Insulation detection circuit and method for high-voltage loop of vehicle and high-voltage electrical system

Abstract

The invention relates to an insulation detection circuit for a high-voltage loop of a vehicle, which comprises a first bridge branch, a second bridge branch, a third bridge branch and a controller, and is characterized in that the first bridge branch and the second bridge branch are connected in series between a positive direct-current bus and a negative direct-current bus; the third bridge branch is connected to the two ends of the second bridge branch in parallel, and the controller is configured to selectively switch on the first bridge branch and / or the second bridge branch so that the insulation detection circuit can be in different connection states. The controller is further configured to detect voltage values at predetermined voltage dividing points in the third bridge branch in different connection states, and determine the insulation function condition in the vehicle high-voltage loop based on the detected voltage values. The invention also relates to an insulation detection method for a high-voltage circuit of a vehicle, and a high-voltage electrical system comprising the circuit.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and more specifically, to an insulation detection circuit and method for a vehicle high-voltage circuit, and a high-voltage electrical system including the insulation detection circuit. Background Art

[0002] With the popularity of new energy vehicles (such as electric vehicles or hybrid vehicles), the design requirements for the safety of new energy vehicles are becoming more and more stringent. For example, for electric vehicles, the voltage of their battery packs is as high as 400V or more. As the power battery pack ages, the insulation performance between the vehicle body and the battery pack will be damaged. If the insulation performance between the battery pack and the vehicle body fails, there is a risk of high-voltage electric shock to passengers. Therefore, it is necessary to accurately monitor the insulation performance between the vehicle's high-voltage circuit and the vehicle body in real time to ensure the safety of the in-vehicle equipment and passengers to the greatest extent possible.

[0003] The insulation detection function for the vehicle's high-voltage circuit is usually implemented using a bridge detection circuit. However, the existing detection scheme needs to consider the leakage current under the bridge arm withstand voltage test, so it is necessary to select a high-voltage switch device, and the bridge arm resistance value cannot be lower than a certain limit. The combination of a high-resistance bridge arm and the Y capacitor in the system will increase the acquisition time. A complete acquisition cycle is required to determine whether the system insulation function is abnormal through the calculated insulation resistance. This acquisition cycle usually takes more than 10 seconds, which is time-consuming and costly. Summary of the invention

[0004] In view of this, according to a first aspect of the present invention, an insulation detection circuit for a vehicle high voltage circuit is proposed, wherein the vehicle high voltage circuit comprises a positive DC bus connected to a positive electrode of a battery pack and a negative DC bus connected to a negative electrode of the battery pack.

[0005] The insulation detection circuit includes a first bridge branch, a second bridge branch, a third bridge branch and a controller, wherein the first bridge branch and the second bridge branch are connected in series between the positive DC bus and the negative DC bus, and the third bridge branch is connected in parallel to both ends of the second bridge branch.

[0006] The controller is configured to selectively connect the first bridge branch and / or the second bridge branch to put the insulation detection circuit in different connection states,

[0007] The controller is further configured to respectively detect the voltage value at a predetermined voltage dividing point in the third bridge branch under different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the detected voltage value.

[0008] Advantageously, the first bridge branch has a fixed resistor R1 and a switch K1 connected in series with each other, the second bridge branch has a fixed resistor R2 and a switch K2 connected in series with each other, and the third bridge branch has a fixed resistor R3 and a sampling resistor M2 connected in series with each other, the on-off of the switch K1 and the switch K2 is controlled by the controller, and the voltage value at the predetermined voltage dividing point is the voltage across the sampling resistor M2, wherein the controller is further configured to selectively control the on-off of the switch K1 and the switch K2 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M2 in different connection states.

[0009] Advantageously, the second bridge branch further comprises a sampling resistor M1 connected in series with the fixed resistor R2 and the switch K2, wherein the controller is further configured to determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1 and the sampling resistor M2 in different connection states.

[0010] Advantageously, the insulation detection circuit further comprises a fourth bridge branch having a switch K3, one end of the switch K3 being connected to a common node between the first bridge branch and the second bridge branch, and the other end being connected to the vehicle body ground, wherein the controller is further configured to selectively control the on and off of switches K1, K2 and K3 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1 and the sampling resistor M2 in different connection states.

[0011] Advantageously, the fourth bridge branch further comprises a sampling resistor M3 connected in series with the switch K3.

[0012] The controller is further configured to selectively control the on and off of switches K1, K2 and K3 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltages across the sampling resistors M1, M2 and M3 in different connection states.

[0013] Advantageously, the controller is further configured to perform the following operations:

[0014] Closing the switch K1 and the switch K3, and opening the switch K2, so that the insulation detection circuit enters the first connection state;

[0015] Reading a voltage U1_1 across the sampling resistor M1, a voltage U2_1 across the sampling resistor M2, and a voltage U3_1 across the sampling resistor M3 in the first connection state;

[0016] Determine whether the voltage value U1_1, the voltage value U2_1, and the voltage value U3_1 in the first connection state fall within respective first threshold ranges; and

[0017] If at least one of the voltage value U1_1, the voltage value U2_1, and the voltage value U3_1 in the first connection state does not fall within the corresponding first threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

[0018] Advantageously, the controller is further configured to perform the following operations when the voltage value U1_1, the voltage value U2_1 and the voltage value U3_1 in the first connection state all fall within their respective first threshold ranges:

[0019] Closing the switch K1, the switch K2 and the switch K3 to put the insulation detection circuit into a second connection state;

[0020] reading a voltage U1_2 across the sampling resistor M1, a voltage U2_2 across the sampling resistor M2, and a voltage U3_2 across the sampling resistor M3 in the second connection state;

[0021] Determine whether the voltage value U1_2, the voltage value U2_2, and the voltage value U3_2 in the second connection state fall within respective second threshold ranges; and

[0022] If at least one of the voltage value U1_2, the voltage value U2_2 and the voltage value U3_2 in the second connection state does not fall within the corresponding second threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

[0023] Advantageously, the controller is further configured to perform the following operations when the voltage value U1_2, the voltage value U2_2 or the voltage value U3_2 in the second connection state all fall within the respective second threshold ranges:

[0024] Closing the switch K2 and the switch K3 and opening the switch K1, so that the insulation detection circuit enters the third connection state;

[0025] Reading a voltage U1_2 across the sampling resistor M1, a voltage U2_3 across the sampling resistor M2, and a voltage U3_3 across the sampling resistor M3 in the third connection state;

[0026] Determine whether the voltage value U1_3, the voltage value U2_3, and the voltage value U3_3 in the third connection state fall within respective third threshold ranges; and

[0027] If at least one of the voltage value U1_3, the voltage value U2_3 and the voltage value U3_3 in the third connection state does not fall within the corresponding third threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

[0028] Advantageously, the controller is further configured to perform the following operations when the voltage value U1_3, the voltage value U2_3 or the voltage value U3_3 in the third connection state all fall within the respective third threshold ranges:

[0029] Calculate the insulation resistance Rp between the positive DC bus and the vehicle body ground and the insulation resistance Rn between the negative DC bus and the vehicle body ground based on the voltage value U2_1 across the sampling resistor M2 in the first connection state, the voltage value U2_3 across the sampling resistor M2 in the third connection state, and the total voltage provided by the battery pack;

[0030] reporting the insulation resistance Rp and the insulation resistance Rn to a vehicle control unit; and

[0031] When the insulation test stop instruction is received, the switch K1 , the switch K2 and the switch K3 are opened.

[0032] Advantageously, the controller is further configured to:

[0033] Calculating the insulation resistance Rp and the insulation resistance Rn based on the voltage value U2_1 across the sampling resistor M2 in the first connection state, the voltage value U2_2 across the sampling resistor M2 in the second connection state, and the total voltage provided by the battery pack; or

[0034] The insulation resistance Rp and the insulation resistance Rn are calculated based on the voltage value U2_2 across the sampling resistor M2 in the second connection state, the voltage value U2_3 across the sampling resistor M2 in the third connection state, and the total voltage provided by the battery pack.

[0035] Advantageously, the controller is further configured to perform a state self-check on the insulation detection circuit based on voltages across the sampling resistor M1 , the sampling resistor M2 , and the sampling resistor M3 in different connection states.

[0036] Advantageously, the switch K1 , the switch K2 and the switch K3 are electronic switches or relays.

[0037] According to a second aspect of the present invention, it also relates to a high voltage electrical system for a vehicle, the system comprising:

[0038] Vehicle high voltage circuits; and

[0039] Insulation detection circuit as described above.

[0040] According to a third aspect of the present invention, there is also provided a method for performing insulation detection on a vehicle high voltage circuit using the insulation detection circuit as described above, the method comprising the following steps:

[0041] selectively connecting the first bridge branch and / or the second bridge branch to put the insulation detection circuit in different connection states,

[0042] Under different connection states, respectively detecting the voltage values ​​at the predetermined voltage dividing points in the third bridge branch; and

[0043] An insulation function condition in the vehicle high-voltage circuit is determined based on the detected voltage value.

[0044] In summary, the insulation detection circuit for a vehicle high voltage circuit according to the present invention can achieve at least one of the following advantages:

[0045] -It has good voltage resistance, reduces the resistance value on the circuit bridge arm, and shortens the working time of insulation test;

[0046] - The three-stage measurement procedure improves the speed of determining the insulation status of the high-voltage circuit; and

[0047] - The simultaneous sampling of three signals, M1, M2 and M3, realizes the state self-check and data verification procedures during the test process, and improves the reliability of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] By incorporating the accompanying drawings and Figure 1 With reference to the specific embodiments used to illustrate certain principles of the present invention, other features and advantages of the method of the present invention will become clear or be described in more detail.

[0049] Figure 1 A circuit diagram of an insulation detection circuit for a vehicle high voltage circuit according to a first embodiment of the present invention is shown.

[0050] Figure 2 A circuit diagram of an insulation detection circuit for a vehicle high voltage circuit according to a second embodiment of the present invention is shown.

[0051] Figure 3 A circuit diagram of an insulation detection circuit for a vehicle high voltage circuit according to a third embodiment of the present invention is shown.

[0052] Figure 4 A circuit diagram showing an insulation detection circuit for a vehicle high voltage circuit according to a fourth embodiment of the present invention is shown.

[0053] Figure 5 A flow chart of a method for performing insulation testing on a vehicle high voltage circuit according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0054] The insulation detection circuit for a vehicle high voltage circuit according to the present invention will be described below with reference to the accompanying drawings and by way of example. In the following description, many specific details are set forth so that a person skilled in the art can more fully understand the present invention. However, it is obvious to a person skilled in the art that the present invention may be implemented without some of these specific details. Instead, any combination of the following features and elements may be considered to implement the present invention, regardless of whether they relate to different embodiments. Therefore, the following various aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims.

[0055] The applicant has found that the existing insulation detection scheme for the vehicle high-voltage circuit is generally to connect an insulation detection circuit in parallel at both ends of the vehicle battery pack. The insulation detection circuit usually uses an unbalanced bridge method to perform insulation detection.

[0056] Specifically, a bridge circuit is used to detect the insulation resistance Rp and Rn of the high-voltage positive busbar (connected to the positive electrode of the battery pack) to the vehicle body ground KL31 and the high-voltage negative busbar (connected to the negative electrode of the battery pack) to the vehicle body ground KL31. By judging whether these two insulation resistances Rp and Rn are within the set range, it is determined whether there is an abnormal insulation function. For example, if a certain insulation resistance is detected to be too low, it means that there is a greater risk of leakage in the corresponding high-voltage line. At this time, the battery controller can be notified to execute a fault response, such as warning of insulation faults, disconnecting high-voltage relays, etc. The insulation detection and insulation fault alarm mechanism can better monitor the insulation failure of the vehicle, thereby protecting the driver or passengers from the risk of electric shock.

[0057] However, the existing bridge detection scheme has the following defects:

[0058] -Since the leakage current under the bridge arm withstand voltage test needs to be considered, it is necessary to select high withstand voltage switching devices, and the bridge arm resistance value cannot be lower than a certain limit;

[0059] - The combination of high-resistance bridge arms and Y capacitors in the system will increase the acquisition time. A complete acquisition cycle is required to determine whether the system insulation function is abnormal through the calculated insulation resistance. This acquisition cycle usually takes more than 10 seconds, which is time-consuming and costly.

[0060] In order to solve the above defects in the existing insulation detection scheme, the present invention proposes a new insulation detection circuit for a vehicle high-voltage circuit. The circuit has good voltage resistance, and the selection of the resistance bridge arm is not limited by the insulation resistance requirements and the voltage resistance test requirements. A lower resistance value can be selected, which reduces the insulation resistance measurement time.

[0061] Figure 1 A circuit diagram of an insulation detection circuit for a vehicle high voltage circuit according to a first embodiment of the present invention is shown. The vehicle high voltage circuit includes a positive DC bus HV+ connected to the positive electrode of the battery pack and a negative DC bus HV- connected to the negative electrode of the battery pack.

[0062] The insulation detection circuit includes a first bridge branch B1, a second bridge branch B2, a third bridge branch B3 and a controller ( Figure 1 The first bridge branch B1 and the second bridge branch B2 are connected in series between the positive DC bus HV+ and the negative DC bus HV-, and the third bridge branch B3 is connected in parallel to both ends of the second bridge branch B2. The controller is configured to selectively connect the first bridge branch B1 and / or the second bridge branch B2 to put the insulation detection circuit in different connection states.

[0063] Specifically, the controller is configured to respectively detect the voltage value at a predetermined voltage dividing point in the third bridge branch B3 under different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the detected voltage value.

[0064] In the first embodiment, the first bridge branch B1 has a fixed resistor R1 and a switch K1 connected in series, the second bridge branch B2 has a fixed resistor R2 and a switch K2 connected in series, and the third bridge branch B3 has a fixed resistor R3 and a sampling resistor M2 connected in series. The on and off of the switches K1 and K2 are controlled by the controller, and the voltage value at the predetermined voltage dividing point is the voltage across the sampling resistor M2.

[0065] The controller can selectively control the on and off of the switch K1 and the switch K2 to put the insulation detection circuit in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M2 in different connection states. For example, if the voltage value across the sampling resistor M2 is within a preset range in the first connection state, the insulation test in other connection states can be further performed, or the test process can be directly terminated. On the contrary, if the voltage value is not within the preset range, it indicates that the insulation condition in the high-voltage circuit in the first connection state is abnormal.

[0066] Figure 2FIG. 2 shows a circuit diagram of an insulation detection circuit for a vehicle high voltage circuit according to a second embodiment of the present invention. Figure 1 The difference of the first embodiment in the embodiment is that, in addition to the sampling resistor M2 in the third bridge branch B3, the second bridge branch B2 also includes a sampling resistor M1 connected in series with the fixed resistor R2 and the switch K2.

[0067] Among them, the controller can determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1 and the sampling resistor M2 in different connection states. For example, if the voltage values ​​across the sampling resistors M1 and M2 in the first connection state are both within their respective preset ranges, insulation tests in other connection states can be further performed, or the test process can be directly terminated. On the contrary, if the voltage value across at least one of M1 and M2 is not within the preset range, it indicates that the insulation condition in the high-voltage circuit in the first connection state is abnormal. As a result, multiple sampling data can be verified with each other, which improves the reliability of the test results.

[0068] Figure 3 The circuit diagram of the insulation detection circuit for a vehicle high voltage circuit according to the third embodiment of the present invention is shown. The difference between the third embodiment and the first and second embodiments is that, in addition to the first, second and third bridge branches B1, B2 and B3, the insulation detection circuit in the third embodiment further includes a fourth bridge branch B4, and the fourth bridge branch B4 has a switch K3.

[0069] One end of the switch K3 is connected to a common node between the first bridge branch B1 and the second bridge branch B2 , and the other end of the switch K3 is connected to a vehicle body ground KL31 .

[0070] The controller can be configured to selectively control the on and off of switches K1, K2 and K3 to put the insulation detection circuit in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistors M1 and M2 in different connection states.

[0071] Figure 4 The circuit diagram of the insulation detection circuit for a vehicle high voltage circuit according to the fourth embodiment of the present invention is shown. The fourth embodiment is different from the third embodiment in that the fourth bridge branch B4 further has a sampling resistor M3 connected in series with the switch K3.

[0072] The controller may be configured to selectively control the on and off of the switch K1, the switch K2, and the switch K3 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1, the sampling resistor M2, and the sampling resistor M3 in different connection states. For example, if the voltage values ​​across the sampling resistors M1, M2, and M3 are all within their respective preset ranges in the first connection state, insulation tests in other connection states may be further performed, or the test process may be terminated directly. On the contrary, if the voltage value across at least one of the sampling resistors M1, M2, and M3 is not within the preset range, it indicates that the insulation condition in the high-voltage circuit in the first connection state is abnormal.

[0073] In this article, the switch K1 , the switch K2 and the switch K3 may be electronic switches (such as MOS tubes, triodes, etc.) or relays.

[0074] Figure 5 A flow chart of a method for performing insulation testing on a vehicle high voltage circuit according to an exemplary embodiment is shown. The method can be particularly used Figure 4 The insulation detection circuit shown in the following is performed. Figure 5 The operating steps of this method are described in detail.

[0075] When the controller receives an instruction to start the insulation detection function, it can execute a first insulation test procedure. In the first test procedure, the switches K1 and K3 are closed, and the switch K2 is opened, so that the insulation detection circuit enters a first connection state.

[0076] Subsequently, in the first connection state, a voltage U1_1 across the sampling resistor M1 , a voltage U2_1 across the sampling resistor M2 , and a voltage U3_1 across the sampling resistor M3 are read.

[0077] By judging whether the voltage value U1_1, the voltage value U2_1 and the voltage value U3_1 in the first connection state fall within their respective first threshold ranges, the insulation function status in the high-voltage circuit can be determined.

[0078] If at least one of the voltage values ​​U1_1, U2_1 and U3_1 in the first connection state does not fall within the corresponding first threshold range, it indicates that the insulation function in the vehicle high-voltage circuit is abnormal. Otherwise, it indicates that the preliminary insulation diagnosis result is normal, and the second insulation test procedure is further executed, or the test process can be directly terminated.

[0079] In the second test procedure, the switches K1, K2 and K3 are closed to put the insulation detection circuit into the second connection state, and then the voltage U1_2 across the sampling resistor M1, the voltage U2_2 across the sampling resistor M2 and the voltage U3_2 across the sampling resistor M3 are read in the second connection state.

[0080] By judging whether the voltage value U1_2, the voltage value U2_2 and the voltage value U3_2 in the second connection state fall within their respective second threshold ranges, the insulation function status in the high-voltage circuit can be verifiably determined.

[0081] If at least one of the voltage values ​​U1_2, U2_2 and U3_2 in the second connection state does not fall within the corresponding second threshold range, it indicates that the insulation function in the vehicle high-voltage circuit is abnormal. Otherwise, it indicates that the preliminary insulation diagnosis result is normal, and the third insulation test procedure is further executed, or the test process can be directly terminated.

[0082] In the third test procedure, the switches K2 and K3 are closed and the switch K1 is opened, so that the insulation detection circuit enters the third connection state. Then, the voltage U1_2 across the sampling resistor M1, the voltage U2_3 across the sampling resistor M2, and the voltage U3_3 across the sampling resistor M3 are read in the third connection state.

[0083] By judging whether the voltage values ​​U1_3, U2_3 and U3_3 in the third connection state fall within the third threshold range, the insulation function status in the high-voltage circuit can be verifiably determined.

[0084] Among them, if at least one of the voltage value U1_3, the voltage value U2_3 and the voltage value U3_3 in the third connection state does not fall within the corresponding third threshold range, it indicates that the insulation function in the vehicle high-voltage circuit is abnormal. Otherwise, it indicates that the preliminary insulation diagnosis result is normal. Subsequently, the insulation resistance values ​​Rp and Rn can be calculated based on the voltage across the sampling resistor M2 in different connection states (based on the conventional circuit voltage division principle and Ohm's law), and the calculated insulation resistance values ​​Rp and Rn are reported to the vehicle control unit. After reporting the insulation resistance value, the insulation detection circuit can continue to execute the next insulation test program until an insulation test stop instruction is received, and then switches K1, K2 and K3 can be disconnected to end the test program.

[0085] When determining the insulation resistance Rp and Rn, calculations can be performed based on the total voltage provided by the battery pack and any combination of the following parameters:

[0086] A voltage value U2_1 across the sampling resistor M2 in the first connection state and a voltage value U2_3 across the sampling resistor M2 in the third connection state;

[0087] The voltage value U2_1 across the sampling resistor M2 in the first connection state and the voltage value U2_2 across the sampling resistor M2 in the second connection state; or

[0088] The voltage value U2_2 across the sampling resistor M2 in the second connection state and the voltage value U2_3 across the sampling resistor M2 in the third connection state.

[0089] At the vehicle control unit, the final insulation function status can be determined based on the insulation resistance values ​​Rp and Rn. For example, if the insulation resistance values ​​Rp and Rn are greater than the preset resistance values, it indicates that the insulation condition in the high-voltage circuit is normal; otherwise, it indicates that the insulation function in the high-voltage circuit is abnormal.

[0090] Although in Figure 5 The embodiment of the present invention shows a complete operation flow including three test programs, but those skilled in the art can understand from the description in the specification that the three test programs can also be executed separately or partially. For example, the method can include only one or two of the first test program, the second test program and the third test program, and the operation order of each test program is not limited to the order listed in the above embodiment. For example, the third test program can be executed first, and then the second or first test program can be executed. All these variations fall within the protection scope of the present invention.

[0091] According to an optional embodiment, the insulation detection circuit / method is also special in that the insulation detection circuit can be self-checked based on the voltages across the sampling resistor M1, the sampling resistor M2, and the sampling resistor M3 in different connection states. For example, in the second connection state (switches K1, K2, and K3 are all closed), if the voltage across the sampling resistor M2 is zero, it indicates that the insulation detection circuit itself is abnormal.

[0092] In addition, an exemplary embodiment of the present invention further provides a high-voltage electrical system for a vehicle, characterized in that the system includes a vehicle high-voltage circuit; and an insulation detection circuit according to any one of the above embodiments of the present invention.

[0093] In summary, the insulation detection circuit for a vehicle high voltage circuit according to the present invention can achieve at least one of the following advantages:

[0094] -It has good voltage resistance, reduces the resistance value on the circuit bridge arm, and shortens the working time of insulation test;

[0095] - The three-stage measurement procedure improves the speed of determining the insulation status of the high-voltage circuit; and

[0096] - The simultaneous sampling of three signals, M1, M2 and M3, realizes the state self-check and data verification procedures during the test process, and improves the reliability of the test results.

[0097] Those skilled in the art will appreciate that the various steps of the method according to the present invention are not limited to being implemented in the order listed above. In addition, in the present invention, the terms "comprise" and "include" indicate that in addition to the steps directly and clearly stated in the specification and claims, the technical solution of the present application does not exclude the situation of having other steps that are not directly or clearly stated.

[0098] Although the present invention has been disclosed as above with preferred embodiments, the present invention is not limited thereto. Any changes and modifications made by any person skilled in the art without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention, and therefore the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. An insulation detection circuit for a vehicle high-voltage circuit, wherein the vehicle high-voltage circuit comprises a positive DC bus (HV+) connected to the positive electrode of a battery pack and a negative DC bus (HV-) connected to the negative electrode of the battery pack, characterized in that: The insulation detection circuit comprises a first bridge branch (B1), a second bridge branch (B2), a third bridge branch (B3) and a controller, wherein the first bridge branch (B1) and the second bridge branch (B2) are connected in series between the positive DC bus (HV+) and the negative DC bus (HV-), and the third bridge branch (B3) is connected in parallel to both ends of the second bridge branch (B2). The controller is configured to selectively connect the first bridge branch (B1) and / or the second bridge branch (B2) to put the insulation detection circuit in different connection states, The controller is further configured to respectively detect the voltage value at a predetermined voltage dividing point in the third bridge branch (B3) under different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the detected voltage value.

2. The insulation detection circuit according to claim 1, characterized in that: The first bridge branch (B1) comprises a fixed resistor R1 and a switch K1 connected in series, the second bridge branch (B2) comprises a fixed resistor R2 and a switch K2 connected in series, the third bridge branch (B3) comprises a fixed resistor R3 and a sampling resistor M2 connected in series, the on-off of the switches K1 and K2 are controlled by the controller, and the voltage value at the predetermined voltage dividing point is the voltage across the sampling resistor M2. The controller is further configured to selectively control the on and off of switches K1 and K2 to place the insulation detection circuit in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M2 in different connection states.

3. The insulation detection circuit according to claim 2, characterized in that: The second bridge branch (B2) further comprises a sampling resistor M1 connected in series with the fixed resistor R2 and the switch K2. The controller is further configured to determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1 and the sampling resistor M2 in different connection states.

4. The insulation detection circuit according to claim 3, characterized in that: The insulation detection circuit further includes a fourth bridge branch (B4) having a switch K3, one end of the switch K3 being connected to a common node between the first bridge branch (B1) and the second bridge branch (B2), and the other end being connected to the vehicle body ground (KL31). The controller is further configured to selectively control the on and off of switches K1, K2 and K3 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltage across the sampling resistor M1 and the sampling resistor M2 in different connection states.

5. The insulation detection circuit according to claim 4, characterized in that: The fourth bridge branch (B4) further comprises a sampling resistor M3 connected in series with the switch K3, The controller is further configured to selectively control the on and off of switches K1, K2 and K3 so that the insulation detection circuit is in different connection states, and determine the insulation function status in the vehicle high-voltage circuit based on the voltages across the sampling resistors M1, M2 and M3 in different connection states.

6. The insulation detection circuit according to claim 5, characterized in that: The controller is further configured to perform the following operations: Closing the switch K1 and the switch K3, and opening the switch K2, so that the insulation detection circuit enters the first connection state; Reading a voltage U1_1 across the sampling resistor M1, a voltage U2_1 across the sampling resistor M2, and a voltage U3_1 across the sampling resistor M3 in the first connection state; Determine whether the voltage value U1_1, the voltage value U2_1, and the voltage value U3_1 in the first connection state fall within respective first threshold ranges; and If at least one of the voltage value U1_1, the voltage value U2_1, and the voltage value U3_1 in the first connection state does not fall within the corresponding first threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

7. The insulation detection circuit according to claim 6, characterized in that: The controller is further configured to perform the following operations when the voltage value U1_1, the voltage value U2_1, and the voltage value U3_1 in the first connection state all fall within their respective first threshold ranges: Closing the switch K1, the switch K2 and the switch K3 to put the insulation detection circuit into a second connection state; reading a voltage U1_2 across the sampling resistor M1, a voltage U2_2 across the sampling resistor M2, and a voltage U3_2 across the sampling resistor M3 in the second connection state; Determine whether the voltage value U1_2, the voltage value U2_2, and the voltage value U3_2 in the second connection state fall within respective second threshold ranges; and If at least one of the voltage value U1_2, the voltage value U2_2 and the voltage value U3_2 in the second connection state does not fall within the corresponding second threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

8. The insulation detection circuit according to claim 7, characterized in that: The controller is further configured to perform the following operations when the voltage value U1_2, the voltage value U2_2 or the voltage value U3_2 in the second connection state all fall within the respective second threshold ranges: Closing the switch K2 and the switch K3 and opening the switch K1, so that the insulation detection circuit enters the third connection state; Reading a voltage U1_2 across the sampling resistor M1, a voltage U2_3 across the sampling resistor M2, and a voltage U3_3 across the sampling resistor M3 in the third connection state; Determine whether the voltage value U1_3, the voltage value U2_3, and the voltage value U3_3 in the third connection state fall within respective third threshold ranges; and If at least one of the voltage value U1_3, the voltage value U2_3 and the voltage value U3_3 in the third connection state does not fall within the corresponding third threshold range, it indicates that an insulation function abnormality occurs in the vehicle high-voltage circuit.

9. The insulation detection circuit according to claim 8, characterized in that: The controller is further configured to perform the following operations when the voltage value U1_3, the voltage value U2_3 or the voltage value U3_3 in the third connection state all fall within the respective third threshold ranges: Calculating the insulation resistance Rp between the positive DC bus (HV+) and the vehicle body ground (KL31) and the insulation resistance Rn between the negative DC bus (HV-) and the vehicle body ground (KL31) based on the voltage value U2_1 across the sampling resistor M2 in the first connection state, the voltage value U2_3 across the sampling resistor M2 in the third connection state, and the total voltage provided by the battery pack; reporting the insulation resistance Rp and the insulation resistance Rn to a vehicle control unit; and When the insulation test stop instruction is received, the switch K1 , the switch K2 and the switch K3 are opened.

10. The insulation detection circuit according to claim 9, characterized in that: The controller is further configured to: Calculating the insulation resistance Rp and the insulation resistance Rn based on the voltage value U2_1 across the sampling resistor M2 in the first connection state, the voltage value U2_2 across the sampling resistor M2 in the second connection state, and the total voltage provided by the battery pack; or The insulation resistance Rp and the insulation resistance Rn are calculated based on the voltage value U2_2 across the sampling resistor M2 in the second connection state, the voltage value U2_3 across the sampling resistor M2 in the third connection state, and the total voltage provided by the battery pack.

11. The insulation detection circuit according to any one of claims 5 to 8, characterized in that: The controller is further configured to perform a state self-check on the insulation detection circuit based on voltages across the sampling resistor M1 , the sampling resistor M2 , and the sampling resistor M3 in different connection states.

12. The insulation detection circuit according to any one of claims 5 to 10, characterized in that: The switch K1 , the switch K2 and the switch K3 are electronic switches or relays.

13. A high voltage electrical system for a vehicle, characterized in that: The system includes: Vehicle high voltage circuits; and An insulation detection circuit according to any one of claims 1 to 12.

14. A method for performing insulation detection on a vehicle high voltage circuit using the insulation detection circuit according to any one of claims 1 to 12, characterized in that: The method comprises the following steps: selectively connecting the first bridge branch (B1) and / or the second bridge branch (B2) to place the insulation detection circuit in different connection states, Under different connection states, respectively detecting the voltage values ​​at the predetermined voltage dividing points in the third bridge branch (B3); as well as An insulation function condition in the vehicle high-voltage circuit is determined based on the detected voltage value.

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