Contactless power receiving device, contactless power supply system, and power supply line

Abstract

To provide a technology that suppresses the reduction in received power while eliminating the need to suppress reflected waves in the power supply line.SOLUTION: In a non-contact power receiving device 20, a power acquisition circuit 22 acquires a first AC power from a traveling wave propagating along a power supply line 10 connected with an AC power supply at one end from one end toward the other end, and a second AC power from a reflected wave propagating along the power supply line 10 from the other end toward the one end.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] (Cross - reference to related applications) This application is based on Japanese Patent Application No. 2021 - 19679 filed on February 10, 2021, claims the benefit of its priority, and all the contents of the patent application are incorporated herein by reference.

[0002] (Technical Field) The present disclosure relates to a non - contact power receiving device, a non - contact power supply system, and a power supply line.

Background Art

[0003] [[ID=~]] Conventionally, a non - contact power supply system that transmits power to a vehicle without contact and runs the vehicle with the transmitted power has been proposed. For example, Patent Document 1 discloses a non - contact power supply system during running that arranges a plurality of coils along the running path of a vehicle and switches the coil for power transmission according to the position of the vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors recognized that supplying power to vehicles from transmission lines installed along roads makes it easier to install transmission lines over a wide area compared to techniques using multiple coils, thereby reducing the cost of contactless power supply systems. However, when reflected waves are present in the transmission line, there are locations where the current of the forward wave and the current of the reflected wave cancel each other out, and when power is supplied using a magnetic field, the received power decreases at these locations due to the magnetic field. Also, there are locations in the transmission line where the voltage of the forward wave and the voltage of the reflected wave cancel each other out, so when power is supplied using an electric field, the received power decreases at these locations. If terminating resistors are installed in the transmission line to suppress reflected waves, power loss occurs due to the terminating resistors. Therefore, the inventors recognized that it is desirable to suppress the decrease in received power while eliminating the need to suppress reflected waves.

[0006] One exemplary objective of this disclosure is to provide a technology that can suppress the reduction in received power while eliminating the need to suppress reflected waves in the power transmission line. [Means for solving the problem]

[0007] To solve the above problems, a contactless power receiving device in one aspect of the present disclosure includes a power acquisition circuit that acquires a first AC power from a traveling wave propagating from one end to the other of a power supply line to which an AC power source is connected, and a second AC power from a reflected wave propagating from the other end to the one end of the power supply line.

[0008] Another aspect of the present disclosure is a contactless power supply system. This contactless power supply system comprises a power supply line to which an AC power source is connected at one end, and a contactless power receiving device that receives power from the power supply line. The contactless power receiving device includes a power acquisition circuit that acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other, and a second AC power from a reflected wave propagating along the power supply line from the other end to the one end. A further aspect of the present disclosure is a power supply line. This power supply line is part of a contactless power supply system comprising: a power supply line to which an AC power source is connected at one end; and a contactless power receiving device equipped with a power acquisition circuit that acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other, and a second AC power from a reflected wave propagating along the power supply line from the other end to the first end, the power supply line comprising a conductor to which the AC power source is connected at one end and which is open or short-circuited at the other end.

[0009] Furthermore, any combination of the above components, or any substitution of the components or expressions of this disclosure between methods, systems, etc., is also valid as a form of this disclosure. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a technology that can suppress the reduction in received power while eliminating the need to suppress reflected waves in the power transmission line. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the schematic configuration of a contactless power supply system according to the first embodiment. [Figure 2] Figure 1 is a perspective view of the power supply line. [Figure 3] Figure 1 is an equivalent circuit diagram of the contactless power supply system. [Figure 4] Figure 4(a) is a circuit diagram of a comparative example contactless power supply system, and Figure 4(b) is an equivalent circuit diagram between the power transmission side circuit and the power reception side circuit of Figure 4(a). [Figure 5] This is an equivalent circuit diagram of a non-contact power supply system of a first modified example of the first embodiment. [Figure 6] This is an equivalent circuit diagram of a contactless power supply system, a second modified example of the first embodiment. [Figure 7] This is an equivalent circuit diagram of a third modified example of the first embodiment of a contactless power supply system. [Figure 8] This is an equivalent circuit diagram of a contactless power supply system of a fourth modified example of the first embodiment. [Figure 9]It is a diagram for explaining the schematic configuration of a contactless power supply system according to a fifth modification of the first embodiment. [Figure 10] It is a perspective view of a power supply line according to a sixth modification of the first embodiment. [Figure 11] It is an equivalent circuit diagram of a contactless power supply system according to the second embodiment.

Embodiments for Carrying Out the Invention

[0012] (First Embodiment) FIG. 1 is a diagram for explaining the schematic configuration of a contactless power supply system 1 according to the first embodiment. FIG. 2 is a perspective view of the power supply line 10 in FIG. 1. FIG. 3 is an equivalent circuit diagram of the contactless power supply system 1 in FIG. 1.

[0013] The contactless power supply system 1 performs wireless power supply to a moving body 100 on a moving path such as a road. The contactless power supply system 1 can supply power whether the moving body 100 is stopped or moving. The moving body 100 is a vehicle such as an automobile. The contactless power supply system 1 includes a power supply line 10 and a contactless power receiving device 20.

[0014] An AC power supply 18 is connected to one end of the power supply line 10, and the other end of the power supply line 10 is open. The other end of the power supply line 10 may be short-circuited. The power supply line 10 includes a first conductor 12a and a second conductor 12b arranged in parallel along the road at a predetermined interval. AC power is supplied from the AC power supply 18 between one end of the first conductor 12a and one end of the second conductor 12b. The first conductor 12a and the second conductor 12b are each plate-shaped elongated electrodes, also called power transmission electrode plates. The first conductor 12a and the second conductor 12b may be mesh-shaped electrodes. Although not shown, the power supply line 10 is covered with asphalt or the like and embedded in the road. The road is also called an electrified road.

[0015] The power supply line 10 functions as a transmission line for high-frequency power supplied from the AC power supply 18. Based on the characteristic impedance of the power supply line 10, a voltage V and a current I are generated in the power supply line 10, and an electric field E and a magnetic field H are generated. The power supply line 10 supplies power to the non-contact power receiving device 20 by both the electric field E and the magnetic field H.

[0016] The frequency of the AC power supply 18 can be appropriately determined by experiments and simulations based on the characteristics of the power supply line 10 as a transmission line and the relationship between the wavelength and the size of the moving body 100, and is, for example, 1 MHz to 100 MHz. The shorter the length of the power supply line 10, the higher the frequency is preferable.

[0017] The non-contact power receiving device 20 is mounted on the moving body 100. The moving body 100 moves on the power supply line 10, and during the stop and movement of the moving body 100, the non-contact power receiving device 20 receives power from the power supply line 10. The received power is used for driving the wheels of the moving body 100 and the like.

[0018] As described above, since the other end of the power supply line 10 is open, in addition to the traveling wave, there is a reflected wave in the power supply line 10. The non-contact power receiving device 20 receives power from both the traveling wave and the reflected wave by utilizing the principle of a directional coupler.

[0019] As shown in FIGS. 1 and 3, the non-contact power receiving device 20 includes a power acquisition circuit 22, a power combining circuit 24, a smoothing circuit 26, and a load 28.

[0020] The power acquisition circuit 22 has a coil 30 that magnetically couples to the first conductor 12a and the second conductor 12b, a first electrode 32 that electrically couples to the first conductor 12a, and a second electrode 34 that electrically couples to the second conductor 12b.

[0021] The power acquisition circuit 22 acquires a first AC power from a traveling wave propagating along the power supply line 10 from one end to the other via the coil 30, the first electrode 32, and the second electrode 34, and acquires a second AC power from a reflected wave propagating along the power supply line from the other end to the first end. One end of the coil 30 outputs the first AC power to the power combining circuit 24, and the other end of the coil 30 outputs the second AC power to the power combining circuit 24.

[0022] The coil 30 is positioned on the bottom surface of the vehicle body 102 of the mobile body 100, such that the coil surface is substantially parallel to the road. In other words, the coil 30 is positioned so that the magnetic flux generated from the first conductor 12a and the second conductor 12b passes through the coil 30. The magnetic flux is maintained to pass through the coil 30 when the mobile body 100 is stopped and while it is moving. The coil 30 may include a magnetic core.

[0023] The first electrode 32 and the second electrode 34 are, for example, rectangular metal plates, and are arranged on the bottom surface of the vehicle body 102 of the mobile body 100, so as to be approximately parallel to each other and so as to be approximately parallel to the road. When the mobile body 100 is stopped and moving, the first electrode 32 is maintained facing the first conductor 12a, and the second electrode 34 is maintained facing the second conductor 12b. The areas of the first electrode 32 and the second electrode 34 are, for example, equivalent. The first electrode 32 and the second electrode 34 can also be called receiving electrode plates.

[0024] The first electrode 32 is connected to the midpoint N1 of the coil 30. The midpoint N1 is the point where the inductance between the midpoint N1 of the coil 30 and one end is equal to the inductance between the midpoint N1 of the coil 30 and the other end. In Figure 3, the portion of the coil 30 between the midpoint N1 and one end is represented as the first inductor L1, and the portion of the coil 30 between the midpoint N1 and the other end is represented as the second inductor L2.

[0025] The second electrode 34 is electrically connected to the vehicle body 102 of the mobile unit 100. The vehicle body 102 is made of a conductor such as metal and functions as a common ground in the mobile unit 100. The common ground is at a potential floating above the road, the first conductor 12a, and the second conductor 12b.

[0026] As shown in Figure 3, the first inductor L1 of coil 30 forms a transformer T1 together with the inductance component L10 of the magnetically coupled first conductor 12a. The second inductor L2 of coil 30 forms a transformer T2 together with the inductance component L11 of the magnetically coupled second conductor 12b.

[0027] A first capacitor C1 is formed between the electric field-coupled first electrode 32 and the first conductor 12a. A second capacitor C2 is formed between the electric field-coupled second electrode 34 and the second conductor 12b. The capacitances of the first capacitor C1 and the second capacitor C2 are equivalent. By providing a second electrode 34 separate from the vehicle body 102, the capacitance of the second capacitor C2 can be easily designed. Note that the second electrode 34 does not have to be provided separately from the vehicle body 102. In this case, the vehicle body 102 functions as the second electrode 34, the vehicle body 102 is electric field-coupled to the second conductor 12b, and the second capacitor C2 is formed between the vehicle body 102 and the second conductor 12b.

[0028] The first capacitor C1, transformer T1, and transformer T2 constitute a CM-type, or more specifically, a CCM-type, directional coupler. Assuming that the voltages of the forward wave and the reflected wave are in phase, and their currents are out of phase, the directional coupler configuration allows the received current I1 from the forward wave to flow through the path of the first conductor 12a, the first capacitor C1, and the first inductor L1. The received current I2 from the reflected wave flows through the path of the first conductor 12a, the first capacitor C1, and the second inductor L2. As a result, the first AC power from the forward wave can be output from one end of the coil 30, and the second AC power from the reflected wave can be output from the other end of the coil 30.

[0029] The power combining circuit 24 is connected to both ends of the coil 30, combines the first AC power and the second AC power acquired by the power acquisition circuit 22, and outputs the combined power to the smoothing circuit 26.

[0030] The power combining circuit 24 is a current doubling rectifier circuit and includes a first rectifier element D1, a second rectifier element D2, a third inductor L3, and a fourth inductor L4. The first and second rectifier elements D1 and D2 are diodes. The anode of the first rectifier element D1 is connected to a common ground, and its cathode is connected to one end of the coil 30. The anode of the second rectifier element D2 is connected to a common ground, and its cathode is connected to the other end of the coil 30. One end of the third inductor L3 is connected to one end of the coil 30. One end of the fourth inductor L4 is connected to the other end of the coil 30. The other end of the third inductor L3 and the other end of the fourth inductor L4 are connected, and the combined power is output from these connected nodes.

[0031] Furthermore, a DC-blocking capacitor may be inserted between one end of the coil 30 and the connection node between the cathode of the first rectifier element D1 and one end of the third inductor L3, and a DC-blocking capacitor may be inserted between the other end of the coil 30 and the connection node between the cathode of the second rectifier element D2 and one end of the fourth inductor L4.

[0032] The smoothing circuit 26 smooths the power output from the power combining circuit 24 and supplies the smoothed DC power to the load 28. The smoothing circuit 26 has a smoothing capacitor C6, which includes one end to which the power output from the power combining circuit 24 is supplied and the other end connected to a common ground.

[0033] The power combining circuit 24 and the smoothing circuit 26 output a voltage referenced to the voltage of the second electrode 34, which is the voltage of the common ground.

[0034] DC power is supplied to one end of the load 28, and the other end of the load 28 is connected to a common ground. The load 28 includes, for example, a motor that generates driving force, on-board equipment, a storage battery, etc.

[0035] The incoming current I1 flowing through the first inductor L1 flows through the path of the third inductor L3, smoothing capacitor C6, common ground, second capacitor C2, and second conductor 12b. The first capacitor C1, the first inductor L1, and the second capacitor C2 constitute a series resonant circuit for receiving traveling waves.

[0036] The received current I2 flowing through the second inductor L2 flows through the path of the fourth inductor L4, smoothing capacitor C6, common ground, second capacitor C2, and second conductor 12b. The first capacitor C1, second inductor L2, and second capacitor C2 form a series resonant circuit for receiving reflected waves.

[0037] The resonant frequencies of the series resonant circuit for receiving forward waves and the series resonant circuit for receiving reflected waves are equivalent to the frequency of the AC power supply 18 and fall within a predetermined frequency band that includes the frequency of the AC power supply 18. Series resonance reduces reactance in the current paths of the received currents I1 and I2, thereby suppressing voltage drop due to reactance. Therefore, wireless power transfer can be performed with high transmission efficiency using both electric and magnetic fields.

[0038] Here, we will describe a comparative example of a contactless power supply system that transmits power using both the electric and magnetic fields recognized by the present inventors. Figure 4(a) is a circuit diagram of the comparative example of a contactless power supply system, and Figure 4(b) is an equivalent circuit diagram between the power transmission circuit 110 and the power receiving circuit 112 in Figure 4(a).

[0039] In the comparative example, a parallel circuit of mutual capacitance C40 and leakage inductance L40, as shown in Figure 4(b), is equivalently present between the transmitting circuit 110 and the receiving circuit 112. Mutual capacitance C40 is the sum of the capacitances of capacitors C30 and C32 due to electric field coupling and the parasitic capacitance between magnetically coupled inductors L30 and L32. Leakage inductance L40 is the leakage inductance between magnetically coupled inductors L30 and L32. The parallel circuit of mutual capacitance C40 and leakage inductance L40 resonates in parallel, causing the output voltage of the transmitting circuit 110 to decrease and be transmitted to the receiving circuit 112. As a result, transmission efficiency and transmission capability decrease.

[0040] In contrast, in this embodiment, as described above, series resonance occurs in the path from the first conductor 12a on the power transmission side to the second conductor 12b on the power transmission side via the contactless power receiving device 20, so even if leakage inductance is present, a decrease in transmission efficiency can be suppressed.

[0041] According to this embodiment, since both electric and magnetic fields are used to receive power from both forward and reflected waves, it is possible to suppress the decrease in received power depending on the position of the non-contact power receiving device 20 on the power supply line 10, while eliminating the need to suppress reflected waves on the power supply line 10.

[0042] Since there is no need to suppress reflected waves from the other end of the power transmission line 10, the other end of the power transmission line 10 does not need to be terminated with a termination resistor. Therefore, power loss due to the termination resistor can be eliminated. For example, if the termination resistor is 50Ω and the termination voltage is 300V, the power loss due to the termination resistor is 1.8kW. Such relatively large power losses can be eliminated.

[0043] Furthermore, when impedance mismatch occurs due to other vehicles on the road, reflected waves are generated, but there is no need to suppress these reflected waves. Therefore, power can be supplied with high transmission efficiency regardless of location, even when multiple vehicles are present on the road. If it is necessary to suppress the generation of reflected waves from vehicles, technologies that perform automatic impedance control of termination loads etc. according to the vehicle's position can be considered, but since such control is not necessary, the complexity of the circuit and control, the increase in cost, and the increase in power loss can be suppressed.

[0044] (Modified version of the first embodiment) Various modifications of the contactless power supply system 1 are possible. The following will focus on the differences from the first embodiment.

[0045] Figure 5 is an equivalent circuit diagram of a non-contact power supply system 1, a first modification of the first embodiment. The non-contact power receiving device 20 further includes a resonant capacitor C4 connected between one end and the other end of a coil 30. The resonant capacitor C4 and the coil 30 constitute a parallel resonant circuit. The resonant frequency of the parallel resonant circuit is equivalent to the frequency of the AC power supply 18 and is included in a predetermined frequency band that includes the frequency of the AC power supply 18. Parallel resonance can further reduce reactance that could not be eliminated by series resonance. Therefore, transmission efficiency can be increased.

[0046] Figure 6 is an equivalent circuit diagram of a second modified example of the first embodiment of the contactless power supply system 1. The configuration of the power combining circuit 24 is different. The power combining circuit 24 has a first rectifier element D1, a second rectifier element D2, a third rectifier element D3, and a fourth rectifier element D4. The anode of the third rectifier element D3 is connected to one end of the coil 30. The anode of the fourth rectifier element D4 is connected to the other end of the coil 30. The cathode of the third rectifier element D3 and the cathode of the fourth rectifier element D4 are connected, and the combined power is output from these connection nodes. The first rectifier element D1 and the third rectifier element D3 constitute a voltage doubler rectifier circuit, and the second rectifier element D2 and the fourth rectifier element D4 also constitute a voltage doubler rectifier circuit. Depending on the circuit design, the power acquisition circuit 22 may function as a current source. In that case, rectification and power combining can be performed more appropriately by using a voltage doubler rectifier circuit.

[0047] Figure 7 is an equivalent circuit diagram of a third modified example of the first embodiment of the non-contact power supply system 1. The power acquisition circuit 22 has an adjustment circuit 40 connected between the midpoint N1 of the coil 30 and the second electrode 34, which is a common ground. The adjustment circuit 40 adjusts at least one of the voltage and current at the midpoint N1. This allows the characteristics of the power acquisition circuit 22 to be adjusted. The adjustment circuit 40 has, for example, a resistor or adjustment capacitor connected between the midpoint N1 and the common ground. A resistor and an adjustment capacitor may be connected in parallel between the midpoint N1 and the common ground.

[0048] If the adjustment circuit 40 has a resistor, the resistance value is set to be large enough to minimize the drop in the AC voltage at the midpoint N1. Basically, a DC bias voltage is unlikely to occur at the midpoint N1, but if it does occur for some reason, the resistor can eliminate the DC bias voltage at the midpoint N1. This prevents the DC bias voltage from adversely affecting the operation of the power combining circuit 24.

[0049] If the adjustment circuit 40 has an adjustment capacitor, the AC voltage at the midpoint N1 can be adjusted by dividing the voltage across the first conductor 12a using the first capacitor C1 and the adjustment capacitor of the adjustment circuit 40. This improves the accuracy of separating the forward wave and the reflected wave. The resonant frequency can also be adjusted.

[0050] Figure 8 is an equivalent circuit diagram of a non-contact power supply system 1 of a fourth modification of the first embodiment. The non-contact power receiving device 20 further includes a detection unit 42 and an adjustment unit 44. The detection unit 42 detects the current flowing through the coil 30. The adjustment unit 44 adjusts the inductance of the coil 30 and the capacitance of the first capacitor C1 based on the current detected by the detection unit 42. The adjustment unit 44 may also adjust the capacitance of the second capacitor C2.

[0051] The coil 30 is configured so that the number of turns, i.e., the inductance, can be changed according to the control of the adjustment unit 44. Known techniques can be used to change the number of turns, and for example, it may be changed in steps by switching the conduction and non-conductivity of a switch element (not shown).

[0052] The first capacitor C1 is configured to allow its capacitance to be changed according to the control of the adjustment unit 44. Known techniques can be used to change the capacitance; for example, the area of ​​the first electrode 32 may be changed by switching the conduction and non-conductivity of a switching element (not shown), thereby changing the capacitance in steps.

[0053] The non-contact power receiving device 20 can also receive power using both electric and magnetic fields from a power supply line designed to match a well-known power receiving device that receives power using only an electric field, or from a power supply line designed to match a well-known power receiving device that receives power using only a magnetic field. For example, when receiving power from a power supply line for a power receiving device that uses only an electric field, the current flowing through the coil 30 in the non-contact power receiving device 20, which is designed to match the characteristic impedance of the power supply line 10 in the first embodiment, may be smaller than in the first embodiment. Therefore, the adjustment unit 44 increases the inductance of the coil 30 by a first predetermined amount when the current detected by the detection unit 42 is below a threshold. This makes it possible to increase the current flowing through the coil 30. Also, the adjustment unit 44 decreases the capacitance of the first capacitor C1 by a second predetermined amount when the current detected by the detection unit 42 is below a threshold. This makes it possible to bring the resonant frequency of the series resonant circuit, which changes by adjusting the inductance of the coil 30, closer to the frequency of the AC power supply 18. Therefore, the received power can be increased to match the characteristics of the existing power supply lines.

[0054] Figure 9 is a diagram illustrating the schematic configuration of a fifth modified example of the first embodiment of the contactless power supply system 1. The two first electrodes 32 and the two second electrodes 34 are metal parts inside the wheel 104, respectively. In this configuration as well, the first electrodes 32 can be electrically coupled to the first conductor 12a, and the second electrodes 34 can be electrically coupled to the second conductor 12b. In this case, the degree of freedom in the configuration of the contactless power receiving device 20 can be improved.

[0055] Figure 10 is a perspective view of a power supply line 10 of a sixth modification of the first embodiment. The power supply line 10 is a transmission line including one first conductor 12a. One end of an AC power supply 18 is connected to one end of the first conductor 12a, and the other end of the AC power supply 18 is connected to a grounding rod (not shown) to the ground. A ground path plate may be provided below the first conductor 12a, and the other end of the AC power supply 18 may be connected to the ground path plate. The ground or ground path plate functions as a second conductor. The other end of the first conductor 12a is open. The other end of the first conductor 12a may be short-circuited to the ground or the ground path plate.

[0056] Figure 10 also shows the positional relationship between the coil 30 and the first electrode 32 with respect to the power supply line 10. The coil 30 is positioned such that its coil surface is approximately perpendicular to the road and approximately parallel to the direction in which the first conductor 12a extends. In other words, the coil 30 is positioned so that the magnetic flux generated from the first conductor 12a passes through the coil 30.

[0057] The first electrode 32 is positioned facing the first conductor 12a. The second electrode 34 may or may not be provided, or it may be positioned facing the ground or a ground path plate (not shown). If the second electrode 34 is not provided, the vehicle body 102, which functions as the second electrode, is electrically coupled to the ground or ground path plate, which functions as the second conductor, and a second capacitor C2 is formed between the vehicle body 102 and the ground or ground path plate. The operation of this contactless power supply system 1 is the same as in the first embodiment. This modification allows for greater flexibility in the configuration of the power supply line 10. It also makes it easier to install the power supply line 10.

[0058] The power supply line 10 may include three or more conductors. For example, in the case of three conductors, a central conductor may be placed at the boundary between lanes on a two-lane road, and one conductor may be placed in each lane. Vehicles traveling in one lane receive power from the conductor in that lane and the central conductor. The central conductor is shared by vehicles traveling in both lanes.

[0059] (Second Embodiment) In the second embodiment, the configuration of the power acquisition circuit 22 differs from that of the first embodiment. The differences from the first embodiment will be explained below.

[0060] Figure 11 is an equivalent circuit diagram of the non-contact power supply system 1 according to the second embodiment. The first electrode 32 has a third electrode 36 and a fourth electrode 38. The third electrode 36 is electrically coupled to the first conductor 12a and connected to one end of the coil 30. The fourth electrode 38 is electrically coupled to the first conductor 12a and connected to the other end of the coil 30.

[0061] The third electrode 36 and the fourth electrode 38 are, for example, rectangular metal plates, and are arranged on the bottom surface of the vehicle body 102 of the mobile body 100 such that each plate surface is approximately parallel to the road. When the mobile body 100 is stopped and moving, the third electrode 36 and the fourth electrode 38 are maintained facing the first conductor 12a. The areas of the third electrode 36 and the fourth electrode 38 are, for example, equivalent.

[0062] A first capacitor C1 is formed between the electric field-coupled third electrode 36 and the first conductor 12a. A third capacitor C3 is formed between the electric field-coupled fourth electrode 38 and the first conductor 12a. The capacitances of the first capacitor C1 and the third capacitor C3 are equivalent.

[0063] The first capacitor C1, the third capacitor C3, transformers T1 and T2 constitute a CMC-type directional coupler. Assuming that the voltages of the forward wave and the reflected wave are in phase, and their currents are out of phase, the directional coupler configuration allows the received current I1 from the forward wave to be the sum of the current flowing through the path of the first conductor 12a, the third capacitor C3, the second inductor L2, and the first inductor L1, and the current flowing through the path of the first conductor 12a and the first capacitor C1. The received current I2 from the reflected wave is the sum of the current flowing through the path of the first conductor 12a and the third capacitor C3, and the current flowing through the path of the first conductor 12a, the first capacitor C1, the first inductor L1, and the second inductor L2. As a result, the first AC power from the forward wave can be output from one end of the coil 30, and the second AC power from the reflected wave can be output from the other end of the coil 30. The CMC-type directional coupler allows for a clearer separation of the forward wave and the reflected wave.

[0064] The received current I1 flows through the power combining circuit 24, smoothing capacitor C6, common ground, second capacitor C2, and second conductor 12b.

[0065] The received current I2 flows through the power combining circuit 24, smoothing capacitor C6, common ground, second capacitor C2, and second conductor 12b.

[0066] The inductance of the coil 30 and the capacitances of the first capacitor C1, the third capacitor C3, and the second capacitor C2 may be set so that the reactance is reduced by resonance in the current path from the first conductor 12a to the second conductor 12b. This suppresses the voltage drop due to reactance. Therefore, wireless power transfer can be performed with high transmission efficiency using both electric and magnetic fields.

[0067] The present disclosure has been described above based on embodiments. Those skilled in the art will understand that the present disclosure is not limited to the embodiments described above, that various design changes are possible, and that various modifications are possible, and that such modifications are also within the scope of the present disclosure.

[0068] For example, any two or more of the first to sixth modifications of the first embodiment may be combined. The new embodiment resulting from the combination will have the combined effects of each of the combined embodiments. When combining the first and fourth modifications, the adjustment unit 44 may also adjust the capacitance of the resonant capacitor C4 so that the parallel resonant frequency approaches the frequency of the AC power supply 18 when changing the inductance of the coil 30.

[0069] Each of the first, second, and fourth to sixth modifications of the first embodiment may be combined with the second embodiment. Any two or more of the first, second, and fourth to sixth modifications may be combined with the second embodiment. The new embodiment resulting from the combination will have the combined effects of each of the embodiments that are combined. When the fourth modification is combined with the second embodiment, the adjustment unit 44 may adjust the inductance of the coil 30, the capacitance of the first capacitor C1, and the capacitance of the third capacitor C3 based on the current detected by the detection unit 42.

[0070] The contactless power supply system 1 can be applied to more than just automobiles, such as trains, electric aircraft, amusement park rides like roller coasters, cleaning robots, delivery robots, guidance robots, self-propelled transport equipment in factory premises, and toys like model cars. When applied to electric aircraft, it can supply power while the aircraft is on the ground.

[0071] In this embodiment, an example was described in which the power supply line 10 is located on a road and the contactless power receiving device 20 is mounted on a mobile body 100, but the invention is not limited to this. The power supply line 10 may be located on a charging station, and the contactless power receiving device 20 may be mounted on a portable device such as a smartphone. In this case, the portable device can be charged by placing it at any position on the power supply line 10 of the charging station.

[0072] An outline of one aspect of the present disclosure is as follows: A contactless power receiving device in one aspect of the present disclosure includes a power acquisition circuit that has a coil that magnetically couples to a power supply line to which an AC power source is connected at one end, and a first electrode that electrically couples to the power supply line, and acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other, and a second AC power from a reflected wave propagating along the power supply line from the other end to the one end, via the coil and the first electrode, and a power combining circuit that combines the first AC power and the second AC power acquired by the power acquisition circuit and outputs the combined power. According to this embodiment, it is possible to suppress the decrease in received power while eliminating the need to suppress reflected waves in the power transmission line.

[0073] The power supply line includes a first conductor and a second conductor arranged in parallel, the first electrode is electrically coupled to the first conductor and connected to the midpoint of the coil, one end of the coil outputs the first AC power and the other end of the coil outputs the second AC power, the power acquisition circuit further has a second electrode electrically coupled to the second conductor, and the power combining circuit may output a voltage referenced to the voltage of the second electrode. In this case, a CM-type directional coupler can be configured.

[0074] The first capacitor formed between the first electrode and the first conductor, the portion of the coil between the midpoint and one or the other end, and the second capacitor formed between the second electrode and the second conductor may constitute a series resonant circuit. In this case, the series resonance can reduce the reactance of the current path from the first conductor to the second conductor via the coil.

[0075] The contactless power receiving device may further include a detection unit for detecting the current flowing through the coil, and an adjustment unit for adjusting the inductance of the coil and the capacitance of the first capacitor based on the current detected by the detection unit. In this case, the received power can be increased to match the characteristics of the power supply line.

[0076] The power acquisition circuit may further include an adjustment circuit that adjusts at least one of the voltage and current at the midpoint of the coil. In this case, the characteristics of the power acquisition circuit can be adjusted.

[0077] The power supply line includes a first conductor and a second conductor arranged in parallel, one end of the coil outputs the first AC power, the other end of the coil outputs the second AC power, the power acquisition circuit further has a second electrode that is electrically coupled to the second conductor, and the power combining circuit may output a voltage referenced to the voltage of the second electrode. The first electrode may have a third electrode that is electrically coupled to the first conductor and connected to one end of the coil, and a fourth electrode that is electrically coupled to the first conductor and connected to the other end of the coil. In this case, a CMC type directional coupler can be configured, and the traveling wave and reflected wave can be separated more clearly.

[0078] The contactless power receiving device may further include a detection unit for detecting the current flowing through the coil, and an adjustment unit for adjusting the inductance of the coil, the capacitance of the first capacitor formed between the third electrode and the first conductor, and the capacitance of the third capacitor formed between the fourth electrode and the first conductor, based on the current detected by the detection unit. In this case, the received power can be increased to match the characteristics of the power supply line.

[0079] The contactless power receiving device may further include a resonant capacitor connected between one end and the other end of the coil. In this case, the reactance can be further reduced by parallel resonance between the coil and the resonant capacitor.

[0080] A contactless power supply system according to one aspect of the present disclosure comprises a power supply line to which an AC power source is connected at one end, and a contactless power receiving device that receives power from the power supply line. The contactless power receiving device has a coil that is magnetically coupled to the power supply line and a first electrode that is electrically coupled to the power supply line, and includes a power acquisition circuit that acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other via the first coil and the first electrode, and a second AC power from a reflected wave propagating along the power supply line from the other end to the one end, and a power combining circuit that combines the first AC power and the second AC power acquired by the power acquisition circuit and outputs the combined power. According to this aspect, it is possible to suppress the decrease in received power while eliminating the need to suppress reflected waves in the power supply line.

[0081] The other end of the aforementioned power supply line may be open or short-circuited. In this case, power loss can be reduced compared to when an impedance matching termination resistor is connected to the power supply line. [Industrial applicability]

[0082] This disclosure can be used in contactless power receiving devices and contactless power supply systems. [Explanation of Symbols]

[0083] 1... Contactless power supply system, 10... Power supply line, 12a... First conductor, 12b... Second conductor, 18... AC power supply, 20... Contactless power receiving device, 22... Power acquisition circuit, 24... Power combining circuit, 30... Coil, 32... First electrode, 34... Second electrode, 36... Third electrode, 38... Fourth electrode, 42... Detection unit, 44... Adjustment unit, C1... First capacitor, C2... Second capacitor, C3... Third capacitor, C4... Resonant capacitor, N1... Midpoint.

Claims

1. The power acquisition circuit includes a power acquisition circuit that acquires a first AC power from a traveling wave propagating from one end to the other of a power supply line to which an AC power source is connected, and a second AC power from a reflected wave propagating from the other end to the one end of the power supply line. A non-contact power receiving device characterized by the following features.

2. The aforementioned power supply line includes a first conductor and a second conductor arranged in parallel, The power acquisition circuit includes a coil that magnetically couples the first conductor and the second conductor, a first electrode that electrically couples the first conductor, and a second electrode that electrically couples the second conductor, and acquires the first AC power and the second AC power via the coil, the first electrode and the second electrode. The first electrode is connected to the midpoint of the coil, One end of the coil outputs the first AC power, The other end of the coil outputs the second AC power. The contactless power receiving device according to feature 1.

3. The first capacitor formed between the first electrode and the first conductor, the portion between the midpoint and one or the other end of the coil, and the second capacitor formed between the second electrode and the second conductor constitute a series resonant circuit. The contactless power receiving device according to feature 2.

4. A detection unit for detecting the current flowing through the coil, An adjustment unit adjusts the inductance of the coil and the capacitance of the first capacitor based on the current detected by the detection unit, The contactless power receiving device according to claim 3, further comprising the features described above.

5. The power acquisition circuit further includes an adjustment circuit that adjusts at least one of the voltage and current at the midpoint of the coil. A contactless power receiving device according to any one of claims 2 to 4.

6. The aforementioned power supply line includes a first conductor and a second conductor arranged in parallel, The power acquisition circuit includes a coil that magnetically couples the first conductor and the second conductor, a first electrode that electrically couples the first conductor, and a second electrode that electrically couples the second conductor, and acquires the first AC power and the second AC power via the coil, the first electrode, and the second conductor. One end of the coil outputs the first AC power, The other end of the coil outputs the second AC power, The first electrode is A third electrode is electrically coupled to the first conductor and connected to one end of the coil, A fourth electrode is electrically coupled to the first conductor and connected to the other end of the coil, A non-contact power receiving device according to claim 1, characterized by having the following features.

7. A detection unit for detecting the current flowing through the coil, An adjustment unit adjusts the inductance of the coil, the capacitance of the first capacitor formed between the third electrode and the first conductor, and the capacitance of the third capacitor formed between the fourth electrode and the first conductor, based on the current detected by the detection unit. The contactless power receiving device according to claim 6, further comprising:

8. The coil further comprises a resonant capacitor connected between one end and the other end. A contactless power receiving device according to any one of claims 2 to 7.

9. A power supply line to which an AC power source is connected at one end, A contactless power receiving device that receives power from the aforementioned power supply line, Equipped with, The contactless power receiving device includes a power acquisition circuit that acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other, and a second AC power from a reflected wave propagating along the power supply line from the other end to the one end. A contactless power supply system characterized by the following features.

10. The other end of the aforementioned power supply line is open or short-circuited. The contactless power supply system according to feature 9.

11. A power supply line in a contactless power supply system comprising: a power supply line to which an AC power source is connected at one end; and a contactless power receiving device equipped with a power acquisition circuit that acquires a first AC power from a traveling wave propagating along the power supply line from one end to the other, and a second AC power from a reflected wave propagating along the power supply line from the other end to the one end, The aforementioned AC power supply is connected to one end of a conductor, and the other end is open or short-circuited, A power supply line characterized by the following features.

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