waveform VBB' at the bottom of the diagram.
A voltage shown as is generated (the level of this increased voltage is suppressed to a lower level than in the conventional example by diode D1)
.

Correspondingly, the voltage across the capacitor C2 decreases and an attempt is made to discharge it, but since the diode DI is provided in the discharge path, only a weak current flows. The waveform of the discharge current (■) at this time is shown in the lower part of FIG.

[Effect of the invention 1] According to the present invention, with a simple configuration of simply adding one diode, it is possible to suppress the rise in telephone line voltage [VBB] and prevent damage to the integrated circuit used in the subscriber circuit. .

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention, Figure 2 is a diagram of the embodiment, Figure 3 is a diagram of conventional example 1, Figure 4 is a diagram of conventional example 2, and Figure 5 is a diagram of conventional example. FIG. During the 1st RJA. 10: Subscriber circuit package 100: Circuit power line 101: Earth wire 102: Call power line 11: Diode 12: Bypass capacitor 13: Subscriber circuit M1 diagram ←

Claims (1)

[Claims] In overvoltage protection of subscriber circuits of a time division exchange, a plurality of subscriber circuits (13), a circuit power line for supplying power to each subscriber circuit, a telephone power line, and a ground power line are provided. A subscriber circuit package (10) to which lines are connected, each line having a terminal for connection to an external power supply (14), and a bypass capacitor (12) connected between the telephone power line and the earth line. A diode is provided on the telephone power supply line, the polarity of which is set to block the current when a voltage higher than the normal telephone power supply is generated from the external power supply, and a new subscriber circuit is connected to the power supply. An overvoltage protection circuit for a subscriber circuit, characterized in that it prevents discharge current caused by insertion of a package.