CN1310391C

CN1310391C - A protective circuit

Info

Publication number: CN1310391C
Application number: CNB021537380A
Authority: CN
Inventors: 刘连冰; 史通; 任印峰
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2002-12-03
Filing date: 2002-12-03
Publication date: 2007-04-11
Anticipated expiration: 2022-12-03
Also published as: CN1505231A

Abstract

The present invention discloses a protective circuit which comprises a thermistor connected to a main circuit of a security unit in series, a discharge pipe which is connected between the main circuit of a security unit and a ground wire of a wire distribution frame in parallel, and a warning circuit composed of a warning switch and an indicating lamp, wherein the warning switch is matched with the thermistor; when the thermistor emits heat with persistent high resistance, the warning switch is closed; moreover, the breakdown voltage of the discharge pipe is larger than 240V of peak voltage of commercial power. The present invention can avoid damaging the circuit and a wiring device in the discharge process of current over the ground when a communication circuit is overlapped; moreover, an alarm signal can be sent out. Simultaneously, overvoltage harm due to lightning strike, etc. can be discharged over the ground for protecting the communications device.

Description

A kind of protection circuit

Technical field

The present invention relates to the safety protection technique in the communication system, refer to a kind of protection circuit that is used for distributing frame especially.

Background technology

In order to increase the coverage rate of signal, make the mobile subscriber can use mobile phone whenever and wherever possible, now a lot of mobile communication equipments all have to place the place of some condition differences, even outdoor, just become the problem that an industry utmost point need solve so how to guarantee the safety of equipment.

In the existing communication equipment, main frame generally has the Security Unit that plays protective action in communication line, when civil power is overlapped in the communication line, the Security Unit protection circuit endangers electric current with hazardous voltages and releases over the ground as early as possible, and send alarm signal over time, and then play the effect of protection.Described protection circuit is specifically as shown in Figure 1:

Resistance R 1 and R2 are the outside line line resistance resistances (just by the line resistance of the main frame MDF of telecommunication bureau to terminal) by outside line line length and line footpath and material decision; Resistance R 3 and R4 are the distributing frame overflow protecting element, are semistor PTCR (ceramic material cPTCR or high-molecular organic material pPTCR); FS1, FS2 are the fault alarm switch, and when external cable and civil power cable bond, the breakdown and persistent fever of discharge tube is after a period of time, thereby FS1, FS2 are closed with the direct bleed off over the ground of consequent hazardous voltages; K switch 1 and K2 and discharge tube abating protection device FS1, FS2 interlock are as the protection alarm switch.End points a, b are the outer line end of Security Unit; End points a ', b ' are line end in the Security Unit; End points s is the security unit alarming signal end; Discharge tube can be gas and puts pipe (GDT1, GDT2), also can be semiconductor discharge tube SA1, SA2, and the 220V line voltage can puncture.F1, F2 are fuse, but during especially big electric current moment fuse protection circuit and equipment.A, B are the external cable ports; C is the internal subscriber cable port.

When the 220V civil power is overlapped on a, b place; discharge tube at first breakdown and over the ground the discharge; in the process of releasing over the ground; discharge tube is by short circuit after discharge tube abating protection device FS1 and the FS2 closure; the harm electric current will continue to release over the ground by this discharge tube abating protection device, and at this moment, distributing frame and external cable all have electric current to pass through; Lian Dong K switch 1 and K2 closure are sent alarm simultaneously.

Though the effect that above-mentioned protection circuit can play protection under certain condition, report to the police has following shortcoming:

As line voltage and communication line overlap joint, and external cable is short to make line resistance R1 and R2 hour, then burns Security Unit and module or external cable because of the short circuit earth current of carrying in Security Unit and the external cable produces a large amount of heats too greatly at short notice.

Summary of the invention

The invention provides a kind of protection circuit, produce the problem that a large amount of heats burn Security Unit and module or external cable too greatly at short notice in the short circuit earth current that has line voltage and communication line to overlap and to carry in external cable exists more in short-term because of Security Unit and external cable to solve prior art.

For addressing the above problem, this present invention provides following technical scheme:

A kind of protection circuit; comprise two discharge tubes that are connected between distributing frame Security Unit two main lines and ground wire; be serially connected in two thermistors that are used for overcurrent protection in two main lines respectively; and alarm indication circuit with alarm switch; the puncture voltage of described discharge tube is higher than the civil power crest voltage; described alarm switch cooperates with described thermistor, and is closed after heating a period of time at this thermistor continuous high temperature, makes alarm indication circuit send the alarm indication.

Described discharge tube is gas discharge tube or semiconductor discharge tube.

Described alarm switch is the hot melten type switch.

The shared alarm switch of described two thermistors.

Described alarm switch is two and in parallel, and each alarm switch cooperates with a thermistor.

In said structure, when thermistor had the big electric current of the harm of continuing to flow through, resistance can raise and the evolution of heat, and when harm was removed, resistance can automatically restore to normal operating conditions.

The present invention has cancelled in the prior art fail safe switch of discharge tube and the alarm switch of interlock thereof; the discharge tube that is punctured by the 220V line voltage that is applied in changes into can not be by the discharge tube of 240V civil power peak voltage breakdown; discharge tube only discharges over the ground to the high voltage disruptive discharge pipe that is produced by thunderbolt or power induction and protects; during no longer to civil power and communication line overlap joint hazardous voltages is endangered the protective action that electric current is let out ground; and the fail safe switch and the alarm switch that do not cooperate with discharge tube; can not send alarm signal; let out the situation generation that thereby distributing frame or external cable are burnt in the circuit heating in the ground process because of electric current when having avoided the civil power overlap joint; and it is unaffected to the protection of thunderbolt; city's electrical cables is protected by thermistor with the harm that contacting of communication line produced; the heat that utilizes the thermistor generation simultaneously is with the alarm switch closure, thus the alarm signal of sending.Therefore, the present invention has simple in structure, the characteristics of reliable operation.

Description of drawings

Fig. 1 is the circuit theory diagrams of prior art;

Fig. 2 is circuit theory diagrams of the present invention.

Embodiment

See also Fig. 2:

A kind of protection circuit comprises: two halves conductive discharge pipe GDT1 and GDT2, and described two discharge tubes are connected between distributing frame Security Unit main line and the ground wire, as over-voltage protector; Two thermistor R3, R4 are serially connected in the main line, as over-current protection device; The alarm indication circuit of forming by the alarm switch K3 and the alarm indicator spare of Security Unit, the one end is connected with ground, and the other end is as alarm signal end S, is connected with-48V power supply.

Thermistor R3 and R4 are semistor (PTCR), as the distributing frame overflow protecting element.This thermistor can be the thermistor (cPTCR) of ceramic material or the thermistor (pPTCR) of high-molecular organic material.Alarm switch K3 is the hot melten type switch, cooperates with thermistor R3 and R4, and indicating device is an indicator light, and K3 connects with alarm switch.The puncture voltage of discharge tube is greater than civil power crest voltage 240V, and normal line voltage can not the disruptive discharge pipe, but the more high voltage that thunderbolt etc. produce can the disruptive discharge pipe, by discharge tube with hazardous voltages, harm electric current bleed off over the ground.And hazardous voltages and harm electric current that civil power crest voltage (240V) or following voltage produce when pair overlapping with main line are protected main line by thermistor.

When civil power crest voltage (240V) or following voltage (as normal line voltage 220V) are overlapped on outside the communication line line end, thermistor at first moves and presents high value, and line current is limited in a lower scope so that it can not work the mischief to circuit and equipment.The heat that thermistor R3 or R4 produce makes K switch 3 closures, and indicator light sends alarm signal, and the heat that thermistor sends can not burn out distributing frame.When harm was removed, the thermistor resistance can automatically restore to normal operating conditions.

For the present invention, alarm switch can be two and in parallel constitutes, and each alarm switch cooperates with a thermistor, as long as there is lasting big electric current to pass through in one of them thermistor, all can makes corresponding alarm switch closure and reports to the police.

Discharge tube also can be gas discharge tube; Alarm appliance also is not limited to indicator light, as also can be sound-producing device, or the device of acousto-optic combination etc.

Because the present invention changes discharge tube into can not be by the discharge tube of 240V civil power peak voltage breakdown; discharge tube only discharges over the ground to the high voltage disruptive discharge pipe that is produced by thunderbolt or power induction and protects; during no longer to civil power and communication line overlap joint hazardous voltages is endangered the protective action that electric current is let out ground; and the fail safe switch and the alarm switch that do not cooperate with discharge tube; can not send alarm signal; let out the situation generation that thereby distributing frame or external cable are burnt in the circuit heating in the ground process because of electric current in the time of can effectively avoiding the civil power overlap joint, unaffected to the protection of thunderbolt simultaneously.

Claims

1, a kind of protection circuit; it is characterized in that comprising: be connected to two discharge tubes between distributing frame Security Unit two main lines and the ground wire; be serially connected in two thermistors that are used for overcurrent protection in two main lines respectively; and alarm indication circuit with alarm switch; the puncture voltage of described discharge tube is higher than 240 volts; described alarm switch cooperates with described thermistor, and this thermistor continuous high temperature makes the alarm switch closure after heating a period of time, and alarm indication circuit sends the alarm indication.

2, circuit as claimed in claim 1 is characterized in that described discharge tube is gas discharge tube or semiconductor discharge tube.

3, circuit as claimed in claim 1 is characterized in that described alarm switch is the hot melten type switch.

4, circuit as claimed in claim 1 is characterized in that the shared alarm switch of two thermistors.

5, circuit as claimed in claim 1 is characterized in that described alarm switch is two and in parallel, and each alarm switch cooperates with a thermistor.