Patent Publication Number: US-11050303-B2

Title: Wireless charging apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/817,514, filed on Mar. 12, 2020, which is a continuation of U.S. application Ser. No. 15/832,618, filed on Dec. 5, 2017, now U.S. Pat. No. 10,601,263, which is a continuation of U.S. application Ser. No. 14/657,482, filed on Mar. 13, 2015, now U.S. Pat. No. 9,859,746, which is a continuation of U.S. application Ser. No. 13/474,300, filed on May 17, 2012, now U.S. Pat. No. 9,000,723, which is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2011-0046316, filed on May 17, 2011 in the Korean Intellectual Property Office and to Korean Patent Application No. 10-2012-0052123, filed on May 16, 2012 in the Korean Intellectual Property Office. The contents of each of these applications are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates generally to a wireless charging apparatus and method, and more particularly, to a wireless charging apparatus and method that uses a wireless power receiver to wirelessly receive power from a wireless power transmitter and that charges a battery with the received power. 
     2. Description of Related Art 
     With the continued improvements in the field of Information Technology (IT) and the increasing prevalence of a wide variety of portable electronic products, a variety of techniques have been developed that supply power for portable electronic products. Technology for supplying power typically used a power line in the past. However, wireless power transmission technology, which is capable of wirelessly supplying power, has recently been developed. 
     Wireless power transmission technology includes technology for delivering electrical energy in the form of electromagnetic waves, electromagnetic induction, or electromagnetic resonance, for example. Wireless power transmission technology makes it possible to supply power wirelessly anytime and anywhere, without the use of power lines, such as, electric wires. This wireless power transmission technology is a core technology for wirelessly charging electronic devices, supplying wireless power for and/or wirelessly charging electric cars, supplying wireless power to remote places, and supplying power to ubiquitous wireless sensors. Thus wireless power transmission technology has attracted the attention of the public as a promising technology to replace the existing schemes of supplying power for and/or charging electronic devices using electric wires. 
     For example, when wireless power transmission technology is used for a wireless charging apparatus, the wireless charging apparatus may include a wireless power transmitter for supplying power, and a wireless power receiver for receiving power and charging its battery with the received power. The wireless power transmitter may detect when an object is put on a source resonator by measuring a change in load or a change in resonant frequency from a wireless charging standby state. Upon detecting that the object is put on the source resonator, the wireless power transmitter determines whether the object is an object that may undergo wireless charging, or whether the object is just a metallic object, by performing an authentication process, such as, for example, exchanging an IDentifier (ID) with the object. If the authentication is successful, the wireless power transmitter starts negotiations on power transmission, thereby determining that the object put on the source resonator is a wireless rechargeable-charger (e.g., a wireless power receiver). Upon completion of the negotiations, the wireless power transmitter starts supplying wireless power for charging of the wireless power receiver so that the wireless power receiver may be charged. The wireless power transmitter determines whether the wireless power receiver has been fully charged, and stops its power transmission to the wireless power receiver if the wireless power receiver has been fully charged. 
     In the conventional wireless charging scheme described above, the wireless power transmitter stops its wireless power transmission when the wireless power receiver sends an End Power Transfer (EPT) packet to the wireless power transmitter. Therefore, the wireless power receiver may not perform an auxiliary charge. The term ‘auxiliary charge’, as used herein, may refer to charging that is conducted to supplement the power that has been self-discharged or consumed during use of the wireless power receiver with a full charge status displayed on UI. 
     Since the conventional wireless charging apparatus cannot perform an auxiliary charge, a User Interface (UI) screen may not display a full charge status with the transmission of wireless power interrupted. 
     Therefore, although the wireless charging apparatus has performed wireless charging for a long time, the user may misjudge that the wireless charging apparatus is out of order or malfunctions, because the user can not perceive the full charge status on User Interface (UI) screen. 
     When the battery power of the wireless power receiver drops below a predetermined amount of power due to discharge while in the fully charged state, the wireless power receiver performs recharging instead of the auxiliary charge. During recharging, the wireless power receiver displays a charging status on the UI. Thus, the user may not be able to determine whether the wireless power receiver is performing recharging after being fully charged, or the wireless power receiver is being continuously charged before being fully charged. For example, the user may misjudge that the wireless power receiver is being continuously charged without being fully charged, even though the wireless power receiver is actually being recharged after it was fully charged. 
     SUMMARY 
     The present invention has been made to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention provides a wireless power receiver that includes a communication unit, a power receiver configured to receive transmission power transmitted from a wireless power transmitter at a power receiver of the wireless power receiver, a battery configured to charge with the received transmission power, and a Power Management Integrated Circuit (PMIC) configured to determine whether the battery is fully charged, to control the communication unit to transmit a Charge Status (CS) packet to the wireless power transmitter when the battery is fully charged and to perform an auxiliary charge of the battery by receiving strength-reduced transmission power from the wireless power transmitter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a flow diagram illustrating a wireless charging operation of a wireless charging apparatus that cannot perform an auxiliary charge; 
         FIG. 2  is a diagram illustrating a structure of a wireless charging apparatus, according to an embodiment of the present invention; 
         FIG. 3  is a flow diagram illustrating a wireless charging method, according to an embodiment of the present invention; and 
         FIG. 4  is a diagram illustrating a structure of a Charge Status (CS) packet, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Embodiments of the present invention are described in detail with reference to the accompanying drawings. The same or similar components may be designated by the same or similar reference numerals although they are illustrated in different drawings. Detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring the subject matter of the present invention. 
     Embodiments of the present invention provide a wireless charging apparatus and method for performing an auxiliary charge upon completion of wireless charging between a wireless power transmitter and a wireless power receiver. The wireless charging apparatus may be used for wirelessly charging electronic devices, supplying wireless power for and/or wirelessly charging electric cars, supplying wireless power to remote places, and supplying power to ubiquitous wireless sensors. The wireless charging apparatus may be applied to any devices that can perform wireless power transmission and perform charging by receiving wireless power. 
     A wireless charging operation of a wireless charging apparatus that cannot perform auxiliary charge is described in detail below. Thereafter, a wireless charging apparatus and method are described, which perform an auxiliary charge upon completion of wireless charging. 
       FIG. 1  is a flow diagram illustrating a wireless charging operation between a wireless power transmitter and a wireless power receiver, in which an auxiliary charge is not supported. Referring to  FIG. 1 , a wireless power transmitter  10  charges, or recharges, a battery in a wireless power receiver  50  by transmitting and receiving wireless power, in step  12 . 
     In step  14 , the wireless power receiver  50  determines whether it is in a fully charged state in which its battery is fully charged. If the wireless power receiver  50  is in the fully charged state, the wireless power receiver  50  displays the full charge status indicating that charging of the wireless power receiver  50  is complete. The full charge status is displayed on a UI screen implemented by a display module, such as a Liquid Crystal Display (LCD), so that a user of the wireless power receiver may recognize the fully charged state, in step  16 . 
     In step  18 , the wireless power receiver  50  transmits an End Power Transfer (EPT) packet, having a Charge Complete message, to the wireless power transmitter  10  in accordance with the Wireless Power Consortium (WPC) 1.1 standard. 
     Upon receiving the EPT packet from the wireless power receiver  50 , the wireless power transmitter  10  stops the transmission of wireless power, in step  20 . While the wireless power receiver  50  receives no power, the fully charged battery is discharged little by little, and the full charge status will disappear from the UI screen. 
     In step  22 , the wireless power receiver  50  determines whether the charged power is less than or equal to a predetermined power due to the above-described battery discharge. If the battery power is less than or equal to the predetermined power, the wireless power receiver  50  sends a charging request to the wireless power transmitter  10 , in step  24 . 
     In step  26 , the wireless power transmitter  10  sends a response to the charging request to the wireless power receiver  50 . In step  28 , upon receiving the response to the charging request, the wireless power receiver  50  displays a charging status indicating that the wireless power receiver  50  is charging its battery. The charging status is displayed on the UI screen so that the user may recognize that the wireless power receiver  50  is charging its battery. 
     Thereafter, in step  30 , the wireless power transmitter  10  charges the wireless power receiver  50  by transmitting and receiving wireless power. Steps  14  to  30  may be repeated until wireless power transmission/reception is impossible due to, for example, separating the wireless power receiver  50  from the wireless power transmitter  10 . 
     In the wireless charging apparatus and method described above, the wireless power transmitter  10  stops the transmission of wireless power when the wireless power receiver  50  sends an EPT packet to the wireless power transmitter  10 . Accordingly, the wireless power receiver  50  is prevented from performing an auxiliary charge. 
     Due to the inability of the wireless charging receiver  50  to perform the auxiliary charge, the wireless power receiver  50  doesn&#39;t display a full charge status with its charging interrupted. Thus, if the wireless power receiver  50  doesn&#39;t display a full charge status despite the lapse of a full charge time, the user may consider that the wireless charging apparatus is out of order or malfunctions. 
     In addition, if the battery power is less than or equal to a predetermined power due to the discharge occurring in the fully charged state, the wireless power receiver  50  will perform recharging. The wireless power receiver  50  displays a charging status on the UI. The user may not be able to determine whether the wireless power receiver  50  is performing recharging after being fully charged, or the wireless power receiver  50  is being continuously charged before being fully charged. For example, the user may misjudge that the wireless power receiver  50  is being continuously charged without being fully charged, even though it is actually being recharged after it was fully charged. 
     Accordingly, an embodiment of the present invention provides a wireless charging apparatus and method capable of performing an auxiliary charge upon completion of the wireless charging between a wireless power transmitter and a wireless power receiver. 
       FIG. 2  is a diagram illustrating s structure of a wireless charging apparatus, according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the wireless charging apparatus includes a wireless power transmitter  100  and a wireless power receiver  200 . 
     The wireless power transmitter  100 , which may be embodied as a charging pad, for example, includes a power supply  110 , a first controller  120 , a power converter  130 , a first coil  135 , a first communication unit  140 , and a first display  150 . 
     The power supply  110 , which is a power source, supplies necessary power to the wireless power transmitter  100  and supplies Direct Current (DC) power for wireless power transmission. 
     The first controller  120 , which controls the overall operation of the wireless power transmitter  100 , generates various messages needed for wireless power transmission, sends the generated messages to the first communication unit  140 , receives messages from the first communication unit  140 , and performs control corresponding thereto. The first controller  120  calculates an amount of transmission power based on the information received from the wireless power receiver  200 , and controls the power converter  130  to convert the transmission power. If a CS packet is received through the first communication unit  140  when a battery  240  in the wireless power receiver  200  is fully charged, the first controller  120  detects full charge status information included in the CS packet. The CS packet includes information indicating a battery charge level, and may have a value of 1 to 100. A value of 1 indicates that the battery  240  is almost completely uncharged, and a value of 100 indicates that the battery  240  is fully charged. In the latter case, where the battery  240  in the wireless power receiver  200  is fully charged, the wireless power receiver  200  may transmit a CS packet with a value of 100. Upon receiving a CS packet indicating the full charge of the battery  240  in the wireless power receiver  200 , the first controller  120  controls the first display  150  to display full charge status information thereon, and controls the power converter  130  to reduce a strength of the wireless power to a predetermined strength. 
     The power converter  130  converts a DC voltage provided from the power supply  110  into transmission power so that the converted transmission power may be transmitted to the wireless power receiver  200  through resonance by the first coil  135 . The first coil  135  resonates at the same frequency as that of a second coil  215  in the wireless power receiver  200  so that the transmission power may be transmitted to the wireless power receiver  200 . If the wireless power receiver  200  is fully charged, the power converter  130  reduces the strength of the wireless power (or the strength of transmission power) under control of the first controller  120 . The power converter  130  may reduce the strength of the transmission power so that a predetermined voltage (e.g., 5V) may be maintained, thereby also maintaining the power transmission. 
     The first communication unit  140  forwards a message (e.g., a CS packet) received from the wireless power receiver  200  to the first controller  120 . The first communication unit  140  also sends a message from the wireless power transmitter  100  to the wireless power receiver  200  under control of the first controller  120 . 
     The first display  150  may be a display module, such as, for example, a Light Emitting Diode (LED) or Liquid Crystal Display (LCD), which displays full charge status information indicating that the wireless power receiver  200  has been fully charged, under control of the first controller  120 . 
     The wireless power receiver  200  charges its battery  240  with the power wirelessly provided from the wireless power transmitter  100 , configured as described above. The wireless power receiver  200  may be embodied as a mobile terminal, for example, and includes the second coil  215 , a power receiver  210 , a second controller  220 , a Power Management Integrated Circuit (PMIC, or power management chip)  230 , the battery  240 , a second communication unit  250 , and a second display  260 . 
     If the second coil  215 , a resonant coil, is aligned with the first coil  135  in the wireless power transmitter  100 , an induced current may occur in the second coil  215  due to changes in the magnetic field of the first coil  135 . The second coil  215  resonates at the same frequency as that of the first coil  135  so that the wireless power may be received at the power receiver  210 . 
     The power receiver  210  receives the transmission power from the wireless power transmitter  100  through the second coil  215 , and forwards the received power to the PMIC  230 . 
     The second controller  220 , which controls the overall operation of the wireless power receiver  200 , generates various messages needed for wireless power reception, sends the generated messages to the second communication unit  250 , receives messages from the second communication unit  250 , and performs control corresponding thereto. The second controller  220  controls the power receiver  210  to receive the power transmitted from the wireless power transmitter  100 , and controls the PMIC  230  so that the received power may be charged in the battery  240 . The second controller  220  may receive a full charge message from the PMIC  230  when the battery  240  is fully charged. Upon receiving the full charge message, the second controller  220  controls the second communication unit  250  to transmit a CS packet with a value of 100, which indicates that the battery  240  is fully charged. If the battery  240  is fully charged, the second controller  220  controls the second display  260  to display the full charge status thereon. 
     The PMIC  230 , a power management chip, charges the battery  240  with the power that the power receiver  210  has received. The PMIC  230  monitors the current charge in the battery  240  and the voltage of the battery  240 . If the battery  240  arrives at a full charge condition, the PMIC  230  performs an auxiliary charge while maintaining a jig-on voltage (a voltage fixedly provided to the PMIC  230  at 5V, and sends a full charge message to the second controller  220 . 
     If the battery  240  is fully charged, the second communication unit  250  transmits a CS packet to the wireless power transmitter  100 , receives a message from the wireless power transmitter  100 , and forwards it to the second controller  220 , under control of the second controller  220 . The CS packet includes information indicating a charge level of the battery  240 , and may have a value of 1 to 100, as described above. 
     The second display  260  may be embodied as a display module, such as, for example, an LED or an LCD, and displays full charge status information indicating that the battery  240  in the wireless power receiver  200  has been fully charged, under control of the second controller  220 . 
     In the wireless charging apparatus described in the embodiment of the present invention above, if the battery  240  in the wireless power receiver  200  is fully charged, the wireless power receiver  200  sends a CS packet, instead of an EPT packet, to the wireless power transmitter  100 . Accordingly, an auxiliary charge is performed so that the power transmitted from the wireless power transmitter  100  is continuously transmitted after being reduced, without being interrupted. This prevents the repeated charging and recharging of the battery  240 . 
       FIG. 3  is a flow diagram illustrating a wireless charging method, according to an embodiment of the present invention. 
     Referring to  FIG. 3 , in step  302 , the wireless power transmitter  100  and the wireless power receiver  200  charge the battery  240  in the wireless power receiver  200  by transmitting and receiving wireless power. 
     In step  304 , the wireless power receiver  200  determines whether it is in a fully charged state, in which battery charging has been completed. If the wireless power receiver  200  is in the fully charged state, the wireless power receiver  200  displays a full charge status, indicating the completed charging of the wireless power receiver  200 , on a UI screen of the second display  260 , implemented by a display module such as LCD, in step  306 . 
     In step  308 , the wireless power receiver  200  transmits a CS packet to the wireless power transmitter  100 . The CS packet includes information indicating a charge level of the battery  240 , and may have a value of 1 to 100, as described above. 
       FIG. 4  is a diagram illustrating a structure of a CS packet, according to an embodiment of the present invention. 
     Referring to  FIG. 4 , for the CS packet, a CS packet type defined in the WPC 1.1 standard may be used. B 0  represents one byte, which may include 8 bits of b 7 ˜b 0 . In an embodiment of the present invention, if the battery  240  is fully charged, a CS Value may be 0×63 to indicate a value of 100. 
     Upon receiving the CS packet from the wireless power receiver  200 , the wireless power transmitter  100  displays full charge status information on the first display  150  in step  310 . The wireless power transmitter  100  reduces transmission strength of the wireless power while maintaining the wireless power transmission without interruption, in step  312 . 
     In step  314 , the wireless power receiver  200  receives the reduced wireless power from the wireless power transmitter  100  and keeps a predetermined fixed voltage, thereby performing an auxiliary charge. 
     As is apparent from the foregoing description, the wireless charging apparatus and method of embodiments of the present invention enable an auxiliary charge upon completion of wireless charging between the wireless power transmitter and the wireless power receiver, making it possible for the user to identify the exact full charge status information in the fully charged state. By enabling the auxiliary charge upon completion of the wireless charging between the wireless power transmitter and the wireless power receiver, it is possible that even though the battery is recharged due to the discharge after it was fully charged, the user may not recognize this situation. 
     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.