WO2013077140A1

WO2013077140A1 - Contactless power supply apparatus

Info

Publication number: WO2013077140A1
Application number: PCT/JP2012/077661
Authority: WO
Inventors: Shinichi Haseno; Yoichi Uramoto
Original assignee: Sony Corporation
Priority date: 2011-10-21
Filing date: 2012-10-19
Publication date: 2013-05-30
Also published as: JP2013102665A

Abstract

A feed apparatus (4) including a power transmission section (1) that transmits electric power; a control section (10) that controls the power transmission section; and a stop circuit (114) that prohibits the power transmission section (1) from transmitting electric power regardless of a state of the control section (10) when an abnormal state of the feed apparatus (4) is detected.

Description

DESCRIPTION

Title of Invention

CONTACTLESS POWER SUPPLY APPARATUS Technical Field

[0001 ] The present disclosure relates to a feed system that performs noncontact electric power supply (electric power transmission) to a target device to be fed such as an electronic device, and a feed apparatus applied to such a feed system.

Background

[0002] In recent years, attention has been given to a feed system (such as a noncontact feed system and a wireless charging system) that performs noncontact electric power supply (electric power transmission) to a CE device (consumer electronics device) such as a portable telephone and a portable music player. This makes it possible to start charging merely by placing an electronic device (a secondary-side device) on a charging tray (a primary-side device), instead of inserting (connecting) a connector of a power-supply unit such as an AC adapter into the device. In other words, terminal connection between the electronic device and the charging tray is not necessary.

[0003] A method of performing such noncontact electric power supply includes an electromagnetic induction method. In recent years, a noncontact feed system using a method called a magnetic resonance method utilizing an electromagnetic resonance phenomenon has also been receiving attention. Such noncontact feed systems are disclosed in Patent Literatures 1 to 6, for example.

Citation List

Patent Literature

[0004] PTL1 : Unexamined Japanese Patent Application Publication No.

2001 - 102974

PTL2: International Application Publication No. WO00-2753 1

PTL3 : Unexamined Japanese Patent Application Publication No.

2008-206233

PTL4: Unexamined Japanese Patent Application Publication No.

2002- 34169

PTL5 : Unexamined Japanese Patent Application Publication No. 2005-110399

PTL6: Unexamined Japanese Patent Application Publication No. 2010-63245

Summary

[0005] In a noncontact feed system, a load state of a feed apparatus varies depending on situations and the feed apparatus may be in an overload state, for example. It is desirable to decrease electric power loss as much as possible during electric power transmission (noncontact feeding) even when the load has varied. Specifically, a proposal is desired that makes it possible to decrease electric power loss caused by variation in a load state during electric power transmission using a magnetic field and/or the like.

[0006] It is desirable to provide a feed apparatus and a feed system capable of decreasing electric power loss caused by variation in a load state during electric power transmission using a magnetic field or an electric field.

[0007] A feed apparatus according to an embodiment of the present disclosure includes: a power transmission section that transmits electric power; a control section that controls the power transmission section; and a stop circuit that prohibits the power transmission section from transmitting electric power regardless of a state of the control section when an abnormal state of the feed apparatus is detected.

[0008] The feed apparatus may also include: an interface connected to an external power source and that receives power from the external power source, and the stop circuit may be disposed between the interface and the power transmission section.

[0009] The stop circuit may prohibit the power transmission section from transmitting electric power by blocking the power received from the external power source.

[0010] The feed apparatus may further include a data transmission control section that controls transmission of data to a device receiving the electric power transmitted from the power transmission section.

[0011 ] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the technology as claimed. Brief Description of the Drawings

[0012] The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the specification, serve to explain the principles of the technology.

[0013] [FIG. 1 ] FIG. 1 is a perspective view illustrating an appearance configuration example of a feed system according to a first embodiment of the present disclosure.

[FIG. 2] FIG. 2 is a block diagram illustrating a detailed configuration example of the feed system shown in FIG. 1.

[FIG. 3] FIG. 3 is a circuit diagram illustrating a detailed configuration of each block shown in FIG. 2.

[FIG. 4] FIG. 4 is a timing waveform chart illustrating an example of a control signal supplied to an AC (alternating-current) signal generation circuit.

[FIG. 5] FIG. 5 is a timing diagram illustrating an example of feed periods and communication periods.

[FIG. 6] FIG. 6 is a timing waveform chart illustrating an example of communication operation by pulse-width modulation using the AC signal generation circuit.

[FIG. 7] FIG. 7 is a characteristic diagram schematically illustrating an example of drooping characteristics in an overload state.

[FIG. 8] FIG. 8 is a timing waveform chart for explaining power limiting and distributing function in the overload state. [FIG. 9] FIG. 9 is a schematic diagram for explaining a forceful operation stopping function and a forceful power supply blocking function.

[FIG. 10] FIG. 10 is a circuit diagram illustrating a configuration example of main parts of a feed system according to a second embodiment.

[FIG. 1 1 ] FIG. 1 1 is a timing diagram illustrating an operation example of a power limiting and modulation circuit shown in FIG. 10.

[FIG. 12] FIG. 12 is a timing waveform chart illustrating an example of communication operation by amplitude modulation using the power limiting and modulation circuit shown in FIG. 10.

[FIG. 13] FIG. 13 is a block diagram illustrating a schematic configuration example of a feed system according to a modification example.

[FIG. 14] FIG. 14 is a schematic diagram illustrating a propagation example of an electric field in the feed system shown in FIG. 13.

Description of Embodiments

[0014] Embodiments of the present disclosure will be described below in detail with reference to drawings. The description will be given in the following order.

1 . First embodiment (an example in which communication is performed by pulse-width modulation using an AC signal generation circuit)

2. Second embodiment (an example in which communication is performed also by amplitude modulation using a power limiting circuit)

3. Modification examples (an example of a feed system performing noncontact electric power transmission using an electric field, and other examples)

[First Embodiment]

[General Configuration of Feed System 4]

[0015] FIG. 1 illustrates an appearance configuration example of a feed system (feed system 4) according to a first embodiment of the present disclosure. FIG. 2 illustrates a block configuration example of the feed system 4. The feed system 4 is a system (noncontact feed system) performing noncontact electric power transmission (such as electric power supply, and electric power feeding) using a magnetic field (such as utilizing magnetic resonance and electromagnetic induction, and the same applies hereinafter). The feed system 4 includes a feed apparatus 1 (primary-side device) and one or a plurality of electronic devices (two electronic devices 2A and 2B in this example; secondary-side devices) as target devices to be fed.

[0016] In this feed system 4, for example, as shown in FIG. 1 , the electronic devices 2A and 2B are placed on (or placed near) a power feeding surface (electric power transmission surface) S I of the feed apparatus 1. Thus, electric power is transmitted from the feed apparatus 1 to the electronic devices 2A and 2B. In this example, taking into consideration the case where electric power is concurrently or time-divisionally (sequentially) transmitted to the plurality of electronic devices 2A and 2B, the feed apparatus 1 is shaped like a mat (tray) in which the area of the power feeding surface S I is larger than those of the electronic devices 2 A and 2B, and/or the like targeted to be fed. [Feed Apparatus 1 ]

[0017] The feed apparatus 1 is an apparatus (charging tray) transmitting electric power using a magnetic field to the electronic devices 2A and 2B as described above. The feed apparatus 1 includes a power transmission unit 1 1 and a data transmission section 13 as shown in FIG. 2, for example. The power transmission unit 1 1 includes a power transmission section 1 10, a current detection circuit 1 1 1 , a power limiting circuit 1 12, an alternating-current (AC) signal generation circuit (high-frequency power generation circuit) 1 13, and an operation stop circuit 1 14. Also, the feed apparatus 1 includes a control section 10 including a power transmission control section (modulation processing section) 10A provided in the power transmission unit 1 1 and a data transmission control section 10B provided outside the power transmission unit 1 1 . The power limiting circuit 1 12, the AC signal generation circuit 1 13 , and the operation stop circuit 1 14 correspond to specific but not limitative examples of "power limiting section", "alternating-current signal generation section", and "operation stop section", respectively.

[0018] The power transmission section 1 10 includes a power transmission coil (primary-side coil) L , capacitors C lp and C l s (capacitors for resonance), and/or the like, which are described later. The power transmission section 1 10 performs electric power transmission using AC magnetic field with respect to the electronic devices 2A and 2B (specifically, with respect to a later-described power reception section 210), utilizing the power transmission coil L I and the capacitors C l p and C l s (see an arrow P I in FIG. 2). Specifically, the power transmission section 1 10 has a function of radiating a magnetic field (magnetic flux) from the power feeding surface S I toward the electronic devices 2A and 2B. Also, the power transmission section 110 has a function of mutually performing a predetermined communication operation with the later-described power reception section 210 (see an arrow C I in FIG. 2).

[0019] The AC signal generation circuit 113 generates a predetermined AC signal Sac (high-frequency electric power) used to perform electric power transmission. The AC signal generation circuit 113 uses, for example, electric power supplied from the external power source 9 (primary power source) of the feed apparatus 1 through the later-described power limiting circuit 112 to generate the AC signal Sac. The AC signal generation circuit 1 13 may be configured of a switching amplifier described later, for example. The external power source 9 may be, for example, a power source (for example, electric power supplying capability of about 500 mA and power source voltage of about 5 V) of USB (Universal Serial Bus) 2.0 which is provided in a PC (personal computer) or the like.

[0020] The power limiting circuit 112 is provided on an electric power supply line (later-described electric power supply line Lp) extending from the external power source 9 to the power transmission section 1 10. In particular, the power limiting circuit 112 is provided between a power input terminal (not illustrated) for the external power source 9 and the power transmission section 1 10. The power limiting circuit 1 12 has a function of limiting (performing power limiting operation) electric power to be supplied from the external power source 9 to the power transmission section 1 10. Specifically, although the details will be described later, the power limiting circuit 1 12 functions as an overcurrent limiting circuit (overcurrent protection circuit) limiting an overcurrent when the feed apparatus is in, for example, the overload state or the like. In addition, the power limiting circuit 1 12 has a function of forcefully blocking electric power supply from the external power source 9 to the power transmission section 1 10 in a predetermined case described later.

[0021] The current detection circuit 1 11 detects an input current II which flows from the external power source 9 to the feed apparatus 1 as a whole. Specifically, the current detection circuit 1 1 1 detects (determines) a voltage corresponding to the input current II and outputs the detected voltage to the power limiting circuit 1 12.

[0022] The operation stop circuit 1 14 forcefully stops electric power transmission by for example, the power transmission section 10 and/or the like without depending on the control of electric power transmission by the later-described power transmission control section 10A when an abnormal state (such as an overload state) of the feed apparatus described later is detected.

[0023] The data transmission section 13 mutually performs noncontact data transmission with a later-described data transmission section 23 in each of the electronic devices 2 A and 2B (see an arrow D l in FIG. 2). A method performing such noncontact data transmission may be a method using "Transfer Jet" which is one of short-range wireless transfer technologies, for example.

[0024] The control section 10 is provided upstream of the power limiting circuit 1 12 (closer to the external power source 9 than the power limiting circuit 1 12), in particular, between the power input terminal (not illustrated) for the external power source 9 and the power limiting circuit 112 as shown in FIG. 2. The control section 10 includes a power transmission control section 10A controlling electric power transmission by the power transmission section 1 10 and a data transmission control section 10B controlling data transmission by the data transmission section 13. The control section 10 performs various control operations in the feed apparatus 1 as a whole (feed system 4 as a whole). Specifically, the control section 10 may have a function of optimization control of the transmitted electric power, a function of certificating secondary-side devices, a function of determining that a secondary-side device is present on the primary-side device, a function of detecting incorporation of dissimilar metals, and/or the like in addition to the above-described functions of controlling electric power transmission and controlling data transmission, for example.

[0025] The power transmission control section 10A controls (through the operation stop section 114 in this example) operation of the AC signal generation circuit 1 13 by using a predetermined control signal CTL (control signal provided for electric power transmission) described later, and thereby performs the control of the electric power transmission described above. In addition, the power transmission control section 10A has a function of performing modulation processing by pulse-width modulation (PWM) described later using the control signal CTL.

[Electronic Devices 2A and 2B]

[0026] The electronic devices 2A and 2B may be, for example, stationary electronic devices such as television receivers and/or portable electronic devices including batteries such as mobile phones and digital cameras. The electronic devices 2A and 2B each include, for example, as shown in FIG. 2, a power reception unit 21 , a load 22 which performs a predetermined operation (operation exhibiting the function of the electronic device) in response to the electric power supplied from the power reception unit 21 , and the data transmission section 23. The power reception unit 21 includes a power reception section 210, a rectifier circuit 21 1 , a charge circuit 212, and a battery 213.

[0027] The power reception section 210 includes a power reception coil (secondary-side coil) L2, capacitors (capacitors provided for resonance) C2p and C2s, and/or the like that are described later. The power reception section 210 has a function of receiving electric power transmitted from the power transmission section 1 10 in the feed apparatus 1 , utilizing the power reception coil L2 and the capacitors C2p and C2s and/or the like. The power reception section 210 also has a function of mutually performing the above-described predetermined communication operation with the power transmission section 1 10 (see the arrow C I in FIG. 2).

[0028] The rectifier circuit 21 1 rectifies the electric power (AC electric power) supplied from the power reception section 210 and generates direct-current (DC) electric power.

[0029] The charge circuit 212 charges the battery 213, a battery (not illustrated) in the load 22, and/or the like based on the DC electric power supplied from the rectifier circuit 211.

[0030] The battery 213 stores electric power in response to the charge by the charge circuit 212. The battery 213 may be configured of a rechargeable battery (secondary battery) such as a lithium ion battery, for example. The battery may not be necessarily provided, for example, when only the battery in the load 22 is used.

[0031 ] The data transmission section 23 mutually performs noncontact data transmission with the data transmission section 13 in the feed apparatus 1 as described above (see the arrow D l in FIG. 2).

[Detailed Configurations of Feed Apparatus 1 and Electronic Devices 2A and 2B]

[0032] FIG. 3 is a circuit diagram illustrating a detailed configuration example of each block in the feed apparatus 1 and the electronic devices 2A and 2B shown in FIG. 2.

[Power Transmission Section 1 10]

[0033] The power transmission section 110 includes the power transmission coil LI which performs electric power transmission using a magnetic field (generates magnetic flux) and the capacitors C lp and Cl s which form a LC resonance circuit together with the power transmission coil LI . The capacitor C l s is electrically connected in series to the power transmission coil LI . More specifically, one end of the capacitor C l s is connected to one end of the power transmission coil LI . The other end of the capacitor C l s and the other end of the power transmission coil LI are connected in parallel to the capacitor C l p, and a connection end of the power transmission coil LI and the capacitor C lp is grounded.

[0034] The LC resonance circuit including the power transmission coil L I and the capacitors C lp and C l s, and the LC resonance circuit including the power reception coil L2 and the capacitors C2p and C2s described later are magnetically coupled with each other. Therefore, LC resonance operation at a resonance frequency substantially the same as that of the high-frequency electric power (AC signal Sac) generated by the AC signal generation circuit 1 13 described later is performed.

[Current Detection Circuit 11 1 ]

[0035] The current detection circuit 1 1 1 includes a resister Rl and an error amplifier Al . One end of the resistor Rl is connected to the power input terminal (not illustrated) for the external power source 9 and the other end of the resister Rl is connected to the connection point P0. Thus, the resister Rl is arranged on the electric power supply line Lp. A positive (+ side) input terminal of the error amplifier Al is connected to one end of the resister Rl and a negative (- side) input terminal of the error amplifier Al is connected to the other end of the resister Rl . An output terminal of the error amplifier Al is connected to a positive input terminal of the error amplifier A3 in the power limiting circuit 1 12 described later. Thus, a potential difference (voltage) between the both ends of the resister Rl is inputted to the positive input terminal of the error amplifier A3.

[0036] With this configuration, the current detection circuit 1 11 detects the above-described input current II (current flowing along the electric power supply line Lp) which flows through the resister Rl and outputs a voltage VI corresponding to the magnitude of the input current II from the error amplifier Al to the error amplifier A3.

[Power Limiting Circuit 1 12]

[0037] The power limiting circuit 1 12 includes transistors Trl and Tr2, a comparator A2, the error amplifier A3, and power sources PS2 and PS3. The transistor Trl may be configured of a p-type FET (field effective transistor) and the transistor Tr2 may be configured of an n-type FET. The power source PS2 outputs a predetermined threshold voltage Vth2 (second threshold value) higher than 0 V described later and the power source PS3 outputs a reference voltage Vref described later. It is to be noted that the transistor Trl and the error amplifier A3 correspond to specific but not limitative examples of "transistor" and "error amplifier", respectively.

[0038] A source of the transistor Trl is connected to the connection point P0. A drain of the transistor Trl is connected to one end of the above-described capacitor C lp and to one end of the above-described capacitor C l s. A gate of the transistor Trl is connected to an output terminal of the error amplifier A3. Thus, the transistor Trl is arranged on the electric power supply line Lp. A negative input terminal of the comparator A2 is connected to an output terminal of a comparator A4 in the operation stop circuit 1 14 described later. A positive input terminal of the comparator A2 is connected to the power source PS2. An output terminal of the comparator A2 is connected to a gate of the transistor Tr2. A source of the transistor Tr2 is grounded and a drain thereof is connected to the power source PS3 and to a negative input terminal of the error amplifier A3.

[0039] With this configuration, the power limiting circuit 112 generates an output signal S3 according to the potential difference between the reference voltage Vref and the output voltage (voltage V I corresponding to the input current II ) from the error amplifier Al described above in the error amplifier A3, and supplies the output signal S3 to the gate of the transistor Trl . According to the output signal S3, the power limiting circuit 1 12 limits the magnitude (magnitude of electric power) of a current 12 (a current, out of the above-described input current I I , that flows from the connection point PO to a path leading to the power transmission section 1 10) flowing between the source and drain of the transistor Trl . Thus, electric power supplied from the external power source 9 to the power transmission section 1 10 is limited (the overcurrent in the overload state or in the other states is limited).

[0040] Also, in a predetermined case described later, the operation stop circuit 1 14 controls the magnitude of the reference voltage Vref inputted to the error amplifier A3 , and thereby, the power limiting circuit 1 12 forcefully blocks the electric power supply from the external source 9 to the power transmission section 1 10. Specifically, the magnitude of the reference voltage Vref is controlled according to a voltage comparison result obtained in the comparator A2.

[Control Section 10]

[0041 ] The control section 10 includes the above-described power transmission control section (modulation processing section) 10A and data transmission control section 10B. Input terminals of the power transmission control section 10A and the data transmission control section 10B are each connected to the connection point P0. In other words, the power transmission control section 10A and the data transmission control section 10B are connected to each other in parallel and are arranged before the power limiting circuit 112 (between the external power source 9 and the power limiting circuit 1 12). Therefore, although the details will be described later, a current 13 out of the input current I I constantly flows (irrespective of the load state) from the connection point PO to the path leading to the control section 10.

[Operation Stop Circuit 1 14]

[0042] The operation stop circuit 1 14 includes the comparator A4, a power source PS 1 which outputs a predetermined threshold voltage Vthl (first threshold value) described later that is higher than the second threshold voltage Vth2, and an AND circuit LG l . The comparator A4 and the AND circuit LGl correspond to specific but not limitative examples of "voltage detection section" and "switch section", respectively.

[0043] A positive input terminal of the comparator A4 is connected to the source of the transistor Trl and a negative input terminal thereof is connected to the drain of the transistor Trl through the power source PS 1 . The output terminal of the comparator A4 is connected to the negative input terminal of the comparator A2 and to one input terminal of the AND circuit LG l . The other input terminal of the AND circuit LG l receives the control signal CTL used for electric power transmission from the power transmission control section 10A.

[0044] The control signal CTL is configured of a pulse signal having a predetermined duty ratio as shown in FIG. 3. Pulse-width modulation described later is performed by controlling the duty ratio of the control signal CTL as shown in parts (A) and (B) of FIG. 4, for example.

[0045] With this configuration, the operation stop circuit 114 detects, in the comparator A4, a voltage AV2 (potential difference between the source and drain of the transistor Tr l ) between input and output of the power limiting circuit 1 12, and compares the voltage AV2 with the threshold voltage Vthl . The operation stop circuit 1 14 detects the abnormal state (overload state or the like) of the feed apparatus 1 described later based on the voltage comparison result (magnitude of the detected voltage AV2) and forcefully stops electric power transmission operation of the AC signal generation circuit 113 and the power transmission section 1 10 through the AND circuit LGl according to the detection result.

[Alternating-Current Signal Generation Circuit 113]

[0046] The alternating-current (AC) generation circuit 113 is configured of a switching amplifier (a so-called class-E amplifier) including one transistor Tr3 as a switching device. The transistor Tr3 may be an n-type FET in this example. A source of the transistor Tr3 is grounded, a gate thereof is connected to the output terminal of the AND circuit LGl , and a drain thereof is connected to the drain of the transistor Trl and to one end of the capacitor C lp and one end of the capacitor C l s.

[0047] Having such a configuration, in the AC signal generation circuit 1 13, the transistor Tr3 performs ON and OFF operation (switching operation based on predetermined frequency and duty ratio) according to the output signal (signal S I ) from the AND circuit LGl based on the control signal CTL used for the electric power transmission. In other words, the ON and OFF operation of the transistor Tr3 as a switching device is controlled using the control signal CTL supplied from the power transmission control section 10A. Thereby, the AC signal Sac (AC electric power) is generated based on the DC signal Sdc supplied through the power limiting circuit 1 12 and the AC signal Sac is supplied to the power transmission section 1 10. [Power Reception Section 210]

[0048] The power reception section 210 includes a power reception coil L2 receiving electric power transmitted from the power transmission section 1 10 (from the magnetic flux) and capacitors C2p and C2s forming a LC resonance circuit together with the power reception coil L2. The capacitor C2p is electrically connected in parallel to the power reception coil L2 and the capacitor C2s is electrically connected in series to the power reception coil L2. Specifically, one end of the capacitor C2s is connected to one end of the capacitor C2p and to one end of the power reception coil L2. The other end of the capacitor C2s is connected to one input terminal of the rectifier circuit 21 1. The other end of the power reception coil L2 and the other end of the capacitor C2p are each connected to the other input terminal of the rectifier circuit 21 1.

[0049] The LC resonance circuit including the power reception coil L2 and the capacitors C2p and C2s and the above-described LC resonance circuit including the power transmission coil LI and the capacitors C lp and C l s are magnetically coupled with each other. Therefore, LC resonance operation at a resonance frequency substantially the same as that of the high-frequency electric power (AC signal Sac) generated by the AC signal generation circuit 113 described later is performed.

[Function and Effect of Feed System 4]

[1. Outline of General Operation]

[0050] In the feed system 4, the AC signal generation circuit 1 13 in the feed apparatus 1 supplies a predetermined high-frequency electric power (AC signal Sac) used for electric power transmission to the power transmission coil L I and the capacitors C l p and C l s (LC resonance circuit) in the power transmission section 1 10 based on the electric power supplied from the external power source 9. Thereby, a magnetic field (magnetic flux) is generated in the power transmission coil L I in the power transmission section 1 10. Under such circumstance, when the electronic devices 2A and 2B as the target devices to be fed are placed on (or placed near) the top surface (power feeding surface S I ) of the feed apparatus 1 , the power transmission coil L I in the feed apparatus 1 and the power reception coil L2 in the electronic devices 2A and 2B are located close to each other near the power feeding surface S I .

[0051 ] Thus, when the power reception coil L2 is located close to the power transmission coil L I in which a magnetic field (magnetic flux) is generated, electromotive force is generated in the power reception coil L2 induced by the magnetic flux generated in the power transmission coil L I . In other words, the magnetic field is generated interlinking with each of the power transmission coil L I and the power reception coil L2 due to electromagnetic induction or magnetic resonance. Thereby, electric power is transmitted from the power transmission coil L I side (primary side, feed apparatus 1 side, or power transmission section 1 10 side) to the power reception coil L2 side (secondary side, electronic devices 2A and 2B side, or power reception section 210 side) (see the arrow P I in FIGs. 2 and 3). At this time, the power transmission coil L I on the feed apparatus 1 side and the power reception coil L2 on the electronic devices 2A and 2B side are magnetically coupled with each other due to the electromagnetic induction, magnetic resonance, and/or the like, and thereby, LC resonance operation is performed in the LC resonance circuits.

[0052] In the electronic devices 2 A and 2B, the rectifier circuit 21 1 and the charge circuit 212 receive the AC electric power received by the power reception coil L2 and perform the following charge operation. The rectifier circuit 21 1 converts the AC electric power to predetermined DC electric power. Subsequently, the charge circuit 212 performs charging to the battery 213 or the battery (not illustrated) in the load 22 based on this DC electric power. Thus, charge operation based on the electric power received by the power reception section 210 is performed in the electronic devices 2A and 2B.

[0053] In the present embodiment, the electronic devices 2A and 2B are charged, for example, without terminal connection to the AC adapter or the like, and the charge is readily started (noncontact power feeding is performed) only by placing the electronic devices 2A and 2B on (or near) the power feeding surface S I of the feed apparatus 1 . This leads to reduction in user's effort.

[0054] In such feeding operation, a feed period Tp (charge period) and a communication period Tc (non-charge period) are time-divisionally and periodically (or non-periodically) provided as shown in FIG. 5, for example. In other words, the power transmission control section 10A time-divisionally and periodically (or non-periodically) sets such a feed period Tp and such a communication period Tc. Here, the communication period Tc refers to a period in which the primary-side device (feed apparatus 1 ) and the secondary-side devices (electronic devices 2 A and 2B) perform mutual communication operation therebetween (such as communication operation for mutual device certification and power feeding efficiency control) using the power transmission coil L I and the power reception coil L2 (see the arrow C I in FIGs. 2 and 3). The time ratio of the feed period Tp and the communication period Tc in this example may be about 9: 1 for feed period Tp and communication period Tc, for example.

[0055] In the communication period Tc, communication operation using pulse-width modulation in AC signal generation circuit 1 13 is performed as shown in parts (A) to (D) of FIG. 6, for example. Specifically, the duty ratio of the control signal CTL in the communication period Tc is set (see part (B) of FIG. 6) based on modulation data Dm shown in part (A) of FIG. 6, for example, and thereby communication by pulse-width modulation is performed. It may be difficult in principle to perform frequency modulation during the above-described resonance operation performed by the power transmission section 1 10 and the power reception section 210. Therefore, the use of such pulse-width modulation makes it possible to readily achieve the communication operation.

[0056] Moreover, in the feed system 4, the data transmission section 1 3 in the primary-side device (feed apparatus 1 ) and the data transmission section 23 in the secondary-side devices (electronic devices 2A and 2B) mutually perform noncontact data transmission therebetween as shown by the arrow D l in FIGs. 2 and 3. Therefore, data transmission is performed without connecting the feed apparatus 1 and the electronic devices 2A and 2B through wires or the like for data transmission, and the data transmission is performed only by placing the electronic devices 2A and 2B close to the feed apparatus 1 . This also reduces user's effort. [2. Power Limiting and Distributing Function in Overload State]

[0057] In such a feed system 4, the feed apparatus 1 may be overloaded (in an overload state). Specifically, the feed apparatus 1 may be in the overload state, for example, when the data transmission section 13 suddenly consumes excessively large amount of electric power, when the secondary-side devices (electronic devices 2A and 2B in this example) require excessively large amount of electric power, and/or the like.

[0058] When the feed apparatus 1 becomes such an overload state, current-voltage characteristics are controlled to exhibit a so-called drooping characteristics (characteristics plotted as a hook-like shape) as shown in FIG. 7 for example, and protection against overcurrent is performed. Specifically, in this example, the current detection circuit 111 in the feed apparatus 1 detects the voltage VI corresponding to the current II inputted from the external power source 9. Then, in the power limiting circuit 1 12, the error amplifier A3 outputs the signal S3 according to the potential difference between the voltage V I and the reference voltage Vref, and the magnitude of the current 12 flowing between the source and the drain of the transistor Trl is controlled based on the signal S3. In other words, the magnitude of the current 12 is limited according to the magnitude of the input current II (electric power supply toward the drain of the transistor Trl is limited), and thereby, the power limiting circuit 1 12 performs power limiting operation. For example, in the case where the external power source 9 is a power source of USB 2.0 described above, the feed apparatus 1 is determined to be in the overcurrent state (overload state) when the input current II is equal to or larger than 500 mA (when the electric power is over 2.5 W).

[0059] However, the following issue arises when such power limiting operation is performed on the feed apparatus 1 as a whole (when power supply is limited with respect to the whole blocks in the feed apparatus 1 ). That is, in the case where the feed apparatus 1 becomes the above-described overcurrent state (overload state), when the power supply to the control section 10 (especially, the power transmission control section 10A) that controls the feed apparatus 1 as a whole (feed system 4 as a whole) is limited, the control section 10 stops to operate, thereby causing disadvantage. Namely, the control section 10 (especially, the power transmission control section 10A) is expected to operate normally (it is necessary to constantly secure stable operation) even if the feed apparatus 1 is in the overload state or the like since the power transmission control section 10A also has an important role in securing the safety of the feed system 4, for example.

[0060] Therefore, the control section 10 is arranged before the power limiting circuit 1 12 (between the external power source 9 and the power limiting circuit 1 12) in the feed apparatus 1 of the present embodiment as shown in FIGs. 2 and 3. Thus, the current 13 , out of the input current I I flowing from the external power source 9 to the feed apparatus 1 , constantly (irrespective of the load state) flows to the path leading to the control section 10 from the connection point P0 (see FIG. 3). In other words, electric power supply from the external power source 9 toward the control section 10 is not limited even when the feed apparatus 1 is in the overload state, for example. Thus, electric power supply toward the control section 10 is constantly secured in the feed apparatus 1 , and electric power is preferentially distributed toward the control section 10.

[0061 ] More specifically, for example, as shown with arrows in part (C) of FIG. 8, the current 13 flowing toward the control section 10 (electric power supply toward the control section 10) is not limited even when the current 13 consumed by the control section 10 is drastically increased (when the feed apparatus 1 becomes the overload state). On the other hand, for example, as shown with arrows in part (B) of FIG. 8, the power limiting circuit 1 12 limits the current 12 (power supply to the power transmission section 1 10) supplied toward the power transmission section 1 10 which is located downstream of the power limit circuit 1 12 when the feed apparatus 1 becomes such an overload state. Thus, electric power is preferentially distributed toward the control section 10 than to the power transmission section 1 10.

[0062] Also, for example, as shown with arrows in part (A) of FIG. 8, the input current I I (electric power drawn from the external power source 9) which flows from the external power source 9 to the feed apparatus 1 as a whole is controlled to be the predetermined threshold value Ith (for example, 500 mA when the above-described power source of USB2.0 is used) or less. Thereby, excessive (over supply ability) electric power (input current I I of the threshold value Ith or more) supply from the external power source 9 is avoided. Accordingly, for example, in the case where the power source of USB2.0 provided in a PC is used as the external power source 9, when the feed apparatus 1 attempts to take out a current over the supply ability of the external power source 9, an "alert" signal is prevented from being displayed on the display screen of the PC, for example.

[3. Forceful Operation Stop Function]

[0063] In the feed apparatus 1 of the present embodiment, the operation stop circuit 1 14 performs a forceful stop function as described below.

[0064] First, the comparator A4 detects the voltage AV2 (potential difference between the source and drain of the transistor Tr l ) between the input and the output of the power limiting circuit 1 12 and compares the magnitude of voltage AV2 with that of the threshold voltage Vthl . The threshold voltage Vthl is used to determine whether or not the feed apparatus 1 is in the overload state (overcurrent state) in the normal operation. In other words, whether the feed apparatus 1 is in the appropriate load state or is in the overload state in the normal operation is detected based on the above-described voltage comparison result (the magnitude of the detected voltage AV2). In this example, the feed apparatus 1 is detected to be in the appropriate load state in the normal operation when the voltage AV2 is equal to or less than the threshold value Vthl , while the feed apparatus 1 is detected to be in the overload state in the normal operation when the voltage AV2 is larger than the threshold value Vthl . It is to be noted that this detection sensitivity may be set to be decreased in some degrees by the time constant in wirings between the comparator A4 and the AND circuit LG1 .

[0065] The operation stop circuit 1 14 forcefully stops, without electric power transmission control by the power transmission control section 10A, the electric power transmission operation of the AC signal generation circuit 1 13 and the power transmission section 1 10, using the AND circuit LG l according to the above-described detection result of the load state. In particular, a signal S4 outputted from the comparator A4 becomes a "H (high)" state when the feed apparatus 1 is detected to be in the appropriate load state in the normal operation (AV2<Vthl ). As a result, the signal S I outputted from the AND circuit LG l to the transistor Tr3 in the AC signal generation circuit 1 13 becomes equal to the control signal CTL for electric power transmission supplied from the power transmission control section 10A (the control signal CTL is enabled). Accordingly, the transistor Tr3 is operated to be ON and OFF in response to this control signal CTL, and thereby, the AC signal generation circuit 1 13 and the power transmission section 1 10 perform the normal electric power transmission operation.

[0066] On the other hand, the signal S4 outputted from the comparator A4 becomes a "L (low)" state when the feed apparatus 1 is detected to be in the overload state in the normal operation (AV2>Vthl ). As a result, the signal S I outputted from the AND circuit LGl to the transistor Tr3 in the AC signal generation circuit 1 13 is constantly in the "L" state (the control signal CTL is disabled), and thereby, the transistor Tr3 is constantly in the OFF state (the transistor Tr3 is in the open state). Thus, the AND circuit LGl serves to switch the state of the control signal CTL between the enabled state and the disabled state according to the value of the signal S4 outputted from the comparator A4 (according to whether or not the overload state is detected). The operation stop circuit 1 14 forcefully stops the electric power transmission operation of the AC signal generation circuit 1 13 and the power transmission section 1 10 without the power transmission control by the power transmission control section 10A, by disabling the control signal CTL used for the electric power transmission.

[0067] Moreover, the operation stop circuit 1 14 forcefully stops the communication operation by disabling the control signal CTL likewise when the overload state (overcurrent state) is detected in the communication period Tc as well as in the feed period Tp.

[0068] When the comparator A4 detects that the feed apparatus 1 is recovered (returned) from the overload state to the appropriate load state, the control signal CTL becomes the enabled state again based on the above-described principle. Therefore, the electric power transmission operation is automatically restarted without depending on the control of the electric power transmission by the power transmission control section 10A in this case as well.

[0069] Thus, electric power transmission by the power transmission section 1 10 is forcefully stopped without depending on the control of the electric power transmission by the power transmission control section 10A when the abnormal state (overload state) of the feed apparatus 1 is detected. Therefore, the electric power transmission is rapidly stopped without waiting for the electric power transmission control by the power transmission control section 10A, for example, when the load state of the feed apparatus 1 varies to be the overload state. Accordingly, the length of time to stop the electric power transmission (unnecessary electric power transmission period) is shortened.

[4. Forceful Power Supply Blocking Function]

[0070] When the comparator A4 detects that the voltage AV2 is even larger than the predetermined threshold value Vth2 (>Vth l ), the power limiting circuit 1 12 forcefully performs a power supply blocking function as described below without the electric power transmission control by the power transmission control section 10A.

[0071 ] The threshold voltage Vth2 may define whether or not the power transmission section 1 10 is in one of the failure state and the destroyed state (destruction state) due to a short-circuited state in the feed apparatus 1 and/or the like as shown in FIG. 9, for example. In such a state, the voltage AV2 between the both ends of the transistor Trl in the current limiting circuit 1 12 becomes excessively large, possibly leading to heat generation. Also, the operation stop circuit 1 14 may be inoperable (the above-described forceful operation stop function may not be performed).

[0072] Thus, the comparator A4 also detects whether or not the power transmission section 1 10 is in one of the failure state and the destruction state based on the magnitude of the detected voltage AV2. In particular, the comparator A4 detects that the power transmission section 1 10 is not in any of the failure state and the destruction state when the voltage AV2 is equal to or less than the threshold value Vth2, while the comparator A4 detects that the power transmission section 1 10 is in one of the failure state and the destruction state when the voltage AV2 is larger than the threshold value Vth2.

[0073] When the comparator A4 detects that the voltage AV2 is even larger than the threshold value Vth2 (that the power transmission section 1 10 is in one of the failure state and the destruction state), the power limiting circuit 1 12 forcefully blocks the electric power supply from the external power source 9 to the AC signal generation circuit 1 13 and the power transmission section 1 10 as described below. Specifically, the power limiting circuit 1 12 controls the reference voltage Vref inputted to the error amplifier A3 according to the voltage comparison result obtained in the comparator A2 to constantly make the transistor Trl be in the OFF state, thereby forcefully blocking the electric power supply.

[0074] In particular, in this case (AV2>Vth2), the signal S2 outputted from the comparator A2 is in the "L" state, and therefore, the transistor Tr2 is in the OFF state. The potential at the negative input terminal of the error amplifier A3 decreases from the reference voltage Vref originally supplied from the power source PS3 to be closer to the ground (0 V) accordingly. As a result, the signal S3 outputted from the error amplifier A3 becomes the "H" state, and therefore, the transistor Trl is constantly in the OFF state. Thus, the transistor Trl becomes the OFF state, and thereby, the current 12 stops flowing between the source and the drain of the transistor Trl (12=0 A). Therefore, electric power supply toward the power transmission section 1 10 is forcefully blocked. Then, such a current 12 stopping function due to the positive feedback (overcurrent suppressing function) is performed, and thereby, the operation stop circuit 1 14 operates until the overcurrent is completely stopped even when the operation stop circuit 1 14 is in the inoperable states. Therefore, the above-described heat generation which possibly occurs in the transistor Trl is avoided. Accordingly, heat generation which possibly occurs in the feed apparatus 1 is avoided, for example, even when the power transmission section 1 10 is in one of the failure state and the destruction state (when the operation stop circuit 1 14 is in the inoperable state). [0075] As described above, in the present embodiment, the operation stop circuit 114 forcefully stops electric power transmission without depending on the control of the electric power transmission by the power transmission control section 10A when the abnormal state (overload state) of the feed apparatus 1 is detected. Therefore, unnecessary electric power transmission period is shortened, for example, when the load state of the feed apparatus 1 varies to be the overload state. Accordingly, the electric power loss caused by the variation in the load state during the electric power transmission using a magnetic field is decreased.

[0076] Moreover, the operation stop circuit 1 14 forcefully stops the electric power transmission when the detected voltage (voltage AV2) is larger than the threshold voltage Vthl , and the power limiting circuit 1 12 forcefully blocks the electric power supply to the power transmission section 1 10 when the voltage AV2 is even larger than the threshold voltage Vth2 which is larger than the threshold voltage Vthl . Therefore, overcurrent is completely stopped, for example, even when the power transmission section 110 is in one of the failure state and the destruction state, and thereby, heat generation which possibly occurs in the feed apparatus 1 (transistor Trl ) is avoided. Accordingly, safety in electric power transmission using a magnetic field is improved.

[0077] Moreover, the control section 10 is arranged closer to the external power source 9 than the power limiting circuit 1 12 is. Therefore, the electric power supply from the external power source 9 toward the control section 10 is constantly secured, and thereby, the electric power is preferentially distributed toward the control section 10. Thus, the stable operation of the control section 10 is secured. Therefore, appropriate control is performed irrespective of the load state during the electric power transmission using a magnetic field. Further, the power source protection function and the power source distribution function are clearly defined in the feed system 4 (noncontact feed system). Therefore, safety of the system is also secured.

[0078] In addition, the following advantage is obtained especially when the power transmission section 110 transmits electric power utilizing resonance operation (LC resonance operation). That is, the power transmission section 1 10 is less susceptible to variation in outputted electric power and to be tolerant to, for example, instant electric power block since the resonance operation is performed. In other words, the power transmission section 1 10 continues to operate (continues to transmit electric power) because of a so-called "principle of a pendulum" (inertial law) even when the electric power suddenly varies.

[Second Embodiment]

[0079] Next, description will be given of a second embodiment of the present disclosure. It is to be noted that like numerals are used to designate substantially like components of the first embodiment, and the description thereof is appropriately omitted.

[Configuration of Feed System 4A]

[0080] FIG. 10 is a circuit diagram illustrating a main part configuration of a feed system (feed system 4A) according to the second embodiment. The feed system 4A of the present embodiment includes one feed apparatus 1 A, and two electronic devices 2 A and 2B. The feed apparatus 1 A has a configuration similar to that of the feed apparatus 1 of the first embodiment except that the feed apparatus 1 A includes a power limiting and modulation circuit 1 12A instead of the power limiting circuit 1 12 of the feed apparatus 1 . The power limiting and modulation circuit 1 12A corresponds to a specific but not limitative example of "power limiting section".

[0081 ] The power limiting and modulation circuit 1 12A has, as shown in FIG. 10, a configuration including one OR circuit LG2 additionally to the configuration of the power limiting circuit 1 12 shown in FIG. 3. In the OR circuit LG2, one input terminal of the OR circuit LG2 is connected to the output terminal of the error amplifier A3 and the other input terminal receives the modulation data Dm outputted from the power transmission control section (modulation processing section) 10A. An output terminal of the OR circuit LG2 is connected to the gate of the transistor Trl .

[Function and Effect of Feed System 4A]

[0082] In the feed apparatus 1 A of the present embodiment, the power limiting and modulation circuit 1 12A performs the power limiting operation in a manner similar to that of the power limiting circuit 1 12 of the first embodiment. Further, in addition thereto, the power limiting and modulation circuit 1 12A performs amplitude modulation (AM) operation such as amplitude shift keying (ASK) modulation.

[0083] In particular, for example, as shown in FIG. 1 1 , the power limiting and modulation circuit 1 12A performs the power limiting operation in the feed period Tc, and the power limiting and modulation circuit 1 12A performs the amplitude modulation operation in the communication period Tc. In the communication period Tc (in a light-load state), the power limiting operation of the power limiting and modulation circuit 1 12A is controlled by the power transmission section 10A, and thereby, the above-described communication by amplitude modulation is performed. Thus, in the present embodiment, communication operation by amplitude modulation such as ASK modulation is performed relatively readily.

[0084] In the communication period Tc, communication operation by amplitude modulation in the power limiting and modulation circuit 1 12A is performed in a manner shown in parts (A) to (D) of FIG. 12, for example. Specifically, the modulation data Dm shown in part (A) of FIG. 12, for example, is first supplied to the transistor Trl from the power transmission control section 10A through the OR circuit LG2 in the power limiting and modulation circuit 1 12A. Thereby, the DC signal Sdc outputted on the electric power supply line Lp from the power limiting and modulation circuit 1 12A becomes a signal in which the amplitude is modulated as shown in part (B) of FIG. 12, for example. The AC signal Sac is generated by the AC signal generation circuit 1 13 based on such a DC signal Sdc (see part (C) of FIG. 12), and the communication operation by amplitude modulation is finally performed (see part (D) of FIG. 12).

[0085] In the communication operation by the amplitude modulation utilizing the power limiting operation of the power limiting and modulation circuit 1 12A, the following advantage is obtained compared to the communication operation using pulse-width modulation of the AC signal generation circuit 1 13 described in the first embodiment, for example.

[0086] Specifically, in the communication by pulse-width modulation, the waveform of the AC signal (the voltage V (L I ) between the both ends of the power transmission coil L I in this example) is different (asymmetric) between positive and negative and includes a so-called even-ordered harmonic component (including double wave) as shown with the dashed line in part (D) of FIG. 6, for example. Here, when this AC signal is demodulated in the secondary-side devices (envelope detection), the noise of the even-ordered harmonic component deforms the communication waveform. Therefore, the C/N ratio (carrier to noise ratio) is deteriorated. Accordingly, the communication quality may be deteriorated.

[0087] On the other hand, in the communication by amplitude modulation, the waveform of the AC signal (the voltage V (L I ) between the both ends of the power transmission coil L I ) is matched (symmetric) between positive and negative and includes a so-called odd-ordered harmonic component as shown with the dashed line in part (D) of FIG. 12, for example. Therefore, the C/N ratio is improved when this AC signal is demodulated in the secondary-side devices (envelope detection). Accordingly, the communication quality is improved.

[0088] As described above, in the present embodiment, the power limiting operation of the power limiting and modulation circuit 1 12A is controlled in the communication period Tc, and thereby communication by amplitude modulation is performed. Therefore, the communication quality in the communication period Tc is improved while obtaining the effects in the first embodiment. Also, the power limiting and modulation circuit 1 12A performs both of the power limiting operation and modulation operation (amplitude modulation operation) (has the both function). Therefore, the cost, the number of mounted components, and the size of the apparatus are reduced.

[Modification Example]

[0089] The technology of the present disclosure has been described above with reference to the embodiments. However, the present technology is not limited to the above-described embodiments and various modifications may be made.

[0090] For example, various coils (the power transmission coil and the power reception coil) are used in the above-described embodiments. The coils can have various configurations (shapes). Specifically, the coil may have a spiral shape, a loop shape, a bar shape using a magnetic body, an a-like spiral shape in which a spiral coil is folded in two layers, a spiral shape with more layers, or a helical shape in which the coil is spirally wound in a thickness direction, for example. Moreover, the coil is not limited to a spirally-wound coil made of a wire material having electric conductivity, and may be a pattern coil having electric conductivity made of a printed board, a flexible printed board, and/or the like.

[0091 ] Also, an electronic device is used as an example of the target device to be fed in the above-described embodiments. However, this is not limitative and the target device to be fed may be those other than an electronic device (for example, a vehicle such as an electric car).

[0092] Moreover, the feed apparatus and the electronic devices are described with specific example of each component in the above-described embodiments. However, all of the components are not necessarily provided and other components may be additionally provided. For example, the feed apparatus or the electronic device may include functions such as a communication function, any control functions, a display function, a function of certificating a secondary-side device, a function of determining that a secondary-side device is present on a primary-side device, and a function of detecting incorporation of dissimilar metals.

[0093] Moreover, an example in which a plurality of (two) electronic devices are provided in the feed system is mainly described in the embodiments. However, this is not limitative, and only one electronic device may be provided in the feed system.

[0094] Moreover, a charging tray for small electronic devices (CE devices) such as mobile phones is described as an example of the feed apparatus in the embodiments. However, the feed apparatus is not limited to such a home charging tray and is applicable to a charger for various electronic devices. Also, the feed apparatus is not limited to a tray and may be a stand for electronic devices such as a so-called cradle, for example.

[Example of Feed System Performing Noncontact Electric Power Transmission Using Electric Field]

[0095] Moreover, a feed system is described as an example in the embodiments in which noncontact electric power transmission (feeding) using a magnetic field is performed from the feed apparatus as a primary-side device to electronic devices as secondary-side devices. However, this is not limitative. Specifically, the embodiments and the modifications of the present disclosure are applicable to a feed system performing noncontact electric power transmission using an electric field (electric-field coupling) from a feed apparatus as a primary-side device to an electronic device as a secondary-side device, in which an effect similar to that of the above-described embodiments is obtainable.

[0096] In particular, for example, a feed system shown in FIG. 13 includes one feed apparatus 81 (primary-side device) and one electronic device 82 (secondary-side device). The feed apparatus 81 mainly includes a power transmission section 810 having a power transmission electrode El (primary-side electrode), an AC signal source 81 1 (oscillator), and a grounded electrode Egl . The electronic device 82 mainly includes a power reception section 820 including a power reception electrode E2 (secondary-side electrode), a rectifier circuit 821 , a load 822, and a grounded electrode Eg2. Thus, this feed system includes two pairs of electrodes, that is, the pair of the power transmission electrode El and the power reception electrode E2 and the pair of the grounded electrodes Egl and Eg2. In other words, the feed apparatus 81 (primary-side device) and the electronic device 82 (secondary-side device) each includes an antenna configured of a pair of asymmetric electrodes like a monopole antenna.

[0097] In the feed system having such a configuration, the above-described antennas which are not in contact couple with each other (electric-field couple with each other along the vertical direction of the electrode) when the power transmission electrode El and the power reception electrode E2 are opposed to each other. Then, an induced electric field is generated therebetween, and thereby, electric power transmission using an electric field is performed (see electric power P8 in FIG. 13). In particular, the generated electric field (induced electric filed Ei) propagates from the power transmission electrode E l toward the power reception electrode E2, while the generated induced electric field Ei propagates from the grounded electrode Eg2 toward the grounded electrode Eg l as schematically shown in FIG. 14, for example. Thus, a loop path of the thus-generated induced electric field Ei is formed between the primary-side device and the secondary-side device. In such a noncontact electric power supply system using an electric field, a similar effect is obtainable by applying a similar method to that described in the embodiments.

[0098] It is possible to achieve at least the following configurations from the above-described exemplary embodiments and the modifications of the disclosure.

[0099] ( 1 ) A feed apparatus including:

a power transmission section that transmits electric power;

a control section that controls the power transmission section; and a stop circuit that prohibits the power transmission section from transmitting electric power regardless of a state of the control section when an abnormal state of the feed apparatus is detected.

(2) The feed apparatus of ( 1 ), wherein the power transmission section transmits the electric power by emitting at least one of a magnetic field and an electric field.

(3) The feed apparatus of any one of ( 1 ) to (2), wherein the power transmission section includes an alternating current (AC) signal generating circuit that generates an AC signal for transmitting the electric power.

(4) The feed apparatus of any one of ( 1 ) to (3), further including: an interface that is connected to an external power source and that receives power from the external power source.

(5) The feed apparatus of (4), wherein the stop circuit is disposed between the interface and the power transmission section.

(6) The feed apparatus of (5), wherein the stop circuit prohibits the power transmission section from transmitting electric power by blocking the power received from the external power source.

(7) The feed apparatus of (4), further including:

a current detection circuit that detects an input current

corresponding to the power received from the external power source.

(8) The feed apparatus of claim 7, wherein the current detection circuit outputs a voltage corresponding to the input current to the stop circuit.

(9) The feed apparatus of claim 8, wherein the stop circuit prohibits the power transmission section from transmitting electric power based on the voltage output by the current detection circuit.

(10) The feed apparatus of (4), wherein the control section is disposed between the interface and the stop circuit.

( 1 1 ) The feed apparatus of any one of ( 1 ) to ( 10), further including:

a data transmission control section that controls transmission of data to a device receiving the electric power transmitted from the power transmission section.

( 12) The feed apparatus of ( 1 1 ), wherein the data transmission section controls transmission of data to the device via the power transmission section.

(13) The feed apparatus of any one of ( 1 ) to ( 12), wherein the power transmission section includes a power transmission coil that transmits the electric power via a magnetic field.

( 14) The feed apparatus of ( 13), wherein the power transmission section further includes first and second capacitors that form a resonant circuit with the power transmission coil.

( 15) The feed apparatus of (7), wherein the current detection circuit includes a resistor and a first amplifier.

( 16) The feed apparatus of ( 15), wherein the resistor is disposed between first and second inputs of the first amplifier.

( 17) The feed apparatus of ( 16), further including:

a power limiting circuit including a second amplifier and an output of the first amplifier is output to a first input of the second amplifier.

( 18) The feed apparatus of ( 17), wherein the power limiting circuit includes a first transistor having a source connected to the second input of the first amplifier.

( 19) The feed apparatus of ( 18), wherein a drain of the first transistor is connected to the power transmission section.

(20) The feed apparatus of ( 19), wherein a gate of the first transistor is connected to an output of the second amplifier.

(21) The feed apparatus of (20), wherein the stop circuit includes a third amplifier and a first input of the third amplifier is connected to the input of the first amplifier and a second input of the third amplifier is connected to the drain of the first transistor.

(22) The feed apparatus of (21 ), wherein the power limiting circuit includes a fourth amplifier and a negative input of the fourth amplifier is connected to an output of the third amplifier and an output of the fourth amplifier is connected to a negative input of the second amplifier.

(23) The feed apparatus of (22), wherein a positive input of the fourth amplifier is connected to a power source.

(24) The feed apparatus of (23), wherein an output terminal of the fourth amplifier is connected to a gate of a second transistor.

(25) The feed apparatus of (24), wherein a source of the second transistor is grounded and a drain of the second transistor is connected to a power source and a negative input of the second amplifier.

(26) The feed apparatus of ( 17), further including:

a data transmission control section that controls transmission of data to a device receiving the electric power transmitted from the power transmission section, wherein an output of the data transmission control section is provided to a first input to an OR circuit included in the power limiting circuit.

(27) The feed apparatus of (26), wherein an output of the second amplifier is output to a second input of the OR circuit included in the power limiting circuit.

(28) The feed apparatus of (27), wherein the power limiting circuit includes a first transistor, wherein a source of the first amplifier is connected to the second input of the first amplifier, a drain of the first transistor is connected to the power transmission section, and a gate of the first transistor is connected to an output of the OR circuit.

(29) A feed apparatus including:

a power transmission section performing electric power transmission using one of a magnetic field and an electric field;

a control section including a power transmission control section that performs control of the electric power transmission; and

an operation stop section forcefully stopping the electric power transmission without depending on the control of the electric power transmission by the power transmission control section when an abnormal state of the feed apparatus is detected.

(30) The feed apparatus according to (29), wherein the operation stop section disables a control signal provided for the electric power transmission to forcefully stop the electric power transmission.

(3 1 ) The feed apparatus according to (30), wherein the operation stop section includes a switch section switching the control signal between an enabled state and a disabled state depending on whether or not the abnormal state is detected.

(32) The feed apparatus according to any one of (29) to (3 1 ), further including a power limiting section provided on an electric power supply line that extends from an external power source to the power transmission section.

(33) The feed apparatus according to (32), wherein

the operation stop section includes a voltage detection section detecting a voltage between input and output of the power limiting section, and

the operation stop section forcefully stops the electric power transmission according to a magnitude of the detected voltage detected by the voltage detection section. (34/6) The feed apparatus according to (33), wherein the operation stop section forcefully stops the electric power transmission when the detected voltage is higher than a first threshold value.

(35) The feed apparatus according to (34), wherein the power limiting section forcefully blocks electric power supply to the power transmission section when the detected voltage is higher than a second threshold value that is larger than the first threshold value.

(36) The feed apparatus according to (35), wherein

the power limiting section includes an error amplifier controlling power limiting operation according to a potential difference between a reference voltage and a voltage corresponding to a current inputted from the external power source, and

the power limiting section controls a magnitude of the reference voltage to forcefully block the electric power supply to the power transmission section when the detected voltage is higher than the second threshold value.

(37) The feed apparatus according to (36), wherein

the power limiting section includes a transistor on the electric power supply line, and

the power limiting section controls the magnitude of the reference voltage to turn off the transistor, and thereby forcefully blocks the electric power supply to the power transmission section.

(38) The feed apparatus according to any one of (35) to (37), wherein the first threshold value defines whether or not the feed apparatus is in an overload state in normal operation, and the second threshold value defines whether or not the power transmission section is in one of a failure state and a destruction state.

(39) The feed apparatus according to any one of (34) to (38), wherein the operation stop section is inoperable when the detected voltage is higher than the second threshold value.

(40) The feed apparatus according to any one of (32) to (39), wherein the control section is provided further upstream of the electric power supply line than the power limiting section.

(41 ) The feed apparatus according to any one of (32) to (40), wherein the power transmission control section time-divisionally sets a feed period in which the electric power transmission is performed with respect to a target device to be fed and a communication period in which predetermined communication is performed between the feed apparatus and the target device to be fed, and

the power transmission control section controls power limiting operation of the power limiting section in the communication period to allow communication utilizing amplitude modulation.

(42) The feed apparatus according to (41 ), wherein the power limiting section performs the electric power limiting operation in the feed period and performs amplitude modulation operation in the communication period.

(43) The feed apparatus according to any one of (29) to (42), wherein

the power transmission control section time-divisionally sets a feed period in which the electric power transmission is performed with respect to a target device to be fed and a communication period in which predetermined communication is performed between the feed apparatus and the target device to be fed, and

the operation stop section forcefully stops the communication when the abnormal state is detected in the communication period.

(44) The feed apparatus according to any one of (29) to (43), further including an alternating-current signal generation section generating an alternating-current signal provided for the electric power transmission, wherein

the power transmission control section controls operation of the alternating-current signal generation section to control the electric power transmission.

(45) The feed apparatus according to (44), wherein

the alternating-current signal generation section includes a switching amplifier having a switching device, and

the power transmission control section uses a control signal provided for the electric power transmission to control the switching device to be ON and OFF.

(46) The feed apparatus according to (45), wherein

the power transmission control section controls a duty ratio of the control signal in the communication period to perform communication utilizing pulse-width modulation. (47) The feed apparatus according to any one of (29) to (46), wherein the power transmission section performs the electric power transmission utilizing resonance operation.

(48) A feed system including:

one or a plurality of electronic devices; and

a feed apparatus performing electric power transmission with respect to the one or the plurality of electronic devices, the feed apparatus including

a power transmission section performing the electric power transmission using one of a magnetic field and an electric field, a control section including a power transmission control section that performs control of the electric power transmission, and

an operation stop section forcefully stopping the electric power transmission without depending on the control of the electric power transmission by the power transmission section when an abnormal state of the feed apparatus is detected.

[0100] The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 201 1 -231 765 filed in the Japan Patent Office on October 21 , 201 1 and Japanese Priority Patent Application JP 2012-092847 filed in the Japan Patent Office on April 16, 2012, the entire content of which is hereby incorporated by reference.

[0101 ] It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

Claims

[Claim 1 ] A feed apparatus comprising:

a power transmission section that transmits electric power;

[Claim 2] The feed apparatus of claim 1 , wherein

the power transmission section transmits the electric power by emitting at least one of a magnetic field and an electric field.

[Claim 3] The feed apparatus of claim 1 , wherein

the power transmission section includes an alternating current (AC) signal generating circuit that generates an AC signal for transmitting the electric power.

[Claim 4] The feed apparatus of claim 1 , further comprising:

an interface that is connected to an external power source and that receives power from the external power source.

[Claim 5] The feed apparatus of claim 4, wherein

the stop circuit is disposed between the interface and the power transmission section.

[Claim 6] The feed apparatus of claim 5, wherein

the stop circuit prohibits the power transmission section from transmitting electric power by blocking the power received from the external power source.

[Claim 7] The feed apparatus of claim 4, further comprising:

a current detection circuit that detects an input current corresponding to the power received from the external power source.

[Claim 8] The feed apparatus of claim 7, wherein

the current detection circuit outputs a voltage corresponding to the input current to the stop circuit.

[Claim 9] The feed apparatus of claim 8, wherein

the stop circuit prohibits the power transmission section from transmitting electric power based on the voltage output by the current detection circuit.

[Claim 10] The feed apparatus of claim 4, wherein

the control section is disposed between the interface and the stop circuit.

[Claim 1 1 ] The feed apparatus of claim 1 , further comprising:

[Claim 12] The feed apparatus of claim 1 1 , wherein

the data transmission section controls transmission of data to the device via the power transmission section.

[Claim 13] The feed apparatus of claim 1 , wherein

the power transmission section includes a power transmission coil that transmits the electric power via a magnetic field.

[Claim 14] The feed apparatus of claim 13 , wherein

the power transmission section further includes first and second capacitors that form a resonant circuit with the power transmission coil.

[Claim 15] The feed apparatus of claim 7, wherein

the current detection circuit includes a resistor and a first amplifier.

[Claim 16] The feed apparatus of claim 15, wherein

the resistor is disposed between first and second inputs of the first amplifier.

[Claim 17] The feed apparatus of claim 16, further comprising:

[Claim 18] The feed apparatus of claim 17, wherein

the power limiting circuit includes a first transistor having a source connected to the second input of the first amplifier.

[Claim 19] The feed apparatus of claim 18, wherein

a drain of the first transistor is connected to the power transmission section.

[Claim 20] The feed apparatus of claim 19, wherein

a gate of the first transistor is connected to an output of the second amplifier.

[Claim 21] The feed apparatus of claim 20, wherein

the stop circuit includes a third amplifier and a first input of the third amplifier is connected to the input of the first amplifier and a second input of the third amplifier is connected to the drain of the first transistor.

[Claim 22] The feed apparatus of claim 21 , wherein

the power limiting circuit includes a fourth amplifier and a negative input of the fourth amplifier is connected to an output of the third amplifier and an output of the fourth amplifier is connected to a negative input of the second amplifier.

[Claim 23] The feed apparatus of claim 22, wherein a positive input of the fourth amplifier is connected to a power source.

[Claim 24] The feed apparatus of claim 23 , wherein

an output terminal of the fourth amplifier is connected to a gate of a second transistor.

[Claim 25] The feed apparatus of claim 24, wherein

a source of the second transistor is grounded and a drain of the second transistor is connected to a power source and a negative input of the second amplifier.

[Claim 26] The feed apparatus of claim 17, further comprising:

a data transmission control section that controls transmission of data to a device receiving the electric power transmitted from the power transmission section, wherein

an output of the data transmission control section is provided to a first input to an OR circuit included in the power limiting circuit.

[Claim 27] The feed apparatus of claim 26, wherein

an output of the second amplifier is output to a second input of the OR circuit included in the power limiting circuit.

[Claim 28] The feed apparatus of claim 27, wherein

the power limiting circuit includes a first transistor, and a source of the first amplifier is connected to the second input of the first amplifier, a drain of the first transistor is connected to the power transmission section, and a gate of the first transistor is connected to an output of the OR circuit.