Patent Description:
In the past, devices such as a battery charger has supplied electric power in non-contact state without directly connecting terminal pins to the terminal devices. An electromagnetic induction method is known as such past non-contact power supply transmission method. In this method, a device on an electric power transmission side is equipped with an electric power transmission coil, and a terminal device on a reception side is equipped with an electric power receiving coil. In this electromagnetic induction method, the location of the electric power transmission coil of the transmission-side device is arranged close to the location of the electric power receiving coil of the reception-side device, in order to bond magnetic flux between both coils to send electric power without contact.

Also, what is called a magnetic field resonance method is developed as a method for efficiently supplying electric power without contact to a terminal device which is a certain distance away. In this method, the device on the electric power transmission side and the device on the electric power receiving side are each equipped with a LC circuit consisting of coils and capacitors, which allows the electric field and the magnetic field to resonate between both circuits in order to transmit the electric power wirelessly.

In both of the electromagnetic induction method and the magnetic field resonance method, the device on the electric power transmission side is equipped with an electric power transmission coil, and the device on the electric power receiving side is equipped with an electric power receiving coil. When the electromagnetic induction method is referred to in the following present specification, the electromagnetic induction method also includes a similar non-contact power supply transmission methods such as the magnetic field resonance method.

<FIG> is a diagram illustrating an exemplary configuration of the past, which feeds power by the electromagnetic induction method without contact to a terminal device from an electric power feeding device. An electric power feeding device <NUM> as a primary-side device converts an alternate current power supply <NUM> such as AC 100V, to direct-current low-voltage power supply, with an AC-DC converter <NUM>. The direct-current low-voltage power supply obtained by the AC-DC converter <NUM> is supplied to an electric power transmission driver <NUM>. The electric power transmission driver <NUM> is connected to an electric power transmission circuit, which is connected to a capacitor <NUM> and a primary-side coil <NUM>, and transmission electric power of a predetermined frequency is supplied from the electric power transmission driver <NUM> to the primary-side coil <NUM>.

In a terminal device <NUM> as a secondary-side device, a secondary-side coil <NUM> and a capacitor <NUM> are connect to a rectifier unit <NUM>, so that the secondary-side coil <NUM> receives electric power from the primary-side coil <NUM>. The series circuit of the secondary-side coil <NUM> and the capacitor <NUM> is connected to the rectifier unit <NUM>, so that the rectifier unit <NUM> rectifies the received power supply, to obtain direct current power supply of a predetermined voltage Va. The predetermined voltage Va is, for example, direct-current power that is slightly over <NUM> V.

The direct current power supply obtained by the rectifier unit <NUM> is supplied to a regulator <NUM>, and is regulated at a constant voltage (for example 5V). The direct current power supply of a constant voltage obtained by the regulator <NUM> is supplied to a charge control unit <NUM>, and the charge control unit <NUM> controls charge of the secondary battery <NUM>.

In such configuration of a non-contact electric power feeding system, the regulator <NUM> of the secondary-side device is a series regulator that is normally referred to as a low drop out (LDO), which is employed when the difference between an input voltage and an output voltage is relatively small. Using the LDO as the regulator <NUM> enables a system whose efficiency is high to a certain extent, for reception of electric power as low as about 5W.

In the meantime, in the non-contact electric power transmission, the transmission electric power is desired to be increased. That is, in the current non-contact electric power feeding systems that has been put into practical use, the reception electric power in the terminal device is relatively small electric power of about 1W to 5W. In contrast, in the non-contact transmission by the electromagnetic induction method, the terminal device is desired to obtain larger reception electric power, such as 10W and 15W.

Here, when large electric power is received in the configuration illustrated in <FIG>, the regulator <NUM> using the LDO has a problem of large loss at a coil where a large current flows.

A switching regulator that is called a DC-DC converter is known as a regulator that processes relatively large electric power and high voltage. Patent Literature <NUM> describes parallel use of a regulator using an LDO and a switching regulator in the power supply device. This Patent Literature <NUM> describes use of the switching regulator when the load is large, and use of the regulator with the LDO when the load is small. Further non-contact electric power feeding devices are e.g. known from <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

In the past, as described in Patent Literature <NUM> for example, when using a regulator using an LDO and a switching regulator in parallel, a power supply device, such as an AC adaptor, detects the voltage of input power supply to switch two regulators. Here, the regulator of the secondary-side device of the non-contact electric power feeding system illustrated in <FIG> is not able to employ the same configuration. That is, when the non-contact electric power feeding system illustrated in <FIG> is configured, the input voltage Va of the regulator <NUM> in the terminal device <NUM> is approximately constant. Only current increases as the reception electric power increases. Accordingly, the configuration that switches the regulators on the basis of detected input voltage is unable to be employed.

Here, an example of heat production of the electric power receiving coil by the change of the reception electric power will be described with reference to the table of <FIG> illustrates three examples of the reception electric power, which are 5W, 10W, and 15W. In each example, when the rectifier unit <NUM> rectifies the voltage to 5V, the current value is 1A in the case of the reception electric power 5W, 2A in the case of the reception electric power 5W, and 3A in the case of the reception electric power 5W. The resistance value of the secondary-side coil <NUM> is dependent on the cross-sectional area of the secondary-side coil <NUM>, and therefore is constant in any electric power. In an example of <FIG>, the resistance value of the secondary-side coil <NUM> is set at <NUM>Ω. The electric power loss of the secondary-side coil <NUM> is dependent on the product of the square of current and the resistance value, as in the equation of Q = I2R. Thus, as the current increases, the electric power loss increases. Here, when the conversion ratio between secondary-side electric power loss and temperature is <NUM>/<NUM>. 6W, the heat temperature of the secondary-side coil <NUM> in each reception electric power changes as illustrated in <FIG>. That is, when the reception electric power is 5W, the heat temperature is approximately <NUM>. When the reception electric power is 10W, the heat temperature is approximately <NUM>. When the reception electric power is 15W, the heat temperature is approximately <NUM>.

Note that, in <FIG>, the conversion ratio between secondary-side electric power loss and temperature is set at <NUM>/<NUM>. 6W on the basis of an actual measurement result of the temperature characteristics of two types of terminal devices that include coils for non-contact power feeding. That is, as illustrated in <FIG>, when the temperature characteristics T1 of a certain type of terminal device and the temperature characteristics T2 of another type of terminal device were measured, the characteristics that shows substantially linear increase of temperature in proportion to the change of electric power loss was obtained. The conversion ratio of <NUM>/<NUM>. 6W is obtained from the characteristics calculated by approximating these characteristics T1, T2 by a straight line.

In the meantime, as another problem different from the heat generation, there is a problem of efficiency of power feeding reception in small electric power, when the secondary-side device uses a switching regulator. That is, <FIG> is a diagram illustrating the relationship between reception electric power and electric power receiving frequency. The characteristics W1 corresponds to a regulator using an LDO, and the characteristics W2 corresponds to a switching regulator. As can be understood by comparing these characteristics W1, W2, for example, in the case of the characteristics W1 that uses an LDO, the reception electric power is large near a specific frequency band. On the other hand, in the case of the characteristics W2 that uses a switching regulator, the reception electric power is small, in the frequency band in which the characteristics W1 has large reception electric power.

As described above, an appropriate carrier frequency changes depending on the type of the regulator of the secondary-side device, and the type of the regulator is unable to be selected simply.

The purpose of the present disclosure is to solve the problems of heat generation and low efficiency when transmission electric power is large, in a non-contact electric power feeding system.

The above objects are achieved by the claimed matter according to the independent claims.

A non-contact electric power feeding system of the present disclosure is a non-contact electric power feeding system including an electric power feeding device, and a terminal device configured to receive power fed from the electric power feeding device. The electric power feeding device includes a primary-side coil, a driver configured to supply transmission electric power to the primary-side coil, a primary-side control unit configured to control the transmission electric power supplied by the driver to a plurality of levels, and a primary-side communication unit configured to communicate with a side that receives electric power fed from the primary-side coil. The terminal device includes a secondary-side coil configured to receive electric power, a rectifier unit configured to rectify reception electric power obtained by the secondary-side coil, a regulator configured to convert the reception electric power rectified by the rectifier unit to electric power of a predetermined voltage, a secondary-side communication unit, and a secondary-side control unit configured to control the regulator. The regulator conducts the conversion of the reception electric power by a plurality of methods. The secondary-side control unit controls the method of the voltage transformation conducted by the regulator, on the basis of the information received by the secondary-side communication unit that communicates with the primary-side communication unit.

Also, the terminal device of the present disclosure includes a secondary-side coil configured to receive electric power transmitted from an electric power feeding device, a rectifier unit configured to convert the reception electric power rectified by the rectifier unit to electric power of a predetermined voltage, a communication unit, and a control unit. The regulator conducts conversion of the reception electric power by a plurality of methods. The control unit controls the method of voltage transformation conducted by the regulator, on the basis of the information that the communication unit obtains from the electric power feeding device.

Also, the non-contact electric power feeding device of the present disclosure includes a primary-side coil, a driver configured to supply transmission electric power to the primary-side coil, a communication unit configured to communicate with a device of a side that receives electric power fed from the primary-side coil, and a control unit. The control unit controls the transmission electric power that the driver supplies to the primary-side coil, at a plurality of levels, and decides the transmission electric power on the basis of the information received by the communication unit.

Also, the non-contact electric power feeding method of the present disclosure is applied to a case where non-contact power feeding is conducted from an electric power feeding device including a primary-side coil to a terminal device including a secondary-side coil. In the terminal device, a regulator converts the electric power received by the secondary-side coil to the electric power of a predetermined voltage, by a plurality of methods of conversion. Then, the method of voltage transformation conducted by the regulator is set on the basis of the information obtained in the communication between the electric power feeding device and the terminal device.

According to the present disclosure, the regulator included in the terminal device that receives the electric power transmitted from the electric power feeding device is set in an appropriate type for conducting voltage transformation on the basis of the information instructed from the electric power feeding device.

According to the present disclosure, conversion method of the regulator is set to an efficient, appropriate conversion method, so as to increase the transmission efficiency and effectively prevent the heat generation of the coil, regardless of reception electric power in the terminal device.

Examples of a non-contact electric power feeding system, a terminal device, a non-contact electric power feeding device, and a non-contact electric power feeding method according to embodiments of the present disclosure will be described with reference to drawings, in the following order.

<FIG> is a diagram illustrating an exemplary configuration of a non-contact electric power feeding system according to an example of an embodiment of the present disclosure. The non-contact electric power feeding system of the present disclosure includes an electric power feeding device <NUM> as a primary-side device, and a terminal device (electric power receiving device) <NUM> as a secondary-side device, and feeds electric power without contact by the electromagnetic induction method. The electric power feeding device <NUM> is a device that receives supply such as commercial alternate current power supply and feeds the power supply to the terminal device <NUM> without contact. The terminal device <NUM> includes a load circuit that operates with the power supply supplied from the electric power feeding device <NUM>. Alternatively, the terminal device <NUM> may include a secondary battery that is charged by the power supply supplied from the electric power feeding device <NUM>. The terminal device <NUM> is applicable to various types of terminal devices (electronic devices), such as a mobile phone terminal device and a portable audio player device.

The electric power feeding device <NUM> of the primary-side device converts an alternate current power supply <NUM> such as AC 100V to direct-current low-voltage power supply, with an AC-DC converter <NUM>. The direct-current low-voltage power supply obtained by the AC-DC converter <NUM> is supplied to an electric power transmission driver <NUM>. Use of the alternate current power supply <NUM> is just an example. For example, a direct current power supply may be used as an input power supply. The electric power transmission driver <NUM> is connected to an electric power transmission circuit having a capacitor <NUM> and a primary-side coil <NUM> connected to each other, and transmission electric power of a predetermined frequency is supplied to a primary-side coil <NUM> from the electric power transmission driver <NUM>.

The electric power feeding device <NUM> includes a control unit (primary-side control unit) <NUM> that controls a power feeding process. The control unit <NUM> controls the transmission electric power supplied to the primary-side coil <NUM> from the electric power transmission driver <NUM>. In the electric power feeding device <NUM> of an example of the present embodiment, the transmission electric power is variably settable at a plurality of levels. The control unit <NUM> sets the transmission electric power value at one of the plurality of levels. A specific example of setting of the transmission electric power will be described later.

Also, the electric power feeding device <NUM> includes a communication unit <NUM>. The communication unit <NUM> communicates with the terminal device <NUM> in both direction. For example, the communication unit <NUM> superimposes a transmission signal, on the transmission electric power supplied to the primary-side coil <NUM> from the electric power transmission driver <NUM>, for the purpose of communication. Specifically, the communication unit <NUM> utilizes the frequency of the transmission electric power supplied to the primary-side coil <NUM> as a carrier wave, and modulates information by ASK (amplitude shift keying) or other modulation methods to transmit it. The transmission of information to the communication unit <NUM> from the terminal device <NUM> is conducted by the same method. Alternatively, the transmission of information to the communication unit <NUM> from the terminal device <NUM> may utilize a subcarrier that has a different frequency from the transmission electric power. With respect to the method for transmitting information in both directions together with electric power without contact between adjacent coils, various types of methods has already been put into practical use, for example, for the communication between a non-contact IC card and a reader. An example of the present disclosure may employ any method.

Next, the terminal device <NUM>, which is the secondary-side device, will be described. In the terminal device <NUM>, a secondary-side coil <NUM> and a capacitor <NUM> are connected to a rectifier unit <NUM>, and the secondary-side coil <NUM> receives electric power from the primary-side coil <NUM>. In the case of the electromagnetic induction method, the primary-side coil <NUM> and the secondary-side coil <NUM> are normally located at adjacent positions. The rectifier unit <NUM> rectifies the power supply of a predetermined frequency received by the secondary-side coil <NUM>, to obtain direct current power supply.

Then, the direct current power supply obtained by the rectifier unit <NUM> is supplied to a regulator <NUM>. The regulator <NUM> is a voltage converter that converts the voltage of input power supply to a predetermined voltage. The direct current power supply of a predetermined voltage obtained by the regulator <NUM> is supplied to a load circuit <NUM>. Note that a secondary battery may be charged instead of the load circuit <NUM>.

The regulator <NUM> of an example of the present disclosure performs the conversion of the reception electric power by a plurality of methods. In an example of <FIG>, the regulator <NUM> includes two types of conversion circuits, which are a DC-DC converter <NUM> and an LDO <NUM>. The DC-DC converter <NUM> is referred to as "switching regulator", which is a circuit that switches input power supply with switching elements at a relatively high speed and rectifies and smooths the switched power supply to obtain a desired voltage of direct current power supply. The DC-DC converter <NUM> has a wide variable range of input voltage.

The LDO <NUM> is a series regulator that controls the voltage drop amount in a transistor element to obtain a desired voltage of direct current power supply. The LDO <NUM> has a narrow variable range of input voltage, and converts the voltage efficiently when input voltage is slightly higher than output voltage.

The regulator <NUM> uses the circuit of one of the DC-DC converter <NUM> and the LDO <NUM>, to convert the voltage of the input power supply to a stable constant voltage. The circuit that the regulator <NUM> uses for conversion is decided by an instruction from a control unit (secondary-side control unit) <NUM> that controls electric power reception. In the case of an example of the present disclosure, the DC-DC converter <NUM> is used when the input voltage is a relatively high voltage, and the LDO <NUM> is used when the input voltage is a relatively low voltage. The detail of the selection operation of the DC-DC converter <NUM> and the LDO <NUM> by the control of the control unit <NUM> will be described later.

Also, the terminal device <NUM> includes a communication unit <NUM>, and communicates with the communication unit <NUM> of the electric power feeding device <NUM> in both directions. In order for the communication unit <NUM> to communicate, the series circuit with the secondary-side coil <NUM> and the capacitor <NUM> is connected to the communication unit <NUM>, to detect the signal superimposed on the power supply supplied from the electric power feeding device <NUM>, and thereby receive the signal transmitted from the communication unit <NUM>. Also, the signal transmitted from the communication unit <NUM> is supplied to the series circuit with the secondary-side coil <NUM> and the capacitor <NUM>. Also, the terminal device <NUM> includes a temperature sensor <NUM> that measures the temperature of a vicinity of the secondary-side coil <NUM>. The data of the temperature measured by the temperature sensor <NUM> is supplied to the control unit <NUM>.

The non-contact electric power feeding system of the present disclosure is operable to set the feed electric power at at least three levels, which are 5W, 10W, and 15W, when the power is fed to the terminal device <NUM> from the electric power feeding device <NUM>. Then, when the terminal device <NUM> receives the feed electric power, the input voltage Vx in the regulator <NUM> corresponding to the feed electric power is set, and the regulator <NUM> converts the reception electric power of the input voltage Vx to a constant voltage, and outputs it. The setting of the input voltage Vx in the regulator <NUM> is controlled by the control unit <NUM>. At this time, the control unit <NUM> uses an appropriate one of the DC-DC converter <NUM> and the LDO <NUM>, and controls the conversion, as described above.

<FIG> is a table illustrating examples of feed electric power, reception electric power voltage in the terminal device <NUM> (i.e., the input voltage Vx in the regulator <NUM>), electric power loss, and heat generation. The condition of heat generation is same as the condition in <FIG> that illustrates examples of the past. This <FIG>, illustrates three examples of 5W power feeding, 10W power feeding, and 15W power feeding. When the electric power feeding device <NUM> feeds power in each example of 5W, 10W, and 15W, the input voltages Vx in the regulator <NUM> (secondary-side voltage) are set at 5V, 10V, 15V respectively, and the secondary-side currents obtained in the terminal device <NUM> are set at approximately 1A in each case, in these examples.

The resistance values of the secondary-side coil <NUM> are same in all examples, and the secondary-side currents are 1A for all feed electric power values, and thus the secondary-side electric power losses are <NUM>. 4W for all electric power values. Accordingly, the heat temperatures of the secondary-side coil <NUM> are approximately <NUM> for all electric power values. Note that the heat temperatures illustrated in <FIG> are calculated in accordance with the condition (<NUM>/<NUM>. 6W) set in the examples of <FIG>.

Next, an example of the specific configuration of the regulator <NUM> will be described. Here, three examples including example <NUM>, example <NUM>, and example <NUM> will be described.

<FIG> is a diagram illustrating the configuration of the regulator <NUM> of an example <NUM>. In the configuration illustrated in <FIG>, the DC-DC converter <NUM> and the LDO <NUM> are connected in series. Although, in an example of <FIG> the LDO <NUM> is connected at downstream of the DC-DC converter <NUM>, the inverse connection order may be employed. Only one of the DC-DC converter <NUM> and the LDO <NUM> is in operation. The other one of the DC-DC converter <NUM> and the LDO <NUM>, which halts its operation, outputs the input signal as it is.

<FIG> is a diagram illustrating operating states of the regulator <NUM> of the example of <FIG>. When using the DC-DC converter <NUM>, the control unit <NUM> operates the DC-DC converter <NUM>, and disables the LDO <NUM>, as illustrated in <FIG>. In this way, the power supply converted by the DC-DC converter <NUM> is obtained at the output of the regulator <NUM>.

Also, when using the LDO <NUM>, the control unit <NUM> operates the LDO <NUM>, and disables the DC-DC converter <NUM>, as illustrated in <FIG>. In this way, the power supply converted by the LDO <NUM> is obtained at the output of the regulator <NUM>.

<FIG> is a diagram illustrating the configuration of the regulator <NUM> of an example <NUM>. In the configuration illustrated in <FIG>, the DC-DC converter <NUM> and the LDO <NUM> are connected in parallel. The control unit <NUM> controls one of the DC-DC converter <NUM> and the LDO <NUM> to operate, in such a manner that only the controlled one operates.

<FIG> is a diagram illustrating the configuration of the regulator <NUM> of an example <NUM>. In the configuration illustrated in <FIG>, the DC-DC converter <NUM> and the LDO <NUM> share a common circuit. As illustrated in <FIG>, two transistors Q1, Q2 are connected between an input terminal 210a and a ground potential portion of the regulator <NUM>. The two transistors Q1, Q2 are controlled to be turned on and off by the control unit <NUM>. A connection point between the both transistors Q1, Q2 is connected to the output terminal 210b of the regulator <NUM> via a coil L1. One end of a smoothing capacitor C1 is connected to a connection point between the coil L1 and the output terminal 210b.

A series circuit of resistors R1, R2 for voltage detection is connected between a ground potential portion and a connection point between the transistors Q1, Q2 and the coil L1. Also, a series circuit of resistors R3, R4 for voltage detection is connected between a ground potential portion and a connection point between the coil <NUM>,<NUM> and the output terminal 210b. The control unit <NUM> detects the voltage of a connection point between the resistors R1, R2, and the voltage of a connection point between the resistors R3, R4.

When the regulator <NUM> is used as the DC-DC converter <NUM> in the configuration illustrated in <FIG>, the control unit <NUM> executes switching operation by turning on and off the two transistors Q1, Q2 at a high speed. At this time, the control unit <NUM> monitors the voltage charged to the smoothing capacitor C1 on the basis of the voltage of the connection point between the resistors R3, R4, and controls the switching state of the two transistors Q1, Q2 in such a manner to adjust the detected voltage.

Also, when the regulator <NUM> is used as the LDO <NUM> in the configuration illustrated in <FIG>, the transistor Q1 is controlled as a voltage controlling element. The control unit <NUM> sets the transistor Q2 in an open state. At this time, the control unit <NUM> detects the voltage of the connection point between the resistors R1, R2, and controls the voltage drop amount in the transistor Q1 to adjust the voltage.

Next, an exemplary power feeding process conducted between the electric power feeding device <NUM> and the terminal device <NUM> will be described. Here, two examples: an example <NUM> in which the process is conducted with communication from the electric power feeding device <NUM> (<FIG>), and an example <NUM> in which the process is conducted with communication from the terminal device <NUM> (<FIG>) will be described. In both examples, the primary-side coil <NUM> of the electric power feeding device <NUM>, the secondary-side coil <NUM> of the terminal device <NUM> are adjacent to each other, so that electric power is transmittable.

<FIG> is a flowchart illustrating an exemplary power feeding process of an example <NUM>. The process is described in accordance with <FIG>. First, the control unit <NUM> of the electric power feeding device <NUM>, which is the primary-side device, starts supplying transmission electric power from the electric power transmission driver <NUM> to the primary-side coil <NUM> (step S11). At this time, relatively low electric power for startup is set. That is, the control unit <NUM> sets the electric power lower than electric power such as 5W and 15W, which are described above. This low electric power for startup may be electric power that enables communication between the communication unit <NUM> of the primary side and the communication unit <NUM> of the secondary side. Alternatively, the control unit <NUM> may set the transmission electric power for startup at 5W, which is the smallest electric power among the plurality of settable levels of electric power, which is described above.

By starting electric power transmission in this way, the control unit <NUM> and the communication unit <NUM> of the terminal device <NUM> as the secondary-side device are activated (step S12). At the time of startup, a signal indicating the startup may be transmitted from the communication unit <NUM> of the terminal device <NUM> to the communication unit <NUM> of the electric power feeding device <NUM>.

Then, upon startup of the secondary-side device, the control unit <NUM> of the electric power feeding device <NUM> causes the communication unit <NUM> to transmit a signal for confirming the load electric power that is to be used by the load circuit <NUM> of the terminal device <NUM>, (step S13). When the communication unit <NUM> of the terminal device <NUM> receives the signal for confirming the load electric power, the control unit <NUM> causes the communication unit <NUM> to return the information indicating the load electric power, and the control unit <NUM> of the electric power feeding device <NUM> confirms the load electric power on the basis of the information transmitted.

Then, the control unit <NUM> decides the transmission electric power corresponding to the confirmed load electric power (step S14). For example, the control unit <NUM> selects the transmission electric power that is same as the load electric power or larger than the load electric power. At this time, the control unit <NUM> may transmit the information of the decided transmission electric power, from the communication unit <NUM> to the terminal device <NUM>.

The control unit <NUM> of the terminal device <NUM> determines whether the transmission electric power is larger than or equal to a threshold value THx or smaller than the threshold value THx, on the basis of the information received by the communication unit <NUM>. Here, if the transmission electric power is larger than or equal to the threshold value THx, the control unit <NUM> issues an instruction to use the DC-DC converter <NUM> as the regulator <NUM> (step S15). Also, if the transmission electric power is smaller than the threshold value THx, the control unit <NUM> issues an instruction to use the LDO <NUM> as the regulator <NUM> (step S16). Note that the input voltage of the regulator <NUM> is appropriately set on the basis of the transmission electric power, for example. As an example, when the current is to be kept constant, the control unit <NUM> sets one of the input voltages 5V, 10V, and 15V for the transmission electric power 5W, 10W, and 15W, as illustrated in <FIG>.

Then, the control unit <NUM> of the electric power feeding device <NUM> starts the power feeding with the transmission electric power decided in step S14 (step S17). As described above, according to the process of the flowchart of <FIG>, the regulator <NUM> in the terminal device <NUM> uses an appropriate one of the DC-DC converter <NUM> and the LDO <NUM> to convert the voltage, on the basis of the transmission electric power instructed from the electric power feeding device <NUM>.

<FIG> is a flowchart illustrating the exemplary power feeding process of an example <NUM>. The process is described in accordance with <FIG>. First, the control unit <NUM> of the electric power feeding device <NUM>, which is the primary-side device, starts supplying the transmission electric power from the electric power transmission driver <NUM> to the primary-side coil <NUM> (step S21). At this time, relatively low electric power for startup is set in the same way as the process in step S11 of the flowchart of <FIG>.

By starting electric power transmission in this way, the control unit <NUM> and the communication unit <NUM> of the terminal device <NUM> as the secondary-side device are activated (step S22).

Then, upon startup of the secondary-side device, the control unit <NUM> of the terminal device <NUM> transmits a signal for confirming the transmission electric power of the electric power feeding device <NUM>, from the communication unit <NUM> (step S23). When the communication unit <NUM> of the electric power feeding device <NUM> receives the signal for confirming the transmission electric power, the control unit <NUM> returns the information indicating the transmission electric power from the communication unit <NUM>, and the control unit <NUM> of the terminal device <NUM> confirms the transmission electric power from the information transmitted.

Then, the control unit <NUM> decides the load electric power corresponding to the confirmed transmission electric power (step S24). That is, the control unit <NUM> decides a load electric power consumed by the load circuit <NUM> within a range that does not exceed the presented transmission electric power. Then, the control unit <NUM> determines whether the decided load electric power is larger than or equal to a threshold value THx, or smaller than the threshold value THx. Here, if the load electric power is larger than or equal to the threshold value THx, the control unit <NUM> issues an instruction to use the DC-DC converter <NUM> as the regulator <NUM> (step S25). Also, if the load electric power is smaller than the threshold value THx, the control unit <NUM> instructs the regulator <NUM> to use the LDO <NUM> (step S26). Note that, in this example as well, the input voltage of the regulator <NUM> is appropriately set on the basis of the transmission electric power, for example. As an example, when the current is to be kept constant, the control unit <NUM> sets one of the input voltages 5V, 10V, and 15V for the transmission electric power 5W, 10W, and 15W, as illustrated in <FIG>.

Then, the control unit <NUM> of the electric power feeding device <NUM> starts the power feeding with the transmission electric power notified in step S23 (step S27). As described above, according to the process of the flowchart of <FIG>, in response to the load electric power set in the terminal device <NUM>, the regulator <NUM> uses an appropriate one of the DC-DC converter <NUM> and the LDO <NUM> to convert the voltage.

As illustrated in the flowchart of <FIG> and <FIG>, one of the DC-DC converter <NUM> and the LDO <NUM> is selected for use in the voltage conversion, on the basis of the transmission electric power or the load electric power. Hence, efficient non-contact power feeding is performed in both of small electric power transmission and large electric power transmission, and the heat generation of the secondary-side coil <NUM> is reduced in large electric power transmission.

<FIG> is a flowchart illustrating a variant example of the power feeding process <NUM>. In the flowchart of <FIG> and <FIG>, the setting of the regulator <NUM> is conducted at the start of the power feeding. In contrast, in the variant example <NUM>, the control unit <NUM> of the terminal device <NUM> conducts the setting of the regulator <NUM> on the basis of the temperature detected by the temperature sensor <NUM>.

That is, first, the control unit <NUM> of the terminal device <NUM> instructs the regulator <NUM> to use the LDO <NUM>, assuming that the reception electric power is smaller than the threshold value THx (step S31). Then, after the electric power feeding device <NUM> starts the electric power transmission (step S32), the control unit <NUM> of the terminal device <NUM> receives the electric power for predetermined X seconds (step S33), and determines whether or not the power feeding has finished (step S34). Here, X seconds is, for example, a period about <NUM> seconds.

If the control unit <NUM> determines that the power feeding has finished in step S34, the control unit <NUM> executes the process to finish the electric power reception (step S35). If the control unit <NUM> determines that the power feeding continues in step S34, the control unit <NUM> determines whether or not the temperature detected by the temperature sensor <NUM> is higher than or equal to temperature α °C, which is a predetermined threshold value (step S36). Here, if the control unit <NUM> determines that the temperature is not higher than or equal to α °C, the control unit <NUM> returns to the process of step S33.

If the control unit <NUM> determines that the temperature is higher than or equal to α °C in step S36, the control unit <NUM> instructs the regulator <NUM> to use the DC-DC converter <NUM>, and changes the input voltage of the regulator <NUM> to a high voltage such as 10V (step S37). After changing the setting of the regulator <NUM>, the control unit <NUM> determines whether or not the fed electric power is normally received (step S38). If the control unit <NUM> determines that the fed electric power is not normally received, the control unit <NUM> regards it as an abnormal state and stops the power feeding process (step S39).

If the control unit <NUM> determines that the fed electric power is normally received in step S38, the control unit <NUM> receives the electric power for predetermined X seconds (step S40), and determines whether or not the power feeding has finished (step S41).

If the control unit <NUM> determines that the power feeding has finished in step S41, the control unit <NUM> executes the process to finish the electric power reception (step S42). If the control unit <NUM> determines that the power feeding continues in step S41, the control unit <NUM> determines whether or not the temperature detected by the temperature sensor <NUM> is higher than or equal to temperature α °C, which is a predetermined threshold value (step S43). Here, if the control unit <NUM> determines that the temperature is not higher than or equal to α °C, the control unit <NUM> returns to the process of step S40. If the control unit <NUM> determines that the temperature is larger than or equal to α °C in step S40, the control unit <NUM> stops the power feeding process, which is in an abnormal state (step S44).

As illustrated in the flowchart of <FIG>, the control unit <NUM> decides the conversion method in the regulator <NUM> on the basis of the determination of whether or not the temperature near the secondary-side coil <NUM> is higher than or equal to α °C, which is a predetermined threshold value of temperature, in order to set an appropriate conversion method and input electric power. That is, in the state where the secondary-side coil <NUM> has hardly generated heat, the control unit <NUM> determines that appropriate non-contact power feeding is conducted, and receives electric power in the condition that has been set first. In the state where the secondary-side coil <NUM> has generated heat to a certain extent, the control unit <NUM> determines that the feed electric power is large, and changes the conversion method and the input voltage, to appropriately receive electricity.

Note that the process illustrated in the flowchart of <FIG> may be executed singly. Alternatively, the control unit <NUM> may execute the process illustrated in the flowchart of <FIG>, after executing the process to start the power feeding at the start of the power feeding illustrated in the flowchart of <FIG> or <FIG>, for example.

<FIG> is a flowchart illustrating a variant example of the power feeding process <NUM>. In the variant example <NUM>, the control unit <NUM> of the terminal device <NUM> determines the electric power reception efficiency of the feed electric power, for the purpose of the setting of the regulator <NUM>.

That is, first, the control unit <NUM> of the terminal device <NUM> instructs the regulator <NUM> to select one of the DC-DC converter <NUM> and the LDO <NUM> to conduct conversion (step S51). Then, after the electric power feeding device <NUM> starts the electric power transmission (step S52), the control unit <NUM> of the terminal device <NUM> receives the electric power for predetermined X seconds (step S53), and determines whether or not the electric power reception efficiency of the currently fed electric power is larger than or equal to predetermined β % (step S54). The control unit <NUM> calculates this electric power reception efficiency. For example, the control unit <NUM> acquires the information of the transmission electric power from the electric power feeding device <NUM>, and the control unit <NUM> measures the electric power received by the terminal device <NUM>, and the control unit <NUM> calculates the electric power reception efficiency, using the reception electric power and the feed electric power.

If the control unit <NUM> determines that the electric power reception efficiency is not higher than or equal to β % in step S54, the control unit <NUM> issues an instruction to switch the conversion method of the regulator <NUM> to the other method (step S55). At this time, when the input voltage is to be set, the input voltage is also switched. Thereafter, the control unit <NUM> determines whether or not the power feeding has finished (step S56). If the control unit <NUM> determines that the power feeding has finished in step S56, the control unit <NUM> executes the process to finish the electric power reception (step S57). Then, when the control unit <NUM> determines that the power feeding continues in step S56, the control unit <NUM> receives the electric power for predetermined X seconds (step S58), and determines whether or not the electric power reception efficiency of the currently fed electric power is larger than or equal to predetermined β % (step S59).

Here, if the control unit <NUM> determines that the electric power reception efficiency is larger than or equal to β %, the control unit <NUM> returns to the process of step S58. Also, if the control unit <NUM> determines that the electric power reception efficiency is not larger than or equal to β % in step S59, the control unit <NUM> determines that electricity is not received in a proper state in both setting of the regulator <NUM>, and executes the process to end the power feeding (step S60).

As illustrated in the flowchart of <FIG>, the control unit <NUM> switches the conversion method in the regulator <NUM> on the basis of actual electric power reception efficiency, in order to set appropriate the conversion method and input electric power.

Note that the process illustrated in the flowchart of <FIG> may be executed singly. Alternatively, the control unit <NUM> may execute the process illustrated in the flowchart of <FIG>, after executing the process to start the power feeding at the start of the power feeding illustrated in the flowchart of <FIG> or <FIG>, for example. Alternatively, the control unit <NUM> may use both of the selection process based on temperature illustrated in the flowchart of <FIG> and the selection process based on efficiency illustrated in the flowchart of <FIG>.

In the examples of embodiments described above, the DC-DC converter <NUM> and the LDO <NUM> are provided as the regulator <NUM>. As opposed to this, other two types of regulators that employ different conversion methods may be provided to switch the two types of regulators on the basis of transmission electric power and load electric power. Also, in the embodiment described above, the feed electric power is changed to three steps as illustrated in <FIG>, for example. As opposed to this, the feed electric power may be changed to two steps or four steps or more. Also, the relationship between feed electric power and voltage and current illustrated in <FIG> is just an example, and thus other feed electric power, voltage, and current may be set.

Claim 1:
A terminal device (<NUM>) comprising:
a secondary-side coil (<NUM>) configured to receive electric power transmitted from a primary-side coil (<NUM>) of an electric power feeding device (<NUM>);
a rectifier unit (<NUM>) configured to rectify reception electric power obtained by the secondary-side coil (<NUM>);
a secondary-side communication unit (<NUM>) configured to communicate with the electric power feeding device (<NUM>), the secondary-side communication unit (<NUM>) being configured to receive a small electric power for start-up from the electric power feeding device (<NUM>), the small electric power being electric power that enables communication between the secondary-side communication unit (<NUM>) and the electric power feeding device (<NUM>), the small electric power being smaller than or equal to 5W and a range of settable levels of electric power being larger than or equal to 5W, to transmit a signal to the electric power feeding device (<NUM>) which confirms the electric power of the electric power feeding device (<NUM>), to receive an information which indicates the electric power from the electric power feeding device (<NUM>),
a regulator (<NUM>) including a first regulator (<NUM>) and a second regulator (<NUM>), the regulator being configured to convert the reception electric power rectified by the rectifier unit (<NUM>) to electric power of a predetermined voltage, and to conduct conversion by a first conversion method of the first regulator (<NUM>) or by a second conversion method of the second regulator (<NUM>),
a control unit (<NUM>) configured to determine whether the electric power is larger than or equal to a threshold value on the basis of the information received by the secondary-side communication unit (<NUM>) and to instruct to use the first regulator (<NUM>) if the transmission electric power level is larger than or equal to the threshold value and to use the second regulator (<NUM>) if the transmission electric power level is smaller than the threshold value.