Power transmission device used for non-contact power supply

Abstract

A power transmission device (100, 100b, 100c, 100d, 100e, 100f) used for non-contact power supply comprises: a transformer (TR) provided between an inverter (INV) and a resonance circuit (RC); a sensor (210, 211b, 212b, 211c, 212c, V1, V2, 210e, 210f, 210g) that detects a parameter related to a current flowing between the transformer and the resonance circuit; and an electric leakage detection unit (SC) that detects an electric leakage on the basis of the detected parameter.

Description

Power transmission device used for non-contact power supply Cross-reference to related applications

[0001] This application is based on Japanese Application No. 2024-190935 filed on October 30, 2024, the contents of which are incorporated herein by reference.

[0002] This disclosure relates to a power transmission device used for non-contact power supply.

[0003] Various technologies related to non-contact power supply have been proposed. For example, Patent Document 1 discloses a device for diagnosing leakage current in a power receiving device used in a non-contact power supply system.

[0004] Japanese Patent Application Laid-Open No. 2013-252040

[0005] Patent Document 1 discloses leakage current detection in a power receiving device, but does not disclose leakage current detection in a power transmission device. In particular, since leakage current detection in the AC part of the power transmission device has not been studied, there is room for improvement.

[0006] This disclosure can be realized in the following forms.

[0007] According to a first aspect of the present disclosure, a power transmission device used for non-contact power supply is provided. This power transmission device includes a transformer provided between an inverter and a resonance circuit, a sensor that detects a parameter related to the current flowing between the transformer and the resonance circuit, and a leakage current detection unit that detects leakage current based on the detected parameter.

[0008] According to the power transmission device of this aspect, since it includes a sensor that detects a parameter related to the current flowing between the transformer and the resonance circuit and a leakage current detection unit that detects leakage current based on the detected parameter, leakage current in the power transmission device can be detected with a relatively simple configuration.

[0009] According to another aspect of the present disclosure, a power transmission device for use in contactless power supply is provided. This power transmission device comprises an inverter, a transformer to which power is supplied from the inverter, a plurality of resonant circuits connected to the transformer to which electricity transformed by the transformer is supplied, a single sensor provided between the transformer and the plurality of resonant circuits for detecting parameters related to the current flowing between the transformer and the plurality of resonant circuits, and a leakage detection unit for detecting leakage based on the detected parameters.

[0010] According to this embodiment of the power transmission device, a single sensor is provided between the transformer and the multiple resonant circuits to detect parameters related to the current flowing between the transformer and the multiple resonant circuits. Therefore, a leakage current in the circuit between the transformer and the multiple resonant circuits can be detected by a single sensor. As a result, the power transmission device as a whole can be made more compact compared to a configuration with multiple sensors.

[0011] The above-mentioned and other purposes, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the accompanying drawings. The drawings are as follows: Figure 1 is a schematic diagram showing the schematic configuration of a power transmission device in one embodiment of this disclosure; Figure 2 is a schematic diagram showing the schematic configuration of a power transmission device in a second embodiment; Figure 3 is a schematic diagram showing the schematic configuration of a power transmission device in a third embodiment; Figure 4 is a schematic diagram showing the schematic configuration of a power transmission device in a fourth embodiment; Figure 5 is a schematic diagram showing the schematic configuration of a power transmission device in a fifth embodiment; Figure 6 is a diagram illustrating a sensor composed of a ring-shaped member; Figure 7 is a plan view showing the schematic configuration of a power transmission device in a sixth embodiment; Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 7; Figure 9 is a diagram illustrating a sensor composed of an eight-shaped member; and Figure 10 is a schematic diagram showing the schematic configuration of a power transmission device in a ninth embodiment.

[0012] A. First Embodiment: <Outline Configuration of Power Transmission Device 100> The power transmission device 100 shown in Figure 1 is used in a contactless power supply system. Specifically, the contactless power supply system consists of a power transmission device 100 and a power receiving device (not shown). Power is supplied from the power transmission device 100 to the power receiving device without contact by the resonance of the resonant circuit RC of the power transmission device 100 and the resonant circuit of the power receiving device. The power transmission device 100 is, for example, buried in the road. The power receiving device is, for example, provided on the underside of a vehicle. The power transmission device 100 includes a power supply P, an inverter INV, a transformer TR, a filter circuit FL, a resonant circuit RC, and a sensor circuit 200.

[0013] <Configuration of Power Supply P> Power supply P supplies DC current to inverter INV. Power supply P may also have a function to adjust the voltage.

[0014] <Configuration of Inverter INV> The inverter INV converts direct current (DC) supplied from the power source P into alternating current (AC). The inverter INV is configured to convert DC into AC of a desired frequency. The inverter INV has four switching elements Q1, Q2, Q3, and Q4. The switching elements Q1, Q2, Q3, and Q4 are, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transformers). The AC is supplied to the transformer TR.

[0015] <Configuration of Transformer TR> The transformer TR adjusts the voltage of the supplied AC. The transformer TR is installed between the inverter INV and the resonant circuit RC. The transformer TR has a primary coil 10 and secondary coils 20 and 30. The voltage is adjusted by adjusting the turns ratio between the primary coil 10 and the secondary coils 20 and 30. In this embodiment, a grounding wire 40 is connected to the neutral point NP of the secondary coils 20 and 30. As a result, the circuit between the transformer TR and the resonant circuit RC is grounded.

[0016] In this disclosure, of the pair of lines connected to the outer ends of the secondary coils 20 and 30, the line from connection point CP1 at one end of the secondary coils 20 and 30 to connection point CP2 of the resonant circuit RC (described later) is called the "X phase". The line from connection point CP3 at the other end of the secondary coils 20 and 30 to connection point CP4 of the resonant circuit RC is called the "Y phase". Therefore, the X phase and the Y phase are provided between the transformer TR and the resonant circuit RC, and can be said to connect the transformer TR and the resonant circuit RC. Currents flow in opposite directions through the X phase and the Y phase.

[0017] <Configuration of Filter Circuit FL> The filter circuit FL removes noise contained in the AC. The filter circuit FL is located on the output side (resonant circuit RC side) of the transformer TR. The filter circuit FL has a series filter SF and a parallel filter PF. The series filter SF has a first series reactor SL1 and a second series reactor SL2, and a first series capacitor SC1 and a second series capacitor SC2. The first series reactor SL1 and the first series capacitor SC1 are connected in series with each other and are located in the X phase. The second series reactor SL2 and the second series capacitor SC2 are connected in series with each other and are located in the Y phase. The reactance of the first series reactor SL1 and the reactance of the second series reactor SL2 are equal to each other. Also, the capacitance of the first series capacitor SC1 and the capacitance of the second series capacitor SC2 are equal to each other. The parallel filter PF has a parallel reactor PL and a parallel capacitor PC. The parallel reactor PL and the parallel capacitor PC are connected in parallel to the X and Y phases, respectively.

[0018] <Resonant Circuit RC> The resonant circuit RC resonates with the resonant circuit of the power receiving device. The resonant circuit RC has a power transmitting coil (not shown). The power transmitting coil is magnetically coupled with the power receiving coil of the resonant circuit in the power receiving device. As a result, power is transmitted from the power transmitting device 100 to the power receiving device without contact. The resonant frequency of the resonant circuit RC of the power transmitting device 100 and the resonant frequency of the resonant circuit of the power receiving device are configured to be approximately the same.

[0019] <Configuration of Sensor Circuit 200> The sensor circuit 200 detects leakage current in the power transmission device 100. The sensor circuit 200 includes a sensor 210, an amplifier AMP, and a leakage current detection unit SC. The sensor 210 detects parameters related to the current flowing between the transformer TR and the resonant circuit RC. The "parameters related to the current flowing between the transformer TR and the resonant circuit RC" are, for example, current value, voltage value, magnetic flux, magnetic flux density, etc. In this embodiment, the sensor 210 detects the current flowing through the grounding wire 40. The detection of parameters will be described later. In this embodiment, the sensor 210 is a conductor. The conductor is made of a conductive metal such as copper, for example. The sensor 210 is connected to the grounding wire 40 provided at the neutral point NP of the secondary coils 20 and 30. The amplifier AMP is connected to the sensor 210 and increases the current supplied from the sensor 210.

[0020] The detection of parameters related to the current flowing through the grounding wire 40 by the sensor 210 in this embodiment will be described. When no leakage current occurs, no current flows through the grounding wire 40. In contrast, when a leakage current occurs in any part of the power transmission device 100, a circuit is formed between the location of the leakage current and the grounded location. Due to the leakage current, current flows through the grounding wire 40, and this current also flows through the sensor 210.

[0021] The leakage detection unit SC detects leakage current in the power transmission device 100 based on the current detected by the sensor 210. The leakage detection unit SC is, for example, a computer having a processor and memory. The current amplified by the amplifier AMP is transmitted to the leakage detection unit SC. In this embodiment, the leakage detection unit SC determines that leakage current has occurred when the transmitted current is above a predetermined threshold. In other words, the leakage detection unit SC detects the occurrence of leakage current when the transmitted current is above a predetermined threshold. The threshold is pre-recorded in memory.

[0022] After determining that a ground fault has occurred, the leakage detection unit SC may optionally take actions such as notifying workers or stopping the power transmission from the power transmission device 100.

[0023] According to the power transmission device 100 of the first embodiment described above, since it includes a sensor 210 that detects parameters related to the current flowing between the transformer TR and the resonant circuit RC, and a leakage detection unit SC that detects leakage current based on the detected parameters, leakage current in the power transmission device 100 can be detected with a relatively simple configuration.

[0024] Furthermore, according to the power transmission device 100 of the first embodiment, the sensor 210 detects the current flowing through the grounding wire 40, and the leakage detection unit SC determines that a leakage has occurred when the parameter is above a predetermined threshold. Therefore, leakage can be detected relatively easily using the grounding wire 40.

[0025] Furthermore, according to the power transmission device 100 of the first embodiment, the grounding wire 40 is connected to the neutral point NP on the secondary side of the transformer TR, so the grounding wire 40 can be connected to the center of symmetry in the circuit. This reduces the influence of noise transmitted to the sensor 210 compared to a configuration in which the grounding wire 40 is not connected at such a position.

[0026] B. Second Embodiment: The power transmission device 100b of the second embodiment shown in Figure 2 differs from the power transmission device 100 of the first embodiment in the configuration of the sensor circuit 200b. The other components of the power transmission device 100b of the second embodiment are the same as those of the power transmission device 100 of the first embodiment, so they are denoted by the same reference numerals and their detailed description is omitted.

[0027] The sensor circuit 200b includes sensors 211b and 212b, a leakage detection line 230, an amplifier AMP, and a leakage detection unit SC. In the second embodiment, sensors 211b and 212b detect a parameter related to the difference current between the current flowing through the first series reactor SL1 and the current flowing through the second series reactor SL2. In this embodiment, sensors 211b and 212b detect a change in magnetic flux that occurs when there is a difference between the current flowing through the first series reactor SL1 and the current flowing through the second series reactor SL2. That is, the parameter related to the difference current in this embodiment is magnetic flux. Sensors 211b and 212b are composed of, for example, coils. Sensor 211b is positioned near the first series reactor SL1. Sensor 212b is positioned near the second series reactor SL2. When a difference occurs between the current flowing through the first series reactor SL1 and the current flowing through the second series reactor SL2, the magnetic flux around the first series reactor SL1 and the second series reactor SL2 changes. This causes a change in the magnetic flux passing through sensors 211b and 212b, generating induced electromotive force. Sensors 211b and 212b and the amplifier AMP are connected via a leakage detection wire 230. The leakage detection wire 230 is a conductor made of any conductive metal such as copper. When induced electromotive force is generated in sensors 211b and 212b, the current is transmitted to the leakage detection unit SC via the leakage detection wire 230 and the amplifier AMP. The leakage detection unit SC performs leakage detection, similar to the power transmission device 100 of the first embodiment.

[0028] According to the power transmission device 100 of the second embodiment described above, sensors 211b and 212b detect parameters related to the difference current between the current flowing through the first series reactor SL1 and the current flowing through the second series reactor SL2, and the leakage detection unit SC determines that a leakage has occurred when the parameters are above a predetermined threshold, thus enabling leakage detection with a relatively simple configuration.

[0029] C. Third Embodiment: The power transmission device 100c of the third embodiment shown in Figure 3 differs from the power transmission device 100 of the first embodiment in the configuration of the parallel filter PFc, the connection position of the grounding wire 40c, and the configuration of the sensor circuit 200c. The configuration of the power transmission device 100c of the third embodiment that is not specifically described below is the same as that of the power transmission device 100 of the first embodiment.

[0030] The parallel filter PFc has a first parallel reactor PL1 and a second parallel reactor PL2. The first parallel reactor PL1 and the second parallel reactor PL2 are arranged in parallel with respect to the X phase and the Y phase. The first parallel reactor PL1 and the second parallel reactor PL2 are connected in series with respect to each other. A ground wire 40c is connected to the neutral point NPc between the first parallel reactor PL1 and the second parallel reactor PL2.

[0031] The sensor circuit 200c includes sensors 211c and 212c, a leakage detection line 230, an amplifier AMP, and a leakage detection unit SC. In the third embodiment, sensors 211c and 212c detect a parameter related to the difference current between the current flowing through the first parallel reactor PL1 and the current flowing through the second parallel reactor PL2. In this embodiment, sensors 211c and 212c detect a change in magnetic flux that occurs when there is a difference between the current flowing through the first parallel reactor PL1 and the current flowing through the second parallel reactor PL2. That is, the parameter related to the difference current value in this embodiment is magnetic flux. Sensors 211c and 212c are composed of, for example, coils. Sensor 211c is placed near the first parallel reactor PL1. Sensor 212c is placed near the second parallel reactor PL2. When a leakage current occurs, a difference arises between the current flowing through the first parallel reactor PL1 and the current flowing through the second parallel reactor PL2, causing a change in the magnetic flux around the first parallel reactor PL1 and the second parallel reactor PL2. This changes the magnetic flux passing through sensors 211c and 212c, generating an electromotive force. The generated current flows to the leakage detection unit SC via the leakage detection line 230 and the amplifier AMP, similar to the sensor circuit 200b of the second embodiment. The leakage detection unit SC performs leakage detection, similar to the power transmission device 100 of the first embodiment.

[0032] According to the power transmission device 100c of the third embodiment described above, sensors 211c and 212c detect parameters related to the difference current between the current flowing through the first parallel reactor PL1 and the current flowing through the second parallel reactor PL2, and the leakage detection unit SC determines that a leakage has occurred when the detected parameters are above a predetermined threshold, thus enabling leakage detection with a relatively simple configuration.

[0033] D. Fourth Embodiment: The power transmission device 100d of the fourth embodiment shown in Figure 4 differs from the power transmission device 100 of the first embodiment in the configuration of the parallel filter PFd, the connection position of the grounding wire 40d, and the configuration of the sensor circuit 200d. Among the configurations of the power transmission device 100d of the fourth embodiment, those not specifically described below are the same as those of the power transmission device 100 of the first embodiment.

[0034] The parallel filter PFd has a first parallel capacitor PC1 and a second parallel capacitor PC2. The capacitance of the first parallel capacitor PC1 and the capacitance of the second parallel capacitor PC2 are equal to each other. The first parallel capacitor PC1 and the second parallel capacitor PC2 are provided in parallel with respect to the X phase and the Y phase. The first parallel capacitor PC1 and the second parallel capacitor PC2 are connected in series with respect to each other. A ground wire 40d is connected to the neutral point NPd between the first parallel capacitor PC1 and the second parallel capacitor PC2.

[0035] The sensor circuit 200d includes sensors V1 and V2, a leakage detection line 230d, and a leakage detection unit SC. In the fourth embodiment, sensors V1 and V2 detect parameters related to the difference voltage between the voltage of the first parallel capacitor PC1 and the voltage of the second parallel capacitor PC2. More specifically, sensor V1 measures the voltage of the first parallel capacitor PC1, and sensor V2 measures the voltage of the second parallel capacitor PC2. Sensors V1 and V2 also compare the detected voltages and detect the difference voltage value as a parameter. When a leakage current occurs, a circuit is formed between the leakage point and the ground point. Here, because the area between the first parallel capacitor PC1 and the second parallel capacitor PC2 is grounded, a difference occurs between the voltage of the first parallel capacitor PC1 and the voltage of the second parallel capacitor PC2. Sensors V1 and V2 detect the difference voltage value between the first parallel capacitor PC1 and the second parallel capacitor PC2 and transmit it to the leakage detection unit SC via the leakage detection line 230d. The leakage detection unit SC of this embodiment determines that a leakage current has occurred when the differential voltage value is equal to or greater than a predetermined threshold.

[0036] According to the power transmission device 100d of the fourth embodiment described above, sensors V1 and V2 detect parameters related to the difference voltage between the voltage of the first parallel capacitor PC1 and the voltage of the second parallel capacitor PC2, and the leakage current detection unit SC determines that a leakage current has occurred when the detected parameters are above a predetermined threshold, thus enabling leakage current detection with a relatively simple configuration.

[0037] E. Fifth Embodiment: The power transmission device 100e of the fifth embodiment shown in Figure 5 differs from the power transmission device 100b of the second embodiment in the configuration of the sensor 210e. The configuration of the power transmission device 100e of the fifth embodiment that is not specifically described below is the same as that of the power transmission device 100b of the second embodiment.

[0038] The sensor 210e in the fifth embodiment, like the sensors 211b and 212b in the second embodiment, detects parameters related to the difference current between the current flowing through the first series reactor SL1 and the current flowing through the second series reactor SL2. The sensor 210e in this embodiment differs from the sensors 211b and 212b in the second embodiment in that it is provided across the space between the first series reactor SL1 and the first series capacitor SC1, and between the second series reactor SL2 and the second series capacitor SC2. As shown in Figure 6, the sensor 210e is composed of a ring-shaped member. The material of the ring-shaped member is any magnetic material, such as ferrite. The ring-shaped member has an annular external shape. In this disclosure, "ring-shaped" includes not only an annular shape but also a rectangular frame shape, such as the sensor 210e shown in Figure 6. The X-phase and Y-phase wires are each wrapped around the sensor 210e in a position symmetrical to the line connecting the midpoint of the upper edge US and the midpoint of the lower edge DS. The leakage detection wire 230 is wrapped around the lower edge DS.

[0039] The detection of parameters by the sensor 210e will now be explained. When no leakage current occurs, the current values ​​flowing through the X-phase and Y-phase wrapped around the sensor 210e are approximately the same. At this time, the magnetic flux generated around the X-phase and Y-phase are approximately the same magnitude and in opposite directions, so they cancel each other out. In contrast, if a leakage current occurs in any part of the power transmission device 100e, a difference will occur in the current values ​​flowing through the X-phase and Y-phase. This will cause an imbalance in the magnetic flux generated around the X-phase and Y-phase wrapped around the sensor 210e, and an induced electromotive force will be generated in the sensor 210e. Therefore, it can be said that the sensor 210e in this embodiment detects the change in magnetic flux as a parameter. Due to the induced electromotive force, current flows from the sensor 210e through the leakage current detection line 230 and the amplifier AMP to the leakage current detection unit SC.

[0040] Furthermore, the sensor composed of a ring-shaped member can also be used as a sensor in the power transmission device 100c of the third embodiment.

[0041] According to the sensor 210e of the fifth embodiment described above, since it is composed of a ring-shaped member, each of the X-phase and the Y-phase can be easily attached to symmetric positions in the sensor 210e. As a result, parameters regarding the differential current values of the X-phase and the Y-phase can be detected more accurately.

[0042] F. Sixth Embodiment: The power transmission device 100f of the sixth embodiment shown in FIGS. 7 and 8 is different from the sensor 210e in the fifth embodiment in that a part of the X-phase and the Y-phase is provided on the printed circuit board PR, and the sensor 210f is composed of two parts. Regarding the configuration that is not particularly described below among the configurations of the power transmission device 100f of the sixth embodiment, it is the same as the power transmission device 100e of the fifth embodiment.

[0043] As shown in FIG. 7, the X-phase and the Y-phase near the sensor 210f in the power transmission device 100f are provided on the printed circuit board PR. The connection between the X-phase on the printed circuit board PR and the X-phase outside the printed circuit board PR is made by connecting a connection point CX1 provided at the end of the X-phase on the printed circuit board PR and a connection point CX2 provided at the end of the X-layer outside the printed circuit board PR. Similarly, the connection between the Y-phase on the printed circuit board PR and the Y-phase outside the printed circuit board PR is made by connecting a connection point CY1 and a connection point CY2.

[0044] As shown in FIG. 8, the sensor 210f is composed of a ring-shaped member. Also, the sensor 210f is composed of a first part 211f and a second part 212f. In this embodiment, the first part 211f and the second part 212f have a substantially U-shaped symmetrical shape with respect to each other. The first part 211f and the second part 212f are arranged so as to sandwich the X-phase and the Y-phase provided on the printed circuit board PR in the thickness direction of the printed circuit board PR. Also, one of each pair of protruding parts of the first part 211f and the second part 212f is arranged to be located in a hole H penetrating in the thickness direction of the printed circuit board PR. The first part 211f and the second part 212f are joined by the parts protruding toward the printed circuit board PR side.

[0045] Incidentally, the configuration using the printed circuit board PR and the sensor 210f of the sixth embodiment may be applied to the power transmission device 100c of the third embodiment.

[0046] According to the power transmission device 100f of the sixth embodiment described above, a part of the X-phase and the Y-phase is provided on the printed circuit board PR, and the first part 211f and the second part 212f of the sensor 210f are arranged so as to sandwich the X-phase and the Y-phase provided on the printed circuit board PR. Therefore, the sensor 210f can be easily assembled.

[0047] Further, since the X-phase and the Y-phase sandwiched between the first part 211f and the second part 212f are provided on the printed circuit board PR, it is possible to suppress the displacement of the positions of the X-phase and the Y-phase within the sensor 210f. Thereby, the noise included in the parameter detected by the sensor 210f can be reduced.

[0048] G. Seventh Embodiment: The configuration of the sensor in the power transmission device according to the seventh embodiment is different from that of the power transmission device 100b of the second embodiment. Regarding the configuration that is not particularly described below among the configurations of the power transmission device according to the seventh embodiment, it is the same as that of the power transmission device 100b of the second embodiment.

[0049] In the power transmission device of the seventh embodiment, the sensors 211b and 212b in the power transmission device 100b of the second embodiment shown in FIG. 2, the core of the first series reactor SL1, and the core of the second series reactor SL2 are shared. That is, the sensor and the two cores are constituted by a single member. As shown in FIG. 9, such a sensor 210g and core are constituted by a single figure-eight-shaped member. The material of the figure-eight-shaped member is an arbitrary magnetic material such as ferrite.

[0050] The sensor 210g has an upper side USg, a lower side DSg, a left side LSg, a right side RSg, and a connecting portion 211g. The left side LSg is connected to the left end of the upper side USg and the lower side DSg, respectively, and the right side RSg is connected to the right end of the upper side USg and the lower side DSg, respectively. The connecting portion 211g connects the central portions of the upper side USg and the lower side DSg in the longitudinal direction. The X phase is wound around the left side LSg. The Y phase is wound around the right side RSg. It can also be said that the X phase and the Y phase are wound in positions symmetrical with respect to the connecting portion 211g. The leakage detection wire 230 is wound around the connecting portion 211g. Even with such a sensor 210g, parameters related to the differential current values ​​of the X phase and the Y phase can be detected.

[0051] According to the seventh embodiment of the power transmission device described above, the sensor 210g is shared with the core of the first series reactor SL1 and the core of the second series reactor SL2 in the X and Y phases, so a more compact configuration can be achieved compared to a configuration in which the sensor and core are separate.

[0052] Furthermore, since the sensor 210g is composed of a single figure-eight shaped member, the X-phase and Y-phase can be easily attached to the sensor 210g at mutually symmetrical positions. This allows for more accurate detection of parameters related to the differential current between the X-phase and Y-phase.

[0053] H. Eighth Embodiment: The power transmission device of the eighth embodiment differs from the power transmission device 100c of the third embodiment in the configuration of the sensors. The configuration of the power transmission device of the eighth embodiment that is not specifically described below is the same as that of the power transmission device 100c of the third embodiment.

[0054] In the power transmission device of the eighth embodiment, the sensors 211b and 212b in the power transmission device 100c of the third embodiment shown in Figure 3, the core of the first parallel reactor PL1, and the core of the second parallel reactor PL2 are shared. That is, the sensor and the two cores are made up of a single member. Such a sensor and core can be realized by a single figure-eight shaped member shown in Figure 9.

[0055] According to the eighth embodiment of the power transmission device described above, the sensor is shared between the core of the first parallel reactor PL1 and the core of the second parallel reactor PL2 in the X and Y phases, so a more compact configuration can be achieved compared to a configuration in which the sensor and core are separate.

[0056] Furthermore, since the sensor is composed of a single figure-eight shaped member, the same effects as those provided by the figure-eight shaped member described in the seventh embodiment can be obtained.

[0057] I. Ninth Embodiment: The power transmission device 300 of the ninth embodiment shown in Figure 10 differs from the power transmission device 100 of the first embodiment in that three resonant circuits RC1, RC2, and RC3 are connected to one inverter INV and one transformer TR. Among the various components of the power transmission device 300 of the ninth embodiment, those not specifically described below are the same as those in the power transmission device 100 of the first embodiment.

[0058] As shown in Figure 10, the power transmission device 300 of this embodiment comprises one inverter INV, one transformer TR, three resonant circuits RC1, RC2, and RC3, one sensor 310, an amplifier AMP, and a leakage current detection unit SC. The sensor 310 is provided between the transformer TR and the three resonant circuits RC1, RC2, and RC3. The sensor 310 detects parameters related to the current flowing between the transformer TR and the three resonant circuits RC1, RC2, and RC3. In this embodiment, one sensor 310 is provided for each of the three resonant circuits RC1, RC2, and RC3.

[0059] Such a sensor 310 can be realized, for example, by a sensor 210e using a ring-shaped member as shown in Figures 5 and 6. Specifically, the X-phase and Y-phase connected to each resonant circuit RC1, RC2, and RC3 are arranged to pass through the sensor 310, which is made up of a ring-shaped member. When a leakage current occurs in either the X-phase or Y-phase connecting the transformer TR and each resonant circuit RC1, RC2, and RC3, a dielectric electromotive force is generated in the sensor 210e for the same reasons as explained in the fifth embodiment. As a result, current flows from the sensor 210e to the leakage current detection unit SC via the leakage current detection line 330 and the amplifier AMP.

[0060] According to the ninth embodiment of the power transmission device 300 described above, a single sensor 210 is provided between the transformer TR and the plurality of resonant circuits RC1, RC2, and RC3 to detect parameters related to the current flowing between the transformer TR and the plurality of resonant circuits RC1, RC2, and RC3. Therefore, a leakage current occurring in any of the circuits between the transformer TR and the plurality of resonant circuits RC1, RC2, and RC3 can be detected by the single sensor 210. As a result, the power transmission device 300 as a whole can be made more compact compared to a configuration with multiple sensors.

[0061] J. Other Embodiments 1: (J1) In the above embodiments, the leakage detection unit SC determined that a leakage current had occurred when the detected parameter was above a predetermined threshold, but the disclosure is not limited thereto. The leakage detection unit SC may detect a leakage current in any manner using the parameter. For example, the leakage detection unit SC may determine that a leakage current has occurred when the number of times the detected parameter exceeds a predetermined threshold is greater than or equal to a predetermined number. Alternatively, the leakage detection unit SC may determine that a leakage current has occurred when the detected parameter falls outside a predetermined range.

[0062] (J2) In the first and second embodiments described above, the grounding wire 40 was provided at the neutral point NP, but the disclosure is not limited thereto. The grounding wire 40 may be connected to any point in the X-phase and Y-phase between the transformer TR and the resonant circuit RC.

[0063] (J3) In the seventh and eighth embodiments described above, the sensor was composed of an eight-shaped member, but the disclosure is not limited thereto. The sensor may be a member of any shape made of a magnetic material.

[0064] K. Another Embodiment 2: (K1) In the first embodiment described above, the secondary coils 20 and 30 in the transformer TR may be a single coil or two coils joined together.

[0065] (K2) In the first embodiment described above, the sensor 210 detected current as a parameter, but the disclosure is not limited thereto. The sensor 210 may detect any parameter such as voltage or resistance.

[0066] (K3) In the second and third embodiments described above, sensors 211b, 212b, 211c, and 212c detected magnetic flux as a parameter, but the disclosure is not limited thereto. Sensors 211b, 212b, 211c, and 212c may detect any parameter, such as magnetic flux density.

[0067] (K4) In the fourth embodiment described above, sensors V1 and V2 detected differential voltage values, but the disclosure is not limited thereto. Sensors V1 and V2 may measure the charge amounts of the first parallel capacitor PC1 and the second parallel capacitor PC2 and detect the differential charge amount.

[0068] (K5) In the sixth embodiment described above, the first portion 211f and the second portion 212f were symmetrical and substantially U-shaped, but the disclosure is not limited thereto. The first portion 211f and the second portion 212f may be any shape. The first portion 211f and the second portion 212f may be, for example, L-shaped.

[0069] (K6) In the ninth embodiment described above, the power transmission device 300 may further have any filter circuit. Also, the resonant circuit is not limited to three, but any number of two or more may be provided.

[0070] (K7) In each of the above embodiments, the configuration of the filter circuit FL may be any configuration as long as it does not interfere with the configuration of each embodiment. For example, in the power transmission device 100 of the first embodiment, the parallel reactor PL may be omitted.

[0071] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in each embodiment corresponding to the technical features in the embodiments described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. This disclosure may be implemented, for example, in the following forms.

[0072] This disclosure may be realized in the following forms: [Form 1] A power transmission device (100, 100b, 100c, 100d, 100e, 100f) used for contactless power supply, comprising: a transformer (TR) provided between an inverter (INV) and a resonant circuit (RC); sensors (210, 210e, 210f, 210g, 211b, 212b, 211c, 212c, V1, V2) for detecting parameters related to the current flowing between the transformer and the resonant circuit; and a leakage detection unit (SC) for detecting leakage based on the detected parameters. [Embodiment 2] A power transmission device according to Embodiment 1, wherein the circuit between the transformer and the resonant circuit is grounded by a grounding wire (40), the sensor detects the parameter related to the current flowing through the grounding wire, and the leakage detection unit determines that a leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold. [Embodiment 3] A power transmission device according to Embodiment 2, wherein the grounding wire is connected to the neutral point (NP) on the secondary side of the transformer. [Embodiment 4] A power transmission device according to Embodiment 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the circuit between the transformer and the resonant circuit is grounded by a grounding wire (40b); the filter circuit has a first series reactor (SL1) provided in the X-phase and a second series reactor (SL2) provided in the Y-phase; the sensor detects the parameter related to the difference current between the current flowing through the first series reactor and the current flowing through the second series reactor; and the leakage detection unit determines that a leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold.[Embodiment 5] A power transmission device according to Embodiment 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the filter circuit has a first parallel reactor (PL1) and a second parallel reactor (PL2) connected in parallel to the X-phase and the Y-phase, the first parallel reactor and the second parallel reactor are connected in series with each other, and the first parallel reactor and the second parallel reactor are grounded by a grounding wire (40c), the sensor detects the parameter related to the difference current between the current flowing through the first parallel reactor and the current flowing through the second parallel reactor, and the leakage detection unit determines that a leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold, the power transmission device. [Embodiment 6] A power transmission device according to Embodiment 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the filter circuit has a first parallel capacitor (PL1) and a second parallel capacitor (PL2) connected in parallel to the X-phase and the Y-phase, the first parallel capacitor and the second parallel capacitor are connected in series with each other, and the first parallel capacitor and the second parallel capacitor are grounded by a grounding wire (40d), the sensor detects the parameter related to the difference voltage between the voltage of the first parallel capacitor and the voltage of the second parallel capacitor, and the leakage detection unit determines that leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold, a power transmission device. [Embodiment 7] A power transmission device according to Embodiment 4 or 5, wherein the sensor is composed of a ring-shaped member. [Embodiment 8] A power transmission device according to Embodiment 7, wherein a portion of the X phase and the Y phase is provided on a printed circuit board (PR), the sensor is composed of a first part (211f) and a second part (212f), and the first part and the second part are arranged to sandwich the X phase and the Y phase provided on the printed circuit board in the thickness direction of the printed circuit board.[Embodiment 9] A power transmission device according to Embodiment 4, wherein the sensor is shared with the core of the first series reactor and the core of the second series reactor, respectively. [Embodiment 10] A power transmission device according to Embodiment 9, wherein the shared sensor, the core of the first series reactor, and the core of the second series reactor are each composed of a single figure-eight shaped member. [Embodiment 11] A power transmission device according to Embodiment 5, wherein the sensor is shared with the core of the first parallel reactor and the core of the second parallel reactor, respectively. [Embodiment 12] A power transmission device according to Embodiment 11, wherein the shared sensor, the core of the first parallel reactor, and the core of the second parallel reactor are each composed of a single figure-eight shaped member. [Embodiment 13] A power transmission device (300) used for contactless power supply, comprising: an inverter (INV); a transformer (TR) to which power is supplied from the inverter; a plurality of resonant circuits (RC1, RC2, RC3) connected to the transformer and to which electricity transformed by the transformer is supplied; a single sensor (310) provided between the transformer and the plurality of resonant circuits for detecting parameters related to the current flowing between the transformer and the plurality of resonant circuits; and a leakage detection unit (SC) for detecting leakage based on the detected parameters.

[0073] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A power transmission device (100, 100b, 100c, 100d, 100e, 100f) used for contactless power supply, comprising: a transformer (TR) provided between an inverter (INV) and a resonant circuit (RC); sensors (210, 210e, 210f, 211g, 211b, 212b, 211c, 212c, V1, V2) for detecting parameters related to the current flowing between the transformer and the resonant circuit; and a leakage detection unit (SC) for detecting leakage current based on the detected parameters.

2. A power transmission device according to claim 1, wherein the circuit between the transformer and the resonant circuit is grounded by a grounding wire (40), the sensor detects the parameter related to the current flowing through the grounding wire, and the leakage detection unit determines that leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold.

3. A power transmission device according to claim 2, wherein the grounding wire is connected to the neutral point (NP) on the secondary side of the transformer.

4. A power transmission device according to claim 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the circuit between the transformer and the resonant circuit is grounded by a grounding wire (40b); the filter circuit has a first series reactor (SL1) provided in the X-phase and a second series reactor (SL2) provided in the Y-phase; the sensor detects the parameter related to the difference current between the current flowing through the first series reactor and the current flowing through the second series reactor; and the leakage detection unit determines that a leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold.

5. A power transmission device according to claim 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the filter circuit has a first parallel reactor (PL1) and a second parallel reactor (PL2) connected in parallel to the X-phase and the Y-phase, the first parallel reactor and the second parallel reactor are connected in series with each other, and the first parallel reactor and the second parallel reactor are grounded by a grounding wire (40c), the sensor detects the parameter related to the difference current between the current flowing through the first parallel reactor and the current flowing through the second parallel reactor, and the leakage detection unit determines that a leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold.

6. A power transmission device according to claim 1, further comprising: X-phase and Y-phase provided between the transformer and the resonant circuit; a filter circuit (FL) provided between the transformer and the resonant circuit, wherein the filter circuit has a first parallel capacitor (PL1) and a second parallel capacitor (PL2) connected in parallel to the X-phase and the Y-phase, the first parallel capacitor and the second parallel capacitor are connected in series with each other, and the first parallel capacitor and the second parallel capacitor are grounded by a grounding wire (40d), the sensor detects the parameter related to the difference voltage between the voltage of the first parallel capacitor and the voltage of the second parallel capacitor, and the leakage detection unit determines that leakage has occurred when the detected parameter is greater than or equal to a predetermined threshold.

7. A power transmission device according to claim 4 or 5, wherein the sensor is composed of a ring-shaped member.

8. A power transmission device according to claim 7, wherein a portion of the X phase and the Y phase is provided on a printed circuit board (PR), the sensor is composed of a first portion (211f) and a second portion (212f), and the first portion and the second portion are arranged to sandwich the X phase and the Y phase provided on the printed circuit board in the thickness direction of the printed circuit board.

9. A power transmission device according to claim 4, wherein the sensor is shared with the core of the first series reactor and the core of the second series reactor, respectively.

10. A power transmission device according to claim 9, wherein the shared sensor, the core of the first series reactor, and the core of the second series reactor are each composed of a single figure-eight shaped member.

11. A power transmission device according to claim 5, wherein the sensor is shared with the core of the first parallel reactor and the core of the second parallel reactor, respectively.

12. A power transmission device according to claim 11, wherein the shared sensor, the core of the first parallel reactor, and the core of the second parallel reactor are each composed of a single figure-eight shaped member.

13. A power transmission device (300) used for contactless power supply, comprising: an inverter (INV); a transformer (TR) to which power is supplied from the inverter; a plurality of resonant circuits (RC1, RC2, RC3) connected to the transformer and to which electricity transformed by the transformer is supplied; a single sensor (310) provided between the transformer and the plurality of resonant circuits for detecting parameters related to the current flowing between the transformer and the plurality of resonant circuits; and a leakage detection unit (SC) for detecting leakage current based on the detected parameters.

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