JPH03178256A - Speech current supply circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a telephone current supply circuit that supplies direct current to a terminal connected to an exchange, the present invention relates to a telephone current supply circuit that reduces the amount of heat generated by the telephone current supply circuit, and provides a direct current that is connected to the telephone current supply circuit. The purpose of this is to eliminate the noise superimposed on the power supply and supply DC current to the terminal, and the first and A second resistor is connected in series, a connection point between both resistors is connected to the input part of the first voltage-current conversion circuit via a third resistor, and the connection point of both resistors is connected to the input part of the first voltage-current conversion circuit. a first electronic circuit that outputs a DC voltage connected to a second power supply terminal to the line terminal via a fourth resistor; and fifth and sixth resistors connected in series between the other of the line terminals and the ground. and connect the connection point of both resistors to the input part of the second voltage-current conversion circuit via the seventh resistor,
a second electronic circuit configured to cause a direct current input to the line terminal to flow to the ground via an output circuit of the voltage-current conversion circuit and an eighth resistor; A first circuit that AC-couples the input terminals of the voltage-current conversion circuit.
A communication current supply circuit is configured by the capacitor, and
The DC power supply is powered by connecting ninth to eleventh resistors in series between the DC power source and the ground air, and connecting a second capacitor between the connection point of the ninth and tenth resistors and the ground air. While removing noise, the potentials at the two connection points of the ninth to eleventh resistors are output to the second and first power supply terminals of the first electronic circuit via two amplifiers each having an amplification factor of 1. The system is configured to include a noiseless DC voltage generation circuit.

[Industrial application field]

The present invention relates to a call current supply circuit that supplies direct current to terminals connected to an exchange.

In recent years, the digitalization of exchanges has progressed, and the call current supply circuits that supply direct current to terminals connected to exchanges have also changed from circuits using relay windings to electronic circuits.

The call current supply circuit must have DC resistance below a certain value in order to supply a certain range of DC current to the terminal, while the AC circuit must have high impedance to reduce call loss. . Since it is more difficult to satisfy the above conditions in an electronic circuit that avoids the use of inductance elements as much as possible for miniaturization than in a communication current supply circuit using a relay winding, various ideas have been made.

One of the communication current supply circuits devised to satisfy the above conditions is a communication current supply circuit that uses an operational amplifier to increase the AC impedance between the communication line and the DC power source or the earth. However, this communication current supply circuit has the drawback that it generates a large amount of heat and the noise contained in the DC power supply is transmitted to the line at a high level. Improvements are needed in order to improve.

[Conventional technology]

FIG. 3 is an example of a circuit diagram of a conventional communication current supply circuit.

A and B in Figure 3 are the terminals of the line to which the terminal is connected,
A DC voltage is sent to terminal A from a DC power supply V through a series circuit of resistors R2A and RIA and a series circuit of resistor R1A and transistor QA, and to terminal B, a DC voltage is sent from a DC power supply V through a series circuit of resistors R2A and RIA and a series circuit of resistors R1A and transistor QA.
Earth air is sent through the series circuit of B and the series circuit of resistor REB and transistor Q.

In the above, the DC current in the state where the terminal is connected between the terminals A and B will be explained using the current between the terminal B and the earth as an example.

A DC current flows through terminal B from DC power supply Va through terminal A and the terminal, but the voltage appearing at terminal B is divided by resistor RIB and resistor Rtn, and the potential at division point P1B is the non-inverting input terminal of operational amplifier OPa. (+ terminal), so the operational amplifier OPB has an inverting input terminal (one terminal)
The base current of transistor Q is caused to flow so that the potential at 23 points, that is, the potential at 23 points becomes the same as the potential at the non-inverting input terminal. This causes the transistor Q and the resistor R to be connected to the terminal B.
A current flows through 68. Current also flows from terminal B to the series circuit of resistor RIB and resistor R2B, but since resistor R1B and resistor R2B have high resistance, the main current is the current that passes through transistor QB and resistor REB, and this is the current that flows through the terminal. The same applies to the DC current between terminal A and DC power supply V3, which is a current (earth side), and from DC power supply VB to resistor REA, transistor QA, and terminal A.
The communication current (power supply side) is sent to the terminal via the terminal. Next, the AC impedance between terminal B and the earth will be explained.

When AC (audio) current is input between terminals A and B, point P2
An alternating voltage due to the current appears at A and point P2B, but since they are in opposite phases, they are short-circuited by capacitor C9, and no alternating voltage is input to the non-inverting input terminals of operational amplifiers OPA and OPB. For this reason, the operational amplifiers OP A and OP s do not perform an action to make the potential of the inverting input terminal the same as the potential of the non-inverting input terminal with respect to the AC input.
No alternating current voltage appears at points P3A and P3B. Therefore, no alternating current flows through the circuit connected from the terminal A or B to the DC power supply VB or the earth via the transistor QA or Q and the resistor REA or REII. In other words, the circuit has an extremely high impedance with respect to the AC voltage, and the circuit for supplying the communication current can be a low resistance circuit suitable for supplying the communication current without considering the AC impedance.

From the above, the AC impedance between the terminals A and B and the DC power source V or the earth is only the impedance of the series circuit of resistor RIA and resistor R2A or the series circuit of resistor R+s and resistor R2B, but the series resistance circuit Since it is not a communication current supply circuit, it can have a high impedance for AC input such as voice.

As described above, the circuit of FIG. 3 has low impedance in direct current and high impedance in alternating current, and satisfies the conditions for a current supply circuit.

Next, the power consumption of the circuit shown in FIG. 3 will be described.

The circuit in Figure 3 has a DC power supply voltage of -48V and terminals A and B.
According to the general standard, the minimum current value is 20 mA when the line resistance connected between them is 2000 Ω (including the 100 Ω DC resistance of the telephone), the DC resistance of the current supply circuit is 4.
It is necessary to set it to 00Ω.

The DC resistance of the circuit in Figure 3 is: REA (1+ RIA/R2A) + REB (1+
RIB/R2B), so for example, resistors R1A, R
If 18 is 15 kΩ, resistance R2A and R2H are 5Ω, and resistors REA and REII are 50Ω, the above formula becomes 200
+200Ω, which satisfies the above conditions. in this case,
According to the above operating principle, between terminal A and point P3A and terminal B
The resistance value between and point P3B is 150Ω.

However, if the resistance of the current supply circuit is 200 + 200Ω, the line resistance is 100Ω, which is only the telephone resistance, and the DC power supply voltage is -54V, which is the upper limit of the voltage fluctuation range, the DC current will be 108mA, and the current supply circuit will Power consumption is 0.1082 x 400 = 4.7 W, and heat generation becomes a major problem.

Next, a description will be given of the noise voltage sent to the telephone line when the DC power supply voltage V includes an AC component noise voltage V5.

The capacitance of capacitor Cc in FIG. 3 is made sufficiently large,
Assuming that the impedance is sufficiently smaller than R3A+R3B, AC noise voltages of the same magnitude are applied to the non-inverting input terminals of operational amplifiers OPA and OPa. If this voltage is VAc, then point P3B will also have the same voltage due to the principle of an operational amplifier, so the collector current of transistor QB will be VAC/REB. Also, transistor QA
Since the collector current of is connected to the power supply which contains the noise voltage V5, (VS VAC) / REA
becomes.

The collector current of transistor QA (!=Q,
Since it is a loop current flowing to the terminal via B, the values are equal, and if the collector current is IAC, then IAC = VA
C/REB=(VS VAC)/R[, A. From now on, ■. = vs [1/(R+REB)]Vs =(
RgA+ REB) ・I AC. Terminals A, B
When an impedance RL (not shown) is connected between them, and the voltage across it is V, V=Rt, IAC=Vs [(Rt/(R+RIB)]).

Generally, 600Ω is used as the line termination impedance for RL, so if REA and REB are <50Ω as described above, then V = Vs [RL / (REA+REB)]
= Vs [600/(50+50)]=v
It becomes s X 6. That is, a voltage noise six times the power supply noise Vs of the DC power supply VB is induced between the A and B lines.

[Problem to be solved by the invention]

As described above, the call current supply circuit according to the prior art has the disadvantage that power consumption, that is, heat generation is large, and noise voltage contained in the DC power supply is sent to the subscriber terminal side at a large value.

SUMMARY OF THE INVENTION An object of the present invention is to supply DC current to subscriber terminals by reducing the amount of heat generated by a communication current supply circuit and removing noise superimposed on a DC power supply connected to the communication current supply circuit. .

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In the figure, 1a is one of a pair of line terminals 6a that connects the terminal.
and the noiseless DC voltage generating circuit 3, lb is the second electronic circuit configured between the other line terminal 6b and the ground, 2a and 2b are the first and second electronic circuits. Voltage -
a current conversion circuit, 3 the above-mentioned noiseless DC voltage generation circuit; 4
．． 5 is the first and second amplifier, 7al, 7a2 is the first
The first and second power supply terminals for connecting the DC power supply to the electronic circuit 1a, R+A-R3A, R+a to R3BI R+o
-R3D, REA, and REB are resistors, Cc and C9 are capacitors, and V'8 is a DC power supply.

The first electronic circuit 1a has a resistor RIA and a resistor R2A connected in series between a line terminal (hereinafter simply referred to as a terminal) 6a and a first power supply terminal 7a+, and a connection point between both resistors is connected to a resistor RIA and a resistor R2A through a resistor R3A. The DC voltage connected to the input part of the first voltage-current conversion circuit 2a and connected to the second power supply terminal 7a2 via the first voltage-current conversion circuit 2a is outputted to the terminal 6a via the resistor REA. The second electronic circuit tb connects a resistor RIB and a resistor R2B in series between the terminal 6b and the earth, and connects the connection point between the two resistors to a second voltage-to-current converter via a resistor R3B. It is connected to the input part of the circuit 2b so that the DC current inputted to the terminal 6b via the terminal is passed through the second voltage-current conversion circuit 2b and the resistor REB to the ground. . Further, the input terminals of the two voltage-current conversion circuits 2a and 2b are coupled in an alternating current manner by a first capacitor Cc.

The noiseless DC voltage generation circuit 3 includes the first electronic circuit 1a.
and a DC power supply VB, a resistor RID+ R2DI R3O is connected in series between the DC power supply V8 and the earth, and a second capacitor C9 is connected between the connection point of the resistor RIDI R2O and the earth. The resistor R1, which removes the power supply noise of the DC power supply V8.

The divided potential of the DC power supply VB at the connection point of Rto and the connection point of resistors R2D and R3O is applied to the second and first power supply terminals of the first electronic circuit 1a through the two amplifiers 4.5, respectively. a, 7a.

[For production]

Electronic circuit 1a, lb and capacitor C in Fig. 1
The circuit consisting of electronic circuit 1a is a circuit that performs the same function as the conventional system shown in FIG.
The difference is that the DC power supply v8 is not directly supplied to the DC power source v8, but is supplied via the noiseless DC voltage generation circuit 3.

The functions of the electronic circuits 1a, 1b and the capacitor C6 are the same as those of the conventional system, so a description thereof will be omitted, and the noiseless DC voltage generating circuit 3 will be described below.

The noise-free DC voltage generation circuit 3 is supplied with DC voltage from a DC power supply VB, but the DC power supply V usually contains AC noise. The DC voltage from the DC heavy source ~ r8 is connected to the series circuit of resistors Rzn+R3D and the capacitor CD connected in parallel through the resistor Ran, but the above circuit composed of the resistor and the capacitor becomes a filter circuit. Therefore, the noise voltage, which is an alternating current component, is dropped to the ground, and the connection point between the resistors R+o and R2O is at ground level in terms of alternating current, and is only a direct current potential without noise. Therefore, the connection point between resistor R21) and R2O also provides noiseless direct current.

The DC voltages at the connection point between the resistors RID and R2O and the connection point between the resistors R2D and R2O are respectively applied to the first and second amplifiers 4,
5, voltage-to-current conversion is performed, and the resulting voltage is supplied to power terminals 7a2 and 7a of electronic circuit 1a, respectively. The DC voltage sent from this electronic circuit 1a to the terminal does not contain noise as described above.

Further, the DC voltage supplied from the noiseless DC voltage generation circuit 3 to the voltage-current conversion circuit 2a of the electronic circuit 1a via the power supply terminal 7a2 becomes lower than the voltage of the DC power supply V8, and the voltage supplied to the power supply terminal 7a+ is further reduced. Although it is lower, electronic circuit 1
a, Resistors RIA and R2A in ib, Resistors RIB and R2
The current sent to the terminal can be increased by the voltage division by the resistance divider circuit consisting of B and the action of the voltage-current conversion circuits 2a and 2b compared to the current when the DC power supply VB is directly supplied to the electronic circuit 1a. can. Therefore, if the current value is the same as the current value that would be sent to the terminal when the DC power supply Va is directly supplied to the electronic circuit 1a, the electronic circuit 1a
, ib can increase the DC resistances REA and REB of the current supply circuit. As a result of the above, the electronic circuit 1a,
lb is a current supply circuit that supplies the same DC current value as the conventional one, has a high internal resistance, and makes the power consumption in the electronic circuits 1a and ib smaller than when the DC power supply V8 is directly supplied to the electronic circuit 1a. I can do it.

〔Example〕

FIG. 2 is a circuit diagram of one embodiment of the present invention.

The same symbols are used for the same parts throughout the diagrams,
0PDOPE is an operational amplifier, and Q is a transistor.

Since the electronic circuits 1a and lb are the same as those of the conventional system, their explanation will be omitted, and the noiseless DC voltage generation circuit 3 will be explained below.

The noise-free DC voltage generation circuit 3 receives DC voltage from a DC power supply Va, and the AC noise voltage contained in the DC power supply Va is transmitted through a resistor RID to a series circuit of resistors R2D R2O and in parallel thereto. It is connected to a filter circuit consisting of a connected capacitor C8 and dropped to the ground. Therefore, the connection point between the resistor RID and the resistor R2D and the connection point between the resistor R2D and the resistor R3[+ are both at the earth level in terms of AC, and have only a DC potential without noise. Therefore, only noise-free DC voltage is input to the operational amplifiers OP, OP, but since the operational amplifiers OP and OP are amplifiers with an amplification factor of l, the same DC voltage as the input is input to the electronic circuit 1a. is supplied to the resistor R and the resistor R2A. Since the DC voltage does not include noise, noise-free DC current is sent to the terminal.

Next, the miscellaneous power of the current supply circuit will be explained.

The output voltage 3 of the operational amplifier OP i is equal to the voltage v2 at the connection point between the resistors R2D and R3D, and the voltage V4 at the emitter of the output transistor QD, that is, the output voltage of the operational amplifier OPD is equal to the voltage v2 at the connection point between the resistors R2D and R3D, and the output voltage of the operational amplifier OPD is It becomes equal to the voltage at the connection point ■1. Now, if the resistance between terminals A and B (line resistance including DC resistance of the terminal) is RL, then the communication current flowing through the terminal is 1 = [(V4) +RIA /R2
A (V4+V3)]/[RL+REB(1+RI
B /R2B) +RI! A (1+RIA/R2A)
]. In order to maintain balance between ground and ground, the values of the corresponding elements of electronic circuits 1a and ib are made the same, and R+ =RIA=
RIBI R2=R2A=R2BTR+! =REA=
REB, I = [(V4) +R1/R2(-V4
+ V3 ) ko/[RL + 2 RE (
1+R1/R2) ].

As an example of the subscriber circuit in the above equation, R = 15Ω, R2 = 5Ω, RE = 50ΩVa
”' 48V, V3= 44V, V4= 46V
Applying the value of , when RL = 2000Ω, the talking current ■ is I + = [46 + 3 (46 - 44)] / (2000 +
2X50X4)=21.7Xl0-" (A).

On the other hand, in the conventional circuit where the DC power supply VB is directly connected to the electronic circuit 1a, when VB = 48 V and RL = 2000Ω, the communication current ■ is I l = 48 / (2000 + 2X50X4) =
20. OXl0-3(A).

In the circuit of the present invention, if Rx is the power supply resistance that allows the same current to flow as in the conventional case at RL = 2000Ω, then I l =
[46+3(4644)]/(2000+2RX)=
20. OXl0-' (A), and R, = 300.

That is, in the state of R+/R2=3, Rg (1+R
I/R2) = RE X 4 = 300, so
RE = 75Ω. That is, the conventional R[l =
By changing from 50Ω to R6-75Ω, R,
= 2000Ω, the same current value as the conventional current is obtained.

When the above R, = 75Ω, that is, Rx = 300Ω, if the resistance of only the line becomes 0Ω under the condition of the nearest end, and the resistance of the terminal is 100Ω, the DC power supply becomes V,
= -48V, I l =[46+3(46
-44) /(100+2X300)=74.
3Xl0-3(A). On the other hand, in the conventional circuit, I l = 48 / (100 + 2 x 200) = 9
6. OXl0-3 (A), so the talking current decreases by 21.7 mA.

Note that the DC power source is the upper limit of the voltage fluctuation range, VB =
54 V, the current of the conventional circuit is I = 10
8 Xl0-3(A), whereas the current in the circuit of the present invention is I=8
2.9XIO-3(A), resulting in a reduction of 25.1 mA.

As described above, in the circuit of the present invention, since the communication current can be reduced, the amount of heat generated by the communication current supply circuit is reduced.

In addition, in the circuit of FIG. 2, the resistors RID and R2DR
3D, capacitor C0, and operational amplifier OPE do not need to be provided for each line, and can be used in common for a plurality of communication current supply circuits.

〔Effect of the invention〕

As described above, according to the present invention, the amount of heat generated in the call current supply circuit is reduced, and the noise superimposed on the DC power supply connected to the call current supply circuit is removed, and DC current is supplied to the terminal. This greatly contributes to miniaturization and quality improvement of such communication current supply circuits.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a circuit diagram of an embodiment of the present invention, and FIG. 3 is a circuit diagram of a prior art. In the figure, 1a, lb ・-・-・-electronic circuit 2a, 2b
−−−−・−Voltage-current conversion circuit 3−・−・−・・−・
...-Noiseless DC voltage generation circuit 4.5...-1-
--...Amplifiers 6a, 6b・-m---・-・-
-Line terminals 7a,, 7a2...--Power terminals RIA-R3A, RIB-R3B RID~R3[)--Resistors Cc, Co...--Capacitors. vN Actual egg N11 circuit diagram V of the present invention.

Claims (1)

[Claims] One line terminal (6a) of a pair of line terminals connecting terminals
) and the first power supply terminal (7a_1) that connects the DC power supply, the first and second resistors (R_1_A, R_2_A) are connected in series, and the connection point of both resistors is connected to the third resistor (R_3_A).
) is connected to the input part of the first voltage-current conversion circuit (2a), and connected to the second power supply terminal (7a_2) through the output circuit of the voltage-current conversion circuit (2a). a first electronic circuit configured to output a voltage to the one line terminal (6a) via a fourth resistor (R_E_A);
1a), and the other line terminal (6b) of the pair of line terminals.
) and the fifth and sixth resistors (R_1_B, R_2
_B) are connected in series, and the connection point of both resistors is connected to the seventh resistor (
The second voltage-current conversion circuit (2b
) to the input section of the line terminal (6b) via the terminal.
The DC current input to the voltage-current conversion circuit (2b)
A second electronic circuit (1a, 1b) configured to flow to the ground via the output circuit of the eighth resistor (R_E_B)
and the first and second voltage-current conversion circuits (2a, 2b)
A first capacitor (C
_C) constitutes a communication current supply circuit, and the first electronic circuit (1a) and a DC power supply (V
between the DC power source (V_B) and the earth, the ninth to eleventh resistors (R_1_D, R_2_D, R_3_D) are connected in series between the ninth and tenth resistors (R_1_D, R_
A second capacitor (C_D) is connected between the connection point of
) are connected to remove the power supply noise of the DC power supply (V_B), and the ninth and tenth resistors (R_1_D,
R_2_D) and the 10th and 11th resistors (R
The divided potential of the DC power supply (V_B) at the connection point of _2_D, R_3_D) is applied to the second and first electronic circuits (1a) through two amplifiers (4, 5) with an amplification factor of 1, respectively. A communication current supply circuit characterized by comprising a noiseless DC voltage generation circuit (3) that outputs to power supply terminals (7a_2, 7a_1).