Electrical isolation circuit

Abstract

An electrical isolation circuit (518) includes: an electrical isolator (534) having a first side and a second side; a first communication link (536) connected to the first side of the electrical isolator and connectable to a first transceiver (514); a second communication link (538) connected to the second side of the electrical isolator and connectable to a second transceiver (516); a first reference terminal (520-1) connectable to the first transceiver (514); a second reference terminal (520-2) connectable to the second transceiver (516); and an AC short-circuit capacitor (566) connected between the first reference terminal (520-1) and the second reference terminal (520-2).

Description

Technical Field

[0001] The present disclosure relates to an electrical isolation circuit for a communication interface, and more particularly, to an electrical isolation circuit for use with a battery management system. Background Art

[0002] A battery management system (BMS) is an electronic system that monitors the electrochemical reactions in battery cells and controls the charging and discharging processes of each battery cell. To achieve efficient and safe performance, the BMS can also monitor battery temperature and battery health. In this way, the BMS can avoid defective battery cells and notify the central processing unit (CPU) of the situation of each cell. The BMS can be used in complex energy storage systems such as hybrid electric vehicles (HEVs) and electric vehicles (EVs), as well as in industrial applications such as energy storage systems (ESSs) and uninterruptible power supply (UPS) systems. Summary of the Invention

[0003] According to a first aspect of the present disclosure, there is provided an electrical isolation circuit, the electrical isolation circuit comprising:

[0004] An electrical isolator having a first side and a second side; a first communication link connected to the first side of the electrical isolator and connectable to a first transceiver;

[0005] A second communication link connected to the second side of the electrical isolator and connectable to a second transceiver;

[0006] A first reference terminal connectable to the first transceiver;

[0007] A second reference terminal connectable to the second transceiver; and

[0008] An AC short-circuit capacitor connected between the first reference terminal and the second reference terminal.

[0009] Such an electrical isolation circuit can advantageously: (i) reduce the complexity and component requirements of the EMI filter circuit system; and / or (ii) reduce the voltage tolerance requirements of the transceivers.

[0010] In one or more embodiments, the AC short-circuit capacitor may be a discrete capacitor.

[0011] In one or more embodiments, the electrical isolation circuit may further comprise:

[0012] A first capacitive decoupling circuit connected between the first communication link and the first reference terminal; and

[0013] A second capacitive decoupling circuit connected between the second communication link and the second reference terminal.

[0014] In one or more embodiments, the first communication link may include a first primary link and a first secondary link, and the second communication link may include a second primary link and a second secondary link.

[0015] In one or more embodiments, the first capacitive decoupling circuit may include:

[0016] a first primary decoupling capacitor connected between the first primary link and a first reference terminal; and

[0017] a first secondary decoupling capacitor connected between the first secondary link and the first reference terminal; and

[0018] The second capacitive decoupling circuit may include:

[0019] a second primary decoupling capacitor connected between the second primary link and a second reference terminal; and

[0020] a second secondary decoupling capacitor connected between the second secondary link and the second reference terminal.

[0021] In one or more embodiments, the electrical isolator may include a capacitive electrical isolator. The capacitive electrical isolator may include:

[0022] a primary capacitor connected between the first primary link and the second primary link; and

[0023] a secondary capacitor connected between the first secondary link and the second secondary link.

[0024] In one or more embodiments, the electrical isolator may include a transformer.

[0025] In one or more embodiments, the electrical isolation circuit may have a transceiver voltage tolerance rating and a target BCI requirement that defines the relationship between the continuous current and the frequency. The capacitance value of the AC short - circuit capacitor may be selected based on the transceiver voltage tolerance rating and the target BCI requirement.

[0026] In one or more embodiments, the AC short - circuit capacitor may be a discrete capacitor with a capacitance greater than or equal to 100 pF.

[0027] There is also provided a communication interface, the communication interface including:

[0028] a first transceiver;

[0029] a second transceiver; and

[0030] any electrical isolation circuit disclosed herein.

[0031] In one or more embodiments, the communication interface may have a target BCI requirement that defines the relationship between the continuous current and the injection frequency, and the capacitance value of the AC short - circuit capacitor may be selected based on the following aspects:

[0032] Voltage tolerance of the first transceiver;

[0033] Voltage tolerance of the second transceiver; and

[0034] The target BCI requirement.

[0035] According to another aspect of the present disclosure, a battery management control circuit is provided, and the battery management control circuit includes any one of the plurality of electrical isolation circuits disclosed herein.

[0036] In one or more embodiments, the battery management control circuit may further include:

[0037] A processor, the processor including a transceiver; and

[0038] A plurality of battery management systems, each battery management system including a first transceiver and a second transceiver;

[0039] Wherein each of the plurality of electrical isolation circuits connects adjacent ones of the battery management systems and the processor.

[0040] In one or more embodiments, the first transceiver of one battery management system, the second transceiver of an adjacent battery management system, and an electrical isolation circuit may form an EMI filtering electrical isolation communication interface of the battery management control circuit.

[0041] Although the present disclosure admits various modifications and alternative forms, the features of the present disclosure have been shown by way of example in the drawings and will be described in detail. However, it should be understood that other embodiments other than the specific embodiments described are also possible. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are also covered.

[0042] The foregoing discussion is not intended to represent every example embodiment or every implementation within the scope of the current or future claim sets. The drawings and the following detailed description also illustrate various example embodiments. A more complete understanding of the various example embodiments can be obtained by considering the following detailed description in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] One or more embodiments will now be described by way of example only with reference to the drawings, in which:

[0044] Figure 1 A controller board including a plurality of battery management systems and connected to a string of battery cells is shown;

[0045] Figure 2 A controller board performing a high current injection test is shown Figure 1 thereof;

[0046] Figure 3Illustrate an example EMI filtering technique used in combination with a transformer- and capacitor-based electrical isolation circuit;

[0047] Figure 4 Illustrate an example of a capacitor-based communication interface with a high-voltage tolerant transceiver;

[0048] Figure 5 Illustrate a communication interface including a capacitance-based electrical isolation circuit according to an embodiment of the present disclosure;

[0049] Figure 6 Illustrate a communication interface including a capacitance-based electrical isolation circuit but without a capacitive decoupling circuit according to an embodiment of the present disclosure;

[0050] Figure 7 Illustrate the performance of a communication interface without an AC shorting capacitor;

[0051] Figure 8 Illustrate the performance of a communication interface with an AC shorting capacitor according to an embodiment of the present disclosure; and

[0052] Figure 9 Illustrate a communication interface including a transformer-based electrical isolation circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0053] Generally, BMS topologies are divided into three categories:

[0054] 1. Centralized: In a centralized topology, a single controller has multiple BMSs on the same circuit board (or a group of closely coupled boards). The boards are connected to battery cells by many wires via the respective BMSs of the battery cells.

[0055] 2. Distributed: In a distributed topology, multiple BMS boards are located close to their respective battery cells. The controller is connected to the battery by a single communication cable.

[0056] 3. Modular: A modular topology includes multiple controllers. Each controller processes several battery cells. Communication occurs between the controllers.

[0057] In a battery pack application, a large number of serially connected battery cells can generate a high voltage potential difference, which requires a high level of isolation between components. A transformer can provide an electrically isolated communication link between two BMSs, with each BMS controlling a corresponding battery pack. The transformer can magnetically couple and electrically isolate signals.

[0058] Any on-vehicle communication interface is vulnerable to severe electromagnetic (EM) perturbations or electromagnetic interference (EMI), which are typical features of the vehicle's electrical noise environment. Accordingly, an electrical isolation circuit providing communication between BMSs may include an electromagnetic interference (EMI) filter. Example EMI filters include a common mode choke (CMC) and a center-tapped transformer.

[0059] Figure 1 FIG. shows a controller board 102 connected to a string of battery cells 104. The illustrated controller board 102 can be used in a centralized or modular topology. The controller board includes a central processing unit (CPU) 106. In some examples, the CPU can be a microcontroller. In this example, the CPU is connected to an external higher-level control system via a non-isolated link. The controller board also includes a plurality of BMSs 108 each connected to the string of battery cells 104 via a respective connection cable 110. In some examples, the connection cable 110 can be a ribbon cable. Each BMS 108 is connected to a respective sub-string of battery cells 112 within the string of battery cells 104. Each sub-string of battery cells 112 can be a modular battery pack.

[0060] Each BMS 108 includes a first transceiver 114 and a second transceiver 116. Each of the plurality of BMSs 108 can communicate with an adjacent BMS via the transceivers 114, 116 of the BMS and an intervening electrical isolation circuit 118. For example, the second transceiver 116-1 of the first BMS 108-1 can communicate with the first transceiver 114-2 of the second BMS 108-2 via the second electrical isolation circuit 118-2. Similarly, the second transceiver 116-2 of the second BMS 108-2 can communicate with the first transceiver 114-3 of the third BMS 108-3 via the third electrical isolation circuit 118-3, and so on.

[0061] In this example, the CPU 106 also includes an embedded or stand-alone transceiver 121. The transceiver 121 of the CPU 106 can communicate with the first transceiver 114-1 of the first BMS 108-1 via the first electrical isolation circuit 118-1. In this way, the CPU 106 can communicate with each BMS 108 via the electrical isolation circuit 118. The transceivers 114, 116 of the BMS and the electrical isolation circuit 118 define a series of communication interfaces disposed between a series of BMSs 108. In this example, the BMSs 108 are connected to the CPU 106 in a daisy-chain configuration.

[0062] Each electrical isolation circuit 118 includes an electrical isolator. In this example, the electrical isolator is a transformer that provides electrical isolation between adjacent BMSs 108. Adjacent BMSs are electrically isolated from each other because they do not share a common ground or any other shared reference voltage. Since each BMS 108 has a DC connection to the string of battery cells 104, electrical isolation must be provided to handle the high inter-component voltage differences between adjacent BMSs 108.

[0063] As noted above, a transformer can provide electrical isolation by magnetically coupling and electrically isolating signals. In other examples, the electrical isolator can include one or more capacitors. Compared to a transformer, a capacitor can provide a lower-cost electrical isolator.

[0064] In this example, all of the communication interfaces provided by the electrical isolation circuits 118 between adjacent BMSs 108 are on the same board. However, such communication interfaces can be vulnerable to external EMI. The electrical isolation circuit can also include an EMI filter to provide protection for the communication interface against EM disturbances. Standard test methods in electric vehicle manufacturing can apply such EMI by conduction or radiation. These test methods can verify the system's adequate resistance to EMI. Bulk current injection (BCI) is an example of a conductive EMI test, where current is injected through a cable connected to the battery pack under test.

[0065] Figure 2 Shown performing a BCI test is a controller board 202 and a connected string of battery cells 204 similar to those in Figure 1 The BCI test can include placing injection coils at fixed distances along the connection cable 210 and measuring the system response. In some examples, the connection cable 210 is approximately 2 meters long, and a series of tests are performed by placing injection coils at distances of 15 cm, 45 cm, and 75 cm along the connection cable 210 and then at corresponding distances from the respective BMSs 208.

[0066] The CPU 206 and each BMS 208 are each connected to its own corresponding reference terminal 220. In this way, the CPU 206 and each BMS 208 can each have its own ground connection. The figure shows a ground parasitic capacitance 222 connecting each reference terminal 220 to the ground plane 224 of the system performing the BCI test. The ground parasitic capacitance 222 can be in the range of 1 to 5 pF. Figure 2 Other capacitances shown in the system of

[0067] · BMS capacitance 224 - The potential received by the connection cable 210 is decoupled by the BMS to the corresponding reference terminal 220. The BMS capacitance 224 is approximately 10..100 nF.

[0068] · Electrical isolation capacitor 226 - The parasitic capacitance of the electrical isolation circuit 208 is approximately: (i) 5 to 20 pF for a transformer-based electrical isolation circuit; (ii) 1 to 10 nF for a capacitor-based electrical isolation circuit.

[0069] · Connection cable capacitance 228 - The connection cable 210 having the characteristics of a coupled transmission line with a relatively low even-mode impedance to the docking ground layer 224 includes a distributed capacitance of approximately 600 pF / m.

[0070] During BCI testing, the injection coil is placed on the connection cable. The resulting injected current will follow the lowest impedance path through the connection cable capacitance 228 to the ground layer 224. For an injection at a given connection cable, the current is likely to pass through and / or circulate in the electrical isolation circuit 218 of the adjacent connected BMS 208. In other words, the injected current passes through the communication interface of the chain of BMS 208 on the connection controller board 202. For example, if the BCI injection coil is coupled to the system at the midpoint 230 of the first connection cable 210-1, the resulting current will pass through the first electrical isolation circuit 218-1 and the second electrical isolation circuit 218-2. As another example, when the BCI injection coil is coupled to the system at the midpoint 232 of the last connection cable 210-N, the resulting current may only pass through the last electrical isolation circuit 218-N. Therefore, for the electrical isolation circuit, this test configuration can represent the most stringent test configuration in BCI testing.

[0071] The BCI current passing through the electrical isolation circuit 208 simulates EMI to test the immunity of the communication link. Example BMI test requirements are to verify the sufficient immunity of the communication link to an injected current of 300 mA rms . To withstand such EMI levels, the electrical isolation circuit 208 can include an EMI filter (discussed relative to Figure 3 ), and / or a CPU and BMS transceiver with high tolerance to EMI (discussed relative to Figure 4 ).

[0072] Figure 3 Shows an example EMI filtering technique used in combination with transformer- and capacitor-based electrical isolation circuits. The figure shows: a communication interface 319A based on an unfiltered transformer; a communication interface 319B based on an unfiltered capacitor; a communication interface 319C based on an EMI-filtered transformer; and a communication interface 319D based on an EMI-filtered capacitor.

[0073] The communication interface 319A based on an unfiltered transformer includes a first transceiver 314A, a second transceiver 316A, and an unfiltered-transformer-based electrical isolation circuit 318A. The unfiltered-transformer-based electrical isolation circuit 318A includes an electrical isolator 334A, a first communication link 336A, a second communication link 338A, a first reference terminal 320A-1, and a second reference terminal 320A-2.

[0074] The electrical isolator 334A is located between the first transceiver 314A and the second transceiver 316A. The electrical isolator 334A is a transformer. The first transceiver 314A and the second transceiver 316A can be either a BMS transceiver or one of the transceivers of a CPU. The first receiver 314A is connected to the first reference terminal 320A-1, while the second receiver is connected to the second reference terminal 320A-2. The electrical isolator 334A is connected to the first transceiver 314A through the first communication link 336A and to the second transceiver 316A through the second communication link 338A. In this example, the first and second communication links are two-wire communication links that can communicate through differential signaling.

[0075] The communication interface 319B based on an unfiltered capacitor includes a first transceiver 314B, a second transceiver 316B, and an unfiltered-capacitor-based electrical isolation circuit 318B. The unfiltered-capacitor-based electrical isolation circuit 318B is the same as the unfiltered-transformer-based electrical isolation circuit 318A, except that the electrical isolator 334B includes a pair of capacitors instead of a transformer.

[0076] The communication interface 319C based on an EMI-filtered transformer includes a first transceiver 314C, a second transceiver 316C, and an unfiltered-capacitor-based electrical isolation circuit 318C. The unfiltered-capacitor-based electrical isolation circuit 318C includes the same components as described above with respect to the unfiltered-transformer-based electrical isolation circuit 318A. Additionally, the first communication link 336C and the second communication link 338C include a corresponding first common-mode choke (CMC) 340C and a second common-mode choke 342C. The first CMC 340C and the second CMC 342C include transformers. The circuit 318C also includes a first capacitive decoupling circuit 344C connected between the first communication link 336C and the first reference terminal 320C-1, and a second capacitive decoupling circuit 346C connected between the second communication link 338C and the second reference terminal 320C-2. The electrical isolator 334C is a center-tapped transformer with two center taps. The first center terminal of the transformer is connected to the first reference terminal 320C-1 through a first center-tapped decoupling capacitor 348. Similarly, the second center terminal of the transformer is connected to the second reference terminal 320C-2 through a second center-tapped decoupling capacitor 350.

[0077] The communication interface 319D based on an EMI filtering capacitor includes a first transceiver 314D, a second transceiver 316D, and an electrical isolation circuit 318D based on an unfiltered capacitor. The electrical isolation circuit 318D based on an EMI filtering capacitor includes the same components as those described above with respect to the electrical isolation circuit 318B based on an unfiltered capacitor. Additionally, the circuit 318D further includes a first CMC 340D and a second CMC 342D arranged in the same manner as described with respect to the electrical isolation circuit 318C based on an EMI filtering transformer, as well as a first capacitor decoupling circuit 344D and a second capacitor decoupling circuit 346D. The circuit 318D further includes a first separation terminal circuit 352 coupled between a first communication link 336D and a first reference terminal 320D-1. The first separation terminal circuit 352 is connected to the first communication link 336D between the first CMC 340D and the electrical isolator 334D. The circuit 318D further includes a second separation terminal circuit 354 coupled between a second communication link 338D and a second reference terminal 320D-2. The second separation terminal circuit 354 is connected to the second communication link 338D between the second CMC 342D and the electrical isolator 334D.

[0078] The EMI filtering circuits 318C, 318D can attenuate EMI in the form of common-mode noise to a safe and manageable level. However, compared to the corresponding unfiltered circuits 318A, 318B, the additional components of the EMI filtering circuits 318C, 318D may add a significant amount of cost and complexity to the electrical isolation circuit. Specifically, the solution using a transformer may be particularly expensive. Therefore, a system using multiple electrical isolation circuits, such as Figure 1 and 2 's system, may become prohibitively expensive and complex and include a large number of components.

[0079] Figure 4 An example of a capacitor-based communication interface 419 with high-voltage tolerant transceivers 414, 416 is shown. Compared to the Figure 3 's EMI filtering electrical isolation circuit, the high-voltage tolerant transceivers 414, 416 allow for the use of reduced EMI filtering in the intermediate electrical isolation circuit 418.

[0080] The communication interface 419 based on a reduced EMI filtering capacitor includes a first transceiver 414, a second transceiver 416, and an electrical isolation circuit 418 based on a reduced EMI filtering capacitor. Figure 4 's electrical isolation circuit 418 based on a reduced EMI filtering capacitor includes the same components as those described above with respect to the Figure 3 's electrical isolation circuit 318B based on an unfiltered capacitor. Additionally, Figure 4The circuit 418 also includes a first capacitive decoupling circuit 444 and a second capacitive decoupling circuit 446 arranged in the same manner as described with respect to the electrical isolation circuit based on the EMI filtering transformer. The first communication link 436 also includes a first resistive circuit 456 disposed between the first capacitive decoupling circuit 444 and the electrical isolator 434. Similarly, the second communication link 438 also includes a second resistive circuit 458 disposed between the second capacitive decoupling circuit 446 and the electrical isolator 434.

[0081] The first capacitive decoupling circuit 444 and the second capacitive decoupling circuit 446 are the primary mechanisms for suppressing EMI / common-mode interference in the electrical isolation circuit 418 based on the reduced EMI filtering capacitance. The impedance of the decoupling capacitors 460 of the first capacitive decoupling circuit 444 and the second capacitive decoupling circuit 446 should be high enough to limit the BCI current-to-voltage conversion at the transceiver end to less than the maximum rated voltage or tolerance of the transceiver. Therefore, the circuit design requires a trade-off between the decoupling capacitance value and the transceiver voltage tolerance.

[0082] In one example, the combination of (i) transceivers 414, 416 with a voltage tolerance of ±40V and (ii) decoupling capacitors 460 each having a capacitance of 100 pF can meet the requirements for a 300 mA BCI current injected at a frequency of 10 MHz. rms Transceivers 444, 446 with a voltage tolerance of ±40V may be limited in semiconductor technology for automotive products. The required bidirectional switches with a tolerance of ±40V may require a large silicon area and have high capacitance, resulting in higher switching losses and power consumption.

[0083] If Figure 4 the communication interface 419 uses transceivers 414, 416 with a voltage tolerance less than ±40V, the decoupling capacitors 460 will require a correspondingly higher capacitance value. Capacitance values higher than 100 pF can cause additional current consumption due to switching losses. Higher value decoupling capacitors can also create a low-pass filter (LPF) for any communication signal. This may limit the communication speed.

[0084] The embodiments of the present disclosure described below provide circuit arrangements that can reduce the EMI immunity requirements of the transceiver and the EMI filter circuitry. This in turn can reduce the number and cost of external components and avoid a major performance degradation of the communication interface due to over-filtering.

[0085] Figure 5 A communication interface 519 including an electrical isolation circuit 518 is shown in accordance with an embodiment of the present disclosure. Figure 5 The electrical isolation circuit 518 of can advantageously: (i) reduce the complexity and component requirements of the EMI filter circuitry; and (ii) reduce the voltage tolerance requirements of the transceiver.

[0086] Figure 5 The communication interface 519 includes a first transceiver 514, a second transceiver 516, and an electrical isolation circuit 518. The electrical isolation circuit 518 includes an electrical isolator 534, a first communication link 536, a second communication link 538, a first reference terminal 520-1, and a second reference terminal 520-2.

[0087] The electrical isolator 534 has a first side and a second side, with each side isolated from the other. In this example, the electrical isolator 534 includes a first isolation capacitor 562 and a second isolation capacitor 564. The first communication link 536 connects the first side of the electrical isolator 534 to the first transceiver 514. Similarly, the second communication link 538 connects the second side of the electrical isolator 534 to the second receiver 516. In this way, the first and second transceivers can communicate with each other in an electrically isolated manner. For example, the transceivers can belong to Figure 1 and 2 adjacent BMSs and / or CPUs in a controller board of

[0088] The electrical isolation circuit 518 further includes an AC short-circuit capacitor 566 connected between the first reference terminal 520-1 and the second reference terminal 520-2.

[0089] The AC short-circuit capacitor 566 provides an EMI filtering mechanism for the electrical isolation circuit 518. As discussed further below, the AC short-circuit capacitor 566 can form a low-impedance path in parallel with the electrical isolator 534 between the first reference terminal 520-1 and the second reference terminal 520-2. In this way, most of any EMI current will flow through the AC short-circuit capacitor 566.

[0090] The AC short-circuit capacitor 566 is a discrete capacitor that can be in the range of 100 pF to 100 nF. The AC short-circuit capacitor 566 is not a parasitic capacitance.

[0091] In this example, the electrical isolation circuit 518 further includes: a first capacitive decoupling circuit 544 connected between the first communication link 536 and the first reference terminal 520-1; and a second capacitive decoupling circuit 546 connected between the second communication link 538 and the second reference terminal 520-2. In a manner similar to Figure 3 and 4 the EMI filtering circuits 318C, 318D, 418 of

[0092] The arrangement of the AC shorting capacitor 566 between the reference terminals 520-1, 520-2 of the two electrically isolated transceivers forms a low impedance path for the AC signal. This can determine the maximum amplitude of the AC voltage between the reference terminals 520-1, 520-2, which in turn can determine the amplitude of the common-mode AC voltage, which will affect the operation of the communication interface against injected AC current disturbances. This relaxes the requirements for any other EMI filter circuitry (e.g., capacitive decoupling circuits 544, 546) and the voltage tolerance requirements for the interface transceivers 514, 516. This enables the use of simple EMI filter circuitry including low-cost components and avoids excessive filtering that may limit the performance of the communication interface.

[0093] In the communication interface 519, the capacitance values ​​of the decoupling capacitors 560 of the first capacitive decoupling circuit 544 and the second capacitive decoupling circuit 546 and the voltage tolerances of the first transceiver 514 and the second transceiver 516 may be adjusted relative to their voltage tolerances. Figure 4 The constraints in the communication interface are relaxed. For example, the capacitance C of the decoupling capacitor can be reduced or minimized. DECOUPLING , thereby achieving higher speed communication. In some embodiments, for example, Figure 6 Similarly, the electrical isolation circuit 518 can be used with a relative Figure 4 The communication interface discussed above may be used with a transceiver having a lower voltage tolerance than that described above.

[0094] If the capacitance C of the AC short-circuit capacitor 566 is selected AC-SHORT The communication interface 519 will have adequate EMI filtering if the following conditions are met:

[0095]

[0096]

[0097] Due to C ISOLATION >>C DECOUPLING And C AC SHORT >>C DECOUPLING

[0098] in:

[0099] ·C ISOLATION is the capacitance of the capacitance-based electrical isolator 534;

[0100] ·V CM，MAX is the voltage tolerance of the transceivers 514, 516 (the maximum common-mode voltage amplitude that can be tolerated by the transceiver design or its external protection, or the maximum common-mode voltage that enables trouble-free communication during signal transmission or reception);

[0101] IBCI is the maximum continuous current at injection frequency f BCI As a requirement of the BCI test, the target BCI requirement that defines the relationship between the continuous I BCI and f BCI is typically described by a certain characteristic curve of current versus frequency. The characteristic curve of the target BCI requirement may have a non-linear curvature.

[0102] In the above inequality, it is assumed that during the operation of the drivers of the corresponding transceivers 514, 516, one of the capacitive decoupling circuits 544, 546 (i.e., a pair of decoupling capacitors 560) is short-circuited with a lower impedance.

[0103] Therefore, for the communication interface 519 including the electrical isolation circuit 518 having the AC short-circuit capacitor 566, the transceivers 514, 516 do not have to have a high voltage tolerance, such as ±40V, or the decoupling capacitors 560 do not have to have a high capacitance value. Therefore, the electrical isolation circuit 518 can achieve high-speed communication without being limited by low saturation current and / or high parasitic capacitance of high-voltage devices inside the transceiver and / or excessive external filtering. The AC short-circuit capacitor 566 simplifies the EMI filter design of the electrical isolation circuit 518, and the capacitance value of the AC short-circuit capacitor 566 can be selected using the above inequality.

[0104] Figure 6 shows another communication interface 619 including an electrical isolation circuit 618 according to an embodiment of the present disclosure. Similarly, the Figure 6 features shown in Figure 5 have been given the corresponding reference numerals in the 600 series and will not be described again here.

[0105] The electrical isolation circuit 618 is the same as the Figure 5 electrical isolation circuit, except that there is no capacitive decoupling circuit. The above inequality shows that when considering the performance of the Figure 5 electrical isolation circuit, the capacitance of the capacitive decoupling circuit can be ignored. Therefore, some embodiments of the present disclosure do not include a capacitive decoupling circuit.

[0106] Figure 7 and 8 compare the performance of the example communication interfaces 719, 819 including the electrical isolation circuits 718, 818 with and without the AC short-circuit capacitor. Figure 7 shows the performance of the communication interface 719 without the AC short-circuit capacitor, and Figure 8Shows the performance of the communication interface 819 with an AC short - circuit capacitor 866 connected between a first reference terminal 820 - 1 and a second reference terminal 820 - 2. These figures contain graphs 770, 870 showing the simulated BCI performance of the corresponding communication interfaces 719, 819. The BCI frequency is plotted on the horizontal axis, and the continuous BCI current is on the vertical axis.

[0107] Except for the AC short - circuit capacitor 866, Figure 7 and 8 the electrical isolation circuits 718, 818 are the same. The AC short - circuit capacitor 866 is a 5 nF capacitor. Each electrical isolation circuit 718, 818 includes: an isolator 734, 834 including two 5 nF capacitors; and first and second capacitive decoupling circuits 744, 746, 844, 846, each decoupling circuit including two 22 pF decoupling capacitors 760, 860. The first and second transceivers 714, 716, 814, 816 of the communication interfaces 719, 819 each have a voltage tolerance of ±10V.

[0108] Graphs 770, 870 show the target BCI requirements 772, 872 for a continuous BCI current of 300 mA over a frequency range from 100 kHz to 400 MHz. rms In some examples, the target BCI requirements may have a more complex relationship between the continuous BCI current and the BCI injection frequency. The simulated performance curves 774, 874 on graphs 770, 870 show the values of the simulated performance or the maximum continuous current at which the communication is still fault - free (or at least sufficiently interference - free). For the communication interface 719 without the AC short - circuit capacitor, Figure 7 graph 770 shows that for frequencies less than 100 MHz, the performance curve 774 is below the target BCI requirement 772. In other words, the communication interface 719 has a minimum EMI filtering frequency of 100 MHz. Thus, only the capacitive decoupling circuits 744, 746 do not show immunity to a 300 mA rms BCI injection current.

[0109] Figure 8 Graph 870 for the communication interface 819 including the electrical isolation circuit 818 with the AC short - circuit capacitor 866 shows that for frequencies as low as approximately 1 MHz, the performance curve 874 can meet the target BCI requirement 872. Relative to Figure 7 the electrical isolation circuit 718, the immunity performance of the electrical isolation circuit 818 with the AC short - circuit capacitor 866 shows a two - order - of - magnitude improvement in EMI filtering performance.

[0110] In this example, the 5 nF AC short - circuit capacitor 866 is not sufficient for the communication interface 819 to meet the 300 mA requirement at frequencies less than 1 MHzrms requirements. In other words, the communication interface 819 has a minimum EMI filtering frequency of 1 MHz. The value of the AC short - circuit capacitor 866 can be increased by reducing the minimum EMI filtering frequency to extend the communication interface performance to lower frequencies. However, many applications do not require this level of performance at such low frequencies. Additionally, for various reasons, such as power limitations in a closed - loop or excessive impedance for open - loop BCI injection at low frequencies, meeting the 300 mA rms requirement can be challenging.

[0111] Figure 9 FIG. shows a communication interface 919 including a transformer - based electrical isolation circuit 918 according to an embodiment of the present disclosure. Also shown in Figure 9 are Figure 5 features that have been given corresponding reference numerals in the 900 series of the corresponding figures and will not be described again here.

[0112] Figure 9 Same as Figure 5 except that the electrical isolator 934 is a transformer rather than including a capacitor. The AC short - circuit capacitor 966 operates in the same manner as described with respect to Figure 5 . The transformer - based electrical isolation circuit 918 can also provide sufficient EMI filtering without restricting the transceiver voltage tolerance or decoupling capacitance. However, the transformer - based solution is not as cost - effective as the Figure 5 and 6 capacitor - based communication interfaces. Figure 9 The electrical isolation circuit 918 of Figure 6 includes a first capacitive decoupling circuit 944 and a second capacitive decoupling circuit 946. The decoupling circuits are optional, and other embodiments of the transformer - based electrical isolation circuit can operate in a manner similar to the

[0113] capacitor - based circuits of Figure 5 , 6 without the decoupling circuits. The electrical isolation circuits disclosed with respect to Figure 5 , Figure 5In the example, the first capacitive decoupling circuit 544 includes: a first main decoupling capacitor 560-1 connected between the first main link 536-1 and the first reference terminal 520-1; and a first secondary decoupling capacitor 560-2 connected between the first secondary link 536-2 and the first reference terminal 520-2. Similarly, the second capacitive decoupling circuit 546 includes: a second main decoupling capacitor 560-3 connected between the second main link 538-1 and the second reference terminal 520-2; and a second secondary decoupling capacitor 560-4 connected between the second secondary link 538-2 and the second reference terminal 520-2.

[0114] In other example embodiments, the first and second communication links and the first and second capacitive decoupling circuits may consist of corresponding single links or single capacitors in a single-wire configuration.

[0115] The use of the AC short-circuit capacitor maintains electrical isolation between the BMSs. This can be considered advantageous compared to an alternative method of replacing the AC short-circuit capacitor with a direct DC connection between the highest voltage of the first BMS and the reference terminal of the second BMS (e.g., taking advantage of the fact that the BMSs are connected to the battery cell string in a predefined order). In Figure 1 and Figure 2 implementing this method in the controller board of

[0116] would result in the direct on-board connection of the maximum potential from the battery to the reference terminal of the adjacent BMS. However, connecting to the battery in the wrong order can pose a serious danger that can harm the user. Different sets of connectors can mitigate such risks. However, due to the potential danger, this method may not be acceptable for many BMS applications.

[0117] Unless a specific order is explicitly stated, the instructions and / or flowchart steps in the above figures can be executed in any order. Additionally, those skilled in the art will recognize that although one example instruction set / method has been discussed, the materials in this specification can be combined in various ways to also produce other examples, and should be understood within the context provided in this detailed description.

[0118] In other examples, the instruction sets / methods shown herein, as well as the data and instructions associated therewith, are stored in respective storage devices implemented as one or more non-transitory machine or computer-readable or computer-usable storage media. Such one or more computer-readable or computer-usable storage media are considered part of an article (or article of manufacture). An article or article of manufacture may refer to any single manufactured component or multiple components. As defined herein, non-transitory machine or computer-usable media do not include signals, but such media are capable of receiving and processing information from signals and / or other transitory media.

[0119] Example embodiments of the materials discussed in this specification may be implemented, in whole or in part, via networks, computers, or data-based devices and / or services. These may include clouds, the Internet, intranets, mobile devices, desktop computers, processors, lookup tables, microcontrollers, consumer devices, infrastructure, or other enabling devices and services. As may be used herein and in the claims, the following non-exclusive definitions are provided.

[0120] In one example, one or more of the instructions or steps discussed herein are automated. The term automated or automatically (and its like variants) means controlling the operation of a device, system, and / or process using a computer and / or mechanical / electrical device without human intervention, observation, effort, and / or decision-making.

[0121] It should be understood that any components referred to as being coupled may be directly or indirectly coupled or connected. In the case of indirect coupling, additional components may be disposed between the two components referred to as being coupled.

[0122] In this specification, example embodiments have been presented in accordance with a selected set of details. However, those skilled in the art will understand that many other example embodiments may be practiced including different selected sets of these details. It is intended that the appended claims cover all possible example embodiments.

Claims

1. A battery management control circuit, characterized in that, Comprising: A processor, the processor comprising a transceiver; A plurality of battery management systems for an electric vehicle, each of the battery management systems being connected to battery cells of a respective sub-string of a series battery cell unit, and wherein each battery management system includes a first transceiver and a second transceiver; A plurality of electrical isolation circuits, the electrical isolation circuits connecting one of the adjacent battery management systems and the processor, such that the processor can communicate with each of the battery management systems via the electrical isolation circuits, wherein each electrical isolation circuit includes: An electrical isolator (534), the electrical isolator (534) having a first side and a second side; A first communication link (536), the first communication link (536) being connected to the first side of the electrical isolator and to the first transceiver (514) of one of the battery management systems; A second communication link (538), the second communication link (538) being connected to the second side of the electrical isolator and to the second transceiver (516) of another one of the battery management systems or to the transceiver of the processor; A first reference terminal (520-1), the first reference terminal (520-1) being connected to the first transceiver (514); A second reference terminal (520-2), the second reference terminal (520-2) being connected to the second transceiver (516), wherein the first reference terminal and the second reference terminal include a first ground terminal and a second ground terminal; and An AC short-circuit capacitor (566), the AC short-circuit capacitor (566) being connected between the first reference terminal (520-1) and the second reference terminal (520-2), wherein each electrical isolation circuit further includes: A first capacitive decoupling circuit (544), the first capacitive decoupling circuit (544) being connected between the first communication link (536) and the first reference terminal (520-1); and A second capacitive decoupling circuit (546), the second capacitive decoupling circuit (546) being connected between the second communication link (538) and the second reference terminal (520-2).

2. The battery management control circuit according to claim 1, wherein The AC short-circuit capacitor (566) is a discrete capacitor.

3. The battery management control circuit according to claim 1, characterized in that: The first communication link (536) includes a first main link (536-1) and a first secondary link (536-2); and The second communication link (538) includes a second main link (538-1) and a second secondary link (538-2); The first capacitive decoupling circuit (544) includes: A first main decoupling capacitor (560-1) connected between the first main link (536-1) and the first reference terminal (520-1); and A first secondary decoupling capacitor (560-2) connected between the first secondary link (536-2) and the first reference terminal (520-1); and The second capacitive decoupling circuit (546) includes: A second main decoupling capacitor (560-3) connected between the second main link (538-1) and the second reference terminal (520-2); and A second secondary decoupling capacitor (560-4) connected between the second secondary link (538-2) and the second reference terminal (520-2).

4. The battery management control circuit according to claim 3, wherein The electrical isolator includes a capacitive electrical isolator.

5. The battery management control circuit according to claim 4, wherein The capacitive electrical isolator includes:[[]] A main capacitor (562) connected between the first main link (536-1) and the second main link (538-1); and A secondary capacitor (564) connected between the first secondary link (536-2) and the second secondary link (538-2).

6. The battery management control circuit according to claim 1, wherein The electrical isolator (934) includes a transformer.

7. The battery management control circuit according to claim 1, wherein The electrical isolation circuit has a transceiver voltage tolerance rating and a target BCI requirement that defines the relationship between continuous current and frequency, and wherein the capacitance value of the AC short-circuit capacitor (566) is selected based on the transceiver voltage tolerance rating and the target BCI requirement.

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