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

Abstract

The utility model 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 utility model belongs to the battery protection technical field, especially relates to a kind of overvoltage undervoltage protection circuit, integrated circuit and battery management system. BACKGROUND

[0002] In lithium battery and its series battery pack system, iron lithium battery enters undervoltage state when single voltage is lower than 2.5V, ternary lithium battery enters undervoltage state when single voltage is lower than 2.4V.Battery should enter very low power consumption mode when battery undervoltage, otherwise, with battery further power consumption, it will lead to irreversible damage of battery, and further lead to battery over-consumption to produce internal gas precipitation, cause battery bulging phenomenon.Active material in battery cannot be completely restored, capacity drops or even completely lost.

[0003] Therefore, in the application of multiple battery pack, battery needs to be installed battery management system (Battery Management System, BMS).BMS is mainly composed of analog front end AFE (Active Front End, active front end) rectification / feedback unit, MCU (Microcontroller Unit, microcontroller unit), communication unit, MOS (Metal-Oxide-Semiconductor Field-Effect Transistor, metal-oxide semiconductor field effect transistor) action unit and auxiliary power supply system.Auxiliary power supply must meet the demand of normal work when battery overcharge and overdischarge protection, so auxiliary power supply directly takes power from positive pole BAT+ and negative pole BAT- of battery to generate 12V, 5V and 3.3V and other system required working voltage.

[0004] Generally, existing battery pack mostly uses integrated BUCK step-down IC (Integrated Circuit, integrated circuit) to generate auxiliary power supply.The working voltage range of the BUCK step-down IC is very wide, and it will still work normally in the undervoltage protection voltage range of battery pack, so when battery pack enters undervoltage state, auxiliary power supply is still working.The power consumption of auxiliary power supply is generally in the range of 0.5-3W.In order to protect battery from damage, voltage undervoltage protection circuit needs to be additionally set in the front end of auxiliary power supply, to ensure that when battery pack voltage drops to undervoltage protection range, auxiliary power supply can be turned off.

[0005] Prior art such as Figure 1As shown, it adopts a battery undervoltage detection and protection circuit composed of a stabilizing diode, a CJ431, an optical coupling, a resistor, a capacitor, a Q3P MOS. The circuit has the following disadvantages: 1. The working voltage range of the CJ431 is 3-36V, and when the battery pack is applied beyond 36V, a series stabilizing diode needs to be added for voltage division power supply; 2. The working current of the CJ431 is 1mA, and the power supply branch current of the DZ1 and R3 should be greater than or equal to 1mA; the R1 and R2 constitute a voltage detection, and the protection voltage is VZ=2.5V*(R1+R2) / R2, because the maximum value of the R2 cannot exceed 10K, otherwise the detection accuracy of the CJ431 is reduced, so the minimum value of the detection branch current of the R1 and R2 is Idet_min=2.5V / 10K=0.25mA; therefore the total working power consumption of the whole circuit Iop is greater than or equal to 1.25mA; 3. After the battery enters the undervoltage protection, the power consumption of the circuit remains unchanged as in working time, Ipd is greater than or equal to 1.25mA, which cannot meet the low power consumption requirement; 4. The circuit has many components, the circuit is relatively complex, and the cost is high. Practical new type content

[0006] The utility model provides a kind of overvoltage undervoltage protection circuit, integrated circuit and battery management system, to solve the problems of prior art circuit complexity, high power consumption and wide applicability.

[0007] To solve the above technical problems, the first aspect of the utility model provides an overvoltage undervoltage protection circuit connected to the battery management system circuit of the battery, including an internal power supply unit, a reference voltage source unit, a voltage detection unit, a voltage comparison unit, a logic control unit, a GATE drive unit, a switching unit and a totem pole drive 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 internal circuit.

[0009] The input end of the reference voltage source unit is connected to the output end of the internal power supply unit, and generates 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, for sampling the voltage of the battery, and the voltage sampling signal is sent to another 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 drive unit and / or totem pole drive unit according to the first control signal, and also provides a mode selection interface externally.

[0013] The GATE drive unit generates a switching signal output to the switching unit according to the second control signal.

[0014] The switch unit provides an external power supply interface, and the on-chip switch is turned on or turned off according to a switch signal to connect the positive electrode of the battery and the external power supply interface.

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

[0016] Preferably, the resistance 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 for setting the threshold value of the under-voltage or over-voltage protection.

[0017] Preferably, the resistance connected between the input pin of the voltage detection unit and the positive electrode of the battery is a programmable resistance, which is used for setting the threshold value of the under-voltage or over-voltage protection.

[0018] Preferably, the non-inverting 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 left floating or grounded, which is used for setting the polarity of the external power supply and the logic signal.

[0020] Preferably, the switch unit comprises two PMOS transistors with the same source, the drain of one PMOS transistor is connected to the positive electrode of the battery, the drain of the other PMOS transistor is connected to the external power supply interface, and the switch signal is used for controlling the two PMOS transistors through the gate.

[0021] Preferably, the totem column 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] The second aspect of the utility model further provides an integrated circuit, the integrated circuit is disposed with the over-voltage and under-voltage protection circuit of the first aspect of the utility model, and is used for carrying out under-voltage protection and / or over-voltage protection on the protected battery.

[0024] The third aspect of the utility model further provides a battery management system, which comprises a battery monitoring module, an equalization module, a communication module, a main control unit, a protection module and an auxiliary power supply module, the auxiliary power supply module uses the over-voltage and under-voltage protection circuit of the first aspect of the utility model, and is used for providing low-voltage direct-current power supply for other modules of the system.

[0025] Compared with the prior art, the utility model has the following technical effects:

[0026] 1. The utility model discloses a protection circuit is configured with the under bias resistance and programmable resistance, and has the characteristics of ultra low power consumption current in combination with the utility model circuit structure, and the working power consumption current is less than 6uA when the voltage below 40V is accessed, and the power consumption current is less than 15uA when the working voltage is 40~100V, and when the circuit enters the undervoltage protection, can shut off the auxiliary power supply, so that the power consumption current can be reduced to 1uA, further reduce the peripheral current to protect the battery or battery pack.

[0027] 2. The utility model discloses a protection circuit is configured with the programmable resistance, and can set the undervoltage protection voltage or overvoltage protection voltage in the range of 3~100V, and can flexibly realize the detection and protection of a certain voltage value in the voltage range, compared with the detection circuit formed by discrete electronic components, the utility model has the effects of simple structure, small size, low cost and high reliability.

[0028] 3. The utility model discloses a protection circuit is provided with switch unit and totem pole drive unit, and has electronic switch function and low voltage logic drive signal function, wherein the electronic switch function can provide direct current supply current or disconnect direct current supply, and the low voltage logic drive signal can drive the peripheral MOS switch according to the customer's needs to carry out corresponding protection action.

[0029] 4. The utility model discloses a protection circuit is provided with mode selection interface, and can flexibly adjust the output state of external power supply interface and logic signal output interface, and can be widely used for different customer needs. DRAWINGS

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

[0031] Figure 2 It is the protection circuit structure schematic diagram of the utility model;

[0032] Figure 3 It is the circuit principle diagram of application scheme one of the utility model embodiment;

[0033] Figure 4 It is the Vout output voltage timing diagram of application scheme one of the utility model embodiment;

[0034] Figure 5 It is the circuit principle diagram of application scheme two of the utility model embodiment;

[0035] Figure 6 It is the VDO output voltage timing diagram of application scheme two of the utility model embodiment;

[0036] Figure 7 It is the circuit principle diagram of application scheme three of the utility model embodiment;

[0037] Figure 8 is the VDO output voltage timing diagram of the application scheme three according to the embodiment of the utility model;

[0038] Figure 9 is the circuit principle diagram of the application scheme four according to the embodiment of the utility model;

[0039] Figure 10 is the Vout output voltage timing diagram of the application scheme four according to the embodiment of the utility model;

[0040] Figure 11 is the circuit principle diagram of the application scheme five according to the embodiment of the utility model;

[0041] Figure 12 is the VDO output voltage timing diagram of the application scheme five according to the embodiment of the utility model;

[0042] Figure 13 is the circuit principle diagram of the application scheme six according to the embodiment of the utility model;

[0043] Figure 14 is the VDO output voltage timing diagram of the application scheme six according to the embodiment of the utility model. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the utility model more clear, the following will combine the specific embodiment of the application, and refer to the drawings, the technical scheme of the utility model is clearly and completely described.

[0045] Embodiment one

[0046] The embodiment is a kind of overvoltage undervoltage protection circuit, connect in the battery management system circuit of battery, as shown in Fig. Figure 2 Including internal power supply unit, reference voltage source unit, voltage detection unit, voltage comparison unit, logic control unit, GATE drive unit, switch unit and totem column drive unit;

[0047] The input pin of the internal power supply unit is Vin, connected to the positive pole of battery, the embodiment is applied to the DC circuit needing to detect undervoltage to power supply and make protection action under the condition of battery voltage being 3 ~ 100V, internal power supply unit exports low-voltage DC power supply for the operation of chip circuit.

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

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

[0050] In the embodiment, the resistor R_prg connected between the input pin of the voltage detection unit and the positive pole of the battery is a programmable resistor, for setting the threshold value of the under-voltage or over-voltage protection.

[0051] In some other embodiments of the utility model, the resistor R_prg connected between the input pin V_PRG of the voltage detection unit and the positive pole of the battery is a potentiometer or a variable resistor, such as a single-coil potentiometer, a multi-coil potentiometer, a sliding variable resistor, a rotary potentiometer or a linear potentiometer, which is also used for setting the threshold value V_SET of the under-voltage or over-voltage protection.

[0052] The voltage comparison unit is a voltage comparator in the voltage comparison unit, and the voltage comparison unit outputs a first control signal to the logic control unit. Figure 2 In the embodiment, the reference voltage is input to the non-inverting input end IN+ of the voltage comparison unit, and the voltage sampling signal is input to the inverting input end IN- of the voltage comparison unit.

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

[0054] In one embodiment of the utility model, 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 logic set internally in combination with the first control signal, and also provides a mode selection interface MODE.

[0056] The GATE drive unit generates a switching signal output to the switching unit according to the second control signal.

[0057] The switch unit provides an external power supply interface Vout, and the on-chip switch is turned on or turned off according to a switch signal to connect the positive electrode of the battery and the external power supply interface, that is, to generate an output voltage at the Vout pin or to cut off the output voltage of Vout. Specifically, the switch unit includes two source-connected PMOS tubes, the drain of one PMOS tube is connected to the positive electrode of the battery, and the drain of the other PMOS tube is connected to the external power supply interface Vout, and the switch signal is controlled through the gate of the two PMOS tubes. 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 PMOS pull-up and NMOS pull-down, and provides a logic signal output interface VDO, so as to generate a corresponding required high / low logic drive signal at the VDO output pin.

[0059] The working principle of the utility model is as follows:

[0060] Vin is an IC power input pin, which generates a low-voltage direct-current power supply for the on-chip circuit operation through the internal power supply unit, a low-voltage reference voltage source generates a reference voltage VREF provided to the in-phase input end IN+ of the voltage comparison unit, and the user externally connects a programmable resistor R_prg between the Vin pin and the V_PRG pin to form a sampling of the input voltage Vin with the fixed down resistance Rdown inside the V_PRG pin, and the voltage sampling signal is sent to the reverse input end IN- of the voltage comparison unit, and compared with the VREF voltage. The comparator outputs a corresponding high level or low level to the logic control unit according to the voltage signals of the IN+ and IN- input ends. The logic control unit outputs a signal to the GATE driving unit according to the internal logic setting, and the GATE driving controls the on-chip PMOS tube of the switch unit to be turned on or turned off, so as to generate an output voltage at the Vout pin or cut off the output voltage of Vout. At the same time, the logic control unit outputs a signal to the totem pole driving unit, and the totem pole driving unit is provided with PMOS pull-up and NMOS pull-down, so as to generate a corresponding required high / low logic drive signal at the VDO output pin.

[0061] Among them, the resistance value of the programmable resistor R_prg can set the under-voltage or over-voltage 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 driving unit and the totem pole driving unit, so as to generate different effect sub-model circuits and their applications.

[0062] The resistance value of the lower bias resistor R_down inside the utility model is between 500KΩ and 3MΩ; the VREF reference voltage can be set to the range of 0.5-3.3V. For example, R_down is set to 500KΩ=0.5MΩ, VREF is set to 1.0V, when the circuit protection voltage V_SET is set to 60V, the user programming resistance R_prg, whose resistance value is:

[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 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 power consumption current is less than 13uA.

[0067] The utility model mainly applies to the DC circuit which needs to detect the under-voltage of the power supply and make protection action under 3-100V. The utility model circuit has the characteristics of ultra-low power consumption, in 0-40V voltage application, the normal working power consumption current is less than 6uA, in 40-100V application, the working power consumption current is less than 15uA; when the circuit enters the under-voltage protection state, the power consumption current is less than 5uA.

[0068] When the internal electronic switch of the circuit is turned on, the output Vout=Vin-VFD≈Vin, wherein VFD is the voltage drop generated by the working current flowing through the internal switch circuit, which is normally in the range of 0-300mV, so it can be ignored, and the subsequent description is described according to Vout≈Vin to describe the Vout state when the internal electronic switch is turned on. The Totem-pole driving unit outputs high level Vhigh and low level Vlow two signals, and the signal voltage range is respectively Vhigh in 3.3V-12V; Vlow in 0-0.5V.

[0069] According to the requirements of the use place, the circuit working described in the embodiment can make positive and negative logic under-voltage / over-voltage detection and protection work as shown in the following table:

[0070]

[0071] Correspondingly, the logic control unit outputs the opposite second control signal, so that the voltage of the final output Vout and / or VDO is opposite to the logic described in the above table. As the MODE is suspended and Vin>V_set, if only the opposite logic is performed on Vout, the final output is Vout=0 and VDO=Vlow; if only the opposite logic is performed on VDO, the final output is Vout≈Vin and VDO=Vhigh; if the opposite logic is performed on Vout and VDO at the same time, the final output is Vout=0 and VDO=Vhigh.

[0072] As the MODE is suspended and Vin≤V_set, if only the opposite logic is performed on Vout, the final output is Vout≈Vin and VDO=Vhigh; if only the opposite logic is performed on VDO, the final output is Vout=0 and VDO=Vlow; if the opposite logic is performed on Vout and VDO at the same time, the final output is Vout≈Vin and VDO=Vlow.

[0073] As the MODE is grounded and Vin>V_set, if only the opposite logic is performed on Vout, the final output is Vout≈Vin and VDO=Vlow; if only the opposite logic is performed on VDO, the final output is Vout=0 and VDO=Vhigh; if the opposite logic is performed on Vout and VDO at the same time, the final output is Vout≈Vin and VDO=Vhigh.

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

[0075] The following application schemes are given to explain the utility model in detail.

[0076] Application scheme one

[0077] The under-voltage protection circuit system has an electronic switch output circuit. The specific circuit is shown in the figure Figure 3 The output of the scheme is shown in the figure Figure 4 As Vin>V_set, Vout≈Vin; as Vin≤V_set, Vout=0, that is, the power supply output is cut off when under-voltage protection.

[0078] Application scheme two

[0079] The under-voltage protection circuit system outputs a high-level driving signal. The specific circuit is shown in the figureFigure 5 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows Figure 6 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows

[0080] Application scheme three

[0081] The output low voltage drive signal is output during the under-voltage protection. The specific circuit is as follows Figure 7 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows Figure 8 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows

[0082] Application scheme four

[0083] The Vout output voltage is cut off during the over-voltage protection. The specific circuit is as follows Figure 9 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows Figure 10 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows

[0084] Application scheme five

[0085] The high voltage logic drive signal is output during the over-voltage protection. The specific circuit is as follows Figure 11 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows Figure 12 As shown in the application scheme, the MODE pin is suspended, and the Vout pin is not used. The output of this scheme is as follows

[0086] Application scheme six

[0087] The low voltage logic drive signal is output during the over-voltage protection. The specific circuit is as follows Figure 13As shown, in the application scheme, the MODE pin is left empty, and the Vout pin is not used. The output of the scheme is as shown in the following figure. Figure 14 As shown, the timing diagram of the low voltage logic drive signal output by the application scheme during overvoltage protection, 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 the 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 utility model circuit works normally, can provide the power supply of auxiliary power supply, and simultaneously generates a high level or low level logic signal; if the battery voltage is lower than the undervoltage protection value, the utility model circuit enters the undervoltage protection mode, cuts off the auxiliary power supply loop, and simultaneously generates a low level or high level logic drive signal to the rear-end control circuit unit. It can be widely applied to any direct current circuit system requiring undervoltage detection and protection, and is used as undervoltage detection, power output and protection drive logic of the power supply voltage in the circuit system.

[0090] Meanwhile, the utility model circuit can also be widely applied to a direct current system requiring overvoltage detection and protection. When the direct current power supply voltage is higher than the programmed voltage, the logic level and power supply signal output by the utility model circuit can be used as a protection signal or provide protection drive.

[0091] Embodiment two

[0092] The embodiment is an integrated circuit (IC), which is provided with the overvoltage and undervoltage protection circuit as described in embodiment one, and is used for undervoltage protection and / or overvoltage protection of a protected battery.

[0093] Embodiment three

[0094] The embodiment is a battery management system (BMS), which comprises a battery monitoring module, an equalization 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 embodiment one, and is used for providing low-voltage direct current power supply for other modules of the system.

[0095] The above is only the preferred embodiment of the utility model, and it should be pointed out that, for ordinary skilled persons in the art, without departing from the creative concept of the utility model, a number of modifications and improvements can be made, which all belong to the protection scope of the utility model.

Claims

1. An overvoltage and undervoltage protection circuit connected in a battery management system circuit of a battery, characterized by, The integrated 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 is connected with the positive pole of a battery and outputs low-voltage direct current power for the internal circuit. The input end of the reference voltage source unit is connected with the output end of the internal power supply unit and generates a reference voltage to an input end of the voltage comparison unit. The input end of the voltage detection unit is connected with the positive pole of the battery through a resistor and is used for sampling the voltage of the battery. 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. The GATE driving unit generates a switch signal to the switch unit according to the second control signal. The switch unit provides an external power supply interface and the internal switch is turned on or off 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 pole of the battery is a potentiometer or a rheostat and is used for setting the threshold value of the under-voltage or over-voltage protection.

3. The overvoltage and undervoltage protection circuit according to claim 1, wherein The resistor connected between the input pin of the voltage detection unit and the positive pole of the battery is a programmable resistor and is used for setting the threshold value of the under-voltage or over-voltage protection.

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

5. The overvoltage and undervoltage protection circuit according to claim 1, wherein The mode selection interface can be left floating or grounded and is used for setting the polarity of the external power supply and the logic signal.

6. The over- and under-voltage protection circuit according to claim 1, characterized in that, The switch unit comprises two PMOS transistors with the same source, the drain of one PMOS transistor is connected with the positive pole of the battery and the drain of the other PMOS transistor is connected with the external power supply interface, and the switch signal is controlled through the gate.

7. The over- and under-voltage 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, wherein The voltage comparison unit is a hysteresis comparator.

9. An integrated circuit, characterized by The integrated circuit is provided with the over-voltage and under-voltage protection circuit according to any one of claims 1-8 and is used for protecting the battery from under-voltage and / or over-voltage.

10. A battery management system comprising a battery monitoring module, an equalization module, a communication module, a master control unit, a protection module and an auxiliary power module, characterized in that, The auxiliary power supply module uses the over-voltage and under-voltage protection circuit according to any one of claims 1-8 and is used for providing low-voltage direct current power for other modules of the system.

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