JPS6157165A - Complex terminating constant current feed reverse circuit - Google Patents

Abstract

PURPOSE:To decrease the amount of side tones to permit sufficient calls by putting two-wire AC signals on feed control voltage to returning them to voltage-to-current conversion circuits. CONSTITUTION:A impedance terminating circuit 7 detects AC signals on A and B sides to send an overlapping circuit 6 according to specified transfer characteristics. In the overlapping circuit 6, the AC signal is overlapped with the DC feed control voltage VR' output from a feed control circuit 5 to make a feed control voltage VR, which is input to the voltage-to-current conversion circuits to realize a complex impedance terminal.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a complex termination type constant current feeding reverse circuit, more specifically, to a subscriber of a public telephone network exchange, a private branch exchange telephone, a button telephone device, etc. The present invention relates to an electronic complex termination type constant current feeding reverse circuit that combines constant current feeding, reverse (reversal of feeding polarity), and complex impedance termination in a communication current feeding circuit for a circuit.

[Conventional technology]

In this type of power supply circuit based on conventional technology, constant resistance power supply using a relay was used, and reverse operation was also realized by the relay. Also, regarding impedance termination,
It was based on a DC cutoff capacitor and a 600Ω pure resistor. FIG. 5 shows a connection configuration of an example of a power supply circuit according to this type of conventional technology.

In FIG. 5, the power supply circuit 31 is a constant resistance power supply relay R.
L (the resistance of the winding is usually 440Ω), and r
Is it the power supply (usually -48K), and is the reverse circuit 62 a relay contact? '! ,? 2 (the winding of the relay is not shown), and the reversal of the feeding polarity was performed by the relay contacts (mechanical contacts). In the figure, A and B indicate the communication current. This is a power supply output terminal.

The termination circuit 33 includes DC cutoff capacitors C31r and C32.
(usually 2μF each) and termination resistor RT (usually 600Ω)
Consists of.

Since the power supply circuit according to the conventional technology was configured as described above, it had the following problems. In other words, (1) Since it is a constant resistance power supply system, if the line resistance is small, an excessive power supply current flows, resulting in unnecessary power consumption in the power supply relay. Therefore, there was unnecessary heat generation.

■ Since reverse is performed using a relay contact, noise is generated on the adjacent line when the feeding polarity is reversed. In the case of a branch connection (one set of calls 1, 1, 1, 1, 2). (when using a telephone), the bell of an unused telephone resonated.

there were.

■ Noise occurred during operation.

■ The equivalent impedance of the termination circuit is 600Ω + 1μF.
Therefore, especially when the length of one line is relatively short, such as in communication within a premises, impedance mismatch in the sidetone protection circuit of the telephone becomes noticeable, and sidetone t (the transmitted voice is played back on the own handset) However, the number of calls has increased, making it difficult to make calls.

[Problem that the invention seeks to solve]

The present invention attempts to solve the above-mentioned problems of conventional power supply circuits by converting the power supply circuit into an electronic circuit, realizing constant current power supply and reverse control in one circuit, and further providing complex impedance termination. It is.

[Means for solving problems]

According to the present invention, the magnitude of the output current is proportional to the difference between the applied control voltage and the midpoint of the power supply voltage, and the direction of the output current is bidirectionally outputted according to the polarity of the difference. Two voltage-current conversion circuits are provided, and one of the voltage-current conversion circuits has an output current of the same magnitude but in a different direction from the other voltage-current conversion circuit for the same difference, and A constant current is supplied to the two-wire communication line using the output current of The above problem was solved by forming a termination impedance by inputting the signal into an amplifier having a transfer characteristic, and superimposing the output signal on the control voltage applied to the voltage-current conversion circuit and feeding it back.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an outline of an embodiment of the present invention.

In FIG. 1, 1 and 2 are voltage-current conversion circuits, 3 is a low source voltage midpoint voltage (Fcc/2) generation circuit,
4 is the power supply output terminal A of the voltage-current conversion circuits 1 and 2;
5 is a power supply control circuit, 6 is a superimposition circuit, and 7 is an impedance termination circuit. In addition, A and B are power supply output terminals (call current supply terminals) for the two-wire line, Vcc/2 is the midpoint voltage of the power supply generated by the midpoint voltage generation circuit 3, and P'CM is detected by the detection circuit 4. The midpoint voltage between the A and B terminals, r, is the power supply control circuit 5.
DC power supply control voltage output from the power supply control terminal cl
, the value of which changes depending on the control input to c2, VR is
Detects an AC signal between two wires connected to terminals A and B and inputs it to an amplifier having a preset transfer characteristic,
The output signal (AC) is superimposed on the power supply control voltage Vk.

Now, it is assumed that no alternating current is flowing through the line to which power is supplied from the power supply output terminals A and B, and that the output of the impedance termination circuit 7 is 0 and VR=V'R.

The voltage-current conversion circuits 1 and 2 output a current proportional to the difference between the power supply control voltage VR and the midpoint voltage Voc/2 of the power supply voltage Vco from the power supply output terminals A and B. A current flows in both directions according to the sign of the difference from the voltage Vao/2. Voltage and current changing circuits 1 and 2
One of them, for example 2, has an output current that is equal in magnitude to the other voltage-current conversion circuit 1 but in a different direction for the same above-mentioned difference. That is, equal direct current 1. ．． 12 flows.

Of course, if the polarity of the difference is reversed, the direction of the current 11+I2 is also reversed. The above difference is the power supply intermediate voltage FCC
/2 and the power supply control voltage FRO, and the same difference is given to both voltage-current conversion circuits. However, as can be easily seen from the figure, in the voltage-current conversion circuit 1, the difference (FR-Vco/ 2) is valid, and in the voltage-current conversion circuit 2, the difference (Voc/2-Vx) is valid. Both differences have equal values but opposite polarities.

The A, E terminal intermediate voltage VOM outputted by the midpoint voltage detection circuit 4 between the power supply output terminals A and E is input to the voltage-current conversion circuits 1 and 2, and in the voltage-current conversion circuits 1 and 2, V
cM is always kept constant at yao/2, thereby maintaining a balance between the operations of voltage-current conversion circuits 1 and 2.

The power supply control voltage yJ output from the power supply 1 control circuit 5 is controlled by the control input to the power supply control terminal (:'I+02)
2+Vdayf+Vco/2+Vca/2-Vrd
It can be changed to Here, Vraf is a reference voltage to be described later.

For the above six power supply control voltages rt/, , in the voltage-current conversion circuit 1, the effective difference is J'GO/2+
Vraf −Vco/2= +Vrd + Vco/2
-VOO/2 "0+"O/2-Vrgf -Vc
c/2 = -Vrd, and in the voltage-current conversion circuit 2, the effective difference is -〆rd.

0 and +Vτ-f, and the current 11+I2 initially flows in the direction of the arrow, but when the difference reaches 0, it becomes O, and as the difference changes, it further flows in the direction opposite to the arrow (reverse).

Now, it is assumed that an AC signal such as an audio signal exists on a two-wire line that receives power from power supply output terminals A and B. The impedance termination circuit 7 detects the AC signal between the lines (between terminals A and B), and sends the AC signal to the superimposition circuit B according to a preset transfer characteristic. The alternating current signal is superimposed on the power supply control voltage r'R (DC) outputted from the power supply control voltage r'R (DC) to obtain a power supply control voltage 1/R, which is input to the voltage-current conversion circuits 1 and 2. In this way, complex impedance termination is realized by feeding back the alternating current signals present at the terminals A and H to the voltage-current conversion circuits 1 and 2 on the power supply control voltage V'.

FIG. 2 shows an embodiment of the embodiment shown in FIG. 1. FIG. 2 is a connection diagram of an embodiment of the embodiment shown in FIG. 1 using an operational amplifier. In the figures, reference numerals 1 to 7 correspond to those in FIG. In addition, OP,
~op4, op51. op52, op, and op7 are operational amplifiers, Q++ + 412 r C
21, C22 is the power supply transistor s, RO+R1
1-Rm6 + 41~R26HRsl + R32l
R41~R43+ 41~R56r Ra, + R8
2+ Rγ1~R75r R,, 1+ Rm 2 represents the resistor and its resistance value, and CO1(' 3!
'611 '70"" C72 is a capacitor, Sl, S
2 is an analog switch, Vrdil: g is a quasi-power supply and reference voltage, and Vco is a power supply voltage.

In the midpoint voltage detection circuit B of the power supply voltage, R3I=R3
2, and a midpoint voltage Vco/2, which is obtained by dividing the power supply voltage VCO into two, appears at the connection point, and is outputted via an operational amplifier op, which operates as a voltage follower. Capacitor C3 is for AC bypass.

'Power supply output terminal A of voltage-current conversion circuits 1 and 2.

In the midpoint voltage (common mode voltage) detection circuit 4 between the two voltages, the operational amplifier op4 operates as an addition and subtraction circuit, and outputs Voc - (rB+VA) as the output VOM.

J'AIVB is the 'voltage of terminals A and B, respectively.

'In turtle rolling flow conversion circuits 1 and 2, R1□-R1
□=R13= R16= R2+ = R22= R2
4=R25=R+RI4=RIS=7?23
=R26=αR1 The current flowing to the load at terminals A and B is 12. Let I be. operational amplifier op, , op
2 is the voltage J'RI Vac/2 + P'O, respectively.
Addition and subtraction operations are performed on M, etc. The feeding transistors Qo + C12 and C21°C22 can be considered to operate in unison with the operational amplifiers OP1 and op2, respectively.

It is now assumed that no alternating current signal such as a telephone call signal is present on the line that receives power from the power supply output terminals A and B. Therefore, the impedance termination circuit 7 does not detect the current signal,
Its output is 0, and the superimposition circuit 6 outputs the output r of the electric control circuit 5.
The constant current feeding and reverse operation of this embodiment will be explained assuming that no AC signal is superimposed on tl and therefore it is VR-"R (direct current). In the voltage-current conversion circuit 1, , the power supply control voltage VR is the operational amplifier op
, and the power supply intermediate voltage Voo/2 is also input to one terminal, and in the voltage-current conversion circuit 2, the voltage V
R is connected to one terminal of operational amplifier op3, and t voltage Voc/2
are similarly input to the child terminals, and a difference is created in each of the voltage-current conversion circuits 1 and 2, but the magnitudes are the same but the polarities (positive and negative) are opposite.

Since the settings are as above, the current flowing to the load at terminals A and B is 12. If C, the operation according to the following equation is performed.

'I RE+ = (P'R-Vraf2)/α+(
FOM-Vraf2) ・Song・(1)12 RK
z = (Vn-Vraf2)/α-(Fcu-V
raf2) ... (2) Furthermore, RH" RH2
"RF+", and R3I"R32 in the power supply voltage midpoint voltage generation circuit 3, and R41""R' in the midpoint voltage (in-phase voltage) detection circuit 4 between the power supply output terminals A and B.
If you set it as 42,! , -1. Therefore, l1=I2
= 1, then from the above equation (1) l (2), VoM
-Vraf2, the balance between the operations of both side pressure current conversion circuits 1 and 2 is maintained, and at this time, / ” (Vn -Vraf2) / aRz
−・−・−(3).

Therefore, current I flows according to control voltage VR when VR>Vra
When f2, the direction of the arrow in the drawing, that is, Qo→R
K1 → terminal B → (load) → terminal J -? RE2 →Q
22, and when VB<Vraf2, the flow is the opposite path to the above, that is, Qz+ -+ R12 → terminal A → (
Load) → Flows through the path of terminal B-+Q12. Therefore, by changing the power supply control voltage VR), it is possible to control the magnitude of the power supply 'Kt flow (for example, set it to 0 to stop the power supply) and reverse the direction.

Various circuits can be considered for changing the power supply control voltage VR according to the control information. The power supply side control circuit 5 in FIG. 2 shows only one example.

In the power supply control circuit 5 of FIG. 2, R51-R52-R
53"R54"R5S" 85g, Vr
Let af be the reference voltage.

The operational amplifier ops operates as a non-inverting 1:1 amplifier, and if the switch S2 is turned on by the input of the power supply control terminal C2, 7ss g aO/2, and if the switch S2 is off, Vs wg Vaa, /2+Vrd. Here, V is the output voltage of the operational amplifier op.

If the operational amplifier ops operates as an inverting amplifier and its output voltage is V4, if the switch S1 is on due to the input to the power supply control terminal C, then VB ” VCO
-VB switch5. If is off, r6,000V5 When switch S2 is off, VB = Vraf2 +
Vrgf, so if switch S1 is on, Vs=Vcc/2-meso#f, and if Sl is off, V4=VcC/2+Vref.

Further, when the switch Sz is on, VB = Vraf2 regardless of whether the switch Sl is on or off. Voltage V6
is delayed by a time relay circuit including resistor RO and capacitor CO, and is output as control voltage r'R.

This can be summarized as shown in Table 1).

Table 1, Figure 3 is a diagram showing the timing relationship of changes in the power supply control voltage VR (, 〆'R), the voltage between terminals A and B of voltage-current conversion circuits 1 and 2, and the power supply current /, , 12. °There is. In addition, Fig. 3 @) shows the supply current 1. , 12, 3rd
FIG. 3(b) shows the changes in the voltages at the terminals A and 13, and FIG. 3(C) shows the changes in the power supply control voltage VR over time. Initially, ie, at time to, both switches SI+52 are in the off state, and the supply control voltage V'R is Vraf2, as shown in Table 1.
+Vraf. When the switch Str St is turned on and off, respectively, at time t1, the output voltage V6 of the operational amplifier OF5+ of the power supply control circuit 5 immediately rises to Foa/2-Vrd, but this is delayed by Ro-co. , power supply control voltage 〆R
(=F'R) rises as shown in FIG. 6(C). That is, at time t2, Vco/2- is reached, and after time t3, Vco/2- becomes τ6f.

When the power supply control voltage FR (=F'R) changes as described above, the power supply current 11 + 12 changes as shown in FIG. 6 (α). That is, current 1. ．． 12 and time 1. It starts to decrease at time 12 (〆R=Voo/2)
The current becomes 0), then reverses its direction and starts to increase, and after time t3, the current becomes the same current with the same magnitude as the original, but with the opposite direction.

FIG. 3(b) shows the state of change in voltage between the power supply output terminals (terminals A and B). As can be seen from the figure, the power supply current changes in response to I2.

Contrary to the above, first set the switch 5++52 to the on/off state, and set the power supply control voltage yJ to Vc, c/2-V.
faf, then turn off switch S1+52.
Power supply control voltage 71. as off. The operation is exactly the same except that Koc//2+Vr is changed.

First, set the power supply control voltage r'R to Vco/2-Vrgf
, or set it to 〆Co/2+l'rg/,
In this state, switch S2 is turned on and the power supply control voltage VR
If the current is changed to Voa/2, the current 11+I2 becomes 0, respectively. The voltage between the power supply terminals 4 and 8 also becomes 0.

The current switching time in the above, that is, the feeding current 1, ,
The time required to switch the direction of I2 or to set the magnitude of the current to 0 depends on the time constant of the resistor RO and capacitor Co of the power supply control circuit 5.According to the present invention, in this way, Constant current power supply and reverse control are provided in the same circuit. In addition, since the power supply voltage yac can reduce the paper pressure range up to the maximum load that requires constant current supply, a significant power reduction can be achieved.

Next, the complex termination impedance constituted by the impedance termination circuit 7 and the superimposition circuit 6 will be explained.

It is now assumed that an alternating current signal such as a voice signal is present on the line that receives power from terminals A and B.

R71"R72" in impedance termination circuit 7
Rrs -R74-Rrs and capacitor C
Set the capacity and weight of '11 and C72 sufficiently large. In this case, the operational amplifier op7 of the impedance termination circuit 7 operates as a differential amplifier, and the voltage at terminals A and B is Vm.

The difference in VB, in other words, the voltage of the AC signal present on the line connected to the terminal (, B) is amplified and output.

At this time, since the increase in production is 1, the output of the impedance termination circuit 7 is equal to the voltage of the AC signal between both lines of the line. This signal (output of the impedance termination circuit 7) becomes one input coefficient of the superimposition circuit B. The operational amplifier op6 of the superimposition circuit 6 operates as a subtraction circuit, and receives the voltage rtL input from the power supply control circuit 5.

The 'low voltage (AC) input from the impedance termination circuit 7 is subtracted from (DC). As a result, the AC signal present in the line connected to the terminals A and E is superimposed on the voltage P-/R, and becomes the control voltage VR.
2 and is thus fed back to the output signal of the line.

Because of this operation, the equivalent circuit of the terminal impedance on the power supply circuit side (voltage-current conversion circuits 1 and 2 side) viewed from terminals A and E is as shown in FIG. In FIG. 4, A and B are the terminals of FIGS. 1 and 2; 4. The one corresponding to H, and the opening Z corresponding to the same symbol in the impedance termination device 7 in FIG.

The transfer characteristics of the amplifiers (op6, op7) can be set in advance.

Since the circuit shown in FIG. 4 has a complex impedance that closely simulates the line impedance, it can be well matched with the side sound prevention circuit in the dL phone, thereby reducing the side volume and ensuring good communication.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope thereof.

〔Effect of the invention〕

Since the present invention is configured as described above, according to the present invention, constant current power supply and reverse control are possible using an electronic circuit, and 'paper power consumption is small and noise and bell resonance 9 are not generated during reverse operation.' There is. Furthermore, since the terminal impedance is a complex impedance, the volume on the side of the telephone is reduced, which has the effect of providing a good telephone conversation. Furthermore, since it is possible to integrate the circuit, it has advantages in improving mounting efficiency and making it more economical.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an overview of an embodiment of the present invention, FIG. 2 is a detailed connection configuration diagram of the embodiment of FIG. 1, and FIG. Supply 1 current 11r12
and the voltage of the power supply output terminals A, E. FIG. 4 is a time chart showing the relationship with VB, FIG. 4 is an equivalent circuit of the terminal impedance in this embodiment, and FIG. 5 is a connection diagram of an example of a conventional power supply circuit. 1.2... Voltage-current conversion circuit, 6... Power supply' voltage midpoint voltage (common mode voltage) detection circuit, 5... Power supply control circuit, 6
...Superimposition circuit, 7...Impedance termination circuit, V
OO...Kangen Tsutaatsu, VOM...Supply 1kLl:clI
Midpoint voltage between power terminals A and E, FR...power supply control circuit,
"R... Output voltage of power supply control circuit 5, cl, c2...
・Power supply taste; ≦control terminal, op, -opOPSl +
0P52. OP6+ OPl "" operational amplifier, QCl
,QCl. (221+ Q22... power supply transistor, RO+
R11”””+6 + R21~R26+ R31+
R32TS R41~R431R11~R56+ RK 1
)RE2+R611Ra2r R71~R'lS"・
Resistor, CO+ '3, C6I, C76~Patent-
Applicant Nippon Telegraph and Telephone Public Corporation Patent Attorney Patent Attorney Gobe Tamamushi (2 others) No. 3 Figure F (a) Electricity, pressure (b) Control voltage (c) V Otsumori line spacing

Claims (1)

[Claims] A voltage-current conversion circuit is provided in which the magnitude of the output current is proportional to the difference between the given control voltage and the midpoint of the power supply voltage, and the direction of the output current outputs the current in both directions according to the polarity of the difference. One of the above voltage-current conversion circuits is
For the same difference, the other voltage-current conversion circuit has an output current that is the same in size but in a different direction, and supplies constant current to the two-wire communication line using the two output currents, and inverts the supply polarity using the control voltage, and further detects the alternating current signal between the two lines and inputs it to an amplifier having a preset transfer characteristic, and the output signal is given to the voltage-current conversion circuit. A complex termination type constant current power supply reverse circuit characterized by forming a termination impedance by superimposing and feeding back a control voltage.