JPS63301657A - Call signal generating circuit - Google Patents

Abstract

PURPOSE:To eliminate a transformer, etc., and to miniaturize a circuit by outputting the output of a positive side DC/DC converter during the one half cycle of a ringing cycle and outputting the output of a negative side DC/DC converter during the other half cycle of the ringing cycle. CONSTITUTION:The signal of an oscillator 14 to generate the signal of a call signal frequency is received and the output voltages of a positive side DC/DC converter 10 and a negative side DC/DC converter 12 are mutually outputted from a switch circuit 16. Thus, since a circuit is composed of the composing element of a small size only, the circuit can be miniaturized and a sharing to the circuit is not requested. Moreover, a setting in a line correspondence or in several lines correspondence comes to be possible, even a load dispersion is obtained and also the reliability of a system is improved. Low power consumption and a lowered noise can be obtained, too.

Description

[Detailed Description of the Invention] [1 Already Required] The output of the positive side DC/DC converter is output during one half cycle of the ringing signal period, and the output of the negative side DC/DC is output during the other half of the ringing signal period. The circuit can be miniaturized by outputting the same cycle and eliminating the need for a conventional transformer.

[Industrial application field]

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

With the digitization of exchanges, a subscriber circuit is provided between the subscriber telephone and the digital exchange in order to establish an interface between the digital exchange and the subscriber telephone. When this method is adopted, a call signal (161(z.

Means for supplying an alternating voltage (AC voltage with an effective value of about 75 volts) at a frequency such as 20 Hz is provided in the above-mentioned subscriber circuit.

In addition, the above-mentioned digitization is transitioning from a space-division type to a time-division type, and in line with this, the above-mentioned subscriber circuits are being integrated into circuits in order to achieve miniaturization and higher density. Electronic circuits are now being used in circuits as well.

[Conventional technology]

The subscriber circuit of the digital exchange is the so-called BOR3CHT.
B is a power supply (Battery).
feed), 0 is overvoltage protection jl (Overvolta
geprotection), R is the ringing signal transmission (R
inging), S is line monitoring (S supervising),
ion), C is code/decoding (Codec), H is 2
Line-4 line conversion (Hybrid), T is Test (Testi)
ng).

FIG. 7 is an explanatory diagram of a conventional example, in which 31 is a digital exchange network, 32 is a subscriber circuit, 33 is a subscriber telephone, and 34 is the B (power supply) and S (line monitoring) of the BOR3CRT functions described above. ), H (2-wire to 4-wire conversion), C(
35 is a calling signal oscillator, 36 is a DC power supply, RIO, R11 is a resistor for current limiting, rl is a contact point of a relay (not shown), TIP, RING
is a terminal. 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 the test equipment, and is directly connected to the calling signal transmission. There is no such relationship. Also, the R (calling signal sending) function uses the calling signal oscillator 3.
5 and relay contact rl, etc., and B S
It is provided closer to the subscriber line than the HC 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 calling signal from the calling signal oscillator 35 passes through the bell circuit of the telephone 33 via the resistor R10 and the contact rll, and then reaches the contact r
l, flows to the ground via resistor R11. Further, the ringing signal from the ringing signal oscillator 35 is superimposed on the DC voltage from the DC power supply 36, and when the telephone 33 is off-hook in response to the ringing signal, a DC current from the DC power supply 36 flows.
Off-footer detection can be performed using this direct current. and relay (not shown) upon off-hook detection.
is operated, and the contact rj2 of the relay that caused the sending of the calling signal is switched and connected to stop sending out the calling signal and to 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:
It is limited by the sum of resistors RIO, R11 and subscriber line resistance.

Further, as shown in the figure, the DC power supply 36 may be provided on the resistor RIO side (the ringing signal oscillator 35 side) or on the resistor R11 side, which is selected depending on the system configuration.

Conventionally, a configuration shown in FIG. 8 or 9 has been used to superimpose a ringing signal and a DC voltage and send the superimposed signal to a subscriber's telephone. In FIG. 8, a signal with a frequency of 16112, for example, from an oscillator 43 is amplified by an amplifier 42,
The voltage is supplied to the primary winding of the transformer 41 with a turns ratio of l:n, a voltage with an effective value of about 75 volts is induced in the secondary winding, and the DC voltage of the DC power supply 44 is superimposed on this voltage, so that the contact rl
It is sent to the subscriber's telephone via the . In this case, the transformer 41 boosts the low frequency signal and has a direct current flowing therethrough, so it becomes large.

In FIG. 9, in order to reduce the size of the transformer 41 in FIG. 8, a center tap is provided in the primary winding of the transformer 51.
Current is passed alternately through the windings on both sides of the center tap, and a signal of, for example, 16 Hz from the oscillator 56 is applied to the bases of the transistors 52 and 53 via the non-inverting driver 54 and the inverting driver 55, and is alternately turned on. , an off control is performed, a current is supplied from the power supply 57 connected to the center tap of the primary winding with a turns ratio of 1:n, and the DC voltage from the DC power supply 58 is superimposed on the voltage induced in the secondary winding. The signal is sent to the subscriber's telephone via contact rll of the relay activated when the subscriber is called.

[Problem that the invention seeks to solve]

The conventional calling signal sending circuit includes a transformer 41.51, and this transformer 41.51 has a frequency of 16Hz to
The transformer is used to boost a low frequency signal of about 2511z, and the lower the frequency, the larger the transformer becomes, so the transformer 41.51 for sending out the calling signal also becomes larger. Furthermore, since DC superposition is performed in order to detect the off-footer of the subscriber's telephone, a DC current flows through the transformer 41.51, and it is necessary to prevent the core of the transformer 41.51 from magnetic saturation due to this DC current. Because of this, the core is large. From this point of view, the transformer 41 for transmitting the calling signal.
51 had the disadvantage of being heavy and large.

Furthermore, since the conventional calling signal sending circuit corresponds to a constant voltage source, current limiting resistors R109 and R11 are required. These resistors R10 and R11 are large resistors 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, there was a drawback that the mounting area was large.

In addition, there is a trend toward functional distribution and load distribution in switchboards, but as mentioned above, conventional paging signal sending circuits are forced to share large transformers 41 and 51 due to their cost, so they are not compatible with functional distribution. It was difficult to create such a configuration.

An object of the present invention is to reduce the size and weight of the device, and to easily accommodate functional dispersion.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the present invention. In this figure, 10 is a positive side DC/DC converter, 12 is a negative side D
The C/DC converter 14 is an oscillator that generates a signal at the calling signal frequency. The circuit of the present invention is configured such that the output voltages of both converters are alternately outputted from the switch circuit 16 in response to the signal from the oscillator 14.

[For production]

In the circuit of the present invention, the positive DC voltage generated from the positive side DC/DC converter 10 and the negative DC voltage generated from the negative side DC/DC converter 12 are connected to the switch circuit 16.
The switching signal of the ringing signal frequency is alternately output. Therefore, a ringing signal is generated at the output of the switch circuit 16. Since only small components are used for generating the ringing signal, the load distribution required of the exchange can be met and its reliability can be improved.

〔Example〕

FIG. 2 shows an embodiment of the invention. In this figure, the same reference numerals are given to the parts corresponding to the components in FIG. 1 for reference.

The positive side DC/DC converter 10 connects the earth to a small choke coil Ll, a diode D1, and a capacitor C1.
An NPN) transistor Q1 is connected between the connection point R1 and the connection point St of the circuit formed to the battery V3S through the circuit, and a switching circuit is connected to the base of the transistor Ql via a buffer VFI (for interfacing). It is configured by connecting the output of a signal oscillator (SWO3C) 20. Similarly, the negative side DC/DC converter 12 is also configured. That is, there is a PNP between the connection point RO and the connection point SO of the circuit formed from the earth to the battery VSS via the capacitor CO, the diode DO1, and the small choke coil LO.
) A transistor QO is connected, and a switching signal oscillator 2 is connected to the base of the transistor QO via a buffer VFO.
It is configured by connecting the output of 0.

Switch circuit 16 is shown in FIG. This switch circuit 16 has a positive (IJDC/
A first current mirror circuit 16+ connected to the DC converter 10 and a negative side DC/DC that outputs the power supply voltage -■
A second current mirror circuit 16 connected to the converter 12! and control circuit 16. Consists of. Also, the first current mirror circuit 16. is transistor Q2. Q4, resistors R2 and R4, and transistors Q2. Q4
The base of the transistor Q2 is connected to the collector of the transistor Q2 on the input side. The second current mirror circuit 16g includes transistors Q3. Q5, resistors R3 and R5, and transistors Q3. The base of Q5 is connected to the collector of transistor Q3 on the input side. Note that the current mirror circuit generally has a configuration using a pair of transistors as described above, but various configurations can be adopted.

The control circuit 163 is composed of an operational amplifier OPA, transistors QO, Ql, and a resistor RO. The oscillator 14 is connected to the non-inverting input terminal (+) of the operational amplifier OPA, and the output terminal of the transistors QO, Ql is connected to the non-inverting input terminal (+) of the operational amplifier OPA. The bases of the transistors QO and Ql are connected to each other, and the inverting input terminal (-) of the operational amplifier OPA is connected to the emitters of these transistors QO and Ql, and the ground is connected through a resistor RO.

The operation of the above circuit configuration will be explained.

Positive side DC/DC converter 10 also negative side DC/DC
The operating principle of converter 12 is almost the same. That is, the transistor Q1 is turned on/off by the signal from the oscillator 20.
When it is turned off, the electrical energy stored in the coil Ll when it is turned on is transferred to the capacitor C1, the diode D1, and the battery VSS when the transistor Ql is off.
It is discharged via an electrical path leading to the ground. Also, when the transistor QO is turned on/off by the signal from the oscillator 20, the electrical energy stored in the coil LO when the transistor QO is turned on is transferred to the earth, the capacitor CO, the diode DO1, the battery, and the earth when the transistor QO is off. The charge is drawn in through the energizing path to the air. This operation is the transistor Q
This is repeated every time I or QO is turned on/off, and a predetermined positive DC voltage +V is generated at the output point 01 and a predetermined negative DC voltage -■ is generated at the output point OO.

Further, the operation of the switch circuit 16 is as follows.

Transistor Q2. Assuming that the base-emitter voltages of Q4 are equal and that the current amplification factor hrt is sufficiently large, the current mirror circuit 16. input current! The relationship between , and output current l is R2・1. =R4・■4 ...(1), so 14 = (R2/R4)・■. ...(2)
becomes. Therefore, when R2>R4, the output current I4 can be controlled with a small input current I0.

Similarly, in the current mirror circuit 16, 1, -
(R3/R5) ・11 The relationship is as shown in (3).

The operational amplifier OPA operates so that the signal voltage ■ applied to the non-inverting input terminal (+) and the voltage applied to the inverting input terminal (-) are at the same potential (imaginary short). , the emitter potentials of the transistors QO, Ql become the same as the signal voltage V. Current amplification factor hF of transistors QO and Ql! Assuming that is sufficiently large, when the signal voltage V is positive, the current 1o flowing through the transistor QO is: (4) = ■s/RO...(4) However, the current I flowing through the transistor Ql is It becomes 0. Also, when the signal voltage ■ has negative polarity, the current flows through the transistor Q1! , is L=Vs/RO (5), but the current io flowing through the transistor QO is zero.

Note that the signal voltage ■s is selected so as to be equal to or lower than the reverse breakdown voltage between the bases and emitters of the transistors QO and Ql.

A current It flows corresponding to the polarity of the signal voltage ■s.

By Io, the current mirror circuit 16. ．． Current 1s and I multiplied by R3/R5 and R2/R4 from 16□, respectively
The sum of n is sent to the telephone set as a ringing signal current 1out via a relay contact of a relay (not shown) that is activated when the exchange sends a ringing signal.

Z is the load impedance including the phone impedance.
When L, the output voltage Vout is Vout = 1o
ut Red Zt...(6). However, this output voltage Vout never exceeds the power supply voltage +V, -V. Furthermore, when the telephone goes off-hook in response to a ringing signal, its impedance becomes approximately zero, and thus the output voltage Vout decreases. Therefore, off-footer detection is possible.

FIG. 4 is an explanatory diagram of the operation, and (a) is an oscillation frequency of 16H.
The signal of voltage v1 from the oscillator 14 of Z is shown, and this signal causes currents of 1. ．． 1. flows. This current■. ,
Since I becomes the input terminal of the current mirror circuit, the calling signal current 1out is as shown in (d).

Further, the output voltage Vout is as shown in (e).

Also, when the load impedance ZL is large, the output voltage Vout tends to increase as shown by the dotted line in (f), but
The output voltage cannot increase beyond the power supply voltages +V, -V. In this state, the current mirror circuits 16+, 1
Since the transistors Q5 and Q4 on the output side of 6g are saturated and the resistors R5 and R4 are also set to low values, they are connected to the power supply with low impedance, and the output voltage Vout is as shown by the solid line. It will be clamped within the power supply voltage +V and -V.

Since the switch circuit 16 operates as described above, alternating positive and negative DC voltages are generated at its output SO at 1611z. Therefore, the switching equipment operates the calling signal sending relay, and the relay contact outputs S from the calling signal generating circuit.
When switched to the O side, the above-mentioned positive and negative DC voltages, ie the ringing signal, are sent to the subscriber current machine.

In this example, for each DC/DC converter,
By providing the oscillator 20 and making its deity different, not only the effective value of the calling signal but also the DC component of the signal can be arbitrarily set.

Further, FIG. 5 shows another embodiment of the present invention. In this embodiment, in order to reduce the power consumption and the number of nozzles in the calling signal sending circuit, the switching signal sources for both converters and the switching signal source for the switch circuit in the embodiment in FIG. 1 are configured as follows. There is a special feature of it. That is, the switching signal for the positive side DC/DCC/formula-ta 0 is a NAND circuit 32 which receives the calling signal sending control signal SD, the signal from the oscillator 14 that has passed through the inverter 30, and the signal from the oscillator 20, and outputs the circuit output. The switching signal for the negative side DC/DC converter 12 uses the signal appearing at the output of the OR circuit 34 which receives the control signal SD and the signal from the oscillator 14.20. or,
For the switching signal of the switch circuit 16, the control signal SD and the signal of the oscillator 14 are received by an OR circuit 36, and a signal appearing at the circuit output is used.

According to this switching signal source, the switching signal of 32KH2 from the oscillator 20 is output from the NAND circuit 32 to the positive side DC/DC during the high level period of the oscillator 14, as shown in (4) in FIG. Supplied to converter 10. The conversion operation in the converter 10 is the same as described above. Also, from the OR circuit 34, (
5), during the low level period of the output signal of oscillator 14, a 32 KHz switching signal from oscillator 16 is provided to negative side DC/DC converter 12.

In this converter 12 as well, a conversion operation similar to that described above occurs.

In addition, the switching signal is supplied to the switch circuit 16 only when the signal SD is applied, as shown in (6) in FIG. Since these devices stop operating during unnecessary time periods for sending out a calling signal, power consumption can be reduced and the noise generated therein will not occur during that period.

〔Effect of the invention〕

As described above, according to the present invention, since the circuit is constructed using only small-sized components, the circuit can be downsized and there is no need to share the circuit. Therefore, it becomes possible to provide the circuit of the present invention for a line or for several lines, which contributes to load distribution and improves the reliability of the system. Furthermore, lower power consumption and lower noise can be achieved.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing an example of the circuit configuration of the switch circuit 16, and FIG.
The figure is a signal waveform diagram of each part of the switch circuit 16, FIG. 5 is a diagram showing another embodiment of the present invention, FIG. 6 is a signal timing chart of each part of a circuit of another embodiment of the present invention, and FIG. 7 is a diagram of a conventional example. FIG. 8 is an explanatory diagram of the main part of the conventional example, and FIG. 9 is an explanatory diagram of the main part of the conventional example. In Figures 1 to 3 and 5, 10 is the positive side D.
C/DC converter (choke coil L1, diode D1, capacitor C1, transistor Q1, oscillator 2
0), 12 is a negative side DC/DC converter (choke coil LO, diode Do, capacitor Co, transistor QO, oscillator 20), 14 is an oscillator, 16 is a switch circuit (current mirror circuit 161°16)
□, control circuit 163). Akira Kotoro's β block diagram Figure 1 - ■ Circuit end bi-column of switch circuit 16 However, 7 Switch circuit 16. Each p's No. 49 residence 1 sho kuse drawing $ 4 Otsu August 4 color example circuit Each death's 4 ■ time > 4 yards Fig. 6 Conventional 8 ri escape drawing Fig. 7

Claims (2)

[Claims] (1) Positive side DC/DC converter (10) and negative side DC
/DC converter (12), an oscillator (14) that generates a signal at the calling signal frequency, and a switch that alternately outputs the outputs of both the converters (10, 12) in response to the output signal of the oscillator (14). A calling signal generation circuit consisting of a circuit (16). (2) The calling signal generating circuit according to claim 1, further comprising a circuit that connects a switching signal oscillator only during a calling signal cycle period corresponding to the switching inputs of both converters (10, 12). .