Over-voltage and under-voltage protection circuit, integrated circuit and battery management system

Abstract

The invention discloses an overvoltage and undervoltage protection circuit, an integrated circuit and a battery management system. The protection circuit comprises an internal power supply unit, a reference voltage source unit, a voltage detection unit, a voltage comparison unit, a logic control unit, a GATE driving unit, a switch unit and a totem pole driving unit. The internal power supply unit provides a low-voltage direct-current power supply for working of an on-chip circuit; the reference voltage source unit generates reference voltage, and the voltage detection unit samples voltage signals and inputs the voltage signals to the voltage comparison unit. The voltage comparison unit controls the logic control unit, the logic control unit controls the GATE driving unit and / or the totem pole driving unit, the GATE driving unit controls the switch unit, the switch unit provides an external power supply interface, and the on-chip switch connects or disconnects the connection between the positive electrode of the battery and the external power supply interface; and the totem pole driving unit provides a logic signal output interface. The protection circuit is simple in structure, low in power consumption and wide in application range.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery protection, and in particular relates to an overvoltage and undervoltage protection circuit, an integrated circuit and a battery management system. Background Art

[0002] In lithium batteries and their series battery pack systems, when the cell voltage of a lithium iron battery is lower than 2.5V, and when the cell voltage of a ternary lithium battery is lower than 2.4V, it enters an undervoltage state. When the battery is undervoltage, the battery should enter an extremely low power consumption mode, otherwise, as the battery further consumes power, it will cause irreversible damage to the battery, which will lead to internal gas precipitation due to excessive power consumption, resulting in battery bulging, etc. The active substances in the battery cannot be fully restored, and the capacity decreases or even completely loses.

[0003] Therefore, in multi-cell battery pack applications, the battery needs to be equipped with a battery management system (BMS). BMS is mainly composed of an analog front-end AFE (Active Front End) rectifier / feedback unit, an MCU (Microcontroller Unit), a communication unit, a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) action unit, and an auxiliary power supply system. The auxiliary power supply must meet the requirement of normal operation during overcharge and over-discharge protection of the battery. Therefore, the auxiliary power supply directly draws power from the positive electrode BAT+ and the negative electrode BAT- of the battery to generate 12V, 5V, 3.3V and other operating voltages required by various systems.

[0004] Generally, existing battery packs use integrated BUCK buck IC (Integrated Circuit) to generate auxiliary power. The operating voltage range of the BUCK buck IC is very wide, and it will still work normally within the undervoltage protection voltage range of the battery pack. Therefore, when the battery pack enters the undervoltage state, the auxiliary power supply is still working. The power consumption of the auxiliary power supply is generally in the range of 0.5 to 3W. In order to protect the battery from damage, it is necessary to add an additional voltage undervoltage protection circuit at the front end of the auxiliary power supply to ensure that the auxiliary power supply can be turned off when the battery pack voltage drops into the undervoltage protection range.

[0005] Existing technologies such as Figure 1As shown, a battery undervoltage detection and protection circuit is formed by a voltage stabilizing diode, CJ431, an optical coupler, a resistor, a capacitor, and a Q3PMOS. The disadvantages of this circuit are: 1. The operating voltage range of CJ431 is 3~36V. In battery pack applications exceeding 36V, a series voltage regulator diode is required for voltage division and power supply; 2. The operating current of CJ431 is 1mA, and the current of DZ1 and R3 power supply branches should be ≥1mA; R1 and R2 constitute voltage detection, and the protection voltage is VZ=2.5V×(R1+R2) / R2. Because the maximum value of R2 cannot exceed 10K, otherwise the detection accuracy of CJ431 will be reduced, so the minimum value of the branch current detected by R1 and R2 is Idet_min=2.5V / 10K=0.25mA; therefore, the total operating current consumption of the entire circuit is Iop≥1.25mA; 3. After the battery enters undervoltage protection, the circuit current consumption remains unchanged from that during operation, Ipd≥1.25mA, which cannot meet the low power consumption requirements; 4. There are many circuit components, the circuit is complex, and the cost is high. Summary of the invention

[0006] The present invention provides an overvoltage and undervoltage protection circuit, an integrated circuit and a battery management system, aiming to solve the problems of complex circuits, high power consumption and limited applicability in the prior art.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides an overvoltage and undervoltage protection circuit, which is connected to a battery management system circuit of a battery, and includes an internal power supply unit, a reference voltage source unit, a voltage detection unit, a voltage comparison unit, a logic control unit, a GATE driving unit, a switch unit and a totem pole driving unit;

[0008] The input pin of the internal power supply unit is connected to the positive electrode of the battery, and outputs a low-voltage DC power supply for the operation of the on-chip circuit;

[0009] The input end of the reference voltage source unit is connected to the output end of the internal power supply unit to generate a reference voltage to an input end of the voltage comparison unit;

[0010] The input end of the voltage detection unit is connected to the positive electrode of the battery through a resistor, and is used to sample the battery voltage. The voltage sampling signal is sent to the other input end of the voltage comparison unit;

[0011] The voltage comparison unit outputs a first control signal to the logic control unit;

[0012] The logic control unit generates a second control signal to the GATE driving unit and / or the totem pole driving unit according to the first control signal, and also provides a mode selection interface externally;

[0013] The GATE driving unit generates a switch signal according to the second control signal and outputs it to the switch unit;

[0014] The switch unit provides an external power supply interface, and the on-chip switch opens or closes the connection between the positive electrode of the battery and the external power supply interface according to the switch signal;

[0015] The totem pole driving unit provides a logic signal output interface.

[0016] Preferably, the resistor connected between the input pin of the voltage detection unit and the positive electrode of the battery is a potentiometer or a variable resistor, which is used to set the threshold of undervoltage or overvoltage protection.

[0017] Preferably, the resistor connected between the input pin of the voltage detection unit and the positive electrode of the battery is a programmable resistor, which is used to set the threshold of undervoltage or overvoltage protection.

[0018] Preferably, the non-phase input of the voltage comparison unit is a reference voltage, and the inverting input is a voltage sampling signal.

[0019] Preferably, the mode selection interface can be suspended or grounded to set the polarity of external power supply and logic signals.

[0020] Preferably, the switch unit includes two PMOS tubes with connected sources, a drain of one PMOS tube connected to the positive electrode of the battery, and a drain of the other PMOS tube connected to an external power supply interface, and a switch signal controls the two PMOS tubes through gates.

[0021] Preferably, the totem pole driving unit is provided with a PMOS pull-up and an NMOS pull-down.

[0022] Preferably, the voltage comparison unit is a hysteresis comparator.

[0023] A second aspect of the present invention further provides an integrated circuit, wherein the integrated circuit is equipped with the overvoltage and undervoltage protection circuit as described in the first aspect of the present invention, and is used to perform undervoltage protection and / or overvoltage protection on a protected battery.

[0024] The third aspect of the present invention also proposes a battery management system, including a battery monitoring module, a balancing module, a communication module, a main control unit, a protection module and an auxiliary power supply module. The auxiliary power supply module uses the overvoltage and undervoltage protection circuit as described in the first aspect of the present invention to provide low-voltage DC power for other modules of the system.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] 1. The protection circuit proposed in the present invention has the characteristics of ultra-low power consumption current by configuring the bias resistor and the programmable resistor, combined with the circuit structure of the present invention. When the access voltage is below 40V, the working current consumption is less than 6uA; when the working voltage is 40-100V, the current consumption is less than 15uA. When the circuit enters the under-voltage protection, the auxiliary power supply can be turned off, so that the current consumption can be reduced to within 1uA, further reducing the peripheral current to protect the battery or battery pack.

[0027] 2. The protection circuit proposed in the present invention can flexibly set the protection voltage through the connected programmable resistor, and can set the undervoltage protection voltage or overvoltage protection voltage in the range of 3 to 100V, and can flexibly realize the detection and protection of a certain voltage value within the voltage range. Compared with the detection circuit composed of discrete electronic components, the present invention has the effects of simple structure, small size, low cost and high reliability.

[0028] 3. The protection circuit proposed in the present invention has both the function of an electronic switch and the function of providing a low-voltage logic drive signal by setting a switch unit and a totem pole drive unit. The electronic switch function can provide a DC power supply current or disconnect the DC power supply, and the low-voltage logic drive signal can drive the peripheral MOS switch to perform corresponding protection actions according to customer needs.

[0029] 4. The protection circuit proposed in the present invention can flexibly adjust the output states of the external power supply interface and the logic signal output interface through the set mode selection interface, and can be widely applied to different customer needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the protection circuit structure of the prior art;

[0031] Figure 2 It is a schematic diagram of the protection circuit structure of the present invention;

[0032] Figure 3 is a circuit schematic diagram of application solution 1 described in an embodiment of the present invention;

[0033] Figure 4 is a timing diagram of the Vout output voltage of the application scheme 1 described in the embodiment of the present invention;

[0034] Figure 5 is a circuit schematic diagram of application solution 2 described in an embodiment of the present invention;

[0035] Figure 6 is a VDO output voltage timing diagram of application solution 2 described in an embodiment of the present invention;

[0036] Figure 7 is a circuit schematic diagram of application solution 3 described in an embodiment of the present invention;

[0037] Figure 8 1 is a VDO output voltage timing diagram of application solution 3 described in an embodiment of the present invention;

[0038] Fig. 9 is a circuit schematic diagram of application scheme 4 described in an embodiment of the present invention;

[0039] Fig.10 1 is a timing diagram of the Vout output voltage of the fourth application scheme described in the embodiment of the present invention;

[0040] Fig.11 is a circuit schematic diagram of application scheme 5 described in an embodiment of the present invention;

[0041] Fig.12 is a VDO output voltage timing diagram of application scheme 5 described in an embodiment of the present invention;

[0042] Fig.13 is a circuit schematic diagram of application scheme 6 described in an embodiment of the present invention;

[0043] Fig.14 This is a VDO output voltage timing diagram of application scheme 6 described in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in combination with specific embodiments of the present application and with reference to the accompanying drawings.

[0045] Embodiment 1

[0046] This embodiment is an overvoltage and undervoltage protection circuit, which is connected to a battery management system circuit of a battery. Figure 2 As shown, it includes an internal power supply unit, a reference voltage source unit, a voltage detection unit, a voltage comparison unit, a logic control unit, a GATE driving unit, a switch unit and a totem pole driving unit;

[0047] The input pin of the internal power supply unit is Vin, which is connected to the positive electrode of the battery. This embodiment is applied to a DC circuit that needs to perform undervoltage detection and protection action on the power supply when the battery voltage is 3-100V. The internal power supply unit outputs a low-voltage DC power supply for the on-chip circuit to work.

[0048] The reference voltage source unit is Figure 2 The low-voltage reference voltage source in the circuit has an input end connected to the output end of the internal power supply unit, obtains a low-voltage DC power input, and generates a reference voltage VREF to an input end of the voltage comparison unit through an internal circuit.

[0049] The input end of the voltage detection unit is connected to the positive electrode Vin of the battery through the resistor R_prg for sampling the battery voltage. After the current passes through the resistor R_prg, the voltage generated by the voltage reduction is sampled by the voltage detection unit to generate a sampling signal which is sent to the other input end of the voltage comparison unit.

[0050] In this embodiment, the resistor R_prg connected between the input pin of the voltage detection unit and the positive electrode of the battery is a programmable resistor, which is used to set the threshold of undervoltage or overvoltage protection. The programmable resistor and the fixed down-bias resistor Rdown set inside the V_PRG pin of the voltage detection unit form a sample of the input voltage Vin, and the voltage sampling signal is sent to the other input end of the voltage comparison unit. The programmable resistor is connected to an external control circuit, and the element that changes the resistance value through electronic control can support higher automation and precision.

[0051] In some other embodiments of the present invention, the resistor R_prg connected between the input pin V_PRG of the voltage detection unit and the positive electrode of the battery is a potentiometer or a variable resistor, such as a single-turn potentiometer, a multi-turn potentiometer, a sliding variable resistor, a rotary potentiometer or a linear potentiometer, which is also used to set the threshold V_SET of undervoltage or overvoltage protection.

[0052] The voltage comparison unit is Figure 2 The voltage comparator in the embodiment outputs a first control signal to the logic control unit. In this embodiment, the reference voltage is input to the in-phase input terminal IN+ of the voltage comparison unit, and the voltage sampling signal is input to the in-phase input terminal IN- of the voltage comparison unit. The comparator outputs a corresponding high level or low level to the logic control unit according to the voltage signals at the IN+ and IN- input terminals.

[0053] In some other embodiments of the present invention, the input signals of the non-inverting input terminal IN+ and the inverting input terminal IN- can be swapped, but the judgment logic in the subsequent logic control unit needs to be adjusted accordingly.

[0054] In one embodiment of the present invention, the voltage comparison unit is a hysteresis comparator.

[0055] The logic control unit generates a second control signal to the GATE drive unit and / or the totem pole drive unit according to the internally set logic and the first control signal, and also provides a mode selection interface MODE to the outside. The mode selection interface MODE can be suspended or grounded, and is used to set the polarity of the external power supply and logic signal.

[0056] The GATE driving unit generates a switch signal according to the second control signal and outputs the switch signal to the switch unit.

[0057] The switch unit provides an external power supply interface Vout, and the on-chip switch opens or closes the connection between the positive electrode of the battery and the external power supply interface according to the switch signal, that is, generates an output voltage at the Vout pin or cuts off the Vout output voltage. Specifically, the switch unit includes two PMOS tubes with connected sources, a drain of one PMOS tube is connected to the positive electrode of the battery, and a drain of the other PMOS tube is connected to the external power supply interface Vout, and the switch signal controls the two PMOS tubes through the gate. A resistor Rg is also connected in parallel between the source and the gate of the two PMOS tubes.

[0058] The totem pole driving unit is provided with a PMOS pull-up and an NMOS pull-down, and provides a logic signal output interface VDO, so that a corresponding high / low logic driving signal required is generated at the VDO output pin.

[0059] The working principle of the present invention is as follows:

[0060] Vin is the power supply input pin of IC. The internal power supply unit generates a low-voltage DC power supply for the on-chip circuit. The low-voltage reference voltage source generates a reference voltage VREF and provides it to the in-phase input terminal IN+ of the voltage comparison unit. The user connects an external programmable resistor R_prg between the Vin pin and the V_PRG pin, and forms a sampling of the input voltage Vin with the fixed down-bias resistor Rdown inside the V_PRG pin. The voltage sampling signal is sent to the reverse input terminal IN- of the voltage comparison unit and compared with the VREF voltage. The comparator outputs the corresponding high level or low level to the logic control unit according to the voltage signal of the IN+ and IN- input terminals. The logic control unit outputs a signal to the GATE drive unit according to the internally set logic. The GATE drive then controls the on-chip PMOS tube of the switch unit to turn on or off, thereby generating an output voltage at the Vout pin or cutting off the Vout output voltage. At the same time, the logic control unit outputs a signal to the totem pole drive unit. The totem pole drive unit is equipped with a PMOS pull-up and an NMOS pull-down, thereby generating the required high / low logic drive signal at the VDO output pin.

[0061] The resistance value of the programmable resistor R_prg can set the undervoltage or overvoltage protection threshold V_SET. The calculation method is: V_SET = VREF × (R_prg + R_down) / R_down. The logic control unit can generate positive logic or negative logic to the GATE drive unit and the totem pole drive unit, thereby generating sub-model circuits with different effects and their applications.

[0062] The resistance of the down-bias resistor R_down in the present invention is between 500KΩ and 3MΩ; the VREF reference voltage can be set to the range of 0.5 to 3.3V. For example, if R_down is set to 500KΩ = 0.5MΩ and VREF is set to 1.0V, when the circuit sets the protection voltage V_SET to 60V, the user-programmed resistor R_prg has a resistance of:

[0063] R_prg=V_SET×R_down / VREF-R_down=60×0.5 / 1.0-0.5=29.5MΩ.

[0064] At this time, the calculation formula of the maximum current Idet_max used for circuit protection voltage detection is as follows:

[0065] Idet_max=100V / (R_prg+R_down)=100 / (29.5+0.5)=3.33uA.

[0066] The internal working current of the circuit is less than 10uA, so the overall current consumption is less than 13uA.

[0067] The present invention is mainly used in DC circuits that need to detect undervoltage of the power supply and take protective actions at 3-100V. The circuit of the present invention has the characteristics of ultra-low power consumption. In 0-40V voltage applications, the normal working current consumption is less than 6uA, and in 40-100V applications, the working current consumption is less than 15uA; when the circuit enters the undervoltage protection state, the current consumption is less than 5uA.

[0068] When the electronic switch inside the circuit is turned on, the output Vout = Vin-VFD≈Vin, where VFD is the voltage drop caused by the working current flowing through the internal switch circuit. Under normal circumstances, VFD is in the range of 0 to 300mV, so it can be ignored. The subsequent descriptions are all based on Vout≈Vin to describe the Vout state when the internal electronic switch is turned on. The totem pole drive unit outputs two signals, high level Vhigh and low level Vlow, and the signal voltage ranges are respectively Vhigh between 3.3V and 12V; Vlow between 0 and 0.5V.

[0069] According to the requirements of the use site, the circuit described in this embodiment can be used for under / overvoltage detection and protection, and can be used for positive and negative logic as shown in the following table:

[0070]

[0071] Correspondingly, the logic control unit outputs the opposite second control signal, so that the voltage logic of the final output Vout and / or VDO is opposite to the logic described in the above table. If MODE is left unconnected and Vin>V_SET, if only Vout is subjected to the opposite logic, the final output is Vout=0, VDO=Vlow; if only VDO is subjected to the opposite logic, the final output is Vout≈Vin, VDO=Vhigh; if both Vout and VDO are subjected to the opposite logic, the final output is Vout=0, VDO=Vhigh.

[0072] If MODE is left floating and Vin≤V_set, if only Vout is subjected to the opposite logic, the final output is Vout≈Vin, VDO=Vhigh; if only VDO is subjected to the opposite logic, the final output is Vout=0, VDO=Vlow; if both Vout and VDO are subjected to the opposite logic, the final output is Vout≈Vin, VDO=Vlow.

[0073] If MODE is grounded and Vin>V_SET, if only Vout is subjected to the opposite logic, the final output is Vout≈Vin, VDO=Vlow; if only VDO is subjected to the opposite logic, the final output is Vout=0, VDO=Vhigh; if Vout and VDO are subjected to the opposite logic at the same time, the final output is Vout≈Vin, VDO=Vhigh.

[0074] If MODE is grounded and Vin≤V_set, if only Vout is subjected to the opposite logic, the final output is Vout=0, VDO=Vhigh; if only VDO is subjected to the opposite logic, the final output is Vout≈Vin, VDO=Vlow; if Vout and VDO are subjected to the opposite logic at the same time, the final output is Vout=0, VDO=Vlow.

[0075] Several application scenarios are given below to explain the present invention in detail.

[0076] Application Solution 1

[0077] Undervoltage protection with electronic switch output circuit system. Specific circuits such as Figure 3 As shown in the figure, in this application solution, the MODE pin is left floating and the VDO pin is not used. Figure 4 As shown, in this application solution, when Vin>V_SET, Vout≈Vin; when Vin≤V_SET, Vout=0, that is, the power supply output is cut off during undervoltage protection.

[0078] Application Solution 2

[0079] Output high level drive signal during undervoltage protection. Figure 5As shown in the figure, in this application, the MODE pin is left floating and the Vout pin is not used. Figure 6 As shown, this is the timing diagram of the output of the high-level drive signal during undervoltage protection of this application solution. When Vin>V_SET, VDO=Vlow(0~0.5V); when Vin≤V_SET, VDO=Vhigh(3.3V~12), that is, the high-level drive signal is output during undervoltage protection.

[0080] Application Solution 3

[0081] Output low level drive signal during undervoltage protection. Figure 7 As shown in Figure 1, in this application, the MODE pin is grounded and the Vout pin is not used. The output of this solution is shown in Figure 1. Figure 8 As shown, this is the timing diagram of the output of the low-level drive signal during undervoltage protection of this application solution. When Vin>V_SET, VDO=Vhigh(3.3V~12V); when Vin≤V_SET, VDO=Vlow(0~0.5V), that is, the low-level drive signal is output during undervoltage protection.

[0082] Application Solution 4

[0083] The Vout output voltage is cut off during overvoltage protection. The specific circuit is as follows Fig. 9 As shown in Figure 1, in this application, the MODE pin is grounded and the VDO pin is not used. The output of this solution is shown in Figure 1. Fig.10 As shown, this is the Vout output voltage timing diagram during overvoltage protection of this application solution. When Vin>V_SET, Vout=0; when Vin≤V_SET, Vout≈Vin, that is, the power supply output is cut off during overvoltage protection.

[0084] Application Solution 5

[0085] Output high voltage logic drive signal during overvoltage protection. Specific circuit is as follows Fig.11 As shown in Figure 1, in this application, the MODE pin is grounded and the Vout pin is not used. The output of this solution is shown in Figure 1. Fig.12 As shown, this is the timing diagram of the high voltage logic drive signal output during overvoltage protection of this application solution. When Vin>V_SET, VDO=Vhigh(3.3V~12V); when Vin≤V_SET, VDO=Vlow(0~0.5V), that is, the high voltage logic drive signal is output during overvoltage protection.

[0086] Application Solution 6

[0087] Output low voltage logic drive signal during overvoltage protection. Fig.13 As shown in the figure, in this application, the MODE pin is left floating and the Vout pin is not used. Fig.14 As shown, this is the timing diagram of the low voltage logic drive signal output during overvoltage protection of this application solution. When Vin>V_SET, VDO=Vlow(0~0.5V); when Vin≤V_SET, VDO=Vhigh(3.3V~12), that is, the low voltage logic drive signal is output during overvoltage protection.

[0088] The above application can also use the VDO pin and Vout pin at the same time.

[0089] When the user can program the undervoltage protection, if the battery voltage is higher than the programmed undervoltage protection value, the circuit of the present invention works normally, can provide power for the auxiliary power supply, and generate a high-level or low-level logic signal at the same time; if the battery voltage is lower than the undervoltage protection value, the circuit of the present invention enters the undervoltage protection mode, cuts off the auxiliary power supply circuit, and generates a low-level or high-level logic drive signal to the back-end control circuit unit. It can be widely used in any DC circuit system that needs undervoltage detection and protection, as the undervoltage detection of the power supply voltage in the circuit system, power supply output and providing protection drive logic.

[0090] At the same time, the circuit of the present invention can also be widely used in DC current systems that require overvoltage detection and protection. When the DC supply voltage is higher than the programming voltage, the logic level and power supply signal output by the circuit of the present invention can be used as a protection signal or provide protection drive.

[0091] Embodiment 2

[0092] The present embodiment is an integrated circuit (IC), which is equipped with the overvoltage and undervoltage protection circuit as described in the first embodiment, and is used to perform undervoltage protection and / or overvoltage protection on the protected battery.

[0093] Embodiment 3

[0094] The present embodiment is a battery management system (BMS), including a battery monitoring module, a balancing module, a communication module, a main control unit, a protection module and an auxiliary power supply module. The auxiliary power supply module uses the overvoltage and undervoltage protection circuit as described in Example 1 to provide low-voltage DC power for other modules of the system.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An overvoltage and undervoltage protection circuit, connected to a battery management system circuit of a battery, characterized in that: It includes an internal power supply unit, a reference voltage source unit, a voltage detection unit, a voltage comparison unit, a logic control unit, a GATE driving unit, a switch unit and a totem pole driving unit; The input pin of the internal power supply unit is connected to the positive electrode of the battery, and outputs a low-voltage DC power supply for the operation of the on-chip circuit; The input end of the reference voltage source unit is connected to the output end of the internal power supply unit to generate a reference voltage to an input end of the voltage comparison unit; The input end of the voltage detection unit is connected to the positive electrode of the battery through a resistor, and is used to sample the battery voltage. The voltage sampling signal is sent to the other input end of the voltage comparison unit; The voltage comparison unit outputs a first control signal to the logic control unit; The logic control unit generates a second control signal to the GATE driving unit and / or the totem pole driving unit according to the first control signal, and also provides a mode selection interface externally; The GATE driving unit generates a switch signal according to the second control signal and outputs it to the switch unit; The switch unit provides an external power supply interface, and the on-chip switch opens or closes the connection between the positive electrode of the battery and the external power supply interface according to the switch signal; The totem pole driving unit provides a logic signal output interface.

2. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The resistor connected between the input pin of the voltage detection unit and the positive electrode of the battery is a potentiometer or a variable resistor, which is used to set the threshold of undervoltage or overvoltage protection.

3. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The resistor connected between the input pin of the voltage detection unit and the positive electrode of the battery is a programmable resistor, which is used to set the threshold of undervoltage or overvoltage protection.

4. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The non-inverting input of the voltage comparison unit is a reference voltage, and the inverting input is a voltage sampling signal.

5. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The mode selection interface can be suspended or grounded, and is used to set the polarity of external power supply and logic signals.

6. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The switch unit includes two PMOS tubes with connected sources, a drain of one PMOS tube connected to the positive electrode of the battery, and a drain of the other PMOS tube connected to the external power supply interface, and a switch signal controls the two PMOS tubes through the gate.

7. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The totem pole driving unit is provided with a PMOS pull-up and an NMOS pull-down.

8. The overvoltage and undervoltage protection circuit according to claim 1, characterized in that: The voltage comparison unit is a hysteresis comparator.

9. An integrated circuit, characterized in that: The integrated circuit is equipped with the overvoltage and undervoltage protection circuit according to any one of claims 1 to 8, and is used to perform undervoltage protection and / or overvoltage protection on the protected battery.

10. A battery management system, comprising a battery monitoring module, a balancing module, a communication module, a main control unit, a protection module and an auxiliary power supply module, characterized in that: The auxiliary power supply module uses the overvoltage and undervoltage protection circuit as described in any one of claims 1 to 8, and is used to provide low-voltage DC power for other modules of the system.

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