Power transmitting device and wireless power transmission system containing this

Abstract

Power transmission device (101) comprising: a first coil (103); a first resonant coil (107); a detector (109); and a control device (109), wherein the first coil (103) is connected via a coupler (105) to a high-frequency power source (104), wherein the first resonant coil (107) is connected to a variable capacitor (106) and is electromagnetically coupled to the first coil (103) and wherein electromagnetic resonance occurs between the first resonant coil (107) and a second resonant coil (111) which is electromagnetically coupled to a second coil (113) in a power receiving device (102), wherein the detector (109) detects the strength of a parameter S11 output by the coupler (105), and wherein the control device (109) has a function for changing a capacitance value of the variable capacitor (106) and a resonant frequency of a signal output by the high-frequency power source (104), wherein it sets the capacitance value of the variable capacitor (106) to 0, wherein it sets a frequency at which the magnitude of the parameter S11 is changed under a condition that the capacitance value of the variable capacitor (106) is 0, at the time at which the resonant frequency of the signal output by the high-frequency power source (104) is changed, as a resonant frequency of the second resonant coil (111), wherein it sets a resonant frequency of the first resonant coil (107), after the capacitance value of the variable capacitor (106) has been set, in accordance with the resonant frequency of the second resonant coil (111),and setting the oscillation frequency of the signal output by the high-frequency power source (104) as the resonant frequencies of the first resonant coil (107) and the second resonant coil (111).

Description

TECHNICAL AREA

[0001] The present invention relates to power transmitters and to systems for wireless transmission of power that include the power transmitters. STATE OF THE ART

[0002] Various types of electronic devices are becoming more widespread, and a wide variety of products are being introduced to the market. In recent years, portable electronic devices such as mobile phones and digital video cameras have become widespread. Furthermore, electrically powered vehicles, such as electric cars, are also appearing on the market.

[0003] Mobile phones, digital video cameras, and electric vehicles contain batteries, which are energy storage devices. The batteries are charged while in direct contact with household AC power sources, which in many cases also serve as power transmission devices. In a structure without a battery, or in a structure where the electrical power stored in a battery is not used, electrical power is transferred directly from a household AC power source to an electronic device via a wire or similar device so that the electronic device can operate.

[0004] On the other hand, methods are being researched and developed for wirelessly charging batteries or wirelessly transmitting electrical power to loads. Common methods include electromagnetic coupling (also known as electromagnetic induction), radio wave technology (also known as microwave technology), and resonance technology. Electronic devices, such as small household appliances, that utilize electromagnetic coupling are becoming increasingly common.

[0005] To increase the efficiency of electrical power transmission, systems for resonant wireless power transmission have been developed, as disclosed in references 1 to 3. [Reference to literature] Reference 1: Japanese published patent application JP 2010-193 598 A Reference 2: Japanese published patent application JP 2010-239 690 A Reference 3: Japanese published patent application JP 2010-252 468 A REVELATION OF THE INVENTION

[0006] In a system for resonant wireless power transmission, as disclosed in Reference 1, it is important to increase the efficiency of electrical power transmission that the resonant frequency of a device receiving electrical power (hereinafter referred to as a power receiving device) is compatible with the resonant frequency of a device transmitting electrical power (hereinafter referred to as a power transmitting device).

[0007] In particular, the resonant frequency of the power receiving device changes depending on its arrangement or similar characteristics. Therefore, it is important to monitor for changes in the resonant frequency of the power receiving device caused by the power transmitting device.

[0008] However, a structure becomes complex if the resonant frequency of the power receiver is measured, the measured resonant frequency is fed back to the power transmitter, and the resonant frequency of the power transmitter is changed. Reference 3 discloses a specific example of such a complex structure. Reference 3 discloses a structure in which each power receiver includes a circuit for monitoring changes in the resonant frequency. Since the additional provision of a circuit in each power receiver increases costs, this structure is impractical.In particular, in a transmission using four elements, in which electrical power is wirelessly transmitted between a first coil (also referred to as a power transmitting coil) of a power transmitting device and a second coil (also referred to as a power receiving coil) of a power receiving device via a first resonant coil and a second resonant coil by means of a resonance method, it is inexpedient to provide a means for measuring a resonant frequency in the power receiving device, since the size of the power receiving device is further increased.

[0009] Thus, it is an object of an embodiment of the present invention to provide a device for the resonant transmission of power, with which a resonant frequency matching between resonant coils of the power transmitting device and a power receiving device can be carried out only by changing the design of the structure of the power transmitting device and with which the efficiency of the transmission of electrical power can be increased, and a system for the wireless transmission of power which includes the power transmitting device.

[0010] One embodiment of the present invention is not a structure in which the resonant frequency of a power transmitter is set after the resonant frequency of a power receiver has been directly measured, but rather a structure in which the resonant frequencies of a power receiver and a power transmitter are estimated after the reflection of an electromagnetic field for transmitting electrical power to the power receiver by the power transmitter has been monitored. In particular, in one embodiment of the present invention, the resonant frequency of a power transmitter is estimated under the condition that a capacitance component in a resonant coil of the power transmitter is controlled in such a way that the monitoring of the reflection of an electromagnetic wave is not affected.More precisely, once the capacitance value of a variable capacitor in a resonant coil of the power receiving device has been set to 0, a parameter S11 is recorded, which provides a value in a scattering matrix (hereinafter referred to as a parameter S) at the time when the reflection of an electromagnetic wave is monitored for the transmission of electrical power, whereby the frequency of the electromagnetic wave is changed and the resonant frequency of the power transmitting device is estimated on the basis of the parameter S11.

[0011] One embodiment of the present invention is a power transmitter comprising a first coil, a first resonant coil, a detector, and a control device. The first coil is connected to a high-frequency power source via a coupler. The first resonant coil is connected to a variable capacitor and is electromagnetically coupled to the first coil, with electromagnetic resonance occurring between the first resonant coil and a second resonant coil, which is electromagnetically coupled to a second coil in a power receiver. The detector detects the magnitude of a parameter S11 output by the coupler. The control device has a function for changing the capacitance value of the variable capacitor and the oscillation frequency of a signal output by the high-frequency power source, setting the capacitance value of the variable capacitor to 0 and selecting a frequency.where the strength of parameter S11 is changed, under the condition that the capacitance value of the variable capacitor is 0, at the time at which the oscillation frequency of the signal output by the high-frequency power source is changed, as the resonant frequency of the second resonant coil, where it sets the resonant frequency of the first resonant coil, after the capacitance value of the variable capacitor has been set, in accordance with the resonant frequency of the second resonant coil, and where it sets the oscillation frequency of the signal output by the high-frequency power source as the resonant frequencies of the first resonant coil and the second resonant coil.

[0012] One embodiment of the present invention is a power transmitter comprising a first coil, a first resonant coil, a detector, and a control device. The first coil is connected to a high-frequency power source via a coupler. The first resonant coil is connected to a variable capacitor and is electromagnetically coupled to the first coil, with electromagnetic resonance occurring between the first resonant coil and a second resonant coil, which is electromagnetically coupled to a second coil in a power receiver. The detector detects the magnitude of a parameter S11 output by the coupler. The control device has a function for changing the capacitance value of the variable capacitor and the oscillation frequency of a signal output by the high-frequency power source, setting the capacitance value of the variable capacitor to 0 and selecting a frequency.where the strength of parameter S11 is changed, under the condition that the capacitance value of the variable capacitor is 0, at the time at which the oscillation frequency of the signal output by the high-frequency power source is changed, as the resonant frequency of the second resonant coil is set, where it sets the resonant frequency of the first resonant coil after the capacitance value of the variable capacitor has been set, in accordance with the resonant frequency of the second resonant coil, and where it changes a frequency at which the strength of parameter S11, under the condition that the capacitance value of the variable capacitor is set to a capacitance value based on the resonant frequency of the second resonant coil, is changed at the time at which the oscillation frequency of the signal output by the high-frequency power source is changed,as the oscillation frequency of the signal output by the high-frequency power source.

[0013] In one embodiment of the present invention, the power transmitter device may include a memory circuit in which the capacitance value of the variable capacitor for setting the resonant frequency of the first resonant coil is stored based on the resonant frequency of the second resonant coil, wherein the memory circuit may be connected to the control device.

[0014] One embodiment of the present invention is a wireless power transmission system comprising a power transmitter and a power receiver. The power transmitter includes a first coil, a first resonant coil, a detector, and a control device. The first coil is connected to a high-frequency power source via a coupler. The first resonant coil is electromagnetically coupled to the first coil and is connected to a variable capacitor. The detector senses the magnitude of a parameter S11 output by the coupler. The control device has a function for changing the capacitance value of the variable capacitor and the oscillation frequency of a signal output by the high-frequency power source, setting the capacitance value of the variable capacitor to 0 and selecting a frequency at which the magnitude of parameter S11 is determined under certain conditions.that the capacitance value of the variable capacitor is 0, is changed at the time the oscillation frequency of the signal output by the high-frequency power source is changed, is set as a resonant frequency of a second resonant coil, setting the resonant frequency of the first resonant coil, after the capacitance value of the variable capacitor has been set, in accordance with the resonant frequency of the second resonant coil, and setting the oscillation frequency of the signal output by the high-frequency power source as the resonant frequencies of the first resonant coil and the second resonant coil. The power receiving device includes the second resonant coil, which induces electromagnetic resonance with the first resonant coil and which is connected to a capacitor and to a second coil, which is electromagnetically coupled to the second resonant coil and connected to a load.

[0015] One embodiment of the present invention is a wireless power transmission system comprising a power transmitter and a power receiver. The power transmitter includes a first coil, a first resonant coil, a detector, and a control device. The first coil is connected to a high-frequency power source via a coupler. The first resonant coil is electromagnetically coupled to the first coil and is connected to a variable capacitor. The detector senses the magnitude of a parameter S11 output by the coupler. The control device has a function for changing the capacitance value of the variable capacitor and the oscillation frequency of a signal output by the high-frequency power source, setting the capacitance value of the variable capacitor to 0 and selecting a frequency at which the magnitude of parameter S11 is determined under certain conditions.that the capacitance value of the variable capacitor is 0, is changed at the time at which the oscillation frequency of the signal output by the high-frequency power source is changed, as the resonant frequency of the second resonant coil is set, whereby it sets the resonant frequency of the first resonant coil, after the capacitance value of the variable capacitor has been set, in accordance with the resonant frequency of the second resonant coil, and wherein it is a frequency at which the magnitude of parameter S11 is changed, under the condition that the capacitance value of the variable capacitor is set to a capacitance value based on the resonant frequency of the second resonant coil, at the time at which the oscillation frequency of the signal output by the high-frequency power source is changed,as the oscillation frequency of the signal output by the high-frequency power source. The power receiving device includes the second resonant coil, which induces electromagnetic resonance with the first resonant coil and is connected to a capacitor and to a second coil, which is electromagnetically coupled to the second resonant coil and connected to a load.

[0016] In one embodiment of the present invention, the power transmitter in the wireless power transmission system may include a memory circuit in which the capacitance value of the variable capacitor for setting the resonant frequency of the first resonant coil is stored based on the resonant frequency of the second resonant coil, wherein the memory circuit may be connected to the control device.

[0017] In accordance with one embodiment of the present invention, it is possible to create a device for resonant transmission of power, with which a resonant frequency matching between resonant coils of the power transmitting device and a power receiving device can be carried out only by changing the design of the structure of the power transmitting device and with which the efficiency of the transmission of electrical power can be increased, and a system for wireless transmission of power which includes the power transmitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The attached drawings show: Fig. 1 a structure in embodiment 1; Fig. 2 a structure in embodiment 1; Fig. 3 a structure in embodiment 1; Fig. 4 a structure in embodiment 1; Fig. 5A to 5C structures in embodiment 1; Fig. 6 a structure in embodiment 2; and Fig. 7A and Fig. 7B Structures in embodiment 3. BEST EXECUTION OF THE INVENTION

[0019] With reference to the drawings, embodiments of the present invention are described below. It should be noted that the present invention can be implemented in several different ways, and those skilled in the art will readily appreciate that types and details of the present invention can be modified in various ways without departing from the inventive concept and the scope of protection of the present invention. Thus, the present invention should not be understood as being limited to the description of embodiments. It should be noted that in the structures of the invention described below, reference numerals designating the same sections are used jointly in different drawings.

[0020] It should be noted that the size, layer thickness, or signal shape of each component shown in the drawings and the like in embodiments are, in some cases, exaggerated for clarity. Thus, the embodiments of the present invention are not limited to these dimensions.

[0021] It is noted that terms such as "first", "second", "third" and "nth" (where n is a natural number) are used in this description to avoid confusion between components and do not restrict the number of components. (Version 1)

[0022] In this embodiment, a device for resonant wireless transmission of power and a system for resonant wireless transmission of power are described in an embodiment of the present invention.

[0023] Fig. Figure 1 is a block diagram of a power transmitting device and a power receiving device. Fig. Figure 1 illustrates the transmission of electrical power with an electromagnetic wave by resonance of a first resonant coil in the power transmitting device and a second resonant coil in the power receiving device.

[0024] Fig. Figure 1 illustrates a power transmitting device 101 and a power receiving device 102. The power transmitting device 101 includes a first coil 103 (also referred to as a power transmitting coil), a high-frequency power source 104, a coupler 105 (also referred to as a directional coupler), a first resonant coil 107, a variable capacitor 106, a detector 108, a control device 109, and a storage circuit 110.

[0025] The power receiving device 102 includes a second resonant coil 111, a capacitor 112, a second coil 113 (also referred to as a power receiving coil) and a load 114.

[0026] In Fig. The first coil 103 is connected to the high-frequency power source 104 via the coupler 105. The first coil 103 can be a coil formed by winding a wire. Since the position of the power transmitter 101 is not particularly restricted compared to the position of the power receiver 102, the first coil 103 in the power transmitter 101 has greater design flexibility than the second coil 113 in the power receiver 102.

[0027] It is noted that when it is explicitly described that “A is connected to B”, the case that A is electrically connected to B, the case that A is functionally connected to B, and the case that A is directly connected to B are included.

[0028] In Fig. 1 The high-frequency power source 104 is a power supply circuit for outputting a signal whose frequency is successively changed in accordance with the control by the control device 109.

[0029] It is noted that the high-frequency power source 104 may contain a voltage-controlled oscillator (VCO) or the like, so that the frequency of an output signal is changed in accordance with the voltage input from the control device 109.

[0030] In this embodiment, there is no particular limitation on the frequency that is set into oscillation by an alternating current signal output by the high-frequency power source 104 in the power transmitting device 101 (such a frequency being referred to as an oscillation frequency), whereby an oscillation frequency can be used at which electrical power can be transmitted by a resonance method. The oscillation frequency of an electromagnetic wave for power transmission can, for example, be in the frequency range from several kilohertz to several gigahertz. In particular, in this embodiment, the frequency range of several megahertz is preferred with regard to transmission efficiency, since resonance (magnetic resonance) can be induced.

[0031] In Fig. In this embodiment, the coupler 105 (the directional coupler) is a circuit for detecting a parameter S in the circuit containing the high-frequency power source. In this embodiment, the coupler 105 detects a parameter S11, which indicates the loss due to reflection between a two-wire terminal of the first coil 103 and a two-wire terminal of the second resonant coil 111.

[0032] In Fig. The first resonant coil 107 is connected to the variable capacitor 106. The first resonant coil 107 can be a coil formed by winding a wire. There are no particular restrictions on the shape of the first resonant coil 107; however, the first resonant coil 107 in the power transmitter 101 has greater design flexibility than the second resonant coil 111 in the power receiver 102, since the position of the power transmitter 101 is not particularly restricted compared to the position of the power receiver 102. It is noted that signals for the wireless supply of electrical power are transmitted and received wirelessly between the first coil 103 and the first resonant coil 107 by electromagnetic coupling.Furthermore, signals for the wireless supply of electrical power are transmitted and received between the first resonant coil 107 and the second resonant coil 111 via electromagnetic resonance. Electromagnetic resonance is used in resonant wireless power transmission. Through electromagnetic resonance, electrical power, higher than that generated by electromagnetic coupling, can be transmitted from an electric or magnetic field within a distance of 1 m or less.

[0033] The variable capacitor 106 in Fig. 1 can be, for example, a varactor diode that utilizes the width of a depletion layer due to a semiconductor material, so that the capacitance is changed by an externally applied voltage. Alternatively, the variable capacitor 106 can be a microelectromechanical system (MEMS), such that the capacitance is changed by an externally applied voltage.

[0034] In Fig. 1. The detector 108 detects the strength of the parameter S11 obtained in the coupler 105. More precisely, the detector 108 is a circuit that converts the strength of the parameter S11, which is an analog value, into a digital value and sends the strength of the parameter S11, which is the digital value, to the control device 109.

[0035] In Fig. The control device 109 has a function for changing the capacitance value of the variable capacitor 106 and the oscillation frequency of a signal output by the high-frequency power source 104. The control device 109 performs several different operations.

[0036] More precisely, the control device 109 has a function for setting the capacitance value of the variable capacitor 106 to 0. Furthermore, the control device 109 has a function for adjusting the voltage to be applied to the high-frequency power source 104, provided that the capacitance value of the variable capacitor 106 is 0, in such a way that the oscillation frequency of the high-frequency power source 104 is successively changed.

[0037] It is noted that the expression “the capacitance value of the variable capacitor 106 is set to 0” in this patent specification means that the capacitance value of the variable capacitor 106 is set in such a way that the first resonant coil 107 between the first coil 103 and the second resonant coil 111 does not affect transmitted and received signals.

[0038] It is noted that when the oscillation frequency of the high-frequency power source 104 is successively changed, provided that the capacitance value of the variable capacitor 106 is 0, the parameter S11 obtained in the coupler 105 is changed in accordance with the change in the oscillation frequency of the high-frequency power source 104. In the following description, a peak frequency at which the parameter S11, obtained by successively changing the oscillation frequency of the high-frequency power source 104 under the condition that the capacitance value of the variable capacitor 106 is 0, is changed, is designated f0. It is noted that the frequency f0 detected by the control device 109 can be estimated as the resonant frequency of the second resonant coil 111.

[0039] Fig. Figure 2 is a graph in which the horizontal axis represents the oscillation frequency of the high-frequency power source 104 and the vertical axis represents the strength of the parameter S11 obtained in the detector 108. More precisely, a frequency f represents the strength (dB) of a magnetic field that specifies the strength of the parameter S11, while the frequency f is varied from 2.0 to 4.0 MHz.

[0040] In Fig. 2 is the peak frequency f0 at the time when the strength of parameter S11, obtained in detector 108, is changed, estimated at 3 MHz. In other words, when the oscillation frequency is 3 MHz, the strength of parameter S11 is low and the power loss due to reflection between the first coil 103 and the second resonant coil 111 is low.

[0041] It is noted that in this patent specification, “the peak frequency at the time at which the strength of parameter S11 is changed” is a frequency at the time at which the strength of parameter S11, as in Fig. As shown in Figure 2, the peak frequency decreases noticeably when the oscillation frequency is successively changed and then quickly returns to its original strength. It is noted that the peak frequency at the time the strength of parameter S11 is changed could be described as "a frequency at which the strength of parameter S11 is changed".

[0042] It is noted that Fig. Figure 3 is a graph in which the horizontal axis represents the oscillation frequency of the high-frequency power source 104 and the vertical axis represents the strength of the magnetic fields of parameter S11 and parameter S21 obtained in the coupler 105 if electromagnetic resonance occurs between the first resonant coil 107 and the second resonant coil 111. Parameter S21 indicates the efficiency of the electrical power transmission in parameter S.

[0043] As from Fig. As is clear, the frequencies f0 at which the parameter S11 obtained in detector 108 is changed are estimated to be around 2.6 MHz and 3.6 MHz. In other words, the power loss due to reflection is low when the oscillation frequencies are 2.6 MHz and 3.6 MHz. Similarly, the frequencies f0 at which the parameter S21 is changed are estimated to be around 2.6 MHz and 3.6 MHz. Fig. Figure 3 shows that the peak of parameter S11 is compatible with the peak of parameter S21. That is, the efficiency of electrical power transmission is high when the oscillation frequencies are 2.6 MHz and 3.6 MHz. In other words, if the frequency f0 is obtained by monitoring a change in the oscillation frequency of parameter S11, a frequency with high electrical power transmission efficiency, i.e., the resonant frequency of the second resonant coil 111, can be estimated.

[0044] Furthermore, the control device 109 has a function for changing the capacitance value of the variable capacitor 106 to a value based on the frequency f0 after the frequency f0 has been detected. In addition, the control device 109 has a function for fixing the oscillation frequency of the high-frequency power source 104 to the frequency f0 while the capacitance value of the variable capacitor 106 is set to the value based on the frequency f0.

[0045] In Fig. 1 The memory circuit 110 stores a lookup table in which the voltage for setting the capacitance of the variable capacitor 106 by the control device 109 is estimated in advance, so that the control device 109 sets the resonant frequency of the first resonant coil 107 in accordance with the frequency f0, which is the resonant frequency of the second resonant coil 111.

[0046] In Fig. 1. A coil formed by winding a wire can be used as the second resonant coil 111. There is no specific restriction on the shape of the second resonant coil 111; however, the second resonant coil 111 in the power receiving device 102 is preferably designed to be smaller than the first resonant coil 107 in the power transmitting device 101, since the power receiving device 102 must be smaller than the power transmitting device 101. In particular, the quality factor of the second resonant coil 111 is preferably high. More precisely, the quality factor of the second resonant coil 111 is preferably 1000 or more. It is noted that signals for the wireless supply of electrical power are transmitted and received between the second resonant coil 111 and the first resonant coil 107 by electromagnetic resonance.

[0047] Although Fig. As illustrated by the capacitor 112, the capacitor 112 can be a parasitic capacitance that is created at the time of the formation of the second resonant coil 111. Alternatively, the capacitor 112 can be a capacitor that is provided in advance, independently of the second resonant coil 111.

[0048] In Fig. 1. A coil formed by winding a wire can be used as the second coil 113. There is no particular restriction on the shape of the second coil 113; however, the second coil 113 in the power receiving device 102 is preferably designed to be smaller than the first coil 103 in the power transmitting device 101, since the power receiving device 102 must be smaller than the power transmitting device 101. It is noted that the signals for wirelessly supplying electrical power are sent and received between the second coil 113 and the second resonant coil 111 by electromagnetic coupling.

[0049] In Fig. 1. The load 114 must operate via wireless power transmission. For example, a battery, an electric motor, or the like can be used. More precisely, an electronic device powered by a battery, such as a mobile phone or an electric vehicle, can be used. It is noted that in the power receiving device 102, between the load 114 and the second coil 113, a circuit such as a DC converter or a rectifier circuit can be provided to convert the AC voltage sent to the second coil 113 into a DC voltage used in the load 114.

[0050] Fig. Figure 4 is a flowchart of a wireless system for power transmission in the present invention. Fig. 5A to 5C are schematic diagrams in the flowchart in Fig. 4.

[0051] In step 201 in Fig. 4. The capacitance value of the variable capacitor 106 in the power transmitter 101 is set to 0 by control with the control device 109. In other words, in step 201 in Fig. 4, as shown in the schematic diagram in Fig. As shown in 5A, the variable capacitor 106 and the first resonant coil 107 (the dotted lines in the diagram) should not be affected by a signal output from the first coil 103.

[0052] In step 202 in Fig. 4 In the power transmission device 101, the oscillation frequency of the high-frequency power source 104 is sampled by control with the control device 109 in such a way that the oscillation frequency of the high-frequency power source 104 is successively changed.

[0053] In step 203 in Fig. Step 4 determines in the power transmitter 101 whether the control device 109 detects the frequency f0, at which the magnitude of parameter S11 changes when the oscillation frequency of the high-frequency power source 104 is successively changed. If the frequency f0 is not detected, in step 203 a modification of the power receiver or the like by a user is required, and the steps from step 201 onward are repeated. In other words, in steps 202 and 203 in Fig. 4, as shown in the schematic diagram in Fig. As shown in Figure 5B, a frequency is determined at which power loss due to reflection between the first coil 103 and the second resonant coil 111 is reduced, while the variable capacitor 106 and the first resonant coil 107 (the dotted lines in the diagram) are not affected by a signal output from the first coil 103. The frequency f0 is determined over the series of steps.

[0054] If the frequency f0 is detected in step 203, it will be determined in step 204. Fig. 4. The capacitance value of the variable capacitor is set in accordance with the frequency f0. The capacitance value of the variable capacitor 106 can be set with reference to the lookup table stored in the memory circuit 110. The lookup table stores the applied voltage based on the capacitance value of the variable capacitor 106, which is set in accordance with the frequency f0, i.e., with a pre-estimated resonant frequency.

[0055] In step 205 in Fig. 4 In the power transmitting device 101, the voltage to be applied to the high-frequency power source 104 is set by control with the control device 109 such that the frequency f0 is set as the oscillation frequency of the high-frequency power source 104. In other words, in steps 204 and 205 in Fig. 4, as shown in the schematic diagram in Fig. As shown in Figure 5C, a resonant frequency adjustment is carried out in such a way that a resonance occurs between the first resonant coil 107 and the second resonant coil 111 by applying a voltage to the variable capacitor 106 and an output is obtained from the high-frequency power source 104 whose oscillation frequency is the frequency f0.

[0056] In accordance with one embodiment of the present invention, it is possible to create a resonant transmitting device with which a resonant frequency matching between resonant coils of the power transmitting device and a power receiving device can be carried out only by changing the design of the structure of the power transmitting device and with which the efficiency of the transmission of electrical power can be increased, and a system for resonant wireless transmission of power.

[0057] This embodiment can be combined with any of the structures described in the other embodiments as required. (Version 2)

[0058] This embodiment describes the case where the schedule in Fig. 4 different steps have been added in embodiment 1.

[0059] It is noted that the control device 109 in Fig. In embodiment 1, as described in this embodiment, the control device 109 has a function for changing the capacitance value of a variable capacitor and the oscillation frequency of a signal output by a high-frequency power source. More precisely, the control device 109 has a function for setting the capacitance value of the variable capacitor 106 to 0. Furthermore, the control device 109 has a function for setting a voltage to be applied to the high-frequency power source 104 such that the oscillation frequency of the high-frequency power source 104 is successively changed, provided that the capacitance value of the variable capacitor 106 is 0. The control device 109 also has a function for changing the capacitance value of the variable capacitor 106 to a value based on the frequency f0, in accordance with the frequency f0, after the frequency f0 has been detected.Furthermore, the control device 109 has a function for setting a frequency, whereby the strength of the parameter S11 is adjusted at the time when the oscillation frequency of the signal output by the high-frequency power source is changed, while the capacitance value of the variable capacitor 106 is set to the value based on the frequency f0 when the oscillation frequency of the signal output by the high-frequency power source is changed.

[0060] It is noted that steps 201 to 204 in Fig. 6 similar to those of the schedule in Fig. 4 in embodiment 1.

[0061] While in step 301 in Fig. 6 in the power transmitting device 101 the capacitance value of the variable capacitor 106 is set to the value set in accordance with the frequency f0, which is the resonant frequency, the oscillation frequency of the high-frequency power source 104 is sampled by the control with the control device 109 in such a way that the oscillation frequency of the high-frequency power source 104 is successively changed.

[0062] In step 302 in Fig. Step 6 determines in the power transmitter 101 whether the control device 109 detects the peak of a frequency at which the magnitude of parameter S11 is changed when the oscillation frequency of the high-frequency power source 104 is successively changed. In step 302, if the peak of the frequency is not detected, a user must modify a power receiver or the like, repeating the steps from step 201 onwards.

[0063] In step 303 in Fig. 6 determines whether the peak of the frequency in step 302 corresponds to two peaks of (f0 + Δf) and (f0 - Δf) that are separated from the frequency f0 detected in step 203.

[0064] If in step 303 it is determined that the number of peaks of the frequency is two, then in step 304 in Fig. 6 In the power transmitter 101, the voltage to be applied to the high-frequency power source 104 is set by control with the control device 109 such that the frequency (f0 + Δf) or the frequency (f0 - Δf) is set as the oscillation frequency of the high-frequency power source 104. It is noted that the frequency (f0 + Δf) or the frequency (f0 - Δf) at which the magnitude of the parameter S11 detected by a detector is lower is preferably used as the oscillation frequency.

[0065] If in step 303 it is determined that the peak frequency is f0, then in step 305 in Fig. 6 in the power transmitting device 101 the voltage to be applied to the high-frequency power source 104 is set by control with the control device 109 in such a way that the frequency f0 is set as the oscillation frequency of the high-frequency power source 104.

[0066] In accordance with one embodiment of the present invention, it is possible to create a device for resonant wireless power transmission, in which resonant frequency matching between the resonant coils of the power transmitter and a power receiver can be achieved solely by modifying the design of the power transmitter's structure, and in which the efficiency of electrical power transmission can be increased, and a system for resonant wireless power transmission. In particular, in this embodiment's structure, a decrease in electrical power transmission efficiency caused by the frequency peak spacing due to reduced distance between a receiver and a power transmitter can be suppressed while the resonant frequencies of the resonant coils are matched to each other.

[0067] This embodiment can be combined with any of the structures described in the other embodiments as required. (Version 3)

[0068] In this embodiment, applications of the wireless power transmission system described above are presented. It should be noted that applications of a wireless power transmission system in the present invention can include, for example, portable electronic devices such as a mobile phone, a digital video camera, a computer, a portable information terminal (e.g., a mobile computer, a portable gaming machine, or an e-book reader), and an image display device including a recording medium (more precisely, a Digital Versatile Disc (DVD)). Furthermore, an electrically powered vehicle, such as an electric car, can be considered. Examples of such electronic devices are described below with reference to the drawings.

[0069] Fig. Figure 7A illustrates an application of a wireless system for transmitting power to a mobile telephone and a portable information terminal, comprising a power transmitter 701, a mobile telephone 702A containing a power receiver 703A, and a mobile telephone 702B containing a power receiver 703B. The wireless power transmission system in the above embodiment can be provided between the power transmitter 701 and the power receiver 703A, as well as between the power transmitter 701 and the power receiver 703B.Thus, it is possible to create a device for resonant wireless transmission of power, in which a resonant frequency matching between resonant coils of the power transmitting device and a power receiving device can be carried out only by changing a design of the structure of the power transmitting device and in which the efficiency of the transmission of electrical power can be increased, and a system for resonant wireless transmission of power.

[0070] Fig.Figure 7B illustrates an application of a wireless power transmission system to an electric vehicle, which is an electric propulsion vehicle, comprising a power transmitter 711 and an electric vehicle 712 containing a power receiver 713. The wireless power transmission system in the above embodiment can be provided between the power transmitter 711 and the power receiver 713. Thus, it is possible to create a device for wireless resonant power transmission, in which resonant frequency matching between the resonant coils of the power transmitter and a power receiver can be achieved simply by modifying the design of the power transmitter structure, thereby increasing the efficiency of electrical power transmission, and a system for resonant wireless power transmission.

[0071] As described above, the wireless system for transmitting power in the above embodiment can be used in a power-driven object.

[0072] This embodiment can be combined with any of the structures described in the other embodiments as required. REFERENCE MARK

[0073] 101: Power transmitting device, 102: Power receiving device, 103: First coil, 104: High-frequency power source, 105: Coupler, 106: Variable capacitor, 107: First resonant coil, 108: Detector, 109: Control device, 110: Memory circuit, 111: Second resonant coil, 112: Capacitor, 113: Second coil, 114: Load, 201: Step, 202: Step, 203: Step, 204: Step, 205: Step, 301: Step, 302: Step, 303: Step, 304: Step, 305: Step, 701: Power transmitting device, 702A: Mobile telephone, 702B: Mobile telephone, 703A: Power receiving device, 703B: Power receiving device 711: Power transmitting device, 712: Electric vehicle and 713: Power receiving device.

[0074] This application is based on Japanese patent application serial no. 2010-263048, filed with the Japanese Patent Office on November 26, 2010, the entire content of which is included here by reference.

Claims

Power transmitting device (101) comprising: a first coil (103); a first resonant coil (107); a detector (109); and a control device (109), wherein the first coil (103) is connected via a coupler (105) to a high-frequency power source (104), wherein the first resonant coil (107) is connected to a variable capacitor (106) and is electromagnetically coupled to the first coil (103), and wherein electromagnetic resonance occurs between the first resonant coil (107) and a second resonant coil (111) which is electromagnetically coupled to a second coil (113) in a power receiving device (102), wherein the detector (109) detects the strength of a parameter S11 output by the coupler (105), and wherein the control device (109) has a function for changing a capacitance value of the variable capacitor (106) and an oscillation frequency of a signal output by the high-frequency power source (104),wherein it sets the capacitance value of the variable capacitor (106) to 0, wherein it sets a frequency at which the magnitude of the parameter S11 is changed under a condition that the capacitance value of the variable capacitor (106) is 0, at the time at which the oscillation frequency of the signal output by the high-frequency power source (104) is changed, as a resonant frequency of the second resonant coil (111), wherein it sets a resonant frequency of the first resonant coil (107), after the capacitance value of the variable capacitor (106) has been set, in accordance with the resonant frequency of the second resonant coil (111), and wherein it sets the oscillation frequency of the signal output by the high-frequency power source (104) as the resonant frequencies of the first resonant coil (107) and the second resonant coil (111). Power transmitting device (101) according to claim 1, which further comprises a storage circuit (110) in which the capacitance value of the variable capacitor (106) for setting the resonant frequency of the first resonant coil (107) is stored on the basis of the resonant frequency of the second resonant coil (111), wherein the storage circuit (110) is connected to the control device (109). Power transmitting device (101) according to claim 1, wherein the control device (109) sets a frequency at which the strength of the parameter S11 is changed under a condition that the capacitance value of the variable capacitor (106) is set to a capacitance value based on the resonant frequency of the second resonant coil (111), at the time at which the oscillation frequency of the signal output by the high-frequency power source (104) is changed, as the oscillation frequency of the signal output by the high-frequency power source (104). System for wireless power transmission comprising a power transmitter (101) according to claim 1 and the power receiver (102), wherein the power receiver (102) includes the second resonant coil (111) which causes electromagnetic resonance with the first resonant coil (107) and which is connected to a capacitor (112) and to a second coil (113) which is electromagnetically coupled to the second resonant coil (111) and which is connected to a load (114). System for wireless power transmission according to claim 4, wherein the power transmitter device (101) includes a memory circuit (110) in which the capacitance value of the variable capacitor (106) for setting the resonant frequency of the first resonant coil (107) is stored on the basis of the resonant frequency of the second resonant coil (111), and wherein the memory circuit (110) is connected to the control device (109).

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