Patent Description:
As a technique for transmitting power by radio, a technique is well known which utilizes electromagnetic induction. In the power transmission which utilizes electromagnetic induction, current is supplied to one of two coils positioned closely to each other such that electromagnetic force is generated in the other coil by intermediation of magnetic fluxes generated from the one coil.

However, according to the power transmission which utilizes the electromagnetic induction, the two coils must be positioned closely to each other. Therefore, the power transmission has a problem that the distance over which the power can be transmitted is restricted. Further, if the axes of the coils upon electromagnetic induction coupling are brought out of alignment with each other, then the transmission efficiency is degraded. Therefore, the alignment upon coupling is significant.

In the meantime, a method wherein resonance of an electromagnetic field is utilized to transmit power has been proposed recently. According to the resonance type radio power transmission, power can be transmitted over such a distance as three to four meters and besides high power can be transmitted. Therefore, resonance type radio power transmission has an advantage that also a system which does not have a secondary cell, that is, a rechargeable battery, on the reception side can be constructed readily.

Further, the resonance type radio power transmission has little influence on any other electronic apparatus because energy is not transmitted if it has no resonating mechanism. Further, there is an advantage also in that, even if the alignment upon coupling is not very good, the transmission efficiency does not drop very much.

A power transmission system which uses a resonance phenomenon in a magnetic field is disclosed, for example, in <CIT> (hereinafter referred to as Patent Document <NUM>).

An example of a configuration of the power transmission system which uses a magnetic field resonance phenomenon is shown in <FIG> particularly shows an example of a system configuration where a power transmitting apparatus <NUM> of a supplying source of power and a power receiving apparatus <NUM> of a supplying destination or receiving side of power are provided in a one-by-one corresponding relationship to each other.

Referring to <FIG>, the power transmitting apparatus <NUM> includes a resonance element <NUM>, an excitation element <NUM> and a frequency signal generation section <NUM>.

The resonance element <NUM> is formed, for example, from an air-core coil in the form of a loop coil. The excitation element <NUM> is formed, for example, from an air-core coil, which is connected at the opposite ends thereof to two output terminals of the frequency signal generation section <NUM>. The resonance element <NUM> and the excitation element <NUM> are placed in a relationship wherein they are coupled strongly with each other by electromagnetic induction.

The air-core coil which forms the resonance element <NUM> has not only inductance but also coil internal capacitance and has a self resonance frequency which depends upon the inductance and the capacitance.

The frequency signal generation section <NUM> generates a frequency signal of a frequency equal to the self resonance frequency of the resonance element <NUM>. The frequency signal generation section <NUM> may be formed from a Colpitts type oscillation circuit, a Hartley type oscillation circuit or the like.

Though not shown, the power transmitting apparatus <NUM> receives supply of power from an ac power supply so that a frequency signal is generated from the frequency signal generation section <NUM>.

Meanwhile, the power receiving apparatus <NUM> include a resonance element <NUM>, an excitation element <NUM>, a rectification circuit <NUM> and a load <NUM>.

The resonance element <NUM> is formed, for example, from an air-core coil in the form of a loop coil similarly to the resonance element <NUM>. The excitation element <NUM> is formed, for example, from an air-core coil, which is connected at the opposite ends thereof to two input terminals of the rectification circuit <NUM>. The resonance element <NUM> and the excitation element <NUM> are configured so as to have a relationship wherein they are coupled strongly to each other by electromagnetic induction.

The air-core coil which forms the resonance element <NUM> has not only inductance but also coil internal capacitance and has a self resonance frequency which depends upon the inductance and the capacitance similarly as in the resonance element <NUM>.

The self resonance frequencies of the resonance element <NUM> and the resonance element <NUM> are equal to each other and a frequency fo.

In such a system configuration as described above, the frequency signal generation section <NUM> in the power transmitting apparatus <NUM> supplies a frequency signal equal to the self resonance frequency fo of the resonance elements <NUM> and <NUM> to the excitation element <NUM>.

Accordingly, ac current of the frequency fo flows to the air-core coil of the excitation element <NUM>, and induction current of the same frequency fo is induced in the resonance element <NUM> formed similarly from an air-core coil by electromagnetic induction.

In the circuit configuration of <FIG>, the self resonance frequency of the air-core coil which forms the resonance element <NUM> of the power receiving apparatus <NUM> is the frequency fo and coincides with the self resonance frequency of the resonance element <NUM> of the power transmitting apparatus <NUM>. Accordingly, the resonance element <NUM> of the power transmitting apparatus <NUM> and the resonance element <NUM> of the power receiving apparatus <NUM> have a magnetic field resonance relationship and exhibit a maximum coupling amount and minimum loss at the frequency fo.

Since the resonance element <NUM> of the power transmitting apparatus <NUM> and the resonance element <NUM> of the power receiving apparatus <NUM> in the present circuit configuration have a magnetic field resonance relationship as described above, ac current is supplied in a contactless fashion from the resonance element <NUM> to the resonance element <NUM> at the resonance frequency fo.

In the power receiving apparatus <NUM>, induction current is induced in the excitation element <NUM> by electromagnetic induction by ac current appearing in the resonance element <NUM>. The induction current induced in the excitation element <NUM> is rectified into dc current by the rectification circuit <NUM> and supplied as power supply current to the load <NUM>.

In this manner, a magnetic field resonance phenomenon is utilized to transmit power by radio from the power transmitting apparatus <NUM> to the power receiving apparatus <NUM>.

A relationship between the frequency of the frequency signal from the frequency signal generation section <NUM> in the power transmission system of the configuration shown in <FIG> and the coupling amount in magnetic field resonance is illustrated in <FIG>. As can be seen apparently from <FIG>, the power transmission system of the configuration of <FIG> indicates frequency selectivity wherein a maximum coupling amount is obtained at the resonance frequency fo.

<FIG> illustrates a relationship between the distance D between the resonance element <NUM> of the power transmitting apparatus <NUM> and the resonance element <NUM> of the power receiving apparatus <NUM> and the coupling amount in magnetic field resonance. From <FIG>, it can be recognized that, although the coupling amount increases as the distance decreases, where the distance is very short, the coupling amount is rather low. Thus, it can be recognized that a certain distance exists at which the coupling amount is maximum at a certain resonance frequency.

<FIG> illustrates a relationship between the resonance frequency and the distance between resonance elements at which a maximum coupling amount is obtained. From <FIG>, it can be seen that a maximum coupling amount is obtained if, where the resonance frequency is low, the distance between the resonance elements is increased, but where the resonance frequency is high, the distance between the resonance elements is decreased.

As described above, in the power transmission system of the resonance type, even if the distance between the power transmitting apparatus and the power receiving apparatus is comparatively great or even if the coupling axes are somewhat out of alignment with each other, power transmission can be carried out.

Therefore, it is possible to transmit power from a single power transmitting apparatus <NUM> of a power supplying source to a plurality of power supplying destinations as seen in <FIG>, which illustrates that power is transmitted to two power receiving apparatus 20A and 20B as power supplying designations. It is to be noted that the power receiving apparatus 20A and 20B have a configuration quite same as that of the power receiving apparatus <NUM> described hereinabove and include like components which are indicated by like reference symbols with suffixes A and B added thereto, respectively.

It is assumed here that the self resonance frequency of the resonance element <NUM> of the power transmitting apparatus <NUM> and the self resonance frequency of resonance elements 21A and 21B of the two power receiving apparatus 20A and 20B are equal to each other.

Since the coupling amount between a power supplying source and a power supplying destination increases as the distance between the resonance elements decreases, in the example shown in <FIG>, the power receiving apparatus 20B has a coupling amount greater than that of the power receiving apparatus 20A to the power transmitting apparatus <NUM>.

Since power to be supplied from the power supplying source to the power supplying destination increases as the distance between the resonance elements increases, the power supplied from the power transmitting apparatus <NUM> is relatively higher to the power receiving apparatus 20B than to the power receiving apparatus 20A.

Incidentally, apart from a case wherein it is necessary to render operative both of the power receiving apparatus 20A and the power receiving apparatus 20B and supply of dc current to loads is demanded, a case wherein there is no necessity to render one of the two apparatus operative matters.

In particular, each of the power receiving apparatus described above is configured such that it normally receives power transmitted thereto by radio. Therefore, even where any of the power receiving apparatus does not demand reception of power, if the power receiving apparatus is positioned such that it can receive supply of power from the power transmitting apparatus <NUM>, then power is supplied to the power receiving apparatus uselessly and rectified by the rectification circuit <NUM> and then consumed.

Thus, if a plurality of power receiving apparatus have a magnetic field resonance relationship with the power transmitting apparatus <NUM> as seen in <FIG>, then electric energy from the power transmitting apparatus <NUM> is distributed and transmitted to the plural power receiving apparatus. Therefore, the power received by each of the power receiving apparatus decreases in response to the number of such power receiving apparatus, resulting in a problem that the power receiving apparatus which demands reception of power cannot receive sufficient power from the power transmitting apparatus.

Particularly if the power receiving apparatus 20B positioned nearer to the power transmitting apparatus <NUM> in <FIG> need not operate and does not demand reception of power, the power to be supplied to the power receiving apparatus 20A which demands reception of power decreases in a distribution relationship, which is not efficient.

Therefore, it is desirable to provide an apparatus and a method which can eliminate such a problem as described above.

<CIT> discloses another wireless resonant power receiver and shows the features in the preambles of claims <NUM> and <NUM>.

In order to solve the above problem, a power receiving apparatus according to claim <NUM> and an alternative power receiving apparatus according to claim <NUM> are provided.

with the power receiving apparatus according to the invention, power transmitted thereto through the coupling through a resonance relationship from the power transmitting apparatus can be repeated so as to be transmitted to a different power receiving apparatus without consuming the power wastefully.

In the following, power receiving apparatus and power transmission systems including the power receiving apparatus are described with reference to the accompanying drawings. Power Receiving Apparatus According to the First Embodiment not covered by the claims.

<FIG> shows an example of a configuration of a power receiving apparatus according to a first embodiment. Those parts shown in <FIG> which are identical to those parts of the power receiving apparatus in the power transmission system shown in <FIG> are denoted by identical reference symbols.

Referring to <FIG>, the power receiving apparatus <NUM> according to the first embodiment includes a resonance element <NUM>, an excitation element <NUM>, a rectification circuit <NUM>, a load <NUM>, and a power supply controlling switch <NUM> provided on a current path between the excitation element <NUM> and the rectification circuit <NUM>.

The resonance element <NUM> is formed, for example, from an air-core coil in the form of a loop coil similarly to the resonance element <NUM>.

The excitation element <NUM> is formed, for example, from an air-core coil, which is connected at a terminal thereof to one of input terminals of the rectification circuit <NUM>. The excitation element <NUM> is connected at the other terminal of the air-core coil thereof to the other one of the input terminals of the rectification circuit <NUM> through the power supply controlling switch <NUM>.

The resonance element <NUM> and the excitation element <NUM> are configured so as to have a relationship in which they are coupled strongly to each other by electromagnetic induction.

The air-core coil of the resonance element <NUM> has not only inductance but also coil internal capacitance and has a frequency fo which depends upon the inductance and the capacitance. As described hereinabove, the frequency fo of the resonance element <NUM> is equal to the self resonance frequency of the resonance element <NUM> of the power transmitting apparatus <NUM>.

The power supply controlling switch <NUM> may be formed from a mechanical switch which is manually operated by a user or a relay switch or a semiconductor switch which switches on and off in response to a predetermined operation by a user.

When the power supply controlling switch <NUM> is in an on or closed state, the resonance element <NUM> in the power receiving apparatus <NUM> is coupled to the resonance element <NUM> of the power transmitting apparatus <NUM> through a magnetic field resonance relationship therebetween, and similar operation to that described above is carried out. In particular, induction current is induced in the excitation element <NUM> by electromagnetic induction by ac current appearing in the resonance element <NUM>. The induction current induced in the excitation element <NUM> is rectified into dc current by the rectification circuit <NUM> and then supplied as power supply current to the load <NUM>.

On the other hand, when the power supply controlling switch <NUM> is in an off or open state, no current flows through the excitation element <NUM>. Accordingly, even if the resonance element <NUM> of the power transmitting apparatus <NUM> and the resonance element <NUM> of the power receiving apparatus <NUM> are coupled to each other through the magnetic field resonance relationship therebetween and ac current flows through the resonance element <NUM>, no induction current flows through the excitation element <NUM>.

In other words, when the power supply controlling switch <NUM> is off, supply of ac current from the resonance element <NUM> to the rectification circuit <NUM> is blocked.

Accordingly, when the power supply controlling switch <NUM> is off, no dc current is supplied to the load <NUM> in the power receiving apparatus <NUM>, and no power is consumed in the power receiving apparatus <NUM>.

However, the resonance element <NUM> of the power receiving apparatus <NUM> in which the power supply controlling switch <NUM> is off in this manner can be coupled to the resonance element of a different power receiving apparatus through a magnetic field resonance relationship. Then, if such a different power receiving apparatus as just mentioned exists, then ac magnetic field energy transmitted to the resonance element <NUM> of the power receiving apparatus <NUM> in which the power supply controlling switch <NUM> is off is sent to the resonance element of the different power receiving apparatus.

In other words, the resonance element <NUM> of the power receiving apparatus <NUM> in which the power supply controlling switch <NUM> is off acts as a repeater which transmits ac magnetic field energy supplied thereto from the power transmitting apparatus <NUM> to the resonance element of the different power receiving apparatus.

The state wherein the resonance element <NUM> acts as a repeater is described more particularly with reference to <FIG> which shows a power transmission system according to an embodiment not covered by the claims.

Referring to <FIG>, in the power transmission system shown, while power is supplied from the power transmitting apparatus <NUM> of a power supplying source to a certain power receiving apparatus 200A, there exists a different power receiving apparatus 200B which can be coupled to the power transmitting apparatus <NUM> through a magnetic field resonance relationship.

In the power transmission system of <FIG>, the power receiving apparatus 200A and 200B have a configuration quite similar to that of the power receiving apparatus <NUM> described hereinabove and includes like components to those of the power receiving apparatus <NUM>. Such like components are denoted by like reference symbols with the suffixes A and B added thereto, respectively.

In the power transmission system of <FIG>, it is shown that the power receiving apparatus 200B which need not receive supply of power is positioned nearer to the power transmitting apparatus <NUM> which serves as a power supplying source than the power receiving apparatus 200A to which power is to be supplied and therefore has a coupling amount to the power transmitting apparatus <NUM> greater than that of the power receiving apparatus 200A.

Further, in the power transmission system of <FIG>, the power receiving apparatus 200A and the power receiving apparatus 200B have such a positional relationship to each other that they are coupled to each other through a magnetic field resonance relationship.

Further, in the power transmission system shown in <FIG>, the power supply controlling switch 25A of the power receiving apparatus 200A is in an on or closed state in order that the power receiving apparatus 200A may receive supply of power from the power transmitting apparatus <NUM> of a power supply source. Meanwhile, since the power receiving apparatus 200B need not receive supply of power from the power transmitting apparatus <NUM>, the power supply controlling switch <NUM> is in an off or open state.

Accordingly, between the power transmitting apparatus <NUM> and the power receiving apparatus 200A, the resonance elements <NUM> and 21A are coupled to each other through a magnetic field resonance relationship, and since the power supply controlling switch 25A is on, induction current flows through the excitation element 22A. The induction current induced in the excitation element 22A is rectified into dc current by the rectification circuit 23A and supplied as power supply current to the load <NUM> not shown in <FIG>.

In the meantime, between the power transmitting apparatus <NUM> and the power receiving apparatus 200B, the resonance elements <NUM> and 21B are coupled to each other through a magnetic field resonance relationship. Consequently, ac magnetic field energy from the power transmitting apparatus <NUM> is transmitted to the resonance element 21B of the power receiving apparatus 200B. However, in the power receiving apparatus 200B, since the power supply controlling switch is in an off or open state, no induction current flows to the excitation element 22B, and no current is supplied to the rectification circuit 23B and no power is consumed.

Here, the power receiving apparatus 200A and the power receiving apparatus 200B have such a positional relationship that they are coupled to each other through a magnetic field resonance relationship. Accordingly, ac magnetic field energy transmitted from the power transmitting apparatus <NUM> to the resonance element 21B of the power receiving apparatus 200B is sent to the resonance element 21A of the power receiving apparatus 200A.

In other words, in the power transmission system of <FIG>, part of the ac magnetic field energy sent out from the power transmitting apparatus <NUM> is sent to the resonance element 21A of the power receiving apparatus 200A through the resonance element 21B of the power receiving apparatus 200B.

In the power transmission system of <FIG>, ac magnetic field energy sent from the power transmitting apparatus <NUM> to the power receiving apparatus 20B is consumed in the power receiving apparatus 20B. However, in the power transmission system of <FIG>, such ac magnetic field energy is not consumed but is sent to the power receiving apparatus 200A through the power receiving apparatus 200B.

In this manner, the power receiving apparatus 200A receives supply of power from the power transmitting apparatus <NUM> through coupling by a direct magnetic field resonance relationship and further receives supply of power through the power receiving apparatus 200B. Accordingly, in the power transmission system of <FIG>, the power receiving apparatus 200A can receive all of the ac magnetic field energy sent out from the power transmitting apparatus <NUM>. Consequently, the power receiving apparatus 200A can receive supply of power efficiently.

It is to be noted that, since the power supply controlling switch 25A in the power receiving apparatus 200A which is to receive supply of power from the power transmitting apparatus <NUM> is in an on state as can be seen from <FIG>, the power receiving apparatus 200A may have the configuration of the power receiving apparatus <NUM> shown in <FIG> which does not include the power supply controlling switch <NUM>. In particular, in the power transmission system of <FIG>, all of the power receiving apparatus may not include the configuration of the power receiving apparatus <NUM> of the present embodiment.

It is to be noted that, while, in the first embodiment described above, the power supply controlling switch <NUM> is a mechanical switch or a relay switch, the power supply controlling switch <NUM> may otherwise have a configuration of a semiconductor switch. In this instance, a controlling section formed, for example, from a microcomputer for receiving an operation input of a user is provided such that it controls the power supply controlling switch <NUM> to switch in response to an operation input of the user indicative of whether or not the power receiving apparatus should be rendered operative. In particular, if the user inputs an instruction operation for rendering the power receiving apparatus operative, then the control section controls the power supply controlling switch to an on state, but if the user inputs another instruction operation for rendering the power receiving apparatus inoperative, then the control section controls power supply controlling switch to an off state. Power Receiving Apparatus of the Second Embodiment not covered by the claims.

In the power receiving apparatus <NUM> of the first embodiment, the power supply controlling switch is controlled to switch only in response to an operation of the user. In contrast, in the power receiving apparatus of the second embodiment, the power supply controlling switch is automatically controlled to switch.

<FIG> shows an example of a configuration of the power receiving apparatus <NUM> of the second embodiment. The power receiving apparatus <NUM> includes several common components to those of the power receiving apparatus <NUM> of the first embodiment, and overlapping description of the common components of the power receiving apparatus <NUM> is omitted herein to avoid redundancy.

Referring to <FIG>, the power receiving apparatus <NUM> shown includes a battery 301B of the rechargeable type and further includes a charging circuit <NUM> for charging the rechargeable battery 301B, a power supply switch <NUM>, a control section <NUM> and an operation section <NUM>.

The power receiving apparatus <NUM> further includes a power supply controlling switch circuit <NUM> in place of the power supply controlling switch <NUM>. The power supply controlling switch circuit <NUM> is formed, for example, from a semiconductor switching element.

In the present second embodiment, the power receiving apparatus <NUM> receives radio power transmitted from the power transmitting apparatus <NUM> and uses the radio power to charge the battery 301B and then supplies power supply current to a load.

The charging circuit <NUM> charges the battery 301B with dc current from the rectification circuit <NUM> when the power supply controlling switch circuit <NUM> is on. In the power receiving apparatus <NUM>, the charging circuit <NUM> has a function of detecting that the battery 301B is charged up and notifying the control section <NUM> of such charge up.

The power supply switch <NUM> is interposed between an output terminal of the rectification circuit <NUM> and the load <NUM> and controlled between on and off in accordance with a switching signal from the control section <NUM>. Also this power supply switch <NUM> is formed, for example, from a semiconductor switching element.

When the power supply controlling switch circuit <NUM> is on and the power supply switch <NUM> is on, the power receiving apparatus <NUM> receives radio power transmitted from the power transmitting apparatus <NUM>, and while the battery 301B is charged by the charging circuit <NUM>, the power receiving apparatus <NUM> supplies power also to the load <NUM>.

The control section <NUM> includes, for example, a microcomputer, and power is normally supplied from the battery 301B to the control section <NUM>.

The operation section <NUM> includes a power supply key and is connected to the control section <NUM>. If the operation section <NUM> receives an operation input information of the power supply key, then it decides whether the operation input information represents an operation to switch on the power supply or another operation to switch off the power supply. Then, the control section <NUM> controls the power supply switch <NUM> to an on state or an off state in response to a result of the decision.

On the other hand, if the control section <NUM> receives a notification from the charging circuit <NUM> that the charging circuit 301B is charged up, then it switches off the power supply controlling switch circuit <NUM>. Accordingly, at this time, the power receiving apparatus <NUM> does not consume ac magnetic field energy sent thereto from the power transmitting apparatus <NUM>, and the resonance element <NUM> acts as a repeater of the ac magnetic field energy as described hereinabove.

If the battery 301B is not charged up, then the control section <NUM> controls the power supply controlling switch circuit <NUM> to an on state, and the power receiving apparatus <NUM> converts ac magnetic field energy sent thereto from the power transmitting apparatus <NUM> into dc current by means of the rectification circuit thereof and then consumes the dc current.

<FIG> illustrates processing operation by the control section <NUM> for controlling the power supply controlling switch circuit <NUM> between on and off.

The control section <NUM> first checks a notification of charge up from the charging circuit <NUM> at step S101. Then at step S102, the control section <NUM> decides whether or not the battery 301B is in a charged up state at step S102. If it is decided that the battery 301B is not in a charged up state, then the control section <NUM> controls the power supply controlling switch circuit <NUM> to be kept on at step S103. Thereafter, the processing returns to step S101.

On the other hand, if it is decided at step S102 that the battery 301B is in a charged up state, then the control section <NUM> controls the power supply controlling switch circuit <NUM> to change over to an off state at step S104. Thereafter, the processing returns to step S101.

In the power receiving apparatus <NUM> of the present second embodiment, when the battery 301B is in a charged up state, it need not receive supply of power from the power transmitting apparatus <NUM>, and consequently, the power supply controlling switch circuit <NUM> is switched off automatically.

Accordingly, with the power receiving apparatus <NUM> of the present second embodiment, different from the power receiving apparatus <NUM> of the first embodiment, even if the user does not manually carry out a switching operation of the power supply controlling switch, it is possible to prevent unnecessary consumption of ac magnetic field energy and achieve efficient radio power transmission. Further, where all of a plurality of power receiving apparatus which receive ac magnetic field energy from the power transmitting apparatus <NUM> have the configuration of the power receiving apparatus <NUM> of the second embodiment, the time before all of the plural power receiving apparatus are placed into a fully charged stage can be reduced.

In particular, where all of the batteries of the plural power receiving apparatus <NUM> are not in a charged up state, ac magnetic field energy from the power transmitting apparatus <NUM> is distributed to the plural power receiving apparatus <NUM> to carry out charging. However, in a power reception state wherein the batteries are in a charged up state, the power supply controlling switch circuit <NUM> is off and acts as a repeater for the ac magnetic field energy. Therefore, the ac magnetic field energy to be transmitted to a power receiving apparatus which has a battery which is not in a charged up state as yet increases.

Consequently, since ac magnetic field energy from the power transmitting apparatus <NUM> can be transmitted efficiently until all of a plurality of power receiving apparatus are placed into a charged up state, the time before all of the plural power receiving apparatus are placed into a charged up state can be reduced.

In the third embodiment, a charging system or charging apparatus for charging the power receiving apparatus <NUM> of the second embodiment is described. <FIG> show appearance of the charging system as a power transmission system of the present third embodiment.

In the charging system of the present embodiment, a power transmitting apparatus <NUM> is provided in the inside of a box-shaped charging cradle, and a plurality of power receiving apparatus <NUM> are placed on the charging cradle.

<FIG> shows a top plan of a charging cradle <NUM> which forms the charging system of the present embodiment, and <FIG> shows a cross section taken along line X-X.

The charging cradle <NUM> is formed in a flattened box shape made of a non-magnetic material. In the inside of the charging cradle <NUM>, the power transmitting apparatus <NUM> serving as a power supplying source is disposed at a central position of the charging cradle <NUM>. A broken line shown in <FIG> indicates an air-core coil which forms the resonance element <NUM> of the power transmitting apparatus <NUM>.

On a receiving face 400A of the charging cradle <NUM> which receives a plurality of power receiving apparatus <NUM>, a plurality of marks MK each indicative of a position at which a power receiving apparatus <NUM> is to be placed, in the example of <FIG>, a plurality of circular marks, are provided, for example, by printing.

As seen in <FIG>, the marks MK are provided such that the centers thereof are positioned on a circle at an equal distance from the position of the center of the charging cradle <NUM> at which the power transmitting apparatus <NUM> is disposed. This is because it is intended to make all of the coupling amounts through a magnetic field resonance relationship between the plural power receiving apparatus <NUM> placed on the charging cradle <NUM> and the power transmitting apparatus <NUM> equal to each other.

In particular, in the present charging cradle <NUM>, if a power receiving apparatus <NUM> is placed at one of the plural marks MK, then on whichever one of the plural marks MK the power receiving apparatus <NUM> is placed, the power receiving apparatus <NUM> can receive ac magnetic field energy of an equal magnitude from the power transmitting apparatus <NUM>.

Further, if a plurality of power receiving apparatus <NUM> are placed on the charging cradle <NUM>, then ac magnetic field energy is first distributed and supplied equally to all of the power receiving apparatus <NUM> from the power transmitting apparatus <NUM>.

Then, if the battery 301B of any of the power receiving apparatus <NUM> is placed into a charged up state, then the resonance element of the power receiving apparatus <NUM> now acts as a repeater of the ac magnetic field energy as described hereinabove. Accordingly, to any other power receiving apparatus <NUM> whose battery 301B is not in a charged up state, ac magnetic field energy is additionally transmitted through the repeater in addition to the ac magnetic field energy originally supplied thereto from the power transmitting apparatus <NUM>.

In particular, the power receiving apparatus <NUM> whose battery 301B is fully charged does not consume the ac magnetic field energy being received till then but repeats the ac magnetic field energy to the other power receiving apparatus <NUM> whose battery 301B is not in a charged up state. Accordingly, the ac magnetic field energy to be applied to the other power receiving apparatus <NUM> whose battery 301B is not in a fully charged state increases from that till then.

Therefore, with the charging system of the present embodiment, it can charge a plurality of power receiving apparatus efficiently.

Also in the present fourth embodiment, the present invention is applied to a charging system as an example of a power transmission system similarly to the third embodiment.

Although the charging system of the present fourth embodiment has a basic configuration which includes a charging cradle similar to that in the third embodiment, it is different from the third configuration in that each of a power transmitting apparatus of a supplying source of charging power and a power receiving apparatus for receiving the charging power include a communication section.

In the present fourth embodiment, each power receiving apparatus sends a residual charging amount of a battery to the power transmitting apparatus.

The power transmitting apparatus produces a charging schedule plan in response to the received residual charging amounts of the plural power receiving apparatus and sends a controlling instruction for placing the power supply controlling switch circuit into an on state or an off state to each of the plural power receiving apparatus in accordance with the charging schedule plan.

Each of the power receiving apparatus executes an operation to place the power supply controlling switch circuit thereof into an on or off state in response to the controlling instruction from the power transmitting apparatus.

Consequently, in the charging system of the present fourth embodiment, the plural power receiving apparatus can be charged up rapidly in appropriate charging time.

<FIG> shows an example of a configuration of the power transmitting apparatus <NUM> and the power receiving apparatus <NUM> which form the charging system of the present fourth embodiment. Those parts shown in <FIG> which are identical to those shown in abovementioned embodiments are denoted by identical reference symbols.

Referring to <FIG>, the power transmitting apparatus <NUM> includes a control section <NUM> and a communication section <NUM> in addition to a resonance element <NUM>, an excitation element <NUM> and a frequency signal generation section <NUM>.

In <FIG>, the excitation element <NUM> is provided between the resonance element <NUM> and the rectification circuit <NUM> so that impedance conversion is carried out to carry out effective ac power transmission, but the excitation element is omitted in the first invention according to claim <NUM>.

In particular, both terminals of the resonance element <NUM> are connected to one and the other one of the input terminal of the rectification circuit <NUM>, and the power supply controlling switch is provided between one of both terminals of the resonance element <NUM> and one of the input terminals of the rectification circuit <NUM>.

Further, according to the first invention, the power supply controlling switch is changed over to a state wherein ac current from the resonance element <NUM> is supplied to the rectification circuit <NUM> when supply of the power from the power transmitting apparatus is received by the power receiving apparatus. Further, when supply of the ac current from the resonance element <NUM> to the rectification circuit <NUM> is to be blocked, the power supply controlling switch cuts off the connection between one of the terminals of the resonance element <NUM> and one of the input terminals of the rectification circuit <NUM> and changes over so that both terminals of the resonance element <NUM> are connected to each other to form a loop coil. Consequently, the resonance element <NUM> is placed into a state wherein it can carry out magnetic field resonance coupling with a different resonance element.

The control section <NUM> is configured including, for example, a microcomputer and analyzes information received from the power receiving apparatus <NUM> through the communication section <NUM> or produces and transmits transmission information to the power receiving apparatus <NUM> through the communication section <NUM>.

The communication section <NUM> is formed, for example, from a Bluetooth unit or a ZigBee unit.

Further, similarly to the power receiving apparatus <NUM> of the second embodiment, the power receiving apparatus <NUM> includes a power supply controlling switch circuit <NUM>, a charging circuit <NUM> for charging a battery 301B, a power supply switch <NUM>, a control section <NUM> and an operation section <NUM> and additionally includes a communication section <NUM>.

The charging circuit <NUM> notifies the control section <NUM> of a residual charging amount or battery remaining amount of the battery 301B and of a charged up state, a little different from that in the second embodiment.

In the present fourth embodiment, the control section <NUM> transmits the residual charging amount or battery remaining amount of the battery 301B received from the charging circuit <NUM> to the power transmitting apparatus <NUM> through the communication section <NUM> together with identification information of the power receiving apparatus <NUM> itself.

In the present fourth embodiment, it is possible for a user to input additional information such as whether or not charging is demanded urgently or charging may be carried out slowly through the operation section <NUM>.

Upon such notification of the residual charging amount, the control section <NUM> additionally transmits the additional information to the power transmitting apparatus <NUM>.

Further, when the control section <NUM> receives a notification representing that the battery 301B is charged up from the charging circuit <NUM>, it switches off the power supply controlling switch circuit <NUM> and transmits a notification that the battery 301B is charged up to the power transmitting apparatus <NUM> through the communication section <NUM> together with the identification information of the power receiving apparatus <NUM> itself.

When the control section <NUM> of the power transmitting apparatus <NUM> receives a notification of a residual charging amount or a notification of full charge from the power receiving apparatus <NUM>, then it produces or modifies a charging schedule plan. Then, the control section <NUM> produces on/off controlling instructions for the power supply controlling switch circuit to each of the plural power receiving apparatus in accordance with the charging schedule plan and then transmits the controlling instructions through the communication section <NUM>.

<FIG> is a flow chart illustrating processing operation executed by the control section <NUM> of the power transmitting apparatus <NUM>.

The processing operation in <FIG> is carried out when plural power receiving apparatus <NUM> as power supplying destinations are placed on the charging cradle and the power supply for the charging system is switched on to supply power to the power transmitting apparatus <NUM>.

The control section <NUM> receives a residual charging amount and additional information to the residual charging amount from the plural power receiving apparatus <NUM> which are power supplying destinations at step S111 at the communication section <NUM>.

Then, the control section <NUM> produces a charging schedule plan for the plural power receiving apparatus <NUM> from the received residual charging amounts and additional information at step S112.

In particular, the control section <NUM> recognizes identification information of each power receiving apparatus from the received information and then checks the residual charging amount, emergency for charging and so forth of each power receiving apparatus. Then, the control section <NUM> produces an optimum charging schedule plan based on the received information and determines, in accordance with the charging schedule plan, which power supply controlling switching circuit <NUM> is to be switched on or off in the power receiving apparatus.

Then, the control section <NUM> transmits the determined on/off controlling information for the power supply controlling switching circuits <NUM> of the power receiving apparatus <NUM> to the respective power receiving apparatus <NUM> in a matched relationship with the identification information through the communication section <NUM> at step S113.

Then, the control section <NUM> monitors reception of charge up information from any power receiving apparatus <NUM> at step S114 and decides, if it is decided that such charge up information is received, whether or not all of the power receiving apparatus <NUM> are charged up at step S115.

If it is decided at step S115 that not all of the power receiving apparatus <NUM> are charged up, then the control section <NUM> decides whether or not the charging schedule plan need be revised for those power receiving apparatus <NUM> which are not charged up at step S116. In particular, since there possibly is a case wherein, for example, while the battery is not charged up, the power supply controlling switching circuit <NUM> in an off state need be changed to an on state, the necessity for the change and so forth is decided.

If it is decided at step S116 that the charging schedule plan need not be revised, then the processing of the control section <NUM> returns to step S114.

On the other hand, if it is decided at step S116 that the charging schedule need be revised, then the control section <NUM> re-produces a charging schedule plan for the power receiving apparatus other than the power receiving apparatus which is or are charged up. Then, the control section <NUM> produces, in accordance with the re-produced charging schedule plan, an on/off controlling instruction for each of the power supply controlling switching circuit <NUM> of the power receiving apparatus <NUM> other than those power receiving apparatus <NUM> which is or are charged up and transmits the on/off controlling instruction to the pertaining power receiving apparatus <NUM> at step S117. Then, the processing returns to step S114 to repetitively carry out the processes at the steps beginning with step S114.

If it is decided at step S115 that all of the power receiving apparatus <NUM> are charged up, then the control section <NUM> switches off the main power supply to the power transmitting apparatus <NUM> and then ends the processing routine.

<FIG> illustrates processing operation to be executed by the control section <NUM> of the power receiving apparatus <NUM>.

The control section <NUM> transmits identification information (ID) of the power transmitting apparatus <NUM> itself, a residual charging amount and additional information to the power transmitting apparatus <NUM> which is a power supplying source through the communication section <NUM> at step S201.

Then, the control section <NUM> decides whether or not a switching on or off instruction for the power supply controlling switching circuit <NUM> from the power transmitting apparatus <NUM> is received through the communication section <NUM> at step S202.

If it is decided at step S202 that such a switching on or off instruction for the power supply controlling switching circuit <NUM> is not received, then the control section <NUM> repetitively carries out the process at step S202.

On the other hand, if it is decided at step S202 that a switching on or off instruction for the power supply controlling switching circuit <NUM> is received, then the control section <NUM> controls switching on or off of the power supply controlling switching circuit <NUM> in accordance with the received instruction at step S203.

Then, the control section <NUM> decides at step S204 whether or not the power supply controlling switching circuit <NUM> is off. If it is decided that the power supply controlling switching circuit <NUM> is off, then the processing returns to step S202 to repetitively carry out the processes at the steps beginning with step S202.

On the other hand, if it is decided at step S204 that the power supply controlling switching circuit <NUM> is not off, then the control section <NUM> decides whether or not the battery 301B is charged up at step S205.

If it is decided at step S205 that the battery 301B is not charged up, then the processing of the control section <NUM> returns to step S202 to repetitively carry out the processes at the steps beginning with step S202.

On the other hand, if it is decided at step S205 that the battery 301B is charged up, then the control section <NUM> transmits charge up information together with the ID of the power receiving apparatus <NUM> itself to the power transmitting apparatus <NUM> which is a power supplying source through the communication section <NUM> at step S206.

Further, the control section <NUM> changes over the power supply controlling switching circuit <NUM> to an off state at step S207 and then ends the processing routine.

It is to be noted that, in the description of the embodiments given above, only a case is described wherein the power receiving apparatus <NUM> in which the power supply controlling switch is in an off state repeats ac magnetic field energy from the power transmitting apparatus <NUM> to a different power receiving apparatus. However, in a situation wherein the power supply controlling switch is in an off state in a plurality of power receiving apparatus <NUM>, it sometimes occurs that a power receiving apparatus transmits alternating current magnetic field energy transmitted thereto from a different power receiving apparatus which operates as a repeating apparatus to a further different power receiving apparatus.

The power transmission system of the fourth embodiment described above is a charging system. However, in an example not covered by the claims, each of the plural power receiving apparatus may not include a rechargeable battery but may include a function for issuing a notification regarding whether or not the power receiving apparatus itself need operate to the power transmitting apparatus. On the other hand, the power transmitting apparatus may include a function for issuing an instruction for on/off control of the power supply controlling switching circuit of the power receiving apparatus based on the notification.

With such a power transmission system as just described, the power transmitting apparatus monitors the information regarding whether or not the power transmitting apparatus need operate from the power receiving apparatus and issues an instruction for on/off control of the power supply controlling switching circuit so that suitable power supply can be usually carried out for any power receiving apparatus for which power supply is demanded.

It is to be noted that, while a case wherein a resonance relationship between resonance elements is magnetic field resonance is described in the description of the embodiments, the present invention can be applied also to electric field resonance.

The present application contains subject matter related to that disclosed in Japanese Priority Patent Application <CIT>.

Claim 1:
A power receiving apparatus (<NUM>), comprising:
a resonance element (<NUM>) having a specific resonance frequency and adapted to couple in a non-contacting relationship to a power transmitting apparatus (<NUM>) through a resonance relationship;
rectification means (<NUM>) configured to rectify alternating current of the resonance frequency in response to energy received by said resonance element (<NUM>);
a switching means;
a radio communication section (<NUM>) adapted to communicate with the power transmitting apparatus (<NUM>);
a battery (301B);
a charging circuit (<NUM>) adapted to charge the battery (301B) with direct current from the rectification means; and
a control section (<NUM>);
characterized in that
the switching means is a change-over switch (<NUM>) provided between one of the terminals of the resonance element (<NUM>) and one of the input terminals of the rectification means and adapted to cut off a power supply connection between said one of the terminals of the resonance element and said one of the input terminals of the rectification means, and when cutting off said power supply connection, further adapted to connect the terminals of the resonance element together to form a loop coil;
the control section (<NUM>) is configured to transmit a residual charging amount of the battery (301B) to the power transmitting apparatus (<NUM>) through the radio communication section (<NUM>);
wherein the power receiving apparatus (<NUM>) is configured to execute an operation to place said change-over switch (<NUM>) either into the power supply connection state or the loop coil state in response to a controlling instruction from the power transmitting apparatus, said controlling instruction produced by the power transmitting apparatus in accordance with a charging schedule plan, which is produced or modified by the power transmitting apparatus in response to the received residual charging amount.