JPH056947B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A constant current circuit consisting of a constant current source that draws current and a constant current source that sends out current is connected to two wires of a subscriber circuit, and the subscriber telephone is connected to the constant current circuit. In contrast, a calling signal consisting of a constant current in the positive and negative directions is sent out, and a small and lightweight calling signal sending circuit can be constructed.

[Industrial application field]

The present invention relates to a calling signal sending circuit for sending out a calling signal to a subscriber telephone.

The ringing signal that rings the bell of the subscriber's telephone to notify the user of an incoming call is sent out from the ringing signal sending circuit at a frequency of 16Hz or 20Hz and as an AC voltage with an effective value of about 75V at a predetermined intermittent ratio. It is desired to reduce the weight and size of such a calling signal sending circuit, thereby reducing the size of the switching equipment.

[Conventional technology]

The subscriber circuit has a so-called BORSCHT function, where B is battery feed, O is overvoltage protection, R is ringing, S is line supervision, and C. is codec, H is 2-wire to 4-wire conversion (Hybrid), and T is Testing.
It is.

FIG. 6 is an explanatory diagram of a conventional example, where 31 is a network of digital exchanges, 32 is a subscriber circuit,
33 is a subscriber telephone, 34 is the aforementioned BORSCHT
Of the functions, B (power supply), S (line monitoring), H (2
35 is a calling signal oscillator, 36 is a DC power supply, R
10 and R11 are resistors for current limiting, rl is a contact point of a relay (not shown), and TIP and RING are terminals.
Note that the O (overvoltage protection) function, which is not included in the circuit 34 of the BSHC function, is configured by distributedly connected varistors, etc., and the T (test) function is a connection configuration with a test device. Further, the R (calling signal sending) function is realized by a calling signal oscillator 35, a relay contact rl, etc., and is provided closer to the subscriber line than the BSHC function circuit 34. Further, the calling signal oscillator 35 and the DC power supply 36 are shared by a plurality of subscriber circuits.

When the contact rl of the relay (not shown) is in the state shown, the ringing signal from the ringing signal oscillator 35 passes through the bell circuit of the telephone 33 via the resistor R10 and the contact rl, and then via the contact rl and the resistor R11. Flows into the earth. Further, a DC voltage from a DC power source 36 is superimposed on the ringing signal oscillator 35, and when the telephone 33 is off-hook in response to the ringing signal, a DC current from the DC power source 36 flows, so that off-hook detection can be performed using this DC current. can. Then, upon detection of off-hook, a relay (not shown) is operated and its contact RL is switched and connected to stop sending out the calling signal and connect the telephone 33 to the network 31 via the circuit 34. The DC current from the DC power supply 36 at this time is the resistance R10, R
11 plus the subscriber line resistance.

Further, the DC power supply 36 has a resistor R10 as shown in the figure.
There are cases in which it is provided on the side (the calling signal oscillator 35 side) and cases where it is provided on the resistor R11 side, and the selection is made depending on the system configuration.

Conventionally, a configuration shown in FIG. 7 or 8 has been used to superimpose a calling signal and a DC voltage and send the superimposed signal to a subscriber's telephone. In FIG. 7, a signal with a frequency of, for example, 16 Hz from an oscillator 43 is amplified by an amplifier 42 and supplied to the primary winding of a transformer 41 with a turns ratio of 1:n, and the effective value of 75 V is applied to the secondary winding.
DC power supply 44 is applied to this voltage.
DC voltage is superimposed and sent to the subscriber's telephone via contact RL. In this case, the transformer 41 boosts the low frequency signal and has a direct current flowing therethrough, so it becomes large.

In FIG. 8, in order to reduce the size of the transformer 41 shown in FIG. 7, a center tap is provided in the primary winding of the transformer 51, and current is alternately passed through the windings on both sides of the center tap. For example, a 16 Hz signal from 56 is applied to the bases of transistors 52 and 53 via a non-inverting driver 54 and an inverting driver 55, and is controlled to turn on and off alternately, and is connected to the center tap of the primary winding with a turns ratio of 1:n. A current is supplied from a power source 57, and a DC voltage from a DC power source 58 is superimposed on the voltage induced in the secondary winding, and the superimposed voltage is sent to the subscriber telephone via a contact RL.

We have previously proposed a calling signal sending circuit which is configured so that the transformers 41 and 51 described above can be omitted and is made smaller and lighter. That is, as shown in FIG. 9, a first constant current source 61 for drawing current and a second constant current source 62 for sending current are provided, and a signal source 63 is provided.
The inverting driver 66 of the control circuit 64 controls the first constant current source 61, and the non-inverting driver 67 controls the second constant current source 62 in response to a signal from the telephone 65 via contact RL. In addition, a constant current value that alternates between positive and negative directions is sent out as a calling signal. Note that 68 is a circuit having a BSCH function.

[Problem that the invention seeks to solve]

The conventional calling signal sending circuit includes a transformer 41,
51, and this transformer 41, 51
The transformer boosts a low frequency signal of about 16 Hz to 25 Hz, and the lower the frequency, the larger the transformer becomes, so the transformers 41 and 51 for sending the calling signal also become larger. Furthermore, since DC superposition is performed to detect off-hook of subscriber telephones, DC current flows through the transformers 41 and 51, and the cores of the transformers 41 and 51 are prevented from being magnetically saturated by this DC current. Since it is necessary to do this, the core becomes large. From this point of view as well, the transformers 41 and 51 for transmitting the calling signal have the disadvantage of being heavy and large.

Furthermore, since the conventional calling signal sending circuit corresponds to a constant voltage source, the current limiting resistor R1 is
0, R11 is required. These resistors R10,
R11 is a large resistor of several watts, taking into consideration the heat generated by the current flowing when the telephone is off-hook, and the heat generated by the current caused by ground faults in the subscriber line. However, the disadvantage was that the mounting area was large.

In addition, there is a tendency for switching equipment to distribute functions and load distribution, but as mentioned above, the size of the ring signal sending circuit increases, so it is common to install one to several circuits in common throughout the entire switching equipment. It was hot. Therefore, 1~
It was difficult to construct a more reliable system by installing a calling signal sending circuit for every several dozen lines and distributing the calling signal sending function.

In order to overcome these drawbacks, the previously proposed paging signal sending circuit shown in FIG. 9 can omit the transformer and current limiting resistor, so it is possible to create a subscriber circuit that is suitable for the functional distribution of the exchange. Can be configured. In that case, the configuration is such that the ringing signal sending circuit is connected to one of the two wires of the subscriber circuit, and the power supply voltages V _DD and V _SS need to be high. In order to obtain this, the chip area becomes large.

An object of the present invention is to reduce the size and weight, lower the power supply voltage, and facilitate integration into an integrated circuit.

[Means for solving problems]

The calling signal sending circuit of the present invention uses a current mirror circuit, and this current mirror circuit has a function of supplying an output current proportional to an input current. Since the output current is also constant, a constant current circuit can be constructed. Hereinafter, in the present invention, a configuration consisting of a current mirror circuit that supplies an output current proportional to an input current will be referred to as a constant current source or a constant current circuit. The present invention
This device combines such constant current sources to send out a calling signal as a differential signal, and will be explained with reference to FIG.

A first constant current circuit 1 consisting of a first constant current source 3 that draws current and a second constant current source 4 that sends out current, and a third constant current source 5 that draws current.
and a second constant current circuit 2 consisting of a fourth constant current source 6 that sends current, and
The first constant current circuit 1 is connected to one of the two wires connected to the circuit 12 of the BSCH function via the contact rl, and the second constant current circuit 2 is connected to the other wire via the contact rl.
Connect via.

Also, a first constant current source 3 of the first constant current circuit 1,
The fourth constant current source 6 of the second constant current circuit 2 is operated simultaneously by the output signal of the inverting driver 10, and the second constant current source 4 of the first constant current circuit 1 and
A control circuit 8 is provided which performs control to operate the third constant current source 5 of the second constant current circuit 2 and the third constant current source 5 simultaneously according to the output signal of the non-inverting driver 11, alternately according to the signal from the signal source 7. .

When the first constant current circuit 1 draws current,
The second constant current circuit 2 sends out current, and when the first constant current circuit 1 sends out current, the second constant current circuit 2 draws in current, so the terminal
A calling signal as a differential signal is sent to the telephone set 9 connected to TIP and RING via contact rl.

[Effect]

For example, when the signal from the signal source 7 has negative polarity, the first constant current source 3 of the first constant current circuit 1 and the fourth constant current source 6 of the second constant current circuit 2 operate simultaneously. A constant current is sent out from the fourth constant current source 6 to which the power supply voltage V _DD is applied, and a constant current is drawn by the first constant current source 3 to which the power supply voltage V _SS is applied. Also, when the signal from the signal source 7 is of positive polarity, the first
The second constant current source 4 of the constant current circuit 1 and the third constant current source 5 of the second constant current circuit 2 operate simultaneously, and the second constant current source to which the power supply voltage V _DD is applied 4
A constant current is sent out from the constant current source 5, and a constant current is drawn by the third constant current source 5 to which the power supply voltage V _SS is applied. Therefore, a calling signal as a differential signal is sent to the telephone 9, and the telephone 9 receives the respective power supply voltages of the first constant current circuit 1 and the second constant current circuit 2.
A voltage of |V _DD |+|V SS |, which is the sum of the absolute values of V _DD and V _SS , will be applied, and even if _the respective power supply voltages are reduced, the bell of the telephone 9 will ring sufficiently. A signal can be sent.

〔Example〕

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

FIG. 2 is a block diagram of an embodiment of the present invention,
The case where a current mirror circuit is used as a constant current source is shown. In the figure, 21 is a first constant current circuit, 22 is a second constant current circuit, 23 and 25 are first and third constant current sources 3 to which a power supply voltage V _SS is applied,
5, 24 and 26 are current mirror circuits that constitute the second and fourth constant current sources 4 and 6 to which the power supply voltage V _DD is applied, 27 is a signal source, 28 is a control circuit, 29 is a telephone, 30 is
In the BSCH function circuit, TIP and RING are terminals of the subscriber circuit, and RL is a contact point of a relay (not shown).

The control circuit 28 causes the currents I ₀ and I ₃ to flow in the direction of the arrow during the positive polarity period of the signal of the cycle of the calling signal from the signal source 27, and the first current mirror circuit 23 of the first constant current circuit 21 , draws in a current proportional to this current I ₀ , and the second current mirror circuit 26 of the second constant current circuit 22 sends out a current proportional to this current I ₃ . At this time, since the currents I ₁ and I ₂ are set to 0, a current flows from the terminal TIP side to the telephone 29, and a calling signal is sent to the terminal RING side.

In addition, during the period in which the signal from the signal source 27 is of negative polarity,
Since the control circuit 28 causes currents I ₁ and I ₂ to flow in the directions of the arrows, a current flows from the terminal RING side to the telephone 29 in proportion to the currents I ₀ and I ₂ , and a ringing signal is drawn into the terminal TIP side. is sent. In this way, a ringing signal corresponding to the period of the signal from the signal source 27 is sent to the telephone 29 via the contact rl.

The first and second constant current circuits 21 and 22 supply a constant current using the telephone 29 and the subscriber line as loads, and the output voltage thereof is proportional to the load impedance. However, even if the load impedance is large, it will not rise above the power supply voltage V _SS or V _DD , ensuring safety, and even in the event of a ground fault, only the set constant current will flow. , no overcurrent flows, and therefore no current limiting resistor is required.

Further, when the telephone 29 goes off-hook in response to a ringing signal, the impedance of the telephone 29 becomes almost zero, and the output voltage decreases. Therefore, off-hook can be detected from this drop in output voltage. That is, off-hook detection can be performed without particularly performing DC superimposition. Note that the power supply voltage V _DD ,
V _SS , for example, +(75/2)V and -(75/2)V
When set to , the output voltage will be ±75V around 0V.
It becomes a calling signal with an amplitude of . Also +(27/2)V and -
When set to (123/2) V, the ringing signal has an amplitude centered around -48V, making it possible to send out a ringing signal that looks like a superimposed direct current.

FIG. 3 is a circuit diagram of a main part of an embodiment of the present invention, where the same reference numerals as in FIG. 2 indicate the same parts, and the first current mirror circuit 23 of the first constant current circuit is
The second current mirror circuit 24 is composed of transistors Q3 and Q5 and resistors R3 and R5.
The first current mirror circuit 25 of the second constant current circuit is composed of transistors Q2 and Q4 and resistors R2 and R4.
5 and resistors R13 and R15, the second
The current mirror circuit 26 includes a transistor Q1
2, Q14 and resistors R12, R14. The control circuit also includes operational amplifiers OPA0,
OPA1 and transistors Q0, Q1, Q10,
Q11, and resistors R0, R10, R16, and R17.

In the current mirror circuits 23 to 26, a current proportional to the current flowing through the transistor on the input side flows through the transistor on the output side. For example, in the current mirror circuit 23, the current I ₁ flowing through the transistor Q3 on the input side. The relationship between the current I ₅ flowing through the transistor Q5 on the output side is I ₅ = (R3/R5)・I ₁ ...(1), so by selecting the relationship R3>R5, the input current can be reduced. A large output current can be controlled by

In addition, since the operational amplifiers OPA0 and OPA1 have an output voltage such that the input voltage at the non-inverting input terminal (+) and the input voltage at the non-inverting input terminal (-) are equal, the operational amplifiers OPA
When the input signal to the non-inverting input terminal (+) of R0 is positive, transistor Q0 is turned on and transistor Q1 is turned off, so that the voltage across resistor R0 has the same positive polarity as the input signal. A current I ₀ flows through. Conversely, when the input signal has negative polarity, transistor Q0 is off and transistor Q1 is on.
Current _I1 flows so that the voltage across resistor R0 has the same negative polarity as the input signal. these currents
Currents I _{4 and} I ₅ proportional to I ₀ and I 1 flow into the telephone 29 via contact rl.

Further, when the input signal from the signal source 27 to the inverting input terminal (-) of the operational amplifier OPA1 is of positive polarity, the transistor Q11 is turned on and the transistor Q10 is turned off, and a negative voltage is generated across the resistor R10. Since the non-inverting input terminal (+) is grounded, a current _I11 flows such that the inverting input terminal (-) is at the ground potential. Conversely, when the input signal is of negative polarity, transistor Q10 is turned on and transistor Q11 is turned off, a positive voltage is generated across resistor R10, and current _I10 flows. Currents I ₁₄ and I ₁₅ proportional to these currents I ₁₀ and I ₁₁ flow into the telephone 29 via contact rl. In this case, I ₄ =I ₁₅ ,
The relationship is I ₅ = I ₁₄ .

FIG. 4 is an explanatory diagram of the operation of one embodiment of the present invention, in which a indicates a signal from the signal source 27, and during the positive polarity period of this signal, operational amplifiers OPA0 and OPA
1, currents I ₀ and I ₁₁ flow as shown in b and e, and currents I ₄ and I ₁₅ flow in proportion thereto. Also, during the period of negative polarity of the signal, the operational amplifiers OPA0,
Currents I ₁ and I ₁₀ flow as shown in c and d due to the output of OPA 1, and currents I ₅ and I ₁₄ flow in proportion thereto. Therefore, the calling signal sent to the telephone set 29 is as shown in f.

Furthermore, as shown in g, the output voltage of the first constant current circuit is clamped within the power supply voltages V _DD and V _SS even when the load impedance is large, so safety is ensured. Also, the output voltage of the second constant current circuit is also equal to the power supply voltages V _DD and V _SS as shown in h.
It will be clamped within.

A first constant current circuit and a second
Depending on the power supply with the constant current circuit, approximately |V _DD |+|
A voltage of V _SS | is applied, and the power supply voltages V _DD and V _SS are reduced by 1/2 compared to the case where a ringing signal is sent from only one of the two wires of the subscriber circuit.
It can be done.

FIG. 5 shows a main circuit of another embodiment of the present invention, and the same reference numerals as in FIG. 3 indicate the same parts. This embodiment uses a current mirror circuit to perform current reversal, OPA is an operational amplifier, R1 is a resistor,
Q20 to Q29 are transistors, V _CC and V _EE are power supply voltages, and CI1 to CI4 are current mirror circuits.

Operational amplifier according to the signal from the signal source 27
Transistors Q0 and Q1 are controlled to be turned on and off alternately by the output of OPA. When the signal is of positive polarity, transistor Q0 is turned on, current flows through transistor Q20 on the input side of current mirror circuit CI1, and current proportional to the current flows through transistors Q21 and Q22 on the output side. The current flowing through transistor Q21 is a current mirror circuit.
A current proportional to that current flows through transistor Q28 on the input side of CI4, and a current proportional to that current flows through transistor Q28 on the output side.
It flows to 29. This current becomes the current I ₀ flowing through the transistor Q2 of the second constant current source 24 of the first constant current circuit. Further, the current flowing through the transistor Q22 of the current mirror circuit CI1 becomes the current _I11 flowing through the transistor Q13 of the first constant current source 25 of the second constant current circuit. Therefore, the current sent out from the second constant current source 24 of the first constant current circuit flows to be drawn into the first constant current source 25 of the second constant current circuit.

Furthermore, when the signal from the signal source 27 is of negative polarity, the transistor Q1 is turned on and the current mirror circuit is activated.
A current flows through the transistor Q23 on the input side of CI2, and a current proportional to the current flows through the transistors Q24 and Q25 on the output side. The current flowing through this transistor Q24 is the second current flowing through the second constant current circuit.
The current flowing through the transistor Q12 of the constant current source 26 becomes _I10 , and the current flowing through the transistor Q25 flows through the transistor Q26 on the input side of the current mirror circuit CI3, and a current proportional to that current flows through the transistor Q27 on the output side. . This current becomes the current _I1 flowing through the transistor Q3 of the first constant current source of the first constant current circuit. Therefore, the second
The current sent from the second constant current source 26 of the constant current circuit is transmitted to the first constant current source 26 of the first constant current circuit.
It flows as if being drawn into 3.

The above-mentioned operation is repeated and a contact is made to the telephone 29.
A ringing signal is sent via rl, and the output voltages of the first and second constant current circuits are the same as in the previous embodiment.

The present invention is not limited to the above-described embodiments, and various additions and changes can be made.

〔Effect of the invention〕

As explained above, the present invention has a first constant current circuit 1 having first and second constant current sources 3 and 4 each consisting of a current mirror circuit, and third and fourth constant current sources 3 and 4 each consisting of a current mirror circuit. A second constant current circuit 2 having constant current sources 5 and 6 of Since the calling signal is sent from the current circuit, a current exceeding the set current will not flow in the event of off-hook or faults such as ground faults, and a current limiting resistor is not required.

Furthermore, since the calling signal is sent from each of the two wires of the subscriber circuit, the power supply voltages V _DD and V _SS of each sending circuit are halved compared to when sending from one wire. be able to. Therefore,
This means that a circuit configuration with a low breakdown voltage is required, and even if the circuit scale increases slightly, the low breakdown voltage configuration has the advantage that it is very easy to integrate the circuit.
It is also possible to distribute the functions by providing a calling signal sending circuit corresponding to the subscriber circuit, which can contribute to improving the reliability of the system.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a circuit diagram of a main part of an embodiment of the invention, and Fig. 4 is an embodiment of the invention. FIG. 5 is a main circuit diagram of another embodiment of the present invention, FIG. 6 is an explanatory diagram of a conventional example, and FIGS.
The figure is an explanatory diagram of the main part of a conventional example, and FIG. 9 is a block diagram of a previously proposed calling signal sending circuit. 1 and 2 are first and second constant current circuits, 3 and 5 are first constant current sources, 4 and 6 are second constant current sources, 7 is a signal source, 8 is a control circuit, 9 is a telephone, 10 is an inverting driver, 11 is a non-inverting driver, 12 is BSCH
Functional circuit, RL is the relay contact, V _DD , V _SS are the power supply voltages, 21 is the first constant current circuit, 22 is the second constant current circuit, 23 to 26 are current mirror circuits, 2
7 is a signal source, 28 is a control circuit, 29 is a telephone, 3
0 is a BSCH function circuit.

Claims (1)

[Scope of Claims] 1. In a calling signal sending circuit that sends out a calling signal to a subscriber's telephone, a first circuit comprising a current mirror circuit that draws current and supplies an output current proportional to an input current.
a constant current source 3, and a second constant current source 4, which is composed of a current mirror circuit that sends out an output current and supplies an output current proportional to the input current. It consists of a first constant current circuit 1 connected to the line, and a current mirror circuit that draws current, and a third constant current circuit that supplies an output current proportional to the input current.
the other of the two lines of the subscriber circuit; a second constant current circuit 2 connected to the line; the first constant current source 3 that draws current into the first constant current circuit 1; and the second constant current source 3 that sends out current to the second constant current circuit 2. The second constant current source 4 and the second constant current circuit 2 perform control to simultaneously supply current from the fourth constant current source 6 and send current to the first constant current circuit 1. In order to control the operation of supplying current from the third constant current source 5 which draws current at the same time, the first, The fourth constant current source 3, 6 and the second and third constant current source 4, 5 each include a control circuit 8 that applies the input current for current drawing and current sending. A calling signal sending circuit.