A battery protection circuit and system

Abstract

The application provides a battery protection circuit and system, which comprises a first detection terminal VDD, a second detection terminal VM, a third detection terminal G, a discharge control terminal DO connected with the control terminal of a discharge power switch and a charge control terminal CO connected with the control terminal of a charge power switch, wherein the discharge power switch and the charge power switch are collectively referred to as a charge-discharge switch, the first detection terminal VDD is connected with the positive electrode of a battery cell, the second detection terminal VM is connected with the positive electrode P+ of the battery, and the third detection terminal G is connected with the negative electrode of the battery cell; the discharge power switch and the charge power switch are connected between the first detection terminal VDD and the second detection terminal VM. Compared with the prior art, the battery protection circuit can be manufactured by a process without bearing negative voltage, and meanwhile, the battery protection circuit and system can be commonly applied to other chips.

Description

[Technical Field]

[0001] This invention relates to the field of circuit design, and in particular to a battery protection circuit and system constructed using a high-side NMOS switch. [Background Technology]

[0002] In existing technologies, low-side NMOS switches are generally used to construct battery protection circuits. Please refer to [reference needed]. Figure 1 As shown, it is a circuit diagram of a battery protection system in the prior art. Figure 1 The battery protection system shown includes a battery cell BAT1, a battery protection circuit (or battery protection chip) 110, a charging power switch (or charging power transistor) FET2, a discharging power switch (or discharging power transistor) FET1, and a resistor R1. The battery protection circuit 110 is constructed using a low-side NMOS switch. A disadvantage of this approach is that the battery protection circuit (or battery protection chip) 110 requires a manufacturing process capable of withstanding negative voltages, which increases costs. Additionally, it results in the battery protection circuit (or battery protection chip) 110 not sharing a common ground with other chips in the system application, which is detrimental to signal transmission.

[0003] Therefore, it is necessary to propose an improved technical solution to overcome the above problems. [Summary of the Invention]

[0004] One of the objectives of this invention is to provide a battery protection circuit and system that can be manufactured using a process that does not require the battery protection circuit (or battery protection chip) to withstand negative voltage, while also enabling the battery protection circuit (or battery protection chip) to share a ground with other chips in the system application.

[0005] According to one aspect of the present invention, a battery protection circuit is provided, comprising a first detection terminal VDD, a second detection terminal VM, a third detection terminal G, a discharge control terminal DO connected to the control terminal of a discharge power switch, and a charging control terminal CO connected to the control terminal of a charging power switch, wherein the discharge power switch and the charging power switch are collectively referred to as a charge-discharge switch, the first detection terminal VDD is connected to the positive terminal of the battery cell, the second detection terminal VM is connected to the positive terminal P+ of the battery, and the third detection terminal G is connected to the negative terminal of the battery cell; the discharge power switch and the charging power switch are connected between the first detection terminal VDD and the second detection terminal VM.

[0006] According to another aspect of the present invention, a battery protection system is provided, comprising: a battery cell;

[0007] The invention includes a charging power switch and a discharging power switch, collectively referred to as a charge-discharge switch; a battery protection circuit comprising a first detection terminal VDD, a second detection terminal VM, a third detection terminal G, a discharge control terminal DO connected to the control terminal of the discharging power switch, and a charging control terminal CO connected to the control terminal of the charging power switch. The first detection terminal VDD is connected to the positive terminal of the battery cell, the second detection terminal VM is connected to the positive terminal P+ of the battery, and the third detection terminal G is connected to the negative terminal of the battery cell. The discharge power switch and the charging power switch are connected between the first detection terminal VDD and the second detection terminal VM. Compared with existing technologies, this invention uses a high-side NMOS switch to construct the battery protection circuit and system, thereby enabling the battery protection circuit (or battery protection chip) to be manufactured using a process that does not require negative voltage, while allowing the battery protection circuit (or battery protection chip) to share a ground with other chips in the system application. Furthermore, this invention aims to achieve high-precision current detection. [Attached Image Description]

[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0009] Figure 1 This is a circuit diagram of a battery protection system in the prior art;

[0010] Figure 2 This is a circuit diagram of the battery protection system in one embodiment of the present invention;

[0011] Figure 3 For example, in one embodiment of the present invention Figure 2 The circuit diagram of the battery protection circuit shown is shown.

[0012] Figure 4 For example, in one embodiment of the present invention Figure 3 The circuit diagram of the virtual ground voltage regulator VGR is shown below.

[0013] Figure 5 For example, in one embodiment of the present invention Figure 3 The circuit diagram of the discharge overcurrent detection module IDet1 is shown below;

[0014] Figure 6 For example, in one embodiment of the present invention Figure 3 The circuit diagram of the charging overcurrent detection module IDet2 is shown below;

[0015] Figure 7 For the purposes of this invention Figure 5 and Figure 6 The diagram shows a circuit diagram of a positive temperature coefficient voltage generator (VPTC) in one embodiment.

Detailed Implementation Methods

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The term "an 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 invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms "connected," "linked," and "connected" used herein to indicate electrical connection refer to direct or indirect electrical connection.

[0018] Please refer to Figure 2 As shown, it is a circuit diagram of the battery protection system in one embodiment of the present invention. Figure 2 The battery protection system shown includes battery cell BAT1, battery protection circuit (or battery protection chip) 210, charging power switch (or charging power transistor) FET2, and discharging power switch (or discharging power transistor) FET1. For ease of description, the charging power switch FET2 and the discharging power switch FET1 will be collectively referred to as the charge-discharge switch below; the sum of the on-resistances of the charging power switch FET2 and the discharging power switch FET1 is called the on-resistance of the charge-discharge switch.

[0019] The battery protection circuit 210 includes three detection terminals (or connection terminals) and two control terminals. The three detection terminals are the first detection terminal VDD, the second detection terminal VM, and the third detection terminal G. The two control terminals are the charging control terminal CO and the discharging control terminal DO. The first detection terminal VDD is connected to the positive terminal B+ of battery cell BAT1, the third detection terminal G is connected to the negative terminal B- of battery cell BAT1, the second detection terminal VM is connected to the positive terminal P+ of the battery, the charging control terminal CO is connected to the control terminal of the charging power switch FET2, and the discharging control terminal DO is connected to the control terminal of the discharging power switch FET1. The discharging power switch FET1 and the charging power switch FET2 are connected in series between the positive terminal B+ (or the first detection terminal VDD) of battery cell BAT1 and the positive terminal P+ (or the second detection terminal VM) of the battery. The negative terminal B- of battery cell BAT1 is directly connected to the negative terminal P- of the battery.

[0020] The charging power switch (or charging power transistor) FET2 includes a diode (not shown) parasitic within it. The discharging power switch FET1 includes a diode (not shown) parasitic within it. Wherein, in Figure 2 In the specific implementation shown, the charging power switch (or charging power transistor) FET2 is an NMOS (N-channel Metal Oxide Semiconductor) transistor; the discharging power switch FET1 is an NMOS transistor; the drain of NMOS transistor FET1 is connected to the drain of NMOS transistor FET2, the source of NMOS transistor FET1 is connected to the positive terminal B+ (or the first detection terminal VDD) of battery cell BAT1, and the source of NMOS transistor FET2 is connected to the positive terminal P+ (or the second detection terminal VM) of the battery.

[0021] The battery protection circuit 210 is powered by the voltage of battery cell BAT1 (i.e., the cell voltage). The battery protection circuit 210 provides charging and discharging protection for battery cell BAT1 by controlling the on / off state of the discharge power switch FET1 and the charging power switch FET2. Under normal conditions, the battery protection circuit 210 controls both the discharge power switch FET1 and the charging power switch FET2 to be on simultaneously, allowing both charging and discharging. If an abnormality occurs during charging, the battery protection circuit 210 controls the charging power switch FET2 to be off, thus cutting off the charging circuit, but discharging is still possible. If an abnormality occurs during discharging, the battery protection circuit 210 controls the discharge power switch FET1 to be off, thus cutting off the discharging circuit, but charging is still possible.

[0022] In one embodiment, the battery protection circuit 210 performs discharge overvoltage detection or charging overvoltage detection by sampling the voltage of the first detection terminal VDD. For example, when the battery protection circuit 210 detects that the voltage of the first detection terminal VDD (which reflects the voltage of the battery cell BAT1) is lower than the discharge overvoltage protection threshold and continues to exceed the discharge overvoltage protection delay time, it controls the discharge power switch FET1 to be open-circuited (or turned off) by setting the discharge control terminal DO to a low level (e.g., its low-level voltage is equal to the voltage of the first detection terminal VDD); when the battery protection circuit 210 detects that the voltage of the first detection terminal VDD (which reflects the voltage of the battery cell BAT1) is higher than the charging overvoltage protection threshold and continues to exceed the charging overvoltage protection delay time, it controls the charging power switch FET2 to be open-circuited (or turned off) by setting the charging control terminal CO to a low level (e.g., its low-level voltage is equal to the voltage of the positive terminal P+ of the battery).

[0023] In one embodiment, the battery protection circuit 210 performs discharge overcurrent detection or charging overcurrent detection by sampling the voltage of the first detection terminal VDD and the voltage of the second detection terminal VM. When the battery protection circuit 210 detects that the difference between the voltage of the first detection terminal VDD and the voltage of the second detection terminal VM is higher than the discharge overcurrent protection threshold and continues to exceed the discharge overcurrent protection delay time, it controls the discharge power switch FET1 to be open-circuited (or turned off) by setting the discharge control terminal DO to a low level (e.g., its low-level voltage is equal to the voltage of the first detection terminal VDD); when the battery protection circuit 210 detects that the difference between the voltage of the second detection terminal VM and the voltage of the first detection terminal VDD is higher than the charging overcurrent protection threshold and continues to exceed the charging overcurrent protection delay time, it controls the charging power switch FET2 to be open-circuited (or turned off) by setting the charging control terminal CO to a low level (e.g., its low-level voltage is equal to the voltage of the positive terminal P+ of the battery).

[0024] When no abnormal situation occurs as described above, the charging control terminal CO outputs a high level (e.g., this high level voltage is VDD+VF), controlling the charging power switch FET2 to turn on; the discharging control terminal DO outputs a high level (e.g., this high level voltage is VDD+VF), controlling the discharging power switch FET1 to turn on, where VDD is the voltage of the first detection terminal VDD, and VF is the threshold voltage of the discharging power switch FET1 or the charging power switch FET2.

[0025] In summary, because this invention uses a high-side NMOS switch to construct such a... Figure 2 The battery protection circuit and system shown in this invention allow the battery protection circuit (or battery protection chip) to be manufactured using a process that does not require the battery to withstand negative voltage, while also enabling the battery protection circuit (or battery protection chip) to share a ground with other chips in the system application.

[0026] It should be noted that directly using the voltage difference between the first detection terminal VDD and the second detection terminal VM (for example, the difference between the voltage of the first detection terminal VDD and the voltage of the second detection terminal VM, or the difference between the voltage of the second detection terminal VM and the voltage of the first detection terminal VDD) as current sampling information may lead to inaccurate current detection. This is because the voltage difference between the first detection terminal VDD and the second detection terminal VM reflects the voltage drop across the discharge power switch FET1 and the charging power switch FET2. Taking discharge overcurrent detection as an example, during normal discharge, the difference between the voltage of the first detection terminal VDD and the voltage of the second detection terminal VM is equal to I.Ron, where I is the discharge current and Ron is the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2. The on-resistances of the discharge power switch FET1 and the charging power switch FET2 change with their gate-source voltage. When a constant voltage VR is used as the voltage threshold for discharge overcurrent detection (i.e., the difference between the constant reference voltage VR and the voltage at the first detection terminal VDD minus the voltage at the second detection terminal VM is compared; if the difference exceeds the constant reference voltage VR, a discharge overcurrent is detected, and a corresponding discharge prohibition operation is performed), the actual corresponding discharge overcurrent detection current threshold is Ith = VR / Ron, where VR is the aforementioned constant reference voltage, and Ron is the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2. Ron changes with the gate-source voltages of the discharge power switch FET1 and the charging power switch FET2. Furthermore, the on-resistance Ron also changes with the temperature of the discharge power switch FET1 and the charging power switch FET2. When Ron changes, the discharge overcurrent detection current threshold Ith changes accordingly. In practical applications, it is best to keep the discharge overcurrent detection current threshold Ith constant.

[0027] Therefore, this invention provides a battery protection circuit and system that uses the voltage difference between the first detection terminal VDD and the second detection terminal VM as current detection information. The overcurrent detection voltage threshold VR mimics the characteristic that the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2 changes with temperature. During normal charging and discharging, the gate-source voltages of the discharge power switch FET1 and the charging power switch FET2 are kept constant, thereby achieving a precise overcurrent detection current threshold Ith. This overcurrent detection current threshold Ith does not change with cell voltage or with temperature changes in the discharge power switch FET1 and the charging power switch FET2. This enables high-precision overcurrent detection.

[0028] Please refer to Figure 3 As shown, this is one embodiment of the present invention. Figure 2The circuit diagram of the battery protection circuit 210 shown is shown. Figure 3 The battery protection circuit shown includes an overvoltage detection module VDet310, a discharge overcurrent detection module IDet1320, a charging overcurrent detection module IDet2330, a logic module Logic340, a power pre-adjustment module 350, a first drive circuit DRV1360, and a second drive circuit DRV2370.

[0029] The overvoltage detection module VDet310 detects the charging and discharging circuit of cell BAT1 based on the first detection terminal VDD and the third detection terminal G, and outputs the corresponding voltage detection signal. The overvoltage detection module VDet310 can be implemented using existing technologies.

[0030] The discharge overcurrent detection module IDet1320 detects the discharge circuit of cell BAT1 based on the first detection terminal VDD and the second detection terminal VM, and outputs the corresponding discharge current detection signal EDI.

[0031] The charging overcurrent detection module IDet2330 detects the charging circuit of cell BAT1 based on the first detection terminal VDD and the second detection terminal VM, and outputs the corresponding charging current detection signal ECI.

[0032] The logic module Logic340 generates charging control signals and discharging control signals based on the discharge current detection signal EDI output by the discharge overcurrent detection module IDet1320 and the charging current detection signal ECI output by the charging overcurrent detection module IDet2330.

[0033] The first driving circuit DRV1360 is used to drive and process the charging control signal output by the logic module Logic340, and provide the processed charging control signal to the charging control terminal CO.

[0034] The second driving circuit DRV2370 is used to drive and process the discharge control signal output by the logic module Logic340, and provide the processed discharge control signal to the discharge control terminal DO.

[0035] exist Figure 3 In the specific embodiment shown, the ground terminal of the first driving circuit DRV1360 is connected to the second detection terminal VM, and the ground terminal of the second driving circuit DRV2370 is connected to the first detection terminal VDD. That is, the ground level of the first driving circuit DRV1360 is the voltage of the second detection terminal VM, and the ground level of the second driving circuit DRV2370 is the voltage of the first detection terminal VDD.

[0036] The input terminal of the power pre-adjustment module 350 is connected to the first detection terminal VDD, and its output terminal is connected to the power supply terminal of the first drive circuit DRV1360 and the power supply terminal of the second drive circuit DRV2370. The power pre-adjustment module 350 generates a supply voltage VO based on the voltage of the first detection terminal VDD. The supply voltage VO is output through the output terminal of the power pre-adjustment module 350. The supply voltage VO is relatively constant with the voltage of the first detection terminal VDD. Specifically, the supply voltage VO is greater than the voltage of the first detection terminal VDD, and the difference between the supply voltage VO and the voltage of the first detection terminal VDD is constant. The supply voltage VO supplies power to the first drive circuit DRV1360 and the second drive circuit DRV2370. Thus, during normal charging and discharging, the battery protection circuit 210 keeps the gate-source voltage of the discharge power switch FET1 and the charging power switch FET2 constant.

[0037] exist Figure 3 In the specific embodiment shown, the power pre-adjustment module 350 includes an adaptive charge pump 352 and a virtual ground voltage regulator VGR354. The input terminal of the adaptive charge pump 352 is connected to a first detection terminal VDD, which boosts the voltage of the first detection terminal VDD and outputs a voltage VCP that is larger than the voltage of the first detection terminal VDD. In one embodiment, the boost factor of the adaptive charge pump 352 varies with the voltage of the first detection terminal VDD. The input of the virtual ground regulator VGR354 is connected to the output of the adaptive charge pump ChargePump352. Its output serves as the output VO of the power supply pre-adjustment module 350. Unlike traditional regulators, the virtual ground regulator VGR354 operates with the voltage of the first detection terminal VDD as the virtual reference ground level (i.e., the virtual ground regulator VGR354 is controlled with the voltage of the first detection terminal VDD as the virtual ground level). Based on the output voltage VCP of the adaptive charge pump ChargePump352, it generates a constant supply voltage VO relative to the voltage of the first detection terminal VDD, that is, it maintains VO-VDD as a constant value (e.g., VO-VDD = 5V).

[0038] Please refer to Figure 4 As shown, this is one embodiment of the present invention. Figure 3 The circuit diagram of the virtual ground voltage regulator VGR354 is shown. Figure 4The virtual ground voltage regulator shown includes a MOSFET MPP, an operational amplifier OP1, a reference voltage source VR, and a voltage divider circuit 410. The positive terminal of the reference voltage source VR is connected to the first input terminal of the operational amplifier OP1, and its negative terminal is connected to the first detection terminal VDD. The first connection terminal of the MOSFET MPP is connected to the output terminal VCP of the adaptive charge pump ChargePump352, its second connection terminal is connected to the output terminal VO of the power supply pre-adjustment module, and its control terminal is connected to the output terminal of the operational amplifier OP1. The voltage divider circuit 410 includes a second resistor R2 and a first resistor R1 connected in series between the output terminal VO of the power supply pre-adjustment module and the first detection terminal VDD. The connection node between the second resistor R2 and the first resistor R1 is connected to the second input terminal of the operational amplifier OP1.

[0039] exist Figure 4 In the specific embodiment shown, the first input terminal and the second input terminal of the operational amplifier OP1 are its inverting input terminal and non-inverting input terminal, respectively; the MOS transistor MPP is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the MOS transistor MPP are the source, drain and gate of the PMOS transistor, respectively.

[0040] exist Figure 4 In the virtual ground voltage regulator shown, the reference voltage source VR is designed with the voltage of the first detection terminal VDD as the virtual ground level (i.e., the reference ground level of the reference voltage source VR is the voltage of the first detection terminal VDD), and the difference between the positive voltage VIM of the reference voltage source VR and the voltage of the first detection terminal VDD remains constant. Figure 4 In the specific embodiment shown, the ground terminal of operational amplifier OP1 is connected to the third detection terminal G of battery protection circuit 210. That is, the ground level of operational amplifier OP1 adopts the voltage of the third detection terminal G (which is the true ground level of the entire chip). The advantage of this is that the output of operational amplifier OP1 can be as low as the voltage of the third detection terminal G, which can provide a larger driving voltage (i.e., a larger gate-source voltage) for MOS transistor MPP. Compared with the ground level of operational amplifier OP1 adopting the voltage of the first detection terminal VDD, it has the advantage of stronger driving capability.

[0041] Please refer to Figure 5 As shown, this is one embodiment of the present invention. Figure 3 The circuit diagram shown is for the discharge overcurrent detection module IDet1320. Figure 5The discharge overcurrent detection module shown detects discharge overcurrent by sampling the voltage difference between the first detection terminal VDD and the second detection terminal VM. The discharge overcurrent detection module generates a reference voltage VR1 (i.e., the voltage threshold VR1 for discharge overcurrent detection). The reference voltage VR1 mimics the characteristic that the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2 changes with their temperature (i.e., the change of the reference voltage VR1 with temperature is consistent with the change of the on-resistance of the charge and discharge switches with temperature). Figure 5 The discharge overcurrent detection module shown compares the voltage difference between the first detection terminal VDD and the second detection terminal VM to see if it is higher than the reference voltage VR1, and outputs a corresponding discharge current detection signal EDI.

[0042] Figure 5 The discharge overcurrent detection module shown includes a reference voltage generation circuit 510, a comparator Comp, and a subtractor Sub. The reference voltage generation circuit 510 acquires the temperature values ​​of the charge / discharge switches (i.e., charging power switch FET2 and discharging power switch FET1), and calculates a corresponding reference voltage VR1 based on these temperature values. This reference voltage VR1 is then output through its output terminal. The reference voltage VR1 mimics the change in the on-resistance of the charge / discharge switches (i.e., the sum of the on-resistances of charging power switch FET2 and discharging power switch FET1) with temperature. In other words, the change in reference voltage VR with temperature corresponds to the change in the on-resistance of the charge / discharge switches with temperature. For example, if the on-resistance of the charge / discharge switches increases with increasing temperature, then the resistance value of the reference voltage VR1 increases with increasing temperature; conversely, if the on-resistance of the charge / discharge switches decreases with decreasing temperature, then the resistance value of the reference voltage VR1 decreases with decreasing temperature. The reference voltage VR1 can also be referred to as the voltage threshold VR1 for discharge overcurrent detection.

[0043] The subtractor Sub subtracts the voltage at the first detection terminal VDD from the voltage at the second detection terminal VM to generate the detection voltage VIS1.

[0044] The first input terminal of comparator Comp is connected to the output terminal of reference voltage generation circuit 510 to receive the reference voltage VR1 output by reference voltage generation circuit 510, and its second input terminal is connected to the output terminal of subtractor Sub to receive the detection voltage VIS1 output by subtractor Sub. Comparator Comp is used to compare the magnitudes of the reference voltage VR1 output by reference voltage generation circuit 510 and the detection voltage VIS1 output by subtractor Sub, and outputs a corresponding discharge overcurrent detection signal EDI through its output terminal based on the comparison result.

[0045] exist Figure 5In the specific embodiment shown, the first input terminal and the second input terminal of comparator Comp are its negative input terminal and its positive input terminal, respectively. Comparator Comp compares the reference voltage VR1 and the detection voltage VIS1. When the detection voltage VIS1 is greater than the reference voltage VR1, the discharge overcurrent detection signal EDI output by comparator Comp becomes high; when the detection voltage VIS1 is less than the reference voltage VR1, the discharge overcurrent detection signal EDI output by comparator Comp becomes low.

[0046] exist Figure 5 In the specific embodiment shown, the reference voltage generation circuit 510 includes a temperature sensing module T_Sens 512, a positive temperature coefficient voltage generator VPTC 514, a zero temperature coefficient voltage generator VZTC 516, a multiplier M1, a multiplier M2, and an adder Add.

[0047] The temperature sensing module T_Sens512 is used to conduct heat from the charge and discharge switches (i.e., the charging power switch FET2 and the discharging power switch FET1) to the positive temperature coefficient voltage generator VPTC514, so that the temperature of the positive temperature coefficient voltage generator VPTC514 is the same as the temperature of the charge and discharge switches.

[0048] The positive temperature coefficient voltage generator VPTC514 generates a positive temperature coefficient voltage V1 based on its own temperature (i.e., the positive temperature coefficient voltage V1 increases with increasing temperature) and outputs the positive temperature coefficient voltage V1 through its output terminal. In a preferred embodiment, the positive temperature coefficient voltage V1 is proportional to the temperature of the charge and discharge switches (i.e., the charging power switch FET2 and the discharging power switch FET1).

[0049] The zero-temperature coefficient voltage generator VZTC516 generates a zero-temperature coefficient voltage V2 (i.e., the zero-temperature coefficient voltage V2 does not change with temperature) and outputs this zero-temperature coefficient voltage V2. Multiplier M1 multiplies the positive temperature coefficient voltage V1 by a fixed coefficient K1 to obtain a positive temperature coefficient voltage V3. Multiplier M2 multiplies the zero-temperature coefficient voltage V2 by a fixed coefficient K2 to obtain a zero-temperature coefficient voltage V4. Adder Adds the positive temperature coefficient voltage V3 and the zero-temperature coefficient voltage V4 to generate a reference voltage VR1.

[0050] Alternatively, VR1 can be expressed as K1.V1 + K2.V2, where K1 is a fixed coefficient, K2 is a fixed coefficient, V1 is the positive temperature coefficient voltage, and V2 is the zero temperature coefficient voltage.

[0051] For different charging power switches FET2 and discharging power switches FET1, their on-resistance characteristics may be different. The corresponding reference voltage VR1 can be generated by modifying the coefficients K1 and K2 so that the change of reference voltage VR1 with temperature is consistent with the change of on-resistance of the charging and discharging switches (i.e., the sum of the on-resistances of charging power switch FET2 and discharging power switch FET1) with temperature. In other words, the reference voltage VR1 imitates the change of on-resistance of the charging and discharging switches with temperature.

[0052] Figure 5 The zero-temperature coefficient voltage generator VZTC516 shown can be implemented using various bandgap reference circuits or other zero-temperature coefficient reference voltage generation circuits in the prior art. In one implementation, coefficients K1 and K2 can be implemented using analog voltage signals (which can be an adjustable reference voltage), and the corresponding multipliers M1 and M2 can also be implemented using analog multipliers; in another implementation, coefficients K1 and K2 can be implemented using digital signals, and the corresponding multipliers M1 and M2 can also be implemented using digital multipliers.

[0053] Please refer to Figure 6 As shown, this is one embodiment of the present invention. Figure 3 The circuit diagram shown is for the charging overcurrent detection module IDet2330. Figure 6 The charging overcurrent detection module shown detects charging overcurrent by sampling the difference between the voltage at the second detection terminal VM and the voltage at the first detection terminal VDD. The charging overcurrent detection module internally generates a reference voltage VR2 (i.e., the voltage threshold VR2 for charging overcurrent detection). This reference voltage VR2 mimics the characteristic that the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2 changes with their temperature (i.e., the change of the reference voltage VR2 with temperature is consistent with the change of the on-resistance of the charge and discharge switches with temperature). Figure 6 The charging overcurrent detection module shown compares the difference between the voltage at the second detection terminal VM and the voltage at the first detection terminal VDD to see if it is higher than the reference voltage VR2, and outputs a corresponding charging current detection signal ECI.

[0054] Figure 6 The charging overcurrent detection module shown is Figure 5 The structure and working principle of the discharge overcurrent detection module shown are similar.

[0055] Figure 6 The charging overcurrent detection module shown includes a reference voltage generation circuit 610, a comparator Comp, and a subtractor Sub.

[0056] The reference voltage generation circuit 610 acquires the temperature values ​​of the charge / discharge switches (i.e., charging power switch FET2 and discharging power switch FET1), and calculates the corresponding reference voltage VR2 based on these temperature values. This reference voltage VR2 is then output through its output terminal. The reference voltage VR2 mimics the change in the on-resistance of the charge / discharge switches (i.e., the sum of the on-resistances of charging power switch FET2 and discharging power switch FET1) with temperature. In other words, the change in reference voltage VR2 with temperature corresponds to the change in the on-resistance of the charge / discharge switches with temperature. For example, if the on-resistance of the charge / discharge switches increases with increasing temperature, then the resistance value of the reference voltage VR2 also increases with increasing temperature; conversely, if the on-resistance of the charge / discharge switches decreases with decreasing temperature, then the resistance value of the reference voltage VR2 also decreases with decreasing temperature. The reference voltage VR2 can also be referred to as the voltage threshold VR2 for charging overcurrent detection.

[0057] The subtractor Sub subtracts the voltage at the second detection terminal VM from the voltage at the first detection terminal VDD to generate the detection voltage VIS2.

[0058] The first input terminal of comparator Comp is connected to the output terminal of reference voltage generation circuit 610 to receive the reference voltage VR2 output by reference voltage generation circuit 610, and its second input terminal is connected to the output terminal of subtractor Sub to receive the detection voltage VIS2 output by subtractor Sub. Comparator Comp is used to compare the magnitudes of the reference voltage VR2 output by reference voltage generation circuit 610 and the detection voltage VIS2 output by subtractor Sub, and outputs a corresponding charging overcurrent detection signal ECI through its output terminal based on the comparison result. Figure 6 In the specific embodiment shown, the first input terminal and the second input terminal of comparator Comp are its positive input terminal and its negative input terminal, respectively. Comparator Comp compares the reference voltage VR2 and the detection voltage VIS2. When the detection voltage VIS2 is greater than the reference voltage VR2, the charging overcurrent detection signal ECI output by comparator Comp goes low; when the detection voltage VIS2 is less than the reference voltage VR2, the charging overcurrent detection signal ECI output by comparator Comp goes high.

[0059] exist Figure 6 In the specific embodiment shown, the reference voltage generation circuit 610 includes a temperature sensing module T_Sens 612, a positive temperature coefficient voltage generator VPTC 614, a zero temperature coefficient voltage generator VZTC 616, a multiplier M1, a multiplier M2, and an adder Add.

[0060] The temperature sensing module T_Sens612 is used to conduct heat from the charge and discharge switches (i.e., the charging power switch FET2 and the discharging power switch FET1) to the positive temperature coefficient voltage generator VPTC614, so that the temperature of the positive temperature coefficient voltage generator VPTC614 is the same as the temperature of the charge and discharge switches.

[0061] The positive temperature coefficient voltage generator VPTC614 generates a positive temperature coefficient voltage V1 based on its own temperature (i.e., the positive temperature coefficient voltage V1 increases with increasing temperature) and outputs the positive temperature coefficient voltage V1 through its output terminal. In a preferred embodiment, the positive temperature coefficient voltage V1 is proportional to the temperature of the charge and discharge switches (i.e., the charging power switch FET2 and the discharging power switch FET1).

[0062] The zero-temperature coefficient voltage generator VZTC616 generates a zero-temperature coefficient voltage V2 (i.e., the zero-temperature coefficient voltage V2 does not change with temperature) and outputs this zero-temperature coefficient voltage V2. Multiplier M1 multiplies the positive temperature coefficient voltage V1 by a fixed coefficient K3 to obtain a positive temperature coefficient voltage V5. Multiplier M2 multiplies the zero-temperature coefficient voltage V2 by a fixed coefficient K4 to obtain a zero-temperature coefficient voltage V6. Adder Adds the positive temperature coefficient voltage V5 and the zero-temperature coefficient voltage V6 to generate a reference voltage VR2.

[0063] Alternatively, VR2 can be expressed as K3.V1 + K4.V2, where K3 and K4 are fixed coefficients, V1 is the positive temperature coefficient voltage, and V2 is the zero temperature coefficient voltage.

[0064] For different charging power switches FET2 and discharging power switches FET1, their on-resistance characteristics may be different. The corresponding reference voltage VR2 can be generated by modifying the coefficients K3 and K4 so that the change of reference voltage VR2 with temperature is consistent with the change of on-resistance of the charging and discharging switches (i.e., the sum of the on-resistances of charging power switch FET2 and discharging power switch FET1) with temperature. In other words, reference voltage VR2 imitates the change of on-resistance of the charging and discharging switches with temperature.

[0065] Figure 6 The zero-temperature coefficient voltage generator VZTC616 shown can be implemented using various bandgap reference circuits or other zero-temperature coefficient reference voltage generation circuits in the prior art. In one implementation, coefficients K3 and K4 can be implemented using analog voltage signals (which can be an adjustable reference voltage), and the corresponding multipliers M3 and M4 can also be implemented using analog multipliers; in another implementation, coefficients K3 and K4 can be implemented using digital signals, and the corresponding multipliers M3 and M4 can also be implemented using digital multipliers.

[0066] Please refer to Figure 7 As shown, it is the present invention as follows. Figure 5 and Figure 6 The diagram shows a circuit diagram of a positive temperature coefficient voltage generator (VPTC) in one embodiment. Figure 7 The positive temperature coefficient voltage generator VPTC shown includes MOSFETs MP1, MP2 and MP3, resistors R3 and R4, operational amplifier OP2, and bipolar transistors Q1 and Q2.

[0067] In this configuration, the first terminal of MOSFET MP1 is connected to the power supply, and its second terminal is connected to node A; the first terminal of bipolar transistor Q1 is connected to node A, and its second terminal and control terminal are both grounded; the first terminal of MOSFET MP2 is connected to the power supply, its control terminal is connected to the control terminal of MOSFET MP1, and its second terminal is connected to node B; the first terminal of bipolar transistor Q2 is connected to node B via resistor R1, and its second terminal and control terminal are both grounded; the first input terminal of operational amplifier OP2 is connected to node A, its second input terminal is connected to node B, and its output terminal is connected to the control terminal of MOSFET MP1; the first terminal of MOSFET MP3 is connected to the power supply, its control terminal is connected to the control terminal of MOSFET MP2, and its second terminal is connected to the output terminal V1 of the positive temperature coefficient voltage generator VPTC; one end of resistor R2 is connected to the output terminal V1 of the positive temperature coefficient voltage generator VPTC, and the other end is grounded.

[0068] exist Figure 7 In the specific embodiment shown, MOS transistors MP1, MP2, and MP3 are all PMOS transistors. The first connection terminal, the second connection terminal, and the control terminal of MOS transistors MP1, MP2, and MP3 are the source, drain, and gate of the PMOS transistors, respectively. Bipolar transistors Q1 and Q2 are both PNP bipolar transistors. The first connection terminal, the second connection terminal, and the control terminal of bipolar transistors Q1 and Q2 are the emitter, collector, and base of the PNP bipolar transistors, respectively. Resistors R1 and R2 are resistors of the same type. The first input terminal and the second input terminal of operational amplifier OP2 are its negative input terminal and its positive input terminal, respectively.

[0069] In other embodiments, bipolar transistors Q1 and Q2 can also be NPN bipolar transistors; the specific connection relationship will not be described again to avoid repetition.

[0070] exist Figure 7In the illustrated embodiment, operational amplifier OP2 is adjusted so that its positive and negative inputs are equal. Therefore, the voltage across resistor R3 is equal to Vbe1 - Vbe2, where Vbe1 is the base-emitter voltage of bipolar transistor Q1, and Vbe2 is the base-emitter voltage of bipolar transistor Q2. The voltage across resistor R3 is a positive temperature coefficient voltage. MOSFETs MP3, MP2, and MP1 form a current mirror, with MOSFET MP3 replicating the current of MOSFET MP2. The current across resistor R3 is equal to (Vbe1 - Vbe2) / R3, which is also equal to the current of MOSFET MP2 and MP3. The voltage across resistor R4 is equal to (Vbe1 - Vbe2)R4 / R3, where R3 and R4 are the resistance values ​​of resistors R3 and R4, respectively. Resistors R3 and R4 are of the same type, so their temperature coefficients cancel each other out. Therefore, the voltage across resistor R4 (i.e., the voltage at the output V1 of the positive temperature coefficient voltage generator VPTC) is also a positive temperature coefficient voltage.

[0071] To facilitate understanding of the present invention, the following is based on... Figure 2 , Figure 3 , Figure 5 and Figure 7 This invention provides a detailed description of the working process of the battery protection circuit and system provided by the present invention.

[0072] The discharge overcurrent detection module IDet1320 detects the difference between the voltage at the first detection terminal VDD and the voltage at the second detection terminal VM. When the IDet1320 detects that the difference between the voltage at the first detection terminal VDD and the voltage at the second detection terminal VM is greater than the reference voltage VR1 (i.e., the voltage threshold VR1 for discharge overcurrent detection), the discharge current detection signal EDI output by the IDet1320 goes high. If EDI goes high, the logic module Logic340 can time it. If the discharge overcurrent protection delay time is exceeded, the discharge control terminal DO is controlled to go low, controlling the discharge power switch FET1 to turn off, thereby preventing discharge.

[0073] The charging overcurrent detection module IDet2330 detects the difference between the voltage at the second detection terminal VM and the voltage at the first detection terminal VDD. When the IDet2330 detects that this difference exceeds the reference voltage VR2 (i.e., the overcurrent detection voltage threshold VR2), the charging current detection signal ECI output by the IDet2330 goes low. If ECI goes low, the logic module Logic340 can time it. If the overcurrent protection delay time is exceeded, the charging control terminal CO goes low, controlling the charging power switch FET2 to turn off, thus preventing charging.

[0074] During normal charging and discharging, the gate voltage of the discharge power switch FET1 and the charging power switch FET2 is the power supply voltage VO output by the power supply pre-adjustment module 350. Since the power supply voltage VO is relatively constant with the voltage of the first detection terminal VDD, the gate-source voltage of the discharge power switch FET1 and the charging power switch FET2 is constant.

[0075] In summary, because this invention uses a high-side NMOS switch to construct such a... Figure 2 The battery protection circuit and system shown in this invention allow the battery protection circuit (or battery protection chip) to be manufactured using a process that does not require the battery to withstand negative voltage, while also enabling the battery protection circuit (or battery protection chip) to share a ground with other chips in the system application.

[0076] Furthermore, the battery protection circuit and system provided by this invention use the voltage difference between the first detection terminal VDD and the second detection terminal VM as current detection information. The overcurrent detection voltage thresholds VR1 and VR2 mimic the characteristic that the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2 changes with temperature. During normal charging and discharging, the gate-source voltages of the discharge power switch FET1 and the charging power switch FET2 are kept constant, thereby achieving a precise overcurrent detection current threshold Ith. This overcurrent detection current threshold Ith does not change with cell voltage or with temperature changes in the discharge power switch FET1 and the charging power switch FET2. Thus, high-precision overcurrent detection can be achieved.

[0077] In this invention, terms such as “connection,” “linked,” “connected,” and “joined” that indicate electrical connection, unless otherwise specified, indicate direct or indirect electrical connection.

[0078] It should be noted that any modifications made by those skilled in the art to the specific embodiments of the present invention do not depart from the scope of the claims. Accordingly, the scope of the claims is not limited to the foregoing specific embodiments.

Claims

1. A battery protection circuit comprising a first detection terminal VDD, a second detection terminal VM and a third detection terminal G, a discharge control terminal DO connected to a control terminal of a discharge power switch and a charge control terminal CO connected to a control terminal of a charge power switch, wherein, The discharge power switch and the charging power switch are collectively referred to as a charge-discharge switch, and the charge-discharge switch is characterized in that, The first detection terminal VDD is connected to the positive electrode of the battery cell, the second detection terminal VM is connected to the positive electrode P+ of the battery, and the third detection terminal G is connected to the negative electrode of the battery cell; The discharge power switch and the charging power switch are connected between the first detection terminal VDD and the second detection terminal VM, The battery protection circuit further comprises: A discharge overcurrent detection module for detecting the discharge loop of the battery cell based on the first detection terminal VDD and the second detection terminal VM to output a corresponding discharge current detection signal EDI; A charging overcurrent detection module for detecting the charging loop of the battery cell based on the first detection terminal VDD and the second detection terminal VM to output a corresponding charging current detection signal ECI; A logic module for generating a charging control signal and a discharging control signal according to the discharge current detection signal EDI and the charging current detection signal ECI; A first drive circuit for driving the charging control signal and providing the driven charging control signal to the charging control terminal CO; A second drive circuit for driving the discharging control signal and providing the driven discharging control signal to the discharging control terminal DO; A power pre-adjustment power supply module having an input terminal connected to the first detection terminal VDD and an output terminal connected to the power terminals of the first drive circuit and the second drive circuit, the power pre-adjustment power supply module generating a supply voltage VO based on the voltage of the first detection terminal VDD, the supply voltage VO being output through the output terminal of the power pre-adjustment power supply module, and the difference between the supply voltage VO and the voltage of the first detection terminal VDD being constant, The discharge overcurrent detection module comprises: A reference voltage generation circuit for obtaining the temperature value of the charge-discharge switch and obtaining a corresponding reference voltage VR1 based on the obtained temperature value of the charge-discharge switch, and outputting the reference voltage VR1 through the output terminal, the reference voltage VR1 changing with temperature in the same way as the on-resistance of the charge-discharge switch changes with temperature; A subtractor for subtracting the voltage of the second detection terminal VM from the voltage of the first detection terminal VDD to generate a detection voltage VIS1; A comparator having a first input terminal receiving the reference voltage VR1 output by the reference voltage generation circuit and a second input terminal receiving the detection voltage VIS1 output by the subtractor, the comparator being configured to compare the reference voltage VR1 and the detection voltage VIS1 and output a corresponding discharge overcurrent detection signal EDI through the output terminal based on the comparison result, The reference voltage generation circuit comprises a temperature sensing module T_Sens, a positive temperature coefficient voltage generator VPTC, a zero temperature coefficient voltage generator VZTC, a multiplier M1, a multiplier M2, and an adder Add The temperature sensing module T_Sens is configured to conduct heat of the temperature of the charge and discharge switch to the positive temperature coefficient voltage generator VPTC, so that the temperature of the positive temperature coefficient voltage generator VPTC is consistent with the temperature of the charge and discharge switch. The positive temperature coefficient voltage generator VPTC is configured to generate a positive temperature coefficient voltage V1 based on the temperature of the positive temperature coefficient voltage generator VPTC, and output the positive temperature coefficient voltage V1 through an output terminal of the positive temperature coefficient voltage generator VPTC. The zero temperature coefficient voltage generator VZTC is configured to generate a zero temperature coefficient voltage V2, and output the zero temperature coefficient voltage V2 through an output terminal of the zero temperature coefficient voltage generator VZTC. The multiplier M1 is configured to multiply the positive temperature coefficient voltage V1 by a fixed coefficient K1 to obtain a positive temperature coefficient voltage V3. The multiplier M2 is configured to multiply the zero temperature coefficient voltage V2 by a fixed coefficient K2 to obtain a zero temperature coefficient voltage V4. The adder Add is configured to add the positive temperature coefficient voltage V3 and the zero temperature coefficient voltage V4 to generate the reference voltage VR1.

2. The battery protection circuit according to claim 1, wherein the discharge power switch is an NMOS transistor, and the charge power switch is an NMOS transistor.

3. The battery protection circuit according to claim 2, wherein when no charge abnormality or discharge abnormality occurs, the charge control terminal CO outputs a high level voltage VDD+VF, and the discharge control terminal DO outputs a high level voltage VDD+VF, wherein VDD is a voltage of the first detection terminal VDD, and VF is a threshold voltage of the discharge power switch or the charge power switch. The power pre-adjustment supply module comprises: an adaptive charge pump, an input terminal of which is connected to the first detection terminal VDD, and the adaptive charge pump is configured to boost the voltage of the first detection terminal VDD and output an output voltage VCP greater than the voltage of the first detection terminal VDD through an output terminal of the adaptive charge pump; 4. The battery protection circuit of claim 1, wherein, a virtual ground voltage regulator, an input terminal of which is connected to the output terminal of the adaptive charge pump, and an output terminal of the virtual ground voltage regulator serves as an output terminal of the power pre-adjustment supply module, and the virtual ground voltage regulator is configured to generate the supply voltage VO based on the output voltage VCP of the adaptive charge pump.

5. The battery protection circuit according to claim 4, wherein the virtual ground voltage regulator comprises a MOS transistor MPP, an operational amplifier OP1, a reference voltage source VR, and a voltage dividing circuit. ​ ​ ​ The positive electrode of the reference voltage source VR is connected with the first input end of the operational amplifier OP1, and the negative electrode is connected with the first detection end VDD; the first connection end of the MOS tube MPP is connected with the output end of the adaptive charge pump, the second connection end is connected with the output end of the power pre-adjustment power supply module, and the control end is connected with the output end of the operational amplifier OP1; the voltage dividing circuit comprises the second resistor R2 and the first resistor R1 which are connected in series between the output end of the power pre-adjustment power supply module and the first detection end VDD, and the connection node between the second resistor R2 and the first resistor R1 is connected with the second input end of the operational amplifier OP1.

6. The battery protection circuit according to claim 5, wherein, the first input end and the second input end of the operational amplifier OP1 are the inverting input end and the non-inverting input end respectively; the MOS tube MPP is a PMOS transistor, and the first connection end, the second connection end and the control end of the MOS tube MPP are the source, the drain and the gate of the PMOS transistor respectively; the ground end of the operational amplifier OP1 is connected with the third detection end G.

7. The battery protection circuit according to claim 1, wherein, based on the characteristic of the on-resistance of the charge-discharge switch, the coefficients K1 and K2 are modified so that the reference voltage VR1 changes with temperature in the same way as the on-resistance of the charge-discharge switch changes with temperature; the positive temperature coefficient voltage V1 is proportional to the temperature of the charge-discharge switch; the multiplier M1 and the multiplier M2 are implemented by analog multipliers, and the coefficients K1 and K2 are implemented by analog voltage signals; or the multiplier M1 and the multiplier M2 are implemented by digital multipliers, and the coefficients K1 and K2 are implemented by digital voltage signals.

8. The battery protection circuit of claim 1, wherein, The charge overcurrent detection module comprises: a reference voltage generation circuit for obtaining the temperature value of the charge-discharge switch, and obtaining the corresponding reference voltage VR2 based on the obtained temperature value of the charge-discharge switch, and outputting the reference voltage VR2 through the output end, wherein the reference voltage VR2 changes with temperature in the same way as the on-resistance of the charge-discharge switch changes with temperature; a subtracter for subtracting the voltage of the first detection end VDD from the voltage of the second detection end VM to generate a detection voltage VIS2; a comparator, the first input end of which receives the reference voltage VR2 output by the reference voltage generation circuit, and the second input end of which receives the detection voltage VIS2 output by the subtracter, the comparator being configured to compare the reference voltage VR2 and the detection voltage VIS2, and output a corresponding charge overcurrent detection signal ECI through the output end based on the comparison result.

9. The battery protection circuit according to claim 8, wherein, the reference voltage generation circuit comprises a temperature sensing module T_Sens, a positive temperature coefficient voltage generator VPTC, a zero temperature coefficient voltage generator VZTC, a multiplier M1, a multiplier M2 and an adder Add The temperature sensing module T_Sens is configured to conduct heat of the temperature of the charge-discharge switch to the positive temperature coefficient voltage generator VPTC, so that the temperature of the positive temperature coefficient voltage generator VPTC is consistent with the temperature of the charge-discharge switch; The positive temperature coefficient voltage generator VPTC is configured to generate a positive temperature coefficient voltage V1 based on the temperature of the positive temperature coefficient voltage generator VPTC, and output the positive temperature coefficient voltage V1 through an output terminal of the positive temperature coefficient voltage generator VPTC; The zero temperature coefficient voltage generator VZTC is configured to generate a zero temperature coefficient voltage V2, and output the zero temperature coefficient voltage V2 through an output terminal of the zero temperature coefficient voltage generator VZTC; The multiplier M1 is configured to multiply the positive temperature coefficient voltage V1 by a fixed coefficient K3 to obtain a positive temperature coefficient voltage V5; The multiplier M2 is configured to multiply the zero temperature coefficient voltage V2 by a fixed coefficient K4 to obtain a zero temperature coefficient voltage V6; The adder Add is configured to add the positive temperature coefficient voltage V5 and the zero temperature coefficient voltage V6 to generate the reference voltage VR2.

10. The battery protection circuit according to claim 9, wherein: based on a characteristic of the on-resistance of the charge-discharge switch, the coefficients K3 and K4 are modified so that the reference voltage VR2 changes with temperature in a manner consistent with the on-resistance of the charge-discharge switch changing with temperature; the positive temperature coefficient voltage V1 is directly proportional to the temperature of the charge-discharge switch; the multipliers M1 and M2 are implemented as analog multipliers, and the coefficients K3 and K4 are implemented as analog voltage signals; or the multipliers M1 and M2 are implemented as digital multipliers, and the coefficients K3 and K4 are implemented as digital voltage signals.

11. The battery protection circuit according to claim 1 or 9, wherein: the positive temperature coefficient voltage generator VPTC comprises MOS transistors MP1, MP2 and MP3, resistors R3 and R4, an operational amplifier OP, and bipolar transistors Q1 and Q2, a first connection terminal of the MOS transistor MP1 is connected to a power supply terminal, and a second connection terminal of the MOS transistor MP1 is connected to a node A; a first connection terminal of the bipolar transistor Q1 is connected to the node A, and a second connection terminal and a control terminal of the bipolar transistor Q1 are both grounded; a first connection terminal of the MOS transistor MP2 is connected to the power supply terminal, a control terminal of the MOS transistor MP2 is connected to a control terminal of the MOS transistor MP1, and a second connection terminal of the MOS transistor MP2 is connected to a node B; a first connection terminal of the bipolar transistor Q2 is connected to the node B through the resistor R3, and a second connection terminal and a control terminal of the bipolar transistor Q2 are both grounded; a first input terminal of the operational amplifier OP is connected to the node A, a second input terminal of the operational amplifier OP is connected to the node B, and an output terminal of the operational amplifier OP is connected to the control terminal of the MOS transistor MP1; a first connection terminal of the MOS transistor MP3 is connected to the power supply terminal, a control terminal of the MOS transistor MP3 is connected to the control terminal of the MOS transistor MP2, and a second connection terminal of the MOS transistor MP3 is connected to an output terminal V1 of the positive temperature coefficient voltage generator VPTC; one end of the resistor R4 is connected to the output terminal V1 of the positive temperature coefficient voltage generator VPTC, and the other end of the resistor R4 is grounded.

12. The battery protection circuit according to claim 11, characterized in that, the MOS transistors MP1, MP2 and MP3 are PMOS transistors, and the first connection end, the second connection end and the control end of the MOS transistors MP1, MP2 and MP3 are the source, the drain and the gate of the PMOS transistors, respectively; the bipolar transistors Q1 and Q2 are PNP bipolar transistors, and the first connection end, the second connection end and the control end of the bipolar transistors Q1 and Q2 are the emitter, the collector and the base of the PNP bipolar transistors, respectively; the resistors R1 and R2 are of the same type.

13. A battery protection system, characterized by It comprises: a battery cell; a charging power switch and a discharging power switch, which are collectively referred to as a charging and discharging switch; the battery protection circuit according to any one of claims 1-12.

Images