Network equipment and communication method

Abstract

The invention discloses network equipment and a communication method. The network equipment comprises an advanced physical layer APL port physical layer PHY and a hybrid interface circuit, the APL PHY is connected with the hybrid interface; the mixed interface is used for connecting instrument equipment; the hybrid interface circuit is connected with the hybrid interface; the hybrid interface circuit is compatible with a single-pair power over Ethernet (PoDL) mode, an analog input (AI) mode and an analog output (AO) mode; in the PoDL mode, the power supply supplies power to the instrument equipment; in the AI mode, the power supply supplies power to the hybrid interface; and in the AO mode, the voltage is converted into current corresponding to the control signal of the instrument equipment. According to the technical scheme, an interface of traditional instrument equipment can be compatible on the basis of APL communication.

Description

Technical Field

[0001] The present application relates to the field of industrial communication technology, and in particular to a network device and a communication method. Background Art

[0002] At present, most industrial communications are based on low-speed communication protocols such as analog signals 4mA~20mA, digital signals Highway Addressable Remote Transducer (HART), Profibus PA, Fieldbus Foundation (FF), etc., and their speeds are usually around tens of kps. The IEEE 802.3cg standard specifies Single Pair Ethernet (SPE) that can provide a communication rate of 10Mbps on a pair of twisted pairs, and use Power over Data Line (PoDL) to power industrial field instruments and equipment during communication. After the IEEE802.3cg standard was approved, the Advanced Physical Layer (APL) series of standardized solutions were embedded in the Ethernet-APL technology to achieve the expansion of the Ethernet physical layer standard, and design specifications that meet the field communication requirements of the process industry were formulated.

[0003] However, the current mainstream instrumentation equipment in the industry is mainly 4mA ~ 20mA, and the PoDL pins of the APL switch are incompatible with the interfaces of mainstream instruments, resulting in the inability to directly plug the interfaces of the APL switch and the interfaces of traditional instrumentation equipment. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a network device and a communication method, which can be compatible with the interface of traditional instrument equipment based on APL communication.

[0005] In a first aspect, an embodiment of the present application provides a network device, including: an advanced physical layer APL port physical layer PHY and a hybrid interface circuit; the APL PHY is connected to the hybrid interface; the hybrid interface is used to connect to an instrument device; the hybrid interface circuit is connected to the hybrid interface; the hybrid interface circuit is compatible with a single-pair Ethernet power supply PoDL mode, an analog input AI mode, and an analog output AO mode; in the PoDL mode, the power supply supplies power to the instrument device; in the AI ​​mode, the power supply supplies power to the hybrid interface; in the AO mode, the voltage is converted into a current corresponding to a control signal of the instrument device.

[0006] The hybrid interface circuit in the network device provided in the embodiment of the present application is compatible with the single-pair Ethernet power supply PoDL mode, analog input AI mode and analog output AO mode. In AI mode, the power supply supplies power to the hybrid interface; in AO mode, the output current can be controlled, so that the current conversion circuit can output a current in the range of 4mA to 20mA in AO mode. In PoDL power supply mode, power can be supplied to the instrument equipment. Therefore, the switch integrates the communication and PoDL power supply functions of APL, as well as the 4mA to 20mA AI and AO functions of the instrument equipment, to achieve compatibility of the APL interface with the interfaces of mainstream instrument equipment.

[0007] In one possible implementation, the interface of the instrument device is in AI mode, and the network device controls the hybrid interface circuit to work in AO mode. This allows the network device to control the instrument device, for example, the instrument device is a switch or valve, and can execute the command sent by the network device to perform an action.

[0008] A possible implementation method also includes: a controller, a current conversion circuit and a detection circuit, and the current conversion circuit and the detection circuit are both connected to the controller. In PoDL mode, the controller is used to control the current conversion circuit to be turned off, and the power supply directly supplies power to the device end; in AI mode, the controller is used to control the current conversion circuit to be turned off, and the DC voltage is directly provided to the hybrid interface, and the detection circuit is used to detect the current of the hybrid interface and provide it to the controller; in AO mode, the controller is used to control the current conversion circuit to convert the DC voltage into a current corresponding to the control signal of the device end.

[0009] In a possible implementation, the controller is used to control the current conversion circuit to output a direct current, and the direct current is less than a minimum value of a current range in the AI ​​mode.

[0010] Since the effective current range of AI's 4mA-20mA instrument interface is 4mA-20mA, the current value of the detection signal can be set to detect a DC current whose detection current is less than 4mA. This current value will be ignored by AI's 4mA-20mA instrument and will not cause the actuator on the device to perform an action incorrectly.

[0011] In one possible implementation, the controller is also used to control the current conversion circuit to output a current that varies within the PoDL mode range, and use the voltage range detected by the detection circuit to determine whether the interface of the instrument equipment is in PoDL mode. If the interface of the instrument equipment is in PoDL mode, the hybrid interface circuit is controlled to operate in PoDL mode.

[0012] The hybrid interface circuit provided in the embodiment of the present application can automatically identify whether the interface of the instrument device is in PoDL mode, thereby automatically controlling the hybrid interface circuit to operate in PoDL mode to provide power for the instrument device.

[0013] In a possible implementation method, the controller is also used to control the current conversion circuit to output a current that changes within the AO mode range, and use the changing voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in AO mode. If the interface of the instrument equipment is in AO mode, the hybrid interface circuit is controlled to operate in AI mode.

[0014] The hybrid interface circuit provided in the embodiment of the present application can automatically identify whether the interface of the instrument device is in AO mode. When the interface of the instrument device is in AO mode, the hybrid interface circuit is automatically controlled to operate in AI mode to receive the signal sent by the instrument device.

[0015] In a possible implementation, the current conversion circuit includes: a digital-to-analog converter and a voltage-to-current converter; the input and output ends of the digital-to-analog converter are respectively connected to a controller and a voltage-to-current converter; the voltage-to-current converter is also used to connect a DC / DC circuit; the controller is used to send a voltage-controlled digital signal to the digital-to-analog converter; the analog-to-digital converter is used to convert the voltage-controlled digital signal into a voltage-controlled analog signal; and the voltage-to-current converter is used to convert the voltage output by the DC / DC circuit into a current according to the voltage-controlled analog signal.

[0016] The current conversion circuit provided in the embodiment of the present application can use a digital-to-analog converter to convert a digital signal into an analog signal, and the voltage-to-current converter can convert a voltage signal into a current signal.

[0017] In a possible implementation, the detection circuit includes: a detection resistor, a current-to-voltage circuit and an analog-to-digital converter; the first end and the second end of the detection resistor are respectively connected to the output end of the current conversion circuit and the hybrid interface; the current-to-voltage circuit is used to connect the two ends of the detection resistor and send the voltage across the two ends of the detection resistor to the analog-to-digital converter; the analog-to-digital converter is used to convert the voltage sent by the current-to-voltage circuit into a digital voltage and send it to a controller.

[0018] The detection circuit provided in the embodiment of the present application can use a detection resistor with a small resistance value to detect the current, but due to the small resistance value, the power consumption can be ignored. The current-to-voltage circuit can convert the current into voltage, and the analog-to-digital converter can convert the analog signal into a digital signal, which is convenient for the controller to directly process.

[0019] In a possible implementation, the detection circuit also includes: a voltage divider circuit and a selection switch; the first end and the second end of the voltage divider circuit are respectively connected to the first end of the detection resistor and the ground; the first input end and the second input end of the selection switch are respectively connected to the output end of the current-to-voltage circuit and the output end of the voltage divider circuit, and the output end of the selection switch is connected to the input end of the analog-to-digital converter; a controller is used to control the output end of the selection switch to be connected to the first input end in PoDL mode and AI mode; in AO mode, it is used to control the output end of the selection switch to be connected to the second input end; the analog-to-digital converter is used to connect the output end of the selection switch to the first input end, collect the current of the detection resistor and send it to the controller; when collecting, the output end of the selection switch is connected to the second input end, detect the voltage of the voltage divider circuit and send it to the controller, and the controller controls the current output of the current conversion circuit according to the voltage detected by the analog-to-digital converter.

[0020] The detection circuit in the hybrid interface circuit provided in the embodiment of the present application can not only realize current detection, but also realize voltage detection, and the switching between current detection and voltage detection can be realized by selecting a switch.

[0021] A possible implementation method also includes: an automatic range switching circuit; the input and output ends of the automatic range switching circuit are respectively connected to the output end of the selection switch and the input end of the analog-to-digital converter; the automatic range switching circuit at least includes an amplifier, which is used to change the gain of the amplifier according to the voltage of the output end of the selection switch.

[0022] In order to expand the range of the detection signal, the hybrid interface circuit provided in the embodiment of the present application also includes an automatic range switching circuit, which can automatically switch the range according to the size of the signal. For example, if the current exceeds the preset current, the automatic range switching circuit can also automatically switch the range to achieve high current monitoring. If the monitored current exceeds the maximum supply current negotiated by PoDL and the power supply is not prevented from exceeding the limit, the controller disconnects the path switch and stops the power supply.

[0023] In a possible implementation, the automatic range switching circuit includes: a hysteresis comparator, an amplifier, a first resistor, a second resistor and a third resistor; the first input terminal and the second input terminal of the hysteresis comparator are respectively connected to the output terminal of the selection switch and the reference voltage, the first input terminal of the amplifier is connected to the output terminal of the selection switch, the second input terminal of the amplifier is connected to the first end of the first resistor, the second end of the first resistor is connected to the output terminal of the amplifier through the second resistor, the output terminal of the hysteresis comparator is connected to the control terminal of the controllable switch tube, the first end and the second end of the controllable switch tube are respectively connected to the first end of the third resistor and the ground, and the second end of the third resistor is connected to the second end of the first resistor.

[0024] The embodiments of the present application do not specifically limit the specific implementation form of the automatic range switching circuit, for example, a variable gain amplifier controlled by a program of a controller, or an adjustable gain analog front-end circuit integrated into an ADC, etc., and can also be a circuit built with analog devices. The embodiments of the present application do not specifically limit the scope of the range, for example, it can meet the automatic switching of the range from a few mA, tens of mA, to hundreds of mA.

[0025] A possible implementation also includes: a path switch; a first end and a second end of the path switch are respectively connected to the output end of the DC / DC circuit and the first end of the detection resistor; a control end of the path switch is connected to a controller; and the controller is further used to control the path switch to be turned on in PoDL mode or AI mode, and to control the path switch to be turned off in AO mode.

[0026] The path switch can realize the switching of whether the DC / DC circuit provides voltage or current to the line.

[0027] A possible implementation method also includes: a correction switch and a reference current source; the reference current source and the correction switch are connected in series and connected between the second end of the detection resistor and the ground; the control end of the correction switch is connected to the controller; the controller is also used to control the correction switch to turn on when the current of the detection resistor is greater than the preset current.

[0028] The APL switch provided in the embodiment of the present application also has an automatic calibration function, in order to avoid the detection current being too large, which may affect the change of the resistance value of the detection resistor and cause the result of the detection current to be offset. That is, the automatic correction function is to achieve more accurate detection. Taking current detection as an example, since the resistance value of the detection resistor Rsense is generally very small, such as only a few ohms, when a large current flows through the detection resistor Rsense, it is easily affected by the thermal effect and causes the resistance value to change, thereby causing the detection current to be offset and the detection to be inaccurate.

[0029] A possible implementation manner further includes: a coupling-decoupling network; the APL PHY is connected to the hybrid interface through a differential capacitor in the coupling-decoupling network; and the hybrid interface circuit is connected to the hybrid interface through a filter inductor in the coupling-decoupling network.

[0030] In a possible implementation, the current signal range of the AI ​​mode and the AO mode is 4 mA-20 mA.

[0031] In a possible implementation, the controller is further configured to, if the AI ​​mode is not met, control the current conversion circuit to output a constant current within the PoDL mode range, and use the voltage detected by the detection circuit to determine whether it is the PoDL detection mode.

[0032] In a second aspect, the embodiment of the present application further provides a communication method of a network device, the network device comprising an APL port physical layer PHY and a hybrid interface circuit; the APL The PHY is connected to a hybrid interface; the hybrid interface circuit is compatible with the single-pair Ethernet power supply PoDL mode, the analog input AI mode and the analog output AO mode; the hybrid interface is used to connect the instrument equipment; the hybrid interface circuit is connected to the hybrid interface; the hybrid interface circuit includes: a current conversion circuit and a detection circuit; the method includes: controlling the current conversion circuit to output a detection current, using the voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in the AI ​​mode, and the interface of the instrument equipment is in the AI ​​mode, and controlling the hybrid interface circuit to work in the AO mode; the detection current is a sinusoidal alternating current or a direct current current less than the minimum value of the current interval of the AI ​​mode; the interface of the instrument equipment is not in the AI ​​mode, controlling the current conversion circuit to output a current that changes within the PoDL mode range, and using the voltage range detected by the detection circuit to determine whether the interface of the instrument equipment is in the PoDL mode, and the interface of the instrument equipment is in the PoDL mode, and controlling the hybrid interface circuit to work in the PoDL mode; the interface of the instrument equipment is not in the PoDL mode, controlling the current conversion circuit to output a current that changes within the AO mode range, and using the changing voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in the AO mode, and the interface of the instrument equipment is in the AO mode, and controlling the hybrid interface circuit to work in the AI ​​mode.

[0033] The communication method provided in the embodiment of the present application is compatible with the single-pair Ethernet power supply PoDL mode, the analog input AI mode and the analog output AO mode; it can automatically identify the interface type of the instrument equipment and automatically adapt to the interface type of the instrument equipment to realize the control of the instrument equipment or receive the signal of the instrument equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a working diagram of a traditional APL switch;

[0035] Figure 2 A schematic diagram of the operation of the APL switch provided in the embodiment of the present application;

[0036] Figure 3 An interface diagram of an APL switch provided in an embodiment of the present application;

[0037] Figure 4 An internal architecture diagram of an APL switch provided in an embodiment of the present application;

[0038] Figure 5 An internal architecture diagram of another APL switch provided in an embodiment of the present application;

[0039] Figure 6 An internal architecture diagram of another APL switch provided in an embodiment of the present application;

[0040] Figure 7 An internal architecture diagram of another APL switch provided in an embodiment of the present application;

[0041] Figure 8 An internal architecture diagram of another APL switch provided in an embodiment of the present application;

[0042] Fig. 9 A schematic diagram of a coupling-decoupling network provided in an embodiment of the present application;

[0043] Fig.10 A schematic diagram of another coupling-decoupling network provided in an embodiment of the present application;

[0044] Fig.11 A flow chart of adaptive detection for the hybrid interface module provided in the embodiment of the present application;

[0045] Fig.12 An architectural diagram of an internal filter of an instrument device provided in an embodiment of the present application;

[0046] Fig.13 A schematic diagram of another type of detection interface provided in an embodiment of the present application;

[0047] Fig.14 A flow chart of a communication method of an APL switch provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution provided by the embodiments of the present application, the application scenario is first introduced below.

[0049] The APL switch is applied to the process industry to enable all Ethernet access to the process industry field network. The embodiments of the present application do not specifically limit the types of instruments or sensors connected to the APL switch. For example, the instrument can detect various physical quantities, such as temperature, pressure, liquid level or flow rate. In addition, the APL switch can also output signals to the instrument equipment, such as controlling the instrument equipment, such as controlling switches or valves. When the PoDL mode of the APL switch includes detection mode, power supply mode and sleep mode. In detection mode, the APL switch outputs a current in the range of 9mA to 16mA to the instrument equipment. If the detection feedback voltage is within the preset range, the power supply mode is entered. In power supply mode, the APL switch provides voltage to the instrument equipment. The sleep mode is to enter the sleep mode when the current in the detection circuit is less than the preset current threshold.

[0050] However, the current APL switches are not compatible with traditional data interfaces. For example, in the instrumentation equipment in the petrochemical industry, the signals transmitted by mainstream instruments are mainly 4mA~20mA. The ground pins inside the mainstream instruments are connected differently from the ground pins in the PoDL of the APL switch, resulting in the mismatch between the PoDL interface of the APL switch and the 4mA~20mA interface of the instrumentation equipment.

[0051] See also Figure 1 ,This figure is a schematic diagram of the working scenario of a traditional APL switch.

[0052] The interfaces in the conventional APL switch 100 only include APL PHY and PoDL, which can realize the transmission of APL data or PoDL power supply, that is, the meter device 200 includes APL data transmission requirements and PoDL power supply requirements.

[0053] However, since the power supply pins of PoDL are not compatible with the pins of 4mA~20mA, the output pins of PoDL include the power supply pin and the GND pin, where the power supply pin provides power voltage output for the instrument equipment. The 4mA~20mA pins include the power supply pins V+ and V-, where V- is connected to a 250Ω resistor to GND. Therefore, if the two interface pins are directly compatible, a 250Ω resistor will be connected in series, resulting in most of the power supply power being lost by the resistor when PoDL is powered.

[0054] In order to solve the above technical problems, the embodiment of the present application provides a network device, which can be a switch or a gateway device, the gateway device can be an Internet of Things gateway, and the switch can be, for example, an APL switch. For ease of understanding, the network device APL switch is used as an example for introduction in the following embodiment. The network device includes a hybrid interface circuit, which is compatible with the power supply function of PoDL and the analog input (AI, Analog Input) and analog output (AO, Analog Output) functions of 4mA~20mA. The AO function of the interface of the 4mA~20mA signal corresponds to the output signal, that is, outputting the control signal to the instrument, and the AI ​​function corresponds to the input signal, that is, receiving the detection signal of the instrument. AI and AO do not affect each other, so that each functional mode can work independently, and is applied to data communication and power supply at the process industry site, which can not only meet the needs of future Ethernet access, but also be compatible with mainstream 4mA~20mA data transmission.

[0055] See also Figure 2 , which is a schematic diagram of the working scenario of the APL switch provided in an embodiment of the present application.

[0056] The APL switch 100 provided in the embodiment of the present application includes an APL PHY and a hybrid interface circuit, wherein the hybrid interface circuit is compatible with PoDL power supply and 4mA~20mA data transmission functions, and can realize APL data transmission, PoDL power supply, and 4mA~20mA AI and AO functions with the corresponding instrument equipment 200. In some embodiments, AI, AO and PoDL can only realize one of the functions at the same time, and the host computer can trigger the APL switch 100 to select one of the functions, or manually trigger one of the functions, or automatically trigger and select one of the functions, which is not specifically limited in the embodiment of the present application.

[0057] For easier understanding, see Figure 3 , which is a schematic diagram of an interface of an APL switch 100 provided in an embodiment of the present application.

[0058] The APL switch 100 provided in the embodiment of the present application includes a hybrid interface circuit 101 and a hybrid interface 102. The hybrid interface circuit 101 is connected to the hybrid interface 102. The hybrid interface 102 can be connected to an AI function instrument of a 4mA-20mA instrument, or an AO function instrument of a 4mA-20mA instrument, or an APL interface instrument of an instrument. The APL interface instrument and the APL switch 100 can realize APL data transmission and PoDL power supply.

[0059] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0060] See also Figure 4 , which is an internal architecture diagram of an APL switch 100 provided in an embodiment of the present application.

[0061] The Ethernet physical layer APL switch 100 provided in the embodiment of the present application includes: an APL port physical layer PHY10 and a hybrid interface circuit;

[0062] APL PHY10 is connected to hybrid interface 102; hybrid interface 102 is used to connect instrument equipment; hybrid interface circuit is connected to hybrid interface 102;

[0063] The hybrid interface circuit 102 is compatible with the single-pair Ethernet power supply PoDL mode, the analog input AI mode and the analog output AO mode;

[0064] In PoDL mode, the power supply supplies power to the instrument equipment;

[0065] In AI mode, the power supply supplies power to the hybrid interface 102;

[0066] In AO mode, the voltage is converted into a current corresponding to the control signal of the instrument device.

[0067] A possible implementation is Figure 4 As shown, the hybrid interface circuit includes: a controller 20, a current conversion circuit 30 and a detection circuit 40; the current conversion circuit 30 and the detection circuit 40 are both connected to the controller 20;

[0068] The controller 20 in the hybrid interface circuit provided in the embodiment of the present application can control the hybrid interface circuit to operate in one of the following three modes: PoDL mode, AI mode of 4mA~20mA and AO mode of 4mA~20mA.

[0069] In the PoDL power supply mode, the controller 20 is used to control the current conversion circuit 30 to convert the DC voltage into the current of the PoDL mode to provide power to the instrument equipment, and the power supply current of the PoDL mode is 9mA to 16mA. The embodiment of the present application does not specifically limit the source of the DC voltage. For example, the DC voltage can be provided by the direct current / direct current (Direct Circuit / Direct Circuit, DC / DC) circuit 50 included in the APL switch 100. The current conversion circuit 30 can convert the voltage provided by the DC / DC circuit 50 into a current for output. The current conversion circuit 30 can be implemented using a voltage-to-current circuit or a voltage-to-current chip. In another possible implementation, the control signal sent by the controller 20 is a digital signal, and the current conversion circuit 30 also has a digital-to-analog conversion function, that is, converting the control signal sent by the controller 20 into an analog signal. In another embodiment, the control signal sent by the controller 20 is an analog signal.

[0070] The embodiment of the present application does not specifically limit the specific implementation form of the controller 20. For example, it can be implemented by a micro control unit (MCU). The controller 20 can send a control signal to the current conversion circuit 30, and the control signal indicates the size of the current output by the current conversion circuit. The current conversion circuit 30 can change the output current according to the control signal sent by the controller 20.

[0071] In AI mode, that is, the APL switch receives a signal from the instrument device, the controller 20 is used to control the bypass of the current conversion circuit 30, such as controlling the shutdown of the current conversion circuit 30, that is, the current conversion circuit 30 does not output current. The DC / DC circuit 50 provides a DC voltage to the hybrid interface 102 without passing through the current conversion circuit 30, that is, the DC / DC circuit 50 provides a working voltage to the line through the detection resistor in the detection circuit 40. In a possible implementation, the current conversion circuit 30 is bypassed. The detection circuit 40 is used to detect the current of the hybrid interface 102 and provide it to the controller 20. The instrument device detection circuit 40 can convert the current signal into a voltage signal for detection, and send the detection result to the controller 20, thereby realizing the AI ​​function of 4mA to 20mA.

[0072] In AO mode, that is, the APL switch 100 needs to output a current of 4mA to 20mA to the instrument equipment to realize the control of the instrument of the instrument equipment, which may include controlling the switch on and off or the valve switch of the instrument equipment. At this time, the controller 20 is used to control the current conversion circuit 30 to convert the DC voltage into the current corresponding to the control signal. For example, the current range corresponding to the control signal of the instrument equipment is 4mA to 20mA. At this time, the detection circuit 40 can be in the voltage detection mode, and the voltage in the circuit is detected in real time and sent to the controller 20. The controller 20 controls the output current of the current conversion circuit 30 according to the detection result of the detection circuit 40 to prevent the voltage in the circuit from exceeding the limit and causing overvoltage.

[0073] The APL switch provided in the embodiment of the present application does not specifically limit the method of selecting the working mode, and can be automatically selected or externally triggered.

[0074] The hybrid interface circuit in the APL switch provided in the embodiment of the present application includes a controller, a current conversion circuit and a detection circuit. In the AO mode, the controller can control the magnitude of the output current of the current conversion circuit, and then the current conversion circuit can output a current in the range of 4mA to 20mA in the AO mode. The detection circuit can realize signal detection in the AI ​​mode of 4mA to 20mA, and in the PoDL power supply mode, the APL switch can power the instrument equipment. Therefore, the switch integrates the communication and PoDL power supply functions of APL, as well as the 4mA to 20mA AI and AO functions of the instrument equipment, to achieve compatibility of the APL interface with the interface of mainstream instruments.

[0075] See also Figure 5 , which is an internal architecture diagram of another APL switch provided in an embodiment of the present application.

[0076] The APL switch provided in the embodiment of the present application, the current conversion circuit includes: a digital analog converter (DAC) 31 and a voltage-current converter 32;

[0077] The input and output ends of the DAC 31 are connected to the controller 20 and the voltage-to-current converter 32 respectively;

[0078] The voltage-to-current converter 32 is also used to connect to the DC / DC circuit 50;

[0079] The controller 20 is used to send a voltage control digital signal to the DAC 31;

[0080] DAC 31, for converting the voltage-controlled digital signal into a voltage-controlled analog signal;

[0081] The voltage-to-current converter 32 is used to convert the voltage output by the DC / DC circuit 50 into a current according to the voltage control analog signal.

[0082] The detection circuit 40 includes: a detection resistor Rsense, a current-to-voltage circuit 41 and an analog-to-digital converter (ADC) 42 ; the resistance of Rsense is generally small, only a few ohms, so its loss can be ignored.

[0083] The first and second ends of the detection resistor Rsense are respectively connected to the output end of the current conversion circuit and the hybrid interface 102; specifically, the first end of Rsense is connected to the output end of the voltage-current converter 32, that is, the output current of the voltage-current converter 32 passes through the detection resistor Rsense.

[0084] The current-to-voltage circuit 41 is used to connect the two ends of the resistor Rsense, detect the voltage across the resistor Rsense and send the detected voltage value to the ADC 42; the function of the current-to-voltage circuit 41 is to convert the detected current flowing through Rsense into a voltage on Rsense. The current-to-voltage circuit 41 can be implemented using a built circuit or a chip, and the embodiment of the present application does not make specific limitations.

[0085] ADC 42 is used to convert the analog voltage sent by the current-to-voltage circuit 41 into a digital voltage and send it to the controller 20. Since the controller 20 can only process digital signals, ADC 42 is required to convert the analog signal into a digital signal.

[0086] from Figure 5It can be seen from the detection circuit shown that the APL switch provided in the embodiment of the present application can realize current detection on the line, especially working in AI mode, detecting the current signal sent by the instrument equipment. When the APL switch works in AO mode, ADC42 can also detect the current on the line and send it to the controller 20 to form a closed-loop feedback. The controller 20 can adjust the control signal output to DAC 31 to adjust the current size on the line.

[0087] In addition, the APL switch provided in the embodiment of the present application further includes: a path switch 60;

[0088] A first end and a second end of the path switch 60 are connected to an output end of the DC / DC circuit 50 and a first end of a detection resistor Rsense, respectively;

[0089] The controller 20 is further configured to control the path switch 60 to be turned on in the PoDL mode or the AI ​​mode, and to control the path switch 60 to be turned off in the AO mode.

[0090] The embodiment of the present application does not specifically limit the specific type of the path switch 60, for example, it can be a controllable switch tube, for example, it can be implemented by a metal-oxide-semiconductor (MOS) tube or a diode. The path switch 60 can receive a control signal sent by the controller 20 to turn on or off the circuit between the DC / DC circuit and Rsense. The controller 20 controls the DC / DC circuit 50 to provide voltage or current to the line by controlling the path switch 60.

[0091] When the path switch 60 is turned on, the DC / DC circuit 50 is connected to the first end of Rsense, which is equivalent to the turned-on path switch 60 bypassing the voltage-to-current converter (V / I) 32, that is, V / I 32 no longer outputs current to the first end of Rsense, and the DC / DC circuit 50 provides voltage to the line through Rsense.

[0092] When the path switch 60 is turned off, the DC / DC circuit 50 is electrically connected to the first end of Rsense via the DAC 31 and the V / I 32, and the V / I 32 converts the voltage provided by the DC / DC circuit 50 into a current and provides it to the first end of Rsense. The detection circuit provided in the embodiment of the present application can not only detect the current on the line, but also detect the voltage on the line, which is described in detail below in conjunction with the accompanying drawings.

[0093] See also Figure 6 , this figure is an internal architecture diagram of another APL switch provided in an embodiment of the present application.

[0094] The APL switch provided in the embodiment of the present application, the detection circuit further includes: a voltage divider circuit and a selection switch MUX;

[0095] The selector switch MUX is controlled by the controller 20 , and its function is to switch between current sampling and voltage sampling by the ADC 42 . The voltage divider circuit divides the voltage on the line so that the detected voltage meets the range of the ADC 42 .

[0096] The voltage divider circuit includes a fifth resistor R5 and a sixth resistor R6. The first end of the sixth resistor R6 is connected to the first end of Rsense, and the second end of the sixth resistor R6 is grounded through the fifth resistor R5. The first end of the sixth resistor R6 is the first end of the voltage divider circuit, the second end of the fifth resistor R5 is the second end of the voltage divider circuit, and the second end of the sixth resistor R6 is the output end of the voltage divider circuit, that is, the output divided voltage.

[0097] The first end and the second end of the voltage divider circuit are connected to the first end of the detection resistor Rsense and the ground respectively;

[0098] The selection switch MUX can be implemented by a multi-way selection switch or a selector. In the embodiment of the present application, a multi-way selection switch or a selector with an input terminal greater than or equal to 2 can be selected.

[0099] The first input terminal and the second input terminal of the selection switch MUX are respectively connected to the output terminal of the current-to-voltage circuit 41 and the output terminal of the voltage divider circuit, i.e., the second terminal of R6, and the output terminal of the selection switch MUX is connected to the input terminal of the ADC 42. In a possible implementation, the current-to-voltage circuit 41 can be implemented using an amplifier.

[0100] The controller 20 is used to control the output end of the selection switch MUX to be connected to the first input end in PoDL mode and AI mode, that is, the current of Rsense can be detected; in AO mode, it is used to control the output end of the selection switch MUX to be connected to the second input end, that is, the voltage on the line can be detected.

[0101] ADC 42 is used to connect the output end of the selection switch MUX with the first input end, collect the current of the detection resistor Rsense and send it to the controller; connect the output end of the collection selection switch MUX with the second input end, detect the voltage of the voltage divider circuit and send it to the controller.

[0102] The controller 20 controls the current output by the V / I 32 according to the voltage detected by the ADC 42 .

[0103] In addition, the APL switch provided in the embodiment of the present application can also realize automatic switching of the detection range of current or voltage, which is described in detail below with reference to the accompanying drawings.

[0104] See also Figure 7, which is an internal architecture diagram of another APL switch provided in an embodiment of the present application.

[0105] The APL switch provided in the embodiment of the present application includes: an automatic range switching circuit 43;

[0106] The input and output of the automatic range switching circuit 43 are connected to the output of the selection switch MUX and the input of the ADC 42 respectively;

[0107] The automatic range switching circuit 43 at least includes an amplifier, which is used to change the gain of the amplifier according to the voltage at the output end of the selection switch MUX, thereby realizing automatic switching of the range of the sampled voltage or current.

[0108] The embodiment of the present application does not specifically limit the specific implementation form of the automatic range switching circuit 43, for example, a variable gain amplifier controlled by the controller 20, or an adjustable gain analog front-end circuit integrated into the ADC 42, etc., and can also be a circuit built with analog devices. The embodiment of the present application does not specifically limit the scope of the range, for example, it can meet the automatic switching of the range from a few mA, tens of mA, and hundreds of mA.

[0109] The following introduces three modes of the APL switch provided in the embodiment of the present application working in PoDL: detection mode, power supply mode and sleep mode.

[0110] In the PoDL detection mode, the controller 20 performs PoDL mode detection, the controller 20 controls the path switch 60 to be disconnected, and sends a voltage control digital signal to the DAC 31; the DAC 31 converts the voltage control digital signal into a voltage control analog signal; the V / I 32 converts the voltage output by the DC / DC circuit 50 into a current according to the voltage control analog signal, specifically outputs a current in the range of 9mA to 16mA, and changes the current value in this range. At this time, the selection switch MUX is connected to the voltage divider circuit, that is, the common end of R5 and R6 is connected, and the ADC42 detects the feedback voltage and sends it to the controller 20. The controller 20 determines whether the feedback voltage is between 4.05V and 4.7V. If the feedback voltage of the instrument device is within this range, the PoDL power supply mode for the instrument device is entered (according to the standard process specified by PoDL), and the power supply mode is entered if the interaction is successful.

[0111] In the PoDL power supply mode, the controller 20 turns on the access switch, and the DC / DC circuit 50 supplies power to the instrument equipment. At this time, it is necessary to limit and monitor the working current in the power supply mode. At this time, the detection circuit is in the current detection mode. Specifically, the controller 20 sets the detection circuit to the current detection mode, and the MUX is connected to the current-to-voltage circuit 41; the ADC 42 monitors the magnitude of the power supply current in real time. If the current exceeds the first preset current value, the automatic range switching circuit 43 automatically switches the range to achieve large current monitoring. If the monitored current exceeds the maximum power supply current negotiated by PoDL and the power supply power is not prevented from exceeding the limit, the controller disconnects the access switch and stops the power supply.

[0112] In the PoDL sleep mode, the controller 20 monitors the small current (between 1.25mA and 1.85mA) in the line, and the controller 20 controls the path switch 60 to be closed. The DC / DC circuit 50 first provides voltage to the line through the path switch 60. At this time, the controller 20 controls the MUX to be connected with the current-to-voltage circuit 41, and the detection circuit is in the current detection mode, that is, the ADC42 detects the current of Rsense and sends it to the controller 20. The controller 20 determines that the current is lower than the second preset current value, and the automatic range switching circuit 43 can also automatically switch the range to realize the monitoring of small currents.

[0113] In order to facilitate those skilled in the art to understand the automatic range switching circuit provided in the embodiment of the present application, a specific implementation method of the automatic range switching circuit is introduced below in conjunction with the accompanying drawings.

[0114] See also Figure 8 , this figure is an internal architecture diagram of another APL switch provided in an embodiment of the present application.

[0115] The APL switch provided in the embodiment of the present application, the automatic range switching circuit includes: a hysteresis comparator U3, an amplifier U2, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4;

[0116] The first input terminal and the second input terminal of the hysteresis comparator U3 are respectively connected to the output terminal of the selection switch MUX and the reference voltage, the first input terminal of the amplifier U2 is connected to the output terminal of the selection switch MUX, the second input terminal of the amplifier U2 is connected to the first terminal of the first resistor R1, the second terminal of the first resistor R1 is connected to the output terminal of the amplifier U2 through the second resistor R2, the output terminal of the hysteresis comparator U3 is connected to the control terminal of the controllable switch tube U6, the first terminal and the second terminal of the controllable switch tube U6 are respectively connected to the first terminal of the third resistor R3 and the ground, the second terminal of the third resistor R3 is connected to the second terminal of the first resistor R1. The second input terminal of the amplifier U2 is grounded through the fourth resistor R4.

[0117] In the embodiment of the present application, the controllable switch tube U6 is described as a MOS tube as an example, but it can also be implemented by other controllable semiconductor devices.

[0118] The reference voltage may be provided by a voltage source, such as Figure 8 As shown, the second input terminal of the hysteresis comparator U3 is grounded through a voltage source.

[0119] Figure 8 The function of the automatic range switching circuit provided is to adapt to a larger voltage or current detection range. The working principle is that when the voltage output by the selection switch MUX exceeds the hysteresis voltage of the hysteresis comparator U3, the hysteresis comparator U3 outputs a drive signal to drive the MOS tube U6 to turn on, so that the third resistor R3 is connected to the circuit, thereby changing the feedback coefficient of the amplifier U2, thereby realizing the adjustment of the gain of the amplifier U2.

[0120] In a possible implementation, the APL switch provided in the embodiment of the present application also has an automatic calibration function, in order to avoid the detection current being too large, which may affect the change in the resistance value of the detection resistor and cause the result of the detection current to be offset. That is, the automatic correction function is to achieve more accurate detection. Taking current detection as an example, since the resistance value of the detection resistor Rsense is generally very small, such as only a few ohms, when a large current flows through the detection resistor Rsense, it is easily affected by the thermal effect and causes the resistance value to change, thereby causing the detection current to be offset and the detection to be inaccurate.

[0121] Continue to see Figure 8 , the APL switch provided in the embodiment of the present application further includes: a correction switch and a reference current source U5;

[0122] The reference current source U5 and the correction switch are connected in series and connected between the second end of the detection resistor Rsense and the ground; the control end of the correction switch is connected to the controller 20 .

[0123] The controller 20 is also used to control the correction switch to turn on when the current of the detection resistor Rsense is greater than the preset current. Since the reference current source U5 is a bypass current source and is not affected by the power current, the thermal effect caused by the large current can be avoided. The reference current source U5 is only connected during calibration. When calibration is not required, the controller 20 controls the correction switch to turn off.

[0124] The following formula is used to introduce the calculation method of the correction coefficient K:

[0125] I=K*U ADC1

[0126] I+ΔI=K*U ADC2

[0127] K=ΔI / (U ADC2 -UADC1 )

[0128] in:

[0129] I is the current flowing through Rsense when the reference current source U5 is not connected;

[0130] U ADC1 It is the voltage sampled by ADC when the reference current source U5 is not connected;

[0131] ΔI is the reference current output by the reference current source U5;

[0132] U ADC2 It is the current flowing through Rsense when the reference current source U5 is connected.

[0133] In a specific implementation, the APL switch provided in the embodiment of the present application further includes: a coupling-decoupling network;

[0134] The APL PHY connects to the hybrid interface through differential capacitors C1 and C2 in the coupling-decoupling network;

[0135] The hybrid interface circuit is connected to the hybrid interface via a filter inductor L in a coupling-decoupling network.

[0136] The two capacitors C1 and C2 form a differential channel to isolate DC signals and low-frequency signals, and form a high-speed signal path with APL PHY to provide APL data transmission and reception. The inductor L is used to filter high-speed APL data, provide a low-speed signal path, and connect to the low-speed PoDL and 4mA~20mA hybrid interface circuit.

[0137] The coupling and decoupling network provided in the embodiment of the present application is not limited to Fig. 9 The architecture shown can also be implemented by other coupling-decoupling networks, such as Fig.10 , which is a schematic diagram of another coupling-decoupling network provided in an embodiment of the present application.

[0138] Fig.10 In addition to including Fig. 9In addition to the differential capacitors C1 and C2 and the filter inductor L, the first isolation transformer T1 and the second isolation transformer T2 are also included, wherein the APL PHY is connected to the two ends of the first winding of the first isolation transformer T1, the first end of the second winding of the first isolation transformer T1 is connected to the first differential capacitor C1, and the second end of the second winding of the first isolation transformer T1 is connected to the second differential capacitor C2. The PoDL and 4mA-20mA hybrid interface circuit are connected to the first end of the first winding and the first end of the second winding of the second isolation transformer T2, the second end of the first winding and the second end of the second winding of the second isolation transformer T2 are respectively connected to the first end of the first winding and the first end of the second winding of the filter inductor, and the second end of the first winding and the second end of the second winding of the filter inductor L are respectively connected to the first end and the second end of the hybrid interface. It should be understood that the first end of the hybrid interface is a data or power interface, and the first end of the hybrid interface is generally grounded.

[0139] The hybrid interface circuit in the APL switch provided in the embodiment of the present application can also realize interface adaptation, that is, automatically identify the interface type of the instrument equipment and adjust the working mode to adapt to the operation of the instrument equipment. The specific implementation method is described in detail below.

[0140] The hybrid interface circuit sends a detection signal and senses the signal fed back by the instrument device interface, thereby determining the physical layer differences of different interface types and identifying the instrument interface type of the instrument device. In the hybrid interface module provided by the embodiment of the present application, since the controller can control the size of the detection signal, the detection signal will not cause malfunction of the 4mA to 20mA actuator of the instrument device interface type AI, such as a switch or valve.

[0141] See also Fig.11 , which is a flow chart of adaptive detection performed by the hybrid interface module provided in an embodiment of the present application.

[0142] The hybrid interface module detects the interface types of instrument equipment, including AI's 4mA~20mA, AO's 4mA~20mA and PoDL interfaces.

[0143] S1101: The controller controls the current conversion circuit to output a sinusoidal AC current, and uses the voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in AI mode.

[0144] When the interface of the instrument equipment is in AI mode, the hybrid interface circuit is controlled to work in AO mode.

[0145] The embodiment of the present application first performs AI mode detection in order to exclude the possibility that the instrument device is in AI mode. Otherwise, subsequent detection may cause the detection signal to be mistakenly regarded by the AI ​​device as a real signal.

[0146] When the APL switch works in AO mode, it needs to output current to the line to provide the specified current to the instrument equipment, so as to control the instrument at the other end (valves, switches, etc.). In this mode, the controller controls the current conversion circuit to provide current to the cable. At this time, the detection circuit is in voltage detection mode, and the voltage fed back by the instrument equipment in the line is detected in real time.

[0147] For example, the hybrid interface circuit generates a sinusoidal AC signal Is of positive or negative 0.5 mA and a frequency of 1.2 kHz or 2.2 kHz through a current conversion circuit as a detection signal; the above current and frequency values ​​are only examples, and other sinusoidal AC currents or other frequencies can also be used. Then the peak-to-peak voltage Vsense fed back to the hybrid interface circuit by the instrument equipment is detected through the detection circuit; by calculating whether the impedance of the instrument interface connected to the instrument equipment is approximately equal to 250 ohms (taking into account detection errors and cable impedance errors), it can be determined whether the interface type of the instrument equipment is 4mA~20mA of AI, and the impedance calculation formula is: R=Vsense / Is.

[0148] The circuit of the instrument equipment supporting the 4mA~20mA interface is compatible with the Highway Addressable Remote Transducer (HART) signal, where HART includes 1.2kHz and 2.2kHz sine waves, with a signal amplitude of plus or minus 0.5mA or plus or minus 500mV, superimposed on the two-wire 4mA~20mA current loop. Fig.12 As shown, it is an internal architecture diagram of the instrument device 200. In order to solve the interference of HART signal on 4mA~20mA detection, the instrument device is usually provided with a filter before the internal ADC sampling to filter out the HART signal. The instrument device includes a filter 21 and an ADC. The ADC is used to sample the signal sent by the APL switch received by the instrument device, for example, the detection signal in the embodiment of the present application. Due to the existence of the filter 21, the detection signal sent by the APL switch will not be sampled by the ADC to control the actuator action. Therefore, the detection signal provided in the embodiment of the present application can use a detection signal similar to HART, and the detection signal will be filtered out by the filter in the 4~20mA circuit of the instrument device AI, so the detection signal provided in the embodiment of the present application will not cause the actuator of the instrument device to malfunction.

[0149] The embodiment of the present application does not specifically limit the internal structure of the filter 21. Fig.12 This is just an example, including two inductors and two capacitors, and for example, it may also include one inductor and one capacitor.

[0150] The above introduction is that the APL switch sends an AC sinusoidal signal to the instrument equipment to detect the interface type of the instrument equipment. This function requires the DAC and ADC in the hybrid interface module to support a working rate of 1.2kHz or 2.2kHz, which has high performance requirements for DAC and ADC and high overall cost. In order to achieve the low-cost goal using low-rate DAC and ADC, the following introduces another implementation method, in which the APL switch sends a DC signal to the instrument equipment to detect the interface type of the instrument equipment.

[0151] See also Fig.13 , which is a schematic diagram of another type of detection interface provided in an embodiment of the present application.

[0152] The controller controls the current conversion circuit to output a direct current, and the direct current is less than the minimum value of the current range of the AI ​​mode; and the voltage detected by the detection circuit is used to determine whether the resistance of the instrument equipment complies with the AI ​​mode.

[0153] Since the effective current range of AI's 4mA-20mA instrument interface is 4mA-20mA, the current value of the detection signal can be set to detect a DC current less than 4mA. This current value will be ignored by AI's 4mA-20mA instrument and will not cause the actuator of the instrument equipment to perform actions incorrectly. A possible implementation method, for example, can select a 2mA DC current as the detection signal, the controller controls the current conversion circuit to output 2mA to the line, and sets the detection circuit to the voltage detection mode to detect whether the voltage fed back by the instrument interface of the instrument equipment is around 0.5V, thereby determining whether the impedance of the instrument interface of the instrument equipment is 250 ohms. In addition, the voltage detection mode is also used to monitor the voltage in the line to prevent excessively high voltage from being output to the line and damaging the instrument interface of the instrument equipment.

[0154] If it does not meet the AI ​​mode, continue to execute S1102;

[0155] S1102: The controller controls the current conversion circuit to output a current that varies within the PoDL mode range, and uses the voltage range detected by the detection circuit to determine whether the interface of the instrument device is in the PoDL mode.

[0156] The interface of the instrument equipment is in PoDL mode, and the hybrid interface circuit is controlled to work in PoDL mode.

[0157] The reason why the embodiment of the present application detects the PoDL mode first and then detects the AO mode is that the voltage of the PoDL mode is higher than the voltage of the AO mode.

[0158] S1103: The controller controls the current conversion circuit to output a current that changes within the AO mode range, and uses the change voltage detected by the detection circuit to determine whether the interface of the instrument device is in AO mode. When the current changes, the voltage changes accordingly, and it can be determined that the instrument device is a constant current source.

[0159] When the interface of the instrument equipment is in AO mode, the hybrid interface circuit is controlled to work in AI mode.

[0160] It should be understood that when the APL switch needs to work in AI mode, the instrument equipment is in AO mode. The APL switch needs to detect the current in the line when working in AI mode. In this mode, the DC / DC circuit provides a suitable power supply, and the controller opens the path switch to provide power supply voltage to the line. At this time, the instrument equipment instrument is an AO interface, which can convert various physical quantities (temperature, pressure, liquid level, flow, etc.) into current output to the line. Therefore, the detection circuit is set to current detection mode, and Rsense converts the current in the line into voltage through the current-to-voltage circuit to realize the detection of the current in the line, thereby realizing the function of AI.

[0161] Based on an APL switch provided in the above embodiment, an embodiment of the present application further provides a communication method of an APL switch, which is described in detail below with reference to the accompanying drawings.

[0162] See also Fig.14 , which is a flow chart of a communication method of an APL switch provided in an embodiment of the present application.

[0163] The communication method of the APL switch provided by the embodiment of the present application, wherein the APL switch includes an APL port physical layer PHY and a hybrid interface circuit; the APL PHY is connected to the hybrid interface; the hybrid interface is used to connect the instrument equipment; the hybrid interface circuit is connected to the hybrid interface; the hybrid interface circuit includes: a current conversion circuit and a detection circuit;

[0164] The method includes:

[0165] S1401: Control the current conversion circuit to output the detection current, and use the voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in AI mode; the detection current is a sinusoidal AC current or a DC current less than the minimum value of the current interval of the AI ​​mode. If yes, execute S1402. If not, that is, the interface of the instrument equipment is not in AI mode, execute S1403.

[0166] S1402: The interface of the instrument equipment is in AI mode, and the control hybrid interface circuit works in AO mode.

[0167] S1403: Control the current conversion circuit to output a current that varies within the PoDL mode range, and use the voltage range detected by the detection circuit to determine whether the interface of the instrument device is in the PoDL mode; if yes, execute S1404. If not, that is, the interface of the instrument device is not in the PoDL mode, execute S1405.

[0168] S1404: The interface of the instrument device is in PoDL mode, and the hybrid interface circuit is controlled to work in PoDL mode;

[0169] S1405: Adjust the output voltage, detect whether the current in the cable changes with the adjustment of the output voltage and detect whether the cable current is a constant current. If so, execute S1406.

[0170] S1406: The interface of the instrument equipment is in AO mode, and the hybrid interface circuit is controlled to work in AI mode.

[0171] The specific implementation of the automatic identification interface of S1401, S1403 and S1405 can be found in Fig.11 The description of the corresponding parts will not be repeated here.

[0172] It should be understood that in order to avoid malfunction of the instrument equipment, the above steps have a sequence relationship, that is, the APL switch first identifies the AI ​​mode of the instrument equipment. If it is not the AI ​​mode, since the voltage of the PoDL mode is greater than that of the AO mode, it is necessary to identify the PoDL mode first. If it is not the PoDL mode, then identify the AO mode.

[0173] The APL switch provided in the embodiment of the present application can automatically identify the interface of the instrument device through the above steps. After identifying the interface of the instrument device, it cooperates with the instrument device to set the working mode of the internal hybrid interface circuit, so as to communicate data or supply power with the instrument device. The communication method provided in the embodiment of the present application can realize the automatic identification of the AI, AO and PoDL modes of the instrument device, so as to be compatible with the instrument devices of the above three modes, and realize the compatibility of APL communication with the interface of traditional instrument devices.

[0174] Since the specific manners of the APL switch working in the AI, AO or PoDL mode have been introduced in the above embodiments, they will not be repeated here.

[0175] The above is only a preferred embodiment of the present application and does not constitute any formal limitation to the present application. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present application using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present application, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still fall within the scope of protection of the technical solution of the present application.

Claims

1. A network device, characterized in that: include: Advanced physical layer APL port physical layer PHY and hybrid interface circuit; The APL PHY is connected to a hybrid interface; the hybrid interface is used to connect to an instrument device; the hybrid interface circuit is connected to the hybrid interface; The hybrid interface circuit is compatible with single-pair Ethernet power supply PoDL mode, analog input AI mode and analog output AO mode; In the PoDL mode, a power supply supplies power to the instrument device; In the AI ​​mode, the power supply supplies power to the hybrid interface; In the AO mode, the voltage is converted into a current corresponding to the control signal of the instrument device.

2. The network device according to claim 1, characterized in that: Instrument equipment: The interface of the instrument equipment is in the AI ​​mode, and the hybrid interface circuit is controlled to work in the AO mode.

3. The network device according to claim 1 or 2, characterized in that: Also includes: A controller, a current conversion circuit and a detection circuit, wherein the current conversion circuit and the detection circuit are both connected to the controller.

4. The network device according to claim 3, characterized in that: The controller is used to control the current conversion circuit to output a direct current, and the direct current is less than a minimum value of a current interval of the AI ​​mode.

5. The network device according to claim 3 or 4, characterized in that: The controller is also used to control the current conversion circuit to output a current that varies within the PoDL mode range, and use the voltage range detected by the detection circuit to determine whether the interface of the instrument device is in the PoDL mode. If the interface of the instrument device is in the PoDL mode, the hybrid interface circuit is controlled to operate in the PoDL mode.

6. The network device according to any one of claims 3 to 5, characterized in that: The controller is also used to control the current conversion circuit to output a current that changes within the AO mode range, and use the changed voltage detected by the detection circuit to determine whether the interface of the instrument equipment is in the AO mode. If the interface of the instrument equipment is in the AO mode, the hybrid interface circuit is controlled to operate in the AI ​​mode.

7. The network device according to any one of claims 3 to 6, characterized in that: The current conversion circuit includes: a digital-to-analog converter and a voltage-to-current converter; The input end and the output end of the digital-to-analog converter are connected to the controller and the voltage-to-current converter respectively; The voltage-to-current converter is also used to connect a DC / DC circuit; The controller is used to send a voltage control digital signal to the digital-to-analog converter; The analog-to-digital converter is used to convert the voltage-controlled digital signal into a voltage-controlled analog signal; The voltage-to-current converter is used to convert the voltage output by the DC / DC circuit into a current according to the voltage control analog signal.

8. The network device according to any one of claims 3 to 6, characterized in that: The detection circuit includes: a detection resistor, a current-to-voltage circuit and an analog-to-digital converter; The first end and the second end of the detection resistor are connected to the output end of the current conversion circuit and the hybrid interface respectively; The current-to-voltage circuit is used to connect the two ends of the detection resistor and send the voltage across the two ends of the detection resistor to the analog-to-digital converter; The analog-to-digital converter is used to convert the voltage sent by the current-to-voltage circuit into a digital voltage and send it to the controller.

9. The network device according to claim 8, characterized in that: The detection circuit also includes: a voltage divider circuit and a selection switch; The first end and the second end of the voltage divider circuit are connected to the first end of the detection resistor and the ground respectively; The first input terminal and the second input terminal of the selection switch are respectively connected to the output terminal of the current-to-voltage conversion circuit and the output terminal of the voltage divider circuit, and the output terminal of the selection switch is connected to the input terminal of the analog-to-digital converter; The controller is used to control the output end of the selection switch to be connected to the first input end in the PoDL mode and the AI ​​mode; and to control the output end of the selection switch to be connected to the second input end in the AO mode; The analog-to-digital converter is used to conduct the output end of the selection switch with the first input end, collect the current of the detection resistor and send it to the controller; when the output end of the selection switch is conducted with the second input end, detect the voltage of the voltage divider circuit and send it to the controller, and the controller controls the current output by the current conversion circuit according to the voltage detected by the analog-to-digital converter.

10. The network device according to claim 9, characterized in that: Also includes: Automatic range switching circuit; The input end and the output end of the automatic range switching circuit are connected to the output end of the selection switch and the input end of the analog-to-digital converter respectively; The automatic range switching circuit at least includes an amplifier, which is used to change the gain of the amplifier according to the voltage at the output end of the selection switch.

11. The network device according to claim 10, characterized in that: The automatic range switching circuit comprises: a hysteresis comparator, an amplifier, a first resistor, a second resistor and a third resistor; The first input terminal and the second input terminal of the hysteresis comparator are respectively connected to the output terminal of the selection switch and the reference voltage, the first input terminal of the amplifier is connected to the output terminal of the selection switch, the second input terminal of the amplifier is connected to the first end of the first resistor, the second end of the first resistor is connected to the output terminal of the amplifier through the second resistor, the output terminal of the hysteresis comparator is connected to the control terminal of the controllable switch tube, the first end and the second end of the controllable switch tube are respectively connected to the first end of the third resistor and the ground, and the second end of the third resistor is connected to the second end of the first resistor.

12. The network device according to claim 10, characterized in that: Also includes: Access switch; The first end and the second end of the path switch are respectively connected to the output end of the DC / DC circuit and the first end of the detection resistor; the control end of the path switch is connected to the controller; The controller is further configured to control the path switch to be turned on in the PoDL mode or the AI ​​mode, and to control the path switch to be turned off in the AO mode.

13. The network device according to any one of claims 8 to 12, characterized in that: Also includes: Calibration switch and reference current source; The reference current source and the correction switch are connected in series between the second end of the detection resistor and the ground; the control end of the correction switch is connected to the controller; The controller is further used to control the correction switch to be turned on when the current of the detection resistor is greater than a preset current.

14. The network device according to any one of claims 1 to 13, characterized in that: Also includes: Coupling and decoupling networks; The APL PHY is connected to the hybrid interface via a differential capacitor in the coupling-decoupling network; The hybrid interface circuit is connected to the hybrid interface via a filter inductor in the coupling-decoupling network.

15. The network device according to any one of claims 1 to 14, characterized in that: The current signal range of the AI ​​mode and the AO mode is 4mA-20mA.

16. The network device according to any one of claims 3 to 15, characterized in that: The controller is further configured to, if the AI ​​mode is not met, control the current conversion circuit to output a constant current within the PoDL mode range, and use the voltage detected by the detection circuit to determine whether the PoDL detection mode is met.

17. A communication method for a network device, characterized in that: The network device includes an APL port physical layer PHY and a hybrid interface circuit; the APL PHY is connected to the hybrid interface; the hybrid interface circuit is compatible with a single-pair Ethernet power supply PoDL mode, an analog input AI mode and an analog output AO mode; the hybrid interface is used to connect instrument equipment; The hybrid interface circuit is connected to the hybrid interface; The hybrid interface circuit comprises: a current conversion circuit and a detection circuit; The method includes: Control the current conversion circuit to output a detection current, and use the voltage detected by the detection circuit to determine whether the interface of the instrument device is in the AI ​​mode. If the interface of the instrument device is in the AI ​​mode, control the hybrid interface circuit to work in the AO mode; the detection current is a sinusoidal alternating current or a direct current that is less than the minimum value of the current interval of the AI ​​mode; The interface of the instrument device is not in the AI ​​mode, controlling the current conversion circuit to output a current that varies within the PoDL mode range, using the voltage range detected by the detection circuit to determine whether the interface of the instrument device is in the PoDL mode, and if the interface of the instrument device is in the PoDL mode, controlling the hybrid interface circuit to operate in the PoDL mode; The interface of the instrument device is not the PoDL mode, the current conversion circuit is controlled to output a current that changes within the AO mode range, and the changing voltage detected by the detection circuit is used to determine whether the interface of the instrument device is the AO mode. If the interface of the instrument device is the AO mode, the hybrid interface circuit is controlled to operate in the AI ​​mode.

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