Protection circuits for battery management systems

Abstract

Systems and methods are provided for a battery management system (BMS) having a protection circuit. In one example, a vehicle battery system may include a BMS including an interruption circuit coupled to a short-circuit protection circuit and a battery pack, the short-circuit protection circuit including a diode array, a cathode of the diode array coupled to a positive terminal post of the battery pack and an anode of the diode array coupled to a negative terminal post of the battery pack. In some examples, the interruption circuit may further be coupled to a reverse bias protection circuit including a switchable current path disposed between a control input of the interruption circuit and an output of the interruption circuit. In this manner, the vehicle battery system may be protected from unexpected voltage conditions by the BMS redirecting and dissipating overcurrent through the interruption circuit.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to each of U.S. Provisional Application No. 63 / 036,346, entitled "PROTECTION CIRCUIT FOR BATTERY MANAGEMENT SYSTEM," filed June 8, 2020, and U.S. Provisional Patent Application No. 63 / 042,963, entitled "PROTECTION CIRCUIT FOR BATTERY MANAGEMENT SYSTEM," filed June 23, 2020. The entire contents of each of the above-identified applications are hereby incorporated by reference for all purposes.

[0002] FIELD OF THE INVENTION The present disclosure relates generally to battery management systems, particularly including protection circuits for battery packs in vehicles. [Background technology]

[0003] Lithium-ion secondary (rechargeable) batteries are commonly used to start and power electric vehicles and hybrid electric vehicles. Depending on the power requirements and applications, multiple lithium-ion batteries may be assembled into a battery pack. For example, a 48V battery pack may be installed in an electrically assisted hybrid vehicle (BAHV) to power the BAHV during operations with low engine loads, such as coasting, braking, and idling.

[0004] Under certain conditions, such as during a short circuit event, relatively high currents (e.g., up to 1700 A) may be generated across the battery pack or across a battery management system (BMS) electrically coupled to the battery pack. Such high currents may lead to voltage spikes that cause degradation of electronic components included in the BMS, such as metal-oxide semiconductor field-effect transistors (MOSFETs) and / or other switches and relays.

[0005] Accordingly, protection circuits have been developed to mitigate such voltage spikes. As an example, a current-sensing circuit may be implemented in a BMS to detect higher currents characteristic of a short-circuit event, allowing the BMS to timely switch off a given MOSFET that is at risk of receiving a higher current. However, if a higher current is detected in time to successfully switch off the MOSFET within the BMS, stored energy in inductive elements, such as within the electrical load, or in the electrical lines connecting the battery system components may cause the MOSFET to conduct (i.e., reach its breakdown voltage) and enter avalanche mode. Thus, the MOSFET may be at risk of degradation even when switched off. Summary of the Invention

[0006] The inventors have identified the above problems and determined a solution to at least partially solve them. In one example, a vehicle battery system is provided, the vehicle battery system including: a battery management system (BMS) including an interruption circuit electrically coupled to a short-circuit protection circuit; and a battery pack, the battery pack having a positive supply line electrically coupled to the interruption circuit and a ground return line electrically coupled to the short-circuit protection circuit, the short-circuit protection circuit including a diode array, the diode array having a cathode electrically coupled to the positive terminal post of the battery pack and an anode electrically coupled directly to the negative terminal post of the battery pack. In this manner, the vehicle battery system can be protected from degradation by redirecting and dissipating current resulting from undesirable voltage conditions.

[0007] In one example, a vehicle battery system is provided having a battery pack coupled to a BMS. Specifically, a positive supply line of the battery pack may be electrically coupled to a drain terminal of a MOSFET included in the BMS, and a ground return line of the battery pack may be electrically coupled to a diode array. Furthermore, a gate terminal and a source terminal of the MOSFET may be electrically coupled to a reverse bias protection circuit, and the source terminal may be further electrically coupled to the diode array. Thus, in a higher current environment associated with the application of a reverse bias voltage or a short circuit event, the gate-source voltage (V GS ) is achieved by redirecting current to a low-current leakage transistor in the reverse-bias protection circuit, reducing the threshold voltage (V th ) or less. In this way, the reverse bias protection circuit can maintain an off state in the MOSFET even during the application of a reverse bias voltage or a short circuit event.

[0008] The diode array may provide an additional, low-resistance path for current dissipation when the MOSFET is switched off due to a reverse bias voltage or short-circuit condition. Specifically, the diode array may be coupled between the positive and negative terminal posts of the battery pack so that current may circulate through the electrical load and the diode array, thereby dissipating stored energy in the vehicle battery system. In this manner, the reverse bias protection circuit and the diode array may work in cooperation to redirect and dissipate excess current generated in the vehicle battery system, thereby preventing the MOSFET from switching on and exceeding its breakdown voltage when switched off.

[0009] It should be understood that the foregoing Summary is provided to introduce in a simplified form a selection of concepts that are further described in the Detailed Description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the Detailed Description. Moreover, the claimed subject matter is not limited to implementations that solve any disadvantage noted above or in any portion of the present disclosure. [Brief explanation of the drawings]

[0010] [Figure 1A] 1 shows a schematic diagram of an exemplary battery pack assembly. [Figure 1B] 1 shows a schematic diagram of an exemplary battery pack assembly with at least a portion of the outer housing removed to expose a plurality of stacked battery cells. [Figure 2] FIG. 1 is a high-level block diagram of a vehicle battery system including a battery management system. [Figure 3A] 1 shows a schematic circuit diagram of a reverse bias protection circuit included in a battery management system. [Figure 3B] 1 shows a schematic circuit diagram of a short circuit protection circuit. [Figure 4] 1 shows a flowchart of a method for managing current flow during a reverse bias voltage condition. [Figure 5A] 1 shows first and second exemplary operation sequences of a BMS. [Figure 5B] 10 illustrates a third exemplary operation sequence of the BMS. [Figure 6] 1 shows a schematic diagram of an exemplary printed circuit board assembly for implementing a battery management system. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following description relates to a system and method for a protection circuit for a battery pack, such as a lithium-ion battery pack for powering an electric vehicle or a hybrid electric vehicle. The lithium-ion battery pack may include multiple lithium-ion battery cells assembled in a stacked configuration. As an example, the lithium-ion battery pack may be a 48V battery pack for starting or powering an electrically assisted hybrid vehicle (BAHV). Furthermore, the protection circuit may be included in a battery management system (BMS) coupled to the lithium-ion battery pack.

[0012] Specifically, the protection circuit may maintain the shutdown circuit in an off state upon the application of an unexpected reverse bias voltage, for example, due to a reverse polarity event. The shutdown circuit may include one or more field effect transistors (FETs), such as metal-oxide semiconductor FETs (MOSFETs), junction gate FETs (JFETs), other types of transistors, or combinations thereof. In one example, the shutdown circuit may be a single MOSFET. In additional or alternative examples, the protection circuit may include a low-current leakage transistor, such as a bipolar junction transistor (BJT), which generates a near-zero collector-emitter voltage (V) when a reverse bias voltage is applied to the source terminal of the MOSFET. CE ) to maintain the MOSFET gate-source voltage (V GS ) to the threshold voltage (V th ) or less.

[0013] The protection circuit may further protect the interruption circuit from reaching a breakdown voltage and becoming conductive when switched off, for example, when a voltage spike is detected by the BMS during a short-circuit event. Specifically, the protection circuit may include a diode array coupled to the source terminal of the MOSFET, and the cathode and anode of the diode array may be further coupled to an electrical load coupled to the battery pack and the BMS, respectively. In one example, the diode array may include multiple flyback or freewheeling diodes. Thus, energy stored before or during a voltage spike may be circulated and dissipated across the diode array and the electrical load. In this way, the interruption circuit, and therefore the BMS and lithium-ion battery pack, may be protected from voltage spikes caused by both reverse polarity conditions, for example, due to negative electrical noise or incorrectly coupled positive and negative leads to the terminal posts of the lithium-ion battery pack, and short-circuit conditions that may otherwise send the MOSFET into avalanche mode. Furthermore, the protection circuitry provided by the present disclosure can protect the BMS from relatively high currents (e.g., up to 1700 A) even at relatively high temperatures (e.g., up to 140°C) and can extend acceptable lifetime degradation so that the BMS can continue to function within the expected lifetime of the individual hardware components contained therein.

[0014] As used herein, when referring to two components of a circuit, "coupled" can also refer to "electrically coupled" unless otherwise specified. Thus, when referring to two components of a circuit, "directly coupled" can refer to the two components being electrically coupled without any electrical components (e.g., resistors, transistors, capacitors, etc.) disposed between them, except for electrical conductors (such as wires and / or bus bars). Furthermore, a transistor described as being "on" allows current to flow through the transistor, whereas a transistor described as being "off" prevents or substantially limits the flow of current through the transistor ("substantially" is sometimes used herein as a modifier meaning "effectively").

[0015] FIG. 1A illustrates an exemplary battery pack assembly for a vehicle system. FIG. 1B illustrates a battery pack assembly with at least a portion of its external housing removed, thereby exposing a battery pack including a plurality of stacked lithium-ion battery cells. The battery pack may be included in the exemplary vehicle battery system of FIG. 2, where the battery pack may be coupled to a BMS. The BMS may include a protection circuit, example circuits of which are shown in FIGS. 3A and 3B. In some examples, the protection circuit may be configured to maintain a shutdown circuit of the BMS in an off state when a switch-on request is not received. In additional or alternative examples, the protection circuit may be configured to maintain at least one component of the shutdown circuit in an off state even when a switch-on request is received, thereby preventing current flow from one or more of the plurality of stacked lithium-ion battery cells to the electrical load. However, it should be understood that in such examples, energy stored in the vehicle battery system may circulate through the electrical load. Accordingly, a method for managing current flow through the shutdown circuit, which may include, for example, maintaining the shutdown circuit in an off state and dissipating any stored energy, is provided in FIG. 4. An example operational sequence of a BMS for managing current flow through the interruption and protection circuits is provided in Figures 5A and 5B. Figure 6 provides one example printed circuit board assembly (PCBA) for implementing a BMS including protection circuits, which may include multiple bus bars for coupling various components within the vehicle battery system and mitigating parasitic inductance.

[0016] 1A, a schematic diagram 100 is shown illustrating a battery pack assembly 102. The battery pack assembly 102 may be configured to start or power a vehicle, such as an electric vehicle or a hybrid electric vehicle. For example, the battery pack assembly 102 may include a 48V battery pack including a plurality of lithium-ion battery cells (as described in detail below with reference to FIG. 1B).

[0017] The multiple lithium ion battery cells may be arranged in a stacked configuration and removably enclosed within an external housing 104. Accordingly, the external housing 104 may be constructed of a material having low electrical conductivity, such as plastic or other polymer, to reduce short circuit events within the vehicle. The external housing 104, shown in FIG. 1A as a right-angle prism, may be shaped to be a clearance fit within the vehicle such that the battery pack assembly 102 may be in coplanar contact with one or more components of the vehicle, such as one or more engine components.

[0018] The outer housing 104 may be further configured to include openings or cavities for interfacing components of the battery pack assembly 102. For example, the outer housing 104 may be configured to expose a positive terminal post 106 and a negative terminal post 108, which may each be, for example, a land-locked terminal. That is, the positive terminal post 106 and the negative terminal post 108 may be insert molded in place on the outer housing 104. Inside the vehicle, the positive terminal post 106 and the negative terminal post 108 may be electrically coupled to a positive lead and a negative lead, respectively, such that the battery pack assembly 102 may form a closed circuit with the vehicle's electrical loads, thereby providing power to the vehicle.

[0019] The positive terminal post 106 and the negative terminal post 108 may be configured with different colors, shapes, symbols, etc. to indicate which of the terminal posts 106, 108 is positive and which is negative. For example, the positive terminal post 106 may be red and indicated with a plus sign (+), and the negative terminal post 108 may be black and indicated with a minus sign (-). Nevertheless, in some situations, the positive and negative leads may be incorrectly coupled, resulting in the positive lead being coupled to the negative terminal post 108 and the negative lead being coupled to the positive terminal post 106. In such a situation, a reverse bias of the applied potential difference may occur, and the battery pack assembly 102 may unexpectedly discharge without protection thereagainst. Therefore, as described below with reference to FIGS. 2 and 3A, the battery pack assembly 102 may include a BMS with a reverse bias protection circuit, which may be coupled to the plurality of lithium-ion battery cells and an electrical load. In this way, the MOSFETs of the BMS may remain switched off during application of the reverse bias voltage so that degradation of the individual battery cells and the BMS may be mitigated.

[0020] In some examples, the external housing 104 may be configured to expose a network management interface 110. In one example, the network management interface 110 may be communicatively coupled to a vehicle's local interconnect network (LIN) 112 via a wired or wireless connection. Thus, in some examples, the network management interface 110 may include a physical connector for mating with a complementary connector affixed to a wire extending from a LIN bus.

[0021] In some examples, the outer housing 104 may include a top cover 114a removably secured to an enclosure base 114b, such that the top cover 114a may be temporarily removed to replace or diagnose one or more of the plurality of lithium-ion battery cells.

[0022] 1B, a schematic diagram 150 illustrating a battery pack 152 is shown. In some examples, the battery pack 152 may be included in the battery pack assembly 102 of FIG. 1A, with the top cover 114a removed from the battery pack assembly 102 to expose a plurality of lithium-ion battery cells 154 removably secured to the enclosure base 114b. It should be understood, therefore, that each lithium-ion battery cell 154 may represent a basic unit from which a battery pack of any size, any power, and having any number of lithium-ion battery cells 154 may be constructed. It should further be understood that other embodiments not shown in FIG. 1B may include a battery pack having only one lithium-ion battery cell.

[0023] In some examples, the plurality of lithium ion battery cells 154 may be arranged in a stacked configuration, and each of the plurality of lithium ion battery cells 154 may be a prismatic pouch electrochemical cell. Thus, each of the plurality of lithium ion battery cells 154 may include a positive electrode and a negative electrode immersed in a liquid electrolyte, and each of the positive electrode, negative electrode, and electrolyte may be enclosed by a sealed pouch.

[0024] Additionally, each of the plurality of lithium ion battery cells 154 may expose a positive electrode tab 156 and a negative electrode tab 158 that may be configured to couple to a positive electrode and a negative electrode, respectively. Accordingly, each of the plurality of lithium ion battery cells 154 may be electrically coupled to the positive terminal post 106 and the negative terminal post 108 described in detail above with reference to FIG. 1A . In some examples, the plurality of lithium ion battery cells 154 may be electrically coupled to one another in series and / or parallel by one or more bus bars (not shown in FIG. 1B ), whereby the one or more bus bars may be electrically coupled to a plurality of electrode tabs 156, 158 on the plurality of lithium ion battery cells 154, respectively. The one or more bus bars may further be electrically coupled to one of the terminal posts 106, 108, such that the plurality of lithium ion battery cells 154 may be electrically coupled to the terminal posts 106, 108, thereby providing power to a system, such as a vehicle.

[0025] Each lithium-ion battery cell 154 in the battery pack 152 may be identical to one another. Furthermore, the total number of lithium-ion battery cells 154 and each of the electrical coupling configurations (e.g., parallel count and series count) of the battery pack 152 may define its electrical characteristics and performance ratings. As an example, the battery pack 152 may be configured in a "4S4P" configuration having 16 lithium-ion battery cells 154 in four subgroups, where the subgroups may be electrically configured in series and the four lithium-ion battery cells 154 in each subgroup may be electrically coupled in parallel. In some examples, the total number of lithium-ion battery cells 154 may be an odd number. In other examples, the total number of lithium-ion battery cells 154 may be an even number.

[0026] The plurality of lithium ion battery cells 154 may be held in a stacked configuration by bands 160. As shown, one or more bands 160 may surround the plurality of lithium ion battery cells 154 to prevent displacement of the individual lithium ion battery cells 154 relative to one another.

[0027] 2, a high-level block diagram 200 illustrating a vehicle battery system 202 is shown. The vehicle battery system 202 may include a battery pack 204 (such as battery pack 152 of FIG. 1B), which may include one or more lithium-ion battery cells 222. As shown, a positive supply line 252 may couple a positive end of the battery pack 204 to an electrical load 206 (e.g., a belt-integrated starter / generator, an integrated starter / generator, etc.) via a BMS 208, and a ground return line 254 may couple the electrical load 206 to a negative end of the battery pack 204. Specifically, the positive supply line 252 of the battery pack 204 may be coupled to an input 256a of an interruption circuit 210, and an output 256c of the interruption circuit 210 may be coupled to the electrical load 206. Additionally, a control input 256b of the interruption circuit 210 may be coupled to a driver integrated circuit (IC) 212 of the BMS 208 via a protection circuit 214. Accordingly, the driver IC 212 may be communicatively coupled to a controller 272, which may store machine-readable instructions in a non-transitory storage device, the instructions being executable by the controller 272 to enable various functions of the BMS 208, such as receiving and transmitting switch requests and monitoring the vehicle battery system 202. For example, the current sensing circuit 232, coupled to the positive supply line 252 via node 270, may transmit measurements of the current flowing in the interruption circuit 210 to the controller 272, which may be enabled to generate switch requests and adjust battery system operating conditions in response to the measurements received therefrom. While the controller 272 is shown in FIG. 2 as being included within the driver IC 212, it should be understood that in other examples, the controller 272 may be located external to the driver IC 212.

[0028] As further shown, the positive terminal post 216 may be coupled to a line coupling the BMS 208 to the electrical load 206, and the negative terminal post 218 may be coupled to a line (ground return line 254) coupling the electrical load 206 to the battery pack 204. (Additionally or alternatively, the positive and negative terminal posts 216, 218 may be coupled to the BMS 208 via respective bus bars (not shown in FIG. 2 ). Thus, it should be understood that the electrical load 206 may be located external to the battery pack 204. A diode array 234 may be further coupled to each of the positive and negative terminal posts 216, 218, with the anode of each diode in the diode array 234 directly coupled to the negative terminal post 218 and the cathode of each diode in the diode array 234 directly coupled to the positive terminal post 216. A shunt resistor 262 may be further disposed along the ground return line 254 coupling the battery pack 204 to the negative terminal post 218.

[0029] Shut-off circuit 210 may be coupled to other components in vehicle battery system 202 via input 256a, control input 256b, and output 256c. Thus, the voltage at control input 256b relative to the voltage at output 256c may control the operational state of shutdown circuit 210. For example, if the relative voltage across control input 256b and output 256c is less than a threshold operating voltage, then shutdown circuit 210 may be in an off state. Conversely, if the relative voltage across control input 256b and output 256c is greater than or equal to the threshold operating voltage, then shutdown circuit 210 may be in an on state. In this manner, shutdown circuit 210 may operate as a switch to selectively allow current flow from input 256a to output 256c, depending on the voltage applied to control input 256b.

[0030] Shutdown circuit 210 may include one or more FETs, such as MOSFETs or JFETs, other types of transistors, or combinations thereof. In some examples, shutdown circuit 210 may be a single MOSFET, such as an n-channel enhancement-mode MOSFET or a p-channel enhancement-mode MOSFET. In such examples, input 256a may be a drain terminal, control input 256b may be a gate terminal, and output 256c may be a source terminal. Thus, as an exemplary embodiment, the operation of shutdown circuit 210 may be described below as the operation of MOSFET 210 having drain terminal 256a, gate terminal 256b, and source terminal 256c.

[0031] Specifically, the MOSFET 210 operates at zero gate-source voltage (V GS ) at source terminal 256c. S ) at the gate terminal 256b relative to the G ) i.e., V GS V GS is the V of MOSFET210 th , then MOSFET 210 may switch from an off state to an on state. When in the on state, MOSFET 210 may allow current flow from drain terminal 256a to source terminal 256c. Conversely, when in the off state, MOSFET 210 may prevent or limit (e.g., substantially limit) current flow therethrough.

[0032] During battery operation, a switch-on request may be received by driver IC 212 (V th (greater than)V GSmay be output to switch the MOSFET 210 to an ON state. However, in some situations, the MOSFET 210 may be unintentionally switched from an OFF state to an ON state without any feedback from the driver IC 212. For example, a higher current or short circuit voltage profile may be caused by a reverse polarity event, by negative electrical noise in the vehicle battery system 202, etc.

[0033] Specifically, as implied by equation (1), a negative V S is a positive V GS Therefore, significant negative V S Any event that would generate a voltage difference may result in the unintentional switching of MOSFET 210. V GS = V G -V S (1) As just one example, V G is zero and V S If is negative, V GS is a positive value, and V GS The positive value of V th If the MOSFET 210 is greater than .gtoreq..times ...

[0034] Accordingly, a protection circuit is provided herein for maintaining the MOSFET in an off state during unexpected voltage peaks in the vehicle battery system. For example, a protection circuit 214 may be included in the BMS 208 to protect the MOSFET 210 from unintentional switching on by dissipating energy stored in the vehicle battery system 202 during a short circuit or higher current situation. Thus, the protection circuit 214 may be configured to protect the MOSFET 210 from unintentional switching on by dissipating energy stored in the vehicle battery system 202 during a short circuit or higher current situation. G and V S , can be controlled by maintaining V near or substantially zero, thereby controlling the gate terminal 256b and the source terminal 256c of the MOSFET 210. GS The magnitude of can be kept low, and V th It cannot be exceeded.

[0035] For circuits that do not include the reverse bias protection circuitry described herein, current in a charge pump included in the driver IC 212 may drain to compensate for leakage current in the MOSFET 210 during a reverse bias condition. Thus, the vehicle battery system 202 may lose stored charge in the charge pump, and as a result, the driver IC 212 may not be able to effectively source current to various portions of the vehicle battery system 202 (e.g., to switch on the MOSFET 210 when a switch-on request is actually received). Thus, a sudden negative V S is generated in MOSFET 210, the current drawn from the charge pump may become undesirably poor.

[0036] In contrast, in the present disclosure, the threshold V S Beyond negative V S When a voltage drop is detected, protection circuit 214 prevents the charge pump from draining. Specifically, as described in more detail below with reference to FIG. 3A, a current path may be provided within protection circuit 214 through a pair of diodes in series to allow current to flow to gate terminal 256b of MOSFET 210.

[0037] V GSを V th To keep the voltage drop below the threshold voltage, the protection circuit 214 may further include a switchable current path disposed between the gate terminal 256b and the source terminal 256c. The switchable current path may include a transistor or switching device, such as a BJT, that prevents an unexpected negative V S In response to the detection of V GS low to keep MOSFET 210 in an off state. Thus, by reducing the current drain on the charge pump and preventing MOSFET 210 from turning on in the absence of any switch-on request, protection circuit 214 may mitigate degradation of BMS 208 and one or more lithium-ion battery cells 220 in battery pack 204, thereby allowing BMS 208 to continue its expected function, such as protecting battery pack 204 from deep discharge.

[0038] In this manner, the BMS 208 may be configured to, upon detection of a reverse bias voltage at the output 256c of the shutoff circuit 210 (e.g., at the source terminal 256c of the MOSFET 210), conduct current through the switchable current path of the protection circuit 214. The BMS 208 may be further configured to prevent current flow through the switchable current path in response to the absence of a reverse bias voltage at the output 256c of the shutoff circuit 210 (e.g., at the source terminal 256c of the MOSFET 210).

[0039] 2, it should be understood that the BMS 208 may include an array of MOSFETs. Accordingly, aspects of the present disclosure may be applied to each MOSFET in the array of MOSFETs, such that each MOSFET in the array of MOSFETs may be protected from unexpected switching on.

[0040] The BMS 208 may further be enabled to switch the MOSFET 210 off from a previously requested on state. For example, during a short-circuit event, a voltage spike (e.g., a change in magnitude of a voltage above a threshold voltage, a voltage greater than the voltage of the battery pack, etc.) may generate an overcurrent that may partially bypass the electrical load 206 and flow along the positive supply line 252 toward the MOSFET 210. Therefore, to prevent the overcurrent from degrading the MOSFET 210, a current detection circuit 232 may be implemented to detect the overcurrent and enable the driver IC 212 to execute the switch-off request and open the MOSFET 210.

[0041] Thus, in one example, current sense circuit 232 may be electrically coupled to positive supply line 252 at node 270. However, it should be understood that in other examples, current sense circuit 232 may be coupled to other lines or components of vehicle battery system 202, such as ground return line 254. Current sense circuit 232 may further be communicatively coupled to driver IC 212 via a controller 272 included therein. Current sense circuit 232 may detect the current passing through node 270 and obtain a measurement thereof, which may be transmitted to driver IC 212. Controller 272 may then generate a switch request to driver IC 212. In this manner, the BMS may protect MOSFETs and other components of the vehicle battery system from undesirable currents that may result from a short-circuit event.

[0042] Furthermore, it may be possible to reduce the likelihood of reaching the breakdown voltage of MOSFET 210 even when MOSFET 210 is switched off. Specifically, less energy stored before or during a voltage spike may be transferred to MOSFET 210 to prevent MOSFET 210 from entering avalanche mode, which may put MOSFET 210 at risk of degradation. In BMS 208, diode array 234 may provide a low resistance path for the dissipation of stored energy.

[0043] Specifically, diode array 234 may include a plurality of flyback or freewheeling diodes, where the anode of each of the plurality of freewheeling diodes may be directly coupled to negative terminal post 218 and the cathode of each of the plurality of freewheeling diodes may be directly coupled to positive terminal post 216. When MOSFET 210 is switched off in response to a short-circuit event, negative terminal post 218 may have a higher potential than positive terminal post 216 because positive terminal post 216 may have a lower potential thereat. Thus, when an overcurrent accumulated in electrical load 206 flows along ground return line 254 to negative terminal post 218, the potential difference created between the positive and negative terminal posts 216, 218 may cause current to be drawn across diode array 234. It should be appreciated that due to the potential difference created when MOSFET 210 is switched off, current may begin to flow across diode array 234 substantially immediately after MOSFET 210 is switched off. Specifically, the multiple freewheeling diodes may be characterized by a fast forward response time that creates a low resistance path. As shown, a shunt resistor 262 may be implemented to further redirect current across the low resistance path provided by the diode array 234.

[0044] Because MOSFET 210 may be kept off by protection circuit 214, the current that passed across diode array 234 may further pass across electrical load 206 and be received again at negative terminal post 218. In this manner, an overcurrent may circulate through each of the electrical load and diode array. As the current circulates, energy may be dissipated from vehicle battery system 202 (e.g., via heat) until the (decaying inductive) current decreases below a threshold current manageable by MOSFET 210. Driver IC 212 may then be enabled to switch MOSFET 210 on again in response to a switch-on request generated by controller 272, an external controller, or an operator of vehicle battery system 202. However, it should be understood that the low resistance path that may be provided by diode array 234 may allow current to circulate therethrough whenever MOSFET 210 is switched off. That is, in some examples, the low resistance path may circulate and dissipate up to 1700 A of current whenever the MOSFET 210 is switched off. For example, the low resistance path may circulate and dissipate 200-300 A of current when the vehicle battery system 202 is powered down as expected, and may circulate and dissipate greater than 1000 A of current during and after a short circuit event. In this manner, the diode array may redirect and dissipate stored energy when the vehicle battery system is powered down, regardless of whether the BMS switches off the MOSFET in response to an operator request or a short circuit event.

[0045] 3A, a schematic diagram 300 is shown illustrating an example circuit of a reverse bias protection circuit 314 included in a BMS 308. In some examples, one or more components described with reference to FIG. 3A may be substituted for the vehicle battery system 202 described above with reference to FIG. 2. For example, the BMS 208 of FIG. 2 and the BMS 308 of FIG. 3A may be the same or equivalent circuits. The numbering of the components of the circuit in FIG. 3A has been adapted for their incorporation into FIG. 3A.

[0046] As shown in FIG. 3A , the BMS 308 may further include a shutoff circuit 310 (e.g., a MOSFET or other known transistor) and a driver IC 312, each coupled to a reverse bias protection circuit 314. The MOSFET 310 may include a drain terminal 356 a (input), a gate terminal 356 b (a control input that may control the operating state of the MOSFET 310), and a source terminal 356 c (output). The drain terminal, or input 356 a, may be directly coupled to a positive terminal of a battery pack (not shown in FIG. 3A ) via a positive supply line 352. The gate terminal, or control input 356 b, may be coupled to the driver IC 312 via the reverse bias protection circuit 314. The source terminal, or output 356 c, may be directly coupled to the reverse bias protection circuit 314. The source terminal 356 c may further be directly coupled to a positive battery output terminal 316 (also referred to herein as a positive terminal 316), which is directly coupled to the (external) electrical load 306. The electrical load 306 may also be directly coupled to the negative battery output terminal of the battery pack via a ground return line 354. It should be understood that the electrical load 306 may be located external to the battery pack (i.e., the electrical load 306 may not be part of the battery pack). As further shown, various junctions of two or more electrical conductors or wires may be represented by nodes 370a, 370b, 370c, 370d, 370e, 370f, 370g, 370h, 370i, 370j, and 370k, respectively. The dashed directional arrow 382 indicates an exemplary current flow during expected switching on of the MOSFET 310 during normal circuit operation, as described below. That is, the directional arrow 382 indicates an exemplary current flow when the MOSFET 310 is in an on state, and the low-current leakage transistor 358 of the reverse bias protection circuit 314 is in an off state in the absence of reverse bias at the positive terminal 316.

[0047] MOSFET 310 may further include a body diode 356d. In some situations, such as during a reverse polarity event or when significant negative electrical noise builds up in the battery system and reverse bias protection circuit 314 is not present, a reverse bias voltage may be applied across body diode 356d when MOSFET 310 is in the off state. Body diode 356d may then trigger and unexpectedly switch MOSFET 310 from the off state to the on state.

[0048] During such an event when a reverse bias voltage is applied and the reverse bias protection circuit 314 is not present, a higher current profile may occur within the battery system. Therefore, a significant amount of energy may be stored, and the stored energy may be dissipated through the weakest (i.e., least resistive) channel within the battery system. For example, without the reverse bias protection circuit 314, the higher current may flow through the body diode 356d to ground, thus overloading the MOSFET 310. Therefore, a reverse bias protection circuit 314 is provided herein to control such higher current. As described in detail below and exemplified above with reference to FIG. 2, the reverse bias protection circuit 314 controls the V G and V S MOSFET 310 may be protected from reverse bias voltages by maintaining each of these at near or substantially 0 V. Accordingly, dotted directional arrow 384 illustrates an exemplary current flow during a reverse bias voltage condition, which may redirect the current through reverse bias protection circuit 314 as described below. That is, directional arrow 384 illustrates an exemplary current flow when MOSFET 310 is in an off state and low current leakage transistor 358 of reverse bias protection circuit 314 is in an on state. Thus, a current path is shown originating at ground 366, passing through diodes 364a and 364b, through resistors 362a and 362b, through diode 364d, through resistor 362c, through transistor 358, through node 370e, and terminating at electrical load 306.

[0049] As shown, driver IC 312 may have three pins 368a, 368b, and 368c so that the timing of the outputs therefrom may be varied. Specifically, pin 368a may be used to turn MOSFET 310 on, pin 368b may be used to turn MOSFET 310 off, and pin 368c may be used to control the V GS Thus, pin 368a may provide a voltage (e.g., 5 V) that can be delivered to gate terminal 356b of MOSFET 310 to switch MOSFET 310 on, and pin 368b may be used as a reference pin for controlling V G to ground, and pin 368c can S , may be coupled to the source terminal 356c of MOSFET 310 to reference the pin 368a. In some examples, the switching mechanism of pin 368a may be slower than the switching mechanism of 368b. That is, the resistance of resistor 362a coupled between pin 368a and MOSFET 310 may be higher than the resistance of resistor 362b coupled between pin 368b and MOSFET 310.

[0050] Without the reverse bias protection circuit 314, a significant negative V S When is applied, V GS is the V of the MOSFET 310 th However, the reverse bias protection circuit 314 prevents the voltage from increasing beyond V G and V S The two main functions of the reverse bias protection circuit 314 are to protect the MOSFET 310 by maintaining the V GS V th A low current leakage transistor 358 may be provided to protect various components to maintain:

[0051] For example, when a reverse bias voltage is applied, diode 364f may prevent excessive current from flowing from pin 368c to the source terminal 356c of MOSFET 310 through resistor 362g coupled therebetween. Specifically, current may instead be sourced from ground 366 through diode 364f, as indicated by directional arrow 384. As shown, in some examples, diode 364f may be a Schottky diode because a Schottky diode may have a relatively low forward voltage drop, such that diode 364f may be closer to ground 366. Furthermore, configuring diode 364f to be oriented as shown may prevent current from flowing back to ground 366 when MOSFET 310 is controllably turned on. Furthermore, resistors 362f and 362g are provided in parallel to limit current flow from pin 368c, and may also be connected to ground 366 to limit the voltage at pin 368c to a negative V S is detected and may remain near zero during expected battery operation and near a reference value. When MOSFET 310 is off, current may continue to flow to electrical load 306 through positive terminal 316 due to the inductive characteristics of electrical load 306. Thus, node 370j may have a negative voltage. To continue the flow of current to electrical load 306 and prevent current from flowing out of pin 368c, diode 364f and node 370j are provided to form a new circuit path for providing current to electrical load 306.

[0052] Similarly, and as further shown, diodes 364a and 364b may be coupled in series to prevent excessive current from flowing from charge pump 320 in driver IC 312 to gate terminal 356b of MOSFET 310 through pin 368a and resistor 362a coupled therebetween. Specifically, as indicated by directional arrow 384, negative V SWhen a power failure is unexpectedly detected, current may instead be sourced from ground 366 through diodes 364a and 364b. Thus, diodes 364a and 364b may be low-leakage diodes that provide low leakage current during unexpected battery operation. In this manner, the controllability of the battery system, and thereby BMS 308, through driver IC 312 may be protected. Furthermore, by configuring diodes 364a and 364b to be oriented as shown, current may be prevented from flowing back to ground 366 when it is provided by charge pump 320 in response to a switch-on request at driver IC 312, as indicated by directional arrow 382.

[0053] In some examples, as further shown, the driver IC 312 may be communicatively coupled to a controller 372, which may store machine-readable instructions in a non-transitory storage device, the instructions being executable by the controller 372 to enable various functions of the BMS 308, such as receiving and transmitting switch requests, monitoring the battery system, etc. While the controller 372 is shown in FIG. 3A as being contained within the driver IC 312, it should be understood that in other examples, the controller 372 may be located external to the driver IC 312.

[0054] Reverse bias voltage, i.e., negative V S is detected at the source terminal 356c of the MOSFET 310, the generated current may be sourced from ground 366 through diode 364f (e.g., via resistor 362f) toward node 370f and low-current leakage transistor 358. In some examples, diode 364e may be a Zener diode or a transient voltage suppressor (TVS) diode so that diode 364e can clamp the voltage across it at a set voltage, such as 8.5V.

[0055] In some examples, the low current leakage transistor 358 may be a BJT that includes an input (e.g., collector) terminal 360a, a control input (e.g., base) terminal 360b, and an output (e.g., emitter) terminal 360c. The source voltage V S A voltage of approximately 8.5 volts relative to may be generated at node 370f via diode 364e, and this voltage may be pulled down through the voltage divider formed by transistors 362e and 362d, allowing current to flow into base terminal 360b, thereby switching transistor 358 from an off state to an on state.

[0056] As shown, the anode of diode 364e may be coupled to emitter terminal 360c, and the cathode of diode 364e may be coupled directly to node 370f. In this manner, the anode of diode 364e may be at a higher voltage than the anode of emitter terminal 360c, and diode 364e may couple the base-emitter voltage (V BE ) can function to stabilize

[0057] Therefore, negative V S When a negative V S It is switched on through the V BE Therefore, low-current leakage transistor 358 may be viewed as a switch that allows current to flow from diodes 364a and 364b to source terminal 356c, as indicated by directional arrow 384. Current may flow through resistor 362a to resistor 362b, then to diode 364d, then to resistor 362c, then through transistor 358, before reaching node 370k, which is directly coupled to source terminal 356c. The current flow is proportional to V G V S , thereby preventing MOSFET 310 from switching on.

[0058] Specifically, when low current leakage transistor 358 is turned on, V G is the emitter voltage (V E ) can be quickly pulled down to V GS is the V of the low current leakage transistor 358 CE Therefore, V CE When V drops below 1 V, for example, across collector terminal 360a and emitter terminal 360c, GS is V th may be kept below a value and MOSFET 310 may remain in an off state.

[0059] On the other hand, during expected battery operation, low current leakage transistor 358 may be switched off and pin 368a may provide a voltage to V G may be pulled up to turn on MOSFET 310. When MOSFET 310 is turned on, current may flow from drain terminal 356a to source terminal 356c and to electrical load 306. MOSFET 310 may be turned off via pin 368b. Current flow from drain terminal 356a to source terminal 356c may be prevented when MOSFET 310 is turned on. In this manner, a switchable current path including low-current leakage transistor 358 may be electrically coupled to MOSFET 310, the switchable current path being disposed between gate terminal 356b of MOSFET 310 and source terminal 356c of MOSFET 310.

[0060] In some examples, diodes 364c and 364d may further be provided as blocking diodes to maintain the direction of current flow to driver IC 312 via pin 368b and to low-current leakage transistor 358 via resistor 362c, respectively. Thus, as shown, diode 364c may be oriented in the desired direction of current flow to driver IC 312 via pin 368b when MOSFET 310 is controllably switched off, and diode 364d may be oriented in the desired direction of current flow to low-current leakage transistor 358 via resistor 362c to protect MOSFET 310 from unexpected reverse-bias voltage across source terminal 356c. In one example, each of diodes 364c and 364d may be a diode having a relatively low forward voltage drop, such as a Schottky diode.

[0061] In this way, current flows through the negative V S In response to a negative voltage being applied to node 370e, current may flow from nodes 370b and 370c, coupled to gate terminal 356b of MOSFET 310, to nodes 370d and 370e, coupled to source terminal 356c of MOSFET 310. Thus, a negative voltage at source terminal 356c may prevent MOSFET 310 from turning on. Such current flow may be enabled by activating low-current leakage transistor 358 disposed between nodes 370b and 370c and nodes 370d and 370e. In some examples, current may flow from ground 366 through diodes 364a and 364b to nodes 370b and 370c. However, current may flow from nodes 370b and 370c to nodes 370d and 370e when a negative V is applied to node 370e. S In response to the absence of , it may not flow from nodes 370b and 370c to nodes 370d and 370e.

[0062] In some examples, the circuit illustrated by schematic diagram 300 may be implemented in a vehicle battery system to prevent MOSFET 310 from turning on even when a switch-on request is received. As an example, MOSFET 310 may be one of multiple MOSFETs arranged in an array. Each of MOSFETs 310 may be electrically coupled to one of multiple lithium-ion battery cells in a battery pack. In some examples, when a switch-on request is received, a portion of the lithium-ion battery cells may be utilized to provide power to the vehicle battery system, and the remaining portion may be kept off by reverse bias protection circuit 314.

[0063] As indicated by directional arrows 382 and 384, a negative V S Regardless of whether MOSFET 310 is switched on or off in response to MOSFET 310 being ...

[0064] Referring now to FIG. 3B, a schematic diagram 350 is shown illustrating an example circuit of a short-circuit protection circuit 390. It should be understood that the components of the short-circuit protection circuit 390 may be included in or coupled to the BMS 308 described above with reference to FIG. 3A. Thus, in some examples, one or more components described with reference to FIG. 3B may be substituted for the vehicle battery system described above with reference to FIG. 2. The numbering of the components of the circuit in FIG. 3B has been adapted for their incorporation into FIG. 3B.

[0065] As shown in FIG. 3B , the short-circuit protection circuit 390 may include a diode array 334. The diode array 334 may be an array of flyback or freewheeling diodes arranged in parallel. As shown, the anodes of all of the diodes in the diode array 334 may be directly coupled to each other, and the cathodes of all of the diodes in the diode array 334 may be directly coupled to each other. While four individual diodes are shown in the schematic diagram 350 as being included in the diode array 334, it should be understood that FIG. 3B depicts an exemplary embodiment and should be understood as non-limiting. Thus, the total number of diodes in the diode array 334 may be less than, equal to, or greater than four.

[0066] An electrical load 306, characterized by an inductance 374a and a resistance 362h, may be coupled to the diode array via a positive battery output terminal 316 and a negative battery output terminal 318 (also referred to herein as the negative terminal 318). Specifically, the diode array 334 may be electrically coupled to the positive terminal 316 via a line 386 and to the negative terminal 318 via a line 388. Additionally, because the electrical load 306 may be coupled to the positive terminal 316 via a line 392 and to the negative terminal 318 via a ground return line 354, a short circuit protection circuit 390 may be coupled between the diode array 334 and the electrical load 306.

[0067] Dashed directional arrow 396 indicates an exemplary current flow following the expected switching on of MOSFET 310 (described above with reference to FIG. 3A) during normal circuit operation. Specifically, current may flow from source terminal 356c (described above with reference to FIG. 3A) of MOSFET 310 via line 394 to positive terminal 316, from which current may flow across electrical load 306 to provide power to a battery-powered system. From electrical load 306, current may flow along ground return line 354. Negative It may flow to terminal 318 and to the battery pack (not shown in FIG. 3B). In this way, a closed circuit may be formed between the battery pack, the MOSFET, and the electrical load during normal circuit operation.

[0068] The dashed directional arrow 398 illustrates an exemplary current flow during a short-circuit condition in which the MOSFET 310 (described above with reference to FIG. 3A ) is open or off. During such a condition, current may not flow to the battery pack, but instead may circulate through the electrical load 306 and the diode array 334. That is, the directional arrow 398 illustrates current flow when the MOSFET 310 is maintained in an off state by the reverse bias protection circuit 314 (described above with reference to FIG. 3A ). Current may flow from the reverse bias protection circuit 314 via line 394 to the positive terminal 316, from which the current may flow to the electrical load 306. Specifically, current may flow from ground 366 to a lower voltage formed at the positive terminal 316. The lower voltage may be generated when the MOSFET 310 is open. For example, when MOSFET 310 is opened to stop current flow to electrical load 306, inductance 374a attempts to maintain the current by inducing a voltage of opposite polarity to the voltage at the positive and negative terminals 316, 318 when MOSFET 310 is closed, or off. From electrical load 306, current may flow along ground return line 354 to negative terminal 318.

[0069] Because the inductance 374a of the electrical load 306 attempts to maintain current flow by inducing a voltage of opposite polarity, the diode array 334 is forward biased, thereby allowing current to flow from the negative terminal 318 to the positive terminal 316. Thus, in response to a short-circuit condition, a low resistance path may be provided by the diode array 334, which may recirculate excess current within the electrical load 306. In this manner, by coupling the source terminal of the MOSFET to a short-circuit protection circuit including an array of freewheeling diodes, the positive terminal, the electrical load, and the negative terminal, the MOSFET may be protected from degradation (e.g., by entering avalanche mode when the MOSFET is conducting in the off state) because the excess current may be redirected by the short-circuit protection circuit.

[0070] As further shown, lines 386, 388 may be characterized by parasitic inductances 374b, 374c, respectively. As described in detail below with reference to FIG. 6, parasitic inductances 374b, 374c may be at least partially mitigated via bus bars (not shown in FIG. 3B) coupling positive terminal 316 to line 386 and negative terminal 318 to line 388, respectively. Thus, by reducing parasitic inductances 374b, 374c via the bus bars, the direction of current may more easily be changed along directional arrow 398 and across diode array 334. In some examples, a shunt resistor (not shown in FIG. 3B) may be further disposed along ground return line 354 between the battery pack and negative terminal 318 to further assist in changing the direction of current along directional arrow 398 and across diode array 334.

[0071] Referring now to FIG. 4, a flow chart illustrating a method 400 for providing reverse bias and short circuit protection to a battery interrupt circuit is shown. Reverse bias and short circuit protection may be provided via the circuits shown in FIGS. 2-3B. In general, during application of reverse bias voltage within a vehicle battery system, such as due to an unintentional reverse polarity event or accumulated negative electrical noise, the interrupt circuit may be at risk of unintentional switching on. In a specific example where the interrupt circuit is a MOSFET, the V GS (e.g., if V is sufficiently negative) S (via) the V thIf the voltage rises above , then the MOSFET may unintentionally switch on, potentially discharging and degrading the vehicle battery system. Furthermore, even when the MOSFET is switched off, the MOSFET may still be conducting if a short-circuit condition causes the MOSFET to reach its breakdown voltage and enter avalanche mode, degrading the MOSFET and thereby the vehicle battery system. Therefore, the method provided herein may detect a short-circuit condition, switch the MOSFET off, ensure the MOSFET is off by passing current through a reverse-bias protection circuit, and dissipate the stored energy through the short-circuit protection circuit.

[0072] Method 400 is described below with respect to the systems and components shown in FIGS. 1A-3B. For example, in some examples, method 400 may be implemented in BMS 208 of FIG. 2 or BMS 308 of FIG. 3A (and FIG. 3B). In such examples, the steps of method 400, or portions thereof, may represent actions that, in the physical world, occur via hardware devices, such as BMS 208 or one or more components of BMS 308. It should be understood that method 400 may be implemented with other systems and components without departing from the scope of the present disclosure. It should further be understood that individual steps described with reference to method 400 may be added, deleted, substituted, or interchanged within the scope of the present disclosure.

[0073] Method 400 may begin at 402 of FIG. 4 , where method 400 may include responding to detecting a reverse bias voltage at the positive battery terminal or responding to an unintentional switching on of the shutdown circuit. If a reverse bias voltage or an unintentional switching on is not detected, desired battery operation may proceed. Specifically, method 400 may proceed to 404, where method 400 may include determining whether a switch-on request was received at the driver IC or at a controller coupled to the driver IC. Specifically, the switch-on request may be a command to switch the shutdown circuit of the BMS from an off state to an on state. If a switch-on request is not received, method 400 may return to 402.

[0074] If a switch-on request is received, method 400 may proceed to 406, where method 400 may include turning on the battery pack to power the vehicle by switching on a shut-off circuit of the BMS and closing a battery circuit of the vehicle battery system. Specifically, the positive supply line may provide power from the battery pack to the vehicle's (external) electrical loads. However, it should be understood that the reverse bias protection circuit may mitigate degradation of the vehicle battery system even when a switch-on request is received, such as when negative electrical noise accumulates in the vehicle battery system.

[0075] At 408, the method 400 may include determining whether the current detected by the current detection circuit of the BMS is greater than a threshold current. In some examples, the threshold current may be selected to maintain the expected life of the interruption circuit. Specifically, the threshold current may be less than or equal to a maximum current that can be managed by the interruption circuit without excessive degradation thereof (e.g., beyond expected degradation resulting from normal battery operation beyond the life of the interruption circuit). In some examples, the current may be a first current flowing along a positive supply line between the battery pack and the interruption circuit.

[0076] If it is determined that the detected current is less than or equal to the threshold current, method 400 may proceed to 410 to maintain the current vehicle battery system operating state. Specifically, the vehicle battery system may continue to provide power to the vehicle until a switch-off request is received. Method 400 may then end.

[0077] If the detected current is determined to be greater than a threshold current at 408, or if a reverse bias voltage or unintentional switch-on is detected at 402, protection of battery operation may proceed. In particular, the reverse bias protection circuit may prevent the interruption circuit from coupling the battery cells to an electrical load, thereby mitigating degradation of the vehicle battery system. Additionally, the short circuit protection circuit may circulate and dissipate stored energy across an external load to further mitigate degradation of the vehicle battery system by preventing the interruption circuit from reaching a breakdown voltage.

[0078] The method 400 may proceed to 412, where the method 400 may include sourcing a current (e.g., a second current from ground) through a low-current leakage transistor in the reverse bias protection circuit toward an output of the shutdown circuit. In some examples, the low-current leakage transistor may be a BJT and the shutdown circuit may be a MOSFET, such that its collector terminal may be coupled to the gate terminal (control input) of the MOSFET and its emitter terminal may be coupled to the source terminal (output) of the MOSFET. The emitter terminal of the low-current leakage transistor may further be coupled to the anode of a Zener diode, and the base terminal of the low-current leakage transistor may be coupled to the cathode of the Zener diode. In other examples, a TVS diode may be used.

[0079] At 414, the method 400 supplies a V of the low current leakage transistor through a Zener diode. BE , to switch on the low current leakage transistor. Further, by coupling the cathode and anode of the Zener diode to the base and emitter terminals of the low current leakage transistor, respectively, V BEmay be clamped to a set value below 8.5V, for example.

[0080] At 416, the method 400 calculates a V CE Specifically, when the low current leakage transistor is switched on, the voltage across the collector and emitter terminals (i.e., V CE ) can be reduced to a low value, e.g., less than 1 V, and maintained at a low value. Thus, by coupling the control input of the shutoff circuit to the collector terminal of the low-current leakage transistor and the output of the shutoff circuit to the emitter terminal of the low-current leakage transistor, the voltage difference between the control input of the shutoff circuit and the output of the shutoff circuit can be maintained accordingly. In an example where the shutoff circuit is a MOSFET, the gate terminal of the MOSFET can be coupled to the collector terminal of the low-current leakage transistor, and the source terminal of the MOSFET can be coupled to the emitter terminal of the low-current leakage transistor. V GS can be maintained by turning on the transistor. In this way, V GS is the V of the MOSFET th Since the voltage Vcc can be kept below 1 V, the MOSFET can be kept in an off state.

[0081] At 418, method 400 may include circulating a current (e.g., each of the first current and the second current) through a diode array of the external load and the short-circuit protection circuit. Specifically, the emitter terminal of the low-current leakage transistor may be further coupled to the diode array, which may include a plurality of flyback or freewheeling diodes to provide a low-resistance path for redirecting the current away from the drain terminal of the MOSFET.

[0082] At 420, method 400 may include determining whether the overcurrent has dissipated. In one example, the overcurrent may be an amount of current in a vehicle battery system that exceeds a threshold current. If the overcurrent has not dissipated, method 400 may return to 418. If the overcurrent has dissipated, method 400 may return to 402. It should be appreciated that even when the overcurrent has dissipated, current may continue to circulate through the external load and diode array until a switch-on request is received (e.g., at 404).

[0083] Referring now to FIG. 5A, a timeline 500 illustrating first and second exemplary operational sequences of the vehicle battery system of FIGS. 1A-3B is shown. Specifically, the vehicle battery system may be configured with one or more shutdown circuits, such as one or more MOSFETs, coupled to one or more protection circuits. A given shutdown circuit may be switched on in response to a switch-on request being received by the vehicle battery system, thereby allowing current to flow through the given shutdown circuit to power a vehicle in which the vehicle battery system may be implemented. However, in some examples, a given shutdown circuit may be in an off state when a reverse bias voltage is applied to the output of the given shutdown circuit. In such examples, the protection circuit coupled to the given shutdown circuit may include a low-current leakage transistor, such as a bipolar junction transistor (BJT). When switched on, the low-current leakage transistor may be configured to maintain a voltage applied across the control input and output of the given shutdown circuit to prevent the given shutdown circuit from being unintentionally switched on. In this manner, the protection circuit may mitigate degradation of the vehicle battery system by reducing the likelihood of unintentional activation of the shut-off circuit. In some examples, the vehicle battery system may include BMS 208 or BMS 308, described above with reference to Figures 2 and 3A, respectively.

[0084] Timeline 500 illustrates shutoff circuit states with solid curves 501 and 503, voltages applied to the outputs (e.g., sources) of the shutoff circuit with solid curves 511 and 513, the voltage difference between the control input of the shutoff circuit and the output of the shutoff circuit with solid curves 521 and 523, low current leakage transistor states with solid curves 531 and 533, and V of the low current leakage transistor with solid curves 541 and 543. BE The solid curves 551 and 553 show the V CE Additionally, dashed curves 522 and 524 represent a first threshold voltage for the voltage applied across the control input and output at which the shutdown circuit state can switch between an off state and an on state. When the shutdown circuit includes a MOSFET, the voltage applied to the output (curves 511 and 513) is the V S and the voltage difference across the control input and output (curves 521 and 523) is the V GS and the first threshold voltage (curves 522 and 524) is V th It should be understood that this may be the case.

[0085] All curves are plotted over time along the abscissa, with time increasing from left to right on the abscissa. Additionally, the dependent variable represented by each curve described above is plotted along its respective ordinate, with the dependent variable increasing from bottom to top of a given ordinate (unless otherwise stated or indicated).

[0086] At t1, a first exemplary operating sequence of the vehicle battery system may begin. Between t1 and t2, the shutdown circuit state (curve 501) and the low-current leakage transistor state (curve 531) may each be in an off state. At t2, a negative voltage may be detected at the output of the shutdown circuit (curve 511), for example, due to a reverse-bias voltage condition. In response to the negative voltage being detected at the output, the direction of current may be diverted to a Zener diode (or TVS diode) coupled to the low-current leakage transistor.

[0087] At t3, the low current leakage transistor may switch from an off state to an on state (curve 531). Thus, the low current leakage transistor may be coupled to a current path with lower resistance than the blocking circuit, so that current may flow through the low current leakage transistor instead of the blocking circuit.

[0088] Therefore, after t3, V CE may be significantly decreased from a first value to a second value and then maintained at the second value (curve 551). CE may decrease from about 12 V to less than 1 V (e.g., near or substantially to 0 V) ​​and then be maintained there. BE increases and may level off at a value below that clamped by the Zener diode (curve 541). For example, V BE may increase to approximately 0.7 V. Furthermore, in a vehicle battery system corresponding to the illustrated example, the control input of the interruption circuit may be coupled to the collector terminal of a low-current leakage transistor, and the output of the interruption circuit may be coupled to the emitter terminal of the low-current leakage transistor. Thus, the voltage difference across the control input and output (curve 521) may be maintained below, for example, a first threshold voltage (curve 522). For example, the voltage difference across the control input and output may be maintained correspondingly below 1 V (e.g., near or substantially at 0 V). In this manner, the protection circuit may prevent the voltage difference across the control input and output from reaching the first threshold voltage, so that the interruption circuit may remain in an off state (curve 501). Between t3 and t4, an extended time interval is indicated by a break in the abscissa where a cause of a negative voltage at the output of the interruption circuit, such as a reverse-bias voltage condition, may end.

[0089] At t4, a second exemplary operating sequence of the vehicle battery system may begin. Thus, between t4 and t5, the shutoff circuit state (curve 503) and the low current leakage transistor state (curve 533) may each be in an off state.

[0090] At t5, a switch-on request may be received by the vehicle battery system of the interruption circuit, and a voltage may be applied to the control input of the interruption circuit. Thus, between t5 and t6, the voltage difference across the control input of the interruption circuit and the output of the interruption circuit may increase until, at t6, the first threshold voltage is reached (curve 524) and the interruption circuit switches from an OFF state to an ON state (curve 523). The voltage difference across the control input and output may continue to increase to a constant voltage value. Correspondingly, after t6, the voltage applied to the output of the interruption circuit may increase to a constant (positive) voltage value (curve 513).

[0091] During the second exemplary operating sequence, the V of the low current leakage transistor BE and V CE Each of V remains at a constant voltage value close to or substantially at 0V (curves 543 and 553, respectively). Thus, during the second exemplary operating sequence, V BE does not reach the second threshold voltage (curve 544), and the low current leakage transistor remains in the off state (curve 533). Thus, in some instances, the protection circuit may not operate in response to the vehicle battery system receiving a request to switch on the cutoff circuit.

[0092] Referring now to FIG. 5B, a timeline 550 illustrating a third example operational sequence of the vehicle battery system of FIGS. 1A-3B is shown. Specifically, the vehicle battery system may be configured with one or more shutdown circuits, such as one or more MOSFETs, coupled to one or more protection circuits. A given shutdown circuit may be switched on in response to a switch-on request received by the vehicle battery system, thereby allowing current to flow through the given shutdown circuit to power a vehicle in which the vehicle battery system may be implemented. However, in some examples, a given shutdown circuit may be switched off in response to a short-circuit condition being detected. In such examples, the protection circuit coupled to the given shutdown circuit may include a low-current leakage transistor, such as a BJT. When switched on, the low-current leakage transistor may be configured to reduce and maintain a voltage applied at the control input and output of the given shutdown circuit to prevent the given shutdown circuit from being unintentionally switched on. The protection circuit may further include a diode array, such as an array of flyback or freewheeling diodes, coupled to each of the low-current leakage transistor and the external load. In this manner, the protection circuit may mitigate degradation of the vehicle battery system during a short-circuit condition by circulating and dissipating excess current across the diode array and the external load while maintaining the shutdown circuit in an off state. In some examples, the vehicle battery system may include the BMS 208 described above with reference to FIG. 2 or the BMS 308 described above with reference to FIG. 3A (and FIG. 3B).

[0093] Timeline 550 shows the shutoff circuit state with solid curve 506, the current sensed by the BMS with solid curve 566, the voltage difference between the input and output of the shutoff circuit with solid curve 576, the voltage difference across the diode array (i.e., the voltage difference between the cathode and anode of the array of freewheeling diodes) with solid curve 586, the state of the low current leakage transistor with solid curve 536, and the V of the low current leakage transistor with solid curve 546. BE The solid curve 556 shows the V of a low current leakage transistor. CEAdditionally, dashed curve 567 represents the threshold current at which switching off can be generated for the interrupter circuit, and dashed curve 577 represents the breakdown voltage of the interrupter circuit above which the interrupter circuit may enter avalanche mode. When the interrupter circuit includes a MOSFET, the voltage difference across the input and output (curve 576) is proportional to the drain-source voltage (V DS ) can be used.

[0094] All curves are plotted over time along the abscissa, with time increasing from left to right on the abscissa. Additionally, the dependent variable represented by each curve described above is plotted along its respective ordinate, with the dependent variable increasing from bottom to top of a given ordinate (unless otherwise stated or indicated).

[0095] At t7, a third exemplary operating sequence of the vehicle battery system may begin. Between t7 and t8, the state of the interruption circuit (curve 506) may be on, and the state of the low-current leakage transistor (curve 536) may be off. Just before t8, the detected current may increase (curve 566) toward the threshold current (curve 567) as a result of a short-circuit condition in the vehicle battery system. At the same time, the voltage difference across the input and output of the interruption circuit may increase (curve 576).

[0096] In response to the detected current (curve 566) reaching the threshold current (curve 567), at t8 the shutdown circuit may switch from an on state to an off state (curve 506) to prevent current flow therethrough and reduce the detected current. Further, in response to the shutdown circuit switching off, the direction of current may be diverted from ground to a Zener diode (or TVS diode) coupled to a low current leakage transistor.

[0097] As further shown at t8, the voltage difference across the diode array may decrease and drop below 0 V (curve 586), allowing the diode array to provide a first current path with lower resistance than the interruption circuit. Thus, excess current that has accumulated in the vehicle battery system as a result of the short-circuit condition may be redirected to the first current path. In this manner, after the interruption circuit is switched off, current may circulate and dissipate through the diode array and the external load coupled thereto.

[0098] At t9, the low-current leakage transistor may switch from an off state to an on state (curve 536). Thus, the low-current leakage transistor may be coupled to a second current path with lower resistance than the blocking circuit, so that current may flow through the low-current leakage transistor instead of the blocking circuit. Current may then continue to flow from the low-current leakage transistor to the diode array.

[0099] After t9, V CE may decrease significantly, for example, from about 12 V to less than 1 V, to near or substantially 0 V (curve 556). BE increases and may level off at a value clamped by the Zener diode (curve 546). For example, V BE may increase to approximately 0.7 V. Furthermore, in a vehicle battery system corresponding to the illustrated example, the control input of the shutdown circuit may be coupled to the collector terminal of the low-current leakage transistor, and the output of the shutdown circuit may be coupled to the emitter terminal of the low-current leakage transistor. Correspondingly, the voltage difference across the control input and the output may decrease in magnitude to less than 1 V, near or substantially 0 V. In this manner, the protection circuit may prevent the voltage difference across the control input and the output from reaching the first threshold voltage, so that the shutdown circuit may remain in an off state (curve 506).

[0100] Furthermore, as a result of the redirection and dissipation of current provided by the diode array and the external load, the voltage difference across the input and output of the interruption circuit (curve 576) may level off. Furthermore, because the interruption circuit is in an off state (curve 506), the voltage difference across the diode array (curve 586) may also level off at a positive value (although current may continue to flow from the low-current leakage transistor to the diode array). Specifically, because the interruption circuit is kept open by redirecting current to the low-current leakage transistor via the second current path, and the voltage difference across its input and output is maintained below the breakdown voltage (curve 577) by redirecting current to the diode array via the first current path, additional current from the battery pack is limited (e.g., substantially limited) from flowing across the interruption circuit, and the voltage difference across the diode array stabilizes. In this manner, the protection circuit may prevent the voltage difference across the input and output of the interruption circuit from reaching the breakdown voltage, thereby preventing the interruption circuit from entering avalanche mode when switched off.

[0101] Referring now to FIG. 6, a schematic diagram 600 is shown illustrating a printed circuit board assembly (PCBA) 624. The PCBA 624 may include a printed circuit board (PCB) 626 having various electronic components printed, soldered, or otherwise affixed thereto. In one example, the PCBA 624 may implement a BMS, such as the BMS 208 described above with reference to FIG. 2 or the BMS 308 described above with reference to FIG. 3A (and FIG. 3B). Thus, the PCBA 624 may include various circuits and electronic components operative to monitor the battery system. For example, the PCBA 624 may include a shut-off circuit formed from an array of MOSFETs 610, whose inputs and outputs may be coupled to a first bus bar 628 a and a second bus bar 628 b, respectively. PCBA 602 may further include an array of flyback or freewheeling diodes 634, where the cathodes and anodes of the freewheeling diodes 634 may be coupled to second bus bar 628b and third bus bar 628c, respectively. It should further be understood that additional electronic components may be printed, soldered, or otherwise affixed on a side of PCB 626 opposite the side of PCB 626 shown in FIG. 6. As a non-limiting example, the array of freewheeling diodes 634 may include two freewheeling diodes on one side of PCB 626 (as shown in FIG. 6) and two freewheeling diodes on the other side of PCB 626 (not shown in FIG. 6).

[0102] As shown, bus bars 628a, 628b, and 628c are connected to couplings 630a, 630b, and 630c, respectively. 3Couplings 630a, 630b, 630c may be independently configured to couple (directly or via conductors) bus bars 628a, 628b, 628c to battery terminals (e.g., electrode tabs, terminal posts, etc., not shown in FIG. 6 ) of the battery system. As a first example, first bus bar 628a may couple a positive supply line of a battery pack to an input of an array of MOSFETs 610 via coupling 630a. As a second example, second bus bar 628B may couple a positive terminal post to each of the outputs of the array of MOSFETs 610 and each of the cathodes of an array of freewheeling diodes 634 via coupling 630b. As a third example, third bus bar 628c may couple a negative terminal post to each of the anodes of an array of freewheeling diodes 634 via coupling 630c. Each of the first and second bus bars 628a, 628b may be coupled to one or more MOSFETs 610 in the array of MOSFETs 610, such that when one or more MOSFETs 610 are switched on, a circuit between a given pair of battery terminals may be closed.

[0103] Bus bars 628a, 628b, and 628c may further include pins 636a, 636b, and 636c, respectively. Pins 636a, 636b, and 636c may respectively couple bus bars 628a, 628b, and 628c to various electronic components included in PCBA 624. As a first example, pin 636a may independently and directly couple first bus bar 628a to each of the inputs of the array of MOSFETs 610. As a second example, pin 636b may independently and directly couple second bus bar 628b to each of the outputs of the array of MOSFETs 610 and the cathodes of the array of freewheeling diodes 634. As a third example, pin 636c may independently and directly couple third bus bar 628c to each of the anodes of the array of freewheeling diodes 634. The pins 636a, 636b, 636c may further function as shunts to distribute current and may structurally stabilize the bus bars 628a, 628b, 628c, respectively.

[0104] Dashed directional arrow 696 indicates an exemplary current flow when the interruption circuit is in the on state. Specifically, as indicated by directional arrow 696, the BMS may be configured to sequentially pass current from the first bus bar 628a to the second bus bar 628b to the third bus bar 628c when the interruption circuit is in the on state, so that the current may be directed across the electrical load to the battery pack rather than through the array of freewheeling diodes 634.

[0105] Additionally, dashed directional arrow 698 indicates an example current flow when the interruption circuit is in the off state. Specifically, as shown by directional arrow 698, the BMS may be configured to direct current from the third bus bar 826c to the second bus bar 628b when the interruption circuit is in the off state, such that the direction of the current may be changed across the array of freewheeling diodes 634.

[0106] The bus bars 628a, 628b, 628c may be further configured to reduce parasitic inductance present in the battery system. As a first example, the first bus bar 628a may be configured to reduce parasitic inductance between the battery pack and the array of MOSFETs 610. As a second example, the second bus bar 628b may be configured to reduce parasitic inductance between the cathodes of the array of freewheeling diodes 634 and the positive terminal post. As a third example, the third bus bar 628c may be configured to reduce parasitic inductance between the anodes of the array of freewheeling diodes 634 and the negative terminal post. In this manner, the battery system may include multiple bus bars for redirecting and distributing current during both expected and unexpected operation of the battery system.

[0107] Thus, a vehicle battery system is provided that includes a battery pack coupled to a battery management system (BMS), where the BMS may include at least some components of a reverse bias protection circuit for maintaining a shutdown circuit in an off state during an unexpected voltage condition and a short circuit protection circuit for circulating and dissipating an overcurrent generated via the unexpected voltage condition. The BMS may further include a current detection circuit for detecting an overcurrent or abnormal current flow indicative of the unexpected voltage condition. In some examples, the shutdown circuit may include a metal oxide semiconductor field effect transistor (MOSFET). Specifically, the reverse bias protection circuit prevents the gate-source voltage (V) of the MOSFET from rising unless the current detected by the current detection circuit is dissipated via the short circuit protection circuit and unless a switch-on request is received at the BMS. GS ) to the threshold voltage (V th ) below . In some examples, the short-circuit protection circuit may include a diode array coupled between the positive and negative terminal posts of the battery pack, such that the diode array may be further coupled to an electrical load of the vehicle battery system. The diode array may therefore provide a low resistance path for current dissipation by allowing current to circulate across it and across the electrical load. The technical effect of providing both a reverse bias protection circuit and a short-circuit protection circuit is that the MOSFET may both be maintained in an off state and the MOSFET may be prevented from entering avalanche mode during application of a reverse bias voltage or a short-circuit event. Thus, the MOSFET, and thereby the entire vehicle battery system, may be protected from degradation during unexpected voltage conditions.

[0108] In one example, a vehicle battery system includes a battery management system including a MOSFET, a battery pack having a plurality of stacked battery cells, a positive supply line of the battery pack coupled to the MOSFET, and a reverse bias protection circuit coupled to the MOSFET, wherein the reverse bias protection circuit reduces a gate-to-source voltage (V GS ) to the MOSFET threshold voltage (V th ) below the reference voltage.

[0109] In another example, a vehicle battery system includes a battery management system (BMS) including an interruption circuit electrically coupled to a reverse bias protection circuit; and a battery pack having a plurality of stacked battery cells, wherein a positive supply line of the battery pack is electrically coupled to the interruption circuit, the reverse bias protection circuit including an input electrically coupled to a control input of the interruption circuit, an output electrically coupled to an output of the interruption circuit, and a control input electrically coupled to the output of the interruption circuit. The first example of the vehicle battery system further includes the input of the reverse bias protection circuit, the output of the reverse bias protection circuit, and the control input of the reverse bias protection circuit being included in a switchable current path of the reverse bias protection circuit, the switchable current path being disposed between the control input of the interruption circuit and the output of the interruption circuit. A second example of the vehicle battery system, optionally including the first example of the vehicle battery system, further includes the BMS configured to flow current through the switchable current path when detecting a reverse bias voltage at the output of the interruption circuit, and the BMS further configured to prevent current flow through the switchable current path in response to the absence of a reverse bias voltage at the output of the interruption circuit. A third example of a vehicle battery system, optionally including one or more of the first and second example vehicle battery systems, further includes: the reverse bias protection circuit includes one or more diodes, the one or more diodes configured to direct current to the switchable current path upon detection of a reverse bias voltage. A fourth example of a vehicle battery system, optionally including one or more of the first through third example vehicle battery systems, further includes: an input of the reverse bias protection circuit, an output of the reverse bias protection circuit, and a control input of the reverse bias protection circuit include a low current leakage transistor coupled to a Zener diode, the Zener diode coupled to a base-emitter voltage (V BEA fifth example of a vehicle battery system, optionally including one or more of the first through fourth example vehicle battery systems, further includes a fifth example of a vehicle battery system, wherein the low current leakage transistor and the blocking circuit are configured to switch on the low current leakage transistor by increasing the collector-emitter voltage (V CE ) is configured to reduce a voltage across the control input of the shutoff circuit and the output of the shutoff circuit when the low current leakage transistor is switched on. A sixth example of a vehicle battery system optionally including one or more of the first through fifth examples of the vehicle battery system further includes: CE reduces to and remains below 1 V when the low current leakage transistor is switched on. A seventh example vehicle battery system optionally including one or more of the first through sixth example vehicle battery systems further includes: the BMS includes a driver integrated circuit, the driver integrated circuit electrically coupled to the reverse bias protection circuit via three pins. An eighth example vehicle battery system optionally including one or more of the first through seventh example vehicle battery systems further includes: the three pins include a first pin configured to switch the shutdown circuit to an on state, a second pin configured to switch the shutdown circuit to an off state, and a third pin configured as a reference pin for controlling a voltage across a control input of the shutdown circuit and an output of the shutdown circuit.

[0110] In yet another example, a battery management system includes a protection circuit including a low-current leakage junction transistor and a MOSFET including a drain terminal, a gate terminal, and a source terminal, where the drain terminal is directly coupled to a positive supply line of a battery pack having a plurality of battery cells, the source terminal is directly coupled to each of an electrical load and the low-current leakage junction transistor, and the gate terminal is coupled to the low-current leakage junction transistor, and the protection circuit maintains the MOSFET in an off state in response to a reverse bias voltage being applied to the source terminal. A first example of the battery management system further includes: the low-current leakage junction transistor including a collector terminal, a base terminal, and an emitter terminal; the collector terminal of the low-current leakage junction transistor is coupled to the gate terminal of the MOSFET via each of a first resistor and a first diode; and the emitter terminal of the low-current leakage junction transistor is directly coupled to the source terminal of the MOSFET. A second example battery management system, optionally including the first example battery management system, is configured such that the protection circuit includes a second diode, the second diode being a Zener diode, the emitter terminal further coupled to the anode of the second diode, the base terminal coupled to the cathode of the second diode via a second resistor, and the second diode is configured to apply a base-emitter voltage (V BE ) to switch the low current leakage junction transistor to an ON state. A third example battery management system, optionally including one or more of the first and second example battery management systems, further includes a first diode coupled to the collector terminal to maintain a direction of current flow to the low current leakage junction transistor in response to the reverse bias voltage being applied to the source terminal. A fourth example battery management system, optionally including one or more of the first through third example battery management systems, further includes a fourth example battery management system, optionally including one or more of the first through third example battery management systems, further includes a fourth example MOSFET, optionally including one or more of the first through third example battery management systems, further including a fourth example MOSFET, optionally including one or more of the first through third example battery management systems, further including a fourth example MOSFET, wherein reducing and maintaining the MOSFET in an OFF state reduces the collector-emitter voltage (V CE) and the MOSFET is maintained at the gate-source voltage (V GS ) to the MOSFET threshold voltage (V th A fifth example battery management system, optionally including one or more of the first through fourth example battery management systems, further includes maintaining the V of the low current leakage junction transistor in the off state by correspondingly maintaining the V below CE Reducing and maintaining V CE is reduced to below 1V, and V CE to be below 1 V. A sixth example of a battery management system optionally including one or more of the first through fifth examples of the battery management system further includes a driver integrated circuit coupled to the protection circuit, the driver integrated circuit configured to switch the MOSFET to an on state in response to receiving a switch-on request generated via a controller coupled to the driver integrated circuit. A seventh example of a battery management system optionally including one or more of the first through sixth examples of the battery management system further includes the driver integrated circuit including a first output, a second output, and a third output, the first output being connected to a voltage (V G ), and the second output is configured to pull up V G to ground, and the third output is configured to pull the voltage at the source terminal (V S ). An eighth example of a battery management system, optionally including one or more of the first through seventh examples of the battery management system, further includes two diodes coupled to a first output of the driver integrated circuit to provide current to the gate terminal in response to a reverse bias voltage being applied to the source terminal. A ninth example of a battery management system, optionally including one or more of the first through eighth examples of the battery management system, further includes two diodes coupled to a second output of the driver integrated circuit to provide current to the gate terminal in response to a reverse bias voltage being applied to the source terminal. Gis pulled to ground. A tenth example battery management system optionally including one or more of the first through ninth examples battery management system further includes a diode coupled to the third output of the driver integrated circuit to source current toward the source terminal in response to the reverse bias voltage being applied to the source terminal.

[0111] In yet another example, a method for managing current flow through a battery pack interruption circuit includes, in response to a negative voltage being applied to the second node, allowing current to flow from a first node coupled to a control input of the battery pack interruption circuit to a second node coupled to an output of the battery pack interruption circuit while preventing current flow to the output across the control input. The first example of the method further includes, in response to the absence of negative voltage at the second node, not allowing current to flow from the first node to the second node. A second example of the method, optionally including the first example of the method, further includes enabling current to flow from the first node to the second node by operating a transistor. A third example of the method, optionally including one or more of the first and second example of the method, further includes current flowing from ground to the transistor by flowing through two diodes.

[0112] In yet another example, a vehicle battery system includes a battery management system (BMS) including: an interruption circuit electrically coupled to a short-circuit protection circuit; and a battery pack optionally having a plurality of stacked battery cells, wherein a positive supply line of the battery pack is electrically coupled to the interruption circuit and a ground return line of the battery pack is electrically coupled to the short-circuit protection circuit, the short-circuit protection circuit including a diode array, a cathode of the diode array electrically coupled directly to a positive terminal post of the battery pack and an anode of the diode array electrically coupled directly to a negative terminal post of the battery pack. The first example of the vehicle battery system further includes: the interruption circuit is further electrically coupled to a reverse bias protection circuit, the reverse bias protection circuit including a switchable current path, the switchable current path being disposed between a control input of the interruption circuit and an output of the interruption circuit. A second example of a vehicle battery system, optionally including the first example of the vehicle battery system, further includes: the BMS configured to switch off the interruption circuit in response to a short-circuit condition in the vehicle battery system; and the BMS further configured to maintain the interruption circuit in an off state by passing current through the switchable current path and circulating current through the diode array. A third example of a vehicle battery system, optionally including one or more of the first and second example of the vehicle battery system, further includes: an electrical load electrically coupled to the cathode and the anode of the diode array; and circulating current through the diode array further includes circulating current through the electrical load. A fourth example of a vehicle battery system, optionally including one or more of the first through third example of the vehicle battery system, further includes: the diode array including a plurality of flyback diodes electrically coupled in parallel.A fifth example of a vehicle battery system, optionally including one or more of the first through fourth example vehicle battery systems, further includes a first bus bar electrically coupling the positive supply line to an input of the interruption circuit, a second bus bar electrically coupling the positive terminal post to each of the output of the interruption circuit and the cathode of the diode array, and a third bus bar electrically coupling the negative terminal post to the anode of the diode array. A sixth example of a vehicle battery system, optionally including one or more of the first through fifth example vehicle battery systems, further includes the BMS configured to sequentially pass current from the first bus bar to the second bus bar to the third bus bar when the interruption circuit is in an on state, and the BMS further configured to pass current from the third bus bar to the second bus bar when the interruption circuit is in an off state. A seventh example of a vehicle battery system optionally including one or more of the first through sixth examples of the vehicle battery system further includes: the second bus bar configured to reduce a first parasitic inductance between the diode array and the positive terminal post; and the third bus bar configured to reduce a second parasitic inductance between the diode array and the negative terminal post. An eighth example of a vehicle battery system optionally including one or more of the first through seventh examples of the vehicle battery system further includes: the BMS further includes a driver integrated circuit electrically coupled to the shutdown circuit via three pins. A ninth example of a vehicle battery system optionally including one or more of the first through eighth examples of the vehicle battery system further includes: a first pin configured to switch the shutdown circuit to an on state, a second pin configured to switch the shutdown circuit to an off state, and a third pin configured as a control input of the shutdown circuit and a reference pin for controlling a voltage across an output of the shutdown circuit. A tenth example of a vehicle battery system, which optionally includes one or more of the first through ninth examples of the vehicle battery system, further includes a shunt resistor electrically coupling the battery pack to the diode array.

[0113] In yet another example, a battery management system includes a protection circuit including an array of low-current leakage junction transistors and freewheeling diodes, and a MOSFET including a drain terminal, a gate terminal, and a source terminal, wherein the drain terminal is directly coupled to a positive supply line of a battery pack optionally having a plurality of battery cells, the source terminal is directly coupled to the low-current leakage junction transistor, the source terminal is further coupled to the array of freewheeling diodes, and the gate terminal is coupled to the low-current leakage junction transistor, wherein the protection circuit is configured to switch the MOSFET from an on state to an off state and maintain the MOSFET in the off state in response to detecting a voltage greater than the voltage of the battery pack. A first example of the battery management system further includes: the low-current leakage junction transistor including a collector terminal, a base terminal, and an emitter terminal; the collector terminal of the low-current leakage junction transistor is coupled to the gate terminal of the MOSFET through a resistor and a diode; and the emitter terminal of the low-current leakage junction transistor is directly coupled to the source terminal of the MOSFET. A second example of the battery management system, optionally including the first example of the battery management system, further includes the diode maintaining a direction of current flow to the low current leakage junction transistor in response to detecting a voltage greater than the voltage of the battery pack. A third example of the battery management system, optionally including one or more of the first and second example of the battery management system, further includes an emitter terminal of the low current leakage junction transistor coupled to the array of freewheeling diodes via a bus bar to maintain a direction of current flow to the array of freewheeling diodes in response to detecting a voltage greater than the voltage of the battery pack. A fourth example of the battery management system, optionally including one or more of the first through third example of the battery management system, further includes a driver integrated circuit coupled to the MOSFET through the protection circuit, the driver integrated circuit configured to open or close the MOSFET in response to receiving a switching request generated via the controller coupled to the driver integrated circuit.A fifth example of a battery management system, optionally including one or more of the first through fourth examples of the battery management system, further includes a current detection circuit electrically coupled to the MOSFET and communicatively coupled to the driver integrated circuit, the current detection circuit configured to obtain a measurement of a current flowing in the MOSFET and send the measurement to the controller, and the controller configured to detect a voltage greater than a voltage of the battery pack based on the measurement.

[0114] In yet another example, a method for managing current flow through an interruption circuit of a battery pack includes: passing current from a first battery terminal to an external load; preventing current flow from a second battery terminal to the first battery terminal when the interruption circuit is closed; and passing current from the second battery terminal to the first battery terminal when the interruption circuit is open. The first example of the method further includes passing current from a first node coupled to a control input of the interruption circuit to a second node coupled to an output of the interruption circuit while preventing current flow to the output across the control input in response to detecting a current between the battery pack and the interruption circuit greater than a threshold current; and not passing current from the first node to the second node in response to detecting a current between the battery pack and the interruption circuit less than or equal to the threshold current. A second example of the method, which optionally includes the first example of the method, further includes opening the interruption circuit to limit current flow therethrough in response to detecting a current greater than the threshold current.

[0115] The following claims particularly point out certain combinations and subcombinations that are deemed novel and unobvious. These claims may refer to "an" element or "first" element, or their equivalents. Such claims should be understood to include the incorporation of one or more such elements, without requiring or excluding more than one such element. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed through amendment of the present claims or through the presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope than the original claims, are deemed to be encompassed within the subject matter of this disclosure.

Claims

1. 1. A vehicle battery system, comprising: a battery management system (BMS) including a shutdown circuit electrically coupled to the short circuit protection circuit; a battery pack, wherein a positive supply line of the battery pack is electrically coupled to the interruption circuit and a ground return line of the battery pack is electrically coupled to the short circuit protection circuit; Equipped with The short circuit protection circuit comprises a diode array, the cathode of the diode array being electrically coupled directly to the positive terminal post of the battery pack and the anode of the diode array being electrically coupled directly to the negative terminal post of the battery pack. Vehicle battery system.

2. 2. The vehicle battery system of claim 1, wherein the shutdown circuit is further electrically coupled to a reverse bias protection circuit, the reverse bias protection circuit including a switchable current path, the switchable current path being disposed between a control input of the shutdown circuit and an output of the shutdown circuit.

3. the BMS is configured to switch off the interruption circuit in response to a short circuit condition in the vehicle battery system; the BMS is further configured to maintain the interruption circuit in an off state by passing a current through the switchable current path and circulating the current across the diode array; An electrical load is electrically coupled to the cathode and the anode of the diode array, and circulating the current through the diode array further includes circulating the current through the electrical load.

3. The vehicle battery system of claim 2.

4. the diode array comprises a plurality of flyback diodes electrically coupled in parallel; or The vehicle battery system further includes a shunt resistor electrically coupling the battery pack to the diode array. The vehicle battery system according to any one of claims 1 to 3.

5. a first bus bar electrically coupling the positive supply line to an input of the interruption circuit; a second bus bar electrically coupling the positive terminal post to each of the output of the isolation circuit and the cathode of the diode array; a third bus bar electrically coupling the negative terminal post to the anode of the diode array; The vehicle battery system of any one of claims 1 to 4, further comprising:

6. the BMS is configured to allow current to flow continuously from the first busbar to the second busbar to the third busbar when the interruption circuit is in an on state, and the BMS is further configured to allow the current to flow from the third busbar to the second busbar when the interruption circuit is in an off state; or The second bus bar is configured to reduce a first parasitic inductance between the diode array and the positive terminal post, and the third bus bar is configured to reduce a second parasitic inductance between the diode array and the negative terminal post.

6. The vehicle battery system of claim 5.

7. 7. The vehicle battery system of claim 1, wherein the BMS further comprises a driver integrated circuit electrically coupled to the shutdown circuit via three pins.

8. The three pins are: a first pin configured to switch the interruption circuit to an on state; a second pin configured to switch the interruption circuit to an off state; a third pin configured as a reference pin for controlling the voltage across the control input of the interruption circuit and the output of the interruption circuit; 8. The vehicle battery system of claim 7, comprising:

9. 1. A battery management system, comprising: a protection circuit comprising an array of low current leakage junction transistors and freewheeling diodes; 1. A MOSFET having a drain terminal, a gate terminal, and a source terminal, the drain terminal is directly coupled to a positive supply line of a battery pack; the source terminal is directly coupled to the low current leakage junction transistor, the source terminal is further coupled to the array of freewheeling diodes; The gate terminal is coupled to the low current leakage junction transistor. the MOSFET; Equipped with The protection circuit is configured to switch the MOSFET from an on state to an off state and maintain the off state in response to detecting a voltage greater than a voltage of the battery pack. Battery management system.

10. the low current leakage junction transistor having a collector terminal, a base terminal, and an emitter terminal; the collector terminal of the low current leakage junction transistor is coupled to the gate terminal of the MOSFET through a resistor and a diode; The emitter terminal of the low current leakage junction transistor is directly coupled to the source terminal of the MOSFET. The battery management system of claim 9 .

11. the diode maintains a direction of current flow to the low current leakage junction transistor in response to the voltage being detected to be greater than the voltage of the battery pack; or the emitter terminal of the low current leakage junction transistor is coupled to the array of freewheeling diodes via a bus bar to maintain a direction of current flow to the array of freewheeling diodes in response to detecting the voltage greater than the voltage of the battery pack. The battery management system of claim 10.

12. 12. The battery management system of claim 9, further comprising a driver integrated circuit coupled to the MOSFET via the protection circuit, the driver integrated circuit configured to open or close the MOSFET in response to receiving a switching request generated via a controller coupled to the driver integrated circuit.

13. further comprising a current sensing circuit electrically coupled to the MOSFET and communicatively coupled to the driver integrated circuit; The current detection circuit is configured to obtain a measurement of a current flowing through the MOSFET and transmit the measurement to the controller, and the controller is configured to detect the voltage greater than the voltage of the battery pack based on the measurement. The battery management system of claim 12.

14. 1. A method for managing current flow through an interrupt circuit of a battery pack, comprising: conducting current from a first battery terminal to an external load and preventing current flow from a second battery terminal to the first battery terminal when the interruption circuit is closed; allowing the current to flow from the second battery terminal to the first battery terminal when the interruption circuit is open; in response to detecting the current between the battery pack and the interruption circuit being greater than a threshold current, flowing the current from a first node coupled to a control input of the interruption circuit to a second node coupled to an output of the interruption circuit while preventing current flow to an output across a control input; and in response to detecting the current between the battery pack and the interruption circuit being equal to or less than the threshold current, not allowing the current to flow from the first node to the second node; A method comprising:

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