Abstract:
The present disclosure relates to a sensor network, machine type communication (MTC), machine-to-machine (M2M) communication, and technology for internet of things (IoT). The present disclosure may be applied to intelligent services based on the above technologies, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method for transmitting power transmitting unit (PTU) presence information is provided. The method includes receiving an advertisement message from a power receiving unit (PRU); determining whether a current state is a state that power is supplied to a resonator; and outputting PTU presence information indicating that a PTU exists, or transmitting the PTU presence information to a management server, if the current state is the state that the power is not supplied to the resonator.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Oct. 8, 2014 assigned Serial No. 10-2014-0135787, the entire disclosure of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to an apparatus and method for transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network, and more particularly, to an apparatus and method for transmitting/receiving PTU presence information based on a Bluetooth low energy (BLE) scheme in a wireless charging network. 
       BACKGROUND 
       [0003]    The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the internet of things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The internet of everything (IoE), which is a combination of the IoT technology and the big data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a machine-to-machine (M2M) communication, machine type communication (MTC), and so forth have been recently researched. 
         [0004]    Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing information technology (IT) and various industrial applications. 
         [0005]    Mobile terminals such as a mobile phone, a personal digital assistant (PDA) and the like are driven with rechargeable batteries due to their nature, and the battery of the mobile terminal is charged through supplied electronic energy by using a separate charging apparatus. In general, separate contact terminals are arranged outside of the charging apparatus and the battery, and the charging apparatus and the battery are electrically connected to each other through contact between the contact terminals. 
         [0006]    However, since the contact terminal of each of the charging apparatus and the battery is outwardly protruded in such a contact type charging scheme, the contact terminal is easily contaminated by a rogue object and thus the battery charging is not correctly performed. Further, the battery charging may also not be correctly performed in a case where the contact terminal is exposed to moisture. 
         [0007]    Recently, various charging schemes such as a wireless charging scheme, a non-contact charging scheme, and the like have been developed and used for electronic devices to prevent abnormal charging in the contact type charging scheme. 
         [0008]    Such a wireless charging scheme is based on wireless power transmission/reception, and corresponds to, for example, a system in which a battery can be automatically charged if the battery is laid on a charging pad without the need of a connection between the mobile phone and a separate charging connector. In general, the wireless charging scheme is known to be found in wireless electrical toothbrushes or wireless electric shavers. Accordingly, a waterproof function can be improved since electronic products are wirelessly charged through the wireless charging scheme, and the portability of electronic devices can be increased since there is no need to provide a wired charging apparatus. Therefore, schemes related to the wireless charging scheme are expected to be significantly developed in the coming age of electric cars. 
         [0009]    The wireless charging scheme largely includes an electromagnetic induction scheme using a coil, a resonance scheme using a resonance, and a radio frequency (RF)/microwave radiation scheme converting electrical energy to a microwave and then transmitting the microwave. 
         [0010]    Up to now, the electromagnetic induction scheme is considered mainstream, but it is expected that the day will come when all electronic products are wirelessly charged, anytime and anywhere, without a wire in the near future. The expectation is strengthened due to recent successful experiments that wirelessly transmitted power to a destination spaced away by dozens of meters through the use of microwaves at home and abroad. 
         [0011]    The electromagnetic induction scheme transmits electric power between a primary coil and a secondary coil. When a magnet is moved in a coil, an induction current occurs. By using the induction current, a magnetic field is generated at a transferring end, and electric current is induced according to a change of the magnetic field so as to make energy at a reception end. The phenomenon is referred to as magnetic induction, and the electromagnetic induction scheme using magnetic induction has high energy transmission efficiency. 
         [0012]    With respect to the resonance scheme, Prof. Soljacic of Massachusetts Institute of Technology (MIT) announced a system in which electricity is wirelessly transferred using an electric power transmission principle of the resonance scheme based on a coupled mode theory to allow a device to be charged even when the device is separated from a charging device by several meters (m). The MIT team&#39;s wireless charging system employs resonance, which is the tendency for a tuning fork to oscillate at a particular frequency causing a wine glass next to the tuning fork to oscillate at the same frequency. The research team makes an electromagnetic wave containing resonating electrical energy instead of making resonating sounds. The resonating electrical energy is directly transferred only when there is a device having a resonance frequency and having parts of electrical energy which are not used and instead are reabsorbed into an electromagnetic field. Since the electrical energy is reabsorbed into an electromagnetic field instead of spreading in the air, unlike other electromagnetic waves, the electrical energy does not affect surrounding devices or people. 
         [0013]    Meanwhile, a power receiving unit (PRU) wirelessly receives power from a PTU. In order to normally receive the power from the PTU, the PTU needs to exist within a range that it is possible to perform a wireless charging operation with the PTU. So, in order for the PRU to exist within the range that it is possible to perform the wireless charging operation with the PTU, the PTU needs to detect information regarding whether the PTU exists. 
         [0014]    However, in wireless charging schemes which have been proposed up to now, a PTU does not inform a location of the PTU, so a PRU may not detect whether the PTU exists. 
         [0015]    For example, a PRU may be a mobile station, and a PTU may be a wireless charging apparatus. Generally, the wireless charging apparatus is located at the interior or exterior of a building, and does not transmit information indicating that the wireless charging apparatus exists. So, a user of the mobile station does not discover the wireless charging apparatus, and the user suffers the inconvenience of wandering in or out of the building in order to discover the location of the wireless charging apparatus. Thus, the user of the mobile station may not discover the wireless charging apparatus at all. In this case, the user of the mobile station may not get to charge a battery of the mobile station. 
         [0016]    So, there is a need for a scheme to transmit/receive PTU presence information in a wireless charging network. 
         [0017]    The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
       SUMMARY 
       [0018]    An aspect of the present disclosure is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to propose an apparatus and method for transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network. 
         [0019]    Another aspect of the present disclosure is to propose an apparatus and method for transmitting/receiving PTU presence information based on a Bluetooth Low Energy (BLE) scheme in a wireless charging network. 
         [0020]    Another aspect of the present disclosure is to propose an apparatus and method for transmitting/receiving PTU presence information thereby enabling transmitting/receiving PTU presence information when power is supplied to a resonator included in a PTU in a wireless charging network. 
         [0021]    Another aspect of the present disclosure is to propose an apparatus and method for transmitting/receiving PTU presence information thereby enabling transmitting/receiving PTU presence information even though power is supplied to a resonator included in a PTU, receiving a signal strength of an advertisement message from a PRU and determining whether the received signal strength is less than a threshold received signal strength in a wireless charging network. 
         [0022]    In accordance with an aspect of the present disclosure, a method for transmitting power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes receiving an advertisement message from a power receiving unit (PRU); determining whether a current state is a state that power is not supplied to a resonator; and outputting PTU presence information indicating that a PTU exists, or transmitting the PTU presence information to a management server, if the current state is the state that the power is supplied to the resonator. 
         [0023]    In accordance with another aspect of the present disclosure, a method for transmitting power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes receiving an advertisement message from a power receiving unit (PRU); determining whether a current state is a state that power is not supplied to a resonator; determining whether received signal strength of the advertisement message received from the PRU is greater than or equal to threshold received signal strength if the current state is the state that the power is supplied to the resonator; and outputting PTU presence information indicating that a PTU exists if the received signal strength of the advertisement message received from the PRU is greater than or equal to the threshold received signal strength. 
         [0024]    In accordance with another aspect of the present disclosure, a method for receiving power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes transmitting an advertisement message to a PTU; and receiving PTU presence information from a management server, wherein the PTU presence information is transmitted to the management server if a state of the PTU is a state that power is supplied to a resonator when the PTU corresponding to the PTU presence information receives the advertisement message from a power receiving unit (PRU). 
         [0025]    In accordance with another aspect of the present disclosure, a method for receiving power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes transmitting an advertisement message to a PTU; and receiving PTU presence information from a management server, wherein the PTU presence information is transmitted to the management server if a state of the PTU is a state that power is supplied to a resonator and received signal strength which is received in the PTU is less than threshold received signal strength when the PTU corresponding to the PTU presence information receives the advertisement message from a power receiving unit (PRU). 
         [0026]    In accordance with another aspect of the present disclosure, a method for transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes receiving PTU presence information from a PTU; and transmitting the PTU presence information to a power receiving unit (PRU), wherein the PTU presence information is transmitted to a management server if a state of the PTU is a state that power is supplied to a resonator when the PTU corresponding to the PTU presence information receives an advertisement message from the PRU. 
         [0027]    In accordance with another aspect of the present disclosure, a method for transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network is provided. The method includes receiving PTU presence information from a PTU; and transmitting the PTU presence information to a power receiving unit (PRU), wherein the PTU presence information is transmitted to a management server if a state of the PTU is a state that power is supplied to a resonator and received signal strength of an advertisement message which the PTU receives is less than threshold received signal strength when the PTU corresponding to the PTU presence information receives the advertisement message from the PRU. 
         [0028]    In accordance with another aspect of the present disclosure, a power transmitting unit (PTU) in a wireless charging network is provided. The PTU includes a receiver configured to perform an operation of receiving an advertisement message from a power receiving unit (PRU); and a controller configured to perform an operation of determining whether a current state is a state that power is not supplied to a resonator, and an operation of outputting PTU presence information indicating that a PTU exists, or transmitting the PTU presence information to a management server, if the current state is the state that the power is supplied to the resonator. 
         [0029]    In accordance with another aspect of the present disclosure, a power transmitting unit (PTU) in a wireless charging network is provided. The PTU includes a receiver configured to perform an operation of receiving an advertisement message from a power receiving unit (PRU); and a controller configured to perform an operation of determining whether a current state is a state that power is not supplied to a resonator, an operation of determining whether received signal strength of the advertisement message received from the PRU is greater than or equal to threshold received signal strength if the current state is the state that the power is supplied to the resonator, and an operation of controlling to output PTU presence information indicating that a PTU exists if the received signal strength of the advertisement message received from the PRU is greater than or equal to the threshold received signal strength. 
         [0030]    In accordance with another aspect of the present disclosure, a power receiving unit (PRU) in a wireless charging network is provided. The PRU includes a transmitter configured to perform an operation of transmitting an advertisement message to a power transmitting unit (PTU); and a receiver configured to perform an operation of receiving PTU presence information from a management server, wherein the PTU presence information is transmitted to the management server if a state of the PTU is a state that power is supplied to a resonator when the PTU corresponding to the PTU presence information receives the advertisement message from the PRU. 
         [0031]    In accordance with another aspect of the present disclosure, a power receiving unit (PRU) in a wireless charging network is provided. The PRU includes a transmitter configured to perform an operation of transmitting an advertisement message to a power transmitting unit (PTU); and a receiver configured to perform an operation of receiving PTU presence information from a management server, wherein the PTU presence information is transmitted to the management server if a state of the PTU is a state that power is supplied to a resonator and a received signal strength received in the PTU is less than a threshold received signal strength when the PTU corresponding to the PTU presence information receives the advertisement message from the PRU. 
         [0032]    In accordance with another aspect of the present disclosure, a management server in a wireless charging network is provided. The management server includes a receiver configured to perform an operation of receiving power transmitting unit (PTU) presence information from a PTU; and a transmitter configured to perform an operation of transmitting the PTU presence information to a power receiving unit (PRU), wherein the PTU presence information is transmitted to a management server if a state of the PTU is a state that power is supplied to a resonator when the PTU corresponding to the PTU presence information receives an advertisement message from the PRU. 
         [0033]    In accordance with another aspect of the present disclosure, a management server in a wireless charging network is provided. The management server includes a receiver configured to perform an operation of receiving power transmitting unit (PTU) presence information from a PTU; and a transmitter configured to perform an operation of transmitting the PTU presence information to a power receiving unit (PRU), wherein the PTU presence information is transmitted to a management server if a state of the PTU is a state that power is supplied to a resonator and received signal strength of an advertisement message which the PTU receives is less than threshold received signal strength when the PTU corresponding to the PTU presence information receives the advertisement message from the PRU. 
         [0034]    Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure. 
         [0035]    Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The above and other aspects, features and advantages of certain exemplary embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
           [0037]      FIG. 1  schematically illustrates a structure of a wireless charging network according to an embodiment of the present disclosure; 
           [0038]      FIG. 2  schematically illustrates an example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure; 
           [0039]      FIG. 3  schematically illustrates another example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure; 
           [0040]      FIG. 4  schematically illustrates an example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure; 
           [0041]      FIG. 5  schematically illustrates another example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure; 
           [0042]      FIG. 6  schematically illustrates a graph on a time axis of a power amount which a PTU in  FIG. 5  applies; 
           [0043]      FIG. 7  schematically illustrates an operation of a PRU in a case that an error including a cross-connection occurs in a wireless charging network according to an embodiment of the present disclosure; 
           [0044]      FIG. 8  schematically illustrates a graph on a time axis of an amount of power which a PTU in  FIG. 7  supplies; 
           [0045]      FIG. 9  schematically illustrates an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0046]      FIG. 10  is a graph on an x axis of an amount of power supplied by a PTU in  FIG. 9 ; 
           [0047]      FIG. 11  schematically illustrates an inner structure of each of a PTU and a PRU in an SA mode in a wireless charging network according to an embodiment of the present disclosure; 
           [0048]      FIG. 12  schematically illustrates an advertisement procedure and a discovery procedure in a conventional wireless charging network; 
           [0049]      FIG. 13  schematically illustrates an example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0050]      FIG. 14  schematically illustrates another example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0051]      FIG. 15  schematically illustrates an example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure; 
           [0052]      FIG. 16  schematically illustrates another example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure; 
           [0053]      FIG. 17  schematically illustrates an example of a process of transmitting PTU presence information to a PRU through a management server in a PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0054]      FIG. 18  schematically illustrates an example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure; 
           [0055]      FIG. 19  schematically illustrates another example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure; 
           [0056]      FIG. 20  schematically illustrates a process of transmitting wireless charging operation state information for a specific PRU to an associated PRU which is associated with the specific PRU in a state that a wireless charging operation is performed between a PTU and the specific PRU in a wireless charging network according to an embodiment of the present disclosure; 
           [0057]      FIG. 21  schematically illustrates an example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0058]      FIG. 22  schematically illustrates another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0059]      FIG. 23  schematically illustrates still another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure; 
           [0060]      FIG. 24  schematically illustrates an inner structure of a PTU in a wireless charging network according to an embodiment of the present; 
           [0061]      FIG. 25  schematically illustrates an inner structure of a PRU in a wireless charging network according to an embodiment of the present; and 
           [0062]      FIG. 26  schematically illustrates an inner structure of a management server in a wireless charging network according to an embodiment of the present. 
       
    
    
       [0063]    Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. 
       DETAILED DESCRIPTION 
       [0064]    The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
         [0065]    The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
         [0066]    It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
         [0067]    Although ordinal numbers such as “first,” “second,” and so forth will be used to describe various components, those components are not limited herein. The terms are used only for distinguishing one component from another component. For example, a first component may be referred to as a second component and likewise, a second component may also be referred to as a first component, without departing from the teaching of the inventive concept. The term “and/or” used herein includes any and all combinations of one or more of the associated listed items. 
         [0068]    The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “has,” when used in this specification, specify the presence of a stated feature, number, step, operation, component, element, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, elements, or combinations thereof. 
         [0069]    The terms used herein, including technical and scientific terms, have the same meanings as terms that are generally understood by those skilled in the art, as long as the terms are not differently defined. It should be understood that terms defined in a generally-used dictionary have meanings coinciding with those of terms in the related technology. 
         [0070]    According to various embodiments of the present disclosure, an electronic device may include communication functionality. For example, an electronic device may be a smart phone, a tablet personal computer (PC), a mobile phone, a video phone, an e-book reader, a desktop PC, a laptop PC, a netbook PC, a personal digital assistant (PDA), a portable multimedia player (PMP), an mp3 player, a mobile medical device, a camera, a wearable device (e.g., a head-mounted device (HMD), electronic clothes, electronic braces, an electronic necklace, an electronic appcessory, an electronic tattoo, or a smart watch), and/or the like. 
         [0071]    According to various embodiments of the present disclosure, an electronic device may be a smart home appliance with communication functionality. A smart home appliance may be, for example, a television, a digital video disk (DVD) player, an audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washer, a dryer, an air purifier, a set-top box, a TV box (e.g., Samsung HomeSync™, Apple TV™, or Google TV™), a gaming console, an electronic dictionary, an electronic key, a camcorder, an electronic picture frame, and/or the like. 
         [0072]    According to various embodiments of the present disclosure, an electronic device may be a medical device (e.g., magnetic resonance angiography (MRA) device, a magnetic resonance imaging (MRI) device, computed tomography (CT) device, an imaging device, or an ultrasonic device), a navigation device, a global positioning system (GPS) receiver, an event data recorder (EDR), a flight data recorder (FDR), an automotive infotainment device, a naval electronic device (e.g., naval navigation device, gyroscope, or compass), an avionic electronic device, a security device, an industrial or consumer robot, and/or the like. 
         [0073]    According to various embodiments of the present disclosure, an electronic device may be furniture, part of a building/structure, an electronic board, electronic signature receiving device, a projector, various measuring devices (e.g., water, electricity, gas or electro-magnetic wave measuring devices), and/or the like that include communication functionality. 
         [0074]    According to various embodiments of the present disclosure, an electronic device may be any combination of the foregoing devices. In addition, it will be apparent to one having ordinary skill in the art that an electronic device according to various embodiments of the present disclosure is not limited to the foregoing devices. 
         [0075]    According to various embodiments of the present disclosure, for example, a power receiving unit (PRU) may be an electronic device. 
         [0076]    An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network. 
         [0077]    An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving PTU presence information based on a Bluetooth low energy (BLE) scheme in a wireless charging network. 
         [0078]    An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving PTU presence information thereby enabling transmitting/receiving PTU presence information when power is supplied to a resonator included in a PTU in a wireless charging network. 
         [0079]    An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving PTU presence information thereby enabling transmitting/receiving PTU presence information even though power is supplied to a resonator included in a PTU and a received signal strength of an advertisement message received from a PRU is less than a threshold received signal strength in a wireless charging network. 
         [0080]    A method and apparatus proposed in various embodiments of the present disclosure may be applied to various mobile communication systems such as a Long Term Evolution (LTE) mobile communication system, an LTE-Advanced (LTE-A) mobile communication system, a High Speed Downlink Packet Access (HSDPA) mobile communication system, a High Speed Uplink Packet Access (HSUPA) mobile communication system, a High Rate Packet Data (HRPD) mobile communication system proposed in a 3rd Generation Project Partnership 2 (3GPP2), a Wideband Code Division Multiple Access (WCDMA) mobile communication system proposed in the 3GPP2, a Code Division Multiple Access (CDMA) mobile communication system proposed in the 3GPP2, an Institute of Electrical and Electronics Engineers (IEEE) 802.16m communication system, an IEEE 802.11 communication system, an Evolved Packet System (EPS), a Mobile Internet Protocol (Mobile IP) system, a Wireless Universal Serial Bus (Wireless USB) system and/or the like. 
         [0081]    In an embodiment of the present disclosure, it will be assumed that a wireless charging network uses a wireless charging scheme which is based on an Alliance for Wireless Power (A4WP) standard. In an embodiment of the present disclosure, a PRU detects a PTU based on a discovery scheme proposed in the BLE scheme. Here, the discovery scheme is a scheme of discovering neighbor devices during a long beacon period. 
         [0082]    Firstly, a concept of a wireless charging system which may be applied to an embodiment of the present disclosure will be described with reference to  FIGS. 1 to 11 , and methods of transmitting/receiving PTU presence information according to various embodiments of the present disclosure will be described with reference to  FIGS. 12 to 26 . 
         [0083]    A structure of a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 1 . 
         [0084]      FIG. 1  schematically illustrates a structure of a wireless charging network according to an embodiment of the present disclosure. 
         [0085]    Referring to  FIG. 1 , the wireless charging network includes a PTU  111 , and at least one PRU, e.g., N PRUs, i.e., a PRU# 1   113 - 1 , a PRU# 2   113 - 2 , . . . , a PRU#N  113 -N. 
         [0086]    The PTU  111  wirelessly transmits power to each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. The PTU  111  may wirelessly transmit power to a PRU which is authenticated through a preset authentication procedure. 
         [0087]    The PTU  111  establishes a wireless connection with each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. For example, the PTU  111  may transmit wireless power to each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N through an electromagnetic wave. 
         [0088]    Each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N receives wireless power from the PTU  111  to perform charging for a battery included in each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. Each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N transmits a message including at least one of a request for transmitting wireless power, information necessary for receiving wireless power, state information of each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N, information for controlling the PTU  111  (i.e., control information), and the like to the PTU  111 . 
         [0089]    Likewise, the PTU  111  transmits a message including at least one of state information of the PTU  111 , information for controlling each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N (i.e., control information), and the like to each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. 
         [0090]    Each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N transmits a message indicating a charging state to the PTU  111 . 
         [0091]    The PTU  111  includes a display unit, and displays a state of each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N based on a message received from each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. The PTU  111  may display information on the amount of time that is expected until charging for each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N is completed. 
         [0092]    The PTU  111  transmits a control signal (or a control message) that controls to disable a wireless charging function to each of the PRU# 1   113 - 1 , the PRU# 2   113 - 2 , . . . , the PRU#N  113 -N. A related PRU receives the control signal, which controls to disable the wireless charging function from the PTU  111 , and disables the wireless charging function. 
         [0093]    A structure of a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 1 , and an example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 2 . 
         [0094]      FIG. 2  schematically illustrates an example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure. 
         [0095]    Referring to  FIG. 2 , a PTU  200  includes a power transmitter  211 , a controller  212 , a communication unit  213 , a display unit  214 , and a storage  215 . A PRU  250  includes a power receiver  251 , a controller  252 , and a communication unit  253 . 
         [0096]    The power transmitter  211  supplies power which the PTU  200  requests, and wirelessly supplies the power to the PRU  250 . The power transmitter  211  may supply the power in an alternating current (AC) waveform, or convert the power of a direct current (DC) waveform into power of the AC waveform using an inverter to supply the power in the AC waveform. 
         [0097]    The power transmitter  211  may be implemented in a form of an embedded battery or in a form of a power receiving interface so as to receive power from outside thereof and supply the power to the other components. It will be easily understood by those skilled in the art that the power transmitter  211  is not limited to supplying power in AC waves. 
         [0098]    The controller  212  controls the overall operation of the PTU  200 . The controller  212  may control the overall operation of the PTU  200  based on an algorithm, a program, or an application requested by a control, which is read from the storage unit  215 . The controller  212  may be implemented in a form such as central processing unit (CPU), a microprocessor, or a mini-computer. 
         [0099]    The communication unit  213  communicates with the PRU  250  based on a preset scheme. The communication unit  213  receives power information from the PRU  250 . Here, the power information includes at least one of a capacity of the PRU  250 , a residual amount of the battery, a number of times of charging, an amount of use, a battery capacity, a proportion of the remaining battery capacity, and the like. Further, the communication unit  213  transmits a charging function control signal controlling a charging function of the PRU  250 . The charging function control signal may be a control signal of controlling the power receiver  251  included in the PRU  250  so as to enable or disable the charging function. The power information may include information on at least one of an insertion of a wire charging terminal, a transition from a stand-alone (SA) mode into a non-stand-alone (NSA) mode, error state release, and the like. 
         [0100]    The communication unit  213  may receive a signal from another PTU (not shown in  FIG. 2 ) as well as the PRU  250 . 
         [0101]    The controller  212  displays a state of the PRU  250  based on the message which is received from the PRU  250  through the communication unit  213  on the display unit  214 . The controller  212  may display time that it is expected until the PRU  250  is fully charged on the display unit  214 . 
         [0102]    While the power transmitter  211 , the controller  212 , the communication unit  213 , the display unit  214 , and the storage  215  are described as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the power transmitter  211 , the controller  212 , the communication unit  213 , the display unit  214 , and the storage  215  may be incorporated into a single unit. 
         [0103]    While the power receiver  251 , the controller  252 , and the communication unit  253  are described as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the power receiver  251 , the controller  252 , and the communication unit  253  may be incorporated into a single unit. 
         [0104]    An example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 2 , and another example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 3 . 
         [0105]      FIG. 3  schematically illustrates another example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure. 
         [0106]    Referring to  FIG. 3 , a PTU  200  includes a power transmitter  211 , a controller/communication unit (MCU &amp; Out-of-band Signaling)  212 / 213 , a driver (Power Supply)  217 , an amplifier (Power Amp)  218 , and a matching unit (Matching Circuit)  216 . A PRU  250  includes a power receiver  251 , a controller/communication unit  252 / 253 , a rectifier  254 , a DC/DC converter  255 , a switching unit (Switch)  256 , and a load unit (Client Device Load)  257 . 
         [0107]    The driver  217  outputs DC power having a preset voltage value. The voltage value of the DC power output from the driver  217  may be controlled by the controller/communication unit  212 / 213 . 
         [0108]    The DC power output from the driver  217  is output to the amplifier  218 . The amplifier  218  amplifies the DC power by a preset gain. Further, the amplifier  218  converts the DC power into AC power based on a signal input from the controller/communication unit  212 / 213 . So, the amplifier  218  outputs the AC power. 
         [0109]    The matching unit  216  performs impedance matching. For example, the matching unit  216  may adjust impedance viewed from the matching unit  216  to control output power to be high efficient or high output power. The matching unit  216  may also adjust impedance based on a control of the controller/communication unit  212 / 213 . The matching unit  216  includes at least one of a coil and a capacitor. The controller/communication unit  212 / 213  controls a connection state with at least one of the coil and the capacitor, and accordingly, performs impedance matching. 
         [0110]    The power transmitter  211  transmits input AC power to the power receiver  251 . The power transmitter  211  and the power receiver  251  may be implemented with resonance circuits which have the same resonance frequency. For example, the resonance frequency may be determined to be 6.78 MHz. 
         [0111]    Meanwhile, the controller/communication unit  212 / 213  communicate with the controller/communication unit  252 / 253  included in the PRU  250 , and perform a communication (WiFi, ZigBee, or BT/BLE), for example, with a bi-directional 2.4 GHz frequency. 
         [0112]    The power receiver  251  receives charging power. 
         [0113]    The rectifier  254  rectifies wireless power received by the power receiver  251  in the form of DC, and is implemented in a form of bridge diode. The DC/DC converter  255  converts the rectified power based on a preset gain. For example, the DC/DC converter  255  converts the rectified power so that a voltage of an output end becomes 5V. Meanwhile, a minimum value and a maximum value of a voltage which may be applied may be preset for a front end of the DC/DC converter  255 . 
         [0114]    The switching unit  256  connects the DC/DC converter  255  to the load unit  257 . The switching unit  256  may be held in an on/off state under a control of the controller  252 . Here, the switching unit  256  may be omitted. If the switching unit  256  is in an on state, the load unit  257  may store converted power which is input from the DC/DC converter  255 . 
         [0115]    Another example of an inner structure of each of a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 3 , and an example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 4 . 
         [0116]      FIG. 4  schematically illustrates an example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure. 
         [0117]    Referring to  FIG. 4 , the wireless charging network includes a PTU  400  and a PRU  450 . The PTU  400  supplies power at operation  401 . If the power is supplied, the PTU  400  may configure an environment at operation  402 . 
         [0118]    The PTU  400  enters a power saving mode at operation  403 . In the power saving mode, the PTU  400  applies different types of power detection beacons by their own periods, this will be described in more detail with reference to  FIG. 6 , and a detailed description thereof will be omitted herein. For example, in  FIG. 4 , the PTU  400  may apply power detection beacons at operations  404  and  405 , and power values of the power detection beacons may be different. A part or all of the power detection beacons may have power enough to drive a communication unit included in the PRU  450 . For example, the PRU  450  may drive the communication unit by the part or all of the power detection beacons to communicate with the PTU  400  at operation  406 . The above state will be referred to as a null state. 
         [0119]    The PTU  400  detects load change due to an arrangement of the PRU  450 . The PTU  400  enters a low power mode at operation  408 . The low power mode will be described with reference to  FIG. 6 , and a detailed description will be omitted herein. The PRU  450  drives a communication unit based on power received from the PTU  400  at operation  409 . 
         [0120]    The PRU  450  transmits a PTU searching signal to the PTU  400  at operation  410 . The PRU  450  may transmit the PTU searching signal as an advertisement message which is based on a BLE scheme. The PRU  450  may periodically transmit the PTU searching signal. The PRU  450  may transmit the PTU searching signal until the PRU  450  receives a response signal from the PTU  400  or it reaches a preset time. 
         [0121]    Upon receiving the PTU searching signal from the PRU  450 , the PTU  400  transmits a PRU response signal at operation  411 . The PRU response signal may be used for establishing a connection between the PTU  400  and the PRU  450 . 
         [0122]    The PRU  450  transmits a PRU static signal at operation  412 . The PRU static signal may be a signal indicating a state of the PRU  450 , and may request to join a wireless charging network which the PTU  400  manages. 
         [0123]    The PTU  400  transmits a PTU static signal at operation  413 . The PTU static signal which the PTU  400  transmits may be a signal indicating capability of the PTU  400 . 
         [0124]    If the PTU  400  and the PRU  450  transmit/receive the PRU static signal and the PTU static signal, the PRU  450  periodically transmits a PRU dynamic signal at operations  414  and  415 . The PRU dynamic signal may include at least one parameter which is measured in the PRU  450 . For example, the PRU dynamic signal may include power information of a back end of a rectifier of the PRU  450 . The state of the PRU  450  will be referred to as a boot state at operation  407 . 
         [0125]    The PTU  400  enters a power transfer mode at operation  416 , and transmits a PRU control signal as a command signal which commands the PRU  450  to perform a charging operation at operation  417 . In the power transfer mode, the PRU  450  may transmit charging power. 
         [0126]    The PRU control signal transmitted by the PRU  450  may include information enabling/disabling the charging of the PRU  450  and permission information. The PRU control signal may be transmitted whenever a charging state is changed. The PRU control signal may be transmitted, for example, every 250 ms, or transmitted if a parameter is changed. The PRU control signal may be set to be transmitted within preset threshold time, for example, within 1 sec even though the parameter is not changed. 
         [0127]    The PRU  450  changes a configuration based on the PRU control signal and transmits the PRU dynamic signal for reporting the state of PRU  450  at operations  418  and  419 . The PRU dynamic signal transmitted by the PRU  450  may include at least one of information on a voltage, information on a current, information on a state of the PRU  450 , and information on temperature. The state of the PRU  450  will be referred to as an on state at operation  421 . 
         [0128]    The PRU dynamic signal may have a data structure as shown in Table 1. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Field 
                 Octets 
                 Description 
                 Use 
                 Units 
               
               
                   
               
             
             
               
                 optional fields 
                 1 
                 defines which optional fields are 
                 mandatory 
                   
               
               
                   
                   
                 populated 
               
               
                 Vrect 
                 2 
                 DC voltage at the output of the 
                 mandatory 
                 mV 
               
               
                   
                   
                 rectifier. 
               
               
                 Irect 
                 2 
                 DC current at the output of the 
                 mandatory 
                 mA 
               
               
                   
                   
                 rectifier. 
               
               
                 Vout 
                 2 
                 voltage at charge/battery port 
                 optional 
                 mV 
               
               
                 lout 
                 2 
                 current at charge/battery port 
                 optional 
                 mA 
               
               
                 temperature 
                 1 
                 temperature of PRU 
                 optional 
                 Deg. C. 
               
               
                   
                   
                   
                   
                 from −40 C. 
               
               
                 Vrect min dyn 
                 2 
                 The current dynamic minimum 
                 optional 
                 mV 
               
               
                   
                   
                 rectifier voltage desired 
               
               
                 Vrect set dyn 
                 2 
                 desired Vrect (dynamic value) 
                 optional 
                 mV 
               
               
                 Vrect high dyn 
                 2 
                 The current dynamic maximum 
                 optional 
                 mV 
               
               
                   
                   
                 rectifier voltage desired 
               
               
                 PRU alert 
                 1 
                 warnings 
                 mandatory 
                 Bit field 
               
               
                 RFU 
                 3 
                 undefined 
               
               
                   
               
             
          
         
       
     
         [0129]    In Table 1, the PRU dynamic signal may include at least one field. The at least one field includes optional field information, voltage information of a back end of a rectifier of a PRU (Vrect), current information of the back end of the rectifier of the PRU (Irect), voltage information of a back end of a DC/DC converter of the PRU (Vout), current information of the back end of the DC/DC converter of the PRU (Tout), temperature information (temperature), minimum voltage value information of the back end of the rectifier of the PRU (Vrect min dyn), optimal voltage value information of the back end of the rectifier of the PRU (Vrect set dyn), maximum voltage value information of the back end of the rectifier of the PRU (Vrect high dyn), alert information (PRU alert), and the like. The PRU dynamic signal may include at least one of the above fields. 
         [0130]    For example, at least one voltage setting value (e.g., the minimum voltage value information (Vrect min dyn) of the back end of the rectifier of the PRU, the optimal voltage value information (Vrect set dyn) of the back end of the rectifier of the PRU, and the maximum voltage value information (Vrect high dyn) of the back end of the rectifier of the PRU, and the like) determined according to a charging state may be included in a corresponding field and then transmitted. As described above, the PTU which receives the PRU dynamic signal controls wireless charging voltage to be transmitted to each PRU based on the voltage setting values included in the PRU dynamic signal. 
         [0131]    The PRU alert information may be formed as a data structure as shown in Table 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                 0 
               
               
                   
               
             
             
               
                 over- 
                 over- 
                 over- 
                 Charge 
                 TA 
                 Tran- 
                 restart 
                 RFU 
               
               
                 voltage 
                 current 
                 temper- 
                 Complete 
                 detect 
                 sition 
                 request 
               
               
                   
                   
                 ature 
               
               
                   
               
             
          
         
       
     
         [0132]    In Table 2, the PRU alert information (PRU Alert) may include a bit for a restart request, a bit for a transition, and a bit for detecting an insertion of a travel adapter (TA) (TA detect). The bit for the TA detect indicates a bit informing that a terminal for wired charging is connected to a PRU providing wireless charging. The transition indicates a bit informing a PTU that a PRU is reset before a communication integrated circuit (IC) of the PRU is switched from an SA mode to an NSA mode. The bit for the restart request indicates a bit informing a PRU that a PTU is ready to restart charging when the charging is disconnected due to the PTU reducing power because of an over-current state or an over-temperature state and then the state returning to a normal state. 
         [0133]    Further, the PRU alert information may also be formed as a data structure as shown in Table 3. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 7 
                 6 
                 5 
                 4 
                 3 
                 2 
                 1 
                 0 
               
               
                   
               
             
             
               
                 PRU 
                 PRU 
                 PRU over- 
                 PRU Self 
                 Charge 
                 Wired 
                 Mode 
                 Mode 
               
               
                 over- 
                 over- 
                 temperature 
                 Protection 
                 Complete 
                 Charger 
                 Transition 
                 Transition 
               
               
                 voltage 
                 current 
                   
                   
                   
                 Detect 
                 Bit 1 
                 Bit 0 
               
               
                   
               
             
          
         
       
     
         [0134]    In Table 3, PRU alert information includes an over voltage field, an over current field, an over temperature field, a PRU self protection field, a charge complete field, a wired charger detect field, a mode transition field, and the like. If the over voltage field is set to 1, it may indicate that a voltage Vrect of a PRU exceeds a limit of the over voltage. Further, the over current field and the over temperature field may be set in the same way as the over voltage field. The PRU self protection field indicates that a PRU directly reduced a load of power and thus needs to protect itself. In this case, the PRU is not required to change to a charging state. 
         [0135]    Bits for a mode transition according to an embodiment of the present disclosure may be set to a value necessary for notifying a duration that a mode transition procedure is performed to a PTU. The bits for the mode transition may be expressed as Table 4. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Value (Bit) 
                 Mode Transition Bit Description 
               
               
                   
               
             
             
               
                 00 
                 No Mode Transition 
               
               
                 01 
                 2 s Mode Transition time limit 
               
               
                 10 
                 3 s Mode Transition time limit 
               
               
                 11 
                 6 s Mode Transition time limit 
               
               
                   
               
             
          
         
       
     
         [0136]    In Table 4, ‘00’ indicates that there is no mode transition, ‘01’ indicates that time which is required for completing mode transition is a maximum of 2 seconds, ‘10’ indicates that time which is required for completing mode transition is a maximum of 3 seconds, and ‘11’ indicates that time which is required for completing mode transition is a maximum of 6 seconds. 
         [0137]    For example, when 3 seconds or less are spent for completing a mode transition, the mode transition bit may be set as ‘10’. Prior to starting a mode transition procedure, a PRU may restrict the procedure such that there is no change in impedance during the mode transition procedure. The restriction is implemented by changing an input impedance setting to match 1.1 W power draw. So, a PTU may control power (ITX_COIL) for the PRU based on the setting, and accordingly, maintain the power (ITX_COIL) for the PRU during a mode transition period. 
         [0138]    So, if the mode transition period is set by the mode transition bit, the PTU may maintain the power (ITX_COIL) for the PRU during the mode transition time, e.g., 3 seconds. That is, the PTU may maintain a connection even though a response is not received from the PRU for 3 seconds. However, after the mode transition time passes, the PTU unit may be considered a rogue object (foreign substance) and thus power transmission may be terminated. 
         [0139]    Referring back to  FIG. 4 , the PRU  450  may detect an error occurrence. The PRU  450  transmits an alert signal to the PTU  400  at operation  420 . The alert signal may be transmitted in a form of a PRU dynamic signal or a PRU alert signal. For example, the PRU  450  may transmit a PRU alert field of Table 1 reflecting an error state to the PTU  400 . Alternatively, the PRU  450  may transmit a single alert signal indicating the error state to the PTU  400 . Upon receiving the alert signal, the PTU  400  enters a latch fault mode at operation  422 , and the PTU  450  enters a null state at operation  423 . 
         [0140]    An example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 4 , and another example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 5 . 
         [0141]      FIG. 5  schematically illustrates another example of an operation between a PTU and a PRU in a wireless charging network according to an embodiment of the present disclosure. 
         [0142]    Another example of an operation between a PTU and a PRU in a wireless charging network in  FIG. 5  will be described in more detail with reference to  FIG. 6 . 
         [0143]      FIG. 6  schematically illustrates a graph on a time axis of a power amount which a PTU in  FIG. 5  applies. 
         [0144]    As shown in  FIG. 5 , a PTU initiates an operation at operation  501 . The PTU resets an initial configuration at operation  503 . The PTU transits into a power saving mode at operation  505 . The power saving mode may be a duration that the PTU supplies a different power to a power transmitter. For example, the power saving mode may be a duration that the PTU supplies a second detection power  601  and  602  and a third detected power  611 ,  612 ,  613 ,  614 , and  615  as described in  FIG. 6  to a power transmitter. The PTU may periodically supply the second detection power  601  and  602  by a second period. If the second detection power  601  and  602  are supplied, the PTU may supply the second detection power  601  and  602  during a second duration. The PTU may periodically supply the third detection power  611 ,  612 ,  613 ,  614 , and  615  by a third period. If the third detection power  611 ,  612 ,  613 ,  614 , and  615  are supplied, the PTU may supply the third detection power  611 ,  612 ,  613 ,  614 , and  615  during a third duration. In  FIG. 6 , power of each of the third detection power  611 ,  612 ,  613 ,  614 , and  615  is different, however, the power of each of the third detection power  611 ,  612 ,  613 ,  614 , and  615  may be different or the same. 
         [0145]    The PTU may output the third detection power  611  and then output the third detection power  612  having the same power amount. As described above, if the PTU outputs the third detection power having the same power amount, the power amount of the third detection power may have a power amount by which a smallest PRU, e.g., a PRU designated as category  1  can be detected. For example, a category may be determined based on a size of a PRU, and a description thereof will be omitted herein. 
         [0146]    Alternatively, the PRU may output the third detection power  611  and then output the third detection power  612  having a different power amount. As described above, if the PTU outputs the third detection power having the different power amount, each of the power amounts of the third detection power may be a power amount by which the PRUs designated as category  1  to category  5  can be detected. For example, the third detection power  611  may have a power amount by which a PRU designated as category  5  can be detected, the third detection power  612  may have a power amount by which a PRU designated as category  3  can be detected, and the third detection power  613  may have a power amount by which a PRU designated as category  1  can be detected. 
         [0147]    Meanwhile, the second detection power  601  and  602  may be power which may drive the PRU. More specifically, the second detection power  601  and  602  may have a power amount which may drive the controller and the communication unit included in the PRU. 
         [0148]    The PTU may supply the second detection power  601  and  602  and the third detection power  611 ,  612 ,  613 ,  614 , and  615  to the power receiver by a second period and a third period, respectively. If the PRU is arranged on the PTU, impedance viewed from a point of the PTU may be changed. The PTU detects a change in the impedance while the second detection power  601  and  602  and the third detection power  611 ,  612 ,  613 ,  614 , and  615  are supplied. For example, the PTU may detect the change in the impedance while the third detection power  615  is supplied. 
         [0149]    So, the PTU may detect an object at operation  507 . If the object is not detected at operation  507 , the PTU maintains a power saving mode in which different power is periodically supplied at operation  505 . 
         [0150]    Meanwhile, if there is the change in the impedance and thus the object is detected at operation  507 , the PTU enters a low power mode at operation  509 . The low power mode is a mode in which the PTU supplies driving power having a power amount by which the controller and the communication unit included in the PRU may be driven. For example, in  FIG. 6 , the PTU supplies driving power  620  to a power transmitter. The PRU receives the driving power  620  to drive a controller and a communication unit. The PRU performs a communication with the PTU with a predetermined scheme based on the driving power  620 . For example, the PRU may transmit/receive data required for an authentication and join a wireless charging network managed by the PTU based on the data. However, if a rogue object, not the PRU, is arranged, data transmission/reception may not be performed. So, the PTU determines whether the arranged object is a rogue object at operation  511 . For example, if the PTU does not receive a response from the object within preset time, the PTU may determine the object is a rogue object. 
         [0151]    If the object is determined as the rogue object at operation  511 , the PTU enters a latch fault mode at operation  513 . If the object is not determined as the rogue object at operation  511 , the PTU performs a join operation at operation  519 . For example, the PTU may periodically supply first power  631  to  634  by a first period in  FIG. 6 . The PTU may detect a change in impedance while supplying the first power. For example, if the rogue object is removed at operation  515 , the PTU may detect an impedance change and determine that the rogue object is removed. If the rogue object is not removed at operation  515 , the PTU may not detect the impedance change and determine that the rogue object is not removed. 
         [0152]    If the rogue object is not removed, the PTU may output at least one of a lamp and a warning sound to inform a user that a state of the PTU is an error state. So, the PTU may include an output unit that outputs at least one of the lamp and the warning sound. 
         [0153]    If it is determined that the rogue object is not removed at operation  515 , the PTU maintains the latch fault mode at operation  513 . If it is determined that the rogue object is removed at operation  515 , the PTU enters the power saving mode again at operation  517 . For example, the PTU may supply the second power  651  and  652  and the third power  661  to  665 , as shown in  FIG. 6 . 
         [0154]    As described above, if the rogue object not the PRU is arranged, the PTU enters the latch fault mode. Further, the PTU may determine whether the rogue object is removed based on the impedance change which is based on the power supplied in the latch fault mode. That is, a condition of the entrance into the latch fault mode in an embodiment of  FIGS. 5 and 6  may be the arrangement of the rogue object. 
         [0155]    Meanwhile, the PTU may have various latch fault mode entrance conditions as well as the arrangement of the rogue object. For example, the PTU may be cross-connected with the arranged PRU, in this case, the PTU may enter the latch fault mode. 
         [0156]    So, if the cross-connection occurs, the PTU is required to return to an initial state and the PRU is required to be removed. The PTU may set the cross-connection by which the PRU arranged on another PTU joins the wireless charging network as the latch fault mode entrance condition. 
         [0157]    An operation of a PRU in a case that an error including a cross connection occurs in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 7 . 
         [0158]    The control method in  FIG. 7  will be described in more detail with reference to  FIG. 8 . 
         [0159]      FIG. 8  schematically illustrates a graph on a time axis of an amount of power which a PTU in  FIG. 7  supplies. 
         [0160]    The PTU initiates an operation at operation  701 . Further, the PTU resets an initial configuration at operation  703 . The PTU enters a power saving mode at operation  705 . The power saving mode may be an interval that the PTU supplies power having a different amount to a power transmitter. For example, the power saving mode may be an interval that the PTU supplies second detection power  801  and  802  and third detection power  811 ,  812 ,  813 ,  814 , and  815  to a power transmitter in  FIG. 8 . The PTU may periodically supply the second detection power  801  and  802  by a second period. If the PTU supplies the second detection power  801  and  802 , the PTU may supply the second detection power  801  and  802  during a second interval. The PTU may periodically supply the third detection power  811 ,  812 ,  813 ,  814 , and  815  by a third period. If the PTU supplies the third detection power  811 ,  812 ,  813 ,  814 , and  815 , the PTU may supply the third detection power  811 ,  812 ,  813 ,  814 , and  815  during a third interval. Meanwhile, although it is illustrated that power values of the third detection power  811 ,  812 ,  813 ,  814 , and  815  are different from each other, the power values of the third detection power  811 ,  812 ,  813 ,  814 , and  815  may be different or the same. 
         [0161]    Meanwhile, the second detection power  801  and  802  may be power which may drive a PRU. More specifically, the second detection power  801  and  802  may have a power amount which may drive a controller and a communication unit included in the PRU. 
         [0162]    The PTU may supply the second detection power  801  and  802  and the third detection power  811 ,  812 ,  813 ,  814 , and  815  to the power receiver by a second period and a third period, respectively. If the PRU is arranged on the PTU, impedance viewed from a point of the PTU may be changed. The PTU may detect an impedance change while the second detection power  801  and  802  and the third detection power  811 ,  812 ,  813 ,  814 , and  815  are supplied. For example, the PTU may detect the impedance change while the third detection power  815  is supplied. So, the PTU may detect an object at operation  707 . If the object is not detected at operation  707 , the PTU maintains a power saving mode in which different power is periodically supplied at operation  705 . 
         [0163]    Meanwhile, if the impedance is changed and thus the object is detected at operation  707 , the PTU enters a low power mode at operation  709 . The low power mode is a mode in which the PTU supplies driving power having a power amount by which a controller and a communication unit included in the PRU may be driven. For example, in  FIG. 8 , the PTU may supply driving power  820  to the power transmitter. The PRU receives the driving power  820  to drive the controller and the communication unit. The PRU may perform a communication with the PTU with a preset scheme based on the driving power  820 . For example, the PRU may transmit/receive data required for an authentication and join a wireless charging network managed by the PTU based on the data. 
         [0164]    Thereafter, the PTU enters a power transmission mode in which charging power is transmitted at operation  711 . For example, the PTU supplies charging power  821  and the charging power may be transmitted to the PRU as illustrated in  FIG. 8 . 
         [0165]    At operation  713 , the PTU may determine whether an error occurs in a power transmission mode. The error may be the arrangement of a rogue object on the PTU, a cross-connection, an over voltage, an over current, over temperature, and the like. The PTU may include a sensing unit that may measure the over voltage, the over current, over temperature, and the like. For example, the PTU may measure a voltage or a current at a reference position. If the measured voltage or current is larger than a threshold, it is determined that a condition of the over voltage or the over current is satisfied. Alternatively, the PTU may include a temperature sensing means which measures temperature at the reference position of the PTU. If the temperature at the reference position is larger than a threshold, the PTU determines that a condition of the over temperature is satisfied. 
         [0166]    Meanwhile, if an over voltage, over current, or over temperature state is determined according to a measurement value of the temperature, voltage, or current, the PTU prevents the over voltage, over current, or over temperature by reducing a wireless charging power by a preset value. At this time, if a voltage value of the reduced wireless charging power is less than a preset minimum value (for example, a minimum voltage value (Vrect min dyn) of a back end of a rectifier of the PRU), the wireless charging is stopped, so that a voltage setting value may be re-adjusted according to an embodiment of the present disclosure. 
         [0167]    Although it has been illustrated that the error occurs since the rogue object is additionally arranged on the PTU in an embodiment of  FIG. 8 , the error is not limited thereto and it will be easily understood by those skilled in the art that the PTU operates through a similar process with respect to the arrangement of the rogue object, the cross-connection, the over voltage, the over current, and the over temperature. 
         [0168]    If the error does not occur at operation  713 , the PTU maintains a power transmission mode at operation  711 . If the error occurs at operation  713 , the PTU enters a latch fault mode at operation  715 . For example, the PTU supplies first power  831  to  835  as illustrated in  FIG. 8 . 
         [0169]    Further, the PTU may output an error occurrence display including at least one of a lamp and a warning sound during the latch fault mode. If it is determined that the rogue object is not removed at operation  717 , the PTU maintains the latch fault mode at operation  715 . 
         [0170]    Meanwhile, if it is determined that the rogue object is removed at operation  717 , the PTU enters the power saving mode again at operation  719 . For example, the PTU may supply second power  851  and  852  and third power  861  to  865  in  FIG. 8 . 
         [0171]    In the above description, an operation in a case that an error occurs while a PTU transmits charging power has been discussed. Hereinafter, an operation in a case that a plurality of PRUs on a PTU receives charging power will be described. 
         [0172]    An operation of a PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 9 . 
         [0173]      FIG. 9  schematically illustrates an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0174]    The operating process in  FIG. 9  will be described in more detail with reference to  FIG. 10 . 
         [0175]      FIG. 10  is a graph on an x axis of an amount of power supplied by a PTU in  FIG. 9 . 
         [0176]    As illustrated in  FIG. 9 , a PTU transmits charging power to a first PRU at operation  901 . The PTU allows a second PRU to additionally join a wireless charging network at operation  903 . The PTU transmits charging power to the first and the second PRU at operation  905 . More specifically, the PTU supplies a sum of the charging power required by the first PRU and the second PRU to a power receiver. 
         [0177]    An embodiment of operations  901  to  905  is illustrated in  FIG. 10 . For example, the PTU maintains a power saving mode that second detection power  1001  and  1002  and third detection power  1011  to  1015  are supplied. Thereafter, the PTU detects the first PRU and enters a low power mode in which a detection power  1020  is maintained. Then, the PTU enters a power transmission mode that first charging power  1030  is supplied. The PTU detects the second PRU and allows the second PRU to join the wireless charging network. Further, the PTU may supply second charging power  1040  having a power amount corresponding to a sum of the power amount required by the first PRU and the second PRU. 
         [0178]    Referring back to  FIG. 9 , the PTU detects an error occurrence at operation  907  while transmitting charging power to both the first PRU and the second PRU at operation  905 . Here, the error may be arrangement of a rogue object, cross-connection, an over voltage, an over current, an over temperature, and the like. If the error does not occur at operation  907 , the PTU may maintain the supply of the second charging power  1040 . 
         [0179]    If the error occurs at operation  907 , the PTU enters a latch fault mode at operation  909 . For example, the PTU may supply first power  1051  to  1055  by a first period in  FIG. 10 . The PTU determines whether both the first PRU and the second PRU are removed at operation  911 . For example, the PTU may detect an impedance change while supplying the first power  1051  to  1055 . The PTU may determine whether both the first PRU and the second PRU are removed based on whether impedance is returned to an initial value. 
         [0180]    If it is determined that both the first PRU and the second PRU are removed at operation  911 , the PTU enters a power saving mode at operation  913 . For example, as described in  FIG. 10 , the PTU may supply second power  1061  and  1062  and third power  1071  to  1075  by a second period and a third period, respectively. 
         [0181]    As described above, even if the PTU applies charging power to a plurality of PRUs, the PTU may easily determine whether the PRU or a rogue object is removed when an error occurs. 
         [0182]    An inner structure of each of a PTU and a PRU in a stand-alone (SA) mode in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 11 . 
         [0183]      FIG. 11  schematically illustrates an inner structure of each of a PTU and a PRU in an SA mode in a wireless charging network according to an embodiment of the present disclosure. 
         [0184]    Referring to  FIG. 11 , a PTU  1100  includes a communication unit  1111 , a power amplifier (PA)  1120 , and a resonator  1130 . The PRU  1150  includes a communication unit  1151 , an application processor (AP)  1152 , a power management integrated circuit (PMIC)  1153 , a wireless power integrated circuit (WPIC)  1154 , a resonator  1155 , an interface power management IC (IFPM)  1157 , a travel adapter (TA)  1158 , and a battery  1159 . 
         [0185]    The communication unit  1111  may be implemented with a WiFi/BT combo IC, and may perform a communication with the communication unit  1151  based on a preset scheme, e.g., a BLE scheme. For example, the communication unit  1151  included in the PRU  1150  may transmit a PRU dynamic signal with a data structure as described in Table 1 to the communication unit  1111  included in the PTU  1100 . 
         [0186]    As described above, a PRU dynamic signal may include at least one of voltage information, current information, and alert information of the PRU  1150 . 
         [0187]    Based on a received PRU dynamic signal, a power value output from the PA  1120  may be adjusted. For example, if the over voltage, the over current, and the over temperature are applied to the PRU  1150 , a power value output from the PA  1120  may be reduced. Further, if a voltage or current of the PRU  1150  is less than a preset value, a power value output from the PA  1120  may be increased. 
         [0188]    Charging power from the resonator  1130  may be wirelessly transmitted to the resonator  1155 . 
         [0189]    The WPIC  1154  rectifies the charging power received from the resonator  1155  and performs DC/DC conversion. The WPIC  1154  drives the communication unit  1151  or charges the battery  1159  using the converted power. 
         [0190]    Meanwhile, a wired charging terminal may be inserted into the TA  1158 . A wired charging terminal such as 30-pin connector or a universal serial bus (USB) connector may be inserted into the TA  1158 , and the TA  1158  may receive power supplied from an external power source to charge the battery  1159 . 
         [0191]    The IFPM  1157  may process power supplied from the wired charging terminal to output the processed power to the battery  1159  and the PMIC  1153 . 
         [0192]    The PMIC  1153  manages wirelessly received power or power received through a wire, and power supplied to each of components of the PRU  1150 . The AP  1152  receives power information from the PMIC  1153  and controls the communication unit  1151  to transmit the PRU dynamic signal for reporting the power information. 
         [0193]    The TA  1158  may be connected to a node  1156  connected to the WPIC  1154 . If a wired charging connector is inserted into the TA  1158 , a preset voltage, for example, 5V may be supplied to the node  1156 . The WPIC  1154  monitors voltage supplied to the node  1156  to determine whether the TA  1158  is inserted. 
         [0194]    Meanwhile, the AP  1152  has a stack in a predetermined communication scheme, for example, a WiFi/BT/BLE stack. So, in the wireless charging, the communication unit  1151  loads the stack from the AP  1152  and then communicates with the communication unit  1111  included in the PTU  1100  using a BT or BLE communication scheme based on the stack. 
         [0195]    However, a state may occur in which data for performing a wireless power transmission may not be fetched from the AP  1152  since the AP  1152  is turned off or in which power is lost so that the AP  1152  may not remain in an on state while the data is fetched from a memory within the AP  1152 . 
         [0196]    If a residual capacity of the battery  1159  is less than a minimum power threshold, the AP  1152  is turned off, and the wireless charging may be performed using some components for the wireless charging within the PRU  1150 , for example, the communication unit  1151 , the WPIC  1154 , and the resonator  1155 . A state in which the AP  1152  may not be turned on will be referred to as a dead battery state. 
         [0197]    Since the AP  1152  is not driven in the dead battery state, the communication unit  1151  may not receive a stack in a predetermined communication scheme, for example, a WiFi/BT/BLE stack from the AP  1152 . For such a case, some of the stacks in the predetermined communication scheme, for example, the BLE stack, are fetched within a memory of the communication unit  1151  from the AP  1152  and stored in the memory. Accordingly, the communication unit  1151  may communicate with the PTU  1100  for the wireless charging using the stack in the communication scheme stored in the memory, that is, a wireless charging protocol. At this time, the communication unit  1151  may include a memory, and the BLE stack may be stored in a memory in a form of a read only memory (ROM) in the SA mode. 
         [0198]    As described above, a mode in which the communication unit  1151  performs the communication using the stack of the communication scheme stored in the memory will be referred to as the SA mode. Accordingly, the communication unit  1151  may manage a charging process based on the BLE stack. 
         [0199]    The concept of a wireless charging network which is applicable to an embodiment of the present disclosure has been described with reference to  FIGS. 1 to 11 . 
         [0200]    A process of transmitting/receiving PTU presence information in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIGS. 12 to 26 . 
         [0201]    An advertisement procedure and a discovery procedure in a conventional wireless charging network will be described with reference to  FIG. 12 . 
         [0202]      FIG. 12  schematically illustrates an advertisement procedure and a discovery procedure in a conventional wireless charging network. 
         [0203]    Referring to  FIG. 12 , the wireless charging network supports a BLE scheme. In order for a PTU to supply power to a PRU, there is a need of establishing a BLE connection between the PTU and the PRU. So, the PTU and the PRU need to establish the BLE connection. The BLE connection is used for determining whether the PRU is compatible with the PTU and controlling wireless power supply. 
         [0204]    If the BLE connection is not established between the PTU and the PRU yet, the PTU performs an advertisement procedure and the PRUs perform a discovery procedure to establish a BLE connection with the PTU. The advertisement procedure is a procedure that transmits an advertisement message without limiting receiving devices, and the discovery procedure is a procedure that discovers the advertisement message. 
         [0205]    In  FIG. 12 , a short beacon is periodically transmitted, and used for detecting an impedance shift. A long beacon is periodically transmitted, and used for receiving the advertisement message. The long beacon is transmitted during tLONG_BEACON, and a period of the long beacon is tLONG_BEACON_PERIOD. The short beacon is transmitted during tSHORT_BEACON, and a period of the short beacon is tCYCLE. 
         [0206]    Regardless of a preset period, upon detecting that an impedance shift occurs using the short beacon, the PTU may transmit the long beacon as soon as possible from a time when the PTU detects the impedance shift. 
         [0207]    When the PTU discovers a PRU using a discovery procedure, if the following two conditions are satisfied, the PRU may perform an operation of establishing a BLE connection and transmitting power: 
         [0208]    (1) Condition 1: Case that a received signal strength of an advertisement message which a PTU receives is greater than or equal to a preset threshold for a received signal strength. 
         [0209]    That is, if the received signal strength of the received advertisement message is greater than or equal to the preset threshold received signal strength, the PTU performs an operation of establishing a BLE connection and transmitting power by performing remaining procedures with a related PRU. For example, the received signal strength may be determined based on various metrics such as received signal code power (RSCP), reference signal received power (RSRP), a reference signal strength indicator (RSSI), reference signal received quality (RSRQ), a carrier-to-interference noise ratio (CINR), a signal-to-noise ratio (SNR), a block error rate (BLER), and the like. The threshold received signal strength may be set to an ADV_PWR_MIN value used in an A4WP standard. 
         [0210]    (2) Condition 2: Case that a PTU detects an impedance shift at a time which is close to a time that the PTU receives an advertisement message. For example, the time which is close to the time that the PTU receives the advertisement message may be a time within a preset threshold time from the time that the PTU receives the advertisement message. The impedance shift occurs if the PTU is very close to a related PRU, that is, a distance between the PTU and the related PRU is shorter than a threshold distance. 
         [0211]    That is, upon detecting the impedance shift at the time that is close to the time that the PTU receives the advertisement message, the PTU performs an operation of establishing a BLE connection and transmitting power by performing remaining procedures with a related PRU. 
         [0212]    As described in  FIG. 12 , in a conventional wireless charging network, if a condition 1 and a condition 2 are satisfied, a PTU performs an operation to establish a BLE connection and transmit power by performing remaining procedures. So, if at least one of the condition 1 and the condition 2 is not satisfied, the PTU ignores an advertisement message received from a PRU, so the operation of establishing the BLE connection and transmitting the power is not performed between the PTU and the PRU. 
         [0213]    If one of the condition 1 and the condition 2 is satisfied, the PTU transmits a connection request message to the PRU when the PTU receives a specific advertisement message, for example, the eleventh advertisement message from the PRU or a preset time (e.g., 1700 ms) elapses. 
         [0214]    If power is not supplied to a resonator included in the PTU, i.e., the PTU is in a un-powered state, even though the PTU receives an advertisement message from a related PRU, the PTU ignores the advertisement message. 
         [0215]    So, an embodiment of the present disclosure proposes a new operating process for a case that in which condition 1 and a condition 2 are not satisfied and an advertisement message may be discovered, and a case that only a condition 1 is satisfied. That is, an embodiment of the present disclosure proposes a PTU detection operation for a case that a received signal strength condition of a BLE scheme is satisfied even though a PRU is not close enough to cause an impedance shift to a PTU, and a case that the PTU may detect a related advertisement message even though the PRU is not close enough to cause the impedance shift to the PTU and the received signal strength condition of the BLE scheme is not satisfied. This will be described below. 
         [0216]    An example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 13 . 
         [0217]      FIG. 13  schematically illustrates an example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0218]    Referring to  FIG. 13 , it will be assumed that the PTU is connected to a management server. 
         [0219]    A PTU generates a long beacon signal at operation  1311 . The PTU receives an advertisement message from a PRU at operation  1313 . The PTU determines whether a state of the PTU is an un-powered state, i.e., a state in which power is not supplied to a resonator included in the PTU at operation  1315 . If the state of the PTU is the un-powered state, the PTU detects a charging attempt from the PRU, and performs a charging operation with the PRU at operation  1317 . That is, the PTU transmits power to the PRU. It will be understood by those of ordinary skill in the art that the charging operation is not performed between the PTU and the PRU if the PTU does not detect the charging attempt. 
         [0220]    If the state of the PTU is the not an un-powered state, the PTU generates an alarm, that is, the PTU outputs PTU presence information or transmits PTU presence information to a management server through an advertisement message at operation  1319 . The alarm indicates that the PTU exists, and may be implemented with various forms. The alarm will be described below, so a detailed description will be omitted herein. The advertisement message may include various parameters. A process of transmitting the advertisement message to the management server in the PTU will be described below, so a detailed description will be omitted herein. 
         [0221]    As described in  FIG. 13 , a PTU may perform a charging operation with a PRU even though power is not supplied to a resonator, that is, the PTU is in a un-powered state. That is, as described in  FIG. 13 , in an embodiment of the present disclosure, the PTU may perform the charging operation with the PRU in a case that a received signal strength condition of a BLE scheme is satisfied even though the PRU is not close enough to cause an impedance shift to the PTU, and a case that the PTU may detect a related advertisement message even though the PRU is not close enough to cause the impedance shift to the PTU and the received signal strength condition of the BLE scheme is not satisfied. 
         [0222]    Although  FIG. 13  illustrates an example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure, various changes could be made to  FIG. 13 . For example, although shown as a series of operations, various operations in  FIG. 13  could overlap, occur in parallel, occur in a different order, or occur multiple times. 
         [0223]    An example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 13 , and another example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 14 . 
         [0224]      FIG. 14  schematically illustrates another example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0225]    Referring to  FIG. 14 , it will be assumed that the PTU is connected to a management server. 
         [0226]    A PTU generates a long beacon signal at operation  1411 . The PTU receives an advertisement message from a PRU at operation  1413 . The PTU determines whether a state of the PTU is an un-powered state, i.e., a state that power is not supplied to a resonator included in the PTU at operation  1415 . If the state of the PTU is the un-powered state, the PTU detects a charging attempt from the PRU, and performs a charging operation with the PRU at operation  1417 . That is, the PTU transmits power to the PRU. It will be understood by those of ordinary skill in the art that the charging operation is not performed between the PTU and the PRU if the PTU does not detect the charging attempt. 
         [0227]    If the state of the PTU is the not un-powered state, the PTU determines whether received signal strength of an advertisement message received from the PRU is greater than or equal to a preset threshold received signal strength at operation  1419 . The threshold received signal strength may be adaptively set according to a state of the wireless charging network. For example, the threshold received signal strength may be set to an ADV_PWR_MIN value used in an A4WP standard. 
         [0228]    If the received signal strength is greater than or equal to the threshold received signal strength, the PTU generates an alarm, that is, the PTU outputs PTU presence information at operation  1421 . The alarm indicates that the PTU exists, and may be implemented with various forms. The alarm will be described below, so a detailed description will be omitted herein. 
         [0229]    If the received signal strength is not greater than or equal to the threshold received signal strength, that is, the received signal strength is less than the threshold received signal strength, the PTU transmits PTU presence information to a management server through an advertisement message at operation  1423 . The advertisement message may include various parameters. A process of transmitting the advertisement message to the management server in the PTU will be described below, so a detailed description will be omitted herein. 
         [0230]    As described in  FIG. 14 , a PTU may perform a charging operation with a PRU even though power is not supplied to a resonator, that is, the PTU is in a un-powered state. That is, as described in  FIG. 14 , in an embodiment of the present disclosure, the PTU may perform the charging operation with the PRU in a case that a received signal strength condition of a BLE scheme is satisfied, even though the PRU is not close enough to cause an impedance shift to the PTU, and a case that the PTU may detect a related advertisement message even though the PRU is not close enough to cause the impedance shift to the PTU, and the received signal strength condition of the BLE scheme is not satisfied. 
         [0231]    Although  FIG. 14  illustrates another example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure, various changes could be made to  FIG. 14 . For example, although shown as a series of operations, various operations in  FIG. 14  could overlap, occur in parallel, occur in a different order, or occur multiple times. 
         [0232]    Another example of an operating process of a PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 14 , and an example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 15 . 
         [0233]      FIG. 15  schematically illustrates an example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure. 
         [0234]    Referring to  FIG. 15 , the wireless charging network includes a PTU  1511  and a PRU  1515 . The PTU  1511  outputs PTU presence information indicating that that the PTU  1511  exists periodically or if a specific condition is satisfied. The specific condition may be a condition as described in  FIGS. 13 and 14 , so a detailed description will be omitted herein. 
         [0235]    In  FIG. 15 , the PTU  1511  outputs the PTU presence information indicating that the PTU  1511  exists using a display unit, for example, by a flickering light emitting diode (LED). Although not shown in  FIG. 15 , it will be understood by those of ordinary skill in the art that the PTU  1511  may output the PTU presence information indicating that the PTU  1511  exists using a display unit, for example, by generating a beep or playing a voice message. 
         [0236]    An example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 15 , and another example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 16 . 
         [0237]      FIG. 16  schematically illustrates another example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure. 
         [0238]    Referring to  FIG. 16 , the wireless charging network includes a PRU  1611  and a PTU  1613 . The PTU  1613  outputs PTU presence information indicating that the PTU  1613  exists periodically and if a specific criterion is satisfied. The specific criterion may be a criterion as described in  FIGS. 13 and 14 , so a detailed description thereof will be omitted herein. 
         [0239]    In  FIG. 16 , the PTU  1613  outputs PTU presence information indicating that the PTU  1613  exists using a display unit, for example, by displaying a specific message ‘Please put in here’ on a liquid crystal display (LCD). Although not shown in  FIG. 16 , it will be understood by those of ordinary skill in the art that the PTU  1613  may output the PTU presence information indicating that the PTU  1613  exists using the display unit, for example, by generating a beep or playing a voice message. 
         [0240]    Another example of outputting PTU presence information in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 16 , and an example of a process of transmitting PTU presence information to a PRU through a management server in a PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 17 . 
         [0241]      FIG. 17  schematically illustrates an example of a process of transmitting PTU presence information to a PRU through a management server in a PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0242]    Referring to  FIG. 17 , the wireless charging network includes a PTU  1711 , a management server  1713 , and a PRU  1715 . 
         [0243]    The PTU  1711  transmits PTU presence information indicating that the PTU  1711  exists through an advertisement message to the management server  1713  periodically or if a specific criterion is satisfied. The management server  1713  transmits the PTU presence information to the PRU  1715  based on the advertisement message received from the PTU  1711 . The specific criterion may be a criterion as described in  FIGS. 13 and 14 , so a detailed description thereof will be omitted herein. 
         [0244]    The advertisement message may include various parameters, and the various parameters may indicate the PTU presence information. For example, the various parameters may be at least one of a parameter indicating geographical location of the PTU  1711  and a parameter indicating location that it is possible to perform a wireless charging operation using the PTU  1711 , and the like. The parameter indicating the a geographical location of the PTU  1711  may not be included in the advertisement message. In this case, it will be assumed that the management server  1713  previously knows the geographical location of the PTU  1711 . 
         [0245]    Upon receiving the advertisement message from the PTU  1711 , the management server  1713  may transmit PTU presence information indicating that the PTU  1711  exists based on a location of PRUs to related PRUs, e.g., the PRU  1715 . The management server  1713  determines PRUs to which the management server  1713  will transmit PTU information based on a location information of PRUs and accuracy information, e.g., quality of position (QoP) stored in the management server  1713 . The management server  1713  transmits the PTU presence information to the determined PRUs, e.g., the PRU  1715 . 
         [0246]    Upon receiving the PTU presence information from the management server  1713 , the PRU  1715  outputs the PTU presence information. A case that the PTU presence information is output based on a parameter indicating a location that it is possible to perform a wireless charging operation using the PTU  1711  is shown in  FIG. 17 . That is, the PRU  1715  outputs a message “Wireless charging is possible in restaurant A” on a display unit of the PRU  1715  based on the PTU presence information received from the management server  1713 . 
         [0247]    Although not shown in  FIG. 17 , the PRU  1715  may output the PTU presence information indicating that the PTU  1711  exists using a display unit, e.g., by generating a beep or playing a voice message. 
         [0248]    An example of a process of transmitting PTU presence information to a PRU through a management server in a PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 17 , and an example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 18 . 
         [0249]      FIG. 18  schematically illustrates an example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure. 
         [0250]    Referring to  FIG. 18 , the wireless charging network includes a management server  1811  and a PRU  1815 . For example, the management server  1811  transmits PTU presence information to the PRU  1815  through a cloud service  1813 . The cloud service  1813  may be implemented with various forms, and a detailed description thereof will be omitted herein. 
         [0251]    An example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 18 , and another example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 19 . 
         [0252]      FIG. 19  schematically illustrates another example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure. 
         [0253]    Referring to  FIG. 19 , the wireless charging network includes a management server  1911  and a PRU  1915 . For example, the management server  1911  transmits PTU presence information to the PRU  1915  through a push notification service  1913 . The push notification service  1913  may be implemented with various forms, and a detailed description thereof will be omitted herein. 
         [0254]    Another example of a process of transmitting PTU presence information to a PRU in a management server in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 19 . A process of transmitting wireless charging operation state information for a specific PRU to an associated PRU which is associated with the specific PRU in a state that a wireless charging operation is performed between a PTU and the specific PRU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 20 . 
         [0255]      FIG. 20  schematically illustrates a process of transmitting wireless charging operation state information for a specific PRU to an associated PRU which is associated with the specific PRU in a state that a wireless charging operation is performed between a PTU and the specific PRU in a wireless charging network according to an embodiment of the present disclosure. 
         [0256]    Referring to  FIG. 20 , the wireless charging network includes a PTU  2011 , a management server  2013 , a PRU# 1   2015 - 1 , and a PRU# 2   2015 - 2 . It will be assumed that the PRU# 1   2015 - 1  and the PRU# 2   2015 - 2  are PRUs which have a relationship. 
         [0257]    As described in  FIG. 20 , upon performing a wireless charging operation with the PRU# 1   2015 - 1 , the PTU  2011  transmits wireless charging operation state information indicating a wireless charging operation state between the PTU  2011  and the PRU# 1   2015 - 1  to the PRU# 2   2015 - 2  through the management server  2013 . The wireless charging operation state information may include information indicating a current charging state of the PRU# 1   2015 - 1 , information indicating time until it is predicted that the PRU# 1   2015 - 1  is fully charged, and the like. 
         [0258]    For example, the management server  2013  transmits wireless charging operation state information for the PRU# 1   2015 - 1  to another PRU which works with a service account of the PRU# 1   2015 - 1  using a push alarm. The wireless charging operation state information helps a user of the PRU# 1   2015 - 1  to easily know wireless charging related information even though power of the PRU# 1   2015 - 1  is exhausted. 
         [0259]    Upon receiving the wireless charging operation state information for the PRU# 1   2015 - 1  from the management server  2013 , the PRU# 2   2015 - 2  outputs the PTU presence information. In  FIG. 20 , the wireless charging operation state information includes information indicating a time that it is expected until the PRU# 1   2015 - 1  is fully charged. That is, the PRU# 2   2015 - 2  displays a message, e.g., a message “It takes 15 minutes until it is fully charged” on a display unit included in the PRU# 2   2015 - 2  based on the wireless charging operation state information received from the management server  2013 . 
         [0260]    Although not shown in  FIG. 20 , the PRU# 2   2015 - 2  may output wireless charging operation state information for the PRU# 1   2015 - 1  using a display unit, e.g., by generating a beep or playing a voice message. 
         [0261]    A process of transmitting wireless charging operation state information for a specific PRU to an associated PRU which is associated with the specific PRU in a state that a wireless charging operation is performed between a PTU and the specific PRU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 20 . An example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 21 . 
         [0262]      FIG. 21  schematically illustrates an example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0263]    Referring to  FIG. 21 , the wireless charging network includes a PRU  2111 , a PTU  2113 , a management server  2115 , and a mobile type PTU  2117 . The mobile type PTU  2117  may have an associated relation with the PTU  2113 , and controls the PRU  2111  to perform a wireless charging operation through the mobile type PTU  2117  if the management server  2115  detects a location of the PRU  2111 . That is, the management server  2115  transmits an advertisement message including PTU presence information indicating a location of the mobile type PTU  2117  to the PRU  2111 . Thus, the PRU  2111  may perform a wireless charging operation with the mobile type PTU  2117 . The mobile type PTU  2117  performs a wireless charging operation with the PRU  2111  under a control of the management server  2115  unlike a conventional PTU. That is, a location of the mobile type PTU  2117  may be changed under a control of the management server  2115 . The location of the mobile type PTU  2117  may be a location which has been already registered at the management server  2115 , or location of the PRU  2111  which the management server  2115  detects. 
         [0264]    An example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 21 , and another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 22 . 
         [0265]      FIG. 22  schematically illustrates another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0266]    Referring to  FIG. 22 , the wireless charging network includes a mobile type PTU  2211 , a PRU# 1   2213 , and a PRU# 2   2215 . The mobile type PTU  2211  may have a relation with a PTU (not show in  FIG. 22 ), and performs a wireless charging operation with a PRU which is detected through the mobile type PTU  2211  if a management server (not show in  FIG. 22 ) detects a location of at least one of the PRU# 1   2213  and the PRU# 2   2215 . The mobile type PTU  2211  performs a wireless charging operation with the detected PRU under a control of the management server unlike a conventional PTU. That is, a location of the mobile type PTU  2211  may be changed under a control of the management server. The location of the mobile type PTU  2211  may be a location that is previously registered at the management server or location of a PRU that the management server detects. 
         [0267]    Another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 22 , and still another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure will be described with reference to  FIG. 23 . 
         [0268]      FIG. 23  schematically illustrates another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure. 
         [0269]    Referring to  FIG. 23 , the wireless charging network includes a mobile type PTU  2311 . The mobile type PTU  2311  may have an associated relationship with a PTU (not shown in  FIG. 23 ), and controls a management server (not shown in  FIG. 23 ) to perform a wireless charging operation with a PRU (not shown in  FIG. 23 ) which is detected through the mobile type PTU  2311  if the management server detects location of the PRU. The mobile type PTU  2311  performs a wireless charging operation with the PRU under a control of the management server unlike a conventional PTU. That is, location of the mobile type PTU  2311  may be changed under a control of the management server. The location of the mobile type PTU  2311  may be a location that is previously registered at the management server or location of the PRU that the management server detects. 
         [0270]    For example, if the PRU performs a beacon service such as an iBeacon, and the like, a PRU which transmits a BLE beacon is deployed at a place that physical access is difficult, e.g., a ceiling in order to prevent the BLE beacon from being stolen and damaged. In this case, the mobile type PTU  2311  may result in convenience of management related to how a PRU actively performs a charging operation if power of the related PRU is insufficient. Further, the mobile type PTU  2311  may include an additional binder device in order to supply power without consuming energy for maintaining a levitation state. 
         [0271]    Another example of an operating process of a mobile type PTU in a wireless charging network according to an embodiment of the present disclosure has been described with reference to  FIG. 23 , and an inner structure of a PTU in a wireless charging network according to an embodiment of the present will be described with reference to  FIG. 24 . 
         [0272]      FIG. 24  schematically illustrates an inner structure of a PTU in a wireless charging network according to an embodiment of the present. 
         [0273]    Referring to  FIG. 24 , a PTU  2400  includes a transmitter  2411 , a controller  2413 , a receiver  2415 , and a storage unit  2417 . 
         [0274]    The controller  2413  controls the overall operation of the PTU  2400 . More particularly, the controller  2413  controls the PTU  2400  to perform a wireless charging operation according to an embodiment of the present disclosure, e.g., an operation related to an operation of transmitting PTU presence information. The operation related to the operation of transmitting the PTU presence information according to an embodiment of the present disclosure is performed in the manner described with reference to  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0275]    The transmitter  2411  transmits various signals, various messages, and the like to a management server, a PRU, and the like under a control of the controller  2413 . The various signals, the various messages, and the like transmitted in the transmitter  2411  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0276]    The receiver  2415  receives various signals, various messages, and the like from the management server, the PRU, and the like under a control of the controller  2413 . The various signals, the various messages and the like received in the receiver  2415  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0277]    The storage unit  2417  stores a program and various data necessary for the operation of the PTU  2400 , information related to the operation of transmitting the PTU presence information according to an embodiment of the present disclosure, and the like. The storage unit  2417  stores the various signals, the various messages, and the like received in the receiver  2415 . 
         [0278]    While the transmitter  2411 , the controller  2413 , the receiver  2415 , and the storage unit  2417  are described as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter  2411 , the controller  2413 , the receiver  2415 , and the storage unit  2417  may be incorporated into a single unit. 
         [0279]    An inner structure of a PTU in a wireless charging network according to an embodiment of the present has been described with reference to  FIG. 24 , and an inner structure of a PRU in a wireless charging network according to an embodiment of the present will be described with reference to  FIG. 25 . 
         [0280]      FIG. 25  schematically illustrates an inner structure of a PRU in a wireless charging network according to an embodiment of the present. 
         [0281]    Referring to  FIG. 25 , a PRU  2500  includes a transmitter  2511 , a controller  2513 , a receiver  2515 , and a storage unit  2517 . 
         [0282]    The controller  2513  controls the overall operation of the PRU  2500 . More particularly, the controller  2513  controls the PRU  2500  to perform a wireless charging operation according to an embodiment of the present disclosure, e.g., an operation related to an operation of receiving PTU presence information. The operation related to the operation of receiving the PTU presence information according to an embodiment of the present disclosure is performed in the manner described with reference to  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0283]    The transmitter  2511  transmits various signals, various messages, and the like to a management server, a PTU, and the like under a control of the controller  2513 . The various signals, the various messages, and the like transmitted in the transmitter  2511  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0284]    The receiver  2515  receives various signals, various messages, and the like from the management server, the PTU, and the like under a control of the controller  2513 . The various signals, the various messages and the like received in the receiver  2515  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0285]    The storage unit  2517  stores a program and various data necessary for the operation of the PRU  2500 , information related to the operation of receiving the PTU presence information according to an embodiment of the present disclosure, and the like. The storage unit  2517  stores the various signals, the various messages, and the like received in the receiver  2515 . 
         [0286]    While the transmitter  2511 , the controller  2513 , the receiver  2515 , and the storage unit  2517  are described as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter  2511 , the controller  2513 , the receiver  2515 , and the storage unit  2517  may be incorporated into a single unit. 
         [0287]    An inner structure of a PRU in a wireless charging network according to an embodiment of the present has been described with reference to  FIG. 25 , and an inner structure of a management server in a wireless charging network according to an embodiment of the present will be described with reference to  FIG. 26 . 
         [0288]      FIG. 26  schematically illustrates an inner structure of a management server in a wireless charging network according to an embodiment of the present. 
         [0289]    Referring to  FIG. 26 , a management server  2600  includes a transmitter  2611 , a controller  2613 , a receiver  2615 , and a storage unit  2617 . 
         [0290]    The controller  2613  controls the overall operation of the management server  2600 . More particularly, the controller  2613  controls the management server  2600  to perform a wireless charging operation according to an embodiment of the present disclosure, e.g., an operation related to an operation of transmitting/receiving PTU presence information. The operation related to the operation of transmitting/receiving the PTU presence information according to an embodiment of the present disclosure is performed in the manner described with reference to  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0291]    The transmitter  2611  transmits various signals, various messages, and the like to a PRU, a PTU, and the like under a control of the controller  2613 . The various signals, the various messages, and the like transmitted in the transmitter  2611  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0292]    The receiver  2615  receives various signals, various messages, and the like from the PRU, the PTU, and the like under a control of the controller  2613 . The various signals, the various messages and the like received in the receiver  2615  have been described in  FIGS. 1 to 23 , and a description thereof will be omitted herein. 
         [0293]    The storage unit  2617  stores a program and various data necessary for the operation of the management server  2600 , information related to the operation of transmitting/receiving the PTU presence information according to an embodiment of the present disclosure, and the like. The storage unit  2617  stores the various signals, the various messages, and the like received in the receiver  2615 . 
         [0294]    While the transmitter  2611 , the controller  2613 , the receiver  2615 , and the storage unit  2617  are described as separate units, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter  2611 , the controller  2613 , the receiver  2615 , and the storage unit  2617  may be incorporated into a single unit. 
         [0295]    As is apparent from the foregoing description, an embodiment of the present disclosure enables transmitting/receiving power transmitting unit (PTU) presence information in a wireless charging network. 
         [0296]    An embodiment of the present disclosure enables transmitting/receiving PTU presence information based on a BLE scheme in a wireless charging network. 
         [0297]    An embodiment of the present disclosure enables transmitting/receiving PTU presence information thereby enabling to transmit/receive PTU presence information when power is supplied to a resonator included in a PTU in a wireless charging network. 
         [0298]    An embodiment of the present disclosure enables transmitting/receiving PTU presence information thereby enabling to transmit/receive PTU presence information even though power is supplied to a resonator included in a PTU and received signal strength of an advertisement message received from a PRU is less than threshold received signal strength in a wireless charging network. 
         [0299]    Certain aspects of the present disclosure may also be embodied as computer readable code on a non-transitory computer readable recording medium. A non-transitory computer readable recording medium is any data storage device that can store data, which can be thereafter read by a computer system. Examples of the non-transitory computer readable recording medium include read only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The non-transitory computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, code, and code segments for accomplishing the present disclosure can be easily construed by programmers skilled in the art to which the present disclosure pertains. 
         [0300]    It can be appreciated that a method and apparatus according to an embodiment of the present disclosure may be implemented by hardware, software and/or a combination thereof. The software may be stored in a non-volatile storage, for example, an erasable or re-writable ROM, a memory, for example, a RAM, a memory chip, a memory device, or a memory integrated circuit (IC), or an optically or magnetically recordable non-transitory machine-readable (e.g., computer-readable), storage medium (e.g., a compact disk (CD), a digital versatile disk (DVD), a magnetic disk, a magnetic tape, and/or the like). A method and apparatus according to an embodiment of the present disclosure may be implemented by a computer or a mobile terminal that includes a controller and a memory, and the memory may be an example of a non-transitory machine-readable (e.g., computer-readable), storage medium suitable to store a program or programs including instructions for implementing various embodiments of the present disclosure. 
         [0301]    The present disclosure may include a program including code for implementing the apparatus and method as defined by the appended claims, and a non-transitory machine-readable (e.g., computer-readable), storage medium storing the program. The program may be electronically transferred via any media, such as communication signals, which are transmitted through wired and/or wireless connections, and the present disclosure may include their equivalents. 
         [0302]    An apparatus according to an embodiment of the present disclosure may receive the program from a program providing device which is connected to the apparatus via a wire or a wireless and store the program. The program providing device may include a memory for storing instructions which instruct to perform a content protect method which has been already installed, information necessary for the content protect method, and the like, a communication unit for performing a wired or a wireless communication with a graphic processing device, and a controller for transmitting a related program to a transmitting/receiving device based on a request of the graphic processing device or automatically transmitting the related program to the transmitting/receiving device. 
         [0303]    While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.