Lead-acid battery protection circuit and lead-acid battery

Abstract

The utility model relates to the technical field of battery protection, and discloses a lead-acid battery protection circuit and a lead-acid battery, and the protection circuit comprises a main control unit which is connected with a charging switch, a pre-discharging branch circuit and a main discharging switch in parallel; the first end of the charging switch is connected with the anode of an external power supply, the first end of the main control unit is connected with the cathode of the external power supply, and the second end of the charging switch is connected with the second end of the main control unit; the first end of the pre-discharge branch and the first end of the main discharge switch are both connected with the positive electrode of an external power supply, and the second end of the pre-discharge branch and the second end of the main discharge switch are both connected with the positive electrode of a load; the third end of the master control unit is connected with the cathode of the load. According to the utility model, the problem of misjudgment of over-current or short-circuit protection of the lead-acid battery protection board on the load is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of battery protection, in particular to a lead-acid battery protection circuit and a lead-acid battery. Background Art

[0002] Existing electric vehicles mainly use lead-acid batteries, and some use lithium batteries. The main function of the lithium battery management unit BMS (abbreviation of Battery Management System) is to detect the voltage, current, temperature, capacity and even other environmental parameters of the lithium battery during charging and discharging to ensure that they are within a safe range, and to protect the battery. However, lead-acid batteries can only be protected by detecting their voltage or current alone, and do not have a protective effect similar to that of the lithium battery management unit BMS. The protection effect is poor, and it is very easy to cause misjudgment of protection.

[0003] At present, electric vehicle controllers are equipped with large-capacity capacitors. Due to the charging effect of the capacitors, a very large current will be generated when the capacitors are connected, which will cause the protection circuit to misjudge the discharge working state and easily damage the controller. In addition, if the load is directly connected, the charging of the capacitors will instantly generate a large current, which will exceed the overcurrent or short-circuit protection value, resulting in misjudgment of the overcurrent or short-circuit protection state. Therefore, a lead-acid battery protection circuit is urgently needed to overcome the defect of misjudgment of the lead-acid battery protection board. Utility Model Content

[0004] In view of this, the utility model provides a lead-acid battery protection circuit and a lead-acid battery to solve the problem of misjudgment of overcurrent or short-circuit protection of the load by the lead-acid battery protection board.

[0005] In a first aspect, the utility model provides a lead-acid battery protection circuit, the protection circuit comprising: a main control unit, a charging switch, a pre-discharge branch and a main discharge switch;

[0006] The charging switch, the pre-discharge branch and the main discharge switch are connected in parallel;

[0007] The first end of the charging switch and the first end of the main control unit are both connected to the positive electrode of the external power supply, the second end of the main control unit is connected to the negative electrode of the external power supply, and the second end of the charging switch is connected to the third end of the main control unit;

[0008] The first end of the pre-discharge branch and the first end of the main discharge switch are both connected to the positive electrode of the external power supply, and the second end of the pre-discharge branch and the second end of the main discharge switch are both connected to the positive electrode of the load; the fourth end of the pre-discharge branch is connected to the third end of the main control unit; the third end of the main discharge switch is connected to the fifth end of the main control unit;

[0009] When the main control unit detects abnormal charging or discharging, the charging switch is used to disconnect and then cut off the input, and the discharging switch is used to disconnect and then cut off the output; when the main control unit detects that the load changes from off to on, the pre-discharge branch is used to charge the load to a preset voltage and then the main control unit controls the main discharge switch to open.

[0010] The lead-acid battery protection circuit provided by the utility model is connected in parallel through a charging switch, a pre-discharge branch and a main discharge switch. When a main control unit detects abnormal charging or abnormal discharge, the charging switch is used to disconnect and then cut off the input, and the discharge switch is used to disconnect and then cut off the output; when the main control unit detects that the load is turned on from off, the pre-discharge branch is used to charge the load to a preset voltage, and then the main control unit controls the main discharge switch to open, and then charges the load. At this time, the charging of the capacitor in the external controller connected to the load will not generate a large current in time to cause it to exceed the overcurrent or short-circuit protection value, thereby preventing the protection circuit from misjudging the load overcurrent or short-circuit protection.

[0011] In an optional embodiment, the pre-discharge branch includes a pre-discharge switch and a pre-discharge resistor, the first end of the pre-discharge switch serves as the first end of the pre-discharge branch, and the first end of the pre-discharge switch is connected to the positive pole of the external power supply; the second end of the pre-discharge switch is connected to the first end of the pre-discharge resistor, and the second end of the pre-discharge resistor is connected to the positive pole of the load.

[0012] The lead-acid battery protection circuit provided by the utility model has a pre-discharge branch realized by a pre-discharge switch and a pre-discharge resistor. When discharging, the discharge switch is opened in advance to limit the discharge current through the pre-discharge resistor, and the main discharge switch is opened after the load is charged to a preset voltage. At this time, the charging of the capacitor in the external controller connected to the load will not generate a large current in time to cause the current to exceed the overcurrent or short-circuit protection value, thereby preventing the protection circuit from misjudging the load overcurrent or short-circuit protection.

[0013] In an optional implementation, the main control unit includes a first detection interface, and the protection circuit further includes a DC / DC module and a first connection terminal arranged between the DC / DC module and the main control unit;

[0014] A first end of the DC / DC module is connected to the positive electrode of the external power supply, a second end of the DC / DC module is connected to the first end of the first connection terminal, a second end of the first connection terminal is connected to the positive electrode of the load, and a third end of the first connection terminal is connected to the first detection interface;

[0015] When the first detection interface is connected to the first connection terminal, the DC / DC module is used to convert the high voltage of the external power supply into the low voltage required by the load.

[0016] The lead-acid battery protection circuit provided by the utility model converts the high voltage of the external power supply into the low voltage required by the load through the DC / DC module, so that the converted low voltage meets the voltage requirement of the external controller of the load. The DC / DC module is integrated into the protection circuit, so that the main control unit can save the space for adding modules and the part for heat dissipation, thereby solving the problem that the high-voltage to low-voltage module occupies the space of the main control unit and is not conducive to heat dissipation.

[0017] In an optional implementation, the main control unit further includes a first line-through interface and a second detection interface, and the protection circuit further includes a second connection terminal arranged between the charging switch and the main control unit;

[0018] The first end of the second connection terminal is connected to the second end of the charging switch, the second end of the second connection terminal is connected to the first one-line interface, and the third end of the second connection terminal is connected to the second detection interface, and the second detection interface serves as the third end of the main control unit.

[0019] The lead-acid battery protection circuit provided by the utility model can transmit the battery status information to the second connection terminal in real time through the first one-line interface. Once an abnormality is found, the second connection terminal will actively cut off charging, thereby greatly reducing the probability of accidents.

[0020] In an optional implementation, the main control unit further includes a third detection interface, and the protection circuit further includes a discharge interface;

[0021] The first end of the discharge interface is connected to the positive electrode of the load, the second end of the discharge interface is connected to the negative electrode of the load, and the third end of the discharge interface is connected to the third detection interface.

[0022] The lead-acid battery protection circuit provided by the utility model is connected to a load such as an electrical device through a set discharge interface, so that the connection between the lead-acid battery protection circuit and the load is more convenient, and the main control unit is connected to the discharge interface to monitor the working status of the discharge interface in real time, so as to protect the load in real time.

[0023] In an optional implementation, the main control unit further includes a short circuit recovery interface, a second one-line interface and a main output enable interface, and the protection circuit further includes a third connection terminal;

[0024] The first end of the third connection terminal is connected to the short circuit recovery interface, the second end of the third connection terminal is connected to the second line through interface, the third end of the third connection terminal is connected to the main output enable interface, and the fourth end of the third connection terminal is connected to the negative pole of the external power supply and the negative pole of the load.

[0025] The lead-acid battery protection circuit provided by the utility model can clear the protection state through the short-circuit recovery interface when the protection circuit triggers the short-circuit protection, so that the battery can be quickly restored to the working state, which is convenient and quick. Through the second one-line interface, various information such as the voltage, current, temperature and switch state of the lead-acid battery can be provided to the main control unit. The main control unit can detect the lead-acid battery in real time and provide safe and stable battery discharge control. The lead-acid battery can receive the control signal of the main control unit through the main output enable interface, so as to control the switch state of the load access.

[0026] In an optional implementation, the main control unit further includes an interface for a temperature sensor, and the protection circuit further includes a fourth connection terminal;

[0027] The fourth connection terminal is connected to the temperature sensor interface.

[0028] The lead-acid battery protection circuit provided by the utility model is connected to an external temperature sensor through a temperature sensor interface on a main control unit, so as to detect the temperature of the lead-acid battery in real time and perform corresponding temperature protection.

[0029] In an optional embodiment, the protection circuit further includes a current sensor;

[0030] The first end of the current sensor is connected to the negative electrode of the external power supply, the second end of the current sensor is connected to the negative electrode of the load, and the third end of the current sensor is connected to the fifth end of the main control unit.

[0031] The lead-acid battery protection circuit provided by the utility model collects the current signal of the battery pack through the current sensor, thereby judging faults such as overcurrent and short circuit, detecting the current size in the lead-acid battery in real time, and providing the main control unit with the current value for current control and electric energy metering.

[0032] In a second aspect, the utility model provides a lead-acid battery, including a battery pack and a lead-acid battery protection circuit according to the first aspect or any corresponding embodiment thereof;

[0033] A lead-acid battery pack, i.e., the external power supply of the first aspect mentioned above, wherein the lead-acid battery pack is composed of a plurality of lead-acid batteries connected in series, and the lead-acid battery pack is connected to the power supply end of the lead-acid battery protection circuit, and is used to power the lead-acid battery protection circuit and the load, or to be charged by the power supply on the load side.

[0034] The lead-acid battery provided by the utility model prevents the main control unit from misjudging the charging and discharging state through the lead-acid battery protection circuit, thereby solving the problem of misjudgment of the lead-acid battery protection board. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a structural schematic diagram of a lead-acid battery protection circuit according to an embodiment of the utility model;

[0037] Figure 2 is a structural schematic diagram of another lead-acid battery protection circuit according to an embodiment of the utility model;

[0038] Figure 3 It is a schematic diagram of a process of controlling charging of a lead-acid circuit protection circuit according to an embodiment of the utility model;

[0039] Figure 4 It is a schematic diagram of a flow chart of a lead-acid circuit protection circuit controlling discharge according to an embodiment of the utility model;

[0040] Figure 5 It is a flow chart of the structure of another lead-acid battery protection circuit according to an embodiment of the utility model;

[0041] Figure 6 It is a schematic structural diagram of a lead-acid battery according to an embodiment of the utility model. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0043] In this embodiment, a lead-acid battery protection circuit is provided. According to the structural schematic diagram of the lead-acid battery protection circuit of the embodiment of the utility model, as shown in FIG. Figure 1 As shown, the protection circuit includes:

[0044] A main control unit 11, a charging switch 12, a pre-discharge branch 13 and a main discharge switch 14, the charging switch 12, the pre-discharge branch 13 and the main discharge switch 14 are connected in parallel; the first end of the charging switch and the first end of the main control unit are both connected to the positive pole of the external power supply 15, the second end of the main control unit is connected to the negative pole of the external power supply, and the second end of the charging switch is connected to the third end of the main control unit; the first end of the pre-discharge branch and the first end of the main discharge switch are both connected to the positive pole of the external power supply, and the second end of the pre-discharge branch and the second end of the main discharge switch are both connected to the positive pole of the load 16; the fourth end of the pre-discharge branch is connected to the third end of the main control unit; the third end of the main discharge switch is connected to the fifth end of the main control unit; when the main control unit detects abnormal charging or abnormal discharging, the charging switch is used to disconnect and then cut off the input, and the discharge switch is used to disconnect and then cut off the output; when the main control unit detects that the load is turned from off to on, the pre-discharge branch is used to charge the load to a preset voltage and then the main control unit controls the main discharge switch to turn on. Figure 2 As shown, the external power source 15 can be implemented by a lead-acid battery pack.

[0045] For example, Figure 3 As shown, Figure 3 It is a flow chart of the lead-acid circuit protection circuit controlling charging according to the embodiment of the utility model. The lead-acid battery is preset to be connected to the lead-acid battery protection circuit through the charger. When the lead-acid battery is charged, it is first determined whether the charger is connected to the main control unit. When the charger is connected, it indicates that the handshake between the charger and the main control unit is successful; otherwise, the handshake fails, the charging switch is turned off, and the charging is terminated. When the charger is connected, the main control unit controls the charging switch to start charging the lead-acid battery, and obtains the working status of the battery through the main control unit. When an abnormal working status is detected (including charging abnormalities caused by charger failure or battery aging), the abnormal working status is obtained, and the charging switch is turned off to terminate the charging. Similarly, when an abnormality occurs in charging, the main control unit turns off the main discharge switch, quickly cuts off the discharge output, and prevents accidents. It should be noted that a large number of capacitors are integrated inside the main control unit. When the load is turned from off to on, the pre-discharge branch will be opened first to limit the discharge current. The load will be charged to the preset voltage before the main discharge switch is turned on. At this time, the charging of the capacitor in the external controller connected to the load will not generate a large current that exceeds the overcurrent or short-circuit protection value, thereby preventing the protection circuit from misjudging the load overcurrent or short-circuit protection.

[0046] In an optional embodiment, if Figure 5As shown, the pre-discharge branch includes a pre-discharge switch and a pre-discharge resistor. The first end of the pre-discharge switch serves as the first end of the pre-discharge branch, and the first end of the pre-discharge switch is connected to the positive electrode of the external power supply; the second end of the pre-discharge switch is connected to the first end of the pre-discharge resistor, and the second end of the pre-discharge resistor is connected to the positive electrode of the load. Specifically, when the lead-acid battery is discharged, the pre-discharge switch is opened in advance to limit the discharge current through the pre-discharge resistor, and the load is charged to a preset voltage before the main discharge switch is opened. At this time, the charging of the capacitor in the external controller connected to the load will not generate a large current in time to exceed the overcurrent or short-circuit protection value, thereby preventing the protection circuit from misjudging the load overcurrent or short-circuit protection. The preset voltage is set according to actual needs and is not specifically limited here.

[0047] Generally speaking, a large-capacity capacitor is installed in the external controller of the load. Due to the charging effect of the capacitor, a very large current will be generated when the capacitor is connected, which will cause the protection circuit to misjudge the load overcurrent or short-circuit protection. The lead-acid battery protection circuit provided in the embodiment of the present invention is provided with a pre-discharge switch and a pre-discharge resistor. When discharging, the pre-discharge switch is opened in advance to limit the discharge current through the pre-discharge resistor, and the load is charged to a preset voltage before the main discharge switch is opened. At this time, the charging of the capacitor in the external controller connected to the load will not generate a large current in time to cause it to exceed the overcurrent or short-circuit protection value, thereby preventing the protection circuit from misjudging the load overcurrent or short-circuit protection.

[0048] In an optional embodiment, if Figure 5 As shown, the main control unit includes a first detection interface, such as Figure 2 and Figure 4 As shown, the protection circuit also includes a DC / DC module and a first connection terminal arranged between the DC / DC module and the main control unit; the first end of the DC / DC module is connected to the positive pole of the external power supply, the second end of the DC / DC module is connected to the first end of the first connection terminal, the second end of the first connection terminal is connected to the positive pole of the load, and the third end of the first connection terminal is connected to the first detection interface; when the first detection interface is connected to the first connection terminal, the DC / DC module is used to convert the high voltage of the external power supply into the low voltage required by the load.

[0049] Specifically, the first detection port can be a secondary loop insertion detection port, and the secondary loop refers to the first connection terminal outside the load, and the first connection terminal can be implemented by a 5557 terminal (electronic connector). It should be noted that the main control unit controls the secondary loop insertion detection signal through the secondary loop insertion detection port, and can control the working state of the DC / DC module. The DC / DC module is turned on only when the secondary loop is connected, thereby realizing low power consumption of the protection circuit. The high voltage of the lead-acid battery is converted into the low voltage required by the load through the DC / DC module, and the working power is provided to the main control unit through the first connection terminal.

[0050] The voltage of a lead-acid battery is usually higher than 36V, while the operating voltage of the external controller of the load is a low voltage of less than 12V. The lead-acid battery protection circuit provided by the embodiment of the present invention provides a DC / DC module in the protection circuit to convert the high voltage of the external power supply into the low voltage required by the load, so that the converted low voltage meets the voltage requirement of the external controller of the load, and can also save space for adding a high-low voltage conversion module in the main control unit, which is beneficial to the heat dissipation of the lead-acid battery protection circuit.

[0051] In an optional embodiment, if Figure 4 As shown, the main control unit also includes a first line-through interface and a second detection interface, and the protection circuit also includes a second connection terminal arranged between the charging switch and the main control unit; the first end of the second connection terminal is connected to the second end of the charging switch, the second end of the second connection terminal is connected to the first line-through interface, and the third end of the second connection terminal is connected to the second detection interface, and the second detection interface serves as the third end of the main control unit.

[0052] Specifically, the first one-line interface can be implemented by using a charger one-line interface to provide an interface for an external charger to access the main control unit. The second detection interface can be implemented by using a charger insertion detection interface, and the second connection terminal can be implemented by using a 5557 terminal or an external charger. For example, the second connection terminal is implemented by using an external charger. Figure 2 As shown, when charging the lead-acid battery, the external charger is connected to the main control unit through the charger one-line interface. After the main control unit and the external charger are connected, various information such as battery voltage, current, temperature, and switch status can be obtained. The main control unit obtains an access signal indicating whether the external charger is connected through the charger insertion detection interface. The main control unit detects the external charger through the charger one-line interface, and can detect the charging status of the lead-acid battery in real time, providing safe and stable charging control.

[0053] The traditional charging method is simple and crude, and the charger is directly connected to the battery for charging. The charger cannot know the current status of the battery. Once the battery is overheated or over-voltage occurs, the charger cannot actively cut off the power, which may cause an accident. The lead-acid battery protection circuit provided by the embodiment of the present invention provides a charging one-line interface in the main control unit for safer and more reliable charging. The status information of the lead-acid battery can be transmitted to the charger in real time through the charging one-line interface. Once an abnormality is found, the main control unit closes the charging one-line interface, so that the charger will actively cut off the charging, thereby greatly reducing the probability of abnormal charging accidents.

[0054] In an optional embodiment, if Figure 4As shown, the main control unit also includes a third detection interface, and the protection circuit also includes a discharge interface; the first end of the discharge interface is connected to the positive electrode of the load, the second end of the discharge interface is connected to the negative electrode of the load, and the third end of the discharge interface is connected to the third detection interface.

[0055] Specifically, the load in the protection circuit is the main power consumption circuit, referred to as the main circuit. The third detection interface can be inserted into the detection interface of the main circuit, and the main circuit insertion detection interface is used to determine whether the main circuit is connected. The discharge interface is mainly used to connect the main circuit or other loads except the main circuit. The main circuit or other loads except the main circuit can be conveniently and quickly connected to the main control unit through the discharge interface, and the discharge working state of the lead-acid battery is controlled by the main control unit.

[0056] In an optional embodiment, if Figure 4 As shown, the main control unit also includes a short-circuit recovery interface, a second one-line interface and a main output enable interface, and the protection circuit also includes a third connection terminal; the first end of the third connection terminal is connected to the short-circuit recovery interface, the second end of the third connection terminal is connected to the second one-line interface, the third end of the third connection terminal is connected to the main output enable interface, and the fourth end of the third connection terminal is connected to the negative pole of the external power supply and the negative pole of the load.

[0057] Specifically, the second one-line interface can be an output one-line interface, and the third connection terminal is implemented by a 5557 terminal. The third connection terminal is connected to the main control unit through the output one-line interface, and can provide the main control unit with various information such as the voltage, current, temperature, and switch status of the lead-acid battery. The main control unit can monitor the lead-acid battery in real time and provide safe and stable discharge control for the load. The main output enable interface is used to receive the main output enable signal sent by the main control unit, so as to control the main discharge switch state of the main output. It should be noted that the main output enable interface will only be unlocked when the main circuit is correctly connected, otherwise the main output enable interface will not be opened even if the main output enable signal of the main control unit is received, so as to provide safety protection for the lead-acid battery.

[0058] The lead-acid battery protection circuit provided by the embodiment of the present invention is provided with an output one-line interface in the main control unit, and discharge devices such as the third connection terminal can monitor the status of the lead-acid battery in real time. Once an abnormality occurs, the output can be cut off in time, thereby greatly reducing the probability of abnormal discharge accidents.

[0059] For example, Figure 4As shown, the process of controlling the discharge of a lead-acid battery by a lead-acid battery protection circuit is taken as an example to illustrate the process of controlling the discharge of a lead-acid battery by a lead-acid battery protection circuit. When the main control unit detects that the secondary circuit is connected through the secondary circuit insertion, the DC / DC module is turned on, and the high voltage of the lead-acid battery is converted into the low voltage required by the load through the DC / DC module. The main control unit detects whether the main circuit is correctly connected through the main circuit insertion detection port. When the main circuit is correctly connected, the main output enable interface is turned on. At this time, the main control unit controls the pre-discharge switch to turn on, and limits the discharge current through the pre-discharge resistor. Then, it is determined whether the discharge interface voltage is greater than 80% of the lead-acid battery voltage (this voltage is used as the above-mentioned preset voltage). If so, the main discharge switch is turned on and the pre-discharge switch is turned off. The main control unit obtains the discharge working state of the lead-acid battery. When the discharge is abnormal (including abnormal states such as the lead-acid battery charge and discharge times have been exhausted and the lead-acid battery electrolyte is insufficient), the main discharge switch is turned off to end the discharge.

[0060] In an optional embodiment, if Figure 5 As shown, the main control unit also includes a temperature sensor interface, and the protection circuit also includes a fourth connection terminal; the fourth connection terminal is connected to the temperature sensor interface. The third connection terminal is implemented by a 5557 terminal or an external temperature sensor. In actual application, the temperature sensor is attached to the surface of the lead-acid battery and connected to the temperature sensor interface of the main control unit. The main control unit monitors the lead-acid battery temperature in real time through the temperature sensor and performs corresponding temperature protection.

[0061] In an optional embodiment, if Figure 2 As shown, the protection circuit also includes a current sensor; the first end of the current sensor is connected to the negative pole of the external power supply, the second end of the current sensor is connected to the negative pole of the load, and the third end of the current sensor is connected to the sixth end of the main control unit. Specifically, the current sensor is used to collect the current signal of the lead-acid battery and transmit it to the main control unit. After the main control unit receives the current signal transmitted by the current sampling resistor, it can determine faults such as overcurrent and short circuit. Figure 5 As shown, the current sensor can also be replaced by a current sampling resistor.

[0062] The present invention also provides a lead-acid battery. Figure 6 As shown, including a battery pack and the above Figure 1 and Figure 2 He Ru Figure 5 The lead-acid battery protection circuit shown; the lead-acid battery pack, that is, the external power supply recorded in the above embodiment, the lead-acid battery pack is composed of a plurality of lead-acid batteries connected in series, the lead-acid battery pack is connected to the power supply end of the lead-acid battery protection circuit, the lead-acid battery pack is used to power the lead-acid battery protection circuit and the load, or is charged by the power supply on the load side.

[0063] The lead-acid battery provided by the utility model prevents the main control unit from misjudging the charging and discharging state through the lead-acid battery protection circuit, thereby solving the problem of misjudgment of the lead-acid battery protection board.

[0064] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A lead-acid battery protection circuit, characterized in that: The protection circuit comprises: a main control unit, a charging switch, a pre-discharge branch and a main discharge switch; The charging switch, the pre-discharge branch and the main discharge switch are connected in parallel; The first end of the charging switch and the first end of the main control unit are both connected to the positive electrode of the external power supply, the second end of the main control unit is connected to the negative electrode of the external power supply, and the second end of the charging switch is connected to the third end of the main control unit; The first end of the pre-discharge branch and the first end of the main discharge switch are both connected to the positive electrode of the external power supply, and the second end of the pre-discharge branch and the second end of the main discharge switch are both connected to the positive electrode of the load; the fourth end of the pre-discharge branch is connected to the third end of the main control unit; the third end of the main discharge switch is connected to the fifth end of the main control unit; When the main control unit detects abnormal charging or discharging, the charging switch is used to disconnect and then cut off the input, and the discharging switch is used to disconnect and then cut off the output; when the main control unit detects that the load is turned from off to on, the pre-discharge branch is used to charge the load to a preset voltage and then the main control unit controls the main discharge switch to open.

2. The protection circuit according to claim 1, characterized in that: The pre-discharge branch includes a pre-discharge switch and a pre-discharge resistor. The first end of the pre-discharge switch serves as the first end of the pre-discharge branch, and the first end of the pre-discharge switch is connected to the positive electrode of the external power supply; the second end of the pre-discharge switch is connected to the first end of the pre-discharge resistor, and the second end of the pre-discharge resistor is connected to the positive electrode of the load.

3. The protection circuit according to claim 1, characterized in that: The main control unit includes a first detection interface, and the protection circuit also includes a DC / DC module and a first connection terminal arranged between the DC / DC module and the main control unit; The first end of the DC / DC module is connected to the positive electrode of the external power supply, the second end of the DC / DC module is connected to the first end of the first connection terminal, the second end of the first connection terminal is connected to the positive electrode of the load, and the third end of the first connection terminal is connected to the first detection interface; When the first detection interface is connected to the first connection terminal, the DC / DC module is used to convert the high voltage of the external power supply into the low voltage required by the load.

4. The protection circuit according to claim 1, characterized in that: The main control unit further includes a first line-through interface and a second detection interface, and the protection circuit further includes a second connection terminal arranged between the charging switch and the main control unit; The first end of the second connection terminal is connected to the second end of the charging switch, the second end of the second connection terminal is connected to the first one-line interface, the third end of the second connection terminal is connected to the second detection interface, and the second detection interface serves as the third end of the main control unit.

5. The protection circuit according to claim 1, characterized in that: The main control unit further includes a third detection interface, and the protection circuit further includes a discharge interface; The first end of the discharge interface is connected to the positive electrode of the load, the second end of the discharge interface is connected to the negative electrode of the load, and the third end of the discharge interface is connected to the third detection interface.

6. The protection circuit according to claim 1, characterized in that: The main control unit further includes a short circuit recovery interface, a second one-line interface and a main output enable interface, and the protection circuit further includes a third connection terminal; The first end of the third connection terminal is connected to the short-circuit recovery interface, the second end of the third connection terminal is connected to the second one-line interface, the third end of the third connection terminal is connected to the main output enable interface, and the fourth end of the third connection terminal is connected to the negative pole of the external power supply and the negative pole of the load.

7. The protection circuit according to claim 1, characterized in that: The main control unit further includes an interface for a temperature sensor, and the protection circuit further includes a fourth connection terminal; The fourth connection terminal is connected to the temperature sensor interface.

8. The protection circuit according to claim 1, characterized in that: The protection circuit also includes a current sensor; The first end of the current sensor is connected to the negative electrode of the external power supply, the second end of the current sensor is connected to the negative electrode of the load, and the third end of the current sensor is connected to the sixth end of the main control unit.

9. A lead-acid battery, characterized in that: A lead-acid battery pack and a lead-acid battery protection circuit as claimed in any one of claims 1 to 8; A lead-acid battery pack, i.e., the external power supply as described in claim 1, wherein the lead-acid battery pack is composed of a plurality of lead-acid batteries connected in series, the lead-acid battery pack is connected to the power supply end of the lead-acid battery protection circuit, and the lead-acid battery pack is used to power the lead-acid battery protection circuit and the load, or to be charged by the power supply on the load side.

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