Series battery protection circuit

Abstract

The present invention provides a series battery protection circuit, comprising: several stages of battery modules connected in series between the positive and negative electrodes of a battery pack, each of which includes a single-cell battery, a protection switch and a single-cell battery protection module; the single-cell battery is connected in series with the protection switch, and the single-cell battery protection module generates a turn-off signal and protects the current battery module based on the turn-off signal; a turn-off signal level shift module that transmits the turn-off signal of any stage of battery module to other stages of battery modules; a voltage transient suppression module connected between the positive and negative electrodes of the battery pack for absorbing spike voltages and slowing down the change rate of the total voltage between the positive and negative electrodes of the battery pack. The present invention reliably realizes the function of protecting a higher-voltage series battery with a charging and discharging switch device having a lower withstand voltage, protecting both the overall series battery and each series-connected battery, with high safety performance and low cost.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit design, and particularly to a series battery protection circuit. Background Art

[0002] With the vigorous promotion of energy conservation, emission reduction and environmental protection travel, new energy vehicles have become the general trend. The world is committed to the research and development of cleaner and more environmentally friendly vehicles, and lithium-ion power batteries have achieved unprecedented development. However, the inherent vulnerability of lithium-ion batteries poses a hidden danger to lithium-ion power battery vehicles. How to better protect lithium-ion power batteries has become the goal of several engineers' long-term struggle. However, to date, there has been little progress in the protection of series-connected lithium-ion batteries or battery packs. A compromise has been made in terms of cost and improvement of protection performance, and there has been no substantial breakthrough.

[0003] A series battery protection solution one is proposed in the prior art, such as Figure 1As shown in the figure, it includes n - stage series - connected batteries. Each battery is respectively connected in series with a protection switch device (S1, S2... Sn), and each single - cell battery has its own single - cell battery protection module with a protection switch device. If a single - cell battery in the series - connected batteries is turned off, the voltage across the two sides of the turned - off protection switch will bear all the variable voltages from the total input and output of the series - connected batteries. To ensure safety, each protection switch device must be a high - voltage - withstand switch device that can withstand the total input and output voltage of the series - connected batteries. Suppose the normal output of 13 ternary lithium - ion series - connected batteries is 48V. Once a short - circuit occurs, the protection switch device of a certain single - cell battery in the battery pack will turn off first (due to the inevitable differences in the built - in protection delay time of the chip, when a short - circuit occurs, the protection switch devices of each single - cell battery in series will not all turn off automatically. Most likely, a certain switch will turn off alone). Based on the basic principle that the voltage across the battery remains unchanged, the node connected to the negative terminal of the high - voltage battery of the turned - off protection switch device will become negative (defining the negative terminal PK - of the battery as the ground level), and the node connected to the positive terminal of the low - voltage battery will become positive. The voltage difference across the protection switch device will become the output voltage of the entire series - connected batteries, that is, the voltage difference across the protection switch device at this time is 48V. Due to the voltage - withstand requirement, the self - protection switch device of each series - connected battery will adopt a switch device with a voltage withstand exceeding 48V, such as a switch device with a voltage withstand of 80V or even 100V. And because more than a dozen or even dozens of switch devices need to be connected in series, the internal resistance of the 80V or even 100V voltage - withstand switch device must also be small (even less than 10 milliohms) to ensure that after dozens of them are connected in series, the internal resistance will not be too large. This will result in a very high cumulative cost for more than a dozen or even dozens of protection switch devices operating at 48V in the circuit. In addition, if precise current protection (+ / - 10% accuracy) is to be achieved for each single - cell battery, high - precision and high - power current - sampling resistors (Rsns1, Rsns2... Rsnsn) need to be added to each series - connected single - cell battery. For a 400V / 500A application, dozens of high - precision and high - power current - sampling resistors need to be connected in parallel for each single - cell battery. For a total of 100 single - cell batteries, thousands of such high - precision and high - power current - sampling resistors are required; and the current cost of a single high - precision and high - power current - sampling resistor is usually nearly 0.5 yuan RMB, and the total cost of thousands of high - precision and high - power current - sampling resistors is extremely high, reaching several thousand yuan.

[0004] To avoid the excessively high cost caused by equipping each single - cell battery with a high - voltage and low - impedance switch device as above, the current common practice is that each single - cell battery in the series - connected batteries no longer has a switch device, and each single - cell battery no longer has its own separate protection module. Instead, a thermistor (such as: Tesla) is used for rough protection on each series - connected single - cell battery, or simply each single - cell battery no longer has any protection, but unified combined protection is carried out. For example Figure 2As shown, in the second series battery protection solution proposed in the prior art, a charging switch tube S1 and a discharging switch tube S2 are added to the negative terminal P- of the series battery. When an abnormality occurs, the discharging switch tube S2 and the charging switch tube S1 are turned off for protection. When a certain battery is overcharged or under-discharged, the protection signal is transmitted level by level through adjacent chips to the chip directly connected to the charging switch tube S1 and the discharging switch tube S2, and this chip is used to execute the turn-off. The above solution abandons the self-protection of each series battery, avoids using a large number of high-voltage switch tubes, and can greatly reduce the cost. However, when a short-circuit large current discharge occurs between several series-connected batteries in this solution (for example, an accidental impact causes a metal conductor to short-circuit at the positive and negative terminals of one battery or multiple series-connected batteries, as shown in Figure 2 ), there is no protection ability. Even if the charging switch tube S1 and the discharging switch tube S2 are turned off, there is no effect in preventing the large current discharge. In addition, this solution limits the application of the series battery equalization circuit. Each series battery abandons its own precise current protection, making it impossible to apply an equalization circuit with a current of 2.0 A or greater between the batteries. Because once a slightly larger current equalization circuit is applied, each battery needs to have its own precise overcurrent protection to avoid damage to the relevant batteries caused by overcurrent or short-circuit due to the failure of the equalization circuit; at the same time, abnormal short-circuits of the relevant equalization circuit connection wires all require each series battery to have its own precise overcurrent protection circuit module. The existing mainstream series battery solutions cannot perform equalization in real time, resulting in an excessive repair frequency of the series battery pack, which is an urgent pain point in the battery industry that needs to be solved now.

[0005] Based on the analysis of the above two solutions, Solution 2 has inherent defects that are difficult to easily make up for, but the cost is low; while Solution 1 has a complete protection function, but uses a number of low-impedance high-voltage charge and discharge switch devices, and the cost is too high. Therefore, how to reduce the cost while ensuring the complete protection function of the series battery has become one of the problems that need to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a series battery protection circuit for solving the problem that the protection function and cost of series batteries in the prior art cannot be taken into account at the same time.

[0007] To achieve the above purpose and other related purposes, the present invention provides a series battery protection circuit, which at least includes:

[0008] Several levels of battery modules connected in series between the positive electrode of the battery pack and the negative electrode of the battery pack, a turn-off signal level shift module, and a voltage transient suppression module;

[0009] Each battery module includes single cells, a protection switch, and a single-cell battery protection module; the single cells are connected in series with the protection switch, and the single-cell battery protection module generates a shutdown signal based on the detection signal of the current battery module or the output signal of the shutdown signal level shift module, and controls the protection switch based on the shutdown signal to protect the current battery module;

[0010] The shutdown signal level shift module is connected to each level of battery modules, and is used to transmit the shutdown signal of any level of battery module to other levels of battery modules, so that each level of battery module takes protection operations;

[0011] The voltage transient suppression module is connected between the positive pole and the negative pole of the battery pack, and is used to absorb the spike voltage and slow down the change rate of the total voltage between the positive pole and the negative pole of the battery pack.

[0012] Optionally, the single-cell battery protection module includes a detection unit and a logic processing unit; the detection unit receives the detection signal and generates a corresponding protection signal; the logic processing unit is connected to the output ends of the detection unit and the shutdown signal level shift module, and generates the shutdown signal of the current level of battery module based on the protection signal or the shutdown signal of other levels of battery modules.

[0013] More optionally, the detection unit includes one or more combinations of an undervoltage detection sub-unit, an overvoltage detection sub-unit, an overtemperature detection sub-unit, a discharge overcurrent detection sub-unit, and a charge overcurrent detection sub-unit.

[0014] Optionally, each battery module further includes a bypass diode connected in parallel across the series structure of the single cell and the protection switch; the anode of the bypass diode is connected to the protection switch, and the cathode is connected to the single cell.

[0015] Optionally, each battery module further includes a voltage-dividing resistor connected in parallel across the protection switch.

[0016] Optionally, each battery module further includes a bypass capacitor, the bypass capacitor is connected in parallel across the protection switch, or the bypass capacitor is connected in parallel across the series structure of the single cell and the protection switch.

[0017] Optionally, the turn-off signal level shift module includes a first resistor, a second resistor, a Darlington current amplifier, and transistors corresponding to each battery module one by one; the first ends of the transistors are connected to the positive electrodes of the single cells in the corresponding battery modules, the second ends are connected to the negative electrode of the battery pack via the first resistor, and the control ends are connected to the turn-off signals of the corresponding battery modules; the first end of the Darlington current amplifier is connected to the corresponding battery module and connected to the positive electrode of the battery pack via the second resistor, the second end is connected to the negative electrode of the battery pack, and the control end is connected to the second ends of the transistors; wherein, each transistor is a PNP triode or a PMOS transistor.

[0018] More optionally, the turn-off signal level shift module further includes a voltage limiting unit corresponding to each battery module one by one, and each voltage limiting unit includes a current limiting resistor and a Zener diode; the first end of the current limiting resistor is connected to the first end of the Darlington current amplifier, and the second end is connected to the corresponding battery module; the cathode of the Zener diode is connected to the second end of the current limiting resistor, and the anode is connected to the negative electrode of the single cell in the corresponding battery module.

[0019] More optionally, the first ends and the control ends of the transistors are respectively connected to the corresponding ports via a resistor.

[0020] More optionally, the Darlington current amplifier is replaced by an NPN triode or an NMOS transistor

[0021] Optionally, the voltage transient suppression module includes a capacitor, or a series-parallel structure of a capacitor and a resistor, or a series-parallel structure of a capacitor and an inductor.

[0022] More optionally, the protection switch is replaced by a series-connected discharge switch and a charge switch; the turn-off signal level shift module is replaced by a parallel-connected discharge turn-off signal level shift module and a charge turn-off signal level shift module, the discharge turn-off signal level shift module receives the turn-off signal of the discharge switch in any stage of the battery module and transmits it to other stages of the battery modules, and the charge turn-off signal level shift module receives the turn-off signal of the charge switch in any stage of the battery module and transmits it to other stages of the battery modules.

[0023] More optionally, each protection switch, discharge switch, and charge switch includes a plurality of parallel-connected switches.

[0024] As described above, the series battery protection circuit of the present invention has the following beneficial effects:

[0025] The series battery protection circuit of the present invention uses a charging and discharging switch device with a relatively low withstand voltage to protect a series battery with a relatively high voltage. It can protect both the overall series battery and each series-connected battery. At the same time, it solves the problem that short circuits between series batteries cannot be protected, and has high safety performance. In addition, the series battery protection circuit of the present invention uses a switch device with a low withstand voltage, greatly reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It shows a schematic circuit diagram of a first prior art series battery protection solution.

[0027] Figure 2 It shows a schematic circuit diagram of a second prior art series battery protection solution.

[0028] Figure 3 It shows a schematic structural diagram of a series battery protection circuit of the present invention.

[0029] Figure 4 It shows another schematic structural diagram of a series battery protection circuit of the present invention.

[0030] Figure 5 It shows yet another schematic structural diagram of a series battery protection circuit of the present invention.

[0031] Figure 6 It shows still another schematic structural diagram of a series battery protection circuit of the present invention.

[0032] DESCRIPTION OF REFERENCE NUMERALS

[0033] 11 to 1n First to nth stage battery modules

[0034] 111 to 1n1 First to nth single-cell battery protection modules

[0035] 111a Detection unit

[0036] 111b Logic processing unit

[0037] 2 Shutdown signal level shift module

[0038] 2a Discharge shutdown signal level shift module

[0039] 2b Charge shutdown signal level shift module

[0040] 21 Darlington current amplifier

[0041] 221 to 22n First to nth voltage limiting units

[0042] 3 Voltage transient suppression module DETAILED DESCRIPTION OF THE INVENTION

[0043] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] Please refer to Figures 3 to 6 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0045] Embodiment 1

[0046] As Figure 3 shown, this embodiment provides a series battery protection circuit, and the series battery protection circuit includes:

[0047] Several levels of battery modules, a turn-off signal level shift module 2, and a voltage transient suppression module 3.

[0048] Figure 3 shown, each level of battery module is connected in series between the positive electrode PK+ of the battery pack and the negative electrode PK- of the battery pack.

[0049] Specifically, in this embodiment, it includes n levels of battery modules (n is a natural number greater than or equal to 2. In actual use, the number of battery modules is not less than 2 levels), which are respectively denoted as the first-level battery module 11, the second-level battery module 12... the nth-level battery module 1n, and each level of battery module is connected in series in turn. The first-level battery module 11 includes a first single-cell battery Bat1, a first protection switch K1, and a first single-cell battery protection module 111.

[0050] More specifically, the first single-cell battery Bat1 is connected in series with the first protection switch K1; as an example, the positive electrode B1+ of the first single-cell battery Bat1 is used as the positive electrode PK1+ of the first-level battery module 11, the first end of the first protection switch K1 is connected to the negative electrode B1- of the first single-cell battery Bat1, and the second end of the first protection switch K1 is used as the negative electrode PK1- of the first-level battery module 11 and is connected to the negative electrode PK- of the battery pack.

[0051] More specifically, the first single-cell battery protection module 111 generates a first shutdown signal based on the detection signal of the first-stage battery module 11 or the output signal of the shutdown signal level shift module 2, and controls the first protection switch K1 to turn off or on based on the first shutdown signal to protect the first battery module 11. As an example, the first single-cell battery protection module 111 includes a detection unit 111a and a logic processing unit 111b. The detection unit 111a receives the detection signal and generates a corresponding protection signal. The detection unit 111a includes, but is not limited to, one or a combination of an undervoltage detection sub-unit CMP1, an overvoltage detection sub-unit CMP2, an overtemperature detection sub-unit OT, an over-discharge current detection sub-unit CMP3, and an overcharge current detection sub-unit CMP4. In this embodiment, the undervoltage detection sub-unit CMP1 is connected to the positive electrode B1+ of the first single-cell battery Bat1, compares the positive electrode voltage of the first single-cell battery Bat1 with a first reference voltage Vref1 to determine whether the first single-cell battery Bat1 is undervoltaged, and outputs a corresponding undervoltage protection signal. The overvoltage detection sub-unit CMP2 is connected to the positive electrode B1+ of the first single-cell battery Bat1, compares the positive electrode voltage of the first single-cell battery Bat1 with a second reference voltage Vref2 to determine whether the first single-cell battery Bat1 is overvoltaged, and outputs a corresponding overvoltage protection signal. The overtemperature detection sub-unit OT determines whether the first single-cell battery Bat1 is overheated based on an internal temperature detection device and outputs a corresponding overtemperature protection signal. The over-discharge current detection sub-unit CMP3 is connected to the negative electrode B1- of the first single-cell battery Bat1, converts the negative electrode current of the first single-cell battery Bat1 into an induced voltage and compares it with a third reference voltage Vref3 to determine whether the discharge current of the first single-cell battery Bat1 is too large, and outputs a corresponding overcurrent discharge protection signal. The overcharge current detection sub-unit CMP4 is connected to the second end of the first protection switch K1, converts the current at the second end of the first protection switch K1 into an induced voltage and compares it with a fourth reference voltage Vref4 to determine whether the charge current of the first single-cell battery Bat1 is too large, and outputs a corresponding overcurrent charge protection signal. The logic processing unit 111b is connected to the output ends of the detection unit 111a and the shutdown signal level shift module 2, and generates a shutdown signal (the first shutdown signal) of the first-stage battery module 11 based on each protection signal or the shutdown signal of other-stage battery modules.

[0052] It should be noted that the number, type, and connection relationship of the detection subunits in the detection unit 111a can be set according to actual needs, and are not limited to this embodiment. The negative electrode PK2- of the second-stage battery module 12 is connected to the positive electrode PK1+ of the first-stage battery module 11, and includes a second single-cell battery Bat2, a second protection switch K2, and a second single-cell battery protection module 121. By analogy, the negative electrode PKn- of the nth-stage battery module 1n is connected to the positive electrode of the previous stage, and the positive electrode PKn+ of the nth-stage battery module 1n is connected to the battery pack positive electrode PK+, and includes an nth single-cell battery Batn, an nth protection switch Kn, and an nth single-cell battery protection module 1n1. This embodiment only takes the first-stage battery module 11 as an example for specific description. The structures and principles of each stage of battery module are the same and will not be elaborated here one by one.

[0053] It should be noted that the over-discharge current detection subunit CMP3 and the over-charge current detection subunit CMP4 in this embodiment are implemented by the applicant's authorized Chinese patent "A Charge and Discharge Over-Current Protection Circuit" (application number 201921942910.6). Without adding a high-precision and high-power current sampling resistor, high-precision charge and discharge over-current protection for each single-cell battery can be achieved, greatly saving costs. Thus, further optimizing the series battery protection and significantly improving the protection performance under the condition that the cost of the present invention is close to that of the existing solution, protecting both the overall series battery and each single cell.

[0054] As Figure 3 shown, the turn-off signal level shift module 2 is connected to each stage of battery module, and is used to transmit the turn-off signal of any stage of battery module to other stages of battery modules, so that each stage of battery module takes protection operations.

[0055] Specifically, in this embodiment, the turn-off signal level shift module 2 includes a first resistor R_1, a second resistor R_2, a Darlington current amplifier 21, and transistors (a first transistor Q1, a second transistor Q2... an nth transistor Qn) corresponding to each battery module one by one. As an example, each transistor uses a PNP triode. In actual use, transistors that conduct when receiving a low level at the control terminal are applicable to the present invention, including but not limited to triodes and MOS transistors, which will not be elaborated here one by one; the collector of the first transistor Q1 is connected to the negative pole PK- of the battery pack via the first resistor R_1, the base is connected to the first turn-off signal, and the emitter is connected to the positive pole B1+ of the first single-cell battery Bat1; similarly, the collectors of the second transistor Q1... the nth transistor Qn are connected to the negative pole PK- of the battery pack via the first resistor R_1, the bases are respectively connected to the turn-off signals of the corresponding-stage battery modules, and the emitters are respectively connected to the positive poles of the corresponding single-cell batteries. The first end of the Darlington current amplifier 21 is connected to the corresponding battery module and is connected to the positive pole PK+ of the battery pack via the second resistor R_2, the second end is connected to the negative pole PK- of the battery pack, and the control end is connected to the second ends of each transistor; as an example, the Darlington current amplifier 21 includes a first NPN transistor Q11 and a second NPN transistor Q12. The collector of the first NPN transistor Q11 is connected to the collector of the second NPN transistor Q12 and serves as the first end of the Darlington current amplifier 21. The base of the first NPN transistor Q11 serves as the control end of the Darlington current amplifier 21. The emitter of the first NPN transistor Q11 is connected to the base of the second NPN transistor Q12, and the emitter of the second NPN transistor Q12 is connected to the negative pole PK- of the battery pack.

[0056] As another implementation manner of the present invention, the first ends and the control ends of each transistor are respectively connected to the corresponding ports via a resistor. In this embodiment, the base of the first transistor Q1 is connected to the turn-off signal of the first-stage battery module 11 via the resistor R11, and the emitter is connected to the positive pole B1+ of the first single-cell battery Bat1 via the resistor R12; the base of the second transistor Q2 is connected to the turn-off signal of the second-stage battery module 12 via the resistor R21, and the emitter is connected to the positive pole B2+ of the second single-cell battery Bat2 via the resistor R22; the base of the nth transistor Qn is connected to the turn-off signal of the nth-stage battery module 1n via the resistor Rn1, and the emitter is connected to the positive pole Bn+ of the nth single-cell battery Batn via the resistor Rn2.

[0057] As another implementation manner of the present invention, the turn-off signal level shift module 2 further includes voltage limiting units corresponding to each battery module one by one, denoted as the first voltage limiting unit 221, the second voltage limiting unit 222... the nth voltage limiting unit 22n respectively. The first voltage limiting unit 221 includes a first current limiting resistor RL1 and a first Zener diode ZD1. The first end of the first current limiting resistor RL1 is connected to the first end of the Darlington current amplifier 21, and the second end is connected to the logic processing unit 111b of the first-stage battery module 11. The cathode of the first Zener diode ZD1 is connected to the second end of the first current limiting resistor RL1, and the anode is connected to the negative electrode B1- of the first single-cell battery Bat1. The second voltage limiting unit 222 includes a second current limiting resistor RL2 and a second Zener diode ZD2, and is connected between the second-stage battery module 12 and the first end of the Darlington current amplifier 21; and so on. The nth voltage limiting unit 22n includes an nth current limiting resistor RLn and an nth Zener diode ZDn, and is connected between the nth-stage battery module 1n and the first end of the Darlington current amplifier 21. In this embodiment, only the first voltage limiting unit 221 is taken as an example for specific description. The structures and principles of each voltage limiting unit are the same and will not be elaborated one by one here.

[0058] Specifically, if a certain cell in the series-connected batteries is abnormal, the corresponding single-cell battery protection module outputs a turn-off signal (usually changes from high level to low level) to turn off its protection switch. At the same time, the base level of the corresponding transistor in the turn-off signal level shift module 2 is pulled down, and the transistor conducts. The current flows in from the emitter of the transistor and flows out through the collector to the first resistor R_1. When the voltage on the first resistor R_1 is higher than Vbe_Q11 + Vbe_Q12 (about 1.4V as an example), the Darlington current amplifier 21 changes from off to on, and pulls down the voltage at the first end of the Darlington current amplifier 21 (the collectors of the first NPN transistor Q11 and the second NPN transistor Q12) (down to 0.5V or lower). The forced turn-off input pins of other single-cell battery protection modules (the connection ports between the Darlington current amplifier 21 and the corresponding logic processing unit) change from the normal high level to the low level, and corresponding turn-off signals for other protection switches are generated, thereby protecting the series-connected battery modules at all levels.

[0059] Meanwhile, in order to ensure that the voltage output by the turn-off signal level shift module 2 to each battery module is neither too high nor too low compared to the voltage of the corresponding battery, a current-limiting resistor and a Zener diode (a 5V Zener diode is used as an example) are used to implement voltage limitation. The maximum input voltage is limited to VBn + 5V (corresponding to the negative terminal voltage VBn of a single battery plus +5V), and the minimum input voltage is limited to VBn - 0.7V (corresponding to the negative terminal voltage VBn of a single battery minus 0.7V. If it is the first battery, the minimum input voltage limit is 0 volts). The current-limiting resistor limits the current flowing through the clamping Zener diode. Taking a 400V battery application as an example, if an abnormality occurs, the voltage at the first terminal of the Darlington current amplifier 21 is pulled down to 0.5V or lower. The negative terminal voltage of the highest-level (the nth level) single battery in the series battery is 396V (the single-battery voltage is 4.0V). The voltage difference across the nth current-limiting resistor RLn in the nth voltage-limiting unit 22n is 396V - 0.7V (the forward conduction voltage of the Zener diode is 0.7V) = 395.3V. To avoid excessive self-discharge current of the battery itself during abnormal turn-off, the resistance value of the nth current-limiting resistor RLn should be large enough. In this embodiment, a 10 MΩ resistor is selected. When the nth current-limiting resistor RLn is 10 MΩ, 395.3V divided by 10 MΩ = 39.5 μA. That is, when the battery is abnormal and in the turn-off state, the self-discharge current at this point of the battery with the highest voltage in the series battery is 39.5 μA.

[0060] It should be noted that in this embodiment, the turn-off signal level shift module 2 is composed of low-cost devices such as triodes, resistors, and Zener diodes, which can greatly reduce costs.

[0061] As Figure 3 shown, the voltage transient suppression module 3 is connected between the positive pole PK+ and the negative pole PK- of the battery pack, and is used to absorb the spike voltage and slow down the change rate of the total voltage between the positive pole PK+ and the negative pole PK- of the battery pack.

[0062] Specifically, in practical applications, when all protection switches need to be turned off, there is a time delay. At the same time, the turn-off signal level shift module 2 also has a time delay of hundreds of nanoseconds or even microseconds. The voltage transient suppression module 3 can provide a stable total voltage between the positive electrode PK+ and the negative electrode PK- of the battery pack, avoiding the generation of a huge voltage difference across the turned-off series switches by a large current (such as 200A) during the time delay, assisting in ensuring that the voltage across each turned-off protection switch does not change suddenly, and during the period from the turn-off of the first protection switch to the turn-off of the last protection switch, the voltage rise amplitude of the voltage transient suppression module 3 is less than the voltage difference between the withstand voltage of the switching device and the voltage value of a single battery. The voltage transient suppression module 3 gives all the protection switches connected in series between the positive electrode PK+ and the negative electrode PK- of the battery pack more time to complete the turn-off, providing a smooth voltage environment for evenly distributing the total voltage of the series batteries (the voltage between the positive electrode PK+ and the negative electrode PK- of the battery pack) among all the devices connected in series between the positive electrode PK+ and the negative electrode PK- of the battery pack.

[0063] Specifically, in this embodiment, the voltage transient suppression module 3 includes a capacitor C. One end of the capacitor C is connected to the positive electrode PK+ of the battery pack, and the other end is connected to the negative electrode PK- of the battery pack. In actual use, the voltage transient suppression module 3 includes, but is not limited to, series-parallel structures of capacitors and resistors, series-parallel structures of capacitors and inductors. It is not limited to the circuit structures listed in this embodiment. Any circuit structure that can absorb the glitch voltage and slow down the change rate of the total voltage between the positive electrode PK+ and the negative electrode PK- of the battery pack is applicable to the present invention.

[0064] The working principle of the series battery protection circuit in this embodiment is as follows:

[0065] During charging, if an abnormality is detected in a certain battery, the single-battery protection module corresponding to this battery turns off the protection switch of this battery and, at the same time, transmits the turn-off signal to all other series batteries through the turn-off signal level shift module 2 to turn off the protection switches of other series batteries. At this time, all the protection switches of the series batteries are in the off state. Under the action of the voltage transient suppression module 3, the total input charging voltage of the series batteries will not change transiently, and the total input charging voltage will be distributed among each series battery and its turned-off protection switch; after the voltage is distributed, the withstand voltage requirement of the protection switch is greatly reduced, and switching devices with a lower withstand voltage can be used. If the voltage, internal resistance, and other properties of each series battery are exactly the same, and the properties of the series protection switches are also exactly the same, the total input charging voltage will be evenly distributed among each series battery and its turned-off protection switch.

[0066] During discharging, if an abnormality is detected in a certain battery cell, the single-cell battery protection module corresponding to this battery cell, while turning off the protection switch of this battery cell, transmits the turn-off signal to all other series-connected batteries through the turn-off signal level shift module 2 and turns off the protection switches of other series-connected batteries. At this time, all the protection switches of the series-connected batteries are in the off state. Under the action of the voltage transient suppression module 3, the total output voltage of this series-connected battery will not experience a transient change, and the total output charging voltage will be distributed across each series-connected battery and its protection switch in the off state until the total output voltage of this series-connected battery decays to zero. After the voltage is distributed, the withstand voltage requirement of the protection switch is greatly reduced at this time, and a switch device with a lower withstand voltage can be used. If the voltage, internal resistance, and other properties of each series-connected battery are exactly the same, and the properties of the series-connected charging switches are also exactly the same, the total output charging voltage will be evenly distributed across each series-connected battery and its protection switch in the off state.

[0067] Embodiment 2

[0068] As Figure 4 shown, this embodiment provides a series-connected battery protection circuit, which is different from Embodiment 1 in that each battery module further includes a bypass diode, a voltage-dividing resistor, and a bypass capacitor.

[0069] As an implementation manner of the present invention, each battery module further includes a bypass diode connected in parallel across the two ends of the series structure of the single-cell battery and the protection switch to enhance the safety redundancy of the instantaneous current mutation. Specifically, as Figure 4 shown, the first bypass diode D1 is connected in parallel across the two ends of the series structure of the first single-cell battery Bat1 and the first protection switch K1. The anode of the first bypass diode D1 is connected to the second end of the first protection switch K1, and the cathode is connected to the positive electrode B1+ of the first single-cell battery Bat1. Similarly, the anode of the second bypass diode D2 is connected to the second end of the second protection switch K2, and the cathode is connected to the positive electrode B2+ of the second single-cell battery Bat2. And so on, the anode of the nth bypass diode Dn is connected to the second end of the nth protection switch Kn, and the cathode is connected to the positive electrode Bn+ of the nth single-cell battery Batn.

[0070] Specifically, each bypass diode is used to achieve freewheeling discharge after the corresponding protection switch is turned off, thereby reducing the withstand voltage requirement for the protection switch of each battery cell; at the same time, the battery cells without abnormalities can choose to continue power supply or turn off the protection switch. During discharge, if an abnormality is detected in a certain battery cell, the single-cell battery protection module of this battery cell will turn off the protection switch of this battery cell. At this time, in the series loop, due to the diodes connected in parallel at the positive terminals of two adjacent battery cells, the discharge current no longer passes through the turned-off battery cell and the protection switch of this battery cell, but passes through the diode connected in parallel at the positive terminals of two adjacent battery cells. Due to the bypass effect of this diode, the voltage change across the turned-off protection switch will be less than the sum of the voltage of this single battery cell and the forward conduction voltage of the bypass diode (by selecting a diode with an appropriate current, it can be ensured to be less than 10V under the condition of low cost), so the withstand voltage requirement is greatly reduced; that is, after adding a diode connected in parallel at the positive terminals of two adjacent series-connected battery cells to each series-connected battery, a switching device with a lower withstand voltage can be used for the discharge switch of each series-connected battery cell; the diodes connected in parallel at the positive terminals of two adjacent battery cells must be selected according to the actual current magnitude requirement of the application circuit, which will not be elaborated here one by one.

[0071] As another implementation manner of the present invention, each battery module further includes a voltage-dividing resistor connected in parallel across the protection switch. Specifically, as Figure 4 shown, the first voltage-dividing resistor R1 is connected in parallel across the first protection switch K1, the second voltage-dividing resistor R2 is connected in parallel across the second protection switch K2, and the nth voltage-dividing resistor Rn is connected in parallel across the nth protection switch Kn.

[0072] Specifically, when all the protection switches are in the off state, each voltage-dividing resistor can better achieve the equal division of the total input-output voltage of the series-connected battery cells to each battery cell and each protection switch, avoiding the generation of floating nodes. The magnitude of the voltage-dividing resistor is determined by the self-discharge current magnitude requirement of the series-connected battery cells, which will not be elaborated here one by one.

[0073] As yet another implementation manner of the present invention, each battery module further includes a bypass capacitor, which is used to suppress the induced electromotive force caused by the parasitic inductance formed by the long metal connection between two battery cells or two battery packs, resulting in a huge voltage difference when the protection switch of this battery cell is turned off. As an example, each bypass capacitor is connected in parallel across the protection switch, as Figure 4As shown, the first bypass capacitor C1 is connected in parallel across both ends of the first protection switch K1, the second bypass capacitor C2 is connected in parallel across both ends of the second protection switch K2, and the nth bypass capacitor Cn is connected in parallel across both ends of the nth protection switch Kn. As another example, the bypass capacitors are connected in parallel across both ends of the series structure of the single-cell battery and the protection switch, that is, each bypass capacitor is connected in parallel across both ends of the corresponding bypass diode, which will not be elaborated one by one here. In this embodiment, each bypass capacitor uses a ceramic capacitor with a capacitance of 1 μF to 10 μF. In actual use, capacitors with different capacitances and types can be selected based on actual design requirements, and this embodiment is not limiting.

[0074] Embodiment 3

[0075] As Figure 5 shown, this embodiment provides a series battery protection circuit. The difference from Embodiment 2 is that the protection switch is replaced by a series-connected discharge switch and charge switch. Correspondingly, the turn-off signal of the discharge switch has its own independent discharge turn-off signal level shift module 2a, and the turn-off signal of the charge switch also has its own independent charge turn-off signal level shift module 2b.

[0076] Specifically, in the first-stage battery module 11, the first charge switch K1a and the first discharge switch K1b are connected in series and then connected to the negative electrode B1- of the first single-cell battery Bat1. The positions of the first charge switch K1a and the first discharge switch K1b can be interchanged, and this embodiment is not limiting. In the second-stage battery module 12, the second charge switch K2a and the second discharge switch K2b replace the second protection switch K2. In the nth-stage battery module 1n, the nth charge switch Kna and the nth discharge switch Knb replace the nth protection switch Kn. And each turn-off signal is transmitted to the control end of each switch through a driving stage.

[0077] Specifically, correspondingly, the turn-off signals of each charge switch are transmitted to the charge turn-off signal level shift module 2b and then transmitted to other-stage battery modules based on the charge turn-off signal level shift module 2b; the turn-off signals of each discharge switch are transmitted to the discharge turn-off signal level shift module 2a and then transmitted to other-stage battery modules based on the discharge turn-off signal level shift module 2a. The circuit structures of the discharge turn-off signal level shift module 2a and the charge turn-off signal level shift module 2b are the same as those of the turn-off signal level shift module 2 (the component numbers in the discharge turn-off signal level shift module 2a and the charge turn-off signal level shift module 2b correspond one by one to those of the turn-off signal level shift module 2 and are distinguished by the suffixes a and b), which will not be elaborated one by one here.

[0078] As another implementation manner of the present invention, the Darlington current amplifier 21 is replaced by an NPN transistor. As Figure 5As shown, the emitter of the NPN transistor is connected to the negative pole PK- of the battery pack, the base is connected to the second ends of the transistors, and the collector is connected to the corresponding battery module and connected to the positive pole PK+ of the battery pack via the second resistor (R_2, R_2a or R_2b).

[0079] Embodiment 4

[0080] As Figure 6 shown, this embodiment provides a series battery protection circuit, which is different from Embodiment 3 in that the triode is replaced by a MOS transistor. Specifically, each PNP transistor is replaced by a PMOS transistor, and each NPN transistor is replaced by an NMOS transistor. The specific connection relationship will not be elaborated here one by one.

[0081] It should be noted that, as an example, each protection switch, discharge switch, and charging switch described in the present invention includes a plurality of parallel switches, and the number of parallel switches is set based on the flowing current, which will not be elaborated here one by one.

[0082] Based on the basic series circuit voltage division principle that if there are n identical series devices in a series circuit, the voltage across each series device will be 1 / n of the voltage of the entire series circuit, the present invention equips each series battery with an identical single-cell protection module and a protection switch. When an abnormal protection occurs in a certain cell, while turning off the protection switch of this cell, the turn-off signal is transmitted to other series batteries through the turn-off signal level shift module 2, and the protection switches of other series batteries are immediately turned off. At this time, all switches in the series battery are in the off state. According to the series circuit voltage division principle, the total voltage of n series batteries will be distributed among n identical units composed of the series single cells and their protection switches in the off state, and the voltage across both sides of each such identical unit is 1 / n of the total voltage of the series battery. For example, for 100 ternary lithium-ion series batteries with a combined voltage output of 370V to 420V, after all switches are turned off, there are 100 identical units in total, and the voltage distributed to a single unit is 420V÷100 = 4.2V. Considering practical applications, a 420V induced electromotive force is often generated in a 420V application, that is, a combined voltage of 420 + 420 = 840V is generated. At this time, the voltage evenly distributed among 100 identical units is: 840÷100 = 8.4V. Considering that the maximum voltage fluctuation of a single cell is from 0V to 4.5V, that is, the operating voltage of the protection switch is 8.4V, and adding a withstand voltage safety redundancy of more than 50%, the withstand voltage value of the protection switch of a single cell can be set to 13V, which is much smaller than the withstand voltage value of the switch device in the existing solution 1. The above is based on the situation where all protection switches can be turned off simultaneously. The analysis shows that a 13V withstand voltage charge and discharge switch device used in each series cell can achieve the protection of lithium-ion series batteries with a voltage of up to 420V. In practical applications, there is a time delay difference of hundreds of nanoseconds or even several microseconds in the turn-off signal level shift module 2 to turn off all switches, and the large current turn-off will bring spike voltages that will affect the reliability of the protection.

[0083] To avoid a large voltage difference across the protection switch of a certain battery cell caused by the time delay difference in the turn-off signal level shift module 2 in high-current applications, a high-voltage large capacitor (voltage transient suppression module 3) is connected between the positive pole PK+ and the negative pole PK- of the battery pack to suppress the instantaneous voltage change caused by a short-circuit current of up to several hundred amperes. According to the withstand voltage value of the protection switch, the capacitance value of the high-voltage large capacitor is calculated as follows: Assume that the current limit charge and discharge current or the limit short-circuit current of the application circuit instantaneously increases from 1A to 500A, the time delay difference of the turn-off signal level shift module 2 is 2μs, the withstand voltage value of the protection switch of each battery protection module is 13V, and the voltage of a single battery is 4.2V. According to the formula ΔI*t = C*ΔV, the capacitance value C of this high-voltage large capacitor is C = ΔI*t / ΔV = (500A - 1A)*2μs / (13V - 4.2V) = 113.4μF. Considering factors such as the fluctuation of the capacitance value caused by the ambient temperature and the attenuation during long-term use, a 100% redundancy is reserved for calculation, and the selected value of this high-voltage large capacitor is 220μF. Of course, other devices can also be used to achieve the function of suppressing voltage transients in the present invention, which still falls within the scope of the patent rights.

[0084] A 220μF large capacitor is connected in parallel between the positive pole PK+ and the negative pole PK- of the battery pack. As long as all the switching devices on the series-connected batteries are in the off state within a time difference of 2μs, after 100 switching protection devices with a 13V withstand voltage (including protection switches or series-connected discharge switches and charging switches) and a single battery are connected in series to form the same unit, the protection of a 400V high-voltage series-connected battery can be achieved.

[0085] In summary, the present invention provides a series battery protection circuit, including: several stages of battery modules connected in series between the positive electrode and the negative electrode of the battery pack, a turn-off signal level shift module, and a voltage transient suppression module; each stage of battery module includes a single battery, a protection switch, and a single battery protection module; the single battery is connected in series with the protection switch, and the single battery protection module generates a turn-off signal based on the detection signal of the current battery module or the output signal of the turn-off signal level shift module, and controls the protection switch based on the turn-off signal to protect the current battery module; the turn-off signal level shift module is connected to each stage of battery module, and is used to transmit the turn-off signal of any stage of battery module to other stages of battery modules, so that each stage of battery module takes protection operations; the voltage transient suppression module is connected between the positive electrode and the negative electrode of the battery pack, and is used to absorb spike voltages and slow down the change rate of the total voltage between the positive electrode and the negative electrode of the battery pack. The present invention reliably realizes the function of protecting a higher voltage series battery with a lower withstand voltage charge and discharge switch device, and under the condition of being close to the cost of the existing solution, the present invention protects both the overall series battery (or series battery pack) and each series battery (or each series battery pack), increases the protection function compared with the existing solution, and greatly improves the safety performance of the series battery (or series battery pack). At the same time, the problem that the short circuit between series batteries cannot be protected in the existing mainstream protection solution is solved. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0086] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A series battery protection circuit, characterized in that, the series battery protection circuit at least includes: several stages of battery modules connected in series between the positive electrode and the negative electrode of the battery pack, a turn-off signal level shift module and a voltage transient suppression module; Each stage of battery module includes a single cell, a protection switch and a single cell protection module; the single cell is connected in series with the protection switch, and the single cell protection module generates a turn-off signal based on the detection signal of the current battery module or the output signal of the turn-off signal level shift module, and controls the protection switch based on the turn-off signal to protect the current battery module; The turn-off signal level shift module is connected to each stage of battery module, and is used to transmit the turn-off signal of any stage of battery module to other stages of battery modules, so that each stage of battery module takes protection operations; The voltage transient suppression module is connected between the positive electrode and the negative electrode of the battery pack, and is used to absorb spike voltages and slow down the change rate of the total voltage between the positive electrode and the negative electrode of the battery pack; Wherein, the turn-off signal level shift module includes a first resistor, a second resistor, a Darlington current amplifier and a transistor corresponding to each battery module; the first end of each transistor is connected to the positive electrode of the single cell in the corresponding battery module, the second end is connected to the negative electrode of the battery pack via the first resistor, and the control end is connected to the turn-off signal of the corresponding battery module; the first end of the Darlington current amplifier is connected to the corresponding battery module and connected to the positive electrode of the battery pack via the second resistor, the second end is connected to the negative electrode of the battery pack, and the control end is connected to the second end of each transistor; The Darlington current amplifier includes a first triode and a second triode, the collectors of the first triode and the second triode are connected and used as the first end of the Darlington current amplifier, the base of the first triode is used as the control end of the Darlington current amplifier, the emitter of the first triode is connected to the base of the second triode, and the emitter of the second triode is connected to the negative electrode of the battery pack.

2. The series battery protection circuit according to claim 1, characterized in that: The single cell protection module includes a detection unit and a logic processing unit; the detection unit receives a detection signal and generates a corresponding protection signal; the logic processing unit is connected to the detection unit and the output end of the turn-off signal level shift module, and generates a turn-off signal of the current stage of battery module based on the protection signal or the turn-off signal of other stages of battery modules.

3. The series battery protection circuit according to claim 2, characterized in that: The detection unit includes one or a combination of an undervoltage detection sub-unit, an overvoltage detection sub-unit, an overtemperature detection sub-unit, a discharge overcurrent detection sub-unit, and a charge overcurrent detection sub-unit.

4. The series battery protection circuit according to claim 1, characterized in that: Each battery module further includes a bypass diode connected in parallel across the series structure of the single cell and the protection switch; the anode of the bypass diode is connected to the protection switch, and the cathode is connected to the single cell.

5. The series battery protection circuit according to claim 1, It is characterized in that: Each battery module further includes a voltage-dividing resistor connected in parallel across the protection switch.

6. The series battery protection circuit according to claim 1, It is characterized in that: Each battery module further includes a bypass capacitor, the bypass capacitor is connected in parallel across the protection switch, or the bypass capacitor is connected in parallel across the series structure of the single battery and the protection switch.

7. The series battery protection circuit according to claim 1, It is characterized in that: Each transistor is a PNP triode or a PMOS transistor.

8. The series battery protection circuit according to claim 1, It is characterized in that: The turn-off signal level shift module further includes a voltage-limiting unit corresponding to each battery module, and each voltage-limiting unit includes a current-limiting resistor and a Zener diode; the first end of the current-limiting resistor is connected to the first end of the Darlington current amplifier, and the second end is connected to the corresponding battery module; the cathode of the Zener diode is connected to the second end of the current-limiting resistor, and the anode is connected to the negative electrode of the single battery in the corresponding battery module.

9. The series battery protection circuit according to claim 1, It is characterized in that: The first end and the control end of each transistor are respectively connected to the corresponding port via a resistor.

10. The series battery protection circuit according to claim 1, It is characterized in that: The Darlington current amplifier is replaced by an NPN triode or an NMOS transistor.

11. The series battery protection circuit according to claim 1, It is characterized in that: The voltage transient suppression module includes a capacitor, or a series-parallel structure of a capacitor and a resistor, or a series-parallel structure of a capacitor and an inductor.

12. The series battery protection circuit according to any one of claims 1 to 11, It is characterized in that: The protection switch is replaced by a series-connected discharge switch and a charge switch; the turn-off signal level shift module is replaced by a parallel-connected discharge turn-off signal level shift module and a charge turn-off signal level shift module, the discharge turn-off signal level shift module receives the turn-off signal of the discharge switch in any stage of the battery module and transmits it to other stages of the battery module, and the charge turn-off signal level shift module receives the turn-off signal of the charge switch in any stage of the battery module and transmits it to other stages of the battery module.

13. The series battery protection circuit according to claim 12, It is characterized in that: Each protection switch, discharge switch and charge switch includes a plurality of switches connected in parallel.

Images