New energy vehicle insulation detection circuit, method, system and new energy vehicle

Abstract

The present invention provides a new energy vehicle insulation detection circuit, method, system and new energy vehicle, belonging to the technical field of new energy vehicles. A series of large resistors (e.g., MΩ level) for measurement are simultaneously incorporated into the positive busbar and the negative busbar to the vehicle body ground, and a set of voltages of the positive busbar and the negative busbar to the vehicle body ground are measured respectively. Then, one of the small resistors (e.g., KΩ level) is short-circuited to obtain a new set of voltages of the positive busbar and the negative busbar to the vehicle body ground, and the insulation resistance is calculated based on the relationship between the two sets of voltages and resistances. Since the resistance value between the positive busbar and the negative busbar changes slightly, the resulting voltage divider value change is also small, which does not cause a long Y capacitor charging and discharging time, making the insulation detection more timely and stable, and avoiding false alarms or failure to meet regulatory requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a new energy vehicle insulation detection circuit, method, system and new energy vehicle. Background Art

[0002] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] To meet ever-increasing demands for range or shorter charging times, vehicle bus voltages are constantly increasing. Therefore, the reliability and stability of vehicle insulation testing are becoming increasingly important. Currently, insulation testing for new energy vehicles generally follows the national standard method outlined in GB18384. This involves repeatedly inserting 1MΩ resistors between the positive busbar and vehicle ground, and between the negative busbar and vehicle ground. The insulation resistance is calculated by sampling the voltages of the positive and negative busbars relative to vehicle ground before and after the resistors are inserted. However, due to increasing vehicle voltages and the increasing number of high-voltage components, and driven by EMC requirements, the capacitance of the Y capacitors on the busbars of these high-voltage components is also increasing. The total capacitance of the Y capacitors between the positive and negative busbars relative to vehicle ground can reach microfarads (where the Y capacitors are the capacitors connected between the positive busbar and vehicle ground, and the negative busbar and vehicle ground, respectively).

[0004] The inventors discovered that because the vehicle's insulation resistance is generally tens of megohms (MΩ) or even higher, when a 1MΩ test resistor is incorporated, the voltage divider value between the positive busbar or negative busbar and the vehicle body ground will change significantly. Since the Y capacitor needs to be charged and discharged, the voltage divider value changes very slowly. If the sampled voltage between the vehicle's positive busbar and ground and the negative busbar and vehicle body ground is read before charging and discharging is completed, it will cause inaccurate detection and false alarm of insulation faults. If the sampled voltage is read after charging and discharging is completed and the voltage stabilizes, it will cause detection delays and the insulation resistance value cannot be detected in time. Summary of the Invention

[0005] In order to address the deficiencies of the prior art, the present invention provides a new energy vehicle insulation detection circuit, method, system, and new energy vehicle. Since the resistance value on the positive busbar or the negative busbar changes slightly, the resulting voltage divider value change is also small, which will not cause a long Y capacitor charging and discharging time, making insulation detection more timely and stable, and avoiding false alarms or failure to meet regulatory requirements.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides an insulation detection circuit for a new energy vehicle.

[0008] A new energy vehicle insulation detection circuit, wherein a first voltage-dividing resistor, a first switching resistor, and a first sampling resistor are sequentially connected in series between the positive busbar and the vehicle body ground, and a second voltage-dividing resistor, a second switching resistor, and a second sampling resistor are sequentially connected in series between the negative busbar and the vehicle body ground;

[0009] A first end of a first sampling resistor is connected to a vehicle body ground, a second end of the first sampling resistor is used to be connected to a first sampling port of a processor, a first end of a second sampling resistor is connected to a vehicle body ground, and a second end of the second sampling resistor is used to be connected to a second sampling port of the processor;

[0010] A first electronic switch is connected in parallel at both ends of the first switching resistor, a second electronic switch is connected in parallel at both ends of the second switching resistor, the resistance of the first voltage-dividing resistor and the second voltage-dividing resistor are in the megohm range, the resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

[0011] As an optional implementation, the resistance values ​​of the first switching resistor and the second switching resistor are both in the kilo-ohm range or the hundred-ohm range.

[0012] As an optional implementation, the first electronic switch and the second electronic switch are both optical MOS electronic switches.

[0013] As an optional implementation, a first relay is connected between the first voltage-dividing resistor and the first switching resistor, a second relay is connected between the second voltage-dividing resistor and the second switching resistor, a first diode is connected in parallel at both ends of the first relay, and a second diode is connected in parallel at both ends of the second relay.

[0014] As an optional implementation, the first voltage-dividing resistor includes a plurality of resistors with a resistance of 1 MΩ connected in series, and the second voltage-dividing resistor includes a plurality of resistors with a resistance of 1 MΩ connected in series.

[0015] As an optional implementation, the resistance of the first voltage-dividing resistor is the same as that of the second voltage-dividing resistor, the resistance of the first switching resistor is the same as that of the second switching resistor, and the resistance of the first sampling resistor is the same as that of the second sampling resistor.

[0016] A second aspect of the present invention provides a new energy vehicle insulation detection method.

[0017] A new energy vehicle insulation detection method, using the new energy vehicle insulation detection circuit described in the first aspect of the present invention, includes the following steps:

[0018] Controlling the first electronic switch and the second electronic switch to be disconnected, and the processor collecting and obtaining the first positive bus sampling voltage and the first negative bus sampling voltage;

[0019] If the positive bus sampling voltage is greater than the negative bus sampling voltage, the first electronic switch is closed, the second electronic switch remains open, and the processor collects again to obtain the second positive bus sampling voltage and the second negative bus sampling voltage; according to the first positive bus sampling voltage, the first negative bus sampling voltage, the second positive bus sampling voltage, the second negative bus sampling voltage, the first voltage dividing resistor, the first switching resistor, the first sampling resistor, the second voltage dividing resistor, the second switching resistor, and the second sampling resistor, the positive bus insulation resistance and the negative bus insulation resistance are obtained;

[0020] If the positive bus sampling voltage is greater than the negative bus sampling voltage, the second electronic switch is closed, the first electronic switch remains open, and the processor collects and obtains the third positive bus sampling voltage and the third negative bus sampling voltage again; the positive bus insulation resistance and the negative bus insulation resistance are obtained according to the first positive bus sampling voltage, the first negative bus sampling voltage, the third positive bus sampling voltage, the third negative bus sampling voltage, the first voltage dividing resistor, the first switching resistor, the first sampling resistor, the second voltage dividing resistor, the second switching resistor and the second sampling resistor.

[0021] As an optional implementation method, whether there is a positive busbar insulation fault is determined based on the comparison between the positive busbar insulation resistance and the first preset value, and whether there is a negative busbar insulation fault is determined based on the comparison between the negative busbar insulation resistance and the second preset value.

[0022] A third aspect of the present invention provides an insulation detection system for new energy vehicles.

[0023] A new energy vehicle insulation detection system, comprising the new energy vehicle insulation detection circuit and a processor according to the first aspect of the present invention;

[0024] A first voltage-dividing resistor, a first switching resistor, and a first sampling resistor are sequentially connected in series between the positive busbar and the vehicle body ground; a second voltage-dividing resistor, a second switching resistor, and a second sampling resistor are sequentially connected in series between the negative busbar and the vehicle body ground;

[0025] A first end of a first sampling resistor is connected to a vehicle body ground, a second end of the first sampling resistor is connected to a first sampling port of a processor, a first end of a second sampling resistor is connected to a vehicle body ground, and a second end of the second sampling resistor is connected to a second sampling port of the processor;

[0026] A first electronic switch is connected in parallel to both ends of the first switching resistor, and a second electronic switch is connected in parallel to both ends of the second switching resistor;

[0027] The resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

[0028] A fourth aspect of the present invention provides a new energy vehicle, comprising the new energy vehicle insulation detection circuit described in the first aspect of the present invention.

[0029] A fifth aspect of the present invention provides a new energy vehicle, which adopts the new energy vehicle insulation detection method described in the second aspect of the present invention.

[0030] A sixth aspect of the present invention provides a new energy vehicle, comprising the new energy vehicle insulation detection system described in the third aspect of the present invention.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. In the new energy vehicle insulation detection circuit, method, system, and new energy vehicle described in the present invention, the resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, and both N1 and N2 are greater than or equal to 10. Since the resistance value on the positive busbar or the negative busbar changes slightly, the resulting voltage-dividing value change is also small, which will not cause a long Y capacitor charging and discharging time, making insulation detection more timely and stable, and avoiding false alarms or failure to meet regulatory requirements.

[0033] 2. The new energy vehicle insulation detection circuit, method, system and new energy vehicle described in the present invention, compared with the traditional insulation detection method, avoids the excessive voltage fluctuation of the positive busbar and the negative busbar to the vehicle body ground when the switching resistor is incorporated, which causes the positive busbar and the negative busbar to stabilize for a long time to ground due to the presence of the Y capacitor, thereby greatly improving the accuracy and stability of the detection.

[0034] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 This is a connection diagram of the insulation detection circuit for a new energy vehicle provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0041] Example 1:

[0042] like Figure 1 As shown, embodiment 1 of the present invention provides an insulation detection circuit for a new energy vehicle, wherein a first voltage-dividing resistor (R1 and R2 connected in series), a first switching resistor R3, and a first sampling resistor R5 are sequentially connected in series between the positive busbar P+ and the vehicle body ground GND, and a second voltage-dividing resistor (R11 and R12 connected in series), a second switching resistor R13, and a second sampling resistor R9 are sequentially connected in series between the negative busbar P- and the vehicle body ground GND;

[0043] A first end of a first sampling resistor R5 is connected to the vehicle body ground GND, a second end of the first sampling resistor R5 is used to be connected to a first sampling port of a processor, a first end of a second sampling resistor R9 is connected to the vehicle body ground, and a second end of the second sampling resistor R9 is used to be connected to a second sampling port of the processor;

[0044] A first electronic switch S1 is connected in parallel to both ends of the first switching resistor R3, and a second electronic switch S2 is connected in parallel to both ends of the second switching resistor R13;

[0045] The resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

[0046] In this embodiment, the preferred resistance value of the first voltage-dividing resistor is 2 MΩ (i.e., R1 and R2 connected in series are 1 MΩ each), the resistance value of the second voltage-dividing resistor is 2 MΩ (i.e., R11 and R12 connected in series are 1 MΩ each), the resistance value of the first switching resistor is 200 KΩ, and the resistance value of the second switching resistor is 200 KΩ. At this time, N1 is 10 and N2 is 10.

[0047] It can be understood that in some other embodiments, the first voltage-dividing resistor and the second voltage-dividing resistor are composed of multiple MΩ-level resistors connected in series to ensure that the withstand voltage of each resistor is within a safe range; the resistance of the first switching resistor R3 is one order of magnitude lower than that of the first voltage-dividing resistor and can be set to the KΩ level, and the resistance of the second switching resistor R13 is one order of magnitude lower than that of the second voltage-dividing resistor and can be set to the KΩ level; or, as long as N1 and N2 are greater than or equal to 10, those skilled in the art can select the resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, the first switching resistor and the second switching resistor within this range.

[0048] In this embodiment, the first sampling resistor R5 and the second sampling resistor R9 are selected to have a relatively low resistance to ensure that their voltage division values ​​are within the sampling range of the processor AD port. In this embodiment, 3.52KΩ is preferably used.

[0049] In this embodiment, the voltage divider resistor, the switching resistor, and the sampling resistor used in this embodiment are all high-precision resistors, such as resistors with a precision of 0.1%, to ensure the accuracy of the sampling and calculation values.

[0050] In this embodiment, a first end of R1 is connected to the positive bus, a second end of R1 is connected to a first end of R2, a first reed switch relay T1 is connected in series between R2 and R3, a first end of the first reed switch relay T1 is connected to a power supply VCC, a second end of the first reed switch relay is connected to a second end of R2, a third end of the first reed switch relay T1 is connected to a first end of R3, and a fourth end of the first reed switch relay T1 is used to connect to a first control port of a processor;

[0051] A first end of the first reed switch relay T1 is connected to the cathode end of the first diode D1 , and a fourth end of the first reed switch relay T1 is connected to the anode end of the first diode D1 .

[0052] A first end of R11 is connected to the negative bus, a second end of R11 is connected to a first end of R12, a second reed switch relay T2 is connected in series between R12 and R13, a first end of the second reed switch relay T2 is connected to a power supply VCC, a second end of the second reed switch relay T2 is connected to a second end of R12, a third end of the second reed switch relay T2 is connected to a first end of R13, and a fourth end of the second reed switch relay T2 is used to connect to a second control port of the processor;

[0053] A first end of the second reed switch relay T2 is connected to the cathode end of the second diode D2 , and a fourth end of the second reed switch relay T2 is connected to the anode end of the second diode D2 .

[0054] In this embodiment, the first electronic switch and the second electronic switch use a combined AQW216HAXC88 optocoupler relay. Ports 1, 2, 7, and 8 of the AQW216HAXC88 constitute the first electronic switch, ports 1 and 2 of the AQW216HAXC88 are respectively connected to the diode, and ports 7 and 8 of the AQW216HAXC88 are respectively connected to the switch; ports 3, 4, 5, and 6 of the AQW216HAXC88 constitute the second electronic switch, ports 3 and 4 of the AQW216HAXC88 are respectively connected to the diode, and ports 5 and 6 of the AQW216HAXC88 are respectively connected to the switch.

[0055] The first end of R3 is connected to port 8 of AQW216HAXC88, the second end of R3 is connected to port 7 of AQW216HAXC88, the first end of R13 is connected to port 5 of AQW216HAXC88, and the second end of R13 is connected to port 6 of AQW216HAXC88;

[0056] Port 1 of AQW216HAXC88 is connected to the 3V3 power supply through R6, port 2 of AQW216HAXC88 is connected to the 3V3 power supply through R7, port 3 of AQW216HAXC88 is connected to the 3V3 power supply through R8, and port 4 of AQW216HAXC88 is connected to the 3V3 power supply through R10.

[0057] In this embodiment, a capacitor C1 is connected in parallel across the first sampling resistor R5, and a capacitor C3 is connected in parallel across the second sampling resistor R9. The second end of the first sampling resistor R5 is connected to the first end of the resistor R4, the second end of the resistor R4 is connected to the first sampling port of the processor, and the second end of the resistor R4 is connected to the vehicle ground GND via the capacitor C2. The second end of the second sampling resistor R9 is connected to the first end of the resistor R14, the second end of the resistor R14 is connected to the second sampling port of the processor, and the second end of the resistor R14 is connected to the vehicle ground GND via the capacitor C4.

[0058] The second end of resistor R4 is connected to GND through a first diode group (TEP05), and the second end of resistor R14 is connected to GND through a second diode group. The first diode group includes a third diode and a fourth diode connected in reverse, with the cathode terminal of the third diode connected to the second end of R4, the positive terminal of the third diode connected to the positive terminal of the fourth diode, and the negative terminal of the fourth diode connected to GND; the second diode group includes a fifth diode and a sixth diode connected in reverse, with the cathode terminal of the fifth diode connected to the second end of R14, the positive terminal of the fifth diode connected to the positive terminal of the sixth diode, and the negative terminal of the sixth diode connected to GND.

[0059] The parameters of the electronic components described in this embodiment are as follows:

[0060] R1 (resistance: 1MΩ), R2 (resistance: 1MΩ), R3 (resistance: 200KΩ), R4 (resistance: 510Ω), R5 (resistance: 3.52KΩ), R6 (resistance: 330Ω), R7 (resistance: 20KΩ), R8 (resistance: 330Ω), R9 (resistance: 3.52KΩ), R10 (resistance: 20KΩ), R11 (resistance: 1MΩ), R12 (resistance: 1MΩ), R13 (resistance: 200KΩ), R14 (resistance: 510Ω);

[0061] C1 (capacitance value: 100pF), C2 (capacitance value: 0.1μF), C3 (capacitance value: 100pF), C4 (capacitance value: 0.1μF).

[0062] Example 2:

[0063] Embodiment 2 of the present invention provides an insulation detection method for a new energy vehicle. The method utilizes the insulation detection circuit for a new energy vehicle described in embodiment 1. Two identical bias resistors are connected between the high-voltage positive busbar and the negative busbar and the electric chassis, respectively. A processor controls electronic switches S1 and S2 to switch the magnitude and sequence of the two connected resistors. The voltage divider values ​​of the positive and negative busbars on the measured resistors are measured under different connection resistances, thereby calculating the insulation resistance Rp of the positive busbar to the vehicle body ground and the insulation resistance Rn of the negative busbar to the vehicle body ground.

[0064] like Figure 1 As shown, let:

[0065] Rp and Rn are the insulation resistance of the positive and negative terminals of the high-voltage busbar to ground; Up and Un are the voltages of the positive and negative terminals of the high-voltage busbar to ground before the switch is closed; Up' and Un' are the voltages of the positive and negative terminals of the battery pack to ground after the switch is closed; Usp and Usn are the voltages collected by the processor before the switch is closed; Usp' and Usn' are the voltages collected by the processor after the switch is closed; G is the fixed gain of the voltage signal acquisition circuit, which is designed to be 2.5 in this embodiment.

[0066] The implementation steps are:

[0067] S1: After power is turned on, the control reed switches T1 and T2 are connected, the electronic switches S1 and S2 are opened, and the processor collects the voltages U1 (i.e., the first positive bus sampling voltage) and U2 (i.e., the first negative bus sampling voltage);

[0068] S2: Compare the magnitudes of U1 and U2. If U1 > U2, then close switch S1. The processor collects the voltages U1' (i.e., the sampling voltage of the second positive bus) and U2' (i.e., the sampling voltage of the second negative bus) again. According to Kirchhoff's law, at the vehicle body ground "GND" point, the incoming current is equal to the outgoing current, and the following calculation relationship holds:

[0069] When S1 and S2 are both open:

[0070] (1)

[0071] When S1 is closed and S2 is open:

[0072] (2)

[0073] By combining the above formulas, we get:

[0074] (3)

[0075] S3: If U1 < U2, then close switch S2. The processor collects the voltages U1' (i.e., the sampling voltage of the third positive bus) and U2' (i.e., the sampling voltage of the third negative bus) again, and the following calculation formula holds:

[0076] When S1 is open and S2 is closed:

[0077] (4)

[0078] By combining formula (1), we get:

[0079] (5)

[0080] where

[0081]

[0082] In this embodiment, the above steps are an operation for one insulation detection. After one detection is completed, the above steps are repeated, and the insulation detection value is fed back in real time according to the design requirements and it is judged whether there is an insulation fault. At the same time, the connected bias resistors (including voltage-dividing resistors, switching resistors, and sampling resistors) can be flexibly adjusted according to the actual vehicle conditions to ensure the reliability and stability of the vehicle's insulation detection value.

[0083] Embodiment 3:

[0084] Embodiment 3 of the present invention provides a new energy vehicle insulation detection system, including the new energy vehicle insulation detection circuit and the processor described in Embodiment 1 of the present invention;

[0085] A first voltage-dividing resistor, a first switching resistor, and a first sampling resistor are sequentially connected in series between the positive busbar and the vehicle body ground; a second voltage-dividing resistor, a second switching resistor, and a second sampling resistor are sequentially connected in series between the negative busbar and the vehicle body ground;

[0086] A first end of a first sampling resistor is connected to a vehicle body ground, a second end of the first sampling resistor is connected to a first sampling port of a processor, a first end of a second sampling resistor is connected to a vehicle body ground, and a second end of the second sampling resistor is connected to a second sampling port of the processor;

[0087] A first electronic switch is connected in parallel to both ends of the first switching resistor, and a second electronic switch is connected in parallel to both ends of the second switching resistor;

[0088] The resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

[0089] The specific circuit structure is the same as that provided in Example 1 and will not be described again here.

[0090] Example 4:

[0091] Embodiment 4 of the present invention provides a new energy vehicle, comprising the new energy vehicle insulation detection circuit described in Embodiment 1 of the present invention.

[0092] Example 5:

[0093] Embodiment 5 of the present invention provides a new energy vehicle, which adopts the new energy vehicle insulation detection method described in Embodiment 2 of the present invention.

[0094] Example 6:

[0095] Embodiment 6 of the present invention provides a new energy vehicle, including the new energy vehicle insulation detection system described in Embodiment 3 of the present invention.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A new energy vehicle insulation detection circuit, characterized by: A first voltage-dividing resistor, a first switching resistor, and a first sampling resistor are sequentially connected in series between the positive busbar and the vehicle body ground; a second voltage-dividing resistor, a second switching resistor, and a second sampling resistor are sequentially connected in series between the negative busbar and the vehicle body ground; A first end of a first sampling resistor is connected to a vehicle body ground, a second end of the first sampling resistor is used to be connected to a first sampling port of a processor, a first end of a second sampling resistor is connected to a vehicle body ground, and a second end of the second sampling resistor is used to be connected to a second sampling port of the processor; A first electronic switch is connected in parallel at both ends of the first switching resistor, a second electronic switch is connected in parallel at both ends of the second switching resistor, the resistance of the first voltage-dividing resistor and the second voltage-dividing resistor are in the megohm range, the resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

2. The new energy vehicle insulation detection circuit according to claim 1, characterized in that: The resistance values ​​of the first switching resistor and the second switching resistor are both in the kilo-ohm range or the hundred-ohm range.

3. The new energy vehicle insulation detection circuit according to claim 1, characterized in that: The first electronic switch and the second electronic switch are both optical MOS electronic switches.

4. The new energy vehicle insulation detection circuit according to claim 1, characterized in that: A first relay is connected between the first voltage-dividing resistor and the first switching resistor, a second relay is connected between the second voltage-dividing resistor and the second switching resistor, a first diode is connected in parallel at both ends of the first relay, and a second diode is connected in parallel at both ends of the second relay.

5. The new energy vehicle insulation detection circuit according to claim 1, characterized in that: The first voltage-dividing resistor includes a plurality of resistors with a resistance of 1 MΩ connected in series, and the second voltage-dividing resistor includes a plurality of resistors with a resistance of 1 MΩ connected in series.

6. The new energy vehicle insulation detection circuit according to any one of claims 1 to 5, characterized in that: The resistance value of the first voltage-dividing resistor is the same as the resistance value of the second voltage-dividing resistor, the resistance value of the first switching resistor is the same as the resistance value of the second switching resistor, and the resistance value of the first sampling resistor is the same as the resistance value of the second sampling resistor.

7. A new energy vehicle insulation detection method, characterized by: The new energy vehicle insulation detection circuit according to any one of claims 1 to 6 includes the following steps: Controlling the first electronic switch and the second electronic switch to be disconnected, and the processor collecting and obtaining the first positive bus sampling voltage and the first negative bus sampling voltage; If the positive bus sampling voltage is greater than the negative bus sampling voltage, the first electronic switch is closed, the second electronic switch remains open, and the processor collects again to obtain the second positive bus sampling voltage and the second negative bus sampling voltage; according to the first positive bus sampling voltage, the first negative bus sampling voltage, the second positive bus sampling voltage, the second negative bus sampling voltage, the first voltage dividing resistor, the first switching resistor, the first sampling resistor, the second voltage dividing resistor, the second switching resistor, and the second sampling resistor, the positive bus insulation resistance and the negative bus insulation resistance are obtained; If the positive bus sampling voltage is less than the negative bus sampling voltage, the second electronic switch is closed, the first electronic switch remains open, and the processor collects and obtains the third positive bus sampling voltage and the third negative bus sampling voltage again; the positive bus insulation resistance and the negative bus insulation resistance are obtained according to the first positive bus sampling voltage, the first negative bus sampling voltage, the third positive bus sampling voltage, the third negative bus sampling voltage, the first voltage dividing resistor, the first switching resistor, the first sampling resistor, the second voltage dividing resistor, the second switching resistor and the second sampling resistor.

8. The new energy vehicle insulation detection method according to claim 7, characterized in that: Based on the comparison between the positive busbar insulation resistance and the first preset value, it is determined whether there is a positive busbar insulation fault. Based on the comparison between the negative busbar insulation resistance and the second preset value, it is determined whether there is a negative busbar insulation fault.

9. A new energy vehicle insulation detection system, characterized by: Including the new energy vehicle insulation detection circuit and processor according to any one of claims 1 to 6; A first voltage-dividing resistor, a first switching resistor, and a first sampling resistor are sequentially connected in series between the positive busbar and the vehicle body ground; a second voltage-dividing resistor, a second switching resistor, and a second sampling resistor are sequentially connected in series between the negative busbar and the vehicle body ground; A first end of a first sampling resistor is connected to a vehicle body ground, a second end of the first sampling resistor is connected to a first sampling port of a processor, a first end of a second sampling resistor is connected to a vehicle body ground, and a second end of the second sampling resistor is connected to a second sampling port of the processor; A first electronic switch is connected in parallel to both ends of the first switching resistor, and a second electronic switch is connected in parallel to both ends of the second switching resistor; The resistance of the first voltage-dividing resistor is N1 times the resistance of the first switching resistor, and the resistance of the second voltage-dividing resistor is N2 times the resistance of the second switching resistor, where N1 and N2 are both constants greater than or equal to 10.

10. A new energy vehicle, characterized by: It includes the new energy vehicle insulation detection circuit described in any one of claims 1-6; or, adopts the new energy vehicle insulation detection method described in any one of claims 7-8; or, includes the new energy vehicle insulation detection system described in claim 9.

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