TW202322583A - Communication terminal and communication system capable of preventing voltage signal attenuation and being less susceptible to reflected wave - Google Patents

Abstract

The invention relates to a communication terminal (100), which may transmit a voltage signal that is superimposed by a voltage at a specific first reference voltage. The communication terminal 100 is provided with an impedance adjustment circuit 120, which will switch the output impedance of the communication terminal 100 during the time period T0 that data is transmitted by the voltage signal superimposed by a voltage at the specific first reference voltage.

Description

Communication terminal, and communication system

The disclosure relates to a communication terminal and a communication system.

Conventionally, communication systems for load control using 2-wire signal lines have been popularized. The communication system is constituted by connecting the host computer as the central control device, that is, the sending terminal, and the communication terminals such as switches, by using 2-wire signal lines. The communication system has the characteristics of connection or branching of 2-wire signal lines and free configuration of communication terminals (called free topology), which can realize flexible system configuration. According to this communication system, a communication system can be realized with less wiring in a large-scale building. In Patent Document 1, an example of a communication system is disclosed. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2019-204638

[Problem to be Solved by the Invention]

In the communication system, there is an increase in the number of communication terminals and a demand for high-speed and large-capacity communication. As a response, it is considered to increase the frequency of the signal transmitted from the transmission terminal. However, if the signal frequency is increased, the influence of reflected waves cannot be ignored due to the impedance mismatch between the signal line and the transmission terminal or communication terminal. Due to the influence of reflected waves, signal reading errors will occur at the communication terminal.

In order to suppress the reflected waves of high frequency signals, impedance matching is usually obtained. Specifically, an impedance equal to the characteristic impedance of the transmission line is connected (terminated) to the receiving terminal to suppress the influence of reflected waves. However, since the communication system has a plurality of receiving terminals, if each device connected to the communication system is terminated, the voltage signal will be attenuated, and there is a possibility that the signal cannot be read.

The purpose of this disclosure is to provide a communication terminal and a communication system, which can prevent voltage signal attenuation and be less affected by reflected waves in a communication system with a plurality of communication terminals. [Technical means to solve the problem]

The communication terminal of the present disclosure transmits a voltage signal superimposed on a specific first reference voltage through a signal line. The communication terminal is characterized by having an impedance adjustment circuit for switching the output impedance of the communication terminal during data transmission by a voltage signal with a voltage superimposed on a specific first reference voltage. [Effect of Invention]

According to the communication terminal of the present disclosure, in a communication system having a plurality of communication terminals, the attenuation of the voltage signal can be prevented, and it is not easily affected by reflected waves.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, directions, numerical values, and the like are examples for facilitating understanding of the present disclosure, and may be appropriately changed in accordance with applications, purposes, specifications, and the like. In addition, it is conceivable from the beginning to selectively combine the constituent elements of the embodiments and modifications described below.

First, the overall configuration and schematic operation of a communication system using the communication terminal of the present disclosure will be described.

FIG. 1 is a structural diagram of a communication system 10 . The communication system 10 includes: a transmission unit 20 , a switch 31 serving as a communication terminal 30 and a terminal unit 32 . To the terminal unit 32, lighting fixtures 50a-50d are connected via relays 40a-40d. The lighting fixtures 50 a to 50 d are control objects of the communication system 10 . Furthermore, in addition to these devices, the communication system 10 may also be connected with other switches, other terminal units, other control objects, etc., but the illustration is omitted. The communication system 10 is a system in which the transmission unit 20 serves as the center and can control the lighting fixtures 50a to 50d, which are the control objects of the communication system 10, and the like. Control of lighting fixtures refers to on-off control, dimming control, scene control, monitoring control, etc. of lighting fixtures. Scene control is to adjust the brightness and color of lighting fixtures according to the installation places of lighting fixtures such as Japanese-style rooms, Western-style rooms, bedrooms, study rooms, etc., in the morning, daytime, evening, meal time, party time, etc. control. Monitoring and control refers to monitoring the control status of lighting fixtures. Furthermore, these controls can be performed by operating the switch 31 .

The communication system 10 adopts, for example, a time-division multiplexing method, and the signal line 60 is constituted by a 2-wire type. In the signal line 60, a signal (information) is transmitted by a pulse signal generated by a potential difference between two lines. In addition, in the communication system 10 , for example, a periodic transmission method is adopted, and the signal sent from the transmission unit 20 continuously passes through all the devices connected to the signal line 60 . Each machine confirms the content of the signal, and according to the content, the machine that needs the signal receives the signal. For example, each machine receives the signal when it contains its own address information, and ignores the signal when it does not contain its own address information. In this way, even if it is a signal sent from the transmission unit 20 that does not target itself, the device connected to the signal line 60 can still confirm its content.

The transmission unit 20 is a host controller that acts as the center in the communication system 10 . The transmitting unit 20 transmits the signal from the switch 31 connected to the signal line 60 to the terminal unit 32 . The switch 31 and the terminal unit 32 in FIG. 1 are the communication terminals 30 of this disclosure. Furthermore, the transmission unit 20 may further have the function of an adapter connected to the host system. It can also be set to control the configuration of the related equipment based on the signal from the host system.

The switch 31 is a wall switch or the like provided for the user to control the lighting fixtures 50a to 50d (turn on, off, dimming, etc.). For example, the switch 31 has four operation parts 31a-31d as shown in FIG. Each operation part has, for example, two states of an on state and an off state, and the lighting fixture corresponding to each operation part can be turned on and off by the user's operation.

For example, each operation part is provided with address information, and the address information and lighting fixtures are correspondingly established in a one-to-one manner.

The terminal unit 32 is a device that transmits the signal transmitted from the transmission unit 20 to the relays 40a to 40d. The terminal unit 32 has a plurality of terminals, and the relays 40a to 40d are connected to the plurality of terminals.

The relays 40a to 40d are switches for switching on and off the power supply to the lighting fixtures 50a to 50d connected to each of them. For example, when each relay receives an instruction to turn on the power supply from the terminal unit 32, it turns on the power supply to the lighting fixture connected to itself, and when it receives an instruction to turn off the power supply, it turns on the power supply to the lighting fixture connected to itself. The power supply to lighting fixtures is shut off. Furthermore, the terminal unit 32 and the relays 40a to 40d may be integrally formed.

In addition, it may also be configured such that instead of the terminal unit 32 and the relays 40a to 40d, a protocol conversion adapter of the DALI (registered trademark) method is used, and the protocol conversion adapter and a plurality of lighting fixtures 50a to 50d are connected via communication lines. .

The lighting fixtures 50a-50d are installed in the ceiling etc. of the building of a facility, for example. Each lighting fixture can be switched on and off, and the dimming rate (brightness) can be changed, for example, by a signal from the transmission unit 20 . The light source of lighting equipment is LED, fluorescent lamp, etc., but not particularly limited.

According to such a communication system 10 , there is no need for wiring for one-to-one connection between the control object and the switch 31 . In the communication system 10, only the signal line 60 including 2 wires may be required. Thereby, for example, in a large-scale building, the wiring of the communication system 10 can be reduced.

As mentioned above, in the communication system 10, the example which applied the control target to the lighting fixture was demonstrated, but the control target is not limited to a lighting fixture. The communication system 10 may also be configured to control other devices such as air conditioners.

In the communication system 10, when increasing the number of connected terminals or increasing the signal information between the terminals, in order to maintain the response of the system, a response to increase the frequency of the signal is adopted. If the voltage signal sent by the signal line is increased in frequency, the influence due to the reflected wave will become more and more obvious.

Previously, since each communication terminal connected to the communication system had an impedance matching circuit on the input side, the influence of reflected waves was prevented. However, as explained in the previous subject, if the number of communication terminals increases, the voltage signal sent from the transmission unit will attenuate, and there is a possibility that the signal cannot be read. The communication terminal disclosed in this disclosure has a structure that is not affected by reflected waves and suppresses attenuation of signals.

FIG. 2 shows a configuration diagram of a communication system 10 including a communication terminal 100 of this embodiment. In the following description, the terminal for sending signals among the communication terminals 30 in the communication system 10 shown in FIG. The signal lines of the receiving terminals 300-1, 300-2 are respectively the transmission lines 600-1, 600-2 and will be described. In addition, any one of the communication terminals 30 shown in FIG. 1 becomes the communication terminal 100 when transmitting a signal, and operates as the receiving terminal 300-1 etc. when not transmitting a signal. Neither the communication terminal 100 nor the receiving terminals 300-1 and 300-2 of this embodiment has a terminal resistor on the input. Thereby, the attenuation of the voltage signal which is the previous problem can be prevented. Furthermore, although only 300-1 and 300-2 are shown as receiving terminals, it is of course possible to further have a plurality of receiving terminals.

The communication system 10 of this embodiment suppresses reflected waves by adjusting the output impedance of the communication terminal 100 . However, always performing impedance adjustment means that lower impedance is always connected to the transmission line, which may affect the transmission line. Therefore, in the communication system 10 of the present embodiment, a configuration is adopted in which the output impedance is adjusted during the transmission of the voltage signal Vs1.

The communication terminal 100 of this embodiment has a transmission circuit 110 and an impedance adjustment circuit 120 . The impedance R1 is the input impedance of the communication terminal 100 . Specifically, the impedance R1 is equivalent to the impedance of the power supply circuit included in the communication terminal 100, and is set to a high impedance.

The sending circuit 110 is a circuit for sending the voltage signal Vs1. Transmitting circuit 110 In the communication system 10, all of the transmitting unit 20, the communication terminal 100, and the receiving terminals 300-1 and 300-2 have the same configuration.

The transmission circuit 110 generates a voltage signal Vs1 whose voltage is superimposed on a first reference voltage VH not shown, and outputs it to the transmission line 600-3 through an output impedance Rtx. The voltage signal Vs1 is, for example, a voltage signal superimposed with a negative voltage from the first reference voltage VH. The output impedance Rtx is an impedance determined by the configuration of the transmission circuit 110 of the communication terminal 100 .

The transmitting circuit 110 is equivalently constituted by a series circuit of an output impedance Rtx and a switching element Tr1. When the transmission circuit 110 transmits the voltage signal Vs1, the switching element Tr1 is turned on and off by the serial signal V_Rx generated by a microcomputer, etc., and the voltage signal Vs1 synchronized with the serial signal V_Rx is output to the transmission line 600-3.

The impedance adjustment circuit 120 is composed of an impedance adjustment element Ra, a switching element Tr2 and a reference voltage Vup, and is connected to the transmission circuit 110 in parallel. The impedance adjustment circuit 120 is a circuit in which the impedance adjustment element Ra is connected in parallel to the transmission circuit 110 via the switching element Tr2 from a specific reference voltage Vup in a power supply circuit not shown in the communication terminal 100 . The reference voltage Vup may be set to the same value as the first reference voltage VH, or may be another reference voltage in the power supply circuit of the communication terminal 100 . The switching element Tr2 is configured to be turned on during the transmission period of the voltage signal Vs1 by the impedance adjustment control signal Va. As will be described later, the impedance adjustment control signal Va is generated by a microcomputer constituting the control circuit of the communication terminal 100 in conjunction with the serial signal V_Rx and timing. The impedance adjustment circuit 120 becomes active (operating state) when the impedance adjustment control signal Va is at a high level (high potential), and becomes inactive (stop state) when it is at a low level (low potential). Specifically, when the impedance adjustment control signal Va is at a high level, the switch element Tr2 is turned on, and the output impedance of the communication terminal 100 is adjusted by connecting the reference voltage Vup to one end of the transmission circuit 110 through the impedance adjustment element Ra.

The impedance adjustment element Ra is set to a value sufficiently larger than the impedance Rtx. Therefore, the impedance adjustment control signal Va becomes a high level, and when the switch element Tr2 is turned on, the reference voltage Vup is output from the output terminal T1 through the impedance Ra.

The impedance adjusting element Ra is preferably equal to the characteristic impedance R0 of the transmission line 600-3. Reflected waves from the receiving terminals 300 - 1 and 300 - 2 are input to the communication terminal 100 . Therefore, by matching the impedance adjustment element Ra to the characteristic impedance R0, the communication terminal 100 does not output reflected waves, so normal data transmission can be performed without distorting the voltage signal Vs1. However, it is not necessary to make the impedance adjustment element Ra completely coincide with the characteristic impedance R0. The error of the impedance is allowable to the extent that it does not affect the reading of the voltage signal Vs1 of each receiving terminal 300-1, 300-2.

When the impedance adjustment circuit 120 of this embodiment is in operation, the output impedance of the communication terminal 100 becomes the composite impedance of impedances Rtx, Ra, and R1 when the switching element Tr1 is turned on, and becomes the combined impedance of impedances Ra and R1 when the switching element Tr1 is turned off. The synthetic impedance. When the voltage signal Vs1 is not transmitted, the impedance adjustment circuit 120 is set to a stop state, and the impedance adjustment element Ra is disconnected, so that the output impedance of the communication terminal 100 becomes R1, which becomes high impedance.

FIG. 3 shows the specific circuit configuration of the transmission circuit 110 and the impedance adjustment circuit 120 of the communication terminal 100 of this embodiment. The transmitting circuit 110 and the impedance adjusting circuit 120 of the communication terminal 100 are connected in parallel with respect to the output terminals T1-T2.

The transmission circuit 110 is connected in parallel with the equivalent impedance R1 of the power supply circuit of the communication terminal 100, and outputs a voltage signal Vs1 superimposed with a voltage synchronized with the serial signal V_Rx. The serial signal V_Rx is a signal synchronized with the voltage signal Vs1 output to the transmission line. The serial signal V_Rx is generated by a microcomputer (not shown) of the communication terminal 100 .

The transmitting circuit 110 receives the serial signal V_Rx from the microcomputer, drives the transistor Q1 (hereinafter referred to as Q1) with the signal inverted by the operational amplifier AMP, and outputs a voltage that will be synchronized with the serial signal V_Rx between the output terminals T1-T2. Voltage signal Vs1 at the first reference voltage VH. The impedance Rtx is connected to the output terminals T1-T2 of the transmission line through the transmission circuit 110 .

The impedance adjustment circuit 120 includes a series circuit of the impedance adjustment element Ra connected to the output terminal T1 and the capacitor C1 through a PMOSFET Q2 (hereinafter referred to as Q2) for the reference voltage Vup, and an NMOSFET Q3 (referred to as Q3) to control the on-off of Q2. Denoted as Q3 below).

The source terminal of Q2 is connected to the reference voltage Vup, and the drain terminal of Q2 is connected to one end of the impedance adjustment element Ra. The gate terminal of Q2 is connected to the other end of the resistor R3 with one end connected to the reference voltage Vup, and further connected to the drain terminal of Q3. The source terminal of Q3 is connected to circuit ground GND. The gate terminal of Q3 is input with the impedance adjustment control signal Va of the impedance adjustment circuit 120 generated by the microcomputer.

The impedance adjustment circuit 120 is in an operating state while the impedance adjustment control signal Va is at a high level. That is, if the impedance adjustment control signal Va is at a high level, Q3 is turned on, the gate terminal of Q2 becomes a low potential, and the source-drain terminal of Q2 is turned on. If so, the reference voltage Vup is output to the output terminal T1 through the impedance adjustment element Ra and the capacitor C1. The capacitor C1 is a DC cutoff capacitor for preventing the DC voltage from flowing from the output terminal T1 to the impedance adjustment circuit 120 . The capacitance value of the capacitor C1 is set to a sufficiently small impedance with respect to the impedance adjustment element Ra.

Next, the operation sequence of the impedance adjustment circuit 120 will be described. FIG. 4 shows the action timing of the impedance adjustment control signal Va and the serial signal V_Rx. The period T0 during which the serial signal V_Rx repeats a high level and a low level is a period during which the voltage signal Vs1 is sent. When the impedance adjustment control signal Va is at a high level, the impedance adjustment circuit 120 is in an active state, and during a low level period, the impedance adjustment circuit 120 is in an inactive state.

The impedance adjustment control signal Va becomes a high level earlier than the start of the serial signal V_Rx (the beginning of the period T0 ) at a time Td1 , and becomes a lower level at a time Td2 later than the end of the serial signal V_Rx (the end of the period T0 ). Therefore, the impedance adjustment circuit 120 starts to operate at a predetermined time Td1 earlier than the start of data transmission by the voltage signal Vs1. In addition, the impedance adjustment circuit 120 stops operating after a specific time Td2 after the data transmission by the voltage signal Vs1 is completed.

The reason why the operation starts at a specific time Td1 earlier than the start of data transmission by the voltage signal Vs1 is that it is effectively used as the installation time of the impedance adjustment circuit 120 . A capacitor C1 is connected in series to the impedance adjustment circuit 120, and it functions as a period in which the capacitor C1 is set to the potential of the output terminal T1 of the transmission line before data transmission is started. Thereby, it is possible to prevent the potential from becoming unstable immediately after data transmission is started.

The reason why the end of the operation is delayed by a specific time Td2 after the end of the data transmission by the voltage signal Vs1 is to prevent reflection waves returning from each receiving terminal from remaining. When the impedance adjustment circuit 120 stops operating simultaneously with the end of the serial signal V_Rx (end of data transmission), the voltage signal Vs1 at least equivalent to the last transmitted data is received under the high impedance R1 that does not match the characteristic impedance of the transmission line. the reflected wave. In this case, reflected waves remain in the transmission line, which may affect the next data transmission. By extending the operation of the impedance adjustment circuit 12 for an appropriate time Td2, reflection waves can be suppressed from remaining in the transmission line.

In addition, this invention is not limited to the above-mentioned embodiment and its modification, It goes without saying that various changes and improvements can be made within the scope of the matter described in the claim of this application.

10: Communication system 20: Transmission unit 30, 100: communication terminal 31: switch 31a~31d: Operation Department 32: Terminal unit 40a~40d: Relay 50a~50d: load (lighting fixtures) 60: Signal line (transmission line) 110: Sending circuit 120: Impedance adjustment circuit 300-1, 300-2: receiving terminal 600-1, 600-2, 600-3: transmission lines AMP: operational amplifier C1: Capacitor GND: circuit ground Q1: signal drive transistor Q2: PMOSFET Q3:NMOSFET R1, R3: Impedance Ra: Impedance adjustment element Rtx: output impedance T0: period T1, T2: output terminals Td1, Td2: time Tr1, Tr2: switching elements Va: impedance adjustment control signal VH: the first reference voltage V_Rx: serial signal Vs1: voltage signal Vup: reference voltage

Fig. 1 is a configuration diagram of the communication system of the embodiment. Fig. 2 is a configuration diagram of a communication system having a communication terminal of the embodiment. Fig. 3 is a circuit diagram of an example of an impedance adjustment circuit of the embodiment. FIG. 4 is a diagram illustrating an operation sequence of the impedance adjustment circuit of the communication terminal according to the embodiment.

10: Communication system

20: Transmission unit

100: communication terminal

110: Sending circuit

120: Impedance adjustment circuit

300-1, 300-2: receiving terminal

600-1, 600-2, 600-3: transmission lines

R1: Impedance

Ra: Impedance adjustment element

Rtx: output impedance

T1, T2: output terminal

Tr1, Tr2: switching elements

Va: impedance adjustment control signal

VH: the first reference voltage

V_Rx: serial signal

Vs1: voltage signal

Vup: reference voltage

Claims (8)

A communication terminal that transmits a voltage signal superimposed on a specific first reference voltage through a signal line, and has The impedance adjustment circuit switches the output impedance during the period of sending data by the aforementioned voltage signal. The communication terminal according to claim 1, wherein the impedance adjustment circuit stops operating after the transmission of the data is completed. The communication terminal according to claim 1 or 2, wherein the impedance adjustment circuit starts to operate before starting the transmission of the data. The communication terminal according to any one of claims 1 to 3, wherein the impedance adjustment circuit switches the output impedance to the characteristic impedance of the signal line. The communication terminal according to any one of claims 1 to 4, wherein the aforementioned impedance adjustment circuit has impedance adjustment element, One end of the aforementioned impedance adjustment element is connected to one of the aforementioned signal lines, and the other end is connected to a specific voltage of the power supply circuit of the aforementioned communication terminal via a switch. The communication terminal according to any one of claims 1 to 5, wherein the impedance adjustment circuit has a DC cut-off capacitor connected in series to the impedance adjustment element. The communication terminal according to any one of claims 1 to 6, wherein the specific voltage of the aforementioned power supply circuit is a voltage different from the aforementioned first reference voltage. A communication system, comprising: the communication terminal according to any one of claims 1 to 7; and One or more receiving terminals, which receive the aforementioned data sent from the aforementioned communication terminals.

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