Ground fault detection device

Abstract

To more accurately detect occurrence of a ground fault. In a vehicle-mounted system (1) including a conductive path (20) that is a path for supplying electric power from a first power supply (31) to a second load (12), a ground fault detection device (50) detects a ground fault of the conductive path (20). The ground fault detection device (50) has a voltage detection section (51) that detects a voltage value of the conductive path (20), a current detection section (52) that detects a current value of the conductive path (20), and a control section (53) that determines whether a ground fault has occurred in the conductive path (20) based on an evaluation value that is a value that becomes larger as the voltage value detected by the voltage detection section (51) becomes smaller and the current value detected by the current detection section (52).

Description

Technical Field

[0001] This disclosure relates to grounding fault detection devices. Background Technology

[0002] The overcurrent detection device disclosed in Patent Document 1 is installed in a load drive circuit. The load drive circuit has a semiconductor switch installed in the conductive path connecting the DC power supply and the load. The drive and stop of the load are controlled by switching the on and off actions of this semiconductor switch. The overcurrent detection device has the following structure: it compares the voltage across the semiconductor switch with a preset judgment voltage, and if the voltage exceeds the judgment voltage, it outputs an overcurrent judgment signal to determine abnormalities such as grounding faults.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-49664 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In structures like the overcurrent detection device in Patent Document 1, which detects the voltage value of a conductive path and uses it for anomaly determination, ground faults in the conductive path may be falsely detected based on changes in voltage values ​​such as surge voltages. Therefore, there is a need for structures that can more accurately detect the occurrence of ground faults.

[0008] Therefore, the purpose of this disclosure is to detect the occurrence of grounding faults more accurately.

[0009] Technical solutions for solving the problem

[0010] The ground fault detection device of this disclosure detects ground faults in a vehicle-mounted system that includes a conductive path, wherein the conductive path is a path supplying power from a power source to a load, and wherein the ground fault detection device has:

[0011] The voltage detection unit detects the voltage value of the conductive path;

[0012] The current detection unit detects the current value in the conductive path; and

[0013] The determination unit determines whether a grounding fault has occurred in the conductive path based on the evaluation value and the current value detected by the current detection unit. The evaluation value is a value that increases as the voltage value detected by the voltage detection unit decreases.

[0014] Invention Effects

[0015] The purpose of the grounding fault detection device disclosed herein is to detect the occurrence of grounding faults more accurately. Attached Figure Description

[0016] Figure 1 This is a block diagram that schematically illustrates the vehicle system according to Embodiment 1.

[0017] Figure 2 This is a general example. Figure 1 The circuit diagram of the cutting mechanism.

[0018] Figure 3 It means by Figure 1 An explanatory diagram showing an example of the time-varying current value detected by the current detection unit and the time-varying voltage value detected by the voltage detection unit.

[0019] Figure 4 It is a schematic representation in Figure 1 An illustration of an example of the time-varying detection voltage in an onboard system when a ground fault occurs in the conductive path.

[0020] Figure 5 It is a schematic representation in Figure 1 This is an illustration of an example of the time variation of the product of the evaluation value and the detection current, and the time variation of the power value in a vehicle-mounted system under the condition that a ground fault occurs in the conductive path.

[0021] Figure 6 It means in Figure 1 An illustration of an example of the time-varying current and power value of a vehicle-mounted system under the condition of an impulse voltage.

[0022] Figure 7 It means in Figure 1 The diagram illustrates an example of the time variation of the product of the evaluation value and the detection current, and the time variation of the detection current, in the case of a ground fault in the vehicle system. Detailed Implementation

[0023] The embodiments of this disclosure are illustrated below. Furthermore, the features [1] to [5] shown below can be combined arbitrarily without contradiction.

[0024] [1] A ground fault detection device for detecting ground faults in a vehicle-mounted system including a conductive path, wherein the conductive path is a path supplying power from a power source to a load, wherein the ground fault detection device comprises:

[0025] The voltage detection unit detects the voltage value of the conductive path;

[0026] The current detection unit detects the current value in the conductive path; and

[0027] The determination unit determines whether a grounding fault has occurred in the conductive path based on the evaluation value and the current value detected by the current detection unit. The evaluation value is a value that increases as the voltage value detected by the voltage detection unit decreases.

[0028] In the ground fault detection device of this disclosure [1], when a ground fault occurs in the conductive path, the evaluation value and current value increase, thus enabling the detection of ground faults in the conductive path by understanding the increase in the evaluation value and current value. When a surge voltage is applied to the conductive path, the evaluation value changes; however, it is difficult for the current value to change, thus suppressing false detections of ground faults based on surge voltage. When an impulse current flows into the conductive path, the current value increases; however, it is difficult for the evaluation value to change, thus suppressing false detections of ground faults based on impulse current. Therefore, the ground fault detection device can more accurately detect the occurrence of ground faults in the conductive path.

[0029] [2] In the ground fault detection device of [1] above, the evaluation value can be the value of the subtraction operation obtained by subtracting the voltage value from the predetermined set value.

[0030] The ground fault detection device described in [2] above can realize a determination method in which the smaller the voltage value, the larger the evaluation value, by reflecting the difference between the voltage value and the predetermined set value in the evaluation value.

[0031] [3] In the ground fault detection device of [2] above, the vehicle-mounted system may include: a first conductive path, to which a power supply is electrically connected; a second conductive path, to which a load is electrically connected; a cut-off section disposed between the first and second conductive paths, for cutting off the power supply from the first conductive path to the second conductive path; and a Zener diode, wherein the anode of the Zener diode is electrically connected to the second conductive path, the cathode of the Zener diode is electrically connected to the first conductive path, and the Zener diode is connected in parallel with the cut-off section. A voltage detection section can detect the voltage value of the first conductive path. The set value may be greater than the breakdown voltage of the Zener diode.

[0032] In the case of a ground fault detection device described in [3] above, even if a surge voltage is generated in the first conductive path and the voltage value increases to the point that the Zener diode breaks down, the subtraction value obtained by subtracting the voltage value from the set value will not become a negative value, thus making it easy to grasp the state of the voltage value.

[0033] [4] In any of the above [1] to [3] ground fault detection devices, the determination unit may determine that a ground fault has occurred in the conductive path if the product of the evaluation value and the current value detected by the current detection unit, or the correction value obtained by correcting the product, reaches a threshold.

[0034] The ground fault detection device described in [4] above uses the product of the evaluation value and the current value, or its correction value, which increases when a ground fault occurs. Therefore, it can use a value with a larger change in state to determine the ground fault. Thus, the ground fault detection device can detect the occurrence of ground faults in the conductive path more accurately.

[0035] [5] In the ground fault detection device of [4] above, the evaluation value can be a value obtained by subtracting the voltage value detected by the voltage detection unit from a predetermined set value. The determination unit can determine that a ground fault has occurred in the conductive path when the product of the evaluation value and the current value detected by the current detection unit reaches a threshold.

[0036] The ground fault detection device described in [5] above can determine the ground fault by using the product of the evaluation value and the current value, which increases when the ground fault occurs, based on the simple calculation formula that determines that the smaller the voltage value, the larger the evaluation value.

[0037] [Details of the embodiments disclosed herein]

[0038] <Implementation Method 1>

[0039] Figure 1 The vehicle system 1 shown is, for example, installed in a hybrid electric vehicle. The vehicle system 1 includes a vehicle power supply unit 10, a first load 11, a second load 12, and a conductive path 20. The vehicle power supply unit 10 is a structure that supplies power to the first load 11 and the second load 12 via the conductive path 20. The conductive path 20 is a path for supplying power from the first power source 31 and the second power source 32 (described later) to the first load 11 and the second load 12.

[0040] The first load 11 and the second load 12 are electrical loads that operate by receiving power from the first power source 31 and the second power source 32, described later. The first load 11 and the second load 12 are, for example, an electric motor, an electric power steering system, a shift-by-wire system, etc. The first load 11 and the second load 12 are electrically connected to the conductive path 20.

[0041] In this disclosure, the term "electrical connection" preferably refers to a structure in which the two connected objects are connected in a state of mutual conduction (a state in which current can flow) so that their potentials are equal. However, it is not limited to this structure. For example, an "electrical connection" can also be a structure in which an electrical component is sandwiched between two connected objects and the two connected objects are connected in a state of conduction.

[0042] The conductive path 20 has a first conductive path 21 and a second conductive path 22. The first conductive path 21 is electrically connected to the second conductive path 22. The first power supply 31 and the first load 11 are electrically connected to the first conductive path 21. The second power supply 32 and the second load 12 are electrically connected to the second conductive path 22.

[0043] The vehicle-mounted power supply unit 10 includes a first power source 31, a second power source 32, a cut-off mechanism 40, and a ground fault detection device 50. The first power source 31 and the second power source 32 are, for example, power sources such as lithium-ion batteries and double-layer capacitors.

[0044] The cutting mechanism 40 is positioned between the conductive paths 20. The cutting mechanism 40 is located between the first conductive path 21 and the second conductive path 22. The cutting mechanism 40 functions to switch between an energized state and an inactive state between the first power supply 31 and the second power supply 32 based on a control signal from the control unit 53 (described later).

[0045] like Figure 2 As shown, the cutting mechanism 40 includes multiple cutting section units 60, multiple first Zener diodes 71, and multiple second Zener diodes 72. Furthermore, the number of cutting section units 60 is not limited and can be arbitrary. The multiple cutting section units 60 are connected in parallel. Each cutting section unit 60 includes a first cutting section 61 and a second cutting section 62. The first cutting section 61 and the second cutting section 62 are configured, for example, as N-channel MOSFETs. The first cutting section 61 and the second cutting section 62 cut off the conductive path 20. The first cutting section 61 cuts off the power supply from the first conductive path 21 to the second conductive path 22. The drain of the first cutting section 61 is electrically connected to the first conductive path 21. The source of the first cutting section 61 is electrically connected to the source of the second cutting section 62. The second cutting section 62 cuts off the power supply from the second conductive path 22 to the first conductive path 21. The drain of the second cutting section 62 is electrically connected to the second conductive path 22. Control signals (on or off signals) from the control unit 53, described later, are input to the gate of the first cut-off section 61 and the gate of the second cut-off section 62.

[0046] The first Zener diode 71 and the second Zener diode 72 are examples of the "Zener diode" of the present invention. The first Zener diode 71 is connected in parallel with the first cutoff portion 61. The anode of the first Zener diode 71 is electrically connected to the second conductive path 22 via the second cutoff portion 62 and the second Zener diode 72. Specifically, the anode of the first Zener diode 71 is electrically connected to the source of the first cutoff portion 61 and the source of the second cutoff portion 62. The cathode of the first Zener diode 71 is electrically connected to the first conductive path 21 and the drain of the first cutoff portion 61. The second Zener diode 72 is connected in parallel with the second cutoff portion 62. The anode of the second Zener diode 72 is electrically connected to the first conductive path 21 via the first cutoff portion 61 and the first Zener diode 71. Specifically, the anode of the second Zener diode 72 is electrically connected to the source of the first cutoff portion 61 and the source of the second cutoff portion 62. The cathode of the second Zener diode 72 is electrically connected to the drain of the second conductive path 22 and the second cutoff portion 62. The first Zener diode 71 and the second Zener diode 72 have the same structure, for example, and the breakdown voltage of the first Zener diode 71 is the same as that of the second Zener diode 72.

[0047] The ground fault detection device 50 functions to detect ground faults in the conductive path 20. The ground fault detection device 50 includes a voltage detection unit 51, a current detection unit 52, and a control unit 53.

[0048] The voltage detection unit 51 is configured, for example, as a known voltage detection circuit. The voltage detection unit 51 detects the voltage of the first conductive path 21 and outputs a signal corresponding to the voltage of the first conductive path 21. The signal corresponding to the voltage of the first conductive path 21 is input to the control unit 53.

[0049] The current detection unit 52 is positioned between the first conductive paths 21. The current detection unit 52 is configured, for example, to include a resistor and a differential amplifier, and to output a value representing the current flowing in the first conductive path 21 (specifically, an analog voltage corresponding to the value of the current flowing in the first conductive path 21) as a current value. The current value output from the current detection unit 52 is configured to be input to the control unit 53, for example.

[0050] The control unit 53 is an example of the "determination unit" of the present invention. The control unit 53 is configured, for example, as an information processing device with arithmetic and information processing functions. The control unit 53 can be configured as a microcomputer or as an information processing device other than that. The control unit 53 determines whether a ground fault has occurred in the conductive path 20 (e.g., the second load 12) based on the voltage value detected by the voltage detection unit 51 (hereinafter also referred to as the detection voltage) and the current value detected by the current detection unit 52 (hereinafter also referred to as the detection current). Specifically, the control unit 53 determines whether a ground fault has occurred in the conductive path 20 (e.g., the second load 12) based on the evaluation value and the detection current.

[0051] The evaluation value is determined by increasing the value as the detection voltage decreases. The evaluation value is, for example, based on a predetermined setpoint and the detection voltage. The setpoint is, for example, a fixed value preset by the control unit 53 during the circuit design of the vehicle system 1. Alternatively, the setpoint may be set as a variable by the control unit 53 and determined at each specified time (such as when the ignition switch is switched to the ON state) using a predetermined formula or table (a table showing the setpoint and other variables).

[0052] The evaluation value is, for example, a value obtained by subtracting the detection voltage from a set value. For instance, if the set value is set to A and the detection voltage is set to V, the evaluation value is represented by AV. Thus, by reflecting the difference between the reference value (set value) and the detection voltage in the evaluation value, a method can be implemented where a smaller detection voltage results in a larger evaluation value. The set value A is a value larger than the output voltage of the first power supply 31 and the output voltage of the second power supply 32. Therefore, in the event of a ground fault in the conductive path 20, the evaluation value remains positive and increases. The set value A is a value larger than the breakdown voltage of the Zener diodes 71 and 72. Even if a surge voltage or similar event occurs in the conductive path 20 and the detection voltage increases to the point where the Zener diodes 71 and 72 break down, the subtraction value obtained by subtracting the detection voltage from the set value will not become negative in the event of a ground fault in the second conductive path 22, making it easier to monitor the state of the detection voltage.

[0053] The control unit 53 compares the evaluation value with the product of the detected current and a threshold. For example, the threshold is set to be greater than the power (product of the detected voltage and the detected current) when an inrush current is generated in the conductive path 20. The threshold is, for example, a value that is 1.5 times the power (product of the detected voltage and the detected current) when an inrush current is generated in the conductive path 20. If the product of the evaluation value and the detected current reaches the threshold, the control unit 53 determines that a ground fault has occurred in the conductive path 20.

[0054] For example, consider the case where power is supplied from the first power source 31 to the first load 11 and the second load 12. When a ground fault occurs in the conductive path 20, both the evaluation value and the detection current increase. Therefore, the control unit 53 can detect the ground fault in the conductive path 20 by understanding the increase in both the evaluation value and the current value. In particular, by using the product of the evaluation value and the current value, which both increase when a ground fault occurs, for ground fault determination, a value with a larger change in state can be used to determine the ground fault. When a surge voltage is applied to the conductive path 20, the detection voltage changes and the evaluation value changes; on the other hand, it is difficult for the detection current to change (the product of the evaluation value and the detection current is smaller than that during a ground fault), thus suppressing the possibility of mistakenly detecting the surge voltage as a ground fault. Furthermore, when an inrush current flows into the conductive path 20, the detection current increases; on the other hand, it is difficult for the evaluation value to change, thus suppressing the possibility of mistakenly detecting the inrush current as a ground fault. Therefore, the ground fault detection device 50 can more accurately detect the occurrence of a ground fault in the conductive path 20.

[0055] When the control unit 53 determines that a ground fault has occurred in the conductive path 20, it outputs a control signal (disconnect signal) to the disconnection mechanism 40 (the gate of the first disconnection unit 61 and the gate of the second disconnection unit 62). Based on the control signal (disconnect signal) from the control unit 53, the disconnection mechanism 40 switches the first power supply 31 and the second power supply 32 from an on-state to an off-state. Therefore, the vehicle's power system (e.g., the power system on the first conductive path 21 side) can be separated from the ground fault location (e.g., the second load 12), suppressing voltage drop in the power system and achieving voltage stabilization.

[0056] Figure 3 It means Figure 1 This is an explanatory diagram illustrating an example of the time-varying changes in the detected current and the time-varying changes in the detected voltage in the vehicle-mounted system 1. Hereinafter, the case of supplying power from the first power source 31 to the first load 11 and the second load 12 is considered. For example... Figure 3 As shown, when a ground fault occurs in conductive path 20 (e.g., the second load 12), the detection voltage drops sharply, and the detection current begins to increase. When the ground fault detection device 50 detects a ground fault and the disconnection mechanism 40 initiates disconnection control of conductive path 20, the detection current begins to drop from the normal operating voltage (the output voltage of the first power supply 31), and a surge voltage is generated in conductive path 20. For example, when a surge voltage is generated, the Zener diode (e.g., the first Zener diode 71) breaks down, and the detection voltage is clamped to the breakdown voltage. After the disconnection mechanism 40 completes disconnection control of conductive path 20, both the detection voltage and the detection current are in the same state as before the ground fault occurred.

[0057] Figure 4 It is a schematic representation of the meaning of the word. Figure 1 An illustration of an example of the time-varying evaluation value detected by the vehicle's onboard system 1. The evaluation value (AV) is determined by... Figure 4 The shaded area shown represents the value. The setpoint A is a value greater than the output voltage of the first power supply 31. Therefore, in the event of a ground fault in the conductive path 20 (e.g., the second load 12), the evaluation value remains positive and increases. After the cut-off control by the cut-off mechanism 40 begins, a surge voltage is generated, and the Zener diode (e.g., the first Zener diode 71) breaks down. However, since the setpoint A is a value greater than the breakdown voltage of the Zener diodes 71 and 72, the evaluation value (AV) will not become negative.

[0058] Figure 5 It means by Figure 1 An explanatory diagram illustrating an example of the time variation of the product of the detected voltage and detected current (the so-called power value) and the time variation of the product of the evaluation value and the current value detected by the vehicle-mounted system 1. (See diagram for example.) Figure 5 As shown, after a ground fault occurs in conductive path 20, the product of the evaluation value and the current value increases at a greater rate than the product of the detection voltage and the detection current. Therefore, the ground fault detection device 50 can use the value (product of the evaluation value and the current value) that changes significantly with time to determine the ground fault.

[0059] like Figure 5 As shown, when the disconnection mechanism 40 initiates the disconnection control of the conductive path 20, the product of the detected voltage and the detected current increases sharply due to the generation of the surge voltage. On the other hand, after the disconnection mechanism 40 initiates the disconnection control of the conductive path 20, the product of the evaluation value and the current value decreases sharply. Therefore, by using the product of the evaluation value and the current value for ground fault determination, the ground fault detection device 50 does not detect a sharp increase in power based on the surge voltage after the disconnection control begins, thereby suppressing false detections of ground faults based on surge voltage.

[0060] Figure 6 It means in Figure 1 This is an illustration of an example of the time variation of the detection current and the time variation of the power value (the product of the detection voltage and the detection current) in the vehicle-mounted system 1 when an impulse voltage is generated in the conductive path 20. Figure 6As shown, when an inrush current is generated, the maximum detected current (also called the inrush current value) detected by the current detection unit 52 is 72A. The maximum detected power value when the inrush current is generated is 1050W. Here, for example, a value approximately 1.5 times the inrush current value (108A) is used as the threshold current for determining the occurrence of a ground fault in the conductive path 20. For example, a value approximately 1.5 times the maximum power value when the inrush current is generated (1580W) is used as the threshold power for determining the occurrence of a ground fault in the conductive path 20.

[0061] Figure 7 It means in Figure 1 This is an illustration of an example of the time variation of the detection current and the time variation of the product of the evaluation value and the detection current in the case of a ground fault occurring in the conductive path 20 of the vehicle-mounted system 1. Figure 7 As shown, the product of the evaluation value and the detection current increases over time, reaching the threshold power (1580W) at time t1. The setpoint included in the evaluation value is 30. The detection current increases over time, reaching the threshold current (108A) at time t2. The time t1 for the product of the evaluation value and the detection current to reach the threshold power is approximately 30μs earlier than the time t2 for the detection current to reach the threshold current. This is because, by using the product of the evaluation value and the current value, which both increase when a ground fault occurs, it is possible to determine a ground fault using a value that changes significantly.

[0062] Next, the effects of the structures involved in this disclosure will be illustrated.

[0063] In the ground fault detection device 50 of this disclosure, the control unit 53 determines whether a ground fault has occurred in the conductive path 20 based on an evaluation value and a current value detected by the current detection unit 52. The evaluation value is a value that increases as the voltage detected by the voltage detection unit 51 decreases. Therefore, when a ground fault occurs in the conductive path 20, both the evaluation value and the current value increase, allowing for the detection of a ground fault in the conductive path 20 by recognizing these increases. When a surge voltage is applied to the conductive path 20, the evaluation value changes; however, changes in the current value are less likely to occur, thus suppressing false detections of ground faults based on surge voltage. When an inrush current flows into the conductive path 20, the current value increases; however, changes in the evaluation value are less likely to occur, thus suppressing false detections of ground faults based on inrush current. Therefore, the ground fault detection device 50 can more accurately detect the occurrence of ground faults in the conductive path 20.

[0064] In the ground fault detection device 50 disclosed herein, the evaluation value is a value obtained by subtracting the voltage value detected by the voltage detection unit 51 from a predetermined set value. Therefore, the ground fault detection device 50 can realize a method of determining that the smaller the voltage value, the larger the evaluation value, by reflecting the difference between the voltage value and the set value in the evaluation value.

[0065] In the ground fault detection device 50 disclosed herein, a first Zener diode 71 is included. The anode of the first Zener diode 71 is electrically connected to the second conductive path 22, and the cathode is electrically connected to the first conductive path 21. The first Zener diode 71 is connected in parallel with the first cut-off portion 61. The set value is greater than the breakdown voltage of the first Zener diode 71. Therefore, even if a ground fault occurs in the second conductive path 22, and the voltage value of the first conductive path 21 increases to the point where the first Zener diode 71 breaks down due to a surge voltage, the subtraction value obtained by subtracting the voltage value from the set value will not be negative, thus making it easy to grasp the state of the voltage value.

[0066] In the ground fault detection device 50 of this disclosure, when the product of the evaluation value and the current value detected by the current detection unit 52 reaches a threshold, the control unit 53 determines that a ground fault has occurred in the conductive path 20. Therefore, the ground fault detection device 50 uses the product of the evaluation value and the current value, which increases when a ground fault occurs, and thus can use a value with a larger change in state to determine the ground fault. Therefore, the ground fault detection device 50 can more accurately detect the occurrence of ground faults in the conductive path 20.

[0067] In the ground fault detection device 50 of this disclosure, the evaluation value is a value obtained by subtracting the detection voltage from a set value. When the product of the evaluation value and the detection current reaches a threshold, the control unit 53 determines that a ground fault has occurred in the conductive path 20. Thus, the ground fault detection device 50 can determine a ground fault by using the product of the evaluation value and the current value, which increases when a ground fault occurs, based on a simple calculation formula that determines that the smaller the voltage value, the larger the evaluation value.

[0068] <Other Implementation Methods>

[0069] This disclosure is not limited to the embodiments described above and the accompanying drawings. For example, all combinations of features of the embodiments described above or later can be made without contradiction. Furthermore, any feature of the embodiments described above or later can be omitted unless explicitly stated as an essential feature. Moreover, the embodiments described above can also be modified in the following ways.

[0070] In Implementation 1, the subtraction value obtained by subtracting the detection voltage from the set value is shown as the evaluation value. However, any other structure is possible as long as the value increases as the detection voltage decreases. For example, the evaluation value could also be the reciprocal of the detection voltage.

[0071] In Embodiment 1, an example is shown where the setpoint A included in the evaluation value for ground fault determination is a fixed value or a variable, but it can also be other values. For example, the setpoint A can also be a structure that corrects a fixed value at regular intervals (such as when the ignition switch is switched to the ON state). For example, the setpoint A can also be a value determined based on temperature (such as the temperature of the conductive path 20).

[0072] In Embodiment 1, the evaluation value is set as a subtraction operation value obtained by subtracting the detection voltage from the set value. However, other values ​​may also be used as the value based on the set value and the detection voltage. For example, the evaluation value may also be the absolute value of the difference between the set value and the detection voltage. In this case, by setting the set value to a value larger than the output voltage of the power supply (first power supply 31 and second power supply 32), the set value increases positively in the event of a ground fault in the conductive path 20. Alternatively, the evaluation value may be a value obtained by multiplying the set value by a predetermined number (constant, etc.) on the detection voltage. Furthermore, the evaluation value may also be a subtraction operation value obtained by subtracting the detection voltage from the set value, or a value obtained by multiplying the absolute value of the difference between the set value and the detection voltage by a predetermined number (constant, etc.).

[0073] In Implementation 1, the product of the evaluation value and the detection current was used in the ground fault determination. However, other values ​​can be used as long as the ground fault occurrence is determined based on the evaluation value and the detection current. For example, the occurrence of a ground fault can also be determined based on the value obtained by adding the evaluation value and the detection current.

[0074] In Implementation 1, in the ground fault determination, the product of the evaluation value and the detection current and a threshold are compared. However, it is also possible to compare the correction value (the correction value obtained by correcting the product of the evaluation value and the detection current by adding or multiplying by a predetermined value) with the threshold.

[0075] In Implementation 1, in the ground fault determination, if the product of the evaluation value and the detection current reaches a threshold, it is determined that a ground fault has occurred in the conductive path 20. However, it is also possible to determine that a ground fault has occurred in the conductive path 20 if the increase rate of the product of the evaluation value and the detection current reaches a predetermined value.

[0076] In Embodiment 1, an example is shown of detecting a ground fault occurring in a second conductive path 22 (a second load, etc.) based on the voltage and current values ​​detected in the first conductive path 21. However, it is also possible to detect a ground fault occurring in the first conductive path 21 (a first load, etc.) based on the voltage and current values ​​detected in the second conductive path 22 (formed in a structure in which a voltage detection unit and a current detection unit are provided in the second conductive path 22).

[0077] Furthermore, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope set forth in the claims or their equivalents.

[0078] Label Explanation

[0079] 1…In-vehicle system

[0080] 10…Vehicle-mounted power supply unit

[0081] 11…First Load

[0082] 12…Second load

[0083] 20…conductive path

[0084] 21…First conductive path

[0085] 22…Second conductive path

[0086] 31…First Power Supply

[0087] 32…Second power supply

[0088] 40…cutting mechanism

[0089] 50…Ground fault detection device

[0090] 51…Voltage Detection Section

[0091] 52… Current Detection Section

[0092] 53…Control Department (Decision-Making Department)

[0093] 60… Cut-off section unit

[0094] 61…First Cutting Section

[0095] 62…Second Cutting Section

[0096] 71… First Zener Diode (Zener Diode)

[0097] 72… Second Zener diode (Zener diode).

Claims

1. A ground fault detection device for detecting ground faults in a vehicle-mounted system comprising a conductive path, wherein the conductive path is a path supplying power from a power source to a load, wherein, The ground fault detection device has the following features: The voltage detection unit detects the voltage value of the conductive path; The current detection unit detects the current value of the conductive path; and The determination unit determines whether a ground fault has occurred in the conductive path based on an evaluation value and the current value detected by the current detection unit. The evaluation value is a value that increases as the voltage value detected by the voltage detection unit decreases. The evaluation value is a subtraction value obtained by subtracting the voltage value from a predetermined set value.

2. The grounding fault detection device according to claim 1, wherein, The vehicle-mounted system includes: A first conductive path, wherein the power supply is electrically connected to the first conductive path; A second conductive path, wherein the load is electrically connected to the second conductive path; The cutting section is disposed between the first conductive path and the second conductive path to cut off the power supply from the first conductive path to the second conductive path. and A Zener diode, wherein the anode of the Zener diode is electrically connected to the second conductive path, the cathode of the Zener diode is electrically connected to the first conductive path, and the Zener diode is connected in parallel with the cut-off portion. The voltage detection unit detects the voltage value of the first conductive path. The set value is greater than the breakdown voltage of the Zener diode.

3. The grounding fault detection device according to claim 1 or 2, wherein, If the product of the evaluation value and the current value detected by the current detection unit, or the correction value obtained by correcting the product, reaches a threshold, the determination unit determines that a grounding fault has occurred in the conductive path.

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