Patent Description:
Recently, wireless or non-contact charging technologies have been developed, which are now widely used for a variety of electronic devices, such as wireless electric toothbrushes or wireless electric shavers.

Using wireless charging technology, which is based on wireless power transmission and reception, a battery of an electronic device, such as a mobile phone, may be automatically recharged if, for example, a user simply places the mobile phone on a charging pad without connecting a separate charging connector to the mobile phone.

Wireless charging technologies may be roughly classified into a coil-based electromagnetic induction scheme, a resonant scheme, and a Radio Frequency (RF)/microwave radiation scheme, which delivers electrical energy by converting it into microwaves.

Although the electromagnetic induction scheme has been used more often, recently, experiments using an RF/microwave radiation scheme have been successful. Thus, it is expected that in the near future, more types of electronic products will be recharged wirelessly.

The electromagnetic induction-based power transmission transmits power between a primary coil and a secondary coil. For example, an induced current occurs, when a magnet is moved around a coil. Using this principle, a transmitter generates a magnetic field, and in a receiver, a current is induced depending on a change in magnetic field, thereby producing energy. This power transmission method has excellent energy transmission efficiency.

As for the resonant scheme, power can be wirelessly transferred to an electronic device by using the Coupled Mode Theory, even though the electronic device is located several meters away from a charging device. The resonant scheme is based on a physics concept, wherein if a tuning fork rings, a nearby wine glass may also ring at the same frequency. However, the resonant scheme resonates electromagnetic waves containing electrical energy, instead of resonating sounds. The resonated electrical energy is directly delivered only to devices having the same resonant frequency, and any unused portion is reabsorbed as electromagnetic fields instead of being spread into the air. Thus, unlike other electromagnetic waves, the resonated electrical energy should not affect adjacent devices and a human body.

<CIT> discloses a wireless power system including wireless power transmit and receive units. The wireless power transmit unit includes a wireless power transmit circuit that generates a wireless power magnetic field and a transmit unit transceiver that transceives a communication regarding the wireless power magnetic field in accordance with a control channel protocol. The wireless power receive unit includes a wireless power receive circuit, a transceiver, and a processing module. The wireless power receive circuit converts the wireless power magnetic field into a voltage. The receive unit processing module is operable to: identify the control channel protocol; determine whether the receive unit transceiver is capable of communication using the control channel protocol; and, when the receive unit transceiver is capable of communication using the control channel protocol, coordinate configuration of the receive unit transceiver to transceive the communication regarding the wireless power magnetic field via the control channel. Document <CIT> discloses a further wireless power system in which a power transmitter is capable to adapt the transmitted power to the current number of power receivers.

Although wireless charging schemes are garnering a great deal of attention and research, no standard has been proposed for the priority of wireless charging, a search for a wireless power transmitter and receiver, a selection of a communication frequency between the wireless power transmitter and receiver, an adjustment of wireless power, a selection of matching circuits, and a distribution of communication time for each wireless power receiver in one charging cycle. In particular, a standard is required for a wireless power transmitter to determine addition and removal of a wireless power receiver to and from a wireless power network managed by the wireless power transmitter.

Accordingly, the present invention is designed to address at least the problems and/or disadvantages described above and to provide at least the advantages described below.

An aspect of the present invention is to provide a standard for the overall operation of a wireless power transmitter and a wireless power transmitter receiver.

Another aspect of the present invention is to provide a wireless power transmitter and method for determining addition and removal of a wireless power receiver to and from a wireless power network managed by the wireless power transmitter.

In accordance with an aspect of the present invention, a method for transmitting wireless power in a wireless power network managed by a power transmitter according to claim <NUM> is provided.

In accordance with another aspect of the present invention, a wireless power transmitter according to claim <NUM> is provided.

The above and other aspects, features, and advantages of certain embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:.

Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, specific details such as detailed configuration and components are merely provided to assist the overall understanding of these embodiments of the present invention. Therefore, it should be apparent to those skilled in the art that various changes and modifications of the embodiments described herein can be made. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

<FIG> illustrates a wireless charging system according to an embodiment of the present invention.

Referring to <FIG>, the wireless charging system includes a wireless power transmitter <NUM> and wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. The wireless power transmitter <NUM> wirelessly transmits power <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n to the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, respectively. More specifically, the wireless power transmitter <NUM> wirelessly transmits the power <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n only to the wireless power receivers that are authorized by performing a predetermined authentication procedure.

The wireless power transmitter <NUM> forms electrical connections with the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-n. For example, the wireless power transmitter <NUM> transmits wireless power in the form of an electromagnetic wave to the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n.

Additionally, the wireless power transmitter <NUM> performs bi-directional communication with the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. The wireless power transmitter <NUM> and the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n process and exchange packets <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, each configured in a predetermined frame. The wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n may be implemented as, for example, mobile communication terminals, Personal Digital Assistants (PDAs), a Personal Multimedia Players (PMPs), smart phones, etc..

The wireless power transmitter <NUM> wirelessly supplies power to the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n using the resonant scheme. When the wireless power transmitter <NUM> uses the resonant scheme, the distance between the wireless power transmitter <NUM> and the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n may be preferably <NUM> or less. However, when the wireless power transmitter <NUM> uses the electromagnetic induction scheme, the distance between the wireless power transmitter <NUM> and the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n may be preferably <NUM> or less.

The wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n charge a battery mounted therein by receiving wireless power from the wireless power transmitter <NUM>. Further, the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-n may transmit, to the wireless power transmitter <NUM>, a signal requesting the transmission of the wireless power, information for receiving the wireless power, status information of the wireless power receiver, control information for the wireless power transmitter <NUM>, etc..

The wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n may send a message indicating their charging status to the wireless power transmitter <NUM>.

The wireless power transmitter <NUM> may include a display that displays a status of each of the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n, based on the messages received from the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. In addition, the wireless power transmitter <NUM> may display an estimated time remain until the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n will be fully charged.

Further, the wireless power transmitter <NUM> may transmit a control signal for disabling the wireless charging function of the wireless power receivers <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-n. Basically, upon receiving the disable control signal for the wireless charging function from the wireless power transmitter <NUM>, a wireless power receiver will disable the wireless charging function.

<FIG> is a block diagram illustrating a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention.

Referring to <FIG>, the wireless power transmitter <NUM> includes a power transmitter <NUM>, a controller <NUM>, and a communication unit <NUM>. The wireless power receiver <NUM> includes a power receiver <NUM>, a controller <NUM>, and a communication unit <NUM>. Herein, the term "unit" refers to a hardware device or a combination of hardware and software.

The power transmitter <NUM> wirelessly supplies power to the wireless power receiver <NUM> via the power receiver <NUM>. The power transmitter <NUM> supplies power in an Alternating Current (AC) waveform. However, when the power transmitter <NUM> receives power in a Direct Current (DC) waveform, e.g., from a battery, the power transmitter <NUM> supplies power in an AC waveform, after converting the DC waveform into the AC waveform using an inverter. The power transmitter <NUM> may be implemented as a built-in battery, or may be implemented as a power receiving interface, which receives power from an outside source, e.g., an outlet, and supplies it to other components. It will be understood by those of ordinary skill in the art that the power transmitter <NUM> has no limit as long as it is capable of supplying power in an AC waveform.

Additionally, the power transmitter <NUM> may provide AC waveforms to the wireless power receiver <NUM> in the form of an electromagnetic wave. Accordingly, the power transmitter <NUM> may also include an additional loop coil, so that it may transmit or receive predetermined electromagnetic waves. When the power transmitter <NUM> is implemented with a loop coil, an inductance L of the loop coil is subject to change. It will be understood by those of ordinary skill in the art that the power transmitter <NUM> has no limit as long as it is capable of transmitting and receiving electromagnetic waves.

The controller <NUM> controls the overall operation of the wireless power transmitter <NUM>, e.g., using an algorithm, program, or application, which is read out from a memory (not shown). The controller <NUM> may be implemented as a Central Processing Unit (CPU), a microprocessor, a minicomputer, etc..

The communication unit <NUM> communicates with the communication unit <NUM> in the wireless power receiver <NUM> using Near Field Communication (NFC), Zigbee, Infrared Data Association (IrDA), Visible Light Communication (VLC), Bluetooth, Bluetooth Low Energy (BLE), etc. Additionally, the communication unit <NUM> may perform communication using the IEEE <NUM>. <NUM> Zigbee communication scheme or the BLE scheme. In addition, the communication unit <NUM> may use a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) algorithm.

The communication unit <NUM> transmits signals associated with information about the wireless power transmitter <NUM>. For example, the communication unit <NUM> may unicast, multicast, or broadcast the signals.

Table <NUM> below illustrates a data structure of a signal transmitted from the wireless power transmitter <NUM>, e.g., at stated periods, according to an embodiment of the present invention.

In Table <NUM>, the `frame type' field, which indicates a type of the signal, indicates that the signal is a Notice signal. Further, the `protocol version' field, which indicates a type of a communication protocol, is allocated, e.g., <NUM> bits, and the `sequence number' field, which indicates a sequential order of the signal, may be allocated, e.g., <NUM> byte. The sequence number increases, e.g., in response to a transmission/reception step of the signal.

The `network ID' field, which indicates a network ID of the wireless power transmitter <NUM>, may be allocated, e.g., <NUM> byte, and the `Rx to Report (schedule mask)' field, which indicates wireless power receivers that will make a report to the wireless power transmitter <NUM>, may be allocated, e.g., <NUM> byte.

Table <NUM> below illustrates an example of an `Rx to Report (schedule mask)' field according to an embodiment of the present invention.

In Table <NUM>, Rx1 to Rx8 correspond to first to eighth wireless power receivers, respectively. Based on Table <NUM>, a wireless power receiver, whose schedule mask number is represented as '<NUM>', i.e., Rx1, Rx6, Rx7, and Rx8, may make a report.

In Table <NUM>, the 'Reserved' field, which is reserved for future use, is allocated, e.g., <NUM> bits, and the `Number of Rx' field, which indicates a number of wireless power receivers adjacent to the wireless power transmitter <NUM>, is allocated, e.g., <NUM> bits.

The signal in the form of the frame in Table <NUM> may be implemented such that it is allocated to Wireless Power Transmission (WPT) in the IEEE <NUM>. <NUM> data structure.

Table <NUM> illustrates the IEEE <NUM>. <NUM> data structure.

As shown in Table <NUM>, the IEEE <NUM>. <NUM> data structure includes `Preamble', `Start Frame Delimiter (SFD), `Frame Length', `WPT', and `Cyclic Redundancy Check (CRC)<NUM>' fields. Further, the data structure shown in Table <NUM> may be included in the WPT field of Table <NUM>.

The communication unit <NUM> receives power information from the wireless power receiver <NUM>. The power information may include at least one of a capacity of the wireless power receiver <NUM>, a battery level, a charging count, usage, a battery capacity, and a battery percentage. The communication unit <NUM> transmits a charging function control signal for controlling the charging function of the wireless power receiver <NUM>. For example, the charging function control signal may enable or disable the charging function by controlling the power receiver <NUM> in the specific wireless power receiver <NUM>.

The communication unit <NUM> also receives signals from other wireless power transmitters (not shown). For example, the communication unit <NUM> may receive a Notice signal in the form of Table <NUM> from another wireless power transmitter.

Although <FIG> illustrates the power transmitter <NUM> and the communication unit <NUM> in different hardware structures, the power transmitter <NUM> and the communication unit <NUM> may also be configured in a single hardware structure.

The wireless power transmitter <NUM> and the wireless power receiver <NUM> exchange various signals. In accordance with an embodiment of the present invention, using this capability, a charging process is provided by joining the wireless power receiver <NUM> to a wireless power network managed by the wireless power transmitter <NUM>.

<FIG> is a block diagram illustrating a wireless power receiver according to an embodiment of the present invention.

Referring to <FIG>, the wireless power receiver <NUM> includes a power receiver <NUM>, a controller <NUM>, a communication unit <NUM>, a rectifier <NUM>, a DC/DC converter <NUM>, a switching unit <NUM>, and a charging unit <NUM>. Because a description of the power receiver <NUM>, the controller <NUM>, and the communication unit <NUM> has already been provided in relation to <FIG>, a repetitive description will be omitted here.

The rectifier <NUM>, e.g., a bridge diode, rectifies the wireless power received from the power receiver <NUM> in the form of DC power. The DC/DC converter <NUM> converts the rectified power by a predetermined gain. For example, the DC/DC converter <NUM> convert the rectified power so that a voltage at its output terminal <NUM> is 5V. The possible minimum and maximum values of the voltage applied to a front end <NUM> of the DC/DC converter <NUM> may be set in advance, and information about these values may be recorded in an 'Input Voltage MIN' field and an `Input Voltage MAX' field of a Request Join signal, respectively, as will be described in more detail below. In addition, a rated voltage value and a rated current value at the rear end <NUM> of the DC/ DC converter <NUM> may be written in a `Typical Output Voltage' field and a `Typical Output Current' field of the Request Join signal.

The switching unit <NUM> connects the DC/DC converter <NUM> to the charging unit <NUM>, under control of the controller <NUM>. The charging unit <NUM> stores the converted power received from the DC/DC converter <NUM>, if the switching unit <NUM> is in an on-state.

<FIG> is a flowchart illustrating a method in wireless power transmitter and receiver according to an exemplary embodiment.

Referring to <FIG>, the wireless power transmitter detects an object located near the wireless power transmitter in step S301. For example, upon detecting a change in load, the wireless power transmitter determines whether a new object is located near the wireless power transmitter. Alternatively, the wireless power transmitter may detect nearby objects based on voltage, current, phase, temperature, etc..

In step S303, the wireless power receiver searches for a wireless power transmitter from which it will receive wireless power in at least one channel. For example, the wireless power receiver transmits a wireless power transmitter search signal to at least one wireless power transmitter, and selects a wireless power transmitter from which it will receive wireless power, based on a wireless power transmitter search response signal received in response to the wireless power transmitter search signal. In addition, the wireless power receiver may form a communication network with the wireless power transmitter from which it will receive wireless power.

In step S305, the wireless power receiver joins the wireless power network managed by the wireless power transmitter from which it will receive wireless power. For example, the wireless power receiver transmits a join request signal (hereinafter referred to as a `Request Join signal') to the wireless power transmitter from which it will receive wireless power, and in response, the wireless power receiver receives a join response signal (hereinafter referred to as a 'Response Join signal') from the wireless power transmitter. The Response Join signal may include join permission/prohibition information, which the wireless power receiver uses to determine whether joining the wireless power network managed by the wireless power transmitter is permitted or not.

In step S307, the wireless power receiver and the wireless power transmitter enter a standby state, wherein the wireless power transmitter may transmit a command signal to the wireless power receiver. The wireless power receiver transmits a report signal or an Acknowledgment (Ack) signal in response to the received command signal. If the command signal includes a charge start command, the wireless power receiver may start charging in step S309.

<FIG> is a circuit diagram illustrating a wireless power transmitter according to an exemplary embodiment.

Referring to <FIG>, the wireless power transmitter includes an input terminal <NUM> receiving a driving voltage VDD. A first end of a coil <NUM> is connected to the input terminal <NUM>, and a second end of the coil <NUM> is connected to a node <NUM>, to which an end of a Field Effect Transistor (FET) element <NUM>, an end of a coil <NUM>, and an end of a capacitor <NUM> are connected. The other end of the FET element <NUM> is grounded. In addition, the other end of the capacitor <NUM> is also be grounded. The other end of the coil <NUM> is connected to a first end of a capacitor <NUM>. A second end of the capacitor <NUM> is connected to a filter <NUM>, which is connected to an end of a capacitor <NUM> and an end of a coil <NUM>. The other end of the capacitor <NUM> is grounded.

The wireless power transmitter measures a load or impedance at the input terminal <NUM>, in order to detect nearby objects. For example, if a new object is placed near the wireless power transmitter, an abrupt load change is detected. Thus, the wireless power transmitter determines that a new object is placed nearby.

Similarly, the wireless power transmitter measures a load or impedance at the input terminal <NUM>, in order to detect an object moving away from the wireless power transmitter. For example, when the measured load abruptly decreases, the wireless power transmitter determines that an object previously placed nearby, has not moved away.

The wireless power transmitter detects the load at the input terminal <NUM>, and also at a front end <NUM> or a rear end <NUM> of the filter <NUM>. That is, the wireless power transmitter determines the a new nearby object or the absence of an object by detecting the loads at various parts.

Alternatively, the wireless power transmitter may determine the a new nearby object or the absence of an object based on a voltage value or a current value.

<FIG> are graphs illustrating a current and a voltage, respectively, which are measured in the wireless power transmitter over the time, according to exemplary embodiments.

In <FIG>, a current value measured at one point of the wireless power transmitter is 'a' from the start of the measuring until time t1. After the time t1, the measured current is `b'. As can be understood from the graph of <FIG>, the current undergoes an abrupt change from 'a' to 'b' at time t1. Further, by detecting the abrupt change, the wireless power transmitter may determine the a new nearby object or the absence of a previous nearby object.

In <FIG>, a voltage value measured at one point of the wireless power transmitter is 'c' from the start of the measuring until time t1. After t1, the measured voltage value is 'd'. As is apparent from the graph of <FIG>, the voltage value undergoes an abrupt change from 'c' to 'd' at time t1. Further, by detecting the abrupt change, the wireless power transmitter may determine the a new nearby object or the absence of a previous nearby object.

<FIG> is a graph illustrating a temperature measured at one point of a wireless power transmitter over the time, according to an exemplary embodiments.

Referring to <FIG>, the temperature measured at one point of the wireless power transmitter linearly increases. Specifically, the temperature measured at one point of the wireless power transmitter increases with a slope of `e' until a time t1. After time t1, the temperature increases with a slope of `f'. As can be understood from <FIG>, the slope for the increasing temperature undergoes an abrupt change from `e' to 'f' at time t1. Further, by detecting the abrupt change, the wireless power transmitter may determine the a new nearby object or the absence of a previous nearby object.

<FIG> is a graph illustrating a phase at one point of a wireless power transmitter according to an exemplary embodiment.

Referring to <FIG>, a voltage <NUM> and a current <NUM> at one point of the wireless power transmitter do not overlap until a specific time. After the specific time, the voltage <NUM> and the current <NUM> may partially overlap, as the phase at one point of the wireless power transmitter is changed. As the voltage <NUM> and the current <NUM> partially overlap, a power loss may occur. That is, the wireless power transmitter may detect an abrupt phase change by detecting the power loss. By detecting the abrupt change, the wireless power transmitter may determine the a new nearby object or the absence of a previous nearby object.

In addition, the wireless power transmitter may determine the proximity of an object using an Infrared (IR) sensor or based on a user input.

<FIG> is a timing diagram illustrating load detection and signal transmission in a wireless power transmitter according to an exemplary embodiment.

Referring to <FIG>, a controller (TX MCU) <NUM> of the wireless power transmitter determines a channel on which it will perform communication, and a network ID in step S510. For example, the wireless power transmitter may set any one of IEEE <NUM>. <NUM> channels <NUM>, <NUM>, <NUM>, and <NUM> as a communication channel. Further, the wireless power transmitter sets a network ID such that it does not duplicate that of another wireless power transmitter <NUM> in the communication channel.

The controller holds the detection state in steps S502 and S515, and transmits detection powers <NUM> and <NUM> for a valid detection period tdet at a stated detection period of stated detection periods of tdet_per.

Accordingly, the controller <NUM> may detect an object in step S511. The detection power and the size of the valid detection period are determined depending on the minimum power and time that the controller <NUM> uses to determine whether there is a candidate device for wireless charging within a valid range by detecting a change in a load value of its power transmitter, i.e., a resonator. That is, because the candidate device, i.e., a metal object, is detected from a change in load of the resonator, the controller <NUM> minimizes the power consumption in the detection state by periodically generating a sine wave with a low voltage, which has a size capable of detecting a load value of the resonator, for a short time required to detect the load value of the resonator. The detection state is maintained for the valid detection period until a new device is detected.

For example, if a wireless power receiver is placed on or over the wireless power transmitter, the controller <NUM> detects a change in load, and determines that an object is placed nearby the wireless power transmitter. For example, the controller <NUM> detects the abrupt change in load as illustrated in <FIG>, or detects an abrupt change in various other criteria as illustrated in <FIG>.

In <FIG>, it is assumed that the controller <NUM> has not detected an abrupt change. Accordingly, the controller <NUM> applies the detection powers <NUM> and <NUM> at stated detection periods, without changes in applied power.

In addition, a communication unit (TX RF) <NUM> transmits a Notice signal at stated periods in steps S514 and S517. For example, the Notice signal may have the data structure shown in Table <NUM> above.

Another wireless power transmitter <NUM> using the communication channel receives the Notice signal transmitted from the communication unit <NUM>. The Notice signal, as described in conjunction with Table <NUM>, may indicate a network ID of the wireless power transmitter, or indicate a schedule of the wireless power receiver that will perform communication with the wireless power transmitter. In addition, the Notice signal is transmitted at stated periods, e.g., every <NUM>, so it may be used as a synchronization signal.

<FIG> and <FIG> are timing diagrams illustrating a power supply operation between a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention.

Referring to <FIG>, a controller <NUM> of a wireless power transmitter detects a change in load by applying detection power <NUM> at stated periods in step S601. In addition, a communication unit <NUM> transmits a Notice signal at stated periods in step S603. In <FIG>, the controller <NUM> of the wireless power transmitter does not detect an abrupt change in load in step S601.

In step S604, a user <NUM> places a wireless power receiver near the wireless power transmitter.

In step S607, the controller <NUM> re-applies detection power, after the preset period, and detects an abrupt change in load, caused by placing the receiver in step S604. If a device is detected within a valid detection period, the controller <NUM> applies driving power (or registration power) Preg, which is greater than the detection power <NUM> by a value <NUM>. The driving power drives a controller <NUM> of the wireless power receiver.

Accordingly, the controller <NUM> is driven (or powered on) in step S605, and initializes a communication unit <NUM> in step S606. The controller <NUM> determines the presence of the wireless power receiver depending on the presence of a pulse initiated by the controller <NUM>. The controller <NUM> may update the wireless power receiver, the presence of which is determined by the controller <NUM>, in a device control table.

<FIG> illustrates an example of a device control table according to an embodiment of the present invention.

Referring to <FIG>, the device control table is used to manage each wireless power receiver's session ID, company ID, product ID, load characteristic, current characteristic, voltage characteristic, efficiency characteristic, current status, a voltage at a front end of a DC/DC converter of the wireless power receiver, a voltage at a rear end of the DC/DC converter of the wireless power receiver, and a current at the rear end of the DC/DC converter of the wireless power receiver. The current status indicates whether the wireless power receiver is in the standby state after being fully charged, whether the wireless power receiver is in the standby state due to the lack of charging power, whether the wireless power receiver is being charged in a Constant Voltage (CV) mode, or whether the wireless power receiver is being charged in a Constant Current (CC) mode.

Referring again to <FIG>, the communication unit <NUM> uses a second channel under control of the controller <NUM>. In the example of <FIG>, the second channel is used by another wireless power transmitter <NUM>, and is different from the channel used by the communication unit <NUM>. Accordingly, the channel used by the communication unit <NUM> will be referred to as "a first channel".

The order in which the controller <NUM> determines a search channel may be set in advance, e.g., using IEEE <NUM>. <NUM> channels <NUM>, <NUM>, <NUM> and <NUM>. Further, the initial search channel searched by the controller <NUM> may be determined at random.

In step S610, the communication unit <NUM> transmits a wireless power transmitter search signal in the second channel. For example, the wireless power transmitter search signal, i.e., a Search signal, may have a data structure as shown in Table <NUM>.

In Table <NUM>, `frame type', which indicates a type of the signal, indicates that the signal is a Search signal. Further, the `protocol version' field, which indicates a type of a communication protocol, is allocated, e.g., <NUM> bits, and the `sequence number' field, which indicates a sequence order of the signal, is allocated, e.g., <NUM> byte. For example, the sequence number increases, for example, in response to a transmission/reception step of the signal. That is, if the sequence number of the Notice signal in Table <NUM> is <NUM>, the sequence number of the Search signal in Table <NUM> is <NUM>.

The `Company ID' field, which indicates manufacturer information for the wireless power receiver, is allocated, e.g., <NUM> byte, the `Product ID' field, which indicates product information for the wireless power receiver, e.g., serial number information of the wireless power receiver may be written in this field, is allocated, e.g., <NUM> bytes, the 'Impedance' field, which indicates impedance information for the wireless power receiver, is allocated, e.g., <NUM> bits, and the 'class' field, which indicates rated power information for the wireless power receiver, is allocated, e.g., <NUM> bits.

In <FIG>, three wireless power transmitters use the second channel, by way of example. In steps S611, S613, and S615, respectively, the three wireless power transmitters <NUM> transmit a wireless power transmitter search response signal to the communication unit <NUM>, in response to the wireless power transmitter search signal,.

The wireless power transmitter search response signal, i.e., a Response Search signal, may have a data structure as shown in Table <NUM>.

In Table <NUM>, the `frame type', which indicates a type of the signal, indicates that the signal is a Response Search signal. The 'Reserved' field, which is reserved for use, is allocated, e.g., <NUM> bits, and the `sequence number' field, which indicates a sequential order of the signal, is allocated, e.g., <NUM> byte. The sequence number increases, for example, in response to a transmission/reception step of the signal. The `network ID' field, which indicates a network ID of the wireless power transmitter, is allocated, e.g., <NUM> byte.

Based on the wireless power transmitter search response signal received on the second channel, the controller <NUM> identifies channel information and network ID information for each of the three wireless power transmitters <NUM> that use the second channel, in steps S612, S614, and S616. In addition, the controller <NUM> stores the identified channel information and network ID information, and Received Signal Strength Indication (RSSI) strength for each channel, in step S617.

In step S618, the communication unit <NUM> transmits a Search signal. Upon failure to receive a Search Response signal to the Search signal, the communication unit <NUM> transmits a Search signal twice more in steps S619 and S620. If the communication unit <NUM> fails to receive a Search Response signal to the Search signal, even after transmitting the Search signal three times, the controller <NUM> changes or switches the search channel to another channel.

In <FIG>, the controller <NUM> changes the search channel to the first channel, by way of example.

The communication unit <NUM> transmits a Search signal using the first channel in step S621. The communication unit <NUM> receives the Search signal, and the controller <NUM> updates the device control table illustrated in <FIG>, based on the Search signal in step S622. In addition, the controller <NUM> generates a Search Response signal corresponding to the Search signal.

The communication unit <NUM> transmits the generated Search Response signal to the communication unit <NUM> in step S623.

Based on the Search Response signal received on the first channel, the controller <NUM> identifies channel information and network ID information of the wireless power transmitter that uses the first channel in step S624. In addition, the controller <NUM> may store the identified channel information and network ID information, and RSSI strength for each channel. The communication unit <NUM> transmits the Search signal three more times in steps S625, S626, and S627.

Thereafter, the wireless power receiver determines a communication channel on which it will perform communication, and a wireless power transmitter from which it will receive wireless power, in step S628. That is, based on the stored channel information and RSSI information, the wireless power receiver determines the communication channel and the wireless power transmitter from which it will receive wireless power. For example, the wireless power receiver may determine a channel with a minimum RSSI value as a communication channel. Thereafter, the communication unit <NUM> of the wireless power receiver forms a pairing with the communication unit <NUM>.

Thereafter, the wireless power transmitter and receiver enter into a joined state.

In step S629, the wireless power receiver generates a Request Join signal based on information about the determined communication channel and the determined wireless power transmitter from which it will receive wireless power. The communication unit <NUM> transmits the generated Request Join signal to the communication unit <NUM> in step S630.

For example, the Request Join signal has a data structure as shown in Table <NUM>.

In Table <NUM>, the `frame type', which indicates a type of the signal, indicates that the signal is a Request Join signal. Additionally, the 'Reserved' field, which is reserved for future use, is allocated, e.g., <NUM> bits, and the 'sequence number' field, which indicates a sequential order of the signal, is allocated, e.g., <NUM> byte. The sequence number increases, for example, in response to a transmission/reception step of the signal.

The `network ID' field, which indicates a network ID of the wireless power transmitter, is allocated, e.g., <NUM> byte, and the `Product ID' field, which indicates product information for the wireless power receiver, e.g., serial number information of the wireless power receiver, is allocated, e.g., <NUM> bytes. The 'Input Voltage MIN' field, which indicates a minimum voltage value applied to a front end of a DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte, the `Input Voltage MAX' field, which indicates a maximum voltage value applied to a rear end of the DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte, the `Typical Output Voltage' field, which indicates a rated voltage value applied to the rear end of the DC/DC inverter (not shown) of the wireless power receiver, is allocated, for example, <NUM> byte, and the `Typical Output Current' field, which indicates a rated current value applied to the rear end of the DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte.

Based on the received Request Join signal, in step S630, the controller <NUM> of the wireless power transmitter determines whether to join the wireless power receiver in the wireless power network. The controller <NUM> of the wireless power transmitter may determine whether to join the wireless power receiver in the wireless power network, based on the device control table illustrated in <FIG>. For example, the wireless power transmitter may not permit the joining of the wireless power receiver, when the wireless power receiver requires a greater amount of power than an available amount of power that the wireless power transmitter may supply.

When the wireless power transmitter determines to join the wireless power receiver in the wireless power network, the controller <NUM> allocates a session ID to the wireless power receiver. The controller <NUM> generates a Response Join signal including the session ID or join permission/prohibition information. In step S632, the controller <NUM> controls the communication unit <NUM> to transmit the generated Response Join signal to the communication unit <NUM> of the wireless power receiver.

For example, the Response Join signal has a data structure as shown in Table <NUM>.

In Table <NUM>, the `frame type', which indicates a type of the signal, indicates that the signal is a Response Join signal. Additionally, the 'Reserved' field, which is reserved for future use, is allocated, e.g., <NUM> bits, and the 'sequence number' field, which indicates a sequential order of the signal, is allocated, e.g., <NUM> byte. The sequence number increases, for example, in response to a transmission/reception step of the signal.

The `network ID' field, which indicates a network ID of the wireless power transmitter, is allocated, for example, <NUM> byte, and the `Permission' field, which indicates whether the joining of the wireless power receiver in the wireless power network is permitted or prohibited, is allocated, e.g., <NUM> bits. For example, if the 'Permission' field indicates '<NUM>', it indicates that the wireless power receiver has permission to join, but if the `Permission' field indicates `<NUM>', it indicates that the wireless power receiver is prohibited from the joining. The `Session ID' field indicates a session ID that the wireless power transmitter allocates to the wireless power receiver, for control of the wireless power network. For example, the `Session ID' is allocated <NUM> bits.

The communication unit <NUM> of the wireless power receiver may transmit the Request Join signal until it receives a Response Join signal from the communication unit <NUM> of the wireless power transmitter.

The controller <NUM> of the wireless power receiver determines whether it is permitted to join, by analyzing the received Response Join signal, and identifies the allocated session ID in step S633.

In step S635, the communication unit <NUM> transmits an Ack signal to the communication unit <NUM>. The communication unit <NUM> may transmit the Response Join signal until it receives an Ack signal from the communication unit <NUM>. In step S636, the controller <NUM> identifies the Ack signal with the channel and network ID, and registers the wireless power receiver in the wireless network in step S637. For example, the controller <NUM> manages the joined wireless power receiver using the device control table illustrated in <FIG>.

In addition, the controller <NUM> may control the joined wireless power receiver to enter the standby state. For example, the controller <NUM> controls the wireless power receiver to stay in the standby state, if the charging of the wireless power receiver is completed, or if the transmit power is not sufficient to charge the capacity of the charging unit of the wireless power receiver.

In step S638, the controller determines that there is no change in load, by detecting the current load. In step S639, the controller <NUM> increases applied power to charging power for charging. The communication unit <NUM> of the wireless power transmitter transmits a Notice signal in step S640, indicating a wireless power receiver with which it will perform communication, among the wireless power receivers. The controller <NUM> of the wireless power transmitter indicates the wireless power receiver with which it will perform communication, using an Rx to Report (schedule mask) field of the Notice signal.

In step S641, the communication unit <NUM> transmits a command signal to start charging. Basically, a command signal, i.e., Command signal, indicates a command that the wireless power receiver is to carry out. For example, the Command signal may have a data structure as shown in Table <NUM>.

In Table <NUM>, the `frame type', which indicates a type of the signal, indicates that the signal is a Command signal. The `Session ID' field indicates a session ID that the wireless power transmitter allocates to each of wireless power receivers, for control of the wireless power network. For example, the `Session ID' field is allocated <NUM> bits. The `sequence number' field, which indicates a sequential order of the signal, is allocated, e.g., <NUM> byte. The sequence number increases, for example, in response to a transmission/reception step of the signal.

The `network ID' field, which indicates a network ID of the wireless power transmitter, is allocated, e.g., <NUM> byte, the `command Type' field, which indicates a type of the command, is allocated, e.g., <NUM> bits, and the 'Variable' field, which supplements the Command signal, is allocated, e.g., <NUM> bits.

The `command Type' field and the 'Variable' field may have various examples as shown in Table <NUM>.

In Table <NUM>, `Charge start' is a command to instruct the wireless power receiver to start charging, `Charge finish' is a command to instruct the wireless power receiver to finish charging, `Request report' is a command to instruct the wireless power receiver to transmit a report signal, 'Reset' is an initialization command, Channel scan' is a command to scan channels, and `Channel change' is a command to change a communication channel.

In step s642, the controller <NUM> of the wireless power receiver may start charging based on the Command signal. In step S643, the controller <NUM> of the wireless power receiver starts charging by turning on a switching unit between a DC/DC converter and a charging unit.

In step S644, the communication unit <NUM> transmits an Ack signal, and in step S645, the communication unit <NUM> transmits a Command signal to request a report. The Command signal is a Command signal with command Type=Request report.

Upon receiving the Command signal transmitted in step S646, the controller <NUM> measures the current power situation in step S647. In step S648, the controller <NUM> generates a Report signal including the current power situation information based on the measurement results. In step S649, the communication unit <NUM> transmits the generated Report signal to the communication unit <NUM>.

The Report signal is a signal for reporting the current status of the wireless power receiver to the wireless power transmitter. For example, the Report signal may have a data structure as shown in Table <NUM>.

In Table <NUM>, the `frame type' field, which indicates a type of the signal, indicates that the signal is a Report signal. The `Session ID' field indicates a session ID that the wireless power transmitter allocates to the wireless power receiver, for control of the wireless power network. For example, the `Session ID' field is allocated <NUM> bits.

Additionally, the `sequence number' field, which indicates a sequential order of the signal, is allocated, e.g., <NUM> byte. The sequence number increases, for example, in response to a transmission/reception step of the signal.

The `network ID' field, which indicates a network ID of the wireless power transmitter, is allocated, e.g., <NUM> byte, the `Input Voltage' field, which indicates a voltage value applied to a front end of a DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte, the 'Output Voltage' field, which indicates a voltage value applied to a rear end of the DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte, and the 'Output Current' field, which indicates a rated current value applied to the rear end of the DC/DC inverter (not shown) of the wireless power receiver, is allocated, e.g., <NUM> byte.

The wireless power transmitter may transmit the Command signal until it receives a Report signal or an Ack signal from the wireless power receiver. If the wireless power transmitter fails to receive a Report signal or an Ack signal from a specific wireless power receiver for an allotted time, the wireless power transmitter may retransmit the Command signal to the specific wireless power receiver for an extra time.

<FIG> is a flowchart illustrating a method in a wireless power transmitter according to an exemplary embodiment.

Referring to <FIG>, the wireless power transmitter periodically outputs detection power for detecting a change in load in step S701. If a change in the load is not detected (No in step S703), the wireless power transmitter continues to periodically output the detection power in step S701. However, if a change in load is detected (Yes in step S703), the wireless power transmitter outputs driving power for communication with a wireless power receiver in step S705. For example, the driving power is an amount of power capable of driving a controller of the wireless power receiver.

In step S707, the wireless power transmitter determines whether a Search signal is received within a predetermined period. If no Search signal is received within the predetermined period (No in step S707), the wireless power transmitter outputs detection power in step S701. However, if a Search signal is received within the predetermined period (Yes in step S707), the wireless power transmitter generates and transmits a Search Response signal in step S709. In step S711, the wireless power transmitter receives a Request Join signal in step S711, and in step S713, generates and transmits a Response Join signal, in response to the Request Join signal.

<FIG> and <FIG> are timing diagrams illustrating an operation wherein a wireless power receiver fails to join a wireless power network managed by a wireless power transmitter, according to an exemplary embodiment.

Referring to <FIG>, a controller <NUM> of the wireless power transmitter periodically outputs detection power <NUM> and performs load detection in steps S811 and S815, and periodically transmits a Notice signal in steps S813 and S816.

A user <NUM> places a wireless power receiver on or over the wireless power transmitter in step S817, and a controller <NUM> detects a change in load in step S814. The controller <NUM> increases applied power to driving power by a value <NUM>, and a communication unit <NUM> of the wireless power receiver is initialized by a controller <NUM> of the wireless power receiver in step S818. The communication unit <NUM> transmits a wireless power transmitter search signal and a wireless power transmitter search response signal in another channel, and stores related information in steps S819 to S827.

Additionally, the communication unit 803transmits a wireless power transmitter search signal, receives a wireless power transmitter search response signal by changing channels, and stores related information in steps S828 to S830.

The controller <NUM> determines a wireless power transmitter from which it will receive wireless power in step S831, and generates a Request Join signal in step S832. The communication unit <NUM> transmits the generated Request Join signal to the communication unit <NUM> in step S833.

The controller <NUM> permits joining of the wireless power receiver, and allocates a session ID thereto in step S834. The communication unit <NUM> transmits a Response Join signal to the communication unit <NUM> in step S835. However, in <FIG> and <FIG>, the Response Join signal fails to be received at the communication unit <NUM> of the wireless power receiver.

The communication unit <NUM> retransmits the Request Join signal in step S836, because it has failed to receive the Response Join signal in step S835. However, the retransmitted Request Join signal also fails to be received at the communication unit <NUM>. The communication unit <NUM> retransmits the Request Join signal in step S837, because it has failed to receive the Response Join signal.

In step S838, the controller <NUM> permits the joining of the wireless power receiver, and allocates a session ID thereto. The communication unit <NUM> transmits a Response Join signal to the communication unit <NUM> in step S839.

In step S840, the communication unit <NUM> transmits an Ack signal for the Response Join signal to the communication unit <NUM> in step S840. However, the Ack signal fails to be received at the communication unit <NUM>.

The controller <NUM> notifies of an occurrence of an error in step S841, when it determines that the signal transmission/reception has failed three times for a registration limit time (or a join limit time) Tregistration_limit. The `three times' is a mere example, and is subject to change.

In accordance with another embodiment of the present invention, the controller <NUM> of the wireless power transmitter may immediately notify the error, upon a lapse of the registration limit time, regardless of the number of the signal transmission/reception failures, in step S841.

For the notification of the error, visual or acoustic indicator devices may be used to generate an alert tone or to blink a Light Emitting Diode (LED). Additionally, the occurrence of the error may be output on a display (not shown).

The controller <NUM> determines whether to remove the cause of an error, by load detection in step S842. The notification of the occurrence of an error may be repeated in step S843, until the wireless power receiver is removed from the wireless power transmitter.

The controller <NUM> may determine whether to remove the wireless power receiver, based on whether the load has returned to the initial load.

Accordingly, the controller <NUM> periodically applies the detection power <NUM>, and determines in steps S842 and S845 whether the load has returned to the initial load. When the load returns to the initial load, as the user <NUM> removes the wireless power receiver from the wireless power transmitter in step S844, the controller <NUM> of the wireless power transmitter stops the notification of the occurrence of an error.

<FIG> and <FIG> are timing diagrams illustrating a method for determining to remove a wireless power receiver from a wireless power network managed by a wireless power transmitter according to an exemplary embodiment.

Referring to <FIG>, a wireless power transmitter outputs charging power <NUM> to a wireless power receiver. In step S911, a communication unit <NUM> of the wireless power transmitter transmits a Notice signal. The wireless power receiver determines whether to perform communication, by identifying an `Rx to Report (schedule mask)' field in the Notice signal.

A controller <NUM> of the wireless power transmitter generates a Command signal including its session ID information in step S912, and controls the communication unit <NUM> to transmit the Command signal to a communication unit <NUM> of the wireless power receiver in step S913. A controller <NUM> of the wireless power receiver analyzes the Command signal in step S914, and generates a Report signal including information about the current power situation in step S915. The communication unit <NUM> transmits the generated Report signal to the communication unit <NUM> in step S916. The controller <NUM> performs impedance matching and the like, based on the received Report signal in step S917.

A user <NUM> removes the wireless power receiver in step S918. In step S919, the controller <NUM> detects a change in load. The communication unit <NUM> transmits a Notice signal in step S920, and transmits a Command signal in step S921. The communication unit <NUM> does not receive a Report signal in step S922 due to the removal of the wireless power receiver. The communication unit <NUM> of the wireless power transmitter continues to transmit the Command signal during one superframe cycle, which is a period where a Notice signal is transmitted, in steps S921 and S923. However, the communication unit <NUM> fails to receive the Report signal in steps S922 and S924.

The controller <NUM> performs load detection again in step S925, transmits a Notice signal even during the next one superframe cycle in step S926, and transmits a Command signal in steps S927 and S929. Even during that cycle, the communication unit <NUM> fails to receive the Report signal in steps S928 and S930. The controller <NUM> performs load detection again in step S931, transmits a Notice signal even during the next one superframe cycle in step S932, and transmits a Command signal in steps S933 and S935. Even during that cycle, the communication unit <NUM> of the wireless power transmitter fails to receive the Report signal in steps S934 and S936.

If the communication unit <NUM> fails to receive a Report signal or an Ack signal even during three superframe cycles, the controller <NUM> determines, in step S937, that the wireless power receiver is removed. As a result, the controller <NUM> reduces the applied power to detection power by a value <NUM>.

Thereafter, the controller <NUM> performs load detection again by periodically applying detection power in step S939, and the communication unit <NUM> transmits a Notice signal in step S940. As described above, the wireless power transmitter may reliably determine whether the wireless power receiver is removed, contributing to prevention of power waste.

<FIG> is a flowchart illustrating a method joining a wireless power receiver and transmitting charging power in a wireless power transmitter according to an exemplary embodiment. In <FIG>, it is assumed that a wireless power transmitter and one wireless power receiver are already performing charging.

Referring to <FIG>, the wireless power transmitter transmits first charging power to a first wireless power receiver in step S1001. A user then places a second wireless power receiver on or near the wireless power transmitter.

The wireless power transmitter detects a change in load based on the placement of the second power receiver in step S1003. Upon failure to detect the change in load (No in step S1003), the wireless power transmitter continues to transmit the first charging power to the first wireless power receiver in step S1001.

However, when the wireless power transmitter detects the change in load (Yes in step S1003), the second wireless power receiver transmits a Search signal and the wireless power transmitter receives the Search signal in step S1005. The wireless power transmitter generates and transmits a Search Response signal in response to the Search signal in step S1007. In addition, the wireless power transmitter receives a Request Join signal from the second wireless power receiver in step S1009, and transmits a Response Join signal corresponding thereto in step S1011. Accordingly, the second wireless power receiver may join in the wireless power network managed by the wireless power transmitter, and the wireless power transmitter further transmits second charging power in step S1013.

<FIG> and <FIG> are timing diagrams illustrating a power supply operation between a wireless power transmitter and two wireless power receivers according to an embodiment of the present invention. Specifically, in <FIG> and <FIG>, a first wireless power receiver <NUM> is already performing charging by receiving first charging power from the wireless power transmitter.

Referring to <FIG>, a controller <NUM> of the wireless power transmitter transmits first charging power <NUM> for charging the first wireless power receiver <NUM>. In step S1111, the controller <NUM> periodically detects a change in load, using the first charging power <NUM>. Further, a communication unit <NUM> of the wireless power transmitter transmits a Notice signal in step S1113. A `Number of Rx' field of the Notice signal includes information indicating that the number of wireless power receivers presently being charged is one.

The controller <NUM> generates a Command signal including a session ID of the first wireless power receiver <NUM> in step S1114, and the communication unit <NUM> transmits the generated Command signal in step S1115. A `Request report' is written in a command Type field of the Command signal. The first wireless power receiver <NUM> measures its current power situation based on the Command signal, generates a Report signal including its current power situation, and transmits the Report signal to the communication unit 1102in step S1116.

The controller <NUM> manages the power situation based on the received Report signal, and performs impedance matching in step S1117.

A user places a second wireless power receiver <NUM> on or near the wireless power transmitter, and the controller <NUM> detects an abrupt change in load in step S1120. The second wireless power receiver <NUM> generates a Search signal including a product ID and transmits the Search signal to the communication unit <NUM> in step S1118. The controller <NUM> identifies the product ID of the second wireless power receiver <NUM> based on the received Search signal, and manages the product ID by registering it in a device control table as illustrated in <FIG>, in step S1119. In step S1121, the communication unit <NUM> transmits a Search Response signal corresponding to the Search single.

The second wireless power receiver <NUM> transmits a Request Join signal to the communication unit <NUM> in step S1122. In response, the communication unit <NUM> transmits a Response Join signal in step S1123. The controller <NUM> determines whether to permit joining of the second wireless power receiver <NUM> and transmits a Response Join signal including the permission of joining. In response, the second wireless power receiver <NUM> transmits an Ack signal in step S1124 and enters a standby state after joining in the network.

The controller <NUM> transmits second charging power <NUM> for charging the second wireless power receiver <NUM>. In addition, the communication unit <NUM> transmits a Command signal including a charge start command to the second wireless power receiver <NUM> in step S1126. The second wireless power receiver <NUM> performs charging by turning on a switching unit connected to a charging unit thereof, based on the Command signal. In addition, the second wireless power receiver <NUM> transmits an Ack signal in step S1127.

The controller <NUM> checks for a change in load, after a lapse of the predetermined period, in step S1128. If there is no change in load, the controller <NUM> of the wireless power transmitter transmits the same charging powers, i.e., the first and second charging powers.

In step S1129, the communication unit <NUM> transmits a Notice signal. In addition, the communication unit <NUM> transmits a Command signal to each of the first and second wireless power receivers <NUM> and <NUM> in steps S1130 and S1132. The communication unit <NUM> receives a Report signal from each of the first and second wireless power receivers <NUM> and <NUM> in steps S1131 and S1133.

After a lapse of the predetermined period, the communication unit <NUM> transmits a Notice signal in step S1134. In addition, the communication unit <NUM> transmits a Command signal to the first and second wireless power receivers <NUM> and <NUM> in steps S1135 and S1137, respectively. The communication unit <NUM> receives a Report signal from the first and second wireless power receivers <NUM> and <NUM> in steps S1 <NUM> and S1138, respectively.

<FIG> illustrates timing split diagrams for a wireless power transmitter according to an embodiment of the present invention.

Referring to <FIG>, where the wireless power transmitter manages only the first wireless power receiver <NUM>, a half of the full superframe cycle is allocated as a time <NUM> for communication with the first wireless power receiver <NUM>, while the other half is allocated as a contention period <NUM>. The contention period may be a period allocated for a case where communication is not performed.

Referring to <FIG>, when the second wireless power receiver <NUM> has joined in the wireless power network, the wireless power transmitter splits the allocated full period <NUM> into three equal parts, and allocates them to a period <NUM> for communication with the first wireless power receiver <NUM>, a period <NUM> for communication with the second wireless power receiver <NUM>, and a contention period <NUM>, respectively.

<FIG> is a flowchart illustrating a method in a wireless power transmitter according to an embodiment of the present invention.

Referring to <FIG>, the wireless power transmitter transmits a Command signal for requesting a Report signal in step S1301. Upon failure to receive a Report signal (No in step S1303), the wireless power transmitter waits for reception of a Report signal in the next superframe cycle. Upon failure to receive a Report signal during the next three superframe cycles (Yes in step S1305), the wireless power transmitter determines in step S1307 that the wireless power receiver is removed. In step S1309, the wireless power transmitter reduces the charging power required to charge the wireless power receiver before power transmission.

However, if a Report signal is received (Yes in step S1303), the wireless power transmitter transmits a Command signal after the next superframe cycle.

<FIG> illustrates changes in allotted times due to a removal of a wireless power receiver according to an embodiment of the present invention.

Referring to <FIG>, when a wireless power transmitter manages two wireless power receivers, the wireless power transmitter splits the full superframe cycle into three equal parts, and allocate them to a period <NUM> for communication with a first wireless power receiver, a period <NUM> for communication with a second wireless power receiver, and a contention period <NUM>, respectively, as illustrated in <FIG>. However, if, for example, the second wireless power receiver is removed, the wireless power transmitter splits the full superframe cycle into two equal parts, and allocates them to a period <NUM> for communication with the first wireless power receiver and a contention period <NUM>, respectively, as illustrated in <FIG>.

<FIG> illustrates device control tables that are used for managing wireless power receivers in a wireless power transmitter according to an embodiment of the present invention.

In <FIG>, a wireless power transmitter manages first to third wireless power receivers. Accordingly, the wireless power transmitter allocates session IDs of <NUM>, <NUM>, and <NUM> to the first to third wireless power receivers, respectively. Thereafter, if it is determined that the second wireless power receiver is removed, the wireless power transmitter deletes the session ID allocated for the second wireless power receiver from the device control table. The wireless power transmitter allocates the session ID for the second wireless power receiver to the third wireless power receiver, as illustrated in <FIG>. Otherwise, the wireless power transmitter manages the third wireless power receiver to keep its session ID, as illustrated in <FIG>.

<FIG> and <FIG> are timing diagrams illustrating an operation wherein one of two wireless power receivers is removed from a wireless power network managed by a wireless power transmitter, according to an embodiment of the present invention.

Referring to <FIG>, a controller <NUM> of the wireless power transmitter transmits charging power <NUM> for charging first and second wireless power receivers <NUM> and <NUM>. Because no change in load is detected in step S1611, the controller <NUM> continues to transmit the charging power <NUM>. In addition, a communication unit <NUM> of the wireless power transmitter transmits a Notice signal to the first and second wireless power receivers <NUM> and <NUM> in steps S1613 and S1614. The communication unit <NUM> generates a Command signal in step S1615, and transmits the generated Command signal to the first wireless power receiver <NUM> in step S1616. The first wireless power receiver <NUM> generates a Report signal and transmits it to the communication unit <NUM> in step S1617. The controller <NUM> determines the current power situation by analyzing the Report signal, and performs impedance matching in step S1618.

The communication unit <NUM> transmits a Command signal to the second wireless power receiver <NUM> in step S1619, and receives a Report signal from the second wireless power receiver <NUM> in step S1620.

A user removes the first wireless power receiver <NUM>, and the controller <NUM> detects an abrupt change in load in step S1621. As described above with reference to <FIG>, the controller <NUM> may determine whether the first wireless power receiver <NUM> is removed, based on various criteria, e.g., the load, in various positions of the wireless power transmitter.

In step S1622, the communication unit <NUM> transmits a Notice signal to the second wireless power receiver <NUM>. In step <NUM>, the communication unit <NUM> transmits a Command Request Report signal to the first wireless power receiver <NUM>. In step S1624, the first wireless power receiver <NUM> may not return a Report signal. In step <NUM>, the communication unit <NUM> transmits a Command Request Report signal to the second wireless power receiver <NUM>. In step S <NUM>, the second wireless power receiver <NUM> may return a Report signal.

In step S1627, the controller <NUM> detects no change in load. The communication unit <NUM> transmits a Notice signal in steps S1628 and S1629. The communication unit <NUM> transmits a Command signal to the first wireless power receiver <NUM> in step S1630, but fails to receive a Report signal in step S1631 because of the removal of the first wireless power receiver <NUM>. Subsequently, the communication unit <NUM> transmits a Command signal to the second wireless power receiver <NUM> in step S1632, and the second wireless power receiver <NUM> transmits a Report signal in step S1633.

The controller <NUM> detects no change in load in step S1634. In steps S1635 and S1636, the communication unit <NUM> transmits a Notice signal. The communication unit <NUM> transmits a Command signal to the first wireless power receiver <NUM> in step S1637, but fails to receive a Report signal in step S1638 because of the removal of the first wireless power receiver <NUM>. Subsequently, the communication unit <NUM> transmits a Command signal to the second wireless power receiver <NUM> in step S1639, and the second wireless power receiver <NUM> transmits a Report signal in step S1640.

Upon failure to receive a Report signal from the first wireless power receiver <NUM>, e.g., during three superframe cycles, the controller <NUM> of the wireless power transmitter determines in step S1641 that the first wireless power receiver <NUM> has been removed. Thereafter, the controller <NUM> reduces first charging power <NUM>.

The controller <NUM> performs load detection in step S1643, and transmits a Notice signal in step S1644. The communication unit <NUM> transmits a Command signal only to the second wireless power receiver <NUM> in step S1645, and receives a Report signal in response thereto in step S1646.

<FIG> and <FIG> are timing diagrams illustrating communication between a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention. Specifically, <FIG> and <FIG> are timing diagrams for a wireless power transmitter and a wireless power receiver performing communication based on a BLE scheme.

Referring to <FIG>, a controller <NUM> of the wireless power transmitter checks for a change in load by applying detection power <NUM> at stated periods in step S <NUM>. In addition, a communication unit <NUM> of the wireless power transmitter transmits a Notice signal at stated periods in step S1703. In <FIG>, the controller <NUM> fails to detect an abrupt change in load in step S1701.

In step S1704, a user <NUM> places the wireless power receiver on or near the wireless power transmitter.

In step S1707, the controller <NUM> re-applies detection power after the superframe cycle, and detects an abrupt change in load. When a device is detected within a valid detection period, the controller <NUM> applies driving power (or registration power) Preg, which is greater than the detection power <NUM> by a value <NUM>. The driving power may be power capable of driving a controller <NUM> of the wireless power receiver.

A controller <NUM> of the wireless power receiver is driven (or powered on) in step S1705, and initializes a communication unit <NUM> of the wireless power receiver in step S <NUM>. The controller <NUM> determines the presence of the wireless power receiver depending on the presence of a pulse that is initiated by the controller <NUM>. The controller <NUM> may update the wireless power receiver, the presence of which is determined by the controller <NUM>, in a device control table.

For example, the device control table manages each wireless power receiver's session ID, company ID, product ID, load characteristic, current characteristic, voltage characteristic, efficiency characteristic, current status, a voltage at a front end of a DC/ DC converter of the wireless power receiver, a voltage at a rear end of the DC/DC converter of the wireless power receiver, and a current at the rear end of the DC/DC converter of the wireless power receiver. The current status is information indicating whether the wireless power receiver is in the standby state after being fully charged, whether the wireless power receiver is in the standby state due to the lack of charging power, whether the wireless power receiver is being charged in a CV mode, or whether the wireless power receiver is being charged in a CC mode.

The communication unit <NUM> uses a second channel under control of the controller <NUM>. The second channel is a channel used by another wireless power transmitter <NUM>, which is different from the channel used by the communication unit <NUM>. Accordingly, the channel used by the communication unit <NUM> is called a first channel.

The order, in which the controller <NUM> determines a search channel, may be set in advance, and the initial search channel searched by the controller <NUM> may be randomly selected from the BLE channels.

The communication unit <NUM> transmits a wireless power transmitter search signal in the second channel in step S1710. The wireless power transmitter search signal may include device information of the wireless power receiver. For example, the device information of a wireless power receiver may include an ID of the wireless power receiver and information about a device of the wireless power receiver. The information about a device of a wireless power receiver may include at least one of a company, a serial number, a protocol version, a hardware version, and a parameter associated with charging of the wireless power receiver.

In <FIG>, three wireless power transmitters use the second channel, and each of the three wireless power transmitters <NUM> may transmit a wireless power transmitter search response signal to the communication unit <NUM> in response to the wireless power transmitter search signal in steps S1711, S1714, and S1717. The communication unit <NUM> transmits a response signal or an Ack signal to the three wireless power transmitters <NUM> in steps S1713, S1716, and S1719.

The communication unit <NUM> transmits a Search signal in steps S1720, S1721, and S1722.

The controller <NUM> may change the search channel to the first channel. The communication unit <NUM> transmits a Search signal using the first channel in step S1723. The communication unit <NUM> receives the Search signal, and the controller <NUM> stores identifier information of the wireless power receiver and an RSSI value in step S1724. The controller <NUM> compares the stored RSSI with an RSSI threshold in step S1725, and determines whether to respond to the Search signal in step S1726.

When the wireless power transmitter determines to respond, the communication unit <NUM> transmits a Response signal in step S1728. The Response signal may include device information of the wireless power transmitter. The device information of a wireless power transmitter may include an ID of the wireless power transmitter.

The controller <NUM> controls the communication unit <NUM> of the wireless power receiver in step S1732, and the communication unit <NUM> transmits an identifier and device information of the wireless power receiver in step S1729. The controller <NUM> receives the identifier and device information in step S1730, and determines whether to join the wireless power receiver in step S1731.

When the wireless power transmitter determines to join the wireless power receiver, the communication unit <NUM> transmits a Connection signal to the communication unit <NUM> in step S1733. The Connection signal may include information such as a keep-alive period, and an address of each of a wireless power transmitter and a wireless power receiver. The wireless power receiver determines an ID of the wireless power transmitter and parameters, based on the received Connection signal in step S1734.

In accordance with an alternative embodiment of the present invention, the communication unit <NUM> may form a communication network by transmitting a Connection signal in step S1733, immediately after receiving the Search signal from the wireless power receiver in step S1723.

The communication unit <NUM> transmits a parameter signal `TX parameter' of the wireless power transmitter to the communication unit <NUM> of the wireless power receiver in step S1735. The parameter signal of a wireless power transmitter may include at least one of an identifier of the wireless power transmitter, the wireless power receiver's identifier, company, serial number, protocol version and hardware version, the amount of available charging power of the wireless power transmitter, the number of wireless power receivers presently being charged, the amount of presently charged power, and the amount of available surplus power.

The communication unit <NUM> transmits a parameter signal 'RX parameter' of the wireless power receiver in step S1736. The controller <NUM> receives parameters of the wireless power receiver in step S1737 and determines whether to join the wireless power receiver in the wireless power network by analyzing the parameters of the wireless power receiver in step S <NUM>. The controller <NUM> generates a `Permission info' signal indicating whether to permit the joining, in step S1739, and transmits the join permission signal to the communication unit <NUM> of the wireless power receiver in step S1740. The subsequent charging process in steps S1741 to S1752 is the same as that in <FIG> and <FIG>, which has already been described above. Accordingly, a repetitive detailed description of steps S1741 to S1752 will be omitted here.

As described above, embodiments of the present invention may reliably perform wireless charging based on the Zigbee scheme and the BLE scheme.

As is apparent from the foregoing description, various embodiments of the present invention provide a procedure in which a wireless power transmitter determines to join or remove a wireless power receiver from a wireless power network, thereby preventing power waste.

Claim 1:
A method for transmitting wireless power in a wireless power network managed by a wireless power transmitter(<NUM>), the method comprising:
transmitting, by one resonator of the wireless power transmitter (<NUM>), a first power for charging a first power receiver(<NUM>-<NUM>);
while outputting the first power for charging the first power receiver, receiving through a communication unit of the wireless power transmitter, a first signal from a second power receiver(<NUM>-<NUM>), the first signal being a wireless power transmitter search signal;
transmitting, through the communication unit, a second signal corresponding to the first signal to the second power receiver, the second signal being a search response signal;
receiving, through the communication unit, from the second power receiver, a third signal, the third signal being a request join signal;
based on determining that the wireless power transmitter is capable of providing power to the second power receiver based on information in the third signal, transmitting, to the second power receiver through the communication unit, a fourth signal being a response join signal, and a command signal enabling the second power receiver to perform charging by turning on a switching unit of the second power receiver which is connected to a charging unit of the second power receiver, and
transmitting, by the one resonator, a second power for charging the first power receiver(<NUM>-<NUM>) and the second power receiver(<NUM>-<NUM>), wherein the second power is greater than the first power.