JP3494468B2 - Hybrid circuit and device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid circuit for performing 4-wire / 2-wire conversion of a communication path and a data communication device such as a modem incorporating the same, and more particularly to a 4-wire type circuit in a front end section. The present invention relates to a hybrid circuit having means for insulating between terminals of a two-wire line and an apparatus using the hybrid circuit.

[0002]

2. Description of the Related Art In order to perform data communication via a public switched line network, a modem is required in a communication path, and a hybrid circuit for performing 4-wire / 2-wire conversion of the communication path is required in this device. And

FIG. 16 is a block diagram showing a configuration of a general modem provided between a conventionally known personal computer (personal computer) and a public switched line network. A terminal interface 1 and a controller 2 are shown. When,
It is composed of a digital signal processing circuit 3 and a front end section 4, and the front end section 4 is composed of a 4-wire / 2-wire hybrid circuit 5 and a network control section 6. 4 lines /
As the two-wire hybrid circuit 5, for example, US Pat. No. 3,955,051 specification (May 4,1976).
Fig. 2, FIG. 3 (Reference 1) and “CMOS I
lntegrated Circuit Data Bo
ok ”PP. 200-201, SIERRA SEMI
As described in CONDUCTOR (JAN. 1992) (reference 2), various types have been proposed in the past, but none of them has insulation between the 4-wire line and the 2-wire line. , It is not possible to connect to the public line as it is. Therefore, conventionally, as shown in FIG. 17, in addition to the hybrid circuit 5, a line transformer L that enables data communication while insulating between the lines is provided in the front end portion.
Is provided. However, line transformers for data communication tend to have larger outer dimensions as they have better transmission characteristics, with an inductance of 1 henry and a withstand voltage of 1000.
If you try to obtain practically sufficient transmission characteristics with a transformer that can pass a current of V or more and that flows through the line, even the smallest one will have a thickness of about 1 cm, and the front end will be smaller and thinner. There was a limit to the conversion. Therefore, in order to further reduce the size and thickness of the front end, it is essential to develop a circuit configuration that enables data communication while insulating between lines without using a line transformer or the like. Is.

Conventionally, a balanced resistance bridge circuit is used in a hybrid circuit, and a line transformer or a coupling capacitor is connected between the bridge circuit and a two-wire line, and the bridge circuit and the transmission terminal of the four-wire line are connected. Between
Also, connect operational amplifiers (differential type and feedback type) between the bridge circuit and the receiving terminals of the four-wire line, and balance these operational amplifiers so that the transmission signal does not leak to the receiving terminals. In addition, there is known a 4-wire / 2-wire conversion hybrid circuit in which the bridge circuit and the transmission terminal as well as the bridge circuit and the reception terminal are insulated from each other. As a known example of this type, for example, Japanese Patent Laid-Open No.
There is 223622 gazette (reference 3).

Further, conventionally, in a front end of a modem, a two-wire line is connected to the hybrid circuit, and the hybrid circuit and the four-wire line are connected between the hybrid circuit and the four-wire line modem transmission terminal. Insert a pulse width modulator between the modem reception terminal and
It is known that a photo coupler is used to transmit a pulse signal and a transformer is unnecessary. As a known example of this kind,
For example, there is JP-A-3-32147 (Reference 4).

[0006]

In the above-mentioned conventional front end section using the balanced resistance bridge circuit, there is a transmitter terminal (transmitter output terminal) and a receiver terminal (receiver input terminal) both of which are grounded at one end. It is necessary to insulate the bridge circuit in which at least one of the two balance points is floating from the ground. Further, it is necessary to prevent the signal applied to the bridge circuit from the transmission terminal from leaking to the reception terminal. For this reason, in the conventional hybrid circuit using the bridge circuit, the transmission signal is always canceled by the reception side operational amplifier to prevent leakage to the reception terminal by always combining the operational amplifier, and the operational amplifier is indispensable.

However, in such a balanced bridge type hybrid circuit using an operational amplifier, in-phase noise coming from a two-wire line (noise coming in-phase on two lines forming a two-wire line) is effective. It turns out that it cannot be removed. That is, when the frequency of the common mode noise is within the operating frequency band of the operational amplifier on the receiving side, most of the common mode noise is canceled by the operational amplifier unit and does not appear at the reception terminal, but the frequency of the common mode noise is the frequency of the operational amplifier of the operational amplifier. It was found that when the frequency is high enough to exceed the frequency band, the original operation of this operational amplifier is not performed, and this noise appears at the receiving terminal.

As a result of various studies on this problem, the present invention has found that this problem can be solved by combining an insulating interface device such as an optical coupling device (eg, photocoupler) in a balanced bridge type hybrid circuit.

Therefore, an object of the present invention is to overcome the problems of the prior art described above and to use an operational amplifier by combining an insulating interface element such as an optical coupling element on the 4-wire line side of a balanced bridge type hybrid circuit. Even if it is not necessary, the transmission terminal and the reception terminal on the 4-wire line side can be insulated from the bridge circuit, the transmission signal is prevented from leaking to the reception terminal, and the operational amplifier is not used. A hybrid circuit that effectively removes noise up to high frequencies and uses this
To provide a device .

Another object of the present invention is to provide a front end portion which is thin and has good transmission characteristics.

In general, it is known from Reference 4 that the public line and the terminal are insulated from each other by a photocoupler. However, in the above Reference 4, since only the pulse signal is transmitted to the photocoupler, the PWM is used. It is indispensable to use a modulator, the structure is complicated, and it is not necessarily advantageous for downsizing and cost reduction.

[0012]

In order to achieve the above object, the present invention has the following constitution.

(1) The transmitter side connected to the transmitter terminal
4 consisting of a line and a receiving side line connected to the receiving terminal
Formed by a wire line and a two-wire line connected to the transmitting and receiving terminals
Hybrid circuit that performs 4-wire / 2-wire conversion of the established communication path
Resistance or resistance and impedance
Balanced bridge circuit connected to each other and the balanced bridge circuit.
One pair of connection points in a diagonal position in the bridge connection of the circuit
A first connection between the transmission line of the 4-wire line and the transmission line of the 4-wire line
Insulation interface element and the balanced bridge circuit
The other pair of connecting points diagonally located in the bridge connection and the four lines
A second insulating cable for connecting the receiving side line of the expression line
Interface device and the bridge of the balanced bridge circuit.
Connect the two-wire circuit to two adjacent connection points with a ridge connection.
Continued.

(2) In the above (1), the first and second insulation
The edge interface elements are optical coupling elements,
First optical coupling element as an insulating interface element
The primary side of the child is a 4-wire type, and the secondary side is connected to the transmission side line.
Are respectively connected to one connection point pair of the balanced bridge circuit,
Second optical coupling as second insulating interface element
The secondary side of the element is connected to the receiving side of the 4-wire line, and the primary side is
They are connected to the other pair of connection points of the balanced bridge circuit, respectively.
It is something.

(3) The transmitting side connected to the transmitting terminal
4 consisting of a line and a receiving side line connected to the receiving terminal
Formed by a wire line and a two-wire line connected to the transmitting and receiving terminals
Hybrid circuit that performs 4-wire / 2-wire conversion of the established communication path
The two resistive elements and the first and second insulating interfaces
Interface element, and one resistance and the first insulation interface.
Interface element and the other resistor and the second resistor
The isolated interface element of the
A balanced bridge circuit composed of ridge connections and a balanced bridge circuit.
Of the two resistors of the circuit and the first and second isolation interfaces
The connection point of the interface element and the transmission line of the 4-wire line
A third insulation interface element connected to
A 4-wire circuit is used for the first and second insulation interface elements.
Connect the line on the receiving side, and the adjacent 2 of the balanced bridge circuit
A two-wire line is connected to one connection point.

(4) In the above (3),
Each of the insulation interface elements 3 is an optical coupling element.
As a first and second insulation interface element
The primary side of the optical coupling element is a bridge connection with a balanced bridge circuit
And the secondary side is connected to the receiving side of the 4-wire type line,
Of the optical coupling element as the third insulation interface element
The primary side is connected to the transmission side line of the 4-wire type line, and 2
The next side is the connection point of the two resistors of the balanced bridge circuit and
Connected to the connection point of the second insulation interface element
ing.

(5) In the above (4), the first and second insulation
Secondary side of optical coupling element as edge interface element
Connect the serials in series, and connect one end of this series connection to the secondary side.
Connect the receiving line of the 4-wire line to the connection point of the master
It is a thing.

(6) In the above (4), the first and second insulation
The secondary side of the optical coupling element as the edge interface element
A differential amplifier circuit to which the output signal is supplied
Connect the receiving line of the 4-wire line to the output terminal of the line
It is a thing.

(7) The transmission side connected to the transmission terminal
4 consisting of a line and a receiving side line connected to the receiving terminal
Formed by a wire line and a two-wire line connected to the transmitting and receiving terminals
Hybrid circuit that performs 4-wire / 2-wire conversion of the established communication path
In the road, two resistors and the first isolation interface
An impedance circuit including an element and a second insulating interface
Bridge connection with impedance circuit including base element
The balanced bridge circuit and the balanced bridge circuit
The connection point between the resistors and the connection point between the impedance circuits
A third insulation interface connected to the transmission side line of the 4-wire type line.
And a first insulating interface and a second insulating interface.
Connect the receiving side of the 4-wire type line to the base element and balance
Two adjacent connection points in the bridge connection of the bridge circuit
The two-wire line is connected to.

(8) In (7 ) above, the first, second, and second
Each of the insulation interface elements 3 is an optical coupling element.
As a first and second insulation interface element
The primary side of the optical coupling element is a bridge connection with a balanced bridge circuit
And the secondary side is connected to the receiving side of the 4-wire type line,
Of the optical coupling element as the third insulation interface element
The primary side is connected to the transmission line of the 4-wire line and the secondary side
Between the two resistors of the bridge connection of the balanced bridge circuit
Connected to the connection point and the connection point between the impedance circuits
ing.

(9) In (8 ) above, the first and second insulation
The secondary side of the optical coupling element as the edge interface element
The output signals are added differentially, and the receiving side of the 4-wire line
Is supplied to the line.

(10) Transmission side connected to transmission terminal
Line and the line on the receiving side connected to the receiving terminal
Formed with a 4-wire line and a 2-wire line connected to the transmitting and receiving terminals
A hybrid that performs 4-wire / 2-wire conversion of the created communication path
In the circuit, three resistors and a two-wire circuit, or
Bridge between two resistors, impedance and two-wire system
Balanced bridge circuit connected and balanced bridge circuit
Bridge connection, one pair of connecting points diagonally and 4 lines
First isolation in-line connecting between the transmission side line of the expression line
Bridge connection of the interface element and the balanced bridge circuit
Connected between the connection points that form the other connection point diagonally
And second and third insulation interface elements
E, 4-wire type for the second and third insulation interface elements
It is a connection of the line on the receiving side of the line.

(11) In the above (7), the first insulating layer
The interface element is the first optical coupling element and the second insulating interface.
The interface element is the second and third optical coupling elements.
The primary side of the first optocoupler is a 4-wire line transmission
The bridge connection of the balanced bridge circuit on the secondary side to the side line
The second and third optical couplings are respectively connected to one of the connection point pairs.
The primary side of the element is diagonal with a bridge connection of a balanced bridge circuit
On the other side of the connection point, the secondary side receives the 4-wire line
It is connected to the receiving side line.

(12) In (11 ) above, the second and third
The primary side of the optical coupling element is the bridge of the balanced bridge circuit.
Two connections that make up the other pair of connection points that are diagonally connected
The points are push-pull connected to each other.

(13) In (7 ) above, the first and second
The insulating interface elements are optical coupling elements,
Of the optical coupling element as the first insulating interface element
The primary side is a 4-wire type transmission line and the secondary side is a balanced line.
Connected to one of the connection points of the bridge connection of the ridge circuit
Optical coupling as a second insulating interface element
The primary side of the element is diagonal with a bridge connection of a balanced bridge circuit
On the other side of the connection point, the secondary side receives the 4-wire line
It is connected to the receiving side line.

(14) In the above (13), the second optical connection
Operates as a DC voltage regulator on the secondary side of the compound element,
In addition, a load circuit that operates as a constant current circuit in alternating current is provided
It is a thing.

[0027]

[0028]

The operation based on the above configuration will be described.

As shown in FIG. 15, the transmission terminals E and F of the 4-wire type circuit are connected to the connection points A and C of the balanced bridge circuit, and the 4-wire type circuit is connected to the connection points B and D of the balanced bridge circuit. When the receiving terminals G and H of are connected and the transmitting and receiving terminals J and K of the two-wire line are connected to the connection points C and D of the balanced bridge circuit, the transmitting terminals E of the four-wire line are connected by the principle of the balanced bridge. The signal of F is transmitted to the transmission / reception terminals J, K of the 2-wire line via the balanced bridge circuit, and the signal of the transmission / reception terminals J, K of the 2-wire line is received by the 4-wire line via the balanced bridge circuit. It is transmitted to G and H. On the other hand, the signals at the transmission terminals E and F of the 4-wire line are canceled by the balanced bridge circuit and are not transmitted to the reception terminals G and H of the 4-wire line. Thereby, 4-line / 2-line conversion of the communication path can be realized.

However, when this hybrid circuit is applied to a modem, since the negative side terminals F and H of the four-wire line are normally dropped to the common ground terminal, the bridge circuit and the four
If the line circuit is not insulated, the connection points C-D and the transmission / reception terminals J-K are short-circuited, and the hybrid circuit does not function.

However, according to the present invention, a current detector using an optical coupling element (for example, a photocoupler) or a Hall element, and an element such as an isolation amplifier are connected to the primary side and the secondary side of the apparatus. It provides electrical isolation and allows data transmission from a device connected to the primary side to a device connected to the secondary side. Therefore, if these elements are used for insulation between the 4-wire line and the 2-wire line of the hybrid circuit and between the transmission side terminal and the reception side terminal of the 4-wire line, the negative side terminal F of the 4-wire line , H can function as a normal hybrid circuit even if they are dropped to a common ground terminal.

Further, when in-phase noise (noise having the same potential as the potentials of the terminals J and K with respect to ground and having the same potential with respect to the ground) arrives at the transmission / reception terminals J and K of the two-wire line, the connection point D and the connection point C are connected. Since the potentials are the same and the potentials at the connection point D and the connection point B are the same, this noise does not appear between the receiving terminals G and H. In this case, since no operational amplifier or the like is used, a hybrid circuit can be obtained in which the received signal from which common-mode noise is removed is obtained in all frequency bands even when the common-mode noise frequency is high.

[0033]

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

<First Embodiment> FIG. 1 shows the configuration of a hybrid circuit according to the first embodiment. The hybrid circuit of this example has four components as shown in FIG.
Four fixed resistors R ₁ , R ₂ , between the two-wire line and the two-wire line,
A balanced bridge circuit 11 composed of R ₃ and R ₄ is provided, and connection points A and C at one diagonal position (balanced point) of the balanced bridge circuit 11 and a transmission terminal of a transmission side of a 4-wire type line (hereinafter
Below, referred to as a transmission terminal of a 4-wire line) E and F are insulated from each other by the first photocoupler 12, and connection points B and D at the other diagonal position (balance point) of the balanced bridge circuit 11 are also provided.
And the receiving terminal of the line on the receiving side of the 4-wire system (hereinafter, 4-wire system)
G and H, which are called receiving terminals of the line, are insulated by the second photocoupler 13. The balanced bridge circuit 11
Transmission / reception terminals J and K of a two-wire line are connected to connection points C and D at positions adjacent to each other. The first photo coupler 1
2 is a light emitting diode 12a and the light emitting diode 12a
And a phototransistor 12b for receiving light from the second photocoupler 13, and the second photocoupler 13 includes the light emitting diode 1
3a and a phototransistor 13b for receiving the light from the light emitting diode 13a.

The operation of the hybrid circuit according to the first embodiment will be described below.

In the hybrid circuit of this example, when a signal is applied between the transmission terminals E and F of the 4-wire line, an optical signal corresponding to the transmission signal is emitted from the light emitting diode 12a,
The electromotive force signal corresponding to the optical signal is the phototransistor 1.
It is output from 2b. This signal is then applied to the connection points AC of the balanced bridge circuit 11.

Since the voltage between the connection points C and D of the balanced bridge circuit 11 is almost the voltage applied to the connection points A and C divided by the resistance ratio of the bridge, the transmission terminal of the four-wire line is connected. The signal applied between E and F is transmitted to the transmission / reception terminals J and K of the two-wire line. However, since the connection points B and D have almost the same potential with respect to the voltage applied to the connection point A-C, the reception terminals G and H of the signal applied between the transmission terminals E and F of the four-wire line. Leakage into the is prevented.

On the other hand, when a signal is applied to the transmission / reception terminals J and K of the two-wire line, the potential of the connection point D is equal to the potential of the transmission / reception terminal J, and the potential of the connection point B bridges the potential of the transmission / reception terminal J. Since the voltage is divided by the resistance ratio of, the potential difference occurs between the connection points B and D. Therefore, an optical signal corresponding to this potential difference is emitted from the light emitting diode 13a, and an electromotive force signal corresponding to the optical signal is transmitted to the phototransistor 13b.
Since it is output from, the signal applied to the transmission / reception terminals J and K of the two-wire line is transmitted to the reception terminals G and H of the four-wire line.

Now, common-mode noise from the two-wire line to the transmission / reception terminals J and K (noise in which the noise potential levels of the terminals J and K with respect to the ground point (not shown) are almost the same and changes to the same phase)
Consider the case when comes. In this case, since a voltage due to this noise is not generated between the terminals J and K, this common-mode noise does not appear between the ground points BD where the divided voltage value of the voltage between the terminals JK is generated. Therefore, it is possible to obtain a hybrid circuit having a simple configuration and resistant to common-mode noise.

As described above, the hybrid circuit of this embodiment has the balanced bridge 1 between the 4-wire line and the 2-wire line.
1 is provided between the transmission terminals E and F of the 4-wire line and the connection points A and C of the balanced bridge 11, and the reception terminals G and H of the 4-wire line and the connection point B of the balanced bridge 11, The feature is that the photocouplers 12 and 13 are provided between the photocoupler and D. Based on this configuration, in a hybrid circuit using a conventional balanced bridge, it is possible to omit the operational amplifier (operational amplifier) that is indispensable for dropping the transmission terminal and the reception terminal of the 4-wire line to the common ground terminal. Therefore, even if the transmission terminal F and the reception terminal H of the 4-wire line are dropped to the common ground terminal by the extremely simple configuration using only the balance bridge 11 and the photocouplers 12 and 13, the hybrid function of the balance bridge is lost. No signal leaks from the transmission terminals E and F of the 4-wire line to the reception terminals G and H without being disturbed, and the common-mode noise that arrives at the transmission / reception terminals J and K from the 2-wire line side is received. It is possible to realize 4-line / 2-line conversion of a communication path that does not appear at terminals G and H. Further, in this case, since the operational amplifier is not used, it is possible to effectively remove common-mode noise in all frequency bands including noise in a high frequency band outside the operational amplifier operation band, which cannot be removed by the conventional device using the operational amplifier.

FIG. 14 shows an example of a communication device using a card type modem having the hybrid circuit of this embodiment.
In the figure, 801 is a personal computer, 802 is a card type modem, 8
Reference numeral 03 is a connector. The card type modem 802 includes a digital section and a PCMCI in addition to an analog section (see FIG. 11 described later) including the hybrid circuit of this embodiment.
The A interface etc. are also built in. As shown, the thickness of the photo coupler used in the modem 802 is 2
Since it is about mm, the thickness of the modem itself is 2 mm to 5 m.
With a thickness of about m, it can be made very thin.

The card type modem 802 shown in FIG. 14 can be applied to the circuits of the following second to ninth embodiments as well as this embodiment.

In the present embodiment, the circuits connected to the two-wire line, that is, the bridge, the secondary side of the transmitting photocoupler, and the primary side of the receiving photocoupler,
The feature is that it operates only by the current flowing through the two-wire system. Therefore, no other power supply means is required. This is convenient for modem applications.

<Second Embodiment> FIG. 2 shows the configuration of a hybrid circuit according to the second embodiment. In the hybrid circuit of the present example, as shown in the figure, among the elements constituting the balanced bridge circuit 11, the elements connected between the connection points BC and the elements connected between the connection points CD are It is characterized in that it is replaced with third and fourth photocouplers 14 and 15 for preventing leakage from the transmission terminals E and F of the 4-wire line to the reception terminals G and H.

The operation of the hybrid circuit according to the second embodiment will be described below.

When a signal is applied between the transmission terminals E and F of the four-wire line, this signal is transmitted via the first photocoupler 12 to the connection point A of the balanced bridge circuit 11 in the same manner as described above.
-C.

The voltage between the connection points C and D of the balanced bridge circuit 11 is almost the voltage applied to the connection points A and C divided by the resistances R ₁ and R ₄ of the bridge and the primary impedances of the photocouplers 14 and 15. The signal applied between the transmission terminals E and F of the four-wire line is transmitted to the transmission / reception terminals J and K of the two-line line because it is compressed. However, for the voltage applied to the connection points AC, the third and fourth photocouplers 1
Since almost equal currents flow in 4 and 15, a through current corresponding to a signal flows between the voltage sources Vcc and GND in the receiving circuit, but the potential of the terminal G connected to the midpoint between Vcc and GND does not change. Therefore, leakage of the signal applied between the transmission terminals E and F of the four-wire line to the reception terminals G and H is prevented.

On the other hand, when a signal is applied to the transmission / reception terminals J and K of the two-wire line, the potential of the connection point D is equal to the potential of the transmission / reception terminal J, and the potential of the connection point B bridges the potential of the transmission / reception terminal J. Since the voltage is divided by the resistors R ₁ and R ₄ and the primary side impedance of the photocouplers 14 and 15, a potential difference occurs between the connection points BD. Therefore, an optical signal corresponding to this potential difference is transmitted from the light emitting diodes 14a and 15a, and an electromotive force signal corresponding to the optical signal is output from the phototransistors 14b and 15b, so that the transmission / reception terminals J and K of the two-wire line are connected. Is transmitted to the receiving terminals G and H of the 4-wire line.

The hybrid circuit of this example also has the same effects as the hybrid circuit of the first embodiment.

<Third Embodiment> FIG. 3 shows the configuration of a hybrid circuit according to the third embodiment. In the hybrid circuit of this example, the outputs of the phototransistors 14b and 15b on the secondary side of the two photocouplers 14 and 15 having the same characteristics, which are connected to the receiving terminals G and H of the 4-wire line, are differentiated by the differential amplifier 16. It is characterized by dynamic amplification. Other parts are configured in the same manner as the hybrid circuit of the second embodiment.

The hybrid circuit of the present example has a third circuit for the signal applied to the connection points AC of the balanced bridge circuit 11.
Since almost equal currents flow through the fourth photocouplers 14 and 15, the potentials at the input terminals G and H of the differential amplifier 16 become substantially equal, and therefore the transmission terminals E and 4 of the 4-wire line are connected.
Leakage of the signal applied between F to the receiving terminals G and H is prevented. In addition, regarding the signal transmission from the transmission terminals E and F of the 4-wire type line to the 2-wire type line and the signal transmission from the 2-wire type line to the receiving terminal of the 4-wire type line, the hybrid circuit of the second embodiment is used. Since it is the same as, the description of the operation will be omitted.

The hybrid circuit of this embodiment has the same effects as the hybrid circuit according to the first or second embodiment, and the secondary outputs of the photocouplers 14 and 15 are differentially amplified by the differential amplifier 16. Since it is applied to the receiving terminal of the 4-wire type line, a larger gain can be obtained at the receiving terminal of the 4-wire type line.

<Fourth Embodiment> FIG. 4 shows a fourth embodiment of the present invention. The fourth to seventh examples are examples in which the hybrid circuit of the present invention is applied to a modem.

In FIG. 4, T is a transmission terminal of a digital signal processing circuit 3 (see FIG. 16) which constitutes a modem, R is its reception terminal, L ₁ and L ₂ are two-wire lines which constitute a telephone line, and a code Reference numerals 101 and 102 are resistors provided on the primary side of the photocouplers 12 and 13, and reference numeral 103 is a two-wire line L ₁ ,
This is a diode bridge for keeping the polarity of the DC voltage applied to the photocouplers 12 and 13 constant regardless of the polarity of the DC voltage applied to L ₂ . As is apparent from this figure, the negative side terminals of the digital signal processing terminals T and R are dropped to the common ground terminal.

In the present embodiment, the resistance 111 (resistance value R ₁ ), the resistance 112 (resistance value R ₂ ), the resistance 113 and the capacitor 114, and the impedance of the two-wire lines L ₁ and L ₂ (combined impedance R 1). ₃ ) and the resistor 115 (resistance value R ₄ ) form a balanced bridge circuit 11 for adding a hybrid function. The secondary side 12b of the first photocoupler 12 is connected between the connection points A and C of the balanced bridge circuit 11, and the primary side 13a of the second photocoupler 13 is connected between the connection points B and D. Insulation is achieved between the terminals.

Since the operation principle of the modem of this example is the same as that of the hybrid circuit according to the first embodiment, its explanation is omitted to avoid duplication. The modem of this example can prevent leakage of a signal from the transmission terminal T of the digital signal processing circuit to the reception terminal R.

<Fifth Embodiment> FIG. 5 shows a fifth embodiment of the present invention. The modem of this example is characterized in that a commercially available photocoupler is not sufficient in terms of transmission efficiency and allowable current, and a current amplification circuit using a transistor is added to compensate for this. In this figure, reference numeral 2
Reference numerals 10 and 220 denote current mirror circuits which are current amplifier circuits, and the other parts corresponding to those in FIG. 4 have the same reference numerals.

The first current mirror circuit 210 is the first photo coupler 1 connected to the transmission terminal T of the 4-wire line.
2 which amplifies the output current, and includes two transistors 211, 212 and three resistors 213, 214, 2
15 and two capacitors 216 and 217 connected in parallel to the resistors 213 and 214. Photo coupler 1
The output current of 2 is the combined impedance of the resistor 213 and the capacitor 216, and the resistor 214 and the capacitor 217.
It is amplified at a ratio according to the ratio to the combined impedance of.

The second current mirror circuit 220 is the second photocoupler 1 connected to the receiving terminal R of the 4-wire type line.
Which amplifies the input current of 3 and includes two transistors 221, 222 and three resistors 223, 224, 2
25 and two capacitors 226 and 227 connected in parallel to the resistors 223 and 224. Photo coupler 1
The input current of 3 is the combined impedance of the resistor 223 and the capacitor 226, the resistor 224 and the capacitor 227.
It is amplified at a ratio according to the ratio to the combined impedance of.

Since the operation principle of the modem of this example is the same as that of the hybrid circuit according to the first embodiment, its explanation is omitted to avoid duplication. The modem of this example has the same effect as that of the modem of the fourth embodiment, and since a current amplifier is provided on the secondary side of the first photocoupler 12 and the primary side of the second photocoupler 13, sufficient transmission is possible. There is an effect that efficiency can be obtained and signal transmission can be stabilized. Although the current mirror circuit is used as the current amplifier circuit in the present embodiment, it is of course possible to apply another current amplifier circuit instead of the current mirror circuit.

<Sixth Embodiment> FIG. 6 shows a sixth embodiment of the present invention. The modem of this embodiment is characterized by applying the hybrid circuit of the second embodiment. In this figure, reference numeral 320 is a current mirror circuit which is a current amplifier circuit, reference numeral 330 is a reference voltage source, reference numeral 340 is a resistor, and the same reference numerals are displayed in other portions corresponding to FIGS. 2 and 4. There is.

In the present embodiment, the balanced bridge circuit 1
1 is the resistance 311 connected between the connection points A and B, the resistors 312 and 313 and the capacitor 317 connected between the connection points B and C, the primary impedance of the third photocoupler 14, and the connection point C. Resistor 31 connected between -D
4, 315, a capacitor 318, a primary side impedance of the fourth photocoupler 15, and a resistor 316 connected between the connection points DA. Resistance 31
When the resistance values of ₁ to 316 are R _{1 to} R ₆ , respectively,
R ₁ = R ₆ , R ₅ = R ₁ + R ₆ , R ₃ = R ₄ , R ₂ = line impedance (impedance of the two-wire line seen from the balanced bridge circuit 11) and the capacitor 31
The bridges can be balanced by setting the capacitance of 7,318 so that the impedance is sufficiently low in the used frequency band. The secondary side of the first photocoupler 12 is connected between the connection points A and C of the balanced bridge circuit 11, the primary side of the third photocoupler 14 is connected between the connection points B and C, and the connection point C , D is connected to the primary side of the fourth photocoupler 15 to insulate the terminals.

The current mirror circuit 320 amplifies the output current of the photocoupler 12 connected to the transmission terminal T of the 4-wire line, and includes two transistors 321 and 3.
22 and two resistors 323 and 324. The output current of the photocoupler 12 is amplified by a ratio according to the ratio of the resistors 323 and 324.

The reference voltage source 330 is composed of a Zener diode 331 and a resistor 332, and includes a photo coupler 14
Is connected to the secondary side via a resistor 340.

The operation of the modem of this embodiment will be described below.

The signal applied to the transmission terminal T of the 4-wire system is connected to the connection point AC of the balanced bridge circuit 11 via the resistor 101, the photocoupler 12 and the current mirror circuit 320.
Transmitted in between. In this signal, the impedance between the connection points C and D is R _CD , and the impedance between the connection points D and A is R
_{When DA} , it is multiplied by R _CD / (R _DA + R _CD ) times and transmitted to the terminals L ₁ and L ₂ of the two-wire line.

On the other hand, the signals applied to the terminals L ₁ and L ₂ of the two-wire line are directly transmitted between the connection points C and D of the balanced bridge circuit 11. This signal has an impedance between connection points B and C as R _BC and an impedance between connection points A and B as R _BC .
_When the impedance between _AB and the connection point D-A is R _DA , it is approximately R _BC / (R _AB + R _DA + R _BC ) times and is transmitted between the connection points B-C. Therefore, the photocoupler 15,
When the signal currents flowing on the secondary side of 14 are I ₁ and I ₂ , respectively, I ₁ : I ₂ = 1: {R _BC / (R _AB + R _DA + R _BC )}
Then, when I ₁ and I ₂ are not equal, the difference component of the signal current flows through the resistor 340, and the receiving terminal R of the four-wire line is
A signal voltage of | I ₁ −I ₂ | × R ₃₄₀ is transmitted through the reference voltage.

Further, for the signal applied to the transmission terminal T of the 4-wire line, I ₁ and I ₂ are equal to each other.
The current flowing through the photocouplers 14 and 15 penetrates from V _CC to ground. Therefore, no signal current flows through the resistor 340, and no signal is transmitted to the receiving terminal R of the 4-wire line.

The modem of this embodiment also has the same effect as the modem of the fifth embodiment.

<Seventh Embodiment> FIG. 7 shows a seventh embodiment of the present invention. The modem of this example is characterized by applying the hybrid circuit of the third embodiment. In this figure, reference numeral 410 indicates a differential amplifier, reference numerals 420 and 421 indicate resistances, and the other portions corresponding to those in FIG. 6 have the same reference numerals.

The differential amplifier 410 includes operational amplifiers 411 and
412, resistors 413 to 417, a capacitor 418,
419 and amplifies the difference component of the signals applied to the connection points X and Y. For other parts, refer to the above 6th
Since it is the same as the modem of the embodiment, its description is omitted to avoid duplication.

As described in the sixth embodiment, the signal applied to the transmission terminal T of the 4-wire type circuit is transmitted between the connection points A to C of the balanced bridge circuit 310, and the two lines are connected from the connection points C to D. It is transmitted to the terminals L ₁ and L ₂ of the formula line. On the other hand, the signals applied to the terminals L ₁ and L ₂ of the _two- wire line are transmitted to the receiving terminal R of the four-wire line via the balanced bridge circuit 310. Further, with respect to the signal applied to the transmission terminal T of the four-wire line, the currents I ₁ and I ₂ flowing at the connection points X and Y are almost equal, so that the output of the differential amplifier 410 becomes almost zero, No signal is transmitted to the receiving terminal R of the 4-wire line.

Therefore, the modem of this embodiment also has the same effect as the modem of the sixth embodiment.

<Eighth Embodiment> FIGS. 8A and 8B show an eighth embodiment of the present invention. In this embodiment, in the hybrid circuit of the first embodiment, two sets of transmitting or receiving photocouplers are used, and two photocouplers are provided with signals having opposite phases and equal amplitudes, so-called push-pull. It is what makes it work. Figure 8 (a)
Shows an actual circuit, and FIG. 8B shows an equivalent circuit thereof. The figure shows the case where the receiving photocoupler has a push-pull configuration. In the figure, 450 to 452 are capacitors for passing an AC signal and blocking DC, 453 is a constant current diode,
Z indicates the line impedance, and the other parts corresponding to those in FIG. 1 are designated by the same reference numerals. In the case of a modem, for example, ITU-T (formerly CCITT) V.2 is a standard for performing full-duplex communication at 2400 bps. There is 22 bis. This is the carrier frequency of the caller modem and the callee modem, 1200 Hz and 2400 Hz, respectively, 1 to 2.
Since the frequency of the ratio is used, the second harmonic distortion becomes a problem. If the push-pull operation is performed, even harmonics cancel each other out, and good communication can be expected.

In FIG. 8A, the photocoupler 14 is for + phase reception, the photocoupler 15 is for −phase reception, and the photocoupler 12 is for transmission. Try to perform class action. The photocoupler 14 and the photocoupler 15 are connected in series in terms of direct current, and are applied with the same value of direct current bias. However, the condenser 452 causes the photocoupler 1
Since the anode of No. 4 and the cathode of the photocoupler 15 are connected, a signal of opposite phase is applied in terms of AC.

Therefore, when an AC voltage is applied between the terminals J and K, and thus an AC voltage is applied between the connection points D and B,
When the amplitude swings in the + direction, the current of the photocoupler 14 increases and the current of the photocoupler 15 decreases. Further, when the amplitude swings in the-direction, the current of the photocoupler 15 increases.

When the push-pull operation is performed in this way,
The even-order harmonic distortion is canceled out, the gain is increased by 6 dB, and the random noise is increased by only 3 dB. As a result, the S / N is improved by 3 dB. Similarly, the transmission photocoupler 12 can also be configured as a push-pull structure to remove even-order harmonic distortion.

This embodiment also has the same effects as the first embodiment.

<Ninth Embodiment> FIG. 9 shows a ninth embodiment of the present invention. This embodiment is intended to improve one of the problems caused by the product variation of the photocoupler in each of the above-mentioned embodiments. This problem will be described with reference to the embodiment shown in FIG. When a photocoupler is used, an appropriate DC bias current is applied to the photocoupler on the primary side. At this time, a current that flows by multiplying the bias current on the primary side by the current transfer efficiency of the photocoupler flows on the secondary side.

In the present invention, an electronic circuit may be connected to the subsequent stage of the photocoupler secondary side. For example, when the circuit of FIG. 4 is used for the NCU (Network Control Unit) of the modem, the secondary side 13b of the photocoupler 13 is used in this circuit.
Is received by the load resistor 116 having a resistance value RL, and the terminal G
Is connected to an electronic circuit in the subsequent stage by resistance-capacitance coupling (not shown).

In this circuit, the product variation of the photo coupler tends to affect the operating point of the circuit. That adversely affects the maximum allowable output voltage of the circuit. The maximum allowable output voltage of the circuit will be described below by analyzing the operation of this circuit.

In the embodiment according to FIG. 4, the DC potential V of the secondary output terminal G of the photocoupler 13 is the power supply voltage Vcc, the value of the resistor 116 is RL, and the photocoupler 1
When the direct current flowing on the secondary side of 3 is I ₂ , it is determined by V = Vcc-I ₂ × RL. As described above, the current flowing to the secondary side of the photocoupler is proportional to the transmission efficiency of the photocoupler, and therefore the DC potential of the secondary side output terminal is also proportional to the current transmission efficiency of the photocoupler.

The maximum allowable output voltage at the output terminal G of the photocoupler depends on the DC potential V at the output terminal of the photocoupler. The reason is that the output voltage of the photocoupler swings in positive and negative directions around the DC potential V of the output terminal (usually ½ of the power supply voltage Vcc), and when swinging in the positive direction, the power supply voltage Vcc is changed. This is because there is a restriction that the voltage cannot be exceeded and a restriction that the voltage cannot fall below the GND potential when swinging in the negative direction.

In order to maximize the maximum allowable output, the DC potential V of the output terminal is designed to be 1/2 of the power supply voltage Vcc when the current transfer efficiency of the photocoupler is maximum. However, in the case of such a design, assuming that the current transfer efficiency of the photocoupler varies ± 6 dB around the standard value, the current transfer efficiency becomes the standard value (maximum value of 2).
In the case of 1), the DC potential of the output terminal becomes 3/4 of the power supply voltage Vcc. At this time, the maximum allowable swing width in the plus direction is Vcc- (3/4) Vcc = (1/4) Vcc. Therefore, the maximum allowable output is a peak-to-peak value of about 1 of the power supply voltage Vcc. / 2.

As one example, when the power supply voltage is 3.3 V and the secondary side direct current is 1 mA, the value of the resistance RL is 3.3 ÷ (4 × 1 × 10 ³ ) = 825Ω.

Incidentally, such a problem is caused by the load resistance (R
Similarly, when L) 116 is connected between the photocoupler 13 and the ground point GND and the output is taken out from both ends of the resistor 116, the same occurs.

When the input impedance of the subsequent electronic circuit is sufficiently high, the "current → voltage conversion efficiency" at the coupling portion between the photocoupler output terminal and the subsequent electronic circuit is proportional to the value of RL. Therefore, if the value of RL can be effectively increased, the “current-voltage conversion efficiency” can be increased.

The ninth embodiment shown in FIG. 9 provides one means for solving the above problems.

In this embodiment, the photo coupler 13 is used in the above example.
In place of the resistor connected to the output terminal of, the power supply circuit 510 of an electronic circuit is connected as a load. The load power supply circuit 510 includes transistors 511,
512, resistors 513 and 514, and a bypass capacitor 515, which are connected between the secondary side of the photocoupler 13 and the ground. The load power supply circuit 510 operates as a constant voltage circuit in terms of direct current and operates as a constant current circuit in terms of alternating current. In FIG. 9, the same reference numerals are displayed in the portions corresponding to those in FIG. 520 is a line driver (output driver), 540 is a semiconductor inductor circuit, 550 is a rectifier circuit, and 551 and 552 are power supplies.

The load power supply circuit 510 will be described. Since the transistors 511 and 512 function as a bypass of the current that flows in the photocoupler 13, the DC current and the load power supply circuit 510 do not flow.
The currents flowing through are equal. And the photo coupler output terminal G
The DC potential V _{OUT at} is _calculated as follows. V _OUT = {(R ₅₁₃ + R ₅₁₄ ) × V _BE × 2} / R ₅₁₄ ≈Vcc / 2 where R ₅₁₄ is the value of the resistor 514 and R ₅₁₃ is the resistor 5
The value of 13 is V _{BE, which} is the base-emitter voltage for each of the transistors 511 and 512.

In this embodiment, the DC potential at the photocoupler output terminal G does not change much depending on the flowing current.
Therefore, if the DC potential is set to about 1/2 of the power supply voltage Vcc in advance, the output voltage can be swung up to the full power supply voltage.

This means that the maximum allowable output voltage can be doubled as standard as compared with the circuit of FIG. 4 described above.

On the other hand, the load power supply circuit 510 operates as a constant current circuit in terms of alternating current. The operation will be described. A capacitor 5 is provided at the base terminal of the transistor 511.
15 is connected, and the resistors 513, 514 and the capacitor 515 form a low-pass filter. By the action of this low-pass filter, the transistors 511, 514 are
A signal with a frequency lower than the cutoff frequency of the filter is transmitted to the. Therefore, the circuit does not respond to signals with a frequency higher than the cutoff frequency of the filter,
A constant current will continue to flow. Therefore, this circuit operates as a constant current circuit in terms of alternating current.

As a result of this operation, the impedance of this circuit is the series value of resistors 513,514. That is, the value of the AC load resistance viewed from the photocoupler 13 is the series value of the resistors 513 and 514. This resistor 51
The series value of 3,514 can be easily set to several tens of KΩ.

As described above, the "current-to-voltage conversion efficiency" is proportional to the resistance value of this portion. In this example,
The resistance value can be easily increased several tens of times as compared with the example according to FIG. 4 described above. Therefore, the efficiency can be increased accordingly.

In the above embodiment, the load power supply circuit 510 is provided between the secondary side of the photocoupler 13 and the ground. However, instead of this, a similar load power supply circuit 510 is provided.
Can be provided between the secondary side of the power supply Vcc and the power supply Vcc. In addition to this, a similar load power supply circuit can be provided as a secondary load of the transmission photocoupler 12.

This embodiment also has the same effect as the above-mentioned embodiments.

<Tenth Embodiment> FIG. 10 shows the first embodiment of the present invention.
0 Example is shown. The present embodiment is an application of the present invention to a wireless transceiver. It is used when one antenna of the wireless transceiver is used for both transmission and reception.

In FIG. 10, 601 is an antenna and 602 is F.
M transmitter, 603 is FM receiver, 604 is a constant current diode, 605 is a load resistance (RL), and the portions corresponding to those in FIG. Antenna 601
Is used for both transmission and reception, and the impedance Z and the remaining impedance elements R1 to R3 form a four-terminal balanced bridge 11. As in the other embodiments, the bridge 11 is connected to the receiving photocoupler 13 to separate the transmission signal and the reception signal.

When the present embodiment is used in the wireless communication at a relatively short distance, the signal level of the received signal can be made higher than the signal level of the transmitted signal leaking into the receiving circuit due to the imbalance of the bridge. it can.

The FM receiver has the property of selectively receiving only the signal with a higher signal level when radio waves of the same frequency enter. This is called the capture effect. By utilizing this capture effect and combining this embodiment, it is possible to perform bidirectional communication using the same frequency for the transmission frequency and the reception frequency.
The present embodiment can be applied even when the transmission carrier frequency and the reception carrier frequency are different.

In this embodiment, the photocoupler only needs to be provided between the bridge and either the receiver or the transmitter, whereby both the transmission terminal and the negative terminal of the reception terminal can be grounded.

<Eleventh Embodiment> FIG. 11 is a block diagram showing a schematic structure of an analog portion including a 4-wire / 2-wire converting portion and an NCU portion of a modem in which the embodiment of FIG. 9 is mounted. Figure 9
The same reference numerals are given to the portions corresponding to. In addition, in the present embodiment, in addition to the one in FIG. 9, a photocoupler variation compensation circuit 560, a temperature compensation circuit 561, a calling circuit 562,
Also, a surge absorber 563 is added.

<Twelfth Embodiment> FIGS. 12 and 13 are explanatory views of a twelfth embodiment of the present invention. FIG.
FIG. 12 is a diagram for explaining the operation. In this embodiment, in a signal transmission circuit (signal transmission circuit) for transmitting a signal to a line using a photocoupler, even if the characteristics of the current transfer rate of the photocoupler vary around the standard value, this variation is compensated for. It is designed to always obtain an appropriate output, and can be used, for example, in the photocoupler variation compensating circuit 560 in the embodiment shown in FIG. In this case, the power supply Vcc and the ground in FIG. 13 can be taken not from the terminal side but from the line side.

Generally, when a signal is transmitted to a telephone line using a modem or the like, the maximum transmission level is fixed. The maximum and minimum values for the current transfer rate of the photocoupler are centered around the standard value.However, if the maximum output level is specified, it is assumed that the current transfer rate of the photocoupler is maximum. The sending circuit must be designed so that the sending level does not exceed a specified level.

However, in the case of mass-produced photocouplers, the standard value of the current transfer rate is 3 to 5 dB lower than the maximum value even if they are carefully selected. Therefore, if the circuit is designed assuming the maximum current transfer rate, the output power is 3 to 5 dB below the limit value of the maximum output level when the standard value photocoupler is used without adjustment.
It will be low.

Since the photo coupler is a kind of semiconductor,
The distribution of the current transfer rate of the photocoupler group in the same production lot has the most standard value (median value), as is known in various distribution curves such as normal distribution. , There are few that take values around the maximum and minimum values. Therefore, there is a problem in that it is desired to increase the output power within the range of the limit value, but the output power becomes low when the most standard photocoupler is used.

The horizontal axis x in FIG. 12 shows the current transfer rate of the photocoupler normalized and its standard value set to 1. That is, as described above, when the current transfer rate is distributed in a certain range for the photocoupler group belonging to a certain group and the distribution is not random but mountain-shaped based on statistical properties, this mountain-shaped The current transfer rate (the current transfer rate of the photocoupler with the largest number of samples) at the top of is shown normalized to the standard value 1. When the distribution is random, the median value of the distribution is normalized to the standard value 1 and shown. 12
The vertical axis y of indicates the output value of each part of the signal transmission circuit (signal transmission circuit) using the photocoupler.

In FIG. 13, the signal transmission circuit (corresponding to the photocoupler variation compensation circuit 560 of FIG. 11 as described above) is a voltage control type variable gain amplifier (multiplication circuit) 7
01, current transmissibility x detection (measurement) circuit 702, 2-
The x operation circuit 703 and the signal component removal circuit 704 are included. The detection circuit 702 has a resistor 705, and the arithmetic circuit 703 has resistors 706 and 708 and a reference power source (Er) 71.
1 and a differential amplifier 710, and a signal component removal circuit 704
Has a resistor 709 and a capacitor 712. Reference numeral 12 is a photocoupler on the transmission terminal side. As described above, the current transfer rate x is the secondary current I ₂ / primary current I _{1 of the} photocoupler.
Is a normalized value of.

When a constant input is applied to the primary side of the photocoupler, the output of the photocoupler is proportional to the current transfer rate x, so that the output y of the amplifier 701 during no adjustment (when not controlled) is y.
Is similarly proportional to the current transfer rate x of the photocoupler.
As shown by the straight line of 2, it is given by y = x (1). (Note that when x = 1, the values are normalized so that y = 1). On the other hand, the control input to the amplifier 701 (the output of the signal component removing circuit 704) is given by y = k (2-x) (2) as shown by the straight line in FIG. 12, when k is a real number. (In FIG. 12, it is shown by normalizing to k = 1). Therefore, the output of the amplifier 701 during control is obtained by multiplying the equations (1) and (2) as shown in FIG.
As shown by the quadratic curve of y = k {x (2-x)} = k {1- (x-1) ² } (3).

As is clear from the comparison between the straight line and the quadratic curve, when the amplifier 701 is uncontrolled (straight line), the maximum allowable output (y =) at the standard current transfer rate (x = 1).
If the amplifier 701 is designed so as to obtain 1), the output of the amplifier 701 exceeds the maximum allowable output when the current transfer coefficient deviates from the standard value to the right side (x> 1) in the figure. . Therefore, when the present embodiment is not applied, the amplifier 701 at the standard current transfer rate (x = 1) is used.
The output value of 3 dB to 5 than the maximum allowable output as described above.
It was set to a low value by dB.

On the other hand, in this embodiment, as is clear from the quadratic curve, the value of y becomes maximum at x = 1, so that the current transfer rate x of the photocoupler is a standard value (x =
The value of y is x regardless of the deviation from 1) to either side.
The value when = 1 is never exceeded. Therefore, the amplifier 701 can be designed so that the maximum allowable output (close to the maximum output) can be obtained when the current transfer rate x of the photocoupler is the standard value 1. Therefore, by using photocouplers with various variations. An efficient output can always be obtained.

The present embodiment can be applied not only to the photocoupler 12 on the transmitting side but also to the photocouplers 13 to 15 on the receiving side.

<Others> In the first to tenth embodiments, only the case where the photocoupler is used as the insulating interface element has been described, but an optical coupling element other than the photocoupler may be used, and , Current detection using Hall element
Source current, transistor and base current to this transistor
It is also possible to use an insulating interface element other than the optical coupling element, such as an insulating amplifier and a semiconductor relay , each of which is composed of a minute transformer for supplying the .

Further, one of the resistors forming the balanced bridge in each of the above-described embodiments may use the circuit impedance.

Further, in the above embodiment, only the hybrid circuit and the modem incorporating the hybrid circuit have been described, but in addition, the hybrid circuit according to the embodiment may be incorporated to form a telephone line switch or repeater. it can.

[0117]

As described above, according to the present invention,
A balanced bridge circuit is provided between the 4-wire line and the 2-wire line, and an insulating interface element such as a small photocoupler is provided between the terminals of each line, or
Short-circuiting the sides of the balanced bridge circuit because some of the components of the balanced bridge circuit that are interposed between the two-wire line and the two-wire line have been replaced with an insulating interface element such as a small photocoupler. Can be used by grounding both the transmission terminal and the reception terminal of the 4-wire type line.
It is possible to realize 4-line / 2-line conversion of a communication path with a thin hybrid circuit of a small number of small circuit components without using a large transformer.

Further, common-mode noise of a wide frequency band arriving at the 2-wire line is prevented from being mixed into the receiving terminal of the 4-wire line, and the S / N can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a hybrid circuit according to a first embodiment.

FIG. 2 is a circuit diagram of a hybrid circuit according to a second embodiment.

FIG. 3 is a circuit diagram of a hybrid circuit according to a third embodiment.

FIG. 4 is a circuit diagram of a modem according to a fourth embodiment.

FIG. 5 is a circuit diagram of a modem according to a fifth embodiment.

FIG. 6 is a circuit diagram of a modem according to a sixth embodiment.

FIG. 7 is a circuit diagram of a modem according to a seventh embodiment.

FIG. 8 is a circuit diagram of a hybrid circuit according to an eighth embodiment.

FIG. 9 is a circuit diagram of a modem according to a ninth embodiment.

FIG. 10 is a circuit diagram of an FM transceiver according to a tenth embodiment.

FIG. 11 is a block diagram showing a schematic configuration of a modem according to an eleventh embodiment.

FIG. 12 is an operation explanatory diagram of a signal transmission circuit according to a twelfth embodiment.

FIG. 13 is a circuit diagram of a signal transmission circuit according to a twelfth embodiment.

FIG. 14 is a diagram showing an appearance of a communication device to which the hybrid circuit of the present invention is applied.

FIG. 15 is an explanatory view of the operation of the present invention.

FIG. 16 is a block diagram of a conventionally known modem.

FIG. 17 is a configuration diagram of a front end portion of a conventionally known modem.

[Explanation of symbols]

11 Balanced bridge circuit 12 to 15 Photo coupler

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-3-231520 (JP, A) JP-A-60-42946 (JP, A) JP-A-54-136252 (JP, A) JP-A-54- 23355 (JP, A) JP 51-46043 (JP, A) JP 53-124948 (JP, A) JP 57-99041 (JP, A) JP 50-138709 (JP, A) JP-A-2-241232 (JP, A) JP-A-3-191625 (JP, A) JP-A-60-19328 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 3/00

Claims (11)

(57) [Claims] 1. A communication formed by a 4-wire type line consisting of a transmitting side line connected to a transmitting terminal and a receiving side line connected to a receiving terminal and a 2-wire type line connected to a transmitting / receiving terminal. In a hybrid circuit for performing 4-wire / 2-wire conversion of a road, a balanced bridge circuit in which a resistor or a resistor and an impedance are bridge-connected, and one connecting point pair diagonally located in the bridge connection of the balanced bridge circuit A first insulating interface element connecting between the transmission side line of the 4-wire type line, the other connecting point pair diagonally located in the bridge connection of the balanced bridge circuit, and the 4-wire type line A second insulating interface element for connecting to a line on the receiving side, and the two-wire line is connected to two adjacent connection points in the bridge connection of the balanced bridge circuit. Bridging circuit. 2. The first and second insulating interface elements are optical coupling elements, respectively, and the primary side of the first optical coupling element as the first insulating interface element is the four-wire line. The secondary side is connected to the transmission side line, and the secondary side is connected to the one pair of connection points of the balanced bridge circuit, and the secondary side of the second optical coupling element as the second insulating interface element is the 4-wire type line. 2. The hybrid circuit according to claim 1, wherein a primary side of the receiving side line is connected to the other pair of connection points of the balanced bridge circuit, respectively. 3. A communication formed by a 4-wire line consisting of a transmitter side line connected to a transmitter terminal and a receiver side line connected to a receiver terminal and a two-line type line connected to a transmitter / receiver terminal. In a hybrid circuit for performing 4-line / 2-line conversion of a path, the hybrid circuit includes two resistance elements and first and second insulation interface elements, and one of the resistances and the first insulation interface element face each other, and A balanced bridge circuit in which the other resistor and the second insulating interface element are bridge-connected in a facing relationship, a connection point of the two resistors of the balanced bridge circuit, and the first and second
A third insulating interface element for connecting the connection point of the second insulating interface element to the line on the transmitting side of the 4-wire type circuit, and the first, second, and third insulating interface elements .
Each of the interface elements is an optical coupling element, and the optical elements as the first and second insulating interface elements are provided.
The primary side of the coupling element is bridge-connected with the balanced bridge circuit.
And the secondary sides are connected in series, this series connection
The four-wire circuit is connected to one end of the body and the connection point between the secondary sides.
A line on the receiving side is connected to the optical coupling element as the third insulating interface element.
The primary side of the child is connected to the transmission line of the 4-wire circuit.
The secondary side is the connection of the two resistors of the balanced bridge circuit.
Point and connection point between the first and second insulation interface elements
And two adjacent two in the bridge connection of the balanced bridge circuit.
A hybrid circuit , wherein the two-wire line is connected to a connection point . 4. A line on the transmission side connected to the transmission terminal and a receiving line.
4-wire type line consisting of the receiving side line connected to the receiving terminal
And a two-wire line connected to the transmitting and receiving terminals.
A hybrid circuit that performs 4-wire / 2-wire conversion of the channel
The two resistance elements and the first and second insulation interface elements.
A resistor, and one of the resistor and the first insulating interface.
Of the second element and the other of the resistance and the second resistance.
The edge interface element and the edge
A balanced bridge circuit that is connected in the same way, a connection point of the two resistors of the balanced bridge circuit, the first
The connection point of the second insulation interface element and the four-wire type
A third insulating interface connected to the transmission side line of the line
A Esu element, said first, second, third insulating interface element respectively, an optical coupling device, first, the primary side of the photocoupler device of the second insulating interface device the Rutotomoni are bridge-connected in a balanced bridge circuit, an increase of the differential output signal of the secondary side is supplied
A width circuit is provided, and the 4-wire circuit is connected to the output terminal of the differential amplifier circuit.
Line is connected to the receiving side line, the primary side of the optical coupling element as the third insulating interface element is connected to the transmitting side line of the 4-wire type line, and the secondary side is the balanced bridge circuit. Connected to the connection point of the two resistors and the connection point of the first and second insulating interface elements, and adjacent to each other in the bridge connection of the balanced bridge circuit.
A hybrid circuit , wherein the two-wire line is connected to a connection point . 5. A line on the transmission side connected to the transmission terminal and a receiving line.
4-wire type line consisting of the receiving side line connected to the receiving terminal
And a two-wire line connected to the transmitting and receiving terminals.
A hybrid circuit that performs 4-wire / 2-wire conversion of the channel
The two resistors and the first isolation interface element.
Impedance circuit and second isolated interface element
A flat bridge consisting of an impedance circuit and a bridge connection
The equilibrium bridge circuit, the connection point between the resistors of the balanced bridge circuit, and the impedance
Connect the connection point between the dance circuits to the transmitter side of the 4-wire line.
Equipped with a third insulation interface element connected to the line
Well, the first, second and third insulation interface elements are
Each of the optical coupling elements is the optical coupling element and the optical elements serving as the first and second insulating interface elements.
The primary side of the coupling element is a bridge connection in the balanced bridge circuit.
And the secondary side output signals are differentially added,
The optical coupling element which is supplied to the receiving side line of the 4-wire type line and serves as the third insulating interface element.
The primary side of the child is connected to the transmission line of the 4-wire circuit.
The secondary side is the resistance of the bridge connection of the balanced bridge circuit.
A connection point between the resistors and a connection point between the impedance circuits
Connected to two adjacent bridge connections of the balanced bridge circuit.
A hybrid circuit , wherein the two-wire line is connected to a connection point . 6. A transmission side line connected to a transmission terminal and a receiving side.
4-wire type line consisting of the receiving side line connected to the receiving terminal
And a two-wire line connected to the transmitting and receiving terminals.
A hybrid circuit that performs 4-wire / 2-wire conversion of the channel
And three resistors and the two-wire circuit, or two resistors
The impedance and the two-wire circuit are bridge-connected
Balanced bridge circuit and the bridge connection of the balanced bridge circuit
Between the pair of connection points and the transmission side line of the 4-wire type line
A first insulation interface element to be connected to the other, which is diagonally positioned by the bridge connection of the balanced bridge circuit
The second and third connection points connected between the connection points that form one connection point pair.
An insulating interface element, and
The third insulating interface elements are the first, second, and third, respectively.
Two optical coupling elements, the primary side of the first optical coupling element being the transmitting side of the four-wire line.
The secondary side is connected to the bridge of the balanced bridge circuit.
And the primary side of the second and third optical coupling elements are respectively connected to the one pair of connection points of
The other pair of connecting points in the diagonal position in the bridge connection of the circuit
Between the two connection points forming
And the secondary sides are connected in series, and this series connection body
Of the 4-wire line at one end of the line and at the connection point between the secondary sides.
A hybrid circuit characterized in that the receiving side line is connected . 7. A communication formed by a 4-wire type line consisting of a transmitting side line connected to a transmitting terminal and a receiving side line connected to a receiving terminal, and a 2-wire type line connected to a transmitting / receiving terminal. In a hybrid circuit that performs 4-wire / 2-wire conversion of a road, three resistors and the two-wire circuit, or two resistors
A balanced bridge circuit in which the impedance and the two-wire line are bridge-connected, and a bridge connection of the balanced bridge circuit, which is in a diagonal position.
Between the pair of connection points and the transmission side line of the 4-wire type line
A first insulation interface element to be connected to the other, which is diagonally positioned by the bridge connection of the balanced bridge circuit
A second insulation cable connected between the connection points of the one connection point pair.
Interface element, and the first and second insulating interfaces.
Each of the interface elements is an optical coupling element, and the optical coupling element as the first insulating interface element.
The primary side of the child is the secondary side of the transmission line of the 4-wire line.
Is the one connection point of the bridge connection of the balanced bridge circuit
The optocoupler as the second insulating interface element , which is connected to each pair .
The primary side of the child is diagonal with the bridge connection of the balanced bridge circuit
The secondary side is connected to the other connecting point pair at the position
Connected to the receiving side line of the line and the secondary
On the side, it operates as a constant voltage circuit for DC, and for AC
A hybrid circuit that is equipped with a load circuit that operates as a constant current circuit. 8. The insulating interface element is a current detector using a Hall element.
1. The hybrid circuit according to 1 . 9. The hybrid circuit of claim 1, wherein said insulating interface element is an insulating amplifier for supplying a base current to the transistor and the transistor. 10. A modem comprising the hybrid circuit according to any one of claims 1-9. 11. claimed comprising a hybrid circuit according to any one of claims 1 to 9, an output terminal of the transmitting terminal that the sender of the line is connected to the four-wire line transmitter, the 4 The receiving terminal to which the line on the receiving side of the wire line is connected is an input terminal of the receiver, and the transmitting / receiving terminal to which the 2-wire line is connected is a terminal of a transmitting / receiving antenna. Wireless transceiver.