JP7203359B2 - Communication circuit of gas safety equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a communication circuit for a gas safety device used in a gas supply line.

FIG. 6 is a configuration diagram of a conventional communication device, which independently includes both a one-to-one communication circuit and a bus communication circuit (see FIG. 2 of Patent Document 1. In Patent Document 1, gas shown as a communication circuit on the side of a wireless terminal device connected to a security device). The reason for providing both the one-to-one communication circuit and the bus communication circuit is to enable connection with a terminal device having only one of them. As a simple configuration, there is also a gas safety device having only a one-to-one communication circuit.

The one-to-one communication circuit includes a positive communication terminal DT, a negative communication terminal SG, a receiving circuit RXD, a transmitting circuit TXD, and an enable circuit END, and is connected to a DC voltage source VDD and a circuit ground GND, The receiving circuit RXD has a receiving resistor R21 and a receiving signal terminal RTD, the transmitting circuit TXD has a transmitting switch SW8 and a transmitting resistor R9, and the enable circuit END has an enable switch SW9, a diode D3 and an enable resistor R10.

At the time of transmission, by closing the enable switch SW9 for a predetermined time, an activation request is transmitted to the terminal side connected via the positive communication terminal DT and the negative communication terminal SG. The communication terminal DT is maintained at High voltage. By closing the transmission switch SW8, the positive communication terminal DT is set to Low voltage to transmit the space signal, and by opening the transmission switch SW8, the positive communication terminal DT is set to High voltage to transmit the mark signal. At the time of reception, the transmission switch SW8 and the enable switch SW9 are opened, and the mark signal or space signal sent from the terminal device is taken out from the reception signal terminal RTD.

An example of a standard for one-to-one communication circuits is the N-line standard. In the N-line standard, the maximum rating of the High voltage of the positive communication terminal DT is stipulated as 6 V, but the minimum value of the High voltage is not stipulated and can be freely set by the device designer. . In addition, the diode D3 of the enable circuit is not obligated to be mounted by the N line standard, but while the DC voltage source VDD used in many gas safety devices is 3.6 V or less, the positive communication terminal DT Since the maximum rating is stipulated as 6V, it is mounted for the purpose of preventing a reverse voltage from being applied to the enable switch SW9.

The bus communication circuit includes a positive communication terminal U1, a negative communication terminal U2, a receiver circuit RXU, a transmitter circuit TXU, and an enable circuit ENU, and is connected to a DC voltage source VDD and a circuit ground GND. The RXU has a reception resistor R22 and a reception signal terminal RTU, the transmission circuit TXU has a transmission switch SW10 and a transmission resistor R11, and the enable circuit ENU has an enable switch SW11 and an enable resistor R12.

During transmission, by closing the enable switch SW11, the positive communication terminal U1 is maintained at a high voltage. By closing the transmission switch SW10, the positive communication terminal U1 is set to Low voltage to transmit the space signal, and by opening the transmission switch SW10, the positive communication terminal U1 is set to High voltage to transmit the mark signal. At the time of reception, the transmission switch SW10 and the enable switch SW11 are opened, and the mark signal or space signal sent from the terminal device is extracted from the reception signal terminal RTU.

An example of a bus communication circuit standard is the U bus standard. In the U bus standard, the voltage of the positive communication terminal U1 is changed to High level by connecting the positive communication terminal U1 to the DC voltage source VDD through a resistor. The range of voltage values of the DC voltage source VDD is defined to be 2.2V to 3.6V. Unlike the maximum voltage of the positive communication terminal DT of the N-line standard, which is 6V, the voltage of the positive communication terminal U1 of the U-bus standard never exceeds 3.6V. Since the reverse voltage applied to the enable switch SW11 can be reduced accordingly, the diode is not necessarily required.

On the other hand, unlike the N-line positive communication terminal DT, the U-bus positive communication terminal U1 has a lower limit for the High voltage defined by the standard, which cannot be freely set by the device designer. Therefore, if a diode is used in the enable circuit ENU, it becomes necessary to keep the voltage value of the DC voltage source VDD high by the voltage drop of the diode. In that case, it is disadvantageous in terms of design because the cost increases due to the addition of a booster circuit and the like. For the above reasons, the enable circuit ENU of the bus communication circuit is usually not equipped with a diode.

The resistance of the receiving circuit defines the magnitude of the current that flows when transmitting the mark signal to the receiving side. The resistance value should be determined in consideration of the balance between noise resistance and current consumption from the conditions required by each standard. Actually, the N-line standard and the U-bus standard have different resistance values, and FIG. 6 also assumes that the receiving resistor R21 of the receiving circuit RXD and the receiving resistor R22 of the receiving circuit RXU have different values.

JP 2017-045227 A

In the conventional configuration, the one-to-one communication circuit and the bus communication circuit exist as independent circuits, and the terminal block is also provided with independent terminals, resulting in a problem of high cost. Although the basic configuration of the one-to-one communication circuit and the bus communication circuit are similar, the specifications of the voltage and reception resistance are different, so it was not possible to share them, and they were installed as separate independent circuits. rice field. An object of the present invention is to achieve cost reduction by integrating the circuits of the one-to-one communication circuit and the bus communication circuit.

In order to solve the above conventional problems, the communication circuit of the gas safety device of the present invention includes a positive communication terminal, a negative communication terminal connected to the circuit ground, a DC voltage source as a power supply, and the positive communication terminal. a receiving circuit capable of switching a resistance connected between the negative communication terminals between a first resistance value for one-to-one communication and a second resistance value for bus communication; a transmission circuit that generates a transmission signal; a Schottky barrier diode; an enable resistor; and an enable circuit that connects the Schottky barrier diode and the enable resistor in series to the positive communication terminal and the DC voltage source. By using a Schottky barrier diode with a small voltage drop in the enable circuit, when used as a one-to-one communication circuit, reverse voltage is prevented from being applied to the enable switch, and when used as a bus communication circuit, To eliminate the need to increase the voltage value of the DC voltage source while satisfying the lower limit requirement for the High voltage of the positive communication terminal. Also, by making it possible to switch the receiving resistance value between R1 and R2, a common circuit that operates as either a one-to-one communication circuit or a bus communication circuit is realized.

By making a common circuit that operates as either a one-to-one communication circuit or a bus communication circuit, conventionally mounted independent circuits are integrated into one circuit, and a circuit that boosts the voltage of a DC voltage source. Since there is no need to add , the number of parts can be reduced, and the number of terminals on the terminal block can be reduced, resulting in cost reduction.

FIG. 1 is a configuration diagram showing a communication circuit of a gas safety device according to Embodiment 1 of the present invention; A configuration diagram of a receiving circuit different from the receiving circuit shown in FIG. A configuration diagram showing a communication circuit of a gas safety device according to Embodiment 2 of the present invention. (a) A configuration diagram of a terminal device connected to a one-to-one communication circuit of a gas safety device, (b) A configuration diagram of a terminal device connected to a bus communication circuit of a gas safety device Configuration diagram of reverse connection protection circuit Configuration diagram showing a communication circuit of a conventional gas safety device

In a first invention, a positive communication terminal, a negative communication terminal connected to a circuit ground, a DC voltage source as a power supply, and a resistor connected between the positive communication terminal and the negative communication terminal are connected in one-to-one communication. a receiving circuit switchable between a first resistance value for bus communication and a second resistance value for bus communication; a transmitting circuit for generating a transmission signal between the positive communication terminal and the negative communication terminal; a Schottky barrier diode; an enable resistor; and an enable circuit connecting the Schottky barrier diode and the enable resistor in series between the positive communication terminal and the DC voltage source.

Further, since the Schottky barrier diode provided in the enable circuit has a feature that the voltage drop is smaller than that of a general switching diode, when used as a bus communication circuit, the DC There is no need to increase the voltage value of the voltage source. When used as a one-to-one communication circuit, the enable switch is prevented from being subjected to a reverse voltage. By making it possible to arbitrarily switch between the receiving resistor for one-to-one communication and the receiving resistor for bus communication, a common circuit that operates as both a one-to-one communication circuit and a bus communication circuit is realized.

Therefore, conventionally mounted as an independent circuit is integrated into one, and the number of parts can be reduced. Also, since the number of terminals on the terminal block is reduced, cost reduction can be realized.

According to a second invention, in the first invention, the receiving circuit includes a diode detection circuit for detecting the presence or absence of a diode in a terminal device connected between the positive communication terminal and the negative communication terminal.

In addition to the first invention, by providing the function of detecting the presence or absence of a diode in the terminal device, the communication device of the terminal device connected to the gas safety device has a diode between the positive communication terminal DT and the negative communication terminal SG. It can be determined whether it is an N-line communication circuit or a U-bus communication circuit having a diode between the positive communication terminal U1 and the negative communication terminal U2.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited by this embodiment. Also, in describing each embodiment, descriptions of restrictions on standards that are not necessarily required are omitted for the sake of simplicity of description.

(Embodiment 1)
FIG. 1 is a configuration diagram showing a communication circuit of a gas safety device according to Embodiment 1 of the present invention. It has an enable circuit ENC, a DC voltage source VDD, and a circuit ground GND, and can operate as a circuit for either one-to-one communication or bus communication.

The receiving circuit RXC1 selects the first receiving resistor R1 for one-to-one communication, the second receiving resistor R2 for bus communication, the first receiving resistor R1 and the second receiving resistor R2, and connects the positive communication terminal DT/U1. and a negative communication terminal SG/U2, and a reception signal terminal RTC. Therefore, by switching the resistance selector switch SW1, the first receiving resistor R1 is selected when one-to-one communication is performed, and the second receiving resistor R2 is selected when bus communication is performed. The resistance connected between U1 and the negative communication terminal SG/U2 can be switched between a first resistance value for one-to-one communication and a second resistance value for bus communication.

A signal transmitted from an external device (not shown) connected to the positive communication terminal DT/U1 and the negative communication terminal SG/U2 is received by extracting a mark signal or a space signal from the reception signal terminal RTC as a reception signal. Data values are confirmed.

The transmission circuit TXC includes a transmission resistor R3 and a transmission switch SW2 that connects the transmission resistor R3 between the positive communication terminal DT/U1 and the negative communication terminal SG/U2. The resistance value of the transmission resistor R3 is determined so as to satisfy both the conditions required for the transmission resistors R9 and R11 in FIG. That is, the resistance value is determined to satisfy the requirements for both one-to-one communication and bus communication. A space signal or a mark signal is transmitted to the external device by opening and closing the transmission switch SW2.

The enable circuit ENC includes an enable switch SW3, a Schottky barrier diode SD, and an enable resistor R4. The enable switch SW3 connects a Schottky barrier diode SD and an enable resistor R4, which are connected in series, to a DC voltage source VDD. , and when bus communication is performed, the same opening/closing operation as that of the enable switch SW11 in FIG. 6 is performed.

The Schottky barrier diode SD uses a Schottky barrier diode with a smaller voltage drop than a general switching diode, so that when used as a bus communication circuit, it satisfies the lower limit requirement for the high voltage of the positive communication terminal U1 of the U bus standard. , so that the voltage value of the DC voltage source does not need to be increased. When used as a one-to-one communication circuit, a reverse voltage is prevented from being applied to the enable switch SW3. The resistance value of the enable resistor R4 is determined so as to satisfy both the conditions required for the enable resistors R10 and R12 in FIG. That is, the resistance value is set to satisfy the requirements for both one-to-one communication and bus communication.

As described above, the communication circuit shown in FIG. 1 uses the Schottky barrier diode SD with a small voltage drop in the enable circuit ENC, thereby supporting different voltage specifications between the one-to-one communication circuit and the bus communication circuit. , a common circuit that operates as either a one-to-one communication circuit or a bus communication circuit by enabling the resistance selector switch SW1 to switch the reception resistance value between the first reception resistance R1 and the second reception resistance R2. It's becoming Therefore, conventionally mounted as an independent circuit is integrated into one, and the number of parts can be reduced. Also, since the number of terminals on the terminal block is reduced, cost reduction can be realized.

In this embodiment, the standard for one-to-one communication is assumed to be the N-line standard or the H-line standard, and the standard for bus communication is assumed to be the U-bus standard.

FIG. 2 is a configuration diagram of a receiving circuit different from the receiving circuit shown in FIG. The receiving circuit RXC2 includes a second receiving resistor R2 for bus communication, a resistor R5, a resistor changeover switch SW4, and a reception signal terminal RTC. The second receiving resistor R2 is a receiving resistor for bus communication, as in FIG. is the resistance determined to be equal to The resistance value of resistor R5 is represented by the following formula. It should be noted that in the numerical formulas shown below, the sign of each resistor represents the resistance value.

R5=R1×R2/(R2-R1)
The resistance selector switch SW4 is a switch that is selected when switching between one-to-one communication and bus communication. , the resistance value of the first receiving resistor R1 is equal to the combined resistance value of the resistors R5, and the receiving resistance value becomes the resistance value of the second receiving resistor R2 alone by opening the resistance changeover switch SW4 when performing bus communication. Therefore, it has a function of switching the resistance connected between the positive communication terminal DT/U1 and the negative communication terminal SG/U2 between a first resistance value for one-to-one communication and a second resistance value for bus communication.

As described above, the receiving circuit RXC2 shown in FIG. 2 has the same function as the receiving circuit RXC1 shown in FIG. 1, so even if the receiving circuit RXC1 shown in FIG. 1 is replaced with the receiving circuit RXC2 shown in FIG. can be obtained.

(Embodiment 2)
FIG. 3 is a configuration diagram showing a communication circuit of a gas safety device according to Embodiment 2 of the present invention, and some components are added to FIG. 1 described in Embodiment 1. In FIG. The added components are the diode detection resistor R6 and the diode detection resistor connection switch SW5 in the receiver circuit RXC3, the detection signal switch SW6 for transmitting a signal for detecting the presence or absence of the diode in the terminal device, and the current limiting resistor R7. is a diode detection circuit DSC. It also shows a state in which a terminal device TM is connected in addition to this communication circuit via a positive communication terminal DT/U1 and a negative communication terminal SG/U2.

The diode detection resistor connection switch SW5 and the detection signal switch SW6 operate as mutually interlocked switches. Normally, the detection signal switch SW6 is connected to the circuit ground GND side, and the diode detection resistor connection switch SW5 is open. behave exactly the same.

On the other hand, when trying to detect the presence or absence of the diode of the terminal device TM, the detection signal switch SW6 is connected to the current limiting resistor R7 side, and the diode detection resistor connection switch SW5 is closed. At this time, a voltage is applied to the negative communication terminal SG/U2 from the DC voltage source VDD through the current limiting resistor R7. Then, the type of the connected terminal device TM is determined by thresholding the voltage level of the reception signal terminal RTC.

After that, when the detection signal switch SW6 is connected to the circuit ground GND side and the diode detection resistor connection switch SW5 is opened to return to normal operation, based on the determination result, the connection of the resistance changeover switch SW1 is connected to the first receiving resistor R1 or Either of the second receiving resistors R2 is set.

When the voltage level of the reception signal terminal RTC is lower than the threshold value, the resistance values of the diode detection resistor R6 and the current limiting resistor R7 are determined to be connected to the terminal device for one-to-one communication, and the reception signal When the voltage level of the terminal RTC is higher than the threshold value, it is determined that the terminal device for bus communication is connected. The connection state of the resistance changeover switch SW1 when trying to detect the presence or absence of the diode of the terminal device TM is determined in advance at the time of design, but it is preferable to connect to the one with the larger resistance value. is.

Next, the internal circuit configuration of the terminal device TM will be described, and then the method of designing the resistance values of the diode detection resistor R6 and the current limiting resistor R7 will be described.

FIG. 4 is a configuration diagram of a terminal device connected to the communication circuit of the gas safety device, showing the internal circuit configuration of TM in FIG. For simplification of explanation, only circuit elements necessary for explaining the present embodiment are shown.

FIG. 4(a) shows a one-to-one communication circuit of a terminal device. The terminal device TM1 has a receiving resistor R8 and is connected to the communication terminals (positive communication terminal DT/U1 and negative communication terminal SG/U2) of the communication circuit of the present embodiment. The resistance value of the receiving resistor R8 is the same as that of the first receiving resistor R1 in FIG.

FIG. 4(b) shows the bus communication circuit of the terminal device. The terminal device TM2 has a diode D1 and is connected to the communication terminals (positive communication terminal DT/U1 and negative communication terminal SG/U2) of the communication circuit of the present embodiment. The diode D1 is mounted on the bus communication circuit as a reverse connection protection diode.

A method of designing the resistance values of the diode detection resistor R6 and the current limiting resistor R7 for detecting the presence or absence of a diode in the terminal device will be described below with reference to FIGS. 3 and 4. FIG. Here, it is assumed that the detection signal switch SW6 is connected to the current limiting resistor R7 side, the diode detection resistor connection switch SW5 is closed, and the resistance changeover switch SW1 is designed to be connected to the second receiving resistor R2. . First, the combined resistance value RSUM of the internal resistances of the receiver circuit RXC3 can be obtained by the following formula, since the second receiver resistor R2 and the diode detection resistor R6 are connected in parallel.

RSUM=R2×R6/(R2+R6)
Next, when the terminal device TM1 shown in FIG. 4A is connected as the terminal device TM in FIG. 3, the voltage value V1 of the reception signal terminal RTC is represented by the following formula.

V1=VDD×RSUM/(R7+R8+RSUM)
Also, when the terminal device TM2 shown in FIG. 4B is connected as TM in FIG. expressed.

V2=(VDD−VF)×RSUM/(R7+RSUM)
Then, the voltage threshold VTH is set so as to satisfy the following formula.

V1<VTH<V2
Here, the diode detection resistor R6 and the current limiting resistor R7 are arranged so that the voltage difference between the voltage threshold value VTH and the voltage value V1 and the voltage difference between the voltage value V2 and the voltage threshold value VTH are both as large as possible. should be selected. This is because even if there are variations in voltage, temperature, component constant values, and other factors, the conditions defined by the formulas are more likely to hold. For this purpose, the diode detection resistor R6 is selected so that the value of the combined resistance value RSUM is sufficiently smaller than that of the reception resistor R8. should be low. Further, by selecting the current limiting resistor R7 so that the combined resistance value RSUM is sufficiently larger than the current limiting resistor R7, the voltage value V2 of the reception signal terminal RTC when the terminal device TM2 is connected can be increased. do it.

In addition, from the viewpoint of cost reduction, the diode detection resistor R6, It is desirable to select current limiting resistor R7.

As described above, the communication circuit shown in FIG. 3 is provided with the diode detection circuit DSC for detecting the presence or absence of the diode of the terminal device TM, so that the communication circuit of the terminal device TM connected to the gas safety device is connected to the positive electrode. Either an N-line communication circuit (FIG. 4(a)) without a diode between the communication terminal DT and the negative communication terminal SG or a U-bus communication circuit (FIG. 4A) with a diode between the positive communication terminal U1 and the negative communication terminal U2. 4(b)). Based on the determination result, it can be operated as a circuit for either one-to-one communication or bus communication.

FIG. 5 is a configuration diagram of a reverse connection protection circuit, which may be used by being inserted between the positive communication terminals DT/U1 and SG/U2 of this embodiment. The reverse connection protection circuit PRT includes a diode D2 and a switch SW7, and the switch SW7 operates as a switch interlocked with the diode detection resistor connection switch SW5 and the detection signal switch SW6 in FIG.

Specifically, during normal operation, the switch SW7 is closed, the diode detection resistor connection switch SW5 is open, and the detection signal switch SW6 is connected to the circuit ground GND side. , the switch SW7 is open, the diode detection resistor connection switch SW5 is closed, and the detection signal switch SW6 is connected to the current limiting resistor R7 side. The reason why the opening/closing control of the switch SW7 is performed in this way is that when the terminal device TM shown in FIG. 3 is connected to the terminal device TM1 in FIG. and the negative communication terminal SG/U2), the receiving resistor R8 in FIG.

Providing the reverse connection protection circuit PRT in the communication circuit of the gas safety device is not an essential condition for obtaining the effect of the present embodiment, but the U bus standard stipulates the mounting of a diode for reverse connection protection. Therefore, it is necessary to comply with the U bus standard.

INDUSTRIAL APPLICABILITY The present invention can be used as a communication circuit for a gas safety device used in a gas supply line.

DT/U1 Positive communication terminal SG/U2 Negative communication terminal RTC Receive signal terminal RXC1, RXC2, RXC3 Receiving circuit TXC Transmitting circuit ENC Enable circuit VDD DC voltage source GND Circuit ground DSC Diode detection circuit R4 Enable resistor SD Schottky barrier diode

Claims (2)

a positive communication terminal;
a negative communication terminal connected to circuit ground;
a DC voltage source as a power source;
a receiving circuit capable of switching a resistance connected between the positive communication terminal and the negative communication terminal between a first resistance value for one-to-one communication and a second resistance value for bus communication;
a transmission circuit for generating a transmission signal between the positive communication terminal and the negative communication terminal;
a Schottky barrier diode, an enable resistor, an enable circuit connecting the Schottky barrier diode and the enable resistor in series between the positive communication terminal and the DC voltage source;
A communication circuit of a gas safety device with a 2. The communication circuit of a gas safety device according to claim 1, wherein said receiving circuit includes a diode detection circuit for detecting the presence or absence of a diode in a terminal device connected between said positive communication terminal and said negative communication terminal.

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