JP2000228693A - Hybrid coupled circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a hybrid coupled circuit that does not use a transformer. SOLUTION: A driving signal corresponding to a transmission signal from a transmitting terminal Ti is generated by a photocoupler driving circuit having an amplifier 52b, and a photocoupler 51 makes current corresponding to the transmission signal flow through a line via terminals L1 and L2. A driving signal corresponding to voltage on the line is generated by a photocoupler driving circuit 54, and a photocoupler 53 to which the driving signal is inputted outputs current corresponding to the voltage on the line. An output current of the photocoupler 53 is converted into voltage by current/voltage conversion circuit 55, and a direct current component is cut by a capacitor 56. An addition circuit 57 extracts a received signal alone from a voltage signal given from the capacitor 56 by canceling a transmission signal part on the terminal Ti and gives the received signal to a receiving terminal To.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid coupling circuit used in a communication terminal or the like that performs communication via a telephone line.

[0002]

2. Description of the Related Art A hybrid coupling circuit is a circuit required for a communication terminal, such as a telephone, for transmitting transmission / reception signals in real time using a line constituted by a pair of transmission lines, and which can identify transmission / reception. In addition, the transmission signal is sent to the other party, but it does not appear at the receiving terminal of its own terminal. is there. FIG. 2 is a circuit diagram showing a configuration example of a hybrid combination circuit used in a conventional telephone. This hybrid coupling circuit is a circuit provided in a conventional telephone that only performs transmission and reception of audio signals. The telephone has a talker (T) 1 for converting voice into an AC transmission signal, and a receiver (R) 2 for converting a received signal into voice, and a hybrid coupling circuit includes a hybrid transformer 3 and an impedance element 4. It is configured.

[0003] One end of the primary winding 31 of the transformer 3 is
The other end of the primary winding 31 is connected to one terminal L1 of a telephone analog front end circuit (hereinafter, referred to as an AFE circuit) having a function of connecting between the telephone and the transmission line. Through the other terminal L2 of the AFE circuit. The talker 1 is connected between the midpoint Tc of the primary winding 31 and the terminal L2. The receiver 2 is connected between both ends of the secondary winding 32 of the transformer 3. The impedance of the impedance element 4 is set so as to correspond to the characteristic impedance of the line. In this hybrid coupling circuit,
A received signal coming from the line is provided to the receiver 2 via the transformer 3, and the received signal is converted into voice. The transmission signal generated by the talker 1 is transmitted to the hybrid transformer 3
Is transmitted from the middle point Tc of the primary winding 31 to the AFE circuit and the impedance element 4 on both sides. At this time, since the transmission signal flows equally to both sides from the middle point Tc of the primary winding 31, no current corresponding to the transmission signal flows in the receiver 2, and the transmission signal does not appear in the receiver 2.

The hybrid coupling circuit shown in FIG. 2 is sufficient when only transmitting and receiving voice. However, when it is used for a modem function circuit or other telecommunication circuits, the talker 1 is used.
And the ground of the receiver 2 cannot be shared, that the DC potential must be adjusted to the exchange via the line, or that the transmission / reception signal from the exchange is a balanced signal, and the unbalanced operation of the general single-sided ground. There are drawbacks such as mismatch. Therefore, a hybrid coupling circuit as shown in FIG. 3 is used for a communication terminal using a modem or the like. FIG. 3 is a circuit diagram showing another example of the conventional hybrid coupling circuit. This hybrid coupling circuit includes a transformer 11. Primary winding 11 of transformer 11
1 are connected to two terminals L1 and L2 of the AFE circuit, respectively. A transmission terminal Ti to which a transmission signal Vi is supplied from a talker (not shown) has a capacitor 12
And the resistor 13 are connected in series, and the resistor 13 is connected to the inverting input terminal (−) of the operational amplifier 14. The positive-phase input terminal (+) of the operational amplifier 14 is connected to the ground,
The output terminal and the inverted input terminal of the operational amplifier 14 are connected by a resistor 15.

The output terminal of the operational amplifier 14 is connected to the inverting input terminal of an operational amplifier 17 via a resistor 16. The positive-phase input terminal of the operational amplifier 17 is connected to the ground, and the output terminal and the inverting input terminal of the operational amplifier 17 are connected by the resistor 18. Resistance value of resistance 16 and resistance 1
8, the operational amplifier 17 has a gain of -1.
Is configured to be amplified. The output terminal of the operational amplifier 17 is connected to one end of the secondary winding 112 of the transformer 11. One end of the resistor 19 and one end of the resistor 20 are connected to the other end of the secondary winding 112 of the transformer 11. The other end of the resistor 19 is connected to the output terminal of the operational amplifier 14, and the other end of the resistor 20 is connected to the inverting input terminal of the operational amplifier 21. The positive-phase input terminal of the operational amplifier 21 is connected to the ground, and the output terminal and the inverting input terminal of the operational amplifier 21 are connected by a resistor 22. One terminal of a capacitor 23 is connected to the output terminal of the operational amplifier 21, and the other electrode of the capacitor 23 is connected to a receiving terminal To of a receiver (not shown).

This hybrid coupling circuit has the disadvantage that the DC potential must be adjusted to the exchange via the line, and the unbalanced operation of the common one-side ground because the transmission / reception signal from the exchange is a balanced signal. The disadvantage of the absence is solved by coupling with the AFE circuit by the transformer 11. Further, the common ground for the voltage Vi of the transmission signal and the voltage Vo of the reception signal is determined by the amplifier 1.
4, 17, 21 and resistors 13, 15, 16, 12, 1
The problem is solved by a sidetone prevention circuit composed of 9, 20, 22 and capacitors 12, 23. By using the transformer 11, DC coupling with the line side is cut off,
It is a well-known fact that a balanced signal can be combined with an unbalanced operation of a general single-sided ground.
17, 21 and resistors 13, 15, 16, 12, 19, 2
The following describes that sidetone prevention is performed by the sidetone prevention circuit composed of 0 and 22 and capacitors 12 and 23.

[0007] The DC component of the transmission signal is cut by the capacitor 12, and only the AC component is input to the operational amplifier 14 via the resistor 13. The operational amplifier 14 includes resistors 13 and 15
Amplify the AC component of the transmission signal Vi with the gain specified by The operational amplifier 17 generates an inverted-phase signal of the amplified transmission signal by amplification with a gain of one. This operational amplifier 1
7 and the amplified transmission signal output from the operational amplifier 14 are combined with the secondary winding 112 and the resistor 1.
9 flows into the series circuit. As a result, the transmission AC signal is sent to the AFE circuit via the transformer 11.
At this time, if the resistance value of the resistor 19 is matched with the impedance of the AFE circuit and the line viewed from the secondary winding 112 through the transformer 11, the connection between the secondary winding 112 of the transformer 11 and the resistor 19 is made. Since the point is a neutralization point between the amplified transmission signal and the reverse phase signal, the transmission signal does not appear at the connection point. Therefore, no transmission signal appears at the output terminal of the amplifier 21 whose gain is defined by the resistors 20 and 22.

On the other hand, the received signal transmitted from the exchange of the office reaches the primary winding 111 of the transformer 11 via the line and the AFE circuit, and is guided to the secondary winding 112. One end of the secondary winding 112 of the transformer 11 is connected to the output terminal of the operational amplifier 17 having a low impedance, which is equivalent to connecting to the ground for a received signal. Secondary winding 1 of transformer 11
12 is connected to the output terminal of the low-impedance operational amplifier 15 via a resistor 19, which is equivalent to connecting the received signal to the ground via the resistor 19. Here, assuming that the resistance value of the resistor 20 is sufficiently larger than the resistance value of the resistor 19, the impedance of the transformer 11 viewed from the primary winding 111 (line) of the transformer Is the impedance converted by the turns ratio. If this impedance is adjusted to the characteristic impedance Ro of the line, a good terminal that prevents reflection of the received signal to the station side can be obtained. The received signal appearing at the connection point between the secondary winding 112 of the transformer 11 and the resistor 19 is amplified to an appropriate level by an operational amplifier 21 whose gain is defined by the resistors 20 and 22, The minute is cut and the received signal voltage Vo
From the receiving terminal To to the receiver.

As described above, the transmission signal is transmitted to the line side, but does not appear at the reception terminal To, and only the reception signal from the line appears at the reception terminal To at an appropriate level, thereby realizing a side tone prevention function. Have been. Note that when the DC bias at the transmission terminal Ti and the reception terminal To may be the ground potential, the capacitors 12 and 23 can be omitted.

[0010]

However, the hybrid coupling circuits shown in FIGS. 2 and 3 use the transformers 3 and 11, respectively. Therefore, the hybrid coupling circuit becomes heavy and large and expensive. further,
Since the transformers 3 and 11 are easily affected by magnetic noise, a technically satisfactory hybrid coupling circuit cannot be formed.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is provided in a communication terminal connected to a paired line and has a reception terminal and a transmission terminal. The received signal supplied through the line is supplied to the receiving terminal, and the transmitted signal supplied to the transmitting terminal is transmitted to the line without leaking to the receiving terminal. A first photocoupler driving circuit, a first photocoupler, a second photocoupler driving circuit,
, A current / voltage conversion circuit, a first capacitor, and an addition circuit.

The first photocoupler drive circuit is a circuit for generating a first drive signal according to a transmission voltage on a transmission terminal. The first photocoupler has an input connected to the first photocoupler drive circuit and an output optically coupled to the input and connected to a line, and is driven by the first drive signal. The output unit sends a current corresponding to the transmission voltage to the line as a transmission signal. The second photocoupler driving circuit is a circuit that generates a second driving signal according to the line voltage. The second photocoupler has an input connected to the second photocoupler drive circuit and an output optically coupled to the input, and is driven by the second drive signal to output a line voltage from the output. To output a current corresponding to. The current / voltage conversion circuit is a circuit that is connected to the output section of the second photocoupler and converts the output current of the second photocoupler into a voltage signal. The first capacitor is connected to the current / voltage conversion circuit and has a function of cutting a direct current component in the voltage signal. The addition circuit is connected to the first capacitor and the transmission terminal, receives the transmission voltage and the DC signal from which the DC component has been cut, and cancels a component corresponding to the transmission voltage in the voltage signal by an addition operation of these components. To extract the received signal, and to provide the extracted received signal to the receiving terminal.

By adopting such a configuration, a first drive signal corresponding to the transmission voltage on the transmission terminal is generated by the first photocoupler drive circuit, and a current corresponding to the first drive signal is generated. , Are output from the first photocoupler as transmission signals and supplied to the line. When an AC voltage corresponding to the received signal given from the line is applied via the line, the second photocoupler driving circuit generates a second drive signal corresponding to the voltage of the line, and Is output from the second photocoupler. Current /
The output current of the second photocoupler is converted into a voltage signal by the voltage conversion circuit. The DC component of the voltage signal is cut by the first capacitor and applied to the adding circuit. Here, even when a voltage corresponding to the transmission signal appears on the line, the voltage is similarly supplied to the addition circuit on the output voltage of the current / voltage conversion circuit via the first capacitor. By adding the transmission voltage from the terminal and the output voltage of the current / voltage conversion circuit via the first capacitor, the component corresponding to the transmission voltage is canceled, and only the reception signal is extracted and given to the reception terminal.

In a second aspect, the first aspect of the first aspect is provided.
Has an input section connected in series to the input section of the first photocoupler and an output section optically coupled to the input section, and the output section of the first photocoupler outputs from the output section. A negative feedback circuit including a third photocoupler that outputs a current having the same value as the current to be supplied is formed in the path, and the second photocoupler driving circuit has an input connected in series to an input section of the second photocoupler. Feedback circuit having a first photocoupler and a fourth photocoupler that outputs a current having the same value as the current output from the output unit of the second photocoupler from the output unit. Is formed. By employing such a configuration, the first photocoupler driving circuit generates the first drive signal according to the amount of negative feedback, but flows to the output section of the third photocoupler which is a path for negative feedback. The current and the current flowing to the output of the first photocoupler become the same. Similarly, the second photocoupler driving circuit generates a second drive signal according to the amount of negative feedback, and the current flowing through the output of the fourth photocoupler, which is a path for negative feedback, and the second photocoupler And the current flowing through the output section becomes the same.

According to a third aspect, in the hybrid coupling circuit according to the second aspect, the following configuration is provided. That is, the second photocoupler driving circuit has a resistor having one end connected to one of the lines, and a current flowing through the resistor flows to an output section of the fourth photocoupler.
Negative feedback is established. One end is connected to one of the lines, and a constant current circuit is provided for supplying power by supplying a constant current from one of the lines to a portion of the second photocoupler driving circuit other than the resistor. By adopting such a configuration, the variation of the current flowing through the line appears only in the current flowing through the second and fourth output units, and the current has a value determined by the line voltage and the resistance. .

According to a fourth aspect, in the hybrid coupling circuit according to the third aspect, the following configuration is provided. That is, the second photocoupler driving circuit is connected in series to the resistor connected to the line, and is connected in parallel to the resistor and the second capacitor, and a second capacitor through which a current in which a DC component is cut is passed through the resistor. A DC bias supply unit for supplying a DC bias current to the second photocoupler; and a current flowing through a resistor, a second capacitor, and the DC bias supply unit flowing to an output unit of the fourth photocoupler. The configuration is such that feedback is established. By adopting such a configuration, a DC bias current that does not depend on the line voltage flows from the DC bias supply unit to the output unit of the fourth photocoupler. An alternating current flows through the output section.

According to a fifth aspect of the present invention, the hybrid coupling circuit according to the first to third or fourth aspects has the following configuration. That is, the first photocoupler drive circuit includes a first DC bias supply unit that supplies a DC bias current to the first photocoupler, and a first AC drive unit that generates an AC transmission voltage corresponding to the transmission voltage. It consists of. By employing such a configuration, a DC bias current for driving the first photocoupler is generated in the first DC bias supply unit.

According to a sixth aspect, in the hybrid coupling circuit according to the first to third or fifth aspects, the following configuration is provided. That is, the second photocoupler driving circuit includes a second DC bias supply unit for supplying a DC bias current to the second photocoupler, and a second AC driving unit for generating an AC reception voltage corresponding to a line voltage. It is composed of By employing such a configuration, a DC bias current that is not linked to a voltage change of a line for driving the second photocoupler is generated in the second DC bias supply unit.

According to a seventh aspect of the present invention, in the hybrid coupling circuit of the first to fifth or sixth aspects, the current / voltage conversion circuit is provided with a third DC bias supply section for supplying a DC bias current, and The DC bias current is added to the output current of the photocoupler and then converted to the voltage signal. By employing such a configuration, the DC bias voltage component of the voltage signal output from the current / voltage conversion circuit can be returned to near zero. According to an eighth aspect, in the hybrid coupling circuit according to the first to sixth or seventh aspects, the first transistor or the current mirror circuit for amplifying the output current of the first photocoupler, or the second transistor.
At least one of a second transistor or a current mirror circuit that amplifies the output current of the photocoupler. By employing such a configuration, even if the conversion efficiency of the first and second photocouplers is low, the first
And the second transistor compensates it.

According to a ninth aspect, in the hybrid coupling circuit according to the first to eighth aspects, the hybrid coupling circuit is connected to the transmission terminal,
A voltage amplifier circuit for amplifying the transmission voltage is provided. By employing such a configuration, even when the amplitude of the transmission voltage is low, it is amplified by the voltage amplifier circuit.
According to a tenth aspect, in the hybrid coupling circuit according to the ninth aspect, the following configuration is provided. That is, a third capacitor for AC coupling between the transmission terminal and the voltage amplifier circuit, a fourth capacitor for AC coupling between the voltage amplifier circuit and the first photocoupler circuit, a voltage amplifier circuit and an addition circuit. There is provided at least one of a fifth capacitor for AC coupling between the first and second capacitors or a sixth capacitor for AC coupling between the addition circuit and the receiving terminal. By adopting such a configuration, the DC component is cut by AC coupling by the third to sixth capacitors, so that only the AC component is supplied to the voltage amplifier circuit, the first photocoupler driving circuit or the adding circuit. Will be entered.

In the eleventh invention, the communication terminal is provided in a communication terminal which is constituted by a balanced cable and is connected to a paired line.
A hybrid coupling having a receiving terminal and a transmitting terminal, wherein a receiving signal provided through the line is provided to the receiving terminal, and a transmitting signal provided to the transmitting terminal is transmitted to the line without leaking to the receiving terminal. The circuit has the following configuration. That is, a first amplifier circuit having an output impedance sufficiently lower than the characteristic impedance of the balanced cable, connected to the transmission terminal, and amplifying the voltage on the transmission terminal as a transmission signal, and a characteristic impedance of the balanced cable. A second amplifier circuit having an output impedance sufficiently lower than that of the first amplifier circuit and connected to the output terminal of the first amplifier circuit, and outputting a signal in reverse phase to the amplified transmission signal;
A first matching resistor connected between the output terminal of the second amplifier circuit and one of the lines, and a second matching resistor connected between the output terminal of the first amplifier circuit and the other of the line And an input terminal connected to a first connection point to which the first matching resistor and one of the lines are connected, and a signal voltage appearing at the first connection point and a transmission signal output by the first amplifier circuit. The input terminal is connected to a third connection point where the third amplifier circuit that adds the voltage and the voltage at a constant gain ratio, and the second connection point where the second matching resistor and the other of the lines are connected, and appears at the second connection point. A fourth amplifier circuit for amplifying the signal voltage in a phase opposite to that of the third amplifier circuit, and a fifth amplifier for adding the output signal of the third amplifier circuit and the output signal of the fourth amplifier circuit at a constant gain ratio And a circuit.

According to a twelfth aspect, in the hybrid coupling circuit according to the eleventh aspect, the second amplifier is connected to the first amplifier.
The phase frequency characteristic is improved by adopting a configuration that amplifies the transmission signal by using an amplifier that obtains an output of a phase opposite to that of the amplifier.

By adopting such a configuration, if the input impedance of the third and fourth amplifier circuits is made sufficiently higher than the characteristic impedance of the line, the output terminal of the first amplifier circuit and the output terminal The first and second matching resistors and the impedance corresponding to the characteristic impedance of the line are connected in series between the output terminal of the second amplifier circuit and the signal obtained by amplifying the voltage of the transmission terminal. Given to the line in the form. The in-phase components on the paired lines are canceled by being added by the fifth amplifier circuit via the third amplifier circuit and the fourth amplifier circuit, so that only the differential component is output from the fifth amplifier circuit. Appears at the output terminal. Here, if the gain of each amplifier circuit is adjusted, the output voltage component of the first amplifier circuit, which should be included in the differential component on the output terminal of the fifth amplifier circuit via the third amplifier circuit, becomes , Can be erased by the output voltage component of the first amplifier circuit included in the output signal of the fourth amplifier circuit.

According to a thirteenth aspect or a fourteenth aspect, in the hybrid coupling circuit according to the eleventh or twelfth aspect, the signal voltage appearing at the first connection point and the signal voltage appearing at the second connection point are added at a constant gain ratio. A first amplifier circuit for adding and amplifying a voltage on the transmission terminal and an output signal of the sixth amplifier circuit at a constant gain ratio, and a second amplifier circuit for the first amplifier circuit. The addition amplification result of the circuit or the voltage on the transmission terminal and the output signal of the sixth amplifier circuit are added and amplified at a constant gain ratio, and the third amplifier circuit determines the signal voltage appearing at the first connection point and the signal voltage. The addition result of the first amplifier circuit and the output signal of the sixth amplifier circuit are added and amplified at a constant gain ratio. By employing such a configuration, the output voltage of the sixth amplifier circuit becomes zero for the differential component of the voltage on the paired line, and the output voltage is effectively output only for the in-phase component. .
The output voltage of the sixth amplifier circuit is added and amplified by the first and second amplifier circuits, respectively. Here, when the gains of the first to third amplifier circuits are adjusted such that the output voltages of the first to third amplifier circuits become the voltages of the in-phase components, the first to third matching resistors are turned off. The current due to the in-phase component on the line hardly flows.

According to a fifteenth aspect, in the hybrid coupling circuit according to the twelfth or fourteenth aspect, the first and second hybrid coupling circuits are provided.
Amplifying the transmission signal before the amplifier circuit of
By providing the seventh amplifier circuit for the second amplifier circuit, it is possible to amplify and transmit a minute transmission signal.

According to a sixteenth aspect, in the hybrid coupling circuit according to the eleventh to fifteenth aspects, instead of using the first to fifth amplifier circuits, a signal voltage appearing at the first connection point and the second voltage are supplied to the second connection point. , The output voltage of the first or second amplifier circuit, and the output voltage of the sixth amplifier circuit, if present, at a constant gain ratio. With the configuration using the eighth amplifier circuit for amplification, the entire circuit is simplified and power consumption can be reduced.

According to a seventeenth aspect, in the hybrid coupling circuit according to the eleventh or sixteenth aspect, the following configuration is provided. In other words, a first circuit which is inserted and connected between one of the lines and the first connection point and cuts the input and output of DC current.
And a second capacitor inserted and connected between the other end of the line and the first connection point to cut off the input and output of the direct current. By adopting such a configuration, there is no input / output of DC current from the line.

According to the eighteenth and nineteenth aspects, the hybrid coupling circuit according to the seventeenth aspect has the following configuration. That is, first transient current bypass means connected between the first connection point side electrode of the first capacitor and the second connection point side electrode of the second capacitor and bypassing the transient current. Second transient current bypass means connected between the first connection point electrode of the first capacitor and the ground, and bypassing the transient current; and a second connection point electrode of the second capacitor. And at least one of a third transient current bypass unit that is connected between the power supply and the ground and bypasses the transient current. By adopting such a configuration, even if the charging current of the first and second capacitors generated at the time of connection between the line and the hybrid coupling circuit or the like flows as a transient current, the charging current is first, The current is bypassed by any of the second and third transient current bypass units.

According to a twentieth aspect, in the hybrid coupling circuit according to the eleventh to nineteenth aspects, a capacitor coupling (cutting a DC input signal) is used in an addition input section of the first to eighth amplifier circuits. The DC component is prevented from being amplified and transmitted, and the output dynamic range of the amplifier can be effectively used.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 4 is a block diagram showing the relationship between a central office exchange and communication terminals. The exchange 41 of the station and the communication terminal 42 are connected by a pair of lines 43 constituted by a local cable or the like. The exchange 41 is provided with a DC power supply 41a,
The DC voltage Vdc1 generated by the DC power supply 41a
An AC signal from an AC signal source 41b having an output impedance 41c whose value is Rs is superimposed on
Is to be given. The DC resistance and capacitance per unit length of the line 43 are determined by standards, and the overall DC resistance RL, characteristic impedance Ro, and the like are determined from these standard values. In the communication terminal 42, the line 43
Is connected to the AFE circuit 42a. The hybrid coupling circuit 42b is connected to the terminals L1 and L2 of the AFE circuit 42a. The AFE circuit 42a includes a circuit for connecting / disconnecting the hybrid coupling circuit 42b to / from the line 43, a polarity inversion detecting unit, a bell signal detecting unit, an off-hook current forming unit, a dial pulse generating unit, and the like.

FIG. 1 is a circuit diagram of a hybrid coupling circuit showing a first embodiment of the present invention in FIG. This hybrid coupling circuit corresponds to the first invention, and prevents DC coupling between the terminal 42 and the line 43 and the transmission terminal Ti and the reception terminal To connected to a modem (not shown). , The transmission voltage V given from the terminal Ti.
a first photocoupler 51 for passing an output current according to i to the AFE circuit 42a, and a first photocoupler driving circuit 52 for driving a light emitting diode 51a which is an input part of the photocoupler 51 according to the transmission voltage Vi. And The collector and the emitter of the phototransistor 51b, which is the output section of the photocoupler 51, are connected to the line 43 via the terminals L1 and L2 of the AFE circuit 42a.

The first photocoupler driving circuit 52 includes an operational amplifier 52a having a positive-phase input terminal (+) connected to a terminal Ti and an output terminal connected to the anode of a photodiode 51a, and two resistors 52b. , 52c. The resistor 52b connects between the inverting input terminal (-) of the amplifier 52a and the DC voltage Vdc2. The resistor 52c sets the potential of the positive-phase input terminal of the amplifier 52a, and is connected between the positive-phase input terminal and the ground. The cathode of the photocoupler 51a is connected to a connection point between the inverting input terminal of the amplifier 52 and the resistor 52b. The hybrid coupling circuit further includes a second photocoupler 53 and a second photocoupler driving circuit 54. A current / voltage conversion circuit 55 and a first capacitor 56 are provided on the output side of the photocoupler 53. And an adder circuit 57 are connected in order. Photo coupler 5
3, while preventing DC coupling between the line 43 and the terminal,
An output current corresponding to the line voltage is caused to flow to the receiving side of the terminal, and has a light emitting diode 53a as an input unit and a phototransistor 53b as an output unit. The photocoupler driving circuit 54 drives the light emitting diode 53a in accordance with the line voltage, and includes a resistor 54a. One end of the resistor 54a is connected to one of the lines 43 via the terminal L1 of the AFE circuit 42a.
The other end is connected to the anode of the light emitting diode 53a. The cathode of the light emitting diode 53a is the AFE circuit 4.
It is connected to the other side of the line 43 via the terminal L2 of 2a. The emitter of the phototransistor 53b of the photocoupler 53 is connected to the power supply voltage (-V). Current /
The voltage conversion circuit 55 is a circuit for converting the output current of the photocoupler 53 into a voltage signal on the terminal side. The inverting input terminal (-) is connected to the collector of the phototransistor 53b. It comprises an operational amplifier 55a connected to the ground, and a negative feedback resistor 55b connecting between the output terminal and the inverting input terminal of the amplifier 55a.

The capacitor 56 is connected to the current / voltage conversion circuit 5
5 cuts the DC component of the output voltage, and one electrode is connected to the output terminal of the amplifier 55a. The addition circuit 57 is a circuit that adds the output voltage of the current / voltage conversion circuit 55 from which the DC component has been cut and the transmission voltage Vi at an appropriate ratio, cancels the transmission voltage Vi, and amplifies the transmission voltage Vi. Is connected to one end of the resistor 57a, a resistor 57b having one end connected to the terminal Ti and the other end connected to the other end of the resistor 57a, and an inverting input terminal connected to a connection point between the resistors 57a and 57b. (-) Is connected and the operational amplifier 57c is connected to the positive-phase input terminal (+) to the ground. A resistor 57d is connected between the output terminal and the inverting input terminal of the amplifier 57c, and a negative feedback is applied to the amplifier 57c. The output terminal of the amplifier 57c is connected to the terminal To.

Next, the operation of the hybrid combination circuit of FIG. 1 will be described. The positive input terminal of the amplifier 52a is connected to the resistor 52
c, and the output terminal of the amplifier 52a is connected to the input photodiode 51a of the photocoupler 51.
To the inverting input terminal of the amplifier 52a, and to the power supply Vdc2 via a resistor 52b. Therefore, assuming that the input current of the amplifier 52a is small and the voltage drop at the resistor 52c is negligible, negative feedback is applied to the amplifier 52a such that the DC potential of the inverting input terminal becomes the ground potential. Therefore, the DC current Idc1 flows through the photodiode 51a and the resistor 52b.
Assuming that the resistance value of the resistor 52b is R52b, the DC current I
dc1 can be represented by the following equation (1). Idc1 = -Vdc2 / R52b (1) In this state, when the AC transmission voltage Vi is input to the positive-phase input terminal of the amplifier 52a, the photodiode 51a and the resistor 52b further receive the following equation (2). AC current Iac1
Flows through the photodiode 51a, and Idc1 and Idc1
The combined current IR1 of ac1 flows to generate an optical signal. Iac1 = Vi / R52b (2) Since a negative optical signal cannot be generated in the photocoupler 51, if the DC voltage Vdc2 is always maintained at a voltage value satisfying the following expression (3), Iac1 << Idc1, and
An optical signal reflecting the change in the voltage Vi can be generated. Vi <<-Vdc2 (3) The output phototransistor 51b of the photocoupler 51 has a current of the following formula (4) obtained by multiplying the combined current IR1 of the currents Idc1 and Iac1 by the conversion efficiency B1 of the photocoupler 51. I51b flows. I51b = B1 (Idc1 + Iac1) = (B1 / R52b) (-Vdc2 + Vi) (4)

On the other hand, the light emitting diode 53a of the photocoupler 53 has a supply voltage Vdc1 output from the DC power supply 41a of the exchange 41, a DC resistance RL of the line 43, and a resistance R54a of a resistor 54a of the photocoupler driving circuit 54.
And a DC current based on the DC current (Vdc2 (B1 / R52b)) output from the photocoupler 51, and further, the following AC current flows. The AC current flowing through the light emitting diode 53a of the photocoupler 53 is the AC signal source 41b of the exchange 41.
, The AC current determined by the signal source impedance Rs, the characteristic impedance Ro of the line 43, and the resistance value R54a, the AC current (Vi (B1 / R52b)) output from the photocoupler 51, and the signal source of the exchange 41. There is an alternating current determined by the impedance Rs, the characteristic impedance Ro of the line 43, and the resistance value R54a.

The input resistance of the photocoupler 53 is
When the DC current Idc2 flowing through the light emitting diode 53a of the photocoupler 53 is obtained by assuming that it is sufficiently small and negligible compared to the resistance value R54a of a, it can be expressed by the following equation (5). Idc2 = Vdc1 / (RL + R54a + RS) + Vdc2 (B1 / R52b) (RL + RS) / (RL + RS + R54a) (5)

Further, the signal source impedance RS and the resistance R54a, which is a resistance for seeing the terminal 42 from the line 43, are adjusted to the characteristic impedance Ro of the line 43,
Since S = R54a = Ro and the principle is explained, ignoring the loss to the AC signal on the line 43, the exchange 4
The AC signal current Is input to the photodiode 53a is generated by the voltage Vs generated by the AC signal source 41b.
Is represented by the following equation (6). Is = Vs / (2Ro) (6) The output AC current of the photocoupler 51 (Vi (B1 / R52)
According to b)), the AC signal current Io input to the photodiode 53a is expressed by the following equation (7). Io = −Vi (B1 / R52b) · Ro / (Ro + Ro) = − Vi · B1 / (2R52b) (7)

Since the AC signal current Io is also the amount of the signal sent to the line 43, the transmission voltage VoL to the line 43 is expressed by the following equation (8). VoL = Io · Ro = −Vi · B1 · Ro / (2R52b) (8)

The current I53b flowing through the output phototransistor 53b of the photocoupler 53 is
Using the conversion efficiency B2 in the above equation, the following equation (9) is used. I53b = B2 (Idc2 + Is + Io) (9) Also in this case, the DC current component Idc2 needs to be larger than the sum of the peak values of the AC signal current components Is and Io. The output voltage Vr of the current / voltage conversion circuit 55 composed of the amplifier 55a and the resistor 55b is
Assuming that the resistance value of the resistor 55b is R55b, the following (1)
0). Vr = I53b R55b = B2Idc2 + VsB2R55b / (2Ro) -ViB1B2R55b / (2R52b) (10)

The DC component B2 · Idc2 of the output voltage Vr of the current / voltage conversion circuit 55 is cut by the capacitor 56, and only the AC component Vrac of the following equation (11) is given to the addition circuit 57. Vrac = Vs · B2 · R55b / (2Ro) −Vi · B1 · B2 · R55b / (2R52b) (11) The first term of the equation (11) is a signal component transmitted from the line 43 side. And the second term is a loopback component of the transmission signal of the terminal. If the loopback component is canceled at the time of addition by the addition circuit 57, reception having a sidetone prevention function can be realized.

The output voltage Vo of the adding circuit 57 is equal to
The resistance values of 7a, 57b, and 57d are R57a,
R57b and R57d can be expressed by the following (12). Vo = -Vrac.R57d / R57a-Vi.R57d / R57b =-(Vs.B2.R55b / (2Ro) -Vi.B1.B2.R55b / (2R52b)) R57d / R57a -Vi.R57d / R57b ..・ (12)

Therefore, if the resistance is selected so as to satisfy the following equation (13), the loopback component is canceled. Then, the output voltage of the adder circuit 57, that is, the received signal of the terminal 42, can be expressed by equation (14). B1 • B2 • R55b • R57d / (2R52b • R57a) = R57d / R57b B1 • B2 • R55b • R57b / (2R52b • R57a) = 1 •• (13) Vo = -Vs • B2 • R55b • R57d / (2Ro) · R57a) · · · (14) Thus, the transmission signal Vi is sent to the line 43 side.
Only the reception signal from the line 43 does not appear at the reception terminal To, but appears at the reception terminal To, thereby realizing a hybrid coupling circuit having a sidetone prevention function.

As described above, in the first embodiment,
As shown in FIG. 1, the first and second photocouplers 51, 53
And photocoupler driving circuits 52 and 54 for driving the photocouplers 51 and 53 based on the voltage Vi or the voltage of the line 43, a current / voltage conversion circuit 55, a capacitor 56, and an addition circuit 57. So the following (1)
Advantages such as (3) are obtained. (1) A hybrid coupling circuit that prevents direct-current coupling with the line 43 without using a transformer can be realized. (2) Since no transformer is used, magnetic noise can be prevented from entering, and a high-quality hybrid coupling circuit can be realized. (3) Since no transformer is used, not only the weight and size of the hybrid coupling circuit can be reduced, but also the cost can be reduced. If the output dynamic range of the adding circuit 57 is sufficient, the same effect can be obtained even if the capacitor 56 is moved between the adding circuit 57 and the receiving terminal To.

Second Embodiment FIG. 5 is a circuit diagram of a hybrid coupling circuit showing a second embodiment of the present invention, and is common to elements in FIG. 1 showing the first embodiment and common elements. Are given. This hybrid coupling circuit is a circuit provided together with the AFE circuit 42a in the communication terminal 42 in FIG. 4 similarly to the first embodiment, and includes a transmission terminal Ti, a reception terminal To similar to FIG. First and second photocouplers 51 and 53;
It has a capacitor 56 and an addition circuit 57, and includes first and second photocoupler driving circuits 58 and 59 and a current / voltage conversion circuit 60, which are different from those of the first embodiment.

The photocoupler driving circuit 58 is connected between the terminal Ti and the light emitting diode 51a of the photocoupler 51, and has the same operational amplifier 52a as in FIG.
Has a resistor 52b having one end connected to the inverting input terminal and a resistor 52c having one end connected to the positive-phase input terminal. The other end of the resistor 52b is connected to one electrode of a newly provided capacitor 58a. The other electrode of the capacitor 58a and the other end of the resistor 52c are connected to the ground. The photocoupler driving circuit 58 includes:
Further, a first DC bias supply unit 58b composed of a constant current source is provided. DC bias supply unit 58b
Is connected to the cathode of the light emitting diode 51a of the photocoupler 51. Amplifier 52a, resistors 52b, 52
c and the capacitor 58a constitute a first AC drive unit that generates an AC signal according to the AC signal voltage Vi input from the terminal Ti, and perform a substantial addition operation with the current output from the DC bias supply unit 58b. Works to do.

The photocoupler driving circuit 59 has the same resistor 54a as in the first embodiment connected to one of the lines 43 via the terminal L1 of the AFE circuit 42a. The other end of the resistor 54a is connected to one electrode of a newly provided capacitor 59a. The other electrode of the capacitor 59a is connected to the anode of the light emitting diode 53a of the photocoupler 53. This photocoupler driving circuit 5
9 is further provided with a second DC bias supply unit 59b. The DC bias supply unit 59b is connected between a connection point between the capacitor 59a and the anode of the light emitting diode 53a and the terminal L1. Resistance 54a
And the capacitor 59a constitute a second AC drive unit for performing drive according to the AC voltage between the lines 43, and function to perform a substantial addition operation with the current Ib2 output from the DC bias supply unit 59b. .

The current / voltage conversion circuit 60 has an operational amplifier 55a similar to that shown in FIG. 1 having two input terminals connected to the ground and the collector of the phototransistor 53b of the photocoupler 53, respectively, and a negative feedback to the amplifier 55a. A DC bias supply element 60a having a resistance 55b to be applied and newly provided is connected to the inverting input terminal of the amplifier 55a. The DC bias supply element 60a
It functions so as to add the DC bias current Ib3 to the input side of the current / voltage conversion circuit 60.

Next, the operation of the hybrid combination circuit of FIG. 5 will be described. In the photocoupler driving circuit 58, the resistance 52
Since the capacitor 58a is connected in series with the capacitor b, the DC current Idc1 flowing through the resistor 52b becomes zero, and only the AC voltage current corresponding to the voltage Vi flows. The DC bias supply unit 58b supplies a DC bias current Ib1 necessary for driving the photocoupler 51. The AC current and the DC bias current Ib1 are added to the light emitting diode 51a of the photocoupler 51 and given, and the light emitting diode 51a is driven.

In the photocoupler driving circuit 59, the resistor 54
Since the capacitor 59a is connected in series to the resistor a, the DC current as in the equation (5) does not flow through the resistor 54a, and only the AC signal current flows. The DC bias supply unit 59b
A DC bias current Ib2 necessary to drive the input light emitting diode 53a of the photocoupler 53 flows. The AC signal current and the DC bias current Ib2 are supplied to the light emitting diode 53a of the photocoupler 53, and the light emitting diode 53a is driven. By providing the DC bias supply units 58b and 59b in this manner, the DC bias current for the light emitting diodes 51a and 53a can be set independent of the power supply voltage and the voltage between the lines 43, and each DC bias current can be set. Can be set to an optimal and stable value. In particular, the line voltage is effective because it varies depending on the distance of the line 43, that is, the DC resistance RL.

The DC bias currents corresponding to the DC bias currents Ib1 and Ib2 set by the DC bias supply units 58b and 59b in the photocoupler driving circuits 58 and 59 flow to the light emitting diode 53a of the photocoupler 53.
A corresponding current including a DC component is output from the phototransistor 53b. Therefore, the output signal of the current / voltage conversion circuit 60 also has a DC bias voltage. If the current value supplied by the DC bias supply unit 60a in the current / voltage conversion circuit 60 is set to a value that is substantially equal to the DC component output from the phototransistor 53b and is subtracted, the current / voltage conversion is performed. The output DC bias voltage of circuit 60 can be returned to near zero. As a result, the finite dynamic range of the current / voltage conversion circuit 60 can be used effectively, and an AC signal voltage with less distortion can be applied to the subsequent stage. Capacitor 56 and addition circuit 5
7 performs the same operation as in the first embodiment, extracts only the received signal, and supplies it to the receiving terminal To.

As described above, in the second embodiment,
Not only have the same advantages as (1) to (3) of the first embodiment, but also the following advantages (4) and (5). (4) The photocoupler driving circuits 58 and 59 are provided with DC bias supply units 58b and 59b, respectively.
Since the DC bias current for driving the light emitting diodes 51a and 53a in the circuit 53 is set independent of the power supply voltage and the line voltage in the line 43, each DC bias current is optimized and stable. Can be a value. (5) Since the DC bias supply unit 60a is provided on the input side of the current / voltage conversion circuit 60, the current / voltage conversion circuit 60
, The DC bias voltage in the output signal can be set near zero, and the output voltage range can be used effectively for an AC signal (the dynamic range can be used effectively for an AC signal).

Third Embodiment FIG. 6 is a circuit diagram of a hybrid coupling circuit showing a third embodiment of the present invention, and is common to elements in FIG. 1 showing the first embodiment and common elements. Are given. This hybrid coupling circuit is a circuit provided together with the AFE circuit 42a in the communication terminal 42 in FIG. 4 similarly to the first embodiment, and has the same transmission terminal Ti, reception terminal To, first and second terminals as those in FIG. It has second photocouplers 51 and 53, a current / voltage conversion circuit 55, a capacitor 56, and an addition circuit 57, and has first and second photocoupler driving circuits 61 and 62 different in configuration from the first embodiment. It has.
The photocoupler driving circuit 61 includes an operational amplifier 52a and resistors 52b and 52c similar to those of the first embodiment, and a third photocoupler 61a having the same characteristics as the photocoupler 51 is newly incorporated in the negative feedback path. ing. The photo coupler 61a includes a light emitting diode 61aa and a photo transistor 61ab.

The light emitting diode 61aa is connected in series between the light emitting diode 51a in the photocoupler 51 and the ground, the collector of the phototransistor 61ab is connected to the power supply voltage (+ V), and the output transistor 61ab is The emitter is connected to the inverting input terminal (-) of the amplifier 52a.

As in the first embodiment, the photocoupler driving circuit 62 has a resistor 54a having one end connected to one end of the line 43 via the terminal L1 of the AFE circuit 42a. And a fourth Darlington-connected transistor 62b, 62c. The photo coupler 62a includes a light emitting diode 62aa and a photo transistor 62ab. The collector of the phototransistor 62ab is connected to the other end of the resistor 54a,
The emitter of the phototransistor 62ab is connected to the other side of the line 43 via the terminal L2 of the AFE circuit 42. The anode of the light emitting diode 62aa is connected to the cathode of the light emitting diode 53a of the photocoupler 53, and the cathode of the light emitting diode 62aa is connected to the collectors of the transistors 62b and 62c. The base of the transistor 62b is a phototransistor 62a
b and the connection point of the resistor 54a. The emitter of the transistor 62b is connected to the base of the transistor 62c.
It is connected to the other of the lines 43 via the E circuit 42.
Photocoupler 62a and two transistors 62b, 62
and c constitute a negative feedback circuit, and the output current of the photocoupler 62a flows according to the line voltage in the line 43.

Next, the operation of the hybrid coupling circuit will be described. In the first embodiment, since the light emitting diode 51a of the photocoupler 51 is connected between the output terminal of the amplifier 52a and the resistor 52b, the transmission voltage Vi, the DC bias power supply Vdc2, and the resistance R52b of the resistor 52b are different. The determined current passed through the light emitting diode 51a. On the other hand, in the hybrid coupling circuit of FIG.
A photocoupler 51 is connected between the output terminal 2a and the ground.
The light emitting diodes 51a and 61aa of the photocoupler 61a are connected in series, and the emitter of the phototransistor 61ab of the photocoupler 61a is connected to the inverting input terminal of the amplifier 52a so that negative feedback is established. Vdc2 and the resistance value R5 of the resistor 52b
2b flows through the phototransistor 61ab of the photocoupler 61a. The same current as this current also flows through the phototransistor 51b of the photocoupler 51 and is output to the line 43.

In the first embodiment, since the resistor 54a is connected to the light emitting diode 53a of the photocoupler 53, the current determined by the line voltage of the line 43 and the resistance R54a of the resistor 54a is: The light emitting diode 5
Flowed to 3a. On the other hand, in FIG. 6, the Darlington-connected transistors 62b and 62c operate as amplifiers, and negative feedback is established by the photocoupler 62a. Therefore, the line-to-line voltage of the line 43 and the resistance R54 of the resistor 54a.
and the current determined by the conversion efficiency of the photocoupler 62a is the phototransistor 62a of the photocoupler 62a.
b. In the photocoupler 53 having the light emitting diode 53a connected in series with the phototransistor 62ab, the phototransistor 53b allows a current having the same value as that of the phototransistor 62ab to flow. Here, if a high conversion efficiency is used for the photocouplers 53 and 62a, the current for the AC signal at each drive input side can be ignored with respect to the current for the AC signal at each drive output side. The output currents of 53 and 62a become current values determined by the line voltage of the line 43 and the resistance value R54a. Other operations in the hybrid coupling circuit in FIG. 6 are the same as those in the first embodiment.

As described above, in the third embodiment,
Since no transformer is used, (1) to (1) of the first embodiment
In addition to the same advantages as (3), the following (6),
It has advantages such as (7). (6) A current obtained by dividing the transmission voltage Vi by the resistance value R52b of the resistor 52b flows through the phototransistor 61ab of the photocoupler 61a constituting the negative feedback circuit of the operational amplifier 52a, and receives the same drive as the photocoupler 61a. A current equal to that of the phototransistor 61ab flows through the phototransistor 51b of the photocoupler 51. As a result, even if the relationship between the input and output of the photocouplers 51 and 61a is, for example, non-linear, the current sent out to the line 43 maintains the value of (Vi / R52b) and is not distorted.

(7) A current obtained by dividing the line voltage of the line 43 by the resistance R54a of the resistor 54a flows through the phototransistor 62ab of the photocoupler 62a constituting a negative feedback circuit for the Darlington-connected transistors 62b and 62c. In the phototransistor 53b of the photocoupler 53, a current having the same value as the current flowing in the phototransistor 62ab flows. As a result, even if the relationship between the inputs and outputs of the photocouplers 53 and 62a is, for example, non-linear, the output current of the photocoupler 53, which becomes the received signal current, is not distorted.

Fourth Embodiment FIG. 7 is a circuit diagram of a hybrid coupling circuit showing a fourth embodiment of the present invention, and the elements common to those in FIG. 6 showing the third embodiment are common. Reference numerals are attached. This hybrid coupling circuit is a photocoupler driving circuit 6 shown in FIG.
2 is changed to a photocoupler driving circuit 63,
Other configurations are the same as those in FIG.

As in the third embodiment, the photocoupler driving circuit 63 includes a resistor 54a having one end connected to one end of the line 43 via the terminal L1 of the AFE circuit 42a, a photocoupler 62a, and two Darlingtons. It has transistors 62b and 62c connected. A phototransistor 62ab of a photocoupler 62a is connected to the other end of the resistor 54a.
Of the phototransistor 62ab
Is connected to the other end of the line 43 via the terminal L2 of the AFE circuit 42a. Anode of light emitting diode 62aa of photocoupler 62a and AFE circuit 42a
And a terminal L1 of the constant current circuit 6 newly provided.
The cathode of a zener diode 63b is connected to a connection point between the constant current circuit 3a and the anode of the light emitting diode 62aa. The anode of the Zener diode 63b is connected to the emitter of the transistor 62c.

The light emitting diode 53 of the photocoupler 53 is connected between the cathode of the light emitting diode 62aa and the collectors of the transistors 62b and 62c connected in Darlington.
a is connected. The connection positions of the light emitting diode 53a and the light emitting diode 62aa can be reversed as shown in FIG. In the photocoupler driving circuit 63,
Power is supplied from the line 43 side to circuits other than the resistor 54a in the drive circuit 63 through the constant current circuit 63a, and a constant current value I63a flowing from the constant current circuit 63a is determined by a photocoupler. The current is larger than the maximum current (the DC bias current + the maximum value of the AC signal current) flowing through the light emitting diodes 53a and 62aa of 53 and 62a. An extra current that does not completely flow through the light emitting diodes 53a and 62aa flows through the Zener diode 63b. Note that, as described above, the Zener diode 63b only allows the above-described extra current to flow, and can be appropriately replaced with an element composed of a plurality of forward-series connected diodes.

Next, the operation of the hybrid combination circuit of FIG. 7 will be described. The basic operation is the same as in the third embodiment. Here, when the AC signal voltage in the line 43 fluctuates, the current flowing through the light emitting diodes 53a and 62aa of the serial photocouplers 53 and 62a fluctuates. The fluctuation is caused by the action of the constant current circuit 63a and the zener diode 63b. The difference does not result in a change in the terminal current of the AFE circuit 42a. The fluctuation of the terminal current of the AFE circuit 42a is only the fluctuation of the current flowing to the phototransistor 62ab of the photocoupler 62a that flows the same current as the phototransistor 53b of the photocoupler 53. Moreover,
This becomes the current determined by the change in the line voltage of the line 43 and the resistance value R54a of the resistor 54a, and the linearity is improved. Compared with the third embodiment, the effect of the conversion efficiency of the photocouplers 53 and 62a on the AC signal operation can be made completely zero, and the restriction of using a high conversion efficiency can be removed.

As described above, in the fourth embodiment,
Not only has the same advantages as the third embodiment, but also the following advantages (8) and (9). (8) The terminal current of the AFE circuit 42a varies only by the variation of the current flowing through the phototransistor 62ab of the photocoupler 62a, and the current value is determined by the line voltage and the resistance value of the resistor 54. , The linearity is improved, and the occurrence of distortion can be prevented. (9) The restriction on the conversion efficiency in the photocouplers 53 and 62a can be released.

Fifth Embodiment FIG. 8 is a circuit diagram of a hybrid coupling circuit showing a fifth embodiment of the present invention. Common elements are the same as those shown in FIG. 5 showing the second embodiment. Are given. This hybrid coupling circuit is different from the hybrid coupling circuit according to the second embodiment in that a first transistor 64 for amplifying the output current of the first photocoupler 51 and a second transistor for amplifying the output current of the second photocoupler 53 are provided. Two transistors 65
And a voltage amplifier circuit 66 for amplifying the terminal transmission voltage Vi
A third capacitor 67 for AC coupling between the voltage amplifier circuit 66 and the transmission terminal Ti;
A fourth capacitor 68 for AC-coupling between the input terminal 6 and the input side of the photocoupler driving circuit 58;
And a resistor 57b of the adder circuit 57 for AC coupling.
And a sixth capacitor 70 for AC coupling between the output terminal of the adder circuit 57 and the receiving terminal To. The voltage amplifier circuit 66 includes a resistor 66a having one end connected to the capacitor 67, and a resistor 66a.
Is connected to an input terminal of the amplifier 66b, and a resistor 66c for applying a negative feedback from the output terminal of the amplifier 66b to the input terminal.

However, the capacitors 67 to 70 can be omitted (short-circuited) when direct connection is possible with matching DC bias at each connection point. In addition, transistors 64 and 65
Also, the voltage amplifier circuit 66 can be omitted if the current or voltage at the corresponding location can be maintained at a certain level or higher.

Next, the operation of the hybrid combination circuit shown in FIG. 8 will be described. The DC bias supplied to the photocouplers 51 and 53 is necessary only for driving them, and only the AC signal needs to be amplified or added. Even if it is cut, there is no problem in the amplification and the addition operation. By cutting the DC component, it becomes possible to use an amplifier dedicated to an AC signal whose DC bias varies with the power supply voltage or temperature. The configuration of an amplifier dedicated to an AC signal is generally simpler than that of an operational amplifier that amplifies linearly including a DC component.

The basic operation of the hybrid combination circuit including the transistors 64 and 65, the voltage amplifier circuit 66, and the capacitors 67 to 70 is the same as that of the first to fourth embodiments. In addition, the transmission voltage Vi which is a transmission signal
Voltage amplifier circuit 66 and transistors 64 and 6
5, the value of V in the above equations (1) to (14)
The value of i is replaced by the following (15), and the conversion efficiencies B1 and B2 are further replaced by (16). Vi → Vi · R66c / R66a (15) where: R66c; resistance value of resistor 66c R66b; resistance value of resistor 66b R66c / R66b; gain of voltage amplifier circuit 66 B1 → B1 · b1 B2 → B2 · b2 · ··· (16) where b1; current amplification factor of transistor 64 b2; current amplification factor of transistor 65

In the fifth embodiment configured as described above, in addition to the advantages of the second embodiment, the following (1)
Advantages such as 0) to (12) are obtained. (10) Since the voltage amplifier circuit 66 is provided, the transmission voltage V
Even if i has a low level amplitude, it can be handled. (11) Since the transistors 64 and 65 are provided, even if the conversion efficiencies B1 and B2 of the photocouplers 51 and 53 are low, the output current is amplified, so that there is no problem. (12) Since the capacitors 67 to 70 are provided, it is possible to use an amplifier dedicated to an AC signal having a simple structure. Further, the DC bias at the transmission terminal Ti and the reception terminal To can be set freely. The transistors 64 and 65
May be replaced by a Darlington connection transistor, and by replacing the current mirror circuit with a current amplification factor of 1 or more, the distortion at the time of amplifying the output current of the photocouplers 51 and 53 can be reduced.

Sixth Embodiment FIG. 9 is a circuit diagram of a hybrid coupling circuit according to a sixth embodiment of the present invention. This hybrid coupling circuit,
As in the first embodiment, the communication terminal 42 in FIG.
A circuit provided together with the AFE circuit 42a, having a transmission terminal Ti and a reception terminal To,
Has a sufficiently lower output impedance than the characteristic impedance Ro of the balanced type cable constituting the terminal T.
The first amplifier circuit 71 amplifies the transmission voltage Vi given from i. The amplifier circuit 71 includes a resistor 71a having one end connected to the terminal Ti, an operational amplifier 71b having the other end of the resistor 71a connected to the inverting input terminal (-),
It comprises a resistor 71c connected between the output terminal of the amplifier 71b and the inverting input terminal, and the positive-phase input terminal of the amplifier 71b is connected to the ground.

The output terminal of the amplifier 71b, which is the output terminal of the first amplifier circuit 71, has an output impedance that is sufficiently lower than the characteristic impedance Ro of the line 43, and the voltage Vo1 given from the amplifier 71b is gained. A second amplifier circuit 72 that outputs the inverted-phase transmission voltage signal Vo2 inverted at zero dB is connected, and an output terminal of the amplifier circuit 72 has a first matching resistor 7 having a resistance value of Ro / 2.
3 is connected to one end. The other end of the resistor 73 is connected to a terminal L1 of the AFE circuit 42a at a first connection point N1,
It is connected to one of the lines 43 via the terminal L1. The amplifier circuit 72 includes a resistor 72a having one end connected to the output terminal of the amplifier 71b, an operational amplifier 72b having the other end of the resistor 72a connected to the inverting input terminal (−), and an output terminal of the amplifier 72b. A positive-phase input terminal of the amplifier 72b is connected to the ground. The output terminal of the amplifier 72b is the output terminal of the amplifier circuit 72.

The output terminal of the first amplifier circuit 71 is further connected to one end of a second matching resistor 74, and the other end of the resistor 74 is connected to the AFE circuit 42a at a second connection point N2.
Is connected to the other terminal L2. The resistance value of the resistor 74 is Ro / 2. The output terminal of the first amplifier circuit 71 and the other end of the first matching resistor 73 are connected to a third amplifier circuit 75. The amplifier circuit 75 is a circuit that adds a signal voltage appearing at a connection point N1 to which the matching resistor 73 is connected and a voltage output from the amplifier circuit 71 at a constant gain ratio, and one end is connected to the connection point N1. It has an addition resistor 75a and an addition resistor 75b having one end connected to the output terminal of the amplifier circuit 71. The other ends of the resistors 75a and 75b are both connected to the inverting input terminal (-) of the operational amplifier 75c. The output terminal and the inverting input terminal of the amplifier 75c are connected by a resistor 75d, and the positive input terminal of the amplifier 75c is connected to the ground. The output terminal of the amplifier 75c is the amplifier circuit 75
Output terminal.

This hybrid coupling circuit further includes:
A fourth amplifier circuit 76 for amplifying a signal voltage appearing on the terminal L2 side is provided. The amplifier circuit 76 has a connection point N
2, an operational amplifier 76a whose terminal L1 is connected to the positive-phase input terminal (+), a resistor 76b connected between the inverting input terminal (-) of the amplifier 76a and the ground, It comprises a resistor 76c connecting the output terminal and the inverting input terminal. The output terminal of the amplifier 76a is the output terminal of the amplifier circuit 76. A fifth amplifier circuit 77 is connected to the output sides of the third and fourth amplifier circuits 75 and 76. The amplifier circuit 77 includes a resistor 77a having one end connected to an output terminal of the amplifier circuit 75,
A resistor 77 having one end connected to the output terminal of the amplifier circuit 76
b. The other ends of these resistors 77a and 77b are both connected to the inverting input terminal (-) of the operational amplifier 77c. The output terminal and the inverting input terminal of the amplifier 77c are connected by a resistor 77d, and the positive-phase input terminal of the amplifier 77c is connected to the ground. Amplifier 77c
Are the output terminals of the amplifier circuit 77 and are connected to the reception terminal To.

Next, the operation of the hybrid combination circuit shown in FIG. 9 will be described. The amplifier circuit 71 includes a terminal-side transmission voltage Vi.
The purpose is to obtain an output impedance sufficiently lower than the characteristic impedance Ro. When the transmission voltage from the transmission terminal Ti is given with a sufficient amplitude necessary for transmission and an output impedance sufficiently low with respect to the characteristic impedance Ro, the amplifier circuit 71 can be omitted. The resistance value of each of the matching resistors 73 and 74 is set to Ro / 2, and the resistance value R75a of the addition resistor 75a of the amplifier circuit 75 for performing addition and the amplifier circuit 76
And the input resistance of the amplifier 76a of the
If it is set sufficiently high with respect to o, when viewed from the terminals L1 and L2 to the line 43 side constituted by the balanced cable, in the passing AC signal frequency band, it looks like the resistance Ro which is the characteristic impedance of the balanced cable. .

In such a setting, the resistance 75a and the input resistance of the amplifier circuit 76 can be ignored, and the transmission voltage V
A resistor 73 and a line are connected between an output terminal of an amplifier circuit 71 that outputs a voltage Vo1 obtained by amplifying i and an output terminal of an amplifier circuit 72 that outputs a reverse-phase transmission voltage Vo2 that is the reverse phase of the output voltage Vo1. This means that the characteristic impedance Ro and the resistor 74 are connected in series. Therefore, assuming that the resistance values of the resistors 73 and 74 are R73 and R74, the terminal L
1 and the output voltage VL2o on the terminal L2 are expressed by the following equations (17) to (20). Vo2 = −Vo1 (17) VL1o = (Vo2−Vo1) (Ro + R74) / (Ro + R74 + R73) + Vo1 = −2Vo · 0.75 + Vo1 = −0.5Vo1 (18) VL2o = (Vo2−Vo1) ) (R74) / (Ro + R74 + R73) + Vo1 = −2Vo1 · 0.25 + Vo1 = 0.5Vo1 (19) VLo = VL1o−VL2o = −Vo1 (20)

As described above, the voltage Vo1 obtained by amplifying the transmission voltage Vi on the terminal side by the amplifier circuit 71 is provided between the terminal L1 and the terminal L2.
Is transmitted in the form of a balanced signal having an output impedance Ro. On the other hand, each of the resistors 75a, 75d, 76
b, 76c, 77a, 77b, 77d are respectively set to R75a, R75d, R76b, R76c, R7.
7a, R77b, and R77d, the gain G1 of the path added by the amplifier circuit 77 from the terminal L1 via the amplifier circuit 75, and the gain G2 of the path added by the amplifier circuit 77 from the terminal L2 via the amplifier circuit 76. Becomes the following equations (21) and (22). G1 = (R75d / R75a) (R77d / R77a) (21) G2 = − ((R76b + R76c) / R76b) (R77d / R77b) · (22)

Received voltage VL at terminal L1 with respect to ground
1 and the reception voltage VL2 at the terminal L2 are amplified by the gains G1 and G2 as shown in the following equation (23), and are amplified by the amplifier circuit 77.
Is output as the output voltage Vo. Vo = G1 · VL1 + G2 · VL2 (23) Here, if the absolute values of the gains G1 and G2 are set to be the same, the common mode noise in which the potentials of the terminals L1 and L2 fluctuate in the same phase with respect to the ground is obtained. , And does not appear in the output voltage Vo of the amplifier circuit 77. That is, the following equations (24) to (26) are obtained. G1 = −G2 = G (24) VL1 = VL2 = Vcom (25) Vo = VL1 · G−VL2 · G〜 = (VL1−VL2) G = (Vcom−Vcom) G = 0 ·・ ・ (26)

On the other hand, a balanced signal in which the potentials of the terminals L1 and L2 fluctuate in the opposite phase with respect to the ground is expressed by the following (2)
7), the output voltage Vo is increased by the addition as shown in the equations (28).
Appears in VL1 = −VL2 = Vs / 2 (27) Vo = ((Vs / 2) − (− Vs / 2)) G = Vs · G (28) The resulting balanced signal appears in the output voltage Vo of the amplifier circuit 77, and the common mode noise is canceled and eliminated.

VL1o = −0.5 V in the above equation (18)
o1 and VL2o = 0.5Vo1 in the equation (19) also appear as Vox in the output voltage Vo of the amplifier circuit 77.
This can be expressed by Expression (29) by Expression (26). Vox = (VL1o−VL2o) G = (− 0.5Vol−0.5Vol) G = (− Vol) G (29) However, regarding the output voltage Vo1 of the amplifier circuit 71,
There is a path that is added via the resistor 75b of the amplifier circuit 75 and appears in the output voltage Vo of the amplifier circuit 77. The gain in this path is G3, and the resistance of the resistor 75b is R75b.
Then, the voltage Voy appearing in the output voltage Vo of the amplifier circuit 77 on this path is expressed by the following equations (30) and (31). Therefore, the component of the voltage Vi in the output voltage Vo is expressed by Expression (32). G3 = (R75d / R75b) (R77d / R77a) (30) Voy = Vo1 · G3 (31) Vo = Vox + Voy = Vo1 (G3-G) (32)

Here, if the gain G3 is set to be equal to the gain G, the transmission voltage Vi on the terminal side becomes equal to the reception terminal To.
, And a side-tone prevention function is realized, making it a hybrid coupling circuit suitable for balanced cables. Eventually, FIG.
Is a circuit of the same type as the conventional circuit of FIG. 3 in which a center tap is provided in a transformer coil connected to the line side and the center tap is connected to the ground.

FIG. 10 is a circuit diagram showing an improved example of the hybrid coupling circuit of FIG. 9, and FIG. 11 is a circuit diagram showing an equivalent circuit of FIG. Elements in FIG. 10 and FIG. 11 that are common to those in FIG. 9 are denoted by common reference numerals. If the hybrid coupling circuit of FIG. 9 is directly connected to a telephone line on which a large DC voltage is superimposed, a large current may flow. Therefore, in the hybrid coupling circuit of FIG. 10, the terminal L1 and the first connection point N1 are connected by the first capacitor 81, and the terminal L2 and the second connection point N1 are connected.
2 is connected by a second capacitor 82. The capacitance values of these capacitors 81 and 82 are set to be the same, thereby preventing DC coupling between the line and the hybrid coupling circuit. FIG. 11 shows this as an equivalent circuit using a transformer.

The hybrid coupling circuit of this improved example includes:
Further, the transmission terminal Ti and the resistor 71a in the amplifier circuit 71
, A fourth capacitor 84 that AC-couples between the amplifier circuit 71 and the resistor 72a in the amplifier circuit 72, and a first connection point N1.
A fifth capacitor 85 for AC coupling between the amplifier circuit 75 and a resistor 75a in the amplifier circuit 75; a sixth capacitor 86 for AC coupling between the amplifier circuit 71 and the resistor 75b in the amplifier circuit 75; A seventh capacitor 87 for AC coupling between the connection point N2 and the positive-phase input terminal of the amplifier 76a in the amplifier circuit 76, and an eighth capacitor for AC coupling between the amplifier circuit 75 and the resistor 77a in the amplifier circuit 77. Capacitor 8
8, the amplifier circuit 76 and the resistor 77b in the amplifier circuit 77
A ninth capacitor 89 for AC-coupling between the amplifier circuit 77 and a first capacitor 89 for AC-coupling between the amplifier circuit 77 and the receiving terminal To.
0 capacitor 90 is provided. By providing these capacitors 83 to 90, as in the fifth embodiment, the DC component of the input signal in each of the amplifier circuits 71, 72, and 75 to 77 is cut off.
b, 72b, 75c, 76a, 77c may be dedicated to AC signals.

As described above, in the sixth embodiment,
It has the following advantages (13) to (16). (13) Amplifier circuits 71 and 7 connected as shown in FIG.
The provision of the matching resistors 73, 74 and the matching resistors 73, 74 makes it possible to transmit and receive a balanced signal to and from the line 43 of the balanced cable and to realize a hybrid coupling circuit capable of eliminating common mode noise. (14) By connecting the terminals L1 and L2 with the capacitors 81 and 82, a hybrid coupling circuit that prevents DC coupling with a capacitor that is less expensive than a transformer or a photocoupler can be realized.

(15) Since no transformer is used, a lightweight and compact hybrid coupling circuit resistant to magnetic induction noise can be realized. (16) Depending on the operating conditions of the photocoupler, there is a high possibility that the input and output become non-linear and distortion occurs.
Since the circuit of FIG. 10 does not include a non-linear element such as a photocoupler, a hybrid coupling circuit having high linearity with respect to an AC signal can be realized.

Seventh Embodiment FIG. 12 is a circuit diagram of a hybrid coupling circuit showing a seventh embodiment of the present invention, and has the same elements as those in FIGS. 9 and 10 showing the sixth embodiment. Are denoted by the same reference numerals. This hybrid coupling circuit is provided with the capacitors 81, 82, 83, and 90 shown in FIG. 10 in the circuit shown in FIG. 9, and the first connection point N1 side electrode of the capacitor 81 and the second connection point N2 side of the capacitor 82. Varistor 91 as first transient current bypass means connected between electrodes
A varistor 92, which is a second transient current bypass means connected between the first connection point N 1 side electrode of the capacitor 81 and the ground, and a second connection point N 2 side electrode of the capacitor 82. A varistor 93, which is a third transient current bypass unit connected to the ground, is newly provided, and the other configuration is the same as the circuit of FIG.

Next, the operation of the hybrid coupling circuit will be described. Since the operation for preventing the side signal from the AC signal and the operation for removing the common mode noise are the same as those in the sixth embodiment, the varistors 91 to 9 are used here.
Operation 3 will be described. At the time of connection to the line 43 or the like, a charging current transiently flows through the capacitors 81 and 82. Sixth
In this embodiment, these currents flow to the output side of the amplifier circuit 72 via the resistor 73, and also flow to the output side of the amplifier circuit 71 via the resistor 74. Therefore, the output sides of these amplifier circuits 71 and 72 have to be capable of withstanding the current. On the other hand, the varistors 91 to 9
In the hybrid coupling circuit shown in FIG. 12 having the circuit No. 3, if any one of the varistors 91 to 93 is turned on at the time of connection, the varistor 91 is turned on, and the transient charging current is bypassed. Therefore, the load on the output side of the amplifier circuits 71 and 72 is reduced, and the transient response time is also reduced.

As described above, in the seventh embodiment,
Since the varistors 91 to 93 are further provided for the hybrid coupling circuit in which the capacitors 81 and 82 are provided in the circuit of FIG. 9, the following advantages (17) and (18) are obtained. (17) Since the charging current of the capacitors 81 and 82 generated at the time of transition is bypassed by the varistors 91 to 93 which are turned on, the current flowing into the output side of the amplifier circuits 71 and 72 is reduced, and the burden can be reduced. . (18) Transient response characteristics at the time of connection can be shortened.

Eighth Embodiment FIG. 13 is a circuit diagram of a hybrid coupling circuit showing an eighth embodiment of the present invention, and FIG. 14 is a circuit diagram showing an equivalent circuit of FIG. Elements common to those in FIG. 9 showing the sixth embodiment in FIGS. 13 and 14 are denoted by the same reference numerals. In this hybrid coupling circuit, a sixth amplifier circuit 94 is newly provided in the hybrid coupling circuit of the sixth embodiment, and the first amplifier circuit 71 makes the output signal of the amplifier circuit 94 and the transmission voltage Vi have a constant gain. The second amplifier circuit 72 is configured to add the output signal of the amplifier circuit 94 and the output signal of the amplifier circuit 71 at a constant gain ratio. It has a configuration.

The amplifier circuit 94 adds the signal voltage VL1 appearing at the terminal L1 and the signal voltage VL2 appearing at the terminal L2 at a constant gain ratio. And a resistor 94b having one end connected to L2. These resistors 94a, 94b
Is connected to the inverting input terminal (-) of the operational amplifier 94c. The positive input terminal of the amplifier 94c is connected to the ground, and the inverting input terminal and the output terminal of the amplifier 94c are connected by a resistor 94d. The output terminal of the amplifier 94c is the output terminal of the amplifier circuit 94. The output terminal of the amplifier circuit 94 is connected to the resistor 71 d in the amplifier circuit 71.
To the inverting input terminal of the amplifier 71b. The output terminal of the amplifier circuit 94 is connected to the inverting input terminal of the amplifier 72b via the resistor 72d in the amplifier circuit 72. The output terminal of the amplifier circuit 94 is the amplifier circuit 7
5 is connected to an inverting input terminal of an amplifier 75c via a resistor 75e.

Next, the operation of the hybrid coupling circuit will be described. The input impedance of the amplifier circuit 94 is set sufficiently higher than the characteristic impedance Ro of the line 43 composed of a balanced cable, and the gain determined by the resistance values of the resistors 94a and 94d in the amplifier circuit 94, and the resistance of the resistors 94b and 94d are determined. The gain determined by the resistance value of the resistor 94d is set equal. By doing so, the output voltage V94 of the amplifier circuit 94 cancels each other for the differential signal between the terminals L1 and L2 and becomes zero, and the output voltage V94 for the in-phase signal (common mode noise). Is obtained by amplification and addition with the set gain.

That is, assuming that the resistance values of the resistors 94a, 94b and 94d are R94a, R94b and R94d, respectively, the voltage value V94 is as follows: V94 =-(R94d / R94a) VL1- (R94d / R94b) VL2 = -G1 (VL1 + VL2 Where G1 = R94d / R94a = R94d / R
94b. Here, in the case of a differential signal, VL
Since 1 = Vs and VL2 = −Vs, V94 = 0. In the case of an in-phase signal, VL1 = VL2 = Vcom
V94 = −2G1 · Vco
m.

Here, the setting conditions of the amplifier circuits 71 and 72 will be described. Amplifier circuit 9 for in-phase signal Vcom
Voltage V7 obtained by amplifying the output voltage V94 of No. 4 by the amplifier 71b.
The gain of the amplifier 71b is set as follows so that 1 becomes equal to (or slightly smaller than) the in-phase signal Vcom. When the resistance value of the resistor 71c is R71c and the resistance value of the resistor 71d is R71d, V71 = − (R71c / R71d) V94 = 2G1 · G2 · Vcom ≦ Vcom G2 = (R71c / R71d) ∴2G1 · G2 ≦ 1 Thus, the gains G1 and G2 are set.

The output signal of the amplifier circuit 72 is a signal having an opposite phase to the output voltage V71 from the amplifier circuit 71, and further, the voltage V94 from the amplifier circuit 94 is applied to the ratio of the resistance values of the resistors 72c and 72d (R72c / R72d). ), The voltage amplified by the gain determined in the above is added. (R72c / R7) so that the voltage V72 resulting from the addition becomes equal to or slightly smaller than the in-phase signal Vcom.
2d) is set as follows. V72 = -V71- (R72c / R72d) V94 = -2G1, G2, Vcom + 2G1, G3, Vco
The gains G1, G2 and G3 are set so that m ≦ Vcom G3 = (RR72c / R72d) 2G1 (G3-G2) ≦ 1.

To prevent the output of the sixth amplifier circuit from appearing in the outputs of the third and fifth amplifier circuits due to the common mode noise at the line terminals L1 and L2, the output of the sixth amplifier circuit is connected to a resistor 75e. To the input of the third amplifier circuit. The resistance value of the resistor 75e is set so as to satisfy the following relationship. R75e = R75b (R71d / R71c) With the above setting, the differential signal between the terminal L1 and the terminal L2 cancels each other and the output becomes zero, so that the amplifier circuit 94 can be ignored. . On the other hand, for the in-phase signal Vcom, the same voltage as the in-phase signal Vcom or a voltage slightly smaller than the same is output from the first amplifier circuit 71 and the second amplifier circuit 72. As a result, almost no voltage is generated between the terminals of the matching resistors 73 and 74, and almost no current flows through these resistors 73 and 74. Therefore, for the in-phase signal Vcom which becomes the common mode noise,
When the resistors 73 and 74 are viewed from the terminals L1 and L2, a high-resistance circuit is formed. If this is equivalently expressed, as shown in FIG. 14, a circuit in which a resistor 78 is inserted and connected between the ground and the center tap of the transformer is obtained. When the resistance value of the resistor 78 is infinite, it becomes the same as the conventional FIG.

As described above, in the eighth embodiment,
The amplifier circuit 9 is added to the hybrid coupling circuit of the sixth embodiment.
4, the amplifier circuits 71 and 72 add and amplify the output voltage of the amplifier circuit 94 with an appropriate gain. Therefore, in addition to the same advantages as in the sixth embodiment, the following (19) to (2)
1) It has such advantages. (19) High resistance to common mode noise
The current due to the common mode noise decreases. (20) Since the current due to the common mode noise flows to the ground, which is the middle point of the balanced cable, the ground can be simplified by reducing the current. (21) Furthermore, a hybrid coupling circuit that behaves like a conventional transformer coupling is provided.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, the following modifications are possible. (A) In the second embodiment, three DC bias supply units 58b, 59b, and 60a are provided, but only one of them may be provided. (B) FIG. 15 is a circuit diagram of a hybrid coupling circuit showing a modification of the fourth embodiment.

The DC bias supply units 58b, 59b, 60a shown in the second embodiment can be applied to the hybrid coupling circuits of the third to fifth embodiments. For example, when the DC bias supply unit 58b is applied to the hybrid coupling circuit in the fourth embodiment, as shown in FIG. 15, a DC cut-off circuit is provided between the resistor 52b in the photocoupler driving circuit 61 and the ground or the power supply. Is connected to the capacitor 58a,
A DC bias supply unit 58b is connected between the inverting input terminal of the amplifier 52a and the ground or the power supply. When the DC bias supply unit 59b is applied, a DC cut capacitor 59a is connected between the resistor 54a in the photocoupler driving circuit 63 and the collector of the output transistor 62ab of the photocoupler 62a, and the terminal L1 is connected to the terminal L1. A DC bias supply unit 59b is connected between the transistor 62ab and the collector.

When the DC bias supply unit 60a is applied, the DC bias supply unit 60a is connected between the ground and the inverting input terminal of the amplifier 55a. (C) FIG. 16 is a circuit diagram showing a modified example of the photocoupler. In the fifth embodiment, the transistors 64 and 65 are provided to compensate for the shortage of the conversion efficiency of the photocouplers 51 and 53. However, the conversion efficiency of the photocouplers 51 and 53 may be improved. For example, as shown in FIG. 16, an arbitrary number of light emitting diodes 96 serving as input units are connected in series, and output transistors 97 opposed to the respective light emitting diodes 96 are connected in parallel, so that an output signal having increased conversion efficiency is obtained. Can be taken out. (D) Regarding the configuration of the first photocoupler driving circuit,
A configuration other than the photocoupler driving circuits 52, 58 and 61 is also conceivable.

FIGS. 17A to 17D are circuit diagrams showing other configuration examples of the first photocoupler driving circuit.
Elements common to those in FIGS. 5 and 6 are denoted by common reference numerals. The photocoupler driving circuit in FIG.
This shows a simple configuration example in which the base is a capacitor 6
And a transistor 98 connected to the terminal Ti through the terminal. The base of transistor 98 is connected to power supply voltage Vdc2 by resistor 52c.
Are connected to the ground by a resistor 52b. The collector of the transistor 98 is connected to the photocoupler 5
It is connected to the cathode of one phototransistor 51b.

The circuit example shown in FIG. 17 (b) is obtained by providing a constant voltage gain amplifier function to an AC driver for generating an AC signal, and an amplifier in which a positive-phase input terminal is connected to a transmission terminal Ti. The resistor 99 connects between the inverting input terminal 52a and the ground. A resistor 52c is connected between the positive-phase input terminal of the amplifier 52a and the ground, and a resistor 100 is connected between the inverting input terminal and the output terminal of the amplifier 52a. The output terminal of the amplifier 52a is connected to the light emitting diode 51a of the photocoupler 51 via the resistor 52b and the capacitor 58a.
Up to the above-mentioned capacitor 58a is an AC driving unit, and a connection point between the light emitting diode 51a and the capacitor 58a is:
The DC bias supply unit 58b is connected. FIG.
The circuit example of (c) is a circuit example when the amplifier 52a is an AC amplifier in a photocoupler driving circuit in which the photocoupler 61a is incorporated in a negative feedback path. At this time, the capacitor 6 for AC coupling is connected to the transmission terminal Ti.
7, one electrode of the capacitor 67 is connected, and the other electrode of the capacitor 67 is connected to the inverting input terminal of the amplifier 52a via the resistor 52b.

(D) FIG. 18 is a circuit diagram showing a modification of the current / voltage conversion circuit. The current / voltage conversion circuits 55 and 60 shown in FIGS. 1 and 5 can also be modified. For example, the circuit example in FIG. 18 includes a transistor 101 whose base is connected to the emitter of the output transistor 53b of the photocoupler 53. The collector of the transistor 101 is connected to the power supply voltage (+ V) together with the collector of the output transistor 53b, and the emitter of the transistor 101 is the output terminal of the current / voltage conversion circuit. The base of the transistor 101 is connected to ground via a resistor 55b, and the emitter of the transistor 101
It is connected to ground via an emitter resistor 102. (E) FIGS. 19A to 19C are circuit diagrams showing modified examples of the second photocoupler driving circuit, and are common to elements in FIG. 7 showing the fourth embodiment and common elements. Are given.

These second photocoupler driving circuits are:
The operational amplifier 103 is used, and light emitting diodes 53a and 62aa of serial photocouplers 53 and 62a are connected between differential output terminals of the amplifier 103. However, the plus side or the minus side of the series light emitting diodes 53a and 62aa may be connected to an appropriate potential other than the output terminal of the amplifier 103. (f) FIG. FIG. 14 is a circuit diagram showing a coupling circuit, wherein components common to those in FIG. 13 showing the eighth embodiment are denoted by common reference numerals.

As in the eighth embodiment, the amplifier circuit 94
Can be applied to the hybrid coupling circuit provided with the above-described method, and the concept of providing the transient current bypass unit as in the seventh embodiment can be applied. In the modification of FIG. 20, the capacitors 81 to 83 and 90 applied to the hybrid coupling circuit of FIG.
Third transient current bypass means 91 to 93 are provided, and the eleventh to fourteenth capacitors 105 and 1 are further provided.
06, 107, 108, and 109 are provided.

The capacitor 105 is connected between the connection point N1 and the resistor 94a of the amplifier circuit 94, and couples them by AC. The capacitor 106 is connected between the connection point N2 and the resistor 94b of the amplifier circuit 94, and has a configuration in which they are AC-coupled. The capacitor 107 is connected between the output terminal of the amplifier 94c and the resistor 71d of the amplifier circuit 71, and has a configuration in which they are AC-coupled.
The capacitor 108 is connected between the output terminal of the amplifier 94c and the resistor 72d of the amplifier circuit 72.
Reference numeral 09 is connected between the output terminal of the amplifier 94c and the resistor R72e of the amplifier circuit 75, and has a configuration in which they are AC-coupled. Thus, the capacitors 105, 10
By providing 6, 107, 108, and 109, the amplifier 94c and the like can be configured with an amplifier dedicated to AC. Also, the capacitors 81 and 82 and the transient current bypass means 9 are used.
By providing 1 to 93, it is possible to prevent the inflow of a large current and to protect the output sides of the amplifiers 71b and 72b from the transient current.

(G) Varistor 9 used in the seventh embodiment
1 to 93 can be changed to a switch function element, a Zener diode, or the like which is turned on when connected to the line 43. (H) In the first to eighth embodiments, the AFE circuit 42a
Is not described in detail, but an explanation of the AFE circuit 42a suitable for these embodiments is given below.

FIGS. 21 (a) and 21 (b) are configuration diagrams showing a main part of an AFE circuit applicable to the first to fifth embodiments. In the hybrid coupling circuits of the first to fifth embodiments, it is necessary to supply a DC bias current to the input unit and the output unit of the photocouplers 51 and 53. In a telephone call or communication using a telephone line, it is necessary to flow a loop current Iof serving as an off-hook signal for causing the exchange 41 to recognize that the terminal is in an off-hook state. Thus, the DC bias current and the current Iof flowing through the loop current circuit 110 are
What is necessary is just to set so that the sum with 1 becomes the loop current Iof. FIGS. 21A and 21B show circuit examples set as described above.

For example, in the AFE circuit shown in FIG.
Even if the voltage of the line 43 is inverted, the photocoupler 5
The loop current circuit 11 connected between the full-wave rectifier circuit 111 and the terminal pair of the rectifier circuit 111 on the side of the hybrid coupling circuit 42b so that a constant voltage is applied to the rectifier circuits 1 and 53.
0 and a switch 112, and a switch 113 for connecting and disconnecting the hybrid coupling circuit. The switch 112 is turned on when in an off-hook state. The loop current circuit 110 includes a switch 11
When the switch 2 is on, a DC current Iof1 flows, and a high impedance is exhibited for an AC signal. FIG.
In the AFE circuit 1 (b), the switch 112 is incorporated in the loop current circuit 110, and the same function as the switch 113 in FIG. 1A is performed by the constant current source circuit 114, the switch 115, the resistor 116, the transistor 117, It is configured to be realized by.

FIGS. 22 (a) and 22 (b) are configuration diagrams showing a main part of an AFE circuit applicable to the sixth to eighth embodiments. In the AFE circuit for the hybrid coupling circuit according to the sixth to eighth embodiments, as shown in FIG. 22A, a current loop circuit 120 for flowing a DC current Iof, a switch 121 for turning it on and off, A switch 122 for connecting or disconnecting the terminal L1 from the line 43 and a switch 1 for connecting or disconnecting the terminal L2 from the line 43
23 may be provided.

In FIG. 22 (b), the circuit shown in FIG. 22 (a) can be constituted by a semiconductor element. A full-wave rectifier circuit 125 is provided on the line 43 side, and a current loop circuit through which the current Iof1 flows. Reference numeral 126 denotes a pseudo-inductance circuit or a constant current circuit that can be turned on and off by a photocoupler or the like, and is connected in series between a pair of terminals on the hybrid coupling circuit side of the full-wave rectifier circuit 125. A switch unit 127 corresponding to the switch 122 in FIG. 9A is connected between one terminal of the full-wave rectifier circuit 125 and the terminal L1, and is connected between the other terminal of the full-wave rectifier circuit 125 and the terminal L2. The switch unit 128 corresponding to the switch 123 in FIG. The switch unit 127 includes the full-wave rectifier circuit 12
And a transistor 127 having an emitter connected to the terminal of the full-wave rectifier circuit 125 and a base connected to the other end of the resistor 127a.
27b. The collector of the transistor 127b is connected to the terminal L1. Switch section 128
Is a resistor 128a having one end connected to the other terminal of the full-wave rectifier circuit 125, and a transistor 128b having an emitter connected to the terminal of the full-wave rectifier circuit 125 and a base connected to the other end of the resistor 128a. It is configured.
The collector of the transistor 128b is connected to the terminal L2.

A constant current circuit 129 for driving the switches 127 and 128 and a photocoupler are provided between the other end of the resistor 127a and the other end of the resistor 128a, and the constant current circuit 129 is turned on and off. Switch 130 is connected. Connected between the collectors of the transistors 127b and 128b is a constant current circuit 131 for flowing a DC bias current of the transistors 127a and 128b, and a switch 132 configured by a photocoupler or the like and for turning on and off the constant current circuit 131. ing. Switches 130 and 132 are turned on and off almost simultaneously. The sum of the current flowing through the constant current circuit 129, the current flowing through the constant current circuit 131, and the current flowing through the loop current circuit 126 is:
The off-hook current Iof is configured.

If the current Iof and the current Iof1 are set to be substantially equal, the switches 130 and
By turning on the switch 121 when 132 is off, dial pulses can be generated. Line 4
If 3 is a push button dedicated line, switch 1
The constant current circuit 129 which is turned on and off at 30 is a pseudo inductance circuit or a constant current circuit.
The current flowing through the current loop circuit 1 is made substantially equal to the loop current Iof to provide the function of the current loop circuit 126.
26 may be deleted.

Next, a description will be given of a form in which the deterioration of the transmission signal level and the deterioration of the sidetone prevention function can be reduced in the hybrid coupling circuits in the above-described sixth to eighth embodiments.

In this embodiment, the first amplifier circuit has an output impedance sufficiently lower than the characteristic impedance R0 of the balanced cable, and amplifies the terminal-side transmission voltage Vi in a positive phase (or a negative phase). It is composed of a circuit.
Further, the second amplifier circuit has an output impedance that is sufficiently lower than the characteristic impedance R0 of the balanced cable, and is configured by an amplifier circuit that amplifies the terminal-side transmission voltage Vi in a reverse phase (or a positive phase). .

That is, the first amplifier circuit and the second amplifier circuit have opposite phases and the same gain value, and the input is connected to the terminal side transmission voltage Vi.

FIG. 23 shows a configuration in which this embodiment is applied to the sixth embodiment shown in FIG.

The operational amplifier 71b of the first amplifier circuit 71
The positive-phase input terminal (+) is connected to the transmission terminal Ti, and the negative-phase input terminal (−) is connected to one ends of the resistors 71e and 71f. The other end of the resistor 71e is connected to the ground.
The other end of the resistor 71f is connected to the output terminal of the operational amplifier 71b, the resistor 74 and the resistor 75b.

The operational amplifier 72b of the second amplifier circuit 72
Are connected to the ground, and the negative-phase input terminal (-) is connected to one ends of the resistors 72d and 72e. The other end of the resistor 72d is connected to the transmission terminal Ti.
The other end of the resistor 72e is connected to the output terminal of the operational amplifier 72b and one end of the resistor 73.

The first amplifier circuit 71 and the second amplifier circuit 72 have outputs having the same output amplitude and an output phase relationship different from each other by 180 degrees. Further, the characteristic of the phase delay with respect to the frequency is adjusted in advance. That is, each resistance value is set so as to satisfy the following relationship. (R71e + R71f) / R71e = R72e / R72d where R71e; resistance value of resistor 71e R71f; resistance value of resistor 71f R72d; resistance value of resistor 72d R72e; resistance value of resistor 72e

In the above-described sixth embodiment, if a phase delay occurs in the second amplifier circuit, there is a possibility that the level of the transmission signal is degraded and the side noise prevention function is degraded. In the above-described configuration, since the phase delay characteristics of the first amplifier circuit and the second amplifier circuit are made uniform, even if the transmission frequency is increased and the first and second amplifier circuits have a phase delay,
The phase between the outputs of the first and second amplifier circuits is always 18
It will be 0 degrees different. Therefore, deterioration of the level of the transmission signal and deterioration of the sidetone prevention function can be significantly reduced.

Examples in which such a configuration is applied to the seventh embodiment shown in FIG. 12 and the eighth embodiment shown in FIG. 13 are shown in FIGS. 24 and 25, respectively.

In the example applied to the seventh embodiment of FIG. 24, the positive-phase input terminal (+) of the operational amplifier 71b of the first amplifier circuit 71 is connected to the ground, and the negative-phase input terminal (−) is connected to the ground. Connected to one ends of the resistors 71e and 71f. The other end of the resistor 71e is connected to the capacitor 83 and the positive-phase input terminal (+) of the operational amplifier 72b. Resistance 71f
Is connected to the output terminal of the operational amplifier 71b, the resistor 74 and the resistor 75b.

The operational amplifier 72b of the second amplifier circuit 72
Are connected to one ends of the resistors 72d and 72e. The other end of the resistor 72d is connected to the ground. The other end of the resistor 72e is connected to the output terminal of the operational amplifier 72b and one end of the resistor 73.

In this case as well, each resistance value R71e, R71
f, R72d, and R72e are set so as to satisfy the above relationship. Since the phase relationship is inverted, R71f /
R71e = (R72e + R72d) / R72.

In the example applied to the eighth embodiment shown in FIG. 25, the positive-phase input terminal (+) of the operational amplifier 71b of the first amplifier circuit 71 is connected to one end of a resistor 71a and a resistor 71e. The input terminal (-) is a resistor 71c and a resistor 71d.
Is connected to one end. The other end of the resistor 71a is a transmission terminal Ti
And one end of the resistor 72a. The other end of the resistor 71e is connected to the ground. The other end of the resistor 71d is connected to the output of the operational amplifier 94c, one end of the resistor 72b, and one end of the resistor 75e. The other end of the resistor 75e is connected to an operational amplifier 75c.
Connected to the negative phase input terminal (-).

In this case, since the gains of the first amplifier 71 and the second amplifier 72 are equal (the phases are opposite in phase), each resistance value is set so as to satisfy the following relationship. G = (R71e / (R71a + R71e)) (R71c + R71d) / R71d = R72c / R72a where R71a; resistance value of resistance 71a R71c; resistance value of resistance 71c R71d; resistance value of resistance 71d R71e; resistance value of resistance 71e R72a; Resistance value of resistance 72a R72c; resistance value of resistance 72c

According to such a configuration, since the phase delay characteristics of the first amplifier circuit and the second amplifier circuit are made uniform, the transmission frequency becomes higher and the first and second amplifier circuits have a phase delay. Even if this occurs, the phase between the outputs of the first and second amplifier circuits will always be 180 degrees different.
Therefore, deterioration of the level of the transmission signal and deterioration of the sidetone prevention function can be significantly reduced.

This configuration can be applied to a hybrid coupling circuit using a conventional transformer as shown in FIG. FIG. 26 shows an application example. Since this application example can be easily understood by referring to the above description,
Detailed description is omitted.

Next, a description will be given of embodiments in which the number of elements can be significantly reduced in the hybrid coupling circuits according to the sixth to eighth embodiments.

In this embodiment, the third to fifth amplifier circuits in the sixth to eighth embodiments are replaced with seventh amplifier circuits. The seventh amplifier circuit calculates the output of the first amplifier circuit, the voltage at the connection point between the first matching resistor and one line, and the voltage at the connection point between the second matching resistor and the other line. It has the function of adding at a constant gain ratio. Further, when applied to the eighth embodiment, the output of the first amplifier circuit, the voltage of the connection point between the first matching resistor and one of the lines, the second matching resistor and the other line, And the output of the sixth amplifier circuit is added at a constant gain ratio.

FIG. 27 shows a configuration in which this embodiment is applied to the sixth embodiment shown in FIG.

Here, a seventh amplifier circuit 78 is provided instead of the third amplifier circuit 75, the fourth amplifier circuit 76, and the fifth amplifier circuit 77.

One end of a resistor 78d and one end of a resistor 78e are connected to the positive-phase input terminal (+) of the differential amplifier circuit 78f of the seventh amplifier circuit 78. A resistor 78a, a resistor 78b, a resistor 7
One end of 8c is connected.

The other end of the resistor 78a is connected to the connection point N1, and the other end of the resistor 78b is connected to the output terminal of the first amplifier circuit 71. The other end of the resistor 78c is connected to the receiving terminal Vo and the output of the differential amplifier circuit 78f. The other end of the resistor 78d is connected to the ground, and the other end of the resistor 78e is connected to a connection point N2.
Connected to.

Here, assuming that the voltage at the terminal L1 is V1, the voltage at the terminal L2 is V2, and the output voltage of the first amplifier circuit 71 is Vo1, the output voltage Vo of the seventh amplifier circuit 78 is expressed by the following equation. You. In this case, the resistance value (R) is displayed in the same manner as described above. Vo = V2 (R78d / (R78d + R78e)) ((R78aR78b + R78b R78c + R78cR78a) / (R78aR78b))-V1R78c / R78a-Vo1R78c / R78b (33)

Here, the common mode noise Vco from the line
When the receiving terminal voltage Vo is set to be 0 for m, it can be expressed by the following equation. V1 = V2 = Vcom, Vo1 = 0 Vo = Vcom (R78d / (R78d + R78e)) ((R78aR78b + R78bR78c + R78cR78a) / (R78aR78b)) − VcomR 78c / R78a = 0 Therefore, 0 = (R78d / Rb) 78bR78c + R78cR78a) / (R78aR78b))-R78c / R78a (34)

With respect to the output Vo1 of the first amplifier circuit with respect to the input voltage Vi, the above equations (17) to (20)
As shown in the equation, the output Vlo to the line, the voltage V at the terminal L1
1. The voltage V2 of the terminal L2 is Vlo = -Vo1, V1 = -0.5Vo1, V2 = 0.
5Vo1

For Vo1, the receiving terminal voltage Vo = 0 is set to realize the sidetone prevention function. Vo = 0 = 0.5 Vo1 (R78d / (R78d + R78e)) ((R78aR 78b + R78bR78c + R78cR78a) / (R78aR78b)) + 0. 5Vo1R78c / R78a-Vo1R78c / R78b) Therefore, 0 = (R78d / (R78d + R78e)) ((R78aR78b + R78bR 78c + R78cR78a) / (R78aR78b)) + R78c / R78a-2Vo1R78c / R78b

Here, the following equation is obtained by subtracting the equation (35) from the equation (34). 0 = −2R78c / R78a + 2R78c / R78b (36) Therefore, R78a = R78b (37)

Here, the following is obtained by substituting equation (37) into equation (34). 0 = (R78d / (R78d + R78e)) (R78a + 2R78c) / R78a-R78c / R78a (38) Therefore, R78e / R78d = (R78a + R78c) / R78c or R78e = R78d (R78a + R78c) / R78c (39) Therefore, R78d / (R78d + R78e) = R78c / (R78a + 2R78c) (40)

The output voltage Vo of the receiving terminal with respect to the balanced input Vs between the lines is obtained as follows. V2 = 0.5V
s, V1 = −0.5 Vs, and Equation (37) and (40)
By substituting the equation into the equation (33), V0 = 0.5 Vs (R78d / (R78d + R78e)) ((R78aR78b + R78bR78c + R78cR78a) / (R78aR78b)) + 0.5Vo1R78c / R78a = 0.5Vs ((R78c / (R78a + 2R78)) (R78a + 2R 78c) / R78a + R78c / R78a = VsR78c / R78a (41)

As described above, also in the present configuration, as in the sixth embodiment, a hybrid coupling circuit having functions of removing common mode noise from a line and preventing a side signal from transmitting a signal can be realized. Further, in this configuration, the sixth
The number of elements can be greatly reduced as compared with the embodiment.

FIG. 28 shows a configuration in which this configuration is applied to the form shown in FIG. The positive input terminal (+) of the differential amplifier circuit 78f of the seventh amplifier circuit 78 is connected to a resistor 78d.
And one end of the resistor 78e. Differential amplifier circuit 78
A resistor 78a, a resistor 78b,
One end of the resistor 78c is connected.

The other end of the resistor 78a is connected to the connection point N1, and the other end of the resistor 78b is connected to the output terminal of the first amplifier circuit 71. The other end of the resistor 78c is connected to the receiving terminal Vo and the output of the differential amplifier circuit 78f. The other end of the resistor 78d is connected to the ground, and the other end of the resistor 78e is connected to a connection point N2.
Connected to.

FIG. 29 shows a configuration in which this configuration is applied to the form shown in FIG. The positive input terminal (+) of the differential amplifier circuit 78f of the seventh amplifier circuit 78 is connected to a resistor 78d.
And one end of the resistor 78e. Differential amplifier circuit 78
A resistor 78a, a resistor 78b,
One ends of the resistors 78c and 78g are connected.

The other end of the resistor 78a is connected to the connection point N1, and the other end of the resistor 78b is connected to the output terminal of the first amplifier circuit 71. The other end of the resistor 78c is connected to the receiving terminal Vo and the output of the differential amplifier circuit 78f. The other end of the resistor 78d is connected to the ground, and the other end of the resistor 78e is connected to a connection point N2.
Connected to. The other end of the resistor 78g is connected to the sixth amplifier circuit 9.
4 output terminal.

In these configurations, as in the configuration shown in FIG. 27, it is possible to realize a hybrid coupling circuit having both functions of removing common mode noise from a line and preventing side noise for a transmission signal, and greatly reducing the number of elements. The number can be reduced.

An eighth amplifier circuit 79 is provided before the first and second amplifier circuits of the circuit shown in FIG. 28, that is, between the first and second amplifier circuits and the receiving terminal Ti. 30 is shown in FIG.

The differential amplifier circuit 79 of the eighth amplifier circuit 79
Is connected to the ground, and the negative-phase input terminal (-) is connected to one end of the resistor 79a and the resistor 79c. The other end of the resistor 79a is connected to the capacitor C3, and the other end of the resistor 79c is connected to the output of the differential amplifier 79b.

According to this configuration, the gains of the first and second amplifier circuits can be suppressed low, and when the first and second amplifier circuits are negative feedback amplifier circuits, the amount of negative feedback can be increased. Therefore, the balance between the outputs of the first and second amplifier circuits can be improved.

As illustrated in FIGS. 23 to 30, the inputs of the first and second amplifier circuits are connected to the transmission terminal Ti, or the inputs of the first and second amplifier circuits are connected to the transmission terminal Ti. In an example in which the eighth amplifier circuit is inserted between the terminals Ti, or in which the seventh amplifier circuit is used instead of the third to fifth amplifier circuits, a capacitor coupling is used in the addition input section of the amplifier. A method of cutting the DC component and effectively utilizing the output dynamic range of the amplifier circuit,
Further, a capacitor is connected between the line described in the seventh embodiment and the first and second connection points by using an AC amplifier, or the first connection point is connected to the second connection point. The method of providing the above-mentioned first to third transient current bypass means between each of the point and the ground can be applied. Further, the phase relationship between the amplifier and the photocoupler has been described in accordance with the illustrated circuit.If the phase of the output of the preceding amplifier or the photocoupler is inverted, the sum of the input of the subsequent amplifier is also reduced. By selecting the sign (positive phase or reverse phase) and gain of the addition as appropriate, such as adding in the opposite phase, the side protection function and the reduction of the common mode noise current can be achieved even if a phase relationship different from that described above is used. It is possible.

[0150]

As described in detail above, according to the present invention, the side protection function and the current based on common mode noise can be reduced without using a transformer, so that a transformer as a hybrid coupling circuit is not required. it can. This makes it possible to realize a hybrid coupling circuit that is small, lightweight, low-cost, and resistant to magnetic noise.

Further, according to the present invention, a hybrid coupling circuit that cancels common mode noise on a balanced cable and prevents side noise can be configured without using a transformer. Therefore, the weight of the hybrid coupling circuit can be reduced, and the cost can be reduced. Further, since a transformer is not used, a hybrid coupling circuit having resistance to magnetic noise can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hybrid coupling circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a hybrid combination circuit used in a conventional telephone.

FIG. 3 is a circuit diagram showing another example of a conventional hybrid coupling circuit.

FIG. 4 is a configuration diagram showing a relationship between a central office exchange and communication terminals.

FIG. 5 is a circuit diagram of a hybrid coupling circuit according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram of a hybrid coupling circuit according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a hybrid coupling circuit according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of a hybrid coupling circuit according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram of a hybrid coupling circuit according to a sixth embodiment of the present invention.

FIG. 10 is a circuit diagram showing an improved example of the hybrid coupling circuit of FIG. 9;

FIG. 11 is a circuit diagram showing an equivalent circuit of FIG. 10;

FIG. 12 is a circuit diagram of a hybrid coupling circuit showing a seventh embodiment of the present invention.

FIG. 13 is a circuit diagram of a hybrid coupling circuit showing an eighth embodiment of the present invention.

FIG. 14 is a circuit diagram showing an equivalent circuit of FIG.

FIG. 15 is a circuit diagram of a hybrid coupling circuit showing a modification of the fourth embodiment.

FIG. 16 is a circuit diagram showing a modification of the photocoupler.

FIG. 17 is a circuit diagram showing another configuration example of the first photocoupler driving circuit.

FIG. 18 is a circuit diagram showing a modified example of the current / voltage conversion circuit.

FIG. 19 is a circuit diagram showing a modification of the second photocoupler driving circuit.

FIG. 20 is a circuit diagram showing a hybrid coupling circuit according to a modification of the eighth embodiment.

FIG. 21 is a configuration diagram illustrating a main part of an AFE circuit applicable to the first to fifth embodiments;

FIG. 22 is a configuration diagram illustrating a main part of an AFE circuit applicable to the sixth to eighth embodiments.

FIG. 23 is a circuit diagram showing a hybrid coupling circuit according to a modification of the sixth embodiment.

FIG. 24 is a circuit diagram showing a hybrid coupling circuit according to a modification of the seventh embodiment.

FIG. 25 is a circuit diagram showing a hybrid coupling circuit according to a modification of the eighth embodiment.

26 is a circuit diagram showing an example in which the configuration of FIG. 23 is also applied to a hybrid coupling circuit using a conventional transformer.

FIG. 27 is a circuit diagram showing a hybrid coupling circuit according to a modification of the sixth embodiment.

FIG. 28 is a circuit diagram showing a hybrid coupling circuit according to a modification of the seventh embodiment.

FIG. 29 is a circuit diagram showing a hybrid coupling circuit according to a modification of the eighth embodiment.

FIG. 30 is a circuit diagram showing a hybrid coupling circuit according to a modified example of the hybrid coupling circuit shown in FIG.

[Explanation of symbols]

51, 53 Photocoupler 52, 54, 58, 59, 61, 63 Photocoupler drive circuit 55, 60 Current / voltage conversion circuit 56, 67 to 70, 81 to 90 Capacitor 57 Addition circuit 58b, 59b, 60a DC bias supply unit 71, 72, 75 to 77, 94 Amplifier circuit 73, 74 Matching resistor 91 to 93 Varistor (transient current bypass means) Ti transmission terminal To reception terminal

Claims (20)

[Claims] 1. A communication terminal connected to a paired line, having a receiving terminal and a transmitting terminal, receiving a signal given via the line to the receiving terminal, A hybrid coupling circuit that transmits the given transmission signal to the line without leaking to the reception terminal; a first photocoupler drive circuit that generates a first drive signal according to a transmission voltage on the transmission terminal; An input unit connected to the first photocoupler driving circuit; and an output unit optically coupled to the input unit and connected to the line, and driven by the first drive signal to output from the output unit. A first photocoupler for transmitting a current according to the transmission voltage to the line as the transmission signal, and a second photocoupler for generating a second drive signal according to the voltage of the line
A photocoupler driving circuit, comprising: an input unit connected to the second photocoupler driving circuit; and an output unit optically coupled to the input unit. The output unit is driven by the second driving signal and outputs from the output unit. A second photocoupler that outputs a current according to the voltage of the line, and a current / voltage converter that is connected to an output unit of the second photocoupler and converts an output current of the second photocoupler into a voltage signal A first capacitor connected to the current / voltage conversion circuit to cut a direct current component in the voltage signal; a first capacitor connected to the first capacitor and the transmission terminal; wherein the transmission voltage and the direct current component are The cut voltage signal is input, and an addition operation is performed to cancel the component corresponding to the transmission voltage in the voltage signal and extract the reception signal,
And a summing circuit for applying the extracted reception signal to the reception terminal. 2. The first photocoupler driving circuit has an input section connected in series to an input section of the first photocoupler, and an output section optically coupled to the input section. A negative feedback circuit including a third photocoupler that outputs a current having the same value as the current output from the output unit of the first photocoupler in a path is formed, and the second photocoupler driving circuit includes: An input section connected in series to an input section of the second photocoupler, and an output section optically coupled to the input section, and having the same value as the current output from the output section of the second photocoupler. 2. The hybrid coupling circuit according to claim 1, wherein a negative feedback circuit including a fourth photocoupler that outputs a current of the second type in its path is formed. 3. The second photocoupler drive circuit has a resistor having one end connected to one of the lines, and a current flowing through the resistor flows to an output section of the fourth photocoupler. Negative feedback is established, one end is connected to one of the lines, and a constant current is supplied from one of the lines to a portion of the second photocoupler drive circuit other than the resistor to supply power. 3. The hybrid coupling circuit according to claim 2, further comprising a current circuit. 4. The second photocoupler driving circuit is connected in series to the resistor, and is connected in parallel to the resistor and the second capacitor, with a second capacitor for passing a DC-cut current through the resistor. A DC bias supply unit for supplying a DC bias current to the second photocoupler, and a current flowing through the resistor and the second capacitor and the DC bias supply unit flows to an output unit of the fourth photocoupler. 4. The hybrid coupling circuit according to claim 3, wherein the negative feedback is established. 5. A first photocoupler driving circuit, comprising: a first DC bias supply unit that supplies a DC bias current to the first photocoupler; and a first AC bias voltage that generates an AC transmission voltage corresponding to the transmission voltage. 5. The hybrid coupling circuit according to claim 1, wherein the hybrid coupling circuit comprises: 6. The second photocoupler driving circuit, further comprising: a second DC bias supply unit that supplies a DC bias current to the second photocoupler; and a second DC bias supply unit that generates an AC reception voltage corresponding to the line voltage. 6. The hybrid coupling circuit according to claim 1, wherein the hybrid coupling circuit comprises two AC driving units. 7. The current / voltage conversion circuit is provided with a third DC bias supply unit for flowing a DC bias current, and the DC signal is added to an output current of the second photocoupler, and the voltage signal is added to the output signal. The hybrid coupling circuit according to claim 1, 2, 3, 4, 5, or 6, wherein the hybrid coupling circuit is configured to be converted to: 8. A first transistor or a current mirror circuit for amplifying an output current of the first photocoupler, or a second transistor or a current mirror circuit for amplifying an output current of the second photocoupler. Claim 1, 2, 3, 4, 5, wherein at least one is provided.
8. The hybrid coupling circuit according to 6 or 7. 9. The hybrid coupling according to claim 1, further comprising a voltage amplifier circuit connected to the transmission terminal and amplifying the transmission voltage. circuit 10. A third capacitor for AC coupling between the transmission terminal and the voltage amplifier circuit, a fourth capacitor for AC coupling between the voltage amplifier circuit and the first photocoupler driving circuit, At least one of a fifth capacitor for AC coupling between the voltage amplifier circuit and the addition circuit or a sixth capacitor for AC coupling between the addition circuit and the reception terminal is provided. The hybrid coupling circuit according to claim 9, wherein: 11. A communication terminal comprising a balanced cable and connected to a pair of lines, the terminal having a reception terminal and a transmission terminal, and a reception signal provided through the line is connected to the reception terminal. Wherein the transmission signal applied to the transmission terminal is transmitted to the line without leaking to the reception terminal. The hybrid coupling circuit has an output impedance sufficiently lower than the characteristic impedance of the balanced cable, and A first amplifier circuit connected to a terminal and amplifying a voltage on the transmission terminal as the transmission signal; having a sufficiently low output impedance as compared to the characteristic impedance of the balanced cable; A second amplifier circuit that is connected to an output terminal and outputs a signal having a phase opposite to that of the amplified transmission signal; and an output terminal of the second amplifier circuit. A first matching resistor connected between one of the lines, a second matching resistor connected between an output terminal of the first amplifier circuit and the other of the line, An input terminal is connected to a first connection point where the matching resistor and one of the lines are connected, and a signal voltage appearing at the first connection point and a voltage of a transmission signal output by the first amplifier circuit are determined. A third amplifier circuit for adding and amplifying at a constant gain ratio; an input terminal connected to a second connection point where the second matching resistor and the other of the lines are connected; and a second connection point connected to the second connection point. A fourth amplifier circuit for amplifying the appearing signal voltage in a phase opposite to that of the third amplifier circuit; And a fifth amplifier circuit that performs Hybrid coupling circuit. 12. The first amplifier circuit has an output impedance sufficiently lower than a characteristic impedance of the balanced cable, and amplifies the transmission signal in a positive phase or a negative phase. 12. The hybrid coupling circuit according to claim 11, wherein the amplifier circuit has an output impedance sufficiently lower than a characteristic impedance of the balanced cable and amplifies the transmission signal in a reverse phase or a positive phase. . 13. A sixth amplifier circuit for adding a signal voltage appearing at the first connection point and a signal voltage appearing at the second connection point at a constant gain ratio, wherein the first amplifier circuit comprises: The voltage on the transmission terminal and the output signal of the sixth amplifier circuit are added and amplified at a constant gain ratio. The second amplifier circuit calculates the addition amplification result of the first amplifier circuit and the sixth amplifier circuit. And the output signal of the third amplifier circuit is added and amplified at a constant gain ratio. The third amplifier circuit calculates the signal voltage appearing at the first connection point, the addition amplification result of the first amplifier circuit, and the sixth amplifier circuit. 12. The hybrid coupling circuit according to claim 11, wherein an output signal is added and amplified at a constant gain ratio. 14. A sixth amplifier circuit for adding a signal voltage appearing at the first connection point and a signal voltage appearing at the second connection point at a constant gain ratio, wherein the first amplifier circuit is configured to The voltage on the transmission terminal and the output signal of the sixth amplifier circuit are added and amplified at a constant gain ratio, and the second amplifier circuit converts the voltage on the transmission terminal and the output signal of the sixth amplifier circuit into a constant gain. The third amplifier circuit adds the signal voltage appearing at the first connection point, the addition amplification result of the first amplifier circuit, and the output signal of the sixth amplifier circuit at a constant gain ratio. 13. The hybrid coupling circuit according to claim 12, wherein the circuit is configured to amplify. 15. An eighth amplifier circuit provided before the first and second amplifier circuits, for amplifying the transmission signal and supplying the amplified signal to the first and second amplifier circuits. Item 15. The hybrid coupling circuit according to item 12 or 14. 16. The signal voltage appearing at the first connection point and the signal voltage appearing at the second connection point, and the first or second amplifier, instead of using the first to fifth amplifier circuits. 16. The configuration according to claim 11, wherein a seventh amplifier for adding and amplifying an output voltage of a circuit and an output voltage of the sixth amplifier circuit when there is the sixth amplifier circuit at a constant gain ratio is used. Hybrid coupling circuit. 17. A first capacitor inserted and connected between one of the lines and the first connection point to cut off input / output of DC current, and the other of the line and the second connection point. 17. The hybrid coupling circuit according to claim 11, further comprising a second capacitor inserted and connected between the second capacitor and the second capacitor to cut off input / output of a direct current. 18. A first capacitor connected between the first node electrode of the first capacitor and the second node electrode of the second capacitor, and bypassing a transient current. A transient current bypass unit, a second capacitor connected between the first connection point side electrode of the first capacitor and ground, and bypassing the transient current.
A transient current bypass means, and a third current bypass means connected between the second connection point side electrode of the second capacitor and ground to bypass the transient current.
At least one of the transient current bypass means of
The hybrid coupling circuit according to claim 17, wherein the hybrid coupling circuit is provided. 19. The hybrid coupling circuit according to claim 18, wherein said first to third transient current bypass means are each constituted by a varistor element, a Zener diode, or a switch function element. 20. The hybrid coupling circuit according to claim 11, wherein at least one capacitor coupling is used in an addition input section of said first to eighth amplifier circuits.