Insulation detection system and method for vehicle-mounted charger

Abstract

The invention provides an insulation detection system and method of a vehicle-mounted charger, and relates to the technical field of vehicles, the insulation detection system comprises a switch module, a first monitoring module, a second monitoring module and a control module; the first end of the switch module is connected with a zero line; the first end of the first monitoring module is connected with the second end of the switch module, and the second end is grounded; the first end of the second monitoring module is connected with the live wire, the second end is grounded, and the detection precision of the second monitoring module is different from that of the first monitoring module; the control module is connected with the first monitoring module, the second monitoring module and the controlled end of the switch module, when the insulation resistance value of the vehicle-mounted charger is larger than a first detection threshold value, the switch module is controlled to be switched off, and when the insulation resistance value is smaller than a second detection threshold value, the switch module is controlled to be switched on. The detection precision of the first monitoring module and the detection precision of the second monitoring module in the system are different, different detection requirements can be met through two-way detection, the problem that when the used detection precision is not appropriate, an insulation alarm is triggered by mistake is avoided, and the detection reliability is high.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and more specifically, to an insulation detection system and method for an on-board charger. Background Art

[0002] Currently, the on-board chargers in vehicles can usually achieve bidirectional energy transfer. In order to avoid the risk of AC electric shock, the on-board chargers need to be tested for inverter insulation.

[0003] However, in the related art, when performing inverter insulation testing on on-board chargers, the detection accuracy of the detection equipment on the market varies and is not uniform. When the detection accuracy used is inappropriate, there may be a problem of falsely triggering the insulation alarm, and the detection reliability is low. Summary of the Invention

[0004] To solve the above problems, the present application provides an insulation detection system and method for an on-board charger, aiming to solve the problem in the related art that the detection accuracy is not uniform when performing inverter insulation detection on the on-board charger. When the detection accuracy used is not appropriate, there may be a problem of false triggering of the insulation alarm, and the detection reliability is low.

[0005] In the first aspect, the present application provides an insulation detection system for an on-board charger, comprising a switch module, a first monitoring module, a second monitoring module and a control module; the first end of the switch module is connected to the neutral line of the on-board charger; the first end of the first monitoring module is connected to the second end of the switch module, and the second end of the first monitoring module is grounded; the first end of the second monitoring module is connected to the live wire of the on-board charger, and the second end of the second monitoring module is grounded, and the detection accuracy of the second monitoring module is different from the detection accuracy of the first monitoring module; the control module is connected to the third end of the first monitoring module, the third end of the second monitoring module and the controlled end of the switch module, and the control module is used to control the switch module to disconnect when the insulation resistance value of the on-board charger is greater than the first detection threshold, and to control the switch module to turn on when the insulation resistance value is less than the second detection threshold; wherein the first detection threshold is greater than the second detection threshold.

[0006] In the above technical solution, when the insulation resistance value received by the control module is greater than the first detection threshold, the control module controls the switch module to turn off, and the second monitoring module performs detection according to its detection accuracy. When the insulation resistance value received by the control module is less than the second detection threshold, the control module controls the switch module to turn on, and the first monitoring module starts to operate. That is, at this time, the first monitoring module and the second monitoring module simultaneously perform detection according to their detection accuracy. The detection accuracy of the first monitoring module and the second monitoring module is different, and the detection accuracy of the corresponding second monitoring module when operating independently and when the two are operating together is different, so that the insulation detection system provided by this application can achieve dual-path detection with different accuracy. For example, if one path can meet the detection requirement, the control module can control the switch module to turn off, and the second monitoring module can perform single-path detection. If one path cannot meet the detection requirement, the control module can control the switch module to turn on, and the first monitoring module and the second monitoring module can operate simultaneously to achieve dual-path detection. That is, the insulation detection system can adapt to different detection requirements through dual-path detection, avoiding the problem of false triggering of insulation alarm when the detection accuracy used is not appropriate. The detection consistency and detection reliability provided by this application are high. In addition, using a single insulation detection system can reduce hardware redundancy, that is, avoid configuring separate detection equipment for different accuracy requirements, which can save a certain amount of production costs.

[0007] In combination with the first aspect, in some possible implementations, the insulation detection system also includes a first diode and a second diode; the positive pole of the first diode is connected to the neutral line of the vehicle charger, and the negative pole of the first diode is connected to the first end of the switch module; the positive pole of the second diode is connected to the live wire of the vehicle charger, and the negative pole of the second diode is connected to the first end of the second monitoring module.

[0008] In the above technical solution, when the onboard charger stops operating or experiences an abnormality, the first and second diodes prevent the current in the first and second monitoring modules from flowing back into the onboard charger, thereby protecting the onboard charger and preventing damage to the onboard charger due to reverse current. Furthermore, the unidirectional conductivity of the first and second diodes can be used to rectify the AC output of the neutral and live wires and output it to the first and second monitoring modules.

[0009] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the first monitoring module includes a first grounding unit, a first capacitor and a first amplification unit; the first end of the first grounding unit is connected to the second end of the switching module as the first end of the first monitoring module, the second end of the first grounding unit is connected to the first plate of the first capacitor and the first input end of the first amplification unit, the third end of the first grounding unit and the second plate of the first capacitor are connected to a common ground as the second end of the first monitoring module, and the output end of the first amplification unit is connected to the control module as the third end of the first monitoring module.

[0010] In the above technical solution, the first grounding unit is connected to the output neutral line of the on-board charger via the switch module and the first diode. The first grounding unit can reduce the voltage proportionally and output the voltage after voltage division to the first amplifying unit. The first amplifying unit then performs isolation sampling and outputs it to the control module. Compared with the detection chip, the cost of the first grounding unit and the first amplifying unit is lower. The first capacitor is the Y capacitor of the on-board charger. The first capacitor is used to filter out high-frequency noise and electromagnetic interference on the neutral line to ensure that the on-board charger does not interfere with the power grid or other electronic equipment. At the same time, the first capacitor can also prevent external electromagnetic interference from affecting the normal operation of the charger. Secondly, the first capacitor can improve electromagnetic compatibility to improve the electromagnetic compatibility performance of the on-board charger so that it complies with relevant EMC standards and regulatory requirements.

[0011] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the first grounding unit includes a first resistor, a second resistor, a third resistor and a fourth resistor connected in series; one end of the first resistor is connected to the second end of the switching module as the first end of the first grounding unit, the node where the third resistor and the fourth resistor are connected is connected to the first plate of the first capacitor and the first input end of the first amplification unit as the second end of the first grounding unit, and one end of the fourth resistor is connected to the second plate of the first capacitor as the third end of the first grounding unit.

[0012] In the above technical solution, the resistance values ​​of the first resistor, the second resistor, the third resistor, and the fourth resistor are relatively small, for example, 3Mohm. It is worth noting that 3Mohm has relatively low insulation performance in insulation testing. When the resistance values ​​of the first resistor, the second resistor, the third resistor, and the fourth resistor are small, they can convert the weak signal in the branch into a larger signal that is easier to detect. Specifically, according to Ohm's law, the leakage current generated at the same voltage is larger, and the larger leakage current can also be more easily captured by the control module, thereby improving the detection resolution, allowing the first grounding unit to achieve high-precision detection based on the small resistance resistors in series, that is, to detect the insulation status of the inverter with higher accuracy. Moreover, when the second monitoring module and the first monitoring module are both working, the control module can continuously monitor the insulation status of the inverter output terminal through the first grounding unit and the second grounding unit. Compared with a dedicated detection chip, the cost of the series resistors is much lower than that of the dedicated detection chip, which significantly reduces the hardware cost. Moreover, the resistors themselves are passive components and are not easily affected by electromagnetic interference, and the monitoring reliability is high.

[0013] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the first amplification unit includes a first voltage follower, a fifth resistor and a sixth resistor; the inverting input terminal of the first voltage follower is connected to the second end of the first grounding unit and the first plate of the first capacitor as the first input terminal of the first amplification unit, the non-inverting input terminal of the first voltage follower is connected to one end of the fifth resistor as the second input terminal of the first amplification unit, the output terminal of the first voltage follower is connected to the other end of the fifth resistor and one end of the sixth resistor, and the other end of the sixth resistor is connected to the control module as the output terminal of the first amplification unit.

[0014] In the above technical solution, the first voltage follower can replicate the input signal without changing its amplitude, thereby preventing signal attenuation and improving the reliability of the signal output to the control module. Secondly, a fifth resistor is connected in series with the non-inverting input of the first voltage follower to offset errors caused by the op amp input bias current, effectively balancing the current flow between the two input terminals of the first voltage follower and reducing the DC error voltage. In other words, the provision of the fifth and sixth resistors improves the load matching and isolation of the first voltage follower, thereby enhancing the reliability of the signal output to the control module.

[0015] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the second monitoring module includes a second grounding unit, a second capacitor and a second amplification unit; the first end of the second grounding unit is connected to the negative electrode of the second diode as the first end of the second monitoring module, the second end of the second grounding unit is connected to the first plate of the second capacitor and the first input end of the second amplification unit, the third end of the second grounding unit and the second plate of the second capacitor are commonly connected as the second end of the second monitoring module, and the output end of the second amplification unit is connected to the control module as the third end of the second monitoring module; wherein, the resistance of the first grounding unit is less than the resistance of the second grounding unit.

[0016] In the above technical solution, the second grounding unit is connected to the output live wire of the on-board charger via the second diode. The second grounding unit can reduce the voltage proportionally and output the voltage after voltage division to the second amplifying unit. The second amplifying unit then performs isolation sampling and outputs it to the control module. Compared with the detection chip, the cost of the second grounding unit and the second amplifying unit is lower. The second capacitor is the Y capacitor of the on-board charger. The second capacitor is used to filter out high-frequency noise and electromagnetic interference on the live wire to ensure that the on-board charger does not interfere with the power grid or other electronic equipment. At the same time, the second capacitor can also prevent external electromagnetic interference from affecting the normal operation of the charger. Secondly, the second capacitor can also improve electromagnetic compatibility to improve the electromagnetic compatibility performance of the on-board charger so that it complies with relevant EMC standards and regulatory requirements.

[0017] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the second grounding unit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor and an eleventh resistor connected in series; one end of the seventh resistor is connected to the negative electrode of the second diode as the first end of the second grounding unit, the node where the tenth resistor and the eleventh resistor are connected is connected to the first plate of the second capacitor and the first input end of the second amplification unit as the second end of the second grounding unit, and one end of the eleventh resistor is connected to the second plate of the second capacitor as the third end of the second grounding unit.

[0018] In the above technical solution, the seventh, eighth, ninth, tenth, and eleventh resistors have relatively high resistance values, for example, 30 Mohm. When the resistance values ​​of the seventh, eighth, ninth, tenth, and eleventh resistors are relatively high, the leakage current flowing through these series resistors is very low, thereby keeping the leakage current output of the inverter connected to the series resistors low, and preventing the problem of excessive leakage current. Furthermore, when the second monitoring module is operating, the control module can continuously monitor the insulation status of the inverter output terminal through the second grounding unit. Compared to dedicated detection chips, the cost of series resistors is much lower than that of dedicated detection chips, significantly reducing hardware costs. Furthermore, the resistors themselves are passive components and are not easily affected by electromagnetic interference, resulting in high monitoring reliability.

[0019] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the control module is also used to obtain the voltage signals output by the first monitoring module and the second monitoring module after the switch module is turned on, and determine the target insulation resistance value corresponding to the voltage signal from a preset calibration database based on the voltage signal and report it to the vehicle controller; wherein, the calibration database is determined based on the voltage values ​​collected by the first diode and the second diode, the voltage value between the neutral wire of the on-board charger and the live wire of the on-board charger, and the insulation resistance value between the neutral wire of the on-board charger and the live wire of the on-board charger.

[0020] In the above technical solution, when the control module detects that the insulation resistance value is less than the first detection threshold, it controls the switch module to conduct, obtains the voltage signals output by the first and second monitoring modules, and then substitutes these voltage signals into the calibration database to obtain the target insulation resistance value corresponding to the voltage signals. This target insulation resistance value is the insulation resistance value calibrated by the control module based on the calibration database. After obtaining this target insulation resistance value, the control module reports it to the vehicle controller, making the insulation resistance value reported by the system more accurate and more precise, thereby improving the reliability of the vehicle controller's judgment of the onboard charger status based on this target insulation resistance value.

[0021] In a second aspect, an embodiment of the present application further provides an insulation detection method for a vehicle charger, which is applied to the insulation detection system described in any optional embodiment of the first aspect, and the method includes:

[0022] When the insulation resistance value of the on-board charger is greater than a first detection threshold, the switch module is controlled to be disconnected;

[0023] When the insulation resistance value of the on-board charger is less than the second detection threshold, the switch module is controlled to be turned on, and the first detection threshold is greater than the second detection threshold.

[0024] In the above technical solution, in the insulation detection method provided by the present application, when the received insulation resistance value is greater than the first detection threshold, the control switch module is turned off, and the second monitoring module is used to perform detection according to its detection accuracy. When the received insulation resistance value is less than the second detection threshold, the control switch module is turned on, and the first monitoring module starts to run, that is, at this time, the first monitoring module and the second monitoring module are used to perform detection according to their detection accuracy at the same time. The detection accuracy of the first monitoring module and the second monitoring module are different. Correspondingly, the detection accuracy of the second monitoring module when it runs independently and when the two run together is different, so that the insulation detection system provided by the present application can realize dual-path detection with different accuracy, thereby adapting to different detection requirements, avoiding the problem of false triggering of the insulation alarm when the detection accuracy used is inappropriate, and the detection consistency and detection reliability are high.

[0025] In combination with the second aspect and the above implementation, in some possible implementations, the method further includes:

[0026] After the switch module is turned on, obtaining the voltage signals output by the first monitoring module and the second monitoring module;

[0027] Based on the voltage signal, the target insulation resistance value corresponding to the voltage signal is determined from a preset calibration database and reported to the vehicle controller.

[0028] In the above technical solution, when the switch module is turned on, it obtains the voltage signals output by the first and second monitoring modules. This voltage signal is then entered into a calibration database to obtain the target insulation resistance value corresponding to the voltage signal. This target insulation resistance value is the insulation resistance value calibrated by the control module based on the calibration database. The control module then reports this target insulation resistance value to the vehicle controller, making the insulation resistance value reported by the system more accurate and precise, thereby improving the reliability of the vehicle controller's judgment of the onboard charger status based on this target insulation resistance value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the module structure of an insulation detection system provided in an embodiment of the present application;

[0030] Figure 2 This is a schematic diagram of the circuit structure of an insulation detection system provided in an embodiment of the present application;

[0031] Figure 3 This is a circuit diagram of another insulation detection system provided in an embodiment of the present application;

[0032] Figure 4 This is a circuit diagram of another insulation detection system provided in an embodiment of the present application;

[0033] Figure 5 1 is a circuit diagram of another insulation detection system provided in an embodiment of the present application;

[0034] Figure 6 1 is a curve diagram of peak and valley values ​​of acquisition inversion provided by an embodiment of the present application;

[0035] Figure 7 This is another curve diagram of peak and valley values ​​of acquisition inversion provided by an embodiment of the present application;

[0036] Figure 8 This is a Vadc, (R L-PE / / R N-PE ) and Vrms relationship line graph;

[0037] Figure 9 This is a Vadc, (R L-PE / / R N-PE ) and a two-dimensional interpolation table of Vrms;

[0038] Figure 10 This is a Vadc, (R L-PE / / R N-PE ) and a three-dimensional data map of the calibration database of Vrms;

[0039] Figure 11 This is a schematic diagram of the process structure of an insulation detection method provided in an embodiment of the present application;

[0040] Figure 12 This is a flow chart of another insulation detection method provided in an embodiment of the present application.

[0041] Among them, the reference numerals in the figures are:

[0042] 1. Insulation detection system; 11. Switch module; 12. First monitoring module; 121. First grounding unit; 122. First amplification unit; 13. Second monitoring module; 131. Second grounding unit; 132. Second amplification unit; 14. Control module;

[0043] D1, first diode; D2, second diode; C1, first capacitor; C2, second capacitor; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; R9, ninth resistor; R10, tenth resistor; R11, eleventh resistor; R12, twelfth resistor; R13, thirteenth resistor; U1, first voltage follower; U2, second voltage follower; N, neutral line; L, live line. DETAILED DESCRIPTION

[0044] The following will clearly and thoroughly describe the technical solutions in this application in conjunction with the accompanying drawings. In the description of the embodiments of this application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more than two.

[0045] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to imply or suggest relative importance or implicitly indicate the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0046] With the continuous advancement of power semiconductor and onboard power topology technologies, battery range is increasing, placing higher demands on the functionality of onboard chargers (OBCs), which have gradually evolved from unidirectional to bidirectional OBCs. Bidirectional OBCs enable bidirectional energy transfer, adding AC output capability to vehicles. However, this also increases the risk of AC electric shock. To mitigate this risk, inverter insulation testing and protection are required for OBCs to meet the latest high-voltage safety regulations for electric vehicles.

[0047] Currently, most on-board chargers installed on the market have inverter output capabilities. However, the release of relevant national standards for inverter insulation safety specifications is relatively lagging, and there are no specific regulations for inverter insulation testing solutions. As a result, the capabilities of on-board charger inverter insulation testing on the market vary, and the accuracy of inverter insulation testing also varies. For example, when using a detection chip to perform inverter insulation testing on insulation resistance values ​​in related technologies, the detection accuracy of the detection equipment on the market varies and is not uniform. When the detection accuracy used is not appropriate, the insulation alarm may be falsely triggered, and the detection reliability is low. In addition, the cost of the detection chip is high.

[0048] To this end, the present invention provides an insulation detection system and method for an on-board charger. In this system, the first and second monitoring modules have different detection accuracies. Through dual-path detection, the system can adapt to different detection requirements, avoiding the problem of false insulation alarms caused by inappropriate detection accuracy. This provides high detection consistency and reliability. Furthermore, using a single insulation detection system can reduce hardware redundancy, avoiding the need to configure separate detection equipment for different accuracy requirements, which can save a certain amount of production costs.

[0049] The insulation detection system and method of the on-board charger provided in the embodiments of the present application are exemplarily described below with reference to the figures.

[0050] The embodiment of the present application provides an insulation detection system 1 for a vehicle charger. In one example, Figure 1As shown, the insulation detection system 1 includes a switch module 11, a first monitoring module 12, a second monitoring module 13, and a control module 14. The first end of the switch module 11 is connected to the neutral line N of the on-board charger, the first end of the first monitoring module 12 is connected to the second end of the switch module 11, and the second end of the first monitoring module 12 is grounded. The first end of the second monitoring module 13 is connected to the live line L of the on-board charger, and the second end of the second monitoring module 13 is grounded. The control module 14 is connected to the third end of the first monitoring module 12, the third end of the second monitoring module 13, and the controlled end of the switch module 11. The connection between the control module 14 and the controlled end of the switch module 11 is not shown in the figure, and the connection method can be direct electrical connection or indirect connection.

[0051] In this example, the second ends of the first monitoring module 12 and the second monitoring module 13 are respectively connected to protective earth (PE). The control module 14 can realize the insulation resistance value between the neutral wire N and the live wire L relative to PE through the first monitoring module 12 and / or the second monitoring module 13, that is, the insulation resistance value of the on-board charger. This insulation resistance value can be used to measure the insulation performance of the insulating material between the wires in the circuit to realize inverter insulation detection and protection of the on-board charger. Among them, the first monitoring module 12 is a high-precision monitoring module, and the second monitoring module 13 is a low-precision monitoring module. The control module 14 can control the working status of the first monitoring module 12 and the second monitoring module 13 based on the different insulation resistance values ​​of the on-board charger.

[0052] The detection accuracy of the second monitoring module 13 is different from that of the first monitoring module 12. The following takes the case where the detection accuracy of the second monitoring module 13 is lower than that of the first monitoring module 12 as an example to exemplify the insulation detection system 1 provided in this application.

[0053] For example, the insulation resistance value of the on-board charger received by the control module 14 is greater than the first detection threshold, such as 30MΩ (megaohm), indicating that the on-board charger is in a non-operating state at this time, and the insulation resistance value can be monitored only by the low-precision second monitoring module 13. Then, when the insulation resistance value of the on-board charger is greater than the first detection threshold, the control module 14 controls the switch module 11 to disconnect. At this time, the first monitoring module 12 does not work, and the second monitoring module 13 works. The control module 14 can obtain the insulation resistance value of the on-board charger in real time based on the second monitoring module 13. At this time, the second monitoring module 13 performs detection according to its detection accuracy to achieve low-precision detection. At this time, the insulation resistance value received by the control module 14 is large and will not be reported.

[0054] When the insulation resistance value of the on-board charger received by the control module 14 is less than the second detection threshold, for example, when it is 2MΩ, it indicates that the on-board charger is in working state at this time. The low-precision second monitoring module 13 alone cannot monitor the insulation resistance value, and it is necessary to cooperate with the high-precision first monitoring module 12 to monitor the insulation resistance value. Then, when the insulation resistance value of the on-board charger is less than the second detection threshold, the control module 14 controls the switch module 11 to be turned on. At this time, the first monitoring module 12 and the second monitoring module 13 work together. The control module 14 can obtain the insulation resistance value of the on-board charger in real time based on the first monitoring module 12 and the second monitoring module 13, and correspondingly, high-precision detection can be achieved at this time. At this time, the insulation resistance value received by the control module 14 is small, and the control module 14 will report it to the vehicle control unit (VCU). The VCU then performs fault diagnosis and evaluates the health status of the on-board charger based on the changes in the insulation resistance value reported by the control module 14.

[0055] It is worth noting that the control module 14 in this application will obtain the real-time insulation resistance value of the on-board charger to achieve precise control of the switch module 11, thereby switching the working states of the first monitoring module 12 and the second monitoring module 13.

[0056] The above-mentioned first detection threshold needs to be set greater than the second detection threshold to distinguish the working status of the on-board charger, so as to achieve detection with different accuracies. For example, the first detection threshold can be set to 30MΩ, and the second detection threshold is set to 2MΩ. When the real-time insulation resistance value of the on-board charger received by the control module 14 is greater than 30MΩ, the insulation resistance value is also greater than 2MΩ at this time, indicating that the on-board charger is in a non-working state. When the real-time insulation resistance value of the on-board charger received by the control module 14 is less than 2MΩ, the insulation resistance value is also greater than 30MΩ at this time, indicating that the on-board charger is in a working state (for example, AC charging or inverter insulation).

[0057] There is a correlation between the total resistance of the neutral wire N and the live wire L relative to PE, the corresponding high and low voltage states, and insulation problems. The correlation between the total resistance of the neutral wire N and the live wire L relative to PE, the corresponding high and low voltage states, and insulation problems is shown in Table 1:

[0058] <![CDATA[R L-PE value]]> <![CDATA[R N-PE value]]> DC component in L-PE Insulation problem big big high no big Small Low yes Small big Low yes Small Small Low yes

[0059] Table 1

[0060] In Table 1 above, R L-PE The value is expressed as the insulation resistance between the live wire L and PE, R N-PE"value" represents the insulation resistance between the neutral wire N and PE, "DC component in L-PE" represents the DC component between the live wire L and PE, and "Insulation problem" represents an insulation problem. Table 1 shows that only when both the neutral wire N and the live wire L have high resistances to PE (and both the insulation resistance between the live wire L and PE and the insulation resistance between the neutral wire N and PE are large) can the insulation state be satisfied, meaning that no insulation problem exists. Otherwise, when any of the insulation resistance values ​​of the neutral wire N and the live wire L are unsatisfactory, that is, when the insulation resistance between L and PE is small, the insulation resistance between the neutral wire N and PE is small, or the insulation resistance between L and PE and the insulation resistance between the neutral wire N and PE are both small, the insulation state cannot be satisfied, meaning that an insulation problem exists, and the control module 14 will report the insulation problem to the vehicle controller accordingly.

[0061] In this way, when the insulation resistance value received by the control module 14 is greater than the first detection threshold, the control module 14 will control the switch module 11 to turn off, and the second monitoring module 13 will perform detection according to its detection accuracy. When the insulation resistance value received by the control module 14 is less than the second detection threshold, the control module 14 will control the switch module 11 to turn on, and the first monitoring module 12 will start to operate, that is, at this time, the first monitoring module 12 and the second monitoring module 11 will simultaneously perform detection according to their detection accuracy. The detection accuracy of the first monitoring module 12 and the second monitoring module 13 is different, and the detection accuracy of the corresponding second monitoring module 13 when running independently and when running together is different, so that the insulation detection system 1 provided by the present application can achieve dual-path detection with different accuracy. For example, if one path can meet the detection requirements, the control module 14 can control the switch module 11 to turn off, and the second monitoring module 13 can perform single-path detection. If one path cannot meet the detection requirements, the control module 14 can control the switch module to turn on, and the first monitoring module 12 and the second monitoring module 13 will run simultaneously to achieve dual-path detection. In other words, the insulation detection system 1 can adapt to different detection requirements through dual-path detection, avoiding the problem of false insulation alarms caused by inappropriate detection accuracy, and achieving high detection consistency and reliability. Furthermore, using a single insulation detection system 1 can reduce hardware redundancy, eliminating the need to configure separate detection equipment for different accuracy requirements, which can save a certain amount of production costs.

[0062] Optionally, the switch module 11 may be a hardware switch, an N-type metal oxide semiconductor (NMOS) field effect transistor, a P-type metal oxide semiconductor (PMOS) field effect transistor, an insulated gate bipolar transistor (IGBT), a transistor, a relay circuit, or other devices or circuits capable of realizing on-off functions. For example, Figure 2 As shown, the switch module 11 is a relay, the first end of which is connected to the neutral line N of the vehicle charger, the second end of which is connected to the first end of the first monitoring module 12, and the controlled end of which is connected to the control module 14 (not shown in the figure). The specific structure of the switch module 11 can be set according to actual needs and is not specifically limited in this application.

[0063] To prevent current backflow, in one example, Figure 3 As shown, the insulation detection system 1 also includes a first diode D1 and a second diode D2. The anode of the first diode D1 is connected to the neutral line N of the onboard charger, and the cathode of the first diode D1 is connected to the first end of the switch module 11. The anode of the second diode D2 is connected to the live line L of the onboard charger, and the cathode of the second diode D2 is connected to the first end of the second monitoring module 13.

[0064] In this example, when the onboard charger stops functioning or experiences an anomaly, the first diode D1 and the second diode D2 prevent the current in the first monitoring module 12 and the second monitoring module 13 from flowing back into the onboard charger, thereby protecting the onboard charger and preventing damage to the onboard charger due to reverse current. Furthermore, the unidirectional conductivity of the first diode D1 and the second diode D2 rectifies the AC output of the neutral line N and the live line L and outputs it to the first monitoring module 12 and the second monitoring module 13.

[0065] In the first state, the switch module 11 is disconnected, the second monitoring module 13 is working, and the first monitoring module 12 is not working. In the second state, the switch module 11 is connected, and both the second monitoring module 13 and the first monitoring module 12 are working. In the first state, in order to enable the control module 14 to detect the insulation resistance value based on the second monitoring module 13, in one example, Figure 4As shown, the second monitoring module 13 includes a second grounding unit 131, a second capacitor C2, and a second amplifying unit 132. A first end of the second grounding unit 131 is connected to the cathode of the second diode D2, a second end of the second grounding unit 131 is connected to the first plate of the second capacitor C2 and the first input end of the second amplifying unit 132, a third end of the second grounding unit 131 is commonly grounded to the second plate of the second capacitor C2, and an output end of the second amplifying unit 132 is connected to the control module 14.

[0066] The second grounding unit 131 is connected to the live output line L of the onboard charger via a second diode D2. The second grounding unit 131 proportionally reduces the voltage and outputs the divided voltage to the second amplifying unit 132. The second amplifying unit 132 then performs isolated sampling and outputs the voltage to the control module 14. Compared to a detection chip, the second grounding unit 131 and the second amplifying unit 132 are less expensive.

[0067] The second capacitor C2 is the Y capacitor of the on-board charger. It is used to filter out high-frequency noise and electromagnetic interference (EMI) on the live wire L, ensuring that the on-board charger does not interfere with the power grid or other electronic devices. It also prevents external electromagnetic interference from affecting the normal operation of the charger. Furthermore, the second capacitor C2 improves electromagnetic compatibility (EMC), thereby improving the on-board charger's EMC performance and ensuring compliance with relevant EMC standards and regulations.

[0068] The second grounding unit 131 includes a plurality of resistors, for example, Figure 5 As shown, the second grounding unit 131 includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and an eleventh resistor R11 connected in series. One end of the seventh resistor R7 serves as the first end of the second grounding unit 131 and is connected to the cathode of the second diode D2. The node where the tenth resistor R10 and the eleventh resistor R11 are connected serves as the second end of the second grounding unit 131 and is connected to the first plate of the second capacitor C2 and the first input end of the second amplifying unit 132. One end of the eleventh resistor R11 serves as the third end of the second grounding unit 131 and is commonly connected to the second plate of the second capacitor C2.

[0069] In this example, when the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10 and the eleventh resistor R11 are connected to the output live wire L of the on-board charger (i.e., the output end of the inverter) through the second diode D2, R L-PEThe sum of the insulation resistance values ​​of the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 between the live wire L and PE, that is, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 are insulation resistances. The seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 have relatively large resistance values, for example, 30 Mohm (megaohms). When the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 have relatively large resistance values, such as 30 Mohm (megaohms). Therefore, the leakage current flowing through these series resistors is very small, so that the leakage current output by the inverter connected to the series resistors remains small, and there will be no problem of excessive leakage current. In the first state, the control module 14 can continuously monitor the insulation status of the inverter output end through the second grounding unit 131. Compared with the dedicated detection chip, the cost of the series resistor is much lower than that of the dedicated detection chip, which can significantly reduce the hardware cost. The resistor itself is a passive component, which is not easily affected by electromagnetic interference and has high monitoring reliability.

[0070] In one example, if Figure 5 As shown, the second amplifier unit 132 includes a second voltage follower U2, a twelfth resistor R12, and a thirteenth resistor R13. The inverting input terminal of the second voltage follower U2 is connected to the first input terminal of the second amplifier unit 132 and the second terminal of the second grounding unit 122 (as shown in FIG. Figure 5 The first terminal of the second capacitor C2 is connected to the third resistor R3 and the fourth resistor R4 as shown. The non-inverting input terminal of the second voltage follower U2 is connected to one end of the twelfth resistor R12 as the second input terminal of the second amplifying unit 132. The output terminal of the second voltage follower U2 is connected to the other end of the twelfth resistor R12 and one end of the thirteenth resistor R13. The other end of the thirteenth resistor R13 is connected to the control module 14 as the output terminal of the second amplifying unit 132.

[0071] In this example, the second voltage follower U2 receives the voltage after voltage division by the second grounding unit 131 and isolates the voltage, and the output voltage of the second voltage follower U2 is strictly equal to the input voltage, that is, the gain of the second voltage follower U2 is 1. This allows the second voltage follower U2 to copy the input signal without changing its amplitude to avoid signal attenuation and improve the reliability of the signal output to the control module 14. Secondly, in order to offset the error caused by the input bias current of the op amp, a twelfth resistor R12 is connected in series at the non-inverting input end of the second voltage follower U2. The twelfth resistor R12 is a resistor with the same equivalent input impedance as the feedback network to effectively balance the current flow between the two input ends of the second voltage follower U2 and reduce the DC error voltage. By setting the twelfth resistor R12 and the thirteenth resistor R13, the load matching and isolation effect of the second voltage follower U2 can be improved, and the reliability of the signal output to the control module 14 can be improved.

[0072] Since the resistance value in the second grounding unit 131 is relatively large, the second monitoring module 13 in the first state cannot monitor the insulation resistance when it is less than 1Mohm. Therefore, when the control module 14 detects that the insulation resistance value is less than the second detection threshold (such as 1Mohm, 2Mohm), it is necessary to enter the second state, that is, it is necessary to control the switch module 11 to be turned on to enable the first monitoring module 12 to work. In the second state, in order to enable the control module 14 to detect the insulation resistance value based on the first monitoring module 12, in one example, Figure 4 As shown, the first monitoring module 12 includes a first grounding unit 121, a first capacitor C1, and a first amplifying unit 122. The first end of the first grounding unit 121 is connected to the second end of the switch module 11 as the first end of the first monitoring module 12. The second end of the first grounding unit 121 is connected to the first plate of the first capacitor C1 and the first input end of the first amplifying unit 122. The third end of the first grounding unit 121 is commonly grounded with the second plate of the first capacitor C1. The output end of the first amplifying unit 122 is connected to the control module 14 as the third end of the first monitoring module 12.

[0073] The first grounding unit 121 is connected to the output neutral line N of the onboard charger via the switch module 11 and the first diode D1. The first grounding unit 121 proportionally reduces the voltage and outputs the divided voltage to the first amplifying unit 122. The first amplifying unit 122 then performs isolated sampling and outputs the voltage to the control module 14. Compared to detection chips, the first grounding unit 121 and the first amplifying unit 122 are less expensive.

[0074] The first capacitor C1 is the Y capacitor of the on-board charger. It is used to filter out high-frequency noise and electromagnetic interference on the neutral line N, ensuring that the on-board charger does not interfere with the power grid or other electronic equipment. It also prevents external electromagnetic interference from affecting the normal operation of the charger. Furthermore, the first capacitor C1 improves electromagnetic compatibility, thereby improving the on-board charger's electromagnetic compatibility performance and ensuring compliance with relevant EMC standards and regulations.

[0075] It is worth noting that the resistance of the first grounding unit 121 is smaller than that of the second grounding unit 131 , so that the first grounding unit 121 can detect the insulation state of the inverter with high precision, while the second grounding unit 131 can detect the insulation state of the inverter with low precision.

[0076] The first grounding unit 121 includes a plurality of resistors connected in series, for example, Figure 5 As shown, the first grounding unit 121 may include a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4 connected in series. One end of the first resistor R1 serves as the first end of the first grounding unit 121 and is connected to the second end of the switch module 11. The node where the third resistor R3 and the fourth resistor R4 are connected serves as the second end of the first grounding unit 121 and is connected to the first plate of the first capacitor C1 and the first input end of the first amplifying unit 122. One end of the fourth resistor R4 serves as the third end of the first grounding unit 121 and is commonly connected to the second plate of the first capacitor C1.

[0077] In this example, when the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 are connected to the output neutral line N of the on-board charger (i.e. the output end of the inverter) through the first diode D1, R N-PEThe sum of the insulation resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 between the neutral line N and PE, i.e., the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are the insulation resistances. The resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are relatively small, for example, 3Mohm. Compared to 30Mohm, the resistance value of 3Mohm is reduced by about 10 times. It is worth noting that 3Mohm has relatively low insulation performance in insulation testing. When the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are relatively small, they can convert weak signals in the branch into larger signals that are easier to detect. Specifically, according to Ohm's law, the leakage current generated at the same voltage is larger, and the larger leakage current can be more easily captured by the control module, thereby improving the detection resolution. This allows the first grounding unit 121 to achieve high-precision detection based on the small resistance resistors in series, that is, to detect the insulation status of the inverter with higher accuracy. In the second state, the control module 14 can continuously monitor the insulation state of the inverter output terminal through the first grounding unit 121 and the second grounding unit 131. Compared with the detection chip, the series resistor has lower cost and higher monitoring reliability.

[0078] It is worth noting that the resistances of the first resistor R1 , the second resistor R2 , the third resistor R3 and the fourth resistor R4 in the first grounding unit 121 are smaller than the resistances of the seventh resistor R7 , the eighth resistor R8 , the ninth resistor R9 , the tenth resistor R10 and the eleventh resistor R11 in the second grounding unit 131 .

[0079] In one example, if Figure 4 As shown, the first amplifier unit 122 includes a first voltage follower U1, a fifth resistor R5, and a sixth resistor R6. The inverting input terminal of the first voltage follower U1 is connected to the second terminal of the first grounding unit 121 and the first plate of the first capacitor as the first input terminal of the first amplifier unit 122. The non-inverting input terminal of the first voltage follower U1 is connected to one end of the fifth resistor R5 as the second input terminal of the first amplifier unit 122. The output terminal of the first voltage follower U1 is connected to the other end of the fifth resistor R5 and one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected to the control module 14 as the output terminal of the first amplifier unit 122.

[0080] In this example, the first voltage follower U1 receives the voltage after voltage division by the first grounding unit 121 and isolates the voltage. The output voltage of the first voltage follower U1 is strictly equal to the input voltage, that is, the gain of the first voltage follower U1 is 1. This allows the first voltage follower U1 to copy the input signal without changing its amplitude to avoid signal attenuation and improve the reliability of the signal output to the control module 14. Secondly, in order to offset the error caused by the input bias current of the op amp, a fifth resistor R5 is connected in series with the non-inverting input terminal of the first voltage follower U1. The fifth resistor R5 has the same equivalent input impedance as the feedback network to effectively balance the current flow between the two input terminals of the first voltage follower U1 and reduce the DC error voltage. That is, by setting the fifth resistor R5 and the sixth resistor R6, the load matching and isolation effect of the first voltage follower U1 can be improved, and the reliability of the signal output to the control module 14 can be improved.

[0081] It's worth noting that the first capacitor C1 and the second capacitor C2 are the Y capacitors of the onboard charger. Conventional monitoring of the "live wire L, neutral wire N balance" scheme can be disrupted by the imbalance of the Y capacitors, because the total impedance of the Y capacitors can be as low as 99kΩ, which is much smaller than the insulation resistance (e.g., 10MOhm). When the Y capacitors at the front end of the electrical appliance are unbalanced, the monitoring circuit will interpret the insulation resistance as a problem, causing the inverter output to be interrupted. To avoid this interruption, the related art significantly reduces the insulation resistance shutdown limit, which poses a certain safety hazard.

[0082] To this end, the control module 14 in this application will detect the peak value and valley value of the inversion when the onboard charger is in the inversion state, and average the two detected values. Figure 6 As shown in , when the two detected values ​​(i.e., sample1 and sample2) are the same, it means that the Y capacitors are balanced at this time, and the output of the inverter will not be interrupted. Figure 7 As shown in the figure, when the two detected values ​​differ, that is, when the analog-to-digital conversion (ADC) value obtained from valley and peak detection is larger and smaller, it indicates that the Y capacitor is unbalanced, which will interfere with insulation detection. In this way, by detecting both the peak and valley values ​​when the on-board charger is in the inverter state, the balance of the Y capacitor can be determined based on these two values, eliminating the interference of Y capacitor imbalance on insulation detection and improving detection reliability.

[0083] In one example, the control module 14 is also used to obtain the voltage signals output by the first monitoring module 12 and the second monitoring module 13 after the switch module 11 is turned on, and determine the target insulation resistance value corresponding to the voltage signal from a preset calibration database based on the voltage signal and report it to the vehicle controller.

[0084] The calibration database is a calibration database preset in the control module 14. The calibration database can be determined based on the voltage value Vadc collected by the first diode D1 and the second diode D2, the voltage value Vrms between the neutral line N of the onboard charger and the live line L of the onboard charger, and the insulation resistance value between the neutral line N of the onboard charger and the live line L of the onboard charger. The voltage value Vadc collected by the first diode D1 and the second diode D2 can be determined based on R L-PE 、R N-PE , the capacitance of the live wire L to PE and the capacitance of the neutral wire N to PE are determined by simulation, for example, the data in the following Table 2 can be referred to:

[0085] <![CDATA[The resistance R of the live wire L to PE L-PE > 1Meg, 2.5Meg, 3Meg, 10Meg <![CDATA[Resistance R of neutral line N to PE N-PE > 2.5Meg, 10Meg, 20Meg, 100Meg Capacitance of live wire L to PE 10n, 20n, 30n, 60n Capacitance between neutral line N and PE 10n, 20n, 30n, 60n

[0086] Table 2

[0087] The data in Table 2 are combined in 4×4×4×4 ways to obtain 256 combinations. Then the simulation software is used to implement the 256 combinations in Table 2 one by one to simulate and obtain the corresponding Vadc. The simulation result Vadc is then compared with the insulation resistance value of the neutral line N and the live line L (i.e. R L-PE / / R N-PE ) into different Vrms (e.g. 187V, 205V, 220V, 235V) for simulation, we get Figure 8 The line chart shown. Figure 8 The horizontal axis is Vadc, and the vertical axis is (R L-PE / / R N-PE ), Figure 8 From left to right, they are 187V, 205V, 220V, and 235V. Vadc and (R L-PE / / R N-PE ) based on the relationship between Figure 8 Vadc, (R L-PE / / R N-PE ) and Vrms are made as follows Figure 9 The two-dimensional interpolation table shown, and based on Vadc, (R L-PE / / R N-PE ) and Vrms are generated as follows Figure 10 The algorithm of the two-dimensional interpolation table can adopt mature technology in the art, and the details can be referred to related technologies, which will not be described in detail.

[0088] Based on the above steps, Vadc, (R L-PE / / R N-PE) and Vrms, and stores it in the control module 14. When the control module 14 detects that the insulation resistance value is less than 2MΩ, it will control the switch module 11 to conduct, so that the first monitoring module 12 works. At this time, the control module 14 also needs to report the insulation resistance value to the vehicle controller. In order to ensure the accuracy of the reported data, the control module 14 will obtain the voltage signal output by the first monitoring module 12 and the second monitoring module 13. The voltage signal at this time can be understood as Vadc. Then substitute the voltage signal into the calibration database, and according to Vadc, Vrms and (R L-PE / / R N-PE ) determines the target insulation resistance value based on the resistance matching relationship. This target insulation resistance value can be understood as the insulation resistance value calibrated by the control module 14. The control module 14 reports the calibrated target insulation resistance value based on the calibration database to the vehicle controller. The vehicle controller issues an insulation warning based on this target insulation resistance value and determines the status of the onboard charger.

[0089] In this way, when the control module 14 detects that the insulation resistance value is less than the first detection threshold, it controls the switch module 11 to conduct, obtains the voltage signals output by the first monitoring module 12 and the second monitoring module 13, and then substitutes these voltage signals into the calibration database to obtain the target insulation resistance value corresponding to the voltage signals. This target insulation resistance value is the insulation resistance value calibrated by the control module 14 based on the calibration database. After obtaining this target insulation resistance value, the control module 14 reports it to the vehicle controller, making the insulation resistance value reported by the system more accurate and more precise, thereby improving the reliability of the vehicle controller's judgment of the onboard charger status based on this target insulation resistance value.

[0090] Furthermore, the control module 14 in the present application can also adopt a graded early warning protection mechanism, that is, the control module 14 is also provided with a third detection threshold and a fourth detection threshold, and the relationship between these four detection thresholds is: first detection threshold>second detection threshold>third detection threshold>fourth detection threshold. For example, taking the first detection threshold as 30MΩ, the second detection threshold as 2MΩ, and the third detection threshold as 110KΩ (kilo-ohms) as an example, the third detection threshold is the design limit at this time. When the control module 14 detects that the insulation resistance value is greater than the first detection threshold, the control switch module 11 remains off, and there is no need to report to the vehicle controller at this time. When the control module 14 detects that the insulation resistance value is less than the second detection threshold and greater than the third detection threshold, the control switch module 11 is turned on, and at the same time, the corresponding target insulation resistance value is determined based on the calibration database and reported to the vehicle controller, and the vehicle controller will issue an insulation early warning reminder. When the control module 14 detects that the insulation resistance value is the fourth detection threshold, that is, the insulation resistance value is less than the third detection threshold, the insulation resistance value is lower than the design limit at this time. The control module 14 will convert the voltage signal into a resistance signal proportionally and upload it to the vehicle controller via the bus. At the same time, it will report the third-level fault and perform wave sealing processing. That is, at this time, the control module 14 shuts down the circuit energy transmission to avoid circuit damage, which poses a certain safety hazard.

[0091] Optionally, the control module 14 may be a microcontroller unit (MCU). When the control module 14 is an MCU, the third end of the first monitoring module 12 is connected to the Vref port of the MCU, and the third end of the second monitoring module 13 is connected to the Comp port of the MCU.

[0092] In summary, in the insulation detection system 1 provided by the present application, when the insulation resistance value received by the control module 14 is greater than the first detection threshold, the control module 14 controls the switch module 11 to be turned off, and the second monitoring module 13 performs detection according to its detection accuracy. When the insulation resistance value received by the control module 14 is less than the second detection threshold, the control module 14 controls the switch module 11 to be turned on, and the first monitoring module 12 starts to operate, that is, at this time, the first monitoring module 12 performs detection according to its detection accuracy. The detection accuracy of the first monitoring module 12 and the second monitoring module 13 is different, and the detection accuracy of the corresponding second monitoring module 13 when operating independently and when the two are operating together is different, so that the insulation detection system 1 provided by the present application can achieve dual-path detection with different accuracy. For example, if one path can meet the detection requirement, the control module 14 can control the switch module 11 to be turned off, and the second monitoring module 13 can perform single-path detection. If one path cannot meet the detection requirement, the control module 14 can control the switch module to be turned on, and the first monitoring module 12 and the second monitoring module 13 can operate simultaneously to achieve dual-path detection. In other words, the insulation detection system 1 can adapt to different detection requirements through dual-path detection, avoiding the problem of false insulation alarms caused by inappropriate detection accuracy, and achieving high detection consistency and reliability. Furthermore, using a single insulation detection system 1 can reduce hardware redundancy, eliminating the need to configure separate detection equipment for different accuracy requirements, which can save a certain amount of production costs.

[0093] The embodiment of the present application further provides an insulation detection method for a vehicle charger, which is applied to the insulation detection system described in any of the above optional methods. Figure 11 This is a schematic flow chart of an insulation detection method for a vehicle charger provided in an embodiment of the present application; the method 100 includes S101 and S102; S101 and S102 are described in detail below.

[0094] Among them, the insulation detection system can refer to Figures 1 to 5 The insulation detection system 1 shown; for example, the insulation detection system 1 includes Figure 1 The switch module 11, first monitoring module 12, second monitoring module 13, and control module 14 are shown. The first end of the switch module 11 is connected to the neutral line N of the onboard charger, the first end of the first monitoring module 12 is connected to the second end of the switch module 11, and the second end of the first monitoring module 12 is grounded. The first end of the second monitoring module 13 is connected to the live line L of the onboard charger, and the second end of the second monitoring module 13 is grounded. The control module 14 is connected to the third end of the first monitoring module 12, the third end of the second monitoring module 13, and the controlled end of the switch module 11.

[0095] S101 : When the insulation resistance value of the on-board charger is greater than a first detection threshold, control the switch module to be disconnected.

[0096] Exemplarily, the control module 14 obtains the insulation resistance value of the on-board charger through the second monitoring module 13, and compares the obtained insulation resistance value with a preset first detection threshold (for example, 30MΩ). When the insulation resistance value is greater than the first detection threshold, it is determined that the on-board charger is in a non-working state. The control module 14 controls the switch module 11 to disconnect, and the insulation resistance value can be detected only through the second monitoring module 13.

[0097] S102 : When the insulation resistance value of the on-board charger is less than the second detection threshold, the switch module is controlled to be turned on, and the first detection threshold is greater than the second detection threshold.

[0098] For example, when the control module 14 obtains that the insulation resistance value of the on-board charger is less than the second detection threshold (for example, 2MΩ), it indicates that the on-board charger is in working state at this time. The low-precision second monitoring module 13 alone cannot monitor the insulation resistance value, and it is necessary to cooperate with the high-precision first monitoring module 12 to monitor the insulation resistance value. Then, when the insulation resistance value of the on-board charger is less than the second detection threshold, the control module 14 controls the switch module 11 to turn on. At this time, the first monitoring module 12 and the second monitoring module 13 work together. The control module 14 can obtain the insulation resistance value of the on-board charger in real time based on the first monitoring module 12 and the second monitoring module 13 to achieve high-precision detection.

[0099] It should be noted that the above-mentioned first detection threshold needs to be set greater than the second detection threshold in order to distinguish the working status of the on-board charger, thereby achieving detection with different accuracies. For example, the first detection threshold can be set to 30MΩ, and the second detection threshold is set to 2MΩ. When the real-time insulation resistance value of the on-board charger received by the control module 14 is greater than 30MΩ, the insulation resistance value is also greater than 2MΩ at this time, indicating that the on-board charger is in a non-working state. When the real-time insulation resistance value of the on-board charger received by the control module 14 is less than 2MΩ, the insulation resistance value is also greater than 30MΩ at this time, indicating that the on-board charger is in a working state (for example, AC charging or inverter insulation).

[0100] In an embodiment of the present application, the insulation detection method provided by the present application can control the switch module 14 to be turned off when the received insulation resistance value is greater than the first detection threshold value, that is, at this time, the second monitoring module 13 performs detection according to its detection accuracy, such as low-precision detection. When the received insulation resistance value is less than the second detection threshold value, the switch module 14 is controlled to be turned on, and the first monitoring module 12 starts to run, that is, at this time, the first monitoring module 12 performs detection according to its detection accuracy, such as high-precision detection. The detection accuracy of the first monitoring module 12 and the second monitoring module 13 are different. Correspondingly, the detection accuracy of the second monitoring module 12 when running independently and when the two are running together is different, so that the insulation detection system 1 provided by the present application can realize dual-path detection with different accuracy, thereby adapting to different detection requirements, avoiding the problem of false triggering of insulation alarm when the detection accuracy used is inappropriate, and the detection consistency and detection reliability are high.

[0101] High- and low-precision detection can be achieved when the insulation resistance value is small or large. When the received insulation resistance value is greater than the first detection threshold, the second monitoring module 13 is controlled to perform low-precision detection to meet the insulation detection requirements when the insulation resistance value is large. When the on-board charger is in an operating state (such as AC charging or inverter insulation), the received insulation resistance value is less than the second detection threshold, and the first monitoring module 12 is controlled to be turned on to achieve high-precision detection. At this time, the insulation detection system 1 can simultaneously perform dual-path detection to meet the high-precision detection requirements of the on-board charger, and the detection reliability is high.

[0102] In one example, Figure 12 This is a schematic flow chart of another on-board charger insulation detection method provided in an embodiment of the present application. The method 200 includes S201 and S202. S201 and S202 are described in detail below. Among them, the insulation detection system may refer to Figures 1 to 5 The insulation detection system 1 is shown.

[0103] S201 . After the switch module is turned on, obtain voltage signals output by the first monitoring module and the second monitoring module.

[0104] S202: Determine a target insulation resistance value corresponding to the voltage signal from a preset calibration database based on the voltage signal and report the target insulation resistance value to the vehicle controller.

[0105] For example, the calibration database is a calibration database preset in the control module 14, and the calibration database can be determined based on the voltage value Vadc collected by the first diode D1 and the second diode D2, the voltage value Vrms between the neutral line N of the onboard charger and the live line L of the onboard charger, and the insulation resistance value between the neutral line N of the onboard charger and the live line L of the onboard charger. The voltage value Vadc collected by the first diode D1 and the second diode D2 can be determined based on R L-PE 、R N-PE , the capacitance of the live wire L to PE and the capacitance of the neutral wire N to PE are determined by simulation, for example, the data in Table 2 described in the above insulation detection system 1 can be referred to.

[0106] For example, the data in Table 2 are combined in 4×4×4×4 combinations to obtain 256 combinations. Then, the 256 combinations in Table 2 are implemented one by one using simulation software to simulate and obtain the corresponding Vadc. The simulation result Vadc is then compared with the insulation resistance value of the neutral line N and the live line L (i.e., R L-PE / / R N-PE ) Substitute different Vrms (such as 187V, 205V, 220V, 23.5V) for simulation and get Figure 8 The line chart shown. Figure 8 The horizontal axis is Vadc, and the vertical axis is (R L-PE / / R N-PE ), Figure 8 From left to right, they are 187V, 205V, 220V, and 235V. Vadc and (R L-PE / / R N-PE ) based on the relationship between Figure 8 Vadc, (R L-PE / / R N-PE ) and Vrms are made as follows Figure 9 The two-dimensional interpolation table shown, and based on Vadc, (R L-PE / / R N-PE ) and Vrms are generated as follows Figure 10 The algorithm of the two-dimensional interpolation table can be calculated according to MATLAB or Simulink, which are mature technologies in this field. For details, please refer to the relevant technologies, and no further details will be given.

[0107] It should be noted that, based on the above steps, Vadc, (R L-PE / / R N-PE) and Vrms, and stores it in the control module 14. When the control module 14 detects that the insulation resistance value is less than 2MΩ, it will control the switch module 11 to conduct, so that the first monitoring module 12 works. At this time, the control module 14 also needs to report the insulation resistance value to the vehicle controller. In order to ensure the accuracy of the reported data, the control module 14 will obtain the voltage signal output by the first monitoring module 12 and the second monitoring module 13. The voltage signal at this time can be understood as Vadc. Then substitute the voltage signal into the calibration database, and according to Vadc, Vrms and (R L-PE / / R N-PE ) determines the target insulation resistance value based on the resistance matching relationship. This target insulation resistance value can be understood as the insulation resistance value calibrated by the control module 14. The control module 14 reports the calibrated target insulation resistance value based on the calibration database to the vehicle controller. The vehicle controller issues an insulation warning based on this target insulation resistance value and determines the status of the onboard charger.

[0108] In an embodiment of the present application, when the control module 14 detects that the insulation resistance value is less than the first detection threshold, it controls the switch module 11 to conduct, obtains the voltage signal output by the first monitoring module 12 and the second monitoring module 13, and then substitutes the voltage signal into the calibration database to obtain the target insulation resistance value corresponding to the voltage signal. This target insulation resistance value is the insulation resistance value calibrated by the control module 14 based on the calibration database. After obtaining the target insulation resistance value, the control module 14 reports it to the vehicle controller, making the insulation resistance value reported by the system more accurate and more precise, thereby improving the reliability of the vehicle controller's judgment of the on-board charger status based on the target insulation resistance value.

[0109] Furthermore, the insulation detection method in the present application can also adopt a graded early warning protection mechanism, that is, the insulation detection method is also provided with a third detection threshold and a fourth detection threshold, and the relationship between these four detection thresholds is: first detection threshold>second detection threshold>third detection threshold>fourth detection threshold. For example, taking the first detection threshold as 30MΩ, the second detection threshold as 2MΩ, and the third detection threshold as 110KΩ (kilo-ohms) as an example, the third detection threshold is the design limit at this time. When the control module 14 detects that the insulation resistance value is greater than the first detection threshold, the control switch module 11 remains off, and there is no need to report to the vehicle controller at this time. When the control module 14 detects that the insulation resistance value is less than the second detection threshold and greater than the third detection threshold, the control switch module 11 is turned on, and at the same time, the corresponding target insulation resistance value is determined based on the calibration database and reported to the vehicle controller, and the vehicle controller will issue an insulation early warning reminder. When the control module 14 detects that the insulation resistance value is the fourth detection threshold, that is, the insulation resistance value is less than the third detection threshold, the insulation resistance value is lower than the design limit at this time. The control module 14 will convert the voltage signal into a resistance signal proportionally and upload it to the vehicle controller via the bus. At the same time, it will report the third-level fault and perform wave sealing processing. That is, at this time, the control module 14 shuts down the circuit energy transmission to avoid circuit damage, which poses a certain safety hazard.

[0110] The present application also provides a vehicle comprising the insulation detection system for an on-board charger described in any of the aforementioned optional embodiments and an on-board charger, wherein the neutral and live wires of the on-board charger are connected to the insulation detection system. The vehicle, having the aforementioned insulation detection system, thus achieves all the benefits achievable by the aforementioned insulation detection system, and further description thereof is omitted.

[0111] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0112] In the embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0113] The above content is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. An insulation detection system for a vehicle charger, characterized in that: The insulation detection system comprises: a switch module, wherein a first end of the switch module is connected to a neutral line of the on-board charger; a first monitoring module, wherein a first end of the first monitoring module is connected to a second end of the switch module, and a second end of the first monitoring module is grounded; a second monitoring module, wherein a first end of the second monitoring module is connected to the live wire of the on-board charger, a second end of the second monitoring module is grounded, and a detection accuracy of the second monitoring module is different from that of the first monitoring module; and a control module connected to the third terminal of the first monitoring module, the third terminal of the second monitoring module, and the controlled terminal of the switch module, the control module being configured to control the switch module to be disconnected when the insulation resistance value of the on-board charger is greater than a first detection threshold, and to control the switch module to be connected when the insulation resistance value is less than a second detection threshold; The first detection threshold is greater than the second detection threshold.

2. The insulation detection system according to claim 1, characterized in that: The insulation detection system further comprises: a first diode, wherein the anode of the first diode is connected to the neutral line of the on-board charger, and the cathode of the first diode is connected to the first end of the switch module; and A second diode, wherein the anode of the second diode is connected to the live wire of the on-board charger, and the cathode of the second diode is connected to the first end of the second monitoring module.

3. The insulation detection system according to claim 2, characterized in that: The first monitoring module includes a first grounding unit, a first capacitor and a first amplifying unit; The first end of the first grounding unit is connected to the second end of the switching module as the first end of the first monitoring module, the second end of the first grounding unit is connected to the first plate of the first capacitor and the first input end of the first amplifying unit, the third end of the first grounding unit and the second plate of the first capacitor are commonly connected as the second end of the first monitoring module, and the output end of the first amplifying unit is connected to the control module as the third end of the first monitoring module.

4. The insulation detection system according to claim 3, characterized in that: The first grounding unit includes a first resistor, a second resistor, a third resistor and a fourth resistor connected in series; One end of the first resistor serves as the first end of the first grounding unit and is connected to the second end of the switch module; a node where the third resistor and the fourth resistor are connected serves as the second end of the first grounding unit and is connected to the first plate of the first capacitor and the first input end of the first amplifying unit; and one end of the fourth resistor serves as the third end of the first grounding unit and is commonly connected to the second plate of the first capacitor.

5. The insulation detection system according to claim 3, characterized in that: The first amplifying unit includes a first voltage follower, a fifth resistor and a sixth resistor; The inverting input end of the first voltage follower is connected to the second end of the first grounding unit and the first plate of the first capacitor as the first input end of the first amplifying unit, the non-inverting input end of the first voltage follower is connected to one end of the fifth resistor as the second input end of the first amplifying unit, the output end of the first voltage follower is connected to the other end of the fifth resistor and one end of the sixth resistor, and the other end of the sixth resistor is connected to the control module as the output end of the first amplifying unit.

6. The insulation detection system according to claim 3, characterized in that: The second monitoring module includes a second grounding unit, a second capacitor and a second amplifying unit; The first end of the second grounding unit is connected to the cathode of the second diode as the first end of the second monitoring module, the second end of the second grounding unit is connected to the first plate of the second capacitor and the first input end of the second amplifying unit, the third end of the second grounding unit and the second plate of the second capacitor are connected to a common ground as the second end of the second monitoring module, and the output end of the second amplifying unit is connected to the control module as the third end of the second monitoring module; Wherein, the resistance of the first grounding unit is smaller than the resistance of the second grounding unit.

7. The insulation detection system according to claim 6, characterized in that: The second grounding unit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and an eleventh resistor connected in series; One end of the seventh resistor is connected to the cathode of the second diode as the first end of the second grounding unit, the node where the tenth resistor and the eleventh resistor are connected is connected to the first plate of the second capacitor and the first input end of the second amplifying unit as the second end of the second grounding unit, and one end of the eleventh resistor is connected to the second plate of the second capacitor as the third end of the second grounding unit.

8. The insulation detection system according to any one of claims 2 to 7, characterized in that: The control module is further configured to obtain voltage signals output by the first monitoring module and the second monitoring module after the switch module is turned on, and determine a target insulation resistance value corresponding to the voltage signal from a preset calibration database based on the voltage signal and report the target insulation resistance value to the vehicle controller; The calibration database is determined based on the voltage values ​​collected by the first diode and the second diode, the voltage value between the neutral line of the on-board charger and the live line of the on-board charger, and the insulation resistance value between the neutral line of the on-board charger and the live line of the on-board charger.

9. An insulation detection method for a vehicle charger, applied to the insulation detection system according to any one of claims 1 to 8, characterized in that: The method comprises: When the insulation resistance value of the on-board charger is greater than a first detection threshold, the switch module is controlled to be disconnected; When the insulation resistance value of the on-board charger is less than a second detection threshold, the switch module is controlled to be turned on, and the first detection threshold is greater than the second detection threshold.

10. The insulation detection method according to claim 9, characterized in that: The method further comprises: After the switch module is turned on, obtaining voltage signals output by the first monitoring module and the second monitoring module; Based on the voltage signal, a target insulation resistance value corresponding to the voltage signal is determined from a preset calibration database and reported to the vehicle controller.

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