Charging protection circuit of battery system

Abstract

The invention provides a charging protection circuit of a battery system, the battery system comprises a battery and a charging power switch, and the charging protection circuit comprises a first driving transistor coupled between a positive electrode of the battery and a driving output end; the second driving transistor is coupled between the driving output end and a negative electrode output end; the first resistor is coupled between the driving output end and the negative electrode output end, the driving output end is coupled with the control end of the charging power switch, and the control end of the first driving transistor and the control end of the second driving transistor receive a pre-charging control signal. When the voltage of the battery is lower than a preset charging forbidding voltage threshold value, the voltage difference between the pre-charging control signal and the positive electrode of the battery cannot drive the first driving transistor to be switched on, and the first resistor pulls down the voltage of the driving output end, so that the charging power switch is switched off, and charging is forbidden. Therefore, the function of prohibiting charging when the voltage of the battery is too low can be realized through a simple circuit, and the cost is reduced.

Description

[Technical field]

[0001] The invention relates to the field of circuit design, and in particular to a charging protection circuit for a battery system. [Background technology]

[0002] Figure 1 The present invention is a circuit diagram of a battery protection circuit of a battery system in the prior art. The battery system includes a battery BAT1, a battery protection circuit, a discharge power switch MND and a charging power switch MNC connected in series between the negative electrode B- and the negative electrode output terminal P- of the battery. The positive electrode output terminal P+ is coupled to the positive electrode B+ of the battery. The battery protection circuit includes a charging protection circuit and a discharging protection circuit. The discharge power switch MND and the charging power switch MNC are both NMOS transistors. The source and substrate of the charging power switch MNC are coupled to the negative electrode output terminal P-, the gate of the charging power switch MNC is coupled to the charging drive output terminal CO of the battery protection circuit, and the drain of the charging power switch MNC is coupled to the drain of the discharge power switch MND. The source and substrate of the discharge power switch MND are coupled to the negative electrode B- of the battery, and the gate of the discharge power switch MND is coupled to the discharge drive output terminal DO of the battery protection circuit. When charging protection is required, such as charging overvoltage or charging overcurrent, the battery protection circuit outputs a low-level signal through the charging drive output terminal CO, so that the charging power switch MNC is turned off to prohibit charging. When charging protection is not required, the battery protection circuit outputs a high-level signal through the charging drive output terminal CO, so that the charging power switch MNC is turned on to allow charging. When discharge protection is required, such as discharge overvoltage or discharge overcurrent, the battery protection circuit outputs a low-level signal through the discharge drive output terminal DO, so that the discharge power switch MND is turned off to prohibit discharging. When discharge protection is not required, the battery protection circuit outputs a high-level signal through the discharge drive output terminal DO, so that the charging power switch MND is turned on to allow discharging. The battery is sometimes also referred to as a battery cell.

[0003] Some battery protection circuits have a 0V charging prohibition protection function, that is, when the voltage of the protected battery is lower than a certain threshold (such as close to 0V), the battery protection circuit controls the charging power switch MNC to enter the cut-off state, prohibiting the battery from charging. The industry generally calls this threshold the 0V charging prohibition voltage threshold. Although it is called the 0V charging prohibition voltage threshold, the charging prohibition voltage threshold may not be 0V, but may be higher than 0V.

[0004] Figure 2 FIG. 1 shows a partial circuit diagram of a charging protection circuit with a protection function of prohibiting charging at 0V. Figure 2As shown, the charging protection circuit includes a first driving transistor MP2, a second driving transistor MN2, a first PMOS transistor MP1, a first NMOS transistor NM1, a NOR gate NOR, and a cell voltage detection module (under voltage detector).

[0005] B+ / B- are the positive and negative poles of the battery respectively, NOR is a NOR gate, C_CTRL is a charging control signal with a swing of B+ / B-, and C_CTRL is generated by the charging protection circuit according to the charging situation. NO_CHG is a charging prohibition signal output by the battery cell voltage detection module, and C_PRE is a pre-charging control signal, which is a digital signal after C_CTRL and NO_CHG are logically NORed. When the battery cell voltage detection module detects that the B+ / B- voltage is lower than the 0V charging prohibition voltage threshold Vzv_inh, NO_CHG is controlled to output the B+ potential, and C_PRE is B+, MP2 is cut off, and when VM is connected to a charger, the VM potential is lower than B-, MN2 is turned on, and the potential of the charging drive output terminal CO of the gate of the charging power switch MNC is pulled down to VM, realizing the 0V charging prohibition function, and the VM terminal is coupled to the negative output terminal P-. The existing method requires an additional battery cell voltage detection module, which increases the chip production cost.

[0006] Therefore, it is necessary to propose an improved technical solution to overcome the above problems. [Summary of the invention]

[0007] One of the purposes of the present invention is to provide a charging protection circuit for a battery system, which can realize the function of prohibiting charging when the voltage of the battery is too low through a simple circuit, thereby reducing the cost.

[0008] According to one aspect of the present invention, the present invention provides a charging protection circuit of a battery system, the battery system comprising a battery and a charging power switch, comprising: a first driving transistor coupled between the positive electrode and the driving output end of the battery; a second driving transistor coupled between the driving output end and the negative electrode output end, wherein the driving output end is coupled to the control end of the charging power switch, and the control end of the first driving transistor and the control end of the second driving transistor receive a pre-charging control signal; a first resistor coupled between the driving output end and the negative electrode output end, wherein when the voltage of the battery is lower than a predetermined charging prohibition voltage threshold, the voltage difference between the pre-charging control signal and the positive electrode of the battery cannot drive the first driving transistor to turn on, and the first resistor pulls down the voltage of the driving output end, thereby turning off the charging power switch.

[0009] Furthermore, when the first driving transistor is turned on and the second driving transistor is turned off, the driving output end outputs the charging driving signal to drive the charging power switch to turn on to allow charging; when the first driving transistor is turned off and the second driving transistor is turned on, the driving output end outputs the charging driving signal to turn off the charging power switch to prohibit charging.

[0010] Furthermore, the high level of the pre-charging control signal is the voltage of the positive electrode of the battery, and the low level of the pre-charging control signal is the voltage of the negative electrode of the battery or a predetermined voltage value. When the voltage of the battery is higher than a predetermined charging prohibition voltage threshold, if the pre-charging control signal is at a high level, the first driving transistor is controlled to be cut off and the second driving transistor is turned on; if the pre-charging control signal is at a low level, the first driving transistor is controlled to be turned on and the second driving transistor is cut off; when the voltage of the battery is lower than the predetermined charging prohibition voltage threshold, if the pre-charging control signal is at a low level, the second driving transistor is controlled to be cut off, but at this time the pre-charging control signal cannot control the first driving transistor to be turned on, and the first resistor pulls down the voltage of the driving output terminal, thereby turning off the charging power switch.

[0011] Compared with the prior art, the present invention does not require an additional battery cell voltage detection module, but only requires a first resistor to be set between the drive output terminal and the negative electrode output terminal. When the voltage of the battery (i.e., the voltage difference between the positive electrode and the negative electrode) is lower than a predetermined charging prohibition voltage threshold, the voltage difference between the pre-charge control signal and the positive electrode of the battery cannot drive the first drive transistor to turn on, and the first resistor pulls down the voltage of the drive output terminal, thereby turning off the charging power switch and prohibiting charging.

Brief Description of the Drawings

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0013] Figure 1 A circuit diagram of a battery protection circuit of a battery system in the prior art;

[0014] Figure 2 A partial circuit diagram of a charging protection circuit with a protection function of prohibiting charging at 0V in the prior art is shown;

[0015] Figure 3 It is a partial circuit diagram of a charging protection circuit with a protection function of prohibiting charging according to the present invention in a first embodiment;

[0016] Figure 4 It is a partial circuit diagram of a charging protection circuit with a protection function of prohibiting charging according to the second embodiment of the present invention;

[0017] Figure 5 for Figure 4 Several examples of virtual ground circuits in . [Specific implementation method]

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0020] The present invention provides a charging protection circuit for a battery system, which can realize the function of prohibiting charging when the voltage of the battery is too low through a simple circuit, thereby reducing the cost.

[0021] Figure 3 FIG. 1 is a partial circuit diagram of a charging protection circuit of a battery protection system with a protection function of prohibiting charging according to the present invention in a first embodiment.

[0022] like Figure 1As shown, the battery system includes a battery, a battery protection circuit, a charging power switch MNC and a discharging power switch MND connected in series between the negative electrode B- and the negative electrode output terminal P- of the battery. The positive electrode output terminal P+ is coupled to the positive electrode B+ of the battery. The battery protection circuit includes a charging protection circuit and a discharging protection circuit. The discharging power switch MND and the charging power switch MNC are both NMOS transistors. The source and substrate of the charging power switch MNC are coupled to the negative electrode output terminal P-, the gate of the charging power switch MNC is coupled to the charging drive output terminal CO of the battery protection circuit, and the drain of the charging power switch MNC is coupled to the drain of the discharging power switch MND. The source and substrate of the discharging power switch MND are coupled to the negative electrode B- of the battery, and the gate of the discharging power switch MND is coupled to the discharging drive output terminal DO of the battery protection circuit. When charging protection is required, such as charging overvoltage or charging overcurrent, the battery protection circuit outputs a low-level signal through the charging drive output terminal CO, so that the charging power switch MNC is turned off to prohibit charging. When charging protection is not required, the battery protection circuit outputs a high-level signal through the charging drive output terminal CO, so that the charging power switch MNC is turned on to allow charging. When discharge protection is required, such as discharge overvoltage or discharge overcurrent, the battery protection circuit outputs a low-level signal through the discharge drive output terminal DO, so that the discharge power switch MND is turned off to prohibit discharge. When discharge protection is not required, the battery protection circuit outputs a high-level signal through the discharge drive output terminal DO, so that the charging power switch MND is turned on to allow discharge. The VM terminal is coupled to the negative output terminal P-.

[0023] like Figure 3As shown, the charging protection circuit includes a first driving transistor MP2 coupled between the positive electrode B+ of the battery and the driving output terminal CO; a second driving transistor MN2 coupled between the driving output terminal CO and the negative electrode output terminal P- (the VM terminal is coupled to the negative electrode output terminal P-); and a first resistor R1 coupled between the driving output terminal CO and the negative electrode output terminal P-. The driving output terminal CO is coupled to the control terminal of the charging power switch MNC, and the control terminal of the first driving transistor MP2 and the control terminal of the second driving transistor MN2 receive a pre-charging control signal C_PRE. When the voltage of the battery is lower than a predetermined charging prohibition voltage threshold, the voltage difference between the pre-charging control signal C_PRE and the positive electrode B+ of the battery cannot drive the first driving transistor MP2 to turn on, and the first resistor R1 pulls down the voltage of the driving output terminal CO to the voltage of the negative electrode output terminal P-, so that the charging power switch MNC is turned off, realizing the function of prohibiting charging when the voltage of the battery is lower than the predetermined charging prohibition voltage threshold. This function is the 0V charging prohibition function mentioned in the background. It should be noted here that the predetermined charging prohibition voltage threshold may not be 0V, for example, it may be a value close to 0V, or other values ​​higher than 0V.

[0024] Specifically, in one embodiment, Figure 3 As shown, the first driving transistor is a PMOS (positive channel Metal Oxide Semiconductor) transistor MP2, the source and substrate of the PMOS transistor MP2 are coupled to the positive electrode of the battery, the source of the PMOS transistor MP2 is coupled to the driving output terminal CO (hereinafter referred to as the charging driving output terminal CO), and the gate of the PMOS transistor MP2 serves as the control terminal. The second driving transistor is an NMOS (negative channel Metal Oxide Semiconductor) transistor MN2, the source and substrate of the NMOS transistor MN2 are coupled to the negative output terminal, and the gate of the NMOS transistor MN2 serves as the control terminal.

[0025] Specifically, Figure 3 As shown, the high level of the pre-charge control signal C_PRE is the voltage of the positive electrode B+ of the battery, and the low level of the pre-charge control signal C_PRE is the voltage of the negative electrode B- of the battery. In this embodiment, the predetermined charging prohibition voltage threshold is the conduction threshold |Vth| of the first driving transistor MP2.

[0026] When the voltage of the battery is higher than the predetermined charging prohibition voltage threshold, if the pre-charge control signal C_PRE is at a high level, the first drive transistor MP2 is controlled to be turned off and the second drive transistor MN2 is turned on, and the potential of the charge drive signal output by the drive output terminal CO is equal to the potential of the negative electrode output terminal P-, so that the charging power switch MNC can be turned off to prohibit charging. If the pre-charge control signal C_PRE is at a low level, at this time, the difference between the voltage of the negative electrode B- of the battery and the voltage of the positive electrode B+ of the battery is greater than the conduction threshold of the first drive transistor MP2, at this time, the first drive transistor MP2 can be driven to be turned on, and the second drive transistor MN2 is turned off, and the potential of the charge drive signal output by the drive output terminal CO is equal to the potential of the positive electrode B+ of the battery, so that the charging power switch MNC can be turned on to allow charging. When the first drive transistor MP2 is turned on, the resistor R1 has no ability to pull down the potential of the charge drive signal. In order to reduce power consumption during normal operation, the first resistor R1 is usually set to a larger resistance value to reduce the current flowing through the first resistor R1.

[0027] When the voltage of the battery is lower than the predetermined charging prohibition voltage threshold, that is, the voltage of the battery is lower than the conduction threshold |Vth| of the first driving transistor MP2, if the pre-charging control signal is at a low level (the voltage of the negative electrode B- of the battery), the second driving transistor MN2 is controlled to be turned off, but at this time, since the difference between the voltage of the negative electrode B- of the battery and the voltage of the positive electrode B+ of the battery is less than the conduction threshold of the first driving transistor MP2, the pre-charging control signal C_PRE cannot control the first driving transistor MP2 to be turned on, and at this time, the first resistor R1 pulls down the voltage of the driving output terminal to the voltage of the negative electrode output terminal P-, so that the charging power switch MNC is turned off, realizing the function of prohibiting charging when the voltage of the battery is lower than the predetermined charging prohibition voltage threshold. At this time, if the pre-charging control signal is at a high level, the first driving transistor MP2 is turned off, regardless of whether the second driving transistor MN2 is turned on at this time, the first resistor R1 can pull down the voltage of the driving output terminal to the voltage of the negative electrode output terminal P-, so that the charging power switch MNC is turned off. When connected to a charger, the voltage of the negative output terminal P- will be lower than the voltage of the negative electrode B- of the battery. Therefore, when the voltage of the battery is lower than a predetermined charging prohibition voltage threshold, if the pre-charging control signal is at a high level, the second drive transistor MN2 will be turned on, and the voltage of the drive output terminal will also be reduced to the voltage of the negative output terminal P-, and the charging power switch MNC will be turned off.

[0028] like Figure 3 As shown, the charging protection circuit also includes:

[0029] A first PMOS transistor MP1, a source and a substrate of which are coupled to the positive electrode of the battery, and a gate of which receives a charging control signal C_CTRL;

[0030] The first NMOS transistor NM1 has a source coupled to the negative electrode of the battery, a substrate coupled to the negative electrode of the battery, a drain coupled to the drain of the first PMOS transistor MP1, and a gate receiving the charging control signal C_CTRL. The middle node between the first NMOS transistor NM1 and the first PMOS transistor MP1 outputs the pre-charging control signal C_PRE.

[0031] The high level of the charging control signal C_CTRL is the voltage of the positive electrode B+ of the battery, and the low level of the charging control signal C_CTRL is the voltage of the negative electrode B- of the battery. The charging control signal C_CTRL is a control signal generated by the charging protection circuit as needed to determine whether charging is required. When the charging control signal C_CTRL is at a high level, the first PMOS transistor MP1 is turned off, the first NMOS transistor NM1 is turned on, and the pre-charging control signal C_PRE is at a low level. When the charging control signal C_CTRL is at a low level, the first PMOS transistor MP1 is turned on, the first NMOS transistor NM1 is turned off, and the pre-charging control signal C_PRE is at a high level.

[0032] Figure 4 FIG. 1 is a partial circuit diagram of a charging protection circuit with a protection function of prohibiting charging in a second embodiment of the present invention. Figure 4 The charging protection circuit in Figure 3 The difference between the charging protection circuit in is: Figure 3 The low level of the precharge control signal C_PRE is the voltage of the negative electrode B- of the battery, and Figure 4 The low level of the pre-charge control signal C_PRE in is a predetermined voltage value VG, and the virtual ground circuit 410 coupled between the positive electrode B+ and the negative electrode B- of the battery provides the predetermined voltage value VG. In this embodiment, the voltage difference between B+ and B- must exceed VG+|Vth|, and the first driving transistor MP2 will be turned on to pull up the potential of the charging driving signal CO. That is, in this embodiment, the predetermined forbidden charging voltage threshold is the conduction threshold |Vth|+VG of the first driving transistor MP2, that is, the predetermined forbidden charging voltage threshold is the conduction threshold of the first driving transistor MP2 and the predetermined voltage value. The predetermined forbidden charging voltage threshold can be adjusted by adjusting the predetermined voltage value VG.

[0033] like Figure 4As shown, the substrate of the first NMOS transistor NM1 is coupled to the negative electrode B- of the battery. In other alternative embodiments, if the first NMOS transistor NM1 is an isolated NMOS transistor, its substrate can also be directly connected to the voltage supply terminal VG of the virtual ground circuit 410.

[0034] Figure 5 for Figure 4 Five examples of virtual ground circuit 410 in FIG. Figure 5 As shown, the virtual ground circuit includes a current bias circuit ibias and a voltage generating circuit 411. The voltage generating circuit 411 is coupled between the voltage supply terminal VG of the virtual ground circuit and the negative electrode B- of the battery. The current bias circuit ibias is coupled between the positive electrode B+ of the battery and the voltage supply terminal VG of the virtual ground circuit and provides a bias current to the voltage generating circuit 411. The voltage generating circuit 411 forms the predetermined voltage value at the voltage supply terminal VG based on the bias current.

[0035] In Example 1, the voltage generating circuit is an NMOS transistor MN3. The gate and drain of the NMOS transistor MN3 are coupled to each other to serve as the voltage supply terminal VG, and the substrate and source of the NMOS transistor MN3 are coupled to the negative electrode of the battery.

[0036] In Example 2, the voltage generating circuit is a PMOS transistor MP3, the gate and drain of the PMOS transistor MP3 are coupled to the negative electrode of the battery, and the substrate and source of the PMOS transistor MP3 are coupled to each other to serve as the voltage supply terminal VG.

[0037] In Example 3, the voltage generating circuit is a PMOS transistor MP3, the gate and drain of the PMOS transistor MP3 are coupled to the negative electrode of the battery, the source of the PMOS transistor MP3 serves as the voltage supply terminal VG, and the substrate of the PMOS transistor MP3 is coupled to the positive electrode of the battery.

[0038] In Example 4, the voltage generating circuit is a diode D1, the anode of the diode D1 is the voltage providing terminal VG, and the cathode of the diode D1 is coupled to the negative electrode of the battery.

[0039] In Example 5, the voltage generating circuit is a resistor R2, and the resistor R2 is coupled between the voltage providing terminal VG and the negative electrode of the battery.

[0040] In the present invention, words such as "connect", "connected", "connect", "connected", "coupled", etc., which indicate electrical connection, indicate direct or indirect electrical connection unless otherwise specified. The direct electrical connection indicates a direct connection between two or more objects without any intervening objects, and the indirect electrical connection indicates a connection between two or more objects with one or more objects (such as electrical components or electrical units such as resistors, capacitors, inductors, switches, filters, etc.) intervening.

[0041] It should be noted that any changes made by those skilled in the art to the specific embodiments of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the above specific embodiments.

Claims

1. A charging protection circuit of a battery system, the battery system comprising a battery and a charging power switch, characterized in that: It includes: a first driving transistor coupled between the positive electrode of the battery and the driving output terminal; a second driving transistor coupled between the driving output terminal and the negative output terminal, wherein the driving output terminal is coupled to the control terminal of the charging power switch, and the control terminal of the first driving transistor and the control terminal of the second driving transistor receive a pre-charging control signal; A first resistor is coupled between the driving output terminal and the negative output terminal, wherein when the voltage of the battery is lower than a predetermined charging prohibition voltage threshold, the voltage difference between the pre-charging control signal and the positive electrode of the battery cannot drive the first driving transistor to turn on, and the first resistor pulls down the voltage of the driving output terminal, thereby turning off the charging power switch.

2. The charging protection circuit according to claim 1, characterized in that: When the first driving transistor is turned on and the second driving transistor is turned off, the driving output end outputs the charging driving signal to drive the charging power switch to turn on to allow charging. When the first driving transistor is turned off and the second driving transistor is turned on, the driving output end outputs the charging driving signal to turn off the charging power switch to prohibit charging.

3. The charging protection circuit according to claim 2, characterized in that: The high level of the pre-charge control signal is the voltage of the positive electrode of the battery, and the low level of the pre-charge control signal is the voltage of the negative electrode of the battery or a predetermined voltage value. When the voltage of the battery is higher than a predetermined charging prohibition voltage threshold, if the pre-charging control signal is at a high level, the first driving transistor is controlled to be turned off and the second driving transistor is controlled to be turned on; if the pre-charging control signal is at a low level, the first driving transistor is controlled to be turned on and the second driving transistor is controlled to be turned off; When the voltage of the battery is lower than a predetermined charging prohibition voltage threshold, if the pre-charging control signal is at a low level, the second driving transistor is controlled to be cut off, but at this time the pre-charging control signal cannot control the first driving transistor to be turned on, and the first resistor pulls down the voltage of the driving output terminal, thereby turning off the charging power switch. If the pre-charging control signal is at a high level, the first driving transistor is cut off, and the first resistor will also pull down the voltage of the driving output terminal.

4. The charging protection circuit according to claim 3, characterized in that: It also includes: A first PMOS transistor MP1, a source of which is coupled to the positive electrode of the battery, and a gate of which receives a charging control signal; A first NMOS transistor NM1, whose source is coupled to the negative electrode of the battery or the predetermined voltage value, whose drain is coupled to the drain of the first PMOS transistor MP1, whose gate receives the charging control signal, and an intermediate node between the first NMOS transistor NM1 and the first PMOS transistor MP1 outputs the pre-charging control signal, The high level of the charging control signal is the voltage of the positive electrode of the battery, and the low level of the charging control signal is the voltage of the negative electrode of the battery. When the charging control signal is at a high level, the first PMOS transistor MP1 is turned off, the first NMOS transistor NM1 is turned on, and the pre-charging control signal is at a low level. When the charging control signal is at a low level, the first PMOS transistor MP1 is turned on, the first NMOS transistor NM1 is turned off, and the pre-charging control signal is at a high level.

5. The charging protection circuit according to claim 3, characterized in that: It also includes: a virtual ground circuit coupled between the positive electrode and the negative electrode of the battery, the virtual ground circuit being used to provide the predetermined voltage value so that the low level of the pre-charge control signal is the predetermined voltage value, The predetermined charging prohibition voltage threshold is the sum of the conduction threshold of the first driving transistor and the predetermined voltage value.

6. The charging protection circuit according to claim 5, characterized in that: The virtual ground circuit includes a current bias circuit and a voltage generating circuit. The voltage generating circuit is coupled between the voltage supply terminal VG and the negative electrode of the battery. The current bias circuit is coupled between the positive electrode of the battery and the voltage supply terminal VG of the virtual ground circuit and provides a bias current to the voltage generating circuit. The voltage generating circuit forms the predetermined voltage value at the voltage supply terminal VG based on the bias current.

7. The charging protection circuit according to claim 6, characterized in that: The voltage generating circuit includes a diode D1, a resistor R2, an NMOS transistor MN3 or a PMOS transistor MP3, The gate and drain of the NMOS transistor MN3 are coupled to each other to serve as the voltage supply terminal VG, and the substrate and source of the NMOS transistor MN3 are coupled to the negative electrode of the battery; The gate and drain of the PMOS transistor MP3 are coupled to the negative electrode of the battery, and the substrate and source of the PMOS transistor MP3 are coupled to each other to serve as the voltage supply terminal VG, or the source of the PMOS transistor MP3 serves as the voltage supply terminal VG, and the substrate of the PMOS transistor MP3 is coupled to the positive electrode of the battery.

8. The charging protection circuit according to claim 1, characterized in that: The first driving transistor is a PMOS transistor MP2, the source of the PMOS transistor MP2 is coupled to the positive electrode of the battery, the source of the PMOS transistor MP2 is coupled to the driving output terminal, and the gate of the PMOS transistor MP2 serves as the control terminal. The second driving transistor is an NMOS transistor MN2, the source of the NMOS transistor MN2 is coupled to the negative output terminal, and the gate of the NMOS transistor MN2 serves as a control terminal. The charging power switch is coupled between the negative electrode of the battery and the negative electrode output terminal. The charging power switch is an NMOS transistor MNC. The source of the NMOS transistor MNC is coupled to the negative electrode output terminal, the gate of the NMOS transistor MNC is coupled to the driving output terminal, the drain of the NMOS transistor MNC is coupled to the drain of the discharging power switch MND, and the source of the discharging power switch MND is coupled to the negative electrode of the battery.

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