JP2022127467A - Wireless power supply device - Google Patents

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

The present invention relates to a wireless power feeding device. In particular, the present invention relates to a device that wirelessly supplies electric power to an electric object using electric field coupling regardless of the position of the electric object on a road surface within a wireless power supply area.

In wireless power supply technology, it is known that power transmission efficiency decreases due to standing waves of transmitted power generated in power transmitters such as electrodes and coils in infrastructure equipment. In particular, in order to supply power to a power receiver provided on a moving electric body, it is important to be able to supply power without depending on the relative positions of the power receiver and the power transmitter.

Wireless power supply technologies using electric field coupling include the following.

For example, Patent Literatures 1 and 2 disclose structures of power transmission electrodes for planar power feeding (hereinafter sometimes referred to as "two-dimensional power feeding"). However, no consideration is given to the influence of a drop in power supply due to a standing wave generated in the power transmission electrode.

In addition, Non-Patent Documents 1 and 2 show a system for power feeding while driving. In Non-Patent Document 1, by inserting a so-called left-handed circuit in the middle of the power transmission electrode at regular intervals with respect to the wave wavelength of the power to be transmitted, the standing wave can be canceled and the power supply can be maintained at a constant level. can. Furthermore, Non-Patent Document 2 discloses a system that changes the phase of a standing wave according to the position of an electric body by terminating a transmission line including a power transmission electrode using a variable reactance.

Non-Patent Documents 1 and 2 solve both the reduction in power transmission efficiency and the increase in reflected power due to standing waves, which are one of the problems of power supply while driving. The number of so-called left-handed circuits required to be inserted increases as the number of devices increases, leading to the problem of complication and cost increase of the wireless power supply system. In addition, in Non-Patent Document 2, constant variable control of the termination reactance is required during wireless power feeding, which leads to complication of the wireless power feeding system and an increase in cost.

JP 2016-32425 A Japanese Patent Application Laid-Open No. 2020-43686

Yoshiteru Suzuki, 5 others, "Right-hand and left-hand compound electrified roads for batteryless electric carts with continuous power supply," IEICE Transactions C, vol.J99-C, no.4, pp.133-141, Mar.2016. Sonshu Sakihara, 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 The present invention has been made in view of the above-described problems associated with wireless power supply. An object of the present invention is to provide a power supply device.

A first wireless power supply device according to the present invention is a wireless power supply device that transmits power in a contactless manner to an electric body that moves on a power transmission electrode along the electrode,
a power supply that supplies high frequency power, a gyrator, at least four power receiving electrodes,
at least four transmitting electrodes using transmission lines;
The power transmission electrode has a physical length equal to a positive integral multiple of half the wavelength of the wave of the power to be transmitted, and the power transmission electrode is of two types whose ends are open or short-circuited as appropriate,
the gyrator is mounted between the high frequency power source and the power transmission electrode shorted at the end;
It is characterized by changing the input impedance of the power transmission electrode from a short circuit to an open circuit.

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

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 loaded between the high-frequency power supply and the leading ends of the at least four power transmission electrodes;
a second matching circuit loaded between the open-ended transmitting electrode and a first load connected to the terminal;
a third matching circuit loaded between the short-circuited transmitting electrode and a second load connected to the terminal;
Of the matching circuits, the second and third matching circuits are characterized by being composed of the same inductor element and capacitor element.

According to the wireless power supply device of the present invention, power can be transmitted with high efficiency without being affected by waves in transmitted power. Furthermore, since the circuit configuration does not require active elements, complicated control circuits and control software, a wireless power supply device that operates stably can be implemented at low cost.

1 is a schematic diagram showing an embodiment of a wireless power feeding device according to the present invention; FIG. 1 is a schematic diagram showing a matching circuit according to the present invention; FIG. 4 is a Smith chart showing variations in input impedance depending on the ratio (conversion ratio) of the capacitor and inductor of the gyrator in one embodiment of the wireless power supply device according to the present invention. 1 is a schematic diagram of a circuit topology for impedance matching two ports with input and short-circuit termination in one embodiment of a wireless power supply device according to the present invention; FIG. 4 is a graph showing impedance matching at two ports simultaneously by matching circuits on the input side and the output side in one embodiment of the wireless power supply device according to the present invention. 1 is a schematic diagram of a circuit topology for impedance matching with an input and open and short terminations in an embodiment of a wireless power supply device according to the present invention; FIG. FIG. 4 is a schematic diagram showing an embodiment of the wireless power feeder according to the present invention in which the starting ends of the transmission lines used for the power transmission electrodes are not aligned. 1 is a schematic diagram showing an embodiment in which a phase adjustment circuit is used in a wireless power feeder according to the present invention; FIG. 4 is a graph showing the results of a physical simulation on the position dependence of power transmission efficiency by the wireless power feeder according to the present invention; 5 is a graph showing the results of a physical simulation on position dependence of power reflectance by the wireless power feeder according to the present invention.

Embodiments of the present invention will be described below with reference to the drawings. However, the illustrative drawings and the following description are provided for a thorough understanding of the disclosure and are not intended to limit the claimed subject matter thereby.

Power transmission lines (power transmission electrodes) with different termination conditions or lengths are prepared, and the generation position of the node of the standing wave of the wave of the power to be transmitted is moved. By arranging a power receiving electrode on each of the power transmission lines to receive power, it is possible to realize wireless power feeding that avoids the influence of the wave node of the power to be transmitted. At this time, variable control of termination conditions is not required.

FIG. 1 shows an outline of a wireless power feeding device according to the present invention.

A wireless power supply device according to the present invention includes a power supply, a gyrator, four power receiving electrodes, and an open-ended or short-ended power transmission line. In the wireless power supply device, an electric body having a power receiving electrode is arranged on a power transmission line having a physical length of nλ/2, where n is a natural number and λ is the wave wavelength of transmitted power. At this time, a standing wave is generated on the transmission line according to the wavelength of the transmitted power. The shape of the standing wave differs depending on the termination conditions: under open termination conditions, the power wave node occurs at the center of the transmission line, while under short termination conditions, power wave nodes occur at both ends of the transmission line.

Also, the transmitted power reflectance is the ratio of the reflected power to the power supply to the transmitted power (input power). A large reflected power causes a failure of the power supply in addition to a decrease in power transmission efficiency. Therefore, it is necessary to keep the power reflectance low.

In the physical simulation, a transmission line, a gyrator, and four power receiving electrodes with different termination conditions are used. The gyrator is loaded at the input of a short terminated transmission line and is responsible for changing the input impedance of the transmission line from short to open. This suppresses the occurrence of overcurrent due to a virtual short circuit at the input section in the transmission line on the short-circuit termination side.

As for the electric field distribution generated on the power transmission line, a standing wave node occurs at the center of the transmission line at the open termination, and a standing wave node occurs at the end of the transmission line at the short termination.

When the electric body is positioned in the center of the transmission line, the power transmission efficiency is reduced due to the nodes of the standing wave generated on the transmission line with the open end. On the other hand, in a transmission line with a short-circuited end, the generated standing wave becomes an antinode. Therefore, received power is synthesized from four power receiving electrodes. Combining the received power reduces the effects of the generated standing wave nodes.

FIG. 2 shows a matching circuit according to the present invention. Three matching circuits on the power transmission side, the open termination side, and the short termination side (hereinafter referred to as first to third matching circuits) are required. The matching circuit assumes that a port with a resistance value of 50Ω and a power supply are installed on the power transmission/reception electrodes, and a 50Ω load is installed on the other end (that is, the termination) of the power transmission electrode opposite to the power supply side. , loaded for impedance matching.

The matching circuit must be designed for each termination condition. The second matching circuit for the open termination is designed based on the results of physical simulation when the electric body, ie, the power receiving electrode is installed at the corner of the power transmission line. Also, the third matching circuit for short-circuit termination is designed based on the results of physical simulation when the electric body, that is, the power receiving electrode is placed in the center of the power transmission line.

The design steps for the matching circuit are as follows.

Step 1 Place the receiving electrodes at the antinodes of the power standing wave for open and short termination conditions.

Step 2 Adjust the element values of the gyrator to match the input impedance for each termination condition.

Step 3 Simultaneously perform impedance matching for two ports under one termination condition.

Step 4 A matching circuit is also mounted on the other power receiving electrode to determine the position dependence of the power transmission efficiency.

Conventionally, the high-frequency circuit network has one port for input and two ports for output, so it is necessary to perform impedance matching for three ports at the same time. Since the circuit can be used, it is no longer necessary to perform impedance matching for three ports at the same time. Similarly, when there are three or more loads, a matching circuit can be designed by performing impedance matching for two ports at the same time.

As shown in FIG. 3, when the influence of the inductance generated at the short-circuit end cannot be ignored, the influence can be suppressed by adjusting the conversion ratio of the gyrator. The conversion ratio of the gyrator is the ratio between the characteristic impedance Zc of the power transmission line and the reactance values of the inductor L and 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.

FIG. 4 shows a model for designing an impedance matching circuit with two ports each for input and output. The model can be used as it is even when expanding to three ports for input and output.

FIG. 5 shows calculation results of the impedance matching circuit shown in FIG. Since S21 representing the transmission power is high and S11 representing the reflected power is low, the matching state can be confirmed.

A power transmission efficiency of 99.1% was achieved by simultaneous impedance matching of the two ports in step 3 above.

In FIG. 6, the second and third matching circuits loaded at the open and short terminations are of the same topology and are identical matching circuits with the same element values.

In the above embodiment, both ends of all the power transmission electrodes are aligned and installed within one virtual rectangle, but as shown in FIG. are at the same position, the start positions of the open-ended power transmission lines may be shifted and placed within a single imaginary parallelogram. Two open-ended transmission lines are regarded as one pair, and a plurality of them are arranged in parallel with their positions shifted. By doing so, the power transmitter/receiver is coupled with a constant electric field intensity regardless of the position of the electric body (power receiver). That is, fluctuations in transmission efficiency can be suppressed.

Furthermore, as shown in FIG. 8, the same effect can be obtained by inserting a phase adjustment circuit in place of the matching circuit in the input/output stage of the power transmission line. An effect can be obtained by terminating with an arbitrary phase adjustment circuit (for example, a capacitor or an inductor). Among the phase adjustment circuits close to the power supply, the phase adjustment circuit positioned at the top in FIG. The adjustment circuit corresponds to the gyrator in the wireless power supply device according to the present invention.

Let the power transfer efficiency be the ratio of the combined power P _out2 +P _out3 of the output power P _out2 to the open-terminated load and the output power P _out3 to the short-terminated load to the input power P _in . FIG. 9 shows the result of a physical simulation on position dependence of power transmission efficiency by the wireless power supply device according to the present invention. It is shown that the wireless power supply device according to the present invention can stably transmit 95% or more of power regardless of the position of the electric body having the power receiver.

FIG. 10 shows the results of a physical simulation on position dependence of power reflectance by the wireless power feeder according to the present invention. In the wireless power supply device according to the present invention, the power reflectance is suppressed to within 5% regardless of the position of the electric body provided with the power receiver, and the result of FIG. 9 shows that power can be transmitted with high efficiency. is clear.

Claims (3)

A wireless power supply device that transmits power in a non-contact manner to an electric body that moves on a power transmission electrode along the electrode,
a power supply that supplies high frequency power, a gyrator, at least four power receiving electrodes,
at least four transmitting electrodes using transmission lines;
The power transmission electrode has a physical length equal to a positive integral multiple of half the wavelength of the wave of the power to be transmitted, and the power transmission electrode is of two types whose ends are open or short-circuited as appropriate,
the gyrator is mounted between the high frequency power source and the power transmission electrode shorted at the end;
A wireless power supply device, wherein 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 power received by said power receiving electrode is combined using at least four electrodes. a first matching circuit loaded between the high-frequency power supply and the leading ends of the at least four power transmission electrodes;
a second matching circuit loaded between the open-ended transmitting electrode and a first load connected to the terminal;
a third matching circuit loaded between the short-circuited transmitting electrode and a second load connected to the terminal;
3. The wireless power supply device according to claim 1, wherein the second and third matching circuits of said matching circuits are composed of the same inductor element and capacitor element.

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