Electric leakage detection circuit

Abstract

Provided is an electric leakage detection circuit. An electric leakage 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 of each of the plurality of power supply lines with respect to a ground potential. The self-diagnosis circuit forms a short-circuit path that selectively short-circuits each of the plurality of power supply lines and a connection line of a ground potential. The self-diagnosis circuit has a first limiting resistor and a relay circuit. The first limiting resistor has a plurality of resistive elements electrically connected in series, and one end of the first limiting resistor is electrically connected to a connection line of a ground potential. The relay circuit is provided between the plurality of power supply lines and a side of the first limiting resistor opposite to a connection line having a ground potential, and switches a power supply line to be electrically connected to the first limiting resistor to form a short-circuit path between the plurality of power supply lines.

Description

Technical Field

[0001] The present disclosure relates to a leakage detection circuit. Background Art

[0002] In recent years, the direction of current in power conversion devices such as chargers installed in electric vehicles has been made bidirectional to support both charging and discharging. This has led to the installation of insulation monitoring circuits (leakage detection circuits) that detect leakage current, for example, to prevent electric shock to humans.

[0003] For example, Patent Document 1 discloses a technique related to an insulation state detection device that detects a ground fault or an insulation state relative to a ground potential based on a charge state of a flying capacitor.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-001423 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] For example, in an insulation monitoring circuit, since its failure carries significant risks, an independent self-diagnostic circuit is provided to confirm the integrity of the insulation monitoring circuit itself. In such a situation, for example, miniaturization is required for the on-board charger from the perspective of its portability, while on the other hand, sufficient tolerance to high voltages such as lightning surges is required. Therefore, there is a problem of increasing the circuit scale (size) of the self-diagnostic circuit. In addition, for example, in an on-board charger that can operate by inputting AC voltage from a three-phase AC power supply and a single-phase AC power supply, there is a problem of further increasing the circuit scale of its self-diagnostic circuit.

[0009] One of the problems to be solved by the present disclosure is to suppress an increase in the circuit scale of a self-diagnosis circuit provided in a leakage detection circuit.

[0010] Solutions for solving problems

[0011] The leakage detection circuit involved in 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 lines supplied with AC power, and detects the ground fault current of each of the plurality of power lines relative to the ground potential. The self-diagnosis circuit forms a short-circuit path that selectively short-circuits each of the plurality of power lines with the connection line at the ground potential. The self-diagnosis circuit has a first limiting resistor and a relay circuit. The first limiting resistor has a plurality of resistance elements electrically connected in series, and one end of the first limiting resistor is electrically connected to the connection line at the ground potential. The relay circuit is arranged between the plurality of power lines and the side of the first limiting resistor opposite to the connection line at the ground potential, and switches the power line to be electrically connected to the first limiting resistor to form the short-circuit path among the plurality of power lines.

[0012] According to the present disclosure, it is possible to suppress an increase in the circuit scale of the self-diagnosis circuit provided in the leakage detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram showing an example of the configuration of a charging system according to the embodiment.

[0014] Figure 2 It shows Figure 1 A diagram showing an example of the structure of an insulation monitoring circuit (leakage detection circuit). DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of a self-diagnostic circuit, a leakage detection circuit (insulation monitoring circuit), a power conversion device (on-vehicle charger), a vehicle, and a charging system according to the present disclosure will be described with reference to the accompanying drawings.

[0016] Furthermore, in the description of the present disclosure, components having the same or substantially the same functions as components previously described in the drawings are denoted by the same reference numerals, and descriptions thereof may be omitted as appropriate. Furthermore, even when representing the same or substantially the same parts, they may be shown with different sizes and proportions depending on the drawings. Furthermore, for example, to ensure the visibility of the drawings, in the description of each drawing, only the main components are denoted by reference numerals, and even components having the same or substantially the same functions as components previously described in the drawings may not be denoted by reference numerals.

[0017] Furthermore, in the description of the present disclosure, components having the same or substantially the same functions may be distinguished by appending alphanumeric characters at the end of reference numerals. Alternatively, when multiple components having the same or substantially the same functions are not distinguished, they may be collectively described by omitting alphanumeric characters at the end of reference numerals.

[0018] Figure 1 1 is a diagram showing an example of the configuration of the charging system 1 according to the embodiment. Figure 1 As shown, the charging system 1 includes a vehicle 2 , a load 8 , and a power source 9 . In addition, the vehicle 2 has an onboard charger 21 and a battery 23 .

[0019] The vehicle 2 is, for example, a car, a truck, a bus, a motorcycle, an electric scooter, or any other type of mobile object that is configured to be driven using electric power from a battery 23 .

[0020] Furthermore, the technology according to the embodiment is not limited to the vehicle 2 , and can be applied to various power conversion devices installed in, for example, aircraft, amusement equipment, uninterruptible power supply devices, and the like.

[0021] Furthermore, the vehicle 2 may be configured to operate onboard equipment (electrical components) using power from the battery 23. Examples of such onboard 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 onboard camera.

[0022] The onboard charger 21 is a power conversion device mounted on the vehicle 2. In this embodiment, the onboard charger 21 is configured to operate with both single-phase and three-phase AC power. For example, the onboard charger 21 converts single-phase or three-phase AC power supplied from the power supply 9 into DC power and supplies the DC power to the battery 23. Furthermore, the onboard charger 21 converts DC power from the battery 23 into AC power and supplies the single-phase or three-phase AC power to the load 8 connected to the AC outlet 29a and the in-vehicle outlet 29b of the vehicle 2.

[0023] Furthermore, the onboard charger 21 may not support both single-phase and three-phase, but may be configured to operate with either one. Furthermore, the onboard charger 21 is not limited to single-phase and three-phase (multi-phase), but may be configured to operate with two-phase (multi-phase) AC power.

[0024] The battery 23 stores electric power supplied from the power source 9 via the onboard charger 21. Furthermore, the battery 23 only needs to be able to store electric power for supplying the driving motor (main motor) mounted on the vehicle 2, electrical components, or the load 8 connected to the AC outlet 29a or the in-vehicle outlet 29b of the vehicle 2. For example, any battery such as a lithium-ion battery, a nickel-metal hydride battery, or an all-solid-state battery can be appropriately used as the battery 23.

[0025] Load 8 is detachably connected to AC outlet 29a and in-vehicle outlet 29b of vehicle 2. Load 8 may be, for example, an electronic device such as a home appliance or smartphone that receives power from vehicle 2. Load 8 may also be an external power storage device or power equipment that receives power from vehicle 2, such as a household battery or a power purchasing device at a charging station.

[0026] Here, the AC outlet 29a of the vehicle 2 is a power outlet for charging and discharging the vehicle 2. The AC outlet 29a is provided, for example, at a location accessible from outside the vehicle 2. For example, when charging the vehicle 2, the AC outlet 29a is connected to the power source 9. For example, when discharging the vehicle 2, the AC outlet 29a is connected to the load 8. As an example, the AC outlet 29a of the vehicle 2 supports both single-phase and three-phase AC power, but may also support either type of AC power.

[0027] 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, within the cabin (inside the vehicle) of the vehicle 2. For example, when discharging the vehicle 2, the in-vehicle socket 29b is connected to the load 8. As an example, the in-vehicle socket 29b of the vehicle 2 supports single-phase AC power, but can also support both single-phase and three-phase AC power.

[0028] The power source 9 is, for example, an AC power source such as a power source mounted on a fast charger or a commercial power source. Furthermore, the power source 9 is not limited to a single-phase AC power source or a three-phase AC power source (multi-phase AC power source), and a two-phase AC power source (multi-phase AC power source) may also be used. In this embodiment, the power source 9 that supplies AC power to the onboard charger 21 (power conversion device) of the vehicle 2 is exemplified as a case where either a single-phase or three-phase AC power source can be used.

[0029] like Figure 1 As shown, as an example, the vehicle charger 21 includes an insulation monitoring circuit 211, a power factor correction (PFC: Power Factor Correction) circuit 213 and a DC-DC conversion circuit 214. In addition, the vehicle charger 21 involved in the present disclosure is not limited to Figure 1 For example, in the vehicle charger 21, the power factor improvement circuit 213 is not an essential structure, and other rectification and smoothing circuits can also be used.

[0030] Insulation monitoring circuit 211 is a leakage detection circuit mounted on the onboard charger 21. Insulation monitoring circuit 211 is electrically connected to power factor improvement circuit 213. Furthermore, when load 8 or power source 9 is connected to the onboard charger 21, insulation monitoring circuit 211 is electrically connected to the load 8 or power source 9. Insulation monitoring circuit 211 operates, for example, during discharge of load 8 connected to the onboard charger 21 to detect leakage current.

[0031] The power factor improvement circuit 213 is electrically connected to the insulation monitoring circuit 211 and the DC-DC conversion circuit 214. The power factor improvement circuit 213 rectifies and smoothes the AC voltage from the power supply 9 to generate a DC voltage.

[0032] The DC-DC converter circuit 214 is electrically connected to the power factor correction circuit 213 and the battery 23. The DC-DC converter circuit 214 converts the DC voltage generated by the power factor correction circuit 213 back into an AC voltage, then rectifies and smoothes the voltage to generate a DC voltage of a desired set voltage. Furthermore, the DC-DC converter circuit 214 converts the DC voltage from the battery 23 into an AC voltage, then rectifies and smoothes the voltage to generate a DC voltage of a desired set voltage.

[0033] In addition, the vehicle charger 21 may also include a noise filter (not shown) for suppressing (removing) noise from entering the power supply 9 and noise from flowing out of the power supply 9. The noise filter is provided, for example, in the switch circuit 212 (see Figure 2 ) and the power factor improvement circuit 213, but can also be set in other places.

[0034] Here, the insulation monitoring circuit 211 according to the present disclosure will be described in detail with reference to the drawings.

[0035] Figure 2 It shows Figure 1 FIG. 2 is a diagram showing an example of a structure of an insulation monitoring circuit 211. Figure 1 and Figure 2 As shown, the insulation monitoring circuit 211 includes a self-diagnosis circuit 3 and a ground fault detection circuit 4 .

[0036] The self-diagnostic circuit 3 is electrically connected between the charging and discharging terminals P1 to P3 and PN of the on-vehicle charger 21 and the ground fault detection circuit 4 via a plurality of power supply lines L1 to L3 and N.

[0037] Here, the charging and discharging terminals P1 to P3, PN of the onboard charger 21 are electrically connected to the AC outlet 29a (power outlet for charging and discharging) of the vehicle 2. Multiple power lines L1 to L3, N are connected to the charging and discharging terminals P1 to P3, PN, respectively. Specifically, when the vehicle 2 is charging, AC power from the external power supply 9 is supplied to the multiple power lines L1 to L3, N. Furthermore, when the vehicle 2 is discharging, AC power based on the DC power from the battery 23 is supplied to the multiple power lines L1 to L3, N.

[0038] As an example, power line L1 is a voltage line that carries 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. As an example, power line L2 is not electrically connected to the single-phase AC power supply and is a voltage line that carries, for example, a V-phase (second phase) current from a three-phase AC power supply. As an example, power line L3 is not electrically connected to the single-phase AC power supply and is a voltage line that carries, for example, a W-phase (third phase) current from a three-phase AC power supply. As an example, power line N is a neutral line that is electrically connected to a single-phase or three-phase AC power supply and to ground potential.

[0039] Furthermore, the self-diagnostic circuit 3 is electrically connected between the plurality of power supply lines L1 to L3 and N and a ground line FG functionally grounded to a metal casing or the like of the vehicle 2 .

[0040] Self-diagnostic circuit 3 is a circuit used to confirm the validity of ground fault detection circuit 4, that is, a circuit that performs self-diagnosis in insulation monitoring circuit 211. Specifically, self-diagnostic circuit 3 short-circuits the phases for which ground fault detection by ground fault detection circuit 4 is performed, with ground line FG, which is functionally grounded. In other words, self-diagnostic circuit 3 selectively short-circuits phases L1 to L3 and phase N, that is, each of the multiple power lines L1 to L3 and N, with functionally grounded potential connection line FG.

[0041] like Figure 2 As shown, the self-diagnostic circuit 3 includes a relay circuit 31, a limiting resistor 33, a photorelay 34, and a digital transistor (hereinafter referred to as a "digital transistor") 36. Other circuit elements may be used in place of the digital transistor 36. For example, a bipolar transistor and at least one resistor may be used in place of the digital transistor 36.

[0042] The relay circuit 31 is electrically connected between each of the plurality of power supply lines L1 to L3 and N and the limiting resistor 33. Figure 2 In the example of FIG. 1 , the relay circuit 31 includes three C-contact relays 32 a to 32 c that electrically connect the limiting resistor 33 to any one of the four power supply lines L1 to L3 and N.

[0043] exist Figure 2In the example shown in FIG, one end of the C contact relay 32a is selectively electrically connected to either power supply line L1 or L2, and the other end is electrically connected to the limiting resistor 33 via the C contact relay 32c. Furthermore, one end of the C contact relay 32b is selectively electrically connected to either power supply line L3 or N, and the other end is electrically connected to the limiting resistor 33 via the C contact relay 32c.

[0044] That is to say, in Figure 2 In the example shown, the changeover 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 the break contact (normally closed (NC) contact) of C contact relay 32c is electrically connected to the changeover contact of C contact relay 32a, while the other is electrically connected to the changeover contact of C contact relay 32b. Furthermore, one of the make contact and the break contact of C contact relay 32a is electrically connected to power line L1, while the other is electrically connected to power line L2. Furthermore, one of the make contact and the break contact of C contact relay 32b is electrically connected to power line L3, while the other is electrically connected to power line N.

[0045] In addition, Figure 2 The combination of the C-contact relays 32a and 32b and the power supply lines selectively connected thereto is merely an example, and other combinations such as providing the C-contact relay 32a between the power supply lines L1 and L3 are also possible.

[0046] Furthermore, the number of C-contact relays 32 provided in relay circuit 31 can be appropriately changed depending on the number of target power lines. For example, in a single-phase two-wire system consisting of one voltage line and one neutral line, relay circuit 31 includes a single C-contact relay 32 that electrically connects limiting resistor 33 to either of the two power lines.

[0047] Relay circuit 31 operates each C-contact relay 32a-32c under the control of control circuit 215 (e.g., DSP) of on-board charger 21. This switches the phase to which limiting resistor 33 is connected between the multiple phases corresponding to power lines L1-L3 and N. The phase to which limiting resistor 33 is connected is the phase for which self-diagnosis is performed to confirm the validity of ground fault detection circuit 4. In other words, relay circuit 31 switches the phase for which ground fault detection circuit 4 is functionally grounded, creating a short-circuit, for self-diagnosis purposes, between the multiple phases for which ground fault detection circuit 4 is performing ground fault detection.

[0048] The limiting resistor 33 is electrically connected between the relay circuit 31 and the photorelay 34. The resistance value of the limiting resistor 33 can be appropriately determined based on the voltage withstand requirements of the self-diagnostic circuit 3 against lightning surges, etc. For example, the limiting resistor 33 may include a plurality of high-voltage resistance elements (resistance elements) electrically connected in series. The limiting resistor 33 in this embodiment is an example of a first limiting resistor.

[0049] One end of the photorelay 34 on the light-emitting element side is electrically connected to the isolated 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 end of the digital transistor 36. One end of the photorelay 34 on the light-receiving element side is electrically connected to any one of the power supply lines L1 to L3 and 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 line FG.

[0050] The digital chip 36 is electrically connected between one end of the photorelay 34 on the light-emitting element side, opposite to the isolated power supply 22 of the vehicle 2, and the functionally grounded ground line FG. Furthermore, the control end of the digital chip 36 is electrically connected to a signal line (e.g., GPIO) for supplying control signals from the control circuit 215 of the onboard charger 21.

[0051] The digital chip 36 operates the photorelay 34 according to the control of the control circuit 215 of the vehicle charger 21. As an example, the digital chip 36 turns on the photorelay 34 whenever the power line to which the limiting resistor 33 is connected is switched by the relay circuit 31. For example, the digital chip 36 has a bipolar transistor (not shown). In this case, the base of the bipolar transistor is electrically connected to the GPIO line via an input resistor (not shown), and the emitter is electrically connected to the ground line FG that is functionally grounded via a base-emitter resistor (not shown). For example, in the digital chip 36, the input resistor generates a current according to the voltage level of the GPIO line, thereby generating a collector current corresponding to the magnitude of the generated current. Moreover, the collector of the bipolar transistor of the digital chip 36 is electrically connected to the cathode of the photorelay 34. When the collector current flows in the light-emitting element of the photorelay 34, the switch (not shown) on the light-receiving element side is turned on, thereby functionally grounding the power line selectively connected via the relay circuit 31 and the limiting resistor 33.

[0052] In this manner, the self-diagnostic circuit 3 of this embodiment selectively functionally grounds each of the multiple power lines L1 to L3, and N, creating a short-circuit 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 multiple power lines L1 to L3, and N, creating a short-circuit circuit, the potential of the functionally grounded ground line FG decreases by an amount corresponding to 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 line FG, as described later. Specifically, the self-diagnostic circuit 3 selectively functionally grounds each of the multiple power lines L1 to L3, and N, creating a short-circuit circuit. This prevents the Y capacitor (not shown) provided in the subsequent stage of the ground fault detection circuit 4 in the on-board charger 21 for attenuating common noise from experiencing a breakdown in the Y capacitor, resulting in a state of breakdown in the on-board charger 21 that is the detection target of the insulation monitoring circuit 211.

[0053] Ground fault detection circuit 4 is electrically connected between charging and discharging terminals P1 to P3, PN of onboard charger 21 and switch circuit 212 via power lines L1 to L3, N. Ground fault detection circuit 4 is also electrically connected between power lines L1 to L3, N and functionally grounded ground line FG.

[0054] The ground fault detection circuit 4 detects ground fault (leakage) currents in each of the multiple power lines L1 to L3, and N relative to the ground potential. Specifically, the ground fault detection circuit 4 detects ground fault (leakage) currents generated by insulation breakdown in a target Y capacitor (not shown) between each of the multiple power lines L1 to L3, and N and the functionally grounded ground line FG, located downstream of the ground fault detection circuit 4. Specifically, the ground fault detection circuit 4 detects the insulation condition around the onboard charger 21 by detecting the ground fault current flowing through the detection shunt resistor 44b when the target Y capacitor (not shown) experiences insulation breakdown. The detection range of the ground fault detection circuit 4 is a series of systems forming a closed circuit, including the onboard charger 21, the load 8, and the human body. Furthermore, the ground fault detection circuit 4 can detect currents at all times during discharge from the vehicle 2 and can detect currents before a person experiences an electric shock.

[0055] like Figure 2 As shown, the ground fault detection circuit 4 includes limiting resistors 41 a to 41 d , a high withstand voltage diode 42 , an insulation monitoring on / off circuit 43 , a counter 45 , a counter 48 , a Y capacitor 46 , an insulation determination comparator 47 , and a photocoupler 49 .

[0056] Limiting resistors 41a to 41d are electrically connected in parallel between each of the power lines L1 to L3 and N and the high-voltage diode 42. Each of limiting resistors 41a to 41d has, for example, the same structure as limiting resistor 33 in self-diagnostic circuit 3. Specifically, each of limiting resistors 41a to 41d includes a plurality of high-voltage resistance elements (resistance elements) electrically connected in series. In this embodiment, limiting resistors 41a to 41d are each an example of a second limiting resistor.

[0057] The anode of the high-voltage diode 42 is electrically connected to the side of each of the limiting resistors 41a to 41d opposite the power supply lines L1 to L3 and N. The cathode of the high-voltage diode 42 is electrically connected to one end (the collector of the bipolar transistor) on the light-receiving side of the insulation monitoring on / off circuit 43, similar to the limiting resistor 33 of the self-diagnostic circuit 3. Specifically, the cathode of the high-voltage diode 42 is electrically connected to the functionally grounded potential connection line FG via the shunt resistor 44b for detecting ground fault current.

[0058] The insulation monitoring on / off circuit 43 is comprised of, for example, a photorelay and has the same structure as the photorelay 34 of the self-diagnostic circuit 3. One end of the insulation monitoring 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 monitoring on / off circuit 43 on the light-emitting element side is electrically connected to the output terminal of the data chip 45. One end of the insulation monitoring on / off circuit 43 on the light-receiving element side is electrically connected to the plurality of power supply lines L1 to L3 and N via limiting resistors 41a to 41d and a high-voltage diode 42. The other end of the insulation monitoring on / off circuit 43 on the light-receiving element side is electrically connected to the functionally grounded ground line FG.

[0059] Digital chip 45 has, for example, the same structure as digital chip 36 of self-diagnostic circuit 3. Digital chip 45 is electrically connected between the cathode of the light-emitting element of insulation monitoring on / off circuit 43 and one end of detection shunt resistor 44b. Furthermore, a control end of digital chip 45 is electrically connected to a signal line (e.g., GPIO) for supplying control signals from control circuit 215 of onboard charger 21.

[0060] The digital chip 45 operates the insulation monitoring on / off circuit 43 according to the control of the control circuit 215 of the vehicle charger 21. For example, in the digital chip 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, thereby generating a collector current corresponding to the magnitude of the generated current. Moreover, in the insulation monitoring on / off circuit 43, the collector current of the digital chip 45 flows through the light-emitting element, turning on the switch (not shown) on the light-receiving element side. As a result, the insulation monitoring on / off circuit 43 electrically connects the power lines connected via the limiting resistors 41a to 41d to the detection shunt resistor 44b. In other words, when the insulation monitoring on / off circuit 43 is turned on by the control circuit 215 of the vehicle charger 21, the multiple power lines L1 to L3 and N are electrically connected to the detection shunt resistor 44b via the limiting resistors 41a to 41d and the high-voltage diode 42.

[0061] The detection shunt resistor 44 b is electrically connected between one end of the switch on the light-receiving element side of the insulation monitoring on / off circuit 43 , on the opposite side from the high withstand voltage diode 42 , and the functionally grounded ground line FG.

[0062] One end of Y capacitor 46 is electrically connected to one end of detection shunt resistor 44b on the insulation monitoring on / off circuit 43 side via resistor 44c. The other end of Y capacitor 46 is electrically connected to functionally grounded ground line FG. In other words, Y capacitor 46 is electrically connected in parallel with detection shunt resistor 44b. The RC circuit formed by resistor 44c and Y capacitor 46 is used to adjust the detection time associated with insulation breakdown determination by insulation determination comparator 47.

[0063] One of the pair of input terminals of the insulation determination comparator 47 is electrically connected to one end of the insulation monitoring on / off circuit 43 of the detection shunt resistor 44b via resistor 44c. The other of the pair of input terminals of the insulation determination comparator 47 is electrically connected between resistors 44d and 44e connected in series. These resistors 44d and 44e are electrically connected between the isolated power supply 22 and the functionally grounded ground line FG, generating a reference potential at their connection. In other words, the insulation determination comparator 47 detects the 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 line FG.

[0064] 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, if a Y capacitor (not shown) provided in the downstream stage of ground fault detection circuit 4 experiences insulation breakdown, causing a ground fault current to flow through detection shunt resistor 44b, the voltage level at the output terminal of insulation determination comparator 47 changes to "H (high level)."

[0065] Counting chip 48 has, for example, the same structure as counting chip 45. Counting chip 48 is electrically connected between the cathode of a light-emitting element (not shown) of a photocoupler and a functionally grounded ground line FG. Furthermore, a control terminal of counting chip 48 is electrically connected to the output terminal of insulation determination comparator 47.

[0066] One end of the photocoupler 49 on the light-emitting element side is electrically connected to the isolated power supply 22 via the resistor 44f. The other end of the photocoupler 49 on the light-emitting element side is electrically connected to the output end of the digital chip 48. 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) for supplying a control signal from the control circuit 215 of the vehicle charger 21, and the other is electrically connected to another ground line, for example, that is insulated from the ground line FG.

[0067] Digital chip 48 activates photocoupler 49 according to the output of insulation determination comparator 47. For example, in digital chip 48, an input resistor (not shown) connected to the base of a bipolar transistor (not shown) generates a current based on the voltage level at the output of insulation determination comparator 47, generating a collector current corresponding to the magnitude of the generated current. Furthermore, in photocoupler 49, the collector current from digital chip 48 flows through the light-emitting element, turning on a switch (not shown) on the light-receiving element side, thereby changing the voltage level of the GPIO line. Thus, when ground fault detection circuit 4 detects a ground fault current flowing through detection shunt resistor 44b, it can notify control circuit 215 of onboard charger 21.

[0068] The control circuit 215 of the on-board charger 21 controls the operation of the self-diagnostic circuit 3 and the ground fault detection circuit 4. The control circuit 215 is configured to determine the validity of the ground fault current detection performed by the insulation monitoring circuit 211 based on the respective operating states of the self-diagnostic circuit 3 and the ground fault detection circuit 4 and the detection result of the ground fault current detected by the ground fault detection circuit 4.

[0069] The control circuit 215 can detect insulation breakdown, that is, the occurrence of a ground fault (leakage), of a Y capacitor (not shown) provided in a subsequent stage of the ground fault detection circuit 4 based on the notification of ground fault current detection from the ground fault detection circuit 4 when the insulation monitoring on / off circuit 43 of the ground fault detection circuit 4 is turned on, without operating the self-diagnostic circuit 3.

[0070] When the self-diagnosis circuit 3 is activated to perform self-diagnosis, the control circuit 215 can detect that the ground fault detection circuit 4 is operating normally based on the notification of ground fault current detection from the ground fault detection circuit 4 when the insulation monitoring on / off circuit 43 of the ground fault detection circuit 4 is turned off.

[0071] When the control circuit 215 activates the self-diagnosis circuit 3 to perform self-diagnosis, it can detect a malfunction in the ground fault detection circuit 4 based on the absence of a notification of ground fault current detection from the ground fault detection circuit 4 when the insulation monitoring on / off circuit 43 of the ground fault detection circuit 4 is turned off.

[0072] Furthermore, the self-diagnosis performed by activating the self-diagnosis circuit 3 serves as a secondary safety feature of the on-board charger 21, verifying the validity of the ground fault detection circuit 4. This self-diagnosis can be performed at any time during discharge, when a ground fault current could flow if a functional ground fault occurs and a short circuit occurs. It can be performed at the start or end of discharge, or continuously or intermittently during discharge.

[0073] Furthermore, the control circuit 215 includes, for example, at least one processor (not shown) and at least one memory (not shown), and has a hardware configuration utilizing a conventional computer. For example, a DSP (Digital Signal Processor) can be utilized as the control circuit 215. Furthermore, the control circuit 215 can implement its various functions by, for example, having the processor load a program stored in a ROM (Read Only Memory) or the like into a RAM (Random Access Memory) and execute the loaded program. Alternatively, the control circuit 215 can implement some or all of its functions using dedicated hardware circuits (e.g., semiconductor integrated circuits).

[0074] Furthermore, the control circuit 215 for controlling the operation of the self-diagnostic circuit 3 and the control circuit 215 for controlling the operation of the ground fault detection circuit 4 may be implemented by the same circuit or by different circuits that are independent of each other.

[0075] Alternatively, the control circuit 215 may be implemented by a computer such as an ECU (Electronic Control Unit), a DCU (Domain Control Unit) or an OBU (On Board Unit) installed within the vehicle 2, such as a CDC (Cockpit Domain Controller) that integrates multiple ECUs. Furthermore, the control circuit 215 can exchange information with other ECUs installed in the vehicle and an external power supply (power supply 9) connected to the vehicle via an in-vehicle network including the vehicle's CAN (Controller Area Network), Ethernet (registered trademark), and USB (Universal Serial Bus), and can also communicate with information processing devices external to the vehicle via a network such as the Internet.

[0076] like Figure 1 and Figure 2 As shown, the on-board charger 21 has a switching circuit 212 .

[0077] Switching circuit 212 is electrically connected between insulation monitoring circuit 211 and power factor correction circuit 213 via multiple power lines L1 to L3 and N. Furthermore, switching circuit 212 is electrically connected between discharge terminals PO1 and PON of onboard charger 21 and power factor correction circuit 213 via multiple power lines LO1 and LON. Specifically, power line LO1 is a voltage line branching from any of the multiple power lines L1 to L3. Power line LON is a neutral line branching from power line N.

[0078] Here, the multiple power lines L1 to L3 and N in the embodiments are each an example of a first power line. Furthermore, the multiple power lines LO1 and LON in the embodiments are each an example of a second power line. Furthermore, the power line LO1 in the embodiments is an example of a branched voltage line. Furthermore, the power line LON in the embodiments is an example of a branched neutral line. Furthermore, in the case of a three-phase three-wire system, the power line N in the embodiments is an example of both the first and second power lines.

[0079] Here, the discharge terminals PO1 and PON of the onboard charger 21 are electrically connected to the in-vehicle outlet 29b (discharge power outlet) of the vehicle 2. Multiple power lines LO1 and LON are connected to the multiple discharge terminals PO1 and PON, respectively. For example, the power line LO1 is a voltage line through which single-phase current from the power factor correction circuit 213, based on the DC current from the battery 23, flows. For example, the power line LON is a neutral line electrically connected to the power line N and the ground potential.

[0080] The switching circuit 212 operates under the control of the control circuit 215 of the on-board charger 21. When the vehicle 2 is charging or discharging via the AC outlet 29a, the switching circuit 212 electrically connects the insulation monitoring circuit 211 to the power factor improvement circuit 213 via the plurality of power lines L1 to L3 and N. When discharging from the vehicle 2 via the in-vehicle outlet 29b, the switching circuit 212 electrically connects the discharge terminals PO1 and PON of the on-board charger 21 to the power factor improvement circuit 213 via the plurality of power lines LO1 and LON.

[0081] As described above, in the insulation monitoring circuit 211 (leakage detection circuit) according to the present disclosure, the self-diagnostic circuit 3 includes the relay circuit 31 for switching the power line to be connected to the limiting resistor 33 to form a short-circuit path among the plurality of power lines L1 to L3 and N.

[0082] The greater the voltage resistance requirement for self-diagnostic circuit 3 against lightning surges and other conditions, the greater the number of high-voltage resistance elements connected in series. In such cases, in the self-diagnostic circuit 3 of the present disclosure, relay circuit 31 is provided to share limiting resistor 33 among the multiple power lines for which ground fault detection circuit 4 performs ground fault detection. In the self-diagnostic circuit 3 of the present disclosure, there is no need to provide separate limiting resistors 33 for each of the multiple power lines.

[0083] Therefore, according to the insulation monitoring circuit 211 of the present disclosure, it is possible to suppress the number of high-voltage resistance elements that increases as the voltage required for the self-diagnostic circuit 3 increases. Figure 2 In the illustrated three-phase four-wire configuration, the circuit structure between the relay circuit 31 and the ground line FG can be shared, thereby reducing the number of relays by a factor of 4. As an example, the relay circuit 31 of the present disclosure can also be applied to a three-phase three-wire configuration. In this case, the circuit structure between the relay circuit 31 and the ground line FG can be shared, thereby reducing the number of relays by a factor of 3. As an example, the relay circuit 31 of the present disclosure can also be applied to a single-phase two-wire configuration. In this case, the circuit structure between the relay circuit 31 and the ground line FG can be shared, thereby reducing the number of relays by a factor of 2.

[0084] Furthermore, the circuit size and cost increase corresponding to the number of relay circuits 31 provided in exchange for the circuit configuration between the shared relay circuit 31 and the ground wire FG. However, the relay circuit 31 of the present disclosure can be configured as a general-purpose relay circuit, for example. Furthermore, the short-circuit current of the relay circuit 31 is only a few mA, thus minimizing increases in size and cost. In other words, the circuit size and cost of the additional relay circuit 31 are smaller than the circuit size and cost of the photorelay 34, which is reduced by sharing the circuit.

[0085] In this way, by providing relay circuit 31 and sharing limiting resistor 33, it is possible to reduce the number of components and circuit size of self-diagnostic circuit 3 provided in insulation monitoring circuit 211, thereby reducing its cost. Furthermore, by reducing the circuit size of self-diagnostic circuit 3, the size and volume of the circuit substrate on which it is mounted can be reduced, thereby miniaturizing insulation monitoring circuit 211 and on-board charger 21.

[0086] Furthermore, since the circuit structure after the limiting resistor 33 is also shared, the number of signal lines (e.g., GPIO lines) connecting the control circuit 215 (e.g., microcomputer) and the self-diagnostic circuit 3 can be reduced. This simplifies wiring, thereby increasing the flexibility of component placement in the on-board charger 21. Furthermore, the number of available ports on the control circuit 215 can be increased, allowing the control circuit 215 to be implemented using an inexpensive microcomputer with a small number of GPIO terminals.

[0087] Furthermore, the power lines LO1 and LON, through which current flows to discharge terminals PO1 and PON connected to, for example, an in-vehicle outlet 29b located within the vehicle 2, may also be included in the targets of leakage detection by the ground fault detection circuit 4. In this case, in the ground fault detection circuit 4, limiting resistors of the same structure are electrically connected in parallel with the plurality of limiting resistors 41a to 41d of the plurality of power lines L1 to L3, N, between each of the power lines LO1 and LON and the high-voltage diode 42. Furthermore, in the self-diagnostic circuit 3, for example, a relay circuit 31 switches the phase to which the limiting resistor 33 is connected between the multiple phases corresponding to the plurality of power lines L1 to L3, N, including the power lines LO1 and LON. Even with this configuration, the same effects as those of the aforementioned embodiment can be achieved. Furthermore, the effect of suppressing an increase in the circuit size of the self-diagnostic circuit 3 can be further enhanced by providing the relay circuit 31 and sharing the limiting resistor 33.

[0088] In addition, the power lines N and LON are Figure 2As shown, for example, the power lines N and LON may be branched in switch circuit 212, but this is not limiting. For example, the power lines N and LON may be branched closer to the power source 9 than the connection point of relay circuit 31 to the power line N. With this configuration, if the power lines L01 and L0N, through which the current supplied to discharge terminals PO1 and PON flows, are included in the leakage detection targets of ground fault detection circuit 4, self-diagnosis of the power lines N and LON can be performed simultaneously. Consequently, this configuration can suppress the increase in circuit size of self-diagnosis circuit 3 that would otherwise be associated with the provision of relay circuit 31.

[0089] According to at least one of the above-described embodiments, it is possible to suppress an increase in the circuit scale of the self-diagnostic circuit provided in the leakage detection circuit.

[0090] While 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 ways and can be omitted, replaced, or modified without departing from the spirit of the invention. These embodiments and their variations are intended to be included within the scope and spirit of the invention, as well as within the invention set forth in the claims and their equivalents.

[0091] (Note)

[0092] The following technology is disclosed through the description of the above embodiments.

[0093] (1) A leakage detection circuit comprising:

[0094] 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 with respect to a ground potential in each of the plurality of power supply lines; and

[0095] a self-diagnostic circuit that forms a short-circuit path for selectively short-circuiting each of the plurality of power lines and the connection line at the ground potential;

[0096] Wherein, the self-diagnosis circuit has:

[0097] a first limiting resistor having a plurality of resistance elements electrically connected in series, one end of the first limiting resistor being electrically connected to the connection line of the ground potential; and

[0098] A relay circuit is provided between the plurality of power lines and the side of the first limiting resistor opposite to the ground potential connection line, and switches the power line to be electrically connected to the first limiting resistor to form the short-circuit path among the plurality of power lines.

[0099] (2) The leakage detection circuit according to (1) above, wherein:

[0100] The self-diagnostic circuit further includes a photorelay electrically connected between the first limiting resistor and the connection line to the ground potential.

[0101] (3) The leakage detection circuit according to (1) or (2), wherein:

[0102] The ground fault detection circuit has:

[0103] a plurality of second limiting resistors, each of the plurality of second limiting resistors having a plurality of resistance elements electrically connected in series, the plurality of second limiting resistors being electrically connected to the plurality of power lines;

[0104] a diode having an anode electrically connected to the side of each of the plurality of second limiting resistors opposite to the plurality of power lines, and a cathode electrically connected to the ground potential connection line via the shunt resistor for detecting the ground fault current; and

[0105] An insulation determination comparator 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.

[0106] (4) The leakage detection circuit according to any one of (1) to (3), wherein:

[0107] The AC power is three-phase,

[0108] The plurality of power lines are four lines including three voltage lines and one neutral line,

[0109] The relay circuit includes three C-contact relays electrically connecting the first limiting resistor to any one of the four power supply lines.

[0110] (5) The leakage detection circuit according to any one of (1) to (4), wherein:

[0111] The plurality of power lines include:

[0112] four first power lines, the four first power lines including three voltage lines and one neutral line, to which the AC power is supplied during charging and discharging; and

[0113] 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, is supplied with the AC power during discharge.

[0114] (6) The leakage detection circuit according to (5) above, wherein:

[0115] The second power line includes a branched neutral line branching from the neutral line of the first power line.

[0116] (7) The leakage detection circuit according to any one of (1) to (3), wherein:

[0117] The AC power is single-phase,

[0118] The plurality of power lines are two lines including a voltage line and a neutral line,

[0119] The relay circuit includes a C-contact relay electrically connecting the first limiting resistor to either one of the two power supply lines.

[0120] (8) The leakage detection circuit according to any one of (2) to (7), wherein:

[0121] The photorelay of the self-diagnostic circuit is turned on every time the power supply line to which the first limiting resistor is connected is switched by the relay circuit.

[0122] (9) A power conversion device comprising:

[0123] The leakage detection circuit according to any one of (1) to (8); and

[0124] The control circuit is configured to control the operations of the ground fault detection circuit and the self-diagnosis circuit, and determine the validity of the detection of the ground fault current based on the respective operating states of the ground fault detection circuit and the self-diagnosis circuit and the detection result of the ground fault current detected by the ground fault detection circuit.

[0125] (10) A power conversion device comprising:

[0126] The leakage detection circuit according to any one of (1) to (8); and

[0127] A power conversion circuit is electrically connected to the leakage detection circuit via the plurality of power supply lines and converts the AC power from an external AC power source into DC power.

[0128] (11) A vehicle comprising:

[0129] The power conversion device according to (9) or (10) above, which converts the AC power from an external AC power source into DC power; and

[0130] A battery is charged using the DC power.

[0131] (12) The vehicle according to (11), wherein:

[0132] 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.

Claims

1. A leakage detection circuit, comprising: 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 with respect to a ground potential in each of the plurality of power supply lines; and a self-diagnostic circuit that forms a short-circuit path for selectively short-circuiting each of the plurality of power lines and the connection line at the ground potential; in, The self-diagnostic circuit has: a first limiting resistor having a plurality of resistance elements electrically connected in series, wherein one end of the first limiting resistor is electrically connected to the connection line of the ground potential; as well as A relay circuit is provided between the plurality of power lines and the side of the first limiting resistor opposite to the ground potential connection line, and switches the power line to be electrically connected to the first limiting resistor to form the short-circuit path among the plurality of power lines.

2. The leakage detection circuit according to claim 1, wherein: The self-diagnostic circuit further includes a photorelay electrically connected between the first limiting resistor and the connection line to the ground potential.

3. The leakage detection circuit according to claim 1, wherein: The ground fault detection circuit has: a plurality of second limiting resistors, each of the plurality of second limiting resistors having a plurality of resistance elements electrically connected in series, the plurality of second limiting resistors being electrically connected to the plurality of power lines; a diode having an anode electrically connected to a side of each of the plurality of second limiting resistors opposite to the plurality of power lines, and a cathode electrically connected to the ground potential connection line via the shunt resistor for detecting the ground fault current; as well as An insulation determination comparator 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.

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

5. The leakage detection circuit according to claim 1, wherein: The plurality of power lines include: four first power lines, the four first power 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, is supplied with the AC power during discharge.

6. The leakage detection circuit according to claim 5, wherein: The second power line includes a branched neutral line branched from the neutral line of the first power line.

7. The leakage detection circuit according to claim 1, wherein: The AC power is single-phase, The plurality of power lines are two lines including a voltage line and a neutral line, The relay circuit includes a C-contact relay electrically connecting the first limiting resistor to either one of the two power supply lines.

8. The leakage detection circuit according to claim 2, wherein: The photorelay of the self-diagnostic circuit is turned on every time the power supply line to which the first limiting resistor is connected is switched by the relay circuit.

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