Method and circuit arrangement for monitoring battery cells

Abstract

A circuit arrangement (10) for monitoring a battery cell is designed to receive a first measurement signal representing a cell voltage of the battery cell. The first measurement signal is fed to a main monitoring channel (20) of the circuit arrangement (10) having a first analog-to-digital converter (ADC) (24) and to a redundant monitoring channel (30) of the circuit arrangement (10) having a second ADC (34). A comparison signal is determined as a function of a first output signal (UMAIN) of the main monitoring channel (20) and a second output signal (UAUX) of the redundant monitoring channel (30). If the first output signal (UMAIN does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, the comparison signal is compared with a predetermined first trigger threshold value (TH1). If the first output signal (UMAIN is equal to or greater than a predetermined first voltage value or equal to or less than a predetermined second voltage value, the comparison signal is compared with a predetermined second trigger threshold value (TH2).

Description

Technical Field

[0001] The invention relates to a method and a circuit arrangement for monitoring a battery cell. The battery cell is arranged in a battery, in particular in a traction battery of an electric vehicle. The invention also relates to a monitoring system, a battery system and a vehicle. Background Art

[0002] In the process of electrification of the drive train, higher and higher accuracy requirements are placed on battery monitoring in order to improve the range and operating safety of electric vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and all-electric vehicles (BEV). Here, the important point is the measurement accuracy for single-cell voltage monitoring. In the case of high automotive safety integrity levels (ASIL) of class C or D, it is required that the single-cell voltage is available as a measured value with high accuracy even in the case of unidentified errors. With higher measurement accuracy of the single-cell voltage, the traction battery can be operated closer to the single-cell voltage limit without risk, thereby increasing the achievable range length with the same battery capacity. In recent years, the performance of semiconductor components used for performing battery monitoring has been significantly improved. However, due to high safety requirements, the measurement circuit, such as the analog-to-digital converter for converting the detected voltage sensor signal, must be implemented partially redundantly. Comparing voltage sensor signals. When measuring the single-cell voltage, unavoidable interference effects, so-called ripple interference, occur.

[0003] A trigger threshold for signaling an error to the battery monitoring circuit is preferably provided so that these permissible ripple disturbances are not interpreted as errors in the battery monitoring circuit. Exceeding the trigger threshold leads to an emergency shutdown of the drive train in the worst case, but at least to an incrementing of the service life counter of the traction battery.

[0004] Due to real tolerances in the components of the filter structure connected upstream of the two ADCs, it is not possible to completely filter out or suppress the ripple interference. Since the trigger threshold must be set correspondingly high, the remaining maximum ripple interference determines the battery travel length. With a large trigger threshold, for example, the battery charging process must be limited early and the battery is not fully charged. Summary of the invention

[0005] The object of the present invention is to provide a method and a circuit arrangement for monitoring battery cells which contribute to increasing the achievable driving range of a vehicle with a certain battery capacity.

[0006] This object is achieved by the features of the independent patent claim. Advantageous developments of the invention are characterized in the dependent claims.

[0007] According to a first aspect, the above-mentioned object is achieved by a method for monitoring battery cells of a battery. In this case, a first measurement signal representing a cell voltage of the battery cell is first received by a circuit arrangement, the circuit arrangement having a main monitoring channel and a redundant monitoring channel. The first measurement signal is fed to the main monitoring channel having a first analog-to-digital converter (ADC) and to the redundant monitoring channel having a second ADC. The first ADC performs an analog-to-digital conversion on the first measurement signal and provides a first digital output signal representing the cell voltage of the battery cell. The second ADC performs an analog-to-digital conversion on a signal including the first measurement signal and provides a second digital output signal.

[0008] A comparison signal is determined based on the first output signal of the main monitoring channel and the second output signal of the redundant monitoring channel. If the first output signal does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, the comparison signal is compared with a predetermined first trigger threshold value, and if the comparison signal is greater than the first trigger threshold value, a first error signal is provided to the evaluation unit. If the first output signal is equal to or greater than a predetermined first voltage value or equal to or less than a predetermined second voltage value, the comparison signal is compared with a predetermined second trigger threshold value, and if the comparison signal is greater than the second trigger threshold value, a second error signal is provided to the evaluation unit. In this case, the first voltage value is greater than the second voltage value, and the first trigger threshold value has a greater value than the second trigger threshold value.

[0009] By implementing two different triggering thresholds, the driving range of the battery can be increased with unchanged hardware.

[0010] In this case, the following knowledge is used: the current flowing and thus the ripple disturbance are different depending on the operating range of the battery. In the normal operating range of the battery, each cell of the battery exceeds a lower voltage, which includes the lowest permissible cell voltage, i.e. the critical cell voltage lower limit plus a first voltage value, for example, approximately 0.1 V, and each cell of the battery does not exceed an upper voltage, which includes the maximum permissible cell voltage, i.e. the critical cell voltage upper limit minus a second voltage value, for example, approximately 0.1 V. High currents flow in the normal operating range of the battery, and thus greater ripple disturbances occur. Therefore, in the normal operating range of the battery, the triggering threshold is selected to be larger so that high ripple disturbances do not lead to false alarms.

[0011] In the critical operating range, if the battery is operated near the critical cell voltage, where only low charging currents (at the upper cell voltage limit) or low discharging currents (at the lower cell voltage limit) flow and therefore only small ripple interferences can occur, a reduced trigger threshold is selected.

[0012] In at least one advantageous embodiment of the first aspect, the predetermined first voltage value corresponds to a critical cell voltage upper limit value minus a safety margin voltage value, and the predetermined second voltage value corresponds to a critical cell voltage lower limit value plus a safety margin voltage value.

[0013] In at least one advantageous embodiment of the first aspect, the second error signal is suppressed or ignored depending on the direction of the current flowing into the battery cell.

[0014] If the battery is operated at or near the upper cell voltage limit, but is not charged but discharged, a very large current may occur, and thus a large ripple interference may also occur. However, since the discharge current cannot overcharge the cell at the upper cell voltage limit, the exceeding of the second trigger threshold can be ignored in the case of the corresponding current direction.

[0015] If the battery is operated at or near the lower cell voltage limit, but is not discharged but charged, very large currents and thus large ripple interferences may also occur. However, since the charging current at the lower cell voltage limit cannot discharge the cell deeply, the exceeding of the threshold value can be ignored in the case of the corresponding current direction.

[0016] In at least one advantageous embodiment of the first aspect, the signal is identical to the first measurement signal and the second output signal represents the cell voltage of the battery cell. This enables a simple comparison. However, common mode errors cannot be detected.

[0017] In at least one advantageous design scheme according to the first aspect, the first ADC of the main monitoring channel and the second ADC of the redundant monitoring channel use the same reference voltage for corresponding analog-to-digital conversion, and the reference voltage is provided by a reference voltage source used by one of the two ADCs. The signal includes a differential signal, which represents the difference between the supply voltage or reference voltage of the second ADC and the provided first measurement signal. The second output signal represents a level-shifted single cell voltage signal. In this case, determining the comparison signal based on the first output signal and the second output signal includes adding the first output signal to the second output signal, and if the level shift of the single cell voltage signal is performed with the aid of the supply voltage, subtracting the rated value of the supply voltage of the second ADC, and if the level shift of the single cell voltage signal is performed with the aid of the reference voltage, subtracting the reference voltage.

[0018] The use of a common reference voltage enables the circuit arrangement to be manufactured more cost-effectively and in a space-saving manner and can therefore detect errors in the reference voltage. The circuit arrangement thus also detects common-mode errors (common-mode errors of the reference voltage) and does not require further safety mechanisms. Therefore, no further safety mechanisms are required.

[0019] According to a second aspect, the above-mentioned object is achieved by a circuit arrangement for monitoring battery cells of a battery. The circuit arrangement has a main monitoring channel with a first analog-to-digital converter (ADC) and a redundant monitoring channel with a second ADC. A comparison unit is assigned to the circuit arrangement or the circuit arrangement includes the comparison unit.

[0020] The circuit arrangement is configured to receive a first measurement signal, the first measurement signal representing a cell voltage of the battery cell. The circuit arrangement is configured to provide the first measurement signal to the main monitoring channel and the redundant monitoring channel. The first ADC is configured to perform analog-to-digital conversion on the first measurement signal and provide a first output signal representing the cell voltage of the battery cell. The second ADC is configured to perform analog-to-digital conversion on a signal including the first measurement signal and provide a second output signal.

[0021] The comparison unit is configured to determine a comparison signal based on a first output signal of the main monitoring channel and a second output signal of the redundant monitoring channel. The comparison unit is configured to compare the comparison signal with a predetermined first trigger threshold value if the first output signal does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, and to provide a first error signal to the evaluation unit if the comparison signal is greater than the first trigger threshold value. The comparison unit is further configured to compare the comparison signal with a predetermined second trigger threshold value if the first output signal is equal to or greater than a predetermined first voltage value or equal to or less than a predetermined second voltage value, and to provide a second error signal to the evaluation unit if the comparison signal is greater than the second trigger threshold value. In this case, the first voltage value is greater than the second voltage value, and the first trigger threshold value has a greater value than the second trigger threshold value.

[0022] In at least one advantageous embodiment of the second aspect, the comparison unit is designed to suppress the output of the second error signal as a function of a provided current measurement signal which represents the direction of the current flowing into the battery cell.

[0023] In at least one advantageous embodiment of the second aspect, the signal is identical to the first measurement signal and the second output signal represents the cell voltage of the battery cell.

[0024] In at least one advantageous design solution according to the second aspect, the first ADC of the main monitoring channel and the second ADC of the redundant monitoring channel are configured to use the same reference voltage provided by the reference voltage source for the corresponding analog-to-digital conversion. The signal includes a differential signal, which represents the difference between the supply voltage or reference voltage of the second ADC and the provided first measurement signal. The second output signal represents the level-shifted single cell voltage signal. In this case, determining the comparison signal based on the first output signal and the second output signal includes:

[0025] - adding the first output signal to the second output signal, and

[0026] - if the level shifting of the cell voltage signal is performed with the aid of the supply voltage, subtracting the rated value of the supply voltage of the second ADC, and

[0027] If the level shifting of the cell voltage signal is performed with the aid of a reference voltage, the reference voltage is subtracted.

[0028] According to a third aspect, the object is achieved by a monitoring system for a battery cell. The monitoring system has a circuit arrangement according to the first aspect and a control unit, the control unit being designed to, based on a digital cell voltage signal provided by the circuit arrangement and representing the current cell voltage of the battery cell, predetermine for a comparison unit of the corresponding circuit arrangement: if the digital cell voltage signal does not exceed a predefined first voltage value and exceeds a predefined second voltage value, predetermine a first trigger threshold value, and if the digital cell voltage signal is equal to or greater than a predefined first voltage value or if the digital cell voltage signal is equal to or less than a predefined second voltage value, predetermine a second trigger threshold value.

[0029] According to a fourth aspect, the task is solved by a battery system, which includes a battery having at least one battery cell; for all or at least some of the battery cells, a circuit device according to the second aspect is included; and a control unit is constructed to be a comparison unit of the corresponding circuit device based on a digital measurement signal representing the current cell voltage of the corresponding battery cell provided by the corresponding circuit device: if the digital cell voltage signal does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, the first trigger threshold is predetermined, and if the digital cell voltage signal is equal to or greater than the predetermined first voltage value or if the digital cell voltage signal is equal to or less than the predetermined second voltage value, the second trigger threshold is predetermined.

[0030] According to a fifth aspect, the object is achieved by a vehicle having a battery system according to the fourth aspect.

[0031] Optional designs of the first and second aspects may also exist in other aspects accordingly and have corresponding effects.

[0032] Embodiments of the present invention are explained in more detail below based on the schematic drawings. In the drawings, the same reference numerals are used for elements having substantially the same function, but these elements are not necessarily identical in all details.

[0033] The description of the subject matter presented herein is not limited to each specific implementation.

[0034] As long as it is technically reasonable, the features of different embodiments can be combined with each other to form other embodiments. For example, unless otherwise stated, a variation or modification described with respect to one of the embodiments may also be applicable to other embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An exemplary block diagram shows an exemplary embodiment of a circuit arrangement for monitoring battery cells, and

[0036] Figure 2 An exemplary block diagram of a further exemplary embodiment of a circuit arrangement for monitoring battery cells is shown. DETAILED DESCRIPTION

[0037] It is noted that if an element is referred to as being "connected" or "coupled" to another element, the element may be directly connected or coupled to the other element, or intervening elements may be present. Conversely, if an element is referred to as being "directly" "connected" or "coupled" to another element, there are no intervening elements. Other expressions used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0038] Combine the following Figure 1 The function of a circuit arrangement 10 for monitoring battery cells is explained. Figure 1 is a simplified illustration of a circuit according to the present invention in which many of the essential components are omitted for the sake of clarity.

[0039] Figure 1 An exemplary block diagram of an exemplary embodiment of a circuit arrangement 10 for monitoring battery cells of a battery is shown (in Figure 1 The battery preferably has a plurality of battery cells connected in parallel and / or in series. The battery is designed, for example, as a traction battery for a vehicle.

[0040] The battery cell is connected to the circuit arrangement 10 and the circuit arrangement 10 receives on the input side a first cell potential signal Ucell_p and a second cell potential signal Ucell_c from the battery cell directly or indirectly via a preprocessing unit.

[0041] The circuit arrangement 10 has a main monitoring channel 20 with a first analog-to-digital converter ADC 24 and a redundant monitoring channel 30 with a second ADC 34. The circuit arrangement 10 also has, for example, a comparison unit 40. Alternatively, the comparison unit 40 can be part of the evaluation unit 50.

[0042] The circuit arrangement 10 is preferably designed as an integrated circuit in a semiconductor chip. In particular, a semiconductor chip can have a plurality of such circuit arrangements 10 , so that a plurality of battery cells can be monitored using the semiconductor chip.

[0043] The main monitoring channel 20 has, for example, a first analog filter 22 on the input side. The first ADC 24 is connected downstream of the first filter 22. For example, the first analog filter 22 of the main monitoring channel 20 is directly or indirectly connected to the battery cell. The first analog filter 22 is used to perform signal processing on the cell potential signals Ucell_p and Ucell_n received from the battery cell.

[0044] For example, a digital low-pass filter 26 is connected downstream of the first ADC 24. For example, at the output of the digital low-pass filter 26, a filtered digital cell voltage signal UC representing the cell voltage of the connected battery cell is provided to an evaluation unit 50. The evaluation unit 50 can be a control unit assigned to the circuit arrangement 10 or a higher-level computing unit.

[0045] The redundant monitoring channel 30 of the circuit arrangement 10 has, for example, a second analog filter 32 on the input side. A second ADC 34 is connected downstream of the second filter 32. The second analog filter 32 of the redundant monitoring channel 30 is, for example, directly or indirectly connected to the battery cell. The second analog filter 32 is used to perform signal processing on the cell potential signals Ucell_p, Ucell_n received from the battery cell.

[0046] In an optional design scheme, a first discrete hardware filter 28 and a second discrete hardware filter 38 are connected upstream of the circuit device 10, wherein the first discrete hardware filter 28 is connected upstream of the first filter 22 of the main monitoring path 20, and the second discrete hardware filter 38 is connected upstream of the second filter 32 of the redundant monitoring path.

[0047] The input of the first ADC 24 has a first input terminal for receiving a first measurement signal Uin_p representative of the potential at the positive pole of the battery cell and a second input terminal for receiving a second measurement signal Uin_n representative of the potential at the negative pole of the battery cell.

[0048] The first ADC 24 comprises, for example, a first level converter which is configured to form a first cell potential difference between the first measurement signal Uin_p and the second measurement signal Uin_n, which can also be referred to as a cell voltage Ucell.

[0049] The first ADC 24 furthermore has a converter unit which is designed to carry out the actual analog-to-digital conversion of the cell voltage Ucell and to provide a first digital output signal U_MAIN at an output of the converter unit.

[0050] The input of the second ADC 34 has a first input terminal for receiving a first measurement signal Uin_p representative of the potential at the positive pole of the battery cell and a second input terminal for receiving a second measurement signal Uin_n representative of the potential at the negative pole of the battery cell.

[0051] The second ADC 34 comprises, for example, a first level converter which is configured to form a first cell potential difference between the first measurement signal Uin_p and the second measurement signal Uin_n, which can also be referred to as a cell voltage Ucell.

[0052] The first ADC 34 furthermore has a converter unit which is designed to carry out the actual analog-to-digital conversion of the cell voltage Ucell and to provide a second digital output signal U_AUX at an output of the converter unit.

[0053] Thus, the first ADC 24 and the second ADC 34 receive a first measurement signal representing the cell voltage of the battery cell. The first ADC 24 and the second ADC 34 perform an analog-to-digital conversion of the first measurement signal, respectively, and provide a first output signal U_MAIN or a second output signal U_AUX at their output. In order to check whether the first ADC 24 functions properly, the two output signals U_MAIN, U_AUX are compared with each other. For example, a comparison signal representing the difference of the two output signals U_MAIN, U_AUX is determined.

[0054] In a further step, it is checked whether the comparison signal meets a criterion such that an error can be assumed. That is, an error is detected if, for example, the comparison signal representing the difference between the two output signals U_MAIN, U_AUX exceeds a triggering threshold.

[0055] However, since interferences, in particular ripple interferences which are dependent on the flowing current, can distort the measurement signal, these interferences must be taken into account when selecting the trigger threshold.

[0056] Therefore, if the first output signal U_MAIN does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, the comparison signal is compared with a predetermined first trigger threshold value TH1, wherein the first voltage value represents the upper critical cell voltage minus a margin value equal to, for example, 0.1 V, and the second voltage value represents the lower critical cell voltage plus a further margin value equal to, for example, 0.1 V. If the comparison signal is greater than the first trigger threshold value TH1, a first error signal ERR1 is provided to the evaluation unit 50.

[0057] If the first output signal U_MAIN is equal to or greater than a predetermined first voltage value or equal to or less than a predetermined second voltage value, the comparison signal is compared with a predetermined second trigger threshold TH2, and if the comparison signal is greater than the second trigger threshold TH2, a second error signal ERR2 is provided to the evaluation unit 50.

[0058] For example, the first trigger threshold TH1 has a value of 25 mV and the second trigger threshold TH2 has a value of 12 mV. Thus, for a given battery size, a stroke length gain of 26 mV results.

[0059] Preferably, if the battery is operated at or near the upper limit of the single cell voltage, but is not charged but discharged, the second error signal ERR2 is suppressed. In addition, if the battery is operated at or near the lower limit of the single cell voltage, but is not discharged but charged, the second error signal ERR2 is suppressed.

[0060] Alternatively, it is possible that the evaluation unit 50 sends information to the comparison unit 40 which specifies the current direction. Thus, if the current direction is not critical, the comparison unit 40 can immediately mask the error. For example, the evaluation unit 50 can send an additional flag to the comparison unit 40.

[0061] Figure 2 An exemplary block diagram of a further exemplary embodiment of a circuit arrangement 10 for monitoring battery cells of a battery is shown.

[0062] and Figure 1 Unlike the circuit arrangement 10 shown in FIG. 1 , the first ADC 24 and the second ADC 34 use the same reference voltage source.

[0063] also, Figure 2 The second ADC 34 in the embodiment comprises a second level converter. The second level converter is configured to form a second cell potential difference between the second measurement signal Uin_n and the first measurement signal Uin_p, wherein the second measurement signal Uin_n forms the minuend and the first measurement signal Uin_p forms the subtrahend. The second level converter is further configured to provide a differential signal U for the second ADC 34 by adding the supply voltage VCC of the second ADC 34 to the second cell potential difference. diff .

[0064] Alternatively, the second level converter is configured to provide a differential signal U for the second ADC 34 by adding a reference voltage VREF used by the two ADCs 24, 34 for analog-to-digital conversion to the second cell potential difference. diff .

[0065] The second ADC 34 comprises a converter unit which is configured to perform a differential signal U diff The actual analog-to-digital conversion is carried out and a second output signal U_AUX is provided at the output of the converter unit, which in this case represents the level-shifted cell voltage signal.

[0066] The converter units of the first ADC 24 and the second ADC 34 can be designed identically or differently. In particular, since only comparisons at certain time intervals are sufficient, the second ADC 34 can have a lower resolution and / or a longer settling time. This allows a cost-effective implementation and nevertheless ensures the required reliability.

[0067] The first ADC 24 and the second ADC 34 are configured to convert the cell voltage U cell Or differential signal U diff For analog-to-digital conversion, the reference voltage VREF is the same for both ADCs 24 , 34 .

[0068] Comparator unit 40 of circuit arrangement 10 is designed to determine a comparison value in accordance with a predetermined comparison function from first digital cell voltage signal U_MAIN and from the level-shifted second digital output signal U_AUX.

[0069] If the supply voltage VCC is used for level shifting for the second ADC 34 , the comparison function comprises in particular the sum of the first digital output signal U_MAIN and the level-shifted second digital output signal U_AUX minus the setpoint value VCC_setpoint of the supply voltage of the second ADC 34 .

[0070] Therefore, the numeric comparison mechanism provides the comparison value as a result.

[0071] U_delta=U_MAIN+U_AUX-VCC Equation (1a)

[0072] If a reference voltage VREF is used for level shifting for the second ADC 34 , the comparison function comprises in particular the sum of the first output signal U_MAIN and the second output signal U_AUX minus the reference voltage VREF.

[0073] In this case, the numeric comparison mechanism provides the comparison value as a result.

[0074] U_delta=U_MAIN+U_AUX-VREF Equation (1b)

[0075] The first ADC 24 and the second ADC 34 use the same reference voltage VREF. When the reference voltage VREF is offset upward by 10% due to an error, the first ADC 24 determines the cell voltage for the battery cell to be

[0076] U_MAIN=1.1*U cell Equation (2)

[0077] And the second ADC 34 determines the level-shifted cell voltage as

[0078] U_AUX=1.1*VCC_ist-1.1*U cell Equation (3a)

[0079] Among them U cell VCC_ist is the measured cell voltage of the battery cell, and VCC_ist is the actual value or the actual value of the supply voltage.

[0080] When the reference voltage VREF is used for level shifting, the second ADC 34 determines the level-shifted cell voltage as

[0081] U_AUX=1.1*VREF-1.1*U cell Equation (3b)

[0082] When using the supply voltage VCC for level shifting in the second ADC 34 and assuming that the nominal value VCC_soll and the actual value VCC_ist of the supply voltage are identical,

[0083] VCC_soll=VCC_ist=VCC Equation (4)

[0084] The comparison unit 40 specifies the comparison value as

[0085] U_delta=U_MAIN+U_AUX-VCC=0.1*VCC Equation (5a)

[0086] At a supply voltage of VCC=5V, for example, this corresponds to 0.5V.

[0087] When the reference voltage VREF is used for level shifting the second ADC 34, the comparison value is obtained:

[0088] U_delta=U_MAIN+U_AUX-VREF=0.1*VREF Equation (5b)

[0089] Then, if combined Figure 1As described, the corresponding comparison value is compared with the first triggering threshold value TH1 or the second triggering threshold value TH2 .

[0090] For example, the trigger thresholds TH1 and TH2 are predefined by the evaluation unit 50. The evaluation unit 50 is configured to predefined a first trigger threshold TH1 or a second trigger threshold TH2 for the comparison unit 40 based on a digital cell voltage signal UC provided by the circuit arrangement 10, the digital cell voltage signal UC representing the current cell voltage of the battery cell. In particular, if the digital cell voltage signal UC does not exceed a predefined first voltage value and exceeds a second voltage value, the first trigger threshold TH1 is predefined. If the digital cell voltage signal UC is equal to or greater than the predefined first voltage value, the second trigger threshold TH2 is predefined. If the digital cell voltage signal UC is equal to or less than the predefined second voltage value, the second trigger threshold TH2 is also predefined.

[0091] Reference numerals list

[0092] 10 Circuit Devices

[0093] 20 Main monitoring channels

[0094] 22 First analog filter

[0095] 24 First ADC

[0096] 26 Digital Filter

[0097] 30 redundant monitoring channels

[0098] 32 Second analog filter

[0099] 34 Second ADC

[0100] 40 Comparison unit

[0101] 50 evaluation units

[0102] ERR1 First error signal

[0103] ERR2 Second error signal

[0104] TH1 First trigger threshold

[0105] TH2 Second trigger threshold

[0106] U_MAIN first output signal

[0107] U_AUX Second output signal

[0108] UC Digital single cell voltage signal.

Claims

1. A method for monitoring a battery cell of a battery, wherein - receiving a first measurement signal representing a cell voltage of the battery cell by a circuit arrangement (10), the circuit arrangement having a main monitoring channel (20) and a redundant monitoring channel (30), - feeding said first measurement signal to a main monitoring channel (20) having a first analog-to-digital converter (24) ADC and to a redundant monitoring channel (30) having a second ADC (34), the first ADC (24) performs an analog-to-digital conversion on the first measurement signal and provides a first output signal (U_MAIN) representing the cell voltage of the battery cell, - the second ADC (34) performs an analog-to-digital conversion on a signal including the first measurement signal and provides a second output signal (U_AUX), - determining a comparison signal based on the first output signal (U_MAIN) of the main monitoring channel (20) and the second output signal (U_AUX) of the redundant monitoring channel (30), - if the first output signal (U_MAIN) does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, comparing the comparison signal with a predetermined first trigger threshold value (TH1), and providing a first error signal (ERR1) to an evaluation unit (50) if the comparison signal is greater than the first trigger threshold value (TH1), and - if the first output signal (U_MAIN) is equal to or greater than the first predetermined voltage value or equal to or less than the second predetermined voltage value, comparing the comparison signal with a second predetermined trigger threshold value (TH2), and providing a second error signal (ERR2) to the evaluation unit (50) if the comparison signal is greater than the second trigger threshold value (TH2), The first voltage value is greater than the second voltage value, and the first trigger threshold (TH1) has a larger value than the second trigger threshold (TH2).

2. The method according to claim 1, wherein the predetermined first voltage value corresponds to an upper critical cell voltage value minus a safety margin voltage value, and the predetermined second voltage value corresponds to a lower critical cell voltage value plus a safety margin voltage value.

3. The method according to claim 1 or 2, wherein the second error signal (ERR2) is suppressed or ignored depending on the direction of the current flowing into the battery cell. 4 . The method according to claim 1 , wherein the signal is identical to the first measurement signal and the second output signal (U_AUX) represents the cell voltage of the battery cell. 5 .

5. The method according to any one of claims 1 to 3, wherein - the first ADC (24) of the primary monitoring channel (20) and the second ADC (34) of the redundant monitoring channel (30) use the same reference voltage for corresponding analog-to-digital conversion, the reference voltage being provided by a reference voltage source used by one of the two ADCs (24, 34), the signal comprises a differential signal representing the difference between a supply voltage or a reference voltage of the second ADC (34) and the provided first measurement signal, and the second output signal (U_AUX) represents a level-shifted cell voltage signal, and - Determine the comparison signal according to the first output signal (U_MAIN) and the second output signal (U_AUX) -- add the first output signal (U_MAIN) to the second output signal, and - if the level shifting of the cell voltage signal is performed with the aid of the supply voltage, the nominal value of the supply voltage of the second ADC (34) is subtracted, and If the level shifting of the cell voltage signal is performed with the aid of a reference voltage, the reference voltage is subtracted.

6. A circuit arrangement (10) for monitoring a battery cell of a battery, wherein the circuit arrangement (10) comprises a main monitoring channel (20) with a first analog-to-digital converter ADC (24) and a redundant monitoring channel (30) with a second ADC (34), and a comparison unit (40) is assigned to the circuit arrangement (10) or the circuit arrangement (10) comprises the comparison unit (40), the circuit arrangement (10) is designed to receive a first measurement signal representing a cell voltage of the battery cell and to provide the first measurement signal to the main monitoring channel (20) and the redundant monitoring channel (30), the first ADC (24) is designed to perform an analog-to-digital conversion on the first measurement signal and to provide a first output signal (U_MAIN) representing the cell voltage of the battery cell, the second ADC is designed to perform an analog-to-digital conversion on a signal containing the first measurement signal and to provide a second output signal (U_AUX), the comparison unit (40) is designed to determine a comparison signal as a function of a first output signal (U_MAIN) of the main monitoring channel (20) and a second output signal (U_AUX) of the redundant monitoring channel (30), The comparison unit (40) is designed to - if the first output signal (U_MAIN) does not exceed a predetermined first voltage value and exceeds a predetermined second voltage value, comparing the comparison signal with a predetermined first trigger threshold value (TH1), and providing a first error signal (ERR1) to an evaluation unit (50) if the comparison signal is greater than the first trigger threshold value (TH1), and - if the first output signal (U_MAIN) is equal to or greater than the first predetermined voltage value or equal to or less than the second predetermined voltage value, the comparison signal is compared with a second predetermined trigger threshold value (TH2), and if the comparison signal is greater than the second trigger threshold value (TH2), a second error signal (ERR2) is provided to the evaluation unit (50), The first voltage value is greater than the second voltage value, and the first trigger threshold (TH1) has a larger value than the second trigger threshold (TH2).

7. The circuit arrangement (10) according to claim 6, wherein the comparison unit (40) is designed to suppress the output of the second error signal (ERR2) as a function of a provided current measurement signal which represents the direction of the current flowing into the battery cell.

8. The circuit arrangement (10) as claimed in claim 6 or 7, wherein the signal is identical to the first measurement signal and the second output signal (U_AUX) represents the cell voltage of the battery cell.

9. The circuit arrangement (10) as claimed in claim 6 or 7, wherein - the first ADC (24) of the main monitoring channel (20) and the second ADC (34) of the redundant monitoring channel (30) are configured to use the same reference voltage provided by a reference voltage source for corresponding analog-to-digital conversion, the signal comprises a differential signal representing the difference between a supply voltage or a reference voltage of the second ADC (34) and the provided first measurement signal, and - Determine the comparison signal according to the first output signal (U_MAIN) and the second output signal (U_AUX) -- add the first output signal (U_MAIN) and the second output signal (U_AUX), and - if the level shifting of the cell voltage signal is performed with the aid of the supply voltage, the nominal value of the supply voltage of the second ADC (34) is subtracted, and If the level shift of the cell voltage signal is performed with the aid of the reference voltage, the reference voltage is subtracted.

10. A monitoring system for a battery cell, wherein the monitoring system comprises a circuit arrangement (10) according to any one of claims 6 to 9 and a control unit, the control unit being configured to provide a comparison unit (40) with a digital measurement signal representing the current cell voltage of the battery cell, provided by the circuit arrangement (10). - if the digital cell voltage signal (UC) does not exceed the predetermined first voltage value and exceeds the second voltage value, a first trigger threshold value (TH1) is predetermined, and - if the digital cell voltage signal (UC) is equal to or greater than the predetermined first voltage value, a second trigger threshold value (TH2) is predetermined, and If the digital cell voltage signal (UC) is equal to or less than a predetermined second voltage value, a second triggering threshold value (TH2) is predetermined.

11. A battery system comprising: - a battery having at least one battery cell, a circuit arrangement (10) according to any one of the preceding claims 6 to 9, respectively, for all or at least some of the battery cells, and a control unit, the control unit being designed to provide a comparison unit (40) of the corresponding circuit arrangement (10) with a digital cell voltage signal (UC) representing the current cell voltage of the corresponding battery cell, which is provided by the corresponding circuit arrangement (10); - if the digital cell voltage signal (UC) does not exceed a predetermined first voltage value and exceeds the second voltage value, a first trigger threshold value (TH1) is predetermined, and - if the digital cell voltage signal (UC) is equal to or greater than the predetermined first voltage value, a second trigger threshold value (TH2) is predetermined, and If the digital cell voltage signal (UC) is equal to or less than a predetermined second voltage value, the second trigger threshold value (TH2) is predetermined.

12. A vehicle comprising the battery system according to claim 11.

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