Battery management system and EIS measurement method for battery pack

Abstract

The present invention relates to a battery management system and an EIS measurement method for a battery pack, wherein a decrease in battery capacity (SOC) can be minimized by minimizing losses occurring during an EIS measurement operation, thereby increasing the accuracy of measured EIS. The battery management system comprises: an EIS measurement path that connects both (+) and (-) terminals of the battery pack to each other to provide a path through which an EIS current flows; an EIS measurement resistor (R_EIS) formed in the EIS measurement path to generate an EIS potential difference according to the EIS current; an EIS current frequency adjustment unit in which a plurality of current control switches (SW_1 to SW_n) are connected in parallel with each other and connected in series to the EIS measurement resistor (R_EIS) to adjust an EIS current frequency by connecting or excluding the EIS measurement resistor (R_EIS) to or from the EIS measurement path; and a control unit that adjusts, in response to the magnitude of the EIS current frequency, the number of operating and non-operating states of the plurality of current control switches (SW_1 to SW_n) connected in parallel with each other.

Description

Battery Management System and EIS Measurement Method for Battery Pack

[0001] The present invention relates to a battery management system (BMS) for measuring electrochemical impedance spectroscopy (EIS) of a battery pack, and more specifically, to a battery management system equipped with EIS measurement technology for a battery pack or cell for optimizing battery efficiency, and a method for measuring EIS of a battery pack.

[0002] Recently, active research and development on rechargeable batteries has been underway. Rechargeable batteries are rechargeable batteries that encompass conventional Ni / Cd and Ni / MH batteries, as well as the more recent lithium-ion batteries. Among these, lithium-ion batteries have the advantage of significantly higher energy density compared to conventional Ni / Cd and Ni / MH batteries. Lithium-ion batteries can be manufactured in a compact and lightweight manner, making them widely used as power sources for mobile devices. Recently, their scope of application has expanded to include electric vehicles, drawing attention as a next-generation energy storage medium.

[0003] Electrochemical Impedance Spectroscopy (EIS) is an electrochemical technique that measures impedance curves for multiple alternating current frequencies. EIS is a technique that extracts equivalent circuit parameters of a battery based on impedance values ​​measured after applying an alternating current power source at different frequencies to the battery. EIS is used to estimate the lifespan or condition of a battery.

[0004] As such, EIS is a battery inspection method that verifies cell lifespan and charge capacity by analyzing changes in the sum of components (impedance) when alternating current or voltage is applied. EIS can minimize errors that occur during secondary battery connections. Furthermore, using EIS technology not only drastically reduces inspection time but also significantly lowers inspection costs, offering the advantage of inspecting secondary battery performance while ensuring both productivity and economic efficiency.

[0005] FIG. 1 is a drawing showing an EIS measuring device of a battery pack according to the prior art.

[0006] As illustrated in FIG. 1, an EIS measuring device for a battery pack according to the prior art comprises a battery pack (10) and an EIS measuring resistor (R) connected on the paths at both ends of the battery pack (10) through which current flows from the battery pack (10). EIS ) and a resistor (R) for EIS measurement on a first path connecting the (-) electrode of the battery pack (10). EIS An EIS switch (SW) connected in series with ) and controlling the frequency of the EIS AC current by turning the first path on / off EIS ...includes ). At this time, the EIS measuring device of the battery pack is provided within the BMS (Battery Management System). And the EIS measuring device of the battery pack, based on the control signal transmitted from the BMS, includes an EIS switch (SW EIS It includes a control unit (20) that controls ).

[0007] A BMS board equipped with EIS measurement technology for a battery pack or cell uses an EIS switch (SW) at a predetermined frequency from the BMS's MCU or BMIC for EIS measurement. EISAC current is generated from the battery pack or battery cell by controlling the AC current. At this time, when AC current flows during EIS measurement operation, conduction loss and switching loss occur simultaneously, causing the battery capacity (SOC) to decrease. Therefore, there is a limitation in that the accuracy of the measured EIS decreases if the SOC changes during EIS measurement.

[0008] In addition, the conventional BMS for EIS measurement includes an EIS switch (SW), which is a switch FET that controls the frequency of the AC current for EIS. EIS ) is fixed as one. Therefore, as the frequency changes, the total loss (conduction loss and switching loss) changes, and there is a problem in that loss optimization (minimization) cannot be maintained.

[0009] Prior art documents include (Patent Document 1) Korean Registered Patent Publication No. 10-2703316 (registered on September 2, 2024) and (Patent Document 2) Korean Published Patent Publication No. 10-2024-0027801 (published on March 4, 2024).

[0010] The present invention aims to provide a battery management system and a method for measuring EIS of a battery pack that can increase the accuracy of the measured EIS by minimizing the decrease in the battery capacity (SOC) as a result of minimizing the total loss occurring at every moment during the EIS measurement operation.

[0011] A battery management system according to an embodiment of the present invention comprises: an EIS measurement path that connects the (+) and (-) terminals of a battery pack to provide a path for EIS current to flow; and an ELS measurement resistor (R) formed in the EIS measurement path to generate an ELS potential difference due to the EIS current. EIS A plurality of current control switches (SW_1~SW_n) are connected in parallel, and the EIS measuring resistor (R EIS Connected in series with the EIS measuring resistor (REIS It includes an EIS current frequency control unit that controls the EIS current frequency by connecting or excluding ) to the EIS measurement path; and a control unit that controls the number of operating or non-operating states of a plurality of parallel-connected current control switches (SW_1~SW_n) corresponding to the magnitude of the EIS current frequency.

[0012] The above current control switches (SW_1~SW_n) are composed of FET switches, and the output of the switch control signal of the control unit is connected to the gate terminal of each FET switch.

[0013] The above EIS current frequency control unit is the EIS measurement resistor (R EIS It is connected to ), and the EIS measurement resistor (R EIS It includes a plurality of current control switches (SW_1~SW_n) that connect or exclude the EIS measurement path; and a plurality of buffers, each having its output connected to a switching terminal of the current control switches (SW_1~SW_n).

[0014] The above current control switches (SW_1 to SW_n) are simultaneously switched to turn the EIS measurement path on / off at a predetermined period by a first switch control signal (SW_EIS signal) of the control unit, and their operation is controlled by a second switch control signal (SW_signal1 to SW_signaln) which is different from the first switch control signal (SW_EIS signal).

[0015] The first switch control signal (SW_EIS signal) is simultaneously input to the current control switches (SW_1 to SW_n) to simultaneously control the on / off of each current control switch (SW_1 to SW_n), and the second switch control signal (SW signal 1 to SW signal n) is input as an individual signal to each current control switch (SW_1 to SW_n) to control the current control switches (SW_1 to SW_n) to switch to an operating or non-operating state individually.

[0016] The above current control switches (SW_1~SW_n) are configured as FET switches, and a first switch control signal of the control unit is simultaneously input to each of the buffers, the output of which is connected to the gate terminal of each FET switch, and a second switch control signal of the control unit is input as an individual signal to each of the buffers to individually control the operating or non-operating state of the current control switches (SW_1~SW_n) connected to each buffer.

[0017] The above control unit controls the operation such that when the EIS current frequency becomes greater than a predetermined reference EIS current frequency during an EIS measurement operation, it reduces the number of operating current control switches (SW_1~SW_n) among the plurality of parallel-connected current control switches (SW_1~SW_n) to perform an on / off frequency operation, and when the EIS current frequency becomes smaller than a predetermined reference EIS current frequency, it increases the number of operating current control switches (SW_1~SW_n) among the parallel-connected current control switches (SW_1~SW_n) to perform an on / off frequency operation.

[0018] The above control unit adjusts the period or amplitude of the PWM signal of the first switch control signal for controlling the EIS current frequency adjustment unit.

[0019] The above control unit adjusts the amplitude of the first switch control signal to be smaller when it is necessary to operate at a frequency greater than the reference frequency, and adjusts the amplitude of the first switch control signal to be larger when it is necessary to operate at a frequency smaller than the reference frequency.

[0020] The above control unit is based on a control signal transmitted from an MCU or BMIC, and an EIS switch (SW EIS It is a means for controlling the on / off of ), or is provided outside the BMS and is an EIS switch (SW EIS It is characterized by being a means for controlling the on / off of ).

[0021] A method for measuring EIS of a battery pack according to an embodiment of the present invention is a method for measuring EIS of a battery pack in a current-regulating battery management system for measuring EIS, comprising: an EIS current frequency determination step for determining an EIS current frequency for measuring EIS in the battery management system; a frequency comparison step for comparing the determined EIS current frequency with a predetermined reference EIS current frequency; a switch enable determination step for determining the number of enable switches of a plurality of current control switches (SW_1~SW_n) connected in parallel according to the comparison result; a switch selection step for selectively enabling or disabling the plurality of current control switches (SW_1~SW_n) according to the determined number of enable switches; an EIS current generation step for generating an EIS current by controlling the enabled switches with a switch control signal having a period corresponding to the EIS current frequency determined in the EIS current frequency determination step; and an impedance measurement step for measuring the impedance of the battery pack using the generated EIS current.

[0022] The switch enable determination step determines that if the EIS current frequency is greater than a predetermined reference EIS current frequency, a number of current control switches (SW_1~SW_n) smaller than the reference are determined as enable switches, and if the EIS current frequency is less than a predetermined reference EIS current frequency, a number of current control switches (SW_1~SW_n) larger than the reference are determined as enable switches.

[0023] The switch enable determination step comprises: a step of reducing the number of operating current control switches (SW_1~SW_n) among a plurality of parallel-connected current control switches (SW_1~SW_n) if, based on the comparison result, the determined EIS current frequency is greater than the reference EIS current frequency; and a step of increasing the number of operating current control switches (SW_1~SW_n) among a plurality of parallel-connected current control switches (SW_1~SW_n) if, based on the comparison result, the determined EIS current frequency is not greater than the reference EIS current frequency.

[0024] The above EIS current generation step includes a step of adjusting the EIS current frequency by adjusting the period (amplitude) of a PWM signal corresponding to the determined EIS current frequency.

[0025] According to an embodiment of the present invention, during an EIS measurement operation, the number of FETs configured to form a plurality of parallel-connected current control switches is controlled according to the magnitude of the frequency of the EIS current (AC current for EIS measurement). By doing so, the total loss (conduction loss, switching loss) occurring as the frequency of the EIS current (AC current for EIS measurement) changes is minimized at every moment, thereby minimizing the decrease in the battery capacity (SOC). Since the change in SOC is reduced compared to conventional battery management systems, the accuracy of the measured EIS can be maintained at a high level, and at the same time, power loss from the battery can be minimized.

[0026] The features and advantages of the present invention can be better understood by referring to the following attached drawings together with the detailed description of embodiments of the present invention that follows, and among said drawings:

[0027] FIG. 1 is a drawing showing an EIS measuring device of a battery pack according to the prior art.

[0028] FIG. 2 is a diagram showing the configuration of a battery management system according to an embodiment of the present invention.

[0029] FIG. 3 is a diagram for explaining the operation of the EIS current frequency control unit of FIG. 2.

[0030] FIG. 4 is a diagram illustrating an EIS measurement method of a battery pack according to an embodiment of the present invention.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and the embodiments of the present invention are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. To explain the invention in detail, the drawings may be exaggerated, and like reference numerals in the drawings refer to like elements.

[0032] FIG. 2 is a diagram showing the configuration of a battery management system according to an embodiment of the present invention.

[0033] Referring to FIG. 2, a battery management system according to an embodiment of the present invention comprises an EIS measurement path (L) that connects the (+) and (-) terminals of a battery pack (100) to provide a path for EIS current to flow, and an ELS measurement resistor (R) formed in the EIS measurement path (L) to generate an ELS potential difference due to the EIS current. EIS ) and, an EIS current frequency control unit (200) formed in the EIS measurement path (L) to control the frequency of the EIS current, and an EIS measurement resistor (R EIS It includes a control unit (300) that controls the ) and EIS current frequency control unit (200).

[0034] The battery pack (100) stores electrical energy supplied from a charger. The battery pack (100) includes a battery module configured by connecting at least one battery cell in series or in parallel.

[0035] EIS measured resistance (R EISThe EIS current frequency control unit (200) and the EIS current frequency control unit can be combined and referred to as an EIS measurement unit. The EIS measurement unit is connected to the EIS measurement path (L) at both ends of the battery pack (100). The EIS measurement unit applies a measurement current, which is an alternating current, to the battery pack (100) within the frequency range of the set measurement frequency to measure the impedance of any battery cell.

[0036] For reference, the Battery Management System (BMS) of the battery pack records the measured impedance data according to a set measurement frequency and can visualize it by outputting it as a Nyquist or Bode plot. Through the output Nyquist or Bode plot, the BMS analyzes the change in impedance of the battery cell based on the measured impedance. Through this, the internal resistance, ion mobility, interface characteristics, etc. of the battery pack can be evaluated, and the electrochemical characteristics of the battery pack (100) can be interpreted.

[0037] The EIS current frequency control unit (200) is an EIS measurement resistor (R EIS It is connected in series with ). The EIS current frequency control unit (200) is connected to the EIS measuring resistor (R EIS It includes a plurality of current control switches (SW_1 to SW_n) that connect or exclude the EIS measurement path (L). At this time, the plurality of current control switches (SW_1 to SW_n) are connected in parallel with each other.

[0038] The current control switches (SW_1~SW_n) are turned on / off at a predetermined cycle according to the control of the control unit (300), and the EIS measurement resistor (R EIS A frequency component that is the inverse of a predetermined period is applied to the voltage across the terminals. The current control switches (SW_1~SW_n) can be configured as FET switches.

[0039] The current control switches (SW_1 to SW_n) can be switched to turn the EIS measurement path (L) on / off at a predetermined period by a switch control signal from the control unit (300). For example, if the current control switches (SW_1 to SW_n) are configured as FET switches, the output of the switch control signal from the control unit (300) can be connected to the gate terminal of each FET switch.

[0040]

[0041] Figure 3 is a diagram illustrating the control of the EIS current frequency control unit of Figure 2.

[0042] Referring to FIG. 3, the EIS current frequency control unit (200) has an EIS measurement resistance (R EIS It includes a plurality of current control switches (SW_1~SW_n) that connect or exclude each path branched in parallel from ), and a plurality of buffers (210_1~210_n) whose outputs are respectively connected to the switching terminals of the current control switches (SW_1~SW_n). At this time, the plurality of current control switches (SW_1~SW_n) are each connected in parallel, and the EIS measurement resistor (R EIS It is connected in series with ).

[0043] The current control switches (SW_1 to SW_n) are simultaneously switched to turn the EIS measurement path (L) on / off at a predetermined period by the first switch control signal (SW_EIS signal) of the control unit (300). Then, the operation of the current control switches (SW_1 to SW_n) is controlled by the second switch control signal (SW_signal1 to SW_signaln), which is different from the first switch control signal (SW_EIS signal). That is, by turning the input of the first switch control signal (SW_EIS signal) on / off by the second switch control signal (SW_signal1 to SW_signaln) of each current control switch (SW_1 to SW_n), the parallel path of each switch is selectively controlled by the EIS measurement resistor (R EISIt is connected to ). That is, the first switch control signal (SW_EIS signal) is simultaneously input to the current control switches (SW_1~SW_n) to simultaneously control the on / off of each current control switch (SW_1~SW_n). Then, the second switch control signal (SW signal 1~SW signal n) is input as an individual signal to each current control switch (SW_1~SW_n) to control the current control switches (SW_1~SW_n) to switch to an operating or non-operating state individually.

[0044] For example, when the current control switches (SW_1~SW_n) are configured as FET switches, the first switch control signal of the control unit (300) is input to buffers (210_1~210_n) to which the output is connected to the gate terminal of each FET switch, and is simultaneously input to each switch through the buffers. Then, the second switch control signal of the control unit (300) is input as an enable signal to each of the buffers (210_1~210_n), thereby blocking the first switch control signal input through each buffer (210_1~210_n), and thereby individually controlling the operating or non-operating state of the current control switches (SW_1~SW_n).

[0045]

[0046] Meanwhile, conduction loss and switching loss occur during EIS measurement operation. That is, when the current control switches (SW_1~SW_n) are turned on, the resistance (RDS_ON) and EIS measurement resistance (R) when the FETs corresponding to the current control switches (SW_1~SW_n) are turned on EIS As current flows through ) Conductive loss of magnitude occurs. In addition, EIS measurement resistance (R EIS Switching losses occur due to parasitic capacitors of the FETs, which are current control switches (SW_1~SW_n), as they switch on / off.

[0047] Regarding conduction and switching losses, as the width of the FETs (current control switches SW_1~SW_n) increases, the resistance of the FETs decreases, thereby reducing conduction losses; however, the parasitic capacitance of the FETs increases, causing switching losses to increase. Conversely, as the width of the FETs decreases, the resistance of the FETs increases, thereby increasing conduction losses; whereas the parasitic capacitance of the FETs decreases, thereby reducing switching losses.

[0048] However, regarding conduction and switching losses, switching losses are dominant over conduction losses when the frequency of the EIS current (AC current for EIS measurement) is high, and conversely, conduction losses are dominant over switching losses when the frequency of the EIS current is low.

[0049] By utilizing these properties, the control unit (300) of the present invention controls the operation of the on / off frequency by reducing the number of operating current control switches (SW_1~SW_n) among a plurality of current control switches (SW_1~SW_n) connected in parallel, so that when the EIS current frequency becomes larger (higher) than a predetermined reference EIS current frequency during the EIS measurement operation, the switching loss, which is a more dominant loss, can be reduced. At this time, reducing the number of operating current control switches (SW_1~SW_n) can produce the effect of reducing the size of the FET.

[0050] Conversely, when the EIS current frequency becomes smaller than a predetermined reference EIS current frequency during the EIS measurement operation, the control unit (300) can reduce the conduction loss, which is a more dominant loss, so it controls the operation to perform an on / off frequency operation by increasing the number of operating current control switches (SW_1~SW_n) among the plurality of current control switches (SW_1~SW_n) connected in parallel. At this time, increasing the number of operating current control switches (SW_1~SW_n) can have the effect of increasing the size of the FET.

[0051] However, the aforementioned predetermined reference EIS current frequency may be set differently depending on the type or performance of the battery, and is therefore not numerically limited in this specification. It will be set to a value optimized by the designer or manufacturer when designing or manufacturing the battery.

[0052] In this way, the control unit (300) individually controls the operating or non-operating state of a plurality of current control switches (SW_1 to SW_n) connected in parallel in correspondence with the magnitude of the EIS current frequency.

[0053] Therefore, by minimizing the total losses (conduction losses, switching losses) that occur as the frequency of the EIS current (AC current for EIS measurement) changes at every moment, the decrease in battery capacity (SOC) during EIS measurement can be minimized. Consequently, since the change in SOC is reduced compared to conventional battery management systems, the accuracy of the measured EIS can be maintained at a high level, while simultaneously minimizing battery power loss.

[0054] Additionally, the control unit (300) can control the operation or non-operation state of a plurality of current control switches (SW_1 to SW_n) connected in parallel individually, and adjust the frequency of the EIS measurement current by adjusting the period of the PWM signal of the first switch control signal.

[0055] The control unit (300) generates a predetermined reference period PWM signal as a first switch control signal to generate a predetermined reference EIS current frequency. Then, it sets the number of ON current control switches (SW_1~SW_n) optimized in correspondence with the generated reference period first switch control signal.

[0056] If the control unit (300) needs to operate at a frequency greater than the reference EIS current frequency, it changes the amplitude of the first switch control signal to be smaller and adjusts the second switch control signal so that fewer FET switches are turned on than the number of current control switches set to optimization. And if the control unit (300) needs to operate at a frequency smaller than the reference frequency, it changes the amplitude of the first switch control signal to be larger and adjusts the second switch control signal so that more FET switches are connected.

[0057] Meanwhile, the control unit (300) controls the EIS switch (SW) based on a control signal transmitted from the MCU or BMIC of the BMS. EIS It is a means for controlling the on / off of ), or the MCU / BMIC is configured as a control unit (300), or an EIS switch (SW) is provided outside the BMS EIS It can be a means of controlling the on / off of ).

[0058]

[0059] Hereinafter, an EIS measurement method for a battery pack according to an embodiment of the present invention will be described. The EIS measurement method for a battery pack according to an embodiment of the present invention may be a method for processing a received signal using the aforementioned battery management system, and since the aforementioned details regarding the battery management system can be applied as is, a description of redundant details will be omitted.

[0060] FIG. 4 is a diagram illustrating a method for measuring EIS of a battery pack using a battery management system according to an embodiment of the present invention.

[0061] Referring to FIG. 4, the method for measuring EIS of a battery pack according to an embodiment of the present invention first determines an EIS current frequency for EIS measurement (S10). Then, the determined EIS current frequency is compared with a predetermined reference EIS current frequency (S20).

[0062] If, as a result of comparison (S20), the determined EIS current frequency is greater than the reference EIS current frequency (S30), switching loss occurs during the EIS measurement operation. Therefore, to reduce switching loss, the number of operating current control switches (SW_1~SW_n) among the multiple current control switches (SW_1~SW_n) connected in parallel must be reduced so that the on / off frequency operation is performed (S40). At this time, reducing the number of operating current control switches (SW_1~SW_n) can have the effect of reducing the size of the FET.

[0063] Conversely, if the EIS current frequency determined by the comparison result (S20) is not greater than the reference EIS current frequency (S30), conduction loss occurs. Therefore, to reduce conduction loss, the number of operating current control switches (SW_1~SW_n) among the multiple current control switches (SW_1~SW_n) connected in parallel must be increased so that on / off frequency operation is performed (S50). At this time, increasing the number of operating current control switches (SW_1~SW_n) can have the effect of increasing the size of the FET.

[0064] Thus, the number of enable switches for a plurality of current control switches (SW_1~SW_n) is determined according to the above frequency comparison result (S40)(S50).

[0065] Next, a plurality of current control switches (SW_1~SW_n) are selectively enabled or disabled according to the determined number of enable switches (S60).

[0066] In other words, if the frequency of the determined EIS current is greater than the reference EIS current frequency, a smaller number of current control switches (SW_1~SW_n) than the reference are selected as enable switches. That is, control must be performed to enable on / off frequency operation by reducing the number of operating current control switches (SW_1~SW_n) among the multiple current control switches (SW_1~SW_n) connected in parallel.

[0067] In addition, if the frequency of the determined EIS current is lower than the reference EIS current frequency, a larger number of current control switches (SW_1~SW_n) than the reference are determined as enable switches. That is, control must be performed to enable on / off frequency operation by increasing the number of operating current control switches (SW_1~SW_n) among the multiple current control switches (SW_1~SW_n) connected in parallel.

[0068] In this way, the decrease in battery capacity (SOC) can be minimized by adjusting the total losses (conduction loss, switching loss) that occur as the frequency of the EIS current (AC current for EIS measurement) changes to be minimized at every moment. Since the change in SOC is reduced compared to conventional battery management systems, the accuracy of the measured EIS can be maintained at a high level, while simultaneously minimizing battery power loss.

[0069] Then, an EIS current flowing through the EIS measurement path (L) is generated by the on / off frequency operation of the current control switches (SW_1~SW_n) enabled by a switch control signal having a period corresponding to the determined EIS current frequency (S70).

[0070] The impedance of the battery pack is measured using the generated EIS current to produce EIS measurement data (S80).

[0071] Meanwhile, the EIS current frequency can be adjusted by adjusting the period (or amplitude) of the PWM signal corresponding to the determined EIS current frequency. Through this method, by generating more FET disables or more FET enables, the number of ON current control switches (SW_1 to SW_n) optimized for a predetermined reference frequency EIS current can be set.

[0072]

[0073] In the foregoing, preferred embodiments of the present invention have been described and illustrated using specific terms, but such terms are intended solely to clarify the present invention, and it is obvious that various modifications and changes may be made to the embodiments and described terms of the present invention without departing from the technical spirit and scope of the following claims. Such modified embodiments should not be understood separately from the spirit and scope of the present invention, but should be considered to fall within the scope of the claims of the present invention.

[0074] Meanwhile, the names of the reference numerals used in the present invention are as follows.

[0075] 100: Battery pack, 200: EIS current frequency regulator, 210: Buffer, 300: Control unit, L: EIS measurement path

Claims

1. An EIS measurement path that connects the (+) and (-) terminals of a battery pack to provide a path for EIS current to flow; An ELS measurement resistor (R) formed in the above EIS measurement path, which generates an ELS potential difference due to the EIS current. EIS ); A plurality of current control switches (SW_1~SW_n) are connected in parallel, and the EIS measuring resistor (R EIS Connected in series with the EIS measuring resistor (R EIS An EIS current frequency control unit that controls the EIS current frequency by connecting or excluding ) to the EIS measurement path; and A battery management system comprising a control unit that adjusts the number of operating or non-operating states of a plurality of parallel-connected current control switches (SW_1~SW_n) in correspondence with the magnitude of the EIS current frequency.

2. In Paragraph 1, The above current control switches (SW_1~SW_n) are, A battery management system composed of FET switches, wherein the switch control signal of the control unit is connected to the output of each FET switch at the gate terminal.

3. In Paragraph 1, The above EIS current frequency control unit is, The above EIS measurement resistor (R EIS It is connected to ), and the EIS measurement resistor (R EIS A plurality of current control switches (SW_1~SW_n) that connect or exclude ) to the EIS measurement path; and A battery management system comprising a plurality of buffers, each having its output connected to a switching terminal of the current control switches (SW_1~SW_n).

4. In Paragraph 3, The above current control switches (SW_1~SW_n) are, The EIS measurement path is simultaneously switched on / off at a predetermined period by the first switch control signal (SW_EIS signal) of the control unit, and A battery management system in which the operation of each is controlled by a second switch control signal (SW signal 1 to SW signal n) different from the first switch control signal (SW_EIS signal).

5. In Paragraph 4, The above first switch control signal (SW_EIS signal) is simultaneously input to the current control switches (SW_1~SW_n) to simultaneously control each current control switch (SW_1~SW_n) on / off, and A battery management system in which the above second switch control signals (SW signal 1 to SW signal n) are input as individual signals to each current control switch (SW_1 to SW_n) to control the current control switches (SW_1 to SW_n) to switch to an operating or non-operating state individually.

6. In Paragraph 4, The above current control switches (SW_1~SW_n) are configured as FET switches, and the first switch control signal of the control unit is simultaneously input to each of the buffers, the output of which is connected to the gate terminal of each of the FET switches, and A battery management system in which the second switch control signal of the above control unit is input as an individual signal to each of the above buffers, and the operating or non-operating state of the current control switches (SW_1~SW_n) connected to each buffer is individually controlled.

7. In Paragraph 5 or 6, The above control unit, during EIS measurement operation, When the above EIS current frequency becomes greater than a predetermined reference EIS current frequency, the number of operating current control switches (SW_1~SW_n) among the plurality of parallel-connected current control switches (SW_1~SW_n) is reduced so that on / off frequency operation is performed. A battery management system that controls the operation of on / off frequency operation by increasing the number of operating current control switches (SW_1~SW_n) among the plurality of parallel-connected current control switches (SW_1~SW_n) when the above EIS current frequency becomes smaller than a predetermined reference EIS current frequency.

8. In Paragraph 1, The above control unit is a battery management system that adjusts the period or amplitude of a PWM signal of a first switch control signal for controlling the EIS current frequency control unit.

9. In Paragraph 8, The above control unit is, If it is necessary to operate at a frequency higher than the reference frequency, the amplitude of the first switch control signal is adjusted to be smaller, and A battery management system that significantly adjusts the amplitude of the first switch control signal when it is necessary to operate at a frequency lower than the reference frequency.

10. In Paragraph 1, The above control unit is based on a control signal transmitted from an MCU or BMIC, and an EIS switch (SW EIS It is a means for controlling the on / off of ), or is provided outside the BMS and is an EIS switch (SW EIS A battery management system characterized by being a means for controlling the on / off of ).

11. A method for measuring the EIS of a battery pack in a current-regulating battery management system for EIS measurement, wherein in the battery management system, EIS current frequency determination step for determining the EIS current frequency for EIS measurement; A frequency comparison step for comparing the above-determined EIS current frequency with a predetermined reference EIS current frequency; A switch enable determination step for determining the number of enable switches of a plurality of current control switches (SW_1~SW_n) connected in parallel according to the above comparison result; A switch selection step for selectively enabling or disabling the plurality of current control switches (SW_1~SW_n) according to the number of enable switches determined above; An EIS current generation step for generating an EIS current by controlling the enabled switches with a switch control signal having a period corresponding to the EIS current frequency determined in the EIS current frequency determination step; and A method for measuring EIS of a battery pack, comprising an impedance measurement step of measuring the impedance of the battery pack using the generated EIS current.

12. In Paragraph 11, The above switch enable determination step is, If, based on the comparison result above, the determined EIS current frequency is greater than the reference EIS current frequency, the step of reducing the number of operating current control switches (SW_1~SW_n) among a plurality of current control switches (SW_1~SW_n) connected in parallel; and A method for measuring EIS of a battery pack, comprising the step of increasing the number of operating current control switches (SW_1~SW_n) among a plurality of current control switches (SW_1~SW_n) connected in parallel, if, based on the comparison result above, the determined EIS current frequency is not greater than the reference EIS current frequency.

13. In Paragraph 11, The above EIS current generation step is, A method for measuring EIS of a battery pack comprising the step of adjusting the EIS current frequency by adjusting the period or amplitude of a PWM signal corresponding to the determined EIS current frequency.

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