JPH05175967A - Signal transmitter - Google Patents

Abstract

PURPOSE:To reduce current consumption while supplying power required for the operation of a terminal equipment. CONSTITUTION:A master set 1 and terminal equipments 2, 3 are interconnected by a couple of signal lines Ls. The master set 1 sends a signal to the terminal equipments 2, 3 by turning on/off alternatively a couple of transistors(TRs) Q11, Q12. The terminal equipments 2, 3 rectify and smooth the signal from the master set 1 to obtain a power supply. Furthermore, the terminal equipments 2, 3 turn on/off a TR Q2 to send a signal to the master set 1. A parallel circuit comprising a resistor R2 and a TR Q3 is inserted between the signal line Ls and the power supply. When the master set 1 receives the signal from the terminal equipments 2, 3, the current flowing to the signal line Ls is limited by turning off the TR Q3. When the signal is sent from the master set 1 to the terminal equipments 2, 3, a sufficient current is supplied to the terminal equipments 2, 3 by turning on the Tr Q3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits data by connecting a master unit and a terminal unit through a pair of signal lines, and transmitting a pulse signal from the master unit to the terminal unit through the signal line. At the same time, the present invention relates to a signal transmission device for rectifying and smoothing this pulse signal to obtain a power source for a terminal.

[0002]

2. Description of the Related Art Conventionally, FIG. 3 shows a signal transmission device which connects a master device and a terminal device through a pair of signal lines and transmits and receives data between the master device and the terminal device. A remote monitoring control system having a configuration as shown is known. That is, a plurality of monitoring terminals 2 that monitor the switches S _{1 to} S ₄ and a control terminal that controls the loads L _{1 to} L ₄ via the two-wire signal line Ls to the master device 1. 3 is connected. An individual address is set for each of the terminals 2 and 3, and the master device 1 uses the addresses to set the terminals 2 and 3
Recognize each separately.

From the base unit 1 to the signal line Ls, as shown in FIG.
The transmission signal Vs having the format as shown in (a) is transmitted. That is, a start pulse ST indicating the start of signal transmission, a mode data signal MD indicating the signal mode, an address data signal AD transmitting address data for individually calling the terminals 2 and 3, and loads L _{1 to} L ₄ are controlled. A bipolar (± 24V) consisting of a control data signal CD for transmitting control data, a checksum data signal CS for detecting a transmission error, and a return standby signal WT for setting a period for receiving a return signal from the terminals 2 and 3. ), The data is transmitted by pulse width modulation (see FIG. 4 (b)).

In each of the terminals 2 and 3, when the address data of the transmission signal Vs received via the signal line Ls matches the set address data, the control data of the transmission signal Vs is fetched and the transmission signal Vs The monitoring data signal is sent in the current mode (signal line L in synchronization with the return standby signal WT).
The signal is sent back by changing the current flowing through s).

Further, the master unit 1 is provided with a mode data signal MD
Is set to a dummy mode, and each terminal 2, 3 is provided with a dummy signal transmitting means for transmitting a dummy transmission signal having an empty address which is not set as address data. The master device 1 is generated from any one of the monitoring terminal devices 2 shown in FIG.
The base unit 1 is also provided with an interrupt processing means for accessing the terminal 2 and returning the monitoring data after detecting the terminal 2 that generated the interrupt signal when the interrupt signal Vi as shown in FIG. .. That is, the dummy signal transmitting means always sends the dummy signal to the signal line Ls,
When the interrupt signal Vi generated from the terminal device 2 is detected in synchronization with the start pulse ST of the dummy transmission signal, the interrupt processing means sends the transmission signal Vs in which the master device 1 sets the mode data signal MD in the address confirmation mode. .. When receiving the transmission signal Vs in the address confirmation mode, the terminal 2 that has generated the interrupt signal Vi returns the address data set in the terminal 2 in synchronization with the return standby signal WT of the transmission signal Vs. In this way, the master device 1 acquires the address of the terminal device 2 that has generated the interrupt signal Vi, and accesses the terminal device 2 using the acquired address, thereby receiving the monitoring data from the terminal device 2.

The master device 1 creates control data to be transmitted to the control terminal device 3 to which the corresponding loads L _{1 to} L ₄ are connected based on the monitoring data returned from the terminal device 2, and the control data is also generated. sends a transmission signal Vs to a signal line Ls containing, by transmitting the control data to the terminal 3 for controlling the corresponding controlling the load L ₁ ~L _4. The power of each terminal 2, 3 is obtained by rectifying and smoothing the transmission signal Vs which is constantly transmitted through the signal line Ls, and the terminal 3 for control controls the loads L _{1 to} L ₄ . The power supply for driving the relay for operating is also obtained by the transmission signal Vs. In addition, power to the loads L _{1 to} L ₄ such as lighting equipment is separately supplied from a commercial power source or the like.

By the way, the output circuit connected to the signal line Ls at the base unit 1, as shown in FIG. 5, and an open collector type, the collector of the transistor Q ₁ - pull-up resistor R ₁ an emitter series Connected, this series circuit is connected between both ends of the power supply. Here, the transmission signal Vs is bipolar, but the transmission signal Vs is shown as unipolar in order to simplify the description.

On the other hand, the terminals 2 and 3 are provided with a diode D and a capacitor C for rectifying and smoothing the transmission signal Vs transmitted through the signal line Ls, and supply the voltage across the capacitor C to the terminal circuit 10. In the terminal circuit 10, the signal line L
Predetermined processing is performed based on the transmission signal Vs received via s, and the transmission signal that is a pulse signal is output during the signal return period WT to turn on / off the transistor Q ₂ that is a switching element. The collector-emitter of the transistor Q ₂ is connected between the signal lines Ls and short-circuits between the signal lines Ls when the transistor Q ₂ is on. The base unit 1 detects the current change of the signal line Ls and detects the terminal unit. Receive the monitoring data signals from a few.

[0009]

In the above configuration, when the transistor Q ₂ is turned on when the monitor data signal is returned from the terminals 2 and 3 to the base unit 1, a current flows through the pull-up resistor R _1. Therefore, if the pull-up resistance R ₁ is small, the current consumption increases. On the other hand, if the pull-up resistance R ₁ is large, the current consumption is small, but since the terminals 2 and 3 are supplied with the transmission signal Vs, if the pull-up resistance R ₁ is large, a relatively large amount of current is consumed when the relay is driven. When a large amount is required, a sufficient current cannot be supplied and the signal voltage of the transmission signal Vs drops. That is, the pull-up resistor R ₁ cannot be set to a very large value, which causes a problem that current consumption increases when transmitting the monitor data signal from the terminals 2 and 3.

Further, when the transistor Q ₁ is turned on and off when the transmission signal Vs is transmitted from the parent device 1, when the transistor Q ₁ is turned on, a current flows through the pull-up resistor R ₁ and the transistor Q _1. There is also a problem that current is wasted in the machine 1. SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a signal transmission device capable of reducing current consumption while supplying a current required as a power source to a terminal.

[0011]

In order to achieve the above object, in the invention of claim 1, the master unit and the terminal unit are connected via a pair of signal lines, and the line voltage of the signal lines is switched. By transmitting the pulse signal due to the voltage change from the master unit to the terminal, the terminal unit rectifies and smoothes the pulse signal to obtain power, and switches the short-circuit state and open state between the signal lines to make the current flow. In a signal transmission device that transmits a pulse signal due to a change from the terminal to the master, the master raises the output impedance to the signal line when receiving the pulse signal from the terminal, and The impedance switching means for lowering the output impedance to the signal line when transmitting the pulse signal is provided.

According to the second aspect of the present invention, the master unit has a first switch element which is connected between signal lines and is on / off controlled by a transmission signal, and a first switch element which is connected in series with the first switch element and which receives a transmission signal. A second switch element that is on / off controlled so that the on / off state is opposite to that of the first switch element, and is serially connected to a series circuit of the first switch element and the second switch element. In addition, the series circuit includes a third switch element that is connected between both ends of the power source and is turned on only when receiving a pulse signal from the terminal, and a resistor connected in parallel to the third switch element. , The resistor and the third switch element constitute impedance switching means.

[0013]

According to the structure of claim 1, the output impedance for the signal line is increased when receiving the pulse signal from the terminal, and the output impedance for the signal line is decreased when transmitting the pulse signal to the terminal. Since impedance changing means is provided in the base unit, when transmitting signals from the base unit to the terminal, it is possible to supply sufficient current to the terminal by lowering the output impedance, and the terminal temporarily operates. It is possible to prevent the line voltage from decreasing even if the consumption current increases. Further, when a signal is sent back from the terminal device to the parent device, the output impedance of the parent device becomes high, so that a large current does not flow in the signal line, and wasteful current consumption can be prevented. is there. In short, when returning a signal from the terminal to the base unit, increase the output impedance of the base unit to a level that can secure the minimum amount of current necessary to transmit the pulse signal due to the current change, and reduce the current consumption. ,
On the other hand, for the signal transmitted from the master to the terminal, the output impedance of the master can be lowered to supply a sufficient current to the terminal. As a result, it is possible to reduce the current consumption while securing the required current.

According to a second aspect of the present invention, which is a preferred embodiment of the present invention, when a resistor and a third switch element are connected in parallel to form impedance switching means, and a pulse signal from a terminal is received. Since the third switch element is turned off only in the case of receiving the pulse signal from the terminal, the power source is connected to the signal line through the resistor when the pulse signal is received from the terminal, and the current flowing in the signal line can be limited. it can. On the other hand, when transmitting a pulse signal to the terminal, the third switch element is turned on to connect to the signal line without passing through a resistor, and a sufficient current is supplied to the terminal. be able to. Moreover, since the first switch element and the second switch element are on / off controlled by the transmission signal and are connected so that their on / off states are reversed, the first switch element and the second switch element are connected. One of them is always off, and even if the third switch element is on, the both ends of the power supply are not short-circuited.

[0015]

EXAMPLE In this example, the output circuit connected to the signal line Ls in the base unit 1 is configured as shown in FIG. 1, and includes an npn-type transistor Q ₁₁ and a pnp-type transistor Q ₁₂ . The collector-emitter of is connected in series, and the bases of both transistors Q ₁₁ and Q ₁₂ are connected in common. That is, the transistor Q ₁₂ serves as the first switching element and the transistor Q ₁₁ serves as the second switching element. A resistor R ₂ as a current limiting element is connected to the collector of the transistor Q ₁₁ . A third resistor is placed on both ends of the resistor R ₂ .
Collectors as switching elements of the pnp transistor Q ₃ of the - emitter connected to, turning on or off the transistor Q ₃ by the switching signal. The transistor Q ₃ and the resistor R ₂ constitute impedance switching means. A series circuit of the transistors Q ₁₁ and Q ₁₂ and the resistor R ₂ is connected across the power supply. The signal line Ls is connected to the collector-emitter of the transistor Q ₁₂ and is connected to the transistor Q _12.
ON depending on the transmission signal applied to the bases of ₁₁ and Q ₁₂
Controlled off. The terminals 2 and 3 have the same configuration as the conventional configuration shown in FIG.

Next, the operation will be described. A switching signal for controlling ON / OFF of the transistor Q ₃ is output in synchronization with the transmission signal. That is, the switching signal is at the H level except when the return signal from the terminals 2 and 3 is received (that is, the period in which the return standby signal WT is generated from the master 1). As shown in FIG. 2B, the output impedance from the machine 1 to the signal line Ls becomes high impedance during the period when the return standby signal WT is generated, and becomes low impedance during the other periods.

On the other hand, when the transmission signal which is a binary signal is at the H level, the transistor Q ₁₁ is turned on and the transistor Q ₁₂ is turned off, the line voltage of the signal line Ls becomes equal to the power supply voltage, and the transmission is performed. When the signal is at the L level, the transistor Q ₁₁ is turned off and the transistor Q ₁₂ is turned on so that the line voltage of the signal line Ls becomes 0.
It becomes V. That is, both transistors Q ₁₁ and Q ₁₂ are alternately turned on / off according to the output value of the transmission signal. With this configuration, as shown in FIG. 2A, the transmission voltage can be transmitted by switching the line voltage of the signal line Ls according to the transmission signal. Here, since one of the transistors Q ₁₁ and Q ₁₂ is always off, both transistors Q ₁₁ and Q ₁₂ are transmitted when transmitting the transmission signal to the terminals 2 and 3.
Since no current flows through it, even if the transistor Q ₃ is turned on and both ends of the resistor R ₂ are short-circuited, the power supply is not short-circuited. That is, the output impedance for the signal line Ls can be set low, and the current capacity for the terminals 2 and 3 can be large. In particular, when controlling the loads L _{1 to} L ₄ in the control terminal 3, a large current is temporarily required. However, since the output impedance of the base unit 1 is lowered, the line of the signal line Ls is reduced. It is possible to prevent the voltage drop between terminals and to continue supplying power to the terminals 2 and 3.

When the return signal is transmitted from the terminals 2 and 3 to the base unit 1, the base unit 1 turns off the transistor Q ₃ to output impedance to the signal line Ls as shown in FIG. 2B. To raise. That is, since the power source is connected to the signal line Ls via the resistor R ₂ , the transistor Q
_{When 2} is on, a large current does not flow between the signal lines Ls, and a current mode signal can be transmitted with a small current.

As described above, the base unit 1 to the terminal unit 2,
While a sufficient current can be supplied when transmitting the transmission signal to the master unit 3, when the current mode signal is returned from the terminal units 2 and 3 to the master unit 1, The output impedance can be increased to prevent wasteful current consumption. Although the present embodiment is configured to transmit a unipolar transmission signal, a similar configuration can be adopted even for a bipolar transmission signal, so that the terminals 2 and 3 can be used. If the circuit configuration is such that the impedance can be switched such that the output impedance of the master unit 1 is increased when receiving the return signal and the output impedance of the master unit 1 is reduced at other times, the configuration is limited to the configuration shown in the figure. It is not something that will be done. Further, the number of terminals 2 and 3 is not particularly limited.

[0020]

As described above, the present invention increases the output impedance for the signal line when receiving the pulse signal from the terminal and lowers the output impedance for the signal line when transmitting the pulse signal to the terminal. Since the main unit is provided with an impedance switching means to operate, when transmitting a signal from the main unit to the terminal, it is possible to supply sufficient current to the terminal by lowering the output impedance. It is possible to prevent the line voltage from decreasing even when the current consumption temporarily increases. Further, when a signal is sent back from the terminal device to the parent device, the output impedance of the parent device becomes high, so that a large current does not flow in the signal line, and wasteful current consumption can be prevented. is there. In short, when returning a signal from the terminal to the base unit, increase the output impedance of the base unit to a level that can secure the minimum amount of current necessary to transmit the pulse signal due to the current change, and reduce the current consumption. ,
On the other hand, for the signal transmitted from the master to the terminal, the output impedance of the master can be lowered to supply a sufficient current to the terminal. As a result, there is an advantage that the current consumption can be reduced while supplying a necessary current as a power source to the terminal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part of an embodiment.

FIG. 2 is an explanatory diagram of the operation of the embodiment.

FIG. 3 is a system configuration diagram showing an example of a signal transmission device according to the present invention.

FIG. 4 is an operation explanatory diagram of the signal transmission device according to the present invention.

FIG. 5 is a circuit diagram showing a main part of a conventional example.

[Explanation of symbols]

1 base unit 2 terminal 3 terminal Q ₃ transistor Q ₁₁ transistor Q ₁₂ transistor R ₂ resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeo Koyama 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (2)

[Claims] 1. A master device and a terminal device are connected via a pair of signal lines, and a pulse signal due to a voltage change is transmitted from the master device to the terminal device by switching the line voltage of the signal line, and the terminal device is also connected. In rectification and smoothing the pulse signal to obtain a power source, the signal that changes the current between the signal line and the open state, and transmits the pulse signal from the terminal to the master unit. In the transmission device, the master unit has impedance switching means for increasing the output impedance for the signal line when receiving the pulse signal from the terminal and for lowering the output impedance for the signal line when transmitting the pulse signal to the terminal. A signal transmission device comprising: 2. The base unit, a first switch element connected between signal lines and on / off controlled by a transmission signal, and a first switch element connected in series with the first switch element by the transmission signal. Is connected in series to a series circuit of a second switch element and a second switch element that is on / off controlled so that the on / off state is reversed, and this series circuit is A third switch element, which is connected between both ends of the power supply and is turned on only when receiving a pulse signal from the terminal, and a resistor connected in parallel to the third switch element.
The signal transmission device according to claim 1, wherein the impedance switching means is constituted by the switching element.