Battery protection system

Abstract

The present invention provides a battery protection system, which includes: a battery, a charging power switch, a discharging power switch; a load / charging positive terminal; a load negative terminal P connected to the negative electrode of the battery through the discharging power switch; a charging negative terminal CH connected to the negative electrode of the battery through the charging power switch; a battery protection circuit; and a charger detection circuit connected between the load / charging positive terminal and the negative electrode of the battery. The charger detection circuit is used to detect whether the charging negative terminal CH is connected to a charger, and when it is detected that a charger is connected, the discharging power switch is controlled to be cut off. In this way, when the battery protection system is physically connected to the load, after the charger is connected, the battery stops discharging to the load, and the charger does not supply power to the load, thereby eliminating the risk of charger overload and achieving effective charging of the battery.

Description

[Technical field]

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

[0002] The battery protection system needs to realize the discharge and charge functions with protection at the same time. Figure 1 FIG. 1 is a circuit diagram of a battery protection system in the prior art. Figure 1 As shown, P+ / CH+ is the load / charging positive terminal, which can be connected to the positive pole of the load power supply or the positive pole of the charger output; CH- is the charging negative terminal, which can be connected to the negative pole of the charger output; P- is the load negative terminal, which is not drawn in the figure, and can be connected to the node MID_NODE or CH-. The battery can be a single cell or a plurality of cascaded cells.

[0003] The battery protection circuit is used to detect the charger or load status through the detection terminal VM, and RVM is a current limiting protection resistor. The battery protection circuit can be a battery protection chip. The battery protection circuit controls the NMOS charging power switch MNC through the charging control terminal CO, and controls the NMOS discharge power switch MND through the discharge control terminal DO. VCC is the power pin of the battery protection circuit, and VSS is the ground pin of the battery protection circuit. If the battery includes multiple cells connected in series, the battery protection circuit will have more pins for detecting the voltage of each cell. RS is a current detection resistor. If there is no current detection resistor RS, the on-resistance of the discharge power switch MND or the sum of the on-resistances of the charging power switches MND and MNC is equivalent to the current detection resistor.

[0004] Under the existing technology, if a charger is connected between the positive charging terminal CH+ and the negative charging terminal CH-, and at the same time, a load is connected between the positive load terminal P+ and the negative load terminal P-, the charger will supply power to the load directly or through the charging power switch MNC; if the current required by the load exceeds the limit of the charger at this time, the battery will not be effectively charged, and there will be a risk of charger overload.

[0005] Therefore, it is necessary to propose an improved technical solution to overcome the above problems. [Summary of the invention]

[0006] The present invention provides a battery protection system which can solve one of the above problems.

[0007] According to one aspect of the present invention, the present invention provides a battery protection system, which includes: a battery, a charging power switch, and a discharging power switch; a load / charging positive terminal connected to the positive electrode of the battery; a load negative terminal P-, connected to the negative electrode of the battery through the discharging power switch; a charging negative terminal CH- independent of the load negative terminal P-, connected to the negative electrode of the battery through the charging power switch; a battery protection circuit connected between the positive and negative electrodes of the battery, including a charging control terminal connected to the control terminal of the charging power switch and a discharging control terminal connected to the control terminal of the discharging power switch; a charger detection circuit connected between the load / charging positive terminal and the negative electrode of the battery, including a charger detection terminal connected to the charging negative terminal CH- and an output control terminal connected to the control terminal of the discharging power switch, which is used to detect whether the charging negative terminal CH- is connected to a charger, and when it is detected that a charger is connected, the discharging power switch is controlled to be cut off through the output control terminal.

[0008] In a further embodiment, the charger detection circuit includes: a controlled pull-down path connected between the output control terminal and the negative electrode of the battery; a charger detection unit, which is configured to control the controlled pull-down path to be turned on when it is detected that the negative charging terminal CH- is connected to the charger, so as to pull down the voltage of the output control terminal to turn off the discharge power switch, and control the controlled pull-down path to be disconnected when it is detected that the negative charging terminal CH- is not connected to the charger, and the voltage of the control terminal of the discharge power switch is determined by the discharge control terminal.

[0009] In a further embodiment, the battery protection system further includes: a unidirectional conduction module connected between the load negative terminal P- and the charging power switch, the unidirectional conduction module unidirectionally conducts from the charging power switch to the charging negative terminal CH- to prevent the charger detection circuit from leaking electricity to the negative electrode of the battery through the charging power switch when the charging negative terminal CH- is not connected to the charger.

[0010] In a further embodiment, the battery protection circuit also includes a detection terminal VM, which is connected to the intermediate node M. The battery protection system also includes: a current detection resistor RS connected between the charging power switch and the negative electrode of the battery and between the discharging power switch and the negative electrode of the battery; a unidirectional controlled conductive path connected between the load negative terminal P- and the intermediate node M, and the unidirectional controlled conductive path is unidirectionally controllably conductive from the load negative terminal P- to the charging power switch. When the charger is not connected and the discharge protection is not performed, the battery protection circuit controls the discharge power switch to be turned on through the discharge control terminal. At this time, the battery is allowed to discharge to the load through the load / charging positive terminal, the load negative terminal P-, the discharge power switch, and the current detection resistor RS. The battery protection circuit detects the voltage drop across the current detection resistor RS through the detection terminal VM, and performs discharge overcurrent protection based on the voltage drop across the current detection resistor RS. When the charger is not connected and the battery protection circuit triggers the discharge overcurrent protection, the battery protection circuit controls the discharge power switch to be turned off through the discharge control terminal, and the voltage of the load negative terminal P- is pulled up by the load. At this time, the unidirectional controlled conductive path discharges to the load negative terminal P- through the charging power switch and the current detection resistor RS. The battery protection circuit confirms whether to exit the discharge overcurrent protection based on the voltage of the detection terminal VM. If yes, the battery protection circuit exits the discharge overcurrent protection. , and controls the discharge power switch to be turned on through the discharge control end to resume discharge, if not, continues to control the discharge power switch to be turned off; when the charging protection is not triggered, the battery protection circuit controls the charging power switch to be turned on through the charging control end, and the battery protection circuit controls the unidirectional controlled conductive path to be turned on through the charging control end. When the charger is further connected, the battery is charged through the load / charging positive end, the current detection resistor RS, the charging power switch, the unidirectional conductive module and the charging negative end CH-, and the battery protection circuit detects the voltage drop on the current detection resistor RS through the detection end VM, and performs charging overcurrent protection based on the voltage drop on the current detection resistor RS; when the charger is connected and the battery protection circuit triggers the charging prohibition protection, the battery protection circuit controls the charging power switch to be turned off through the charging control end, and the battery protection circuit controls the unidirectional controlled conductive path to be disconnected through the charging control end.

[0011] Compared with the prior art, the present invention uses an independent load negative terminal P- and charging negative terminal CH- to isolate the charger from the load. When the battery protection system remains physically connected to the load, after the charger is connected, the battery stops discharging the load and the charger does not supply power to the load, thereby eliminating the risk of charger overload and achieving effective charging of the battery.

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 system in the prior art;

[0014] Figure 2 is a circuit diagram of a battery protection system in a first embodiment of the present invention;

[0015] Figure 3 is a circuit diagram of a battery protection system in a second embodiment of the present invention;

[0016] Figure 4 is a circuit diagram of a battery protection system in a third embodiment of the present invention;

[0017] Figure 5 FIG. 4 is a circuit diagram of a battery protection system in a fourth embodiment of the present invention. [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 battery protection system. When the battery protection system is physically connected to a load, after the charger is connected, the battery stops discharging to the load and the charger does not supply power to the load, thereby eliminating the risk of charger overload and achieving effective charging of the battery.

[0021] Figure 2 FIG. 4 is a circuit diagram of a battery protection system in a first embodiment of the present invention. Figure 3 FIG. 1 is a circuit diagram of the battery protection system in the second embodiment of the present invention. Figure 2 and 3As shown, the battery protection system 200 includes: a battery Battery, a charging power switch MNC, a discharging power switch MND; a load / charging positive terminal P+ / CH+ connected to the positive electrode of the battery; a load negative terminal P- connected to the negative electrode B- of the battery through the discharging power switch MND; a charging negative terminal CH- independent of the load negative terminal P-; a battery protection circuit 210 connected between the positive and negative electrodes of the battery; and a charger detection circuit 220 connected between the load / charging positive terminal and the negative electrode B- of the battery. The charging negative terminal CH- is connected to the negative electrode B- of the battery through the charging power switch MNC. The battery protection circuit 210 includes a charging control terminal CO connected to the control terminal of the charging power switch MNC and a discharging control terminal DO connected to the control terminal of the discharging power switch MND. The charger detection circuit 220 includes a charger detection terminal connected to the negative charging terminal CH- and an output control terminal connected to the control terminal of the discharge power switch MND, which is used to detect whether the negative charging terminal CH- is connected to a charger. When it is detected that a charger is connected, the discharge power switch MND is controlled to be turned off through the output control terminal. In this way, after the charger is connected, the battery stops discharging to the load, and the charger does not supply power to the load, thereby eliminating the risk of charger overload and achieving effective charging of the battery.

[0022] The battery may be a single cell or a plurality of cascaded cells.

[0023] like Figure 2 and 3 As shown, the charger detection circuit 220 includes: a controlled pull-down path 221 connected between the output control terminal and the negative electrode B- of the battery and a charger detection unit 222. The charger detection unit 222 is configured to control the controlled pull-down path 221 to be turned on when it is detected that the negative charging terminal CH- is connected to the charger, so as to pull down the voltage of the output control terminal so that the discharge power switch MND is turned off, and control the controlled pull-down path 221 to be turned off when it is detected that the negative charging terminal CH- is not connected to the charger, and the voltage of the control terminal of the discharge power switch MND is determined by the discharge control terminal DO.

[0024] The controlled pull-down path 221 includes a switch device connected between the output control terminal and the negative electrode B- of the battery.

[0025] like Figure 2As shown, the switch device may be an NMOS transistor MN1, the gate of the NMOS transistor MN1 being the control terminal of the switch device, the drain of the NMOS transistor MN1 being the output control terminal of the charger detection circuit, and the source of the NMOS transistor MN1 being connected to the negative electrode of the battery.

[0026] Figure 3 The controlled pull-down path 221 in the battery protection system is Figure 2 The structure of the controlled pull-down path 221 in the battery protection system is different. Figure 3 As shown, the switch device may also be an NPN transistor Q1. The base of the NPN transistor Q1 is the control terminal of the switch device, the collector of the NPN transistor Q1 is the output control terminal of the charger detection circuit, and the emitter of the NPN transistor Q1 is connected to the negative electrode of the battery.

[0027] like Figure 2 As shown, the charger detection unit 222 includes resistors R1, R2, R3 and R4 and a PMOS transistor MP1. Resistors R1 and R2 are connected between the load / charging positive terminal and the charging negative terminal CH-. The gate of the PMOS transistor MP1 is connected to the middle node of the resistors R1 and R2, and its source is connected to the load / charging positive terminal; resistors R3 and R4 are connected between the drain of the PMOS transistor MP1 and the negative electrode of the battery, and the middle node of the resistors R3 and R4 is connected to the control terminal of the switch device. When the charging negative terminal CH- is not connected to the charger, the PMOS transistor MP1 is turned off, the switch device in the controlled pull-down path 221 is turned off, and the voltage of the control terminal of the discharge power switch is determined by the discharge control terminal DO. When the charging negative terminal CH- is connected to the charger, the PMOS transistor MP1 is turned on, the switch device in the controlled pull-down path 221 is turned on, so that the discharge power switch is turned off.

[0028] Figure 3 The charger detection unit 222 in the battery protection system is Figure 2 The structure of the charger detection unit 222 in the battery protection system is different. Figure 3As shown, the charger detection unit 222 includes resistors R1, R2, R3 and R4 and a PNP transistor Q2. Resistors R1 and R2 are connected between the load / charging positive terminal and the charging negative terminal CH-. The base of the PNP transistor Q2 is connected to the middle node of resistors R1 and R2, and its emitter is connected to the load / charging positive terminal. Resistors R3 and R4 are connected between the collector of the PNP transistor Q2 and the negative electrode of the battery, and the middle node of resistors R3 and R4 is connected to the control end of the switch device. When the charging negative terminal CH- is not connected to the charger, the PNP transistor Q2 is turned off, the switch device in the controlled pull-down path 221 is turned off, and the voltage of the control end of the discharge power switch is determined by the discharge control terminal DO. When the charging negative terminal CH- is connected to the charger, the PNP transistor Q2 is turned on, and the switch device in the controlled pull-down path 221 is turned on, so that the discharge power switch is turned off.

[0029] In other embodiments, the charger detection unit 222 may also be other types of circuit structures, as long as it can detect whether the negative charging terminal CH- is connected to the charger and can provide a control signal to the switching device in the controlled pull-down path 221.

[0030] like Figure 2 and 3 As shown, the battery protection system further includes: a resistor RD1 connected between the discharge control terminal DO and the control terminal of the discharge power switch MND; and a resistor RD2 connected between the output control terminal of the charger detection circuit 220 and the control terminal of the discharge power switch MND. The resistor RD2 is sufficiently smaller than the resistor RD1, that is, the resistance of the resistor RD2 enables the voltage at the control terminal of the discharge power switch MND to be low enough to turn it off, that is, when the charger detection circuit detects that a charger is connected, it can control the discharge power switch to be turned off.

[0031] In one embodiment, the resistor RD2 may not be provided, and the resistor RD1 may limit the current and reduce power consumption when the charger detection circuit pulls down the voltage of the control terminal of the discharge power switch MND. Of course, in some embodiments, the resistor RD1 may not be provided.

[0032] like Figure 2 and 3As shown, the battery protection system 100 also includes: a unidirectional conduction module 240 connected between the load negative terminal P- and the charging power switch MNC. The unidirectional conduction module unidirectionally conducts from the charging power switch MNC to the charging negative terminal CH-. When the charging negative terminal CH- is not connected to the charger, the charger detection circuit 220 will pull up the voltage of the charging negative terminal CH- through resistors R1 and R2. At this time, the unidirectional conduction module 240 can prevent the charger detection circuit 220 from leaking to the negative electrode B- of the battery through the charging power switch MNC. The unidirectional conduction module 240 can be a diode D2, the anode of the diode D2 is connected to the charging power switch MNC, and the cathode of the diode D2 is connected to the charging negative terminal CH-.

[0033] like Figure 2 and 3 As shown, the battery protection system 100 further includes a detection terminal VM, which is connected to the charging power switch MNC and the intermediate node M of the unidirectional conduction module 240. The battery protection system 100 further includes: a current detection resistor RS connected between the charging power switch MNC and the negative electrode of the battery and between the discharging power switch MND and the negative electrode of the battery; and a unidirectional controlled conductive path 230 connected between the load negative terminal P- and the intermediate node M. The unidirectional controlled conductive path 230 is unidirectionally controllably conductive from the load negative terminal P- to the charging power switch MNC.

[0034] When the charger is not connected and the discharge protection is not performed, the controlled pull-down path 221 is disconnected, the voltage of the control end of the discharge power switch MND is determined by the discharge control end DO, and the battery protection circuit 210 controls the discharge power switch MND to be turned on through the discharge control end DO. At this time, the battery is allowed to discharge to the load through the load / charging positive end, the load negative end P-, the discharge power switch, and the current detection resistor RS. The battery protection circuit detects the voltage drop across the current detection resistor RS through the detection end VM, and determines whether discharge overcurrent protection is required based on the voltage drop across the current detection resistor RS.

[0035] When the charger is not connected and the battery protection circuit 210 triggers the discharge overcurrent protection, the controlled pull-down path 221 is disconnected, the voltage of the control end of the discharge power switch MND is determined by the discharge control end DO, and the battery protection circuit 210 controls the discharge power switch MND to be turned off through the discharge control end DO. The voltage of the load negative terminal P- is pulled up by the load. At this time, the unidirectional controlled conductive path 230 discharges the load negative terminal P- through the charging power switch MNC and the current detection resistor RS, that is, a weak discharge path is formed. The battery protection circuit 210 determines whether to exit the discharge overcurrent protection based on the voltage of the detection end VM. After the load is removed, the voltage of the load negative terminal P- will be pulled down by the unidirectional controlled conductive path 230. If the load is not removed, the voltage of the load negative terminal P- will continue to maintain a high potential. If the unidirectional controlled conductive path 230 does not exist, even if the load is removed, the voltage of the load negative terminal P- will remain at a high potential, so that the discharge overcurrent protection cannot be released. If yes, the battery protection circuit exits the discharge overcurrent protection, and controls the discharge power switch MND to turn on through the discharge control terminal to resume discharge; if no, the discharge power switch MND continues to be controlled to turn off.

[0036] When the charging protection is not triggered, the battery protection circuit 210 controls the charging power switch MNC to be turned on through the charging control terminal CO, and the battery protection circuit 210 controls the unidirectional controlled conductive path 230 to be turned on through the charging control terminal CO. When the charger is further connected, the controlled pull-down path 221 is turned on, the discharge power switch MND is turned off, and the charger charges the battery through the load / charging positive terminal, the current detection resistor RS, the charging power switch MNC, the unidirectional conduction module 240 and the charging negative terminal CH-. At this time, the negative electrode B- of the battery, the current detection resistor RS, the parasitic diode of the discharge power switch MND, the load negative terminal P-, the unidirectional controlled conductive path 230, the unidirectional conduction module 240, and the charging negative terminal CH- also constitute a weak charging path for charging the battery. The battery protection circuit detects the voltage drop on the current detection resistor RS through the detection terminal VM, and determines whether charging overcurrent protection is required based on the voltage drop on the current detection resistor RS.

[0037] When a charger is connected and the battery protection circuit triggers the charging prohibition protection, the battery protection circuit 210 controls the charging power switch MNC to be turned off through the charging control terminal CO, and the battery protection circuit 210 controls the unidirectional controlled conductive path 230 to be disconnected through the charging control terminal to cut off the weak charging path passing through the unidirectional controlled conductive path 230. In this way, the charging prohibition function is realized.

[0038] like Figure 2 and 3 As shown, the battery protection system 100 further includes: a resistor R5 connected between the detection terminal VM and the connection terminal of the charging power switch MNC connected to the unidirectional conduction module 240, wherein the resistor R5 is also connected between the unidirectional controlled conductive path 230 and the connection terminal of the charging power switch MNC connected to the unidirectional conduction module 240. The resistor R5 can be used for current limiting.

[0039] like Figure 2 and 3 As shown, the unidirectional controlled conductive path 230 includes a diode D1, a resistor R6 and an NMOS transistor MNVM connected in series. Figure 2 In the embodiment, the diode D1, the NMOS transistor MNVM and the resistor R6 are connected in series in sequence. Figure 3 In the embodiment, the diode D1, the resistor R6 and the NMOS transistor MNVM are connected in series in sequence. The gate of the NMOS transistor MNVM is connected to the charging control terminal CO of the battery protection circuit 210, the source of the NMOS transistor MNVM is connected to the connection terminal of the charging power switch MNC connected to the unidirectional conduction module 240, and the drain of the NMOS transistor MNVM is connected to the load negative terminal P-. Since the control terminals of both are connected to the charging control terminal CO of the battery protection circuit 210, the NMOS transistor MNVM and the charging power switch MNC are synchronously turned on or off. In other embodiments, the positions of the diode D1, the resistor R6 and the NMOS transistor MNVM can also be interchanged. In another embodiment, the resistor R6 can also be removed.

[0040] like Figure 2 and 3 As shown, the charging power switch is an NMOS transistor MNC, the source of which is connected to the negative charging terminal CH- through the unidirectional conduction module 240, the drain of which is connected to the negative electrode of the battery through the current detection resistor RS, and the gate of which is the control terminal of the charging power switch MNC. The discharging power switch is an NMOS transistor MND, the source of which is connected to the negative electrode of the battery through the current detection resistor RS, the drain of which is connected to the negative load terminal P-, and the gate of which is the control terminal of the discharging power switch MND.

[0041] Figure 4 is a circuit diagram of a battery protection system in a third embodiment of the present invention; Figure 5 FIG. 4 is a circuit diagram of a battery protection system in a fourth embodiment of the present invention. Figure 4Battery protection system in Figure 2 The battery protection system in the only difference is: Figure 4 The battery protection system in the embodiment further includes: a current detection adjustment resistor RS1 connected between the charging power switch and the current detection resistor RS, wherein the intermediate node between the current detection adjustment resistor RS1 and the current detection resistor RS is connected to the discharge power switch. The charging current will flow through RS, RS1, and the charging power tube MNC, and the current threshold corresponding to the charging overcurrent protection function can be flexibly adjusted by adjusting the current detection adjustment resistor RS1.

[0042] Figure 5 Battery protection system in Figure 2 The battery protection system in the only difference is: Figure 5 The battery protection system in the embodiment further includes: a current detection adjustment resistor RS2 connected between the charging power switch and the unidirectional conduction module, wherein the intermediate node M is located between the current detection adjustment resistor RS2 and the unidirectional conduction module, and the detection terminal VM is connected to the intermediate node M through the resistor R5. The charging current will flow through RS, the charging power tube MNC, and RS2, and the current threshold corresponding to the charging overcurrent protection function can be flexibly adjusted by adjusting the current detection adjustment resistor RS2.

[0043] The present invention uses an independent load negative terminal P- and charging negative terminal CH- to isolate the charger from the load. When the battery protection system remains physically connected to the load, after the charger is connected, the battery stops discharging to the load, and the charger does not supply power to the load, thereby eliminating the risk of charger overload and achieving effective charging of the battery.

[0044] 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.

[0045] 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 battery protection system, characterized in that: It includes: Battery, charging power switch, discharging power switch; A load / charging positive terminal connected to the positive electrode of the battery; A load negative terminal P-, which is connected to the negative electrode of the battery through the discharge power switch; A negative charging terminal CH-, which is independent of the negative load terminal P- and is connected to the negative electrode of the battery through the charging power switch; a battery protection circuit connected between the positive and negative electrodes of the battery, comprising a charging control terminal connected to the control terminal of the charging power switch and a discharging control terminal connected to the control terminal of the discharging power switch; A charger detection circuit connected between the load / charging positive terminal and the negative terminal of the battery comprises a charger detection terminal connected to the charging negative terminal CH- and an output control terminal connected to the control terminal of the discharge power switch, and is used to detect whether the charging negative terminal CH- is connected to a charger. When it is detected that a charger is connected, the discharge power switch is controlled to be cut off through the output control terminal.

2. The battery protection system according to claim 1, characterized in that: The charger detection circuit comprises: a controlled pull-down path connected between the output control terminal and the negative electrode of the battery; A charger detection unit is configured to control the controlled pull-down path to be turned on when it is detected that the negative charging terminal CH- is connected to the charger, so as to pull down the voltage of the output control terminal to turn off the discharge power switch, and control the controlled pull-down path to be disconnected when it is detected that the negative charging terminal CH- is not connected to the charger, and the voltage of the control terminal of the discharge power switch is determined by the discharge control terminal.

3. The battery protection system according to claim 2, characterized in that: The controlled pull-down path includes a switch device connected between the output control terminal and the negative electrode of the battery, The switch device is an NMOS transistor MN1 or an NPN transistor Q1. The gate of the NMOS transistor MN1 is the control terminal of the switch device, the drain of the NMOS transistor MN1 is the output control terminal of the charger detection circuit, and the source of the NMOS transistor MN1 is connected to the negative electrode of the battery; or The base of the NPN transistor Q1 is the control end of the switch device, the collector of the NPN transistor Q1 is the output control end of the charger detection circuit, and the emitter of the NPN transistor Q1 is connected to the negative electrode of the battery.

4. The battery protection system according to claim 3, characterized in that: The charger detection unit includes resistors R1, R2, R3 and R4 and a PMOS transistor MP1 or a PNP transistor Q2. Resistors R1 and R2 are connected between the load / charging positive terminal and the charging negative terminal CH-; The gate of the PMOS transistor MP1 is connected to the middle node of the resistors R1 and R2, and the source of the PMOS transistor MP1 is connected to the load / charging positive terminal; the resistors R3 and R4 are connected between the drain of the PMOS transistor MP1 and the negative electrode of the battery, and the middle node of the resistors R3 and R4 is connected to the control end of the switch device. When the charging negative terminal CH- is not connected to the charger, the PMOS transistor MP1 is turned off, and the switch device is turned off. When the charging negative terminal CH- is connected to the charger, the PMOS transistor MP1 is turned on, and the switch device is turned on; or, The base of the PNP transistor Q2 is connected to the middle node of the resistors R1 and R2, and the emitter thereof is connected to the load / charging positive terminal. The resistors R3 and R4 are connected between the collector of the PNP transistor Q2 and the negative electrode of the battery. The middle node of the resistors R3 and R4 is connected to the control end of the switching device. When the charging negative terminal CH- is not connected to the charger, the PNP transistor Q2 is turned off and the switching device is turned off. When the charging negative terminal CH- is connected to the charger, the PNP transistor Q2 is turned on and the switching device is turned on.

5. The battery protection system according to claim 1, characterized in that: It also includes: a resistor RD1 connected between the discharge control terminal and the control terminal of the discharge power switch; and / or A resistor RD2 is connected between the output control terminal of the charger detection circuit and the control terminal of the discharge power switch, wherein the resistance of the resistor RD2 enables the charger detection circuit to control the discharge power switch to be turned off when detecting that a charger is connected.

6. The battery protection system according to claim 1, characterized in that: It also includes: A unidirectional conduction module connected between the load negative terminal P- and the charging power switch, wherein the unidirectional conduction module is unidirectionally conducted from the charging power switch to the charging negative terminal CH- to prevent the charger detection circuit from leaking electricity to the negative electrode of the battery through the charging power switch when the charging negative terminal CH- is not connected to a charger.

7. The battery protection system according to claim 6, characterized in that: The battery protection circuit further includes a detection terminal VM, wherein the detection terminal VM is connected to an intermediate node M between the charging power switch and the unidirectional conduction module. The battery protection system also includes: A current detection resistor RS connected between the charging power switch and the negative electrode of the battery and between the discharging power switch and the negative electrode of the battery; A unidirectional controlled conductive path connected between the load negative terminal P- and the intermediate node M, wherein the unidirectional controlled conductive path is controllably conductive from the load negative terminal P- to the charging power switch, When the charger is not connected and the discharge protection is not performed, the battery protection circuit controls the discharge power switch to be turned on through the discharge control terminal, and the battery is allowed to discharge to the load through the load / charging positive terminal, the load negative terminal P-, the discharge power switch, and the current detection resistor RS. The battery protection circuit detects the voltage drop across the current detection resistor RS through the detection terminal VM, and determines whether discharge overcurrent protection is required based on the voltage drop across the current detection resistor RS. When the charger is not connected and the battery protection circuit triggers the discharge overcurrent protection, the battery protection circuit controls the discharge power switch to be turned off through the discharge control terminal, and the voltage of the load negative terminal P- is pulled up by the load. At this time, the unidirectional controlled conductive path discharges the load negative terminal P- through the charging power switch and the current detection resistor RS. The battery protection circuit confirms whether to exit the discharge overcurrent protection based on the voltage of the detection terminal VM. If yes, the battery protection circuit exits the discharge overcurrent protection and controls the discharge power switch to be turned on through the discharge control terminal to resume discharging. If not, the discharge power switch continues to be controlled to be turned off. When the charging protection is not triggered, the battery protection circuit controls the charging power switch to be turned on through the charging control terminal, and the battery protection circuit controls the unidirectional controlled conductive path to be turned on through the charging control terminal. When the charger is further connected, the battery is charged through the load / charging positive terminal, the current detection resistor RS, the charging power switch, the unidirectional conduction module and the charging negative terminal CH-. The battery protection circuit detects the voltage drop on the current detection resistor RS through the detection terminal VM, and determines whether charging overcurrent protection is required based on the voltage drop on the current detection resistor RS. When a charger is connected and the battery protection circuit triggers the charging prohibition protection, the battery protection circuit controls the charging power switch to be turned off through the charging control terminal, and the battery protection circuit controls the unidirectional controlled conductive path to be disconnected through the charging control terminal.

8. The battery protection system according to claim 7, characterized in that: It also includes: A resistor R5 is connected between the detection terminal VM and the middle node M, wherein the resistor R5 is also connected between the unidirectional controlled conductive path and the middle node M.

9. The battery protection system according to claim 7, characterized in that: The unidirectional controlled conductive path includes a diode D1, a resistor R6 and an NMOS transistor MNVM connected in series, the gate of the NMOS transistor MNVM is connected to the charging control terminal of the battery protection circuit, the source of the NMOS transistor MNVM is connected to the intermediate node M, and the drain of the NMOS transistor MNVM is connected to the load negative terminal P-.

10. The battery protection system according to claim 7, characterized in that: The charging power switch is an NMOS transistor MNC, the source of the NMOS transistor MNC is connected to the negative charging terminal CH- through the unidirectional conduction module, the drain of the NMOS transistor MNC is connected to the negative electrode of the battery through the current detection resistor RS, and the gate of the NMOS transistor MNC is the control terminal of the charging power switch; The discharge power switch is an NMOS transistor MND, the source of which is connected to the negative electrode of the battery through the current detection resistor RS, the drain of which is connected to the negative load terminal P-, and the gate of which serves as the control terminal of the discharge power switch.

11. The battery protection system according to claim 7, characterized in that: It also includes: a current detection adjustment resistor RS1 connected between the charging power switch and the current detection resistor RS, wherein an intermediate node between the current detection adjustment resistor RS1 and the current detection resistor RS is connected to the discharging power switch; and / or A current detection adjustment resistor RS2 is connected between the charging power switch and the unidirectional conduction module, wherein the intermediate node M is located between the current detection adjustment resistor RS2 and the unidirectional conduction module, and the detection terminal VM is connected to the intermediate node M.

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