JPS637498B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a line current supply method applied when supplying line current from the exchange side to various terminal devices such as telephones. The subscriber circuit of the converter to which terminal equipment that requires line current supply is connected has line current supply (Battery feed.), over voltage protection (Over voltage protection)
Functions such as protection.), ringing signal transmission (Ringing.), monitoring (Supervision.), 2-wire 4-wire conversion (Hybrid.), testing (Test.), and encoding (Coding.) are required. It is called the BOSRCHT function by its initials, but most of it is implemented in the trunk circuit of the exchange. On the other hand, with the progress of integrated circuit technology, the digitization of communication channels has become a reality, and for toll switching 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 Japan Telecommunications and Telephone Public Corporation and Musashino Telecommunications Research Institute), it is not possible to transmit large amplitude signals to subscriber switching systems through digital communication paths.
It is necessary to provide the BORSCHT function in front of the communication path, and there is a particular demand for miniaturization and cost reduction of subscriber circuits. Therefore, the conventional configuration, which mainly consists of electromagnetic parts such as blocking wires called letter coils or relays, cannot achieve the purpose, and it is essential to integrate the subscriber circuit. For example,
“IEICE Technical Research Report” Vol.79, No.34,
As stated in ``A Consideration of Call Current Supply System'' published by SE79-20 (published by the Institute of Electronics and Communication Engineers), a few studies have been carried out. However, simply replacing the function of the letter coil with an electronic circuit will result in a large power loss in the line current supply circuit due to the supply of line current, and heat dissipation will become an issue when integrating these circuits. Solving this problem is considered to be an urgent task at present. In other words, Figure 1 shows the equivalent circuit of the line current supply system when a letter coil is used.
Let R _T be the internal resistance of TE, and let the line resistance of lines L ₁ and L ₂ be
When R _L is the DC resistance of the letter coil LT, R _S is the DC resistance of the letter coil LT, and E is the voltage of the power source B, the line current I _L is expressed by the following equation. I _L = E / R _T + R _L + R _S ...... (1) Also, the power loss P _S in the letter coil LT is as follows: P _S = R _S・I _L ² = R _S / (R _T + R _L + R _S ) ²・E ² ......(2), and when the line resistance R _L is zero, P _S is maximum. Therefore, if the maximum value of P _S is Psmax, then Psmax = R _s / (R _T + R _S ) ²・E ² ......(3), R _T = 50Ω, R _S = 440Ω, E = If it is 48V, Psmax = 4.2W, which is completely unacceptable for integrated circuits. The present invention satisfies such conventional demands and has the purpose of fundamentally solving the conventional problems, and by controlling the voltage supplied to the line according to the line resistance, the voltage in the line current supply circuit is increased. The present invention provides a line current supply system that keeps power loss to a minimum and makes it extremely easy to integrate circuits. The details of the present invention will be explained below with reference to FIG. 2 showing an embodiment, but first, the principle of the present invention will be explained. That is, in Fig. 1, the line resistance R _L and the internal resistance R _T when looking from the line terminals t ₁ and t ₂ to the terminal equipment TE side are
is given by the ratio of the line voltage V _L between the line terminals t ₁ and t ₂ and the line current I _L , so the following equation holds true. R _T +R _L = V _L /I _L ………(4) Therefore, by substituting equation (4) into equation (1), we get
The following equation is obtained. V _L =E−R _S・I _L (5) Therefore, it is sufficient to determine the line voltage V _L based on equation (5). Based on the above principle, the line current supply circuit (hereinafter referred to as supply circuit) is
The LCF is provided with a voltage detection circuit DET _V using a voltage divider etc. to detect the line voltage V _L between the lines L ₁ and L ₂ , and a series resistor DET V to detect the line current I _L. Current detection circuit using an operational amplifier, etc.
DET _I is provided, and this line current detection output is given to an arithmetic circuit CAL, which performs arithmetic operations based on the detection output of the current detection circuit DET _I. In other words, the arithmetic circuit CAL is a current detection circuit
Depending on the line current I _L indicated by the detection output of DET _I , the internal resistance of the predetermined supply circuit LCF is set as R _S
Then, calculate the equation (5) by setting the power supply voltage to E, thereby determining the voltage _VLC to be supplied as the line voltage _VL , and transmitting the signal indicating this voltage _VLC to the comparator CMP. is given to the input. In addition, the detection output of the voltage detection circuit DET _V is given to the other input of the comparator CMP, and here, the actual line voltage V _L indicated by the detection output of the voltage detection circuit DET _V is calculated. The voltage obtained by
A signal based on the difference from V _LC is obtained as an error signal at the output of the comparator CMP, and this error signal controls the power supply conversion circuit CONV, which will be described later, to adjust its output voltage.
V _P changes. Therefore, the output voltage of the power conversion circuit CONV
V _P is controlled in the direction where the error becomes zero, and the comparator
The gain in the so-called transition region, where both inputs of CMP are approximately equal, is large. Therefore, equilibrium occurs when V _LC and V _L are approximately equal, and in practical terms, this state is V _LC =
_{A predetermined line current I L is} supplied from the power conversion circuit CONV to the line between the line terminals t ₁ and t ₂ . Therefore, the output voltage V _P is determined according to the line resistance R _L and internal resistance _RT of the lines L ₁ and L ₂ , so that the voltage loss in the supply circuit LCR is always kept at the minimum value. FIG. 3 is a block diagram including a specific example of the configuration of the arithmetic circuit CAL. The arithmetic circuit CAL is composed of a coefficient unit K and a subtracter _SB . After multiplying the detection output of the current detection circuit DET _I indicating the line current I _L by the resistance setting coefficient Krs, the subtracter SB subtracts it from the voltage setting signal Se indicating the power supply voltage E of the supply circuit LCF. By V _LC S _e −
The calculation K _rs · _IL =E− _RS · _IL is performed. That is, in the arithmetic circuit CAL, the calculation of equation (5) is performed, and by predetermining the coefficients and signals Kre, Se, etc. in accordance with the detection output conditions, the line is calculated based on the calculations corresponding to these. voltage between
A signal is obtained indicating the voltage V _LC that should appear as V _L. Although the coefficient unit K is inserted into the arithmetic circuit CAL in Fig. 3, equation (5) can be transformed as V _L /R _S =E/R _S -I _L ......(6) , a coefficient multiplier K may be inserted between the line voltage detection circuit DET _V and the comparison circuit CMP. In addition, the voltage setting signal Se to be applied to one terminal of the subtracter SB is determined depending on how the coefficient Krs is given, and these coefficients and signals Krs and Se can also be set arbitrarily depending on the conditions of each detection output. can. Note that the coefficient unit K and subtractor SB are generally
It can be configured with an operational amplifier and a voltage divider, but the fourth
The configuration shown in the figure is suitable. FIG. 4a shows a so-called current mirror circuit, in which the output current Iout is proportional to the input current Iin, and
The junction area of transistors Qin and Qout is
If Ain and Aout are used, then Iout/Iin=Aout/Ain (7), and the following relationship holds true: Iout=Aout/Ain・Iin (8). Therefore, for example, the configuration is as shown in FIG. 4b, the line current I _L is made to correspond to the current signal Iin, the voltage setting signal Se is made to correspond to the current signal Ise, and the junction area ratio between transistors Qa and Qb is set to 1:Krs. In, transistors Qc and Qd
If the junction area ratio is 1:1, a current signal Ivlc corresponding to the line voltage _VLC to be supplied can be obtained as shown in the following equation. Ivlc=Ise−Krs・Iil……(9) However, when converting the current signal Ivlc to voltage, it is sufficient to pass the current signal Ivlc to a resistor and take out the terminal voltage, and each input current Ise, Iil To obtain from the voltage, insert a series resistor and then change the input current to
Ise and Iil should be the same. Note that, as shown in FIG. 4c, if a current Ivl indicating the line voltage V _L is applied, the comparator CMP in FIGS. 2 and 3 can also be constructed by a current mirror circuit including transistors Qe and Qf. However, in this case, the current is indicated by the error signal Ivlc-Ivl. In addition, the supply circuit LCF is required to exhibit a predetermined impedance to alternating currents such as communication current and signal current, and in reality, an impedance circuit having a configuration as shown in FIG. 5, for example, is inserted on the output side. . In other words, resistor R ₁ is connected to transistors Q ₁ and Q _2.
~ R ₄ provides a forward bias, and the collector-emitter resistance of transistors Q ₁ and Q ₂ to direct current is extremely low, but capacitor C ₁ provides a forward bias to the bases of transistors Q ₁ and Q ₂ . Since they are at the same potential, they exhibit an impedance determined according to each constant for alternating current applied between terminals t ₁ and t _2. Depending on the selection of the constants, high impedance or A predetermined termination impedance is obtained. This impedance circuit is shown in Table 1 of "A Consideration of Call Current Supply System" on page 58 of "Technical Research Report of the Institute of Electronics and Communication Engineers" Vol. 79, No. 34, SE79-20 (published by the Institute of Electronics and Communication Engineers). Although shown, any method can be applied as long as it exhibits a similar function. Further, the voltage loss due to the insertion of the impedance circuit may be corrected using the voltage setting signal Se or the resistance setting coefficient Krs described above. FIG. 6 is a circuit diagram showing a specific example of the power conversion circuit CONV, where A is a step-down type that obtains an output voltage in a range lower than the input voltage, and B is a step-up type that obtains an output voltage in a range higher than the input voltage. In both cases, there is a blockage line L on a line between input terminal 1 and output terminal 3.
is inserted, and a capacitor C is connected between output terminals 3 and 4, so that the output voltage Vout
A comparison controller CCP is provided to compare the voltage Vr and the reference voltage Vr. The purpose of the explanation of the power supply circuit that follows is to explain the operating principle, so to avoid terminology confusion, we will exemplify the case where the input voltage is positive polarity. It is sufficient to reverse all the polarities, and read the rise in voltage as a fall (increase in absolute value) in the following explanation, and read the height of the voltage value as the magnitude of the absolute value. In the step-down type shown in figure A, a switch _S1 is provided in series to the input side of the blockage line L, and the switch S1 is turned on and off.
Comparison controller for duty ratio based on off time ratio
Output voltage when controlled by CCP and duty ratio is 100%, that is, switch _S1 is in the on state
With Vomax as the upper limit, the output voltage Vout is lowered by decreasing the duty ratio, and the reference voltage Vr and the output voltage Vout are made to match. Note that the capacitor C is used to remove ripples from the output voltage Vout, and the diode _D1 is a flywheel diode that 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 switch is turned on. The output voltage is higher than the input voltage Vin in order to release the electromagnetic energy accumulated in the blockage wire L when the switch _S2 is turned off.
Vout is obtained and the duty ratio of switch S ₂ is near 0%, the output voltage Vomin is set as the lower limit, and the output voltage Vout is increased by increasing the duty ratio to approximately 85%, and the reference voltage Vr and the output voltage Vout are increased. The voltage Vout is matched. Therefore, the input terminal of the comparison controller CCP to which the reference voltage Vr is applied can be used as a terminal to control the output voltage, so the reference voltage Vr is applied to this terminal.
If an error signal is applied instead of Vr, the output voltage of the power supply conversion circuit can be controlled by the error signal, and the operation described in the first embodiment can be achieved. Note that the diode _D2 is provided to prevent the charge in 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 is composed of an oscillator, a comparator, and a modulator that pulse width modulates the output of the oscillator using the output of the comparator, but the comparator is deleted from the comparison controller CCP, The modulator may be driven directly by the error signal; in the step-down type, a simple comparator is used as the comparison controller CCP, and the switch S ₁
There is also a self-excited type that controls, and various control means have been proposed. However, this type of power conversion circuit is
As shown in P151 of Table 2-3, the lower limit output voltage Vomin of the step-up type is approximately 2V higher than the input voltage Vin, and the upper limit voltage Vomax of the step-down type is approximately 1V lower than the input voltage Vin, with a value equal to the input voltage Vin. Unable to obtain output voltage Vout. In other words, in the case of a step-down type, if the loss of each circuit element is ignored, the output voltage Vout will be Given by Eq. Vout=T _S1ON /T _S1ON +T _S1OFF・Vin (10) Here, T _S1ON is the on time of the first switch _S1 ,
T _S1OFF is the off time of the first switch _S1 . However, in reality, the first switch S ₁ and the blockage line L
Due to the loss of , the upper limit Vomax of the output voltage Vout is
1 to more than the theoretical value when the duty ratio is 100%
The value will be 2V lower. In addition, in the case of a boost type, if the loss of each circuit element is ignored, "transistor technology"
P118 of the July 1977 issue (published by CQ Publishing Co., Ltd.),
As shown in equation (18), the output voltage Vout is given by the following equation. Vout＝(Vin・T _S2ON ) ² /2・Iout・_LP (T _S2ON +T _S2OFF
) +Vin......(11) However, Iout is the output current, L _P is the inductance of the blocking wire L, T _S2ON is the on time of the second switch _S2 , and T _S2OFF is the off time of the second switch _S2 . be. Furthermore, the first term on the right side of equation (11) is an increase in the output voltage Vout based on the electromagnetic energy accumulated in the blocking wire L while the second switch _S2 is on, but the second term on the right side Since there is actually a loss due to circuit elements, Vin is the upper limit output voltage Vomax in the buck type.
corresponds to this. FIG. 7 shows a power supply conversion circuit that can obtain a wide range of output voltages in the high and low directions relative to the input voltage using the same circuit, in which the first switch S ₁ and the second switch
S ₂ and diodes D ₁ and D ₂ , which is a combination of the step-down type and step-up type shown in Figure 6. A comparator circuit CPC is provided to compare the output voltage Vout, and this output (a) is ORed.
Give to gate G ₁ , AND gate G ₂ , and each switch
While controlling the output supply of the comparison controller CCP to S ₁ and S ₂ , the AND gate G ₄ is given an output (c) and supplies the output of the pulse generator PG to the second switch S ₂ ; When the output voltage Vout becomes close to the input voltage Vin, a period is provided in which the first switch and the second switch are turned on at the same time, and each switch S ₁ and S ₂ is turned on and off. Assume that it is possible to obtain an output voltage Vout having a value equal to the input voltage Vin, and to also obtain an output voltage Vout between the upper limit output voltage Vomax in the step-down type operation described above and the lower limit output voltage Vomin in the step-up type variable operation. be. FIG. 8 is a block diagram showing a specific example of the comparator circuit CPC, in which comparators CP ₁ to CP ₃ and AND gate G ₁₁
and an inverter IN, and operates according to the input/output characteristics shown in Figure 9, which shows the waveforms of each part. That is, comparator CP ₁ compares input voltage Vin and output voltage Vout, and the difference is calculated by comparator CP1.
CP ₂ and CP ₃ , which are both supplied to comparators CP _{2 and} CP 3.
CP ₃ has a reference voltage based on the relationship shown in Figure 9 centered around input voltage Vin - output voltage Vout = 0.
V _r1 and V _r2 are given to each individual. Therefore, if the output of comparator CP ₁ exceeds the reference voltage V _r1 , the output (a) of comparator CP ₂ becomes "H" (high level), while the output of comparator CP ₁ exceeds the reference voltage V r1.
When V _r2 is exceeded, the output (b) of the comparator CP ₃ turns to "H", and while the output (a) is "L" (low level), the output of the inverter IN is "H". ”
Then, AND gate G ₁₁ is turned on and output (b)
, and AND gate _G11 sets the output (c) to "H" only when the output of comparator _CP1 is between _Vr1 and _Vr2 .
Output (c) acts as a window comparator. Therefore, in FIG. 7, the output voltage
When Vout is lower than the input voltage Vin by more than V _r2 , both outputs (a) and (c) of the comparison circuit CPC are "L", so the AND gates G ₂ and G ₄ are off, and the comparison controller CCP Only the first switch _S1 is turned on and off by the output of
The duty ratio is determined when the output voltage Vout and the output voltage Vout match, whereas the output voltage Vout is output within a range that is approximately equal to the input voltage Vin, that is, the range of the reference voltage V _r1 to _{V r2} shown in Fig. 9. VoltageVout
is input, the output (a) of the comparator circuit CPC is “L”, the output
(c) becomes “H” and the first switch _S1 becomes the comparison controller.
The output from the pulse generator PG is turned on and off by the output of the CCP, and the output from the pulse generator PG is passed through the AND gate _G4 , which is turned on by the output (c) of the comparator circuit CPC, and the RO gate _G3 . switch
The same switch _S2 also performs on/off operations, and due to the interaction between the buck type operation and the boost type operation, _the input voltage Vin becomes an output voltage of approximately the same value.
Vout is generated, and the duty ratio of the first switch _S1 is determined in a state where the reference voltage Vr and the output voltage Vout match. However, for the on/off operation of the first switch _S1 and the second switch _S2 , it is necessary to provide a period in which they are both on at the same time. give to,
The switches S ₁ and S ₂ are assumed to perform on and off operations in synchronization. Also, the output voltage Vout is lower than the input voltage Vin by V _r1
If it becomes higher than that, the output (a) of the comparator circuit CPC becomes "H" and the output (c) becomes "L", so the first switch
When S ₁ turns on, AND gate G ₂ turns on and AND gate G ₄ turns off, and the second switch S ₂ turns on and off according to the output of the comparison controller CCP, changing the operating state of the boost type. becomes. As the pulse generator PG, a multivibrator etc. can be applied, and a frequency dividing circuit that divides the frequency of the clock pulse may be used, and the frequency division 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 rate. Any device can be used as long as it generates a pulse having a duty ratio. In addition, the comparators CP ₂ and CP ₃ in FIG.
In order to avoid unstable operation when the output of comparator CP ₁ is near the reference voltages V _r1 and V _r2 , a device with level hysteresis characteristics is added by combining a Schmitt trigger circuit, etc. It is suitable if used. However, the power conversion circuit CONV is not limited to the above, but various configurations used in so-called switching regulators can be applied as long as the power conversion efficiency is good and the output voltage Vout can be controlled over a wide range. can. Note that the power conversion circuit CONV of the present invention is required to have a change range of output voltage Vout of about 5 to 40 V in practice, so the above-mentioned power conversion circuit is suitable, and as explained in FIG. The input terminal to which the reference voltage Vr of the device CCP is applied can be used as the output voltage control terminal.
The objective is achieved by providing an error signal instead of the reference voltage Vr. That is, the circuit from which the reference voltage Vr is removed in FIG. 7 corresponds to the power conversion circuit CONV in FIG. 3, and the terminal of the comparison controller CCP to which the reference voltage Vr removed in FIG. In the figure, it corresponds to the terminal of the power conversion circuit CONV to which the output of the comparator CMP is applied. In addition, the voltage detection circuit used in the arithmetic circuit CAL
DET _V , each detection output of the current detection circuit DET _I , and
For the voltage setting signal Se, resistance setting coefficient Krs, etc., other signals or detection outputs may be used as long as the relative relationship is the same, and various characteristics of the arithmetic circuit CAL, such as overload, signal-to-noise ratio, stability, The setting signal Se, resistance setting coefficient Krs, etc. can be determined according to characteristics such as errors, and various configurations of the arithmetic circuit CAL can be selected according to conditions. In addition, the same effect can be obtained by using a power supply converter circuit CONV that can control the output current and directly controlling the line current _IL , and the present invention can be freely modified as desired. In other words, in addition to the above-mentioned combination of a voltage divider and operational amplifier or a current mirror circuit, a multi-input adder/subtractor circuit can be constructed using a single operational amplifier, and a coefficient unit K, a subtracter SB, a comparator COM, etc. Integration is also optional. In addition, the power conversion circuit using the arithmetic circuit CAL
Since the line current I _L is stabilized by controlling CONV, the influence of voltage fluctuations of the power supply B on the line current I _L can be eliminated. FIG. 10 is a diagram for explaining that the input terminal of the comparison controller CCP in FIG. 7 to which the reference voltage V _r is applied can be used as the output voltage control terminal (T _c ). Figure 11 shows the number 10 in Figure 3.
Correspondence with each terminal in the figure is added. The operation will be explained below with reference to FIG. The calculation circuit CAL performs a predetermined calculation based on the line current _IL and the voltage setting signal Se and outputs a voltage _VLC . Comparator CMP compares V _LC and line voltage V _L and outputs an error signal to the output of CMP. The error signal is applied to the control terminal T _c (ie, one terminal of the comparison controller CCP of the power conversion circuit in FIG. 10). Next, a process in which V _L is controlled to be equal to V _LC will be described. Note that for the sake of simplicity, the absolute value of the voltage is used. In addition, as a condition, the voltage setting signal S _e
= 10V, the resistance on the terminal equipment TE side is 500Ω, the resistance setting coefficient K _rs is 500, and the voltage drop of the current detection circuit is 0V. As is well known, the comparator CMP has a large gain in the transition region. If this gain (K _cp ) is 1000, a voltage of (V _LC − V _L ) × K _cp is generated at the CMP output, and since this voltage is applied to the control terminal T _c , the output voltage of the power supply conversion circuit is also This will be the same voltage. Now, assuming that the output voltage V _p of the power supply conversion circuit is 0 V, since V _p is 0, both V _L and I _L are 0, so V _LC becomes S _e , and the CMP output is (S _e − V _L ) ×
K _cp = (10-0) x 1000 = 10000V (actually, the circuit is saturated, so for example about 50V). Therefore, V _p starts to rise towards 10000V. The table below shows how V _LC and CMP output change as V _p increases. From this, it can be seen that even when the power conversion circuit shown in FIG. 7 is used, control can be made so that _VLC and _Vp , that is, _VL , are equal. In addition, this _VLC
The operation of matching V L with V _L is based on the principle of negative feedback, which is a well-known principle.

【table】

[Table] As is clear from the above description, according to the present invention, the line current supply circuit that realizes a part of the BORSCHT function is mainly composed of electronic circuits, the internal power consumption is extremely small, and the line current supply circuit realizes a part of the BORSCHT function. By easily converting the supply circuit into an electronic circuit and an integrated circuit, the line current supply circuit can be made smaller, lighter in weight, and lower in price, and great effects can be obtained in various types of switching equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an equivalent circuit of a line current supply circuit, FIG. 2 is a block diagram showing an embodiment of the present invention,
Figure 3 is a block diagram that includes a specific example of the configuration of the arithmetic circuit in Figure 2, Figure 4 is a circuit diagram when a current mirror circuit is applied to the arithmetic circuit, and Figure 5 shows a situation where an impedance circuit is inserted. circuit diagram,
6 and 7 are circuit diagrams showing specific examples of the power conversion circuits in FIGS. 2 and 3, FIG. 8 is a block diagram showing a specific configuration of the comparison circuit in FIG. 7, and FIG. FIG. 8 is an input/output characteristic diagram showing waveforms of each part, and FIGS. 10 and 11 are diagrams for explaining the control operation of the power supply conversion circuit. TE...Terminal equipment, _L1 , _L2 ...Line, LCF...
Supply circuit (line current supply circuit), B...Power supply,
DET _V ...Voltage detection circuit, DET _I ...Current detection circuit, CAL...Arithmetic circuit, CONV...Power conversion circuit, Krs...Resistance setting coefficient, Se...Voltage setting signal, L...Block wire , S ₁ ... switch (first switch), S ₂ ... 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, comprising: (a) a power conversion circuit that converts a power supply voltage to a predetermined voltage and supplies it to the line; ) a voltage detection circuit that detects the line voltage V _L of the line; (c) a current detection circuit that detects the line current I _L with a resistance setting coefficient K _rs ; (d) of the line current supply circuit. The difference between the voltage setting signal S _e indicating the power supply voltage and the line current K _rs · I _L detected with the resistance setting coefficient K _rs , that is, S _e −K _rs ·
an arithmetic circuit that calculates I _L ; (e) a calculation result V _LC of the arithmetic circuit and the line voltage;
and a comparator for comparing V _L with V L, and the comparator output controls the output of the power conversion circuit so that the calculated result V _LC and the line voltage V _L match. .