CN2261682Y

CN2261682Y - Protector for telephone as overcurrent and overvoltage

Info

Publication number: CN2261682Y
Application number: CN 95225407
Authority: CN
Inventors: 陈金革
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-10-20
Filing date: 1995-10-20
Publication date: 1997-09-03
Anticipated expiration: 2005-10-20

Abstract

The utility model provides a protector for over current and overvoltage for a telephone. The utility model comprises an overvoltage protecting circuit and an over current protecting circuit. The utility model is characterized in that an external line is connected with a telephone through the overvoltage protecting circuit and the over current protecting circuit in turn. The overvoltage protecting circuit is composed of a small resistor R1 and a voltage-sensitive resistor R2 which are connected in series with each other, and the over current protecting circuit is composed of a Darlington tube Q1 and a three-electrode tube Q2. Because the utility model is connected between the external line and the telephone so that the damage to the build-in devices in the telephone which is produced by relatively great electric voltage and electric current from the external line can be avoided to guarantee the use safety of the telephone and prolong the service life of the telephone.

Description

Telephone set over-voltage over-current protection device

The utility model relates to the over-voltage over-current protection device that a kind of telephone set is used.

Causing electronic telephone short main cause in useful life at present is the instantaneous pressure by thunder and lightning or generation of static electricity that is added in the telephone set two ends, when telephone set is in talking state and meets thunderbolt, electric current by telephone set is with the excessive catastrophe failure that causes, and the voltage that is added in the telephone set two ends when normally proposing the machine conversation must become low voltage (about 10 volts) suddenly through high voltage (48 volts), this will produce an impulse current, make switch hook meeting sparking when connecting of telephone set, thereby influence the useful life of the semiconductor device of telephone set inside.

In order to overcome above-mentioned deficiency; the purpose of this utility model provides a kind of telephone set over-voltage over-current protection device; feasible instantaneous pressure by thunder and lightning and generation of static electricity does not act directly on the telephone set two ends, thereby protects the safe in utilization of telephone set, prolongs its useful life.

The purpose of this utility model realizes by following technical proposals.

The utility model is made up of overvoltage crowbar and current foldback circuit, and outside line is connected with telephone set with current foldback circuit through overvoltage crowbar successively.

Because of the utility model is connected between outside line and the telephone set, thereby can avoid effectively from the damage of the big voltage of outside line and electric current to the telephone set internal components, guarantee the safe in utilization of telephone set, prolong its useful life, the utility model reliability height do not influence the operate as normal of telephone network, and volume is little, cost is low, simple installation.

Below will be described in further detail the utility model by specific embodiment.

Fig. 1 is a circuit block diagram of the present utility model.

Fig. 2 is circuit theory diagrams of the present utility model.

As Fig. 1, shown in Figure 2, the utility model is made up of overvoltage crowbar and current foldback circuit, outside line is connected with telephone set with current foldback circuit through overvoltage crowbar successively, overvoltage crowbar is made up of the little resistance resistance R 1 of mutual series connection and piezo-resistance R2, its two ends are connected with outside line, current foldback circuit is by diode D1～D4, resistance R 3, R4, capacitor C, Darlington transistor Q1 and triode Q2 form, the input of the polar protective circuit that diode D1～D4 forms, the one end is connected between resistance R 1 and the piezo-resistance R2, and the other end is connected with telephone set; The anode of its output is connected with the collector electrode of Darlington transistor Q1, negative terminal is connected with the emitter of triode Q2, the base stage of Darlington transistor Q1 is connected with the collector electrode of triode Q2, its emitter is connected with the base stage of triode Q2, the collector electrode of Darlington transistor Q1 has a resistance R 3, the collector electrode of triode Q2 has a capacitor C, and its base stage has a sample resistance R4.Its operation principle is when the user mentions the telephone set conversation; talking path is from outside line one end; through resistance R 1; the anode and the resistance R 3 of the polar protective circuit of forming by diode D1～D4; the electric current of the resistance R of flowing through 3 to the capacitor C momentary charge after voltage raise and to make Darlington transistor Q1 conducting; this moment, electric current was got back to the negative terminal of polar protective circuit through R4; get back to the other end of outside line through telephone set; the switch hook of telephone set when connecting just can sparking like this; the semiconductor device of telephone set inside also can not be subjected to the impact of heavy current; this moment the telephone set operate as normal; its operating current is less than 50mA; triode Q2 is in cut-off state; if meet thunderbolt this moment; when the electric current of resistance R 4 will be up to 70mA; triode Q2 enters the service area conducting; Darlington transistor Q1 will be in the constant current power supply state; the suffered power of telephone set no longer increases; be well controlled in the safety operation area, when piezo-resistance R2 both end voltage is elevated to its conduction value, piezo-resistance R2 conducting; thereby discharge the induced current of outside line; after thunder and lightning, the electric current of the resistance R of flowing through 4 descends, and triode Q2 deactivates the district and ends; but the telephone subscriber is normal talking again, thereby guarantees the safe in utilization of telephone set.Capacitor C also plays the electronics filter action to high-frequency signal in circuit, can eliminate the interference of radio wave to telephone set like this.Resistance R 1 plays fuse when strong thunderbolt is met in outside line, thereby further protects the safety of telephone set.

Claims

1. telephone set over-voltage over-current protection device, it includes overvoltage crowbar and current foldback circuit, it is characterized in that outside line is connected with telephone set with current foldback circuit through overvoltage crowbar successively, overvoltage crowbar is made up of the small resistor R1 of mutual series connection and piezo-resistance R2, its two ends are connected with outside line, current foldback circuit is by diode D1～D4, resistance R 3, R4, capacitor C, Darlington transistor Q1 and triode Q2 form, the input of the polar protective circuit that diode D1～D4 forms, the one end is connected between resistance R 1 and the piezo-resistance R2, and the other end is connected with telephone set; The anode of its output is connected with the collector electrode of Darlington transistor Q1, negative terminal is connected with the emitter of triode Q2, the base stage of Darlington transistor Q1 is connected with the collector electrode of triode Q2, its emitter is connected with the base stage of triode Q2, the collector electrode of Darlington transistor Q1 has a resistance R 3, the collector electrode of triode Q2 has a capacitor C, and its base stage has a sample resistance R4.