Wireless power supply device

Abstract

To provide a wireless power supply device that supplies power to an electric mobile body including a power receiver with high efficiency regardless of a relative position between the electric mobile body and a power transmitter installed on a road surface or the like.SOLUTION: A wireless power supply device according to the present invention is to transmit power without contact to an electric mobile body moving on a power transmission electrode along the electrode, and includes a power source that supplies high-frequency power, a gyrator, at least four power reception electrodes, and at least four power transmission electrodes using a power transmission line. A physical length of the power transmission electrode is a positive integer multiple of a half of a wavelength of an undulation of transmission power. As for the power transmission electrode, there are two kinds of power transmission electrodes whose terminals are opened or short-circuited as appropriate. The gyrator is loaded between the high-frequency power source and the power transmission electrode with the short-circuited terminal. An input impedance of the power transmission electrode is changed from the short-circuited state to the open state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless power supply device, and more particularly to a device that wirelessly supplies power to an electric vehicle by using electric field coupling on a road surface within a wireless power supply area, regardless of the position of the electric vehicle. [Background technology]

[0002] It is known that the efficiency of power transmission in wireless power transfer technology is reduced by standing waves of transmitted power generated in power transmitters such as electrodes and coils in infrastructure facilities. In particular, when supplying power to a power receiver installed on a moving electric vehicle, it is important to be able to supply power regardless of the relative positions of the power receiver and the power transmitter.

[0003] Wireless power supply technologies that use electric field coupling include the following:

[0004] For example, Patent Documents 1 and 2 disclose a structure of a power transmission electrode for planar power supply (hereinafter, sometimes referred to as "two-dimensional power supply.") However, they do not consider the influence of a decrease in power supply caused by standing waves generated in the power transmission electrode.

[0005] Non-Patent Documents 1 and 2 disclose systems for power supply while moving. In Non-Patent Document 1, a so-called left-handed circuit is inserted in the middle of the power transmission electrode at a constant interval with respect to the wavelength of the wave of the transmitted power, thereby canceling the standing wave and maintaining the power supply at a constant level. Furthermore, Non-Patent Document 2 discloses a system that changes the phase of the standing wave according to the position of the electric vehicle by terminating the transmission line including the power transmission electrode using a variable reactance.

[0006] Non-Patent Documents 1 and 2 solve the problems of in-motion power supply, namely the decrease in power transmission efficiency and the increase in reflected power caused by standing waves, but Non-Patent Document 1 has a problem that the number of so-called left-handed circuits required to be inserted increases as the power transmission electrode becomes longer, which leads to the complication and increase in cost of the wireless power supply system. Also, Non-Patent Document 2 has a problem that constant variable control of the termination reactance is required during wireless power supply, which leads to the complication and increase in cost of the wireless power supply system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-32425 A [Patent Document 2] JP 2020-43686 A [Non-patent literature]

[0008] [Non-Patent Document 1] Yoshiteru Suzuki and 5 others, "Right-hand left-hand hybrid electrified road for battery-less electric carts running continuously with power supply," IEICE Transactions on Information and Communication Engineers, vol.J99-C, no.4, pp.133-141, Mar.2016. [Non-Patent Document 2] Sonshu Sakihara, and 3 others, “Far-end reactor matching to a traveling load along an RF power transmission line,” IEICE Trans. Electron., vol.E101-A, no.2, pp.396-401, Feb. 2018. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above-mentioned problems related to wireless power supply, and aims to provide a wireless power supply device that supplies power to an electric body with high efficiency regardless of the relative positions of an electric body equipped with a receiver and a power transmitter. [Means for solving the problem]

[0010] A first wireless power supply device according to the present invention is a wireless power supply device that transmits power in a non-contact manner to an electric body that moves along a power transmitting electrode, the wireless power supply device comprising: A power source for supplying high frequency power, a gyrator, and at least four power receiving electrodes; At least four power transmitting electrodes using a transmission line; The power transmitting electrode has a physical length that is a positive integer multiple of half the wavelength of the wave of the power to be transmitted, and the power transmitting electrode is of two types, the ends of which are appropriately open or short-circuited; The gyrator is mounted between the high frequency power source and the power transmitting electrode whose end is short-circuited, The input impedance of the power transmitting electrode is changed from a short circuit to an open circuit.

[0011] A second wireless power supplying device according to the present invention is the first wireless power supplying device according to the present invention, characterized in that the power received by the power receiving electrodes is combined using at least four electrodes.

[0012] A third wireless power supply device according to the present invention is the first and second wireless power supply devices according to the present invention, a first matching circuit that is installed between the high frequency power source and the start ends of at least four of the power transmitting electrodes; a second matching circuit that is connected between the power transmitting electrode having an open end and a first load that is connected to the open end; a third matching circuit that is loaded between the power transmitting electrode whose end is short-circuited and a second load connected to the end; The second and third matching circuits of the matching circuits are characterized in that they are configured with the same inductor element and capacitor element. Effect of the Invention

[0013] According to the wireless power supply device of the present invention, it is possible to transmit power with high efficiency without being affected by the fluctuation of the transmitted power. Furthermore, since the circuit configuration does not require active elements or complex control circuits and control software, it is possible to implement a wireless power supply device that operates stably at low cost. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an embodiment of a wireless power supply device according to the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing a matching circuit according to the present invention. [Diagram 3] 4 is a Smith chart showing a change in input impedance depending on a ratio (conversion ratio) of a capacitor and an inductor of a gyrator in an embodiment of a wireless power supply device according to the present invention. [Figure 4] 1 is a schematic diagram of a circuit topology for performing impedance matching of two ports, an input and a short-circuit termination, in one embodiment of a wireless power supply device according to the present invention. FIG. [Diagram 5] 4 is a graph showing simultaneous impedance matching of two ports by matching circuits on the input side and the output side in one embodiment of a wireless power supply device according to the present invention. [Figure 6] FIG. 2 is a schematic diagram of a circuit topology for impedance matching with an input and open and short-circuit terminations in one embodiment of a wireless power supply device according to the present invention. [Figure 7] FIG. 11 is a schematic diagram showing an embodiment in which the positions of the start ends of the transmission lines used in the power transmitting electrodes in the wireless power supply device according to the present invention are not aligned. [Figure 8] FIG. 1 is a schematic diagram showing an embodiment in which a phase adjustment circuit is used in a wireless power supply device according to the present invention. [Figure 9] 11 is a graph showing the results of a physical simulation regarding the position dependency of power transmission efficiency by a wireless power supply device according to the present invention. [Figure 10]11 is a graph showing the results of a physical simulation regarding the position dependency of power reflection rate by a wireless power supply device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the drawings used in the description and the following description are provided for a thorough understanding of the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] By preparing power transmission lines (power transmission electrodes) with different termination conditions or lengths, the position where the node of the standing wave of the transmitted power wave occurs is moved. By arranging a power receiving electrode on each of the power transmission transmission lines and receiving power, it is possible to realize wireless power transfer that avoids the influence of the node of the transmitted power wave. In this case, there is no need to control the variable termination conditions.

[0017] FIG. 1 shows an overview of a wireless power supply device according to the present invention.

[0018] The wireless power supply device according to the present invention is composed of a power source, a gyrator, four receiving electrodes, and a power transmission line with open or short termination. In the wireless power supply device, an electric body equipped with a receiving electrode is placed on a power transmission line with a physical length of nλ / 2, where n is a natural number and the wavelength of the wave of the transmission power is λ. At this time, a standing wave is generated on the transmission line according to the wavelength of the transmission power. The shape of the standing wave differs depending on the termination condition. Under the open termination condition, the node of the power wave is generated in the center of the transmission line, while under the short termination condition, the node of the power wave is generated at both ends of the transmission line.

[0019] In addition, the reflection rate of transmitted power is the ratio of the power reflected back to the power source to the transmitted power (input power). A large reflected power not only reduces the power transmission efficiency but also causes the power source to break down. Therefore, it is necessary to keep the power reflection rate low.

[0020] In this physical simulation, a transmission line with different termination conditions, a gyrator, and four receiving electrodes are used. The gyrator is loaded on the input section of the transmission line with a short-circuit termination, and plays a role in changing the input impedance of the transmission line from short-circuit to open. This suppresses the generation of overcurrent due to a virtual short circuit at the input section of the transmission line on the short-circuit termination side.

[0021] In the electric field distribution occurring on a power transmission line, a node of a standing wave occurs in the center of the transmission line at an open termination, and a node of a standing wave occurs at the end of the transmission line at a short-circuit termination.

[0022] When the electric body is located in the center of the transmission line, the power transmission efficiency decreases due to the nodes of the standing wave that occur on the open-ended transmission line. On the other hand, in a transmission line with a short-circuited end, the standing wave that occurs becomes an antinode. Therefore, the received power is combined from the four receiving electrodes. By combining the received power, the effect of the nodes of the standing wave that occurs is reduced.

[0023] The matching circuit according to the present invention is shown in Fig. 2. Three matching circuits are required: a power transmitting side, an open termination side, and a short termination side (hereinafter referred to as the first to third matching circuits). The matching circuits are loaded for impedance matching, assuming that a port having a resistance value of 50 Ω and a power source are installed on the power transmitting / receiving electrode, and a 50 Ω load is installed on the other end of the power transmitting electrode opposite the power source side (i.e., the termination).

[0024] The matching circuit needs to be designed for each termination condition. The second matching circuit for open termination is designed based on the results of a physical simulation in which the electric body, i.e., the power receiving electrode, is installed at a corner of the power transmission line. The third matching circuit for short termination is designed based on the results of a physical simulation in which the electric body, i.e., the power receiving electrode, is installed at the center of the power transmission line.

[0025] The steps for designing the matching circuit are as follows:

[0026] Step 1. Place the receiving electrode at the antinode of the power standing wave with open and short circuit termination conditions.

[0027] Step 2: Adjust the gyrator element values ​​to match the input impedance for each termination condition.

[0028] Step 3: Simultaneous impedance matching of two ports is performed under one termination condition.

[0029] Step 4: Load a matching circuit on the other power receiving electrode and determine the position dependency of the power transfer efficiency.

[0030] Conventionally, high-frequency circuit networks have one input port and two output ports, so simultaneous impedance matching of three ports is required, but by following the steps above, a matching circuit designed with simultaneous impedance matching of two ports can be used, eliminating the need for simultaneous impedance matching of three ports. The same is true when there are three or more loads, and a matching circuit can be designed by performing simultaneous impedance matching of two ports.

[0031] As shown in Figure 3, if the effect of inductance occurring at the short circuit at the short circuit termination cannot be ignored, the effect can be suppressed by adjusting the conversion ratio of the gyrator. The conversion ratio of the gyrator is determined by the characteristic impedance Z c and the reactance value of the inductor L and the capacitor C mounted on the gyrator. In the embodiment according to the present invention, the conversion ratio is designed to be 1 in order to reduce the inductance.

[0032] Figure 4 shows a model for designing an impedance matching circuit with two input and two output ports. This model can also be used as is when expanding to three input and three output ports.

[0033] Figure 5 shows the calculation results for the impedance matching circuit shown in Figure 4. The matching state can be confirmed from the fact that S21, which represents the transmitted power, is high and S11, which represents the reflected power, is low.

[0034] By simultaneously matching the impedance of two ports in step 3 above, a power transfer efficiency of 99.1% was achieved.

[0035] In FIG. 6, the second and third matching circuits loaded to the open and short terminations are identical matching circuits having the same topology and the same element values.

[0036] In the above embodiment, both ends of all the power transmitting electrodes are aligned and arranged within one imaginary rectangle, but as shown in FIG. 7, if the nodes of the standing waves of all the power transmitting powers are at the same position, the start positions of the open-ended power transmitting transmission lines may be shifted and arranged so as to be arranged within one imaginary parallelogram. Two open-ended transmission lines are treated as one pair, and multiple pairs are arranged in parallel with their positions shifted. In this way, the power transmitting and receiving devices are coupled with a constant electric field strength regardless of the position of the electric motor (power receiving device). In other words, the fluctuation in transmission efficiency can be suppressed.

[0037] Furthermore, the same effect can be obtained by inserting a phase adjustment circuit instead of a matching circuit at the input / output stage of the power transmission line as shown in Fig. 8. The same effect can also be obtained by terminating the line with an arbitrary phase adjustment circuit (for example, a capacitor or an inductor). Of the phase adjustment circuits close to the power supply, the phase adjustment circuit located at the top in Fig. 8 corresponds to the transmission line at the short-circuit end of the power transmission electrode in the wireless power supply device according to the present invention, and the phase adjustment circuit located at the bottom in the figure corresponds to the gyrator in the wireless power supply device according to the present invention. EXAMPLES

[0038] Power transmission efficiency vs. input power P in Output power P into an open-terminated load for out2 and the output power P out3 The combined power P out2 +P out3 9 shows the results of a physical simulation regarding the position dependency of the power transmission efficiency by the wireless power supply device according to the present invention. It shows that the wireless power supply device according to the present invention can stably transmit 95% or more of the power regardless of the position of the electric body equipped with the power receiver.

[0039] Fig. 10 shows the results of a physical simulation on the position dependency of the power reflection rate by the wireless power supply device according to the present invention. In the wireless power supply device according to the present invention, the power reflection rate is suppressed to within 5% regardless of the position of the electric body equipped with the power receiver, and it is clear that the power can be transmitted with high efficiency, together with the result of Fig. 9.

Claims

1. A wireless power supply device that transmits power in a non-contact manner to an electric body that moves along a power transmission electrode, A power source for supplying high frequency power, a gyrator, and at least four power receiving electrodes; At least four power transmitting electrodes using a transmission line; The power transmitting electrode has a physical length that is a positive integer multiple of half the wavelength of the wave of the power to be transmitted, and the power transmitting electrode is of two types, the ends of which are appropriately open or short-circuited; The gyrator is mounted between the high frequency power source and the power transmitting electrode whose end is short-circuited, A wireless power supply device, characterized in that the input impedance of the power transmission electrode is changed from a short circuit to an open circuit.

2. The wireless power supply device according to claim 1 , wherein the power received by the power receiving electrodes is combined using at least four electrodes.

3. a first matching circuit that is installed between the high frequency power source and the start ends of at least four of the power transmitting electrodes; a second matching circuit that is connected between the power transmitting electrode having an open end and a first load that is connected to the open end; a third matching circuit that is loaded between the power transmitting electrode whose end is short-circuited and a second load connected to the end; 3. The wireless power supply device according to claim 1, wherein the second and third matching circuits of the matching circuits are configured with the same inductor element and capacitor element.

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