Battery simulation test circuit

Abstract

The utility model relates to the technical field of charging test, and discloses a battery simulation test circuit, which comprises a simulation battery unit, a monitoring unit and a discharging unit, and is characterized in that the simulation battery unit is used for being connected with a mainboard, and a charging module on the mainboard is used for charging the simulation battery unit to enter a charging test; one end of the monitoring unit is connected with the simulation battery unit, the other end of the monitoring unit is connected with the mainboard, and the monitoring unit is used for monitoring battery information when the charging module performs charging test on the simulation battery unit; and one end of the discharging unit is connected with the simulation battery unit and the mainboard, and the discharging unit is used for discharging the electric quantity of the simulation battery unit according to a control instruction which is sent by the mainboard and corresponds to the battery information. The battery simulation test circuit disclosed by the utility model not only can replace a real battery and save the test cost of using battery materials, but also can quickly discharge so as to quickly put into the next round of charging test, thereby improving the test efficiency of the charging module.

Description

Technical Field

[0001] The utility model relates to the technical field of charging test, in particular to a battery simulation test circuit. Background Art

[0002] With the continuous development of science and technology, electronic products are becoming more and more intelligent and portable, so more and more products use batteries. In order to increase the battery life, the capacity of the battery configured in the product is getting higher and higher, and safety is becoming more and more important. How to charge the battery quickly and ensure the battery life will greatly test the ability of the charging chip. The better the performance of the charging chip, the more power can be charged in the shortest time, while meeting the battery charging curve, so that the battery will not overheat or overcharge during charging, so as to ensure the battery life.

[0003] Before electronic products leave the factory, the charging module on the product needs to be fully tested. In the traditional testing method, when testing the charging module, a real battery needs to be installed on the MLB (Mother Level Board). Figure 1 As shown, the charging module on the MLB charges the battery from 2.5V to 4.4V and stops. During this period, the charging current, charging temperature, charging efficiency and other parameters are monitored. However, there are two disadvantages in using real batteries for testing: 1. The cost of real batteries is very high, and this batch of batteries cannot be shipped later; 2. Real batteries cannot be discharged quickly, that is, after the previous round of tests is completed, the battery voltage has reached 4.4V and cannot be quickly reduced to 2.5V for a new round of tests, resulting in slow test efficiency and affecting test efficiency.

[0004] Therefore, in order to solve the above problems, the utility model provides a battery simulation test circuit with low cost and high test efficiency. Utility Model Content

[0005] The utility model provides a battery simulation test circuit, aiming to solve the problems of high test cost and low test efficiency when the existing charging module performs charging test.

[0006] In order to solve the above technical problems, the utility model provides a battery simulation test circuit, which includes: a simulated battery cell, which is used to be connected to a mainboard, and a charging module on the mainboard is used to charge the simulated battery cell to enter a charging test; a monitoring unit, one end of which is connected to the simulated battery cell, and the other end is used to be connected to the mainboard, and the monitoring unit is used to monitor the battery information when the charging module performs a charging test on the simulated battery cell; a discharge unit, which is connected to the simulated battery cell and the mainboard, and the discharge unit is used to discharge the power of the simulated battery cell according to a control instruction corresponding to the battery information sent by the mainboard.

[0007] Furthermore, the monitoring unit includes a BQ27546 chip, the SCL pin and SDA pin of the BQ27546 chip are connected to the mainboard through wiring terminals, the BAT pin, REGIN pin and CE pin of the BQ27546 chip are connected to one end of the simulated battery cell, and the SRP pin and SRN pin of the BQ27546 chip are connected to the other end of the simulated battery cell.

[0008] Furthermore, the simulated battery unit includes a supercapacitor, a first connection end of the supercapacitor is connected to the BQ27546 chip, the discharge unit and the charging module, and a second connection end of the supercapacitor is connected to the BQ27546 chip and the charging module.

[0009] Furthermore, the simulated battery unit also includes an operational amplifier, a first resistor and a second resistor, the non-inverting input terminal of the operational amplifier is connected to one end of the first resistor and the second resistor, the other end of the first resistor is connected to the first connection terminal of the supercapacitor, and the other end of the second resistor is connected to the second connection terminal of the supercapacitor; the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the third connection terminal of the supercapacitor.

[0010] Furthermore, the discharge unit includes a discharge control module and a discharge module, one end of the discharge control module is connected to the mainboard, and the other end is connected to the first connection end of the discharge module, the second connection end of the discharge module is connected to the simulated battery unit, and the third connection end of the discharge module is grounded.

[0011] Furthermore, the discharge control module includes a CAT9555 chip, an SDA pin and an SCL pin of the CAT9555 chip are connected to the mainboard, and an IO pin of the CAT9555 chip is connected to the first connection end of the discharge module.

[0012] Furthermore, the discharge module includes a first MOS tube, a cement resistor, a third resistor and a fourth resistor, the gate of the first MOS tube is connected to one end of the third resistor, the other end of the third resistor is connected to the IO pin of the CAT9555 chip, the drain of the first MOS tube is connected to one end of the cement resistor, the other end of the cement resistor is connected to the simulated battery unit, and the source of the first MOS tube is grounded; one end of the fourth resistor is connected between the gate of the first MOS tube and the third resistor, and the other end is grounded.

[0013] Furthermore, it also includes a first protection module and a second protection module, one end of the first protection module is connected to the mainboard, and the other end of the first protection module is connected to the second protection module; one end of the second protection module is connected to the first connection end of the simulated battery cell and the discharge unit, and the other end of the second protection module is connected to the second connection end of the simulated battery cell.

[0014] Further, the first protection module includes a first TVS protection diode and a second TVS protection diode, one end of the first TVS protection diode and the second TVS protection diode is connected to the mainboard, and the other end of the first TVS protection diode and the second TVS protection diode is connected to the second protection module.

[0015] Furthermore, the second protection module includes an MM3511 chip, a second MOS tube and a third MOS tube, the VDD pin of the MM3511 chip is connected to the simulated battery unit and the discharge unit, the DOUT pin of the MM3511 chip is connected to the gate of the second MOS tube, the drain of the second MOS tube is connected to the second connection end of the simulated battery unit, the source of the second MOS tube is connected to the source of the third MOS tube, the gate of the third MOS tube is connected to the COUT pin of the MM3511 chip, and the drain of the third MOS tube is connected to the first protection module and the mainboard.

[0016] The battery simulation test circuit disclosed by the utility model includes a simulated battery cell, a monitoring unit and a discharge unit. The simulated battery cell and the monitoring unit can simulate a real battery for connection with the mainboard. The mainboard obtains the battery information when the charging module performs a charging test on the simulated battery cell through the monitoring unit to realize the full-process charging test of the charging module, thereby ensuring the test performance of the charging module. Moreover, the cost of the components constituting the simulated battery cell and the monitoring unit is low. The simulated battery cell and the monitoring unit replace the real battery, thereby saving the test cost of using battery materials. At the same time, after the simulated battery cell is charged, it can be quickly discharged through the discharge unit so as to quickly put into the next round of charging test, which can improve the test efficiency of the charging module and save test time. The battery simulation test circuit disclosed by the utility model solves the problems of high test cost and low test efficiency when the existing charging module performs charging test. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A charging schematic diagram of a charging module of the prior art of the utility model;

[0019] Figure 2 It is a structural block diagram of a battery simulation test circuit provided by an embodiment of the utility model;

[0020] Figure 3 It is a circuit schematic diagram of a battery simulation test circuit provided by an embodiment of the utility model;

[0021] Reference numerals:

[0022] 10. Battery simulation test circuit; 11. Simulated battery cell; 12. Monitoring unit; 13. Discharge unit; 131. Discharge control module; 132. Discharge module; 14. First protection module; 15. Second protection module. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0025] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in this utility model specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0026] It should be further understood that the term “and / or” used in the present specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0027] Figures 2 to 3 An embodiment of the battery simulation test circuit provided by the utility model is shown. The battery simulation test circuit 10 of this embodiment includes a simulated battery cell 11, a monitoring unit 12 and a discharge unit 13, wherein the simulated battery cell 11 is used to connect to the mainboard, and the charging module on the mainboard is used to charge the simulated battery cell 11 to enter the charging test; one end of the monitoring unit 12 is connected to the simulated battery cell 11, and the other end is used to connect to the mainboard, and the monitoring unit 12 is used to monitor the battery information when the charging module performs a charging test on the simulated battery cell 11; the discharge unit 13 is connected to the simulated battery cell 11 and the mainboard, and the discharge unit 13 is used to discharge the power of the simulated battery cell 11 according to the control instruction corresponding to the battery information sent by the mainboard. The battery simulation test circuit 10 of the utility model can simulate a real battery for connection with a mainboard by simulating a battery cell 11 and a monitoring unit 12. The mainboard obtains the battery information when the charging module performs a charging test on the simulated battery cell 11 through the monitoring unit 12, so as to realize a full-process charging test on the charging module, thereby ensuring the test performance of the charging module. Moreover, the cost of the components constituting the simulated battery cell 11 and the monitoring unit 12 is relatively low. The real battery is replaced by the simulated battery cell 11 and the monitoring unit 12, thereby saving the test cost. At the same time, after the simulated battery cell 11 is charged, it can be quickly discharged through the discharge unit 13 so as to quickly put into the next round of charging test, thereby improving the test efficiency of the charging module and saving the test time.

[0028] In one embodiment, such as this embodiment, Figure 3 As shown, the monitoring unit 12 includes a BQ27546 chip U1, the SCL pin and SDA pin of the BQ27546 chip U1 are connected to the mainboard (not shown) through the wiring terminal J1, the BAT pin, REGIN pin and CE pin of the BQ27546 chip U1 are connected to one end of the simulated battery unit 11, and the SRP pin and SRN pin of the BQ27546 chip U1 are connected to the other end of the simulated battery unit 11. Specifically, the SCL pin and SDA pin of the BQ27546 chip U1 are connected to the mainboard through the flexible cable on the wiring terminal J1, and the mainboard communicates with the BQ27546 chip U1 through I2C to obtain the battery information of the simulated battery unit 11, wherein the battery information includes the battery voltage, the battery power, the battery temperature, etc. More specifically, the SCL pin of the BQ27546 chip U1 is connected to the mainboard via the resistor R15 through the flexible flat cable of the terminal J1; the SDA pin of the BQ27546 chip U1 is connected to the mainboard via the resistor R16 through the flexible flat cable of the terminal J1. Among them, the resistors R15 and R16 are termination resistors, which can improve the signal quality. It should be noted that in this embodiment, the BQ27546 chip U1 is a single-cell lithium-ion battery power monitor for battery pack integration, which is a microcontroller peripheral that can provide power monitoring for a single-cell lithium-ion battery pack and can achieve accurate battery power monitoring.

[0029] Furthermore, the monitoring unit 12 further includes a resistor R12 and a resistor R13, wherein one end of the resistor R12 is connected to the input voltage VCC, and the other end is connected to the resistor R16; one end of the resistor R13 is connected to the input voltage VCC, and the other end is connected to the resistor R15. The resistor R12 and the resistor R13 can provide a pull-up level for the I2C.

[0030] Furthermore, the simulated battery unit 11 includes a supercapacitor EC1 (i.e. Figure 3 The first connection end of the supercapacitor EC1 is connected to the BQ27546 chip U1, the discharge unit 13 and the charging module, and the second connection end of the supercapacitor EC1 is connected to the BQ27546 chip U1 and the charging module. Specifically, the first connection end of the supercapacitor EC1 is connected to the BAT pin, REGIN pin and CE pin of the BQ27546 chip U1, and the second connection end of the supercapacitor EC1 is connected to the SRP pin and SRN pin of the BQ27546 chip U1. It should be noted that in this embodiment, a supercapacitor is configured on the periphery of the BQ27546 chip U1 to simulate a real battery.

[0031] Furthermore, the simulated battery unit 11 also includes an operational amplifier U3, a first resistor R10 and a second resistor R17, the in-phase input terminal of the operational amplifier U3 is connected to one end of the first resistor R10 and the second resistor R17, the other end of the first resistor R10 is connected to the first connection end of the super capacitor EC1, and the other end of the second resistor R17 is connected to the second connection end of the super capacitor EC1; the inverting input terminal of the operational amplifier U3 is connected to the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 is connected to the third connection terminal of the super capacitor EC1. It should be noted that in this embodiment, the third connection terminal of the super capacitor EC1 is between the first connection terminal and the second connection terminal.

[0032] In one embodiment, such as this embodiment, Figure 3 As shown, the discharge unit 13 includes a discharge control module 131 and a discharge module 132. One end of the discharge control module 131 is connected to the main board, and the other end is connected to the first connection end of the discharge module 132. The second connection end of the discharge module 132 is connected to the simulated battery unit 11, and the third connection end of the discharge module 132 is grounded. Specifically, the discharge control module 131 includes a CAT9555 chip U2. The SDA pin and the SCL pin of the CAT9555 chip U2 are connected to the main board through the wiring terminal J1, and the IO pin of the CAT9555 chip U2 is connected to the first connection end of the discharge module 132.

[0033] Further, the discharge module 132 includes a first MOS tube Q1, a cement resistor R1, a third resistor R2 and a fourth resistor R3, the gate of the first MOS tube Q1 is connected to one end of the third resistor R2, the other end of the third resistor R2 is connected to the IO pin of the CAT9555 chip U2, the drain of the first MOS tube Q1 is connected to one end of the cement resistor R1, the other end of the cement resistor R1 is connected to the simulated battery unit 11, and the source of the first MOS tube Q1 is grounded; one end of the fourth resistor R3 is connected between the gate of the first MOS tube Q1 and the third resistor R2, and the other end is grounded. It should be noted that in this embodiment, the first MOS tube Q1 is an NMOS tube.

[0034] In one embodiment, such as this embodiment, Figure 3As shown, the battery simulation test circuit 10 also includes a first protection module 14 and a second protection module 15, one end of the first protection module 14 is connected to the mainboard, and the other end of the first protection module 14 is connected to the second protection module 15; one end of the second protection module 15 is connected to the first connection end of the simulated battery unit 11 and the discharge unit 13, and the other end of the second protection module 15 is connected to the second connection end of the simulated battery unit 11. Specifically, the first protection module 14 includes a first TVS protection diode DZ1 and a second TVS protection diode DZ2, one end of the first TVS protection diode DZ1 and the second TVS protection diode DZ2 are connected to the mainboard, and the other end of the first TVS protection diode DZ1 and the second TVS protection diode DZ2 are connected to the second protection module 15. In this embodiment, the first protection module 14 includes the first TVS protection diode DZ1 and the second TVS protection diode DZ2 to prevent the impact high voltage of the terminal J1 from entering the battery simulation test circuit 10 when plugging and unplugging it from the mainboard.

[0035] Furthermore, in this embodiment, if Figure 3 As shown, the second protection module 15 includes an MM3511 chip U4, a second MOS tube Q2A and a third MOS tube Q2B, the VDD pin of the MM3511 chip U4 is connected to the simulated battery unit 11 and the discharge unit 13, the DOUT pin of the MM3511 chip U4 is connected to the gate of the second MOS tube Q2A, the drain of the second MOS tube Q2A is connected to the second connection end of the simulated battery unit 11, the source of the second MOS tube Q2A is connected to the source of the third MOS tube Q2B, the gate of the third MOS tube Q2B is connected to the COUT pin of the MM3511 chip U4, and the drain of the third MOS tube Q2B is connected to the first protection module 14 and the mainboard. Specifically, the MM3511 chip U4 is a lithium-ion / lithium polymer rechargeable battery protection IC that can prevent overcharging and over-discharging. Its control logic is: when the battery voltage (i.e., the voltage of the simulated battery cell 11) is as high as 4.3V, the COUT pin changes from high to low, the third MOS tube Q2B stops conducting, the charging circuit of the simulated battery cell 11 is interrupted, and charging stops; when the battery voltage is as low as 2.5V, the DOUT pin changes from high to low, the second MOS tube Q2A stops conducting, the discharge circuit of the discharge unit 13 is interrupted, and discharging stops.

[0036] For ease of understanding, the implementation process of the charging module performing a charging test on the battery simulation test circuit 10 of the utility model is described as follows:

[0037] First, the battery simulation test circuit 10 is connected to the mainboard through the terminal J1. At this time, the battery simulation test circuit 10 simulates a real battery. When the mainboard is plugged into the type PC-C charging head and turned on, the mainboard will read the current battery information of the supercapacitor EC1 in the battery simulation test circuit 10 through I2C, including battery voltage, battery power, battery temperature, etc. Since the first connection is the first test, there is no power in the supercapacitor EC1, which is equivalent to a deadbattery (empty battery). The Charger IC (i.e., charging module) of the mainboard will automatically charge the supercapacitor EC1. The charging will go through four different modes, trickle charging, constant current charging, constant voltage charging, and stop charging. During the charging process, the Charger IC will automatically monitor and record parameters such as charging current, charging voltage, charging efficiency, and charging temperature to ensure that the various parameters of the Charger IC meet the design requirements. If a parameter fail is found during the test, the test interface will fail and interrupt the test. At this time, the tester will take away the defective product and analyze it.

[0038] When the Charger IC test of one motherboard is completed, the Charger IC test of the next motherboard will be carried out. Since the supercapacitor EC1 is fully charged in the previous round of testing, the motherboard will send a command to the CAT9555 chip U2 after detecting that the voltage of the supercapacitor EC1 is too high. The CAT9555 chip U2 will output a high level to turn on the first MOS tube Q1. At this time, the supercapacitor EC1 will discharge through the cement resistor R1, and the voltage of the supercapacitor EC1 will continue to decrease. When the motherboard detects that the voltage is lower than 2.5V, it will send a command to let the CAT9555 chip U2 output a low level to turn off the first MOS tube Q1, and the cement resistor R1 will no longer discharge, and then a new round of testing will begin. The test process is the same as the previous round of testing process mentioned above.

[0039] In summary, in the Charger IC test, the battery simulation test circuit 10 can replace the real battery for testing, saving the battery material cost; and the charging test process of the battery simulation test circuit 10 is no different from the original process, and the full process test of the battery can be realized, ensuring the charging test performance of the Charger IC; at the same time, the battery simulation test circuit 10 has its own discharge function, and there is no need to wait too long between the previous round of testing and the next round of testing, so that the battery simulation test circuit 10 can quickly enter the next round of test preparation state, which greatly reduces the test time and improves the test efficiency.

[0040] The battery simulation test circuit provided by the utility model includes a simulated battery cell, a monitoring unit and a discharge unit. The simulated battery cell and the monitoring unit can simulate a real battery for connection with the mainboard. The mainboard obtains the battery information when the charging module performs a charging test on the simulated battery cell through the monitoring unit to realize the full-process charging test of the charging module, thereby ensuring the test performance of the charging module. Moreover, the cost of the components constituting the simulated battery cell and the monitoring unit is low. The simulated battery cell and the monitoring unit replace the real battery, thereby saving the test cost of using battery materials. At the same time, after the simulated battery cell is charged, it can be quickly discharged through the discharge unit so as to quickly put into the next round of charging test, which can improve the test efficiency of the charging module and save test time. The battery simulation test circuit disclosed by the utility model solves the problems of high test cost and low test efficiency when the existing charging module performs charging test.

[0041] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A battery simulation test circuit, characterized in that: include: A simulated battery unit, which is used to be connected to the mainboard, and a charging module on the mainboard is used to charge the simulated battery unit to enter a charging test; A monitoring unit, one end of which is connected to the simulated battery unit and the other end of which is used to be connected to the mainboard, and the monitoring unit is used to monitor the battery information when the charging module performs a charging test on the simulated battery unit; A discharge unit is connected to the simulated battery unit and the main board, and is used to discharge the power of the simulated battery unit according to a control instruction corresponding to the battery information sent by the main board.

2. The battery simulation test circuit according to claim 1, characterized in that: The monitoring unit includes a BQ27546 chip, the SCL pin and SDA pin of the BQ27546 chip are connected to the mainboard through wiring terminals, the BAT pin, REGIN pin and CE pin of the BQ27546 chip are connected to one end of the simulated battery cell, and the SRP pin and SRN pin of the BQ27546 chip are connected to the other end of the simulated battery cell.

3. The battery simulation test circuit according to claim 2, characterized in that: The simulated battery unit includes a super capacitor, a first connection end of the super capacitor is connected to the BQ27546 chip, the discharge unit and the charging module, and a second connection end of the super capacitor is connected to the BQ27546 chip and the charging module.

4. The battery simulation test circuit according to claim 3, characterized in that: The simulated battery unit also includes an operational amplifier, a first resistor and a second resistor, the non-inverting input terminal of the operational amplifier is connected to one end of the first resistor and the second resistor, the other end of the first resistor is connected to the first connection terminal of the supercapacitor, and the other end of the second resistor is connected to the second connection terminal of the supercapacitor; the inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the third connection terminal of the supercapacitor.

5. The battery simulation test circuit according to claim 1, characterized in that: The discharge unit includes a discharge control module and a discharge module, one end of the discharge control module is connected to the mainboard, and the other end is connected to the first connection end of the discharge module, the second connection end of the discharge module is connected to the simulated battery unit, and the third connection end of the discharge module is grounded.

6. The battery simulation test circuit according to claim 5, characterized in that: The discharge control module comprises a CAT9555 chip, an SDA pin and an SCL pin of the CAT9555 chip are connected to the mainboard, and an IO pin of the CAT9555 chip is connected to the first connection end of the discharge module.

7. The battery simulation test circuit according to claim 6, characterized in that: The discharge module includes a first MOS tube, a cement resistor, a third resistor and a fourth resistor, the gate of the first MOS tube is connected to one end of the third resistor, the other end of the third resistor is connected to the IO pin of the CAT9555 chip, the drain of the first MOS tube is connected to one end of the cement resistor, the other end of the cement resistor is connected to the simulated battery unit, and the source of the first MOS tube is grounded; One end of the fourth resistor is connected between the gate of the first MOS tube and the third resistor, and the other end is grounded.

8. The battery simulation test circuit according to claim 1, characterized in that: It also includes a first protection module and a second protection module, one end of the first protection module is connected to the mainboard, and the other end of the first protection module is connected to the second protection module; one end of the second protection module is connected to the first connection end of the simulated battery cell and the discharge unit, and the other end of the second protection module is connected to the second connection end of the simulated battery cell.

9. The battery simulation test circuit according to claim 8, characterized in that: The first protection module includes a first TVS protection diode and a second TVS protection diode, one end of the first TVS protection diode and the second TVS protection diode is connected to the mainboard, and the other end of the first TVS protection diode and the second TVS protection diode is connected to the second protection module.

10. The battery simulation test circuit according to claim 8, characterized in that: The second protection module includes an MM3511 chip, a second MOS tube and a third MOS tube. The VDD pin of the MM3511 chip is connected to the simulated battery unit and the discharge unit, the DOUT pin of the MM3511 chip is connected to the gate of the second MOS tube, the drain of the second MOS tube is connected to the second connection end of the simulated battery unit, the source of the second MOS tube is connected to the source of the third MOS tube, the gate of the third MOS tube is connected to the COUT pin of the MM3511 chip, and the drain of the third MOS tube is connected to the first protection module and the mainboard.

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