Insulation impedance detection circuit and device for battery module

Abstract

An insulation impedance detection circuit and device for a battery module. The insulation impedance detection circuit comprises: a detection port, and an insulation impedance to be measured (Rx) between the detection port and ground, wherein the detection port of the insulation resistance detection circuit is connected to a positive electrode of any battery cell in the battery module; and a processor, separately connected to a first switch (K1), a second switch (K2) and a voltage sampling unit, and configured to determine, on the basis of a voltage sampled by the voltage sampling unit, an impedance value of the insulation impedance to be measured (Rx) and a voltage value (Vx) of the detection port in the process of controlling the connection or disconnection of the first switch (K1) and the second switch (K2), and when it is determined, on the basis of the impedance value of the insulation impedance to be measured (Rx), that the insulation impedance of any battery cell is abnormal, determine, on the basis of the voltage value (Vx) of the detection port, a cell index of any battery cell in the battery module.

Description

An insulation resistance detection circuit and insulation resistance detection device for a battery module

[0001] Cross-reference of related applications

[0002] This disclosure is based on and claims priority to Chinese Patent Application No. 2024119242720, filed on December 25, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of impedance detection technology, and in particular to an insulation impedance detection circuit and insulation impedance detection device for a battery module. Background Technology

[0004] A battery cell is the most basic component of a battery, typically an electrochemical device encapsulated in a metal casing. It's the unit that stores and releases electrical energy, converting chemical energy into electrical energy through a chemical reaction. A battery cell usually consists of a positive electrode, a negative electrode, a separator, and an electrolyte. Common types of battery cells include lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries. When battery cells are used in lithium-ion, nickel-metal hydride, or lead-acid batteries, multiple cells are usually connected in series to form a battery module, which provides higher voltage and capacity.

[0005] To ensure the proper functioning of the battery module, insulation resistance testing is necessary. Currently, insulation resistance testing typically measures the insulation resistance of the entire battery module to determine if any abnormalities exist. However, since a battery module contains multiple cells, testing the insulation resistance of the entire module makes it difficult to pinpoint the cells with abnormal insulation resistance within the module itself. Summary of the Invention

[0006] This disclosure provides an insulation impedance detection circuit and an insulation impedance detection device for a battery module, which can accurately identify cells with abnormal insulation impedance in the battery module.

[0007] This disclosure provides an insulation impedance detection circuit for a battery module, the battery module comprising multiple cells connected in series, the insulation impedance detection circuit comprising: a detection port, the insulation impedance to ground of the detection port to be measured, a first switch, a second switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage sampling unit, and a processor;

[0008] One end of the first resistor and one end of the second resistor are connected to the positive terminal of the battery module, and the other end of the first resistor is connected via the first switch to the node between the insulation impedance to be measured and the ground terminal.

[0009] The other end of the second resistor is connected to one end of the fourth resistor via the node, and the other end of the fourth resistor is connected to the negative terminal of the battery module; the sampling terminal of the voltage sampling unit is connected to both ends of the fourth resistor or the second resistor;

[0010] One end of the third resistor is connected to the node via the second switch, and the other end of the third resistor is connected to the negative terminal of the battery module.

[0011] The detection port of the insulation impedance detection circuit is connected to the positive terminal of any cell in the battery module.

[0012] The processor is connected to the first switch, the second switch, and the voltage sampling unit, respectively, and is configured to determine the impedance value of the insulation impedance to be tested and the voltage value of the detection port based on the voltage sampled by the voltage sampling unit during the process of controlling the first switch and the second switch to open or close; when it is determined that the insulation impedance of any cell is abnormal based on the impedance value of the insulation impedance to be tested, the processor determines the cell number of any cell in the battery module based on the voltage value of the detection port.

[0013] In some embodiments, the insulation resistance detection circuit further includes: a third switch;

[0014] The connection point between the other end of the second resistor and one end of the fourth resistor is connected to the node via the third switch;

[0015] The processor, connected to the third switch, is further configured to control the third switch to engage during the engagement or disengagement of the first switch and the second switch, and to control the third switch to disengage after the voltage is sampled by the voltage sampling unit.

[0016] In some embodiments, the detection port of the insulation resistance detection circuit is detachably connected to the positive terminal of each cell in the battery module.

[0017] The processor is also configured to determine whether the insulation impedance of each battery cell is abnormal.

[0018] In some embodiments, the processor is further configured to control the first switch to engage and control the second switch to disengage, thereby acquiring the first voltage sampled by the voltage sampling unit;

[0019] The first switch is controlled to open and the second switch is controlled to close, thereby acquiring the second voltage sampled by the voltage sampling unit;

[0020] Based on the first voltage and the second voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

[0021] In some embodiments, the processor is further configured to control the first switch to open and control the second switch to open, and to acquire the third voltage sampled by the voltage sampling unit;

[0022] By controlling one of the first switch and the second switch to be engaged and the other switch to be disengaged, the fourth voltage sampled by the voltage sampling unit is obtained;

[0023] Based on the third voltage and the fourth voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

[0024] In some embodiments, the first switch includes a first relay, and the second switch includes a second relay;

[0025] The other end of the first resistor is connected to the node between the insulation impedance to be measured and the ground terminal via the normally open contact of the first relay;

[0026] One end of the third resistor is connected to the node via the normally open contact of the second relay;

[0027] The processor is connected to the coil of the first relay and the coil of the second relay.

[0028] In some embodiments, the processor is further configured to determine that the insulation impedance of any cell is abnormal if the impedance value of the insulation impedance to be measured is less than a preset impedance threshold.

[0029] If the impedance value of the insulation impedance to be tested is greater than or equal to the preset impedance threshold, then the insulation impedance of any cell is determined to be normal.

[0030] In some embodiments, the processor is further configured to acquire the voltage value of a single cell in the battery module, divide the voltage value of the detection port by the voltage value of the single cell to obtain a target quotient, and determine the number of cells in the battery module to which any cell belongs based on the target quotient.

[0031] In some embodiments, the voltage sampling unit includes: an impedance matching module, an operational amplifier, and a voltage divider filter module;

[0032] The input terminal of the impedance matching module is connected to both ends of the fourth resistor or the second resistor, and the output terminal of the impedance matching module is connected to the non-inverting input terminal and the inverting input terminal of the operational amplifier, respectively. The impedance matching module is configured to perform impedance matching on the differential voltage signal across the resistor and then input it to the operational amplifier.

[0033] The output terminal of the operational amplifier is connected to the input terminal of the voltage divider filter module. The operational amplifier is configured to perform op-amp follower operation on the differential voltage signal and output the corresponding single-ended voltage signal.

[0034] The voltage divider filter module is configured to perform voltage divider filtering on the single-ended voltage signal and output the sampled voltage.

[0035] This disclosure also provides an insulation impedance detection device for a battery module, which uses the insulation impedance detection circuit described above to perform insulation impedance detection on the battery module. Attached Figure Description

[0036] Figure 1 is a circuit diagram of an insulation impedance detection circuit for a battery module disclosed in an embodiment of this disclosure;

[0037] Figure 2 is an insulation impedance detection circuit diagram of another battery module disclosed in an embodiment of this disclosure;

[0038] Figure 3 is a circuit diagram of a voltage sampling unit disclosed in an embodiment of this disclosure. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present disclosure.

[0040] In the description of the embodiments of this disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this disclosure.

[0041] In the description of the embodiments of this disclosure, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure based on the specific circumstances.

[0042] In related technologies, insulation impedance detection of battery modules typically involves measuring the insulation impedance of the entire battery module, specifically the insulation impedance of the module's positive terminal to ground, to determine if the insulation impedance of the battery module is abnormal. However, since a battery module contains multiple cells, measuring the insulation impedance of the entire battery module makes it difficult to pinpoint the cells with abnormal insulation impedance within the module. Therefore, this disclosure provides an insulation impedance detection circuit for battery modules that can accurately identify cells with abnormal insulation impedance within the battery module. The insulation impedance detection circuit is shown in Figure 1.

[0043] In this embodiment of the disclosure, the battery module (which may be referred to as the battery terminal) includes multiple cells connected in series. In Figure 1, BAT+ represents the positive terminal of the battery module, and 0V represents the negative terminal of the battery module (i.e., the reference ground). The battery module may include 18 3.3V cells connected in series or 16 3.3V cells connected in series, and the specific configuration is not limited here.

[0044] The insulation impedance detection circuit includes: a detection port, the insulation impedance Rx to be measured relative to the detection port and ground, a first switch K1, a second switch K2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a voltage sampling unit, and a processor (not shown in Figure 1). One end of the first resistor R1 and one end of the second resistor R2 are connected to the positive terminal BAT+ of the battery module. The other end of the first resistor R1 is connected via the first switch K1 to the node between the insulation impedance Rx to be measured and the ground terminal; that is, the first resistor R1 is connected to this node when the first switch K1 is activated. This ground terminal can be signal ground, chassis ground, or protective ground, etc., and is not specifically limited here.

[0045] The other end of the second resistor R2 is connected to one end of the fourth resistor R4 via a node. The other end of the fourth resistor R4 is connected to the negative terminal (0V) of the battery module. The sampling terminal of the voltage sampling unit is connected to either the fourth resistor R4 or the second resistor R2. It can be understood that when the sampling terminal of the voltage sampling unit is connected to the fourth resistor R4, the voltage sampling unit samples the voltage across the fourth resistor R4; when the sampling terminal of the voltage sampling unit is connected to the second resistor R2, the voltage sampling unit samples the voltage across the second resistor R2. In this embodiment, the insulation impedance detection circuit will be described using the voltage sampling unit sampling the voltage across the fourth resistor R4 as an example. In this insulation impedance detection circuit, the voltage sampling unit can also sample the voltage across the second resistor R2, which will not be elaborated further below.

[0046] In this circuit, one end of the third resistor R3 is connected to the node via the second switch K2, and the other end of the third resistor R3 is connected to the negative terminal (0V) of the battery module. The detection port of the insulation impedance detection circuit is connected to the positive terminal of any cell in the battery module. It can be understood that the insulation impedance Rx measured by this detection port relative to ground is the detected insulation impedance of that cell relative to ground, and the voltage Vx at this detection port is the detected voltage of that cell relative to ground.

[0047] The processor, connected to the first switch K1, the second switch K2, and the voltage sampling unit, is further configured to determine the impedance value of the insulation impedance Rx to be measured and the voltage value Vx at the detection port based on the voltage sampled by the voltage sampling unit during the process of controlling the opening or closing of the first switch K1 and the second switch K2. In some embodiments, based on the principle that the node current is 0A, i.e., the input current of the node equals the output current, multiple node current equations containing the impedance value of the insulation impedance to be measured and the voltage value at the detection port can be established by controlling the opening or closing of the first switch K1 and the second switch K2, based on the voltage sampled by the voltage sampling unit, to obtain the impedance value of the insulation impedance to be measured and the voltage value at the detection port. The processor can be a microcontroller unit (MCU) or a digital signal processor (DSP), and the specific implementation is not limited here.

[0048] After obtaining the impedance value of the insulation impedance to be measured and the voltage value of the detection port, the processor can determine whether the insulation impedance of any cell is abnormal based on the impedance value of the insulation impedance to be measured. In some embodiments, in order to enable the cell to effectively insulate itself from ground, the insulation impedance of the cell generally needs to be greater than a preset impedance threshold. The preset impedance threshold can be 10Ω or 20Ω, and is not specifically limited here. If the impedance value of the insulation impedance to be measured is less than the preset impedance threshold, it is determined that the insulation impedance of any cell is abnormal; if the impedance value of the insulation impedance to be measured is greater than or equal to the preset impedance threshold, it is determined that the insulation impedance of any cell is normal.

[0049] When an insulation impedance abnormality is determined for any cell based on the impedance value of the insulation impedance under test, the cell's number within the battery module is determined based on the voltage value at the detection port. In other words, when a cell is determined to have an insulation impedance abnormality, its location within the battery module can be determined. In some embodiments, the processor can acquire the voltage value of a single cell within the battery module. It is understood that the voltage value of each cell in the battery module is the same, and the voltage value of a single cell can be 3.3V or 4.5V; no specific limitation is made here. A target quotient is obtained by dividing the voltage value at the detection port by the voltage value of a single cell, and the cell's number within the battery module is determined based on this target quotient. The voltage value detected at the detection port is divided by the voltage value of a single cell, and rounded up to the nearest whole number to determine the number of cells in the battery module where the insulation impedance is abnormal. For example, if the voltage value of a single cell is 3.3V and the voltage value at the detection port is 6.5V, the target quotient is approximately 1.97. This indicates that the cell in question belongs to the second cell in the battery module, and the detection port is connected to the positive terminal of the second cell (or the negative terminal of the third cell).

[0050] As can be seen, in this embodiment of the present disclosure, by connecting the detection port of the insulation impedance detection circuit to the positive terminal of any cell in the battery module, the processor, during the process of controlling the opening or closing of the first switch and the second switch, determines the impedance value of the insulation impedance to be measured based on the voltage sampled by the voltage sampling unit and the voltage value of the detection port, which are the insulation impedance value of any cell and the corresponding voltage value of any cell in the battery module; when the insulation impedance of any cell is abnormal, the cell number of any cell in the battery module is determined based on the voltage value of the detection port, thus accurately identifying the cell with abnormal insulation impedance in the battery module.

[0051] As shown in Figure 2, in this embodiment of the invention, the insulation impedance detection circuit further includes: a third switch K3; one end of the second resistor R2 is connected to the positive terminal BAT+ of the battery module; the other end of the second resistor R2 is connected in series with one end of the fourth resistor R4; the connection point between the other end of the second resistor R2 and one end of the fourth resistor R4 is connected to a node via the third switch K3; a processor, connected to the third switch K3, is configured to control the third switch K3 to engage during the engagement or disengagement of the first switch K1 and the second switch K2, and to control the third switch K3 to disengage after the voltage sampling unit has sampled the voltage. That is, the processor controls the third switch K3 to engage during the insulation impedance detection process, incorporating the second resistor R2 and the fourth resistor R4 into the node between the insulation impedance to be measured and the ground terminal, so as to correlate the voltage sampled by the voltage sampling unit with the impedance value of the insulation impedance to be measured and the voltage value of the detection port to obtain the corresponding node current equation; after the detection is completed, controlling the third switch K3 to disengage can effectively prevent the current of the second resistor R2 from flowing back into the battery module through the node and the detection port, thus improving the safety of the battery module.

[0052] In this embodiment of the disclosure, the detection port of the insulation impedance detection circuit is detachably connected to the positive terminal of each cell in the battery module, one by one; for example, the detection port can be connected from the positive terminal of the first cell to the positive terminal of the last cell; the processor is further configured to determine the impedance value of the corresponding insulation impedance to be measured when the detection port is connected to the positive terminal of the cell, and determine whether the insulation impedance of the cell is abnormal based on the impedance value of the insulation impedance to be measured, one by one; the insulation impedance of each cell in the battery module can be comprehensively detected, thereby improving the accuracy of insulation impedance detection in the battery module.

[0053] In some embodiments, the detection function of the insulation impedance detection circuit is based on the following principle: the processor is further configured to control the first switch K1 to close and the second switch K2 to open, thereby acquiring the first voltage V1 sampled by the voltage sampling unit, which is the voltage across the fourth resistor R4; based on the principle that the node current is 0, the node current equation can be obtained at this time as follows:

[0054] Where V BAT Vx is the voltage of the battery module, Vx is the voltage of the detection port, and Rx is the insulation resistance to be measured.

[0055] The first switch K1 is opened and the second switch K2 is closed to obtain the second voltage V2 sampled by the voltage sampling unit. Based on the principle that the node current is 0, the node current equation can be obtained at this time as follows:

[0056] Based on the first voltage and the second voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

[0057] Based on Equations 1 and 2, we can obtain:

[0058] In this embodiment of the disclosure, the detection principle of the insulation impedance detection circuit can also be as follows: the processor is further configured to control the first switch K1 to open and control the second switch K2 to open, thereby acquiring the third voltage V3 sampled by the voltage sampling unit; at this time, the obtained node current equation is:

[0059] By controlling either the first switch K1 or the second switch K2 to be closed and the other switch to be open, the fourth voltage V4 sampled by the voltage sampling unit is obtained; when the first switch K1 is closed and the second switch K2 is open, the obtained node current equation is Equation 1 above; when the first switch K1 is open and the second switch K2 is closed, the obtained node current equation is Equation 2 above; based on the third voltage and the fourth voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

[0060] It is understandable that the first switch K1 and the second switch K2 can be controlled to open and close through various control methods, and then the impedance value of the insulation impedance to be measured and the voltage value of the detection port can be obtained based on the voltage sampling unit.

[0061] In some embodiments, the first switch K1 includes a first relay, and the second switch K2 includes a second relay; the other end of the first resistor R1 is connected via the normally open contact of the first relay to a node between the insulation impedance to be measured and the ground terminal; one end of the third resistor R3 is connected via the normally open contact of the second relay to this node; and a processor is connected to the coils of the first and second relays. When the processor does not supply power to the coil of the relay, the normally open contact of the relay remains open; when the processor supplies power to the coil of the relay, the normally open contact of the relay closes, thereby realizing the switching function of the relay.

[0062] In this embodiment, the voltage sampling unit includes: an impedance matching module 301, an operational amplifier IC, and a voltage divider filter module 302; wherein, VPE+ is the voltage at the positive terminal of the resistor, VPE- is the voltage at the negative terminal of the resistor, and VPE+ and VPE- form a differential voltage signal; the input terminal of the impedance matching module 301 is the sampling terminal of the voltage sampling unit, the input terminal of the impedance matching module 301 is connected to both ends of the fourth resistor or the second resistor, and the output terminal of the impedance matching module 301 is respectively connected to the non-inverting input terminal and the inverting input terminal of the operational amplifier IC; wherein, the impedance matching module 301 includes: resistors R5 and R6, diodes D1 and D2. The resistors are diodes D3 and D4, capacitors C1 and C2; the impedance matching module 301 is configured to perform impedance matching on the differential voltage signal across the resistors and then input it to the operational amplifier IC; the output terminal of the operational amplifier IC is connected to the input terminal of the voltage divider filter module 302, and the operational amplifier IC is configured to perform op-amp follower operation on the differential voltage signal and output the corresponding single-ended voltage signal; the voltage divider filter module 302 includes resistors R7 and R8, diodes D5 and D6, and capacitor C3, and is configured to perform voltage divider filtering on the single-ended voltage signal and output the sampled voltage AD_VPE (AD sampling voltage).

[0063] In one feasible approach, the insulation impedance detection circuit can be calibrated by measuring the impedance value of the insulation to be measured and the voltage value of the detection port, based on the impedance value detected by the insulation impedance detection circuit. In some embodiments, impedances of different values ​​can be connected in series between the positive terminal and ground of different battery cells to test the actual battery cell voltage and the actual insulation impedance, as well as the insulation impedance to be measured and the voltage of the detection port detected by the processor. The insulation impedance detection range is generally 0–198 kΩ, and these different impedance values ​​can be resistors of 0.000 kΩ, 0.010 kΩ, 0.0468 kΩ, 0.910 kΩ, 20.45 kΩ, 49.50 kΩ, or 198 kΩ. For example, connecting a 0.000 kΩ resistor in series between the positive terminal and ground of different battery cells yields the following data:

[0064] Wherein, the theoretical Rx is the actual resistance between the positive terminal and ground of different battery cells connected in series, the theoretical Vx is the actual voltage on the battery cell, the displayed Rx is the insulation impedance detected by the insulation impedance detection circuit, and the displayed Vx is the voltage at the detection port detected by the insulation impedance detection circuit; the sampling accuracy is the displayed value divided by the theoretical value. It can be seen that the sampling accuracy of the insulation impedance from 1 to 198 kΩ is ≥96%; the corresponding sampling accuracy of the battery cell voltage is ≥95%, and both the insulation impedance and battery cell voltage sampling accuracies meet the requirements.

[0065] Similarly, the maximum deviation between the displayed Rx and the theoretical Rx can be obtained, as well as the maximum value of the insulation impedance within the measurement range; the sampling linearity of the insulation impedance can be obtained as 1 - the maximum deviation value divided by the maximum value, and the sampling linearity of the insulation impedance is ≥97%; correspondingly, the sampling linearity of the cell voltage is ≥97%, and the sampling linearity of both the insulation impedance and the cell voltage meets the requirements.

[0066] Since battery modules may be used in high and low temperature environments, such as S 3 The operating temperature range for lithium batteries is 0-40℃. In this case, the insulation impedance detection circuit can be placed in high and low temperature environments to verify the circuit. The method for checking the sampling accuracy and linearity is similar to that described above. It can be seen that the sampling accuracy of insulation impedance and cell voltage both meet the requirements in both high and low temperature environments, and the sampling linearity of insulation impedance and cell voltage both meet the requirements.

[0067] This disclosure also provides an insulation impedance detection device for a battery module, which uses the above-described insulation impedance detection circuit to perform insulation impedance detection on the battery module.

[0068] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0069] The above embodiments are only used to illustrate the technical solutions of the embodiments of this disclosure, and are not intended to limit them. Although the embodiments of this disclosure have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure, and they should all be covered within the scope of the claims and specification of the embodiments of this disclosure. Industrial applicability

[0070] By connecting the detection port of the insulation impedance detection circuit to the positive terminal of any cell in the battery module, the processor, during the process of controlling the opening or closing of the first and second switches, determines the impedance value of the insulation impedance to be measured based on the voltage sampled by the voltage sampling unit and the voltage value of the detection port. This value represents the insulation impedance value of any cell and the corresponding voltage value of any cell in the battery module. When the insulation impedance of any cell is abnormal, the number of cells in the battery module to which any cell belongs is determined based on the voltage value of the detection port, thus accurately identifying the cells with abnormal insulation impedance in the battery module.

Claims

1. An insulation resistance detection circuit for a battery module, the battery module comprising multiple cells connected in series, the insulation resistance detection circuit comprising: The system includes a detection port, the insulation impedance of the detection port to ground, a first switch, a second switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage sampling unit, and a processor. One end of the first resistor and one end of the second resistor are connected to the positive terminal of the battery module, and the other end of the first resistor is connected via the first switch to the node between the insulation impedance to be measured and the ground terminal. The other end of the second resistor is connected to one end of the fourth resistor via the node, and the other end of the fourth resistor is connected to the negative terminal of the battery module; the sampling terminal of the voltage sampling unit is connected to both ends of the fourth resistor or the second resistor; One end of the third resistor is connected to the node via the second switch, and the other end of the third resistor is connected to the negative terminal of the battery module. The detection port of the insulation impedance detection circuit is connected to the positive terminal of any cell in the battery module. The processor is connected to the first switch, the second switch, and the voltage sampling unit, respectively, and is configured to determine the impedance value of the insulation impedance to be tested and the voltage value of the detection port based on the voltage sampled by the voltage sampling unit during the process of controlling the first switch and the second switch to open or close; when it is determined that the insulation impedance of any cell is abnormal based on the impedance value of the insulation impedance to be tested, the processor determines the cell number of any cell in the battery module based on the voltage value of the detection port.

2. The insulation resistance detection circuit according to claim 1, wherein, It also includes: a third switch; The connection point between the other end of the second resistor and one end of the fourth resistor is connected to the node via the third switch; The processor, connected to the third switch, is further configured to control the third switch to engage during the engagement or disengagement of the first switch and the second switch, and to control the third switch to disengage after the voltage is sampled by the voltage sampling unit.

3. The insulation resistance detection circuit according to claim 1 or 2, wherein, The detection port of the insulation impedance detection circuit is detachably connected to the positive terminal of each cell in the battery module. The processor is also configured to determine whether the insulation impedance of each battery cell is abnormal.

4. The insulation resistance detection circuit according to any one of claims 1-3, wherein, The processor is further configured to control the first switch to engage and control the second switch to disengage, thereby acquiring the first voltage sampled by the voltage sampling unit. The first switch is controlled to open and the second switch is controlled to close, thereby acquiring the second voltage sampled by the voltage sampling unit; Based on the first voltage and the second voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

5. The insulation resistance detection circuit according to any one of claims 1-4, wherein, The processor is further configured to control the first switch to open and control the second switch to open, and to acquire the third voltage sampled by the voltage sampling unit. By controlling one of the first switch and the second switch to be engaged and the other switch to be disengaged, the fourth voltage sampled by the voltage sampling unit is obtained; Based on the third voltage and the fourth voltage, the impedance value of the insulation impedance to be measured and the voltage value of the detection port are determined.

6. The insulation resistance detection circuit according to any one of claims 1-5, wherein, The first switch includes a first relay, and the second switch includes a second relay; The other end of the first resistor is connected to the node between the insulation impedance to be measured and the ground terminal via the normally open contact of the first relay; One end of the third resistor is connected to the node via the normally open contact of the second relay; The processor is connected to the coil of the first relay and the coil of the second relay.

7. The insulation resistance detection circuit according to any one of claims 1-6, wherein, The processor is further configured to determine that the insulation impedance of any cell is abnormal if the impedance value of the insulation impedance to be measured is less than a preset impedance threshold. If the impedance value of the insulation impedance to be tested is greater than or equal to the preset impedance threshold, then the insulation impedance of any cell is determined to be normal.

8. The insulation resistance detection circuit according to any one of claims 1-7, wherein, The processor is further configured to acquire the voltage value of a single cell in the battery module, divide the voltage value of the detection port by the voltage value of the single cell to obtain a target quotient, and determine the number of cells in the battery module to which any cell belongs based on the target quotient.

9. The insulation resistance detection circuit according to any one of claims 1-8, wherein, The voltage sampling unit includes: an impedance matching module, an operational amplifier, and a voltage divider filter module; The input terminal of the impedance matching module is connected to both ends of the fourth resistor or the second resistor, and the output terminal of the impedance matching module is connected to the non-inverting input terminal and the inverting input terminal of the operational amplifier, respectively. The impedance matching module is configured to perform impedance matching on the differential voltage signal across the resistor and then input it to the operational amplifier. The output terminal of the operational amplifier is connected to the input terminal of the voltage divider filter module. The operational amplifier is configured to perform op-amp follower operation on the differential voltage signal and output the corresponding single-ended voltage signal. The voltage divider filter module is configured to perform voltage divider filtering on the single-ended voltage signal and output the sampled voltage.

10. An insulation impedance detection device for a battery module, wherein the insulation impedance detection circuit described in any one of claims 1 to 9 is used to perform insulation impedance detection on the battery module.

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