Charger detection circuit and BMS system thereof

Abstract

The utility model relates to the technical field of battery management, in particular to a charger detection circuit and a BMS (Battery Management System) thereof. Comprising a first triode, a second triode, a first diode and a second diode, a base electrode of the first triode is connected with a power supply and a positive electrode of the second diode, a negative electrode of the second diode is connected with a negative electrode of a battery end, and an emitting electrode of the first triode is connected with a positive electrode of the first diode; the negative electrode of the first diode is connected with the negative electrode of the charger end, the collector electrode of the first triode is connected with the base electrode of the second triode, the emitter electrode of the second triode is connected with an external power supply, and the collector electrode of the second triode is connected with the main controller. According to the circuit, the connection of the charger is identified by detecting the voltage, the power consumption is low, the circuit does not depend on the current value, the minimum current value of the charger is not limited, and the practicability and the stability are higher.

Description

Technical Field

[0001] The utility model relates to the technical field of battery management, in particular to a charger detection circuit and a BMS system thereof. Background Art

[0002] The BMS system manages and controls the charging and discharging of the battery pack to ensure the healthy and safe operation of the battery pack. The BMS system includes many circuit modules to minimize the power consumption of the battery pack by the BMS system itself. The BMS will automatically enter a sleep state under some special circumstances, and it will shut down most of the circuit modules to minimize its own power consumption. The BMS system requires a detection circuit to detect whether a charger is connected and wake up the BMS system when the charger is connected. The existing charger insertion detection is achieved by detecting the current and outputting the corresponding level. This method has high power consumption and depends on the current value. In addition, this method also limits the minimum value of the charger current.

[0003] Therefore, it is very important for those skilled in the art to design a charger detection circuit with low power consumption and independent of current value. Utility Model Content

[0004] The technical problem to be solved by the embodiments of the utility model is to provide a charger detection circuit with low power consumption and independent of current value, so as to solve the problems in the prior art of high power consumption, dependence on current value and limitation on the minimum value of the charger current.

[0005] The utility model discloses a charger detection circuit, which is used in a BMS system. The BMS system includes a main controller, a battery terminal and a charger terminal. The scheme is that the circuit includes: a first triode, a second triode, a first diode and a second diode. The base of the first triode is respectively connected to an external power supply and a positive electrode of the second diode, the negative electrode of the second diode is connected to the negative electrode of the battery terminal, the emitter of the first triode is connected to the positive electrode of the first diode, the negative electrode of the first diode is connected to the negative electrode of the charger terminal, the collector of the first triode is connected to the base of the second triode, the emitter of the second triode is connected to the external power supply, and the collector of the second triode is connected to the main controller.

[0006] Optionally, a first resistor is arranged between the base of the first transistor and the external power supply, a second resistor is arranged between the collector of the first transistor and the base of the second transistor, and a third resistor is arranged between the anode of the first diode and the anode of the second diode.

[0007] In order to solve the problems existing in the prior art, the utility model also provides a BMS system, which includes the charger detection circuit as described above, and also includes a heating circuit, the control end of the heating circuit is connected to the main controller, and the voltage input end of the heating circuit is connected to the positive electrode of the battery end.

[0008] Optionally, the heating circuit includes a third triode, a fourth triode, a first MOS tube and a heating film, the base of the third triode is connected to the main controller, the base of the fourth triode is respectively connected to the collector of the third triode and the positive electrode of the battery end, the emitter of the fourth triode and the heating film are both connected to the positive electrode of the battery end, the collector of the fourth triode is connected to the gate of the first MOS tube, the drain of the first MOS tube is connected to the heating film, and the source of the first MOS tube is connected to the negative electrode of the charger end.

[0009] Optionally, the heating circuit further includes a third diode, an anode of the third diode is connected to the collector of the fourth transistor, and a cathode of the third diode is connected to the gate of the first MOS transistor.

[0010] Optionally, a secondary protection circuit is further included, wherein a voltage input terminal of the secondary protection circuit is connected to the positive electrode of the battery terminal, and a voltage output terminal of the secondary protection circuit is connected to the negative electrode of the charger terminal.

[0011] Optionally, the secondary protection circuit includes a fifth transistor, a sixth transistor, a second MOS tube and a fuse, one end of the fuse is connected to the battery end, the other end of the fuse is connected to the charger end, the base of the fifth transistor is connected to the main controller, the collector of the fifth transistor is respectively connected to the battery end and the base of the sixth transistor, the emitter of the sixth transistor is connected to the fuse, the collector of the sixth transistor is connected to the gate of the second MOS tube, the drain of the second MOS tube is connected to the fuse, and the source of the second MOS tube is connected to the negative electrode of the battery end.

[0012] Optionally, the secondary protection circuit further includes a fourth diode, an anode of the fourth diode is connected to the collector of the sixth transistor, and a cathode of the fourth diode is connected to the gate of the second MOS transistor.

[0013] Optionally, the secondary protection circuit also includes a first temperature switch, a second temperature switch and a seventh transistor, the first temperature switch and the second temperature switch are respectively connected to the positive electrode of the battery end and the base of the seventh transistor, the emitter of the seventh transistor is grounded, and the collector of the seventh transistor is connected to the base of the sixth transistor.

[0014] Optionally, a fifth diode is arranged on the emitter of the seventh transistor.

[0015] Compared with the prior art, the charger detection circuit provided by the embodiment of the utility model has the beneficial effect that: by designing a charger detection circuit, when the BMS system is in any operating condition except the condition where the charging and discharging MOS are fully turned on (in this operating condition, the battery is in a normal state and can be directly charged and discharged without any detection), as long as a charger is connected, the charger detection circuit can output a high level to the main controller to enable the main controller to start the corresponding control, and the circuit relies on the detection voltage to identify the charger connection, which not only has low power consumption, but also does not depend on the current value, and has no limit on the minimum current value of the charger, and has higher practicality and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The technical solution of the utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0017] In the figure:

[0018] Figure 1 is a circuit diagram of a charger detection circuit provided by an embodiment of the utility model;

[0019] Figure 2 It is a system block diagram of the BMS system provided by the embodiment of the utility model;

[0020] Figure 3 is a circuit diagram of a heating circuit provided by an embodiment of the utility model;

[0021] Figure 4 It is a circuit diagram of a secondary protection circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a preferred embodiment of the present utility model is described in detail.

[0023] like Figure 1 As shown, the utility model provides a specific embodiment of a charger detection circuit.

[0024] A charger detection circuit, reference Figure 1 , used in a BMS system, the BMS system includes a main controller 1, a battery terminal for connecting a battery pack, and a charger terminal for connecting a charger, and the charger detection circuit includes a first transistor Q1, a second transistor Q2, a first diode D1 and a second diode D2.

[0025] Among them, reference Figure 1The base of the first transistor Q1 is connected to the external power supply VCC and the anode of the second diode D2 respectively, the cathode of the second diode D2 is connected to the cathode B- of the battery end, the emitter of the first transistor Q1 is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the cathode PACK- of the charger end, the collector of the first transistor Q1 is connected to the base of the second transistor Q2, the emitter of the second transistor Q2 is connected to the external power supply VCC, and the collector of the second transistor Q2 is connected to the main controller 1.

[0026] Specifically, refer to Figure 1 , the anode of the second diode D2 is connected to the external power supply VCC, the cathode of the second diode D2 is connected to the cathode B- of the battery terminal, the base of the first transistor Q1 is connected between the anode of the second diode D2 and the external power supply VCC, and a connection point M is formed between the base of the first transistor Q1, the anode of the second diode D2 and the power supply path of the external power supply VCC, the emitter of the first transistor Q1 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the cathode PACK- of the charger terminal.

[0027] Further, refer to Figure 1 The base of the second transistor Q2 is connected to the collector of the first transistor Q1, the emitter of the second transistor Q2 is connected to the external power supply VCC, the collector of the second transistor Q2 is connected to the main controller 1, the first transistor Q1 is turned on to control the second transistor Q2 to be turned on, so as to output a corresponding high-level signal to the main controller 1 to inform the main controller 1 that a charger is connected.

[0028] After the charger is connected, the negative electrode PACK- at the charger end is the lowest potential point of the BMS system, the potential of the negative electrode PACK- at the charger end is lower than the potential of the negative electrode B- at the battery end, the voltage drop between the connection point M and the negative electrode PACK- at the charger end is greater than the sum of the voltage drop between the base and the emitter of the first transistor Q1 and the tube voltage drop of the first diode D1, the first transistor Q1 is turned on, thereby controlling the second transistor Q2 to be turned on, and outputting a high level to the main controller 1 to inform the main controller 1 that a charger is connected.

[0029] When the charging MOS tube of the BMS system and the discharging MOS tube of the BMS system are fully turned on, the negative electrode PACK- at the charger end and the negative electrode B- at the battery end are at the same potential, the first transistor Q1 is turned off, the second transistor Q2 is turned off, and a low level is output; after the discharging MOS tube of the BMS system is turned off, the negative electrode PACK- at the charger end and the negative electrode B- at the battery end are at a positive voltage, the first transistor Q1 is turned off, the second transistor Q2 is turned off, and a low level is output; when the charging MOS tube of the BMS system is turned off and the discharging MOS tube of the BMS system is turned on, and when the charging MOS tube of the BMS system is turned off and the discharging MOS tube of the BMS system is turned off, the first transistor Q1 is turned off, the second transistor Q2 is turned off, and a low level is output; this circuit design makes the charger detection circuit usually in the output low level state, and only after the charger is detected, it will output a high level.

[0030] That is to say, when the BMS system is in a dormant or low-temperature state, no matter whether the discharge MOS tube of the BMS system is in an on or off state, as long as the charging MOS of the BMS system is turned off, after the charger is connected, the negative electrode PACK- at the charger end will become the lowest potential point of the BMS system. When the charger voltage is slightly greater than the battery pack voltage, that is, the potential of the negative electrode PACK- at the charger end is slightly less than the potential of the negative electrode B- at the battery end, the first transistor Q1 is turned on, and the second transistor Q2 is also turned on, and the second transistor Q2 outputs a high level, thereby realizing charger detection.

[0031] When the battery pack is in an over-discharge state, the charging MOS tube of the BMS system is turned on, the discharging MOS tube of the BMS system is turned off, and the charger is connected, and the charger voltage is about 0.4V greater than the battery pack voltage, the first transistor Q1 is turned on, and the second transistor Q2 is also turned on, and the charger detection circuit outputs a high level, thereby realizing charger detection.

[0032] Among them, when the main controller 1 of the BMS system controls the charging MOS tube and the discharging MOS tube to perform corresponding state conversion according to the level signal output by the charger detection circuit.

[0033] In order to minimize the consumption of the battery pack circuit, the existing BMS system will automatically enter a dormant state in certain circumstances to shut down most functions, thereby minimizing its own power consumption. For example, the BMS system will enter a dormant state when it is idle for a long time or has not been charged or discharged for a long time. When the battery pack has been over-discharged, the BMS system will enter a dormant state after a delay. In a dormant BMS system, the internal charging MOS tube and discharging MOS tube are both in a turned-off state, and the user cannot charge or discharge the battery pack. Therefore, the BMS system requires a charger detection circuit to realize the charging activation or charging wake-up function, that is, connecting a charger can wake up the BMS system and allow it to turn on the charging MOS tube and the discharging MOS tube for charging and discharging.

[0034] In addition, the existing BMS system needs to prohibit the charger from directly charging the battery pack when the battery pack is at a low temperature, so that the existing BMS system needs to start the heating module first to heat the battery pack after the charger is connected, and only turn on the charging MOS tube after the temperature of the battery pack is higher than the set temperature to charge the battery pack. In this case, the BMS only turns off the charging MOS tube, while the discharging MOS tube is turned on; and when the battery pack is over-discharged, the charging MOS tube is turned on and the discharging MOS tube is turned off. In this state, when the charger is connected, the BMS also needs to be able to recognize the charger connection and quickly turn on the discharging MOS tube. Otherwise, the discharging MOS tube will be burned, which makes the charger detection circuit an important circuit module in the BMS system.

[0035] In this embodiment, by designing a charger detection circuit, when the BMS system is in any operating condition except the condition where the charging and discharging MOS are fully turned on (in this operating condition, the battery is in a normal state and can be directly charged and discharged without any detection), as long as a charger is connected, the charger detection circuit can output a high level to the main controller to enable the main controller to start the corresponding control. The circuit relies on the detection voltage to identify the charger connection, which not only has low power consumption, but also does not depend on the current value, and has no limit on the minimum current value of the charger, and has higher practicality and stability.

[0036] In one embodiment, reference Figure 1 A first resistor R1 is arranged between the base of the first transistor Q1 and the external power supply VCC, a second resistor R2 is arranged between the collector of the first transistor Q1 and the base of the second transistor Q2, and a third resistor R3 is arranged between the anode of the first diode D1 and the anode of the second diode D2.

[0037] Specifically, refer to Figure 1One end of the first resistor R1 is connected to the external power supply VCC, and the other end of the first resistor R1 is respectively connected to the base of the first transistor Q1 and the anode of the second diode D2; one end of the second resistor R2 is connected to the collector of the first transistor Q1, and the other end of the second resistor R2 is respectively connected to the external power supply VCC and the base of the second transistor Q2; one end of the third resistor R3 is connected to the anode of the first diode D1, and the other end of the third resistor R3 is connected to the anode of the second diode D2.

[0038] like Figures 2 to 4 As shown, the utility model also provides a specific embodiment of a BMS system.

[0039] A BMS system, reference Figure 2 The BMS system includes the charger detection circuit 10 as above, and also includes a heating circuit 20, a main controller 1, a charging MOS tube 2, a discharging MOS tube 3, a battery terminal for connecting to a battery pack 30, and a charger terminal for connecting to a charger 40. The control terminal of the heating circuit 20 is connected to the main controller 1, and the voltage input terminal of the heating circuit 20 is connected to the positive electrode B+ of the battery terminal.

[0040] Specifically, when the battery pack is in a low temperature state, the electrolyte and active materials in the electrodes inside it may be frozen or form a lattice-like structure, resulting in a decrease in the ionic conductivity of the electrolyte, making it difficult to carry out normal charging and discharging inside the battery. In addition, at extremely low temperatures, the metallic lithium in the lithium battery may be decomposed and deposited on the surface of the electrode, which may easily cause internal short circuit or damage to the battery. If the battery pack is charged directly through a charger, there will be a greater safety risk.

[0041] Therefore, it is necessary to set up a heating circuit 20 in the BMS system. When the battery pack is in a low temperature state, the heating module needs to be started first to heat the battery pack. Only after the temperature of the battery pack is higher than the set temperature can the charging MOS tube be turned on to charge the battery pack.

[0042] Among them, reference Figure 2 The control end of the heating circuit 20 is connected to the main controller 1 to obtain the control signal of the main controller 1, and is turned on or off according to the control signal of the main controller 1. The voltage input end of the heating circuit 20 is connected to the positive electrode B+ of the battery end to obtain electrical energy, thereby realizing electric heating.

[0043] In one embodiment, reference Figure 2 and Figure 3The heating circuit 20 includes a third triode Q3, a fourth triode Q4, a first MOS tube Q5 and a heating film 201. The base of the third triode Q3 is connected to the main controller 1, the base of the fourth triode Q4 is respectively connected to the collector of the third triode Q3 and the positive electrode B+ of the battery end, the emitter of the fourth triode Q4 and the heating film 201 are both connected to the positive electrode B+ of the battery end, the collector of the fourth triode Q4 is connected to the gate of the first MOS tube Q5, the drain of the first MOS tube Q5 is connected to the heating film 201, and the source of the first MOS tube Q5 is connected to the negative electrode PACK- of the charger end.

[0044] Specifically, refer to Figure 2 and Figure 3 The heating film 201 is arranged on the outer surface of the battery pack, and the heating film 201 is respectively connected to the positive electrode B+ of the battery end and the drain of the first MOS tube Q5 to heat the battery pack. The base of the third triode Q3 is connected to the main controller 1 of the BMS system to obtain a control signal. When the heating is started, the main controller 1 of the BMS system outputs a high level to the base of the third triode Q3, and the third triode Q3 is turned on. The base of the fourth triode Q4 is respectively connected to the positive electrode B+ of the battery end and the collector of the third triode Q3. When the third triode Q3 is turned on, the fourth triode Q4 is also turned on.

[0045] Further, refer to Figure 2 and Figure 3 The heating circuit 20 further includes a third diode D3, an anode of the third diode D3 is connected to the collector of the fourth transistor Q4, and a cathode of the third diode D3 is connected to the gate of the first MOS transistor Q5.

[0046] refer to Figure 2 and Figure 3 When the fourth triode Q4 is turned on, the voltage of the charger can reach the third diode D3 through the fourth triode Q4. The anode of the third diode D3 is connected to the collector of the fourth triode Q4, and the cathode of the third diode D3 is connected to the gate of the first MOS tube Q5. After the charger voltage reaches the third diode D3, a high level is output to the gate of the first MOS tube Q5, so that the first MOS tube Q5 is turned on. When the first MOS tube Q5 is turned on, the voltage of the charger will sequentially pass through the anode B+ of the battery end and the heating film 201 and then return to the cathode PACK- of the charger end, that is, return to the cathode of the charger, so as to achieve heating of the heating film 201.

[0047] Among them, reference Figure 2 and Figure 3The conduction of the fourth transistor Q4 utilizes the voltage of the battery pack itself, that is, when the third transistor Q3 is turned on, the fourth transistor Q4 will be turned on regardless of whether the charger is connected. The heating film 201 is connected in series between the positive electrode B+ at the battery end and the negative electrode PACK- at the charger end through the first MOS tube Q5, so that the heating circuit becomes an independent circuit. Based on this design, when the BMS system heats the heating film 201, it only needs to use the energy of the charger without consuming the energy of the battery itself.

[0048] In one embodiment, reference Figure 2 and Figure 4 The BMS system further includes a secondary protection circuit 50, a voltage input terminal of the secondary protection circuit 50 is connected to the positive electrode B+ of the battery terminal, and a voltage output terminal of the secondary protection circuit 50 is connected to the charger terminal PACK+.

[0049] Specifically, refer to Figure 2 and Figure 4 The secondary protection circuit 50 includes a fifth transistor Q6, a sixth transistor Q7, a second MOS transistor Q8 and a fuse F, one end of the fuse F is connected to the positive electrode B+ of the battery terminal, the other end of the fuse F is connected to the battery output terminal, the base of the fifth transistor Q6 is connected to the main controller 1, the collector of the fifth transistor Q6 is connected to the battery terminal and the base of the sixth transistor Q7 respectively, the emitter of the sixth transistor Q7 is connected to the fuse F, the collector of the sixth transistor Q7 is connected to the gate of the second MOS transistor Q8, and the drain of the second MOS transistor Q8 is connected to the fuse F.

[0050] Further, refer to Figure 2 and Figure 4 The secondary protection circuit 50 further includes a fourth diode D4, an anode of the fourth diode D4 is connected to the collector of the sixth transistor Q7, and a cathode of the fourth diode D4 is connected to the gate of the second MOS transistor Q8.

[0051] Among them, the BMS system protects the battery pack by monitoring the current, voltage and temperature of the battery pack and controlling the on and off of the charging MOS tube and the discharging MOS tube. Under normal circumstances, when any state of the battery pack reaches the protection point, such as overcharge protection or over-discharge protection, the BMS will turn off the charging MOS tube or the discharging MOS tube to play a protective role. This protection is a primary protection.

[0052] Under abnormal circumstances, such as when the charging MOS tube or the discharging MOS tube is damaged, although the BMS system has issued a command to shut down the charging MOS tube or the discharging MOS tube; but in fact, because the charging MOS tube or the discharging MOS tube is damaged, the MOS system itself is directly connected and cannot be shut down. At this time, the BMS system will detect the abnormality, and the BMS system will determine that the primary protection fails. The main controller 1 of the MCU system will output a high level to the base of the fifth transistor Q6, so that the fifth transistor Q6 of the secondary protection circuit 50 is turned on, and the sixth transistor Q7 is also turned on, so that the second MOS tube Q8 is also turned on; the current passes through the fuse F from the positive electrode B+ of the battery end, so that the fuse F is quickly blown, cutting off the entire power circuit, thereby achieving the purpose of protection.

[0053] In one embodiment, reference Figure 2 and Figure 4 The secondary protection circuit 50 also includes a first temperature switch K1, a second temperature switch K2 and a seventh transistor Q9. The first temperature switch K1 and the second temperature switch K2 are respectively connected to the positive electrode B+ of the battery terminal and the base of the seventh transistor Q9. The emitter of the seventh transistor Q9 is grounded. The collector of the seventh transistor Q9 is connected to the base of the sixth transistor Q7, and a fourth diode D4 is also provided at the emitter end of the seventh transistor Q9.

[0054] Specifically, refer to Figure 2 and Figure 4 , the first temperature switch K1 and the second temperature switch K2 are both in the normally open state, and the first temperature switch K1 and the second temperature switch K2 are respectively close to the surface of the battery cell of the battery pack and the MOS tube area of ​​the BMS system itself; when the BMS system fails completely, that is, the main controller 1 has failed, and cannot send a control signal to turn on the fifth transistor Q6, thereby failing to control the conduction of the sixth transistor Q7 and the second MOS tube Q8, and failing to blow the fuse F, the first temperature switch K1 and the second temperature switch K2 can be used to monitor the temperature of the battery cell ring and the temperature of the MOS tube.

[0055] Among them, in the case that the entire BMS system fails, if a large current is used to charge and discharge the battery pack, the damaged MOS tube will heat up quickly in a very short time, so that the first temperature switch K1 or the second temperature switch K2 is closed, and the seventh transistor Q9 is turned on. The conduction of the seventh transistor Q9 makes the sixth transistor Q7 and the second MOS tube Q8 turned on, and the control end of the fuse F is energized, and the fuse F is blown, thereby achieving the purpose of secondary protection.

[0056] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present utility model rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present utility model.

Claims

1. A charger detection circuit, used in a BMS system, wherein the BMS system includes a main controller, a battery terminal and a charger terminal, characterized in that: include: A first triode, a second triode, a first diode and a second diode, the base of the first triode is connected to an external power supply and the positive electrode of the second diode respectively, the cathode of the second diode is connected to the negative electrode of the battery terminal, the emitter of the first triode is connected to the positive electrode of the first diode, the cathode of the first diode is connected to the negative electrode of the charger terminal, the collector of the first triode is connected to the base of the second triode, the emitter of the second triode is connected to the external power supply, and the collector of the second triode is connected to the main controller.

2. The charger detection circuit according to claim 1, characterized in that: A first resistor is arranged between the base of the first transistor and the external power supply, a second resistor is arranged between the collector of the first transistor and the base of the second transistor, and a third resistor is arranged between the anode of the first diode and the anode of the second diode.

3. A BMS system, characterized in that: It comprises the charger detection circuit as described in any one of claims 1-2, and also comprises a heating circuit, the control end of the heating circuit is connected to the main controller, and the voltage input end of the heating circuit is connected to the positive electrode of the battery end.

4. The BMS system according to claim 3, characterized in that: The heating circuit includes a third triode, a fourth triode, a first MOS tube and a heating film, the base of the third triode is connected to the main controller, the base of the fourth triode is respectively connected to the collector of the third triode and the positive electrode of the battery end, the emitter of the fourth triode and the heating film are both connected to the positive electrode of the battery end, the collector of the fourth triode is connected to the gate of the first MOS tube, the drain of the first MOS tube is connected to the heating film, and the source of the first MOS tube is connected to the negative electrode of the charger end.

5. The BMS system according to claim 4, characterized in that: The heating circuit further includes a third diode, an anode of the third diode is connected to the collector of the fourth transistor, and a cathode of the third diode is connected to the gate of the first MOS transistor.

6. The BMS system according to claim 3, characterized in that: It also includes a secondary protection circuit, wherein a voltage input terminal of the secondary protection circuit is connected to the positive electrode of the battery terminal, and a voltage output terminal of the secondary protection circuit is connected to the negative electrode of the charger terminal.

7. The BMS system according to claim 6, characterized in that: The secondary protection circuit includes a fifth transistor, a sixth transistor, a second MOS transistor and a fuse, one end of the fuse is connected to the battery end, the other end of the fuse is connected to the charger end, the base of the fifth transistor is connected to the main controller, the collector of the fifth transistor is respectively connected to the battery end and the base of the sixth transistor, the emitter of the sixth transistor is connected to the fuse, the collector of the sixth transistor is connected to the gate of the second MOS transistor, and the drain of the second MOS transistor is connected to the fuse.

8. The BMS system according to claim 7, characterized in that: The secondary protection circuit further includes a fourth diode, an anode of the fourth diode is connected to the collector of the sixth transistor, and a cathode of the fourth diode is connected to the gate of the second MOS transistor.

9. The BMS system according to claim 8, characterized in that: The secondary protection circuit also includes a first temperature switch, a second temperature switch and a seventh transistor. The first temperature switch and the second temperature switch are respectively connected to the positive electrode of the battery terminal and the base of the seventh transistor. The emitter of the seventh transistor is grounded, and the collector of the seventh transistor is connected to the base of the sixth transistor.

10. The BMS system according to claim 9, characterized in that: A fifth diode is arranged on the emitter of the seventh triode.

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