Leakage judgment system

Abstract

A leakage judgment system (50) is provided for judging whether leakage occurs, the leakage judgment system (50) comprising: a capacitor (C1) having a first end connected to a cathode side power path (L1) and a second end connected to a ground portion (G1); and a switch (SW3) arranged in an electrical path formed in parallel with the capacitor. When the capacitor (C1) is discharged and a predetermined period of time has passed after a controller sets a power-on state between the cathode side power path (L1) and the ground portion (G1) by placing the switch (SW3) in a power-on position, the controller sets a power-on off state between the cathode side power path (L1) and the ground portion (G1) by placing the switch (SW3) in a power-on off position, thereby allowing the capacitor (C1) to charge. The controller then detects a voltage value of the capacitor (C1) and judges whether leakage occurs based on the voltage value.

Description

Technical Field

[0001] An embodiment of the present disclosure relates to a leakage determination system, which is used to determine whether leakage occurs in a circuit including a voltage generator. Background Art

[0002] A known leakage judgment system (i.e., insulation state detection system) judges whether leakage (i.e., non-insulation state) occurs in an electrical system mounted on a vehicle based on a decrease in ground fault resistance using a flying capacitor (i.e., detection capacitor). Such a leakage judgment system charges a flying capacitor disposed between a power line of a voltage generator and a ground line (e.g., a vehicle body), and calculates the ground fault resistance (i.e., insulation resistance between the power line and the ground line) based on a voltage generated in the flying capacitor. The leakage judgment system then judges whether the insulation state is maintained (i.e., whether leakage occurs).

[0003] Generally, in such a leakage judgment system, there are parasitic capacitance and noise removal capacitors between the power line and the ground line, and sometimes the leakage judgment system is greatly affected. That is, since the ground capacitance is also charged at the same time, the voltage of the flying capacitor is erroneously detected.

[0004] More specifically, when the ground capacitance is charged together with the flying capacitor, the amount of change in the charging voltage of the flying capacitor (i.e., the change in the CR time constant) varies according to the value of the ground capacitance. Specifically, when the ground capacitance is relatively large, the amount of change in the charging voltage of the flying capacitor increases, and the detection error is larger at the beginning of charging than when the ground capacitance is relatively small.

[0005] In view of this, the known leakage judgment system delays the time to detect the charging voltage of the flying capacitor by considering the time of charging the grounding capacitor. Specifically, when a given period of time has passed after the start of charging, the charging voltage of the flying capacitor is detected multiple times, and the ground fault resistance is calculated based on the rate of change of the voltage value (i.e., the slope of the voltage value). Therefore, even if there is a grounding capacitor between the power line and the ground line and it has a great influence on the detection of the charging voltage, the detection accuracy of the ground fault resistance can be improved.

[0006] However, even if the known leakage judgment system can reduce the detection error caused by the grounding capacitance, in the case where the grounding capacitance exists, the rate of change of the voltage value is not equal even after a given period of time has passed since the start of charging, unlike the case where the grounding capacitance does not exist. That is, the detection error still exists in the known leakage judgment system. In addition, the larger the grounding capacitance, the larger the detection error. Summary of the invention

[0007] Therefore, in view of the above-mentioned problems, especially as discussed in Japanese Unexamined Patent Application Publication No. 2016-99323, the present invention is made, and the purpose of the present invention is to provide a novel leakage judgment system, which can improve the detection accuracy. That is, one aspect of the present disclosure provides a novel leakage judgment system (50) for judging whether leakage occurs between a power path (L1, L2) connected to a power terminal of a DC power supply (10) and a ground portion (G1). The leakage judgment system includes: a capacitor (C1), the capacitor (C1) having a first end connected to the power path and a second end connected to the ground portion; at least one first switch (SW3 to SW7), the at least one first switch (SW3 to SW7) is configured in an electrical path formed in parallel with the capacitor to switch the state between the power path and the ground portion between a power-on state and a power-off state; and a capacitor voltage detector (52), the capacitor voltage detector (52) detects the voltage value of the capacitor. The leakage judgment system also includes a controller (53) to control the at least one first switch. The controller sets a power-on state between the power path and the ground by placing at least one first switch in a power-on position. When a given period of time has passed after the power-on state is set between the power path and the ground, the controller places at least one first switch in a power-on off position and allows the capacitor to charge. The controller then detects a voltage value of the capacitor and determines whether leakage occurs based on the voltage value.

[0008] According to the configuration as described above, by rotating the first switch, a power-on / off state is set between the power path and the grounding part, and after a given period of time has passed after the capacitor is discharged, the capacitor is controlled to charge, and by rotating the first switch in the opposite direction, a power-on state is set between the power path and the grounding part. That is, the grounding capacitance such as parasitic capacitance existing between the power path and the grounding part is charged before the capacitor starts to charge. Therefore, when the capacitor is charged, the power supply of the grounding capacitance can be suppressed or reduced. Therefore, even if the grounding capacitance changes, the detection error can be reduced. In addition, the period from the start of charging to the time of detecting leakage can be shortened.

[0009] Another aspect of the present disclosure provides a novel leakage judgment system, which is connected to both a cathode side power path (L1) connected to a positive side terminal (P1) of a DC power supply (10) and an anode side power path (L2) connected to an anode side terminal (P2) of the DC power supply. The leakage judgment system (50) judges whether leakage occurs between the cathode side power path and the ground portion (G1), and whether leakage occurs between the anode side power path and the ground portion. The leakage judgment system also includes: a capacitor (C1), the capacitor (C1) having a first end connected to the cathode side power path and a second end connected to the anode side power path, respectively; and a cathode side switch (SW1), the cathode side switch (SW1) switching the state between the cathode side power path and the capacitor between a power-on state and a power-off state. The cathode side switch includes a first end connected to the cathode side power path and a second end connected to the first end of the capacitor, respectively. The leakage judgment system also includes an anode side switch (SW2), and the anode side switch (SW2) is used to switch the state between the anode side power path and the capacitor between the power-on state and the power-off state. The anode side switch includes a first end connected to the anode side power path and a second end connected to the second end of the capacitor. The leakage judgment system also includes a first grounding side switch (SW3), and the first grounding side switch (SW3) switches the state between the grounding part and the capacitor between the power-on state and the power-off state. The first grounding side switch includes a first end connected to the grounding part and a second end connected to the first end of the capacitor. The leakage judgment system also includes a second grounding side switch (SW4), and the second grounding side switch (SW4) switches the state between the grounding part and the capacitor between the power-on state and the power-off state. The second grounding side switch includes a first end connected to the grounding part and a second end connected to the second end of the capacitor. The leakage judgment system further includes: a capacitor voltage detector (52) for detecting a voltage value of the capacitor; and a controller (53) for controlling each of the first to fourth switches. When the cathode side switch is in the power-on position and the anode side switch is in the power-on off position, the capacitor is discharged, and when a predetermined time has passed after the controller sets the power-on state between the cathode side power supply path and the ground by putting the first ground side switch in the power-on position, the controller allows the capacitor to be charged by putting the second ground side switch in the power-on position and putting the first ground side switch in the power-on off position. The controller then detects the voltage value of the capacitor as the first voltage value.In addition, when the cathode side switch is in the power-on off position and the anode side switch is in the power-on position, the capacitor is discharged, and when a predetermined period of time has passed after the controller sets the power-on state between the anode side power path and the ground by setting the second ground side switch in the power-on position, the controller allows the capacitor to be charged by setting the first ground side switch in the power-on position and the second ground side switch in the power-on off position. The controller then detects the voltage value of the capacitor as the second voltage value, and judges whether leakage occurs based on the first voltage value and the second voltage value. According to the configuration as described above, the power-on off state is set between the power path and the ground, and when a predetermined period of time has passed after the capacitor is discharged, the capacitor is charged, and the power-on state is set between the power path and the ground. That is, the ground capacitance such as parasitic capacitance existing between the power path and the ground is charged before the capacitor starts to charge. Therefore, when the capacitor is charged, the power supply of the ground capacitance can be suppressed or reduced. Therefore, even if the ground capacitance changes, the detection error can be reduced. In addition, the period of time from the start of charging to the time of detecting leakage can be shortened.

[0010] In addition, with the above-described configuration of the embodiment of the present disclosure, a single capacitor can be shared to determine the insulation state between the cathode side power path and the ground portion and between the anode side power path and the ground portion, respectively. Therefore, the circuit can be simplified by reducing the number of circuit elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be more fully understood, and its attendant advantages and features will be more readily appreciated, by referring to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0012] Figure 1 is a diagram showing an exemplary circuit of the electric leakage determination system according to the first embodiment of the present disclosure;

[0013] Figure 2 is a flowchart showing an exemplary ground fault resistance calculation process according to the first embodiment of the present disclosure;

[0014] Figure 3A and Figure 3B is a diagram generally illustrating exemplary current flow according to one embodiment of the present invention;

[0015] Figure 4A and Figure 4B is also a diagram generally illustrating exemplary current flow according to one embodiment of the present invention;

[0016] Figure 5 is a timing chart showing time variation of charging voltage in a conventional system;

[0017] Figure 6is a timing diagram showing an exemplary time variation of a charging voltage according to one embodiment of the present disclosure;

[0018] Figure 7 is a diagram showing an exemplary circuit of a leakage determination system according to a second embodiment of the present disclosure;

[0019] Figure 8 is a flowchart showing an exemplary ground fault resistance calculation process according to the second embodiment of the present disclosure;

[0020] Fig. 9 is a diagram showing an exemplary circuit of a leakage determination system according to a third embodiment of the present disclosure;

[0021] Fig.10 : is a flowchart illustrating an exemplary ground fault resistance calculation process according to the third embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Referring now to the drawings, wherein like reference numerals designate like or corresponding parts throughout the several views thereof, and reference Figure 1 , and applicable drawings, describe an exemplary electrical leakage judgment system of a first embodiment of the present disclosure, which is applied to a vehicle, such as a hybrid vehicle, a motor, etc., having a rotating electric motor as a main vehicle-mounted machine.

[0023] like Figure 1 As shown, the vehicle-mounted motor control system of this embodiment of the present disclosure includes a battery pack 10 , a motor 20 , an inverter 30 , and a leakage determination system 50 .

[0024] The battery pack 10 is electrically connected to the motor 20 via the inverter 30. The battery pack 10 is, for example, a secondary battery having a voltage between terminals exceeding 100V, and is formed by connecting a plurality of battery modules in series. Each battery module is also formed by connecting a plurality of battery cells in series. As the battery cells, for example, lithium-ion secondary batteries and nickel-hydrogen secondary batteries can be used. The battery pack 10 corresponds to a DC (direct current) power supply.

[0025] The motor 20 is a rotary electric machine used as a main vehicle-mounted machine and is capable of transmitting power to drive wheels (not shown). In this embodiment of the present disclosure, a three-phase permanent magnet synchronous motor is used as the motor 20 .

[0026] The inverter 30 includes a full-bridge circuit having the same number of upper arms and lower arms as the number of phases of the windings. The current flowing in each winding is adjusted by turning on / off a switch (eg, a semiconductor switching element) provided in each arm.

[0027] In addition, an inverter control system (not shown) is provided in the inverter 30. The inverter control system performs power-on control by turning on / off a switch in the inverter 30 based on various detection information and a request for power operation driving and power generation generated in the motor 20. By doing so, the inverter control system supplies power from the battery pack 10 to the motor 20 via the inverter 30 so that the motor 20 performs power operation driving. In addition, the inverter control system also causes the motor 20 to generate power based on the moving power transmitted from the driving wheel, converts the generated power, and supplies the conversion result to the battery pack 10 via the inverter 30, thereby charging the battery pack 10.

[0028] The cathode side terminal of an electric load such as an inverter 30 is connected to a cathode side power supply path L1 connected to the cathode side power supply terminal of the battery pack 10. The cathode side power supply path L1 is electrically insulated from a ground portion G1 of a vehicle body or the like. Such an insulation state (ground insulation resistance) between the cathode side power supply path L1 and the ground portion G1 can be represented by a ground fault resistance Rp. In addition, between the cathode side power supply path L1 and the ground portion G1, there are capacitors and parasitic capacitance for noise elimination, and the whole is represented by a ground capacitance Cp.

[0029] The anode side terminal of an electric load such as an inverter 30 is connected to the anode side power supply path L2 connected to the anode side power supply terminal of the battery pack 10. The anode side power supply path L2 is also electrically insulated from the ground G1. Such an insulation state (i.e., ground insulation resistance) between the anode side power supply path L2 and the ground G1 can be represented by a ground fault resistance Rn. In addition, between the anode side power supply path L2 and the ground G1, there is a ground capacitance such as a capacitor for noise elimination and a parasitic capacitance, and the whole is represented by a ground capacitance Cn.

[0030] The cathode side power path L1 and the anode side power path L2 are connected to the leakage judgment system 50. The leakage judgment system 50 detects the ground fault resistances Rp and Rn, and judges whether the cathode side power path L1 and the anode side power path L2 are normally insulated from the ground part G1, that is, whether leakage exists. The leakage judgment system 50 is described in more detail below.

[0031] like Figure 1 As shown, the leakage determination system 50 includes: a so-called flying capacitor type insulation resistance detection circuit 51; an A / D (Analog / Digital) converter 52 as a capacitor voltage detector; and a controller 53.

[0032] The insulation resistance detection circuit 51 includes an external terminal P1 connected to the cathode side power supply path L1 , an external terminal P2 connected to the anode side power supply path L2 , and an external terminal P3 connected to the ground portion G1 .

[0033] A first electrical path L11 is provided between the external terminal P1 and the external terminal P3, specifically, between the cathode side power path L1 and the ground G1. In the first electrical path L11, two switches SW1 and SW3 and a resistor R1 are arranged. One end of the switch SW1 is connected to the cathode side power path L1 through the external terminal P1. The other end of the switch SW1 is connected in series to one end of the switch SW3. The other end of the switch SW3 is also connected in series to one end of the resistor R1. The other end of the resistor R1 is connected to the ground G1 through the external terminal P3.

[0034] The second electrical path L12 is also provided between the connection point M1 between the switch SW3 and the resistor R1 and the external terminal P2. Specifically, the second electrical path L12 is provided between the connection point M1 and the anode side power path L2. In the second electrical path L12, two switches SW2 and SW4 are provided. One end of the switch SW2 is connected to the anode side power path L2 through the external terminal P2. The other end of the switch SW2 is connected in series to one end of the switch SW4. The other end of the switch SW4 is connected in series to one end of the resistor R1 via the connection point M1.

[0035] In addition, the insulation resistance detection circuit 51 includes a capacitor C1 which is a so-called flying capacitor. One end of the capacitor C1 is connected to a connection point M2 between the switches SW1 and SW3. The other end of the capacitor C1 is connected to a connection point M3 between the switches SW2 and SW4.

[0036] Therefore, the electrical path formed by including the connection point M2, the capacitor C1, the connection point M3, the switch SW4 and the connection point M1 is connected in parallel with the electrical path formed by including the connection point M2, the switch SW3 and the connection point M1. Specifically, the switch SW3 is arranged in the electrical path (M2, SW3, MI) connected in parallel with the capacitor C1.

[0037] In addition, the electrical path formed by the connection point M3, capacitor C1, connection point M2, switch SW3 and connection point M1 is connected in parallel with the electrical path formed by the connection point M3, switch SW4 and connection point M1. Specifically, switch SW4 is provided in the electrical path (M3, SW4, M1) connected in parallel with capacitor C1.

[0038] Therefore, the switch SW1 corresponds to the cathode side switch, and the switch SW2 corresponds to the anode side switch. In addition, the switch SW3 corresponds to the first ground side switch, and the switch SW4 also corresponds to the second ground side switch.

[0039] One end of the A / D converter 52 is connected to the connection point M2, and the other end thereof is connected to the ground G1. The A / D converter 52 converts a signal (i.e., an analog signal) input via the connection point M2 into a signal (i.e., a digital signal) suitable for processing in the controller 53, thereby outputting a conversion result.

[0040] The controller 53 is mainly composed of a microcomputer including a CPU (central processing unit), a ROM (read only memory) and a RAM (random access memory), and an I / O (input / output) port. When the CPU runs the program stored in the ROM, the controller 53 provides various functions. Here, the various functions can be provided by electronic circuits as hardware or at least partially by software (i.e., computer processing). The controller 53 can be used to determine whether there is leakage by selectively turning on and off various switches SW1 to SW4 as described below.

[0041] Figure 2 is a flowchart showing an exemplary ground fault resistance calculation process periodically performed by the controller 53. Initially, as shown in the figure, the controller 53 discharges the capacitor C1 and charges the ground capacitance Cn for a given period of time. (in step S101).

[0042] Specifically, Figure 3A As shown, switches SW1, SW3, and SW4 are turned on, while switch SW2 is turned off. In this way, current flows from the battery pack 10 into an electrical path formed by the battery pack 10, switch SW1, switch SW3, resistor R1, grounding portion G1, grounding capacitor Cn, and battery pack 10, thereby charging the grounding capacitor Cn. At the same time, current flows from capacitor C1 into an electrical path formed by capacitor C1, switch SW3, switch SW4, and capacitor C1, thereby discharging capacitor C1.

[0043] Subsequently, the controller 53 allows the capacitor C1 to be charged via the ground fault resistor Rn for a predetermined period of time (in step S102). Figure 3BAs shown, switches SW1 and SW4 are turned on, while switches SW2 and SW3 are turned off. In this way, current flows from the battery pack 10 into an electrical path formed by the battery pack 10, switch SW1, capacitor C1, switch SW4, resistor R1, grounding portion G1, ground fault resistor Rn, and battery pack 10, thereby charging capacitor C1. Here, since the grounding capacitor Cn is charged in step S101, the current mostly flows through the ground fault resistor Rn. Therefore, in steps S101 and S102, switch SW3 corresponds to the first switch, and switch SW4 corresponds to the second switch.

[0044] Subsequently, the controller 53 reads (i.e., detects) the first voltage value Vn (charging voltage value) of the capacitor C1 (in step S103). Specifically, the controller 53 turns on the switch SW4 and turns off the switches SW1 to SW3, thereby inputting the voltage value of the capacitor C1 to the A / D converter 52. Next, the controller 53 reads the voltage value of the capacitor C1 converted by the A / D converter 52 via the A / D converter 52 as the first voltage value Vn. More specifically, the controller 53 detects the peak voltage value output from the capacitor C1 as the first voltage value Vn just after the switches SW1 to SW4 are turned on. Therefore, the A / D converter 52 corresponds to a capacitor voltage detector.

[0045] Next, the controller 53 reads the battery voltage value Vb of the battery pack 10 (in step S104). Here, a method of detecting the battery voltage value Vb is optionally adopted. In addition, in order to charge the capacitor C1, for example, the controller 53 turns on the switches SW1 and SW2, and turns off the switches SW3 and SW4. Next, the controller 53 turns on the switch SW4, and turns off the switches SW1 and SW3, so that the capacitor C1 is discharged. Then, the controller 53 inputs the voltage value of the capacitor C1 to the A / D converter 52. The controller 53 preferably detects such a voltage value as the battery voltage value Vb. Therefore, the A / D converter 52 corresponds to the power supply voltage detector 11. In addition, the controller 53 desirably detects the peak voltage value output from the capacitor C1 just after the switches SW1 to SW4 are turned on as the battery voltage value Vb. Otherwise, by providing a power supply voltage detector in the battery pack 10, the detection result can be obtained from the power supply voltage detector. Therefore, the battery voltage value Vb detected in step S104 is represented by the first battery voltage value Vb.

[0046] Subsequently, the controller 53 allows the capacitor C1 to discharge, and allows the grounding capacitor Cp to charge for a predetermined period of time (in step S105). Figure 4AAs shown, the controller 53 turns on the switches SW2, SW3, and SW4, and turns off the switch SW1. In this way, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the grounding capacitor Cp, the grounding part G1, the switch SW4, the switch SW2, and the battery pack 10, thereby charging the grounding capacitor Cp. At the same time, the current flows from the capacitor C1 into the electrical path formed by the capacitor C1, the switch SW3, the switch SW4, and the capacitor C1, thereby discharging the capacitor C1.

[0047] Subsequently, the controller 53 allows the capacitor C1 to be charged via the ground fault resistor Rp for a predetermined period of time (in step S106). Figure 4B As shown, the controller 53 turns on the switches SW2 and SW3, and turns off the switches SW1 and SW4. In this way, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the ground fault resistor Rp, the grounding part G1, the resistor R1, the switch SW3, the capacitor C1, the switch SW2, and the battery pack 10, thereby charging the capacitor C1. Here, since the grounding capacitor Cp is charged in step S106, the current flows mostly through the ground fault resistor Rp. Therefore, in steps S105 and S106, the switch SW4 corresponds to the first switch, and the switch SW3 corresponds to the second switch.

[0048] Subsequently, the controller 53 reads the second voltage value Vp (i.e., the charging voltage value) of the capacitor C1 (in step S107). Specifically, the controller 53 turns on the switch SW4 and turns off the switches SW1 to SW3, thereby inputting the voltage value of the capacitor C1 to the A / D converter 52. The controller 53 reads the voltage value of the capacitor C1 converted by the A / D converter 52 via the A / D converter 52 as the second voltage value Vp. More specifically, the controller 53 detects the peak voltage value output from the capacitor C1 as the second voltage value Vp just after the switches SW1 to SW4 are turned on.

[0049] Subsequently, similarly to step S105, the controller 53 reads the battery voltage value Vb of the battery pack 10 (in step S108). Here, the battery voltage value Vb detected in step S108 is hereinafter referred to as a second battery voltage value Vb2.

[0050] Subsequently, the controller 53 calculates the ground fault resistances Rn, Rp based on the first voltage value Vn and the first battery voltage value Vb1 and the second voltage value Vp and the second battery voltage value Vb2 (in step S109). More specifically, the controller 53 calculates the composite value of the ground fault resistances Rn, Rp using the first to fourth equations listed below, where T represents a time period, C1 represents a capacitance of the capacitor C1, and R1 represents a resistance value of the resistor R1.

[0051] Vp=Vb2×Q×Rp / (Rp+Rn)...(1)

[0052] Vn=Vb1×Q×Rn / (Rp+Rn)...(2)

[0053] Q=1-E^(-W)...(3)

[0054] W=(Rp+Rn)T / (Rp×Rn+Rn×R1+R1×Rp)C1...(4)

[0055] Then, the controller 53 compares the combined value of the ground fault resistances Rn, Rp calculated in this way with the normal combined value of the ground fault resistances Rn, Rp indicating the insulation state to determine whether there is leakage. When the controller 53 determines that there is leakage (that is, when it determines that there is no insulation state), the controller 53 performs various processes accordingly. For example, the controller 53 outputs a warning or isolates the battery pack 10 from the circuit, etc. Specifically, the controller 53 controls the battery pack 10 to stop supplying power therefrom and charging it.

[0056] Now, the exemplary detection method adopted in this embodiment of the present disclosure is described in comparison with the conventional detection method. First, the conventional detection method is described. In the conventional detection method, when the capacitor C1 is discharged, the grounding capacitors Cn and Cp are not charged. Specifically, Figure 2 In steps S101 and S105, in which the ground fault resistance is calculated, the switches SW1 to SW3 are turned off, and the switch SW4 is turned on, thereby discharging the capacitor C1.

[0057] Here, Figure 5 , a time change in the first voltage value Vn and a time change in the second voltage value Vp obtained by a conventional detection method are shown in FIG. Since the capacitor C1 is discharged during the period from the time point T10 to the time point T11, the voltage of the capacitor C1 becomes zero. Subsequently, when the capacitor C1 is charged by the ground fault resistance Rn during the period from the time point T11 to the time point T12, the charging voltage value of the capacitor C1 changes by receiving the influence of the ground fault resistance Rn and the ground capacitance Cn (that is, the influence of the CR time constant). Here, the voltage value detected at any time during the period from the time point T11 to the time point T12 corresponds to the first voltage value Vn.

[0058] Next, during the period from time point T12 to time point T13, since capacitor C1 is discharged, the voltage value of capacitor C1 becomes zero. Subsequently, during the period from time point T13 to time point T14, when capacitor C1 is charged by ground fault resistance Rp, the charging voltage value of capacitor C1 changes by receiving the influence of ground fault resistance Rp and ground capacitance Cp (i.e., the influence of CR time constant). Here, the voltage value detected at any time during the period from time point T13 to time point T14 corresponds to the second voltage value Vp. Figure 5 In FIG. 1 , the solid line represents the change in voltage when each of the ground fault capacitances Cn, Cp is relatively large, and the dotted line represents the change in voltage when each of the ground fault capacitances Cn, Cp is relatively small.

[0059] Therefore, if Figure 5 As understood, in the conventional detection method, the time variation in the first voltage value Vn and the second voltage value Vp varies according to the value of each of the ground fault capacitors Cn, Cp. Specifically, Figure 5 As shown, when the ground fault capacitance Cn is relatively large (as shown by the solid line), the time variation in the first voltage value Vn increases more than when the ground fault capacitance Cn is relatively small (as shown by the dotted line). In particular, since the first voltage value Vn increases logarithmically, the shorter the time that has passed after the start of charging, the larger the detection error.

[0060] Similarly, when the grounding capacitance Cp is relatively large (as shown by the solid line), the time variation of the second voltage value Vp increases more than when the grounding capacitance Cp is relatively small (as shown by the dotted line). In particular, since the second voltage value Vp increases logarithmically, the shorter the time after charging starts, the larger the detection error.

[0061] Now, refer to Figure 6 The time variation of the first voltage value Vn and the second voltage value Vp obtained by the detection method of this embodiment of the present disclosure is described. At time point T20, in step S101, capacitor C1 is discharged and grounding capacitor Cn is charged. Therefore, during the period from time point T20 to time point T21, the voltage of capacitor C1 becomes zero.

[0062] Subsequently, at time point T21, in step S102, capacitor C1 is charged by ground fault resistor Rn. Therefore, during the period from time point T21 to time point T22, the charging voltage of capacitor C1 changes by receiving the influence of ground fault resistor Rn. However, at this time, since ground capacitor Cn has been charged, the influence of ground capacitor Cn can be almost ignored. In addition, at time point T22, the voltage value of capacitor C1 is detected in step S103 as the first voltage value Vn.

[0063] At time point T23, in step S105, capacitor C1 is discharged, while grounding capacitor Cp is charged. Therefore, during the period from time point T23 to time point T24, the voltage of capacitor C1 becomes zero.

[0064] Subsequently, at time point T24, in step S106, capacitor C1 is charged by ground fault resistance Rp. Therefore, during the period from time point T24 to time point T25, the charging voltage value of capacitor C1 changes by receiving the influence of ground fault resistance Rp. However, at this time, since ground capacitor Cp has been charged, the influence of ground capacitor Cp can be almost ignored. In addition, at time point T25, in step S107, the voltage value of capacitor C1 is detected as the second voltage value Vp.

[0065] like Figure 6 As shown, according to the detection method of this embodiment of the present disclosure, although the values ​​of the grounding capacitances Cn and Cp are different from each other, the time changes of the first voltage value Vp and the second voltage value Vn can be almost equal. Figure 6 As shown, the time variation of the first voltage value Vn generated when the grounding capacitance Cn is relatively large (as shown by the solid line) is similar to the time variation of the first voltage value Vn generated when the grounding capacitance Cn is relatively small (as shown by the dotted line). Therefore, the time variation of the first voltage value Vn corresponds to the voltage value of the capacitor C1 during the period from the time point T21 to the time point T22.

[0066] In addition, as shown in the figure, the time variation of the second voltage value Vp generated when the grounding capacitance Cp is relatively large (as shown by the solid line) is similar to the time variation of the second voltage value Vp generated when the grounding capacitance Cp is relatively small (as shown by the dotted line). Here, the time variation of the second voltage value Vp corresponds to the voltage value of the capacitor C1 during the period from the time point T24 to the time point T25.

[0067] Therefore, by the configuration as described above, advantageous benefits as described below can be obtained.

[0068] According to the construction as described above, after the capacitor C1 is discharged, the switches SW1 and SW3 are turned on, and when a given period of time has passed after the power-on state is set between the cathode side power path L1 and the grounding portion G1, the switch SW3 is placed in the power-on off position, thereby setting the power-on off state between the cathode side power path L1 and the grounding portion G1, and charging the capacitor C1. That is, before the capacitor C1 is charged, the grounding capacitor Cn between the cathode side power path L1 and the grounding portion G1 is controlled to be charged. Therefore, when the capacitor C1 is controlled to be charged, the non-concentrated power supply to the grounding capacitor Cn can be suppressed. Therefore, as Figure 6 As shown in FIG. 1 , even if the grounding capacitance Cn changes, the detection error of the first voltage value Vn can be reduced. Figure 6 As shown, when compared with the conventional detection method, the detection error generated immediately after the capacitor C1 starts to be charged can be further reduced. As a result, the period from when the capacitor C1 starts to be charged to when the first voltage value Vn is detected can be shortened.

[0069] Similarly, after the capacitor C1 is discharged, the switches SW2 and SW4 are turned on, and after a given time has passed since the power-on state is set between the anode side power path L2 and the ground portion G1, the switch SW4 is placed in the power-on off position, thereby setting the power-on off state between the anode side power path L2 and the ground portion G1, and charging the capacitor C1. That is, before the capacitor C1 is charged, the grounding capacitor Cp between the anode side power path L2 and the ground portion G1 is controlled to be charged. Therefore, when the capacitor C1 is controlled to be charged, the non-concentrated power supply to the grounding capacitor Cp can be suppressed. Therefore, as Figure 6 As shown in FIG. 1 , even if the grounding capacitance Cp changes, the detection error of the second voltage value Vp can be reduced. Figure 6 As shown, when compared with the conventional detection method, the detection error generated immediately after the capacitor C1 starts to be charged can be further reduced. As a result, the period from when the capacitor C1 starts to be charged to when the second voltage value Vp is detected can be shortened.

[0070] As described above, the calculation error of each of the ground fault resistances Rn, Rp based on the first voltage value Vn and the second voltage value Vp can be reduced or suppressed, and therefore, the accuracy of the leakage judgment based on the ground fault resistances Rn, Rp can be improved. Since the error generated soon after the charging starts is suppressed when compared with the conventional detection method, the detection period for detecting each of the first voltage value Vn and the second voltage value Vp can also be reduced. That is, the period for detecting leakage can be shortened.

[0071] The controller 53 sets the energization state between the cathode side power path L1 (or the anode side power path L2) and the ground portion G1 so that the grounding capacitors Cn and Cp are charged when the capacitor C1 is discharged. More specifically, in step S101, the controller 53 turns on each of the switches SW1, SW3, and SW4, and Figure 3A As shown, the switch SW2 is turned off. In this way, the controller 53 forms an electrical path including the battery pack 10, the switch SW1, the switch SW3, the resistor R1, the grounding part G1, the grounding capacitor Cn and the battery pack 10 to allow current to flow from the battery pack 10 into the electrical path, thereby charging the grounding capacitor Cn. At the same time, the controller 53 also forms an electrical path including the capacitor C1, the switch SW3, the switch SW4 and the capacitor C1 to allow current to flow from the capacitor C1 into the electrical path, thereby discharging the capacitor C1.

[0072] In addition, if Figure 4A As shown, in step S105, the controller 53 turns on the switches SW2, SW3, and SW4, and turns off the switch SW1. In this way, the controller 53 forms an electrical path including the battery pack 10, the grounding capacitor Cp, the grounding part G1, the switch SW4, the switch SW2, and the battery pack 10 to allow current to flow from the battery pack 10 into the electrical path, thereby charging the grounding capacitor Cp. At the same time, the controller 53 forms an electrical path including the capacitor C1, the switch SW3, the switch SW4, and the capacitor C1 to allow current to flow from the capacitor C1 into the electrical path, thereby discharging the capacitor C1.

[0073] Specifically, since the electrical path provided with the capacitor C1 and the electrical path provided with the grounding capacitors Cn and Cp are connected in parallel to each other, when the capacitor C1 is discharged, the controller 53 sets the energization state between the grounding portion G1 and each of the power supply paths L1 and L2. In this way, since the discharge of the capacitor C1 and the charging of the grounding capacitors Cn and Cp can be performed at the same time, the period for charging the grounding capacitors Cn and Cp can be shortened as much as possible, thereby shortening the judgment period.

[0074] In addition, the switch SW3 is provided between the grounding part G1 and the capacitor C1. That is, one end of the switch SW3 is connected to one side of the grounding part G1, and the other end thereof is connected to the side of the connection point M2 connected to the capacitor C1. In addition, one end of the switch SW4 is connected to one side of the grounding part G1, and the other end thereof is connected to the side of the connection point M3 connected to the capacitor C1. Therefore, by the insulation resistance detection circuit 51 constructed as described above, since the number of switch elements is reduced, the construction of the circuit can be simplified. Specifically, the ground fault resistances Rn, Rp can be calculated by the four switches SW1 to SW4.

[0075] Furthermore, by having the insulation resistance detection circuit 51 configured as described above, it is possible to determine whether there is leakage between the cathode side power supply path L1 and the ground portion G1 and between the anode side power supply path L2 and the ground portion G1 by sharing the single capacitor C1. Therefore, by reducing the number of circuit elements, the configuration of the circuit can be simplified.

[0076] When the battery voltage value of the battery pack 10 changes, the charging voltage value generated by the capacitor C1 is negatively affected. In view of this, the controller 53 detects the first battery voltage value Vb1 and the second battery voltage value Vb2 of the battery pack 10 each time the charging voltage value of the capacitor C1 is detected. That is, the controller 53 determines whether there is leakage based on the first voltage value Vb1 and the second battery voltage value Vb2.

[0077] More specifically, the controller 53 detects the first battery voltage value Vb1 of the battery pack 10 each time the first voltage value Vn is detected. Similarly, the controller 53 detects the second battery voltage value Vb2 of the battery pack 10 each time the second voltage value Vp is detected. Subsequently, by using the first to fourth equations described below, the controller 53 also calculates the ground fault resistances Rn and Rp based on the first battery voltage value Vb1 and the second battery voltage value Vb2 and the first voltage value Vn and the second voltage value Vp, and determines whether there is leakage. Therefore, the detection error caused by the change of the battery voltage value is reduced, thereby improving the accuracy of leakage judgment.

[0078] Now, an exemplary electrical leakage determination system 50 of a second embodiment of the present disclosure is described.

[0079] Even if the leakage determination system 50 of the first embodiment of the present disclosure is used, Figure 6 As shown, the time changes of the respective voltage values ​​Vn, Vp also differ slightly from each other according to the values ​​of the grounding capacitances Cn, Cp (i.e., large size and small size). To explain this in more detail, when the grounding capacitances Cn, Cp are relatively small, the detection voltage values ​​Vn, Vp tend to increase more than when the grounding capacitances Cn, Cp are relatively large. That is, such a tendency may be caused by the resistor R1. That is, since the current flows in through the resistor R1 when the grounding capacitances Cn, Cp are charged, it is assumed that the grounding capacitances Cn, Cp cannot be properly charged when the size of the resistor R1 is too large.

[0080] Then, according to the second embodiment of the present disclosure, the configuration of the insulation resistance detection circuit 151 is modified based on the insulation resistance detection circuit 51 of the first embodiment of the present disclosure as described below. Specifically, Figure 7As shown, the wiring portion between the external terminal P1 and the switch SW1 is connected to one end of the switch SW6. The other end of the switch SW6 is connected in series to one end of the resistor R2. In addition, the other end of the resistor R2 is connected to the grounding portion G1. Specifically, a third electrical path L13 (i.e., an electrical path including the capacitor C1) is established in parallel with the capacitor C1, and the switch SW6 and the resistor R2 are configured therein. The switch SW6 is connected in series to the resistor R2 and is connected to the grounding portion G1 via the resistor R2. The size of the resistor R2 is smaller than that of the resistor R1.

[0081] In addition, the wiring portion between the external terminal P2 and the switch SW2 is connected with one end of the switch SW7. The other end of the switch SW7 is connected in series to one end of the resistor R3. In addition, the other end of the resistor R3 is connected to the grounding portion G1. Specifically, a fourth electrical path L14 (i.e., an electrical path including the capacitor C1) is established in parallel with the capacitor C1, and the switch SW7 and the resistor R3 are arranged therein. The switch SW7 is connected in series to the resistor R3 and is connected to the grounding portion G1 via the resistor R3. The size of the resistor R3 is smaller than the size of the resistor R1. In this embodiment of the present invention, the resistors R2 and R3 correspond to the first resistor as a whole, and the resistor R1 corresponds to the second resistor.

[0082] Now, refer to Figure 8 An exemplary ground fault resistance calculation process performed in the second embodiment of the present disclosure is described. Figure 8 As shown, the controller 53 initially allows the capacitor C1 to discharge, while controlling the grounding capacitor Cn to charge for a given period of time (in step S201). Specifically, the controller 53 turns on the switches SW3, SW4, and SW6, while turning off the switches SW1, SW2, and SW7. Therefore, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the switch SW6, the resistor R2, the grounding portion G1, the grounding capacitor Cn, and the battery pack 10, thereby charging the grounding capacitor Cn. At the same time, the current flows from the capacitor C1 into the electrical path formed by the capacitor C1, the switch SW3, the switch SW4, and the capacitor C1, thereby discharging the capacitor C1.

[0083] Next, in steps S202 to S204, the controller 53 turns off the switches SW6 and SW7, and detects the first voltage value Vn and the first battery voltage value Vb1. Here, the processes performed in steps S202 to S204 are respectively equivalent to the processes in steps S102 to S104, and are not described repeatedly. In addition, as described in steps S201 and S202, the switch SW6 corresponds to the first switch, and the switch SW4 corresponds to the second switch.

[0084] Subsequently, the controller 53 allows the capacitor C1 to discharge, while controlling the grounding capacitor Cp to charge for a given period of time (in step S205). Specifically, the controller 53 turns on the switches SW3, SW4, and SW7, while turning off the switches SW1, SW2, and SW6. Therefore, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the grounding capacitor Cp, the grounding portion G1, the resistor R3, the switch SW7, and the battery pack 10, thereby charging the grounding capacitor Cp. At the same time, the current flows from the capacitor C1 into the electrical path formed by the capacitor C1, the switch SW3, the switch SW4, and the capacitor C1, thereby discharging the capacitor C1.

[0085] Next, in steps S206 to S208, the controller 53 turns off the switches SW6 and SW7, and detects the second voltage value Vp and the second battery voltage value Vb2. Here, the processes performed in steps S206 to S208 are respectively equivalent to the processes in steps S106 to S108. In addition, as described in steps S205 and S206, the switch SW7 corresponds to the first switch, and the switch SW3 corresponds to the second switch.

[0086] Subsequently, similar to step S109, the controller 53 calculates the ground fault resistances Rn, Rp based on the first voltage value Vn and the first battery voltage value Vb1 and the second voltage value Vp and the second battery voltage value Vb2, respectively (in step S209). Subsequently, the controller 53 determines whether there is leakage by comparing the composite value of the ground fault resistances Rn, Rp calculated in this way with the composite value of the normal ground fault resistances Rn, Rp (indicating the insulation state).

[0087] Therefore, by the configuration as described above, the benefits described below can be obtained.

[0088] That is, when the value of the resistor R1 located in the electrical path is too large, the grounding capacitors Cn and Cp are not fully charged, which may sometimes cause a detection error. That is, when the resistor R1 that limits the amount of current to charge the capacitor C1 is used to charge the grounding capacitors Cn and Cp, the grounding capacitors Cn and Cp are sometimes not properly charged. In view of this, a plurality of resistors R2 and R3 having values ​​different from the value of the resistor R1 are connected in series to the corresponding switches SW6 and SW7, and current flows through these resistors R2 and R3 to charge the grounding capacitors Cn and Cp. In this way, the grounding capacitors Cn and Cp can be properly charged, thereby being able to suppress detection errors.

[0089] Now, still another exemplary electrical leakage determination system 50 of the third embodiment of the present disclosure is described below.

[0090] Specifically, in Fig. 9, an insulation resistance detection circuit 251 adopted in the third embodiment of the present disclosure is shown. In the insulation resistance detection circuit 251, a bypass path L20 connected in parallel with the capacitor C1 is provided between the connection points M2 and M3 to bypass the capacitor C1. In addition, a switch SW5 is provided as a first switch in the bypass path L20. Therefore, when the grounding capacitors Cn and Cp are charged, the switch SW5 is turned on (i.e., the energized position) to suppress the charging of the capacitor C1.

[0091] In the following, reference is made to Fig.10 An exemplary ground fault resistance calculation process performed in the third embodiment of the present disclosure is described. First, the controller 53 allows the capacitor C1 to discharge (in step S301). Specifically, in order to discharge the capacitor C1, the controller 53 turns on the switches SW3 and SW4, while turning off the switches SW1, SW2, and SW5.

[0092] Subsequently, after the capacitor C1 is discharged, the controller 53 controls the grounding capacitor Cn to be charged (in step S302). Specifically, the controller 53 turns on the switches SW1, SW4, and SW5, and turns off the switches SW2 and SW3. Therefore, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the switch SW1, the switch SW5, the switch SW4, the resistor R1, the grounding portion G1, the grounding capacitor Cn, and the battery pack 10, thereby charging the grounding capacitor Cn.

[0093] Subsequently, the controller 53 turns off the switch SW5 and executes given processes in steps S303 to S305, respectively. Here, since the processes executed in steps S303 to S305 are respectively equivalent to the processes executed in steps S102 to S104, the description will not be repeated.

[0094] Subsequently, similar to the process performed in step S301, the controller 53 allows the capacitor C1 to discharge (in step S306). After the capacitor C1 is discharged, the controller 53 controls the grounding capacitor Cp to charge (in step S307). Specifically, the controller 53 turns on the switches SW2, SW3, and SW5, and turns off the switches SW1 and SW4. Therefore, the current flows from the battery pack 10 into the electrical path formed by the battery pack 10, the grounding capacitor Cp, the grounding portion G1, the switch SW3, the switch SW5, the switch SW2, and the battery pack 10, thereby charging the grounding capacitor Cp. Subsequently, the controller 53 performs the given processes in steps S308 to S311, respectively. Here, since the processes performed in steps S308 to S311 are respectively equivalent to the processes performed in steps S106 to S109, they are not repeatedly described. Then, the controller 53 determines whether there is leakage by comparing the combined value of the ground fault resistances Rn, Rp calculated in this way with the combined value of the normal ground fault resistances Rn, Rp (indicating the insulation state).

[0095] In addition, in the third embodiment of the present invention, a resistor connected in series with the switch SW5 may be used in the bypass path L20 to limit the current. In this case, by appropriately adjusting the amount of current flowing into the grounding capacitors Cn and Cp, the grounding capacitors Cn and Cp can be appropriately charged.

[0096] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications as long as they fall within substantially the same concept as the present invention.

[0097] For example, although the composite value of the ground fault resistances Rn, Rp is calculated in the above-described embodiment of the present disclosure, and the presence or absence of leakage is determined based on the composite value, the present invention is not limited thereto, and each of the ground fault resistances Rn, Rp may be calculated separately for use. That is, it may be determined whether or not there is leakage between the cathode side power supply path L1 and the ground portion G1 and between the anode side power supply path L2 and the ground portion G1, respectively, based on the ground fault resistances Rp, Rn, respectively.

[0098] Furthermore, as a modification of the above-described embodiment of the present disclosure, it may be selectively determined whether leakage exists only between the cathode side power path L1 and the ground G1 or between the anode side power path L2 and the ground G1 .

[0099] In addition, as another variation of the embodiment of the present disclosure as described above, a capacitor charged to determine whether there is leakage between the cathode side power path L1 and the ground portion G1 and a capacitor charged to determine whether there is leakage between the anode side power path L2 and the ground portion G1 can be independently adopted.

[0100] Furthermore, in the second embodiment of the present disclosure as described above, the values ​​of the resistors R2, R3 can be different from each other.

[0101] Furthermore, although the capacitor C1 and the grounding capacitances Cn, Cp are charged at the same time in the second embodiment of the present disclosure, these devices can also be charged at different times from each other.

[0102] Although in the above-described embodiment of the present disclosure, the battery voltage values ​​Vb1 and Vb2 are detected each time the first voltage value Vn and the second voltage value Vp are detected, respectively, only the battery voltage value Vb may be calculated each time the ground fault resistances Rn and Rp are calculated. In addition, for example, when the ground fault resistance calculation process starts, the battery voltage value Vb may be calculated only once.

Claims

1. A leakage judgment system for judging whether leakage occurs between a power path connected to a power terminal of a DC power supply and a grounding portion, the leakage judgment system comprising: a capacitor having a first end and a second end, the first end being connected to the power path and the second end being connected to the ground; at least one switch, the at least one switch being arranged in an electrical path formed in parallel with the capacitor to switch a state set between the power supply path and the ground portion between a power-on state and a power-off state; A capacitor voltage detector, the capacitor voltage detector detects a voltage value of the capacitor; as well as a controller, the controller being configured to control the at least one switch, After the capacitor is discharged, the controller causes the at least one switch to be in an energized position to set the energized state between the power path and the ground, When a given period of time has passed after the energized state is set between the power path and the ground, the controller causes the at least one switch to be in an energized off position and allows the capacitor to be charged, The controller then detects the voltage value of the capacitor and determines whether the leakage occurs based on the voltage value. The at least one switch comprises at least one first switch and at least one second switch, One end of the at least one first switch is connected to the ground portion, and the other end of the at least one first switch is connected to the first end of the capacitor, The at least one second switch is configured between the ground portion and the capacitor, and the at least one second switch has two ends, one end of the at least one second switch is connected to the ground portion, and the other end of the at least one second switch is connected to the second end of the capacitor. The controller places the at least one first switch and the at least one second switch in an energized position, respectively, to allow the capacitor to discharge, while setting an energized state between the power path and the ground portion, When a given period of time has passed after the controller places the at least one first switch and the at least one second switch in the energized position, respectively, the controller switches the position of the at least one first switch to the energized off position while maintaining the at least one second switch in the energized position to allow the capacitor to be charged, The controller then detects the voltage value of the capacitor and determines whether the leakage occurs based on the voltage value.

2. The leakage judgment system according to claim 1, characterized in that: The leakage judgment system also includes: at least one first resistor, the at least one first resistor being arranged in the electrical path, the at least one first resistor being connected in series to the at least one first switch; and a second resistor, the second resistor being arranged in the electrical path, the second resistor being connected in series to the capacitor, The first resistor and the second resistor have values ​​different from each other.

3. The leakage judgment system according to claim 1, characterized in that: The leakage judgment system further includes a power supply voltage detector, which is used to detect the voltage value of the DC power supply. The controller detects the voltage value of the DC power source each time the capacitor is charged, and determines whether the leakage occurs based on the voltage value of the DC power source.

4. A leakage judgment system, connected to both a cathode side power path connected to a cathode side terminal of a DC power supply and an anode side power path connected to an anode side terminal of the DC power supply, to judge whether leakage occurs between the cathode side power path and a ground portion and between the anode side power path and the ground portion, the leakage judgment system comprising: a cathode side switch, the cathode side switch switching the state between the cathode side power path and the capacitor between a power-on state and a power-off state, the cathode side switch having a first end and a second end, the first end of the cathode side switch being connected to the cathode side power path, and the second end of the cathode side switch being connected to the first end of the capacitor; an anode side switch, the anode side switch switching the state between the anode side power supply path and the capacitor between a power-on state and a power-off state, the anode side switch having a first end and a second end, the first end of the anode side switch being connected to the anode side power supply path, and the second end of the anode side switch being connected to the second end of the capacitor; a first grounding part side switch, the first grounding part side switch switches the state between the grounding part and the capacitor between a power-on state and a power-off state, the first grounding part side switch having a first end and a second end, the first end of the first grounding part side switch being connected to the grounding part, and the second end of the first grounding part side switch being connected to the first end of the capacitor; a second grounding portion side switch, the second grounding portion side switch switches the state between the grounding portion and the capacitor between a power-on state and a power-off state, the second grounding portion side switch having a first end and a second end, the first end of the second grounding portion side switch being connected to the grounding portion, and the second end of the second grounding portion side switch being connected to the second end of the capacitor; A capacitor voltage detector, the capacitor voltage detector detects a voltage value of the capacitor; as well as a controller that controls each of the cathode side switch, the anode side switch, the first grounding side switch, and the second grounding side switch, When the cathode side switch is brought into the energized position and the anode side switch is brought into the energized off position, and when a predetermined period of time has passed after the controller sets the energized state between the cathode side power supply path and the ground by bringing the first ground side switch into the energized position after the capacitor is discharged, the controller brings the second ground side switch into the energized position and brings the first ground side switch into the energized off position to allow the capacitor to be charged, and the controller then detects a voltage value of the capacitor as a first voltage value, When a predetermined period of time has passed since the cathode side switch is brought into the energized off position and the anode side switch is brought into the energized position, and the controller sets the energized state between the anode side power supply path and the ground by bringing the second ground side switch into the energized position after the capacitor is discharged, the controller brings the first ground side switch into the energized position and brings the second ground side switch into the energized off position to allow the capacitor to be charged, and the controller then detects a voltage value of the capacitor as a second voltage value, The controller determines whether the electric leakage occurs based on the first voltage value and the second voltage value.

5. The leakage judgment system according to claim 4, characterized in that: The leakage judgment system further includes a power supply voltage detector, which is used to detect the voltage value of the DC power supply. The controller detects the voltage value of the DC power source each time the capacitor is charged, and determines whether the leakage occurs based on the voltage value of the DC power source.

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