Power supply circuit

Abstract

A power supply circuit (40) uses a battery (11) as an input source of power, and supplies power to a battery monitoring unit (31) that monitors the state of the battery. Fuse function units (F1, F2) are provided on current paths (L1, L2) from the battery to the battery monitoring unit, the fuse function units (F1, F2) cutting off a current when a current exceeding a predetermined current flows through the fuse function units (F1, F2). The power supply circuit includes, in the current path, a path resistor (R1) at a position closer to the battery monitoring unit than the fuse function unit, and includes forming circuits (D1, B1, D2, B2) that form a bypass path that causes a current exceeding a predetermined current to flow through the fuse function unit without passing through the path resistor when a short circuit occurs in the path passing through the path resistor.

Description

Citation of Related Applications

[0001] This application is based on Japanese Patent Application No. 2022-195420 filed on December 7, 2022, the contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a power supply circuit suitable for a battery monitoring device. Background Art

[0003] Conventionally, there has been a battery monitoring device including a power supply circuit that uses a battery as a power input source and a battery monitoring IC that operates using the power supplied from the power supply circuit and monitors the state of the battery (see Non-Patent Document 1). Prior Art Documents Non-Patent Documents

[0004] Non-Patent Document 1: Texas Instruments BQ79616-Q1 Data Sheet Rev.D Summary of the Invention

[0005] Currently, a fuse is usually provided in the current path from the battery to the battery monitoring IC. When a short circuit occurs in the power supply circuit, the fuse melts and cuts off the current. However, when the voltage of the battery is low or the resistance value of the resistance in the current path, i.e., the path resistance, is high, the fuse may not melt even if a short circuit occurs. At this time, in a short-circuited state, the discharge from the battery continues, and there is a risk of over-discharge or overheating of the battery. In addition, not limited to a metal fuse that melts due to overcurrent, the same problem occurs when there is a fuse function part, and the fuse function part includes a resettable fuse whose resistance value increases due to overcurrent or an electronic fuse (eFuse) that detects overcurrent and cuts off the current through a MOSFET.

[0006] The present invention is proposed to solve the above problems, and its main object is to cut off the discharge current from the battery at the time of short circuit even when the voltage of the battery as the input source is low or the resistance value of the path resistance is high in a power supply circuit having a path resistance in the current path.

[0007] A first aspect for solving the above problems relates to a power supply circuit, which uses a battery as a power input source and supplies power to a battery monitoring unit that monitors the state of the battery, and in the current path from the battery to the battery monitoring unit, a fuse function part that cuts off the current when a current exceeding a specified current flows is provided, and in the current path, a path resistance is included at a position closer to the battery monitoring unit side than the fuse function part. A forming circuit that forms a bypass path which, when the path through the path resistor is short-circuited, allows a current exceeding the specified current to flow through the fuse function portion without passing through the path resistor.

[0008] According to the above structure, the power supply circuit uses a battery as an input source of power and supplies power to a battery monitoring unit that monitors the state of the battery. In the current path from the battery to the battery monitoring unit, a fuse function portion is provided that cuts off the current when a current exceeding the specified current flows through it. Therefore, in the case of a short circuit in the power supply circuit and a current exceeding the specified current flowing through the fuse function portion, the current can be cut off by the fuse function portion. In addition, the fuse function portion includes a metallic fuse that melts due to overcurrent, a resettable fuse whose resistance value increases due to overcurrent, and an electronic fuse (eFuse) that detects overcurrent and cuts off the current through a MOSFET, etc.

[0009] Here, the power supply circuit includes a path resistor in the current path at a position closer to the battery monitoring unit than the fuse function portion. Therefore, in the case where the voltage of the battery is low or the resistance value of the path resistor is high, even if a short circuit occurs, there is a risk that the current flowing through the fuse function portion does not exceed the specified current and the fuse function portion does not operate. Based on this point, the forming circuit forms a bypass path which, when the path through the path resistor is short-circuited, allows a current exceeding the specified current to flow through the fuse function portion without passing through the path resistor. Therefore, even if the current flowing through the path resistor to the fuse function portion does not exceed the specified current during a short circuit, the current flowing through the bypass path to the fuse function portion can be made to exceed the specified current. Therefore, even when the voltage of the battery as the input source is low or the resistance value of the path resistor is high, the fuse function portion can be made to operate during a short circuit, and the discharge current from the battery can be cut off.

[0010] In the second mode, the forming circuit includes a first energizing element that is connected in parallel with the path resistor to the current path and is energized on the condition that a voltage exceeding a first specified voltage is applied, allowing a current exceeding the specified current to flow through the fuse function portion. According to such a structure, in the case of a short circuit in the power supply circuit and a voltage exceeding the first specified voltage being applied to the first energizing element, the first energizing element connected in parallel with the path resistor to the current path is energized to form a bypass path, allowing a current exceeding the specified current to flow through the fuse function portion. Therefore, the discharge current from the battery can be cut off during a short circuit by a forming circuit with a simple structure. In addition, the first energizing element that is energized on the condition that a voltage exceeding the first specified voltage is applied includes a Zener diode, a TVS diode, a varistor, etc.

[0011] In the third mode, in the current path, at a position closer to the battery monitoring unit than the path resistance and the first current-carrying element, a switching element whose on / off state is controlled by the battery monitoring unit is connected in series. The forming circuit includes a second current-carrying element, and the second current-carrying element is connected in parallel with the battery monitoring unit at a position closer to the battery monitoring unit than the switching element in the current path, and is energized on the condition that a voltage exceeding a second specified voltage lower than the first specified voltage is applied.

[0012] According to the above structure, the switching element is connected in series in the current path at a position closer to the battery monitoring unit than the path resistance and the first current-carrying element, and its on / off state is controlled by the battery monitoring unit. Therefore, when the switching element is normal, the current flowing through the battery monitoring unit or the voltage applied to the battery monitoring unit can be appropriately adjusted. On the other hand, when the switching element is short-circuited, the current flowing through the battery monitoring unit cannot be cut off. Moreover, if the fuse function unit does not work when the voltage of the battery is low or the resistance value of the path resistance is high, it is possible to continue discharging from the battery in a short-circuited state.

[0013] Based on this point, the second current-carrying element is connected in parallel with the battery monitoring unit at a position closer to the battery monitoring unit than the switching element in the current path, and is energized on the condition that a voltage exceeding a second specified voltage lower than the first specified voltage is applied. Therefore, when the switching element is short-circuited and a voltage exceeding the second specified voltage is applied to the second current-carrying element, the second current-carrying element connected in parallel with the battery monitoring unit is energized. As a result, a voltage exceeding the first specified voltage is applied to the first current-carrying element, and the first current-carrying element is energized, forming a bypass path through the first current-carrying element and the second current-carrying element. Therefore, a current exceeding the specified current can flow through the fuse function unit, and the discharge current from the battery can be cut off when the switching element is short-circuited. In addition, the same effect can be achieved when the second current-carrying element connected in parallel with the current path is provided in the battery monitoring unit instead of the power supply circuit.

[0014] When the battery monitoring unit includes a switching element connected in series with the current path from the battery to the battery monitoring unit, the battery monitoring unit usually includes a protection element same as the second current-carrying element in the third mode to prevent the switching element from being short-circuited. Therefore, as in the fourth mode, the same effect as the third mode can also be achieved when having the following structure: the battery monitoring unit includes a switching element whose on / off state is controlled, and the switching element is connected in series with the current path.

[0015] In the fifth mode, a plurality of the current paths are included, path resistors are respectively provided in the plurality of current paths, and the forming circuit includes the first energizing element with respect to the plurality of current paths respectively. According to such a structure, even when any one of the plurality of current paths is short-circuited, the discharge current from the battery can be cut off during short circuit in the same manner as in the second mode.

[0016] In the sixth mode, the forming circuit includes a noise reduction element that reduces the noise applied to the first energizing element and has a resistance value lower than the path resistance. According to such a structure, it is possible to suppress the malfunction or failure of the first energizing element due to noise, and it is possible to suppress the current flowing through the fuse function part from decreasing due to the noise reduction element.

[0017] In the seventh mode, the forming circuit includes: a switch that is connected in parallel with the battery between the fuse function part and the path resistor in the current path; and a switch driving part that closes the switch on the condition that a current exceeding a first current smaller than the specified current flows through the path resistor. According to such a structure, when a short circuit occurs in the power supply circuit and a current exceeding the first current flows through the path resistor, the switch connected in parallel with the battery between the fuse function part and the path resistor in the current path closes to form a bypass path, and a current exceeding the specified current can flow through the fuse function part. Therefore, the discharge current from the battery can be cut off during short circuit.

[0018] In the eighth mode, on the premise of the seventh mode, in the current path, at a position closer to the battery monitoring part than the path resistor, a switch element whose on-off state is controlled by the battery monitoring part is connected in series, and the forming circuit includes a second energizing element that is connected in parallel with the battery monitoring part at a position closer to the battery monitoring part than the switch element in the current path and is energized on the condition that a voltage exceeding a second specified voltage is applied.

[0019] In the above structure, as described above, when the switch element is short-circuited, the current flowing through the battery monitoring part cannot be cut off. Moreover, if the fuse function part does not operate when the voltage of the battery is low or the resistance value of the path resistor is high, there is a possibility that the discharge from the battery continues in a short-circuited state.

[0020] Based on this point, the second energizing element is connected in parallel with the battery monitoring unit at a position on the current path closer to the battery monitoring unit than the switching element, and is energized on the condition that a voltage exceeding a second specified voltage is applied. Therefore, when the switching element is short-circuited and a voltage exceeding the second specified voltage is applied to the second energizing element, the second energizing element connected in parallel with the battery monitoring unit is energized. As a result, a current exceeding the first current flows through the path resistance, the switch closes, and a bypass path through the fuse function unit and the switch is formed. Therefore, a current exceeding the specified current can flow through the fuse function unit, and the discharge current from the battery can be cut off when the switching element is short-circuited.

[0021] In the ninth mode, a plurality of the current paths are included, path resistances are respectively provided in the plurality of current paths, and the forming circuit includes the switch driving unit for each of the plurality of current paths. According to such a configuration, even when any one of the plurality of current paths is short-circuited, the discharge current from the battery can be cut off in the same manner as in the seventh mode.

[0022] The tenth mode relates to a power supply circuit, uses a battery as a power input source, and supplies power to a battery monitoring unit that monitors the state of the battery, in the current path from the battery to the battery monitoring unit, a fuse function unit that cuts off the current when a current exceeding a specified current flows is provided, in the current path, a path resistance is included at a position closer to the battery monitoring unit than the fuse function unit, and includes a cut-off circuit that cuts off the current flowing through the path resistance when a short circuit occurs in the path through the path resistance.

[0023] According to the above configuration, the power supply circuit uses a battery as a power input source and supplies power to a battery monitoring unit that monitors the state of the battery. In the current path from the battery to the battery monitoring unit, a fuse function unit that cuts off the current when a current exceeding a specified current flows is provided. Therefore, when the power supply circuit is short-circuited and a current exceeding the specified current flows through the fuse function unit, the current can be cut off by the fuse function unit.

[0024] Here, the power supply circuit includes a path resistance in the current path at a position closer to the battery monitoring unit than the fuse function unit. Therefore, when the voltage of the battery is low or the resistance value of the path resistance is high, even if a short circuit occurs, there is a risk that the current flowing through the fuse function unit does not exceed the specified current and the fuse function unit does not operate. Based on this point, the cut-off circuit cuts off the current flowing through the path resistance when a short circuit occurs in the path passing through the path resistance. Therefore, even when the current flowing through the path resistance to the fuse function unit does not exceed the specified current during a short circuit, the current flowing through the path resistance can be cut off. Therefore, even when the voltage of the battery of the input source is low or the resistance value of the path resistance is high, the discharge current from the battery can be cut off during a short circuit.

[0025] In the eleventh aspect, the cut-off circuit includes: a switch that is connected in series with the fuse function unit and the path resistance in the current path; and a switch driving unit that turns on the switch on the condition that a current exceeding a first current smaller than the specified current flows through the path resistance. According to such a configuration, when a short circuit occurs in the power supply circuit and a current exceeding the first current flows through the path resistance, the switch connected in series with the fuse function unit and the path resistance in the current path is turned on. Therefore, even when the voltage of the battery of the input source is low or the resistance value of the path resistance is high, the discharge current from the battery can be cut off during a short circuit.

[0026] In the twelfth aspect, the fuse function unit is a first fuse function unit, and the cut-off circuit includes a second fuse function unit. The second fuse function unit is connected in series with a specified element connected in parallel to the current path, and a current exceeding a first current smaller than the specified current does not flow when the specified element does not short-circuit, and cuts off the current on the condition that a current exceeding the first current flows.

[0027] According to the above structure, the fuse functional part operates as a first fuse functional part. The second fuse functional part is connected in series with a specified element connected in parallel to the current path, and when the specified element does not short-circuit, a current not exceeding a first current smaller than the specified current does not flow, and the current is cut off on the condition that a current exceeding the first current flows. Therefore, when the specified element does not short-circuit, the second fuse functional part does not cut off the current, and the current can flow through the specified element. On the other hand, the second fuse functional part cuts off the current when a current exceeding the first current flows. Therefore, when the specified element short-circuits, even if the current flowing through the first fuse functional part does not exceed the specified current and the first fuse functional part does not operate, as long as a current exceeding the first current smaller than the specified current flows through the second fuse functional part, the current can be cut off by the second fuse functional part. Therefore, even when the voltage of the battery of the input source is low or the resistance value of the path resistance is high, the discharge current from the battery can be cut off when the specified element short-circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above objects, other objects, features, and advantages of the present disclosure can be made more apparent by referring to the drawings and the following detailed description. The drawings are as follows. Figure 1 is a block diagram of a battery monitoring device. Figure 2 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the first embodiment. Figure 3 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the first embodiment. Figure 4 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the second embodiment. Figure 5 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the third embodiment. Figure 6 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the fourth embodiment. Figure 7 is a circuit diagram showing a modified example of the power supply circuit and the battery monitoring IC of the fourth embodiment. Figure 8 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the fifth embodiment. Figure 9 is a circuit diagram showing a modified example of the power supply circuit and the battery monitoring IC of the fifth embodiment. Figure 10 is a circuit diagram showing a power supply circuit and a battery monitoring IC of the sixth embodiment. Figure 11This is a circuit diagram showing the power supply circuit and the battery monitoring IC of the seventh embodiment. Figure 12 This is a circuit diagram showing the power supply circuit and the battery monitoring IC of the eighth embodiment. Figure 13 This is a circuit diagram showing a modified example of the power supply circuit and the battery monitoring IC of the eighth embodiment. Figure 14 This is a circuit diagram showing the power supply circuit and the battery monitoring IC of the ninth embodiment. Detailed Embodiments

[0029] (First Embodiment) Hereinafter, with reference to the drawings, a first embodiment that specifically embodies a power supply circuit applicable to a battery monitoring device installed in a vehicle or the like will be described. As Figure 1 shown, the battery monitoring device 10 includes a master unit 20 and a slave unit 30.

[0030] The master unit 20 includes a power supply circuit 21, a communication interface (I / F) 22, a temperature detection interface (I / F) 23, a relay drive unit 24, a microcomputer 25, a communication IC 26, etc. The master unit 20 communicates with the slave unit 30 and monitors the states of the individual cells 12 of the battery 11 and the battery 11 through the slave unit 30. The battery 11 is constituted, for example, by connecting a plurality of individual cells 12 in series, or by connecting in series a plurality of battery modules each having a plurality of individual cells 12 connected in series.

[0031] The slave unit 30 includes a battery monitoring IC 31, a detection circuit 32, a power supply circuit 40, etc. The power supply circuit 40 uses the battery 11 as a power input source and supplies power to the battery monitoring IC. The battery monitoring IC (battery monitoring unit) operates with the power supplied from the power supply circuit 40 and detects the states of the individual cells 12 and the battery 11 through the detection circuit 32. The detection circuit 32 is controlled by the battery monitoring IC and performs voltage detection of the individual cell 12, temperature detection of the individual cell 12, equalization of the voltages of the individual cells 12, etc. In addition, the detection circuit 32 may also perform detection of the current flowing through the individual cell 12 (battery 11), internal pressure detection of the individual cell 12, gas leakage detection from the individual cell 12 (battery 11), etc.

[0032] Figure 2 This is a circuit diagram showing the power supply circuit 40 and the battery monitoring IC 31. On the wiring L1 (current path) from the positive terminal of the battery 11 to the power input terminal (Power) of the battery monitoring IC 31, a fuse F1, a resistor R1, and a transistor T1 are connected in series in this order. On the wiring L2 (current path) from the GND terminal of the battery monitoring IC to the negative terminal of the battery 11, a fuse F2 is connected in series.

[0033] The fuses F1 and F2 (fuse functional parts) are, for example, metal fuses that melt and cut off the current when a current exceeding 0.5 to 1.0 [A] (specified current If) flows through. Additionally, the metal fuses are not limited to those having a fuse element made of a metal with a low melting point in a wire shape, and can also be pattern fuses in which the pattern width of the wiring is made thinner than other parts and is melted by an overcurrent.

[0034] In the wiring L1, between the resistor R1 and the transistor T1, the capacitor C1 is connected in parallel with the battery 11 and the battery monitoring IC 31. The resistor R1 and the capacitor C1 form an RC filter (low-pass filter) that reduces the noise applied to the transistor T1. The resistance value of the resistor R1 (path resistance) is set according to the frequency of the assumed noise, and is, for example, 100 to several k [Ω]. Additionally, the resistor R1 can also be composed of multiple resistors.

[0035] In the wiring L1, between the transistor T1 and the power input terminal of the battery monitoring IC, the capacitor C3 is connected in parallel with the battery 11 and the battery monitoring IC 31. The base of the transistor T1 (switching element) is connected to the drive terminal (Drive) of the battery monitoring IC via an RC filter (low-pass filter) composed of the resistor R2 and the capacitor C2. Additionally, the transistor T1 is not limited to bipolar types and can also be a unipolar type such as a MOSFET.

[0036] The battery monitoring IC 31 controls the on / off period or the opening degree, that is, the on / off state of the transistor T1 based on the output from the drive terminal. By controlling the on / off state of the transistor T1, the battery monitoring IC 31 controls the charge stored in the capacitor C3 and, further, the voltage input to the power input terminal of the battery monitoring IC to a target voltage.

[0037] Here, assume a case where the Zener diode D1 is not connected in parallel with the resistor R1 to the wiring L1 and the capacitor C1 is short-circuited. At this time, depending on the resistance value of the resistor R1, the current flowing through the fuse F1, the resistor R1, the capacitor C1, and the fuse F2 may sometimes decrease to several tens to several hundreds [mA]. At this time, there is a risk that the current flowing through the fuses F1 and F2 does not exceed the specified current If and the fuses F1 and F2 do not melt. As a result, in a short-circuited state, the discharge from the battery 11 continues, and there is a risk of over-discharge or overheating of the battery 11.

[0038] Therefore, in the present embodiment, the Zener diode D1 (first energizing element) is connected in parallel with the resistor R1 to the wiring L1. Through the wiring B1, the anode of the Zener diode D1 is connected to the transistor T1 side with respect to the resistor R1, and the cathode of the Zener diode D1 is connected to the fuse F1 side with respect to the resistor R1. The Zener diode D1 breaks down when a voltage exceeding the first specified voltage V1 is applied, forming a Zener voltage (constant voltage), and the first specified voltage V1 is lower than the lowest voltage within the operating range (variation range) of the voltage of the battery 11. When the capacitor C1 is not short-circuited, the voltage applied to the Zener diode D1 is lower than the first specified voltage V1. The resistance value of the Zener diode D1 in the breakdown state is, for example, several [Ω]. In addition, the Zener diode D1 and the wiring B1 that connects the Zener diode D1 to the wiring L1 constitute a forming circuit.

[0039] Moreover, when the capacitor C1 is short-circuited, the voltage applied to the Zener diode D1 exceeds the first specified voltage V1, and the Zener diode D1 breaks down (energizes). As a result, the current bypasses the resistor R1 and flows sequentially through the fuse F1, the Zener diode D1, the capacitor C1, and the fuse F2. At this time, since the resistance value of the Zener diode D1 in the breakdown state is sufficiently lower than the resistance value of the resistor R1, even if the voltage of the battery 11 is the lowest voltage within the operating range, a current exceeding the specified current If flows through the fuses F1 and F2. That is, the Zener diode D1 is energized on the condition that a voltage exceeding the first specified voltage V1 is applied, and a current exceeding the specified current If flows through the fuses F1 and F2. As a result, at least one of the fuses F1 and F2 melts to cut off the current.

[0040] In addition, it is assumed that Figure 3 there is no case where the Zener diode D2 is connected in parallel with the battery monitoring IC at a position closer to the battery monitoring IC 31 than the transistor T1 in the wiring L1 and the transistor T1 is short-circuited. At this time, the current flowing through the power input terminal of the battery monitoring IC 31 cannot be cut off. Moreover, if neither of the fuses F1 and F2 operates when the voltage of the battery 11 is low or the resistance value of the resistor R1 is high, there is a possibility that the discharge from the battery 11 continues in a short-circuited state.

[0041] Therefore, in the present embodiment, in the wiring L1, a Zener diode D2 is connected in parallel with the battery monitoring IC at a position closer to the battery monitoring IC 31 than the transistor T1. Through the wiring B2, the anode of the Zener diode D2 is connected to the wiring L2, and the cathode of the Zener diode D1 is connected to the wiring L1. The Zener diode D2 breaks down when a voltage exceeding a second specified voltage V2 lower than the above-mentioned first specified voltage V1 is applied, forming a Zener voltage (constant voltage). When the transistor T1 is not short-circuited and the on / off state of the transistor T1 is controlled, the voltage applied to the Zener diode D2 is lower than the second specified voltage V2. The resistance value of the Zener diode D2 in the breakdown state is, for example, several [Ω]. In addition, the Zener diode D1, the wiring B1 connecting the Zener diode D1 to the wiring L1, the Zener diode D2, and the wiring B2 connecting the Zener diode D2 to the wirings L1 and L2 form a circuit.

[0042] Moreover, when the transistor T1 is short-circuited, the voltage applied to the Zener diode D2 exceeds the second specified voltage V2, and the Zener diode D2 breaks down (conducts electricity). Subsequently, the voltage applied to the Zener diode D1 exceeds the first specified voltage V1, and the Zener diode D1 breaks down (conducts electricity). As a result, the current bypasses the resistor R1 and flows sequentially through the fuse F1, the Zener diode D1, the transistor T1, the Zener diode D2, and the fuse F2. At this time, since the resistance values of the Zener diodes D1 and D2 in the breakdown state are sufficiently lower than the resistance value of the resistor R1, even if the voltage of the battery 11 is the lowest voltage within the usable range, a current exceeding the specified current If flows through the fuses F1 and F2. As a result, at least one of the fuses F1 and F2 melts to cut off the current.

[0043] The present embodiment described in detail above has the following advantages.

[0044] · When a short circuit occurs in the path through the resistor R1, the Zener diode D1 and its wiring B1 form a bypass path that allows a current exceeding the specified current If to flow through the fuses F1 and F2 without passing through the resistor R1. Therefore, even when the current flowing through the fuses F1 and F2 through the resistor R1 does not exceed the specified current If during a short circuit, it is possible to make the current flowing through the bypass path into the fuses F1 and F2 exceed the specified current If. Therefore, even when the voltage of the battery 11 of the input source is low or the resistance value of the resistor R1 is high, it is possible to operate the fuses F1 and F2 during a short circuit and cut off the discharge current from the battery 11.

[0045] · When a short circuit occurs in the power supply circuit 40 and a voltage exceeding the first specified voltage V1 is applied to the Zener diode D1, the Zener diode D1 connected in parallel with the resistor R1 to the wiring L1 is energized to form a bypass path, and a current exceeding the specified current If can flow through the fuses F1 and F2. Therefore, the discharge current from the battery 11 can be cut off at the time of short circuit by forming a circuit with a simple structure.

[0046] · The Zener diode D2 is connected in parallel with the battery monitoring IC 31 at a position on the wiring L1 closer to the battery monitoring IC 31 than the transistor T1, and is energized on the condition that a voltage exceeding the second specified voltage V2 lower than the first specified voltage V1 is applied. Therefore, when the transistor T1 is short-circuited and a voltage exceeding the second specified voltage V2 is applied to the Zener diode D2, the Zener diode D2 connected in parallel with the battery monitoring IC 31 is energized. As a result, a voltage exceeding the first specified voltage V1 is applied to the Zener diode D1, the Zener diode D1 is energized, and a bypass path through the Zener diode D1 and the Zener diode D2 is formed. Therefore, a current exceeding the specified current If can flow through the fuses F1 and F2, and the discharge current from the battery 11 can be cut off when the transistor T1 is short-circuited.

[0047] In addition, not limited to the case where the capacitor C1 is short-circuited, the same effect can be obtained when a part between the resistor R1 and the transistor T1 of the wiring L1 is directly short-circuited to the wiring L2.

[0048] In addition, when the Zener diode D2 connected in parallel with the wiring L1 is built in (provided) in the battery monitoring IC 31 instead of the power supply circuit 40, the same effect can be obtained.

[0049] (Second Embodiment) Hereinafter, with reference to the drawings, the second embodiment will be described centering on the differences from the first embodiment. In addition, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0050] As Figure 4 shown, the battery monitoring IC 131 is built in (equipped with) a transistor T1, a resistor R2, and capacitors C2 and C3 for controlling the open / close state. The transistor T1 is connected in series with the wiring L1. The power supply circuit 140 includes a Zener diode D1 and does not include the transistor T1, the resistor R2, and the capacitors C2 and C3.

[0051] Here, when the battery monitoring IC 31 has a transistor T1 connected in series with the wiring L1 from the battery 11 to the battery monitoring IC 131, in order to cope with the situation where the transistor T1 is short-circuited, the battery monitoring IC 131 usually includes a protection element (not shown) identical to the above-mentioned Zener diode D2. Therefore, according to this embodiment, the same effects as those of the first embodiment can also be achieved.

[0052] (Third Embodiment) Hereinafter, with reference to the drawings, the third embodiment will be described centering on the differences from the first embodiment. In addition, for the parts identical to those of the first embodiment, the same reference numerals are used and the description is omitted.

[0053] As Figure 5 shown, the power supply circuit 240 includes: a wiring L1 (current path) from the positive terminal of the battery 11 to the main power input terminal (Power(main)) of the battery monitoring IC 31; and a wiring L0 (current path) from the positive terminal of the battery 11 to the sub-power input terminal (Power(sub)) of the battery monitoring IC 31.

[0054] A resistor R0 (path resistance) is provided in the wiring L2. In the wiring L0, between the resistor R0 and the sub-power input terminal of the battery monitoring IC, a capacitor C0 is connected in parallel with the battery 11 and the battery monitoring IC 31. A Zener diode D0 (first energizing element) identical to the Zener diode D1 is connected in parallel with the resistor R0 to the wiring L0. Through the wiring B0, the anode of the Zener diode D0 is connected to the battery monitoring IC 31 side with respect to the resistor R1, and the cathode of the Zener diode D0 is connected to the fuse F1 side with respect to the resistor R1. That is, in this embodiment, as a forming circuit, with respect to the wirings L1, L0 (multiple wirings), Zener diodes D1, D0 and wirings B1, B0 are respectively included.

[0055] According to the above structure, even when any one of the wirings L1, L0 is short-circuited, the discharge current from the battery 11 can be cut off at the time of short circuit in the same manner as in the first embodiment. For example, when the capacitor C0 (wiring L0) is short-circuited, the voltage applied to the Zener diode D0 exceeds the first specified voltage V1, and the Zener diode D0 breaks down (conducts). As a result, the current bypasses the resistor R0 and flows successively through the fuse F1, the Zener diode D0, the capacitor C0, and the fuse F2. As a result, at least one of the fuses F1, F2 melts to cut off the current.

[0056] (Fourth Embodiment) Hereinafter, with reference to the drawings, the fourth embodiment will be described centering on the differences from the first embodiment. In addition, for the parts identical to those of the first embodiment, the same reference numerals are used and the description is omitted.

[0057] As Figure 6 shown, the power supply circuit 40 includes: a resistor Rf that reduces the noise applied to the Zener diode D1 and has a resistance value lower than that of the resistor R1; and a capacitor Cf. In the wiring L1, between the resistor Rf and the resistor R1, the capacitor Cf is connected in parallel with the battery 11 and the battery monitoring IC 31. The resistor Rf and the capacitor Cf constitute an RC filter (low-pass filter) that reduces the noise applied to the Zener diode D1. The resistance value of the resistor Rf is lower than the resistance value of the resistor R1, for example, several [Ω], and is set to a resistance value at which the fuses F1 and F2 are blown when the capacitor C1 is short-circuited. In addition, the resistor Rf may be composed of multiple resistors.

[0058] According to the above structure, it is possible to suppress the malfunction or failure of the Zener diode D1 due to noise, and it is possible to suppress the reduction of the current flowing through the fuses F1 and F2 due to the resistor Rf. Therefore, even when the voltage of the battery 11 of the input source is low or the resistance value of the resistor R1 is high, the fuses F1 and F2 can be made to operate during a short circuit, and the discharge current from the battery 11 can be cut off.

[0059] In addition, it may also be as Figure 7 shown, instead of Figure 6 the resistor Rf and the capacitor Cf, the power supply circuit 40 includes a resistor Rf connected in series with the Zener diode D1 in the wiring B1. The resistor Rf reduces the noise applied to the Zener diode D1, and the resistance value is lower than that of the resistor R1. The resistance value of the resistor Rf is lower than the resistance value of the resistor R1, for example, several [Ω], and is set to a resistance value at which the fuses F1 and F2 are blown when the capacitor C1 is short-circuited. In addition, the resistor Rf may be composed of multiple resistors.

[0060] According to such a structure, it is also possible to suppress the malfunction or failure of the Zener diode D1 due to noise, and it is possible to suppress the reduction of the current flowing through the fuses F1 and F2 due to the resistor Rf. Therefore, even when the voltage of the battery 11 of the input source is low or the resistance value of the resistor R1 is high, the fuses F1 and F2 can be made to operate during a short circuit, and the discharge current from the battery 11 can be cut off.

[0061] (Fifth Embodiment) Hereinafter, with reference to the drawings, the fifth embodiment will be described centering on the differences from the first embodiment. In addition, for the parts that are the same as those in the first embodiment, the same reference numerals are given and the description is omitted.

[0062] As Figure 8As shown, the power supply circuit 40 includes: a switch S1 connected in parallel with the battery 11 through a wiring B3 between a fuse F1 and a resistor R1 in a wiring L1; and a comparator Cp1 that drives the switch S1. The switch S1 is, for example, an N-channel MOSFET. In the wiring L2, a shunt resistor Rs is connected in series at a position closer to the battery 11 side than the connection point of the capacitor C1. The gate of the switch S1 is connected to the output of the comparator Cp1, the drain is connected to the connection point of the fuse F1 and the resistor R1, and the source is connected to the connection point of the fuse F2 and the shunt resistor Rs. The comparator Cp1 turns on (closes) the switch S1 on the condition that the voltage across both ends of the shunt resistor Rs exceeds a threshold value. The threshold value is set to the following voltage: the voltage applied to the shunt resistor Rs when a specified current If lower than the case where the capacitor C1 is short-circuited and the fuse F1 is blown flows through the shunt resistor Rs. That is, the comparator Cp1 closes the switch S1 on the condition that a current exceeding a first current I1 smaller than the specified current If flows through the resistor R1. The first current I1 is a current smaller than the current flowing through the resistor R1 when the capacitor C1 is short-circuited in the case where the voltage of the battery 11 is the lowest voltage within the usage range (variation range) or the resistance value of the resistor R1 is higher. When the capacitor C1 is not short-circuited, the current flowing through the resistor R1 is less than the first current I1. In addition, the switch driving unit is constituted by the comparator Cp1 and the shunt resistor Rs. The forming circuit is constituted by the switch S1, the wiring B3, the comparator Cp1, and the shunt resistor Rs. In addition, an operational amplifier may be used instead of the comparator Cp1.

[0063] According to the above structure, when the capacitor C1 is short-circuited and a current exceeding the first current I1 flows through the resistor R1, the switch S1 connected in parallel with the battery 11 between the fuse F1 and the resistor R1 in the wiring L1 can be closed to form a bypass path, and a current exceeding the specified current If can flow through the fuses F1 and F2. Therefore, the discharge current from the battery 11 can be cut off during a short circuit.

[0064] In addition, a Zener diode D2 (second energizing element) is connected in parallel with the battery monitoring IC 31 at a position closer to the battery monitoring IC 31 side than the transistor T1 in the wiring L1, and is energized on the condition that a voltage exceeding a second specified voltage V2 is applied. Therefore, when the transistor T1 is short-circuited and a voltage exceeding the second specified voltage V2 is applied to the Zener diode D2, the Zener diode D2 connected in parallel with the battery monitoring IC 31 is energized. As a result, a current exceeding the first current I1 flows through the resistor R1, the switch S1 is closed, and a bypass path passing through the fuse F1, the switch S1, and the fuse F2 in sequence is formed. Therefore, a current exceeding the specified current If can flow through the fuses F1 and F2, and the discharge current from the battery 11 can be cut off when the transistor T1 is short-circuited.

[0065] In addition, it may be as Figure 9As shown, comparator Cp1 turns on (closes) switch S1 when the voltage across resistor R1 exceeds a threshold value. The threshold value is set to the voltage applied to resistor R1 when a specified current If that is lower than the current at which capacitor C1 is short-circuited and fuse F1 blows flows through resistor R1. That is, comparator Cp1 closes switch S1 when a current greater than a first current I1 that is smaller than the specified current If flows through resistor R1. When capacitor C1 is not short-circuited, the current flowing through resistor R1 is less than the first current I1. In addition, the switch driving section is constituted by comparator Cp1 and resistor R1. The forming circuit is constituted by switch S1, wiring B3, comparator Cp1, and resistor R1. In addition, an operational amplifier may be used instead of comparator Cp1.

[0066] (Sixth Embodiment) Hereinafter, with reference to the drawings, the sixth embodiment will be described centering on the differences from the first embodiment. In addition, parts that are the same as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

[0067] As Figure 10 shown, the power supply circuit 40 includes a switch S2 that is connected in parallel with the battery 11 between the fuse F1 and the resistor R1 in the wiring L1. The switch S2 is, for example, a P-channel MOSFET. The gate of the switch S2 is connected to the connection point of the resistor R1, the transistor T1, and the capacitor C1 through the wiring L3, the source is connected to the connection point of the fuse F1 and the resistor R1, and the drain is connected to the connection point of the fuse F2, the capacitor C1, and the GND terminal of the battery monitoring IC. The switch S2 turns on (closes) when the voltage at the connection point of the wiring L1 and the wiring L3 is lower than a threshold value. The threshold value is set to the voltage applied to the connection point of the wiring L1 and the wiring L3 when a specified current If that is higher than the current at which capacitor C1 is short-circuited and fuse F1 blows flows through resistor R1. That is, the switch S2 closes when a current greater than a first current I1 that is smaller than the specified current If flows through resistor R1. The first current I1 is a current that is smaller than the current flowing through resistor R1 when capacitor C1 is short-circuited in the case where the voltage of the battery 11 is at the lowest voltage within the usage range (variation range) or the resistance value of the resistor R1 is high. When capacitor C1 is not short-circuited, the current flowing through resistor R1 is less than the first current I1. In addition, the switch driving section is constituted by the wiring L3. The forming circuit is constituted by the switch S2, the wiring B3, and the wiring L3.

[0068] According to the above structure, when capacitor C1 is short-circuited and a current greater than the first current I1 flows through resistor R1, the switch S2 that is connected in parallel with the battery 11 between the fuse F1 and the resistor R1 in the wiring L1 can be closed to form a bypass path, and a current greater than the specified current If can flow through the fuses F1 and F2. Therefore, the discharge current from the battery 11 can be cut off during a short circuit.

[0069] In addition, when the transistor T1 is short-circuited, the Zener diode D2 (second energizing element) is energized. As a result, a current exceeding the first current I1 flows through the resistor R1, the switch S2 closes, and a bypass path that sequentially passes through the fuse F1, the switch S2, and the fuse F2 is formed. Therefore, a current exceeding the specified current If can flow through the fuses F1 and F2, and the discharge current from the battery 11 can be cut off when the transistor T1 is short-circuited.

[0070] (Seventh Embodiment) Hereinafter, with reference to the drawings, the seventh embodiment will be described centering on the differences from the sixth embodiment. In addition, the same parts as those in the sixth embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0071] As Figure 11 shown, the power supply circuit 540 includes: a wiring L1 (current path) from the positive terminal of the battery 11 to the main power input terminal (Power(main)) of the battery monitoring IC 31; and a wiring L0 (current path) from the positive terminal of the battery 11 to the sub-power input terminal (Power(sub)) of the battery monitoring IC 31.

[0072] A resistor R0 (path resistance) is provided in the wiring L0. In the wiring L0, between the resistor R0 and the sub-power input terminal of the battery monitoring IC, a capacitor C0 is connected in parallel with the battery 11 and the battery monitoring IC 31. The gate of the switch S2 is connected to the connection point of the resistor R1, the transistor T1, and the capacitor C1 via the wiring L3 and the diode D3. The anode of the diode D3 is connected to the gate of the switch S2, and the cathode is connected to the connection point of the resistor R1, the transistor T1, and the capacitor C1. The gate of the switch S2 is connected to the connection point of the resistor R0, the capacitor C0, and the sub-power input terminal (Power(sub)) of the battery monitoring IC via the wiring L4 and the diode D3. The anode of the diode D3 is connected to the gate of the switch S2, and the cathode is connected to the connection point of the resistor R0, the capacitor C0, and the sub-power input terminal (Power(sub)) of the battery monitoring IC. That is, in the present embodiment, as a forming circuit, with respect to the wirings L1 and L0 (a plurality of wirings), the wirings L3 and L4 and the diode D3 (switch driving unit) are respectively included.

[0073] According to the above structure, even when any one of the wirings L1 and L0 is short-circuited, the discharge current from the battery 11 can be cut off during short-circuiting in the same manner as in the sixth embodiment. For example, when the capacitor C0 is short-circuited, the switch S2 closes. As a result, the current bypasses the resistors R1 and R0 and sequentially flows to the fuse F1, the switch S2, and the fuse F2. As a result, at least one of the fuses F1 and F2 melts to cut off the current.

[0074] (Eighth Embodiment) Hereinafter, with reference to the drawings, the eighth embodiment will be described centering on the differences from the fifth embodiment. In addition, parts that are the same as those in the fifth embodiment are denoted by the same reference numerals and their description will be omitted.

[0075] As Figure 12 shown, the power supply circuit 640 includes: a switch S3 that is serially connected to a fuse F1 and a resistor R1 at a position closer to the battery 11 side than the connection point of the resistor R1 (path resistance), the capacitor C1, and the transistor T1 in the wiring L1; and a comparator Cp1 that drives the switch S3. The switch S3 is a normally closed switch that closes when the output from the comparator Cp1 is off and opens when it is on. The comparator Cp1 opens the switch S3 on the condition that the voltage across both ends of the shunt resistor Rs exceeds a threshold value. The threshold value is set to the voltage applied to the shunt resistor Rs when a specified current If that is lower than the current flowing through the shunt resistor Rs when the capacitor C1 is short-circuited and the fuse F1 is blown flows through the shunt resistor Rs. The comparator Cp1 opens the switch S3 on the condition that a current exceeding a first current I1 that is smaller than the specified current If flows through the resistor R1. The first current I1 is a current that is smaller than the current flowing through the resistor R1 when the capacitor C1 is short-circuited in the case where the voltage of the battery 11 is the lowest voltage within the usage range (variation range) or the resistance value of the resistor R1 is higher. When the capacitor C1 is not short-circuited, the current flowing through the resistor R1 is less than the first current I1. That is, in the case of a short circuit occurring in the path through the resistor R1, the comparator Cp1 opens the switch S3 to cut off the current flowing through the resistor R1. In addition, the switch driving unit is constituted by the comparator Cp1 and the shunt resistor Rs, and the cut-off circuit is constituted by the switch S3, the comparator Cp1, and the shunt resistor Rs. In addition, an operational amplifier may be used instead of the comparator Cp1.

[0076] According to the above structure, when the capacitor C1 is short-circuited, even if the current flowing through the fuses F1 and F2 via the resistor R1 does not exceed the specified current If, the current flowing through the resistor R1 can be cut off. Specifically, when the capacitor C1 is short-circuited and a current exceeding the first current I1 flows through the resistor R1, the switch S3 serially connected to the fuse F1 and the resistor R1 in the wiring L1 opens. Therefore, even when the voltage of the battery 11 of the input source is low or the resistance value of the resistor R1 is high, the discharge current from the battery 11 can be cut off during a short circuit.

[0077] In addition, it may be as Figure 13As shown, comparator Cp1 turns on switch S1 when the voltage across resistor R1 exceeds a threshold value. The threshold value is set to the voltage applied across resistor R1 when a specified current If that is lower than the current flowing when capacitor C1 is short-circuited and fuse F1 blows flows through resistor R1. That is, in the case of a short circuit occurring in the path through resistor R1, comparator Cp1 turns on switch S3 to cut off the current flowing through resistor R1. In addition, a switch drive unit is constituted by comparator Cp1 and resistor R1, and a cut-off circuit is constituted by switch S3, comparator Cp1, and resistor R1. In addition, an operational amplifier may be used instead of comparator Cp1.

[0078] (Ninth Embodiment) Hereinafter, with reference to the drawings, the ninth embodiment will be described centering on the differences from the first embodiment. In addition, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

[0079] As Figure 14 shown, power supply circuit 40 includes fuse F3 on wiring L5 that connects capacitor C1 (specified element) to wiring L1 and wiring L2. That is, fuse F3 (second fuse function unit, cut-off circuit) is connected in series with capacitor C1 connected in parallel to wiring L1. Fuse F3 is connected in series with capacitor C1 that is assumed to be short-circuited. Fuse F3 blows and cuts off the current when a current greater than a first current I1 that is smaller than the specified current If at which fuses F1 and F2 (first fuse function units) blow flows through. Specifically, the first current I1 is a current smaller than the current flowing through resistor R1 when capacitor C1 is short-circuited when the voltage of battery 11 is at the lowest voltage within the usage range (variation range) or the resistance value of resistor R1 is higher. When capacitor C1 is not short-circuited (when capacitor C1 is normal), a current greater than the first current I1 that is smaller than the specified current If does not flow through fuse F3.

[0080] According to the above structure, when capacitor C1 is not short-circuited, fuse F3 does not cut off the current and current can flow through capacitor C1. On the other hand, fuse F3 cuts off the current when a current greater than the first current I1 flows through. Therefore, when capacitor C1 is short-circuited, even if the current flowing through fuses F1 and F2 does not exceed the specified current If and fuses F1 and F2 do not operate, a current greater than the first current I1 that is smaller than the specified current If flows through fuse F3, and the current can be cut off by fuse F3. Therefore, even when the voltage of battery 11 of the input source is low or the resistance value of resistor R1 is high, the discharge current from battery 11 can be cut off when capacitor C1 is short-circuited.

[0081] In addition, the power supply circuit 40 includes a fuse F4 that is the same as the fuse F3 on a wiring L6 that connects a Zener diode D2 (a specified component) to the wirings L1 and L2. That is, the fuse F4 (the second fuse functional unit, the cut-off circuit) is connected in series with the Zener diode D2 that is connected in parallel to the wiring L1. The fuse F3 is connected in series with the Zener diode D2 that is assumed to be short-circuited. The fuse F4 is fused and cuts off the current on the condition that a current greater than a first current I1 that is smaller than a specified current If at which the fuses F1 and F2 (the first fuse functional unit) are fused flows through. When the Zener diode D2 is not short-circuited (when the Zener diode D2 is normal), a current greater than the first current I1 that is smaller than the specified current If does not flow through the fuse F4. According to such a structure, when the Zener diode D2 is short-circuited, even if the current flowing through the fuses F1 and F2 does not exceed the specified current If and the fuses F1 and F2 do not operate, a current greater than the first current I1 that is smaller than the specified current If flows through the fuse F4, and the current can be cut off by the fuse F4.

[0082] In addition, in Figure 14 it may also include Figure 12 the switch S3, the comparator Cp1, and the shunt resistor Rs of Figure 13 or the switch S3 and the comparator Cp1 of

[0083] In addition, the first to ninth embodiments and their modified examples may also be changed and implemented as follows.

[0084] · The Zener diodes D1 and D2 (the energized components) that are energized on the condition that a voltage exceeding a first specified voltage V1 and a second specified voltage V2 (specified voltages) is applied are not limited to Zener diodes, and may also be TVS diodes, varistors, etc.

[0085] · The fuses F1 and F2 are not limited to being inside the power supply circuit, and may also be provided on an FPC (substrate) outside the power supply circuit, the battery 11, etc.

[0086] · As the fuses F1 and F2 (the first fuse functional unit) and the fuses F3 and F4 (the second fuse functional unit), a resettable fuse whose resistance value increases due to overcurrent, an electronic fuse (eFuse) that detects overcurrent and cuts off the current through a MOSFET, etc. may also be used. In these cases, the fuses F1 to F4 can also cut off (substantially cut off) the current when a current exceeding the specified current If flows through.

[0087] · In the battery monitoring device 10, the master unit 20 and the slave unit 30 are not limited to a split structure, and may also be an integrated structure including the functions of the master unit 20 and the slave unit 30.

[0088] · The battery monitoring device 10 can be installed in an electric flying vehicle such as a drone or an electric aircraft, or can be installed in a stationary battery.

[0089] In addition, the above-described embodiments and their modified examples can be combined within a combinable range.

[0090] Hereinafter, characteristic structures extracted from the above-described embodiments and modified examples are described. [Structure 1] A power supply circuit, the power supply circuit (40, 140, 240, 340, 440, 540) uses a battery (11) as a power input source and supplies power to a battery monitoring unit (31) that monitors the state of the battery. In a current path (L1, L2) from the battery to the battery monitoring unit, fuse function units (F1, F2) are provided to cut off the current when a current exceeding a specified current flows. In the current path, a path resistance (R1, R0) is included at a position closer to the battery monitoring unit side than the fuse function unit. A forming circuit (D1, B1, D2, B2, D0, B0, S1, S2, B3, Cp1, Rs, R1, L3, L4, D3) for forming a bypass path is included. When a short circuit occurs in the path passing through the path resistance, the bypass path allows a current exceeding the specified current to flow through the fuse function unit without passing through the path resistance. [Structure 2] According to the power supply circuit of Structure 1, the forming circuit includes a first energizing element (D1, D0), and the first energizing element is connected in parallel with the path resistance to the current path and is energized on the condition that a voltage exceeding a first specified voltage is applied, so that a current exceeding the specified current flows through the fuse function unit. [Structure 3] According to the power supply circuit of Structure 2, in the current path, a switching element (T1) whose on-off state is controlled by the battery monitoring unit is connected in series at a position closer to the battery monitoring unit side than the path resistance and the first energizing element. The forming circuit includes a second energizing element (D2), and the second energizing element is connected in parallel with the battery monitoring unit at a position closer to the battery monitoring unit side than the switching element in the current path and is energized on the condition that a voltage exceeding a second specified voltage lower than the first specified voltage is applied. [Structure 4] According to the power supply circuit of Structure 2, the battery monitoring unit includes a switching element (T1) whose on-off state is controlled. The switching element is connected in series with the current path (L1). [Structure 5] The power supply circuit according to any one of Structures 2 to 4 includes a plurality of the current paths (L1, L0), Path resistors (R1, R0) are respectively provided in the plurality of the current paths, The forming circuit includes the first energizing elements (D1, D0) respectively with respect to the plurality of the current paths. [Structure 6] The power supply circuit according to any one of Structures 2 to 5, wherein the forming circuit includes a noise reduction element (Rf) that reduces noise applied to the first energizing element and has a resistance value lower than that of the path resistor.

[0091] Although the present disclosure has been described based on embodiments, it should be understood that the present disclosure is not limited to the above embodiments and structures. The present disclosure also includes various modifications and modifications within an equivalent range. In addition, various combinations and modes, and further combinations and modes including only one element, more than one or less than one of them also fall within the scope and thinking range of the present disclosure.

Claims

1. A power supply circuit, the power supply circuit (40, 140, 240, 340, 440, 540) takes the battery (11) as the input source of power, and supplies power to the battery monitoring unit (31) that monitors the state of the battery. In the current paths (L1, L2) from the battery to the battery monitoring unit, fuse function parts (F1, F2) are provided to cut off the current when a current exceeding a specified current flows through. In the current path, at a position closer to the battery monitoring unit than the fuse function part, path resistors (R1, R0) are included. It includes a forming circuit (D1, B1, D2, B2, D0, B0, S1, S2, B3, Cp1, Rs, R1, L3, L4, D3) that forms a bypass path. When a short circuit occurs in the path passing through the path resistor, the bypass path allows a current exceeding the specified current to flow through the fuse function part without passing through the path resistor.

2. The power supply circuit according to claim 1, wherein: The forming circuit includes a first energizing element (D1, D0), which is connected in parallel with the path resistor to the current path, and is energized on the condition that a voltage exceeding a first specified voltage is applied, so that a current exceeding the specified current flows through the fuse function part.

3. The power supply circuit according to claim 2, wherein: In the current path, at a position closer to the battery monitoring unit than the path resistor and the first energizing element, a switching element (T1) whose opening and closing state is controlled by the battery monitoring unit is connected in series. The forming circuit includes a second energizing element (D2), which is connected in parallel with the battery monitoring unit at a position in the current path closer to the battery monitoring unit than the switching element, and is energized on the condition that a voltage exceeding a second specified voltage lower than the first specified voltage is applied.

4. The power supply circuit according to claim 2, wherein: The battery monitoring unit includes a switching element (T1) whose opening and closing state is controlled. The switching element is connected in series with the current path (L1).

5. The power supply circuit according to any one of claims 2 to 4, wherein: A plurality of the current paths (L1, L0) are included. Path resistors (R1, R0) are respectively provided in the plurality of current paths. The forming circuit includes the first energizing element (D1, D0) for each of the plurality of current paths.

6. The power supply circuit according to any one of claims 2 to 4, wherein: The forming circuit includes a noise reduction element (Rf) that reduces the noise applied to the first energizing element and has a resistance value lower than that of the path resistor.

7. The power supply circuit according to claim 1, wherein: The forming circuit includes: Switches (S1, S2), which are connected in parallel with the battery between the fuse function part and the path resistor in the current path; and A switch driving unit (Cp1, Rs, R1, L3, L4, D3) that closes the switch on the condition that a current greater than a first current smaller than the specified current flows through the path resistor.

8. The power supply circuit according to claim 7, wherein in the current path, at a position closer to the battery monitoring unit than the path resistor, a switch element (T1) whose on / off state is controlled by the battery monitoring unit is connected in series. The forming circuit includes a second energizing element (D2), and the second energizing element is connected in parallel with the battery monitoring unit at a position closer to the battery monitoring unit than the switch element in the current path, and is energized on the condition that a voltage exceeding a second specified voltage is applied.

9. The power supply circuit according to claim 7 or 8, wherein a plurality of the current paths (L1, L0) are included. Path resistors (R1, R0) are respectively provided in the plurality of current paths. The forming circuit includes the switch driving unit (L3, L4, D3) for each of the plurality of current paths.

10. A power supply circuit, the power supply circuit (640, 740) uses a battery (11) as a power input source and supplies power to a battery monitoring unit (31) that monitors the state of the battery. On the current path (L1, L2) from the battery to the battery monitoring unit, a fuse function unit (F1, F2) that cuts off the current when a current exceeding a specified current flows is provided. In the current path, at a position closer to the battery monitoring unit than the fuse function unit, a path resistor (R1) is included. A cut-off circuit (S3, Cp1, Rs, R1, F3, F4) that cuts off the current flowing through the path resistor in the case of a short circuit occurring in the path passing through the path resistor is included.

11. The power supply circuit according to claim 10, wherein the cut-off circuit includes: a switch (S3) that is connected in series with the fuse function unit and the path resistor in the current path; and a switch driving unit (Cp1, Rs, R1) that opens the switch on the condition that a current greater than a first current smaller than the specified current flows through the path resistor.

12. The power supply circuit according to claim 10 or 11, wherein the fuse function unit is a first fuse function unit (F1, F2). The cut-off circuit includes a second fuse function unit (F3, F4), and the second fuse function unit is connected in series with a specified element (C1, D2) connected in parallel to the current path, and a current greater than a first current smaller than the specified current does not flow when the specified element does not short-circuit, and cuts off the current on the condition that a current exceeding the first current flows.

Images