Battery secondary protection circuit

Abstract

The utility model discloses a battery secondary protection circuit, which comprises a charging and discharging protection circuit, a secondary charging protection circuit and a battery equalization circuit, and is characterized in that the charging and discharging protection circuit is used for carrying out charging and discharging protection control on a battery; the secondary charging protection circuit is used for performing charging secondary protection control on the battery; and the battery equalization circuit is used for performing voltage equalization control on the battery. Therefore, the secondary charging protection circuit can perform secondary turn-off control when the charging and discharging protection circuit fails, so that the charging loop can be timely turned off when the battery charging is abnormal, and the lithium battery charging fire is avoided. And meanwhile, the battery equalization circuit is used for performing voltage equalization control on the battery. All the batteries are connected in series and kept in a balanced state, so that the batteries achieve the optimal charging energy efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of battery full charge protection, in particular to a secondary battery protection circuit. Background Art

[0002] In recent years, secondary batteries such as lithium (Li) ion batteries have been widely used. Since the lithium battery pack can be recharged after the first charge is exhausted, so as to achieve repeated cycling use. At present, charging is usually carried out by converting the mains alternating current voltage to charge the lithium battery pack. In the case of unattended, the lithium battery pack is connected to the mains alternating current through the charger for a long time. Due to various reasons, it may cause a short circuit or the lithium battery to catch fire during charging, thus increasing the risk of fire caused by lithium battery charging. Summary of the Utility Model

[0003] The utility model aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the utility model is to provide a secondary battery protection circuit.

[0004] To achieve the above object, according to an embodiment of the utility model, the secondary battery protection circuit includes:

[0005] A charge and discharge protection circuit for controlling the charge and discharge protection of the battery;

[0006] A secondary charge protection circuit for controlling the secondary charge protection of the battery;

[0007] A battery equalization circuit for controlling the voltage equalization of the battery.

[0008] Further, according to an embodiment of the utility model, the charge and discharge protection circuit includes:

[0009] A protection controller U1, the voltage detection terminals of the protection controller U1 are respectively connected to each battery cell to detect the charge and discharge voltages of each battery cell;

[0010] A charge and discharge switch, the charge and discharge switch is arranged on the charge and discharge loop of the battery, and the charge and discharge switch is connected to the charge and discharge control signal output terminal of the protection controller U1 to perform charge and discharge control under the action of the protection controller U1.

[0011] Further, according to an embodiment of the utility model, the charge and discharge switch includes:

[0012] MOS transistor Q1, the gate of the MOS transistor Q1 is connected to the charging control terminal of the protection controller U1, and the source of the MOS transistor Q1 is connected to the negative terminal of the charge and discharge interface;

[0013] MOS transistor Q2, the gate of the MOS transistor Q2 is connected to the discharge control terminal of the protection controller U1, the drain of the MOS transistor Q2 is connected to the drain of the MOS transistor Q1, and the source of the MOS transistor Q2 is connected to the negative terminal of the battery through the secondary charging switch of the secondary charging protection circuit.

[0014] Further, according to an embodiment of the present invention, the charge and discharge protection circuit further includes:

[0015] Current sampling resistor RS1, the current sampling resistor RS1 is arranged on the charge and discharge loop of the battery, the current sampling resistor RS1 is connected to the charge and discharge protection circuit to output a current signal to the charge and discharge protection circuit, and the charge and discharge protection circuit is further used for overcurrent protection control according to the current signal.

[0016] Further, according to an embodiment of the present invention, the charge and discharge protection circuit further includes:

[0017] Thermistor NTC1, one end of the thermistor NTC1 is connected to the reference ground, the other end of the thermistor NTC1 is connected to the temperature detection terminal of the protection controller U1, the other end of the thermistor NTC1 is further connected to one end of the resistor RT, and the other end of the resistor RT is connected to the voltage output terminal of the protection controller U1.

[0018] Further, according to an embodiment of the present invention, the charge and discharge protection circuit further includes a first battery terminal protection circuit, and the first battery terminal protection circuit includes:

[0019] Resistor R1, the second detection terminal of the protection controller U1 is connected to the positive terminal of the second battery through the resistor R1;

[0020] Resistor R2, the first detection terminal of the protection controller U1 is connected to the positive terminal of the first battery through the resistor R2;

[0021] Capacitor C1, one end of the capacitor C1 is connected to the second detection terminal of the protection controller U1, and the other end of the capacitor C1 is connected to the reference ground;

[0022] Capacitor C2, one end of the capacitor C2 is connected to the first detection terminal of the protection controller U1, and the other end of the capacitor C2 is connected to the reference ground.

[0023] Further, according to an embodiment of the present utility model, the secondary charging protection circuit includes:

[0024] A protection controller U2, the voltage detection terminals of the protection controller U2 are respectively connected to each battery cell to detect the charging and discharging voltages of each battery cell;

[0025] A secondary charging switch, the secondary charging switch is arranged on the charging and discharging circuit of the battery, and the secondary charging switch is connected to the charging control signal output terminal of the protection controller U2 to perform secondary charging protection control under the action of the protection controller U2.

[0026] Further, according to an embodiment of the present utility model, the secondary charging protection circuit further includes that the second battery terminal protection circuit includes:

[0027] A resistor R7, the first detection terminal of the protection controller U2 is connected to the positive terminal of the first battery cell through the resistor R7;

[0028] A resistor R6, the second detection terminal of the protection controller U2 is connected to the positive terminal of the second battery cell through the resistor R6;

[0029] A capacitor C3, one end of the capacitor C3 is connected to the second detection terminal of the protection controller U2, and the other end of the capacitor C3 is connected to the reference ground;

[0030] A capacitor C4, one end of the capacitor C4 is connected to the first detection terminal of the protection controller U2, and the other end of the capacitor C4 is connected to the reference ground.

[0031] Further, according to an embodiment of the present utility model, the battery equalization circuit includes:

[0032] A first equalization controller U3, the input terminal of the first equalization controller U3 is connected to both ends of the second battery cell;

[0033] A second equalization controller U4, the input terminal of the second equalization controller U4 is connected to both ends of the first battery cell;

[0034] A MOS transistor Q4, the gate of the MOS transistor Q4 is connected to the output terminal of the first equalization controller U3, the drain of the MOS transistor Q4 is connected to the positive terminal of the second battery cell through a resistor R11, and the source of the MOS transistor Q4 is connected to the negative terminal of the second battery cell;

[0035] A MOS transistor Q5, the gate of the MOS transistor Q5 is connected to the output terminal of the second equalization controller U4, the drain of the MOS transistor Q5 is connected to the positive terminal of the first battery cell through a resistor R12, and the source of the MOS transistor Q5 is connected to the negative terminal of the first battery cell.

[0036] Further, according to an embodiment of the present utility model, the battery balancing circuit further includes that the third battery terminal protection circuit includes:

[0037] A resistor R9, one end of the resistor R9 is connected to the positive terminal of the second battery, and the other end of the resistor R9 is connected to the positive terminal of the first balancing controller U3;

[0038] A resistor R10, one end of the resistor R10 is connected to the positive terminal of the first battery, and the other end of the resistor R10 is connected to the positive terminal of the second balancing controller U4;

[0039] A capacitor C7, one end of the capacitor C7 is connected to the positive terminal of the second battery, and the other end of the capacitor C7 is respectively connected to the negative terminal of the second battery and the negative terminal of the first balancing controller U3;

[0040] A capacitor C8, one end of the capacitor C8 is connected to the positive terminal of the first battery, and the other end of the capacitor C8 is respectively connected to the negative terminal of the first battery and the negative terminal of the second balancing controller U4.

[0041] The battery secondary protection circuit provided by the embodiment of the present utility model uses a charge and discharge protection circuit to perform charge and discharge protection control on the battery; a secondary charge protection circuit is used to perform secondary charge protection control on the battery; and a battery balancing circuit is used to perform voltage balancing control on the battery. In this way, the secondary charge protection circuit can perform secondary turn-off control when the charge and discharge protection circuit fails, ensuring that the charging circuit can be turned off in time when the battery charging is abnormal, and avoiding the lithium battery from catching fire during charging. At the same time, by using the battery balancing circuit to perform voltage balancing control on the battery, it is possible to keep each series-connected battery in a balanced state, thereby enabling the battery to achieve the best charging efficiency. Description of the Drawings

[0042] Figure 1 is a schematic structural diagram of the secondary charge protection circuit and the charge and discharge protection circuit provided by the present utility model;

[0043] Figure 2 is a schematic structural diagram of the battery balancing circuit provided by the present utility model.

[0044] The realization, functional characteristics and advantages of the purpose of the present utility model will be further described with reference to the embodiments and the accompanying drawings. Detailed Embodiments

[0045] To enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present utility model. The terms used in the specification of the present utility model herein are only for the purpose of describing specific embodiments and are not intended to limit the present utility model.

[0046] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present utility model. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0047] Refer to Figure 1 and Figure 2 , an embodiment of the present utility model provides a secondary battery protection circuit, including: a charge and discharge protection circuit, a secondary charge protection circuit, and a battery equalization circuit. The charge and discharge protection circuit is used to control the charge and discharge protection of the battery, thereby avoiding overcharging or over-discharging of the lithium battery and ensuring the service life of the lithium battery.

[0048] The secondary charge protection circuit is used to perform secondary charge protection control on the battery; during the battery charging process, when the lithium battery has abnormal charging, it may cause the problem of the lithium battery catching fire. Therefore, it is necessary to perform secondary shutdown protection control on the lithium battery to avoid the battery charger catching fire and causing a fire.

[0049] The battery equalization circuit is used to perform voltage equalization control on the battery. In order to make the series-connected batteries achieve the best charging energy efficiency. It is necessary to equalize each battery through the battery equalization circuit. In this way, the secondary charge protection circuit can perform secondary shutdown control when the charge and discharge protection circuit fails, ensuring that the charging circuit can be shut down in time when the battery charging is abnormal, and avoiding the lithium battery catching fire during charging. At the same time, by performing voltage equalization control on the battery through the battery equalization circuit, it is possible to make. Each battery in series maintains an equalized state, thereby enabling the battery to achieve the best charging energy efficiency.

[0050] Refer to Figure 1 , the charge and discharge protection circuit includes: a protection controller U1 and a charge and discharge switch. The voltage detection terminals of the protection controller U1 are respectively connected to each battery to detect the charge and discharge voltages of each battery; as Figure 1As shown in the figure, the voltage detection terminals (VSS, VC1, and VC2) of the protection controller U1 are respectively connected to two lithium batteries to detect the charging and discharging voltages of each battery.

[0051] The charging and discharging switch is arranged on the charging and discharging loop of the battery. The charging and discharging switch is connected to the charging and discharging control signal output terminal of the protection controller U1 to perform charging and discharging control under the action of the protection controller U1. As Figure 1 shown in the figure, the charging and discharging switch includes: MOS transistor Q1 and MOS transistor Q2. The gate of the MOS transistor Q1 is connected to the charging control terminal of the protection controller U1, and the source of the MOS transistor Q1 is connected to the negative terminal of the charging and discharging interface; the gate of the MOS transistor Q2 is connected to the discharging control terminal of the protection controller U1, the drain of the MOS transistor Q2 is connected to the drain of the MOS transistor Q1, and the source of the MOS transistor Q2 is connected to the negative terminal of the battery through the secondary charging switch of the secondary charging protection circuit.

[0052] Specifically, when the protection controller U1 needs to open the charging loop, it can output a high-level signal through the CO terminal. This high-level signal can make the MOS transistor Q2 conduct, thereby conducting the charging loop, and the charging electrical appliance can charge the battery. On the contrary, when the protection controller U1 detects charging anomalies, it can output a low-level signal to cut off the MOS transistor Q2, thereby disconnecting the charging loop for charging protection. The discharging control process is controlled by the protection controller U1 outputting high and low levels through the DO terminal, and its control process is the same as that of charging, which will not be repeated here.

[0053] Refer to Figure 1 , the charging and discharging protection circuit further includes: a current sampling resistor RS1. The current sampling resistor RS1 is arranged on the charging and discharging loop of the battery. The current sampling resistor RS1 is connected to the charging and discharging protection circuit to output a current signal to the charging and discharging protection circuit, and the charging and discharging protection circuit is also used to perform overcurrent protection control according to the current signal.

[0054] Specifically, the current sampling resistor RS1 is arranged on the charging and discharging loop of the battery. The current sampling resistor RS1 is connected to the charging and discharging protection circuit to output a current signal to the charging and discharging protection circuit, and the charging and discharging protection circuit is also used to perform overcurrent protection control according to the current signal. The current value of the charging and discharging loop can be obtained in real time through the current sampling resistor RS1, and the charging and discharging protection circuit performs overcurrent protection when the real-time current value exceeds the set value.

[0055] Refer to Figure 1, the charge and discharge protection circuit further includes: a thermistor NTC1, one end of the thermistor NTC1 is connected to the reference ground, the other end of the thermistor NTC1 is connected to the temperature detection terminal of the protection controller U1, and the other end of the thermistor NTC1 is also connected to one end of a resistor RT, and the other end of the resistor RT is connected to the voltage output terminal of the protection controller U1.

[0056] Specifically, a voltage dividing circuit is formed between the thermistor NTC1 and the resistor RT, and the voltage output by the protection controller U1 can be divided and then output to the detection terminal RTS of the protection controller U1. Due to the corresponding relationship between the resistance value of the thermistor NTC1 and the temperature, the corresponding temperature value can be obtained by acquiring the divided voltage value of the thermistor NTC1. When the temperature exceeds the set temperature value, over-temperature protection can be performed.

[0057] Refer to Figure 1 , the charge and discharge protection circuit further includes a first battery terminal protection circuit, and the first battery terminal protection circuit includes: a resistor R1, a resistor R2, a capacitor C1 and a capacitor C2, and the second detection terminal of the protection controller U1 is connected to the positive terminal of the second battery through the resistor R1;

[0058] The first detection terminal of the protection controller U1 is connected to the positive terminal of the first battery through the resistor R2; one end of the capacitor C1 is connected to the second detection terminal of the protection controller U1, and the other end of the capacitor C1 is connected to the reference ground; one end of the capacitor C2 is connected to the first detection terminal of the protection controller U1, and the other end of the capacitor C2 is connected to the reference ground.

[0059] Specifically, the resistors R1 and R2 can limit the current introduced into the detection terminal of the protection controller U1 to avoid damage to the protection controller U1 by large current. The capacitors C1 and C2 can filter out high-frequency strong pulse signals to avoid damage to the protection controller U1.

[0060] Refer to Figure 1 , the secondary charge protection circuit includes: a protection controller U2 and a secondary charge switch, and the voltage detection terminals of the protection controller U2 are respectively connected to each battery to detect the charge and discharge voltage of each battery; as Figure 1 shown, the voltage detection terminals (VSS, VC1 and VC2) of the protection controller U2 are respectively connected to two lithium batteries to detect the charge and discharge voltage of each battery.

[0061] The secondary charging switch (MOS transistor Q3) is provided on the charge and discharge loop of the battery. The secondary charging switch is connected to the charging control signal output terminal of the protection controller U2 to perform secondary charging protection control under the action of the protection controller U2. During the battery charging process, when the lithium battery has abnormal charging, it may cause the problem of the lithium battery catching fire. Therefore, it is necessary to perform secondary turn-off protection control on the lithium battery to avoid the battery charger catching fire and causing a fire. When the protection controller U2 detects abnormal charging, it can output a low-level signal to turn off the secondary charging switch (MOS transistor Q3), thereby performing secondary charging protection.

[0062] Refer to Figure 1 , the secondary battery terminal protection circuit of the secondary charging protection circuit further includes: resistor R7, resistor R6, capacitor C3 and capacitor C4. The first detection terminal of the protection controller U2 is connected to the positive terminal of the first battery through the resistor R7; the second detection terminal of the protection controller U2 is connected to the positive terminal of the second battery through the resistor R6; one end of the capacitor C3 is connected to the second detection terminal of the protection controller U2, and the other end of the capacitor C3 is connected to the reference ground; one end of the capacitor C4 is connected to the first detection terminal of the protection controller U2, and the other end of the capacitor C4 is connected to the reference ground.

[0063] Specifically, the resistors R7 and R6 can limit the current introduced to the detection terminal of the protection controller U2 to avoid damage to the protection controller U2 caused by large current. The capacitors C3 and C4 can filter out high-frequency strong pulse signals to avoid damage to the protection controller U1.

[0064] Refer to Figure 2 , the battery equalization circuit includes: the first equalization controller U3, the second equalization controller U4, the MOS transistor Q4 and the MOS transistor Q5. The input terminal of the first equalization controller U3 is connected to both ends of the second battery; the input terminal of the second equalization controller U4 is connected to both ends of the first battery; the gate of the MOS transistor Q4 is connected to the output terminal of the first equalization controller U3, the drain of the MOS transistor Q4 is connected to the positive terminal of the second battery through the resistor R11, and the source of the MOS transistor Q4 is connected to the negative terminal of the second battery; the gate of the MOS transistor Q5 is connected to the output terminal of the second equalization controller U4, the drain of the MOS transistor Q5 is connected to the positive terminal of the first battery through the resistor R12, and the source of the MOS transistor Q5 is connected to the negative terminal of the first battery.

[0065] Specifically, the working process of the battery equalization circuit is as follows. When the first equalization controller U3 detects that the charging of the second lithium battery is unbalanced, it can output a high-level signal through the OUT signal terminal. This high-level signal acts on the gate of the MOS transistor Q4, enabling the MOS transistor Q4 to conduct. The second battery discharges through the resistor R11, thereby keeping the second battery in an equalized state. The second equalization controller U4 performs equalization control on the first battery, and its working process is the same as that of the first equalization controller U3, which will not be repeated here.

[0066] Refer to Figure 2 , the battery equalization circuit further includes the third battery terminal protection circuit, which includes: resistor R9, resistor R10, capacitor C7, and capacitor C8. One end of the resistor R9 is connected to the positive terminal of the second battery, and the other end of the resistor R9 is connected to the positive terminal of the first equalization controller U3; one end of the resistor R10 is connected to the positive terminal of the first battery, and the other end of the resistor R10 is connected to the positive terminal of the second equalization controller U4; one end of the capacitor C7 is connected to the positive terminal of the second battery, and the other end of the capacitor C7 is respectively connected to the negative terminal of the second battery and the negative terminal of the first equalization controller U3; one end of the capacitor C8 is connected to the positive terminal of the first battery, and the other end of the capacitor C8 is respectively connected to the negative terminal of the first battery and the negative terminal of the second equalization controller U4.

[0067] Specifically, the resistors R9 and R10 can limit the current introduced to the detection terminals of the first equalization controller U3 and the second equalization controller U4, preventing large currents from damaging the first equalization controller U3 and the second equalization controller U4. The capacitors C7 and C8 can filter out high-frequency strong pulse signals, avoiding damage to the first equalization controller U3 and the second equalization controller U4.

[0068] The above are only the embodiments of the present invention, but do not limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing specific embodiments, or perform equivalent replacements on some of the technical features. Any equivalent structures directly or indirectly using the content of the specification and drawings of the present invention in other related technical fields are similarly within the scope of the patent protection of the present invention.

[0069] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0070] Although the embodiments of the present utility model have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present utility model. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present utility model without departing from the principles and purposes of the present utility model, and all are within the protection scope of the present utility model.

Claims

1. A secondary protection circuit for a battery, characterized in that, Including: A charge and discharge protection circuit for controlling the charge and discharge protection of a battery; A secondary charge protection circuit for controlling the secondary charge protection of the battery; A battery equalization circuit for controlling the voltage equalization of the battery.

2. The secondary protection circuit for a battery according to claim 1, wherein The charge and discharge protection circuit includes: A protection controller U1, the voltage detection terminals of which are respectively connected to each battery cell to detect the charge and discharge voltages of each battery cell; A charge and discharge switch disposed on the charge and discharge loop of the battery, the charge and discharge switch being connected to the charge and discharge control signal output terminal of the protection controller U1 to perform charge and discharge control under the action of the protection controller U1.

3. The secondary protection circuit for a battery according to claim 2, characterized in that, The charge and discharge switch includes: A MOS transistor Q1, the gate of which is connected to the charge control terminal of the protection controller U1, and the source of which is connected to the negative terminal of the charge and discharge interface; A MOS transistor Q2, the gate of which is connected to the discharge control terminal of the protection controller U1, the drain of which is connected to the drain of the MOS transistor Q1, and the source of which is connected to the negative terminal of the battery through the secondary charge switch of the secondary charge protection circuit.

4. The secondary protection circuit for a battery according to claim 2, wherein The charge and discharge protection circuit further includes: A current sampling resistor RS1 disposed on the charge and discharge loop of the battery, the current sampling resistor RS1 being connected to the charge and discharge protection circuit to output a current signal to the charge and discharge protection circuit, and the charge and discharge protection circuit is further configured to perform overcurrent protection control according to the current signal.

5. The secondary protection circuit for a battery according to claim 2, characterized in that, The charge and discharge protection circuit further includes: A thermistor NTC1, one end of which is connected to the reference ground, the other end of which is connected to the temperature detection terminal of the protection controller U1, the other end of which is further connected to one end of a resistor RT, and the other end of the resistor RT is connected to the voltage output terminal of the protection controller U1.

6. The secondary protection circuit for a battery according to claim 2, wherein The charge and discharge protection circuit further includes a first battery terminal protection circuit, and the first battery terminal protection circuit includes: A resistor R1, the second detection terminal of the protection controller U1 is connected to the positive terminal of the second battery cell through the resistor R1; A resistor R2, the first detection terminal of the protection controller U1 is connected to the positive terminal of the first battery cell through the resistor R2; A capacitor C1, one end of which is connected to the second detection terminal of the protection controller U1, and the other end of which is connected to the reference ground; A capacitor C2, one end of which is connected to the first detection terminal of the protection controller U1, and the other end of which is connected to the reference ground.

7. The secondary protection circuit for a battery according to claim 1, wherein The secondary charge protection circuit includes: A protection controller U2, the voltage detection terminals of which are respectively connected to each battery cell to detect the charge and discharge voltages of each battery cell; Secondary charging switch, the secondary charging switch is arranged on the charge and discharge loop of the battery, and the secondary charging switch is connected to the charging control signal output end of the protection controller U2 to perform secondary charging protection control under the action of the protection controller U2.

8. The secondary protection circuit for a battery according to claim 7, wherein The secondary charging protection circuit further includes a second battery terminal protection circuit including: Resistor R7, the first detection terminal of the protection controller U2 is connected to the positive terminal of the first battery cell through the resistor R7; Resistor R6, the second detection terminal of the protection controller U2 is connected to the positive terminal of the second battery cell through the resistor R6; Capacitor C3, one end of the capacitor C3 is connected to the second detection terminal of the protection controller U2, and the other end of the capacitor C3 is connected to the reference ground; Capacitor C4, one end of the capacitor C4 is connected to the first detection terminal of the protection controller U2, and the other end of the capacitor C4 is connected to the reference ground.

9. The secondary protection circuit for a battery according to claim 1, wherein The battery equalization circuit includes: First equalization controller U3, the input end of the first equalization controller U3 is connected to both ends of the second battery cell; Second equalization controller U4, the input end of the second equalization controller U4 is connected to both ends of the first battery cell; MOS transistor Q4, the gate of the MOS transistor Q4 is connected to the output end of the first equalization controller U3, the drain of the MOS transistor Q4 is connected to the positive terminal of the second battery cell through the resistor R11, and the source of the MOS transistor Q4 is connected to the negative terminal of the second battery cell; MOS transistor Q5, the gate of the MOS transistor Q5 is connected to the output end of the second equalization controller U4, the drain of the MOS transistor Q5 is connected to the positive terminal of the first battery cell through the resistor R12, and the source of the MOS transistor Q5 is connected to the negative terminal of the first battery cell.

10. The secondary protection circuit for a battery according to claim 9, wherein, The battery equalization circuit further includes a third battery terminal protection circuit including: Resistor R9, one end of the resistor R9 is connected to the positive terminal of the second battery cell, and the other end of the resistor R9 is connected to the positive terminal of the first equalization controller U3; Resistor R10, one end of the resistor R10 is connected to the positive terminal of the first battery cell, and the other end of the resistor R10 is connected to the positive terminal of the second equalization controller U4; Capacitor C7, one end of the capacitor C7 is connected to the positive terminal of the second battery cell, and the other end of the capacitor C7 is respectively connected to the negative terminal of the second battery cell and the negative terminal of the first equalization controller U3; Capacitor C8, one end of the capacitor C8 is connected to the positive terminal of the first battery cell, and the other end of the capacitor C8 is respectively connected to the negative terminal of the first battery cell and the negative terminal of the second equalization controller U4.

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