CN1067197C

CN1067197C - Low internal feed equipment for subscriber's interface

Info

Publication number: CN1067197C
Application number: CN94106842A
Authority: CN
Inventors: 熊焰明
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-06-22
Filing date: 1994-06-22
Publication date: 2001-06-13
Anticipated expiration: 2014-06-22
Also published as: CN1114094A

Abstract

The present invention relates to a low internal resistance feeding device of a subscriber interface, which is in parallel connection with two balanced resistance-capacitance networks with a feeding loop of a direct current call power supply connected with an internal system and an external circuit interface of a stored-program control exchange. The device is mainly composed of constant current circuits CS1, CS2 composed of NPN triode transistors Q6, Q7 and voltage stabilizing diodes D1, D2, and CS1 and CS2 can shunt a 12mA current, and have high resistance to an alternating current; the minimum internal resistance of the constant current feeding of the loop is 500 omega, and a loop current of more than 18mA can be still maintained when the loop resistance is 2K. The device has the advantages of simple structure, capability of thick-film technology production and low manufacturing cost.

Description

Low internal feed equipment for subscriber's interface

The present invention relates to the feeder equipment of telephonic communication system, particularly the low internal resistance feeder equipment of digital spc dial exchange and push-button phone switch system and subscriber line interface.

Modern dial exchange, the extension to the subscriber's line other end provides working power usually, to realize calling, the conversation of extension by dial exchange and another extension.In actual applications, subscriber's line length differs greatly.When proximity condition was worked, user's loop resistance was low, at this moment required the constant current power supply installation holding current in the user interface circuit constant, with the power consumption of limited subscriber interface circuit.Require the DC feedback internal resistance of user interface circuit to be higher than AC impedance simultaneously.Under-48 volts of feeds, if continuous current is 24mA, then the feed internal resistance should be about 1.7K-1.8K, and common AC impedance is 600-900 ohm.Extension is when telecommute, and user's loop resistance is higher.At this moment for using unlikely the dropping to below the 18MA of user's circulation, require the circulation electric supply installation in the user interface circuit to be in the low-resistance operating state.If user's circulation was not less than 18mA (this is Chinese Ministry of Posts and Telecommunications standard) when user's loop resistance was 2K under-48 volts of feeds of requirement, the constant current power supply installation internal resistance in the user interface circuit should be lower than 600 ohm.

Common discrete component user interface circuit, employing degree of balance hybrid coil transformer preferably realizes the conversion of 2/4 line, user interface AC impedance network and direct current tie line are separated, and the minimum internal resistance that makes the direct current constant current feed circuit is about 400 ohm, and the general equal loop resitance of operate as normal that can make is up to 2K.But each transformer occupies bigger space increases the whole volume of automatic telephone, reliability is also relatively poor, existing integrated user interface circuit has semiconductor monolithic integrated circ, as the MC3419 of U.S. MOTOROLA company and the HC-5502 of HARRIS company.Another kind of is thick film hybrid integrated circuit, the MH88612 and the MH89625 that have Canadian MITEL company to release.Utilize semiconductor technology the user interface circuit solution integration of complexity can be monolithic integrated circuit.Adopt three pairs of current mirror circuits to constitute conversion of 2/4 line and local loop testing circuit as MC3419, make 2 line balance ends be high impedance from transmitting terminal feedback sub-fraction alternating current component to receiving terminal, thereby the DC feedback internal resistance is reduced easily interchange.But common shortcoming is to be produced by the monopolization of minority semiconductor manufacturer.MH89625 adopts thick film element to make with the scheme of similar semiconductor circuit, and resultant costs is surging, is difficult to promote.MH88612 is not difficult to promote the use of in China because of meeting the standard laid down by the ministries or commissions of the Central Government owing to no complex impedance function yet.The integrated line user interface circuit of thick film of existing domestic-developed successfully adopts lower cost solution to solve circulation weighing apparatus current feed and port complex impedance, but because this scheme directly seals in the complex impedance network in the circulation constant-current feeding loop, make the minimum internal resistance of loop constant current feed circuit be higher than 900 ohm, limited effective feed distance greatly.

The objective of the invention is to adopt thick film element to make the digital automatic switch-board low internal feed equipment for subscriber's interface of a suitable DR telephone user communication with better simply scheme.

Circuit theory diagrams of the present invention as shown in Figure 1.

The objective of the invention is that this hurdle realizes, constructing a kind of low internal feed equipment for subscriber's interface is connected between the built-in system and external circuit interface of stored-program control exchange, this low internal feed equipment for subscriber's interface comprises by 2 complex impedance unit and forms complex impedance network 1, it is characterized in that: also comprise the constant-current source unit CS1 and the CS2 that directly are connected in parallel respectively or are connected in parallel indirectly on the described complex impedance unit by two, in addition, also comprise circulation constant-current feeding unit 3, this unit strings is connected between the tie point of power supply and one of described constant-current source and corresponding complex impedance unit.Said constant-current source unit CS1, CS2 mainly are made up of NPN transistor Q6, Q7 and voltage stabilizing didoe D1, D2, the tie point Q6 base stage of resistance R 35 and D1 negative pole, the biasing circuit of composition Q6.The Q6 collector electrode links to each other with the R35 other end and constitutes CS1 first end and link to each other equivalently with the direct current of TF end.Q6 emitter series resistance R36 connects and composes second end of CS1 with the D1 positive pole and links to each other in external circuit T line.The tie point Q7 base stage of resistance R 37 and D2 emitter, the biasing circuit of composition Q7.The Q7 collector electrode is connected with first end of the continuous formation of the other end CS2 of R37 and with external circuit R line.Q7 emitter series resistance R38 and D2 be anodal link to each other second end that constitutes CS2 and with the RF end on resistance R38, the collector electrode of triode Q5 in the constant current feed circuit, the tie point of electrochemical capacitor c positive pole is continuous.CS1, CS2 are two identical constant-current sources of parameter roads of becoming soaked with sweat.When between 1,2 ends of CS1, CS2 during change in voltage, because the pressure stabilization function of D1, D2, the voltage drop on feedback resistance R36, the R38 remains unchanged, and the electric current by them is also remained unchanged.Owing to select R35 much larger than R36, R37,, make by approximate 1, the 2 end electric currents of the constant current of R36, R38 almost to keep constant by CS1, CS2 much larger than R38.

For the speech AC signal, constant-current circuit presents higher impedance, much larger than the impedance of two complex impedance networks that are made of R31, R32, C4 and R33, R34, C5.Therefore, after two complex impedance networks of CS1, CS2 and this were in parallel separately, the voice signal input of T, R end, output impedance still mainly contained two complex impedance network decisions.And originally the direct current continuous current by the complex impedance network had and was very most ofly shunted by CS1, CS2.If design CS1, CS2 constant-current circuit remain on about 12mA, suppose that this moment, total loop current was 22mA, only have 10mA to pass through the complex impedance network this moment.Therefore, on them, be parallel with CS1, CS2 after, total T, R end is reduced greatly to the minimum direct current internal resistance of local loop feed.At this moment-48 behind the loop constant current feed circuit of volt power supply by the Q5 formation, series connection input, the output complex impedance network circuit in parallel with CS1, CS2 are held local loop feed in addition to T, R at last.Total feed internal resistance can be reduced to less than 500 ohm, in the time of can guaranteeing loop resitance up to 2K, provides electric current more than the pin 18MA to loop.

Utilize the present invention, seal on two complex impedance networks of user's feed loop at existing user interface circuit, constant-current circuit respectively in parallel, the internal resistance of local loop constant-current feeding is greatly reduced, thereby make automatic telephone switching system can work in higher loop resitance, carry out the telephone communication of longer distance.This apparatus structure is simple, is easy to large-scale production and makes, and scrap build is convenient.

In conjunction with the accompanying drawings and embodiments, further specify characteristics of the present invention, in the accompanying drawing:

Fig. 1 is a circuit theory schematic diagram of the present invention;

Fig. 2 is used in frame principle figure in the digital spc dial exchange device interior system for the present invention;

The circuit theory diagrams that Fig. 3 uses in numerical control numeral dial exchange device interior system for the present invention;

Fig. 4 is another embodiment schematic diagram of constant-current circuit in the low internal feed equipment for subscriber's interface of the present invention;

Fig. 5 is another embodiment schematic diagram of constant-current circuit in the low internal feed equipment for subscriber's interface of the present invention.

Frame principle figure that the present invention uses in digital spc dial exchange device interior system and circuit theory diagrams are respectively shown in Fig. 2,3.Complex impedance network 1 is made up of R31, R32, R33, R34 and C4, C5, directly links to each other with local loop TR line, makes user interface circuit T, the input of R end, and output impedance is plural characteristic.2/4 line change-over circuit 2 is made of IC1, IC3, IC4, Q1 and R1, R4, R5, R6, R7, R9, R10, R11, R12, R14, R15, R15, C1, makes the voice signal of T, R transmitted in both directions be converted to two one-way transmission signals.Wherein the 3rd end is a receiving terminal, connects a decoding circuit.Digital signal after this circuit will exchange is converted to analog signal.The 8th end is a transmitting terminal, connects an encoder.This encoder will be converted to digital signal to carry out time-division switching from the voice signal of T, R line.Loop constant-current feeding unit 3 is made of triode Q5, R27, R28, R29 and capacitor C.Its effect is to use the direct current in the loop of family to keep constant, can make whole subscriber line circuit obtain the short circuit overcurrent protection.Q2, Q3, R29 constitute ringing-current drive circuit 4,14,17 termination ringing-current relay coils wherein, 16 end ground connection, the control section in the 13 terminate switched machines.This circuit is finished the ringing-current break-make control of extension ringer.IC3, R13, R16 and R17 constitute loop detection circuit 5, and function is for detecting the pulse dialing of local loop state and extension.Wherein 20 is to detect output, connects the control section in the switch.

CS1 in the low internal feed equipment for subscriber's interface, the also available PNP triode of CS2 constant-current circuit Q8, Q9 constitute, and circuit as shown in Figure 4.Wherein the D1 positive pole links to each other with the Q8 base stage with the tie point of R35 and constitutes the biasing circuit of Q8, and Q8 emitter series connection R36 and D1 negative pole connect into CS1 the 1st end, and the Q8 collector electrode and the R35 other end connect and compose CS2 the 2nd end.The CS2 that is made of Q9, D2, R37, R38 it constitute with CS1 identical.

CS1 in this device, the also available field effect transistor Q10 of CS2 constant-current circuit, Q11 constitute, as shown in Figure 5.Q10, Q11 drain D constitute the 1st end of CS1, CS2 respectively, and Q10, Q11 source S serial connection source resistance RS is communicated with the 2nd end that grid G separately constitutes CS1CS2 respectively.Source S serial connection source resistance RS makes field effect transistor be operated in the autobias state, and constant-current circuit output size depends primarily on source resistance RS.Since the working method grid voltage of field effect transistor control source electrode, the size of current between the drain electrode.At the autobias state, the pressure drop on the RS provides partially anti-to grid.It is when electric current increases on it that the last pressure drop of RS increases the current situation), grid bias reduces, thereby causes source electrode, and electric current reduces between the drain electrode, and the result makes current balance type constant on certain value.

Claims

1, a kind ofly is used to be connected the built-in system of stored-program control exchange and the low internal feed equipment for subscriber's interface between the external circuit interface, comprise by 2 complex impedance unit and form complex impedance network 1, it is characterized in that: also comprise the constant-current source unit CS1 and the CS2 that directly are connected in parallel respectively on described 2 complex impedance unit by two, be serially connected in the loop constant-current feeding unit 3 between the tie point of power supply and one of described constant-current source and corresponding complex impedance unit.

2, low internal feed equipment for subscriber's interface according to claim 1, it is characterized in that: described constant-current source unit CS1 and CS2 are mainly by NPN transistor Q6, Q7 and voltage stabilizing didoe D1, D2 constitutes, resistance R 35 connects the Q6 base stage with the tie point of D1 negative pole, the biasing circuit of forming Q6, the Q6 collector electrode links to each other with the R35 other end and constitutes CS1 the 1st end and link to each other equivalently with the direct current of TF end, resistance R 37 connects the Q7 base stage with the tie point of D2 emitter, the biasing circuit of forming Q7, the Q7 collector electrode is connected with the 1st end of the continuous formation of R37 other end CS2 and with external circuit R line, Q7 emitter series resistance R38 and D2 be anodal link to each other the 2nd end that constitutes CS2 and with the RF end on resistance R33, the collector electrode of triode Q5 in loop constant-current feeding unit 3 circuit, the tie point of electrochemical capacitor C positive pole links to each other, and described loop constant-current feeding unit piece is by triode Q5, R27, R28, R29 and capacitor C constitute.

3, low internal feed equipment for subscriber's interface according to claim 1 and 2, it is characterized in that: described constant-current source unit CS1, the also available PNP triode of CS2 Q8, Q9 constitute, wherein the D1 positive pole links to each other with the Q8 base stage with the tie point of R35 and constitutes the biasing circuit of Q8, CS1 the 1st end that Q8 emitter series connection R36 and D1 negative pole connect and compose, the Q8 collector electrode and the R35 other end connect and compose CS2 the 2nd end, and the CS2 that is made of Q9, D2, R37, R38 it constitute with CS1 identical.

4, low internal feed equipment for subscriber's interface according to claim 1 and 2, it is characterized in that: the also available field effect transistor Q10 of described constant-current source unit CS1, CS2, Q11 constitute, Q10, Q11 drain D constitute CS1, CS2 the 1st end respectively, Q10, Q11 source S serial connection source resistance R is communicated with the 2nd end that grid G separately constitutes CS1, CS2 respectively.