Digital quantity output channel circuit, digital quantity output system and fault diagnosis method

Abstract

The invention provides a digital quantity output channel circuit, a digital quantity output system and a fault diagnosis method, and relates to the technical field of current limiting protection. When the first switch tube is in a conducting state, the second switch tube is in a conducting state, so that current flows through a load connected with the digital quantity output channel circuit, and when the current flowing through the load is large enough, the third switch tube is in a conducting state, so that the voltage of the control end of the second switch tube rises, and the digital quantity output channel circuit is switched on. The voltage difference between the input end and the control end of the second switch tube is larger than the threshold voltage of the second switch tube, namely, the second switch tube is a P-type switch tube, so that the second switch tube is located in a variable resistance region. When the second switching tube is located in a variable resistance area, as the current flowing through the load is gradually increased, the voltage of the control end of the second switching tube is gradually increased, and as the second switching tube is a P-type switching tube, the equivalent resistance value of the second switching tube is gradually increased, and the current-limiting protection of the digital quantity output channel circuit can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of current limiting protection, and particularly relates to a digital quantity output channel circuit, a digital quantity output system, and a fault diagnosis method. Background Art

[0002] In systems such as DCS, PLC (Programmable Logic Controller), and SIS, the proportion of DO signals output by the digital quantity output channel circuit is very large. Specifically, the DO signal can be used to drive external actuators, such as solenoid valves, switch buttons, etc. Generally, the driving voltage of each DO signal is 24V, and each digital quantity output channel circuit can provide a driving capacity ranging from 50 to 100 mA.

[0003] When a short circuit fault occurs in the load connected to the digital quantity output channel circuit, if the digital quantity output channel circuit is not current-limited and protected, it may cause damage to the digital quantity output channel circuit.

[0004] Therefore, how to implement current limiting protection for the digital quantity output channel circuit is a technical problem to be solved urgently. Summary of the Invention

[0005] In view of this, the present invention provides a digital quantity output channel circuit, a digital quantity output system, and a fault diagnosis method to achieve current limiting protection for the digital quantity output channel circuit.

[0006] To achieve the above object, the embodiments of the present invention provide the following technical solutions:

[0007] The first aspect of the present application provides a digital quantity output channel circuit, including: a first switching tube, a second switching tube, a third switching tube, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; where:

[0008] The input end of the first switching tube is connected to one end of the first resistor, the other end of the first resistor is respectively connected to one end of the second resistor and the control end of the second switching tube, the control end of the first switching tube serves as the control end of the digital quantity output channel circuit, and the output end of the first switching tube is grounded;

[0009] The input end of the second switching tube is connected to one end of the third resistor;

[0010] The other end of the third resistor is connected to the other end of the second resistor, and the connection point serves as the input end of the digital quantity output channel circuit and is connected to the input power supply;

[0011] The output end of the second switching tube serves as the output end of the digital quantity output channel circuit;

[0012] The input terminal of the third switching transistor is connected to the connection point of the third resistor and the second resistor;

[0013] The output terminal of the third switching transistor is connected to the control terminal of the second switching transistor through the fourth resistor;

[0014] The control terminal of the third switching transistor is connected to the input terminal of the second switching transistor through the fifth resistor;

[0015] The third switching transistor is in a conducting state when the sum of the voltage divisions of the third resistor and the fifth resistor is greater than or equal to the threshold voltage of the third switching transistor;

[0016] The voltage difference between the input terminal and the control terminal of the second switching transistor is greater than or equal to the threshold voltage of the second switching transistor when the first switching transistor is in a conducting state.

[0017] Optionally, it further includes: an anti-reverse circuit; where:

[0018] The input terminal of the anti-reverse circuit is connected to the output terminal of the second switching transistor, and the output terminal of the anti-reverse circuit serves as the output terminal of the digital quantity output channel circuit.

[0019] Optionally, it further includes: a voltage detection circuit; where:

[0020] The voltage detection circuit is used to detect the output voltage of the digital quantity output channel circuit.

[0021] The second aspect of the present application provides a digital quantity output system, including: a control unit, a current detection unit, and at least two digital quantity output channel circuits as described in any one of the first aspects of the present application; where:

[0022] The signal output terminal of the current detection unit is connected to the control unit, and the current detection unit is used to detect a target current, and the target current is the sum of the input currents of all the digital quantity output channel circuits;

[0023] The control unit is used to switch the state of the digital quantity output channel circuit when receiving an instruction to detect the output current of any one of the digital quantity output channel circuits, and determine the absolute value of the change in the detection result of the current detection unit before and after the switching as the output current of the digital quantity output channel circuit.

[0024] Optionally, it further includes: a communication unit; where:

[0025] One end of the communication unit is communicatively connected to the control unit, and the other end of the communication unit serves as the communication end of the digital quantity output system.

[0026] A third aspect of the present application provides a fault diagnosis method, which is applied to a control unit in a digital quantity output system as described in any one of the second aspects of the present application; the fault diagnosis method includes:

[0027] When the output voltage of the digital quantity output channel circuit to be detected is less than or equal to a preset voltage and the output current of the digital quantity output channel circuit to be detected is less than or equal to a preset current, a fault prompt indicating that an open circuit fault has occurred in the digital quantity output channel circuit to be detected is output;

[0028] When the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be detected is greater than the rated current, a fault prompt indicating that a short circuit fault has occurred in the load connected to the digital quantity output channel circuit to be detected is output.

[0029] Wherein, the digital quantity output channel circuit to be detected is any digital quantity output channel circuit in the digital quantity output system that is in a conducting state.

[0030] Optionally, it further includes:

[0031] When the output voltage of the digital quantity output channel circuit to be detected is less than the rated voltage, and the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage, and the output current of the digital quantity output channel circuit to be detected is greater than the rated current, a fault prompt indicating that the resistance value of the load connected to the digital quantity output channel circuit to be detected has decreased is output; the rated voltage is greater than the preset voltage.

[0032] Optionally, before, after or at the same time as outputting the fault prompt indicating that the resistance value of the load connected to the digital quantity output channel circuit to be detected has decreased, it further includes:

[0033] Controlling the digital quantity output channel circuit to be detected to alternately be in a conducting state and an open circuit state.

[0034] Optionally, before, after or at the same time as outputting the fault prompt indicating that a short circuit fault has occurred in the load connected to the digital quantity output channel circuit to be detected, it further includes:

[0035] Controlling the digital quantity output channel circuit to be detected to alternately be in a conducting state and an open circuit state.

[0036] Optionally, it further includes:

[0037] When the output voltage of the digital quantity output channel circuit to be detected is equal to the rated voltage and the output current of the digital quantity output channel circuit to be detected is less than or equal to the preset current, a fault prompt indicating that an open circuit fault has occurred in the load connected to the digital quantity output channel circuit to be detected is output.

[0038] As can be seen from the above technical solution, the present invention provides a digital quantity output channel circuit. When the first switching tube is in the conducting state, the voltage difference between the input end and the control end of the second switching tube is greater than or equal to the threshold voltage of the second switching tube. Therefore, in this case, the second switching tube is in the conducting state, and thus current flows through the load connected to the digital quantity output channel circuit. As the current flowing through the above load gradually increases, the sum of the voltage divisions of the third resistor and the fifth resistor gradually increases. Therefore, when the current flowing through the above load is large enough, the sum of the voltage divisions of the third resistor and the fifth resistor is greater than or equal to the threshold voltage of the third switching tube, that is, the third switching tube is in the conducting state, so that the fourth resistor is connected in parallel with the second resistor, which not only increases the voltage at the control end of the second switching tube, but also because the voltage difference between the input end and the control end of the second switching tube is greater than its own threshold voltage, that is, the second switching tube is a P-type switching tube, so at this time the second switching tube is in the variable resistance region. When the second switching tube is in the variable resistance region, as the current flowing through the above load gradually increases, the voltage division of the first resistor also gradually increases, that is, the voltage at the control end of the second switching tube gradually increases. Also because the second switching tube is a P-type switching tube, the equivalent resistance value of the second switching tube gradually increases, thereby restricting the current flowing through the above load. Therefore, the digital quantity output channel circuit can achieve current limiting protection for itself. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0040] Figures 1 - 3 Structural schematic diagrams of three implementation manners of the digital quantity output channel circuit provided by the embodiments of the present application respectively;

[0041] Figures 4 - 6 Structural schematic diagrams of three implementation manners of the digital quantity output system provided by the embodiments of the present application respectively;

[0042] Figures 7 - 11 Flow schematic diagrams of five implementation manners of the fault diagnosis method provided by the embodiments of the present application respectively. Detailed Embodiments

[0043] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0044] In the present application, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "including a..." does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0045] To achieve current limiting protection for the digital quantity output channel circuit, an embodiment of the present application provides a digital quantity output channel circuit, and its specific structure is as Figure 1 shown, specifically including: a first switch tube 10, a second switch tube 20, a third switch tube 30, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The connection relationships between the components are specifically described as follows:

[0046] The input end of the first switch tube 10 is connected to one end of the first resistor R1.

[0047] Optionally, the first switch tube 10 can be a triode or a MOS tube. In actual applications, including but not limited to this, no specific limitation is made here, and it can be determined according to specific circumstances, and all are within the scope of protection of the present application. For example, as Figure 1 shown, the first switch tube 10 is a triode.

[0048] The other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the control end of the second switch tube 20.

[0049] Optionally, the second switch tube 20 can be a MOS tube or a triode. In actual applications, including but not limited to this, no specific limitation is made here, and it can be determined according to specific circumstances, and all are within the scope of protection of the present application. For example, as Figure 1 shown, the second switch tube 20 is a MOS tube.

[0050] The control terminal of the first switching transistor 10 serves as the control terminal of the digital quantity output channel circuit and is connected to the control unit 100 in the system where the digital quantity output channel circuit is located. The output terminal of the first switching transistor 10 is grounded to GND.

[0051] When the first switching transistor 10 receives a signal to turn itself off, the first switching transistor 10 turns off. When the first switching transistor 10 receives a signal to turn itself on, the first switching transistor 10 turns on.

[0052] The input terminal of the second switching transistor 20 is connected to one end of the third resistor R3.

[0053] The other end of the third resistor R3 is connected to the other end of the second resistor R2, and the connection point serves as the input terminal of the digital quantity output channel circuit and is connected to the input power supply 01.

[0054] The output terminal of the second switching transistor 20 serves as the output terminal of the digital quantity output channel circuit and is connected to a corresponding load.

[0055] The input terminal of the third switching transistor 30 is connected at: the connection point of the third resistor R3 and the second resistor R2. The output terminal of the third switching transistor 30 is connected to the control terminal of the second switching transistor 20 through the fourth resistor R4. The control terminal of the third switching transistor 30 is connected to the input terminal of the second switching transistor 20 through the fifth resistor R5.

[0056] Optionally, the third switching transistor 30 can be a triode or a MOS transistor. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific circumstances, all within the protection scope of this application. For example, as Figure 1 shown, the third switching transistor 30 is a triode.

[0057] When the sum of the voltage divisions of the third resistor R3 and the fifth resistor R5 is greater than or equal to the threshold voltage of the third switching transistor 30, the third switching transistor 30 is in the on state. When the sum of the voltage divisions of the third resistor R3 and the fifth resistor R5 is less than the threshold voltage of the third switching transistor 30, the third switching transistor 30 is in the off state.

[0058] Normally, the current at the control terminal of the third switching transistor is very small, so the voltage division of the fifth resistor R5 is also very small and can be ignored. Therefore, when the voltage division of the third resistor R3 is greater than the threshold voltage of the third switching transistor 30, the third switching transistor 30 is in the on state, and when the voltage division of the third resistor R3 is less than or equal to the threshold voltage of the third switching transistor 30, the third switching transistor 30 is in the off state.

[0059] Since one end of the third resistor R3 is connected to the input terminal of the third switching transistor 30, and the other end of the third resistor R3 is connected to the control terminal of the third switching transistor 30 through the fifth resistor R5, the voltage division of the third resistor R3 is equal to the potential of the input terminal of the third switching transistor 30 minus the potential of the control terminal of the third switching transistor 30. Therefore, if the third switching transistor 30 is a bipolar transistor, the third switching transistor 30 is specifically a PNP bipolar transistor.

[0060] When the first switching transistor 10 is in the conducting state, the voltage difference between the input terminal and the control terminal of the second switching transistor 20 is greater than or equal to the threshold voltage of the second switching transistor 20. When the first switching transistor 10 is in the non-conducting state, the voltage difference between the input terminal and the control terminal of the second switching transistor 20 is less than the threshold voltage of the second switching transistor 20.

[0061] It should be noted that by reasonably setting the resistance values of the first resistor R1, the second resistor R2, and the third resistor R3, the voltage difference between the input terminal and the control terminal of the second switching transistor 20 can be made greater than or equal to the threshold voltage of the second switching transistor 20 when the first switching transistor 10 is in the conducting state, and less than the threshold voltage of the second switching transistor 20 when the first switching transistor 10 is in the non-conducting state.

[0062] Since the voltage difference between the input terminal and the control terminal of the second switching transistor 20 is greater than or equal to the threshold voltage of the second switching transistor 20 when the first switching transistor 10 is in the conducting state, and less than the threshold voltage of the second switching transistor 20 when the first switching transistor 10 is in the non-conducting state, if the second switching transistor 20 is a MOS transistor, the second switching transistor 20 is specifically a PMOS transistor.

[0063] When the first switching transistor 10 is in the conducting state and the third switching transistor 30 is in the non-conducting state, the second switching transistor 20 is in the conducting state. When the first switching transistor 10 is in the conducting state and the third switching transistor 30 is in the conducting state, the second switching transistor 20 is in the variable resistance region, that is, the equivalent resistance of the second switching transistor 20 is controlled by the voltage of the control terminal of the second switching transistor 20. In other words, the equivalent resistance of the second switching transistor 20 changes with the change of the voltage of the control terminal of the second switching transistor 20.

[0064] In this embodiment, when the first switching transistor 10 is in the conducting state, the voltage difference between the input terminal and the control terminal of the second switching transistor 20 is greater than or equal to the threshold voltage of the second switching transistor 20. Therefore, in this case, the second switching transistor 20 is in the conducting state, and thus current flows through the load connected to the digital quantity output channel circuit. As the current flowing through the above load gradually increases, the sum of the voltage divisions of the third resistor R3 and the fifth resistor R5 gradually increases. Therefore, when the current flowing through the above load is large enough, the sum of the voltage divisions of the third resistor R3 and the fifth resistor R5 is greater than or equal to the threshold voltage of the third switching transistor 30, that is, the third switching transistor 30 is in the conducting state. As a result, the fourth resistor R4 is connected in parallel with the second resistor R2, which not only increases the voltage at the control terminal of the second switching transistor 20, but also because the voltage difference between the input terminal and the control terminal of the second switching transistor 20 is greater than or equal to its own threshold voltage, that is, the second switching transistor 20 is a P-type switching transistor, so at this time the second switching transistor 20 is in the variable resistance region. When the second switching transistor 20 is in the variable resistance region, as the current flowing through the above load gradually increases, the voltage division of the first resistor R1 also gradually increases, that is, the voltage at the control terminal of the second switching transistor 20 gradually increases. And because the second switching transistor 20 is a P-type switching transistor, the equivalent resistance value of the second switching transistor 20 gradually increases, thereby restricting the current flowing through the above load. Therefore, the digital quantity output channel circuit can achieve current limiting protection for itself.

[0065] Another embodiment of the present application provides another implementation manner of the digital quantity output channel circuit. The difference between this implementation manner and the above implementation manner is as follows:

[0066] In this implementation manner, the resistance value of the fourth resistor R4 is less than a preset resistance value.

[0067] The fact that the resistance value of the fourth resistor R4 is less than the preset resistance value indicates that the resistance value of the fourth resistor R4 is very small. On the contrary, the fact that the resistance value of the fourth resistor R4 is greater than or equal to the preset resistance value indicates that the resistance value of the fourth resistor R4 is not very small. In practical applications, the preset resistance value is set according to the actual situation and is not specifically limited here and can be determined according to the specific situation.

[0068] In this embodiment, because the resistance value of the fourth resistor R4 is very small, when the third switching transistor 30 is in the conducting state, the parallel resistance of the fourth resistor R4 and the second resistor R2 is lower, so that the potential at the control terminal of the second switching transistor 20 becomes larger more significantly, and thus the reliability of the second switching transistor 20 entering the variable resistance region can be improved.

[0069] Another embodiment of the present application provides another implementation manner of the digital quantity output channel circuit. Its specific structure is as Figure 2 shown. On the basis of any of the above implementation manners, this implementation manner further includes: an anti-reverse circuit 40.

[0070] The input end of the reverse connection prevention circuit 40 is connected to the output end of the second switching transistor 20, and the output end of the reverse connection prevention circuit 40 serves as the output end of the digital quantity output channel circuit.

[0071] In a specific example, the reverse connection prevention circuit 40 includes at least two diodes, and the diodes are connected end to end in sequence. The anode of the first diode serves as the input end of the reverse connection prevention circuit 40, and the cathode of the last diode serves as the output end of the reverse connection prevention circuit 40.

[0072] In another specific example, the reverse connection prevention circuit 40 includes a diode. The anode of the diode serves as the input end of the reverse connection prevention circuit 40, and the cathode of the diode serves as the output end of the reverse connection prevention circuit 40. For example, as Figure 2 shown in the reverse connection prevention circuit 40.

[0073] In the above two examples, the diode can be a zener diode or an ordinary TVS (Transient Voltage Suppressor). In practical applications, it includes but is not limited to this, and no specific limitation is made here. It can be determined according to specific situations, and all are within the protection scope of this application. For example, as Figure 2 shown, the diode is a zener diode.

[0074] The above two examples show two implementation manners of the reverse connection prevention circuit 40. No specific limitation is made here. It can be determined according to specific situations, and all are within the protection scope of this application.

[0075] In this embodiment, since the reverse connection prevention circuit 40 is provided at the output end of the digital quantity output channel circuit, if current flows backward into the output end of the digital quantity output channel circuit due to misconnection on site, the reverse connection prevention circuit 40 can prevent the current from flowing backward to a certain extent, thereby reducing the possibility of damage caused by the reverse current flow.

[0076] Another embodiment of this application provides another implementation manner of the digital quantity output channel circuit. Its specific structure is as Figure 3 shown. On the basis of any of the above implementation manners, this implementation manner further includes: a voltage detection circuit 50.

[0077] The acquisition end of the voltage detection circuit 50 is connected to the output end of the second switching transistor 20, and the output end of the voltage detection circuit 50 is connected to the control unit 100 in the system where the digital quantity output channel circuit is located. The voltage detection circuit 50 is used to detect the output voltage of the digital quantity output channel circuit and send it to the control unit 100.

[0078] In this embodiment, since the voltage detection circuit 50 is added, the control unit 100 can obtain the output voltage of the digital quantity output channel circuit, so that the control unit 100 has the ability to diagnose faults in the digital quantity output channel circuit, thereby providing hardware support for the function expansion of the control unit 100.

[0079] Another embodiment of the present application provides a specific implementation manner of the voltage detection circuit 50, and its specific structure is as Figure 3 shown, and it specifically includes: a sixth resistor R6, a seventh resistor R7, and a filtering circuit 51. The connection relationships between the components are specifically described as follows:

[0080] One end of the sixth resistor R6 is connected to the output end of the second switching tube 20, and one end of the seventh resistor R7 is grounded to GND. The other end of the sixth resistor R6 is connected to the other end of the seventh resistor R7, and the connection point is connected to the input end of the filtering circuit 51. The output end of the filtering circuit 51 is connected to the control unit 100.

[0081] The sixth resistor R6 and the seventh resistor R7 are used for voltage division. The voltage division of the seventh resistor R7 first passes through the filtering circuit 51 to eliminate interference to a certain extent, and then is input to the control unit 100. In this way, the control unit 100 can obtain the output voltage of the digital quantity output channel circuit.

[0082] In a specific example, as Figure 3 shown, the filtering circuit 51 includes an eighth resistor R8 and a capacitor C. One end of the eighth resistor R8 is connected to: the connection point between the sixth resistor R6 and the seventh resistor R7. The other end of the eighth resistor R8 is connected to one end of the capacitor C, and the connection point is connected to the control unit. The other end of the capacitor C is grounded.

[0083] The above example only shows a specific implementation manner of the filtering circuit 51. In actual applications, it includes but is not limited to this. No specific limitation is made here, and it can be determined according to specific circumstances, and all are within the protection scope of the present application.

[0084] The above is only a specific implementation manner of the voltage detection circuit 50. In actual applications, it includes but is not limited to this. No specific limitation is made here, and it can be determined according to specific circumstances, and all are within the protection scope of the present application.

[0085] Another embodiment of the present application provides a digital quantity output system, and its specific structure can be referred to Figure 4 ( Figure 4 only two digital quantity output channel circuits 300 are taken as examples for display), and it specifically includes: a control unit 100, a current detection unit 200, and at least two digital quantity output channel circuits 300 as described in any of the above embodiments. The connection relationships between the components are specifically described as follows:

[0086] The input end of the current detection unit 200 is connected to the input power supply 01, and the output ends of the current detection unit 200 are respectively connected to the input ends of the respective digital output channel circuits 300.

[0087] The signal output end of the current detection unit 200 is connected to the control unit 100. The current detection unit 200 is used to detect the target current, and the target current is the sum of the input currents of all the digital output channel circuits 300.

[0088] The control unit 100 is used to switch the state of the digital output channel circuit 300 when receiving an instruction to detect the output current of any digital output channel circuit 300, and determine the absolute value of the change in the detection result of the current detection unit 200 before and after the switch as the output current of the digital output channel circuit 300.

[0089] In a specific example, switching the state of the digital output channel circuit 300 is: switching from a conducting state to an open state, that is, switching the first switching transistor 10 in the digital output channel circuit 300 from a conducting state to a non-conducting state.

[0090] In another specific example, switching the state of the digital output channel circuit 300 is: switching from an open state to a conducting state, that is, switching the first switching transistor 10 in the digital output channel circuit 300 from a non-conducting state to a conducting state.

[0091] The above two examples show two specific implementation manners of switching the state of the digital output channel circuit 300. There is no specific limitation here, and it can be determined according to specific circumstances, and all are within the protection scope of this application.

[0092] In this embodiment, when the control unit 100 receives an instruction to detect the output current of any digital output channel circuit 300, it switches the state of the digital output channel circuit 300, and determines the absolute value of the change in the detection result of the current detection unit 200 before and after the switch as the output current of the digital output channel circuit 300. Therefore, the digital output system obtains the output current of any digital output channel circuit 300, so that the control unit 100 has the ability to diagnose faults in the digital output channel circuit 300, thus providing hardware support for the function expansion of the control unit 100.

[0093] Another embodiment of this application provides another implementation manner of the digital output system. Its specific structure can be referred to Figure 5 ( Figure 5 only shown on the basis of Figure 4 ). On the basis of the previous embodiment, this implementation manner further includes: a communication unit 400. The connection relationship between these devices is specifically described as follows:

[0094] One end of the communication unit 400 is communicatively connected to the control unit 100, and the other end of the communication unit 400 serves as the communication end of the digital quantity output system. The communication unit 400 is used to enable the control unit 100 to communicate and interact with the outside. On the one hand, it can obtain the control instructions of each digital quantity output channel circuit 300, and on the other hand, it can upload the output current of each digital quantity output channel circuit 300, or the output current and output voltage, to the outside.

[0095] In this embodiment, by adding the communication unit 400, the control unit 100 can communicate and interact with the outside, so that the digital quantity output system can communicate and interact with the outside, thereby enabling the digital quantity output system to be applicable to more scenarios.

[0096] Another embodiment of the present application provides another implementation manner of the digital quantity output system, and its specific structure can be referred to Figure 6 ( Figure 6 only shown on the basis of Figure 5 ), and the difference between this implementation manner and any of the above implementation manners is:

[0097] In this implementation manner, the control end of the second switching tube 20 in each digital quantity output channel circuit 300 is also connected to the control unit 100.

[0098] In this embodiment, since the control end of the second switching tube 20 in each digital quantity output channel circuit 300 is also connected to the control unit 100, the control unit 100 can turn on and off the second switching tube 20 in each digital quantity output channel circuit 300, so it provides hardware support for the function expansion of the control unit 100.

[0099] Another embodiment of the present application provides a fault diagnosis method, which is applied to the control unit in the digital quantity output system provided in any of the above embodiments. The specific process of this fault diagnosis method can be referred to Figure 7 ( Figure 7 only shown by taking one execution manner of step S110 and step S130 as an example), and specifically includes the following steps:

[0100] S110. Judge whether the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage, and whether the output current of the digital quantity output channel circuit to be detected is less than or equal to the preset current.

[0101] If the output voltage of the digital quantity output channel circuit to be tested is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be tested is less than or equal to the preset current, then step S120 is executed; if the output voltage of the digital quantity output channel circuit to be tested is greater than the preset voltage, and / or, the output current of the digital quantity output channel circuit to be tested is greater than the preset current, then step S130 is executed.

[0102] Among them, the digital quantity output channel circuit to be tested is any digital quantity output channel circuit in the on-state in the digital quantity output system. In actual applications, each digital quantity output channel circuit in the digital quantity output system takes turns as the digital quantity output channel circuit to be tested.

[0103] The output voltage of the digital quantity output channel circuit to be tested being less than or equal to the preset voltage indicates that the output voltage of the digital quantity output channel circuit to be tested is very small. On the contrary, the output voltage of the digital quantity output channel circuit to be tested being greater than the preset voltage indicates that the output voltage of the digital quantity output channel circuit to be tested is not very small. In actual applications, the preset voltage is set according to the actual situation and is not specifically limited here. Usually, the preset voltage is equal to 0.

[0104] The output current of the digital quantity output channel circuit to be tested being less than or equal to the preset current indicates that the output current of the digital quantity output channel circuit to be tested is very small. On the contrary, the output current of the digital quantity output channel circuit to be tested being greater than the preset current indicates that the output current of the digital quantity output channel circuit to be tested is not very small. In actual applications, the preset current is set according to the actual situation and is not specifically limited here. Usually, the preset current is equal to 0.

[0105] S120. Output a fault prompt indicating that the digital quantity output channel circuit to be tested has an open circuit fault.

[0106] S130. Determine whether the output voltage of the digital quantity output channel circuit to be tested is less than or equal to the preset voltage, and whether the output current of the digital quantity output channel circuit to be tested is greater than the nominal current.

[0107] If the output voltage of the digital quantity output channel circuit to be tested is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be tested is greater than the nominal current, then step S140 is executed; if the output voltage of the digital quantity output channel circuit to be tested is greater than the preset voltage, and / or, the output current of the digital quantity output channel circuit to be tested is less than or equal to the nominal current, then stop executing this fault diagnosis method.

[0108] Among them, the nominal current refers to the current output by the digital quantity output channel circuit to be tested when neither the digital quantity output channel circuit to be tested nor the load it is connected to has a fault. In actual applications, the nominal current is determined according to the specific situation and is not specifically limited here.

[0109] Since the nominal current refers to the current output by the digital quantity output channel circuit under test when there are no faults in the circuit of the digital quantity output channel under test and the load connected thereto, an output current of the digital quantity output channel circuit under test greater than the nominal current indicates that the output current of the digital quantity output channel circuit under test has increased.

[0110] It should be noted that the preset voltage has been described in detail above and will not be elaborated here.

[0111] In a specific example, if the difference between the output current of the digital quantity output channel circuit under test and the nominal current is greater than a first preset value, it is considered that the output current of the digital quantity output channel circuit under test is greater than the nominal current.

[0112] Among them, the difference between the output current of the digital quantity output channel circuit under test and the nominal current being greater than the first preset value indicates that the difference between the output current of the digital quantity output channel circuit under test and the nominal current is large, that is, the output current of the digital quantity output channel circuit under test and the nominal current differ greatly. Conversely, the difference between the output current of the digital quantity output channel circuit under test and the nominal current being less than or equal to the first preset value indicates that the difference between the output current of the digital quantity output channel circuit under test and the nominal current is not large, that is, the output current of the digital quantity output channel circuit under test and the nominal current do not differ greatly. In practical applications, the first preset value is set according to specific circumstances and is not specifically limited here.

[0113] Since it is only when the difference between the output current of the digital quantity output channel circuit under test and the nominal current is greater than the first preset value that the output current of the digital quantity output channel circuit under test is considered greater than the nominal current, it is equivalent to setting a judgment interval, thereby reducing the possibility of misjudgment, and further reducing the possibility of the following situation: sometimes outputting a fault prompt indicating that the load connected to the digital quantity output channel circuit under test has an open circuit fault, and sometimes not outputting.

[0114] The above example is only one implementation manner in which the output current of the digital quantity output channel circuit under test is greater than the nominal current. In practical applications, it includes but is not limited to this. For example, as long as the output current of the digital quantity output channel circuit under test is greater than the nominal current, it is considered that the output current of the digital quantity output channel circuit under test is greater than the nominal current. It is not specifically limited here and can be determined according to specific circumstances.

[0115] S140. Output a fault prompt indicating that the load connected to the digital quantity output channel circuit under test has a short circuit fault.

[0116] In this embodiment, since the output current and output voltage of the digital quantity output channel circuit to be detected are very small when an open - circuit fault occurs in the digital quantity output channel circuit to be detected, when it is detected that the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be detected is less than or equal to the preset current, that is, when both the output current and output voltage of the digital quantity output channel circuit to be detected are very small, it can be determined that an open - circuit fault has occurred in the digital quantity output channel circuit to be detected. Thus, a fault prompt indicating that an open - circuit fault has occurred in the digital quantity output channel circuit to be detected is output at this time to prompt the staff. Therefore, this embodiment can diagnose which digital quantity output channel circuit has an open - circuit fault.

[0117] In addition, since the output voltage of the digital quantity output channel circuit to be detected is very small and the output current of the digital quantity output channel circuit to be detected increases when a short - circuit fault occurs in the load connected to the digital quantity output channel circuit to be detected, when the output voltage of the digital quantity output channel circuit to be detected is less than the preset voltage and the output current of the digital quantity output channel circuit to be detected is greater than the nominal current, it can be determined that a short - circuit fault has occurred in the load connected to the digital quantity output channel circuit to be detected. Thus, a fault prompt indicating that a short - circuit fault has occurred in the load connected to the digital quantity output channel circuit to be detected is output at this time to prompt the staff. Therefore, this embodiment can also diagnose which digital quantity output channel circuit has a short - circuit fault in the connected load.

[0118] The execution order of step S110 and step S130, in addition to Figure 7 this way, can also be: first execute step S130, and execute step S110 when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the nominal current. It can also be: execute step S110 and step S130 simultaneously, and stop executing this fault diagnosis method when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current, and when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the nominal current. In practical applications, including but not limited to this, no specific limitation is made here, and it can be determined according to the specific situation, and all are within the protection scope of this application.

[0119] The above is only a specific embodiment of the fault diagnosis method. In practical applications, including but not limited to this, no specific limitation is made here, and it can be determined according to the specific situation, and all are within the protection scope of this application.

[0120] Another embodiment of this application provides another implementation manner of the fault diagnosis method, and its specific process can be referred to Figure 8 (Figure 8 (Only one execution mode of step S110, step S130, and step S210 is taken as an example for display), after it is determined in the previous embodiment that the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the nominal current, the following steps are further included:

[0121] S210. Determine whether the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage, and whether the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage, and whether the output current of the digital quantity output channel circuit to be detected is greater than the nominal current.

[0122] If the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage, and the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage, and the output current of the digital quantity output channel circuit to be detected is greater than the nominal current, then execute step S220; if the output voltage of the digital quantity output channel circuit to be detected is greater than or equal to the nominal voltage, and / or the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage, and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the nominal current, then stop executing this fault diagnosis method.

[0123] Among them, the nominal voltage refers to the voltage output by the digital quantity output channel circuit to be detected when neither the digital quantity output channel circuit to be detected nor the load connected thereto has a fault. In practical applications, the nominal current is determined according to specific circumstances and is not specifically limited here. In addition, the nominal voltage is greater than the preset voltage.

[0124] Since the nominal voltage refers to the voltage output by the digital quantity output channel circuit to be detected when neither the digital quantity output channel circuit to be detected nor the load connected thereto has a fault, the output voltage of the digital quantity output channel circuit to be detected being less than the nominal voltage indicates that the output voltage of the digital quantity output channel circuit to be detected becomes smaller.

[0125] It should be noted that the preset voltage and the nominal current have been described in detail above and will not be elaborated here.

[0126] In a specific example, if the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is greater than the second preset value, it is considered that the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage.

[0127] Wherein, the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is greater than a second preset value, indicating that the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is very large, that is, the output voltage of the digital quantity output channel circuit to be detected is very different from the nominal voltage. On the contrary, when the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the second preset value, it indicates that the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is not very large, that is, the output voltage of the digital quantity output channel circuit to be detected is not very different from the nominal voltage. In practical applications, the second preset value is set according to specific circumstances and is not specifically limited here. Generally, the second preset value is equal to 3V.

[0128] Since it is considered that the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage only when the difference between the nominal voltage and the output voltage of the digital quantity output channel circuit to be detected is greater than the second preset value, it is equivalent to setting a judgment interval, which can reduce the possibility of misjudgment, and further reduce the possibility of the following situation: sometimes output a fault prompt indicating that the resistance value of the load connected to the digital quantity output channel circuit to be detected decreases, and sometimes not output.

[0129] The above example is only one implementation manner in which the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage. In practical applications, it includes but is not limited to this. For example, as long as the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage, it is considered that the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage. Here, it is not specifically limited and can be determined according to specific circumstances.

[0130] S220. Output a fault prompt indicating that the resistance value of the load connected to the digital quantity output channel circuit to be detected decreases.

[0131] In this embodiment, since when the load connected to the digital quantity output channel circuit to be detected decreases, the output voltage of the digital quantity output channel circuit to be detected becomes smaller, the output voltage of the digital quantity output channel circuit to be detected is not very small, and the output current of the digital quantity output channel circuit to be detected becomes larger. Therefore, when the output voltage of the digital quantity output channel circuit to be detected is less than the nominal voltage, and the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage, and the output current of the digital quantity output channel circuit to be detected is greater than the nominal current, it can be determined that the load connected to the digital quantity output channel circuit to be detected decreases. Thus, at this time, a fault prompt indicating that the resistance value of the load connected to the digital quantity output channel circuit to be detected decreases is output to prompt the staff. Therefore, this implementation manner can also diagnose which digital quantity output channel circuit has a decreased load connected.

[0132] Step S210, step S110, step S130 except Figure 8In addition to this method, it can also be: first execute step S130, execute step S110 when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current, and execute step S210 when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current. It can also be: execute steps S110, S130, and S210 simultaneously. When the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current, and when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current, and when the output voltage of the digital quantity output channel circuit to be detected is greater than or equal to the rated voltage and / or the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current, stop executing this fault diagnosis method. In practical applications, including but not limited to this, no specific limitation is made here, and it can be determined according to specific circumstances, and all are within the protection scope of this application.

[0133] The above is only a specific implementation manner of the fault diagnosis method. In practical applications, including but not limited to this, no specific limitation is made here, and it can be determined according to specific circumstances, and all are within the protection scope of this application.

[0134] Another embodiment of this application provides another implementation manner of the fault diagnosis method, and its specific process can be referred to Figure 9 ( Figure 9 only Figure 8 taking step S230 after step S220 as an example for display), in this implementation manner, before, after, or at the same time as step S220 in the previous implementation manner, the following steps are further included:

[0135] S230. Control the digital quantity output channel circuit to be detected to alternately be in a conducting state and an open state.

[0136] Specifically, by controlling the first switching tube in the digital quantity output channel circuit to be detected in the above digital quantity output system to be intermittently turned on and off, the digital quantity output channel circuit to be detected can be alternately in a conducting state and an open state.

[0137] It should be noted that controlling the first switching tube in the digital quantity output channel circuit to be detected in the above digital quantity output system to be intermittently turned on and off means: controlling the first switching tube to be in a conducting state for a period of time first, and then controlling the first switching tube to be in an off state for a period of time, and then cycling like this.

[0138] According to the specific structure of the digital quantity output channel circuit to be detected, when the first switch tube is in the on state, the second switch tube in the digital quantity output channel circuit to be detected is in the on state, that is, there is current flowing through the second switch tube. When the first switch tube is in the off state, the second switch tube is in the off state, that is, there is no current flowing through the second switch tube. Therefore, by controlling the digital quantity output channel circuit to be detected to alternate between the on state and the off state, the current intermittently flows through the second switch tube, thereby reducing the heat generation of the second switch tube, that is, reducing the heat generation of the digital quantity output channel circuit to be detected, and further reducing the internal temperature of the digital quantity output system.

[0139] Another embodiment of the present application provides another implementation manner of the fault diagnosis method, and the specific process can be referred to Figure 10 ( Figure 10 only Figure 9 taking step S150 after step S140 as an example for illustration on the basis of), this implementation manner further includes the following steps before, after or at the same time as step S140 in any of the above implementation manners:

[0140] S150. Control the digital quantity output channel circuit to be detected to alternate between the on state and the off state.

[0141] It should be noted that controlling the digital quantity output channel circuit to be detected to alternate between the on state and the off state has been described in detail in the previous embodiment, and will not be elaborated here.

[0142] According to the specific structure of the digital quantity output channel circuit to be detected, when the first switch tube is in the on state, the second switch tube in the digital quantity output channel circuit to be detected is in the on state, that is, there is current flowing through the second switch tube. When the first switch tube is in the off state, the second switch tube is in the off state, that is, there is no current flowing through the second switch tube. Therefore, by controlling the digital quantity output channel circuit to be detected to alternate between the on state and the off state, the current intermittently flows through the second switch tube, thereby reducing the heat generation of the second switch tube, that is, reducing the heat generation of the digital quantity output channel circuit to be detected, and further reducing the internal temperature of the digital quantity output system.

[0143] Another embodiment of the present application provides another implementation manner of the fault diagnosis method, and the specific process can be referred to Figure 11 ( Figure 11 taking only one execution manner of step S110, step S130 and step S310 as an example for illustration), this implementation manner further includes the following steps after it is determined in the previous implementation manner that the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current:

[0144] S310. Determine whether the output voltage of the digital quantity output channel circuit to be tested is equal to the nominal voltage, and whether the output current of the digital quantity output channel circuit to be tested is less than or equal to the preset current.

[0145] If the output voltage of the digital quantity output channel circuit to be tested is equal to the nominal voltage, and the output current of the digital quantity output channel circuit to be tested is less than or equal to the preset current, then execute step S320; if the output voltage of the digital quantity output channel circuit to be tested is not equal to the nominal voltage, and / or the output current of the digital quantity output channel circuit to be tested is greater than the preset current, then stop executing this fault diagnosis method.

[0146] It should be noted that the nominal voltage and the preset current have been described in detail in the above embodiments and will not be elaborated here.

[0147] S320. Output a fault prompt indicating that an open circuit fault has occurred in the load connected to the digital quantity output channel circuit to be tested.

[0148] In this embodiment, since when an open circuit fault occurs in the load connected to the digital quantity output channel circuit to be tested, the output voltage of the digital quantity output channel circuit to be tested is normal and the output current of the digital quantity output channel circuit to be tested is very small, so when it is detected that the output voltage of the digital quantity output channel circuit to be tested is equal to the nominal voltage and the output current of the digital quantity output channel circuit to be tested is less than the preset current, it can be determined that an open circuit fault has occurred in the load connected to the digital quantity output channel circuit to be tested. Therefore, at this time, a fault prompt indicating that an open circuit fault has occurred in the load connected to the digital quantity output channel circuit to be tested is output to prompt the staff. Therefore, this embodiment can diagnose which digital quantity output channel circuit has an open circuit fault in the connected load.

[0149] Step S310, step S110, step S130 except Figure 11In addition to this method, it can also be: first, execute step S130, and execute step S110 when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current. When the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current, then execute step S310. It can also be: execute step S110, step S130, and step S310 simultaneously. When the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current, and when the output voltage of the digital quantity output channel circuit to be detected is greater than the preset voltage and / or the output current of the digital quantity output channel circuit to be detected is less than or equal to the rated current, and when the output voltage of the digital quantity output channel circuit to be detected is not equal to the rated voltage and / or the output current of the digital quantity output channel circuit to be detected is greater than the preset current, stop executing this fault diagnosis method. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific situations, and all are within the protection scope of this application.

[0150] In addition, if both step S310 and step S210 are included, they can be executed successively or simultaneously. No specific limitation is made here and it can be determined according to specific situations.

[0151] The above is only a specific implementation manner of the fault diagnosis method. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific situations, and all are within the protection scope of this application.

[0152] Regarding the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, enabling those skilled in the art to implement or use this application. The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A digital output channel circuit, characterized in that: include: a first switch tube, a second switch tube, a third switch tube, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor; wherein: The input end of the first switch tube is connected to one end of the first resistor, the other end of the first resistor is respectively connected to one end of the second resistor and the control end of the second switch tube, the control end of the first switch tube serves as the control end of the digital output channel circuit, and the output end of the first switch tube is grounded; The input end of the second switch tube is connected to one end of the third resistor; The other end of the third resistor is connected to the other end of the second resistor, and the connection point serves as the input end of the digital output channel circuit and is connected to the input power supply; The output end of the second switch tube serves as the output end of the digital output channel circuit; The input end of the third switch tube is connected to: a connection point between the third resistor and the second resistor; The output end of the third switch tube is connected to the control end of the second switch tube through the fourth resistor; The control end of the third switch tube is connected to the input end of the second switch tube through the fifth resistor; The third switch tube is in a conducting state when the sum of the divided voltages of the third resistor and the fifth resistor is greater than or equal to the threshold voltage of the third switch tube; When the first switch tube is in an on state, a voltage difference between the input terminal and the control terminal of the second switch tube is greater than or equal to a threshold voltage of the second switch tube.

2. The digital output channel circuit according to claim 1, characterized in that: Also includes: Anti-reverse circuit; wherein: The input end of the anti-reverse circuit is connected to the output end of the second switch tube, and the output end of the anti-reverse circuit serves as the output end of the digital output channel circuit.

3. The digital output channel circuit according to claim 1 or 2, characterized in that: Also includes: A voltage detection circuit; wherein: The voltage detection circuit is used to detect the output voltage of the digital output channel circuit.

4. A digital output system, characterized in that: include: A control unit, a current detection unit and at least two digital output channel circuits according to any one of claims 1 to 3; wherein: The signal output end of the current detection unit is connected to the control unit, and the current detection unit is used to detect the target current, which is the sum of the input currents of all the digital output channel circuits; The control unit is used to switch the state of any of the digital output channel circuits upon receiving an instruction to detect the output current of the digital output channel circuit, and determine the absolute value of the change in the detection result of the current detection unit before and after the switching as the output current of the digital output channel circuit.

5. The digital quantity output system according to claim 4, characterized in that: Also includes: A communication unit; wherein: One end of the communication unit is connected to the control unit for communication, and the other end of the communication unit serves as a communication end of the digital quantity output system.

6. A fault diagnosis method, characterized in that: A control unit used in a digital output system as claimed in claim 4 or 5; The fault diagnosis method comprises: When the output voltage of the digital quantity output channel circuit to be detected is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be detected is less than or equal to the preset current, outputting a fault prompt indicating that the digital quantity output channel circuit to be detected has a circuit breaker fault; When the output voltage of the digital quantity output channel circuit to be tested is less than or equal to the preset voltage and the output current of the digital quantity output channel circuit to be tested is greater than the nominal current, output a fault prompt indicating that a short circuit fault has occurred in the load connected to the digital quantity output channel circuit to be tested; The digital quantity output channel circuit to be inspected is any digital quantity output channel circuit in the digital quantity output system that is in a pass state.

7. The fault diagnosis method according to claim 6, characterized in that: Also includes: When the output voltage of the digital quantity output channel circuit to be tested is less than the nominal voltage, and the output voltage of the digital quantity output channel circuit to be tested is greater than the preset voltage, and the output current of the digital quantity output channel circuit to be tested is greater than the nominal current, a fault prompt indicating that the resistance of the load connected to the digital quantity output channel circuit to be tested is reduced is output; the nominal voltage is greater than the preset voltage.

8. The fault diagnosis method according to claim 7, characterized in that: Before, after or simultaneously with outputting a fault prompt indicating that the resistance value of the load connected to the digital output channel circuit to be detected is reduced, the method further includes: The digital quantity output channel circuit to be detected is controlled to be alternately in a circuit-opening state and a circuit-breaking state.

9. The fault diagnosis method according to claim 6, characterized in that: Before, after or simultaneously with outputting a fault prompt indicating that a load connected to the digital output channel circuit to be detected has a short circuit fault, the method further includes: The digital quantity output channel circuit to be detected is controlled to be alternately in a circuit-opening state and a circuit-breaking state.

10. The fault diagnosis method according to any one of claims 6 to 9, characterized in that: Also includes: When the output voltage of the digital quantity output channel circuit to be tested is equal to the nominal voltage and the output current of the digital quantity output channel circuit to be tested is less than or equal to the preset current, a fault prompt indicating that a load connected to the digital quantity output channel circuit to be tested has a circuit breaker fault is output.

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