KR100451798B1 - Exchange subscriber circuit comprising over-voltage protection circuit - Google Patents

Abstract

The present invention relates to a circuit for protecting an internal circuit against harmful voltages coming from outside on a subscriber circuit in an exchange.

An exchange subscriber circuit having a hazardous voltage protection circuit according to the present invention comprises a channel codec, a channel slick that is a subscriber line circuit in the exchange, and a primary or negative hazard voltage applied to the tip / ring stage on the channel slick side. A current limiting PTC with current buffering, a primary surge protector with a primary voltage limit according to its operating voltage with respect to the hazardous voltage passing through the current limiting PTC, and a secondary that directs the positive hazard voltage to ground A bridge diode, a voltage limiting element, a diode for reverse current protection, and a zener diode that maintains a fixed voltage value, and the base-emitter voltage is greater than the battery voltage in the reference board, One transistor operates, thereby operating the second transistor to flow voltage and current to ground. Comprising a common secondary protection circuit which protects an internal circuit, and by; The common secondary protection circuit is characterized in that a control resistor is added between the diode and the base terminal of the first transistor.

Description

Switchboard subscriber circuit with hazardous voltage protection circuit {EXCHANGE SUBSCRIBER CIRCUIT COMPRISING OVER-VOLTAGE PROTECTION CIRCUIT}

The present invention relates to a circuit for protecting an internal circuit against harmful voltages introduced from the outside on a subscriber circuit in an exchange, and particularly, it is possible to effectively prevent a countermeasure according to different types of interfaces with fewer circuits. The present invention relates to a circuit that prevents disconnection of a call due to a momentary malfunction occurring in an existing circuit.

1 is a diagram showing a circuit for protecting an internal circuit from a hazard voltage introduced from the outside on a subscriber circuit in a conventional exchange.

Referring to FIG. 1, in an exchange, the subscriber circuit passes a secondary voltage across the primary surge protector 103 via a current limiting PTC 104 via a voice exchange line called a tip / ring. While the audio signal divided into four wires through the bridge diode 102, which is a limiting element, through the channel line slick (Subscriber Line Interface Circuit: 101), the audio signal is transmitted to the system through the channel codec (COder and DECoder: 100). In other words, the voices of other subscribers coming from the system are conveyed in the reverse order.

At this time, not only the current limiting PTC 104 and the primary surge protector 103 are used as the overcurrent and overvoltage protection circuits, but also the bridge diode 102 which is a secondary voltage limiting device is used.

Hereinafter, the operating principle of the circuit diagram of FIG. 1 will be described.

That is, in the circuit as shown in FIG. 1, the instantaneous hazard voltage entering the tip / ring is primarily buffered by the current limiting PTC 104, and the hazard voltage in the process of passing through the primary surge protector 103. The primary voltage limit is dependent on the operating voltage of the primary surge protector 103. For example, when the primary surge protector 103 for the 220V operating voltage is used, the device operates within the error range of the device at 220V and falls to the ground indicated by the frame ground to protect the internal circuit.

In addition, the harmful voltage of about 220V which is not blocked by the primary surge protector 103 goes into the channel slick (subscriber line interface circuit: 101), which is diode 1, in the case of positive voltage depending on whether it is positive or negative voltage. In case of negative voltage, it passes through diodes 2 and 4 to the ground or -48 volts to protect the channel slick 101 side.

Typically, the voltage and current can be prevented by using the current limiting PTC 104 and the primary surge protector 103, but preferably, depending on the type of the channel slick circuit 101 and the channel codec 100, The voltage can be prevented by using the bridge diode 102 as the differential voltage limiting device.

However, in recent years, devices have been integrated to improve yield, and thus, protection circuits for harmful voltages installed in the devices are not fully functioning, so that they tend to apply the protection circuits to the outside. Common second protection circuits are often used, which is becoming an essential circuit trend as international standards for hazardous voltages are strengthened.

FIG. 2 is a diagram illustrating a switch subscriber circuit using a conventional common secondary protection circuit to prevent harmful voltages from entering on the subscriber circuit in the switch.

The circuit for preventing the harmful voltage flowing from the outside shown in FIG. 2 is an improved form than the circuit of FIG. That is, in the hazard voltage protection circuit as shown in FIG. 1, the hazard voltage that falls into the -48 volts side may also go to the -48 volts side connected to the channel slick 101, and if so, If there is no protection circuit in the device or if it is weak, the channel slick 101 may be damaged and may not pass the specification, and there may be a risk of fire due to harmful voltage during actual operation.

Thus, to prevent this, the common secondary protection circuit shown in FIG. 2 is used, where a resistor 1 and a first transistor (transistor 2) when a negative voltage greater than -48 volts crosses the bridge diodes 202 and 302. Reaches the point 1 where the first transistor is operated when the base-emitter voltage of point 2 is about 3 volts higher than the battery voltage in the reference board due to the characteristics of the transistor, and thus the second transistor (transistor 1) is operated. They operate to protect the internal circuitry by flowing voltage and current to ground.

In this case, diode 9 is used for reverse current protection so that negative voltage is used only as reference voltage regardless of battery voltage -48 volts to induce harmful voltage and current to ground. In addition, Zener diode 10 maintains a fixed voltage value to allow voltage and current to flow toward ground.

As a result, it can be directly connected to the -48 volts (battery voltage) on the channel slicks 201 and 301 to prevent a problem from occurring, and it is operated by the hazardous voltage by regulating the voltage of the -48 volts connected to the diode 9. It is possible to control the reference voltage, which is commonly applicable to interface circuits using various kinds of different voltages.

The common secondary protection circuit of FIG. 2 has the advantages described above, but when applied to an interface using various line voltages (for example, wired / wireless telephones, Internet telephones, modern high-tech telephones, etc.) Inconvenient to make a separate power source, and there was a problem of cost increase in the circuit. That is, since all devices cannot control a certain amount or more than the battery voltage used by them, it is necessary to protect the circuit properly by adjusting the reference voltage according to the battery voltage used by the device.

Also, in the case of an interface using a ring or other high voltage, even though the resistance is too small between the -48 volt which becomes the reference voltage in the common secondary protection circuit 205 and the first transistor (transistor 2), it is a normal signal. In spite of this, the common secondary protection circuit 205 may malfunction due to the fact that it may have more than three volts between the emitter and the base of the first transistor at a moment. The furnace was cut off sometimes. This occurs when one common secondary protection circuit 205 is placed on multiple channels to reduce material costs, as shown in FIG. 2, while one channel is busy while ringing or other -48 volts on the other channel. It often occurred when a voltage greater than 3 volts was induced.

If there is a common secondary protection circuit 205 for each channel, there is no such problem, but in this case, there is a problem that a considerable space cost increase and circuit space due to component placement are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an easy operation to adjust the operating voltage with a single control resistor, thereby protecting internal circuits from harmful voltages while facilitating circuit implementation and use.

In addition, it can prevent the disconnection of the call due to a momentary malfunction, and the battery voltage used can be effectively used for different interfaces.

1 is a diagram showing a circuit for protecting an internal circuit from a hazard voltage introduced from the outside on a subscriber circuit in a conventional exchange.

FIG. 2 is a diagram illustrating a switch subscriber circuit using a conventional common secondary protection circuit to prevent harmful voltages from entering on the subscriber circuit in the switch.

3 is a diagram illustrating an exchange subscriber circuit including a common secondary protection circuit in which a resistor is added to a base input terminal of a transistor according to the present invention.

<Description of Major Symbols in Drawing>

400, 500: Channel codec

401, 501: channel slick

402, 502: bridge diode

403, 503: primary surge protector

404, 504: PTC for current limiting

405: common second protection circuit

An exchange subscriber circuit having a hazardous voltage protection circuit according to the present invention comprises a channel codec, a channel slick that is a subscriber line circuit in the exchange, and a primary or negative hazard voltage applied to the tip / ring stage on the channel slick side. A current limiting PTC with current buffering, a primary surge protector with a primary voltage limit according to its operating voltage with respect to the hazardous voltage passing through the current limiting PTC, and a secondary that directs the positive hazard voltage to ground A bridge diode, a voltage limiting element, a diode for reverse current protection, and a zener diode that maintains a fixed voltage value, and the base-emitter voltage is greater than the battery voltage in the reference board, One transistor operates and, accordingly, operates the second transistor to flow voltage and current to ground. Comprising a common secondary protection circuit which protects an internal circuit, and by; The common secondary protection circuit is characterized in that a control resistor is added between the diode and the base terminal of the first transistor.

In addition, by adjusting the control resistance value it is characterized in that the malfunction does not operate even at a normal voltage that differs negatively more than 3 volts compared to the -48 volts battery voltage.

In addition, it is possible to adjust the operating voltage through the control resistor without making a separate reference voltage according to the value of the interface operating battery voltage.

In addition, as the control resistance value is increased, the limiting voltage can be increased proportionally, and as the control resistance value is lowered, the internal circuit can be protected from the hazard voltage that is closer to the reference voltage.

In addition, the control resistor is characterized in that the variable resistor.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a diagram illustrating an exchange subscriber circuit including a common secondary protection circuit in which a resistor is added to a base input terminal of a transistor according to the present invention.

Referring to FIG. 3, the common secondary protection circuit 405 according to the present invention can see a difference of adding a resistor 3 to the base input terminal of the transistor 3 as compared with the conventional common secondary protection circuit (see FIG. 2).

That is, the protection circuit for preventing the harmful voltage according to the present invention includes the channel codecs 400 and 500, the channel slicks 401 and 501, and the secondary protection circuit bridge diodes 402 and 502 constituting the subscriber circuit of the exchange. , Primary surge protectors (403, 503), current limiting PTCs (404, 504), etc., and these multiple channels provide negative hazard voltage through one common secondary protection circuit 405 for cost reduction. And the positive voltage is configured to subtract to the ground via the bridge diodes 402 and 502, and bundle multiple channels into one common secondary protection circuit 405 without changing the reference voltage. Resistor 3 was added to operate, especially to avoid malfunction even with normal voltages that are negatively more than 3 volts different from the -48 volt battery voltage.

As shown in FIG. 3, the instantaneous hazard voltage coming from the tip / ring is primarily buffered by the current limiting PTCs 404 and 504 and passes through the primary surge protectors 403 and 503. Hence, the voltage becomes the primary voltage limit according to the operating voltages of the primary surge protectors 403 and 503.

For example, when the primary surge protectors 403 and 503 for the 220V operating voltage are used, the device operates within the error range of the device at 220V and falls to the ground indicated by the frame ground to protect the internal circuit.

In addition, the hazardous voltage within about 220V enters the channel slicks 401 and 501, which is through the diodes 15/21 and 17/24 in the case of the positive voltage depending on whether the voltage is positive or negative. The channel is protected toward the channel slick 401 by going to ground via diodes 16/22, 18/23, or to point 3, which is the connection between the first transistor (transistor 3) and resistor 2.

At this time, in the case of a momentary hazard voltage, the current is limited by the current limiting PTC 404, but when the resistance value in the tip / ring is large, a small one within 30 ohms is used because it affects the electrical characteristics.

If too small a few ohms do not allow instantaneous current limit, adjust according to the type of interface. However, the larger the resistance value, the greater the instantaneous current limiting effect.

Negative hazard voltage entering the common secondary protection circuit 405, i.e., if the primary surge protector 403 is used at 220 volts, between -51 volts and 220 volts, which is about 3 volts different from the battery voltage, which is -48 volts. When the voltage enters the point 3, the first transistor (transistor 3) operates as in the conventional structure. However, current 3 entering the base input terminal (point 4) of the first transistor (transistor 3) is limited by the resistance 3 between the negative electrode of the point 19 and the diode 19 and accordingly the operation of the first transistor (transistor 3) in accordance with this limit value. The voltage is determined.

In other words, when the resistor 3 is a small value of several hundred ohms, the input current entering the input terminal of the first transistor (transistor 3) is large, and transistor 3 operates easily from a negative voltage larger than -48 volts at point 3. However, if you connect a large resistor value, such as a few kiloohms, it will not work easily even if the voltage at point 3 is greater than the negative reference voltage of -48V.

This prevents the malfunction of the common secondary protection circuit 405 even when using a telephone used in a normal home, that is, even when using a negative voltage of about 200 volts such as a ring.

Because in the case of the ring relay existing between the primary surge protector 403 and the bridge diode 402, spark noise occurs when the contact connected to the ring sticks to the tip / ring and falls, which is negative than the reference voltage of -48 volts. As a large voltage is induced to come in. At this time, since there is an element such as resistor 3, the current limit must be adjusted to adjust the operation of the common secondary protection circuit 405, and it is possible to reduce the material cost by using it as a bundle in several channels.

Also, instead of creating a separate reference voltage according to the interface operating battery voltage value, simply adjusting the value of resistor 3, which is a control resistor, can be used easily.In other words, increasing the value of resistor 3 increases the limiting voltage proportionally. Lowering the value of resistor 3 can prevent it from low hazard voltages close to the reference voltage.

In addition, resistor 3 may be implemented through a variable resistor in order to be able to adjust the resistance value arbitrarily.

As described above, in the circuit for protecting the internal circuit from the harmful voltage coming from the outside on the subscriber circuit in the exchange, the present invention makes it possible to effectively prevent the countermeasures according to different types of interfaces with fewer circuits. .

In particular, the operating voltage can be easily adjusted with a single control resistor, which makes it easy to implement and use the circuit, and prevents a disconnection of the phone due to a momentary malfunction unlike the existing circuit, which has not been able to control it. It can be used efficiently for different interfaces.

Claims (5)

Channel codec, Channel slick, which is the subscriber line circuit in the exchange, A current limiting PTC for performing current buffering for the positive or negative hazard voltage applied to the tip / ring end on the channel slick side; A primary surge protector for limiting the primary voltage to the hazardous voltage through the current limiting PTC and according to its operating voltage; The positive hazard voltage is the bridge diode, a secondary voltage limiting element that leads to ground, With a diode for reverse current protection and a zener diode that maintains a fixed voltage value, if the base-emitter voltage is greater than the battery voltage in the reference board, the first transistor at the point where the negative voltages of multiple channels meet A common secondary protection circuit, thereby protecting the internal circuitry by operating the second transistor to flow voltage and current to ground; And a control resistor is added to the common secondary protection circuit between the diode and the base terminal of the first transistor. The method of claim 1, Switching subscriber circuit having a voltage protection circuit for preventing a malfunction even with a normal voltage that differs negatively more than 3 volts by -48 volts battery voltage by adjusting the control resistance value. The method of claim 1, An exchange subscriber circuit having a voltage protection circuit for controlling the operating voltage through the control resistor without making a separate reference voltage according to the value of the interface operating battery voltage. The method of claim 1, Increasing the control resistance value can increase the hazardous voltage proportionally, and lowering the control resistance value makes it possible to prevent the low hazardous voltage closer to the reference voltage. . The method of claim 1, And the control resistor is a variable resistor.