Wireless power transmission apparatus and wireless power transmission method thereof

A wireless power transmission apparatus for wirelessly transmitting power to a wireless power reception apparatus is provided. The wireless power transmission apparatus includes a power transmitting circuit including a coil and at least one processor to control to transmit, via the power transmitting circuit, a pilot power with changing a frequency of the pilot power within a predetermined frequency range, obtain a magnitude of power wirelessly transmitted to a wireless power reception apparatus based on the transmitted pilot power, determine an operating frequency based on the obtained magnitude, and control to transmit, via the power transmitting circuit, a driving power having the operating frequency to drive the wireless power reception apparatus.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119(a) of a Korean patent application number 10-2018-0014636, filed on Feb. 6, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

The disclosure relates to a wireless power transmission apparatus and a transmission method. More particularly, the disclosure relates to a wireless power transmission apparatus for wirelessly transmitting power to a wireless power reception apparatus and a wireless power transmission method thereof.

2. Description of Related Art

An electronic apparatus according to the related art is connected to a power supplier in a wired manner or is supplied with power through a battery. However, recently, a wireless power transmission apparatus for wirelessly supplying power to an electronic apparatus, a wireless power reception apparatus, and a wireless power transmission/reception system have appeared with the development of electrical and electronic technology.

Wireless power transmission means a power transmission method in which power energy is converted into an electromagnetic wave which may be wirelessly transmitted, and transferred to an electronic apparatus. Here, an apparatus for wirelessly transmitting power is referred to as the wireless power transmission apparatus, and an apparatus for wirelessly receiving power is referred to as the wireless power reception apparatus.

In the case of wireless power transmission, wireless power transmission efficiency may vary depending on a position of the wireless power reception apparatus.

Therefore, in a wireless power transmission technology according to the related art, there has been an inconvenience in that the wireless power reception apparatus needs to be disposed at a predetermined position, or a position of the wireless power reception apparatus needs to be identified through bidirectional communication between the wireless power transmission apparatus and the wireless power reception apparatus.

SUMMARY

Aspects of the disclosure are provided to address at least the above-mentioned problems and/or disadvantages, and to provide at least the advantages described below. Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

Accordingly, an aspect of the disclosure is to provide a wireless power transmission apparatus which sets an operating frequency for wireless power transmission and is capable of wirelessly supplying power to a wireless power reception apparatus through the set operating frequency without a process of fixing a position of the wireless power reception apparatus or communicating with the wireless power reception apparatus, and a wireless power transmission method thereof.

In accordance with an aspect of the disclosure, a wireless power transmission apparatus for wirelessly transmitting power to a wireless power reception apparatus is provided. The apparatus includes a power transmitting circuit including a coil, and at least one processor configured to control to transmit, via the power transmitting circuit, a pilot power with changing a frequency of the pilot power within a predetermined frequency range, obtain a magnitude of power wireless transmitted to a wirelessly power reception apparatus based on the transmitted pilot power, determine an operating frequency based on the obtained magnitude, and control to transmit, via the power transmitting circuit, a driving power having the operating frequency to drive the wireless power reception apparatus.

In accordance with another aspect of the disclosure, a magnitude of the pilot power may be smaller than a magnitude of the driving power.

In accordance with another aspect of the disclosure, the processor may detect a magnitude of a current input to the coil while the pilot power is applied to the coil and identify the magnitude of the power wirelessly transmitted to the wireless power reception apparatus based on the detected magnitude of the current.

In accordance with another aspect of the disclosure, the processor may set a certain frequency within the predetermined frequency range as the operating frequency based on the magnitude of the power wirelessly transmitted to the wireless power reception apparatus by using the pilot power.

In accordance with another aspect of the disclosure, the wireless power transmission apparatus may further include a switch, wherein the processor converts a direct current voltage into an alternating current voltage through a switching operation of the switch and applies the alternating current to the coil.

In accordance with another aspect of the disclosure, the processor may identify a frequency range in which the switching operation of the switch is performed so that a voltage across the switch is 0V within the predetermined frequency range based on the magnitude of the power wirelessly transmitted to the wireless power reception apparatus, and set the certain frequency within the determined frequency range as the operating frequency.

In accordance with another aspect of the disclosure, a wireless power transmission method in which power is wirelessly transmitted to a wireless power reception apparatus is provided. The method includes transmitting a pilot power with changing a frequency of the pilot power within a predetermined frequency range, obtaining a magnitude of power wireless transmitted to a wirelessly power reception apparatus based on the transmitted pilot power, determining an operating frequency based on the obtained magnitude, and transmitting a driving power having the operating frequency to drive the wireless power reception apparatus.

In accordance with another aspect of the disclosure, a magnitude of the pilot power may be smaller than a magnitude of the driving power.

In accordance with another aspect of the disclosure, the wireless power transmission method may further include detecting a magnitude of a current input to the coil while the pilot power is applied to the coil, and identifying the magnitude of the power wirelessly transmitted to the wireless power reception apparatus based on the detected magnitude of the current.

In accordance with another aspect of the disclosure, the wireless power transmission method may further include setting a certain frequency within the predetermined frequency range as the operating frequency based on the magnitude of the power wirelessly transmitted by the wireless power transmission apparatus by using the pilot power.

In accordance with another aspect of the disclosure, the wireless power transmission method may further include converting a direct current voltage into an alternating current voltage through a switching operation of a switch and applying the alternating current voltage to the coil.

In accordance with another aspect of the disclosure, the wireless power transmission method may further include identifying a frequency range in which the switching operation of the switch is performed so that a voltage across the switch is 0 V within the predetermined frequency range based on the magnitude of the power wirelessly transmitted to the wireless power reception apparatus, and setting the certain frequency within the determined frequency range as the operating frequency.

According to the aspects of the disclosure, the wireless power transmission apparatus predicts a position of the wireless power reception apparatus without communicating with the wireless power reception apparatus, and wirelessly provides power to the wireless power reception apparatus by setting the operating frequency depending on the predicted position, thereby making it possible to wirelessly transmit power to the wireless power reception apparatus more conveniently and efficiently.

DETAILED DESCRIPTION

Terms used in the disclosure are used to describe specific embodiments, rather than to limit the scope of the disclosure. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. Throughout the specification, unless described to the contrary, “including” or “comprising” any component will be understood to imply the inclusion of other elements rather than the exclusion of other elements.

A term “-er/or”, “module”, or the like, described in the specification means a processing unit of at least one function or operation, and may be implemented as hardware or software or a combination of hardware and software. In addition, a plurality of “-ers/ors'” or a plurality of “modules'” may be integrated in at least one module, and may be implemented as at least one processor (not illustrated) except for a ‘module’ or a ‘-er/or’ that needs to be implemented as specific hardware.

Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the disclosure pertains may easily practice the disclosure. However, the disclosure may be modified in various different forms, and is not limited to embodiments described herein. In addition, in the drawings, portions unrelated to the description will be omitted, and similar reference numerals will be used to describe similar portions throughout the specification.

Hereinafter, various embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

FIG. 1is a diagram for describing a wireless power system according to an embodiment of the disclosure.

Referring toFIG. 1, a wireless power system includes a wireless power transmission apparatus100and a wireless power reception apparatus200.

The one or more wireless power transmission apparatus100may wirelessly transmit, to the one or more wireless power reception apparatus200, power that is required to drive the one or more wireless power reception apparatus200.

Here, a wireless power transmission manner includes electromagnetic inductive coupling, resonant magnetic coupling, and the like, but embodiments are not limited thereto.

The electromagnetic inductive coupling is a manner in which power is supplied by using a principle of electromagnetic induction. In detail, in the case of the electromagnetic inductive coupling, when an alternating current flows through a coil of the wireless power transmission apparatus100, a magnetic field is generated around the coil and a current is induced in a coil of the wireless power reception apparatus200under the influence of the magnetic field, such that it is possible to transmit power to the wireless power reception apparatus.

The resonant magnetic coupling is a manner in which power is supplied by using a resonance phenomenon. In detail, in the case of the resonant magnetic coupling, the wireless power transmission apparatus100may generate a magnetic field resonating at a resonance frequency and transmit power to the wireless power reception apparatus200designed to have the same resonance frequency.

Although a television (TV) is illustrated as the wireless power reception apparatus200inFIG. 1, the wireless power reception apparatus200is not limited thereto. That is, the wireless power reception apparatus200may include various kinds of electronic apparatuses having a configuration in which the electronic apparatus may be wirelessly supplied with power from the wireless power transmission apparatus100, such as one or more of a mobile phone, a laptop computer, a personal computer, an air-conditioner, a stereo system, and the like. In addition, the wireless power reception apparatus200may include one or more of a movable electronic apparatus such as a domestic or industrial robot, a robotic vacuum cleaner, a drone, an electric vehicle, or the like. Further, even in case of an apparatus which newly appears with technology development, the apparatus may be the wireless power reception apparatus200of the disclosure as long as the apparatus has a configuration in which the apparatus may be wirelessly supplied with power.

The wireless power transmission apparatus100may be implemented as various kinds of electronic apparatuses which may wirelessly transmit power to the wireless power reception apparatus200.

For example, in a wireless power transmission, the wireless power transmission apparatus100and the wireless power reception apparatus200may be required to be disposed within a predetermined distance from each other. Therefore, the wireless power transmission apparatus100may be implemented as an electronic apparatus which may be disposed within a predetermined distance from the wireless power reception apparatus200depending on the kind of wireless power reception apparatus200.

As a specific example, when the wireless power reception apparatus200is implemented as a TV, the wireless power transmission apparatus100may be implemented as an electronic apparatus generally disposed around the TV, such as a speaker, a set-top box, a sound bar, or the like.

According to an embodiment of the disclosure, the wireless power transmission apparatus100may set an operating frequency for wirelessly transmitting power to the wireless power reception apparatus200even without communicating with the wireless power reception apparatus200. The wireless power transmission apparatus100may wirelessly transmit, to the wireless power reception apparatus200, power through the set operating frequency, and this will be described in greater detail below.

FIG. 2is a block diagram for describing a configuration of a wireless power transmission apparatus according to an embodiment of the disclosure.

Referring toFIG. 2, the wireless power transmission apparatus100includes a power transmitting circuit110and at least one processor120.

The power transmitting circuit110wirelessly transmits power to the wireless power reception apparatus200as shown inFIG. 1. In an embodiment of the disclosure, wirelessly transmitting power describes a magnetic induction field that is formed by applying a current to a coil in the power transmitting circuit110. Similarly, in an embodiment of the disclosure, wirelessly receiving power describes a coil that generates an induced electromotive force from a magnetic field formed around the wireless power reception apparatus200.

The power transmitting circuit110may provide power that the wireless power transmission apparatus100requires, and wirelessly provide the power to the wireless power reception apparatus200. The power transmitting circuit110may supply power with an alternating current (AC) waveform, and may also supply power with the AC waveform by converting power with a direct current (DC) waveform into the power with the AC waveform by using an inverter. The power transmitting circuit110may be implemented in a form which includes a battery, or may be implemented in a form which includes a power reception interface to receive power from an outside source.

InFIG. 1, the electromagnetic inductive coupling and the resonant magnetic coupling are described as representative examples of the wireless power transmission manner. However, the use of the electromagnetic inductive coupling and the resonant magnetic coupling as the wireless power transmission manner is merely one embodiment, and the wireless power transmitter110is not limited to wirelessly transmit power by using the electromagnetic inductive coupling or the resonant magnetic coupling. That is, a wireless power transmission manner commercialized in future with technology development may also be used by the power transmitting circuit110to wirelessly transmit power.

The processor120is a component for controlling a general operation of the wireless power transmission apparatus100.

In detail, the processor120may control various hardware and/or software components included in the wireless power transmission apparatus100, and perform various data processing and operations. To this end, the processor120may be implemented as a dedicated processor (for example, an embedded processor) for performing a corresponding operation or as a generic-purpose processor (for example, a central processing unit (CPU)) capable of performing corresponding operations by executing one or more software programs stored in a memory device (not shown).

The processor120may control a magnitude of power transmitted by the power transmitting circuit110. The processor120may control the magnitude of the power wirelessly transmitted by the power transmitting circuit110by, for example, changing a frequency of a voltage applied to the power transmitting circuit110, but embodiments are not limited thereto.

In addition, the processor120may control the magnitude of the power transmitted by the power transmitting circuit110by changing a magnitude of the voltage applied to the power transmitting circuit110. For example, the processor120may transmit low power to the wireless power reception apparatus200by applying a voltage low enough not to drive a load of the wireless power reception apparatus200. Further, the processor120may allow the power transmitting circuit110to transmit adequate power to drive the wireless power reception apparatus200by applying a voltage of which a magnitude is enough to drive the wireless power reception apparatus200. Here, the driving of the wireless power reception apparatus200means that the wireless power reception apparatus200performs a function thereof. For example, in the case where the wireless power reception apparatus200is a TV, the TV in an ON state may display a screen to a user. In this connection, in an embodiment of the disclosure, a voltage high enough to drive the wireless power reception apparatus200is referred to as a driving voltage.

The processor120may use a pilot voltage to identify the driving voltage. In an embodiment of the disclosure, the pilot voltage means a voltage that is applied to the power transmitting circuit110before the wireless power transmission apparatus100wirelessly transmits power to the wireless power reception apparatus200to set an operating frequency and the driving voltage for driving the wireless power reception apparatus200.

A magnitude of the pilot voltage may be small enough so as not to strain the wireless power reception apparatus200even when the wireless power transmission apparatus100wirelessly transmits power while scanning a frequency in a predetermined range. For example, when a magnitude of an alternating current (AC) voltage input to the wireless power transmission apparatus100is 311 V, the pilot voltage may be set to 25 V. However, the magnitude of the pilot voltage is not necessarily limited thereto, and may vary depending on characteristics of the wireless power transmission apparatus100.

The processor120may transmit, via the power transmitting circuit, a pilot power with changing a frequency of the pilot power within the predetermined frequency range. Here, the pilot power may having the pilot voltage.

The processor120may obtain a magnitude of power wirelessly transmitted to the wireless power reception apparatus200based on the transmitted pilot power. The processor120may identify a magnitude of power wirelessly transmitted to the wireless power reception apparatus200by the pilot voltage by changing a frequency of the pilot voltage within a predetermined frequency range.

The processor120may determine the operating frequency based on the obtained magnitude. The processor120may set a certain frequency within the predetermined frequency range as the operating frequency based on a magnitude of the wirelessly transmitted power identified by using the pilot voltage.

Here, the operating frequency is a frequency of a voltage applied to the power transmitting circuit110to wirelessly transmit power to the wireless power reception apparatus200, and may be a frequency with the highest wireless power transmission efficiency in the predetermined frequency range. The wireless power transmission efficiency being high means that a ratio of a magnitude of power wirelessly received by the wireless power reception apparatus200to a magnitude of power wirelessly transmitted by the wireless power transmission apparatus100is high.

After identifying the operating frequency by using the pilot power, the processor120may identify the driving voltage or driving power at which the wireless power reception apparatus200may be driven by increasing a magnitude of the voltage at the identified operating frequency.

In detail, when the wireless power transmission apparatus100wirelessly transmits the power to the wireless power reception apparatus200by using the pilot voltage, the wireless power reception apparatus200wirelessly receiving the power may not perform its original function because the magnitude of the pilot voltage is small.

However, some components of the wireless power reception apparatus200wirelessly receiving the power by using the pilot voltage may be operated. For example, when wirelessly receiving the power by using the pilot voltage, a communicator of the wireless power reception apparatus200is switched into an ON state, such that the wireless power reception apparatus200may communicate with the wireless power transmission apparatus100.

The wireless power reception apparatus200in a state where it may perform communication may transmit, to the wireless power transmission apparatus100, information such as a voltage of a wireless power receiver (not illustrated), a power consumption, or the like.

The wireless power transmission apparatus100may obtain (or predict) a magnitude of power required to drive the wireless power reception apparatus200by using the information received from the wireless power reception apparatus200, such as the voltage of the wireless power receiver (not illustrated), the power consumption, or the like. The wireless power transmission apparatus100may increase the magnitude of the voltage applied to the power transmitting circuit110to wirelessly transmit power at the magnitude required to drive the wireless power reception apparatus200.

In detail, the processor120may identify whether the magnitude of the power transmitted by the power transmitting circuit110is equal to the magnitude of the power required to drive the wireless power reception apparatus200while increasing the magnitude of the voltage applied at the operating frequency identified by using the pilot voltage.

The processor120may increase the magnitude of the voltage applied to the power transmitting circuit110until the magnitude of the power transmitted by the power transmitting circuit110is equal to the magnitude of the power required to drive the wireless power reception apparatus200.

Then, the processor120may identify the magnitude of the voltage applied to the power transmitting circuit110as the driving voltage when the magnitude of the power transmitted by the power transmitting circuit110is equal to the magnitude of the power required to drive the wireless power reception apparatus200.

As such, the processor120may identify the operating frequency at which the power is wirelessly transmitted to the wireless power reception apparatus200by using the pilot voltage and identify the driving voltage applied to the power transmitting circuit110when transmitting the power required to drive the wireless power reception apparatus200by increasing the magnitude of the voltage at the operating frequency.

FIG. 3is a diagram for describing a wireless power transmission apparatus according to an embodiment of the disclosure in detail.

Referring toFIG. 3, the power transmitting circuit110of the wireless power transmission apparatus100may include a power supplier150, an inverter140, and a resonator130.

The power supplier150may generate a certain level of DC voltage by using power input from an outside source or from an internal battery. For example, the power supplier150may receive a commercial AC voltage from the outside, convert the commercial AC voltage into a DC voltage, and convert the DC voltage into a certain level of DC voltage.

The inverter140may receive the DC voltage and output an AC voltage through a switching operation of a switch141.

The resonator130may receive the AC voltage and be magnetically coupled to a resonator (not shown) of the wireless power reception apparatus200, thereby wirelessly providing power. To this end, the resonator130may include a coil131.

The processor120may control the power transmitting circuit110to apply a voltage to the coil131of the power transmitting circuit110.

In detail, the processor120may control the power supplier150to generate a certain level of DC voltage, such that the certain level of DC voltage is supplied to the inverter140. Further, the processor120may control the switching operation of the switch141to adjust a magnitude or frequency of an AC voltage output from the inverter140, thereby adjusting a magnitude or frequency of the AC voltage applied to the coil131.

The processor120may set the operating frequency of the voltage applied to the coil131to wirelessly transmit power to the wireless power reception apparatus200.

In detail, when the wireless power transmission apparatus100or the wireless power reception apparatus200is disposed at a position other than a predetermined position for a resonance characteristic, the resonance characteristic may be changed. In this case, the wireless power transmission apparatus100needs to set the driving voltage and the operating frequency depending on the changed resonance characteristic.

The switch141of the inverter140may be implemented as a transistor. Although two transistors are illustrated inFIG. 3, this is only an example, and the number and/or arrangement of transistors is not limited thereto.

When a positive voltage ((+) voltage) is applied to one of the two transistors, the transistor to which the positive voltage is applied is switched ON, and a negative voltage ((−) voltage) is applied to the other transistor, such that the transistor to which the negative voltage is applied is switched OFF. In contrast, when the negative voltage is applied to one of the two transistors, the transistor to which the negative voltage is applied is switched OFF, and the positive voltage is applied to the other transistor, such that the transistor to which the positive voltage is applied is switched ON.

The processor120may perform the switching operation by changing a direction and a cycle of an input voltage Vin applied to each transistor of the power transmitting circuit110. Further, the processor120may convert the DC voltage applied to the power transmitting circuit110into an AC voltage through the switching operation as described above, thereby applying the AC voltage to the coil131of the power transmitting circuit110.

At a point in time when the voltage applied to the transistor is changed from positive (+) to negative (−), or from negative (−) to positive (+), a voltage across the transistor may be 0 V. That is, the voltage across the switch may be substantially 0 V at a point in time when the switch is turned ON or turned OFF, and such a state is referred to as zero voltage switching (ZVS).

The processor120may identify a ZVS region through the switching operation in the power transmitting circuit110. That is, when the pilot voltage is applied to the wireless power transmission apparatus100, the processor120may identify the ZVS region of the wireless power transmission apparatus100through the switching operation in the power transmitting circuit110.

The processor120may identify the ZVS region through the switching operation after applying the pilot voltage to the wireless power transmission apparatus100, and identify that the wireless power reception apparatus may be driven at a certain frequency in the ZVS region of the wireless power transmission apparatus100.

The resonator130may include the at least one coil131, which is a component for generating a magnetic field required to transmit power from the wireless power transmission apparatus100to the wireless power reception apparatus200.

When the wireless power transmission apparatus100transmits power only by the electromagnetic inductive coupling, the resonator130may include only an induction coil, and when the wireless power transmission apparatus100transmits power only by the resonant magnetic coupling, the resonator130may include only a resonant coil. When the wireless power transmission apparatus100transmits power by a combination of the electromagnetic inductive coupling and the resonant magnetic coupling, the resonator130may include both of the induction coil and the resonant coil. In addition, one induction coil or resonant coil may be provided, or a plurality of induction coils or resonant coils may be provided.

An AC voltage generated through the switching operation of the transistors is applied to the coil131. A magnetic field is generated as an AC current of which a magnitude varies depending on a frequency of the AC voltage flows, and the wireless power transmission apparatus100may transmit power to the wireless power reception apparatus200by using the generated magnetic field. In detail, as a current is induced in a coil (not shown) of the wireless power reception apparatus200under the influence of the magnetic field generated in the wireless power transmission apparatus100, the power may be transmitted to elements within the wireless power reception apparatus200.

The wireless power reception apparatus200may include the resonator (not illustrated) and a device load (not illustrated).

The device load comprises a resistance applied to the wireless power reception apparatus200. The value of the device load may vary depending on the kind or state of the wireless power reception apparatus200. For example, in a state where the TV is turned off, a value of the device load from the point of view of the TV may be 3000Ω. In addition, a capacitance of the device load may be increased or decreased by connecting or removing a resistor with or from the device load.

The resonator (not illustrated) of the wireless power reception apparatus200may include at least one of the induction coil or the resonant coil, similar to the resonator130of the wireless power transmission apparatus100. The coil of the wireless power reception apparatus200may receive power wirelessly transmitted from the wireless power transmission apparatus100by using the magnetic field generated in the wireless power transmission apparatus100. In this case, a magnitude of the power received by the wireless power reception apparatus200may vary depending on the wireless power transmission efficiency.

A graph ofFIG. 4Ashows a magnitude of wirelessly transmitted power with respect to a frequency according to an embodiment of the disclosure.

A graph ofFIG. 4Bshows wireless power transmission efficiency with respect to a frequency according to an embodiment of the disclosure.

Referring toFIG. 4A, graphs310and320show a magnitude of wirelessly transmitted power with respect to a frequency of the pilot voltage when applying the pilot voltage to the wireless power reception apparatus200, and a magnitude of wirelessly transmitted power with respect to a frequency of the driving voltage when applying the driving voltage to the wireless power reception apparatus200, respectively. A horizontal axis of the graph ofFIG. 4Arepresents a frequency of a voltage applied to the wireless power reception apparatus200, and a vertical axis represents a magnitude of power wirelessly received by the wireless power reception apparatus200.

As illustrated inFIG. 4A, the graphs310and320have forms that are similar to each other in a frequency range330in which the wireless power reception apparatus200may be driven. Accordingly, a magnitude of the wirelessly transmitted power at the driving voltage may be obtained by using the pilot voltage.

In detail, the processor120may obtain the magnitude of the power wirelessly transmitted to the wireless power reception apparatus200by using the pilot voltage by changing a frequency of the pilot voltage within a predetermined frequency range, the pilot voltage having a predetermined magnitude and being applied to the coil131.

The processor120may set a certain frequency within the predetermined frequency range as the operating frequency based on the magnitude of the wirelessly transmitted pilot power identified by using the pilot power, and wirelessly transmit the driving power having the operating frequency to drive the wireless power reception apparatus200by applying the driving voltage having the operating frequency to the coil131.

Here, the predetermined frequency range may be a frequency range in which the wireless power reception apparatus200may be driven.

In detail, the processor120may identify the magnitude of the power wirelessly transmitted to the wireless power reception apparatus200by the pilot voltage by changing the frequency of the pilot voltage.

That is, as the frequency of the pilot voltage applied to the coil131is changed, a magnitude of a current flowing through the coil131is changed and thus, the magnitude of the power transmitted to the wireless power reception apparatus200is also changed. Here, the magnitude of the power transmitted to the wireless power reception apparatus200is in proportion to the magnitude of the current input to the coil131. Therefore, the processor120may detect the magnitude of the current input to the coil131while the pilot voltage is applied to the coil131and obtain the power wirelessly transmitted to the wireless power reception apparatus based on the detected magnitude.

Further, the processor120may set a certain frequency within the predetermined frequency range as the operating frequency based on the magnitude of the power wirelessly transmitted by the wireless power transmission apparatus100by the pilot voltage.

To this end, the processor120may identify a frequency range in which the wireless power reception apparatus200may be driven based on the magnitude of the power wirelessly transmitted by the wireless power transmission apparatus100by the pilot voltage.

For example, a case where the magnitude of the power transmitted to the wireless power reception apparatus200is as shown by the graph310ofFIG. 4Ais assumed, the magnitude is obtained by using the pilot voltage.

Referring toFIG. 4A, the magnitude of the power transmitted to the wireless power reception apparatus100may be plotted as a graph having three inflection points.

Here, among the three inflection points of the graph310ofFIG. 4A, an inflection point where a value of the frequency is smallest is referred to as a first inflection point, an inflection point where the value of the frequency is next smallest is referred to as a second inflection point, and an inflection point where the value of the frequency is largest is referred to as a third inflection point. In this case, the magnitude of the wirelessly transmitted power is largest at the first inflection point. In addition, it may be appreciated that a change amount of the power depending on the frequency of the pilot voltage from the first inflection point to the second inflection point is similar to that of the power depending on the frequency of the driving voltage from the first inflection point to the second inflection point.

Here, the processor120may identify the frequency range330between the first inflection point and the second inflection point as the frequency range in which the wireless power reception apparatus200may be driven.

A form of the graph may be changed depending on a resonant topology. For example, the form of the graph may also be plotted as a graph having two inflection points in some cases. Even in this case, the magnitude of the wirelessly transmitted power is largest at a first inflection point, and a frequency range330between the first inflection point and a second inflection point may be identified as the frequency range in which the wireless power reception apparatus200may be driven.

Here, a region in which the magnitude of the wirelessly transmitted power is decreased with the increase of the frequency corresponds to the ZVS region as described above. Therefore, the frequency range330between the first inflection point and the second inflection point may correspond to the ZVS region of the wireless power transmission apparatus100.

The processor120may set a certain frequency within a predetermined frequency range as the operating frequency. Here, the predetermined frequency range may be the frequency range330between the first inflection point and the second inflection point described above, that is, the ZVS region of the wireless power transmission apparatus100. In detail, the processor120may identify the operating frequency in consideration of transmission efficiency of the power wirelessly transmitted from the wireless power transmission apparatus100to the wireless power reception apparatus200.

In detail, the transmission efficiency of the power wirelessly transmitted from the wireless power transmission apparatus100to the wireless power reception apparatus200may vary depending on the frequency. For example, the transmission efficiency may be plotted as the graph350ofFIG. 4B.

Referring toFIG. 4B, the wireless power transmission efficiency may be plotted as a two-directional curve in a form in which the wireless power transmission efficiency is increased with the increase of the frequency, and is decreased again.

Therefore, it may be appreciated that the wireless power transmission efficiency is increased with the increase of the frequency in the frequency range330in which the wireless power reception apparatus200may be driven, that is, the ZVS region. That is, the wireless power transmission efficiency is highest in a region in which the frequency is highest in the ZVS region, that is, at the second inflection point.

However, in case that the second inflection point at which the wireless power transmission efficiency is highest is set as the operating frequency, when power is wirelessly transmitted at a frequency any larger than the operating frequency, an excessive amount of power, that is out of the frequency range in which the wireless power reception apparatus200may be driven, is transmitted to the wireless power reception apparatus200, such that the wireless power reception apparatus200may be overloaded.

In order to prevent the problem as described above from occurring, according to the embodiment of the disclosure, a frequency smaller than the frequency at the second inflection point by a predetermined frequency may be set as the operating frequency340.

The processor120may identify the magnitude of the driving voltage by increasing the magnitude of the pilot voltage after setting the operating frequency. In detail, the processor120identifies the magnitude of the generated power by increasing the magnitude of the voltage at the operating frequency. In this case, when the magnitude of the generated power is equal to a magnitude of adequate power for wireless power transmission, a voltage of the generated power may be identified as the driving voltage.

Here, adequate power means a value of power predetermined in consideration of characteristics of the wireless power reception apparatus200, and may have a different value depending on the kind of wireless power reception apparatus200, or the like. The wireless power transmission apparatus100may store information on the value of the adequate power in a storage (not illustrated).

As such, the processor120may identify the driving voltage by using the operating frequency and the adequate power, and wirelessly transmit, to the wireless power reception apparatus200, the power required to drive the wireless power reception apparatus200.

When wirelessly receiving the power of which the magnitude is equivalent to the adequate power, the wireless power reception apparatus200may turn on the wireless power reception apparatus200. Further, when the wireless power reception apparatus200, which is turned on, includes the communicator (not illustrated), the wireless power reception apparatus200may communicate with other electronic apparatuses including the wireless power transmission apparatus100.

FIG. 5is a flowchart for describing a wireless power transmission method according to an embodiment of the disclosure.

Referring toFIG. 5, a pilot power is transmitted with changing a frequency of the pilot power within a predetermined frequency range at 5510.

Then, a magnitude of power wireless transmitted to a wirelessly power reception apparatus is obtained based on the transmitted pilot power at5520.

Here, the magnitude of the pilot power may be smaller than that of the driving power.

Further, a magnitude of a current input to the coil while the pilot voltage is applied to the coil may be detected, and the magnitude of the power wirelessly transmitted to the wireless power reception apparatus200may be obtained based on the detected magnitude of the current.

Then, the operating frequency is determined based on the obtained magnitude at5530. In detail, when the wireless power transmission apparatus100wirelessly transmits the power to the wireless power reception apparatus200by using the pilot power, the magnitude of the wirelessly transmitted power may vary depending on the frequency. The wireless power transmission apparatus100may identify the operating frequency in a region in which the magnitude of the power wirelessly transmitted to the wireless power reception apparatus200is decreased. That is, a certain frequency within the predetermined frequency range may be set as the operating frequency based on the magnitude of the power wirelessly transmitted by the wireless power transmission apparatus100by using the pilot voltage.

Then, a driving power having the operating frequency to drive the wireless power reception apparatus200is transmitted at5540.

Then, a DC voltage may be converted into an AC voltage through the switching operation of the switch and the AC voltage may be applied to the coil.

Further, a frequency range in which the switching operation of the switch is performed so that a voltage across the switch is 0 V may be identified within the predetermined frequency range based on the magnitude of the power wirelessly transmitted to the wireless power reception apparatus200, and a certain frequency within the identified frequency range may be set as the operating frequency. In detail, when the wireless power transmission apparatus200wirelessly transmits the power to the wireless power reception apparatus200by using the pilot voltage, a region in which the magnitude of the wireless transmitted power is decreased as the frequency is increased appears, and this region corresponds to the ZVS region. Accordingly, it is possible to identify the ZVS region, and a certain frequency within the ZVS region may be set as the operating frequency.

Any of the wireless power transmission methods according to the various embodiments described above may be implemented as a program and be provided to the wireless power transmission apparatus. Particularly, a program including the wireless power transmission method may be stored and provided in a non-transitory computer-readable medium.

The non-transitory computer-readable medium is not a medium that stores data therein for a while, such as a register, a cache, a memory, or the like, but means a medium that semi-permanently stores data therein and is readable by an apparatus. In detail, the programs or applications for the wireless power transmission method may be stored and provided in the non-transitory computer readable medium such as a compact disk (CD), a digital versatile disk (DVD), a hard disk, a Blu-ray disk, a universal serial bus (USB), a memory card, a read only memory (ROM), or the like.

As described above, according to various embodiments of the disclosure, the wireless power transmission apparatus100may wirelessly transmit power to the wireless power reception apparatus200. In particular, the power required to drive the wireless power reception apparatus200may be transmitted without performing communication between the wireless power transmission apparatus100and the wireless power reception apparatus200. Therefore, a time for which the wireless power reception apparatus200is switched from an OFF state to the ON state may be shortened.

Further, various embodiments of the disclosure have been described above, but the content of the disclosure is not limited to the embodiments described above. Accordingly, various modifications may be made by those having ordinary knowledge in the art to which the disclosure pertains without departing from the gist of the disclosure as disclosed in the accompanying claims. These modifications should also be understood to fall within the scope and spirit of the disclosure.