Leakage detection circuit

Abstract

To suppress an expansion in circuit scale regarding a self-diagnosis circuit which is provided in a leakage detection circuit.SOLUTION: A leakage detection circuit comprises a ground fault detection circuit and a self-diagnosis circuit. The ground fault detection circuit is electrically connected to a plurality of power supply lines, to which AC power is supplied, and detects a ground fault current with respect to a ground potential in each of the plurality of power supply lines. The self-diagnosis circuit forms a short-circuit path for selectively short-circuiting each of the plurality of power supply lines to a connection line of the ground potential. The self-diagnosis circuit comprises a first limit resistor and a relay circuit. The first limit resistor includes a plurality of resistive elements, which is electrically connected in series, with one end electrically connected to the connection line of the ground potential. The relay circuit is provided between the plurality of power supply lines and an opposite side of the connection line of the ground potential of the first limit resistor and switches a power supply line, which is electrically connected to the first limit resistor and forms the short-circuit path, between the plurality of power supply lines.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a ground fault detection circuit. [Background technology]

[0002] In recent years, power conversion devices such as chargers installed in electric vehicles, etc., have become equipped with insulation monitor circuits (leakage detection circuits) that detect leakage current to prevent human body electric shock, as the current direction has become bidirectional to accommodate both charging and discharging.

[0003] For example, Patent Document 1 discloses a technique relating to an insulation state detection device that detects a ground fault and an insulation state relative to a ground potential based on the charge state of a flying capacitor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-001423 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, an insulation monitoring circuit is provided with an independent self-diagnosis circuit to verify the viability of the insulation monitoring circuit itself, because its failure carries a significant risk. While on-board chargers are required to be compact for ease of installation, they are also required to have sufficient resistance to high voltages such as lightning surges, which creates a problem of increasing the circuit size (physical dimensions) of the self-diagnosis circuit. Furthermore, for on-board chargers that can operate using AC voltage inputs from both a three-phase AC power supply and a single-phase AC power supply, the circuit size of the self-diagnosis circuit becomes even larger.

[0006] One of the problems to be solved by the present disclosure is to suppress an increase in the circuit size of a self-diagnosis circuit provided in a leakage current detection circuit. [Means for solving the problem]

[0007] A leakage current detection circuit according to the present disclosure includes a ground fault detection circuit and a self-diagnosis circuit. The ground fault detection circuit is electrically connected to a plurality of power supply lines to which AC power is supplied and detects a ground fault current relative to the ground potential of each of the plurality of power supply lines. The self-diagnosis circuit forms a short-circuit path that selectively shorts each of the plurality of power supply lines to the connection line of the ground potential. The self-diagnosis circuit includes a first limiting resistor and a relay circuit. The first limiting resistor has a plurality of resistive elements electrically connected in series and has one end electrically connected to the connection line of the ground potential. The relay circuit is provided between the plurality of power supply lines and the side of the first limiting resistor opposite the connection line of the ground potential and switches between the power supply lines that are electrically connected to the first limiting resistor and form the short-circuit path.

[0008] According to the present disclosure, it is possible to suppress an increase in the circuit size of a self-diagnosis circuit provided in a leakage detection circuit. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a charging system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the insulation monitor circuit (earth leakage detection circuit) of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a self-diagnosis circuit, a leakage detection circuit (insulation monitor circuit), a power conversion device (on-board charger), a vehicle, and a charging system according to the present disclosure will be described with reference to the drawings.

[0011] In the description of the present disclosure, components having the same or substantially the same functions as those described above with respect to the previously-mentioned drawings may be given the same reference numerals, and descriptions thereof may be omitted as appropriate. Furthermore, even when the same or substantially the same parts are shown, the dimensions and proportions may be different depending on the drawing. Furthermore, for example, in order to ensure the visibility of the drawings, reference numerals may be given to only the main components in the description of each drawing, and reference numerals may not be given to components having the same or substantially the same functions as those described above with respect to the previously-mentioned drawings.

[0012] In the description of the present disclosure, components having the same or substantially the same functions may be distinguished by adding an alphanumeric character to the end of the reference symbol. Alternatively, when multiple components having the same or substantially the same functions are not distinguished, they may be collectively described by omitting the alphanumeric character at the end of the reference symbol.

[0013] Fig. 1 is a diagram showing an example of the configuration of a charging system 1 according to an embodiment. As shown in Fig. 1, the charging system 1 includes a vehicle 2, a load 8, and a power source 9. The vehicle 2 also includes an on-board charger 21 and a battery 23.

[0014] The vehicle 2 is any of various types of moving bodies that can be driven using electric power from a battery 23, such as a passenger car, a freight vehicle, a van, a motorcycle, or an electric kick scooter.

[0015] The technology according to the embodiment may be applied not only to the vehicle 2 but also to various power conversion devices provided in, for example, aircraft, amusement facilities, uninterruptible power supplies, and the like.

[0016] The vehicle 2 may be configured to operate on-board equipment (electrical equipment) using power from the battery 23. Examples of the on-board equipment include a navigation system, an audio system, an air conditioner, power windows, a defogger, an ECU (Electronic Control Unit), a GPS (Global Positioning System) module, and an on-board camera.

[0017] The on-board charger 21 is a power conversion device mounted on the vehicle 2. In this embodiment, an on-board charger 21 configured to be operable with either single-phase AC power or three-phase AC power is exemplified. For example, the on-board charger 21 converts single-phase or three-phase AC power supplied from the power source 9 into DC power and supplies the DC power to the battery 23. The on-board charger 21 also converts DC power from the battery 23 into AC power and supplies the single-phase or three-phase AC power to a load 8 connected to an AC socket 29a or an in-vehicle socket 29b of the vehicle 2.

[0018] The on-board charger 21 does not have to be compatible with both single-phase and three-phase, and may be configured to be operable with either one. Furthermore, the on-board charger 21 is not limited to single-phase and three-phase (multiple-phase) AC power, and may be configured to be operable with two-phase (multiple-phase) AC power.

[0019] The battery 23 stores the power supplied from the power source 9 via the on-board charger 21. The battery 23 only needs to store power to supply power to a traction motor (main motor) and electrical components mounted on the vehicle 2, or to a load 8 connected to an AC socket 29a or an in-vehicle socket 29b of the vehicle 2. Any battery, such as a lithium-ion battery, a nickel-metal hydride battery, or an all-solid-state battery, can be used as the battery 23.

[0020] The load 8 is detachably connected to an AC socket 29a or an in-vehicle socket 29b of the vehicle 2. The load 8 may be an electronic device, such as a home appliance or a smartphone, that receives power from the vehicle 2. The load 8 may also be an external power storage device or power facility that receives power from the vehicle 2, such as a home storage battery or a power purchasing device at a charging station.

[0021] Here, AC socket 29a of vehicle 2 is a power socket for charging and discharging vehicle 2. AC socket 29a is provided, for example, in a position accessible from outside vehicle 2. For example, AC socket 29a is connected to power source 9 when charging vehicle 2. For example, AC socket 29a is connected to load 8 when discharging from vehicle 2. As an example, AC socket 29a of vehicle 2 is compatible with both single-phase and three-phase AC power, but may be compatible with either one of them.

[0022] Furthermore, the in-vehicle socket 29b of the vehicle 2 is a power socket for discharging the vehicle 2. The in-vehicle socket 29b is provided, for example, inside the passenger compartment (inside the vehicle) of the vehicle 2. For example, the in-vehicle socket 29b is connected to the load 8 when discharging from the vehicle 2. As an example, the in-vehicle socket 29b of the vehicle 2 is compatible with single-phase AC power, but may be compatible with both single-phase and three-phase AC power.

[0023] The power source 9 is any AC power source, such as a power source installed in a quick charging facility or a commercial power source. The power source 9 is not limited to a single-phase AC power source or a three-phase AC power source (multiple-phase AC power source), and a two-phase AC power source (multiple-phase AC power source) may also be used. In this embodiment, an example is shown in which any single-phase or three-phase AC power source can be used as the power source 9 that supplies AC power to the on-board charger 21 (power conversion device) of the vehicle 2.

[0024] 1, the on-board charger 21 includes, for example, an insulation monitor circuit 211, a power factor correction (PFC) circuit 213, and a DC-DC conversion circuit 214. Note that the on-board charger 21 according to the present disclosure is not limited to the configuration shown in FIG. 1 and may have other configurations. For example, the power factor correction circuit 213 is not an essential component of the on-board charger 21, and other rectifying and smoothing circuits may be used.

[0025] The insulation monitor circuit 211 is a leakage current detection circuit mounted on the on-board charger 21. The insulation monitor circuit 211 is electrically connected to the power factor correction circuit 213. When a load 8 or a power supply 9 is connected to the on-board charger 21, the insulation monitor circuit 211 is also electrically connected to the load 8 or the power supply 9. The insulation monitor circuit 211 operates, for example, when discharging the load 8 connected to the on-board charger 21, to detect leakage current.

[0026] The power factor correction circuit 213 is electrically connected to the insulation monitor circuit 211 and the DC-DC conversion circuit 214. The power factor correction circuit 213 rectifies and smoothes the AC voltage from the power supply 9 to generate a DC voltage.

[0027] The DC-DC conversion circuit 214 is electrically connected to the power factor correction circuit 213 and the battery 23. The DC-DC conversion circuit 214 converts the DC voltage generated by the power factor correction circuit 213 back into an AC voltage, and then rectifies and smooths the converted AC voltage, thereby generating a DC voltage of an arbitrary set voltage. The DC-DC conversion circuit 214 also converts the DC voltage from the battery 23 into an AC voltage, and then rectifies and smooths the converted AC voltage, thereby generating a DC voltage of an arbitrary set voltage.

[0028] The on-board charger 21 may further include a noise filter (not shown) that suppresses (removes) noise from entering from the power supply 9 and noise from leaking to the power supply 9. This noise filter is provided, for example, between the switch circuit 212 (see FIG. 2) and the power factor correction circuit 213, but may also be provided in another location.

[0029] Here, the insulation monitor circuit 211 according to the present disclosure will be described in detail with reference to the drawings.

[0030] Fig. 2 is a diagram showing an example of the configuration of the insulation monitor circuit 211 of Fig. 1. As shown in Fig. 1 and Fig. 2, the insulation monitor circuit 211 has a self-diagnosis circuit 3 and a ground fault detection circuit 4.

[0031] The self-diagnosis circuit 3 is electrically connected between the charging / discharging terminals P1 to P3, PN of the on-board charger 21 and the ground fault detection circuit 4 via a plurality of power supply lines L1 to L3, N.

[0032] Here, the charge / discharge terminals P1-P3, PN of the on-board charger 21 are terminals electrically connected to an AC socket 29a (a power socket for charge / discharge) of the vehicle 2. A plurality of power supply lines L1-L3, N are connected to the plurality of charge / discharge terminals P1-P3, PN, respectively. That is, when the vehicle 2 is being charged, AC power from the external power supply 9 is supplied to the plurality of power supply lines L1-L3, N. Furthermore, when the vehicle 2 is being discharged, AC power based on DC power from the battery 23 is supplied to the plurality of power supply lines L1-L3, N.

[0033] As an example, the power supply line L1 is a voltage line through which a single-phase current from a single-phase AC power supply or, for example, a U-phase (first phase) current from a three-phase AC power supply flows. As an example, the power supply line L2 is not electrically connected to the single-phase AC power supply and is a voltage line through which, for example, a V-phase (second phase) current from a three-phase AC power supply flows. As an example, the power supply line L3 is not electrically connected to the single-phase AC power supply and is a voltage line through which, for example, a W-phase (third phase) current from a three-phase AC power supply flows. As an example, the power supply line N is a neutral line electrically connected to both the single-phase or three-phase AC power supply and the ground potential.

[0034] Furthermore, the self-diagnostic circuit 3 is electrically connected between the plurality of power supply lines L1 to L3, N and a ground wire FG that is functionally grounded to the metallic chassis of the vehicle 2 or the like.

[0035] The self-diagnosis circuit 3 is a circuit for verifying the validity of the ground fault detection circuit 4, that is, a circuit for performing self-diagnosis in the insulation monitor circuit 211. Specifically, the self-diagnosis circuit 3 forms a short circuit with the functionally grounded ground wire FG for the phase for which a ground fault is to be detected by the ground fault detection circuit 4. In other words, the self-diagnosis circuit 3 forms a short-circuit path that selectively shorts the L1 to L3 phases and the N phase, i.e., each of the multiple power supply lines L1 to L3, N, to the connection wire FG at the functionally grounded potential.

[0036] 2, the self-diagnosis circuit 3 includes a relay circuit 31, a limiting resistor 33, a photorelay 34, and a digital transistor 36. Note that other circuit elements may be used instead of the digital transistor 36. For example, a bipolar transistor and at least one resistor may be used instead of the digital transistor 36.

[0037] The relay circuit 31 is electrically connected between each of the multiple power supply lines L1 to L3, N and a limiting resistor 33. In the example of Fig. 2, the relay circuit 31 has three C-contact relays 32a to 32c that electrically connect the limiting resistor 33 to any one of the four power supply lines L1 to L3, N.

[0038] 2, one end of the C-contact relay 32a is selectively and electrically connected to either one of the power supply lines L1, L2, and the other end is electrically connected via the C-contact relay 32c to the limiting resistor 33. Furthermore, one end of the C-contact relay 32b is selectively and electrically connected to either one of the power supply lines L3, N, and the other end is electrically connected to the limiting resistor 33 via the C-contact relay 32c.

[0039] 2, the transfer contact (common contact) of C-contact relay 32c is electrically connected to limiting resistor 33. Furthermore, one of the make contact (normally open (NO) contact) and break contact (normally closed (NC) contact) of C-contact relay 32c is electrically connected to the transfer contact of C-contact relay 32a, and the other is electrically connected to the transfer contact of C-contact relay 32b. Furthermore, one of the make contact and break contact of C-contact relay 32a is electrically connected to power supply line L1, and the other is electrically connected to power supply line L2. Furthermore, one of the make contact and break contact of C-contact relay 32b is electrically connected to power supply line L3, and the other is electrically connected to power supply line N.

[0040] The combination of the C-contact relays 32a, 32b and the power supply lines to which they are selectively connected shown in FIG. 2 is one example, and other combinations are also possible, such as providing the C-contact relay 32a between the power supply lines L1 and L3.

[0041] The number of C-contact relays 32 provided in the relay circuit 31 is changed as appropriate depending on the number of wires in the target power supply line. For example, in the case of a single-phase two-wire system including one voltage wire and one neutral wire, the relay circuit 31 has one C-contact relay 32 that electrically connects the limiting resistor 33 to one of the two power supply lines.

[0042] The relay circuit 31 operates each of the C-contact relays 32a to 32c under the control of the control circuit 215 (e.g., DSP) of the on-board charger 21. As a result, the relay circuit 31 switches the phase to which the limiting resistor 33 is connected among the multiple phases corresponding to the multiple power supply lines L1 to L3, N. The phase to which the limiting resistor 33 is connected is the phase among the multiple phases for which self-diagnosis is performed to confirm the validity of the ground fault detection circuit 4. In other words, the relay circuit 31 switches the phase to which the ground fault detection circuit 4 detects a ground fault and which is to be functionally grounded to form a short circuit for self-diagnosis.

[0043] The limiting resistor 33 is electrically connected between the relay circuit 31 and the photorelay 34. The resistance value of the limiting resistor 33 is determined appropriately depending on the withstand voltage requirements of the self-diagnosis circuit 3 for protection against lightning surges, etc. For example, the limiting resistor 33 includes a plurality of high-voltage resistance elements (resistance elements) electrically connected in series. Here, the limiting resistor 33 according to the embodiment is an example of a first limiting resistor.

[0044] One end of the photorelay 34 on the light-emitting element side is electrically connected to the insulated power supply 22 of the vehicle 2 via a resistor 35. The other end of the photorelay 34 on the light-emitting element side is electrically connected to the output terminal of a digital transistor 36. One end of the photorelay 34 on the light-receiving element side is electrically connected to one of the power supply lines L1 to L3,N via a relay circuit 31 and a limiting resistor 33. The other end of the photorelay 34 on the light-receiving element side is electrically connected to a functionally grounded ground wire FG.

[0045] The digital transformer 36 is electrically connected between one end of the photorelay 34 on the light-emitting element side opposite the insulated power supply 22 of the vehicle 2 and a functionally grounded ground wire FG. In addition, the control end of the digital transformer 36 is electrically connected to a signal line (e.g., GPIO) to which a control signal is supplied from the control circuit 215 of the on-board charger 21.

[0046] The digital transformer 36 operates the photorelay 34 under the control of the control circuit 215 of the on-board charger 21. As an example, the digital transformer 36 turns on the photorelay 34 each time the relay circuit 31 switches the power line connected to the limiting resistor 33. For example, the digital transformer 36 has a bipolar transistor (not shown) whose base is electrically connected to the GPIO line via an input resistor (not shown) and whose emitter is electrically connected to a functionally grounded ground line FG via a base-emitter resistor (not shown). For example, in the digital transformer 36, the input resistor generates a current according to the voltage level of the GPIO line, and generates a collector current according to the magnitude of the generated current. The photorelay 34 has a cathode electrically connected to the collector of the bipolar transistor of the digital transformer 36. When a collector current flows through the light-emitting element, a switch (not shown) on the light-receiving element side is turned on, functionally grounding the power line selectively connected via the relay circuit 31 and the limiting resistor 33.

[0047] As described above, the self-diagnostic circuit 3 according to this embodiment selectively functionally grounds each of the power supply lines L1-L3, N to form a short circuit under the control of the control circuit 215 of the on-board charger 21. When the self-diagnostic circuit 3 selectively functionally grounds each of the power supply lines L1-L3, N to form a short circuit, the potential of the functionally grounded ground wire FG drops by the voltage generated by the limiting resistor. This causes current to flow through the detection shunt resistor 44b, one end of which is electrically connected to the ground wire FG, as described below. In other words, by selectively functionally grounding each of the power supply lines L1-L3, N to form a short circuit, the self-diagnostic circuit 3 can generate a state in which a Y capacitor (not shown) provided downstream of the ground fault detection circuit 4 to attenuate common noise in the on-board charger 21 has experienced dielectric breakdown, i.e., the state of the on-board charger 21 that the insulation monitor circuit 211 is intended to detect, without causing dielectric breakdown of the Y capacitor.

[0048] The ground fault detection circuit 4 is electrically connected between the charging / discharging terminals P1 to P3, PN of the on-board charger 21 and the switch circuit 212 via a plurality of power supply lines L1 to L3, N. The ground fault detection circuit 4 is also electrically connected between the plurality of power supply lines L1 to L3, N and a functionally grounded ground wire FG.

[0049] The ground fault detection circuit 4 is a circuit that detects a ground fault (leakage) current with respect to the ground potential of each of the multiple power supply lines L1 to L3, N. In other words, the ground fault detection circuit 4 is a circuit that detects a ground fault (leakage) current that occurs when a target Y capacitor (not shown) provided downstream of the ground fault detection circuit 4 between each of the multiple power supply lines L1 to L3, N and the functionally grounded ground wire FG experiences insulation breakdown. Specifically, the ground fault detection circuit 4 detects the insulation state around the on-board charger 21 by detecting a ground fault current flowing through the detection shunt resistor 44b when insulation breakdown occurs in the target Y capacitor (not shown). The detection range of the ground fault detection circuit 4 is a series of systems that form a closed circuit including the on-board charger 21, the load 8, a human body, etc. Furthermore, the ground fault detection circuit 4 is capable of constantly detecting discharge from the vehicle 2 and is capable of detecting it before a human body is electrocuted.

[0050] As shown in FIG. 2, the ground fault detection circuit 4 includes limiting resistors 41a to 41d, a high-voltage diode 42, an insulation monitor on / off circuit 43, digital transistors 45 and 48, a Y capacitor 46, an insulation determination comparator 47, and a photocoupler 49.

[0051] Each of the limiting resistors 41a to 41d is electrically connected in parallel between each of the plurality of power supply lines L1 to L3, N and the high-voltage diode 42. Each of the limiting resistors 41a to 41d has a configuration similar to that of the limiting resistor 33 of the self-diagnosis circuit 3, for example. That is, each of the limiting resistors 41a to 41d includes a plurality of high-voltage resistance elements (resistance elements) electrically connected in series. Here, each of the limiting resistors 41a to 41d according to the embodiment is an example of a second limiting resistor.

[0052] The anode of the high-voltage diode 42 is electrically connected to the side of each of the limiting resistors 41a to 41d opposite to the multiple power supply lines L1 to L3, N. The cathode of the high-voltage diode 42 is electrically connected to one end (collector of the bipolar transistor) on the light-receiving element side of the insulation monitor on / off circuit 43, similar to the limiting resistor 33 of the self-diagnosis circuit 3. In other words, the cathode of the high-voltage diode 42 is electrically connected to the connection wire FG of functional ground potential via the shunt resistor 44b for detecting ground-fault current.

[0053] The insulation monitor on / off circuit 43 is configured, for example, by a photorelay and has a configuration similar to that of the photorelay 34 of the self-diagnosis circuit 3. One end of the insulation monitor on / off circuit 43 on the light-emitting element side is electrically connected to the isolated power supply 22 of the vehicle 2 via a resistor 44a. The other end of the insulation monitor on / off circuit 43 on the light-emitting element side is electrically connected to the output terminal of the digital transistor 45. One end of the insulation monitor on / off circuit 43 on the light-receiving element side is electrically connected to the multiple power supply lines L1 to L3, N via limiting resistors 41a to 41d and a high-voltage diode 42. The other end of the insulation monitor on / off circuit 43 on the light-receiving element side is electrically connected to the functionally grounded ground wire FG.

[0054] The digital transformer 45 has a configuration similar to that of, for example, the photorelay 34 of the self-diagnosis circuit 3. The digital transformer 45 is electrically connected between the cathode of the light-emitting element of the insulation monitor on / off circuit 43 and one end of the detection shunt resistor 44b. In addition, the control end of the digital transformer 45 is electrically connected to a signal line (for example, a GPIO) to which a control signal is supplied from the control circuit 215 of the on-board charger 21.

[0055] The digital transformer 45 operates the insulation monitor on / off circuit 43 under the control of the control circuit 215 of the on-board charger 21. For example, in the digital transformer 45, an input resistor (not shown) connected to the base of a bipolar transistor (not shown) generates a current according to the voltage level of the GPIO line, and generates a collector current according to the magnitude of the generated current. When the collector current of the digital transformer 45 flows to the light-emitting element, a switch (not shown) on the light-receiving element side of the insulation monitor on / off circuit 43 is turned on, electrically connecting the power lines connected via the limiting resistors 41a to 41d to the detection shunt resistor 44b. In other words, when the insulation monitor on / off circuit 43 is turned on by the control circuit 215 of the on-board charger 21, it electrically connects the multiple power lines L1 to L3, N to the detection shunt resistor 44b via the limiting resistors 41a to 41d and the high-voltage diode 42.

[0056] The detection shunt resistor 44b is electrically connected between one end of the switch on the light receiving element side of the digital transistor 45 opposite to the high voltage diode 42 and the functionally grounded ground line FG.

[0057] One end of the Y capacitor 46 is electrically connected via a resistor 44c to one end of the detection shunt resistor 44b on the insulation monitor on / off circuit 43 side. The other end of the Y capacitor 46 is electrically connected to the functionally grounded ground wire FG. In other words, the Y capacitor 46 is electrically connected in parallel to the detection shunt resistor 44b. The RC circuit formed by the resistor 44c and the Y capacitor 46 adjusts the detection time for the insulation determination comparator 47 to determine whether or not insulation breakdown has occurred.

[0058] One of the pair of input terminals of the insulation determination comparator 47 is electrically connected via resistor 44c to one end of the detection shunt resistor 44b on the insulation monitor on / off circuit 43 side. The other of the pair of input terminals of the insulation determination comparator 47 is electrically connected between series resistors 44d and 44e. These resistors 44d and 44e are electrically connected between the isolated power supply 22 and the functionally grounded ground wire FG and generate a reference potential at the connection point. That is, the insulation determination comparator 47 detects a ground-fault current flowing through the detection shunt resistor 44b by comparing the potential generated by the detection shunt resistor 44b with the reference potential generated by resistors 44d and 44e. Furthermore, one of the pair of power supply terminals of the insulation determination comparator 47 is electrically connected to the isolated power supply 22, and the other is electrically connected to the functionally grounded ground wire FG.

[0059] The output (voltage level at the output terminal) of insulation determination comparator 47 is based on the value of the current flowing through detection shunt resistor 44b. For example, the voltage level at the output terminal of insulation determination comparator 47 changes to "H (high level)" when a Y capacitor (not shown) provided downstream of ground fault detection circuit 4 experiences insulation breakdown and a ground fault current flows through detection shunt resistor 44b.

[0060] The digital transformer 48 has a configuration similar to that of the digital transformer 45. The digital transformer 48 is electrically connected between the cathode of the light-emitting element (not shown) of the photocoupler and the functionally grounded ground line FG. The control terminal of the digital transformer 45 is electrically connected to the output terminal of the insulation determination comparator 47.

[0061] One end of the photocoupler 49 on the light-emitting element side is electrically connected to the isolated power supply 22 via a resistor 44f. The other end of the photocoupler 49 on the light-emitting element side is electrically connected to the output terminal of the digital transformer 45. One of a pair of terminals on the light-receiving element side of the photocoupler 49 is electrically connected to a signal line (e.g., GPIO) to which a control signal is supplied from the control circuit 215 of the on-board charger 21, and the other is electrically connected to, for example, another ground line insulated from the ground line FG.

[0062] The digital transformer 48 operates the photocoupler 49 in accordance with the output of the insulation determination comparator 47. For example, in the digital transformer 48, an input resistor (not shown) connected to the base of a bipolar transistor (not shown) generates a current according to the voltage level at the output terminal of the insulation determination comparator 47, and generates a collector current according to the magnitude of the generated current. When the collector current of the digital transformer 48 flows to the light-emitting element, the photocoupler 49 turns on a switch (not shown) on the light-receiving element side, changing the voltage level of the GPIO line. As a result, the ground fault detection circuit 4 can notify the control circuit 215 of the on-board charger 21 when it detects a ground fault current flowing through the detection shunt resistor 44b.

[0063] The control circuit 215 of the on-board charger 21 controls the operation of the self-diagnosis circuit 3 and the ground fault detection circuit 4. The control circuit 215 is configured to determine whether or not the insulation monitor circuit 211 has detected a ground fault current, based on the operating states of the self-diagnosis circuit 3 and the ground fault detection circuit 4 and the detection result of the ground fault current by the ground fault detection circuit 4.

[0064] For example, when the self-diagnosis circuit 3 is not operated, the control circuit 215 can detect the occurrence of an insulation breakdown of the Y capacitor (not shown) provided downstream of the ground fault detection circuit 4, i.e., a ground fault (leakage current), based on a notification of a ground fault current detection from the ground fault detection circuit 4 when the insulation monitor on / off circuit 43 of the ground fault detection circuit 4 is turned on.

[0065] For example, when the control circuit 215 operates the self-diagnosis circuit 3 to perform self-diagnosis, it can detect the normal operation of the ground fault detection circuit 4 based on a notification of the detection of a ground fault current from the ground fault detection circuit 4 when the insulation monitor on / off circuit 43 of the ground fault detection circuit 4 is turned off.

[0066] For example, when the control circuit 215 operates the self-diagnosis circuit 3 to perform self-diagnosis, it can detect malfunction of the ground fault detection circuit 4 based on the absence of notification of ground fault current detection from the ground fault detection circuit 4 when the insulation monitor on / off circuit 43 of the ground fault detection circuit 4 is turned off.

[0067] The self-diagnosis performed by operating the self-diagnosis circuit 3 serves as a second safety for the on-board charger 21, verifying the validity of the ground fault detection circuit 4. This self-diagnosis may be performed at any timing during discharge when a ground fault current may flow if a short circuit is formed by functional grounding, and may be performed at the start or end of discharge, or may be performed continuously or intermittently during discharge.

[0068] The control circuit 215 has, for example, at least one processor (not shown) and at least one memory (not shown), and has a hardware configuration using a normal computer. A DSP (Digital Signal Processor), for example, can be used as the control circuit 215. The control circuit 215 may implement each function of the control circuit 215 by, for example, having a processor load a program stored in a ROM (Read Only Memory) or the like into a RAM (Random Access Memory) and executing the loaded program, or may implement some or all of the functions using a dedicated hardware circuit (such as a semiconductor integrated circuit).

[0069] The control circuit 215 that controls the operation of the self-diagnostic circuit 3 and the control circuit 215 that controls the operation of the ground fault detection circuit 4 may be realized by the same circuit, or may be realized by different circuits that are independent of each other.

[0070] The control circuit 215 may be realized by a computer such as an ECU (Electronic Control Unit) provided inside the vehicle 2, a DCU (Domain Control Unit) such as a CDC (Cockpit Domain Controller) integrating multiple ECUs, or an OBU (On Board Unit). The control circuit 215 may transmit and receive information to and from other ECUs mounted on the vehicle or an external power supply (power supply 9) connected to the vehicle via an in-vehicle network including a CAN (Controller Area Network), Ethernet (registered trademark), or USB (Universal Serial Bus (registered trademark)) within the vehicle, or may communicate with an information processing device outside the vehicle via a network such as the Internet.

[0071] As shown in FIGS. 1 and 2, the on-board charger 21 includes a switch circuit 212.

[0072] The switch circuit 212 is electrically connected between the insulation monitor circuit 211 and the power factor correction circuit 213 via a plurality of power supply lines L1 to L3, N. The switch circuit 212 is also electrically connected between the discharge terminals PO1, PON of the on-board charger 21 and the power factor correction circuit 213 via a plurality of power supply lines LO1, LON. That is, the power supply line LO1 is a voltage line branched off from one of the plurality of power supply lines L1 to L3. The power supply line LON is a neutral line branched off from the power supply line N.

[0073] Here, each of the multiple power supply lines L1 to L3, N according to the embodiments is an example of a first power supply line. Also, each of the multiple power supply lines LO1, LON according to the embodiments is an example of a second power supply line. Also, the power supply line LO1 according to the embodiments is an example of a branch voltage line. Also, the power supply line LON according to the embodiments is an example of a branch neutral line. In the case of a three-phase three-wire system, the power supply line N according to the embodiments is an example of a first power supply line and a second power supply line.

[0074] Here, the discharge terminals PO1, PON of the on-board charger 21 are terminals electrically connected to an in-vehicle socket 29b (a power socket for discharging) of the vehicle 2. A plurality of power supply lines LO1, LON are connected to the plurality of discharge terminals PO1, PON, respectively. As an example, the power supply line LO1 is a voltage line through which a single-phase current flows from the power factor correction circuit 213 based on a direct current from the battery 23. As an example, the power supply line LON is a neutral line electrically connected to each of the power supply line N and the ground potential.

[0075] The switch circuit 212 operates under the control of the control circuit 215 of the on-board charger 21. For example, when charging or discharging the vehicle 2 via the AC socket 29a, the switch circuit 212 electrically connects the insulation monitor circuit 211 and the power factor correction circuit 213 via the multiple power supply lines L1 to L3, N. For example, when discharging from the vehicle 2 via the in-vehicle socket 29b, the switch circuit 212 electrically connects the discharge terminals PO1, PON of the on-board charger 21 and the power factor correction circuit 213 via the multiple power supply lines LO1, LON.

[0076] As described above, in the insulation monitor circuit 211 (earth leakage detection circuit) according to the present disclosure, the self-diagnosis circuit 3 has a relay circuit 31 that switches the power supply line connected to the limiting resistor 33 to form a short-circuit path among the multiple power supply lines L1 to L3, N.

[0077] For example, in the limiting resistor 33, the higher the withstand voltage requirement for the self-diagnostic circuit 3, such as against lightning surges, the greater the number of multiple high-voltage resistance elements connected in series. In this regard, in the self-diagnostic circuit 3 according to the present disclosure, the limiting resistor 33 is shared among multiple power supply lines for which ground faults are detected by the ground fault detection circuit 4, due to the provision of the relay circuit 31. In other words, in the self-diagnostic circuit 3 according to the present disclosure, it is not necessary to provide a limiting resistor 33 for each of the multiple power supply lines.

[0078] Therefore, the insulation monitor circuit 211 according to the present disclosure can reduce the number of high-voltage resistance elements, which increases as the withstand voltage requirement for the self-diagnosis circuit 3 increases. For example, in the three-phase, four-wire configuration illustrated in FIG. 2, the circuit configuration between the relay circuit 31 and the ground wire FG can be standardized to reduce the number of resistors by a factor of four. For example, the relay circuit 31 according to the present disclosure may be applied to a three-phase, three-wire configuration, in which case the circuit configuration between the relay circuit 31 and the ground wire FG can be standardized to reduce the number of resistors by a factor of three. For example, the relay circuit 31 according to the present disclosure may be applied to a single-phase, two-wire configuration, in which case the circuit configuration between the relay circuit 31 and the ground wire FG can be standardized to reduce the number of resistors by a factor of half.

[0079] Furthermore, the circuit size and cost increase by the amount of the relay circuit 31 provided in place of the circuit configuration between the shared relay circuit 31 and the ground wire FG. However, the relay circuit 31 according to the present disclosure can be configured, for example, by a general-purpose relay circuit. Furthermore, since the short-circuit current of the relay circuit 31 is on the order of several mA, increases in size and cost can be suppressed. In other words, the circuit size and cost of the added relay circuit 31 are smaller than the circuit size and cost of the photorelay 34, which are reduced by sharing.

[0080] In this way, the provision of the relay circuit 31 and the use of a common limiting resistor 33 make it possible to reduce the number of components and the circuit size and thus the cost of the self-diagnosis circuit 3 provided in the insulation monitoring circuit 211. Furthermore, by reducing the circuit size of the self-diagnosis circuit 3, the size of the circuit board on which it is mounted and the volume occupied by the mounted circuit board are also reduced, allowing for the miniaturization of the insulation monitoring circuit 211 and the on-board charger 21.

[0081] Furthermore, because the circuit configuration subsequent to the limiting resistor 33 is also standardized, it is possible to reduce the number of signal lines (for example, GPIO lines) connecting the control circuit 215, such as a microcomputer, and the self-diagnosis circuit 3. This simplifies wiring, improving the degree of freedom in component placement in the on-board charger 21, increasing the number of available ports in the control circuit 215, and enabling the control circuit 215 to be realized using an inexpensive microcomputer with few GPIO terminals.

[0082] The power supply lines LO1 and LON, through which current flows to the discharge terminals PO1 and PON connected to the interior socket 29b of the vehicle 2, for example, in the passenger compartment, may also be included in the targets of leakage detection by the ground fault detection circuit 4. In this case, for example, in the ground fault detection circuit 4, limiting resistors of the same configuration are electrically connected between each of the power supply lines LO1 and LON and the high-voltage diode 42 in parallel with the limiting resistors 41a to 41d of the power supply lines L1 to L3 and N. Furthermore, for example, in the self-diagnosis circuit 3, the relay circuit 31 switches the phase to which the limiting resistor 33 is connected among the multiple phases corresponding to the multiple power supply lines including the power supply lines LO1 and LON in addition to the multiple power supply lines L1 to L3 and N. This configuration also achieves the same effects as the above-described embodiment. Furthermore, the provision of the relay circuit 31 further enhances the effect of suppressing an increase in the circuit size of the self-diagnosis circuit 3 when the limiting resistor 33 is shared.

[0083] 2, the power supply lines N and LON are branched, for example, at the switch circuit 212, but this is not limiting. For example, the power supply lines N and LON may branch on the power supply 9 side from the connection position of the relay circuit 31 to the power supply line N. With this configuration, when the power supply lines LO1 and LON through which the current supplied to the discharge terminals PO1 and PON flows are included in the targets of leakage detection by the ground fault detection circuit 4, self-diagnosis of the power supply lines N and LON can be performed collectively. Therefore, with this configuration, it is possible to suppress an increase in the circuit size of the self-diagnosis circuit 3 that would be otherwise caused by the provision of the relay circuit 31.

[0084] According to at least one of the embodiments described above, it is possible to suppress an increase in the circuit size of the self-diagnosis circuit provided in the leakage detection circuit.

[0085] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

[0086] (Addendum) The above description of the embodiments discloses the following techniques. (1) a ground fault detection circuit electrically connected to a plurality of power supply lines to which AC power is supplied, and detecting a ground fault current relative to the ground potential of each of the plurality of power supply lines; a self-diagnosis circuit that forms a short-circuit path that selectively short-circuits each of the plurality of power supply lines to the connection line of the ground potential, The self-diagnosis circuit a first limiting resistor having a plurality of resistance elements electrically connected in series, one end of which is electrically connected to the connection line of the ground potential; a relay circuit that is provided between the plurality of power supply lines and the side of the first limiting resistor opposite to the connection line of the ground potential, and that is electrically connected to the first limiting resistor to switch the power supply line in which the short-circuit path is formed between the plurality of power supply lines, Leak detection circuit. (2) the self-diagnosis circuit further includes a photorelay electrically connected between the first limiting resistor and the connection line of the ground potential. The leakage detection circuit according to (1) above. (3) The ground fault detection circuit includes: a plurality of second limiting resistors each having a plurality of resistive elements electrically connected in series and electrically connected to the plurality of power supply lines; a diode having an anode electrically connected to each of the second limiting resistors on the opposite side to the power supply lines and a cathode electrically connected to the ground potential connection line via the ground fault current detection shunt resistor; an insulation determination comparator that detects the ground fault current flowing through the detection shunt resistor by comparing a potential generated by the detection shunt resistor with a reference potential; The leakage detection circuit according to (1) or (2) above. (4) the AC power is three-phase; the plurality of power supply lines are four lines including three voltage lines and one neutral line, the relay circuit includes three C-contact relays that electrically connect the first limiting resistor to any one of the four power supply lines; The leakage detection circuit according to any one of (1) to (3) above. (5) The plurality of power supply lines are a first power supply line having four lines including three voltage lines and one neutral line, to which the AC power is supplied during charging and discharging; and at least one second power supply line including a branch voltage line branched from one of the three voltage lines of the first power supply line, the second power supply line being supplied with the AC power during discharge. The leakage detection circuit according to any one of (1) to (4) above. (6) the second power supply line includes a branch neutral conductor branched from the neutral conductor of the first power supply line; The leakage detection circuit according to (5) above. (7) the AC power is single-phase; the plurality of power supply lines are two-wire, including one voltage line and one neutral line; the relay circuit includes one C-contact relay that electrically connects the first limiting resistor to one of the two power supply lines; The leakage detection circuit according to any one of (1) to (3) above. (8) the photorelay of the self-diagnosis circuit is turned on every time the power supply line to which the first limiting resistor is connected is switched by the relay circuit; A leakage current detection circuit according to any one of claims 1 to 7, which directly or indirectly cites (2) of (2) to (7). (9) The leakage detection circuit according to any one of (1) to (8) above; a control circuit configured to control the operation of the ground fault detection circuit and the self-diagnosis circuit, and to determine whether or not the ground fault current has been detected based on the operation states of the ground fault detection circuit and the self-diagnosis circuit and the detection result of the ground fault current by the ground fault detection circuit. Power conversion device. (10) The leakage detection circuit according to any one of (1) to (8) above; a power conversion circuit electrically connected to the leakage detection circuit via the plurality of power supply lines and configured to convert the AC power from an external AC power supply into DC power. Power conversion device. (11) The power conversion device according to (9) or (10) above, which converts the AC power from an external AC power source into DC power; a battery that is charged using the DC power; vehicle. (12) the power conversion device converts DC power from the battery into AC power and supplies the AC power to an external load connected to the vehicle. vehicle. [Explanation of symbols]

[0087] 1 Charging System 2 vehicles 21 On-board charger (power conversion device) 211 Insulation monitor circuit (earth leakage detection circuit) 212 Switch Circuit 213 Power Factor Correction Circuit 214 DC-DC conversion circuit 22 Isolated power supply 23 Battery 3 Self-diagnosis circuit 31 Relay Circuit 32a~32c C-contact relay 33 Limiting resistor 34 Photorelay 35 Resistance 36 Digital Truck 4. Ground fault detection circuit 41a~41d Limiting resistor 42 High-voltage diode 43 Insulation monitor on / off circuit 44a~44f Resistor 45 Digital Truck 46 Y capacitors 47 Insulation judgment comparator 48 Digital Truck 49 Photocoupler 8 Load 9 Power supply

Claims

1. a ground fault detection circuit electrically connected to a plurality of power supply lines to which AC power is supplied, the ground fault detection circuit detecting a ground fault current relative to the ground potential of each of the plurality of power supply lines; a self-diagnosis circuit that forms a short-circuit path that selectively short-circuits each of the plurality of power supply lines to the connection line of the ground potential, The self-diagnosis circuit a first limiting resistor having a plurality of resistance elements electrically connected in series, one end of which is electrically connected to the connection line of the ground potential; a relay circuit that is provided between the plurality of power supply lines and the side of the first limiting resistor opposite to the connection line of the ground potential, and that is electrically connected to the first limiting resistor to switch the power supply line in which the short-circuit path is formed between the plurality of power supply lines, Leak detection circuit.

2. the self-diagnosis circuit further includes a photorelay electrically connected between the first limiting resistor and the connection line of the ground potential.

2. The earth leakage detection circuit according to claim 1.

3. The ground fault detection circuit includes: a plurality of second limiting resistors each having a plurality of resistive elements electrically connected in series and electrically connected to the plurality of power supply lines; a diode having an anode electrically connected to each of the second limiting resistors on the opposite side to the power supply lines and a cathode electrically connected to the ground potential connection line via a shunt resistor for detecting the ground fault current; an insulation determination comparator that detects the ground fault current flowing through the detection shunt resistor by comparing a potential generated by the detection shunt resistor with a reference potential; 2. The earth leakage detection circuit according to claim 1.

4. the AC power is three-phase; the plurality of power supply lines are four lines including three voltage lines and one neutral line, the relay circuit includes three C-contact relays that electrically connect the first limiting resistor to any one of the four power supply lines; 2. The earth leakage detection circuit according to claim 1.

5. The plurality of power supply lines are a first power supply line having four wires, including three voltage wires and one neutral wire, to which the AC power is supplied during charging and discharging; and at least one second power supply line including a branch voltage line branched from one of the three voltage lines of the first power supply line, the second power supply line being supplied with the AC power during discharge.

2. The earth leakage detection circuit according to claim 1.

6. the second power supply line includes a branch neutral conductor branched from the neutral conductor of the first power supply line; 6. The earth leakage detection circuit according to claim 5.

7. the AC power is single-phase; the plurality of power supply lines are two-wire lines including one voltage line and one neutral line, the relay circuit includes one C-contact relay that electrically connects the first limiting resistor to one of the two power supply lines; 2. The earth leakage detection circuit according to claim 1.

8. the photorelay of the self-diagnosis circuit is turned on every time the power supply line to which the first limiting resistor is connected is switched by the relay circuit; 3. The earth leakage detection circuit according to claim 2.

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