System and method for isolation resistance measurement

Abstract

To provide a system and method for isolation resistance measurement.SOLUTION: A system includes a processing device and a measurement circuit coupled to the processing device. The system further includes an auxiliary voltage supply. The processing device and the measurement circuit are powered by the auxiliary voltage supply. The measurement circuit is to apply a test voltage to a first resistor and measure a voltage drop over the first resistor. The processing device is configured to determine, based on at least the voltage drop, an isolation resistance value between a chassis ground node and at least one of a battery pack or a battery link of a power system.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 536,331, filed Sep. 1, 2023, the contents of which are incorporated by reference herein in their entirety.

[0002] The present disclosure relates generally to the field of battery management, and more particularly to a system and method for insulation resistance measurement. [Background technology]

[0003] The battery management system (BMS) of an electric vehicle (EV) is responsible for managing the performance, health and efficiency of the battery pack. A BMS typically comprises various components including sensors, control units and connection interfaces. These components monitor parameters such as voltage, current, temperature and state of charge to help ensure optimal battery operation and lifespan. Insulation resistance monitoring in a BMS involves detecting potential leakage or breakdown of the insulation between the high-voltage (HV) battery pack and the vehicle chassis and other low-voltage (LV) systems. This monitoring is accomplished by dedicated circuitry that applies test voltages and measures the resulting current or voltage drop to assess insulation integrity and ensure compliance with safety and regulatory standards. Electronic circuits such as those used for insulation resistance monitoring may include individual electronic components such as resistors, transistors and capacitors, among others, connected by conductors or traces through which current may flow.

[0004] The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a block diagram of an insulation resistance measurement system, according to some embodiments. [Diagram 2] FIG. 1 is a block diagram of an insulation resistance measurement system for an EV, according to some embodiments. [Figure 3A] FIG. 2 is a circuit diagram illustrating an insulation resistance measurement circuit according to some embodiments. [Figure 3B] FIG. 2 is a circuit diagram illustrating an insulation resistance measurement circuit according to some embodiments. [Figure 4] FIG. 2 is a simplified circuit diagram illustrating the use of a switch to measure an insulation resistance value using an insulation resistance measurement circuit, according to some embodiments. [Figure 5A] 1 is a flow diagram of a method relating to insulation resistance monitoring, according to some embodiments. [Figure 5B] 1 is a flow diagram of a method relating to insulation resistance monitoring, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] In an electric vehicle (EV), the high voltage (HV) battery pack typically operates at a voltage between 200V and 800V. The low voltage (LV) circuit typically operates at 12V and can be located at the chassis ground node of the vehicle chassis (e.g., the LV circuit uses the vehicle chassis for its ground node). For human safety, the HV battery pack must be isolated from the LV circuit and the vehicle chassis. According to the Federal Motor Vehicle Safety Standards (FMVSS), a resistance of 500Ω / V is required to isolate the HV battery pack from the LV circuit and the vehicle chassis, which corresponds to a leakage current limit of 2mA for a 1000V battery, for example. The insulation resistance is monitored and maintained to detect and prevent failures throughout the life of the vehicle.

[0007] Additionally, the HV battery link side, which connects the HV battery pack to critical vehicle components such as the inverter, charger and DC-DC converter, as well as to the electric motor, requires isolation from the LV circuits and vehicle chassis, which becomes difficult when the HV battery link side is disconnected and floats isolated from the HV battery pack voltage.

[0008] Traditionally, there are two common methods for insulation resistance monitoring. The first, passive insulation monitoring, involves a test load connected to the positive and negative terminals of both the HV battery pack and the HV battery link. This method can be relatively simple and straightforward, but requires both a first device and a first power source for HV battery pack insulation monitoring, and a second device and a second power source for HV battery link insulation monitoring while the HV battery link is floating, which can be costly. The second method, active insulation monitoring, employs a separate test voltage to apply a test current to the ground wire and measure the leakage current. This approach is stable and accurate, and both the HV battery pack side and the HV battery link side can be monitored with a single device. However, it involves a separate 40V AC voltage source that creates a third 40V power domain (in addition to the HV domain and the 12V domain), resulting in a complex and expensive design.

[0009] Aspects and implementations of the present disclosure address these and other challenges of existing technology by employing a system including a processing device (e.g., performing calculations for insulation resistance monitoring) and a measurement circuit coupled to a chassis ground of a LV circuit powered by an auxiliary voltage supply of the EV. Both the processing device and the measurement circuit are powered by the same 12V power domain of the auxiliary voltage supply. The test voltage applied to the resistor by the measurement circuit is also provided by the same auxiliary voltage supply of the EV. The auxiliary voltage supply can be, for example, a 12 volt battery that powers the LV circuit of the EV. The system also includes a chassis ground node. The processing device and the measurement circuit can be coupled to the chassis ground node.

[0010] While performing the insulation resistance monitoring, a test voltage can be applied to the resistor using a measurement circuit. The test voltage applied by the measurement circuit can be supplied by an auxiliary voltage supply. The resistor can be coupled between the measurement circuit and either the battery pack or the battery link. The measurement circuit measures the voltage drop across the resistor, and the processing device determines an insulation resistance value between the chassis ground node and the battery pack or the battery link based on the voltage drop and other known values.

[0011] In some embodiments, the processing device may compare the insulation resistance value to a predetermined threshold, and if the insulation resistance value is below the predetermined threshold, the processing device may generate a fault alert.

[0012] Aspects of the present disclosure are less expensive and simpler than conventional approaches. Aspects of the present disclosure require only a single device to perform insulation resistance monitoring for both the HV battery pack side and the HV battery link side. Aspects of the present disclosure do not require two separate processing devices and two isolated 12V voltage supplies as in conventional passive insulation resistance monitoring. Aspects of the present disclosure do not require a separate AC voltage source to power the processing device and measurement circuitry as in conventional active insulation resistance monitoring. Instead, the processing device and measurement circuitry are powered by an auxiliary voltage supply already included in the EV, resulting in a simple and inexpensive design. The processing device can be coupled to a 12V chassis ground node, for example, and can be powered by the same 12V domain. Aspects of the present disclosure do not require the ability to measure negative voltages as in conventional active insulation resistance monitoring. Aspects of the present disclosure can operate in the range of 0V to 5V (e.g., the operating range of the processing device). Aspects of the present disclosure can detect symmetrical faults that occur when the insulation resistance of both the positive and negative terminals change simultaneously and similarly. Additionally, aspects of the present disclosure can identify asymmetrical faults that occur when the insulation resistance of either the positive or negative terminal changes, but not both at the same time. As described below, other advantages will be apparent to those skilled in the art of battery management system design.

[0013] 1 is a block diagram of an insulation resistance measurement system 100 (also referred to herein as a "system") in accordance with some embodiments. System 100 includes an insulation resistance monitoring unit 101. An example of insulation resistance monitoring unit 101 (e.g., as part of an EV system) is shown and discussed in further detail in FIGS. 2-4. Insulation resistance monitoring unit 101 is shown as a discrete device (e.g., an integrated circuit having input and output pins) for purposes of illustration and not limitation.

[0014] The insulation resistance monitoring unit 101 is a dedicated subsystem that includes a measurement circuit and a processing unit. The measurement circuit includes electrical components. For example, the components of the measurement circuit may include resistors (e.g., for defining a measurement range), capacitors (e.g., for filtering and stabilization), a high impedance voltage sensor (e.g., for detecting leakage current), and a controlled voltage source (e.g., for applying a test voltage). In some embodiments, the controlled voltage source does not need to be integrated as part of the measurement circuit. Instead, the controlled voltage source may be an auxiliary voltage supply of the EV and may be used to apply the test voltage. In some embodiments, the measurement circuit may be used to determine the integrity of the insulation between the high voltage components and ground.

[0015] In at least one embodiment, the processing unit is a microcontroller. In another embodiment, the processing device is a PSoC™ developed by Cypress Semiconductor of San Jose, Calif. In other embodiments, the processing device may be a system on chip (SoC) or other integrated circuit having the circuits and functions described herein. In some embodiments, the processing unit may be a digital signal processor (DSP). In some embodiments, the processing unit processes data collected by the measurement circuitry. In some embodiments, the processing unit may include an analog-to-digital converter (ADC) (e.g., for digitizing analog signals), memory (e.g., for storing measurement data and operational software), and computational logic (e.g., for calculating insulation resistance values). In some embodiments, the processing unit may determine whether the measured insulation resistance values ​​indicate a safe level of insulation or a potential safety hazard and trigger an alert or protective action as appropriate.

[0016] In some embodiments, the insulation resistance monitoring unit 101 may be coupled to a chassis ground node 102. The ground node may be a reference point in an electrical system. In some embodiments, the chassis ground node 102 serves as a common return path for current and as a reference point for measuring electrical potentials in the system 100. In some embodiments, the chassis ground node 102 may be used as a reference for measuring insulation resistance between high voltage components (e.g., battery packs and battery links) and ground to ensure that there are no dangerous leaks or failures in the insulation.

[0017] In some embodiments, insulation resistance measurement system 100 includes an auxiliary voltage supply 103 coupled to insulation resistance monitoring unit 101. Auxiliary voltage supply 103 provides a stable and accurate voltage for insulation resistance monitoring (e.g., for applying a test voltage). In some embodiments, auxiliary voltage supply 103 may be a regulated power supply that can deliver consistent voltage levels necessary for accurate measurements. In some embodiments, auxiliary voltage supply 103 may be a 12 volt battery (e.g., in an EV).

[0018] In some embodiments, the insulation resistance measurement system 100 includes a battery pack 104 (e.g., of a power system 110) coupled to the insulation resistance monitoring unit 101. The insulation resistance measurement system 100 further includes a battery link 105 (e.g., of a power system 110). In some embodiments, the battery pack 104 is part of an EV. In some embodiments, the battery pack 104 is an assembly of multiple battery cells or modules that store electrical energy, for example, for operation of the EV. In some embodiments, the battery pack cells can be arranged in a series-parallel configuration to achieve a desired voltage and capacity. In some embodiments, the battery pack 104 can include a management system for monitoring and balancing the cells, temperature control mechanisms, and protection circuits.

[0019] In some embodiments, the battery link 105 may also be referred to as a high-voltage interconnect system. The battery link 105 may include components such as cables, connectors, and bus bars that connect the battery packs 104 to the EV's powertrain and other high-voltage components. In some embodiments, the battery link 105 may include an inverter (e.g., to convert DC to AC for the motor), an on-board charger (e.g., to charge the battery from an external AC source), and a DC-DC converter (e.g., to step down high-voltage DC for a low-voltage system).

[0020] For example, in an EV, the battery pack 104 and the battery link 105 may be coupled to each other at some times and separated at other times. When coupled, the battery link 105 may facilitate power transfer from the battery pack 104 to the drive train of the EV and other high voltage components. However, for maintenance, safety, or energy management purposes, the battery link 105 can be separated or disconnected from the battery pack 104. This disconnection can interrupt the flow of power and effectively isolate the high voltage components (battery link 105) from the battery pack 104, ensuring safety during service or emergency situations. The ability to separate can be an important feature for both operational flexibility and safety in an EV. However, the ability to separate the battery pack 104 from the battery link 105 presents a challenge for isolation resistance monitoring. For example, there are times when isolated isolation resistance monitoring must be performed on both the battery pack side and the battery link side.

[0021] 2 is a block diagram of an insulation resistance measurement system 200 of an EV, according to some embodiments. Insulation resistance measurement system 200 may be similar to insulation resistance measurement system 100 and may be described with respect to FIG. 1. In some embodiments, insulation resistance measurement system 200 may include or be coupled to the same, more, or fewer components. In some embodiments, insulation resistance measurement system 200 may be included in EV 260.

[0022] In some embodiments, the insulation resistance measurement system 200 includes an insulation resistance monitoring unit 201. The insulation resistance monitoring unit 201 may be the same as or similar to the insulation resistance monitoring unit 101 of Figure 1. In some embodiments, the insulation resistance monitoring unit 201 includes a measurement circuit 206 and a processing device 207.

[0023] In some embodiments, the measurement circuit 206 is coupled to the processing device 207. In some embodiments, the measurement circuit 206 includes electrical components. For example, the components of the measurement circuit may include resistors, capacitors, high impedance voltage sensors, etc. In some embodiments, the measurement circuit may be used to determine the integrity of the insulation between high voltage components and ground. For a detailed description of the measurement circuit 206, see FIGS. 3A-4.

[0024] In some embodiments, the processing device 207 may be a microcontroller, a DSP, a field programmable gate array (FPGA), an application specific integrated circuit, etc. In some embodiments, the processing device 207 processes data collected by the measurement circuitry 206. In some embodiments, the processing device 207 may include an analog-to-digital converter (ADC), memory, and computational logic, etc.

[0025] In some embodiments, the processing device 207 and the measurement circuitry 206 may be coupled to a chassis ground node 202. In some embodiments, the ground node may be a reference point in an electrical system. In some embodiments, the chassis ground node 202 serves as a common return path for current and as a reference point for measuring electrical potentials in the system 200. In some embodiments, the chassis ground node 202 may be used as a reference for measuring insulation resistance between high voltage components and ground (e.g., the vehicle chassis). In some embodiments, the chassis ground node may correspond to the chassis ground node of FIG. 1.

[0026] In some embodiments, the insulation resistance measurement system 200 includes a battery pack 204 coupled to the measurement circuit 206. The insulation resistance measurement system 200 further includes a battery link 205 coupled to the measurement circuit 206.

[0027] In some embodiments, the battery pack 204 and the battery link 205 may be selectively coupled or decoupled from each other. When coupled, the battery link 205 facilitates power transfer from the battery pack 204 to various components of the battery link 205 (e.g., the drive train and other high voltage components of the EV 260). However, for maintenance, safety, or energy management purposes, the battery link 205 can be decoupled or disconnected from the battery pack 204. When decoupled, insulation resistance monitoring must be performed between the chassis ground node 202 and both the battery pack 204 and the battery link 205. In some embodiments, the battery pack 204 and the battery link 205 are selectively coupled via a switch 210.

[0028] In some embodiments, insulation resistance measurement system 200 includes an auxiliary voltage supply 203 coupled to a processing device 207 and a measurement circuit 206. In some embodiments, processing device 207 and measurement circuit 206 are powered by auxiliary voltage supply 203. In some embodiments, auxiliary voltage supply 203 provides a stable and accurate voltage for insulation resistance monitoring (e.g., for applying a test voltage).

[0029] In some embodiments, the insulation resistance measurement system 200 further includes a plurality of switches coupled between the measurement circuit 206 and the battery pack or battery link 205. In some embodiments, the processing device 207 provides a control signal 220 to the switches 213, 214, 215, and 216. In some embodiments, when each of the switches 213-216 is individually closed, a test voltage is applied to a corresponding terminal (e.g., terminal 213B, 214B, 215B, or 216B) of the battery pack 204 or battery link 205. In some embodiments, the test voltage is applied to a terminal of the battery pack 204 or battery link 205 of the power system 250 through a resistor. The test voltage may be applied to any of the terminals 213B, 214B, 215B, or 216B through a resistor.

[0030] For example, the measurement circuit 206 can apply a test voltage to a first resistor (e.g., coupled to a positive terminal of the battery link 205). The test voltage can be connected to the positive terminal of the battery link 205 (e.g., terminal 215B) via the switch 215. The test voltage can also be connected to the negative terminal of the battery link 205 (e.g., terminal 216B) via the switch 216. In some embodiments, the switch 215 and the switch 216 are alternately enabled such that only one of the positive terminal or the negative terminal of the battery link 205 is connected to the test voltage at a time. While the test voltage is connected to the positive terminal of the battery link 205 via the switch 215, the measurement circuit 206 can measure a first voltage drop across the first resistor. While the test voltage is connected to the negative terminal of the battery link 205 via the switch 216, the measurement circuit 206 can apply the test voltage to the first resistor. The measurement circuit 206 may measure a second voltage drop across the first resistor while the test voltage is connected to the negative terminal of the battery link 205 via the switch 216. The processing device 207 may determine an insulation resistance value (e.g., Riso+ or Rios−) between the chassis ground node 202 and at least one of the positive or negative terminal of the battery link 205 of the power system 250 based on the first voltage drop and the second voltage drop.

[0031] In another example, the test voltage can be connected to the positive terminal of the battery pack 204 (e.g., terminal 213B) via the switch 213. While the test voltage is connected to the positive terminal of the battery pack 204 via the switch 213, the measurement circuit 206 can apply the test voltage to the second resistor. The test voltage can also be connected to the negative terminal of the battery pack 204 (e.g., terminal 214B) via the switch 214. In some embodiments, the switch 213 and the switch 214 are alternately enabled such that only one of the positive terminal or the negative terminal of the battery pack 204 is connected to the test voltage at a time. While the test voltage is connected to the positive terminal of the battery pack 204 via the switch 213, the measurement circuit 206 can measure a third voltage drop across the third resistor. While the test voltage is connected to the negative terminal of the battery pack 204 via the switch 214, the measurement circuit 206 can apply the test voltage to the second resistor. While the test voltage is connected to the negative terminal of the battery pack 204 via the switch 214, the measurement circuit 206 can measure a fourth voltage drop across the second resistor. The processing device 207 can determine an insulation resistance value (e.g., Riso+ or Rios-) between the chassis ground node 202 and at least one of the positive or negative terminals of the battery pack 204 of the power system 250 based on the third voltage drop and the fourth voltage drop. In some embodiments, the processing device 207 compares the insulation resistance value (e.g., Riso+ or Riso-) to a predetermined threshold. The processing device 207 further generates an alert in response to the insulation resistance value being less than the predetermined threshold.

[0032] In some embodiments, the test voltage applied by the measurement circuit 206 is provided by the auxiliary voltage supply 203. In some embodiments, the auxiliary voltage supply 203 may be a 12 volt battery (e.g., of the EV260). In some embodiments, the first resistor on the battery link side and the second resistor on the battery pack side may be the same resistance value. For example, in FIG. 3A and FIG. 3B, both the first resistor 371 and the second resistor 372 are both the same resistance value and are both represented as R1.

[0033] In some embodiments, insulation resistance measurement system 200 further includes a switch 212 coupled between measurement circuit 206 and auxiliary voltage supply 203. In some embodiments, processing device 207 provides a control signal 220 to switch 212. In some embodiments, when switch 212 is closed, a test voltage is applied to measurement circuit 206.

[0034] In some embodiments, the insulation resistance measurement system 200 further includes a switch 211 coupled between the measurement circuit 206 and the chassis ground node 202. In some embodiments, the processing device 207 provides a control signal 220 to the switch 211. In some embodiments, the switch 211 connects the chassis ground node 202 to the measurement circuit 206 when closed. Figure 3A is a circuit diagram illustrating an insulation resistance measurement circuit 300A, according to some embodiments.

[0035] In some embodiments, the insulation resistance measurement circuit 300A includes an insulation resistance monitoring unit 301. The insulation resistance monitoring unit 301 may be the same as or similar to the insulation resistance monitoring unit 101 of Figure 1 and / or the insulation resistance monitoring unit 201 of Figure 2. In some embodiments, the insulation resistance monitoring unit 301 includes a measurement circuit 306 and a controller 307.

[0036] In some embodiments, the controller 307 may be a microcontroller, a DSP, a field programmable gate array (FPGA), an application specific integrated circuit, etc. In some embodiments, the controller 307 processes data collected by the measurement circuitry 306. In some embodiments, the controller 307 may include an analog-to-digital converter (ADC), memory and computational logic, etc.

[0037] In some embodiments, the insulation resistance measurement circuit 300A includes a number of terminals (terminals 330, 331, 332, and 333) coupled to the measurement circuit 306. In some embodiments, the terminals include a battery pack terminal, a battery link terminal, and an auxiliary voltage supply terminal. In some embodiments, the terminals 330-333 correspond to at least one of the battery pack 304 or the battery link 305. For example, in some embodiments, the terminals 330 and 331 correspond to the battery link 305. In some embodiments, the terminal 330 corresponds to the positive terminal of the battery link 305, and the terminal 331 corresponds to the negative terminal of the battery link 305. In some embodiments, the terminals 332 and 333 correspond to the battery pack 304. In some embodiments, the terminal 332 corresponds to the positive terminal of the battery pack 304, and the terminal 333 corresponds to the negative terminal of the battery pack 304.

[0038] In some embodiments, the controller 307 is coupled to the measurement circuit 306. In some embodiments, the measurement circuit 306 and the controller 307 are coupled to the chassis ground node 302.

[0039] In some embodiments, the controller 307 is coupled to a plurality of switches (switches 310, 311, 312, 313). In some embodiments, the controller 307 provides control signals to the switches 310-313. In some embodiments, the controller 307 provides control signals to the switches 310, 311, 312, and 313 via nodes 320, 321, 322, and 323, respectively. In some embodiments, the nodes 320-323 are for digital control. In some embodiments, the switches 310-313 are coupled between the measurement circuitry and terminals 330-333. In some embodiments, the switches controlled by the controller 307 may have gate driver circuits between the corresponding nodes and the controller 307.

[0040] In some embodiments, the insulation resistance measurement circuit 300A includes an auxiliary voltage supply 303. In some embodiments, the controller 307 and the measurement circuit 306 are coupled to the auxiliary voltage supply 303. In some embodiments, the controller 307 and the measurement circuit 306 are powered by the auxiliary voltage supply 303. In some embodiments, the measurement circuit 306 applies a test voltage to a first resistor 371. In some embodiments, the test voltage applied by the measurement circuit 306 is provided by the auxiliary voltage supply 303. In some embodiments, the test voltage is applied to a terminal corresponding to the battery link 305 of the power system 350 via the first resistor 371. In some embodiments, the test voltage is applied to a terminal corresponding to the battery pack 304 of the power system 350 via a second resistor 372.

[0041] In some embodiments, the measurement circuit 306 measures the voltage drop across the first resistor 371. In some embodiments, the voltage drop can be measured at a measurement node 381. In some embodiments, the voltage drop can be measured at a measurement node 393. The voltage at node 393 can be adjusted using a voltage divider implemented to divide the voltage to an appropriate range heal to ensure that the resulting voltage level aligns with the input range of the ADC of the controller 307. In some embodiments, the controller 307 determines an insulation resistance value between the chassis ground node 302 and the battery link 305 of the power system 350 based on the voltage drop. In some embodiments, the controller 307 compares the insulation resistance value to a predetermined threshold and generates an alert in response to the insulation resistance value being below the predetermined threshold.

[0042] In some embodiments, the measurement circuit 306 measures the voltage drop across the second resistor 372. In some embodiments, the voltage drop can be measured at a measurement node 382. In some embodiments, the voltage drop can be measured at a measurement node 394. The voltage at node 394 can be adjusted using a voltage divider implemented to divide the voltage to an appropriate range heal to ensure that the resulting voltage level aligns with the input range of the ADC of the controller 307. In some embodiments, the controller 307 determines an insulation resistance value between the chassis ground node 302 and the battery pack 304 of the power system 350 based on the voltage drop. In some embodiments, the controller 307 compares the insulation resistance value to a predetermined threshold and generates an alert in response to the insulation resistance value being below the predetermined threshold.

[0043] In some embodiments, the measurement circuit 306 is coupled to the battery pack 304 , the battery link 305 and the auxiliary voltage supply 303 via switches 310 , 311 , 312 , 313 and 314 and terminals 330 , 331 , 332 , 333 and 334 .

[0044] In some embodiments, the switch 314 is coupled between the measurement circuit 306 and a terminal 334 corresponding to the auxiliary voltage supply 303. In some embodiments, the controller 307 provides a control signal to the switch 314 such that when the switch 314 is closed, a test voltage is applied to the measurement circuit 306. In some embodiments, the controller 307 provides a control signal to the switch 314 via a node 324. In some embodiments, the node 324 is for digital control. In some embodiments, the switches controlled by the controller 307 may have gate driver circuitry between the corresponding node and the controller 307.

[0045] In some embodiments, when each of the switches 310, 311, 312, and 313 is individually closed, a test voltage is applied to a corresponding terminal of the battery pack 304 or the battery link 305. For example, when the switch 310 is closed, the test voltage is applied to the positive terminal 330 of the battery link 305. When the switch 311 is closed, the test voltage is applied to the negative terminal 331 of the battery link 305. When the switch 312 is closed, the test voltage is applied to the positive terminal 332 of the battery pack 304. When the switch 313 is closed, the test voltage is applied to the negative terminal 333 of the battery pack 304.

[0046] Figure 3B is a circuit diagram illustrating an insulation resistance measurement circuit 300B according to some embodiments. Figure 3B illustrates a variation of the system shown in Figure 3A, having similar components and configurations, but incorporating notable differences that will be explained later. For a comprehensive description of elements common to both figures, please refer to the description shown in Figure 3A. All elements introduced in Figure 3A are directly referenced without additional introductory details.

[0047] In some embodiments, the insulation resistance measurement circuit includes a pair of switches. In some embodiments, a first switch 314 can be coupled between the measurement circuit 306 and a first terminal 334 corresponding to the auxiliary voltage supply 303. In some embodiments, a second switch 315 can be coupled between the measurement circuit 306 and a second terminal 335 corresponding to the auxiliary voltage supply. In some embodiments, the second terminal 335 is a terminal of the ground node 302.

[0048] In some embodiments, the controller 307 provides control signals to the switches 314 and 315. In some embodiments, the controller 307 provides control signals to the switches 314 and 315 via nodes 324 and 325, respectively. In some embodiments, the nodes 324 and 325 are for digital control. In some embodiments, the switches controlled by the controller 307 may have gate driver circuits between the corresponding nodes and the controller 307. In some embodiments, when the first switch 314 is closed, a test voltage of 12 volts is applied to the measurement circuit 306. In some embodiments, when the second switch 315 is closed, a zero volt test voltage is applied to the measurement circuit 306. In some embodiments, the zero volt test voltage is from the chassis ground node 302.

[0049] In some embodiments, the measurement node 381 may not be able to drive the resistor divider 375 to the measurement node 393. In some embodiments, the measurement node 393 may be a connection point for an analog voltage. In some embodiments, a controller buffer 391 may be added to the insulation resistance measurement circuit 300B. In some embodiments, when a 12 volt test voltage is applied to the resistor 371 and the battery link Riso+ is less than the battery link Riso-, the voltage level at the measurement node 381 may be greater than 12V (out of range). In some embodiments, when a zero volt test voltage is applied to the resistor 371 and the battery pack Riso+ is greater than the battery pack Riso-, the measurement node 381 is less than 0 volts (out of range). In some embodiments, the controller buffer 391 is powered (e.g., 12V and 0V) by the auxiliary voltage supply 303. In some embodiments, the controller buffer 391 clips the signal from the auxiliary voltage supply when the signal is out of range (e.g., greater than 12V or less than 0V).

[0050] In some embodiments, the measurement circuit 306 measures the voltage drop across the first resistor 371 at the measurement node 393. In some embodiments, the measurement circuit 306 measures the voltage drop across the first resistor 371 at the measurement node 381 when a test voltage of 12 volts is applied and when a test voltage of zero volts is applied to ensure that at least one measurement is not clipped by an operational amplifier (opamp) of the controller buffer 391. The test voltages of 12 volts and zero volts are applied to both the negative and positive terminals of the battery pack 304 and the battery link 305, respectively (e.g., using switches 310-313 to apply the test voltages to each terminal). In some embodiments, when the ADC of the controller 307 has the capability of converting relatively high voltages, the measurement circuit 306 can measure the voltage drop across the first resistor 371 at the measurement node 381. However, when the ADC of the controller 307 is rated for a lower voltage, the voltage drop across the first resistor 371 can be measured at a measurement node 393. The voltage at node 393 can be adjusted using a voltage divider implemented to divide the voltage to the appropriate range healing to ensure that the resulting voltage level aligns with the input range of the ADC of the controller 307.

[0051] In some embodiments, the measurement node 382 may not drive the resistor divider 376 to the measurement node 394. In some embodiments, the measurement node 394 is for an analog voltage. In some embodiments, a controller buffer 392 may be added to the insulation resistance measurement circuit 300B. In some embodiments, when a 12 volt test voltage is applied to the resistor 372 and the battery pack Riso+ is less than the battery pack Riso-, the voltage level at the measurement node 382 may be greater than 12V (out of range). In some embodiments, when a zero volt test voltage is applied to the resistor 372 and the battery link Riso+ is greater than the battery link Riso-, the measurement node 382 may be less than 0 volts (out of range). In some embodiments, the controller buffer 392 is powered by the auxiliary voltage supply 303 (e.g., 12V and 0V). In some embodiments, the controller buffer 392 clips the signal from the auxiliary voltage supply when the signal is out of range (e.g., greater than 12V or less than 0V).

[0052] In some embodiments, when the auxiliary voltage supply goes to 0V, the voltage at measurement nodes 393 and 394 (e.g., at the coupling controller 307) can go negative. In some embodiments, diode clamps 385 and 386 can be added to clamp the negative voltage. In some embodiments, diode clamps 385 and 386 prevent the negative voltage from reaching and potentially damaging the controller 307. In some embodiments, if node leakage is an issue, additional buffers can be added from resistor divider 375 or 376 to the controller 307. For example, additional buffers can be added between measurement node 393 and controller 307 and / or between measurement node 394 and controller 307.

[0053] In some embodiments, the switches controlled by the controller 307 may have gate driver circuits between the corresponding nodes and the controller 307 .

[0054] In some embodiments, the measurement circuit 306 measures the voltage drop across the second resistor 372 at the measurement node 394. In some embodiments, the measurement circuit 306 measures the voltage drop across the second resistor 372 at the measurement node 382 when a test voltage of 12 volts is applied and when a test voltage of zero volts is applied to ensure that at least one measurement is not clipped by the operational amplifier of the controller buffer 392. The test voltages of 12 volts and zero volts are applied to both the negative and positive terminals of the battery pack 304 and the battery link 305, respectively (e.g., using switches 310-313 to apply the test voltages to each terminal). In some embodiments, when the ADC of the controller 307 has the capability to convert relatively high voltages, the measurement circuit 306 can measure the voltage drop across the second resistor 372 at the measurement node 382. However, when the ADC of the controller 307 is rated for a lower voltage, the voltage drop across the second resistor 372 can be measured at the measurement node 394. The voltage at node 394 can be adjusted using a voltage divider implemented to divide the voltage to the appropriate range healing to ensure that the resulting voltage level aligns with the input range of the ADC of the controller 307.

[0055] In some embodiments, the controller 307 determines the insulation resistance value using an equation derived by circuit analysis of the insulation resistance measurement circuit 300B. The equation is described in more detail in FIG. 4. In some embodiments, the derivation of the equation for the insulation resistance measurement circuit 300B may be similar or the same as the derivation of the equation for the insulation resistance measurement circuit 300A. In some embodiments, the equation corresponding to the insulation resistance measurement circuit 300B may be used as the equation corresponding to the insulation resistance measurement circuit 300A, but for the insulation resistance measurement circuit 300B, four measurements are taken for each of the battery packs and battery links. For example, on the battery pack side, measurements are taken when a test voltage of 12 volts is applied to the positive battery pack terminal, a test voltage of zero volts is applied to the positive battery pack terminal, a test voltage of 12 volts is applied to the negative battery pack terminal, and a test voltage of zero volts is applied to the negative battery pack terminal.

[0056] In some embodiments, if leakage is a problem with the measurement node 393, an additional buffer can be added between the controller 307 and the measurement node 393. In some embodiments, if leakage is a problem with the control measurement node 394, an additional buffer can be added between the controller 307 and the measurement node 394.

[0057] 4 is a simplified circuit diagram illustrating the use of switches to measure insulation resistance values ​​using an insulation resistance measurement circuit 400, according to some embodiments. In FIG. 4, only the positive and negative terminals of a battery pack 404 are shown.

[0058] In some embodiments, the controller 407 allows the switches 410-413 to individually connect the positive and negative terminals of either the battery pack 404 or the battery link (e.g., the battery link 305 in FIGS. 3A and 3B) to enable two separate voltage measurements (e.g., the first voltage drop and the second voltage drop in FIGS. 3A and 3B) for either the battery pack 404 or the battery link (e.g., the battery link 305 in FIGS. 3A and 3B). The controller 407 can alternately apply a test voltage to the positive terminal 432 and the negative terminal 433 via the resistor 472. In response to the test voltage being alternately applied to the positive terminal 432 and the negative terminal 433, the measurement circuit 406 can obtain a voltage measurement across the resistor 472. In response to the measurement circuit 406 obtaining voltage measurements (e.g., the first and second voltage drops of methods 500A and 500B), Riso+ and Riso- can be calculated by the controller 407 for either the battery pack 404 or the battery link (e.g., the battery link 305 of FIGS. 3A and 3B). In some embodiments, the insulation resistance monitoring unit 401 includes the controller 407 and the measurement circuit 406. In some embodiments, the insulation resistance monitoring unit may be connected to the battery pack 404 or the battery link. The insulation resistance monitoring unit can make a first voltage measurement and a second voltage measurement corresponding to the positive terminal (e.g., the positive terminal 432) and the negative terminal (e.g., the negative terminal 433) of the battery pack 404 or the positive terminal and the negative terminal of the battery link. The controller 407 can determine an insulation resistance value of the battery pack 404 or the battery link based on the corresponding first and second voltage measurements of either the battery pack 404 or the battery link.

[0059] In some embodiments, the DC voltage measurements are completed using the auxiliary voltage supply 403 (e.g., a 12V power supply) as the test signal. In some embodiments, it is not necessary to generate a square wave signal.

[0060] By using an insulation resistance measurement circuit 400 with separate switches for the positive and negative battery pack terminals, the insulation resistance measurement circuit 400 can be simplified to simplified circuits 400A and 400B. In some embodiments, the simplified circuit 400A corresponds to applying the test voltage to the negative battery pack terminal, and the simplified circuit 400B corresponds to applying the test voltage to the positive battery pack terminal. In some embodiments, selectively applying the test voltage to either the positive or negative battery pack terminal is performed by controlling the switches 412 and 413. In order to back-calculate Riso+ and Riso- for both the battery pack 404 and the battery link (e.g., the battery link 305 in FIGS. 3A and 3B), the voltages of the battery pack 404 and the battery link (e.g., the battery link 305 in FIGS. 3A and 3B) need to be known. In some embodiments, a host (e.g., a battery management system controller, a vehicle control unit, an EV central processor, etc.) provides the voltage for the battery pack 404, and the battery link (e.g., battery link 305 of FIGS. 3A and 3B) is discharged to 0V by the system before the insulation resistance measurement is performed.

[0061] In some embodiments, switches 412 and 413 can be enabled one at a time to measure two different voltages, as described in the previous figures. For example, when switch 412 is enabled and switch 413 is at an open voltage Vm1 (corresponding to the negative terminal of battery pack 404), a measurement can be made at measurement node 482. When switch 413 is enabled and switch 412 is at an open voltage Vm2 (corresponding to the positive terminal of battery pack 404), a measurement can be made at measurement node 482. In some embodiments, voltage is measured only on the positive 12V edge.

[0062] In some embodiments, Vm1 and Vm2 can be used to inversely calculate Riso+ and Rios-. For example, the following formulas represent Vm1 and Vm2:

number

number

[0063] 5A-5B are flow diagrams of methods related to insulation resistance monitoring, according to some embodiments. Methods 500A-B may be implemented by processing logic including hardware (e.g., circuits, dedicated logic, programmable logic, microcode, etc.), software (e.g., instructions executed on a processing device), or a combination thereof. Methods 500A-B may be implemented in whole or in part by insulation resistance monitoring unit 101, insulation resistance measurement system 100, insulation resistance measurement system 200, insulation resistance measurement circuit 300A, insulation resistance measurement circuit 300B, or components thereof. Although shown in a particular sequence or order, unless otherwise indicated, the order of processes can be modified. Thus, the illustrated embodiments should be understood as examples only, and the illustrated processes can be implemented in different orders, and some processes can be implemented in parallel. Additionally, in various embodiments, one or more processes can be omitted. Thus, not all processes are required in all embodiments. Other process flows are possible.

[0064] FIG. 5A is a flow diagram of a method 500A relating to insulation resistance monitoring, according to some embodiments.

[0065] In some embodiments, the method 500A may be a method of monitoring insulation resistance using an insulation resistance monitoring unit.

[0066] Method 500A begins at operation 502 where processing logic connects a processing device to a chassis ground of the EV, the processing device being powered by an auxiliary voltage supply of the EV.

[0067] At operation 504, processing logic connects the measurement circuit to a chassis ground of the EV, the measurement circuit being powered by an auxiliary voltage supply.

[0068] At operation 506, the processing logic applies the test voltage via the measurement circuit to a first terminal of at least one of a battery pack or a battery link of a power system of the EV. In some embodiments, the first terminal is a positive terminal.

[0069] At operation 508, the processing logic measures, using the measurement circuitry, a first voltage drop across a first resistor coupled to the first terminal, the first voltage drop resulting from a test voltage applied to the first terminal via the measurement circuitry.

[0070] At operation 510, the processing logic applies the test voltage to a second terminal of at least one of a battery pack or a battery link of a power system of the EV via the measurement circuit. In some embodiments, the second terminal is a negative terminal and the first terminal is a corresponding positive terminal (e.g., of the battery pack or the battery link). In some embodiments, a set of switches is coupled between the measurement circuit and a positive terminal and a negative terminal of at least one of the battery pack and the battery link. In some embodiments, applying the test voltage to the first terminal includes closing a first switch of the set of switches and opening a second switch to apply the test voltage to the first terminal. In some embodiments, applying the test voltage to the second terminal includes opening a first switch of the set of switches and closing a second switch to apply the test voltage to the second terminal.

[0071] At operation 512, the processing logic uses the measurement circuit to measure a second voltage drop across the first resistor coupled to the second terminal, the second voltage drop resulting from a test voltage applied to the second terminal via the measurement circuit. In some embodiments, a set of switches is coupled between the measurement circuit and the positive and negative terminals of at least one of the battery pack and the battery link.

[0072] At operation 514, the processing logic determines a first insulation resistance value based at least on the first test voltage applied to the first terminal (e.g., the same as the test voltage applied to the first terminal), the measured first voltage drop, the measured second voltage drop, and the resistance value of the first resistor. In some embodiments, determining the first insulation resistance value can be further based on a voltage drop across the first terminal and the second terminal (e.g., V2 in FIG. 4). For example, the voltage drop across the first terminal and the second terminal may be a voltage drop across the positive and negative terminals of either a battery pack or a battery link of the EV's power system.

[0073] At operation 516, processing logic compares the first insulation resistance value to a predetermined threshold.

[0074] At operation 518, processing logic generates an alert in response to the first insulation resistance value being less than the predetermined threshold.

[0075] 5B is a flow diagram of a method 500B relating to insulation resistance monitoring, according to some embodiments. In some embodiments, method 500B may include some or all of the operations of method 500A, as well as additional operations outlined in FIG.

[0076] In some embodiments, the method 500B may be a method of monitoring insulation resistance using an insulation resistance monitoring unit.

[0077] Method 500B begins at operation 526, where processing logic determines a second insulation resistance value based on a test voltage applied to the second terminal (e.g., the same as the test voltage applied to the first terminal), the measured first voltage drop, the measured second voltage drop, and the resistance value of the first resistor. In some embodiments, determining the second insulation resistance value can be further based on a voltage drop across the first terminal and the second terminal (e.g., V2 in FIG. 4). For example, the voltage drop across the first terminal and the second terminal may be a voltage drop across the positive and negative terminals of either a battery pack or a battery link of the EV's power system.

[0078] At operation 528, processing logic compares the second insulation resistance value to a predetermined threshold.

[0079] At operation 530, processing logic generates an alert in response to the second insulation resistance value being less than the predetermined threshold.

[0080] In some embodiments, a pair of switches is coupled between the measurement circuit and the positive and negative terminals of the auxiliary voltage supply. In some embodiments, applying the test voltage includes closing a first switch of the pair of switches and opening a second switch of the pair of switches to apply a test voltage of 12 volts. In some embodiments, applying the test voltage includes opening a first switch of the pair of switches and closing a second switch of the pair of switches to apply a zero volt test voltage.

[0081] In the above description, numerous details are set forth. However, it will be apparent to one skilled in the art having the benefit of this disclosure that embodiments of the present disclosure may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the description.

[0082] Some portions of the detailed descriptions are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is generally conceived here to be a self-consistent sequence of steps leading to a desired result. These steps require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared and otherwise manipulated. It has proven convenient at times, primarily for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[0083] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these physical quantities. As is apparent from the above description, unless otherwise noted, throughout the description, descriptions utilizing terms such as "receive," "adjust," "measure," "determine," "compare," "generate," and the like, will be understood to refer to operations and processes of a computing system or similar electronic computing device that manipulates data represented as physical (e.g., electronic) quantities in the computing system's registers and memory and converts it into other data that is similarly represented as physical quantities in the computing system's memory or registers or other such information storage, transmission, or display devices.

[0084] The word "example" or "exemplary" is used herein to mean serving as an example, illustration, or illustration. An aspect or design described herein as "example" or "exemplary" should not necessarily be construed as preferred or advantageous over other aspects or designs. Rather, use of the term "example" or "exemplary" is intended to present a concept in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any of the obvious inclusive permutations. That is, "X includes A or B" will be satisfied if X includes A, if X includes B, or if X includes both A and B, in any of the foregoing cases. Furthermore, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless otherwise specified or unless the singular form is clearly intended from the context. Furthermore, the use of the terms "an embodiment" or "one embodiment" or "some embodiments" throughout is not intended to refer to one or more of the same embodiment, unless so described.

[0085] The embodiments described herein may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes or may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory computer-readable storage medium, such as, but not limited to, any type of disk, including floppy disks, optical disks, CD-ROMs and magneto-optical disks, read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic or optical cards, flash memory, or any type of medium suitable for storing electronic instructions. The term "computer-readable storage medium" should be interpreted to include a single medium or multiple media (e.g., centralized or distributed databases and / or associated caches and servers) that store one or more sets of instructions. The term "computer-readable medium" should also be interpreted to include any medium that can store, encode or carry a set of instructions for execution by a machine, causing the machine to perform any one or more of the methodologies of the present embodiments. Accordingly, the term "computer-readable storage medium" shall be taken to include, but not be limited to, solid-state memory, optical media, electromagnetic media, and any medium capable of storing a set of instructions for execution by a machine and causing the machine to perform any one or more of the methodologies of the present embodiments.

[0086] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description that follows. Further, the present embodiments are not described with reference to any particular programming language. It will be understood that a variety of programming languages ​​may be used to implement the teachings of the embodiments described herein.

[0087] In the above description, numerous specific details are given, such as examples of specific systems, components, methods, etc., to enhance understanding of some embodiments of the present disclosure. However, it will be apparent to those skilled in the art that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram form so as not to unnecessarily obscure the present disclosure. Thus, the above specific details are merely illustrative. It is believed that certain embodiments differ from these illustrative details and still fall within the scope of the present disclosure.

[0088] It is to be understood that the above description is intended to be illustrative, and not limiting. Many other embodiments will be apparent to those of ordinary skill in the art upon reading and understanding the above description. The scope of the present disclosure should therefore be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0089] In the above description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail, but rather in block diagram form in order to avoid unnecessarily obscuring the understanding of this description.

[0090] Reference in the description to "one embodiment" or "an embodiment" or "some embodiments" means that the particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the disclosure. The phrases "in one embodiment" or "in some embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment or embodiments.

Claims

1. Processing device and A measurement circuit connected to the aforementioned processing device, Auxiliary voltage supply unit, A system equipped with, The processing device and the measurement circuit are powered by the auxiliary voltage supply unit, the measurement circuit applies a test voltage to a resistor and measures the voltage drop across the resistor, and the processing device determines, at least based on the voltage drop, the insulation resistance value between the chassis ground node and at least one of the battery pack or battery link of the power system. The system further comprises a pair of switches, The first switch of the pair of switches is connected between the measuring circuit and the auxiliary voltage supply unit. The second switch of the pair of switches is connected between the measurement circuit and the chassis ground node. When the first switch is closed, a test voltage of 12 volts is applied to the measurement circuit, and when the second switch is closed, a test voltage of zero volts is applied to the measurement circuit. system.

2. The processing device and the measurement circuit are connected to the chassis grounding node. The system according to claim 1.

3. The test voltage applied by the measurement circuit is supplied by the auxiliary voltage supply unit. The system according to claim 1.

4. The test voltage is applied via the resistor to at least one terminal of the battery pack or battery link of the power system. The processing device is The insulation resistance value is compared with a predetermined threshold value, The system generates an alert in response to the insulation resistance value being less than the predetermined threshold. The system according to claim 1.

5. The auxiliary voltage supply unit is a 12-volt battery. The system according to claim 1.

6. Multiple terminals, A measurement circuit connected to the aforementioned multiple terminals, A controller connected to the aforementioned measurement circuit, Auxiliary voltage supply unit, An insulation resistance measuring circuit comprising, The controller is connected to a plurality of switches connected between the measurement circuit and the plurality of terminals, and provides control signals to the plurality of switches. The controller and the measurement circuit are powered by the auxiliary voltage supply unit, the measurement circuit applies a test voltage to a resistor and measures the voltage drop across the resistor, and the controller determines, at least based on the voltage drop, the insulation resistance between the chassis ground node and at least one of the battery pack or battery link of the power system. Insulation resistance measurement circuit.

7. The controller and the measurement circuit are connected to the chassis grounding node. The insulation resistance measurement circuit according to claim 6.

8. The test voltage applied by the measurement circuit is supplied by the auxiliary voltage supply unit. The insulation resistance measurement circuit according to claim 6.

9. The measurement circuit is connected to the battery pack, the battery link, and the auxiliary voltage supply unit via the plurality of switches and the plurality of terminals. The insulation resistance measurement circuit according to claim 6.

10. One of the plurality of switches is connected between the measurement circuit and one of the plurality of terminals corresponding to the auxiliary voltage supply unit, and the controller provides a control signal to the switch, and when the switch is closed, the test voltage is applied to the measurement circuit. The insulation resistance measurement circuit according to claim 9.

11. One of the aforementioned multiple switches is A first switch is connected between the measurement circuit and the first terminal of a plurality of terminals corresponding to the auxiliary voltage supply unit, A second switch is connected between the measurement circuit and the second terminal of the plurality of terminals corresponding to the auxiliary voltage supply unit, The circuit is equipped such that when the first switch is closed, a test voltage of 12 volts is applied to the measurement circuit, and when the second switch is closed, a test voltage of zero volts is applied to the measurement circuit. The insulation resistance measurement circuit according to claim 9.

12. When each of the plurality of switches is individually closed, the test voltage is applied to the corresponding terminal of at least one of the battery pack or the battery link. The insulation resistance measurement circuit according to claim 6.

13. The aforementioned multiple terminals are, Battery pack terminals and Battery link terminal and Auxiliary voltage supply terminals, The test voltage is applied via the resistor to one of the plurality of terminals corresponding to at least one of the battery pack or battery link of the power system. The aforementioned controller, The insulation resistance value is compared with a predetermined threshold value, The system generates an alert in response to the insulation resistance value being less than the predetermined threshold. The insulation resistance measuring circuit according to claim 8.

14. A step of connecting a processing device to the chassis ground of an electric vehicle (EV), wherein the processing device is powered by the auxiliary voltage supply unit of the EV, The step of connecting the measurement circuit to the chassis ground of the EV, wherein the measurement circuit is powered by the auxiliary voltage supply unit, The steps include applying a test voltage to at least one of the battery pack or battery link of the EV's power system via the measurement circuit, A step of measuring a first voltage drop across a first resistor connected to the first terminal using the measurement circuit, wherein the first voltage drop is generated from the test voltage applied to the first terminal via the measurement circuit. The steps include applying the test voltage via the measurement circuit to at least one of the second terminals of the battery pack or battery link of the EV's power system, A step of measuring a second voltage drop across the first resistor connected to the second terminal using the measurement circuit, wherein the second voltage drop is generated from the test voltage applied to the second terminal via the measurement circuit. A step of determining a first insulation resistance value based on the test voltage applied to the first terminal, the measured first voltage drop, the measured second voltage drop, and the resistance value of the first resistor, The steps include comparing the first insulation resistance value with a predetermined threshold value, A step of generating an alert in response to the fact that the first insulation resistance value is less than the predetermined threshold, A method that includes this.

15. The aforementioned method, A step of determining a second insulation resistance value based on the test voltage applied to the second terminal, the measured first voltage drop, the measured second voltage drop, and the resistance value of the first resistor, The steps include comparing the second insulation resistance value with a predetermined threshold value, The steps include generating an alert in response to the second insulation resistance value being less than the predetermined threshold, Further including, The method according to claim 14.

16. Multiple switches are connected between the measurement circuit and the positive and negative terminals of at least one of the battery pack and the battery link. The step of applying the test voltage to the first and second terminals is: In order to apply the test voltage to the first terminal, the steps include closing the first switch among the plurality of switches and opening the second switch, In order to apply the test voltage to the second terminal, the steps include opening the first switch among the plurality of switches and closing the second switch, including, The method according to claim 14.

17. A pair of switches are connected between the measurement circuit and the positive and negative terminals of the auxiliary voltage supply unit. The step of applying the test voltage is: The steps include closing the first switch of the pair of switches and opening the second switch of the pair of switches in order to apply a test voltage of 12 volts, The steps include opening the first switch of the pair of switches and closing the second switch of the pair of switches in order to apply a zero-volt test voltage, including, The method according to claim 14.

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