Power receiver and wireless power supply device using same

Abstract

To provide a power receiver in which power transmission / reception electrodes can be arranged with zero gap, and a wireless power feeding device using the same.SOLUTION: A power receiver has two or more flexible power reception electrodes formed in a proper area, a matching circuit performing impedance matching between a power transmitter and the power receiver when power is transmitted from the power transmitter and received by the power reception electrodes, and a rectification circuit converting AC power loaded on an output end of the matching circuit and received into DC power. A gap between the power transmitter and the power receiver is properly adjusted, so that loss of transmitted / received power is suppressed. A wireless power feeding device using the power receiver is a wireless power feeding device transmitting power by electric field coupling, and comprises a power source, a power transmitter, the power receiver, and a battery. The power transmitter has two or more power transmission electrodes, an inverter converting power obtained from the power source into high-frequency power, and a matching circuit performing impedance matching with the power receiver, and feeds power to the battery by using the power receiver.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power receiver that receives power through electric field coupling and a wireless power supply device that uses the same. [Background technology]

[0002] Wireless power supply technology for electrically-driven objects is being studied. There are several methods, but in the prior art that uses electric field coupling without coils, it is essential to consider not only the shape and number of electrodes for power supply, but also the spacing between the transmitting and receiving electrodes, as well as their relative positions and angles. In addition, it is necessary to address issues such as wear due to mechanical contact of the electrodes and reduced power transmission efficiency due to foreign objects between the transmitting and receiving electrodes.

[0003] For example, Patent Document 1 discloses a technology in which a functional composite material sheet is sandwiched between power transmitting and receiving electrodes to bring the surfaces of the power transmitting and receiving electrodes into close contact and maintain a constant distance between the power transmitting and receiving electrodes, thereby ensuring the coupling capacitance required for contactless power supply using the electric field coupling method.

[0004] Patent Document 2 discloses a structure in which the electrodes, wiring, and base material of the power transmission unit are made flexible to prevent damage due to mechanical contact, etc., and furthermore, allows the unit to be folded or rolled into a cylindrical shape. The power transmission unit requires an elastomer material with electrical conductivity.

[0005] As in the prior art, when wirelessly supplying power to an electric body using an electric field coupling method, there is a problem in preventing a decrease in coupling capacitance caused by the size and material of the electrodes and the gap between the power transmitting and receiving electrodes.

[0006] For example, if the electric body is small, the power receiving electrode will also be small, and the coupling capacity with the power transmitting electrode will decrease, resulting in a decrease in power transmission efficiency. Also, if a foreign object is present between the power transmitting and receiving electrodes, the distance between the power transmitting and receiving electrodes will increase, resulting in a decrease in power transmission efficiency. Furthermore, power loss will occur when power energy passes through a foreign object. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2013-065756 [Patent Document 2] JP 2013-126294 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned problems of the prior art can be solved by ensuring high coupling capacitance by bringing the power transmitting and receiving electrodes sufficiently close to each other to form a zero-gap arrangement. On the other hand, the decrease in power transmission due to a foreign object between the electrodes can be addressed by supplying power from the power source while taking into account the loss, or by changing the frequency of the power source to an appropriate frequency that increases transmission efficiency, but the frequency is subject to the constraints of the power device.

[0009] The present invention has been made in consideration of these problems, and has an object to provide a power receiver in which power transmitting and receiving electrodes are arranged at a zero gap, and a wireless power feeding device using the same. [Means for solving the problem]

[0010] A first power receiver according to the present invention is a power receiver used for wireless power feeding in which power is wirelessly transmitted by electric field coupling, Two or more flexible power receiving electrodes formed to an appropriate area; a matching circuit that performs impedance matching between the power transmitter and the power receiver when power is transmitted from the power transmitter and received by the power receiving electrode; a rectifier circuit that is connected to an output terminal of the matching circuit and converts the received AC power into DC power; The loss of transmitted and received power is suppressed by appropriately adjusting the gap between the power transmitter and the power receiver.

[0011] A second power receiver according to the present invention is the first power receiver, characterized in that the power receiving electrode is a metal film sheet.

[0012] A third power receiver according to the present invention is the first power receiver, characterized in that the power receiving electrode is a dielectric film sheet containing metal particles or metal fibers.

[0013] A fourth power receiver according to the present invention is the power receiver according to any one of the first to third power receivers, comprising: a housing portion that houses the power receiving electrode; and an operation portion that operates the projection and recession of the power receiving electrode; The power receiving electrode is provided so as to be able to protrude from and retract into the housing portion.

[0014] According to the fourth power receiver, it is possible to facilitate the movement of an electric body equipped with the power receiver and to suppress mechanical wear and loss of the power receiving electrode equipped in the power receiver. Furthermore, by appropriately protruding and retracting the housed power receiving electrode to cover the foreign object between the power transmitting and receiving electrodes without being hindered by the foreign object, a zero gap arrangement of the power transmitting and receiving electrodes can be created, thereby suppressing electrical loss.

[0015] A wireless power supply device according to the present invention uses a power receiver according to any one of the first to fourth aspects and transmits power by electric field coupling, The power supply includes a power transmitter, a power receiver, and a battery. The power transmitter includes two or more power transmitting electrodes, an inverter that converts power obtained from a power source into high-frequency power, and a matching circuit that performs impedance matching with the power receiver; The power receiver is used to supply power to the battery. Effect of the Invention

[0016] According to the power receiver of the present invention and the wireless power supply device using the same, the power transmitting and receiving electrodes are arranged at zero gap, and power can be transmitted stably and efficiently even if the power receiver is small or a foreign object is sandwiched between the transmitting and receiving electrodes. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a power receiver according to the present invention and a wireless power supply device using the same; [Diagram 2] 1 is a schematic diagram showing the use of a sheet-shaped power receiving electrode, in which the sheet-shaped electrode is extended and recessed with respect to a power transmitter such as a floor. [Diagram 3] 1 shows an equivalent circuit of a power receiver according to the present invention used in a circuit simulator and a wireless power supply device using the same. [Figure 4] 11 is a graph showing the relationship between power receiving efficiency and heat generation rate in a comparison between a plate-shaped electrode and a sheet-shaped electrode. [Diagram 5] This shows an overview of power transmission measurement in an embodiment of the present invention. Left: A 100 mm high acrylic water tank is placed on top of the power transmitter. Right: A 50 mm high acrylic water tank is covered with a sheet electrode. [Figure 6] 1 shows an overview of power transmission measurement in an embodiment of the present invention. The example shows a case where plate-shaped electrodes are used for both the power transmitter and the power receiver. A 50 mm acrylic water tank is placed between the power transmitter and the power receiver electrodes. [Figure 7] 1 shows an overview of power transmission measurement in an embodiment of the present invention. The example shows a case where a sheet-shaped electrode is used as a power receiver. A 50 mm acrylic water tank is placed between the power transmitting and receiving electrodes. [Figure 8] 1 shows the results of power transmission measurements in an embodiment of the present invention, and is a graph showing the relationship between power transmission efficiency and transmission frequency when a sheet electrode is used. [Figure 9] 1 shows the results of power transmission measurements in an embodiment of the present invention, and is a graph showing the relationship between power transmission efficiency and transmission frequency when using plate-shaped electrodes. [Figure 10] 1 shows the results of power transmission measurements in an embodiment of the present invention, and is a graph showing the relationship between the inter-electrode gap and power transmission efficiency when using plate-shaped electrodes and sheet-shaped electrodes. [Figure 11]1 shows the results of power transmission measurements in an embodiment of the present invention, and is a graph showing the relationship between the power transmission efficiency and the frequency at which the power transmission efficiency is maximized when using a plate-shaped electrode and a sheet-shaped electrode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings.

[0019] The electrodes according to the present invention will be described as follows. An inflexible electrode formed in an appropriate area will be referred to as a plate-shaped electrode. On the other hand, a flexible electrode formed in an appropriate area will be referred to as a sheet-shaped electrode. For example, a plate-shaped electrode is an aluminum plate, and a sheet-shaped electrode is an aluminum thin film sheet.

[0020] In the power receiver according to the present invention, a metal film sheet is used as an electrode. The metal is preferably aluminum, iron, or copper, but is not limited to these metal materials. The electrode may also be a sheet made of a dielectric film containing a cloth woven with metal fibers or metal particles or fibers.

[0021] The electrode may have a protective layer made of an insulator laminated on the whole or part of the electrode.

[0022] In addition, a receiver including a sheet-like electrode according to the present invention may become charged due to friction with a transmitter including a transmitting electrode, but may be provided with a mechanism for removing conductive charges, such as conductive slits.

[0023] The wireless power supply device according to the present invention includes power transmission electrodes on a floor and a road surface, and an electric vehicle including a power receiver is placed on the floor or the like. The foreign object is on the same floor or the like as the electric vehicle and is sandwiched in the space of the gap between the power transmitting and receiving electrodes. In order to realize a zero gap at this time, the power receiver is lowered from the electric vehicle and brought close to the floor or the like, but if a foreign object is present, an extra gap of the height of the foreign object is generated, and the efficiency of power transmission is reduced by the gap. Furthermore, if the foreign object has electrical loss, the efficiency is further reduced.

[0024] By using the sheet-like electrode according to the present invention and spreading the electrode to cover the foreign object on the floor or the like, a zero-gap arrangement is created around the foreign object. This increases the coupling capacitance and improves the power transmission efficiency. Furthermore, since power passes between the transmitting and receiving electrodes in the zero-gap arrangement, the power loss due to the foreign object is suppressed.

[0025] Figure 1 shows an overview of a power receiver according to the present invention and a wireless power supply device using the same. The power transmitter has a high-frequency power source and is composed of an inverter, a matching circuit, an unbalanced-balanced conversion circuit, and a power transmitting electrode. The power receiver receives high-frequency power and converts it to direct current, and is composed of a sheet-like electrode, a matching circuit, a rectifier circuit, and a battery. The sheet-like electrode is housed in the housing of the power receiver so that it can be extended and retracted by the operation unit of the power receiver.

[0026] As shown in Figure 2, when there is no foreign object, the sheet electrode can obtain the coupling capacitance required for power supply by contacting the power transmitter with or without spreading the sheet, or by providing an appropriate distance. On the other hand, when there is a foreign object between the power transmitter and receiver, the sheet electrode is spread so that the power transmitter and receiver are in contact around the foreign object. Because the coupling capacitance required for power supply is obtained around the foreign object, the power loss through the foreign object is reduced, and sufficient power can be transmitted.

[0027] The charge generated in the receiver is stored in the battery as DC voltage. A rectifier circuit is installed in front of the battery, which converts the transmitted AC to DC. Since DC does not flow back through the rectifier circuit, the charge generated in the receiver does not leak through the sheet electrode.

[0028] When a charged foreign object comes into contact with the sheet-like electrode of the present invention, accumulated static electricity may enter the receiver. As a countermeasure against this, a varistor can be installed in front of the rectifier circuit of the receiver. EXAMPLES

[0029] The power receiving efficiency and the rate of heat generation as power loss when a plate-shaped electrode and a sheet-shaped electrode are used as the power receiving electrode are obtained by circuit simulation.

[0030] A situation is set in which a plastic bottle filled with tap water (dielectric constant 80, conductivity 0.02 S / m) is present as a foreign object between the transmitting and receiving electrodes. The transmitting and receiving electrodes are both 200 mm2, and the plastic bottle has a cross section of 64 mm2 and a length of 200 mm. Figure 3 shows an equivalent circuit of a wireless power supply device including a receiver according to the present invention, using a circuit simulator (LTspice (registered trademark) XVII made by Analog Devices). It is assumed that electric field coupling occurs between the sheet-like electrode and the periphery of the plastic bottle at a distance of 1 mm. The coupling capacitance and loss resistance can be calculated as follows. Let the dielectric constant of a vacuum be ε 0 (8.854×10 -12 ) gives Table 1.

[0031] [Table 1]

[0032] The results of the circuit simulation are shown in Figure 4. The power receiving efficiency was defined as the power consumption in the DC load relative to the transmitted power. The heat generation rate was defined as the power loss due to foreign objects relative to the transmitted power. When changing from the plate electrode to the sheet electrode, the power receiving efficiency increased by 35 points, and the heat generation rate decreased by 35 points. In other words, it can be said that the use of the sheet electrode improves the power loss due to foreign objects and increases the received power.

[0033] Figures 5, 6, and 7 show the plate-shaped power transmitting and receiving electrodes, the acrylic water tank, and the sheet-shaped power receiving electrode used in the demonstration experiment. With the plate-shaped electrodes, a gap between the electrodes is generated by the height of the foreign object, i.e., the acrylic water tank. On the other hand, with the sheet-shaped electrodes, by spreading them out to cover the acrylic water tank, there are areas where the gap between the electrodes is zero.

[0034] At the zero gap, the metal transmitting and receiving electrodes are not in direct contact, but instead a 3mm thick plastic cardboard is inserted, and since the cardboard has electrical properties equivalent to an air layer, it is capacitively coupled with the air layer. Measurements were taken with the height of the acrylic water tank changed to 14mm, 20mm, 50mm, and 100mm.

[0035] The power transfer efficiency of the sheet-type electrode and the plate-type electrode is compared. Figures 8 and 9 show the power transfer efficiency (S 21 ) are shown in Fig. 8. When comparing the heights of the acrylic water tanks of 50 mm and 100 mm for the sheet-type electrodes, S 21 On the other hand, in Fig. 9, when comparing the plate-shaped electrodes when the height of the acrylic water tank is 14 mm and 50 mm, the frequency at which S 21 The frequency at which it reaches its maximum fluctuates by about 2 MHz.

[0036] With sheet-type electrodes, a zero-gap portion occurs between the transmitting and receiving electrodes regardless of the height of the acrylic tank, so sufficient coupling capacitance can be formed. In other words, it is possible to keep the impedance constant regardless of the gap between the electrodes. In contrast, with plate-type electrodes, a zero-gap portion does not occur between the transmitting and receiving electrodes, so the coupling capacitance decreases depending on the gap between the electrodes, and the impedance fluctuates. Power transmission efficiency S 21 The frequency at which is maximum depends on the impedance, so it is constant for a sheet electrode but varies for a plate electrode.

[0037] Power transmission efficiency S 21 The relationship between the frequency and the gap between the power transmitting electrodes at which the power transfer efficiency is maximized is shown in Figures 10 and 11. The power transfer efficiency is S 212 × 100(%). From both figures, it can be seen that with the sheet-type electrode, high power transfer efficiency is achieved regardless of the inter-electrode gap, and that there is little variation in the frequency at which the power transfer efficiency is maximized. In other words, it can be seen that it is highly robust against variations in the inter-electrode gap. In contrast, with the plate-type electrode, the power transfer efficiency decreases as the gap between the electrodes increases, and the variation in the frequency at which the power transfer efficiency is maximized is large, indicating that it is not robust against variations in the inter-electrode gap.

Claims

1. A power receiver used for wireless power supply that wirelessly transmits power by electric field coupling, Two or more flexible power receiving electrodes each having an appropriate area; a matching circuit that performs impedance matching between the power transmitter and the power receiver when power is transmitted from the power transmitter and received by the power receiving electrode; a rectifier circuit that is connected to an output terminal of the matching circuit and converts the AC power received into DC power; a housing portion that houses the power receiving electrode; and an operation portion that operates the projection and recession of the power receiving electrode, The power receiving electrode is provided so as to be able to appear and disappear from the housing portion, and The receiver is characterized in that loss of transmitted and received power is suppressed by appropriately adjusting the gap between the transmitter and the receiver.

2. The power receiver according to claim 1 , wherein the power receiving electrode is a metal film sheet.

3. The power receiver according to claim 1 , wherein the power receiving electrode is a dielectric film sheet containing metal particles or metal fibers.

4. A wireless power supply device that uses a receiver according to any one of claims 1 to 3 and transmits power by electric field coupling, The power supply includes a power transmitter, a power receiver, and a battery. The power transmitter includes two or more power transmitting electrodes, an inverter that converts power obtained from a power source into high-frequency power, and a matching circuit that performs impedance matching with the power receiver, A wireless power supplying device that supplies power to the battery using the power receiver.

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