JPH1174900A - Optical radio lan system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical radio LAN system in which a management equipment applies voltages having required levels to a master set without making the size of the master set large. SOLUTION: In the optical radio LAN system consisting of a master set 1 having an optical transmission reception function making optical communication with at least one slave set and a management equipment 15 that connects to the master sets 1 in a star form by wired lines, the management equipment 15 controls power supply voltages applied to each master set 1 via wired lines from the management equipment 15. Thus, the need for a circuit for a commercial power supply is eliminated for each master set 1 and then the management equipment 15 applies stably voltages having required levels to each master set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wireless LAN (local area network) system for transmitting and receiving optical signals through a space, and more particularly to an improvement in a method of supplying power to a base unit used for relaying.

[0002]

2. Description of the Related Art Generally, a LAN connects each personal computer or between them and a host computer in a relatively narrow range, for example, in one and the same building, by wire or wirelessly. And a system for transmitting and receiving information signals. An example of such a system is disclosed in, for example, JP-A-7-283822. An example of this LAN system will be described with reference to FIG. In the figure, reference numeral 1 denotes a master unit provided on a ceiling 2 or the like,
The master unit 1 is provided for each predetermined area range so as to cover a certain area. The base unit 1 has an optical transmission / reception function for transmitting / receiving an optical signal. Although three master units 1 are shown in the illustrated example, the number is not limited. Reference numeral 3 denotes a slave unit, which has an optical transmission / reception function for transmitting and receiving an optical signal similarly to the master unit 1, and performs optical wireless communication with the master unit 1. And
A terminal 4 such as a personal computer, for example, is connected to the slave unit 3, and here, for example, processes and creates data. Reference numeral 5 denotes a management device, which is connected to the master unit 1 via a connection line 6 in a wired star manner.
Each parent device 1 is managed. And this management device 5
For example, it is connected to another management device (not shown) via a LAN cable 7, and signals are transmitted and received in the entire system.

By the way, in order to operate each of the above-described devices, it is necessary to supply power to each device. Naturally, if attention is paid to the master 1, for example,
Supplied power from a commercial power supply via an AC cable. Therefore, base unit 1 has a configuration in which a power supply circuit such as a rectifier circuit and a voltage stabilizing circuit is mounted. Since these power supply circuits and the like are heavy and large in volume, it is difficult to reduce the size and size of the base unit 1 due to the presence of the power supply unit. Therefore,
To solve this problem, DC power is supplied from the management device 5 to each master unit 1 via a connection line 6 connected to the management device 5.

FIG. 7 shows a connection state between the management device 5 and one master unit 1. As the connection line 6, for example, a total of eight wirings 8A, 8B, 9A, 9B, 10A, 10
B, 11A, and 11B, each of which uses four twisted pair cables formed by twisting two of them, and is a so-called 10-BAS that is widely used in a general LAN system.
The ET method is adopted. The transmission transformer TX1 of the management device 5 and the reception transformer RX2 of the slave device 1 are connected via a pair of twisted pair cables, that is, wires 9A and 9B, and transmit information signals from the management device 5 to the master device 1. Further, the receiving transformer RX1 of the management device 5 and the transmitting transformer TX2 of the slave unit 3 are connected via another pair of twisted pair cables, that is, wires 8A and 8B.
Sends an information signal to the management device 5.

[0005] Each transformer uses a so-called pulse transformer. The other two pairs of twisted pair cables are connected in parallel with each other to reduce the wiring resistance of the wirings 10A and 10B and 11A and 11B, and the DC constant voltage power supply 30 of the management device 5 is connected via these wirings. Is connected to the noise filter 13 of the base unit 1 and supplies the supplied voltage Vcc to the base unit body 14. According to this, the surplus wiring 10 from the management device 5
A, 10B, 11A, and 11B can be used to supply power to the base unit 1, so that there is no need to provide a power supply circuit or the like to the base unit 1 itself, and the base unit 1 is reduced in size and weight. be able to.

[0006]

The management device 5
As a matter of course, the length of the connection line connecting the base unit 1 and the base unit 1 differs depending on the installation location of each base unit 1. The length of this connection line may be as short as about 1 m when it is short, and may exceed 100 m when it is long. As described above, when a part of the connection line 6 is used as a power supply line, a voltage drop occurs due to the resistance of the connection line 6, and the received voltage supplied to the base unit 1 is lower than the supply voltage of the management device 5. Become.

Therefore, when the lengths of the connection lines 6 are variously different as described above, in order to stably supply the power supply voltage required for the base unit 1 to the base unit 1 to which the maximum length connection line is connected. It is necessary to output a higher voltage from the management device 5 by the voltage drop due to the connection line. For example, the power supply voltage required for master unit 1 is 15 V, and the current consumption is 50 V.
0 mA (power consumption: 7.5 W), the power supply line of the connection line having the maximum length, that is, the wiring 10A, 10B or 11
Assuming that the forward resistance values of A and 11B are 20Ω, the power supply voltage supplied from the management device 5 needs to be 25V which is higher by 10V than the above 15V. In this case, when an extremely short connection line is connected, approximately 25 V is applied to the base unit 1 with almost no voltage drop due to line resistance, and the base unit 1 consumes 12.5 W of power.

For this reason, the base unit 1 consumes 67% higher power (generates heat) than the power consumption of 7.5 W originally, and the size of the base unit case must be increased for heat dissipation. There were problems such as not being able to do so. The present invention has been made in view of the above problems, and has been made in order to effectively solve the problems. The purpose of the present invention is to reduce the capacity required for the master unit from the management device without increasing the size of the master unit side. It is an object of the present invention to provide an optical wireless LAN system capable of supplying the same voltage.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a master unit having an optical transmission / reception function for performing optical communication with at least one slave unit, and connecting the master unit with a cable. Wireless L consisting of a management device connected in a star configuration by
In the AN system, a power supply voltage supplied from the management device to each parent device via the wire is controlled by the management device. This makes it possible to stably supply a voltage of a predetermined capacity to the master unit without forcing a structural change for heat dissipation.

[0010] As a connection method between the management device and the master unit used here, for example, a well-known 10-BASE-T method using four twisted pair cables can be adopted. In order to control the supply voltage, for example, a management device includes a DC voltage source, a voltage detection unit that detects a received voltage at the master unit via a pair of twisted pair cables, and a control unit that responds to an output of the voltage detection unit. A control unit for controlling the output voltage of the DC voltage source, and the control unit controls an output voltage from the DC voltage source so that the voltage detection unit maintains a predetermined receiving voltage.

Further, as another control method, a management device
A DC constant current power supply may be provided to supply power to the master unit. Normally, the load of the master unit hardly fluctuates. According to this, the DC constant-current power supply controls itself so that the supplied current is always constant, so that the received voltage of the master unit is always substantially constant. As still another control method, both ends of the receiving voltage in the master unit are connected to different twisted pair cables for signal transmission, and power is supplied to the management device using two twisted pair cables. In this management device, a DC voltage source, a voltage detection unit that detects a received voltage at the master unit via the twisted pair cable for signal transmission, and a transmission voltage of the DC voltage source according to an output of the voltage detection unit And a control unit for controlling. Thus, the voltage detection unit detects the received voltage of the master unit, and the control unit controls the DC voltage source so that the received voltage becomes a voltage of a predetermined capacity.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical wireless LAN system according to the present invention will be described below in detail with reference to the accompanying drawings. FIG.
FIG. 2 is a diagram showing a connection state between a management device and a parent device in the optical wireless LAN system according to the first embodiment of the present invention, and FIG. 2 is a circuit configuration diagram showing a voltage detection unit used in the management device. Note that the same parts as those of the conventional device described above are denoted by the same reference numerals and described. As shown in FIG. 1, a master device 1 and a management device 1
5 is electrically connected via a connection line 6.
The parent device 1 and the management device 15 correspond to the portions of the parent device 1 and the management device 5 shown in FIG. 6, and constitute an optical wireless LAN system as a whole.

As the connection line 6, for example, a total of eight wirings 8A, 8B, 9A, 9B, 10A, 10B, 11
Four twisted pair cables formed by twisting two of each of A and 11B are used, and a so-called 10-BASE-T system, which is widely used in a general LAN system, is employed. Transmission TX of management device 15
1 and the receiving transformer RX2 of the base unit 1 are connected via a pair of twisted pair cables, that is, wirings 9A and 9B, and transmit an information signal from the management device 15 to the base unit 1. Also,
The receiving transformer RX1 of the management device 15 and the transmitting transformer TX2 of the master unit 1 are connected to another pair of twisted pair cables,
That is, they are connected via the wirings 8A and 8B, and transmit information signals from the parent device 1 to the management device 15.

The management device 15 includes a DC voltage source 1
2, a voltage detection unit 1 for detecting a received voltage on the base unit 1 side.
6 and a control section 17 for controlling the output voltage of the DC voltage source 12 based on the output, for example, a microcomputer or the like. The management device 1 is connected to the other pair of twisted pair cables 11A and 11B.
5 and the noise filter 13 of the base unit 1
To supply power to the base unit 1. In the base unit 1, the voltage Vcc that has passed through the noise filter 13 provided to break the ground loop is supplied to the base unit main body 14. The Vcc terminal, which is the output of the noise filter 13, is connected to the remaining one. The ground terminal of the noise filter 13 is connected to the other wiring 10B, and the received voltage of the master unit 1 is applied to the wirings 10A, 10B.

On the other hand, in the management device 15, this wiring 1
0A and 10B are connected to the voltage detection unit 16,
The receiving voltage in the master unit 1 is detected.
FIG. 2 shows a schematic circuit configuration of the voltage detection unit 16, and both wirings 10 </ b> A and 10 </ b> B are input to a differential amplifier 18. That is, one wiring 10A is connected to the input resistor R1.
Is connected to one input terminal of the operational amplifier 19 through
A feedback resistor R is provided between the input terminal and the output terminal.
12 are connected. Further, the other wiring 10B is connected to the other input terminal of the operational amplifier 19 via the input resistor R3, and this input terminal is grounded via the ground resistor R4, and constitutes the differential amplifier 18 as a whole.

The output of the differential amplifier 18 is supplied to a comparator 20
Here, the reference voltage is compared with a reference voltage, that is, a voltage required for operation of the base unit 14 of the base unit 1, for example, 15V. The output side of the comparator 20 is connected to an integrating circuit 22 having a predetermined time constant consisting of an output resistor R5 and a capacitor C1.
7. The controller 17 controls the output voltage of the DC voltage source 12 based on the input result signal as described above.

Next, the operation of the system configured as described above will be described. First, the parent device 1 is sent from the management device 15.
When the information signal is sent to the transmission transformer TX1 of the management device 15, the information signal is transmitted to the reception transformer RX2 of the parent device 1 via the wirings 9A and 9B.
When the information signal is transmitted to the transmission device 5, the transmission signal is transmitted from the transmission transformer TX2 of the base unit 1 to the reception transformer RX1 of the management device 15 via the wirings 8A and 8B.

The power required by the base unit 1 is introduced from the DC voltage source 12 of the management unit 15 to the noise filter 13 of the base unit 1 via the wirings 11A and 11B, where the ground loop signal is removed. Then, a voltage is supplied to the main unit 14. Here, the receiving voltage Vcc, which is the output voltage of the noise filter 13, is constantly detected by the voltage detection unit 16 of the management device 15 via the wirings 10A and 10B.
As shown in FIG. 2, the detected value is compared with a reference voltage 21, for example, 15 V by a comparator 20 via a differential amplifier 18. Therefore, the control unit 17 determines that the detected value is one of the reference voltage.
When the voltage is lower than 5 V, the operation is performed so as to increase the sending voltage from the DC voltage source 12, and conversely, when the detected value is equal to one of the reference voltage.
When the voltage is higher than 5 V, the operation is performed so as to lower the transmission voltage.

For example, when the length of the connection line 6 is considerably long and the voltage drop here is large, the control unit 17 causes a correspondingly high voltage to be transmitted, and conversely, the length of the connection line 6 becomes short. If the voltage drop here is small, a correspondingly suppressed low voltage (15 V or more) is transmitted.
For this reason, it is possible to maintain the receiving voltage of the master unit 14 at a voltage required by the master unit body 14, for example, 15V.
In addition, since it is not necessary to incorporate a power supply circuit or the like for a commercial power supply having a large weight and size in the base unit 1 in this manner, the size and weight of the apparatus can be reduced.

Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram showing a connection state between a management device and a parent device in the optical wireless LAN system according to the second embodiment of the present invention. The same parts as those in the configuration shown in FIG. The difference between the second embodiment and the first embodiment is that the management device 15 does not include the DC voltage source 12, the voltage detection unit 16 and the control unit 17, but instead performs DC control. The point is that a current power supply 23 is provided. Here, in the first embodiment, the wirings 10A, 10A,
0B connected in parallel, and a wiring 11
A and 11B are also connected in parallel. Then, these parallel connection wirings 10A, 10B and 11A, 11B are connected between the DC constant current power supply 23 of the management device 15 and the noise filter of the base unit 1 to supply power.

In general, the load of the base unit 1 does not fluctuate so much and is a device of a constant current consumption type. , The current supplied to the base unit 1 is automatically controlled to always maintain a substantially constant value, even if the voltage drop fluctuates depending on the change in the base unit 1.
At a constant value, for example, 15V. Also in this case, since there is no need to incorporate a power supply circuit for commercial power supply into the base unit 1, the size and weight of this device can be reduced. Further, here, unlike the first embodiment, as described above, no feedback line for receiving voltage detection is required, so that the extra wiring 1
The lines 0A and 10B can also be used as power supply lines, and accordingly, the power transmission resistance is reduced and transmission loss can be suppressed.

Next, a third embodiment of the present invention will be described. FIG. 4 is a diagram showing a connection state between a management device and a parent device in an optical wireless LAN system according to a third embodiment of the present invention, and FIG. 5 is a circuit configuration diagram showing a voltage detection unit used in the management device. The same parts as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted. This third embodiment combines the advantages of the first and second embodiments. That is, the management device 15 has the first
A DC voltage source 12, a voltage detector 16, and a controller 17 are provided in the same manner as described in the embodiment. However, as shown in FIG.
Between the output of the operational amplifier 19 and the input of the comparator 20
A signal cut filter 24 for cutting a frequency band of a signal transmitted and received by this system is provided. The reason for this is that, as described later, the wiring 8
A, 8B, 9A, and 9B are used to monitor the received voltage at the base unit 1, and this is for cutting off the information signal that is multiplied at this time.

The output of the secondary-side intermediate tap of the transmitting transformer TX1 of the management device 15 and the output of the secondary-side intermediate tap of the receiving transformer RX1 are connected to the voltage detector 16. I have. In addition, the wirings 10A, 10B, 1
1A and 11B are connected in parallel two by two as in the second embodiment.
2 and the noise filter 13 of the base unit 1 to supply power through four wires.

On the other hand, on the master unit 1 side, the Vcc output of the noise filter 13 is connected to the master unit main body 14, while being connected to the transmission transformer TX2 via the first high resistance R6 of, for example, about 100 KΩ. It is also connected to the next intermediate tap. The ground terminal of the noise filter 13 is connected to the intermediate tap on the secondary side of the receiving transformer RX2 via a second high resistance R7 of, for example, about 100 KΩ. As a result, the information signal transmission wiring 8A,
The received voltage of the master unit 1 is multiplied between 8B and 9A, 9B. Note that the wirings 8A, 8B and 9A, 9B
Since it is electrically floating, it does not adversely affect the information signal.

In this embodiment, since the received voltage Vcc of the master unit 1 is superimposed on the wires 8A, 8B and 9A, 9B, the received voltage Vcc is monitored by the voltage detector 16 of the management device 15. And can be detected.
In this case, the receiving voltage Vcc is the first voltage having a very high resistance value.
And the transmission and reception transformers TX2, RX2 of the master unit 1 via the second high resistances R6, R7, and the wirings 8A, 8B, 9A, 9B are electrically floating. The transmitted information signal is not adversely affected.

The control unit 17 controls the DC voltage source 12 on the basis of the detection value obtained by the voltage detection unit 16 as in the first embodiment. It can be maintained at a constant value, for example, 15V. In the voltage detection unit 16, the input signal to the voltage control unit 16 includes an information signal component. This component is converted to a signal cut filter 24 provided on the output side of the differential amplifier 18 as shown in FIG. Therefore, the detection voltage value is not adversely affected.

According to this embodiment as well, it is not necessary to incorporate a power supply circuit for commercial power supply into the base unit 1, so that the size and weight of this device can be reduced. Also, here, similarly to the second embodiment, four wirings 10A, 10B,
Since power is supplied using 11A and 11B,
The transmission loss can be suppressed to the extent that the power transmission resistance is reduced. Here, the present invention is referred to as 10-BASE-T.
Although the case where the present invention is applied to the system has been described as an example, the present invention is not limited to this, and it is needless to say that the present invention can be applied to other systems.

[0028]

As described above, the optical wireless LAN according to the present invention is
According to the AN system, the following excellent operational effects can be exhibited. Since the power is supplied from the management device to the master unit and the output voltage is automatically controlled, the capacity required for the master unit can be reduced without providing a power supply circuit or the like for the commercial power supply in the master unit. Voltage can be supplied stably, and downsizing and weight reduction of the master unit can be achieved. Also, when power is supplied using a DC constant current power supply or when receiving voltage on the master unit is detected using wiring for transmitting information signals, power is supplied using two twisted pair cables. Therefore, in addition to the above-described effects, the transmission loss can be reduced because the transmission resistance can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a connection state between a management device and a parent device in an optical wireless LAN system according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram illustrating a voltage detection unit used in the management device.

FIG. 3 is a diagram showing a connection state between a management device and a parent device in an optical wireless LAN system according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a connection state between a management device and a parent device in an optical wireless LAN system according to a third embodiment of the present invention.

FIG. 5 is a circuit configuration diagram illustrating a voltage detection unit used in the management device.

FIG. 6 is a configuration diagram illustrating an optical wireless LAN system.

FIG. 7 is a diagram showing a connection state between a management device and a parent device in a conventional optical wireless LAN system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Parent machine, 3 ... Child machine, 4 ... Terminal, 6 ... Connection line, 8
A, 8B, 9A, 9B, 10A, 10B, 11A, 11
B: wiring, 12: DC voltage source, 13: noise filter,
14: main unit body, 15: management device, 16: voltage detection unit,
17: control unit, 18: differential amplifier, 20: comparator, 23
... DC constant current power supply, 24 ... signal cut filter, TX1
... Transformer for transmission, RX1 ... Transformer for reception.

Claims (4)

[Claims] 1. An optical wireless LA comprising: a master unit having an optical transmission / reception function for performing optical communication with at least one slave unit; and a management device for connecting the master unit by wires in a star configuration.
An optical wireless LAN system in the N system, wherein a power supply voltage supplied from the management device to each parent device via the cable is controlled by the management device. 2. The optical wireless LAN system according to claim 1, wherein the management device is connected to each of the base units by a 10-BASE-T system using a twisted pair cable. 3. The control device includes: a DC voltage source; a voltage detection unit that detects a received voltage of the master unit; and a control unit that controls a transmission voltage of the DC voltage source in accordance with an output of the voltage detection unit. The optical wireless LAN system according to claim 1 or 2, further comprising: 4. The optical wireless communication according to claim 1, wherein the management device has a DC constant current power supply, and is configured to supply a constant current power to the master unit. LAN system.