Battery impedance measurement circuit and measurement method

Abstract

The present invention relates to a battery impedance measurement circuit and a measurement method. The battery impedance measurement circuit comprises: a signal generator connected to a plurality of battery cells and used to input a driving current to each battery cell, wherein the signal generator inputs a first driving current to a first battery cell, and the signal generator inputs M second driving currents to M second battery cells adjacent to the first battery cell, respectively, the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer; and a phase controller connected to the signal generator and used to control the phases of the M second driving currents so that the first driving current is equal to the second driving current in the first battery cell. M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M‑m) The measurement cycles are inverted relative to the phase of the first driving current, wherein m=1 to M. The present invention can eliminate the crosstalk of the induced voltage brought by the adjacent battery cells and obtain accurate battery impedance measurement results.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a battery impedance measurement circuit and a measurement method. Background Art

[0002] For automotive electronics, accurate measurement of the state of battery cells is very important. If the results are inaccurate, it will lead to driving safety problems. An effective way to obtain the state of battery cells is to measure the impedance of the battery cells. However, it is difficult to accurately measure the impedance of automotive batteries because automotive batteries are often relatively large battery packs, which include many different components, such as power lines and multiple independent battery cells. When current flows through these components, the magnetic field generated will cause additional interference to the measurement circuit in the impedance measurement circuit, and crosstalk will occur between multiple battery cells. Since the impedance of automotive battery cells is very low, usually less than 1mΩ, the measurement signal in the impedance measurement circuit is at the μV level, which is of the same order of magnitude as the crosstalk voltage generated by the magnetic field generated by the measurement current in the impedance measurement circuit. Therefore, the crosstalk voltage seriously interferes with the voltage signal used for impedance measurement, resulting in inaccurate impedance measurement results. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a battery impedance measurement circuit and method which can accurately remove crosstalk.

[0004] The technical solution adopted by the present invention to solve the above technical problems is a battery impedance measurement circuit, characterized in that it includes: a signal generator connected to a plurality of battery cells, used to input a driving current to each of the battery cells, wherein the signal generator inputs a first driving current to a first battery cell, and the signal generator inputs M second driving currents to M second battery cells adjacent to the first battery cell, respectively, the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer; and a phase controller connected to the signal generator, used to control the phases of the M second driving currents so that in 2 M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first driving current, where m=1 to M.

[0005] In one embodiment of the present invention, it also includes: an analog-to-digital converter connected to both ends of the plurality of battery cells, for converting the analog voltage signal of the battery cell into a digital voltage signal; and an impedance extraction module connected to the signal generator and the analog-to-digital converter, for extracting an impedance signal related to the impedance characteristics of the battery cell.

[0006] In one embodiment of the present invention, it further includes: a digital filter, which receives the impedance signal and filters the impedance signal to allow a direct current component in the impedance signal to pass through.

[0007] In one embodiment of the present invention, it further includes: a synchronous window unit, used to synchronize the digital voltage signal with a window function, and the period of the window function is equal to the measurement period.

[0008] In one embodiment of the present invention, the phase controller inverts the phase of the second driving current at a zero-crossing point of the window function.

[0009] In one embodiment of the present invention, the phase controller reverses the phase of the second drive current at 1 / 2 stabilization time before the zero crossing point of the window function, wherein the stabilization time is the time it takes for the phase to stabilize after being reversed.

[0010] In one embodiment of the present invention, the window function is a triangular window function.

[0011] In order to solve the above technical problems, the present invention also proposes a battery impedance measurement method, which is characterized by comprising: inputting a first driving current into a first battery cell; inputting M second driving currents into M second battery cells adjacent to the first battery cell respectively, wherein the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer; and controlling the phases of the M second driving currents so that in 2 M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first driving current, where m=1 to M.

[0012] In one embodiment of the present invention, it also includes: obtaining the voltage value of each of the battery cells; calculating the impedance of the first battery cell based on the first driving current and the voltage value of the first battery cell; and calculating the impedance of the second battery cell based on the second driving current and the voltage value of the second battery cell.

[0013] In one embodiment of the present invention, it also includes: obtaining multiple voltage values ​​of each of the battery cells within multiple measurement cycles; averaging the multiple voltage values ​​to obtain an average voltage value of each of the battery cells; calculating the impedance of the first battery cell based on the first drive current and the average voltage value of the first battery cell; and calculating the impedance of the second battery cell based on the second drive current and the average voltage value of the second battery cell.

[0014] In one embodiment of the present invention, the number of measurement cycles of the battery impedance measurement method is at least 2 M .

[0015] In one embodiment of the present invention, it also includes: using a window function to synchronize the phase of the second driving current so that the phase is reversed at the zero crossing point of the window function, and the period of the window function is equal to the measurement period.

[0016] In one embodiment of the present invention, it also includes: synchronizing the phase of the second drive current using a window function; obtaining the stabilization time for the phase to stabilize after being inverted; and causing the phase to reverse at 1 / 2 of the stabilization time before the zero crossing point of the window function.

[0017] According to the battery impedance measurement circuit and method of the present invention, the phase of the driving current input to the battery cell is controlled by a phase controller, which can eliminate the crosstalk of the induced voltage brought by the adjacent battery cells, thereby effectively eliminating the error of impedance measurement and obtaining accurate battery impedance measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein:

[0019] Figure 1 is a schematic diagram of a battery impedance measurement circuit;

[0020] Figure 2 It is a schematic diagram of the principle of measuring the impedance of a battery cell using an impedance measuring device;

[0021] Figure 3A and 3B It is a schematic diagram of the crosstalk phenomenon caused by electromagnetic coupling of a battery impedance measurement device;

[0022] Figure 4 is a schematic diagram of a battery impedance measurement circuit according to an embodiment of the present invention;

[0023] Figure 5 is a phase diagram of a driving current in a battery impedance measurement circuit according to an embodiment of the present invention;

[0024] Figure 6 is a phase diagram of a driving current in a battery impedance measurement circuit according to another embodiment of the present invention;

[0025] Figure 7 is a phase diagram of a driving current in a battery impedance measurement circuit according to another embodiment of the present invention;

[0026] Figure 8 is a schematic diagram of a battery impedance measurement circuit according to an embodiment of the present invention;

[0027] Fig. 9is an exemplary flow chart of a battery impedance measurement method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0031] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0032] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0033] It should be understood that when a component is referred to as being "on another component," "connected to another component," "coupled to another component," or "contacting another component," it may be directly on, connected to, coupled to, or contacting the other component, or there may be intervening components. In contrast, when a component is referred to as being "directly on another component," "directly connected to," "directly coupled to," or "directly contacting" another component, there are no intervening components. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0034] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0035] Figure 1 This is a schematic diagram of a battery impedance measurement circuit. Figure 1 As shown, the measurement circuit 100 is used to measure the impedance of the battery 101. In the measurement circuit 100, the signal generator 110 generates a driving current and drives the current to flow into the battery 101. The signal generator 110 can be a sine / cosine wave generator, which can output two signals, one is a sine signal and the other is a cosine signal. The analog-to-digital converter 120 converts the analog voltage signal V from the battery 101 into a Converted into digital voltage signal V d The digital voltage signal V d The output signals of the signal generator 110 are multiplied by the multipliers 131 and 132 to obtain two output signals S1 and S2. The output signal S1 passes through the low-pass filter 141 to output the real part of the impedance value of the battery 101, and the output signal S2 passes through the low-pass filter 142 to output the imaginary part of the impedance value of the battery 101. Figure 1 The measurement circuit 100 shown can also be referred to as a synchronous demodulator, which can realize the function of a bandpass filter. The measurement circuit 100 can be included in an impedance measurement device for measuring battery impedance.

[0036] Figure 2 This is a schematic diagram of the principle of measuring the impedance of a battery cell using an impedance measuring device. Figure 2As shown, the battery cell 210 includes a positive electrode 211 and a negative electrode 212. In order to measure the impedance of the battery cell 210, an impedance measuring device 220 is connected to the battery cell 210. Figure 2 The four-point measurement method shown in the figure is adopted, that is, the impedance measuring device 220 is connected to the negative electrode 212 and the positive electrode 211 of the battery cell 210 through two driving lines 221a and 221b respectively, so as to input the driving current to the battery cell 210; and the impedance measuring device 220 is connected to the negative electrode 212 and the positive electrode 211 of the battery cell 210 through two sensing lines 222a and 222b respectively, so as to measure the voltage generated by the battery cell 210 in response to the driving current. In some examples, the driving lines 221a and 221b are also used to provide current to the impedance measuring device 220. According to Figure 2 The impedance measurement device 220 and the four-point measurement method shown can avoid introducing the impedance of an additional measurement device when measuring the impedance of the battery cell 210 .

[0037] Figure 2 The figure is not intended to limit the relative position of the impedance measurement device 220 and the battery cell 210. In some examples, the battery cell 210 may be relative to Figure 2 The position shown in FIG. 1 is rotated 90 degrees, that is, the battery cell 210 is placed flat, and the positive electrode 211 and the negative electrode 212 are on the same horizontal line.

[0038] Figure 2 The battery cell 210 shown in FIG. 2 is also not limited to one battery cell 210 , and may represent a combination of a plurality of battery cells 210 .

[0039] In some embodiments, the same impedance measuring device can be used to measure multiple battery cells at the same time. Alternatively, an independent impedance measuring device can be configured for each battery cell. The measurement principle can be referred to Figure 2 and its description.

[0040] This manual is based on Figure 2 The following example is shown. Figure 2 In the illustrated embodiment, the negative electrode 212 of the battery cell 210 is closer to the impedance measuring device 220, and the positive electrode 211 is farther from the impedance measuring device 220. Therefore, the driving line 221a and the sensing line 222a connected to the negative electrode 212 in the impedance measuring device 220 are relatively short, and the driving line 221b and the sensing line 222b connected to the positive electrode 211 are relatively long.

[0041] use Figure 2When the four-point measurement method shown is used to measure the battery impedance, the current flowing through the driving line will generate a magnetic field. Although no current flows through the sensing line, the sensing line will be crosstalked by the magnetic field. Since the sensing line 222a is shorter, the magnetic field has a smaller impact on the sensing line 222a, and their impact on the measurement result can be ignored. However, the magnetic field will generate coupling inductance on the longer sensing line 222b, which will in turn generate an induced voltage in the sensing line 222b, and further affect the impedance measurement result of the battery cell.

[0042] Figure 3A and 3B This is a schematic diagram of the crosstalk phenomenon caused by electromagnetic coupling in a battery impedance measurement device. Figure 3A , which shows the impedance measurement of a battery cell. In practice, the battery cell, the drive line and the sense line are all coupled by the magnetic field, thereby inducing a crosstalk voltage. However, the present invention mainly relates to the measurement of battery impedance, and therefore mainly focuses on the crosstalk suffered by the sense line, including the crosstalk caused by the battery cell to the sense line and the drive line to the sense line.

[0043] refer to Figure 3A As shown, the battery cell 310 is equivalent to Figure 2 The battery cell 210 shown in FIG. Figure 3A In the figure, the battery cell 310 represents a battery cell. The impedance measuring device 320 is used to measure the impedance of the battery cell 310. The impedance measuring device 320 is connected to the negative electrode and the positive electrode of the battery cell 310 through two driving lines 321a and 321b respectively, and is used to input a measurement current to the battery cell 310; and the impedance measuring device 320 is connected to the negative electrode and the positive electrode of the battery cell 310 through two sensing lines 322a and 322b respectively, and is used to measure the voltage of the battery cell 310. Figure 3A As shown, the battery inductive reactance L c represents the inductive reactance of the battery cell 310 under magnetic field coupling, and the driving line inductive reactance L F represents the inductive reactance of the driving line 321b under magnetic field coupling, and the inductive reactance of the sensing line L s The coupling parameter K represents the inductive reactance of the sensing line 322b under magnetic field coupling. c The coupling parameter K represents the electromagnetic coupling generated by the battery cell 310 to the sensing line 322b. F It represents the electromagnetic coupling generated by the driving line 321b to the sensing line 322b.

[0044] according to Figure 3A As shown, the crosstalk voltage v generated on the sensing line 322b ind for:

[0045]

[0046] Among them, i c is the current flowing through the battery cell 310, i F is the current on the driving line 321b. Figure 3A As shown, c with i F Equal in size and opposite in direction, that is, i C =-i F Therefore, the above formula (1) can be simplified to:

[0047]

[0048] According to formula (2), the crosstalk voltage only affects the imaginary part of the impedance value in the impedance measurement result. In practice, the crosstalk voltage will also have a certain impact on the real part of the impedance value in the impedance measurement result, but it is not as obvious as the impact on the imaginary part of the impedance value.

[0049] although Figure 3A Only the impedance measurement of one battery cell 310 is shown. In actual measurement, other battery cells adjacent to or close to the battery cell 310 will also be affected by the magnetic field generated by the impedance measuring device 320, thereby generating mutual crosstalk. Multiple battery cells adjacent to or close to each other means that the multiple battery cells may or may not be electrically connected to each other.

[0050] like Figure 3B As shown, the battery cell 331 is adjacent to or close to the battery cell 332 , the impedance measuring device 340 is used to measure the impedance of the battery cell 331 , and the impedance measuring device 350 is used to measure the impedance of the battery cell 332 .

[0051] like Figure 3B As shown, when the impedance measuring device 340 measures the impedance of the battery cell 331, the inductive reactance of the battery cell 331 under magnetic field coupling is L C1 , the inductive reactance of the driving line 341b under magnetic field coupling is L F1 , the inductive reactance of the sensing line 342b under magnetic field coupling is L S1 When the impedance measuring device 350 measures the impedance of the battery cell 332, the inductive reactance of the battery cell 332 under magnetic field coupling is L C2 , the inductive reactance of the driving line 351b under magnetic field coupling is L F2 , the inductive reactance of the sensing line 352b under magnetic field coupling is L S2 .

[0052] like Figure 3B As shown, for the battery cell 331, the sensing line 342b in the impedance measurement device 340 is not only affected by the electromagnetic coupling K of the battery cell 331 in its own measurement circuit, but also by the electromagnetic coupling K C11The electromagnetic coupling K of the driving line 341b F11 In addition, it is also affected by the electromagnetic coupling K from the battery cell 332 in the adjacent measurement circuit. C21 The electromagnetic coupling K of the driving line 351b F21 For the battery cell 332, the sensing line 352b in the impedance measurement device 350 is not only affected by the electromagnetic coupling K of the battery cell 332 in its own measurement circuit, but also by the electromagnetic coupling K C22 The electromagnetic coupling K of the driving line 351b F22 In addition, it is also affected by the electromagnetic coupling K from the battery cell 331 in the adjacent measurement circuit. C12 The electromagnetic coupling K of the driving line 341b F12 .

[0053] For more battery cells and their corresponding impedance measurement devices, more complex crosstalk will occur between the measurement circuits, which will have a serious impact on the impedance measurement results.

[0054] In order to remove the above crosstalk, the battery cells can be divided into multiple groups, and only one battery cell is measured each time. For example, if the crosstalk generated by two battery cells adjacent to the battery cell to be tested is considered, then M=3. The multiple battery cells are numbered sequentially, and every 3 battery cells are taken as a group. First, the first battery cell in each group of battery cells is measured, that is, the battery cells numbered 1, 4, 7, ..., etc.; then the second battery cell in each group of battery cells is measured, that is, the battery cells numbered 2, 5, 8, ..., etc., and so on. Although this method can eliminate crosstalk, it is time-consuming and inefficient because for each battery cell, no data is collected during 2 / 3 of the measurement time.

[0055] When impedance measurement is performed on multiple battery cells, the frequencies of the driving currents input to the multiple battery cells are usually the same. When the frequency of the driving current signal input to the battery cell is fixed, the above formula (2) can be simplified to the following formula (3):

[0056] v ind =factor*i C (3)

[0057] When the current phase of the battery cell changes, the phase of the induced voltage it generates will also change. Therefore, the voltage V of the battery cell can be extracted from the induced voltage. cell .

[0058] by Figure 3BTaking the embodiment shown in the figure as an example, in the case where two impedance measuring devices are used to measure the impedance of two battery cells respectively, it is assumed that the phase of the driving current input from the impedance measuring device 340 to the battery cell 331 remains unchanged, while the phase of the driving current input from the impedance measuring device 350 to the battery cell 332 is reversed in each measurement cycle, that is, the phase changes by 180 degrees. Figure 3B The impedance measuring device 340 is set as Device1, and the battery cell 331 is set as Cell1; the impedance measuring device 350 is set as Device2, and the battery cell 332 is set as Cell2. The impedance measuring devices 340 and 350 both include the following Figure 1 The measurement circuit 100 is shown.

[0059] In the first measurement cycle, the first measured voltage v1(1) of Device1 is:

[0060] v1(1) = v cell1 *sinDevice1 + v ind1,1 *sinDevice1 + v ind1,2 *sinDevice1 (4)

[0061] In formula (4), v ind1,2 It indicates that the driving current in Cell2 is coupled to the induced voltage on the sensing line of Cell1.

[0062] In the second measurement cycle, the second measured voltage v1(2) obtained by Device1 is:

[0063] v1(2)=v cell1 *sinDevice1+v ind1,1 *sinDevice1+(-v ind1,2 )*sinDevice1 (5)

[0065] In the first measurement cycle, the first measured voltage v2(1) obtained by Device2 is:

[0066] v2(1) = v cell2 *sinDevice2 + v ind2,2 *sinDevice2 + v ind2,1 *sinDevice2 (6)

[0067] In formula (6), v ind2,1 It indicates that the driving current in Cell1 is coupled to the induced voltage on the sensing line of Cell2.

[0068] In the second measurement cycle, the second measured voltage v2(2) obtained by Device2 is:

[0069] v2(2)=(-v cell2 )*(-sinDevice2)+(-v ind2,2 )*(-sinDevice2)+v ind2,1 *(-sinDevice2) (7)

[0071] Take the average value of the two measured voltages:

[0072] For Device1:

[0073] v1 = v cell1 *sinDevice1 + v ind1,1 *sinDevice1 (8)

[0074] For Device2:

[0075] v2 = v cell2 *sinDevice2 + v ind2,2 *sinDevice2 (9)

[0076] According to formulas (8) and (9), the measured voltages of Device 1 and Device 2 are only related to the battery cells corresponding to them, thereby eliminating the crosstalk caused by the induced voltages generated by other battery cells.

[0077] The above formula only shows the in-phase component of the AC signal, ie, the sine component (sin), and the same is true for the quadrature component of the AC signal, ie, the cosine component (cos).

[0078] Based on the above findings, the present invention provides a battery impedance measurement circuit and a measurement method.

[0079] Figure 4 FIG. 1 is a schematic diagram of a battery impedance measurement circuit according to an embodiment of the present invention. Figure 4 As shown, the battery impedance measurement circuit 400 includes a signal generator 410 and a phase controller 420. Figure 4 As shown, the battery impedance measurement circuit 400 is connected to a battery pack 401, and the battery pack 401 includes a plurality of battery cells, that is, greater than or equal to 2 battery cells. The battery impedance measurement circuit 400 is used to measure the impedance of each battery cell.

[0080] Combination Figure 3BAccording to the above contents including formulas (4)-(9), the battery cells in the battery pack 401 are divided into two groups, namely a first battery cell and M second battery cells adjacent to the first battery cell, where M is a positive integer. The first battery cell may include one battery cell, and the signal generator 410 inputs a first drive current to the first battery cell. The first drive current has a fixed frequency and phase period. The second battery cell includes a plurality of battery cells, and the signal generator 410 inputs a second drive current to each of the M second battery cells. The frequency of the second drive current is equal to the frequency of the first drive current.

[0081] In a preferred embodiment of the present invention, one signal generator corresponds to one battery cell. In other embodiments, one signal generator may input driving current to multiple battery cells.

[0082] by Figure 3B Taking the embodiment shown as an example, the battery cell 331 may be a first battery cell, and the battery cell 332 may be a second battery cell. Figure 3B In the embodiment, the second battery unit includes only one battery cell 332. In other embodiments, the second battery unit may include a plurality of battery cells.

[0083] In some embodiments, the signal generator 410 may be a sine-cosine wave generator, and the present invention does not limit the specific implementation of the signal generator 410. The driving current I1 input to the battery unit 401 by the signal generator 410 may be a sine signal or a cosine signal.

[0084] refer to Figure 4 As shown, the phase controller 420 is connected to the signal generator 410 and is used to control the phases of the M second drive currents so that M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first driving current, where m=1 to M.

[0085] Figure 5 FIG. 1 is a phase diagram of a driving current in a battery impedance measurement circuit according to an embodiment of the present invention. Figure 3B and Figure 5 As shown, Device1 refers to battery cell 331, i.e., the first battery cell; Device2 refers to battery cell 332, i.e., one of the second battery cells. Figure 5As shown, the phase of Device1 in the first measurement cycle and the second measurement cycle is "+", indicating that the phase of the first driving current input to the first battery cell by the signal generator 410 has not changed. It can be understood that the driving current signal is a sine wave or cosine wave with a certain frequency, and its phase changes over time. Figure 5 The “+” in indicates that the phase of the drive current signal is in accordance with its original setting and is not changed by the outside world. Figure 5 As shown, the phase of Device2 in the first measurement cycle is "+", and the phase in the second measurement cycle is "-", indicating that the second driving current input to the second battery cell by the signal generator 410 did not change in the first measurement cycle, and its phase was reversed in the second measurement cycle, that is, it was reversed 180 degrees.

[0086] Referring to formulas (4)-(9), according to Figure 5 As shown, for the first battery cell, taking the average of the voltage values ​​obtained in the two measurement cycles can remove the crosstalk of the induced voltage caused by the second battery cell; for the second battery cell, taking the average of the voltage values ​​obtained in the two measurement cycles can remove the crosstalk of the induced voltage caused by the first battery cell.

[0087] exist Figure 5 In the example shown, M=1, so the phase controller 420 makes the phase 1 = Within 2 measurement cycles, the phase of the second driving current of the first second battery unit changes every 2 (M-m) =2 0 =1 measurement cycle is a phase reversal relative to the first drive current.

[0088] Figure 6 FIG. 1 is a phase diagram of a driving current in a battery impedance measurement circuit according to another embodiment of the present invention. In this embodiment, the first battery unit is Device 1, and the second battery unit includes two battery units, namely Device 2 and Device 3. Since M = 2, the number of measurement cycles is 2. M =4.

[0089] like Figure 6 As shown, the phases of Device1 in the 1st to 4th measurement cycles are all "+", indicating that the phase of the first driving current input to the first battery cell by the signal generator 410 does not change.

[0090] like Figure 6As shown, the phase of the first second battery cell Device2 in the 1st and 2nd measurement cycles is "+", and the phase in the 3rd and 4th measurement cycles is "-", indicating that the second drive current input to the battery cell by the signal generator 410 is 180 degrees inverted relative to the phase of the first drive current in the 3rd and 4th measurement cycles. Here, m = 1, M = 2, that is, the signal generator 420 makes the phase of the second drive current of the first second battery cell reverse every 2 in the 4 measurement cycles. (M-m) =2 1 =2 measurement cycles relative to the phase reversal of the first drive current.

[0091] like Figure 6 As shown, the phase of the second second battery unit Device3 in the 1st and 3rd measurement cycles is "+", and the phase in the 2nd and 4th measurement cycles is "-". Here, m=2, M=2, that is, the signal generator 420 makes the phase of the second driving current of the second second battery unit change every 2 in the 4 measurement cycles. (M-m) =2 0 =1 measurement cycle is a phase reversal relative to the first drive current.

[0092] As the number of battery cells in the second battery unit increases, the method for reversing the phase of the battery cells can be as follows: Figure 5 and Figure 6 In some embodiments, for each battery cell, a voltage value can be obtained in real time in each measurement cycle using a sliding average method. The voltage value can be an average voltage value obtained by averaging the voltage values ​​of the current measurement cycle and several measurement cycles before the current measurement cycle. The voltage value has removed the crosstalk of the induced voltage caused by other battery cells to the battery cell.

[0093] In other embodiments, the M After a measurement cycle, for each battery cell, an average voltage value is obtained by averaging the voltage values ​​obtained in each measurement cycle. The average voltage value has eliminated the crosstalk of the induced voltage caused by other battery cells to the battery cell.

[0094] refer to Figure 4 As shown, the battery impedance measurement circuit 400 of the present invention may also include an analog-to-digital converter (ADC) 430 and an impedance extraction module 440. The analog-to-digital converter 430 is connected to both ends of the battery cell 401 to convert the analog voltage signal V a Converted into digital voltage signal V d .

[0095] In some embodiments, an analog filter circuit may be included between the analog-to-digital converter 430 and the battery cell 401 to filter out the analog voltage signal V a The noise in the

[0096] The impedance extraction module 440 is connected to the signal generator 410 and the analog-to-digital converter 430. The signal generator 410 outputs a driving current signal to the input end of the impedance extraction module 440, and the analog-to-digital converter 430 outputs a digital voltage signal V d To the input end of the impedance extraction module 440. The impedance extraction module 440 extracts the driving current signal and the digital voltage signal V according to the received d An impedance signal related to the impedance characteristics of the battery cell 401 may be extracted.

[0097] In some embodiments, the impedance extraction module 440 includes a first multiplier 441 and a second multiplier 442. The driving current signal I1 generated by the signal generator 410 is input to the input end of the first multiplier 441, and the driving current signal I2 generated by the signal generator 410 is input to the input end of the second multiplier 442, wherein I1 and I2 are sine signals and cosine signals, respectively, that is, if I1 is a sine signal, I2 is a corresponding cosine signal; if I1 is a cosine signal, I2 is a corresponding sine signal.

[0098] In some embodiments, the battery impedance measurement circuit 400 further includes a digital filter 450 for receiving the impedance signal and filtering the impedance signal to allow the DC component in the impedance signal to pass. d The result M1 multiplied by the driving current signal I1 is input into the digital filter 450, and the real part Zreal of the impedance value of the battery cell 401 can be output through the digital filter 450; the digital voltage signal V d The result M2 multiplied by the driving current signal I2 is input into the digital filter 450 , and the imaginary part Zimag of the impedance value of the battery cell 401 can be output through the digital filter 450 . The results M1 and M2 are both impedance signals related to the impedance characteristics of the battery cell 401 .

[0099] exist Figure 4 Two digital filters 450 are shown in FIG. 4. In other embodiments, the two digital filters 450 may be combined into one, including two input terminals and two output terminals, the two input terminals are used to receive the results M1 and M2 respectively, and the two output terminals are used to output the real part Zreal and the imaginary part Zimag of the impedance value respectively.

[0100] In some embodiments, the digital filter 450 is a low pass filter.

[0101] like Figure 4As shown, the battery impedance measurement circuit 400 also includes a switch 411 and a discharge resistor 412 connected in parallel with the battery cell 401. Among them, the signal generator 410 is connected to the switch 411, and the switch 411 is used to connect or disconnect the connection between the battery cell 401 and the discharge resistor 412. The discharge resistor 412 plays a shunt role. In some embodiments, the signal generator 410 may also include a modulator, such as a pulse density modulator, so that the sine / cosine signal generated by the signal generator 410 is modulated by the modulator and then injected into the battery cell, and the modulation signal is used to control the switch 411 to connect or disconnect the connection with the discharge resistor 412.

[0102] like Figure 4 As shown, in some embodiments, the battery impedance measurement circuit 400 of the present invention further includes a synchronization window unit 460 for making the digital voltage signal V d Synchronized with the window function, the period of which is equal to the measurement period. Figure 4 In the embodiment described above, the synchronous window unit 460 is connected between the analog-to-digital converter 430 and the impedance extraction module 440 to make the digital voltage signal V d Synchronizes with the window function.

[0103] The phase reversal of the battery cell driving current may cause a certain degree of damage to the stable state of the battery, and the use of the synchronous window unit 460 can compensate for the damage.

[0104] Figure 7 FIG. 1 is a phase diagram of a driving current in a battery impedance measurement circuit according to another embodiment of the present invention. Figure 6 The difference of the embodiment shown is that a synchronization window unit 460 is used. Figure 7 As shown, the window function in this embodiment is a triangular window function. The driving currents in Device1, Device2 and Device3 are all synchronized by the synchronization window unit 460, especially making the second battery unit Device2 and Device3 phase inverted at the zero crossing point of the window function, which is equivalent to multiplying the driving current by zero at this point, thereby eliminating the damage caused by the phase inversion to the stability of the driving signal. Figure 7 As shown, in the triangular window function, one of the zero crossing points is circled, i.e., the lowest point of the triangular waveform. In other embodiments, the zero crossing point may also be the midline of the triangular waveform, i.e., the point where the waveform changes from a positive value to a negative value.

[0105] In some embodiments, the time for the phase to stabilize after the inversion is called the stabilization time t. In these embodiments, the phase controller inverts the phase of the second drive current at 1 / 2 stabilization time t before the zero crossing point of the window function. For example, if t is 5% of the measurement cycle, the phase inversion is performed at the moment of 2.5% of the measurement cycle before the zero crossing point of the window function, thereby minimizing the influence of the stabilization time on the measurement result.

[0106] In some embodiments, the stabilization time t can be obtained by measurement or estimation.

[0107] Figure 7 The figure is not used to limit the window function adopted by the synchronous window unit 460 of the present invention. In other embodiments, other types of window functions may also be adopted, such as a Hanning window, a Hamming window, a rectangular window, etc.

[0108] Figure 8 FIG. 4 is a schematic diagram of a battery impedance measurement circuit according to an embodiment of the present invention. Figure 8 Shows Figure 4 An example of the signal generator 410 and the phase controller 420 shown in FIG. In this embodiment, the signal generator 810 is a sine wave generator that can output the amplitude and sign of the sine wave separately. Figure 8 As shown, the amplitude of the sine wave signal is output at the amplitude output terminal 811, and the sign of the sine wave signal is output at the sign output terminal 812. The phase controller 820 is a sign control unit, in which one input terminal 821 receives the sign output from the signal generator 810, and the other input terminal receives the phase control signal 822. If the phase control signal 822 is 0, it means that the sign of the sine wave signal does not need to be changed. If the phase control signal 822 is 1, it means that the sign of the sine wave signal is inverted, that is, if the original sign is "+", it is inverted to "-"; if the original sign is "-", it is inverted to "+". The phase control signal 822 can be set according to the rules described above, so as to obtain the following. Figure 5-7 The phase change results are shown.

[0109] Fig. 9 is an exemplary flow chart of a battery impedance measurement method according to an embodiment of the present invention. The method can be implemented by using the battery impedance measurement circuit described above in the present invention. Therefore, the above drawings and descriptions of the battery impedance measurement circuit can be used to illustrate the battery impedance measurement method of this embodiment, and the repeated contents will not be expanded. Fig. 9 As shown, the battery impedance measurement method of this embodiment includes the following steps:

[0110] Step 910: Input a first driving current to a first battery cell.

[0111] Step 920: Input M second driving currents to M second battery cells adjacent to the first battery cell respectively, the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer.

[0112] Step 930: Control the phases of the M second drive currents so that M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first driving current, where m=1 to M.

[0113] Steps 910 and 920 can be performed by Figure 4 and Figure 8 Step 930 can be performed by Figure 4 and Figure 8 This is performed using the phase controller shown in FIG.

[0114] In some embodiments, the battery impedance measurement method of the present invention further includes:

[0115] Step 940: Obtain the voltage value of each battery cell.

[0116] Step 942: Calculate the impedance of the first battery cell according to the first driving current and the voltage value of the first battery cell.

[0117] Step 944: Calculate the impedance of the second battery cell according to the second driving current and the voltage value of the second battery cell.

[0118] In these embodiments, the sliding average method as described above can be used to obtain the voltage value of each battery cell in real time in each measurement cycle. The voltage value can be an average voltage value obtained by averaging the voltage values ​​of the current measurement cycle and several measurement cycles before it. The voltage value has removed the crosstalk of the induced voltage caused by other battery cells to the battery cell, thereby obtaining an accurate battery cell impedance.

[0119] In some embodiments, the battery impedance measurement method of the present invention further includes:

[0120] Step 950: Obtain multiple voltage values ​​of each battery cell in multiple measurement cycles.

[0121] Step 952: Averaging multiple voltage values ​​to obtain an average voltage value of each battery cell.

[0122] Step 954: Calculate the impedance of the first battery cell according to the first driving current and the average voltage value of the first battery cell.

[0123] Step 956: Calculate the impedance of the second battery cell according to the second driving current and the average voltage value of the second battery cell.

[0124] The averaged voltage value has eliminated the crosstalk of the induced voltage caused by other battery cells to the battery cell, so that the accurate battery cell impedance can be obtained.

[0125] In some embodiments, the number of measurement cycles of the battery impedance measurement method of the present invention is at least 2 M .

[0126] In some embodiments, a window function is used to synchronize the phase of the second driving current so that the phase is reversed at a zero-crossing point of the window function, and a period of the window function is equal to the measurement period.

[0127] In some embodiments, a window function is used to synchronize the phase of the second driving current; a stabilization time is obtained for the phase to stabilize after being inverted; and the phase is inverted at 1 / 2 of the stabilization time before the zero crossing point of the window function.

[0128] According to the battery impedance measurement circuit and method of the present invention, the phase of the driving current input to the battery cell is controlled by a phase controller, which can eliminate the crosstalk of the induced voltage brought by the adjacent battery cells, thereby effectively eliminating the error of impedance measurement and obtaining accurate battery impedance measurement results.

[0129] Although the present invention has been described with reference to the current specific embodiments, a person skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions may be made without departing from the spirit of the present invention. Therefore, any changes or modifications to the above embodiments within the spirit of the present invention will fall within the scope of the claims of this application.

Claims

1. A battery impedance measurement circuit, characterized in that: include: a signal generator connected to the plurality of battery cells, and configured to input a driving current to each of the battery cells, wherein the signal generator inputs a first driving current to a first battery cell, and the signal generator inputs M second driving currents to M second battery cells adjacent to the first battery cell, respectively, and the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer; A phase controller is connected to the signal generator and is used to control the phases of the M second drive currents so that M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first drive current, where m=1 to M; an analog-to-digital converter connected to both ends of the plurality of battery cells and configured to convert analog voltage signals of the battery cells into digital voltage signals; and The impedance extraction module is connected to the signal generator and the analog-to-digital converter, and is used to extract an impedance signal related to the impedance characteristics of the battery cell.

2. The battery impedance measurement circuit according to claim 1, characterized in that: Also includes: The digital filter receives the impedance signal and filters the impedance signal to allow a direct current component in the impedance signal to pass through.

3. The battery impedance measurement circuit according to claim 1, characterized in that: Also includes: A synchronous window unit is used to synchronize the digital voltage signal with a window function, wherein the period of the window function is equal to the measurement period.

4. The battery impedance measurement circuit as claimed in claim 3, characterized in that: The phase controller inverts the phase of the second driving current at a zero crossing point of the window function.

5. The battery impedance measurement circuit as claimed in claim 3, characterized in that: The phase controller inverts the phase of the second driving current at 1 / 2 stabilization time before the zero crossing point of the window function, wherein the stabilization time is the time it takes for the phase to stabilize after being inverted.

6. The battery impedance measurement circuit as claimed in claim 3, characterized in that: The window function is a triangular window function.

7. A battery impedance measurement method, characterized in that: include: Inputting a first driving current to the first battery unit; Inputting M second driving currents respectively to M second battery cells adjacent to the first battery cell, wherein the frequency of the first driving current is equal to the frequency of the second driving current, wherein M is a positive integer; Control the phase of the M second drive currents so that M In a measurement cycle, the phase of the second driving current of the mth second battery unit is every 2 (M-m) The measurement cycles are inverted relative to the phase of the first drive current, where m=1 to M; Obtaining a voltage value of each of the battery cells; Calculating the impedance of the first battery cell according to the first driving current and the voltage value of the first battery cell; as well as The impedance of the second battery cell is calculated according to the second driving current and the voltage value of the second battery cell.

8. The battery impedance measurement method according to claim 7, characterized in that: Also includes: Obtaining a plurality of voltage values ​​of each of the battery cells in a plurality of the measurement cycles; Averaging the multiple voltage values ​​to obtain an average voltage value of each of the battery cells; calculating the impedance of the first battery cell according to the first driving current and the average voltage value of the first battery cell; as well as The impedance of the second battery cell is calculated according to the second driving current and the average voltage value of the second battery cell.

9. The battery impedance measurement method according to claim 7, characterized in that: The number of measurement cycles of the battery impedance measurement method is at least 2 M .

10. The battery impedance measurement method according to claim 7, characterized in that: Also includes: A window function is used to synchronize the phase of the second driving current so that the phase is reversed at a zero-crossing point of the window function, and a period of the window function is equal to the measurement period.

11. The battery impedance measurement method according to claim 7, characterized in that: Also includes: Synchronizing the phase of the second driving current using a window function; Obtaining the stabilization time for the phase to stabilize after being inverted; as well as The phase is reversed at 1 / 2 of the settling time before the zero crossing point of the window function.

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