Overvoltage Protection Circuit

Abstract

An overvoltage protection circuit according to an embodiment of the present invention includes an input terminal to which power is input and an output terminal to which power is output to a load, a first switch located between the input terminal and the output terminal and cutting off output to the load when turned off, a first Zener diode connected to the input terminal and conducting upon sensing an overvoltage, a second switch turned on when the first Zener diode conducts, and a third switch turned on when the first switch is turned on, wherein the first switch is turned on by the power input to the input terminal and is turned off when the third switch is turned on.

Description

[Technical field]

[0001] The present invention relates to an overvoltage protection circuit, and more specifically to an overvoltage protection circuit that cuts off momentary and continuous overvoltages to protect a load. [Background technology]

[0002] In the case of devices that use battery power, such as electric vehicles, an overvoltage protection circuit is applied to protect the inside when a high voltage is input. Figure 1 shows an overvoltage protection circuit applied to a mild hybrid vehicle (mHEV), which receives power input from a 12V battery and a DC-DC converter that converts the 48V voltage of a 48V battery to 12V, outputs it to the battery management system (BMS), and uses a Zener diode to protect against overvoltage.

[0003] In the case of a BMS that uses the basic KL30 power supply (12V battery), the input overvoltage protection circuit uses a Zener diode (D3) to protect the BMS by clamping the overvoltage when an input overshoot occurs. In the mild hybrid car 48V system, the BMS receives the KL30 power supply input in the same way as above, charges the KL30 battery with a 48V / 12V DC-DC converter, and supplies power to the load that uses the KL30 power supply.

[0004] In this case, if a failure occurs in the 48 / 12V DC-DC converter and a 40V OVP (over voltage protection) occurs, damage should not occur to the electrical equipment that is the load connected to it. As shown in Figure 1, if a Zener diode is used, instantaneous OVP can be cut off, but if the Zener diode performs continuous voltage clamping due to continuous OVP, damage will occur due to excessive power dissipation, and there is a problem that the OVP of 40V or more that is continuously input cannot be protected.

[0005] Figure 2 shows an overvoltage protection circuit that uses a regulator rather than a Zener diode. Even if a regulator is used, if continuous OVP is applied, damage can occur due to excessive power dissipation, and there is a problem that continuous input OVP cannot be protected. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be solved by the present invention is to provide an invention relating to an overvoltage protection circuit that protects a load by blocking momentary and continuous overvoltages. [Means for solving the problem]

[0007] In order to solve the above technical problems, an overvoltage protection circuit according to an embodiment of the present invention includes an input terminal to which power is input and an output terminal to which power is output to a load, a first switch located between the input terminal and the output terminal and cutting off output to the load when turned off, a first Zener diode connected to the input terminal and conducting upon sensing an overvoltage, a second switch turned on when the first Zener diode conducts, and a third switch turned on when the first switch is turned on, wherein the first switch is turned on by the power input to the input terminal and is turned off when the third switch is turned on.

[0008] Also, the first switch may be a PMOS, the cathode of the first Zener diode may be connected to the drain of the first switch, and the anode of the first Zener diode may be connected to ground via a first resistor and a second resistor connected in series.

[0009] Also, the second switch may be an NMOS, the gate of the second switch may be connected to a node between the first resistor and the second resistor, the source of the second switch may be connected to ground, and the drain of the second switch may be connected to a third resistor and a fourth resistor connected in series.

[0010] Also, the third switch may be a PMOS, a gate of the third switch may be connected to a node between the third resistor and the fourth resistor, a source of the third switch may be connected to ground via a fifth resistor, and a drain of the third switch may be connected to a drain of the first switch.

[0011] Furthermore, a gate of the first switch may be connected to a node between a source of the third switch and the fifth resistor, a source of the first switch may be connected to the output terminal, and a drain of the first switch may be connected to the input terminal.

[0012] The input may also include a sixth resistor and a second Zener diode connected in parallel between the gate and the drain of the first switch.

[0013] Furthermore, a value of the fifth resistor is greater than a value of the sixth resistor, and the first switch can be turned on by a voltage division of the fifth resistor and the sixth resistor when power is input to the input terminal.

[0014] In addition, the second Zener diode can detect an overvoltage applied to the gate of the first switch.

[0015] Also, the input terminal can receive power from a battery or a DC-DC converter that charges the battery.

[0016] Also, the output terminal may be connected to a battery management system. Effect of the Invention

[0017] According to the embodiment of the present invention, it is possible to cut off not only instantaneous overvoltage but also continuous overvoltage. Since it is realized through a simple circuit configuration, it is easy to utilize PCB space and can be realized at low cost even when adding circuits. [Brief description of the drawings]

[0018] [Figure 1] FIG. 13 is a diagram showing an overvoltage protection circuit according to a comparative example of the present invention. [Diagram 2] FIG. 13 is a diagram showing an overvoltage protection circuit according to a comparative example of the present invention. [Diagram 3] 1 is a block diagram of an overvoltage protection circuit according to an embodiment of the present invention; [Figure 4] 1 is a circuit diagram of an overvoltage protection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] However, the technical concept of the present invention is not limited to some of the embodiments described, but can be realized in various different forms, and one or more of the components of the embodiments can be selectively combined or substituted for each other within the scope of the technical concept of the present invention.

[0021] Furthermore, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as meanings that are commonly understood by a person having ordinary knowledge in the technical field to which the present invention belongs, unless otherwise clearly and specifically defined and described, and commonly used terms such as predefined terms may be interpreted in light of the contextual meaning of the relevant art.

[0022] Furthermore, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0023] In this specification, the singular form can include the plural form unless otherwise specified in the context, and when it is stated as "A and (and) at least one (or more) of B and C", it can include one or more of all combinations of A, B, and C.

[0024] In addition, in describing components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. are used. Such terms are used only to distinguish the components from other components, and do not limit the nature, order, or sequence of the components.

[0025] In addition, when a component is described as being "coupled," "coupled," or "connected" to another component, this includes not only the case where the component is directly "coupled," "coupled," or "connected" to the other component, but also the case where the component is "coupled," "coupled," or "connected" by another component between the component and the other component.

[0026] In addition, when described as being formed or disposed "above" or "below" each component, "above" or "below" includes not only the case where two components are in direct contact with each other, but also the case where one or more additional components are formed or disposed between the two components. In addition, when expressed as "above" or "below," it can include not only the upper direction but also the lower direction based on one component.

[0027] FIG. 3 is a block diagram of an overvoltage protection circuit according to an embodiment of the present invention, and FIG. 4 is a circuit diagram of the overvoltage protection circuit according to the embodiment of the present invention.

[0028] The overvoltage protection circuit 100 according to an embodiment of the present invention includes an input terminal 110, an output terminal 120, a first switch 130, a first Zener diode 140, a second switch 150, and a third switch 160, and may include a second Zener diode, a diode, and a resistor.

[0029] Power is input to the input terminal 110, and power is output to a load from the output terminal 120. The overvoltage protection circuit outputs the power input to the input terminal 110 to the load via the output terminal 120, but prevents the overvoltage power from being output to the load when an overvoltage occurs.

[0030] Here, the input terminal 110 can receive a power input from a battery or a DC-DC converter that charges the battery, and the output terminal 120 is connected to a battery management system. The overvoltage protection circuit 100 according to the embodiment of the present invention can protect a load from an overvoltage that occurs when a battery power source is applied to a load. For example, when a battery power source is input to a battery management system (BMS) in a mild hybrid vehicle (mHEV), the overvoltage protection circuit 100 can protect the battery management system when an overvoltage occurs. Here, the battery management system is a device that manages the charging and discharging of the battery according to the driving state. In the case of a mild hybrid vehicle, not only a 12V battery power source but also a power source converted through a 48V / 12V DC-DC converter by a 48V system can be applied to the battery management system.

[0031] When a momentary overvoltage occurs from a 12V battery or DC-DC converter due to a fault such as a short circuit, the Zener diode can provide protection, but when voltage conversion is not performed normally due to a fault in the DC-DC converter, a voltage higher than the rated voltage of 12V can be continuously input. For example, a power source having an overvoltage of 40V or more can be input to the DC-DC converter, and in this case, the Zener diode is damaged, making it difficult to protect the load. To solve this problem, the overvoltage protection circuit 100 according to an embodiment of the present invention uses a plurality of switches.

[0032] The first switch 130 is located between the input terminal and the output terminal, and cuts off the output to the load when it is turned off. The first switch 130 is connected between the input terminal 110 and the output terminal 120, i.e., to the input line, and plays a role of connecting or cutting off the connection between the input terminal 110 and the output terminal 120. When the first switch 130 is turned off, the connection between the input terminal 110 and the output terminal 120 is cut off, and the power output to the load through the output terminal 120 is cut off, thereby protecting the load from overvoltage.

[0033] When power is input to the input terminal 110, the first switch 130 is turned on by the power input to the input terminal 110. The first switch 130 may be a PMOS, and is turned on by applying a voltage greater than a gate voltage to the gate of the first switch 130 using the power input to the input terminal 110. The first switch 130 to the third switch 160 may be formed of various switching elements such as passive elements instead of MOSFETs.

[0034] When the voltage is within the normal range, the first switch 130 maintains the on state after being turned on. However, when an overvoltage occurs, the first switch 130 is turned off using the first Zener diode 140, the second switch 150, and the third switch 160.

[0035] The first Zener diode 140 is connected to the input terminal 110 and detects an overvoltage and becomes conductive. A Zener diode is a PN junction diode that has a very low and constant breakdown voltage (Zener voltage) characteristic, and when a voltage equal to or greater than the Zener voltage is applied in the reverse direction, a current flows. Using this characteristic, the first Zener diode 140 detects an overvoltage applied to the input terminal 110.

[0036] The first Zener diode 140 is connected to the input terminal 110 in a branched manner, and when an overvoltage equal to or greater than the Zener voltage is applied to the input terminal, the first Zener diode 140 forms a path for current to flow to ground, so that the overvoltage flows to ground instead of the output terminal 120. This makes it possible to protect the load from overvoltage. However, if a continuous overvoltage is applied, the first Zener diode 140 may be damaged, and if damage occurs, normal overvoltage protection will not be performed. Therefore, in order to block the continuous overvoltage, the first switch 130 must be turned off.

[0037] The second switch 150 is turned on when the first Zener diode 140 is conductive, the third switch 160 is turned on when the first switch 130 is turned on, and when the third switch 160 is turned on, the first switch 130 is turned off. If an overvoltage occurs due to the first Zener diode 140 being conductive→the second switch 150 being turned on→the third switch 160 being turned on→the first switch 130 being turned off, a process of protecting the load is performed.

[0038] The first switch 130 is a PMOS, the cathode of the first Zener diode 140 is connected to the drain of the first switch 130, and the anode of the first Zener diode 140 may be connected to ground via a first resistor and a second resistor connected in series. When the first Zener diode 140 is turned on by an overvoltage, a current flows to ground via the first resistor and the second resistor.

[0039] The second switch 150 is an NMOS, and the gate of the second switch 150 is connected to a node between the first resistor and the second resistor, the source of the second switch 150 is connected to ground, and the drain of the second switch 150 can be connected to a third resistor and a fourth resistor connected in series. The NMOS is turned on when the gate-source voltage is higher than a threshold, and is turned off when the gate-source voltage is lower than the threshold. When the first Zener diode 140 is not conductive, it is connected to ground via the second resistor, and the gate-source voltage of the second switch 150 is lower than the threshold and maintains an off state. When the first Zener diode 140 is conductive due to an overvoltage and a current flows through the first resistor and the second resistor, the overvoltage is distributed and applied to the first resistor and the second resistor, and the voltage applied to the second resistor is applied to the gate of the second switch 150, the gate-source voltage of the second switch 150 becomes higher than the threshold, and the second switch 150 is turned on. The voltage applied to the second resistor corresponds to the gate-source voltage of the second switch, and the resistance values ​​of the first resistor and the second resistor can be set so that the second switch 150 is turned on when the magnitude of the overvoltage is equal to or greater than the threshold value. For example, when the Zener voltage of the first Zener diode 140 is 30V, the first Zener diode 140 is set to cut off the overvoltage if it is 40V or greater. If the gate-source voltage threshold of the second switch 150 is 5V, 30V is applied to the first Zener diode 140 if the overvoltage is 40V, and if the magnitudes of the first resistor and the second resistor are set to be the same, 5V is applied to the second resistor, turning on the second switch 150. The values ​​of the first resistor and the second resistor may be set in consideration of voltage loss and errors due to added diodes and elements, or may be set by the user. When the second switch 150 is turned on, a current flows through the third resistor and the fourth resistor.

[0040] The third switch 160 may be a PMOS, the gate of the third switch 160 is connected to a node between the third resistor and the fourth resistor, the source of the third switch 160 is connected to ground via a fifth resistor, and the drain of the third switch 160 is connected to the drain of the first switch 130. The PMOS is turned off when the gate-source voltage is higher than a threshold, and turned on when the gate-source voltage is lower than a threshold. When the second switch 150 is in an off state, the gate of the third switch is connected to the input terminal 110 through the third resistor, but the gate-source voltage of the third switch 160 is higher than the threshold and maintains an off state. When the first Zener diode 140 is conductive due to an overvoltage, the second switch 150 is turned on and a voltage is applied to the third resistor and the fourth resistor, the gate voltage is lowered due to the voltage division of the third resistor and the fourth resistor, so that the gate-source voltage of the third switch 160 is lower than the threshold, and the third switch 160 is turned on.

[0041] The gate of the first switch 130 is connected to a node between the source of the third switch 160 and the fifth resistor, the source of the first switch 130 is connected to the output terminal 120, and the drain of the first switch 130 is connected to the input terminal 110. A sixth resistor and a second Zener diode may be connected in parallel between the gate and drain of the first switch 130. Here, a value of the fifth resistor is greater than a value of the sixth resistor, and the first switch 130 may be turned on by a voltage division of the fifth resistor and the sixth resistor when power is input to the input terminal.

[0042] When a power supply having a normal voltage range is applied to the input terminal, a current flows through the fifth resistor and the sixth resistor, and a voltage is applied to the gate of the first switch 130 connected to the node between the fifth resistor and the sixth resistor. At this time, the voltage across the sixth resistor can be set to be lower than the threshold value by voltage distribution of the fifth resistor and the sixth resistor. As a result, the gate-source voltage of the first switch 130 becomes lower than the threshold value, and the first switch 130 is turned on. When the first switch 130 is turned on, the power supply input to the input terminal 110 is output to the load via the output terminal 120.

[0043] At this time, when the voltage is in the normal range, the value of the fifth resistor and the value of the sixth resistor can be set so that the gate-source voltage of the first switch 130 is lower than the threshold. The values ​​can be set according to the voltage input to the input terminal 110, the threshold of the gate-source voltage of the first switch 130, and the magnitude of the voltage across the fifth resistor and the sixth resistor. For example, in a situation where a battery voltage of 12V is input in the normal range, if the threshold of the gate-source voltage of the first switch 130 is 5V, the gate-source voltage of the first switch 130 becomes the voltage across the sixth resistor. However, if the voltage across the fifth resistor is not higher than the sixth resistor, the gate-source voltage of the first switch 130 becomes lower than the threshold, and the first switch 130 can be turned on. For this reason, the value of the fifth resistor can be set higher than the value of the sixth resistor.

[0044] In order to protect the gate of the first switch 130 during normal operation, a second Zener diode is connected, and the second Zener diode detects an overvoltage applied to the gate of the first switch 130, and when an overvoltage occurs, the second Zener diode can block the overvoltage from being applied to the gate of the first switch 130. When an overvoltage occurs, it may take some time for the first switch 130 to be turned off due to the operations of the first Zener diode 140, the second switch 150, and the third switch 160, so a second Zener diode is connected between the gate and source of the first switch 130 to protect the gate of the first switch 130.

[0045] When an overvoltage occurs and the first Zener diode 140 becomes conductive, the second switch 150 is turned on, and the third switch 160 is turned on. When the third switch 160 is turned on, a current flows along the path of the third switch 160, not through the sixth resistor. When the gate and source of the first switch 130 are connected via the sixth resistor, the voltage of the source of the first switch 130 is higher than the voltage of the gate, the gate-source voltage of the first switch 130 is low (LOW), and the first switch 130 maintains the on state. When the third switch 160 is turned on, the potential difference between the source and gate of the first switch 130 becomes low due to the turning on of the third switch 160, and the gate-source voltage of the first switch 130 becomes higher than the threshold, which makes it high (HIGH), and the first switch 130 is turned off.

[0046] The overvoltage protection circuit 100 according to the embodiment of the present invention can be implemented as a circuit as shown in FIG.

[0047] The overvoltage protection circuit 100 according to the embodiment of the present invention can receive power input from a KL30 power source formed of a 12V battery 220 and a 48V / 12V DC-DC converter 210, and output power to a BMS 230, which is a battery management device. In order to protect the BMS 230 from overvoltage, the overvoltage protection circuit 100 according to the embodiment of the present invention includes a first Zener diode 140 D1, a first switch 130 M1, a second switch 150 M2, and a third switch 160 M3, and can also include a diode D3, a second Zener diode D2, and a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6.

[0048] When power is input through the input terminal, it is output to the output terminal via D3 and M1. Here, D3 prevents power from being output in the reverse direction, i.e., to the input terminal. D1 can be set to a Zener voltage within the overvoltage range to detect and cut off overvoltage. For example, when the normal range of the input voltage is 12V, the Zener voltage can be set to 27V to 28V. This can be set according to the required specifications and the user.

[0049] When a normal voltage is applied, D1 does not conduct due to its diode characteristics, and the gate-source voltage of M2 is lower than the threshold, so it maintains its off state. When M2 is in the off state, a high voltage is applied to the gate of M3 via R3, and the gate-source voltage becomes higher than the threshold, turning it off. When M3 is in the off state, M1's gate-source voltage becomes the voltage applied to R6 due to the voltage distribution of R6 and R5, and M1 can be turned on by setting the resistance values ​​of R6 and R5 so that R6 is lower than the threshold of the gate-source voltage of M1. As a result, when the voltage is in the normal range, D1 does not conduct, M2 and M3 are off, and M1 is turned on, so that the power supply of the normal voltage can be output to the BMS230. D2 serves to detect and prevent overvoltage from being applied to M1.

[0050] During normal operation, when an overvoltage occurs that is greater than the Zener voltage of D1, D1 is turned on, and the voltage across R2 becomes the gate-source voltage of M2 due to the voltage division of R1 and R2, but when the voltage across R2 becomes greater than the gate-source voltage of M2, M2 is turned on. The values ​​of R1 and R2 can be set according to the threshold value so that M2 is turned on when the magnitude of the overvoltage is greater than the threshold value.

[0051] When M2 is turned on, current flows through R3 and R4, and R4 lowers the gate voltage of M3, causing the gate-source voltage of M3 to fall below the threshold and turn on. When M3 is turned on, no current flows through R6, but flows through M3, causing the gate-source voltage of M1 to go from low to high as the potential difference decreases, causing M1 to turn off when its gate-source voltage exceeds the threshold. When M1 is turned off, the power supply output to BMS230 is cut off, and BMS230 can be protected from overvoltage.

[0052] As mentioned above, by using a switch together with a Zener diode, it is possible to cut off overvoltage and protect circuits such as ICs in a BMS connected to a load. Instantaneous overvoltages are detected and cut off by the Zener diode, and for continuous overvoltages, the output to the output terminal can be cut off using a switch that operates in sequence. This makes it possible to cut off overvoltages of 40V or more in devices where continuous overvoltages can occur, such as 48V mild hybrid cars, and provide overvoltage protection. In addition, by implementing the circuit using simple elements, it is easy to utilize PCB space, and adding circuits can be implemented at low cost.

[0053] Those skilled in the art will understand that the present embodiment may be modified without departing from the essential characteristics of the above description. Therefore, the disclosed method should be considered from an illustrative point of view, not a restrictive point of view. The scope of the present invention is shown in the claims, not the above description, and all differences within the scope of the equivalents should be interpreted as being included in the present invention.

Claims

1. An input terminal to which power is input, an output terminal that outputs power to a load, A first switch located between the input terminal and the output terminal, which cuts off the output to the load when turned off, A first Zener diode connected to the input terminal, which senses overvoltage and conducts, A second switch that is turned on when the first Zener diode conducts, A third switch that is turned on when the first switch is turned on, A second Zener diode connected to the first switch, and includes, The first switch is Turned on by the power input to the input terminal, and turned off when the third switch is turned on, The first switch is a PMOS, The second Zener diode is connected to the gate of the first switch, characterized in that, an overvoltage protection circuit.

2. The cathode of the first Zener diode is connected to the first switch, The anode of the first Zener diode is connected to ground through a first resistor and a second resistor connected in series, characterized in that, the overvoltage protection circuit according to claim 1.

3. The second switch is an NMOS, The gate of the second switch is connected to the node between the first resistor and the second resistor, The source of the second switch is connected to ground, The drain of the second switch is connected to a third resistor and a fourth resistor connected in series, characterized in that, the overvoltage protection circuit according to claim 2.

4. The third switch is a PMOS, The gate of the third switch is connected to the node between the third resistor and the fourth resistor, The source of the third switch is connected to ground via a fifth resistor, The drain of the third switch is connected to the drain of the first switch, and the overvoltage protection circuit according to claim 3 is characterized in that.

5. The gate of the first switch is connected to a node between the source of the third switch and the fifth resistor, The source of the first switch is connected to the output terminal, The drain of the first switch is connected to the input terminal, and the overvoltage protection circuit according to claim 4 is characterized in that.

6. The overvoltage protection circuit according to claim 5, characterized in that it includes a sixth resistor connected in parallel with the second Zener diode.

7. The value of the fifth resistor is larger than the value of the sixth resistor, The first switch is turned on by the voltage distribution of the fifth resistor and the sixth resistor when power is input to the input terminal, and the overvoltage protection circuit according to claim 6 is characterized in that.

8. The second Zener diode detects an overvoltage applied to the gate of the first switch, and the overvoltage protection circuit according to claim 1 is characterized in that.

9. The input terminal receives power input from a battery or a DC-DC converter that charges the battery, and the overvoltage protection circuit according to claim 1 is characterized in that.

10. The output terminal is connected to a battery management system (Battery Management System), and the overvoltage protection circuit according to claim 1 is characterized in that.

11. An input terminal to which power is input, An output terminal that outputs power to a load, A first switch that is a PMOS, A first Zener diode connected to the input terminal, including an anode connected to ground through a first resistor and a second resistor connected in series with the cathode connected to the first switch. A second switch, which is an NMOS, includes a gate connected to the node between the first resistor and the second resistor, a source connected to ground, and a drain connected to a third resistor and a fourth resistor connected in series. A third switch, which is a PMOS, includes a gate connected to the node between the third resistor and the fourth resistor. An overvoltage protection circuit, characterized by including a second Zener diode connected in parallel with the gate of the first switch.

12. The overvoltage protection circuit according to claim 10, characterized by including a sixth resistor connected in parallel with the second Zener diode.

13. The overvoltage protection circuit according to claim 12, characterized in that the value of the fifth resistor is larger than the value of the sixth resistor.

14. The overvoltage protection circuit according to claim 13, characterized in that the second Zener diode detects an overvoltage applied to the gate of the first switch.

15. In a battery management device for managing charging and discharging of a battery, Including an overvoltage protection circuit for protecting the battery management device from overvoltage, The overvoltage protection circuit is An input terminal to which a power supply is input, An output terminal for outputting power to a load, A first switch located between the input terminal and the output terminal, which cuts off the output to the load when turned off, A first Zener diode connected to the input terminal, which senses an overvoltage and conducts, A second switch that is turned on when the first Zener diode conducts, A third switch that is turned on when the second switch is turned on, Including a second Zener diode connected to the first switch. The first switch is turned on by the power supply input from the input terminal, and is turned off when the third switch is turned on. The first switch is a PMOS. The cathode of the first Zener diode is connected to the drain of the first switch. The anode of the first Zener diode is connected to ground via a first resistor and a second resistor connected in series. The second switch is an NMOS. The gate of the second switch is connected to the node between the first resistor and the second resistor. The source of the second switch is connected to ground. The drain of the second switch is connected to a third resistor and a fourth resistor connected in series. The second Zener diode is connected to the gate of the first switch, and a battery management device is characterized in that.

16. The third switch is a PMOS. The gate of the third switch is connected to the node between the third resistor and the fourth resistor. The source of the third switch is connected to ground via a fifth resistor. The drain of the third switch is connected to the drain of the first switch, and the battery management device according to claim 15 is characterized in that.

17. The gate of the third switch is connected to the node between the third resistor and the fourth resistor. The source of the third switch is connected to ground via a fifth resistor. The drain of the third switch is connected to the drain of the first switch, and the battery management device according to claim 16 is characterized in that.

18. The battery management device according to claim 17, characterized in that it includes a sixth resistor connected in parallel with the second Zener diode.

19. The battery management device according to claim 15, wherein the second Zener diode detects an overvoltage applied to the gate of the first switch.

20. The battery management device according to claim 15, wherein the input terminal receives a power input from a battery or a DC-DC converter that charges the battery.

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