A general purpose input / output module and fault diagnostic method

Abstract

The application provides a general input and output module and a fault diagnosis method, which are applied to the technical field of safety instrument systems, and the general input and output module comprises an analog quantity input circuit, an analog quantity output circuit, a switching quantity input circuit, a switching quantity output circuit, a differential amplification module, a first analog-digital converter, a second analog-digital converter, a first control module and a second control module; wherein, the analog quantity input circuit, the analog quantity output circuit, the switching quantity input circuit and the switching quantity output circuit have a common general circuit, thereby, the number of devices of the general input and output module is reduced, the architecture complexity of the general input and output module is also reduced, and the manufacturing cost of the general input and output module is reduced; and the fault diagnosis method is used for diagnosing whether there is a fault in the general input and output module, troubleshooting the general input and output module in time, and improving the performance of the general input and output module.

Description

Technical Field

[0001] This invention relates to the field of safety instrumented systems technology, and in particular to a general-purpose input / output module and a fault diagnosis method. Background Technology

[0002] In safety instrumented systems, universal input / output modules can be used to standardize inputs and outputs and improve the flexibility and efficiency of field applications. The inventors discovered that traditional universal input / output modules have complex architectures and circuits, resulting in high manufacturing costs. Summary of the Invention

[0003] In view of this, embodiments of this application provide a general input / output module and a fault diagnosis method. The analog input circuit, analog output circuit, digital input circuit and digital output circuit of the general input / output module provided by this application have common general circuits, thereby reducing the components used in constructing the module, simplifying the circuit of the module and reducing the manufacturing cost of the module.

[0004] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0005] A general-purpose input / output module, comprising:

[0006] Analog input circuit, analog output circuit, digital input circuit, digital output circuit, differential amplifier module, first analog-to-digital converter, second analog-to-digital converter, first control module and second control module;

[0007] The analog input circuit includes a first switch, a general circuit, a second switch, and a first resistor connected in series, with the end of the first resistor not connected to the second switch grounded.

[0008] The general-purpose circuit includes a second resistor, a diode, and a field instrument connected in series.

[0009] The analog output circuit includes a current source, the general circuit, and a third switch connected in series, with the end of the third switch not connected to the general circuit grounded.

[0010] The digital input circuit includes a first switch, the general circuit, a fourth switch, a third resistor, and a fourth resistor connected in series, with the end of the fourth resistor not connected to the third resistor grounded.

[0011] The switch output circuit includes a first switch, the general circuit, and a third switch connected in series, wherein the end of the third switch that is not connected to the general circuit is grounded.

[0012] The first input terminal of the differential amplifier module is connected to the end of the second resistor that is not connected to the diode, the second input terminal is connected to the connection point of the second resistor and the diode, and the output terminal is connected to the first analog-to-digital converter.

[0013] The first control module is used to control the opening and closing states of the second switch, the third switch and the fourth switch, and to receive data from the first analog-to-digital converter;

[0014] The first terminal of the second analog-to-digital converter is connected to the connection point of the first resistor and the second switch, and the second terminal is connected to the connection point of the third resistor and the fourth resistor;

[0015] The second control module is used to control the state of the current source and the first switch, and to receive data from the second analog-to-digital converter.

[0016] Optionally, the differential amplifier module in the aforementioned general input / output module includes:

[0017] The fifth resistor, the sixth resistor, and the differential amplifier;

[0018] One end of the fifth resistor is connected to the positive input terminal of the differential amplifier, and the other end serves as the first input terminal of the differential amplifier.

[0019] One end of the sixth resistor is connected to the negative input terminal of the differential amplifier, and the other end serves as the second input terminal of the differential amplifier.

[0020] A fault diagnosis method, applied to the aforementioned general-purpose input / output module, includes:

[0021] The analog input circuit is diagnosed by applying a preset first diagnostic strategy to obtain the first diagnostic result of the analog input circuit;

[0022] The analog output circuit is diagnosed by applying a preset second diagnostic strategy to obtain a second diagnostic result for the analog output circuit.

[0023] The third diagnostic strategy is applied to diagnose the switch input circuit to obtain the third diagnostic result of the switch input circuit.

[0024] The fourth diagnostic strategy is applied to diagnose the switch output circuit to obtain the fourth diagnostic result of the switch output circuit.

[0025] Optionally, in the above method, applying a preset first diagnostic strategy to diagnose the analog input circuit and obtaining a first diagnostic result for the analog input circuit includes:

[0026] Based on the first diagnostic strategy, the first differential voltage across the second resistor is acquired, and the first current is determined based on the first differential voltage.

[0027] The first voltage of the first resistor is collected, and the second current is determined based on the first voltage;

[0028] Using the first current and the second current, fault diagnosis is performed on the analog input circuit to obtain the first diagnostic result of the analog input circuit.

[0029] Optionally, in the above method, the step of using the first current and the second current to perform fault diagnosis on the analog input circuit and obtain a first diagnostic result for the analog input circuit includes:

[0030] Obtain a first deviation value between the first current and the second current; when the first deviation value exceeds a first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has malfunctioned; when the first deviation value does not exceed the first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has not malfunctioned.

[0031] When the first current is within a preset first current range, a second diagnostic conclusion is generated indicating that the analog input circuit is fault-free; when the first current is less than the minimum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has an open circuit fault; when the first current is greater than the maximum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has a short circuit fault.

[0032] Based on the first diagnostic conclusion and the second diagnostic conclusion, a first diagnostic result for the analog input circuit is generated.

[0033] Optionally, in the above method, applying a preset second diagnostic strategy to diagnose the analog output circuit and obtaining a second diagnostic result for the analog output circuit includes:

[0034] Based on the second diagnostic strategy, the second differential voltage across the second resistor is acquired, and the third current is determined based on the second differential voltage.

[0035] Control the output current of the current source, and determine the output current of the current source as the fourth current;

[0036] Using the third current and the fourth current, fault diagnosis is performed on the analog output circuit to obtain a second diagnostic result for the analog output circuit.

[0037] Optionally, in the above method, the step of using the third current and the fourth current to perform fault diagnosis on the analog output circuit and obtain a second diagnostic result for the analog output circuit includes:

[0038] Obtain a second deviation value between the third current and the fourth current; when the second deviation value exceeds a second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has malfunctioned; when the second deviation value does not exceed the second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has not malfunctioned.

[0039] When the third current is less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has a disconnection fault; when the third current is not less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has not a fault.

[0040] Based on the third and fourth diagnostic conclusions, a second diagnostic result for the analog output circuit is generated.

[0041] Optionally, in the above method, the application of a preset third diagnostic strategy to diagnose the switch input circuit and obtain a third diagnostic result for the switch input circuit includes:

[0042] Based on the third diagnostic strategy, the third differential voltage across the second resistor is acquired, and the fourth current is determined based on the third differential voltage.

[0043] The first voltage is obtained by calculating the fourth current, the resistance value of the third resistor, and the resistance value of the fourth resistor.

[0044] The second analog-to-digital converter is used to sample the first sampled voltage on the fourth resistor, and the first sampled voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the second voltage;

[0045] Connect the field instrument to a preset resistor, collect the output current of the field instrument, and use the output current to obtain first diagnostic information characterizing whether there is a line fault in the switch input circuit;

[0046] Based on the first voltage and the second voltage, fault diagnosis is performed on the switch input circuit to obtain the second diagnostic information of the switch input circuit;

[0047] A third diagnostic result is generated based on the first diagnostic information and the second diagnostic information.

[0048] Optionally, in the above method, the step of performing fault diagnosis on the switch input circuit based on the first voltage and the second voltage to obtain second diagnostic information of the switch input circuit includes:

[0049] Determine the voltage deviation value between the first voltage and the second voltage; when the voltage deviation value exceeds a preset voltage deviation value, generate second diagnostic information indicating that the switch input circuit has failed; when the voltage deviation value does not exceed the preset voltage deviation value, generate second diagnostic information indicating that the switch input circuit has not failed.

[0050] Optionally, in the above method, applying a preset fourth diagnostic strategy to diagnose the switch output circuit and obtaining a fourth diagnostic result for the switch output circuit includes:

[0051] Based on the fourth diagnostic strategy, the fourth differential voltage across the second resistor is acquired, and the fifth current is determined based on the fourth differential voltage.

[0052] Based on the fifth current, a line fault judgment is performed on the switch output circuit to obtain the line fault judgment result of the switch output circuit.

[0053] The first switch, the third switch, and the fourth switch are all controlled to be in the closed state. The second analog-to-digital converter is used to sample the second sampling voltage on the fourth resistor. The second sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the third voltage. Based on the third voltage, the first switch diagnostic sub-result is obtained.

[0054] The first switch and the fourth switch are controlled to be in the closed state, and the third switch is controlled to be in the open state. The second analog-to-digital converter is used to sample the third sampling voltage on the fourth resistor. The third sampling voltage, the resistance value of the third resistor and the resistance value of the fourth resistor are calculated to obtain the fourth voltage. Based on the third voltage, the second switch diagnostic sub-result is obtained.

[0055] The first switch and the third switch are both in the open state, and the fourth switch is in the closed state. The second analog-to-digital converter is used to sample the fourth sampling voltage on the fourth resistor. The fourth sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the fifth voltage. Based on the fifth voltage, the diagnostic sub-result of the third switch is obtained.

[0056] Based on the line fault judgment result, the first switch diagnostic sub-result, the second switch diagnostic sub-result, and the third switch diagnostic sub-result, the fourth diagnostic result of the switch output circuit is obtained.

[0057] Compared with the prior art, this application has the following advantages:

[0058] This application provides a general-purpose input / output module and a fault diagnosis method. The general-purpose input / output module includes an analog input circuit, an analog output circuit, a digital input circuit, a digital output circuit, a differential amplifier module, a first analog-to-digital converter, a second analog-to-digital converter, a first control module, and a second control module. The analog input circuit, analog output circuit, digital input circuit, and digital output circuit share common general-purpose circuits, thereby reducing the number of components in the general-purpose input / output module and lowering its architectural complexity, thus reducing its manufacturing cost. Furthermore, the fault diagnosis method is used to diagnose whether a fault exists in the general-purpose input / output module, enabling timely fault diagnosis and improving its performance. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0060] Figure 1 A circuit structure diagram of a general-purpose input / output module provided in an embodiment of this application;

[0061] Figure 2 A flowchart of a fault diagnosis method provided in an embodiment of this application;

[0062] Figure 3 Example diagram of analog input path provided in the embodiments of this application;

[0063] Figure 4 A flowchart illustrating how a fault diagnosis is performed on an analog input circuit using a first current and a second current, to obtain a first diagnostic result for the analog input circuit, is provided for an embodiment of this application.

[0064] Figure 5 An example diagram of the analog output path provided in the embodiments of this application;

[0065] Figure 6 A flowchart illustrating how a third current and a fourth current are used to diagnose a fault in an analog output circuit to obtain a second diagnostic result for the analog output circuit, as provided in an embodiment of this application.

[0066] Figure 7Example diagram of the digital input path provided in the embodiments of this application;

[0067] Figure 8 A flowchart illustrating how a third diagnostic strategy, pre-defined for application in this embodiment, diagnoses a digital input circuit to obtain the third diagnostic result of the digital input circuit.

[0068] Figure 9 Example diagram of the switch output path provided in the embodiments of this application;

[0069] Figure 10 The flowchart illustrates how the fourth diagnostic strategy preset in the application of this embodiment diagnoses the switch output circuit and obtains the fourth diagnostic result of the switch output circuit. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0072] Terminology Explanation:

[0073] CPLD: Complex Programmable Logic Device.

[0074] ADC: Analog to digital converter.

[0075] In safety instrumented systems, the implementation scheme of general-purpose input / output modules has a complex architecture and complex circuitry, resulting in high manufacturing costs. Furthermore, current general-purpose input / output modules do not diagnose circuit faults from a functional safety perspective, leading to poor performance.

[0076] To address the aforementioned issues, this application provides a general-purpose input / output module and a fault diagnosis method for the module. The solution provided in this application includes common circuits among the analog input circuit, analog output circuit, digital input circuit, and digital output circuit of the general-purpose input / output module. Each circuit is constructed using resistors and switches, resulting in a simple circuit architecture and fewer components, thus reducing the manufacturing cost of the module. Furthermore, this solution provides a fault diagnosis method for the general-purpose input / output module, enabling the detection of faults and timely troubleshooting, thereby improving the module's performance.

[0077] Reference Figure 1 The following is a circuit structure diagram of a general-purpose input / output module provided in an embodiment of this application, and is described in detail below:

[0078] The general-purpose input / output module provided in this application includes: analog input circuit, analog output circuit, digital input circuit, digital output circuit, differential amplifier module, first analog-to-digital converter, second analog-to-digital converter, first control module, and second control module.

[0079] The analog input circuit includes a first switch SW1, a general-purpose circuit 101, a second switch SW1, and a first resistor R1 connected in series. The end of the first resistor R1 that is not connected to the second switch SW2 is grounded. The end of the first switch SW1 that is not connected to the general-purpose circuit 101 is connected to a 24V DC power supply.

[0080] The general circuit 101 includes a second resistor R2, a diode D1, and a field instrument connected in series.

[0081] The analog output circuit includes a current source, a general-purpose circuit 101, and a third switch SW3 connected in series. The end of the third switch SW3 that is not connected to the general-purpose circuit 101 is grounded. The end of the current source that is not connected to the general-purpose circuit 101 is connected to a 24V DC power supply.

[0082] The digital input circuit includes a first switch SW1, a general circuit 101, a fourth switch SW4, a third resistor R3, and a fourth resistor R4 connected in series. The end of the fourth resistor R4 that is not connected to the third resistor R3 is grounded.

[0083] The digital output circuit includes a first switch SW1, a general circuit 101, and a third switch R3 connected in series. The end of the third switch R3 that is not connected to the general circuit 101 is grounded.

[0084] The first input terminal of the differential amplifier module 102 is connected to the end of the second resistor R2 that is not connected to the diode D1, the second input terminal is connected to the connection point of the second resistor R2 and the diode D1, and the output terminal is connected to the first analog-to-digital converter ADC1.

[0085] The first control module CPLD1 is used to control the opening and closing states of the second switch SW2, the third switch SW3 and the fourth switch SW4, and to receive data from the first analog-to-digital converter ADC1.

[0086] The first terminal of the second analog-to-digital converter CPLD2 is connected to the connection point of the first resistor R1 and the second switch SW2, and the second terminal is connected to the connection point of the third resistor R3 and the fourth resistor R4.

[0087] The second control module CPLD2 is used to control the state of the current source and the first switch, and to receive data from the second analog-to-digital converter.

[0088] The differential amplifier module 102 includes a fifth resistor R5, a sixth resistor R6, and a differential amplifier. One end of the fifth resistor R5 is connected to the positive input terminal of the differential amplifier, and the other end serves as the first input terminal of the differential amplifier. One end of the sixth resistor R6 is connected to the negative input terminal of the differential amplifier, and the other end serves as the second input terminal of the differential amplifier. The fifth resistor R5 and the sixth resistor R6 are used to limit the loop circuit and protect the subsequent differential amplifier.

[0089] The first and second control modules in the general-purpose input / output module provided in this application control devices such as switches and ADCs through digital interfaces. The first and second control modules are independent of each other and can be CPLDs or microcontrollers.

[0090] In the general input / output module provided in this application embodiment, the analog input circuit implements the analog input function, the analog output circuit implements the analog output function, the digital input circuit implements the digital input function, and the digital output circuit implements the digital output function.

[0091] In the embodiments provided in this application, the general-purpose input / output module includes an analog input circuit, an analog output circuit, a digital input circuit, a digital output circuit, a differential amplifier module, a first analog-to-digital converter, a second analog-to-digital converter, a first control module, and a second control module. The analog input circuit, analog output circuit, digital input circuit, and digital output circuit share common general-purpose circuits, thereby reducing the number of components in the general-purpose input / output module and lowering its architectural complexity, thus reducing its manufacturing cost.

[0092] Another embodiment of this application provides a fault diagnosis method applied to a general-purpose input / output module. Different functions in the general-purpose input / output module have different diagnosis strategies. Optionally, different functions may need to be configured with different signal types when performing diagnosis.

[0093] Reference Figure 2 The following is a flowchart of a fault diagnosis method provided in an embodiment of this application, which is described in detail below:

[0094] S201. Apply the preset first diagnostic strategy to diagnose the analog input circuit and obtain the first diagnostic result of the analog input circuit.

[0095] For the analog input function of the general input / output module, specifically: the field instrument is a two-wire instrument. The second control module controls the first switch SW1 to close, supplying power to the field instrument through diode D1; the first control module controls the second switch SW2 to close, and the output current of the field instrument is converted into a voltage signal through resistor R1. After being sampled by the second analog-to-digital converter ADC2, it is transmitted to the second control module. The signal path is as follows: Figure 3 As shown.

[0096] Different circuits have different diagnostic strategies. The process of using the first diagnostic strategy to diagnose the analog input circuit is as follows: Based on the first diagnostic strategy, the first differential voltage across the second resistor R2 is collected, and the first current is determined based on the first differential voltage; the first voltage of the first resistor R1 is collected, and the second current is determined based on the first voltage; the first current and the second current are used to diagnose the fault in the analog input circuit, and the first diagnostic result of the analog input circuit is obtained.

[0097] By acquiring the first differential voltage across the second resistor R2, the output current of diode D1 is obtained, and this output current can be determined as the first current. The first voltage across the first resistor R1 is acquired, and the input current can be obtained by measuring the voltage across the first resistor (i.e., the first voltage mentioned above), and this input current is determined as the second current.

[0098] In this application, the two sets of current sampling circuits use independent ADCs and CPLDs, which can ensure that in the event of a single device failure, the other set of circuits can correctly sample the signal.

[0099] Reference Figure 4 The flowchart illustrating how a first current and a second current are used to diagnose faults in an analog input circuit, and how a first diagnostic result of the analog input circuit is obtained, is described in detail below:

[0100] S301. Obtain the first deviation value of the first current and the second current; when the first deviation value exceeds the first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has failed; when the first deviation value does not exceed the first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has not failed.

[0101] The first preset deviation value can be set according to actual needs. Preferably, it can be set to ±5%. Calculate the deviation value between the first current and the second current. This deviation value is the first deviation value.

[0102] When the first deviation value exceeds the first preset deviation value, it is determined that the analog input function of the general input / output module has failed, that is, the function of the analog input circuit has failed, and a first diagnostic conclusion indicating that the analog input circuit has failed is generated. When the first deviation value does not exceed the first preset deviation value, it is determined that the analog input function of the general input / output module has not failed, that is, the function of the analog input circuit has not failed, and a first diagnostic conclusion indicating that the analog input circuit has not failed is generated.

[0103] At this point, the analog input function of the general input / output module can be diagnosed.

[0104] S302. When the first current is within a preset first current range, a second diagnostic conclusion is generated indicating that the analog input circuit is fault-free; when the first current is less than the minimum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has an open circuit fault; when the first current is greater than the maximum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has a short circuit fault.

[0105] The first current range can be set according to actual needs, such as [3.7mA, 20.8mA].

[0106] For example, when the first current is within the first current range, it is determined that the analog input circuit is fault-free, and a second diagnostic conclusion characterizing that the analog input circuit is fault-free is generated; when the first current is less than the minimum value in the first current range, such as 3.7mA, it indicates that the analog input circuit has an open circuit fault, and a second diagnostic conclusion characterizing that the analog input circuit has an open circuit fault is generated; when the first current is greater than the maximum value in the first current range, such as 20.8mA, it indicates that the analog input circuit has a short circuit fault, and a second diagnostic conclusion characterizing that the analog input circuit has a short circuit fault is generated.

[0107] At this point, the first current and the preset first current range can be used to diagnose circuit faults in the analog input circuit.

[0108] Figure 4The execution order of S301 and S302 in the process shown can be replaced, and this application does not limit the execution order of S301 and S302.

[0109] S303. Based on the first and second diagnostic conclusions, generate the first diagnostic result for the analog input circuit.

[0110] The generated first diagnostic result includes a first diagnostic conclusion and a second diagnostic conclusion.

[0111] The diagnostic process provided in this application covers fault detection of analog input functions and circuit testing of analog input circuits. Therefore, it is possible to comprehensively detect faults in analog input circuits and improve the accuracy of fault diagnosis.

[0112] S202. Apply the preset second diagnostic strategy to diagnose the analog output circuit and obtain the second diagnostic result of the analog output circuit.

[0113] For the analog output function of the general-purpose input / output module, specifically: when the first switch SW1 is open, the current source outputs a 0~20mA current, which is then output to the field instrument via diode D1. Simultaneously, the third switch SW3 is closed, providing a return path for the current signal. The signal path is as follows: Figure 5 As shown.

[0114] The process of diagnosing the analog output circuit using the second diagnostic strategy is as follows: Based on the second diagnostic strategy, the second differential voltage across the second resistor is acquired, and the third current is determined based on the second differential voltage; the current source is controlled to output the current, and the output current of the current source is determined as the fourth current; the third current and the fourth current are used to diagnose the fault in the analog output circuit, and the second diagnostic result of the analog output circuit is obtained.

[0115] In the embodiments provided in this application, the output current of the diode can be obtained by measuring the differential voltage across the sampling resistor (i.e., the second differential voltage mentioned above), and this output current is determined as the second current; the current source is responsible for outputting the current and determines the current output current as the fourth current.

[0116] Reference Figure 6 The flowchart illustrating the use of a third current and a fourth current to diagnose faults in an analog output circuit, and the resulting second diagnostic result, is provided in this embodiment of the application. The details are as follows:

[0117] S401. Obtain the second deviation values ​​of the third current and the fourth current; when the second deviation value exceeds the second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has failed; when the second deviation value does not exceed the second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has not failed.

[0118] The second preset deviation value can be set according to actual needs, such as ±5%.

[0119] Calculate the deviation between the third current and the fourth current; this deviation is the second deviation value.

[0120] When the second deviation value exceeds the second preset deviation value, it is determined that the analog output function of the general input / output module has failed, that is, the function of the analog output circuit has failed. At this time, a third diagnostic conclusion characterizing the failure of the analog output circuit is generated.

[0121] When the second deviation value does not exceed the second preset deviation value, it is determined that the analog output function of the general input / output module has not failed, that is, the function of the analog output circuit has not failed, and at this time a third diagnostic conclusion is generated to indicate that the analog output circuit has not failed.

[0122] Thus, by using the third and fourth currents, fault detection can be performed on the analog output function of the general input / output module, and the corresponding detection conclusions can be obtained.

[0123] S402. When the third current is less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has a broken wire fault; when the third current is not less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has not a fault.

[0124] In the embodiments provided in this application, the preset detection current can be set according to actual needs, such as 3.7mA.

[0125] When the third current is less than the preset detection current, the analog output circuit is considered to have an open circuit fault, and a fourth diagnostic conclusion indicating that the analog output circuit has an open circuit fault is generated. When the third current is not less than the preset detection current, the analog output circuit is short-circuited. Although the analog output circuit is short-circuited, it can still work normally, so it is not considered a fault. Therefore, a fourth diagnostic conclusion indicating that the analog output circuit has not had a fault is generated.

[0126] At this point, the circuit fault diagnosis of the analog output circuit is completed using the third and fourth currents.

[0127] This application does not restrict the execution order of S401 and S402.

[0128] S403. Based on the third and fourth diagnostic conclusions, generate the second diagnostic result for the analog output circuit.

[0129] The second diagnostic result includes the third and fourth diagnostic conclusions.

[0130] The diagnostic process provided in this application covers fault detection of analog output functions and circuit testing of analog output circuits. Therefore, it is possible to comprehensively detect faults in analog output circuits and improve the accuracy of fault diagnosis.

[0131] S203. Apply the preset third diagnostic strategy to diagnose the switch input circuit and obtain the third diagnostic result of the switch input circuit.

[0132] For the switch input function of the general input / output module, specifically: the field instrument is a dry contact switch. When the first switch SW1 is closed, the field instrument is powered through diode D1; when the fourth switch SW4 is closed, the signal is converted into a low-voltage signal through the third resistor R3 and the fourth resistor R4. After being sampled by the second analog-to-digital converter ADC2, it is transmitted to the second control module CPLD2. The signal path is as follows: Figure 7 As shown.

[0133] Reference Figure 8 The flowchart below illustrates how the application uses a pre-defined third diagnostic strategy to diagnose the switch input circuit and obtain the third diagnostic result of the switch input circuit, as provided in this embodiment of the application.

[0134] S501. Based on the third diagnostic strategy, the third differential voltage across the second resistor is acquired, and the fourth current is determined based on the third differential voltage.

[0135] By measuring the differential voltage across the sampling resistor R1 (i.e., the third differential voltage mentioned above), the output current of diode D1 can be obtained, and this output current can be identified as the fourth current.

[0136] S502: Calculate the first voltage by taking the fourth current, the resistance value of the third resistor, and the resistance value of the fourth resistor.

[0137] The process of calculating the fourth current, the resistance value of the third resistor, and the resistance value of the fourth resistor is as follows: fourth current * (resistance value of the third resistor + resistance value of the fourth resistor). From this, the voltage is obtained, and this voltage is determined as the first voltage.

[0138] S503. Use the second analog-to-digital converter to sample the first sampled voltage on the fourth resistor, and perform calculations on the first sampled voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor to obtain the second voltage.

[0139] The second analog-to-digital converter ADC2 samples the voltage across the fourth resistor R4 (i.e., the first sampling voltage mentioned above). The process of calculating the first sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor to obtain the second voltage is as follows: first sampling voltage * (resistance value of the third resistor R3 + resistance value of the fourth resistor R4) / resistance value of the fourth resistor R4. The resulting voltage is the second voltage.

[0140] S504. Connect the field instrument to the preset resistor, collect the output current of the field instrument, and use the output current to obtain the first diagnostic information characterizing whether there is a line fault in the switch input circuit.

[0141] By connecting the field instrument to a preset resistor (either in series or in parallel), the corresponding output current is collected. The output current values ​​are different for different connection methods. Based on the output current of different connection methods, it is determined whether there is a line fault in the switch input circuit, and the first diagnostic information is generated, indicating whether the line fault is a short circuit fault.

[0142] Preferably, when there is no fault in the switch input circuit, first diagnostic information indicating that there is no fault in the switch input circuit is generated; when there is a short circuit fault in the switch input circuit, first diagnostic information indicating that there is a short circuit fault in the switch input circuit is generated; when there is an open circuit fault in the switch input circuit, first diagnostic information indicating that there is an open circuit fault in the switch input circuit is generated.

[0143] This completes the circuit fault diagnosis process for the digital input circuit.

[0144] S505. Based on the first voltage and the second voltage, perform fault diagnosis on the switch input circuit to obtain the second diagnostic information of the switch input circuit.

[0145] In this application, a voltage deviation value between a first voltage and a second voltage is determined; when the voltage deviation value exceeds a preset voltage deviation value, it is determined that the switch input function of the general input / output module has failed, that is, the function of the switch input circuit has failed, and at this time, second diagnostic information indicating that the switch input circuit has failed is generated; when the voltage deviation value does not exceed the preset voltage deviation value, it is determined that the switch input function of the general input / output module has not failed, that is, the function of the switch input circuit has not failed, and at this time, second diagnostic information indicating that the switch input circuit has not failed is generated.

[0146] Specifically, for example, calculate the voltage deviation between the first voltage and the second voltage. The preset voltage deviation value can be set according to actual needs, such as ±5%.

[0147] This completes the fault detection of the digital input function of the general-purpose input / output module. This application does not impose any restrictions on the order of the functional testing and circuit testing processes for the digital input circuit.

[0148] S506. Based on the first diagnostic information and the second diagnostic information, generate a third diagnostic result.

[0149] The third test result includes primary and secondary diagnostic information.

[0150] The diagnostic process provided in this application covers fault detection of the digital input function and circuit testing of the digital input circuit. Therefore, it is possible to comprehensively detect faults in the digital input circuit and improve the accuracy of fault diagnosis.

[0151] S204. Apply the preset fourth diagnostic strategy to diagnose the switch output circuit and obtain the fourth diagnostic result of the switch output circuit.

[0152] For the digital output function in the general-purpose input / output module, when the first switch SW1 is closed, a signal is output to the field instrument through diode D1. Simultaneously, the third switch SW3 is closed, providing a return path for the current signal. The signal path is as follows: Figure 9 As shown.

[0153] Reference Figure 10 The flowchart below illustrates how the application uses a pre-defined fourth diagnostic strategy to diagnose the switch output circuit and obtain the fourth diagnostic result of the switch output circuit, as provided in this embodiment of the application.

[0154] S601. Based on the fourth diagnostic strategy, the fourth differential voltage across the second resistor is acquired, and the fifth current is determined based on the fourth differential voltage.

[0155] Measure the differential voltage across the second sampling resistor R2 (i.e., the fourth differential voltage mentioned above). Using this differential voltage, the output current of diode D1 can be obtained, which is the fifth current.

[0156] S602. Based on the fifth current, perform line fault judgment on the switch output circuit and obtain the line fault judgment result of the switch output circuit.

[0157] For the fifth current, when the fifth current is within the preset second current range, it is determined that the circuit of the switch output circuit is fault-free. At this time, a line fault judgment result indicating that the circuit of the switch output circuit is fault-free is generated. The second current range can be set according to actual needs, such as [10mA, 1A]. When the fifth current is less than the minimum value in the second current range, it is determined that the switch output circuit has an open circuit fault. At this time, a line fault judgment result indicating that the switch output circuit has an open circuit fault is generated. For example, the minimum value is 10mA. When the fifth current is greater than the maximum value in the second current range, such as the maximum value is 1A, it is determined that the switch output circuit has a short circuit fault. At this time, a line fault judgment result indicating that the switch output circuit has a short circuit fault is generated.

[0158] Furthermore, this application also provides a method for detecting the switching output function of a general input / output module. During the detection process, the first switch SW1 is closed, and the first switch SW1 is responsible for outputting a switching signal voltage to drive the field instrument load. The third switch SW3 is closed to provide a return path for the current signal. The detection process is as shown in S603-S605.

[0159] S603. Control the first switch, the third switch and the fourth switch to be in the closed state. Use the second analog-to-digital converter to sample the second sampling voltage on the fourth resistor. Perform calculations on the second sampling voltage, the resistance value of the third resistor and the resistance value of the fourth resistor to obtain the third voltage. Based on the third voltage, obtain the diagnostic result of the first switch.

[0160] During the detection process, the second control module controls the first switch SW1 and the third switch SW3 to close, outputting an ON signal, and simultaneously controls the fourth switch SW4 to close. The second analog-to-digital converter ADC2 samples the voltage across the fourth resistor R4, i.e., the second sampling voltage mentioned above, and sends the second sampled voltage to the second control module. Furthermore, in this application, when the circuit is configured for switch output, each switch has its default switching state. When describing the switch output, the closing state of the switches differs under different conditions. In the description, the open / closed state of some switches is mentioned, while that of others is not. The unmentioned switches are all in the open state.

[0161] The second control module performs calculations on the second sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor. The specific process is as follows: second sampling voltage * (resistance value of the third resistor R3 + resistance value of the fourth resistor R4) / resistance value of the fourth resistor. The third voltage is then obtained and used for fault detection.

[0162] When the third voltage is greater than the first preset voltage value, it is determined that the third switch SW3 has failed, and a first switch diagnostic sub-result indicating that the third switch SW3 has failed is generated. When the third voltage is not greater than the first preset voltage value, it is determined that the third switch SW3 has not failed, and a first switch diagnostic sub-result indicating that the third switch SW3 has not failed is generated. When the third voltage is greater than the first preset voltage value, it is determined that the third switch SW3 has failed, and a first switch diagnostic sub-result indicating that the third switch SW3 has failed is generated.

[0163] Furthermore, the first preset voltage value can be set according to actual needs, and the range of the first preset voltage value is usually 0~5V.

[0164] S604. Control the first switch and the fourth switch to be in the closed state, and control the third switch to be in the open state. Use the second analog-to-digital converter to sample the third sampling voltage on the fourth resistor. Perform calculations on the third sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor to obtain the fourth voltage. Based on the third voltage, obtain the second switch diagnostic sub-result.

[0165] During the detection process, the second control module controls the first switch SW1 to close, the fourth switch SW4 to close, and controls the third switch SW3 to open. The second analog-to-digital converter ADC2 samples the voltage across the fourth resistor R4, which is the third sampled voltage, and sends the third sampled voltage to the second control module.

[0166] The second control module performs calculations on the third sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor. The specific process is as follows: third sampling voltage * (resistance value of the third resistor R3 + resistance value of the fourth resistor R4) / resistance value of the fourth resistor. The fourth voltage is then obtained and used for fault detection.

[0167] When the fourth voltage is less than the second preset voltage value, it is determined that the first switch SW1 or the third switch SW3 has failed, and a second switch diagnostic sub-result is generated to indicate that the first switch SW1 or the third switch SW3 has failed; when the fourth voltage is greater than or equal to the second preset voltage value, it is determined that the first switch SW1 and the third switch SW3 have not failed, and a second switch diagnostic sub-result is generated to indicate that the first switch SW1 and the third switch SW3 have not failed.

[0168] Furthermore, the second preset voltage value can be set according to actual needs, and the range of the second preset voltage value is usually 15~24V.

[0169] S605. Control the first switch and the third switch to be in the open state, and control the fourth switch to be closed. Use the second analog-to-digital converter to sample the fourth sampling voltage on the fourth resistor. Perform calculations on the fourth sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor to obtain the fifth voltage. Based on the fifth voltage, obtain the diagnostic result of the third switch.

[0170] During the detection process, the second control module controls the first switch SW1 and the third switch SW3 to open, and controls the fourth switch SW4 to close. The second analog-to-digital converter ADC2 samples the voltage across the fourth resistor R4, which is the fourth sampling voltage, and sends the fourth sampling voltage to the second control module.

[0171] The second control module performs calculations on the fourth sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor. The specific process is as follows: fourth sampling voltage * (resistance value of the third resistor R3 + resistance value of the fourth resistor R4) / resistance value of the fourth resistor R4, which yields the fifth voltage, which is then used for fault diagnosis.

[0172] When the fifth voltage is greater than the third preset voltage value, it is determined that the first switch SW1 or the fourth switch SW4 has failed, and a third switch diagnostic sub-result indicating that the first switch SW1 or the fourth switch SW4 has failed is generated; when the fifth voltage is less than or equal to the third preset voltage value, it is determined that the first switch SW1 and the fourth switch SW4 have not failed, and a third switch diagnostic result indicating that the first switch SW1 and the fourth switch SW4 have not failed is generated.

[0173] Furthermore, based on the diagnostic results of the first switch, the second switch, and the third switch, the fault types of all switches can be obtained.

[0174] Furthermore, the third preset voltage value can be set according to actual needs, and the range of the third preset voltage value is usually 0~5V.

[0175] In the method provided in this application, the three diagnostic steps S603 to S605 can be executed at a fixed cycle during system operation, the diagnostic time for each step is configurable, and disturbances in the switch output should not cause abnormal load operation.

[0176] Preferably, the process of performing functional diagnosis and circuit diagnosis on the switch output circuit is not limited in the order of the two, and they can be performed in parallel.

[0177] S606. Based on the line fault judgment result, the first switch diagnostic sub-result, the second switch diagnostic sub-result, and the third switch diagnostic sub-result, the fourth diagnostic result of the switch output circuit is obtained.

[0178] The generated fourth diagnostic result includes the line fault judgment result, the first switch diagnostic sub-result, the second switch diagnostic sub-result, and the third switch diagnostic sub-result.

[0179] In the embodiments provided in this application, the execution order of steps S201 to S204 is not limited, and they can be executed in parallel.

[0180] The diagnostic process provided in this application covers fault detection of the switch output function and circuit testing of the switch output circuit. Therefore, it can comprehensively detect faults in the switch output circuit and improve the accuracy of fault diagnosis.

[0181] The fault diagnosis solution provided in this application achieves 99% diagnostic coverage of the system, meets the functional safety design requirements of the 1oo1D architecture, has comprehensive diagnostic capabilities, can diagnose any component fault, has the advantage of high diagnostic coverage, and leads to a safe state.

[0182] The fault diagnosis scheme provided in this application embodiment gives a method for diagnosing faults in each unit of a general input / output module. This scheme has a high diagnostic coverage. When any circuit inside the module fails, it can be effectively diagnosed, ensuring that the module is in a safe and controllable state and triggering an alarm.

[0183] It should be noted that the information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0184] The specific implementation processes and derivative methods of the above embodiments are all within the protection scope of this invention.

[0185] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0186] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0187] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A general-purpose input / output module, characterized in that, include: Analog input circuit, analog output circuit, digital input circuit, digital output circuit, differential amplifier module, first analog-to-digital converter, second analog-to-digital converter, first control module and second control module; The analog input circuit includes a first switch, a general circuit, a second switch, and a first resistor connected in series, with the end of the first resistor not connected to the second switch grounded. The general-purpose circuit includes a second resistor, a diode, and a field instrument connected in series. The analog output circuit includes a current source, the general circuit, and a third switch connected in series, with the end of the third switch not connected to the general circuit grounded. The digital input circuit includes a first switch, the general circuit, a fourth switch, a third resistor, and a fourth resistor connected in series, with the end of the fourth resistor not connected to the third resistor grounded. The switch output circuit includes a first switch, the general circuit, and a third switch connected in series, wherein the end of the third switch that is not connected to the general circuit is grounded. The first input terminal of the differential amplifier module is connected to the end of the second resistor that is not connected to the diode, the second input terminal is connected to the connection point of the second resistor and the diode, and the output terminal is connected to the first analog-to-digital converter. The first control module is used to control the opening and closing states of the second switch, the third switch and the fourth switch, and to receive data from the first analog-to-digital converter; The first terminal of the second analog-to-digital converter is connected to the connection point of the first resistor and the second switch, and the second terminal is connected to the connection point of the third resistor and the fourth resistor; The second control module is used to control the state of the current source and the first switch, and to receive data from the second analog-to-digital converter.

2. The general-purpose input / output module according to claim 1, characterized in that, The differential amplifier module includes: The fifth resistor, the sixth resistor, and the differential amplifier; One end of the fifth resistor is connected to the positive input terminal of the differential amplifier, and the other end serves as the first input terminal of the differential amplifier module. One end of the sixth resistor is connected to the negative input terminal of the differential amplifier, and the other end serves as the second input terminal of the differential amplifier module.

3. A fault diagnosis method, characterized in that, Applied to the general-purpose input / output module according to any one of claims 1-2, the method includes: The analog input circuit is diagnosed by applying a preset first diagnostic strategy to obtain the first diagnostic result of the analog input circuit; The analog output circuit is diagnosed by applying a preset second diagnostic strategy to obtain a second diagnostic result for the analog output circuit. The third diagnostic strategy is applied to diagnose the switch input circuit to obtain the third diagnostic result of the switch input circuit. The fourth diagnostic strategy is applied to diagnose the switch output circuit to obtain the fourth diagnostic result of the switch output circuit.

4. The method according to claim 3, characterized in that, The application uses a preset first diagnostic strategy to diagnose the analog input circuit, obtaining a first diagnostic result for the analog input circuit, including: Based on the first diagnostic strategy, the first differential voltage across the second resistor is acquired, and the first current is determined based on the first differential voltage. The first voltage of the first resistor is collected, and the second current is determined based on the first voltage; Using the first current and the second current, fault diagnosis is performed on the analog input circuit to obtain the first diagnostic result of the analog input circuit.

5. The method according to claim 4, characterized in that, The step of using the first current and the second current to perform fault diagnosis on the analog input circuit and obtain a first diagnostic result for the analog input circuit includes: Obtain a first deviation value between the first current and the second current; when the first deviation value exceeds a first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has malfunctioned; when the first deviation value does not exceed the first preset deviation value, generate a first diagnostic conclusion indicating that the analog input circuit has not malfunctioned. When the first current is within a preset first current range, a second diagnostic conclusion is generated indicating that the analog input circuit is fault-free; when the first current is less than the minimum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has an open circuit fault; when the first current is greater than the maximum value in the first current range, a second diagnostic conclusion is generated indicating that the analog input circuit has a short circuit fault. Based on the first diagnostic conclusion and the second diagnostic conclusion, a first diagnostic result for the analog input circuit is generated.

6. The method according to claim 3, characterized in that, The application uses a preset second diagnostic strategy to diagnose the analog output circuit, obtaining a second diagnostic result for the analog output circuit, including: Based on the second diagnostic strategy, the second differential voltage across the second resistor is acquired, and the third current is determined based on the second differential voltage. Control the output current of the current source, and determine the output current of the current source as the fourth current; Using the third current and the fourth current, fault diagnosis is performed on the analog output circuit to obtain a second diagnostic result for the analog output circuit.

7. The method according to claim 6, characterized in that, The step of using the third current and the fourth current to perform fault diagnosis on the analog output circuit and obtaining a second diagnostic result for the analog output circuit includes: Obtain a second deviation value between the third current and the fourth current; when the second deviation value exceeds a second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has failed; when the second deviation value does not exceed the second preset deviation value, generate a third diagnostic conclusion indicating that the analog output circuit has not failed. When the third current is less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has a disconnection fault; when the third current is not less than the preset detection current, a fourth diagnostic conclusion is generated indicating that the analog output circuit has not a fault. Based on the third and fourth diagnostic conclusions, a second diagnostic result for the analog output circuit is generated.

8. The method according to claim 3, characterized in that, The application uses a preset third diagnostic strategy to diagnose the switch input circuit, obtaining a third diagnostic result for the switch input circuit, including: Based on the third diagnostic strategy, the third differential voltage across the second resistor is acquired, and the fourth current is determined based on the third differential voltage. The first voltage is obtained by calculating the fourth current, the resistance value of the third resistor, and the resistance value of the fourth resistor. The second analog-to-digital converter is used to sample the first sampled voltage on the fourth resistor, and the first sampled voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the second voltage; Connect the field instrument to a preset resistor, collect the output current of the field instrument, and use the output current to obtain first diagnostic information characterizing whether there is a line fault in the switch input circuit; Based on the first voltage and the second voltage, fault diagnosis is performed on the switch input circuit to obtain the second diagnostic information of the switch input circuit; A third diagnostic result is generated based on the first diagnostic information and the second diagnostic information.

9. The method according to claim 8, characterized in that, The step of performing fault diagnosis on the switch input circuit based on the first voltage and the second voltage to obtain second diagnostic information of the switch input circuit includes: Determine the voltage deviation value between the first voltage and the second voltage; when the voltage deviation value exceeds a preset voltage deviation value, generate second diagnostic information indicating that the switch input circuit has failed; when the voltage deviation value does not exceed the preset voltage deviation value, generate second diagnostic information indicating that the switch input circuit has not failed.

10. The method according to claim 3, characterized in that, The application uses a preset fourth diagnostic strategy to diagnose the switch output circuit, obtaining a fourth diagnostic result for the switch output circuit, including: Based on the fourth diagnostic strategy, the fourth differential voltage across the second resistor is acquired, and the fifth current is determined based on the fourth differential voltage. Based on the fifth current, a line fault judgment is performed on the switch output circuit to obtain the line fault judgment result of the switch output circuit. The first switch, the third switch, and the fourth switch are all controlled to be in the closed state. The second analog-to-digital converter is used to sample the second sampling voltage on the fourth resistor. The second sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the third voltage. Based on the third voltage, the first switch diagnostic sub-result is obtained. The first switch and the fourth switch are controlled to be in the closed state, and the third switch is controlled to be in the open state. The second analog-to-digital converter is used to sample the third sampling voltage on the fourth resistor. The third sampling voltage, the resistance value of the third resistor and the resistance value of the fourth resistor are calculated to obtain the fourth voltage. Based on the third voltage, the second switch diagnostic sub-result is obtained. The first switch and the third switch are both in the open state, and the fourth switch is in the closed state. The second analog-to-digital converter is used to sample the fourth sampling voltage on the fourth resistor. The fourth sampling voltage, the resistance value of the third resistor, and the resistance value of the fourth resistor are calculated to obtain the fifth voltage. Based on the fifth voltage, the diagnostic sub-result of the third switch is obtained. Based on the line fault judgment result, the first switch diagnostic sub-result, the second switch diagnostic sub-result, and the third switch diagnostic sub-result, the fourth diagnostic result of the switch output circuit is obtained.

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