JP2002094594A - Interface circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interface circuit with power consumption suppressed low by feeding current suitable to a communication speed. SOLUTION: A terminal side 1 is provided with a transistor 12 and a resistor 11 for feeding current quantity corresponding to a 1st communication speed, and a transistor 16 and a resistor 15, and an NCU side 5 is provided with a transistor 52 and a resistor 51, and a transistor 56 and a resistor 55. The terminal side 1 is also provided with a transistor 14 and a resistor 13 for feeding current quantity corresponding to a 2nd communication speed, and a transistor 18 and a resistor 17, and the NCU side 5 is provided with a transistor 54 and a resistor 53, and a transistor 58 and a resistor 57. The current quantity corresponding to the communication speeds is fed to photocouplers 61 and 71 by switching a transistor and a resistor to be used in accordance with the communication speeds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface circuit and, more particularly, to an isolator of a device for collecting data of power, gas, water, security, etc. using a communication line and transmitting the collected data to a remote place. Related to rate system.

[0002]

2. Description of the Related Art In recent years, a meter equipped with a communication function collects data on the amount of use of electric power, gas, water, and the like, and security data, and transmits the collected data to a distant place via a communication line or wireless communication. Is being developed. In such a technology, the collected data is transmitted to a remote site using a communication line, etc., so that noise and lightning surge can be prevented from entering the terminal device such as a measuring instrument from the communication line, and a short circuit accident in the terminal device can be prevented. Terminal device such as a measuring device and a network control device (hereinafter referred to as NCU) for guiding a signal from the terminal device to a telephone line in order to prevent a current from flowing out of the communication line.
Is required.

Conventionally, as an interface circuit for such an isolation, for example, Japanese Patent No. 2,655
As disclosed in Japanese Patent No. 4,039, there is a circuit that transmits a necessary signal while maintaining electrical isolation using a photocoupler.

[0004]

Various communication speeds are used for communication using a communication line.
For this reason, in an interface circuit using a photocoupler as described in the above publication, the amount of current supplied to the photocoupler is set to the amount of current that allows the highest speed communication so as not to cause power shortage during high-speed communication. ing.

Therefore, in the conventional interface circuit, even at the time of low-speed communication that does not require a very large current,
Since a large current for high-speed communication always flows, there is a problem that unnecessary power consumption is performed.

[0006] The present invention has been made in view of the above,
An object of the present invention is to provide an interface circuit capable of improving power consumption corresponding to various communication speeds.

[0007]

According to a first aspect of the present invention, there is provided an interface circuit having transmission means for transmitting a signal between a terminal device and a network control device. The gist of the present invention is to have a current amount switching means for switching the amount of current supplied to the terminal device side and the network control device side in accordance with a plurality of communication speeds.

According to the present invention, the current amount switching means switches the amount of current supplied to each of the terminal device side and the network control circuit side in accordance with a plurality of communication speeds, so that the amount of current most suitable for each communication speed is obtained. It is intended to supply a current and thereby reduce unnecessary power consumption.

According to a second aspect of the present invention, in the interface circuit according to the first aspect, the current amount switching means includes: a plurality of current limiting resistors corresponding to the plurality of communication speeds; The present invention has a plurality of switching transistors provided for each of the transistors, and individually controlling the supply of current to the current limiting resistor.

According to the present invention, the switching transistor is turned on or off according to a plurality of communication speeds,
By controlling the supply of current to the current limiting resistor provided corresponding to a plurality of communication speeds, the amount of current supplied to each of the terminal device and the network control device is to be adapted to the plurality of communication speeds. Is what you do.

According to a third aspect of the present invention, in the interface circuit according to the first or second aspect, the transmission means is formed by a photocoupler.
The photocoupler includes a first photocoupler used when transmitting a signal from the terminal device to the network control device, and a second photocoupler used when transmitting a signal from the network control device to the terminal device. And a photocoupler.

According to the present invention, there is provided a first photocoupler used when transmitting a signal from a terminal device to a network control device, and a second photocoupler used when transmitting a signal from the network control device to the terminal device. Thus, two-way communication can be performed between the terminal device and the network control device.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a configuration of an interface circuit according to a first embodiment of the present invention.

This interface circuit includes power, gas,
This is a circuit for performing only signal transmission in a state of being electrically insulated between a terminal device which is a measuring device such as a water supply and an NCU connected to a communication line.

First, the configuration of the terminal 1 includes a signal control switching transistor 10 for outputting a communication signal,
A first current limiting resistor 11 and a first switching transistor 12 for supplying a current corresponding to a first communication speed when receiving a signal, and a second switching transistor 12 for supplying a current according to a second communication speed when receiving a signal. A second current limiting resistor 13 and a second switching transistor 14, a third current limiting resistor 15 and a third switching transistor 16 for supplying a current corresponding to the first communication speed when transmitting a signal, and a third switching transistor 16 when supplying a signal. 4th for supplying a current corresponding to the communication speed of 2
, A current limiting resistor 17 and a fourth switching transistor 18, and a switching transistor 19 that switches between transmission and reception of signals in response to a switching signal from a control circuit (not shown) on the terminal side 1.

Each of the first switching transistor 12, the second switching transistor 14, the third switching transistor 16, and the fourth switching transistor 18 has an emitter connected to a power supply line, and The power supply to the current limiting resistors connected to the respective collectors is controlled by being turned on or off according to the communication speed by a control circuit (not shown).

On the other hand, the configuration of the NCU 5 is a signal control switching transistor 5 for outputting a communication signal.
0, a first current limiting resistor 51 and a first switching transistor 52 for supplying a current according to a first communication speed when receiving a signal, and for supplying a current according to a second communication speed when receiving a signal Of the second current limiting resistor 53 and the second
A switching transistor 54, a third current limiting resistor 55 and a third switching transistor 56 for supplying a current corresponding to the first communication speed when transmitting a signal, and a current corresponding to the second communication speed when transmitting a signal. A fourth current limiting resistor 57 and a fourth switching transistor 58 for supplying power, a light emitting diode 63 and a phototransistor 6
5, a photocoupler 6 for transmitting a signal from the NCU side 5
1, light emitting diode 73 and phototransistor 7
5, a photocoupler 71 for receiving a signal from the terminal side 1
Consisting of

Each of the first switching transistor 52, the second switching transistor 54, the third switching transistor 56, and the fourth switching transistor 58 has an emitter connected to the power supply line, and the NCU 5 The power supply to the current limiting resistors connected to the respective collectors is controlled by being turned on or off according to the communication speed by a control circuit (not shown).

In this interface circuit, when the third current limiting resistor 15 of the terminal 1 and the first current limiting resistor 51 of the NCU 5 transmit a signal from the terminal 1 at a first communication speed. And a resistance adjusted so that an amount of current suitable for the first communication speed is supplied to the light emitting diode 73 and the phototransistor 75 of the photocoupler 71. When the second current limiting resistor 53 of the NCU 5 transmits a signal from the terminal 1 at a second communication speed different from the first communication speed, an amount of the signal suitable for the second communication speed is used. The current is applied to the light emitting diode 73 of the photocoupler 71 and the phototransistor 75
Is a resistor tuned to be supplied to

The first current limiting resistor 11 of the terminal 1
And the third current limiting resistor 55 on the NCU side 5
When transmitting a signal at a first communication speed from
Is a resistance adjusted so that an amount of current suitable for the communication speed is supplied to the light emitting diode 63 and the phototransistor 65 of the photocoupler 61, and the second current limiting resistor 13 of the terminal 1 and the NCU 5 The second current limiting resistor 57 is
When a signal is transmitted from the NCU side 5 at a second communication speed different from the first communication speed, an amount of current suitable for the second communication speed is supplied to the light emitting diode 63 and the phototransistor 65 of the photocoupler 61. Resistance adjusted to be supplied.

The operation of the thus configured interface circuit in the present embodiment will be described.

First, a case where a signal is transmitted from the terminal 1 at the first communication speed will be described. In this case, the terminal side 1
Therefore, a "low" signal is supplied to the base of the switching transistor 19 for switching between transmission and reception, and the base is set to off.

The first switching transistor 12 on the terminal side 1 and the third switching transistor 1
6 are both turned on by supplying a "low" signal as a control signal to their bases. Also, NCU
The first switching transistor 52 on the side 5 is also turned on by supplying a “low” signal as a control signal to the base. At this time, the "high" signal is supplied to the other switching transistors 14, 18, 54, 56, and 58, and all of them are off. Further, the base signal of the signal control switching transistor 10 is “low”.

Thus, a current corresponding to the first communication speed is supplied to the light emitting diode 73 of the photocoupler 71 by the first current limiting resistor 11 and the third current limiting resistor 15 on the terminal side 1. The preparation is completed, and the phototransistor 75 is ready to be supplied with the current corresponding to the first communication speed by the first current limiting resistor 51 on the NCU side 5.

In this state, when the signal output from the terminal 1 causes the base signal of the switching transistor 10 for signal control to become “high”, the light emitting diode 73 supplies a current corresponding to the first communication speed. Flows to emit light, and the light emission turns on the phototransistor 75,
A current corresponding to the first communication speed is supplied to the phototransistor 75.
Flows from the collector side to the emitter side. As a result, the communication signal from the terminal 1 is transmitted to the NCU 5.

Next, a case where a signal is transmitted from the terminal 1 at the second communication speed will be described. Also in this case, the transmission / reception switching transistor 19 is turned off as in the previous case. Then, the second switching transistor 14 and the fourth switching transistor 18 of the terminal 1 are both "low" as a control signal to their bases.
A signal is supplied and turned on. NCU side 5
The second switching transistor 54 is also turned on by supplying a “low” signal as a control signal to the base. At this time, the other switching transistors 12, 1
Each of 6, 52, 56, and 58 is set off by receiving a "high" signal.

Thus, similarly to the above case, the light emitting diode 73 of the photocoupler 71 has a current corresponding to the second communication speed by the second current limiting resistor 13 and the fourth current limiting resistor 17 on the terminal side 1. Is ready to be supplied, and the phototransistor 75 is ready to be supplied with a current corresponding to the second communication speed by the second current limiting resistor 53 on the NCU side 5.

Then, by the signal output from the terminal side 1,
When the base signal of the signal control switching transistor 10 becomes “high”, a current corresponding to the second communication speed flows through the light emitting diode 73 to emit light, and the light emission turns on the phototransistor 75. , A current corresponding to the second communication speed flows from the collector side of the phototransistor 75 to the emitter side. As a result, the communication signal from the terminal 1 is transmitted to the NCU 5.

Next, a case where a signal is transmitted from the NCU 5 at the first communication speed will be described. In this case, NC
Since transmission from the U side 5, that is, reception of a signal at the terminal side 1, the transmission / reception switching switching transistor 1
The base of 9 is turned on by supplying a "high" signal. As a result, the third current limiting resistor 15 and the fourth current limiting resistor 17 are grounded, and the third switching transistor 16 or the fourth switching transistor 18
As a result, no voltage is applied to the light emitting diode 73, and the transmission from the terminal 1 is stopped.

Then, the first switching transistor 12 on the terminal side 1 and the third switching transistor 56 on the NCU side 5 are both turned on by supplying a "low" signal as a control signal to their bases. You. At this time, the other switching transistors 14, 52, 5
4 and 58 are all turned off by supplying a "high" signal.

Accordingly, the light emitting diode 63 and the phototransistor 65 of the photocoupler 61 correspond to the first communication speed of the first current limiting resistor 11 of the terminal 1 and the third current limiting resistor 55 of the NCU 5. Ready for the supplied current. In this state, when the base signal of the signal control switching transistor 50 becomes “high” due to the signal output from the NCU 5, a current corresponding to the first communication speed flows through the light emitting diode 63. The photo transistor 65 is turned on by this light emission, and a current corresponding to the first communication speed flows from the collector side of the photo transistor 65 to the emitter side.
Thereby, the communication signal from the NCU side 5 is transmitted to the terminal side 1.

Next, a case where a signal is transmitted from the NCU 5 at the second communication speed will be described. Also in this case, the transmission / reception switching transistor 19 is turned on. Then, the second switching transistor 14 of the terminal 1
And the fourth switching transistor 58 on the NCU side 5
Are both turned on by supplying a "low" signal as a control signal to their bases. At this time, the other switching transistors 12, 52, 54, and 56 are all turned off by supplying the "high" signal.

Thus, as in the previous case, the light emitting diode 63 of the photocoupler 61 and the phototransistor 65
Then, a preparation for supplying a current corresponding to the second communication speed by the second current limiting resistor 13 on the terminal side 1 and the fourth current limiting resistor 57 on the NCU side 5 is completed. And N
When the base signal of the signal control switching transistor 50 becomes “high” by the signal output from the CU 5, a current corresponding to the second communication speed flows through the light emitting diode 63 to emit light. As a result, the phototransistor 65 is turned on, and a current corresponding to the second communication speed flows from the collector side of the phototransistor 65 to the emitter side. Thereby, the communication signal from the NCU side 5 is transmitted to the terminal side 1.

As described above, in the present embodiment, the amount of current supplied to the light emitting diode and the phototransistor of the photocoupler is changed according to the communication speed.
The current amount is suitable for the communication speed, so that there is no shortage of current in high-speed communication, and no extra power is consumed even in low-speed communication.

(Other Embodiments) The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.

For example, in the above-described embodiment, two current limiting resistors and a switching transistor are connected in parallel according to the first communication speed for changing the amount of current supplied from the power supply line and the second communication speed. However, instead of this, two current limiting resistors and a switching transistor may be provided in series. In this case, specifically, as shown in FIG. 2, for example, a first switching transistor 102 is inserted in parallel with a first current limiting resistor 101 for a first communication speed, and in the same manner as this, A second current limiting resistor 103 for a second communication speed and a second switching transistor 104 connected in parallel are connected in series. In the control in this case, at the first communication speed, the first switching transistor 102 is turned off so that the current flows to the first current limiting resistor 101, while the second switching transistor 102 is turned off. By turning on the transistor 104 and forming a bypass line for the second current limiting resistor 103, current does not flow through the second current limiting resistor 103. Thus, a current suitable for the first communication speed is supplied.

Conversely, at the second communication speed, the first switching transistor 102 is turned on to serve as a bypass line for the first current limiting resistor 101, and the second switching transistor 104 is turned off to turn off the second current. By allowing the current to flow through the limiting resistor 103, a current corresponding to the second communication speed is supplied.

Even if the current limiting resistors are provided in series as described above, it is possible to supply a current optimum for the communication speed as in the above-described embodiment, and this also causes a shortage of current during high-speed communication. Power consumption during low-speed communication.

In the above-described embodiment, the interface circuit corresponds to the first and second communication speeds corresponding to the two communication speeds.
Three, four, or even more communication speeds may be supported.

In the above embodiment, two photocouplers are used to enable two-way communication between the terminal and the NCU. However, one-way communication from the terminal to the NCU may be used. In this case, one photocoupler may be used, and the present invention can be suitably used even with one photocoupler.

[0042]

As described above, according to the present invention, it is possible to supply an optimum amount of current corresponding to the communication speed in the connection between the terminal unit having the communication function and the NCU. An interface circuit can be provided that does not cause current shortage during high-speed communication and suppresses power consumption during low-speed communication.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an interface circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an arrangement of a current limiting resistor portion as another embodiment.

[Explanation of symbols]

 1 Terminal side 5 NCU side 10, 50 Switching transistor for signal control 11, 51, 101 First current limiting resistor 12, 52, 102 First switching transistor 13, 53, 103 Second current limiting resistor 14, 54, 104 second switching transistor 15, 55 third current limiting resistor 16, 56 third switching transistor 17, 57 fourth current limiting resistor 18, 58 fourth switching transistor 19 switching transistor 61, 71 for transmission / reception switching Coupler 63, 73 Light emitting diode 65, 75 Phototransistor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04Q 9/00 311 H04L 13/00 T 341 307C (72) Inventor Mamoru Suzuki 1-5, Kaigan, Minato-ku, Tokyo No. 20 Tokyo Gas Co., Ltd. (72) Inventor Mitsunori Komaki 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Ken Takeshiro 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Hiroto Uyama 70, Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Yanagicho Business Co., Ltd. 72) Inventor Jiro Ishino 70, Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Yanagicho Works Co., Ltd. (72) Inventor Ikuo Maeda Yanagi-shi, Kawasaki-shi, Kanagawa Prefecture No. 70, Toshiba Yanagicho Office Co., Ltd. (72) Inventor Go Tsuyoshi Morinaga 70, Yanagicho, Kawasaki-shi, Kanagawa Prefecture F-Term, Toshiba Yanagicho Office Co., Ltd. JJ01 5K034 AA05 AA15 CC07 DD01 KK02 MM08 TT04 5K048 AA08 AA16 BA13 BA36 DC01 DC07 EA11 EB10 HA02 HA04 HA06 5K101 KK12 NN38 NN45 QQ11 UU16

Claims (3)

[Claims] 1. An interface circuit comprising a transmitting means for transmitting a signal between a terminal device and a network control device, wherein an amount of current supplied to each of the terminal device side and the network control device side of the transmitting means is a plurality of. An interface circuit comprising current amount switching means for switching according to a communication speed. 2. The current amount switching unit is provided in each of a plurality of current limiting resistors corresponding to the plurality of communication speeds, and individually supplies current to the current limiting resistors. The interface circuit according to claim 1, further comprising: a plurality of switching transistors to be controlled. 3. The transmission means is formed by a photocoupler, wherein the photocoupler includes a first photocoupler used when transmitting a signal from the terminal device to the network control device. The interface circuit according to claim 1, further comprising: a second photocoupler used when transmitting a signal from the network control device to the terminal device.