Insulation detection circuit

Abstract

The utility model belongs to the technical field of detection, and mainly relates to an insulation detection circuit, which comprises at least one detection circuit electrically connected with different voltage platforms, and the detection circuit is a balanced bridge. The balanced bridge comprises a positive ground circuit and a negative ground circuit which are in complementary design, the positive ground circuit comprises a first insulation resistor Rp and a first sampling resistor R2 connected in parallel with the first insulation resistor Rp, and the negative ground circuit comprises a second insulation resistor Rn and a second sampling resistor R4 connected in parallel with the second insulation resistor Rn. The first sampling resistor R2 and the second sampling resistor R4 are respectively connected in series with a first voltage dividing selector and a second voltage dividing selector; different divider resistors are adopted for voltage division or the first sampling resistor and the second sampling resistor with different resistance values are adopted for voltage division, so that an existing insulation detection circuit breaks through the technical barrier that multi-voltage platform insulation detection cannot be achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of detection, and in particular relates to an insulation detection circuit. Background Art

[0002] Compared to traditional vehicles, electric vehicles are equipped with many high-voltage components (including ESS, DC-DC, and motors). Collisions or component aging can degrade the insulation performance of the voltage platform (specifically the battery pack), increasing chassis potential, potentially interfering with onboard devices and the ECU, and even causing a fire. Therefore, enhanced insulation status monitoring is necessary to ensure safety. Insulation testing of the power battery system's ESS has become a critical function within the BMS.

[0003] Existing technologies typically employ direct multimeter testing or on-board balanced or unbalanced bridge testing. Unbalanced bridge testing suffers from large relative errors, significant influence from ground capacitance, and slow detection speed, leaving more room for development in balanced bridge testing. However, existing balanced bridge testing technology often suffers from inaccurate battery pack insulation monitoring and inability to adapt to varying voltage platforms, leading to misjudgments or missed detections in practical applications.

[0004] Based on this, there is an urgent need for an insulation detection circuit suitable for different voltage platforms to solve the defects of the existing technology. Utility Model Content

[0005] The purpose of the utility model is to provide an insulation detection circuit that can be applicable to different voltage platforms in view of the fact that existing insulation detection devices cannot be applicable to different voltage platforms.

[0006] To achieve the above purpose, the following technical solutions are adopted:

[0007] An insulation detection circuit includes at least one detection circuit electrically connected to different voltage platforms, the detection circuit being a balanced bridge;

[0008] The balanced bridge includes a positive ground circuit and a negative ground circuit of complementary design. The positive ground circuit includes a first insulation resistor Rp and a first sampling resistor R2 connected in parallel therewith. The negative ground circuit includes a second insulation resistor Rn and a second sampling resistor R4 connected in parallel therewith. The first sampling resistor R2 and the second sampling resistor R4 are respectively connected in series with a first voltage divider selector and a second voltage divider selector.

[0009] When the positive ground circuit and the negative ground circuit are turned on, the first voltage divider selector and the second voltage divider selector select different resistance values Rn1 and Rn3 for voltage division, and they satisfy:

[0010]

[0011] Or the positive-to-ground circuit includes a first insulation resistor Rp and a first voltage-dividing resistor R1 connected in parallel therewith, and the negative-to-ground circuit includes a second insulation resistor Rn and a second voltage-dividing resistor R3 connected in parallel therewith; the first voltage-dividing resistor R1 and the second voltage-dividing resistor R3 are respectively connected in series with a first sampling selector and a second sampling selector; when the positive-to-ground circuit and the negative-to-ground circuit are turned on, the first sampling selector and the second sampling selector select different resistance values Rn2 and Rn4 for voltage division;

[0012] Among them, U1 is the first positive voltage to ground, and U2 is the first negative voltage to ground.

[0013] This technical solution has the following technical effects:

[0014] The insulation detection circuit of this utility model achieves adaptability to different voltage platforms by introducing voltage divider selectors for the positive and negative ground circuits. In practical applications, when the voltage platform changes, the accuracy of insulation detection can be maintained by adjusting the voltage divider selector or sampling selector. This not only solves the problem of traditional insulation detection devices being unable to adapt to different voltage platforms, but also improves the accuracy and stability of detection.

[0015] As a further improvement to the insulation detection circuit of the present invention, the first voltage divider selector and the second voltage divider selector are matched with the first switch Sn1 and the second switch Sn2 respectively. The first voltage divider selector and the second voltage divider selector respectively select the first switch Sn1 and the second switch Sn2 to control Rn1 of the first voltage divider selector and Rn3 of the second voltage divider selector.

[0016] As a further improvement to the insulation detection circuit of the present invention, the resistance values Rn1 and Rn3 are both 1 MΩ-20 MΩ.

[0017] As a further improvement to the insulation detection circuit of the present invention, the resistance values of the first voltage divider selector and the second voltage divider selector connected to the positive ground circuit and the negative ground circuit are the same.

[0018] As a further improvement to the insulation detection circuit of the present invention, the first switch Sn1 and the second switch Sn2 are used to control the positive and negative poles of the voltage platform to be connected to the corresponding positive-to-ground circuit and negative-to-ground circuit.

[0019] As a further improvement to the insulation detection circuit of the present invention, an analog-to-digital converter is further included that is connected in parallel to both ends of the first sampling resistor R2 and the second sampling resistor R4.

[0020] As a further improvement to the present invention, the resistance values Rn2 and Rn4 are both 1 kΩ-999 kΩ.

[0021] As a further improvement to the present invention, the first sampling resistor R2 and the second sampling resistor R4 are connected to the positive ground circuit and the negative ground circuit with equal resistance.

[0022] As a further improvement to the present invention, there are two detection circuits, each for detecting a different voltage platform.

[0023] As a further improvement to the present invention, the first switch Sn1 corresponds to the first voltage divider selector Rn1 in a one-to-one manner, and the second switch Sn2 corresponds to the second voltage divider selector Rn3 in a one-to-one manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention and constitute a part 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 an improper limitation of the present invention. In the drawings:

[0025] Figure 1 This is one of the insulation detection circuit schematics of Example 1 in the utility model;

[0026] Figure 2 This is the second schematic diagram of the insulation detection circuit of Example 1 in the utility model;

[0027] Figure 3 This is one of the circuit diagrams of the insulation detection circuit of Example 2 of the utility model;

[0028] Figure 4 This is the second circuit diagram of the insulation detection circuit of Example 2 of the utility model;

[0029] Figure 5 This is a flow chart of the insulation detection method of Example 3 in the utility model;

[0030] Figure 6 This is a flow chart of the insulation detection method of Example 4 in the utility model:

[0031] in:

[0032] 1-voltage platform;

[0033] 2-Detection circuit;

[0034] 21-Balanced bridge;

[0035] 22-ground circuit;

[0036] 221 - first voltage divider selector;

[0037] 222 - first sample selector;

[0038] 23-Negative to ground circuit;

[0039] 231 - Second voltage divider selector;

[0040] 232-Second sampling selector. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the embodiments of the present application will be further described in detail with reference to the accompanying drawings. Below, some terms in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

[0043] A battery management system (BMS) is used to protect the safe use of battery packs, ensuring safety during charge and discharge operations within the voltage platform while extending the battery pack's service life. The BMS provides battery management functions, including but not limited to monitoring battery status (e.g., battery voltage, current, temperature, and deformation), calculating the battery's charge level and capacity, controlling battery charging and discharging, and communicating with the battery.

[0044] A battery is a power source composed of at least one cell or battery module. A cell is the smallest unit of a battery and also serves as the energy storage unit. When multiple cells are encapsulated together in a common housing frame and connected to the outside world through a unified boundary, this constitutes a battery module.

[0045] Insulation resistance is a key safety metric for electrical equipment, reflecting its insulation performance. Under specific conditions, a voltage is applied to the insulation, resulting in a measured resistance value that directly impacts the safety of the equipment and its users. Furthermore, insulation resistance, measured when a voltage is applied to an insulator, is not a fixed value but rather varies with the electric field.

[0046] Balanced bridge testing is based on the Wheatstone bridge, a sensor used to measure resistance or capacitance. In practice, it's used to measure insulation resistance. Specifically, the insulation resistance value can be calculated by measuring the voltage across the sampling resistors in the upper and lower arms of the bridge.

[0047] An analog-to-digital converter (ADC) is an electronic device that converts continuously varying analog signals into discrete digital signals. This conversion is typically accomplished by measuring the input voltage and mapping it to a series of binary numbers. ADC performance metrics include resolution (which determines the number of distinct voltage levels it can represent), dynamic range (the ratio of the maximum input signal it can handle to the minimum detectable signal), and conversion speed (the number of conversions it can complete per unit time).

[0048] In addition, the voltage platform described in this application can be a battery pack for various electrical devices. In this application, the focus is on the research of power batteries for pure electric vehicles (because they are on a high-voltage platform, which is the most symbolic). Although other types of batteries are not mentioned in advance, it does not mean that the technical solution of this application is only used for power batteries.

[0049] The power battery of a pure electric vehicle is composed of multiple cells. Based on the power and economic requirements of the pure electric vehicle, the appropriate series and parallel connection method can be used to achieve the required voltage and battery capacity. Insulation resistors are connected to both the positive and negative electrodes of the power battery. The detection system and method are used to measure the equivalent insulation resistance of the positive and negative electrodes of the power battery to the vehicle floor, and the smaller of the two values is used as the final insulation resistance value.

[0050] The present invention will be described in further detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0051] Example 1

[0052] like Figure 1-2 As shown, in this embodiment, the insulation detection circuit includes at least one detection circuit 2 connected to different voltage platforms to adapt to different voltage platforms 1, and each detection circuit 2 is a balanced bridge 21. This design concept includes two detection methods: first, only one detection circuit 2 is used in the insulation detection circuit, and the detection circuit 2 can self-adjust to match different voltage platforms; second, multiple detection circuits 2 are designed to be connected in parallel on the voltage platform 1, with different specifications and parameters.

[0053] The first method works by determining the voltage parameters of the voltage platform 1 to be tested before testing. Using these parameters, the detection circuit 2 is adjusted to match the voltage platform 1 before testing the insulation resistance. Specifically, the second method can have two detection circuits 2, each used to detect a different voltage platform 1. The working principle is that when testing a lower voltage platform 1, the detection circuit 2 matching the lower voltage platform 1 will produce the corresponding result; while when testing a higher voltage platform 1, the detection circuit 2 matching the higher voltage platform 1 will produce the corresponding result.

[0054] The following content will further elaborate on the insulation detection circuit of the first design method as the core content (the design of the second method detection circuit 2 can be obtained by adaptively adjusting the insulation detection circuit of the first design method):

[0055] The balanced bridge 21 includes a complementary positive-to-ground circuit 22 and a negative-to-ground circuit 23. The positive-to-ground circuit 22 includes a first insulation resistor Rp and a first sampling resistor R2 connected in parallel therewith. The negative-to-ground circuit 23 includes a second insulation resistor Rn and a second sampling resistor R4 connected in parallel therewith. The first sampling resistor R2 and the second sampling resistor R4 are connected in series with a first voltage divider selector 221 and a second voltage divider selector 231, respectively.

[0056] When the positive ground circuit 22 and the negative ground circuit 23 are turned on, the first voltage divider selector 221 and the second voltage divider selector 231 select different resistance values Rn1 and Rn3 for voltage division, and they satisfy:

[0057]

[0058] Wherein, U1 is the first positive voltage to ground, and U2 is the first negative voltage to ground. In a specific implementation, voltage platform 1 in this embodiment specifically refers to a battery pack connected in series.

[0059] Preferably, considering that the principle of the above-mentioned technology is to use voltage division to improve the adaptability of the insulation detection device of this embodiment to different voltage platforms, if the first voltage-dividing resistor (corresponding to the first voltage-dividing selector) and the second voltage-dividing resistor (corresponding to the second voltage-dividing selector) remain unchanged, and the resistance values of the first sampling resistor R2 and the second sampling resistor R4 can be changed according to different voltage platforms, the above-mentioned operating principle can also be achieved (the first sampling resistor R2 is connected in series with the first voltage-dividing resistor, and the first sampling resistor R4 is connected in series with the second voltage-dividing resistor). Specifically, the first positive-to-ground circuit 22 includes a first insulation resistor Rp and a first voltage-dividing resistor R1 connected in parallel therewith, and the negative-to-ground circuit 23 includes a second insulation resistor Rn and a second voltage-dividing resistor R3 connected in parallel therewith; the first voltage-dividing resistor R1 and the second voltage-dividing resistor R3 are respectively connected in series with a first sampling selector 222 and a second sampling selector 232; when the positive-to-ground circuit 22 and the negative-to-ground circuit 23 are turned on, the first sampling selector 222 and the second sampling selector 232 select different resistance values Rn2 and Rn4 for voltage division. Since the working principle is the same as the method in which the first voltage-dividing selector 221 and the second voltage-dividing selector 231 select different resistance values Rn1 and Rn3 for voltage division, this embodiment will not be further described.

[0060] Since the technical purpose of this application is to apply the insulation detection circuit disclosed in this application to different voltage platforms 1 (there are significant differences in specific voltage values, such as a 1500V voltage platform 1 and a 150V voltage platform 1), the working principle of the first voltage divider selector 221 and the second voltage divider selector 231 is to adjust the internal voltage value so that it shares different degrees of voltage in the process of being connected in series with the first sampling resistor R2 and the second sampling resistor R4, ultimately achieving the adaptation of the insulation detection circuit to different voltage platforms 1. Specifically, there are many factors that affect the accuracy of insulation resistance detection. For battery pack insulation detection on different voltage platforms 1, the most important factors are the insulation detection loop resistance and the sampling voltage ADC accuracy (it must be noted that the ADC dynamic range should match the maximum amplitude of the signal to be converted, so as to maximize the ADC conversion accuracy and obtain the highest accuracy. This patent is also based on this consideration).

[0061] For example, with a 12-bit ADC and a 5V reference voltage, at voltage platform 1 of 1500V, assuming the resistance values of first and second voltage divider selectors 221 and 231 are 1495kΩ, and the resistance values of the first and second sampling resistors are 5kΩ, the ADC's dynamic range is 0-5V, maximizing ADC conversion accuracy and achieving the highest precision. However, at voltage platform 1 of 150V, the ADC's dynamic range is 0-0.5V, resulting in a significant loss of accuracy. Consequently, insulation resistance detection accuracy is severely compromised.

[0062] Furthermore, in order to more specifically reflect the technical effect of the technical solution of this embodiment, this embodiment will explain in a specific embodiment how to adapt and adjust the resistance values of the first voltage divider selector 221 and the second voltage divider selector 231 for different voltage platforms 1. Specifically, when the voltage platform 1 is 1500V, the resistance values of the first voltage divider selector 221 and the second voltage divider selector 231 are adjusted to 1495kΩ so that the voltage on the sampling resistor falls within the dynamic range of the ADC, i.e., 0-5V, thereby ensuring that the conversion accuracy of the ADC is maximized. When the voltage platform 1 is 150V, the resistance values of the first voltage divider selector 221 and the second voltage divider selector 231 are adjusted so that the voltage on the sampling resistor also falls within the dynamic range of the ADC (but this time it may not be 0-5V, but for example 0-0.5V). Since the dynamic range of the ADC matches the signal amplitude, the conversion accuracy of the ADC can be guaranteed.

[0063] Example 2

[0064] like Figure 2-6 As shown, the difference from Example 1 is that: in order to further improve the adaptability and adjustment capability of the insulation detection circuit of the present application to different voltage platforms 1, the first voltage divider selector 221 and the second voltage divider selector 231 are respectively matched with the first switch Sn1 and the second switch Sn2, and the first voltage divider selector 221 and the second voltage divider selector 231 respectively select the first switch Sn1 and the second switch Sn2 to control Rn1 of the first voltage divider selector 221 and Rn3 of the second voltage divider selector 231.

[0065] Preferably, this embodiment also further adjusts the circuit method of using sampling resistors for voltage division proposed in Example 1. Specifically, the first sampling selector 222 and the second sampling selector 232 are respectively matched with a first switch Sn1 and a second switch Sn2 (in this case, the first switch Sn1 and the second switch Sn2 are only used to match the first sampling selector 222 and the second sampling selector 232, and no longer match the first voltage divider selector 221 and the second voltage divider selector 231). The first sampling selector 222 and the second sampling selector 232 respectively use the first switch Sn1 and the second switch Sn2 to control Rn2 of the first sampling selector 222 and Rn4 of the second sampling selector 232. Specifically, the resistance value range of Rn2 and Rn4 is 1kΩ-999kΩ. Since the specific implementation principle is the same as the method of the first voltage divider selector 221 and the second voltage divider selector 231, this embodiment will only describe the working principle of the method of the first voltage divider selector 221 and the second voltage divider selector 231, and this preferred technical solution will not be repeated.

[0066] In order to more clearly show the circuit principle of this application, in this application Figure 2In the circuit diagram shown, the first switch Sn1 and the second switch Sn2 are labeled as S1, S11...Sn1 and S2, S12...Sn2; Rn1 and Rn3 are labeled as R1, R11...Rn1 and R3, R13...Rn3; Rn2 and Rn4 are labeled as R2, R12...Rn2 and R4, R14...Rn4.

[0067] Furthermore, the first switch Sn1 corresponds one-to-one to Rn1 of the first voltage-dividing selector 221 , and the second switch Sn2 corresponds one-to-one to Rn3 of the second voltage-dividing selector 231 .

[0068] Specifically, in this embodiment, multiple voltage-dividing switches and corresponding voltage-dividing resistors are introduced to more accurately control the resistance value of the voltage-dividing selector. These switches and resistors can adjust the resistance value of the voltage-dividing selector according to different voltage platforms 1, thereby ensuring that the voltage across the sampling resistor always falls within the dynamic range of the ADC mentioned in Example 1, thereby maximizing the ADC's conversion accuracy.

[0069] Specifically, also using the example of Example 1, when voltage platform 1 is 1500V and R2=R4=5kΩ, this embodiment can choose to close S1 in the first switch Sn1, so that R1 is connected to the circuit, and the fixed resistors within the first voltage divider selector 221 together form a total resistance of 1495kΩ. Similarly, for the second voltage divider selector 231, this embodiment can choose to close S2 in the second switch Sn2, so that the second voltage divider resistor R3 is connected to the circuit, and the fixed resistors within the second voltage divider selector 231 together form the same resistance value as the first voltage divider selector 221. In this way, the voltage of the analog-to-digital (ADC) module at both ends of the sampling resistors R2 and R4 can be controlled within a dynamic range of 0 to 5V, achieving high-precision insulation resistance detection.

[0070] When the voltage platform 1 is 150V, by changing the state of the voltage divider switch, different voltage divider resistors are selected to be connected, thereby adjusting the resistance value of the voltage divider selector. For example, it is possible to choose to close S11 in the first, connect R11 to the circuit, and open the other first switch Sn1 at the same time, so that the resistance value of the first voltage divider selector 221 is reduced. For the second voltage divider selector 231, this embodiment also chooses to close S12 in the second switch Sn2, connect R13 to the circuit, and open the other second switch Sn2 at the same time. In this way, this embodiment can ensure that under the lower voltage platform 1, the voltage on the sampling resistor can still fall within the dynamic range of the ADC, thereby achieving high-precision insulation resistance detection (where R11 and R13 are both low-resistance resistors).

[0071] It should be noted that in practical applications, this embodiment may require designing and calibrating the voltage divider switch and voltage divider resistor based on the specific voltage platform 1 and the dynamic range of the ADC. Furthermore, to further improve the accuracy and reliability of insulation resistance detection, this embodiment may also employ other technical means, such as temperature compensation and calibration circuits. These technical means can help this embodiment more accurately measure insulation resistance values and promptly identify and resolve potential electrical safety issues.

[0072] Preferably, the resistance values Rn1 and Rn3 are both 1MΩ-20MΩ. It is known that in practical applications, the resistance range of the insulation resistor is often very large, while the input range of the ADC is limited. In order to obtain high-precision measurement results in different resistance ranges, this embodiment needs to select the resistance value of the voltage divider resistor. In this embodiment, this embodiment sets the resistance range of Rn1 and Rn3 to 1MΩ-20MΩ. The setting of this range takes into account both the input range of the ADC and the actual resistance range of the insulation resistor, thereby ensuring that high-precision insulation resistance detection can be achieved under different voltage platforms 1 and different insulation resistance values.

[0073] Specifically, when the voltage parameter of voltage platform 1 is large, this embodiment requires selecting a voltage divider resistor with a larger resistance value to reduce the voltage across the sampling resistor, thereby avoiding ADC input saturation. When the insulation resistance value is small, this embodiment requires selecting a voltage divider resistor with a smaller resistance value to increase the voltage across the sampling resistor, thereby improving the resolution and conversion accuracy of the ADC. In this embodiment, the resistance range of 1MΩ-20MΩ can cover most practical application scenarios and ensure the accuracy and reliability of insulation resistance detection.

[0074] Furthermore, the resistance values of the first voltage divider selector 221 and the second voltage divider selector 231 connected to the positive ground circuit 22 and the negative ground circuit 23 are consistent. The resistance values of the first sampling resistor R2 and the second sampling resistor R4 connected to the positive ground circuit 22 and the negative ground circuit 23 are equal. It is known that in the balanced bridge 21, the positive ground circuit 22 and the negative ground circuit 23 are specifically the upper and lower bridge arms, and the reason why the voltage divider resistance values of the upper and lower bridge arms are connected to be consistent is to ensure the accuracy of the measurement. When current passes through these resistors, they will form a voltage difference at both ends, and this voltage difference is proportional to the resistance value. If the resistance of the two arms does not match, it may cause deviation in the measurement results and it is impossible to obtain an accurate insulation resistance reading. Consistency ensures that the current distribution and voltage change are the same regardless of which bridge arm is used, so that it is more accurate to calculate the insulation resistance by comparing the voltage ratio on both sides.

[0075] Furthermore, the first switch Sn1 and the second switch Sn2 are used to control the positive and negative poles of the voltage platform 1 to be connected to the corresponding positive-to-ground circuit 22 and negative-to-ground circuit 23. Figure 3 In the circuit diagram shown in FIG. 1 , it can be seen that when the first switch Sn1 (for example, S1, but not limited to S1) is closed, it forms a series circuit with Rn1 (for example, R1, but not limited to R1). In this circuit, current flows from multiple strings of batteries (in Figure 3 The positive terminal of the voltage platform (denoted in the figure) flows through R1 to the lower bridge arm, as this is part of the loop. If the lower bridge arm of Sn2 is open, then the loop only includes the upper bridge arm and the second insulation detection resistor Rn, thus forming a simple voltage divider network, the purpose of which is to provide a theoretical basis for further measuring the first insulation resistance Rp to ground. If the second insulation detection resistor Rn is not present at this time, the first insulation resistance Rp cannot be measured, and the entire circuit is now non-conductive. (However, Rp can be directly calculated using Equation 1 when both Sn1 and Sn2 switches are closed.)

[0076] The measurement process is similar to the previous one, but this part focuses on the low-side switch and the corresponding voltage divider resistor. Figure 3 As shown, when the second switch Sn2 (for example, S2, but not limited to S2) is closed, it forms another series circuit with Rn3 (for example, R3, but not limited to R3). At this time, the current will flow from the negative electrode of the multiple battery strings through R3 to the upper bridge arm because it is part of the newly formed loop.

[0077] If the upper bridge arm is open at this time, then this loop only includes the lower bridge arm and the first insulation detection resistor Rp, thus forming a new voltage divider network, which provides a theoretical basis for further measuring the second insulation resistance Rn. By collecting the voltage value on R4 and combining it with the known resistance values of R1 and R3, this embodiment can further calculate the magnitude of the measured second insulation resistance Rn. If the first insulation detection resistor Rp does not exist at this time, the first insulation resistance Rn cannot be measured, and the entire circuit is not conductive. (However, Rn can be directly calculated using Formula 1 when both Sn1 and Sn2 switches are closed.)

[0078] It is worth noting that in order to accurately measure the insulation resistance, it is necessary to ensure that other non-measurement related circuit parts (such as other ground loops, in this embodiment, the switches and resistors of the bridge arms) are in the off state during the measurement process to avoid interference with the measurement results.

[0079] In summary, by controlling the switching states of different bridge arms and combining the values of the voltage divider resistors, this embodiment can measure the insulation resistance of the positive and negative terminals of multiple battery strings to ground. This measurement method is simple, reliable, and highly accurate, providing a strong guarantee for the safe operation of the battery system.

[0080] Furthermore, an analog-to-digital converter is connected in parallel across the first sampling resistor R2 and the second sampling resistor R4, wherein the analog-to-digital converter is specifically an ADC module. The principle of the ADC module connected in parallel across the sampling resistors to detect the insulation resistance is based on the bridge measurement principle. In the balanced bridge circuit 21, when the resistances are equal (e.g., R1 = R3, R2 = R4), if no current flows, that is, the input signal approaches zero, then the output voltage will also approach zero. At this time, the ADC module reads the voltage drop across the sampling resistor, indicating the state of the insulation resistance.

[0081] During insulation testing, the voltage difference between the measurement point and ground can be adjusted by changing the circuit state (for example, disconnecting the first switch Sn1 and the second switch Sn2), thereby obtaining different resistance-divided voltage values. For example, if the second positive-to-ground voltage U3 = 0 after disconnecting the second switch Sn2, this indicates that there is no Rn resistor or that the Rn resistor is sufficiently larger than the Rp resistor.

[0082] In summary, by connecting the ADC module in parallel to the sampling resistor and measuring the voltage change across the resistor, we can indirectly measure the voltage drop caused by the insulation resistance difference and thus calculate the insulation resistance value. This method allows for adaptive testing of battery packs with different voltage platforms1, improving detection accuracy.

[0083] Specifically, the resistance values R2 and R4 are both 1MΩ-20MΩ. Furthermore, the resistance values of the first sampling resistor R2 and the second sampling resistor R4 are any resistance value in the range of 1-999kΩ. This resistance value is the most commonly used resistance value in the detection device in this case, which can achieve the unification of the sampling resistors.

[0084] like Figure 1-5 As shown, in order to further improve the present invention on the existing insulation detection method, this embodiment discloses a detection method using the above insulation detection circuit, the steps of which are as follows:

[0085] S101, connecting different voltage platforms 1 to the detection circuit 2, and determining the required connection voltage value according to the parameters of the required detection voltage platform 1;

[0086] S201, connecting the first voltage divider selector 221 and the second voltage divider selector 231 to the detection circuit 2, and then starting the first voltage divider selector 221 and the second voltage divider selector 231 according to the voltage value of step S101 to match the corresponding resistance values Rn1 and Rn3;

[0087] In step S301 , the first sampling resistor R2 , the second sampling resistor R4 , and the first insulation resistor Rp and the second insulation resistor Rn obtained in step S201 satisfy a balanced relationship;

[0088] Specifically, the above relationship is shown in Formula I:

[0089]

[0090] Among them, “ / / ” means parallel connection, such as Formula I can be further expressed as:

[0091]

[0092] Other formulas are not described in detail in this embodiment.

[0093] Among them, U1 is the positive voltage to ground, and U2 is the negative voltage to ground;

[0094] S401, when U1 < U2, disconnect the second voltage divider selector 231; when U1 ≥ U2, disconnect the first voltage divider selector 221;

[0095] S501 . Calculate the values of the first insulation resistance Rp and the second insulation resistance Rn according to the conditions of S401 .

[0096] Among them, Rn1 is the resistance value of the first voltage divider selector 221, Rn3 is the resistance value of the second voltage divider selector 231, R2 is the first sampling resistor, R4 is the second sampling resistor, Rp is the first insulation resistor, Rn is the second insulation resistor, U1 is the first positive voltage to ground, and U2 is the first negative voltage to ground.

[0097] In addition, in steps S301 and S401, if the voltage of U1 or U2 is relatively small, it means that the corresponding first insulation resistance Rp or the corresponding second insulation resistance Rn is relatively small. If you want to improve the insulation resistance calculation accuracy, you can reselect a voltage divider resistor or sampling resistor suitable for the first insulation resistance Rp or the second insulation resistance Rn (for example, it is possible that U1 is already suitable and U2 is too small, then you only need to select a voltage divider resistor or sampling resistor for the lower bridge arm that is suitable for Rn). Considering that the first insulation resistance Rp or the corresponding second insulation resistance Rn may have leakage, the above steps will not be further explained and are only used as a preferred method.

[0098] The principle of the above detection method is: first, according to the parameters of the required detection voltage platform 1, the voltage value of the access circuit is determined. Then, based on this voltage value, by selecting the appropriate voltage divider resistor value (that is, the voltage divider resistor that needs to be connected to the first voltage divider selector 221 and the second voltage divider selector 231), it is ensured that the circuit can safely and accurately detect the insulation resistance. Next, by connecting the first voltage divider selector 221 and the second voltage divider selector 231 to the detection circuit 2, a specific voltage divider relationship is formed, and based on this relationship, Formula I is obtained. (This formula describes the relationship between the voltage distribution and resistance in the circuit.)

[0099] Secondly, in order to accurately measure the values of the first insulation resistance Rp and the second insulation resistance Rn, the detection process needs to disconnect the first voltage divider selector 221 or the second voltage divider selector 231 while keeping other conditions unchanged, thereby changing the voltage distribution in the circuit and obtaining a new voltage relationship (Formula II). Finally, using the two voltage relationship formulas (Formula I and Formula II) obtained when connecting and disconnecting the voltage divider selector, the values of the first insulation resistance Rp and the second insulation resistance Rn are obtained by calculation. Since the smaller the insulation resistance value, the greater the risk of leakage, in practice, the smaller value of the two is taken as the final result of the insulation resistance.

[0100] This embodiment selects the voltage divider resistor value based on the parameters of voltage platform 1, ensuring that the insulation detection circuit adapts to the detection requirements of different voltage platforms 1, thereby improving the versatility and flexibility of detection. By connecting and disconnecting the voltage divider selector, the voltage distribution in the circuit can be changed, thereby obtaining two different voltage relationships. These two relationships together constitute the equation system for solving the insulation resistance, ensuring the accuracy and reliability of the measurement.

[0101] In summary, this embodiment, by introducing a voltage divider selector and combining specific detection steps, achieves accurate insulation resistance measurement for different voltage platforms 1, demonstrating its wide applicability and practicality. Furthermore, the detection steps involved in this method are clear and straightforward, making them easy to operate and execute. Furthermore, the use of a formalized calculation method makes the calculation process more simplified and accurate.

[0102] Furthermore, a loop abnormality detection needs to be performed between steps S301 and S401: when the sum of U1 and U2 exceeds the voltage range of voltage platform 1, the insulation detection loop is abnormal.

[0103] In a specific embodiment, taking the scenario where the voltage platform is set to 1500V as an example, when the voltages of all battery strings within the voltage platform remain normal, and the total system voltage (i.e., the sum of U1 and U2) remains stable at around 1500V with a fluctuation range within a preset allowable threshold, we can determine that the system is in normal operation. It is worth noting that the claims of this application only focus on situations where the voltage "exceeds" the preset range. If the actual voltage is lower than this range, it should also be considered that there is an abnormality in the insulation detection circuit.

[0104] However, if the sum of U1 and U2 deviates from the allowable voltage range of voltage platform 1 (i.e., 1500V) (for example, the allowable error range is set between 2% and 5%), whether it is too high or too low, it should be immediately considered an abnormality in the insulation detection circuit. Such abnormality may be caused by deterioration of the insulation material, failure of the detection circuit, or interference from external environmental factors.

[0105] Among them, when the insulation detection is normal, if the first positive voltage to ground U1 = 0, the first insulation resistance Rp is close to 0; if the first negative voltage to ground U2 = 0, the second insulation resistance Rn is close to 0 (that is, a short circuit is detected).

[0106] like Figure 5 As shown, the difference from the above is that this embodiment discloses a calculation method for the first insulation resistance Rp and the second insulation resistance Rn:

[0107] When U1<U2, the second voltage divider selector 231 is disconnected;

[0108] When U3 = 0, it proves that there is no second insulation resistance Rn, or the second insulation resistance Rn is larger than the first insulation resistance Rp, which is obtained by formula I:

[0109] in

[0110] Among them, U3 is the second positive voltage to ground;

[0111] If the condition U3=0 is not met, then Formula II is as follows:

[0112]

[0113] U4 is the second negative voltage to ground in the negative ground circuit 23 (U4=voltage of voltage platform 1-U3); the final insulation resistance value is the smaller value between the first insulation resistance Rp and the second insulation resistance Rn.

[0114] In addition, according to formula I and formula II, we can get:

[0115] Rp=(k-1)(Rn1+R2), where

[0116] in

[0117] When U1≥U2, the first voltage divider selector 221 is disconnected;

[0118] If U4 = 0, it proves that there is no first insulation resistance Rp or the first insulation resistance Rp is sufficiently larger than the second insulation resistance Rn, which is obtained from formula I:

[0119] in

[0120] If the condition of U4=0 is not met, then Formula II is as follows:

[0121]

[0122] According to formula I and formula II, we can get:

[0123] Rn=(k-1)(Rn3+R4), where

[0124] in

[0125] Finally, the actual value of the insulation resistance is the smaller value of the first insulation resistance Rp and the second insulation resistance Rn.

[0126] Among them, Rn1 = R1, R11...Rn1, Rn3 = R3, R13...Rn3, U1 is the first positive low voltage to ground, U2 is the first negative voltage to ground, U3 is the second positive low voltage to ground (U3 = voltage platform 1 voltage - U4), and U4 is the second negative voltage to ground.

[0127] Furthermore, the insulation detection method of this utility model can be combined with other vehicle safety systems, such as battery management systems (BMS) and collision detection systems, to form a complete vehicle safety monitoring network. When abnormal conditions such as insulation degradation or increased chassis potential are detected, an alarm can be immediately triggered and sent to the driver or a remote monitoring center via the vehicle's communication system, allowing timely measures to ensure the safety of the vehicle and passengers.

[0128] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An insulation detection circuit, characterized in that: It comprises at least one detection circuit (2) electrically connected to different voltage platforms (1), wherein the detection circuit (2) is a balanced bridge (21); The balanced bridge (21) includes a positive ground circuit (22) and a negative ground circuit (23) of complementary design; The positive ground circuit (22) includes a first insulation resistor Rp and a first sampling resistor R2 connected in parallel therewith, and the negative ground circuit (23) includes a second insulation resistor Rn and a second sampling resistor R4 connected in parallel therewith; the first sampling resistor R2 and the second sampling resistor R4 are respectively connected in series with a first voltage divider selector (221) and a second voltage divider selector (231); when the positive ground circuit (22) and the negative ground circuit (23) are turned on, the first voltage divider selector (221) and the second voltage divider selector (231) select different resistance values Rn1 and Rn3 or perform voltage division; When the positive ground circuit (22) and the negative ground circuit (23) are turned on, the first voltage divider selector (221) and the second voltage divider selector (231) select different resistance values Rn1 and Rn3 or perform voltage division, and they satisfy: Or the positive-to-ground circuit (22) includes a first insulation resistor Rp and a first voltage-dividing resistor R1 connected in parallel therewith, and the negative-to-ground circuit (23) includes a second insulation resistor Rn and a second voltage-dividing resistor R3 connected in parallel therewith; the first voltage-dividing resistor R1 and the second voltage-dividing resistor R3 are respectively connected in series with a first sampling selector (222) and a second sampling selector (232); when the positive-to-ground circuit (22) and the negative-to-ground circuit (23) are turned on, the first sampling selector (222) and the second sampling selector (232) select different resistance values Rn2 and Rn4 for voltage division; Among them, U1 is the first positive voltage to ground, and U2 is the first negative voltage to ground.

2. The insulation detection circuit according to claim 1, wherein: The first voltage divider selector (221) and the second voltage divider selector (231) are matched with a first switch Sn1 and a second switch Sn2, respectively. The first voltage divider selector (221) and the second voltage divider selector (231) respectively select the first switch Sn1 and the second switch Sn2 to control Rn1 of the first voltage divider selector (221) and Rn3 of the second voltage divider selector (231).

3. The insulation detection circuit according to claim 1 or 2, characterized in that: The resistance values Rn1 and Rn3 are both 1MΩ-20MΩ.

4. The insulation detection circuit according to claim 2, wherein: The resistance values of the first voltage-dividing selector (221) and the second voltage-dividing selector (231) connected to the positive ground circuit (22) and the negative ground circuit (23) are the same.

5. The insulation detection circuit according to claim 2, wherein: The first switch Sn1 and the second switch Sn2 are used to control the positive and negative poles of the voltage platform (1) to be connected to the corresponding positive-to-ground circuit (22) and the negative-to-ground circuit (23).

6. The insulation detection circuit according to claim 1, wherein: The system further includes an analog-to-digital converter connected in parallel to both ends of the first sampling resistor R2 and the second sampling resistor R4.

7. The insulation detection circuit according to claim 1, wherein: The resistance values of Rn2 and Rn4 are both 1kΩ-999kΩ.

8. The insulation detection circuit according to claim 1, wherein: The first sampling resistor R2 and the second sampling resistor R4 are connected to the positive ground circuit (22) and the negative ground circuit (23) with equal resistance.

9. The insulation detection circuit according to claim 1, wherein: The detection circuits (2) are two and are respectively used to detect different voltage platforms (1).

10. The insulation detection circuit according to claim 2, wherein: The first switch Sn1 corresponds one-to-one to Rn1 of the first voltage divider selector (221), and the second switch Sn2 corresponds one-to-one to Rn3 of the second voltage divider selector (231).

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