JPS6046911B2 - Line current supply method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line J line current supply system applied to supply line current from the exchange side to various terminal devices such as telephones.

The subscriber circuit of an exchange to which terminal equipment requiring line current supply is connected is connected to the line current supply (Batteryfe).
ed, ), overvoltage protection (Overvoltagepro
tection,), ringing signal transmission (Ringing)
, Supervision, ), 2-wire 4-wire conversion (Hybrid, ), Test (Test, ), Coding (C
odlng, ), etc., and are called the BORSCHT function by its acronym, but most of these functions are implemented in the trunk circuits of exchanges.

On the other hand, with the progress of integrated circuit technology, the digitization of communication paths has become concrete, and for toll exchange systems, "Research and Practical Report Vol. 28, No. 7, Digital Telephone Toll System DTS-1 Special Feature" ( Although it has been put into practical use as shown in the publication (published by Nippon Telegraph and Telephone Public Corporation and Musashino Telecommunications Research Institute), it is not possible to transmit large amplitude signals to subscriber switching systems using digital communication paths. B.O.
It is necessary to install it on the line side of the communication path for the RSCHT function.
In particular, there is a demand for miniaturization and cost reduction of subscriber circuits.

Therefore, with conventional configurations mainly consisting of electromagnetic parts such as blocking wires called letter coils or relays,
Unable to achieve this goal, the integration of subscriber circuits became an essential requirement, and for example, "IEICE Technical Research Report" Vol. 79, NO. As described in ``An Idea of a Talking Current Supply System'' written in No. 34, SE79-20 (published by the Institute of Electronics and Communication Engineers), a few studies have been carried out.

The above-mentioned letter coil is designed to exhibit a predetermined impedance to alternating currents such as communication current and signal current.

However, if you try to configure an electronic circuit with the same characteristics as a letter coil without making any changes to the existing terminal equipment or power supply voltage conditions, you will not only be able to configure an electronic circuit with the same characteristics as a letter coil, but also the internal resistance of the letter coil. It is necessary to convert it into an electronic circuit.

If this internal resistance is directly implemented using a resistance element, the electronic circuit current supply circuit will have a large power loss, and thermal discharge will become a problem when integrated circuits are integrated.

That is, Fig. 1 shows an equivalent circuit of this line current supply system when a letter coil is used, where the internal resistance of the terminal equipment π is RT1 line Li, the line resistance of L2 is RL1, the DC resistance of letter coil LT is Rs, If power source B is voltage E,
The rotation current based on the line current supply characteristics is expressed by the following equation.

Also, the power loss P$ in the letter coil LT
is Ps=Rsl-1L2, and when the line resistance RL is zero, P is maximum.

Therefore, the maximum value of Ps is set to Ps. If nax, then RT=50Ω, R,=440Ω, and E=48V, then P3. ．． 〜=4.2W, and this value is the integrated circuit j
This would be completely unacceptable.

The present invention was made to solve this problem, and it adds an amount equivalent to the internal resistance value of a conventional letter coil to the measured line resistance value as a calculated value for control purposes. By controlling the supply voltage to the line accordingly, the voltage drop due to the internal resistance of conventional letter coils can be compensated for without power loss, making it extremely easy to integrate the line current supply circuit. The purpose is to supply a current supply method.

FIG. 2 is an embodiment of the present invention, and shows a circuit for compensating for the internal resistance of a conventional letter coil.

Hereinafter, this will be referred to as a line current supply circuit. In order to create an actual line current supply circuit, it is necessary to add an impedance circuit as shown in FIG. Hereinafter, the present invention will be explained in detail with reference to FIG. 2 and subsequent figures.

In the block diagram of Fig. 2, a voltage detection circuit D using a voltage divider etc. is included in the line current supply circuit (hereinafter referred to as supply circuit) ICF to detect the line voltage between the lines Ll and L2.
ETv is provided, and a current detection circuit DET using a series resistor, operational amplifier, etc. is provided in order to simultaneously detect 1L of line current, and the detection power of these is given to the calculation circuit CAL. The circuit CAL is connected to each detection circuit DE.
Calculations are performed based on the detection power of Tv and DETI.

Arithmetic circuit CAI. In the calculation executed at terminals Tl, t2
The line voltage to be applied between the lines EL. I'm looking for.

That is, the line voltage EL is equal to the line current 1L in the case of a letter coil expressed by equation (1). The calculation formula is as follows.

EL=(RT+RL) ●L Here, (RT+RL) is calculated by calculating ■L/IL using the line voltage VL detected by the voltage detection circuit DETv and the line current 1 detected by the current detection circuit DETI. be done.

Further, Rs and E are numerical values fixedly given within the arithmetic circuit CAL.

The line voltage EL determined by the arithmetic circuit CAL is converted into a signal indicating it and input to the comparator CMP.

Further, the other input of the comparator CMP is connected to a voltage detection circuit D.
The detection power of ETv is given, and in this), the actual line voltage indicated by the detection power of the voltage detection circuit DETv is
The difference between L and the line voltage EL determined by calculation is obtained as an error signal, and this error signal controls a power supply conversion circuit CONV, which will be described later, to change its output voltage Vp.

Therefore, the output voltage ■9 of the power conversion circuit CONV is:
The error signal is controlled in the direction of zero, and it is balanced in the state where 1=EL, and the predetermined line voltage EL reaches the power supply conversion circuit C.
It is applied from ONV to the line between terminals Tl and t2. Therefore, the output voltage Vp is determined according to the line resistance RL of the lines L, , l-2, and the power loss in the supply circuit LCF is always kept at the minimum value.

FIG. 3 shows the arithmetic circuit CAl. A block diagram including a specific configuration example of the arithmetic circuit CAl. is the divider SUl,S
It is composed of U2, adder AD, and coefficient unit KM, and the divider SUl calculates ■L/IL=R, calculates the line resistance R looking from the terminals Tl and t2 to the lines Ll and L2 side, and then adds it. The adder AD adds the resistance setting signal S, which indicates the internal resistance of the supply circuit LCF corresponding to the DC resistance R of the letter coil, and the output of the divider SU1. By this, R+R,=R
A signal corresponding to T+RL+R is obtained. Further, the output of the adder pigeon and the output of the divider SUl are given to the divider SU2, and in this case, (RT+RL)/(R
After the calculation of T+RL+R,) is performed, the output is given to the coefficient multiplier KM, where the voltage E of the power supply B is
A coefficient indicating this is to be added.

That is, in the arithmetic circuit CAL, an operation equivalent to the multiplication of the line current 1 and the line resistance (R, +RL) is performed as shown in equation (4), and by determining Rs and E in advance, Based on calculations according to these,
A signal is obtained indicating the line voltage EL to be applied.

Therefore, as a result, line current L is supplied according to the line current supply characteristics shown by equation (1),
In telephones, a volume adjustment means such as a varistor is provided in accordance with the line current supply characteristic of equation (1).
A suitable line current L can be supplied to the terminal equipment TE such as a telephone.

Note that depending on the settings of the detection power of each detection circuit DETv, DETl, the resistance setting signal S, etc., the coefficient multiplier KM may be omitted. FIG. 4 is a diagram showing a case where an impedance circuit exhibiting a predetermined impedance to alternating currents such as communication current and signal current is added to the supply circuit LCF.

That is, transistors Ql and Q2 are connected to resistors R1 to R.
Forward bias is provided by transistor Ql
, Q2 has an extremely low collector-emitter resistance with respect to direct current, but since the bases of transistors Ql and Q2 are at the same potential in terms of alternating current due to capacitor C1, the resistance to alternating current applied between terminals Tl and t2 is On the other hand, it exhibits an impedance determined according to each constant, and depending on the selection of the constants, a high impedance or a predetermined terminal impedance can be obtained.

This impedance circuit is described in "Technical Research Report of the Society of Electronics and Communication Engineers" Vol. 79, NO. 34, SE79-2
0 (published by the Institute of Electronics and Communication Engineers), “One Idea of a Call Current Supply System”, P58. Although shown in Table 1, any one can be applied as long as it exhibits a similar function.

In addition, the voltage loss due to the insertion of an impedance circuit is
It may be corrected using the coefficient from the coefficient multiplier KM or the resistance setting signal Sr.

Figure 5 is a circuit diagram showing a specific example of the power converter circuit CON■, where A is a step-down type that obtains an output voltage in a range lower than the input voltage, and B obtains an output voltage in a range higher than the input voltage. In both cases, a blocking wire L is inserted in the line between the input terminal 1 and the output terminal 3, and a capacitor C is connected between the output terminals 3 and 4. ■． 1X. , and the reference voltage ■
A CP is provided.

In the step-down type shown in figure A, a switch S1 is provided in series to the input side of the blocking wire L, and a comparison controller CCP controls the duty ratio according to the on/off time ratio of the switch S1, and the duty ratio is set to 100. %, that is, the output voltage V when the switch S1 is in the on state.

．． ．． By decreasing the duty ratio, the output voltage is set to the upper limit. ．． t is lowered, the reference voltage ■, and the output voltage V. ut is matched. In addition, capacitor C
is the output voltage ■.

The diode D1 is a flywheel diode used to remove ripples in Ut, and forms a DC circuit between the output terminals 3 and 4 when the switch S1 is turned off. In addition, in the step-up type shown in Figure B, a switch S2 is inserted between the output side of the blocking wire L and the other wire between the input terminal 2 and the output terminal 4, and this The electromagnetic energy accumulated in the blockage line L when
2 is turned off, so the input voltage ■.

The output voltage is higher than V. Output voltage (■) when Ol is obtained and the duty ratio of switch S2 is close to 0%. M
l. ．． By increasing the duty ratio to approximately 85% with the lower limit, the output voltage ■. . 1, the reference voltage V, and the output voltage ■.

It matches Ut. Note that the diode D2 is for preventing the electric charge of the capacitor C from discharging to the input side when the switch S2 is turned on.

In addition, the comparison controller CCP in this case also controls the oscillation. The output of the oscillator, the comparator, and the comparator causes the oscillator to
Out is the output current, Lp is the inductance of the blocking wire L, and T52On is when the switch S2 is on! Between, Ts2.

7F is the off time of switch S2.

Furthermore, the first term on the right side of equation (6) is the output voltage ■ based on the electromagnetic energy accumulated in the blocking wire L while the switch S2 is on. The increase in Ut is the upper limit output voltage V in the step-down type because there is actually a loss due to the circuit elements. This corresponds to maO. Figure 6 shows a power supply conversion Vh'e ring 11 that allows a wide range of output voltages in the high and low directions relative to the input voltage to be obtained using the same circuit.
1 Hachino-420/It is composed of a modulator that modulates the output with pulse width, but in the step-down type, the comparison control EISC
Using a simple comparator as CP, the output voltage ■.

There is also a self-excited type that controls the switch S1 according to changes in o, and various control means have been proposed. However, this type of power conversion circuit is based on "Transistor Technology" published in 1972.
Monthly issue (published by CQ Publishing Co., Ltd.) Pl5l, as shown in Table 2-3, the lower limit output voltage of the boost type is ■.

Mln is the input voltage ■. The upper limit voltage of the step-down type is about 2 V higher than ■. ．． ~ is about 1 V lower than the input voltage VlO, and the input voltage ■, . ．． The output voltage VO. can't get it. In other words, in the case of a step-down type, if the loss of each circuit element is ignored, "Transistor Technology" July 1977 issue:
(Published by CQ Publishing Co., Ltd.) As shown in formula (1) of Pl6, the output voltage V.

ut is given by the following equation. In this case, TslOn is the on time of the switch S1, and LlOon is the off time of the switch S1.

Actually, due to losses in switch S1, blockage coil L, and diode D2, the output voltage becomes ■.

, the upper limit of ■. Max has a value that is 1 to 2 V lower than the theoretical value when the duty ratio is 100%. In the case of a step-up type, if the loss of each circuit element is ignored, as shown in equation (18) in Pll8 of "Transistor Technology" July 1977 issue (published by CQ Publishing Co., Ltd.) , output voltage■.

0t is given by the following equation.

The circuit is shown with a first switch S1 and a second switch S2.
and diodes Dl and D2,
It is a combination of the step-down type and the step-up type shown in Fig. 5, and at the same time, in addition to the comparison controller CCP, the input voltage
.

and output voltage■. A comparator circuit CPC is provided to compare Ut with Ut, and its output a is supplied to 0R gate G1 and AND gate G2 to control the output supply of comparison controller CCP to each switch Sl and S2, while supplying output a to AND gate G4. is given an output c and supplies the output of the pulse generator PG to the second switch S2, resulting in an output voltage V. uO is close to the input voltage Vin r+Clll; 110/. : 廿0/．
When the input voltage becomes low, a period in which the first switch and the second switch are simultaneously turned on is provided to cause each switch Sl and S2 to perform on/off operations, thereby reducing the input voltage
Output voltage ■ with a value equal to 1n.

. 1, and the upper limit output voltage ■ in the step-down type operation described above.

．． ．． ．． and the lower limit output voltage in boost type operation■0. ．． i
, , the output voltage V between. It is assumed that ut can also be obtained. FIG. 7 is a block diagram showing a specific example of the comparison circuit CPC, in which comparators CP1 to CP3, AND gate Gll
and an inverter IN, and operates as shown in the voltage relationship diagram of FIG. 8 showing the waveforms of each part.

That is, the input voltage ■ is determined by the comparator CPl.

and output voltage V. . , and the difference is applied to comparators CP2 and CP3, and along with this, comparator CP2
, CP3 has an input voltage ■. =output voltage V, x. ,=0
Based on the relationship shown in Figure 8, centering on , the reference voltage ■, 1
,■,2 are given to each individual. Therefore, the comparator C
If the output of Pl exceeds the reference voltage ■,1, the comparator CP
If the output a of the comparator CPl becomes ゜゜H゛ (high level), and the output of the comparator CPl exceeds the reference voltage ■, 2, the output a of the comparator CPl becomes
The output b of the inverter IN becomes "H" during the period when the output a is "L" (low level), turning on the AND gate Gll and output b. is passed through, and the output of comparator CPl is ■1 to ■2.
Since the AND gate Gll sets the output e to ゜゛H゛ only during this period, the output acts as a window parator. Therefore, in FIG. 6, the output voltage V.

u, is the input voltage■. When the comparator circuit CP
Since the outputs A and c of C are both ゜゛L゛, AND gate G
2, G4 is in the off state, and only the first switch S1 performs on/off operations according to the output of the comparison controller CCP, and its duty ratio changes according to changes in the reference voltage. ■ and output voltage V. The duty ratio is determined when O, and O match, while the output voltage ■.
The output voltage ■ is in the range where o1 is approximately equal to the input voltage ■1n, that is, in the range of the reference voltages ■1 to ■2 shown in FIG. U
When t is input, the output a of the comparator circuit CPC becomes “L”, and the output C
becomes ゜“H”, and the first switch S1 switches to the comparison controller CC.
The pulse generator P is turned on and off by the output of the comparator circuit CPC, and is turned on by the output c of the comparator circuit CPC through the AND gate G4 and the 0R gate G3.
The output from G is supplied to the second switch S2, which also turns on and off, and due to the interaction between the step-down type operation and the step-up type operation, the input voltage . The output voltage V has a value approximately equal to . Generate ut, reference voltage ■ and output voltage ■
. . 1, the duty ratio of the first switch S1 is determined.

The on/off operation of the first switch S1 and the second switch S2 must be performed during a period in which they are both on at the same time, and the oscillator output in the comparison controller CCP is used as a synchronizing signal to the pulse generator PG. and each switch Sl, S2
It is assumed that the on/off operations are performed in synchronization.

Also, the output voltage V.

ut is the input voltage ■. If it becomes higher than , the comparator circuit CPC
Since the output a becomes ゜゜H゛ and the output c becomes ゛L゛, the first
As switch S1 turns on, AND gate G
2 is on, the AND gate G4 is off, and the second switch S2 is turned on and off by the output of the comparison controller CCP, resulting in a step-up type operating state. As the pulse generator PG, a multi-pipetretor etc. can be applied, and a frequency dividing circuit that divides the clock pulse may be used, and the frequency dividing operation may be controlled by a synchronizing signal, and the frequency dividing circuit may be controlled in synchronization with the synchronizing signal and at a predetermined level. Any device can be used as long as it generates a pulse having a duty ratio of .

In addition, as comparators CP2 and CP3 in FIG.
In order to avoid unstable operation when the output of the comparator CPl is near the reference voltages ■1 and ■1, use a circuit that has level hysteresis characteristics by combining a Schmitt trigger circuit, etc. It is suitable if The Stl power conversion circuit CONV is not limited to the above, but various configurations used in so-called switching regulators can be used as long as the power conversion efficiency is good and the output voltage 0ut can be controlled over a wide range. Applicable. In addition, the power supply conversion circuit CONV of the present invention has an output voltage of ■ in practice.

Since the change range of Ut is required to be about 5 to 40 V, the above-mentioned power supply conversion circuit is suitable, and the purpose can be achieved by providing an error signal as the reference voltage (2). In addition, each detection power and resistance setting signal S of the voltage detection circuit DETvl and the current detection circuit DETl used in the arithmetic circuit CAL is
, etc., other signals or detection power may be used as long as the relative relationship is the same, and the various characteristics of the arithmetic circuit CAL, that is,
The detection force and setting signal Sr can be determined according to characteristics such as overload, signal-to-noise ratio, stability, error, etc., and the arithmetic circuit CAI. The present invention can be freely modified in any way, such as being able to select various configurations.

Note that the arithmetic circuit CAl. By controlling the power conversion circuit CONV by
The influence of voltage fluctuations of power supply B on line current 1L can be eliminated.

As is clear from the above description, according to the present invention, the line current supply circuit, which is suitable also for terminal equipment having a biristor etc. and which realizes a part of the BORSCHT function, is mainly composed of an electronic circuit. At the same time, the internal power consumption is extremely small, and the line current supply circuit can be easily converted into an electronic circuit or an integrated circuit, making the line current supply circuit smaller, lighter, and cheaper.
Great effects can be obtained in various exchanges.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an equivalent circuit of a line current supply system, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram including a specific example of the configuration of the arithmetic circuit in FIG. Fourth
The figure is a circuit diagram showing the situation where an impedance circuit is inserted.
5 and 6 are circuit diagrams showing a specific example of the power conversion circuit in FIGS. 2 and 3, FIG. 7 is a block diagram showing a specific configuration of the comparison circuit in FIG. 6, and FIG. 8 is a voltage relationship diagram showing waveforms of various parts in FIG. 7. FIG.廿...Terminal equipment, Ll, L2...Line, LCF...Supply circuit (line current supply circuit), B.
...Power supply, DETv...Voltage detection circuit,
DETI...Current detection circuit, CAL...
・Arithmetic circuit, CONV...Power conversion circuit, S,
...Resistance setting signal, L...Block wire,
S...Switch (first switch), S2...
Switch (second switch), CCP...comparison controller, CPC...comparison circuit, PG...pulse generator.

Claims (1)

[Scope of Claims] 1. A line current supply circuit that supplies line current to terminal equipment via a line, including a power conversion circuit that converts a power supply voltage E into a predetermined voltage and supplies it to the line, and a line of the line. a voltage detection circuit that detects the line voltage V_L; a current detection circuit that detects the line current I_L at the same time as detecting the line voltage V_L;
From the line side resistance R obtained by dividing by L, a preset value R_S, and the power supply voltage E, the required line voltage E_L,
That is, an arithmetic circuit that calculates E_L=R・E/(R+R_S), the line voltage V_L and the required line voltage E_
and a comparator for comparing L, and the power conversion circuit controls the output voltage using the comparator so that the line voltage V_L and the predetermined line voltage E_L match. Supply method. 2. A patent claim characterized by using an arithmetic circuit that performs calculations based on the detection power of the current detection circuit and the detection power of the voltage detection circuit, and also in response to a resistance setting signal indicating the internal resistance of the power supply conversion circuit side. Line current supply method described in item 1. 3. A power supply consisting of a blockage wire inserted in series into a power supply circuit, and a switch inserted in series into the input side of the power supply circuit, whose on/off duty ratio changes according to the output voltage of the power supply circuit. The line current supply system according to claim 1, characterized in that a conversion circuit is used. 4. A blocking wire inserted in series into a power supply circuit, and a wire inserted between the output side of the blocking wire and both lines of the power supply circuit and having an on/off duty ratio according to the output voltage of the power supply circuit. The line current supply system according to claim 1, characterized in that a power conversion circuit comprising a variable switch is used. 5. A blocking wire inserted in series in the power supply circuit, a first switch inserted in series on the input side of the power supply circuit, and a first switch inserted in the output side of the blocking wire and between both lines of the power supply circuit. and a second switch, which controls the on/off of each switch by setting a period in which each of the switches is simultaneously on depending on the relationship between the input voltage and the output voltage of the power supply circuit. A line current supply system according to claim 1, characterized in that: