Battery system monitoring device

Abstract

The present invention addresses the problem of obtaining a battery system monitoring device capable of suppressing erroneous detection of a diagnosis abnormality in an integration circuit caused by a low-frequency ripple noise. The battery system monitoring device (100) removes first noise included in a cell voltage of a plurality of single cells (101) which are connected in series on the basis of a first time constant, and calculates a cell total voltage by totaling the cell voltages of the plurality of single cells (101) from which the first noise has been removed. Second noise included in a cell voltage between the positive electrode of the highest single cell (101) of the plurality of single cells connected in series and the negative electrode of the lowest single cell (101) thereof is removed on the basis of a second time constant, and VBLK voltage, which is the cell voltage from which the second noise has been removed, is measured. On the basis of the cell total voltage and the VBLK voltage, a determination regarding whether or not to permit a diagnosis of the state of the plurality of single cells (101) is made, and the diagnosis about the state of the plurality of single cells (101) is performed when it has been determined that the diagnosis may be performed.

Description

[Technical Field]

[0001] The present invention relates to a battery system monitoring device. [Background technology]

[0002] Hybrid electric vehicles (HEVs) and electric vehicles (EVs) use battery packs (battery systems) in which multiple secondary battery cells are connected in series to ensure the desired high voltage. In such battery packs, integrated circuits are used to calculate the capacity of each cell and to protect and manage it. The integrated circuits measure, for example, cell voltage (voltage between the terminals of the cells) and perform balancing discharge to equalize the state of charge, i.e., remaining capacity. Furthermore, they also perform various diagnostics of the cells and cell controllers to improve the reliability and safety of the battery packs (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-203593 Summary of the Invention [Problem to be solved by the invention]

[0004] To further enhance the reliability and safety of battery packs, it is important to improve the accuracy of diagnosis by integrated circuits. As a result of extensive research, the applicant has discovered that the accuracy of diagnosis by integrated circuits can be improved by taking into account the possibility of noise being applied superimposed on cell voltages.

[0005] An object of the present invention is to provide a battery system monitoring device that can improve the accuracy of diagnosis of integrated circuits. [Means for solving the problem]

[0006] The battery system monitoring device of the present invention that solves the above problems includes: A battery system monitoring device that monitors the state of a plurality of series-connected cells, a first noise removal unit that removes a first noise included in the voltages of the plurality of single cells based on a first time constant; a total voltage calculation unit that calculates a total voltage by summing the voltages of the plurality of single cells from which the first noise has been removed by the first noise removal unit; a second noise removal unit that removes, based on a second time constant, a second noise included in a series voltage that is a voltage between the positive electrode of the uppermost cell and the negative electrode of the lowermost cell of the plurality of series-connected cells; a series voltage measurement unit that measures the series voltage from which the second noise has been removed by the second noise removal unit; a diagnosis permission determination unit that determines whether to permit diagnosis of the states of the plurality of unit cells based on the total voltage calculated by the total voltage calculation unit and the series voltage measured by the series voltage measurement unit; and a cell monitoring and diagnosing unit that diagnoses the states of the plurality of cells when the diagnosis permission determining unit determines that the cells are diagnosable; The present invention is characterized by having the following. [Effects of the Invention]

[0007] The battery system management device according to the present invention can improve the diagnostic accuracy of integrated circuits. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, problems, configurations, and advantages other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a hybrid vehicle equipped with a battery system including a battery system monitoring device of the present invention; [Figure 2] FIG. 2 is a diagram showing the configuration of a cell controller 200 in FIG. [Figure 3] FIG. 2 is a functional block diagram illustrating the internal functions of a cell monitoring IC. [Figure 4]6 is a flowchart illustrating the process of noise removal by the cell voltage detection line RC filter circuit 220. [Figure 5] 10 is a flowchart illustrating the details of noise removal processing by the VBLK voltage line RC filter circuit 240. [Figure 6] 6 is a flowchart for determining whether or not a diagnosis can be performed by a cell monitoring IC. [Figure 7] A graph showing the voltage difference ΔV between the total cell voltage and the VBLK voltage depending on whether ripple noise is present or not. [Figure 8] Graph showing the difference between the total cell voltage and the VBLK voltage. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] [First embodiment] This embodiment is an example in which the battery system monitoring device according to the present invention is applied to a drive system used in a hybrid electric vehicle (HEV), etc. Note that the present invention is not limited to HEVs, but can be widely applied to various drive systems installed in plug-in hybrid electric vehicles (PHEVs), electric vehicles (EVs), railway vehicles, etc.

[0011] In the following embodiments, a lithium-ion battery with a voltage in the range of 3.0 to 4.2 V (average output voltage: 3.6 V) is assumed as the storage / discharge device, which is the smallest unit of control, but this is not limited to this. Any other device that can store and discharge electricity and whose use is restricted when the SOC (State of Charge), which indicates the state of charge, is too high (overcharging) or too low (over-discharging) will suffice, and here they will be collectively referred to as a single battery or cell.

[0012] In this embodiment, a group of cells is defined as a series connection of a plurality of single cells (generally several to a dozen or so), and a battery module is defined as a series connection of a plurality of such cell groups. Further, a battery pack is defined as a series or parallel connection of a plurality of such cell groups or battery modules. Each cell group is provided with a cell monitoring IC. The cell monitoring IC detects the cell voltage of each single cell and monitors and controls the battery state while performing balancing discharge or the like to equalize the cell voltages.

[0013] <Drive System for HEV> FIG. 1 is a diagram showing a configuration example of a drive system 10 for HEV provided with a battery system monitoring device 100 according to this embodiment. The drive system 10 for HEV includes a battery system monitoring device 100, an inverter 700 connected to the battery system monitoring device 100, and a motor 800 connected to the inverter 700. The battery system monitoring device 100 is connected to the inverter 700 via relays 600 and 610. When the vehicle starts or accelerates, the power discharged from the battery system monitoring device 100 is supplied to the motor 800 through the inverter 700 to assist an engine (not shown) of the HEV 10. When the vehicle stops or decelerates, the regenerative power from the motor 800 is supplied to the battery system monitoring device 100 through the inverter 700 for charging.

[0014] Here, the inverter 700 includes an inverter circuit having a plurality of semiconductor switching elements, a gate drive circuit for the semiconductor switching elements, and a motor controller that generates a pulse signal for PWM control of the gate drive circuit, but is omitted in FIG. 1.

[0015] The battery system monitoring device 100 mainly comprises an assembled battery 103 consisting of a plurality of cells 101, which are lithium ion batteries; a cell controller 200 having a plurality of cell monitoring ICs 300 for battery monitoring and control that detect the cell voltage of each cell 101 for each cell group 102 of the assembled battery 103 and perform balancing discharge operations, etc.; and a battery controller 500 that controls the operation of the cell controller 200 and determines the state of each cell 101.

[0016] The example battery system monitoring device 100 shown in this embodiment has an assembled battery 103 in which 96 lithium ion batteries with a rated capacity of 5.5 Ah are used as single cells 101 and connected in series. A battery controller 500 communicates with multiple cell monitoring ICs 300 via an insulating element group 400 to control the assembled battery 103. The assembled battery 103 has multiple cell groups 102. As described above, a cell monitoring IC 300 is provided for each cell group 102.

[0017] The cell controller 200 uses these multiple cell monitoring ICs 300 to function as a battery management device that manages the assembled battery 103. The assembled battery 103 and the cell controller 200 are connected to each other via a cell voltage detection / discharge line 201.

[0018] The battery controller 500 controls the discharge of the plurality of cells 101 when balancing the charge states of the plurality of cells. The battery controller 500 includes a total voltage detection circuit 501, a charge / discharge current detection circuit 502, and a microcomputer 504. The total voltage detection circuit 501 measures the total voltage of the assembled battery 103. The charge / discharge current detection circuit 502 is connected to a current sensor 503 and detects the charge / discharge current flowing through the assembled battery 103 based on a detection signal from the current sensor 503. The microcomputer 504 communicates between the cell controller 200, the inverter 700, and a higher-level vehicle controller (not shown) such as a vehicle control system (not shown), and controls the entire battery controller 500. Note that the total voltage detection circuit 501 only needs to be able to measure the total voltage of the assembled battery 103, and does not have to be provided inside the battery controller 500 as shown in FIG. 1.

[0019] The inverter 700 also includes a total voltage detection circuit 701 that detects the total voltage of the battery pack 103. Although not shown in Fig. 1, the battery controller 500 performs temperature correction of the battery state parameters based on the temperature of the single cells 101 measured by a temperature detection circuit connected to the cell monitoring IC 300.

[0020] Although not shown in Fig. 1, the cell controller 200 and battery controller 500 are mounted on a single circuit board and housed in a metal case. The battery pack 103 is also housed in a metal case. The cell controller 200 and battery pack 103 are connected by a harness that bundles together multiple voltage detection wires and connection wires for the temperature sensors (not shown) of the cells 101.

[0021] After startup, this battery system monitoring device 100 performs the following operations. The battery controller 500 sends a command to the cell controller 200 to measure the OCV (open circuit voltage) of each battery cell 101. The command is sent from the battery controller 500 to the cell controller 200 via the insulating element group 400. In response to this command, the cell controller 200 measures the OCV of each battery cell 101. The OCV data of each battery cell 101 measured by the cell controller 200 is then sent from the cell controller 200 to the battery controller 500 on a cell group basis. Data transmission from the cell controller 200 to the battery controller 500 also occurs via the insulating element group 400.

[0022] The battery controller 500 converts the received OCV of each cell 101 into SOC and calculates the SOC deviation of each cell 101. Of the multiple cells 101, a cell 101 with an SOC deviation greater than a predetermined value is selected as the target for balancing discharge. The time until the SOC deviation of the cell 101 targeted for balancing discharge becomes zero is then calculated. A command is then sent from the battery controller 500 to the cell controller 200 to perform a control operation to turn on the cell discharge switch 321 of the cell 101 targeted for balancing discharge for this period of time. In response to this command, the cell controller 200 controls the cell discharge switch 321 of the cell 101 targeted for balancing to be on, and the cell 101 targeted for balancing is discharged.

[0023] After the SOC of the battery pack 103 is calculated from the OCV of each battery cell 101 measured as described above, the inverter 700 or a higher-level vehicle controller turns on relays 600 and 610, connecting the battery system monitoring device 100 to the inverter 700. When the inverter 700 receives a charge / discharge command from the higher-level vehicle controller, the inverter 700 operates to drive the motor 800, and the battery system monitoring device 100 performs a charge / discharge operation.

[0024] When the battery system monitoring device 100 starts charging or discharging by turning on the relays 600 and 610, the battery controller 500 measures the total voltage and charging or discharging current at regular intervals using the total voltage detection circuit 501 and the charging or discharging current detection circuit 502. From the obtained total voltage and charging or discharging current values, the battery controller 500 calculates the state of charge (SOC) and internal resistance (DCR) of the battery pack 103 in real time. Furthermore, from these values, the battery controller 500 calculates in real time the current or power that the battery pack 103 can charge or discharge, and transmits this to the inverter 700. The inverter 700 controls the charging or discharging current or power within the range of that current or power.

[0025] FIG. 2 is an explanatory diagram showing the internal configuration of the cell controller 200. As shown in FIG. 2 shows one cell group 102 and the cell monitoring IC 300 corresponding to that cell group 102. Each cell group 102 is formed by connecting n-1 (n is an integer) unit cells 101 (cell 1 to cell n-1) in series.

[0026] The cell groups 102 and the cell monitoring IC 300 that controls them are connected to each other via n cell voltage detection / discharge lines 201 (CL1 to CLn). The n cell voltage detection / discharge lines 201 (CL1 to CLn) are connected on the cell 101 side to the positive and negative terminals of each cell 101 in the battery pack 103. The cell monitoring IC side branches into n cell voltage detection lines 202 (SL1 to SLn) and n cell voltage discharge lines 203 (BL1 to BLn). Each cell voltage detection line 202 (SL1 to SLn) is connected to a voltage detection CV terminal (CV1 to CVn) of the cell monitoring IC 300 via a cell input resistor Rcv221. A cell input capacitor Ccv222 is connected between the CV terminals of the cell monitoring IC 300. The cell input capacitor Ccv222 is a bypass capacitor provided for noise reduction. The cell input capacitor Ccv222 is intended to prevent erroneous diagnosis of the cell monitoring IC (details omitted), and prevents erroneous detection of noise such as ripple voltage caused by the operation of the inverter 700.

[0027] The cell voltage discharge lines 203 (BL1 to BLn) for balancing operation are connected to the BS terminals (BS1 to BSn) of the cell monitoring IC 300 via balancing resistors Rbs231. A balancing capacitor Cbs232 is connected between the BS terminals of the cell monitoring IC 300. The balancing capacitor Cbs232 is a bypass capacitor provided for noise prevention. The balancing capacitor Cbs232 is used to prevent erroneous diagnosis of the cell monitoring IC (details omitted) and prevents erroneous detection due to noise such as ripple voltage caused by the operation of the inverter 700.

[0028] The cell controller 200 has a cell voltage detection line RC filter circuit 220, a cell voltage discharge line RC filter circuit 230, and a VBLK voltage line RC filter circuit 240. The cell voltage detection line RC filter circuit 220 is provided on the cell voltage detection lines 202 (SL1 to SLn) between the branch point of the cell voltage detection lines 202 (SL1 to SLn) and the cell voltage discharge lines 203 (BL1 to BLn) and the cell monitoring IC 300. The cell voltage detection line RC filter circuit 220 is used to remove high-frequency noise superimposed on the voltage signals of each battery 101 input from the cell voltage detection lines 202 (SL1 to SLn) to the cell monitoring IC 300, and is composed of an RC filter having a cell input resistor Rcv221 and a cell input capacitor Ccv222. The cell voltage detection line RC filter circuit 220 has a first time constant. The cell voltage detection line RC filter circuit 220 constitutes a first noise removal unit that removes a first noise contained in the cell voltages of the plurality of single cells 101 based on a first time constant.

[0029] The cell voltage discharge line RC filter circuit 230 is configured by an RC filter having a balancing resistor Rbs 231 and a balancing capacitor Cbs 232. The balancing resistor Rbs 231 is a resistive element for adjusting the cell discharge current flowing in the cell voltage discharge line 203 (BL1 to BLn) during discharge, and is provided in the cell voltage discharge line 203 (BL1 to BLn) between the branch point of the cell voltage detection line 202 (SL1 to SLn) and the cell voltage discharge line 203 (BL1 to BLn) and the cell monitoring IC 300.

[0030] The VBLK voltage line RC filter circuit 240 is intended to remove noise superimposed on the VBLK voltage of the VBLK voltage line 205, and is configured by an RC filter having a VBLK voltage line input resistor 211 and a VBLK voltage line input capacitor 212. The VBLK voltage line RC filter circuit 240 has a second time constant different from the first time constant of the cell voltage detection line RC filter circuit 220.

[0031] The VBLK voltage line input resistor 211 of the VBLK voltage line RC filter circuit 240 is provided on the VBLK voltage line 205. One end of the VBLK voltage line 205 is connected to the positive electrode side of the battery 101 located at the top of the cell group 102, i.e., the battery 101 located on the highest potential side, and the other end is connected to the VBLK terminal of the cell monitoring IC 300. The VBLK voltage line 205 is used to measure the voltage of the entire cell group 102 (VBLK voltage), which is formed by connecting all the battery cells 101 in series. The VBLK voltage line input capacitor 212 has one end connected to the VBLK voltage line 205 and the other end connected to the GND line GL206. The VBLK voltage line RC filter circuit 240 constitutes a second noise elimination unit that eliminates, based on a second time constant, a second noise included in the VBLK voltage, which is the series voltage between the positive electrode of the top battery 101 and the negative electrode of the bottom battery 101 of the multiple battery cells 101 connected in series.

[0032] The cell monitoring IC 300 includes a cell voltage detection unit 310, a balancing switch circuit 320, and a cell discharge control unit 330. The cell voltage detection unit 310 detects the cell voltage of each battery 101 via n cell voltage detection lines 202 (SL1 to SLn). The balancing switch circuit 320 has multiple cell discharge switches 321 connected to the BS terminals (BS1 to BSn) of the cell monitoring IC 300. When turned on, a cell discharge switch 321 causes a cell discharge current to flow from the cell voltage discharge line 203 (BL1 to BLn) through a balancing resistor Rbs231 to the corresponding cell. The cell discharge control unit 330 controls the cell discharge switch 321 of the cell voltage discharge line 203 (BL1 to BLn) that corresponds to the battery 101 to be discharged.

[0033] The power supply terminal VCC of the cell monitoring IC 300 is connected to the positive electrode side of the battery 101 located at the top of the cell group 102, i.e., on the highest potential side, by a power supply line PL204 of the cell monitoring IC 300. The GND terminal of the cell monitoring IC 300 is connected to the negative electrode side of the battery 101 located at the bottom of the cell group 102, i.e., on the lowest potential side, by a GND line GL206 of the cell monitoring IC 300.

[0034] Note that Figure 2 shows an example in which n-1 cells 101 are connected in series in the battery pack 103, but the configuration of the battery pack 103 may be other configurations, such as battery cells connected in parallel and then further connected in series, and the number of battery cells is not limited.

[0035] The cell monitoring IC 300 having the above configuration detects the cell voltage of each battery cell 101 via n cell voltage detection lines 202 (SL1 to SLn) branched from n cell voltage detection / discharge lines 201 (CL1 to CLn). The cell monitoring IC 300 detects the cell voltage of each battery cell 101 from which first noise has been removed by a cell voltage detection line RC filter circuit 220. The cell monitoring IC 300 also detects the discharge voltage of each battery cell 101 via n cell voltage discharge lines 203 (BL1 to BLn) branched from the n cell voltage detection / discharge lines 201 (CL1 to CLn). The cell monitoring IC 300 detects the discharge voltage of each battery cell 101 from which second noise has been removed by a cell voltage discharge line RC filter circuit 230.

[0036] The battery system monitoring device 100 executes predetermined operations for controlling and monitoring the battery pack 103 based on the voltage detection results of each battery cell 101 by the cell monitoring IC 300. For example, the battery system monitoring device 100 estimates the state of charge (SOC) of each battery cell 101, and if there is variation in the state of charge among the batteries 101, controls to turn on the cell discharge switch 321 corresponding to the battery 101 to be discharged among the cell voltage discharge lines 203 (BL1 to BLn). Then, by flowing a cell discharge current through the cell voltage discharge line 203, discharge is performed to equalize the state of charge of each battery 101. In addition, the battery system monitoring device 100 performs various processes and controls based on the cell voltage of each battery cell 101 detected by the cell monitoring IC 300.

[0037] The cell voltage detection line RC filter circuit 220 suppresses noise, mainly ripple voltage, superimposed on the cell voltage due to the operation of the inverter 700. The voltage terminals at both ends of the cell 101 are connected to the BS terminal of the cell monitoring IC 300 via a balancing resistor Rbs231. When the cell discharge switch 321 is turned on, the cell discharge current of the cell 101 flows through the balancing resistor Rbs231 and is discharged.

[0038] Although not shown, the CV terminal is connected to the input terminal of a multiplexer inside the cell monitoring IC 300. The multiplexer selects each cell 101 and outputs its positive electrode potential and negative electrode potential, and is controlled by the output from the multiplexer input selection register in the logic section. The output of the multiplexer is converted into the terminal voltage of each cell 101 via a differential amplifier, and this voltage is converted into a digital value by an AD converter. The operation of the AD converter is controlled by the logic section, and the output of the AD converter is processed in the logic section. In other words, voltage is measured using the differential amplifier and AD converter.

[0039] This AD converter uses a high-speed AD converter, such as a successive approximation type, etc. By using such a high-speed AD converter, it is possible to quickly perform multiplexer diagnosis (details omitted), etc.

[0040] A high-speed AD converter detects and converts noise components directly into AD signals. Therefore, in this embodiment, an RC filter is configured by providing a cell input resistor Rcv221 and a cell input capacitor Ccv222 on each of the cell voltage detection lines 202 connected to the CV terminals for measuring inter-terminal voltages. The RC filter filters out noise before the signal is input to the AD converter via the multiplexer and differential amplifier in the cell monitoring IC. Therefore, even if high-frequency ripple noise superimposed on the cell voltage due to the operation of the inverter 700, for example, can be removed, minimizing its impact on the diagnosis by the cell monitoring IC 300.

[0041] For example, the cutoff frequency of the RC filter at the CV terminal is set to about 50 Hz. This reduces noise (about 20% peak-to-peak, about 20 kHz) caused by switching of the semiconductor switching elements of the inverter 700 to 1 / 100 or less. The time constant of the cell voltage discharge line RC filter circuit 230, which is composed of the balancing resistor Rbs231 and balancing capacitor Cbs232, is small, allowing for fast disconnection detection (details omitted) during balancing current detection.

[0042] In the cell controller 200 of this embodiment, the cell voltage detection line RC filter circuit 220 of the cell voltage detection line 202 and the VBLK voltage line RC filter circuit 240 of the VBLK voltage line 205 have different time constants (first and second time constants). When the filter circuit is configured with an RC filter, the time constant and cutoff frequency are expressed by the following equations (1) and (2). Time constant τ = R × C (1) Cutoff frequency fc=1 / (2·π·τ)=1 / (2·π·R·C)···(2)

[0043] For example, when ripple noise with a ripple noise frequency fnoise of 1 kHz is applied to the circuit, the cutoff frequency fc(Cn) of the cell voltage detection line RC filter circuit 220 of the cell voltage detection line 202 is set to several tens of kHz, and the cutoff frequency fc(VBLK) of the VBLK voltage line RC filter circuit 240 of the VBLK voltage line 205 is set to approximately several hundreds of Hz. The frequency relationship is expressed by the following equation (3). fc(Cn)>fnoise>fc(VBLK)···(3)

[0044] Since the cutoff frequency fc(Cn) of the cell voltage detection line RC filter circuit 220 of the cell voltage detection line 202 is greater than the ripple noise frequency fnoise, the attenuation of the ripple noise is small, and the cell voltage measured by the cell monitoring IC 300 at the stage subsequent to the RC filter (stage subsequent to the cell voltage detection line RC filter circuit 220) is a measured voltage with ripple noise superimposed on it.

[0045] On the other hand, the cutoff frequency fc(VBLK) of the VBLK voltage line 205 by the VBLK voltage line RC filter circuit 240 is smaller than the ripple noise frequency fnoise and is therefore sufficiently attenuated, and the measurement value of the VBLK voltage at the stage subsequent to the RC filter by the cell monitoring IC 300 (the stage subsequent to the VBLK voltage line RC filter circuit 240) is a measurement voltage from which the ripple noise has been removed.

[0046] When the difference ΔV between the total cell voltage obtained by adding up the cell voltages of each battery 101 (cell 1 to cell n-1) obtained by the cell monitoring IC 300 and the VBLK voltage is taken as in equation (4), the VBLK voltage has noise removed, but the cell voltage has ripple noise superimposed on it, resulting in a large difference. |VBLK voltage - total cell voltage|=ΔV (4)

[0047] For example, when ripple noise with a ripple noise frequency fnoise of 20 kHz is applied to the circuit, the cutoff frequency fc(Cn) of the cell voltage detection line RC filter circuit 220 of the cell voltage detection line 202 is set to several tens of kHz, and the cutoff frequency fc(VBLK) of the VBLK voltage line RC filter circuit 240 of the VBLK voltage line 205 is set to several hundreds of Hz. The frequency relationship is expressed by the following equation (5). fc(noise)>fc(Cn)>fc(VBLK)...(5)

[0048] Since the cutoff frequency fc(Cn) of the cell voltage detection line 202 is smaller than the ripple noise frequency fnoise, it is sufficiently attenuated, and the cell voltage measured by the cell monitoring IC 300 downstream of the RC filter (rear of the cell voltage detection line RC filter circuit 220) is a measured voltage from which the ripple noise has been removed.

[0049] On the other hand, the cutoff frequency fc(VBLK) of the RC filter on the VBLK voltage line 205 is smaller than the ripple noise frequency fnoise and is therefore sufficiently attenuated, and the VBLK voltage measured by the cell monitoring IC 300 at the stage subsequent to the RC filter (the stage subsequent to the VBLK voltage line RC filter circuit 240) is a measured voltage from which the ripple noise has been removed.

[0050] If we take the difference ΔV between the total cell voltage, which is the sum of the cell voltages of each battery 101 (cell 1 to cell n-1) obtained by the cell monitoring IC 300, and the VBLK voltage, as shown in equation (4), the difference ΔV will be small because noise has been removed from both the total cell voltage and the VBLK voltage.

[0051] As described above, due to the difference in cutoff frequency between the cell voltage detection line 202 and the VBLK voltage line 205, when low-frequency ripple noise is applied to the circuit, the difference between the total cell voltage and the VBLK voltage value is large, but when high-frequency ripple noise is applied, the difference between the total cell voltage and the VBLK voltage value is small. In this way, the presence or absence of low-frequency ripple noise can be detected by performing noise removal processing on the total cell voltage and the VBLK voltage using RC filter circuits with different time constants, and then calculating the difference ΔV between the total cell voltage and the VBLK voltage after noise removal processing.

[0052] This is explained using the graph in FIG. Figure 7 is a graph showing the deviation of the total cell voltage of cells 1 to 10 when ripple noise is present and when it is not present, and the deviation of the VBLK voltage when ripple noise is present and when it is not present, in a battery system monitoring device using ten cells 101. The example shown in Figure 7 shows the deviation between the measurement results of the total cell voltage of cells 1 to 10 and the VBLK voltage measured by the cell monitoring IC 300 after the RC filter when there is no ripple noise, and the measurement results of the total cell voltage of cells 1 to 10 and the VBLK voltage measured by the cell monitoring IC 300 after the RC filter when ripple noise is applied from 1 kHz to 20 kHz. In the graph of Figure 7, the horizontal axis represents the frequency of the ripple noise, and the vertical axis represents the difference ΔV between the total cell voltage and the VBLK voltage when ripple noise is applied and when it is not applied.

[0053] The cutoff frequency fc(Cn) of the cell voltage detection line RC filter circuit 220 on the cell voltage detection line 202 is set to several tens of kHz, and the cutoff frequency fc(VBLK) of the RC filter on the VBLK voltage line 205 is set to several hundreds of Hz.

[0054] At ripple noise around 1kHz, the total cell voltage has a large deviation of ±1500mV because fc(Cn) > fnoise. The VBLK voltage has a small deviation of ±300mV because fnoise > fc(VBLK).

[0055] At ripple noise frequencies around 20 kHz, the total cell voltage has a small deviation of ±50 mV or less because fc (noise) > fc (Cn), and the VBLK voltage also has a small deviation of ±50 mV or less because fc (noise) > fc (VBLK).

[0056] Figure 8 shows the results of calculating the difference between the total cell voltage and the VBLK voltage. The horizontal axis of Figure 8 represents the difference between the deviation of the total cell voltage and the deviation of the VBLK voltage in Figure 7. As shown in Figure 8, the difference between the deviation of the total cell voltage and the deviation of the VBLK voltage is large, over 1000mV, when the ripple noise is around 1kHz, but is small, under 50mV, when the ripple noise is around 20kHz. Therefore, when the difference ΔV between the total cell voltage and the VBLK voltage is large, it can be determined that low-frequency ripple noise is being applied to the circuit. In this way, by calculating the difference ΔV between the total cell voltage and the VBLK voltage, it is possible to detect the presence or absence of low-frequency ripple noise.

[0057] Next, a process for determining whether or not to perform a diagnosis in the cell monitoring IC will be described. The cell monitoring IC 300 not only measures and equalizes cell voltages, but also performs various diagnostics on communications, the IC's internal power supply, and the IC's internal circuits, enhancing its own reliability and safety. Before performing a diagnostic test, the cell monitoring IC 300 determines whether low-frequency ripple noise is being applied. If it determines that no low-frequency ripple noise is being applied, it performs a diagnostic test. If it determines that low-frequency ripple noise is being applied, it does not perform a diagnostic test due to the risk of misdiagnosis.

[0058] Figure 3 is a functional block diagram explaining the internal functions of the cell monitoring IC, Figure 4 is a flowchart explaining the noise removal processing by the cell voltage detection line RC filter circuit 220, Figure 5 is a flowchart explaining the noise removal processing by the VBLK voltage line RC filter circuit 240, and Figure 6 is a flowchart for determining whether or not diagnosis can be performed by the cell monitoring IC.

[0059] 4, first, the cell voltage detection line RC filter circuit 220 removes a first noise from the voltage of each battery cell 101 (S101). The cell voltage of each battery cell 101 after the first noise has been removed is input from the CV terminal to the cell monitoring IC 300. Then, the cell voltage detection unit 310 of the cell monitoring IC 300 detects the cell voltage of each battery cell 101 (S102).

[0060] 5, the second noise is removed from the VBLK voltage by the VBLK voltage line RC filter circuit 240 on the VBLK voltage line 205 (S201). The VBLK voltage from which the second noise has been removed is input to the cell monitoring IC 300 from the VBLK terminal. Then, the cell voltage detection unit 310 of the cell monitoring IC 300 detects the VBLK voltage (S202).

[0061] 3, the cell monitoring IC 300 has, as internal functions, a cell total voltage calculation unit (total voltage calculation unit) 341, a VBLK voltage measurement unit (series voltage measurement unit) 342, a diagnosis permission determination unit 343, and a cell monitoring IC diagnosis unit (cell monitoring diagnosis unit) 344. The cell total voltage calculation unit 341 calculates the total cell voltage by summing the cell voltages of the individual cells in the cell group 102 corresponding to the cell monitoring IC 300, from which the first noise has been removed (S401).

[0062] Then, the VBLK voltage measurement unit 342 measures the VBLK voltage from which the second noise has been removed and which is input from the VBLK terminal to the cell monitoring IC 300 (S402). Note that the order of calculating the total cell voltage in step S401 and measuring the VBLK voltage in step S402 may be reversed, or may be performed simultaneously.

[0063] The diagnosis permission determination unit 343 calculates the difference ΔV between the total cell voltage from which the first noise has been removed and the VBLK voltage from which the second noise has been removed using the above-mentioned equation (4) (S403). Then, the diagnosis permission determination unit 343 compares the difference ΔV with a preset difference threshold (specified value) Vth (S404). If the difference ΔV is greater than the difference threshold Vth (YES in S404), it determines that low-frequency ripple noise has been applied, masks the diagnosis by the cell monitoring IC 300, and does not permit the cell monitoring IC diagnosis unit 344 to perform the diagnosis (S406). On the other hand, if the difference ΔV is equal to or less than the difference threshold Vth (NO in S404), it determines that low-frequency ripple noise has not been applied, and permits the cell monitoring IC diagnosis unit 344 to perform the diagnosis (S405). The cell monitoring IC diagnosis unit 344 performs the diagnosis when the diagnosis permission determination unit 343 permits the execution of the diagnosis, and does not perform the diagnosis when the diagnosis permission determination unit 343 masks the diagnosis.

[0064] For example, if the threshold value Vth for the difference between the total cell voltage and the VBLK voltage is 50 mV, when the difference ΔV between the total cell voltage and the VBLK voltage is greater than 50 mV, it is determined that low-frequency ripple noise is being applied, and diagnosis of the cell monitoring IC 300, which is heavily affected by low-frequency ripple noise, is masked; in other words, diagnosis is not performed. On the other hand, when the difference ΔV between the total cell voltage and the VBLK voltage is equal to or less than the threshold value 50 mV, it is determined that low-frequency ripple noise is not being applied, and diagnosis is performed.

[0065] For example, ripple noise superimposed on the cell voltage may be applied due to the operation of the inverter 700. While high-frequency ripple noise can be suppressed using an RC filter or the like, the RC filter is less effective on low-frequency ripple noise, making it difficult to suppress low-frequency ripple noise. The battery system monitoring device 100 of this embodiment can accurately determine whether low-frequency ripple noise is being applied to the cell monitoring IC 300, allowing noise countermeasures to be taken in consideration of the possibility of noise application in diagnosis using the cell monitoring IC 300. For example, if low-frequency ripple noise is being applied, the diagnosis using the cell monitoring IC 300 can be masked. Therefore, the influence of noise can be eliminated in diagnosis using the cell monitoring IC 300, improving the diagnostic accuracy.

[0066] In the above embodiment, the cell voltage detection line and the VBLK voltage line 205 are used as an example. However, cell voltages can also be measured on the cell discharge line. The measured voltages on the cell discharge line and the VBLK voltage line may also be used. That is, the cell voltage discharge line RC filter circuit 230 removes a first noise contained in the discharge voltages of the multiple cells 101 based on a first time constant, and the cell monitoring IC 300 sums the discharge voltages of the multiple cells 101 from which the noise has been removed to calculate a total voltage. The cell voltage detection line RC filter circuit 220 then removes noise contained in the VBLK voltage based on a second time constant, and the VBLK voltage measurement unit 342 measures the VBLK voltage from which the noise has been removed. The system may then determine whether to permit diagnosis of the multiple cells 101 based on the total voltage and the VBLK voltage. If it is determined that diagnosis is possible, the system may perform diagnosis of the multiple cells 101.

[0067] The above-described embodiments and modifications are merely examples, and the present invention is not limited to these as long as the features of the invention are not impaired. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0068] 10 HEV drive system, 100 Battery system monitoring device, 101 Cell, 102 Cell group, 103 Assembled battery, 200 Cell controller, 201 Cell voltage detection / discharge line CL, 202 Cell voltage detection line SL, 203 Cell voltage discharge line BL, 204 Power supply line PL, 205 VBLK voltage line, 206 GND line GL, 211 VBLK voltage line input resistor, 212 VBLK voltage line input capacitor, 220 Cell voltage detection line RC filter circuit (first noise removal unit), 221 Cell input resistor Rcv, 222... Cell input capacitor Ccv, 230... Cell voltage discharge line RC filter circuit, 231... Balancing resistor Rbs, 232... Balancing capacitor Cbs, 240... VBLK voltage line RC filter circuit (second noise elimination unit), 300... Cell monitoring IC, 341... Cell total voltage calculation unit (total voltage calculation unit), 342... VBLK voltage measurement unit (series voltage measurement unit), 343... Diagnosis permission determination unit, 344... Cell monitoring IC diagnosis unit (cell monitoring diagnosis unit), 400... Isolation element group, 500... Battery controller, 700... Inverter, 800... Motor

Claims

1. A battery system monitoring device that monitors the state of a plurality of series-connected cells, a first noise removal unit that removes ripple noise included in the voltages of the plurality of single cells based on a first time constant; a total voltage calculation unit that calculates a total voltage by summing the voltages of the plurality of single cells from which the ripple noise has been removed by the first noise removal unit; a second noise removal unit that removes the ripple noise included in a series voltage, which is a voltage between the positive electrode of the uppermost unit cell and the negative electrode of the lowermost unit cell of the plurality of unit cells connected in series, based on a second time constant different from the first time constant; a series voltage measurement unit that measures the series voltage from which the ripple noise has been removed by the second noise removal unit; a diagnosis permission determination unit that determines whether or not to permit diagnosis of the state of the plurality of unit cells by determining whether or not low-frequency ripple noise is present based on the total voltage calculated by the total voltage calculation unit and the series voltage measured by the series voltage measurement unit; and a cell monitoring and diagnosis unit that performs the diagnosis of the state of the plurality of single cells when the diagnosis permission determination unit determines that there is no low-frequency ripple noise and that the diagnosis is possible.

2. The diagnosis permission determination unit The battery system monitoring device according to claim 1, characterized in that it determines whether to permit the diagnosis of the state of the plurality of single cells depending on whether a difference between the total voltage calculated by the total voltage calculation unit and the series voltage measured by the series voltage measurement unit is greater than a preset threshold value.

3. The diagnosis permission determination unit The battery system monitoring device according to claim 2 , wherein the diagnosis is not permitted when the difference is greater than the threshold value, and the diagnosis is permitted when the difference is equal to or less than the threshold value.

4. 2. The battery system monitoring device according to claim 1, wherein the voltages of the plurality of single cells are cell voltages.

5. 2. The battery system monitoring device according to claim 1, wherein the voltages of the plurality of cells are discharge voltages.

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