Power supply circuit

Abstract

To provide a power supply circuit provided with a path resistance in a current path, capable of cutting off a discharge current from a battery during short-circuiting even if a voltage of the battery as an input source is low or a resistance value of pathway resistance is high.SOLUTION: A power-supply circuit (40) supplies power to a battery monitoring part (31) for monitoring a status of a battery (11) using the battery as an input source of the power. Current paths (L1, L2) from the battery to the battery monitoring part are respectively provided with fuse function parts (F1, F2) which interrupt current flowing through the current paths when the current exceeds a prescribed current. The power-source circuit is provided with a path resistance (R1) closer to the battery monitoring part than the fuse function part in the current paths, and comprises a formation circuit (D1, B1, D2, B2) which forms a detour path for flowing the current exceeding the prescribed current to the fuse function part without passing through the path resistance when short circuit occurs on the path including the path resistance.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power supply circuit applied to a battery monitoring device. [Background technology]

[0002] BACKGROUND ART Conventionally, there is a battery monitoring device that includes a power supply circuit that uses a battery as an input power source, and a battery monitoring IC that operates using power supplied from the power supply circuit and monitors the state of the battery (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Texas Instruments BQ79616-Q1 Datasheet Rev. D Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, a fuse is installed in the current path from the battery to the battery monitoring IC, and if a short circuit occurs in the power supply circuit, the fuse will blow and cut off the current. However, if the battery voltage is low or the resistance of the path resistor in the current path is high, the fuse may not blow even if a short circuit occurs. In this case, the battery may continue to discharge while the short circuit is occurring, which could result in over-discharge or overheating of the battery. Similar problems can occur not only with metal fuses that blow when an overcurrent occurs, but also with fuse functional units such as resettable fuses whose resistance increases when an overcurrent occurs, or e-fuses (electronic fuses) that detect overcurrent and cut off the current using a MOSFET.

[0005] The present invention has been made to solve the above-mentioned problems, and its main purpose is to cut off the discharge current from a battery in the event of a short circuit in a power supply circuit having a path resistance in the current path, even if the voltage of the input source battery is low or the resistance value of the path resistance is high. [Means for solving the problem]

[0006] The first means for solving the above problem is: A power supply circuit (40, 140, 240, 340, 440, 540) that 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; The current path includes path resistances (R1, R0) on the battery monitoring unit side relative to the fuse function unit, The circuit includes a forming circuit (D1, B1, D2, B2, D0, B0, S1, S2, B3, Cp1, Rs, R1, L3, L4, D3) that forms a detour path that allows a current exceeding the predetermined current to flow through the fuse function unit without passing through the path resistance when a short circuit occurs in the path that passes through the path resistance.

[0007] According to the above configuration, the power supply circuit uses a battery as an input power source and supplies power to a battery monitoring unit that monitors the state of the battery. A fuse functional unit that cuts off current when a current exceeding a predetermined current flows is provided in the current path from the battery to the battery monitoring unit. Therefore, if a short circuit occurs in the power supply circuit and a current exceeding the predetermined current flows in the fuse functional unit, the fuse functional unit can cut off the current. The fuse functional unit may include a metal fuse that melts when an overcurrent occurs, a resettable fuse whose resistance value increases when an overcurrent occurs, and an e-fuse (electronic fuse) that detects an overcurrent and cuts off the current using a MOSFET.

[0008] Here, the power supply circuit includes a path resistor in the current path closer to the battery monitoring unit than the fuse function unit. Therefore, if the battery voltage is low or the path resistor has a high resistance value, even if a short circuit occurs, the current flowing through the fuse function unit may not exceed a predetermined current, and the fuse function unit may not function. In this regard, the forming circuit forms a detour path that allows a current exceeding the predetermined current to flow to the fuse function unit without passing through the path resistor when a short circuit occurs in the path passing through the path resistor. Therefore, even if the current flowing through the fuse function unit through the path resistor does not exceed the predetermined current during a short circuit, the current flowing through the detour path to the fuse function unit can exceed the predetermined current. Therefore, even if the voltage of the input source battery is low or the resistance value of the path resistor is high, the fuse function unit can function during a short circuit, and the discharge current from the battery can be cut off.

[0009] In a second aspect, the forming circuit includes a first energization element (D1, D0) connected to the current path in parallel with the path resistance and energized when a voltage exceeding a first predetermined voltage is applied, causing a current exceeding the predetermined current to flow through the fuse function unit. With this configuration, when a short circuit occurs in the power supply circuit and a voltage exceeding the first predetermined voltage is applied to the first energization element, the first energization element connected to the current path in parallel with the path resistance is energized, forming a detour path, allowing a current exceeding the predetermined current to flow through the fuse function unit. Therefore, a simple forming circuit can interrupt the discharge current from the battery in the event of a short circuit. The first energization element (energization element) energized when a voltage exceeding the first predetermined voltage is applied includes a Zener diode, a TVS diode, a varistor, etc.

[0010] In the third means, a switching element (T1) whose open / closed state is controlled by the battery monitoring unit is connected in series on the battery monitoring unit side of the path resistance and the first current-carrying element in the current path, and the forming circuit includes a second current-carrying element (D2) connected in parallel with the battery monitoring unit on the battery monitoring unit side of the switching element in the current path, and which is energized when a voltage exceeding a second predetermined voltage lower than the first predetermined voltage is applied.

[0011] According to the above configuration, the switching element is connected in series with the battery monitoring unit closer to the path resistor and the first current-carrying element in the current path, and its open / closed state is controlled by the battery monitoring unit. Therefore, when the switching element is normal, the current flowing to the battery monitoring unit and the voltage applied to the battery monitoring unit are appropriately adjusted. On the other hand, when the switching element is short-circuited, the current flowing to the battery monitoring unit cannot be interrupted. If the fuse function unit does not function when the battery voltage is low or the resistance value of the path resistor is high, there is a risk that the battery will continue to discharge in a short-circuited state.

[0012] In this regard, the second energization element is connected in parallel with the battery monitoring unit on the side of the switching element in the current path closer to the battery monitoring unit and energizes when a voltage exceeding a second predetermined voltage, which is lower than the first predetermined voltage, is applied. Therefore, when the switching element is short-circuited and a voltage exceeding the second predetermined voltage is applied to the second energization element, the second energization element connected in parallel with the battery monitoring unit is energized. This causes a voltage exceeding the first predetermined voltage to be applied to the first energization element, causing the first energization element to energize, forming a bypass path passing through the first and second energization elements. This allows a current exceeding the predetermined current to flow through the fuse function unit, thereby interrupting the discharge current from the battery when the switching element is short-circuited. Note that similar advantages can be achieved even when the second energization element connected in parallel to the current path is provided in the battery monitoring unit rather than in the power supply circuit.

[0013] When the battery monitoring unit includes a switching element connected in series to the current path from the battery to the battery monitoring unit, the battery monitoring unit generally includes a protection element similar to the second current-carrying element of the third means in case the switching element is short-circuited. Therefore, even when the battery monitoring unit includes a switching element whose open / closed state is controlled and the switching element is connected in series to the current path, as in the fourth means, the same effects as those of the third means can be achieved.

[0014] In a fifth aspect, a plurality of the current paths (L1, L0) are provided, each of the plurality of current paths is provided with the path resistance (R1, R0), and the forming circuit is provided with the first current-carrying element (D1, D0) for each of the plurality of current paths. With this configuration, as with the second aspect, even if a short circuit occurs in any of the plurality of current paths, it is possible to cut off the discharge current from the battery in the event of a short circuit.

[0015] In a sixth aspect, the forming circuit includes a noise reduction element (Rf) that reduces noise applied to the first energization element and has a resistance value lower than the path resistance. With this configuration, it is possible to prevent the first energization element from malfunctioning or breaking down due to noise, and also to prevent the current flowing through the fuse functional unit from being reduced by the noise reduction element.

[0016] In a seventh aspect, the forming circuit includes a switch (S1, S2) connected in parallel with the battery between the fuse function unit and the path resistance of the current path, and a switch driver (Cp1, Rs, R1, L3, L4, D3) that closes the switch when a current exceeding a first current smaller than the predetermined current flows through the path resistance. With this 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 parallel with the battery between the fuse function unit and the path resistance of the current path closes to form a detour path, allowing a current exceeding the predetermined current to flow through the fuse function unit. Therefore, discharge current from the battery can be cut off in the event of a short circuit.

[0017] In the eighth means, based on the seventh means, a switching element (T1) whose open / closed state is controlled by the battery monitoring unit is connected in series on the battery monitoring unit side of the path resistance in the current path, and the forming circuit includes a second current-carrying element (D2) connected in parallel with the battery monitoring unit on the battery monitoring unit side of the switching element in the current path, and which is energized when a voltage exceeding a second predetermined voltage is applied.

[0018] In the above configuration, as described above, if the switching element is short-circuited, the current flowing through the battery monitoring unit cannot be cut off. If the fuse function unit does not work when the battery voltage is low or the path resistance is high, there is a risk that the battery will continue to discharge in the short-circuited state.

[0019] In this regard, the second energization element is connected in parallel with the battery monitoring unit on the battery monitoring unit side of the switching element in the current path, and energizes when a voltage exceeding a second predetermined voltage is applied. Therefore, when the switching element is short-circuited and a voltage exceeding the second predetermined voltage is applied to the second energization element, the second energization element connected in parallel with the battery monitoring unit is energized. This causes a current exceeding the first current to flow through the path resistance, closing the switch and forming a bypass path that passes through the fuse function unit and the switch. Therefore, a current exceeding the predetermined current can be passed through the fuse function unit, and the discharge current from the battery can be cut off when the switching element is short-circuited.

[0020] In a ninth aspect, a plurality of the current paths (L1, L0) are provided, each of the plurality of current paths is provided with the path resistance (R1, R0), and the forming circuit is provided with the switch driving unit (L3, L4, D3) for each of the plurality of current paths. With this configuration, as with the seventh aspect, even if a short circuit occurs in any of the plurality of current paths, the discharge current from the battery can be cut off.

[0021] The tenth measure is: A power supply circuit (640, 740) that 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; a path resistor (R1) is provided on the current path closer to the battery monitoring unit than the fuse function unit; The power supply includes an interruption circuit (S3, Cp1, Rs, R1, F3, F4) that interrupts the current flowing through the path resistance when a short circuit occurs in the path that passes through the path resistance.

[0022] According to the above configuration, the power supply circuit uses a battery as an input power source and supplies power to a battery monitoring unit that monitors the state of the battery. A fuse function unit that cuts off current when a current exceeding a predetermined current flows is provided in the current path from the battery to the battery monitoring unit. Therefore, if a short circuit occurs in the power supply circuit and a current exceeding the predetermined current flows in the fuse function unit, the fuse function unit can cut off the current.

[0023] Here, the power supply circuit includes a path resistor in the current path closer to the battery monitoring unit than the fuse function unit. Therefore, if the battery voltage is low or the path resistor has a high resistance value, even if a short circuit occurs, the current flowing through the fuse function unit may not exceed a predetermined current, and the fuse function unit may not function. In this regard, the interrupter circuit interrupts the current flowing through the path resistor when a short circuit occurs in the path passing through the path resistor. Therefore, even if the current flowing through the fuse function unit through the path resistor does not exceed a predetermined current during a short circuit, the interrupter circuit can interrupt the current flowing through the path resistor. Therefore, even if the voltage of the input source battery is low or the resistance value of the path resistor is high, the discharge current from the battery during a short circuit can be interrupted.

[0024] In an eleventh aspect, the interrupter circuit includes a switch (S3) connected in series with the fuse function unit and the path resistor in the current path, and a switch driver (Cp1, Rs, R1) that opens the switch when a current exceeding a first current smaller than the predetermined current flows through the path resistor. With this configuration, 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 series with the fuse function unit and the path resistor in the current path opens. Therefore, even if the voltage of the input source battery is low or the resistance value of the path resistor is high, the discharge current from the battery can be interrupted in the event of a short circuit.

[0025] In a twelfth means, the fuse functional unit is a first fuse functional unit (F1, F2), and the interruption circuit includes a second fuse functional unit (F3, F4) connected in series to a predetermined element (C1, D2) connected in parallel to the current path, and which interrupts the current on the condition that a current exceeding a first current smaller than the predetermined current does not flow when no short circuit occurs in the predetermined element, and a current exceeding the first current flows.

[0026] According to the above configuration, the fuse function unit functions as a first fuse function unit. The second fuse function unit is connected in series with a predetermined element connected in parallel to the current path and cuts off the current when a current exceeding a first current smaller than the predetermined current flows when no short circuit occurs in the predetermined element. Therefore, when no short circuit occurs in the predetermined element, the second fuse function unit does not cut off the current but allows the current to flow through the predetermined element. On the other hand, the second fuse function unit cuts off the current when a current exceeding the first current flows. Therefore, even if a short circuit occurs in the predetermined element and the current flowing through the first fuse function unit does not exceed the predetermined current, the first fuse function unit does not function. However, if a current exceeding the first current smaller than the predetermined current flows through the second fuse function unit, the second fuse function unit can cut off the current. Therefore, even if the voltage of the input source battery is low or the path resistance is high, the discharge current from the battery can be cut off when a short circuit occurs in the predetermined element. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 2 is a block diagram of a battery monitoring device. [Figure 2] FIG. 1 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a first embodiment. [Figure 3] FIG. 1 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a first embodiment. [Figure 4] FIG. 10 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a second embodiment. [Figure 5] FIG. 10 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a third embodiment. [Figure 6] FIG. 10 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a fourth embodiment. [Figure 7] FIG. 10 is a circuit diagram showing a modified example of the power supply circuit and the battery monitoring IC according to the fourth embodiment. [Figure 8] FIG. 10 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a fifth embodiment. [Figure 9] FIG. 13 is a circuit diagram showing a modification of the power supply circuit and the battery monitoring IC of the fifth embodiment. [Figure 10] FIG. 13 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a sixth embodiment. [Figure 11] FIG. 13 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a seventh embodiment. [Figure 12] FIG. 13 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to an eighth embodiment. [Figure 13] FIG. 13 is a circuit diagram showing a modification of the power supply circuit and the battery monitoring IC of the eighth embodiment. [Figure 14] FIG. 13 is a circuit diagram showing a power supply circuit and a battery monitoring IC according to a ninth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] (First embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings, which is embodied in a power supply circuit applied to a battery monitoring device mounted on a vehicle, etc. As shown in Fig. 1, the battery monitoring device 10 includes a master unit 20 and a slave unit 30.

[0029] The parent unit 20 includes a power supply circuit 21, a communication interface (I / F) 22, a temperature detection interface (I / F) 23, a relay driver 24, a microcomputer 25, a communication IC 26, etc. The parent unit 20 communicates with the child unit 30, and causes the child unit 30 to monitor the state of each cell 12 of the battery 11 and the state of the battery 11. The battery 11 is formed, for example, by connecting a plurality of cells 12 in series, or by connecting a plurality of battery modules in series, each of which has a plurality of cells 12 connected in series.

[0030] The slave device 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 an input power source and supplies power to the battery monitoring IC. The battery monitoring IC (battery monitoring unit) operates using power supplied from the power supply circuit 40, and causes the detection circuit 32 to detect the state of each cell 12 and the battery 11. The detection circuit 32 is controlled by the battery monitoring IC, and performs functions such as detecting the voltage and temperature of the cells 12 and equalizing the voltages of the cells 12. The detection circuit 32 may also perform functions such as detecting the current flowing through the cells 12 (batteries 11), detecting the internal pressure of the cells 12, and detecting gas leaks from the cells 12 (batteries 11).

[0031] 2 is a circuit diagram showing the power supply circuit 40 and the battery monitoring IC 31. A fuse F1, a resistor R1, and a transistor T1 are connected in series to a wire 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 F2 is connected in series to a wire L2 (current path) from the GND terminal of the battery monitoring IC to the negative terminal of the battery 11.

[0032] The fuses F1 and F2 (fuse functional portions) are metallic fuses that melt and cut off the current when a current exceeding, for example, 0.5 to 1.0 A (predetermined current If) flows. Note that the metallic fuse is not limited to one having a fuse element made of a wire-shaped metal with a low melting point, but may also be a pattern fuse in which the wiring pattern width is narrower than other portions and melts when an overcurrent occurs.

[0033] A capacitor C1 is connected in parallel with the battery 11 and the battery monitoring IC 31 between the resistor R1 and the transistor T1 on the wiring L1. The resistor R1 and the capacitor C1 form an RC filter (low-pass filter) that reduces noise applied to the transistor T1. The resistance value of the resistor R1 (path resistance) is set according to the expected frequency of the noise, and is, for example, 100 to several kΩ. The resistor R1 may be composed of multiple resistors.

[0034] A capacitor C3 is connected in parallel with the battery 11 and the battery monitoring IC 31 between the transistor T1 and the power input terminal of the battery monitoring IC on the wiring L1. The drive terminal (Drive) of the battery monitoring IC is connected to the base of the transistor T1 (switching element) via an RC filter (low-pass filter) formed by a resistor R2 and a capacitor C2. The transistor T1 is not limited to a bipolar type, and may be a unipolar type such as a MOSFET.

[0035] The battery monitoring IC 31 controls the on / off period or degree of opening, i.e., 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 therefore the voltage input to the power input terminal of the battery monitoring IC, to a target voltage.

[0036] Now, let's consider a case where the Zener diode D1 is not connected in parallel to the resistor R1 on the wiring L1 and the capacitor C1 is short-circuited. In this case, depending on the resistance value of the resistor R1, the current flowing through the fuse F1, resistor R1, capacitor C1, and fuse F2, in that order, may decrease to several tens to several hundred mA. In this case, the current flowing through the fuses F1 and F2 may not exceed the predetermined current If, and the fuses F1 and F2 may not blow. As a result, discharging from the battery 11 continues in the short-circuited state, which may cause the battery 11 to over-discharge or overheat.

[0037] Therefore, in this embodiment, a Zener diode D1 (first current-carrying element) is connected to the wiring L1 in parallel with the resistor R1. The anode of the Zener diode D1 is connected to the transistor T1 side of the resistor R1 by the wiring B1, and the cathode of the Zener diode D1 is connected to the fuse F1 side of the resistor R1 by the wiring B1. The Zener diode D1 breaks down and generates a Zener voltage (constant voltage) when a voltage exceeding a first predetermined voltage V1, which is lower than the lowest voltage in the operating range (fluctuation range) of the battery 11, is applied. When the capacitor C1 is not short-circuited, the voltage applied to the Zener diode D1 is lower than the first predetermined voltage V1. The resistance value of the Zener diode D1 in the breakdown state is, for example, several ohms. The Zener diode D1 and the wiring B1 connecting the Zener diode D1 to the wiring L1 constitute a circuit.

[0038] If capacitor C1 is shorted, the voltage applied to Zener diode D1 exceeds the first predetermined voltage V1, causing Zener diode D1 to break down (conduct). As a result, current bypasses resistor R1 and flows sequentially through fuse F1, Zener diode D1, capacitor C1, and fuse F2. Because the resistance of Zener diode D1 in its breakdown state is sufficiently lower than the resistance of resistor R1, a current exceeding the predetermined current If flows through fuses F1 and F2 even if the battery 11 voltage is at the lowest voltage within its operating range. In other words, Zener diode D1 conducts when a voltage exceeding the first predetermined voltage V1 is applied, causing a current exceeding the predetermined current If to flow through fuses F1 and F2. As a result, at least one of fuses F1 and F2 melts, interrupting the current.

[0039] 3, consider the case where Zener diode D2 is not connected in parallel with the battery monitoring IC on the line L1 closer to the battery monitoring IC 31 than transistor T1, and transistor T1 is short-circuited. In this case, it becomes impossible to cut off the current flowing to the power input terminal of the battery monitoring IC 31. If neither fuse F1 nor F2 operates when the battery 11 voltage is low or the resistance value of resistor R1 is high, there is a risk that discharging from the battery 11 will continue in a short-circuited state.

[0040] Therefore, in this embodiment, a Zener diode D2 is connected in parallel with the battery monitoring IC 31 on the wiring L1 closer to the battery monitoring IC 31 than the transistor T1. The anode of the Zener diode D2 is connected to the wiring L2 via a wiring B2, and the cathode of the Zener diode D1 is connected to the wiring L1. The Zener diode D2 breaks down and generates a Zener voltage (constant voltage) when a voltage exceeding a second predetermined voltage V2, which is lower than the first predetermined voltage V1, is applied. When the transistor T1 is not short-circuited and the open / close state of the transistor T1 is controlled, the voltage applied to the Zener diode D2 becomes lower than the second predetermined voltage V2. The resistance of the Zener diode D2 in the breakdown state is, for example, several ohms. 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.

[0041] If transistor T1 is shorted, the voltage applied to Zener diode D2 exceeds the second predetermined voltage V2, causing Zener diode D2 to break down (conduct). Subsequently, the voltage applied to Zener diode D1 exceeds the first predetermined voltage V1, causing Zener diode D1 to break down (conduct). This causes current to bypass resistor R1 and flow sequentially through fuse F1, Zener diode D1, transistor T1, Zener diode D2, and fuse F2. Because the resistances of Zener diodes D1 and D2 in their breakdown state are sufficiently lower than the resistance of resistor R1, a current exceeding the predetermined current If flows through fuses F1 and F2 even if the battery 11 voltage is at the lowest voltage within its operating range. As a result, at least one of fuses F1 and F2 melts, cutting off the current.

[0042] The present embodiment described above in detail has the following advantages.

[0043] Zener diode D1 and its wiring B1 form a detour path that allows a current exceeding a predetermined current If to flow to fuses F1 and F2 without passing through resistor R1 in the event of a short circuit in the path through resistor R1. Therefore, even if the current flowing through fuses F1 and F2 through resistor R1 does not exceed the predetermined current If in the event of a short circuit, the current flowing through fuses F1 and F2 via the detour path can exceed the predetermined current If. Therefore, even if the voltage of input battery 11 is low or the resistance value of resistor R1 is high, fuses F1 and F2 can be activated in the event of a short circuit, and the discharge current from battery 11 can be cut off.

[0044] If a short circuit occurs in the power supply circuit 40 and a voltage exceeding the first predetermined voltage V1 is applied to the Zener diode D1, the Zener diode D1 connected in parallel to the resistor R1 on the wiring L1 will conduct electricity, forming a detour path that allows a current exceeding the predetermined current If to flow through the fuses F1 and F2. Therefore, this simple circuit configuration can cut off the discharge current from the battery 11 in the event of a short circuit.

[0045] The Zener diode D2 is connected in parallel with the battery monitoring IC 31 on the line L1 closer to the battery monitoring IC 31 than the transistor T1. The Zener diode D2 conducts current when a voltage exceeding a second predetermined voltage V2, which is lower than the first predetermined voltage V1, is applied. Therefore, when the transistor T1 is short-circuited and a voltage exceeding the second predetermined voltage V2 is applied to the Zener diode D2, the Zener diode D2 connected in parallel with the battery monitoring IC 31 conducts current. This causes a voltage exceeding the first predetermined voltage V1 to be applied to the Zener diode D1, causing the Zener diode D1 to conduct current, forming a bypass path through the Zener diodes D1 and D2. This allows a current exceeding the predetermined current If to flow through the fuses F1 and F2, thereby interrupting the discharge current from the battery 11 when the transistor T1 is short-circuited.

[0046] The same effect can be achieved not only when the capacitor C1 is short-circuited, but also when a direct short circuit occurs between the portion of the wiring L1 between the resistor R1 and the transistor T1 and the wiring L2.

[0047] Furthermore, even if the Zener diode D2 connected in parallel to the wiring L1 is built in (provided in) the battery monitoring IC 31 instead of the power supply circuit 40, the same advantageous effects can be achieved.

[0048] (Second embodiment) The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0049] 4, the battery monitoring IC 131 incorporates (is equipped with) a transistor T1 whose open / closed state is controlled, a resistor R2, and capacitors C2 and C3. The transistor T1 is connected in series to a line L1. The power supply circuit 140 includes a Zener diode D1, but does not include the transistor T1, the resistor R2, or the capacitors C2 and C3.

[0050] Here, when the battery monitoring IC 31 has a built-in transistor T1 connected in series to the wiring L1 from the battery 11 to the battery monitoring IC 131, the battery monitoring IC 131 generally has a protection element (not shown) similar to the Zener diode D2 in case the transistor T1 is short-circuited. Therefore, this embodiment can also achieve the same effects as the first embodiment.

[0051] (Third embodiment) The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0052] As shown in FIG. 5, the power supply circuit 240 includes a wiring L1 (current path) from the positive terminal of the battery 11 to the main power supply 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 secondary power supply input terminal (Power(sub)) of the battery monitoring IC 31.

[0053] A resistor R0 (path resistance) is provided on the wiring L2. A capacitor C0 is connected in parallel with the battery 11 and the battery monitoring IC 31 between the resistor R0 and the secondary power supply input terminal of the battery monitoring IC on the wiring L0. A Zener diode D0 (first current-carrying element) similar to the Zener diode D1 is connected to the wiring L0 in parallel with the resistor R0. The anode of the Zener diode D0 is connected to the battery monitoring IC 31 side with respect to the resistor R1 by a wiring B0, 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, the wirings L1 and L0 (plurality of wirings) are provided with Zener diodes D1 and D0 and wirings B1 and B0 as forming circuits, respectively.

[0054] According to the above configuration, regardless of whether a short circuit occurs in the wiring L1 or L0, the discharge current from the battery 11 can be cut off in the event of a short circuit, as in the first embodiment. For example, if the capacitor C0 (wiring L0) is short-circuited, the voltage applied to the Zener diode D0 exceeds the first predetermined voltage V1, causing the Zener diode D0 to break down (conduct). As a result, the current bypasses the resistor R0 and flows sequentially 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 and F2 melts, cutting off the current.

[0055] (Fourth embodiment) The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0056] As shown in FIG. 6, the power supply circuit 40 includes a resistor Rf that reduces noise applied to the Zener diode D1 and has a resistance value lower than that of the resistor R1, and a capacitor Cf. The capacitor Cf is connected in parallel with the battery 11 and the battery monitoring IC 31 between the resistor Rf and the resistor R1 on the wiring L1. The resistor Rf and the capacitor Cf form an RC filter (low-pass filter) that reduces noise applied to the Zener diode D1. The resistance value of the resistor Rf is lower than that of the resistor R1, for example, several ohms, and is set to a resistance value at which the fuses F1 and F2 melt when the capacitor C1 is short-circuited. The resistor Rf may be composed of multiple resistors.

[0057] This configuration prevents Zener diode D1 from malfunctioning or breaking down due to noise, while also preventing the current flowing through fuses F1 and F2 from being reduced by resistor Rf. Therefore, even if the voltage of input battery 11 is low or the resistance of resistor R1 is high, fuses F1 and F2 can be activated in the event of a short circuit, and the discharge current from battery 11 can be cut off.

[0058] As shown in FIG. 7, instead of the resistor Rf and capacitor Cf shown in FIG. 6, the power supply circuit 40 may include a resistor Rf connected in series to the Zener diode D1 on the wiring B1. The resistor Rf reduces noise applied to the Zener diode D1 and has a lower resistance value than the resistor R1. The resistance value of the resistor Rf is lower than that of the resistor R1, for example, several ohms, and is set to a resistance value at which the fuses F1 and F2 melt when the capacitor C1 is short-circuited. The resistor Rf may be composed of multiple resistors.

[0059] This configuration also prevents Zener diode D1 from malfunctioning or breaking down due to noise, while preventing the current flowing through fuses F1 and F2 from being reduced by resistor Rf. Therefore, even if the voltage of input battery 11 is low or the resistance of resistor R1 is high, fuses F1 and F2 can be activated in the event of a short circuit, and the discharge current from battery 11 can be cut off.

[0060] (Fifth embodiment) The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0061] As shown in FIG. 8, the power supply circuit 40 includes a switch S1 connected in parallel to the battery 11 by a line B3 between the fuse F1 and resistor R1 on the line L1, and a comparator Cp1 that drives the switch S1. The switch S1 is, for example, an N-channel MOSFET. A shunt resistor Rs is connected in series to the line L2, closer to the battery 11 than the connection point with 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 between the fuse F1 and resistor R1, and the source is connected to the connection point between the fuse F2 and shunt resistor Rs. The comparator Cp1 turns on (closes) the switch S1 when the voltage across the shunt resistor Rs exceeds a threshold value. The threshold value is set to a voltage lower than the voltage applied to the shunt resistor Rs when the capacitor C1 is short-circuited and a predetermined current If flows through the shunt resistor Rs, causing the fuse F1 to blow. That is, the comparator Cp1 closes the switch S1 when a current exceeding a first current I1, which is smaller than a predetermined current If, flows through the resistor R1. The first current I1 is smaller than the current that flows through the resistor R1 when the capacitor C1 is short-circuited, when the voltage of the battery 11 is at the lowest voltage in the operating range (fluctuation range) or when the resistance value of the resistor R1 is high. When the capacitor C1 is not short-circuited, the current that flows through the resistor R1 is smaller than the first current I1. The comparator Cp1 and the shunt resistor Rs form a switch drive unit. The switch S1, the wiring B3, the comparator Cp1, and the shunt resistor Rs form a circuit. An operational amplifier can also be used instead of the comparator Cp1.

[0062] According to the above configuration, if capacitor C1 is short-circuited and a current exceeding first current I1 flows through resistor R1, switch S1, which is connected in parallel with battery 11 between fuse F1 on line L1 and resistor R1, closes to form a detour path, allowing a current exceeding predetermined current If to flow through fuses F1 and F2. Therefore, the discharge current from battery 11 can be cut off in the event of a short circuit.

[0063] Furthermore, Zener diode D2 (second current-carrying element) is connected in parallel with battery monitoring IC 31 on the line L1 closer to battery monitoring IC 31 than transistor T1, and is conductive when a voltage exceeding second predetermined voltage V2 is applied. Therefore, when transistor T1 is short-circuited and a voltage exceeding second predetermined voltage V2 is applied to Zener diode D2, Zener diode D2 connected in parallel with battery monitoring IC 31 is conductive. As a result, a current exceeding first current I1 flows through resistor R1, closing switch S1, and forming a bypass path that passes through fuse F1, switch S1, and fuse F2 in this order. Therefore, a current exceeding predetermined current If can flow through fuses F1 and F2, and the discharge current from battery 11 can be cut off when transistor T1 is short-circuited.

[0064] As shown in FIG. 9, the comparator Cp1 may turn on (close) the switch S1 when the voltage across the resistor R1 exceeds a threshold value. The threshold value is set to a voltage lower than the voltage applied to the resistor R1 when the capacitor C1 is short-circuited and a predetermined current If, at which the fuse F1 melts, flows through the resistor R1. That is, the comparator Cp1 closes the switch S1 when a current exceeding a first current I1, which is smaller than the predetermined current If, flows through the resistor R1. When the capacitor C1 is not short-circuited, the current flowing through the resistor R1 is smaller than the first current I1. The comparator Cp1 and the resistor R1 form a switch driver. The switch S1, the wiring B3, the comparator Cp1, and the resistor R1 form a circuit. An operational amplifier may be used instead of the comparator Cp1.

[0065] (Sixth embodiment) The sixth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0066] As shown in FIG. 10, the power supply circuit 40 includes a switch S2 connected in parallel with the battery 11 between the fuse F1 and resistor R1 on the line L1. The switch S2 is, for example, a P-channel MOSFET. The gate of the switch S2 is connected to the junction of the resistor R1, the transistor T1, and the capacitor C1 via the line L3. The source of the switch S2 is connected to the junction of the fuse F1 and resistor R1. The drain of the switch S2 is connected to the junction of the fuse F2, the capacitor C1, and the GND terminal of the battery monitoring IC. The switch S2 is turned on (closed) when the voltage at the junction of the line L1 and the line L3 falls below a threshold. The threshold is set to a voltage higher than the voltage applied to the junction of the line L1 and the line L3 when the capacitor C1 is short-circuited and a predetermined current If flows through the resistor R1, causing the fuse F1 to blow. That is, the switch S2 is closed when a current exceeding a first current I1, which is smaller than the predetermined current If, flows through the resistor R1. The first current I1 is smaller than the current that flows through resistor R1 when capacitor C1 is short-circuited, when the battery 11 voltage is at the lowest voltage in its operating range (fluctuation range) or when resistor R1 has a high resistance. When capacitor C1 is not short-circuited, the current that flows through resistor R1 is smaller than the first current I1. The wiring L3 constitutes a switch drive unit. The switch S2, wiring B3, and wiring L3 constitute a formed circuit.

[0067] According to the above configuration, if capacitor C1 is short-circuited and a current exceeding first current I1 flows through resistor R1, switch S2, which is connected in parallel with battery 11 between fuse F1 on line L1 and resistor R1, closes to form a detour path, allowing a current exceeding predetermined current If to flow through fuses F1 and F2. Therefore, the discharge current from battery 11 can be cut off in the event of a short circuit.

[0068] Furthermore, if transistor T1 is short-circuited, Zener diode D2 (second current-carrying element) is energized. This causes a current exceeding first current I1 to flow through resistor R1, closing switch S2 and forming a detour path that passes through fuse F1, switch S2, and fuse F2 in that order. This allows a current exceeding predetermined current If to flow through fuses F1 and F2, and can cut off the discharge current from battery 11 when transistor T1 is short-circuited.

[0069] Seventh embodiment The seventh embodiment will be described below with reference to the drawings, focusing on the differences from the sixth embodiment. Note that the same parts as those in the sixth embodiment will be denoted by the same reference numerals and description thereof will be omitted.

[0070] As shown in FIG. 11, the power supply circuit 540 includes a wiring L1 (current path) from the positive terminal of the battery 11 to the main power supply 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 secondary power supply input terminal (Power(sub)) of the battery monitoring IC 31.

[0071] A resistor R0 (path resistance) is provided on the wiring L0. A capacitor C0 is connected in parallel with the battery 11 and the battery monitoring IC 31 between the resistor R0 and the secondary power supply input terminal of the battery monitoring IC on the wiring L0. The gate of the switch S2 is connected to the connection point between the resistor R1, the transistor T1, and the capacitor C1 via a wiring L3 and a 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 between the resistor R1, the transistor T1, and the capacitor C1. The gate of the switch S2 is connected to the connection point between the resistor R0, the capacitor C0, and the secondary power supply input terminal (Power(sub)) of the battery monitoring IC via a wiring L4 and a 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 between the resistor R0, the capacitor C0, and the secondary power supply input terminal (Power(sub)) of the battery monitoring IC. That is, in this embodiment, the forming circuit includes wires L3 and L4 and a diode D3 (switch driver) for the wires L1 and L0 (plurality of wires).

[0072] According to the above configuration, regardless of whether a short circuit occurs in the wiring L1 or L0, the discharge current from the battery 11 can be cut off in the event of a short circuit, as in the sixth embodiment. For example, if the capacitor C0 is shorted, the switch S2 closes. This causes the current to bypass the resistors R1 and R0 and flow sequentially to the fuse F1, the switch S2, and the fuse F2. As a result, at least one of the fuses F1 and F2 melts, cutting off the current.

[0073] (Eighth embodiment) The eighth embodiment will be described below with reference to the drawings, focusing on the differences from the fifth embodiment. Note that the same parts as those in the fifth embodiment will be denoted by the same reference numerals and description thereof will be omitted.

[0074] As shown in FIG. 12, the power supply circuit 640 includes a switch S3 connected in series with a fuse F1 and resistor R1 on the line L1 closer to the battery 11 than the connection point between the resistor R1 (path resistance), the capacitor C1, and the transistor T1, 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 the output from the comparator Cp1 is on. The comparator Cp1 opens the switch S3 when the voltage across the shunt resistor Rs exceeds a threshold. The threshold is set to a voltage lower than the voltage applied to the shunt resistor Rs when the capacitor C1 is short-circuited and a predetermined current If, at which the fuse F1 melts, flows through the shunt resistor Rs. The comparator Cp1 opens the switch S3 when a current exceeding a first current I1, which is smaller than the predetermined current If, flows through the resistor R1. The first current I1 is smaller than the current flowing through resistor R1 when capacitor C1 is short-circuited, when the battery 11 voltage is at the lowest voltage in its operating range (fluctuation range) or when resistor R1 has a high resistance. When capacitor C1 is not short-circuited, the current flowing through resistor R1 is smaller than the first current I1. In other words, when a short circuit occurs in the path through resistor R1, comparator Cp1 opens switch S3 to cut off the current flowing through resistor R1. The comparator Cp1 and shunt resistor Rs form a switch driver, and the switch S3, comparator Cp1, and shunt resistor Rs form a cutoff circuit. An operational amplifier can also be used in place of comparator Cp1.

[0075] With the above configuration, when capacitor C1 is short-circuited, the current flowing through resistor R1 can be cut off even if the current flowing through fuses F1 and F2 via resistor R1 does not exceed the predetermined current If. Specifically, when capacitor C1 is short-circuited and a current exceeding the first current I1 flows through resistor R1, switch S3, which is connected in series with fuse F1 and resistor R1 on line L1, opens. Therefore, even if the voltage of input source battery 11 is low or the resistance value of resistor R1 is high, the discharge current from battery 11 can be cut off during a short circuit.

[0076] As shown in FIG. 13, the comparator Cp1 may open the switch S1 when the voltage across the resistor R1 exceeds a threshold value. The threshold value is set to a voltage lower than the voltage applied to the resistor R1 when the capacitor C1 is short-circuited and a predetermined current If flows through the resistor R1, enough to blow the fuse F1. In other words, when a short circuit occurs in the path through the resistor R1, the comparator Cp1 opens the switch S3 to cut off the current flowing through the resistor R1. The comparator Cp1 and the resistor R1 form a switch driver, and the switch S3, the comparator Cp1, and the resistor R1 form a cutoff circuit. An operational amplifier may be used instead of the comparator Cp1.

[0077] (Ninth embodiment) The ninth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0078] As shown in FIG. 14, the power supply circuit 40 includes a fuse F3 on wiring L5, which connects a capacitor C1 (predetermined element) to wiring L1 and wiring L2. That is, the fuse F3 (second fuse function unit, interrupter circuit) is connected in series with the capacitor C1, which is connected in parallel to wiring L1. The fuse F3 is connected in series with the capacitor C1, which is likely to be short-circuited. The fuse F3 blows and interrupts the current when a current exceeding a first current I1, which is smaller than the predetermined current If at which the fuses F1 and F2 (first fuse function units) blow, flows. Specifically, the first current I1 is smaller than the current that flows through resistor R1 when capacitor C1 is short-circuited when the battery 11 voltage is at the lowest voltage in its operating range (fluctuation range) or when the resistance value of resistor R1 is high. When capacitor C1 is not short-circuited (when capacitor C1 is normal), no current that exceeds the first current I1, which is smaller than the predetermined current If, flows through the fuse F3.

[0079] According to the above configuration, when there is no short circuit in capacitor C1, fuse F3 does not cut off the current and allows current to flow through capacitor C1. On the other hand, fuse F3 cuts off the current when a current exceeding the first current I1 flows. Therefore, when a short circuit occurs in capacitor C1, even if the current flowing through fuses F1 and F2 does not exceed the predetermined current If and fuses F1 and F2 do not operate, a current exceeding the first current I1, which is smaller than the predetermined current If, flows through fuse F3, allowing fuse F3 to cut off the current. Therefore, even if the voltage of input source battery 11 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.

[0080] The power supply circuit 40 also includes a fuse F4, similar to the fuse F3, on a wiring L6 that connects a Zener diode D2 (predetermined element) to the wiring L1 and the wiring L2. That is, the fuse F4 (second fuse function portion, cutoff circuit) is connected in series with the Zener diode D2, which is connected in parallel with the wiring L1. The fuse F3 is connected in series with the Zener diode D2, which is likely to be short-circuited. The fuse F4 blows and cuts off the current when a current that exceeds a first current I1, which is smaller than the predetermined current If at which the fuses F1 and F2 (first fuse function portion) blow, flows. When the Zener diode D2 is not short-circuited (when the Zener diode D2 is normal), no current that exceeds the first current I1, which is smaller than the predetermined current If, flows through the fuse F4. With this configuration, if a short circuit occurs in the Zener diode D2, even if the current flowing through the fuses F1 and F2 does not exceed the predetermined current If and the fuses F1 and F2 do not operate, a current exceeding the first current I1, which is smaller than the predetermined current If, will flow through the fuse F4, and the current can be cut off by the fuse F4.

[0081] 14 may include the switch S3, comparator Cp1, and shunt resistor Rs of FIG. 12, or the switch S3 and comparator Cp1 of FIG.

[0082] The first to ninth embodiments and their modifications can also be modified and implemented as follows.

[0083] The Zener diodes D1 and D2 (conducting elements) that conduct electricity when a voltage exceeding the first predetermined voltage V1 or the second predetermined voltage V2 (predetermined voltage) is applied are not limited to Zener diodes, but may also be TVS diodes, varistors, etc.

[0084] The fuses F1 and F2 are not limited to being provided within the power supply circuit, but may also be provided on an FPC (substrate) or battery 11 outside the power supply circuit.

[0085] The fuses F1 and F2 (first fuse functional portion) and the fuses F3 and F4 (second fuse functional portion) may be resettable fuses whose resistance increases with an overcurrent, or e-fuses (electronic fuses) that detect an overcurrent and cut off the current using a MOSFET. In these cases, the fuses F1 to F4 can also cut off (substantially cut off) the current when a current exceeding a predetermined current If flows.

[0086] The battery monitoring device 10 is not limited to a configuration in which the master unit 20 and the slave unit 30 are separate units, but may be an integrated configuration that includes the functions of the master unit 20 and the slave unit 30.

[0087] The battery monitoring device 10 may be mounted on an electric flying object such as a drone or an electric airplane, or may be attached to a stationary storage battery.

[0088] The above-described embodiments and their modifications can be combined within the scope of possible combinations.

[0089] Characteristic configurations extracted from the above-described embodiments and modifications will be described below. [Configuration 1] A power supply circuit (40, 140, 240, 340, 440, 540) that 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; The current path includes path resistances (R1, R0) on the battery monitoring unit side relative to the fuse function unit, A power supply circuit comprising a forming circuit (D1, B1, D2, B2, D0, B0, S1, S2, B3, Cp1, Rs, R1, L3, L4, D3) that forms a detour path that allows a current exceeding the predetermined current to flow through the fuse function unit without passing through the path resistance when a short circuit occurs in the path that passes through the path resistance. [Configuration 2] The forming circuit is The power supply circuit according to configuration 1, further comprising a first current-carrying element (D1, D0) connected to the current path in parallel with the path resistance and energized when a voltage exceeding a first predetermined voltage is applied, causing a current exceeding the predetermined current to flow through the fuse function unit. [Configuration 3] a switching element (T1) whose open / closed state is controlled by the battery monitoring unit is connected in series to the current path on the battery monitoring unit side of the path resistance and the first current-carrying element, The forming circuit is The power supply circuit according to configuration 2 further comprises a second current-carrying element (D2) connected in parallel with the battery monitoring unit on the side of the battery monitoring unit closer to the switching element of the current path, and configured to conduct electricity when a voltage exceeding a second predetermined voltage lower than the first predetermined voltage is applied. [Configuration 4] the battery monitoring unit includes a switching element (T1) whose open / closed state is controlled; 3. The power supply circuit according to configuration 2, wherein the switching element is connected in series to the current path (L1). [Configuration 5] The current paths (L1, L0) are provided in plurality, The plurality of current paths are each provided with the path resistances (R1, R0), 5. The power supply circuit according to any one of configurations 2 to 4, wherein the forming circuit includes the first energization elements (D1, D0) for the plurality of current paths, respectively. [Configuration 6] 6. The power supply circuit according to any one of configurations 2 to 5, wherein the forming circuit includes a noise reducing element (Rf) that reduces noise applied to the first energization element and has a resistance value lower than the path resistance. [Explanation of symbols]

[0090] 11...battery, 21...power supply circuit, 31...battery monitoring IC, 40...power supply circuit, 131...battery monitoring IC, 140...power supply circuit, 240...power supply circuit, 540...power supply circuit, B1...wiring, B2...wiring, B3...wiring, Cp1...comparator, D0...zener diode, D1...zener diode, D2...zener diode, D3...diode, F1...fuse, F2...fuse, L1...wiring, L2...wiring, L3...wiring, L4...wiring, R0...resistor, R1...resistor, Rs...shunt resistor, S1...switch, S2...switch.

Claims

1. A power supply circuit (40, 140, 240, 340, 440, 540) that 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; path resistances (R1, R0) are provided on the battery monitoring unit side of the fuse function unit in the current path, A power supply circuit comprising a forming circuit (D1, B1, D2, B2, D0, B0, S1, S2, B3, Cp1, Rs, R1, L3, L4, D3) that forms a detour path that allows a current exceeding the predetermined current to flow through the fuse function unit without passing through the path resistance when a short circuit occurs in the path that passes through the path resistance.

2. The forming circuit is 2. The power supply circuit according to claim 1, further comprising: a first current-carrying element (D1, D0) connected to the current path in parallel with the path resistance, and energized when a voltage exceeding a first predetermined voltage is applied to cause a current exceeding the predetermined current to flow through the fuse function unit.

3. a switching element (T1) whose open / closed state is controlled by the battery monitoring unit is connected in series to the current path on the battery monitoring unit side of the path resistance and the first current-carrying element, The forming circuit is 3. The power supply circuit according to claim 2, further comprising: a second current-carrying element (D2) connected in parallel with the battery monitoring unit on the side of the current path closer to the battery monitoring unit than the switching element, and configured to conduct electricity when a voltage exceeding a second predetermined voltage lower than the first predetermined voltage is applied.

4. The battery monitoring unit includes a switching element (T1) whose open / closed state is controlled, 3. The power supply circuit according to claim 2, wherein the switching element is connected in series with the current path (L1).

5. The current paths (L1, L0) are provided in plurality, The plurality of current paths are each provided with the path resistances (R1, R0), 5. The power supply circuit according to claim 2, wherein the forming circuit includes the first current-carrying elements (D1, D0) for the plurality of current paths, respectively.

6. 5. The power supply circuit according to claim 2, wherein the forming circuit comprises a noise reducing element (Rf) that reduces noise applied to the first current-carrying element and has a resistance value lower than the path resistance.

7. The forming circuit is switches (S1, S2) connected in parallel with the battery between the fuse function unit and the path resistance of the current path; a switch driver (Cp1, Rs, R1, L3, L4, D3) that closes the switch when a current exceeding a first current that is smaller than the predetermined current flows through the path resistor; The power supply circuit of claim 1 , comprising:

8. a switching element (T1) whose open / closed state is controlled by the battery monitoring unit is connected in series to the current path on the battery monitoring unit side of the path resistance; The forming circuit is 8. The power supply circuit according to claim 7, further comprising: a second current-carrying element (D2) connected in parallel with the battery monitoring unit on a side of the current path closer to the battery monitoring unit than the switching element, and configured to conduct electricity when a voltage exceeding a second predetermined voltage is applied.

9. The current paths (L1, L0) are provided in plurality, The plurality of current paths are each provided with the path resistances (R1, R0), 9. The power supply circuit according to claim 7, wherein the forming circuit includes the switch driving units (L3, L4, D3) for the plurality of current paths, respectively.

10. A power supply circuit (640, 740) 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; a path resistor (R1) is provided on the current path closer to the battery monitoring unit than the fuse function unit; an interruption circuit (S3, Cp1, Rs, R1, F3, F4) that interrupts a current flowing through the path resistance when a short circuit occurs in the path passing through the path resistance; The interruption circuit includes: a switch (S3) connected in series to the fuse function unit and the path resistor in the current path; a switch driver (Cp1, Rs, R1) that opens the switch when a current exceeding a first current that is smaller than the predetermined current flows through the path resistor; A power supply circuit comprising:

11. the fuse function unit is a first fuse function unit (F1, F2), The interruption circuit includes:

11. The power supply circuit according to claim 10, further comprising: a second fuse functional unit (F3, F4) connected in series to a predetermined element (C1, D2) connected in parallel to the current path, which prevents a current exceeding a first current smaller than the predetermined current from flowing when no short circuit occurs in the predetermined element, and which cuts off the current when a current exceeding the first current flows.

12. A power supply circuit (640, 740) that 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, a fuse function unit (F1, F2) that cuts off a current when a current exceeding a predetermined current flows is provided in a current path (L1, L2) from the battery to the battery monitoring unit; a path resistor (R1) is provided on the current path closer to the battery monitoring unit than the fuse function unit; an interruption circuit (S3, Cp1, Rs, R1, F3, F4) that interrupts a current flowing through the path resistance when a short circuit occurs in the path passing through the path resistance; the fuse function unit is a first fuse function unit (F1, F2), The interruption circuit includes: a second fuse functional unit (F3, F4) connected in series to a predetermined element (C1, D2) connected in parallel to the current path, which prevents a current exceeding a first current smaller than the predetermined current from flowing when no short circuit occurs in the predetermined element, and which cuts off the current when a current exceeding the first current flows.

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