Fuse blow detection circuit

Abstract

The present application has an object to accurately detect the melting of a fuse. A fuse melting detection circuit (20) disclosed herein is provided in an output circuit (1) connecting a battery (10) and a fuse (12) in series. The fuse melting detection circuit has a detection line (30) connecting a detection resistor (32), a measurement switch (34), and a first resistor (36) in series and connecting the detection line in parallel with the output circuit, a second resistor (38) connected to a connection point (30a) between the measurement switch and the first resistor in the detection line and a connection point (14b) between the battery and the fuse in the output circuit, a first voltage measurement unit measuring a battery voltage Vb of the battery with respect to a reference potential, and a second voltage measurement unit measuring a detection voltage Vra applied to the detection resistor with respect to the reference potential.

Description

Technical Field

[0001] This invention relates to a fuse failure detection circuit. Background Technology

[0002] Japanese Patent Application Publication No. 2008-86069 discloses a vehicle power supply device comprising a driving battery with multiple battery modules connected in series, and a voltage detection circuit for detecting the voltage of the battery modules of the driving battery. In the driving battery, battery cells on the positive and negative sides are connected in series via fuses. The first intermediate connection point between the fuses and the battery cells is connected to the voltage detection circuit via a reference connection line. In the battery cells, multiple battery modules are connected in series at the connection points. The connection points are connected to the voltage detection circuit via a detection switch. The detection switch is divided into multiple switch blocks. In the vehicle power supply device disclosed in the same publication, by switching each switch block on or off, it is possible to detect either a broken reference connection line or a broken fuse, or both.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-86069

[0004] However, the inventors considered the need to accurately detect the melting of fuses in circuits equipped with fuses. Summary of the Invention

[0005] The fuse failure detection circuit disclosed herein is configured in an output circuit in which a battery and a fuse are connected in series. The fuse failure detection circuit includes: a detection line that connects a detection resistor, a measuring switch, and a first resistor in series and in parallel with the output circuit; a second resistor connected to the connection point between the measuring switch and the first resistor in the detection line, and to the connection point between the battery and the fuse in the output circuit; a first voltage measuring unit that measures the battery voltage relative to a reference potential; and a second voltage measuring unit that measures the detection voltage applied to the detection resistor relative to the reference potential. According to this fuse failure detection circuit, the failure of a fuse can be detected with high accuracy.

[0006] Alternatively, the fuse failure detection circuit may also include a control unit configured to determine whether the fuse has failed based on the detection voltage measured by the second voltage measuring unit when the measuring switch is on.

[0007] The control unit can also be configured to determine whether an open-circuit fault has occurred in the measuring switch based on the detection voltage when the measuring switch is in the on state.

[0008] It can also be configured so that the control unit performs the following actions: if the detected voltage is a predetermined first voltage, the process is determined that the fuse has not blown; if the detected voltage is a predetermined second voltage that is lower than the first voltage, the process is determined that the fuse has blown; and if the detected voltage is a predetermined third voltage that is lower than the second voltage, the process is determined that the measuring switch has an open circuit fault.

[0009] The second voltage measuring unit can also measure the detection voltage when the measuring switch is in the open state. The control unit can also determine whether a closed-circuit fault has occurred in the measuring switch based on the detection voltage when the measuring switch is in the open state.

[0010] The resistance value of the first resistor can also be higher than that of the second resistor.

[0011] The resistance value of the second resistor can also be higher than that of the first resistor. Attached Figure Description

[0012] Figure 1 This is a circuit diagram representing output circuit 1.

[0013] Figure 2 This is a circuit diagram of output circuit 1, which indicates the state of switch 34 being closed and the state of fuse 12 not being blown.

[0014] Figure 3 This is a circuit diagram of output circuit 1, which indicates the state of switch 34 being closed and the state of fuse 12 being blown.

[0015] Figure 4 This is a flowchart representing the processing performed by the control unit 50. Detailed Implementation

[0016] Hereinafter, an embodiment of the technology disclosed herein will be described with reference to the accompanying drawings. The embodiments described herein are not intended to specifically limit the invention. Unless otherwise specifically mentioned, the invention is not limited to the embodiments described herein. Furthermore, components and parts that perform the same function are appropriately labeled with the same reference numerals, and repeated descriptions are appropriately omitted.

[0017] <Output Circuit 1>

[0018] Figure 1 This is a circuit diagram representing output circuit 1. For example... Figure 1As shown, the output circuit 1 includes a battery 10, a fuse 12, and a fuse failure detection circuit 20. In this embodiment, a battery module with multiple secondary batteries 10a connected in series is used as the battery 10. The structure of the battery 10 is not particularly limited. For example, a single secondary battery 10a or multiple secondary batteries 10a can be used as the battery 10. The multiple secondary batteries 10a are not limited to being connected in series; they can be connected in parallel, and may include secondary batteries 10a connected in series and secondary batteries 10a connected in parallel. In this specification, "secondary battery" generally refers to an energy storage device that can be repeatedly charged and discharged. In addition to so-called storage batteries (i.e., chemical batteries) such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, it also includes the concept of capacitors (i.e., physical batteries) such as electric double-layer capacitors.

[0019] In output circuit 1, battery 10 and fuse 12 are connected in series. Fuse 12 is provided on connection line 14, which connects the positive terminal of battery 10 to an electrical device (not shown) that is the output object. Connection line 16, which connects battery 10 to an electrical device (not shown) that is the output object, is provided on the negative terminal of battery 10. Connection line 16 on the negative terminal side is connected to reference line 18. Reference line 18 is connected to a reference potential point (not shown) that serves as a reference potential for the potential of battery 10.

[0020] Fuse 12 protects against overcurrent flowing into devices connected to battery 10 and output circuit 1. Fuse 12 is configured to blow if a current exceeding a pre-set rated current flows through it. A fuse-blowing detection circuit 20 is provided in output circuit 1 to detect the blowing of fuse 12.

[0021] <Fuse Failure Detection Circuit 20>

[0022] The fuse-blown detection circuit 20 detects whether the fuse 12 has blown at a predetermined time. The timing of fuse-blown detection is not particularly limited, but it can be performed, for example, before the use of the electrical device. Furthermore, fuse-blown detection can be performed when an abnormality occurs during the use of the electrical device. For example, in the event of an abnormality where no power is supplied to the electrical device, the cause of the abnormality can be determined by detecting the blown fuse. The fuse-blown detection circuit 20 includes a detection line 30, a second resistor 38, a voltage measuring unit 40, and a control unit 50. The detection line 30 includes a detection resistor 32, a measuring switch 34, and a first resistor 36. In this embodiment, the constituent elements of the fuse-blown detection circuit 20 are disposed on the same substrate 20a.

[0023] <Detection line 30>

[0024] In the detection line 30, the detection resistor 32, the measuring switch 34, and the first resistor 36 are connected in series. The measuring switch 34 is disposed between the detection resistor 32 and the first resistor 36. The measuring switch 34 is configured to switch between an on and off state via the control unit 50 described later. Although not particularly limited, a semiconductor switch may be used as the measuring switch 34, for example.

[0025] The end of the detection line 30 on the first resistor 36 side is connected to the connection point 14a of the connection line 14 on the positive side. Additionally, the end of the detection line 30 on the detection resistor 32 side is connected to the connection point 18a of the reference line 18. Therefore, the detection line 30 is connected to the output circuit 1 in parallel via the reference line 18.

[0026] <Second Resistor 38>

[0027] The second resistor 38 is connected to the detection line 30 and the output circuit 1. One end of the second resistor 38 is connected to the connection point 30a between the measuring switch 34 and the first resistor 36 in the detection line 30. The other end of the second resistor 38 is connected to the connection point 14b between the positive terminal of the battery 10 and the fuse 12 in the output circuit 1. In this embodiment, the other end of the second resistor 38 is connected to the connection point 14b via the first connection line 41 described later.

[0028] <Voltage Measurement Unit 40>

[0029] The voltage measuring unit 40 is connected to the output circuit 1 via a first connecting line 41, a second connecting line 42, and a third connecting line 43. The first connecting line 41 is connected between the positive terminal of the battery 10 and the fuse 12. The second connecting line 42 is connected between the negative terminal of the battery 10 and the connection point 18a. The third connecting line 43 is connected between the detection resistor 32 and the measuring switch 34.

[0030] The voltage measuring unit 40 includes a first measuring device 44, a second measuring device 45, and a communication unit 46. In this embodiment, the first measuring device 44 corresponds to the first voltage measuring unit, and the second measuring device 45 corresponds to the second voltage measuring unit. The first measuring device 44 measures the battery voltage Vb of the battery 10 relative to a reference potential. The second measuring device 45 measures the detection voltage Vra applied to the detection resistor 32 relative to the reference potential. The first measuring device 44 and the second measuring device 45 may also include a channel switching circuit (not shown), an A / D converter, etc. Although not shown, the first measuring device 44 may be configured to be connected to the positive and negative terminals of the secondary battery 10a via multiple wirings and be able to measure the voltage of each secondary battery 10a constituting the battery 10. The analog voltage signals measured by the first measuring device 44 and the second measuring device 45 are converted from analog to digital by the A / D converter. The converted digital voltage signal is sent to the communication unit 46. The communication unit 46 includes, for example, a communication interface. The communication unit 46 is connected to the control unit 50 of the fuse blown detection circuit 20 in a manner that enables communication. The communication unit 46 transmits the digitally converted battery voltage Vb and the detection voltage Vra to the control unit 50 of the fuse blown detection circuit 20. Furthermore, the structure of the first voltage measuring unit and the second voltage measuring unit is not particularly limited. The first voltage measuring unit and the second voltage measuring unit can be implemented by multiple voltage measuring devices, or they can be implemented by a single voltage measuring device that can switch the measuring voltage.

[0031] <Control Unit 50>

[0032] The control unit 50 controls the on and off states of the measuring switch 34. Furthermore, the control unit 50 determines whether the fuse 12 has blown based on the voltage measured by the voltage measuring unit 40. The control unit 50 is, for example, a microcomputer. The control unit 50 includes, for example, a communication interface, a CPU, ROM, and RAM.

[0033] The control unit 50 includes an indicator unit 51 and a determination unit 52. The indicator unit 51 and the determination unit 52 may be implemented by multiple processors, for example. The indicator unit 51 indicates the switching between the on and off states of the measuring switch 34. The determination unit 52 determines whether the fuse 12 has blown based on the voltage (in this embodiment, the detection voltage Vra) received from the communication unit 46 of the voltage measuring unit 40.

[0034] However, when the measuring switch 34 is closed, current flows through the detection resistor 32. From the viewpoint of suppressing power consumption of the battery 10, it is preferable that the measuring switch 34 is open when the blown fuse 12 is not detected. For example, if the measuring switch 34 is closed for an extended period, the battery 10 may discharge, and the charge level of the battery 10 may decrease.

[0035] The indicator unit 51 indicates the on / off state of the detection switch 34 when a predetermined time is detected that the fuse 12 has blown. The indicator unit 51 is configured to communicate with the detection switch 34. By sending a switch switching signal from the indicator unit 51 to the detection switch 34, the detection switch 34 can switch between the on and off states. The time of detecting the fuse 12's blowing may also be stored, for example, in the memory of the control unit 50.

[0036] The determination unit 52 of the control unit 50 determines the fuse 12 to be blown based on the detection voltage Vra measured by the second measuring device 45 of the voltage measuring unit 40 when the measuring switch 34 is turned on. Figure 2 This is a circuit diagram showing the output circuit 1 that measures the state of switch 34 when it is closed and fuse 12 is not blown. In this embodiment, the first resistor 36 and the second resistor 38 have the same resistance value Rb. The sensing resistor 32 has a resistance value Ra. Figure 2 As shown, when the fuse 12 has not blown, voltages are applied to the first resistor 36, the second resistor 38 and the detection resistor 32, thereby allowing currents I1, I2 and Ia1 to flow through them respectively.

[0037] Here, the first resistor 36 and the second resistor 38 are connected in parallel and then connected in series with the detection resistor 32. Therefore, the combined resistance of the detection resistor 32, the first resistor 36, and the second resistor 38 is Ra + (Rb / 2). The detection voltage Vra applied to the detection resistor 32 is expressed by the following Equation 1.

[0038] Vra=Vb×Ra / (Ra+(Rb / 2))···Equation 1

[0039] In this specification, the detection voltage Vra, expressed by Equation 1 above, calculated when the detection switch 34 is turned on and the fuse 12 is not blown, is appropriately referred to as the "first voltage". The first voltage V1 is determined based on the resistance values ​​of the resistors used in the fuse blown detection circuit 20 (in this embodiment, the detection resistor 32, the first resistor 36, and the second resistor 38) and the battery voltage Vb measured by the first measuring device 44 of the voltage measuring unit 40.

[0040] On the other hand, if the fuse 12 blows, the voltage measuring unit 40 detects a value different from the detection voltage Vra expressed by Equation 1. Figure 3 This is a circuit diagram of output circuit 1, which indicates the state of switch 34 being closed and fuse 12 being blown. (Example) Figure 3As shown, even when fuse 12 blows, voltage is applied to the second resistor 38 and the sensing resistor 32, causing current Ia2 to flow. However, when fuse 12 blows, the output to the first resistor 36 can be cut off by an output cut-off device (not shown) located between the output terminal of fuse 12 and the output object. No voltage is applied to the first resistor 36, and therefore no current flows.

[0041] Here, the combined resistance of the sensing resistor 32 and the second resistor 38 is Ra + Rb. The sensing voltage Vra applied to the sensing resistor 32 is expressed by the following Equation 2.

[0042] Vra=Vb×Ra / (Ra+Rb)···Equation 2

[0043] In this specification, the detection voltage Vra, calculated by Equation 2 above and calculated when the detection switch 34 is on and the fuse 12 is blown, is appropriately referred to as the "second voltage". The second voltage V2 is a voltage lower than the first voltage V1. The second voltage V2 is the same as the first voltage V1, and is determined based on the resistance value of the resistor used for the fuse blown detection circuit 20 and the battery voltage Vb measured by the first measuring device 44 of the voltage measuring unit 40. For example, in this embodiment, the first voltage is expressed as Vb×Ra / (Ra+(Rb / 2)) (refer to Equation 1). The second voltage V2 is expressed as Vb×Ra / (Ra+Rb) (refer to Equation 2). Therefore, the second voltage V2 is a value lower than the first voltage V1.

[0044] The resistance values ​​of the detection resistor 32, the first resistor 36, and the second resistor 38 are predetermined. The battery voltage Vb of the battery 10 is a value measured by the voltage measuring unit 40 and has no effect on whether the fuse 12 is blown. Therefore, the determination unit 52 of the control unit 50 can determine whether the fuse 12 is blown based on the detection voltage Vra measured by the voltage measuring unit 40 when the detection switch 34 is turned on. For example, if the detection voltage Vra applied to the detection resistor 32 is a first voltage V1 expressed by Equation 1, it is determined that the fuse 12 is not blown; if it is a second voltage V2 expressed by Equation 2, it is determined that the fuse 12 is blown.

[0045] However, the measuring switch 34 installed on the detection line 30 may malfunction due to factors such as aging. In the fuse blown detection circuit 20 described above, not only is the blown fuse 12 detected, but malfunctions of the measuring switch 34 can also be detected. Examples of malfunctions of the measuring switch 34 include open-circuit faults and closed-circuit faults. An open-circuit fault is a condition where the measuring switch 34 is always in an off state. For example, in an open-circuit fault of the measuring switch 34, even when the indicator 51 of the control unit 50 instructs the measuring switch 34 to be switched to the on state, the measuring switch 34 remains in an off state. A closed-circuit fault is a condition where the measuring switch 34 is always in a fixed state. For example, in a closed-circuit fault of the measuring switch 34, even when the indicator 51 of the control unit 50 instructs the measuring switch 34 to be switched to the off state, the measuring switch 34 remains in an on state.

[0046] In addition, in the fuse blown detection circuit 20, the control unit 50 can determine whether the detection switch 34 has an open circuit fault based on the detection voltage Vra when the detection switch 34 is turned on.

[0047] In the event of an open-circuit fault in the measuring switch 34, as described above, even when the indicator 51 indicates that the measuring switch 34 should be switched to the ON state, the measuring switch 34 remains in the OFF state. In this case, a voltage is applied to the first resistor 36 and the second resistor 38, and current flows through the first resistor 36 and the second resistor 38. No voltage is applied to the detection resistor 32, so no current flows. Since no voltage is applied to the detection resistor 32, the measured value of the detection voltage Vra in the voltage measuring unit 40 may become 0. Thus, by detecting that the detection voltage Vra is 0 when the measuring switch 34 is indicated to be ON, it is determined that an open-circuit fault has occurred in the measuring switch 34. Furthermore, in this specification, the detection voltage Vra that can be measured when the measuring switch 34 is OFF will be appropriately referred to as the "third voltage".

[0048] Furthermore, in the fuse blown detection circuit 20, it is possible to determine whether a closed-circuit fault has occurred in the measuring switch 34. In this embodiment, the voltage measuring unit 40 also measures the detection voltage Vra when the measuring switch 34 is in the open state. The control unit 50 determines whether a closed-circuit fault has occurred in the measuring switch 34 based on the detection voltage Vra when the measuring switch is in the open state.

[0049] In the event of a closed-circuit fault in the measuring switch 34, as described above, the measuring switch 34 remains in the on state even when the indicator 51 indicates that the measuring switch 34 should be switched to the off state. In this case, voltages are applied to the first resistor 36, the second resistor 38, and the detection resistor 32, respectively, thereby allowing current to flow. The measured value of the detection voltage Vra in the voltage measuring unit 40 shows a value other than 0. In other words, the detection voltage Vra can become a voltage other than a third voltage. Thus, if the detection voltage Vra is not 0 when the measuring switch 34 is indicated to be in the off state, it is determined that a closed-circuit fault has occurred in the measuring switch 34.

[0050] The following example illustrates the process performed by the control unit 50, but it is not intended to limit the present invention to the situation shown in this manner.

[0051] The circuit structure in this embodiment is the same as that of the output circuit 1 and the fuse blown detection circuit 20 described above. The battery voltage Vb of battery 10 is 48V. The resistance value Ra of the detection resistor 32 is 4.7kΩ. The resistance value Rb of the first resistor 36 is 200kΩ. The resistance value Rb of the second resistor 38 is 200kΩ.

[0052] Furthermore, the detection resistor 32, the first resistor 36, and the second resistor 38 can be determined based on the voltage measurement range of the voltage measuring unit 40 and the maximum voltage that the battery voltage Vb can obtain. The resistance value Ra of the detection resistor 32, relative to the combined resistance value R12+Ra of the first resistor 36, the second resistor 38, and the detection resistor 32, can be set to be below the upper limit Vm of the voltage measurement range of the second measuring unit 45 relative to the maximum value of the battery voltage Vb. In other words, the resistors used are determined in such a way that Ra / (R12+Ra)≤Vm / Vb.

[0053] According to Equation 1 above, the detection voltage Vra (first voltage V1) measured by the second measuring device 45 when the measuring switch 34 is on and the fuse 12 is not blown is calculated to be 2.15V. According to Equation 2 above, the detection voltage Vra (second voltage V2) measured by the second measuring device 45 when the measuring switch 34 is on and the fuse 12 is blown is calculated to be 1.1V. The control unit 50 is configured to calculate the first voltage V1 and the second voltage V2 based on the battery voltage Vb measured by the first measuring device 44.

[0054] Figure 4 This is a flowchart illustrating the process performed by the control unit 50. The process begins at a predetermined time when the fuse 12 is detected to have blown.

[0055] exist Figure 4In step S10, the instruction unit 51 of the control unit 50 performs the process of switching the measurement switch 34 from the off state to the on state. If the measurement switch 34 is switched to the on state, the instruction unit 51 further instructs the voltage measurement unit 40 to measure the battery voltage Vb and the detection voltage Vra. The first measuring device 44 of the voltage measurement unit 40 measures the battery voltage Vb. Here, as described above, the battery voltage Vb is 48V. The second measuring device 45 of the voltage measurement unit 40 measures the detection voltage Vra. The measured battery voltage Vb and detection voltage Vra are sent to the determination unit 52 of the control unit 50 via the communication unit 46. Then, the process proceeds to step S20.

[0056] exist Figure 4 In step S20, the control unit 50 performs a process that determines the fuse 12 is not blown if the detected voltage Vra is the first voltage V1 (here, 2.15V). If the received detected voltage Vra is the first voltage V1, the determination unit 52 sets the determination in step S20 to yes and proceeds to step S21. Furthermore, in this process, considering measurement error, the first voltage V1 can be set to a value with the required amplitude. It can also be set such that if the difference between the detected voltage Vra and the first voltage V1 is within a required difference (although not specifically limited, but for example, within 0.05V), then it is determined that "the detected voltage Vra is the first voltage V1". For example, "the case where the detected voltage is the first voltage" includes the case where the difference between the detected voltage and the first voltage is within the required difference. Hereinafter, the values ​​with the required amplitude can also be set for the second and third voltages in the same way. "The case where the detected voltage is the second voltage" includes the case where the difference between the detected voltage and the second voltage is within the required difference. "The case where the detection voltage is the third voltage" includes cases where the difference between the detection voltage and the third voltage is within the required range.

[0057] In step S21, it is determined that fuse 12 has not blown, and the result is output to a predetermined output target (e.g., a user's terminal with a device equipped with output circuit 1). In step S20, if the detected voltage Vra is not the first voltage V1, the determination in step S20 is set to negative, and the process proceeds to step S30.

[0058] exist Figure 4In step S30, the control unit 50 performs a process to determine that fuse 12 is blown if the detected voltage Vra is the second voltage V2 (here, 1.1V). If the received detected voltage Vra is the second voltage V2, the determination unit 52 sets the determination in step S30 to yes and proceeds to step S31. In step S31, fuse 12 is determined to be blown, and the result is output to a predetermined output target. If the detected voltage Vra is not the second voltage V2 in step S30, the determination in step S30 is set to no, and proceeds to step S40.

[0059] exist Figure 4 In step S40, the control unit 50 performs a process that determines that the measuring switch 34 has an open-circuit fault if the detected voltage Vra is the third voltage V3 (here, 0V). If the received detected voltage Vra is the third voltage V3, the determination unit 52 sets the determination in step S40 to yes and proceeds to step S41. In step S41, it is determined that the measuring switch 34 has an open-circuit fault, and the result is output to a predetermined output target. If the detected voltage Vra is not the third voltage V3 in step S40, the determination in step S40 is set to no, and proceeds to step S42. In step S42, it is determined that there is a possibility that a fault has occurred in the circuit included in the output circuit 1 (e.g., the fuse blown detection circuit 20), and the result is output to a predetermined output target.

[0060] If any of steps S21, S31, S41, or S42 is completed, then proceed to step S50.

[0061] exist Figure 4 In step S50, the instruction unit 51 of the control unit 50 performs a process of switching the measurement switch 34 from the on state to the off state. If the measurement switch 34 is switched to the off state, then, as in step S10, the instruction unit 51 instructs the voltage measurement unit 40 to measure the battery voltage Vb and the detection voltage Vra. The measured battery voltage Vb and the detection voltage Vra are sent to the determination unit 52 of the control unit 50 via the communication unit 46. Then, the process proceeds to step S60.

[0062] exist Figure 4In step S60, the control unit 50 performs a process to determine that the measuring switch 34 has a closed-circuit fault if the detected voltage Vra is not the third voltage V3 (here, 0V). If the received detected voltage Vra is not the third voltage V3, the determination unit 52 sets the determination in step S60 to negative and proceeds to step S61. In step S61, if the measuring switch 34 is determined to have a closed-circuit fault, the result is output to a predetermined output target. If the detected voltage Vra is the third voltage V3 in step S60, the determination in step S60 is positive, and the process of detecting the fuse blowing ends.

[0063] As described above, the fuse blown detection circuit 20 includes: a detection line 30 that connects the detection resistor 32, the measuring switch 34, and the first resistor 36 in series and in parallel with the output circuit 1; a second resistor 38 connected to the connection point 30a between the measuring switch 34 and the first resistor 36 in the detection line 30, and to the connection point 14b between the battery 10 and the fuse 12 in the output circuit 1; a voltage measuring unit 40 that measures the battery voltage Vb of the battery 10 relative to a reference potential and the detection voltage Vra applied to the detection resistor 32 relative to the reference potential; and a control unit 50 that determines whether the fuse 12 has blown based on the detection voltage Vra measured by the voltage measuring unit 40 when the measuring switch 34 is on. According to this structure, the detection voltage Vra is different when the fuse 12 has blown and when it has not blown. By measuring the detection voltage Vra, it is possible to determine whether the fuse 12 has blown. Additionally, a second resistor 38 is provided, connected between the measuring switch 34 and the first resistor 36, and to the input terminal of the fuse 12. Therefore, the detection voltage Vra will have different values ​​when the fuse 12 is blown (1.1V in this example) and when the measuring switch 34 has an open-circuit fault (0V in this example). As a result, it is possible to distinguish between a blown fuse 12 and an open-circuit fault in the measuring switch 34.

[0064] As described above, the constituent components of the fuse-blown detection circuit 20 are disposed on the same substrate 20a. For example, the connection line of the second resistor 38 can be shared with the first connection line 41 that connects the voltage measuring unit 40 to the output circuit 1. In this way, the circuit structure described above can be realized by arranging each constituent component on the substrate 20a. For example, there is no need to connect wiring or devices for detecting the state of the fuse 12 and the switch 34 from outside the substrate 20a. The fuse-blown detection circuit 20 can be constructed with a simple structure disposed only on the substrate 20a.

[0065] In the above embodiment, the first resistor 36 and the second resistor 38 have the same resistance value Rb, but this is not a limitation. The resistance values ​​of the first resistor 36 and the second resistor 38 can be arbitrarily set.

[0066] For example, as in the embodiment described above, when the resistance values ​​of the first resistor 36 and the second resistor 38 are equal, the detection voltage Vra (second voltage V2: 1.1V) when the fuse 12 is blown is approximately half that of the normal detection voltage Vra (first voltage V1: 2.15V) when the fuse 12 is not blown (when the normal condition is normal). Furthermore, when an open-circuit fault occurs in the measuring switch 34, the detection voltage Vra (third voltage V3) is 0V. Therefore, these voltage values ​​are clearly distinguished, making it easy to determine each state. From this perspective, the ratio of the resistance value of the second resistor 38 to the resistance value of the first resistor 36 can be set, for example, to 0.9 to 1.1.

[0067] Furthermore, the higher the resistance value of the second resistor 38 is compared to the resistance value of the first resistor 36, the lower the detection voltage Vra (second voltage V2) when the fuse 12 is blown is compared to the detection voltage Vra (first voltage V1) when the fuse 12 is not blown. In other words, the difference between the first voltage V1 and the second voltage V2 becomes larger. Therefore, it is easy to detect whether the fuse 12 is blown.

[0068] Conversely, the higher the resistance value of the first resistor 36 is compared to the resistance value of the second resistor 38, the higher the detection voltage Vra (second voltage V2) when the fuse 12 has blown is compared to the detection voltage Vra (first voltage V1) when the fuse 12 is intact. Therefore, the difference between the second voltage V2 and the third voltage V3 becomes larger. As a result, in the event of a circuit fault, it is easy to detect whether the fault is due to a blown fuse 12 or an open-circuit fault in the measuring switch 34. Thus, the resistance values ​​of the first resistor 36 and the second resistor 38 can be set according to the structure of the output circuit 1 and the purpose of setting up the fuse blow detection circuit 20.

[0069] The above provides various descriptions of the technology disclosed herein. Unless otherwise specified, the embodiments described herein are not intended to limit the invention. Furthermore, the fuse burn detection circuit disclosed herein can be modified in various ways, and the constituent elements and processes mentioned herein can be appropriately omitted or combined without causing any particular problems.

Claims

1. A fuse failure detection circuit, configured in an output circuit where a battery and a fuse are connected in series. The fuse failure detection circuit is characterized by having: The detection line connects the detection resistor, the measuring switch, and the first resistor in series, and connects them in parallel with the output circuit. The second resistor is connected to the connection point between the measuring switch and the first resistor in the detection line, and to the connection point between the battery and the fuse in the output circuit; The first voltage measuring unit measures the battery voltage relative to a reference potential; The second voltage measuring unit measures the detection voltage applied to the detection resistor relative to the reference potential; and The control unit is configured to: determine whether the fuse has blown based on the detection voltage measured by the second voltage measuring unit when the measuring switch is in the on state; and determine whether the measuring switch has experienced an open-circuit fault based on the detection voltage when the measuring switch is in the on state. The control unit is configured to perform the following processes: If the detection voltage is a predetermined first voltage, the process is to determine that the fuse has not blown. The process of determining that the fuse has blown when the detected voltage is a predetermined second voltage that is lower than the first voltage; and If the detected voltage is a predetermined third voltage that is lower than the second voltage, the process is to determine that the measuring switch has an open circuit fault.

2. The fuse failure detection circuit according to claim 1, characterized in that, The second voltage measuring unit also measures the detection voltage when the measuring switch is in the open state. The control unit determines whether a closed-circuit fault has occurred in the measuring switch based on the detection voltage when the measuring switch is in the open state.

3. The fuse failure detection circuit according to claim 1 or 2, characterized in that, The resistance value of the first resistor is higher than the resistance value of the second resistor.

4. The fuse failure detection circuit according to claim 1 or 2, characterized in that, The resistance value of the second resistor is higher than that of the first resistor.

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