Patent Publication Number: US-2021169145-A1

Title: Aerosol generating system and method of operating the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/KR2020/000720 filed Jan. 15, 2020, claiming priority based on Korean Patent Application No. 10-2019-0005229 filed Jan. 15, 2019 and Korean Patent Application No. 10-2019-0082228 filed Jul. 8, 2019. 
    
    
     TECHNICAL FIELD 
     One or more embodiments of the present disclosure relate to an aerosol generating system, and more particularly, to an aerosol generating system that generates an aerosol through induction heating, and a method of operation of the same. 
     BACKGROUND ART 
     Recently, the demand for alternative methods to overcome the shortcomings of general cigarettes has increased. Accordingly, there is growing demand for a method of generating aerosol by heating an aerosol generating material in cigarettes, rather than by burning cigarettes. 
     Research has actively been conducted lately on a method of generating an aerosol within a heating-type aerosol generating device by applying a magnetic field to a susceptor such that the susceptor is heated by electromagnetic induction to generate an aerosol. 
     DESCRIPTION OF EMBODIMENTS 
     One or more embodiments of the present disclosure provide an aerosol generating system including an aerosol generating device including a coil that performs a charging operation for receiving electric power to charge a power supply and a heating operation for heating a susceptor, and a charging device for transmitting electric power. 
     Embodiments of the present disclosure are not limited thereto. It is to be appreciated that other embodiments will be apparent to those skilled in the art from consideration of the specification and the accompanying drawings of the present disclosure described herein. 
     Solution to Problem 
     According to an aspect of the present disclosure, there is provided an aerosol generating system including an aerosol generating device including an induction coil that performs a heating operation for heating a susceptor arranged in a cigarette insertion portion and a charging operation for receiving electric power from the outside to charge a power supply, and a charging device including a transmission coil that transmits electric power to the induction coil. 
     The aerosol generating device may selectively perform the heating operation or the charging operation through the induction coil. 
     The charging device may further include a first impedance matching portion connected to the transmission coil, the aerosol generating device may further include a second impedance matching portion connected to the induction coil, and an impedance value of the second impedance matching portion may be a value between an impedance value of the susceptor and an impedance value of the first matching portion. 
     The aerosol generating device may further include a heating impedance matching portion having a first impedance value for applying a magnetic field to the susceptor during the heating operation, and a reception impedance matching portion having a second impedance value for receiving electric power from the charging during the charging operation, and the charging device may further include a transmission impedance matching portion that is connected to the transmission coil and has the second impedance value. 
     For the charging operation, the induction coil and the transmission coil may be aligned such that their central axes coincide with each other. 
     In addition, for the charging operation, the induction coil and the transmission coil may be arranged to overlap at least in part. 
     Moreover, for the charging operation, the transmission coil may be inserted into the cigarette insertion portion. 
     The cigarette insertion portion of the aerosol generating device may include a first empty space, the susceptor may protrude from a bottom surface of the first empty space, the charging device may include a protrusion portion around which the transmission coil is wound and a second empty space formed in the protrusion portion, and for the charging operation, the protrusion portion may be inserted into the first empty space, and the susceptor may be inserted into the second empty space. 
     When the charging device is coupled for the charging operation, the induction coil and the transmission coil may be separated by a certain distance from each other in an axial direction. 
     According to another aspect of the present disclosure, there is provided an aerosol generating device including: a cigarette insertion portion into which a cigarette is inserted; a susceptor arranged in the cigarette insertion portion; a power supply; an induction coil that performs a heating operation for heating the susceptor by applying a magnetic field to the susceptor and a charging operation for receiving electric power to charge the power supply according to a magnetic field applied from an external power source; and a controller for controlling operation of the induction coil. 
     The aerosol generating device may further include a heating impedance matching portion having a first impedance value for applying a magnetic field to the susceptor during the heating operation, and a reception impedance matching portion having a second impedance value for receiving electric power from the external power source during the charging operation. 
     The aerosol generating device may further include a switch that selectively connects the induction coil to the heating impedance matching portion or the reception impedance matching portion. 
     According to another aspect of the present disclosure, there is provided a charging device including a transmission coil that transmits electric power by generating a magnetic field according to flow of a current; and a controller that transmits electric power to an induction coil of an aerosol generating device by controlling the current, wherein the induction coil of the aerosol generating device performs a heating operation for heating a susceptor and a charging operation for receiving electric power to charge a power supply according to an applied magnetic field. 
     The charging device may further include: a protrusion portion around which the transmission coil is wound; an empty space formed in the protrusion portion; and a shield member arranged along an inner surface of the empty space to prevent the magnetic field generated by the transmission coil from being transmitted into the empty space. 
     The charging device may include the shield member including the transmission coil, and the transmission coil may be separated by a certain distance from the induction coil in an axial direction for the charging operation. 
     According to another aspect of the present disclosure, there is provided a method of operation of an aerosol generating device, the method including selecting any one of a charging mode for receiving electric power from the outside through an induction coil to charge a power supply or a heating mode for heating a susceptor by generating a magnetic field in the induction coil, and receiving electric power through the induction coil or heating the susceptor through the induction coil, according to a selected mode. 
     According to another aspect of the present disclosure, there is provided an aerosol generating system including a holder that heats an aerosol generating material to generate an aerosol, and a cradle that includes a cavity in which the holder is accommodated, wherein the holder may include a holder battery and a holder power receiver connected to the holder battery, and the cradle may include a cradle battery and a cradle power transmitter connected to the cradle battery. The holder power receiver may receive electric power wirelessly from the cradle power transmitter to charge the holder battery, and the location of the cradle power transmitter may be changed according to whether the holder is accommodated in the cavity or not. 
     The cradle may include a first side in parallel to a lengthwise direction of the cradle and a second side perpendicular to the first side, and the cradle power transmitter may be moved between a first position inside the cradle opposite the first side and a second position inside the cradle opposite the second side. 
     As the cradle power transmitter is moved between the first position and the second position, the shape of the cradle power transmitter may be changed. 
     When the holder is accommodated in the cavity, the cradle power transmitter is located at the first position inside the cradle opposite the first side, and when the holder is not accommodated in the cavity, the cradle power transmitter is located at the second position inside the cradle opposite the second side. 
     The cradle may further include a holder accommodation detection sensor for detecting whether the holder is accommodated in the cavity or not, and when the holder accommodation detection sensor detects that the holder is accommodated in the cavity, the cradle power transmitter may be moved from the second position to the first position. 
     The holder may include a third side on which the holder power receiver is positioned, and when the holder is not accommodated in the cavity, as the third side of the holder is positioned on the second side of the cradle such that the holder power receiver faces the cradle power transmitter, the holder power receiver may receive electric power wirelessly from the cradle power transmitter. 
     The holder may include the third side on which the holder power receiver is positioned, and when the holder is accommodated in the cavity, as the third side of the holder is positioned on the first side of the cradle such that the holder power receiver faces the cradle power transmitter, the holder power receiver may receive electric power wirelessly from the cradle power transmitter. 
     A first seating groove corresponding to the curvature of the holder may be formed on the second side of the cradle such that the holder is seated. 
     The cradle power transmitter may include a flexible printed circuit board (FPCB), and a coil on the FPCB, and when the cradle power transmitter is located at the first position, the FPCB may have a curved shape to correspond to the curvature of the first side, and when the cradle power transmitter is located at the second position, the FPCB may have a flat shape. 
     The holder power receiver may include a FPCB, and a coil on the FPCB, and the FPCB may have a curved shape to correspond to the curvature of the third side. 
     The cradle power transmitter may include a FPCB, and a coil on the FPCB, and when the cradle power transmitter is located at the first position, the FPCB may have a curved shape to correspond to the curvature of the first side, and when the cradle power transmitter is located at the second position, the FPCB may have a curved shape to correspond to the curvature of the first seating groove. 
     The aerosol generating device may further include a wireless charging pad including an external power transmitter, and the cradle may further include a cradle power receiver. As the holder or the cradle is seated on one side of the wireless charging pad, the holder power receiver or the cradle power receiver may receive electric power wirelessly from the external power transmitter to charge the holder battery or the cradle battery. 
     A second seating groove corresponding to the curvature of the holder or the cradle may be formed on one side of the wireless charging pad such that the holder or the cradle is seated. 
     The external power transmitter may include a FPCB, and a coil on the FPCB, and the FPCB may have a curved shape to correspond to the curvature of the second seating groove. 
     As the cradle in which the holder is accommodated is seated on one side of the wireless charging pad, the holder power receiver may receive electric power wirelessly from the cradle power to charge the holder battery, and the cradle power receiver may receive electric power wirelessly from the external power transmitter to charge the cradle battery. 
     According to another aspect of the present disclosure, there is provided a cradle including: a cavity in which a holder is accommodated; a battery; and a power transmitter connected to the battery, wherein the location of the power transmitter is changed according to whether the holder is accommodated in the cavity or not. 
     Advantageous Effects of Disclosure 
     According to an embodiment, a charging operation for receiving electric power and a heating operation for heating a susceptor are performed through a coil of an aerosol generating device, thus the aerosol generating device may be simplified and miniaturized, and user convenience may be improved. 
     According to an embodiment, a power transmitter of a cradle is moved according to whether a holder is accommodated in a cavity of the cradle, so that a power receiver of the holder and the power transmitter of the cradle may be arranged to face each other in either case. Thus, when the power receiver of the holder receives electric power wirelessly from the power transmitter of the cradle, charging efficiency of a holder battery may be improved. 
     According to an embodiment, the power receiver of the holder and the power transmitter of the cradle include FPCBs, so that the power receiver of the holder and the power transmitter of the cradle may be curved. Thus, a corresponding area between the power receiver of the holder and the power transmitter of the cradle is increased, so that charging efficiency of a holder battery is increased when the power receiver of the holder receives electric power wirelessly from the power transmitter of the cradle. 
     Embodiments of the present disclosure are not limited thereto. It is to be appreciated that other embodiments will be apparent to those skilled in the art from consideration of the specification and the accompanying drawings of the present disclosure described herein. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an aerosol generating system, according to an embodiment of the present disclosure. 
         FIGS. 2 and 3  are diagrams illustrating an aerosol generating device, according to an embodiment. 
         FIG. 4  is a flowchart of a method of operation of an aerosol generating device, according to an embodiment. 
         FIG. 5  is a diagram illustrating an aerosol generating device into which a cigarette is inserted, according to an embodiment. 
         FIG. 6  is a view showing an example of the cigarette. 
         FIG. 7  is a diagram illustrating a charging device, according to an embodiment. 
         FIG. 8  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to an embodiment. 
         FIG. 9  is a diagram illustrating a shield member formed in a charging device coupled in the manner according to  FIG. 8 . 
         FIG. 10  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to another embodiment. 
         FIG. 11  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to another embodiment. 
         FIG. 12  a diagram illustrating a shield member formed in a charging device coupled in the manner according to  FIG. 11 . 
         FIG. 13  is a diagram illustrating an operation of charging an aerosol generating device through a charging device, according to an embodiment. 
         FIG. 14  is a conceptual diagram illustrating a power transmitter and a power receiver used for wireless charging, according to an embodiment. 
         FIG. 15  is a diagram illustrating an example of an aerosol generating system before a holder is accommodated in a cradle, according to an embodiment. 
         FIGS. 16 and 17  are diagrams illustrating examples of an aerosol generating system before and after a holder is accommodated in a cradle, according to an embodiment. 
         FIG. 18  is a diagram illustrating an example in which a cradle is seated on a wireless charging pad, according to an embodiment. 
     
    
    
     BEST MODE 
     According to an aspect of the present disclosure, there is provided an aerosol generating system including an aerosol generating device including an induction coil that performs a heating operation for heating a susceptor arranged in a cigarette insertion portion and a charging operation for receiving electric power from the outside to charge a power supply, and a charging device including a transmission coil that transmits electric power to the induction coil. 
     According to another aspect of the present disclosure, there is provided an aerosol generating device including: a cigarette insertion portion into which a cigarette is inserted; a susceptor arranged in the cigarette insertion portion; a power supply; an induction coil that performs a heating operation for heating the susceptor by applying a magnetic field to the susceptor and a charging operation for receiving electric power to charge the power supply according to a magnetic field applied from an external power source; and a controller for controlling operation of the induction coil. 
     According to another aspect of the present disclosure, there is provided a charging device including a transmission coil that transmits electric power by generating a magnetic field according to flow of a current; and a controller that transmits electric power to an induction coil of an aerosol generating device by controlling the current, wherein the induction coil of the aerosol generating device performs a heating operation for heating a susceptor and a charging operation for receiving electric power to charge a power supply according to an applied magnetic field. 
     According to another aspect of the present disclosure, there is provided a method of operation of an aerosol generating device, the method including selecting any one of a charging mode for receiving electric power from the outside through an induction coil to charge a power supply or a heating mode for heating a susceptor by generating a magnetic field in the induction coil, and receiving electric power through the induction coil or heating the susceptor through the induction coil, according to a selected mode. 
     MODE OF DISCLOSURE 
     With respect to the terms used to describe the various embodiments, general terms which are currently and widely used are selected in consideration of functions of structural elements in the various embodiments of the present disclosure. However, meanings of the terms can be changed according to intention, a judicial precedence, the appearance of new technology, and the like. In addition, in certain cases, a term which is not commonly used can be selected. In such a case, the meaning of the term will be described in detail at the corresponding portion in the description of the present disclosure. Therefore, the terms used in the various embodiments of the present disclosure should be defined based on the meanings of the terms and the descriptions provided herein. 
     In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms “-er”, “-or”, and “module” described in the specification mean units for processing at least one function and/or operation and can be implemented by hardware components or software components and combinations thereof. 
     Hereinafter, the present disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the present disclosure are shown such that one of ordinary skill in the art may easily work the present disclosure. The disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. 
     Throughout the specification, an aerosol generating device may include a device that uses an aerosol generating material to generate an aerosol that is directly inhaled into user&#39;s lungs through the user&#39;s mouth. For example, the aerosol generating device may include a holder. 
     In the specification, the term “puff” refers to inhalation of the user, and the inhalation may refer to a situation in which the user pulls the aerosol into the user&#39;s mouth, nasal cavity, or lungs through the user&#39;s mouth or nose. 
     Hereinafter, the present disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the present disclosure are shown such that one of ordinary skill in the art may easily work the present disclosure. The disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. 
       FIG. 1  is a diagram illustrating an aerosol generating system, according to an embodiment of the present disclosure. Referring to  FIG. 1 , the aerosol generating system may include an aerosol generating device  100  and a charging device  200 . The aerosol generating device  100  may include an induction coil  130 , a susceptor  110 , a power supply  140 , and a controller  150 . The charging device  200  may include a transmission coil  220 . 
     The aerosol generating device  100  may receive electric power from the charging device  200  through the induction coil  130  by using electromagnetic induction to charge the power supply  140 . In addition, the aerosol generating device  100  may heat the susceptor  110  through the induction coil  130  by using electromagnetic induction to heat an aerosol generating material. 
     In the operation of charging the aerosol generating device  100  through the induction coil  130 , the transmission coil  220  may operate as a transmission coil Tx that transmits electric power, and the induction coil  130  may operate as a reception coil Rx that receives the electric power transmitted by the transmission coil  220 . 
     Reception and transmission of the electric power between the induction coil  130  and the transmission coil  220  may be performed in a wireless or non-contact way. The induction coil  130  and the transmission coil  220  may use a charging method using electromagnetic induction, or a magnetic field resonance method in which electric power is transferred at a resonance frequency of the transmission coil  220  and the reception coil. As for the details, a configuration commonly used in the art may be employed. 
     For example, according to the charging method using electromagnetic induction, the charging device  200  may control a current flowing through the transmission coil  200  to generate an alternating magnetic field. Eddy current may be induced to the induction coil  130  of the aerosol generating device  100  because of the alternating magnetic field generated by the transmission coil  220 . The aerosol generating device  100  may supply electric power to the power supply  140  and charge the power supply  140  by using the eddy current flowing through the induction coil  130 . In other words, the transmission coil  220  transmits electric power to the induction coil  130  by applying the magnetic field to the induction coil  130  such that the eddy current is induced in the induction coil  130 . 
     The aerosol generating device  100  may further include a charger for supplying electric power to the power supply  140 , and a regulator for controlling the voltage supplied to the charger. 
     In an operation of heating the aerosol generating device  100  through the induction coil  130 , the controller  150  of the aerosol generating device  100  may control the current flowing through the induction coil  130  to generate a magnetic field, and an induced current may be generated in the susceptor  110  because of the magnetic field. The induction heating is a well-known phenomenon that can be explained by Faraday&#39;s Law of induction and Ohm&#39;s Law, and refers to a phenomenon that when magnetic induction in a conductor changes, a changing electric field is generated in the conductor. 
     As described above, if the electric field is generated in the conductor, the eddy current flows in the conductor according to Ohm&#39;s law, and the eddy current generates heat proportional to current density and conductor resistance. Heat generated from the susceptor  110  may be transferred to the aerosol generating material and vaporize the aerosol generating material to generate an aerosol. 
     In other words, when electric power is supplied to the induction coil  130 , a magnetic field may be generated in the induction coil  130 . When an alternating current is applied to the induction coil  130  by the power supply  140 , the magnetic field generated in the induction coil  130  may periodically change its direction. When the susceptor  110  is exposed to the alternating magnetic field generated in the induction coil  130  that periodically changes a direction, the susceptor  110  may generate heat to heat a cigarette  300 . 
     When an amplitude or frequency of the alternating magnetic field formed by the induction coil  130  changes, a temperature at which the susceptor  110  heats the cigarette  300  may also change. The controller  150  may control electric power supplied to the induction coil  130  to regulate the amplitude or frequency of the alternating magnetic field generated by the induction coil  130 , and thus the temperature of the susceptor  110  may be controlled. 
     According to an embodiment, the induction coil  130  and the transmission coil  220  may be implemented as a solenoid. Material of a conductor constituting the solenoid may include copper (Cu). However, embodiments of the present disclosure are not limited thereto. The material of the conductor constituting the solenoid may include any one of silver (Ag), gold (Au), aluminum (Al), tungsten (W), zinc (Zn), and nickel (Ni) that have a low specific resistance value to allow a high current to flow, or an alloy including at least one thereof. 
     According to one or more embodiments of the present disclosure, the susceptor  110  may include a magnetic material. When an alternating magnetic field is applied to a magnetic material, energy may be lost from the magnetic material due to eddy current loss and hysteresis loss, and the lost energy may be released from the magnetic material as thermal energy. The greater the amplitude or frequency of the alternating magnetic field applied to the magnetic material is, the more thermal energy may be released from the magnetic material. 
     According to one or more embodiments of the present disclosure, the susceptor  110  may include a metal or carbon. The susceptor  110  may include at least one of ferrite, a ferromagnetic alloy, stainless steel, and aluminum. Alternatively, the susceptor  110  may include at least one of graphite, molybdenum, silicon carbide, niobium, a nickel alloy, a metal film, ceramic such as zirconia or the like, a transition metal such as nickel (Ni), cobalt (Co), or the like, and a metalloid such as boron (B) or phosphorus (P). 
     According to an embodiment, the susceptor  110  may be included in the aerosol generating material in the form of fragments, flakes, strips, or the like. According to another embodiment, the susceptor  110  may be arranged in the aerosol generating device  100 . An embodiment in which the susceptor  110  is arranged in a cigarette insertion portion  120  will be described later in greater detail with reference to  FIG. 5 . 
     The power supply  140  of the aerosol generating device  100  may supply electric power needed for each component of the aerosol generating device  100  to operate. For example, the power supply  140  may supply electric power needed for the induction coil  130  to generate the magnetic field. Magnitude of the electric power supplied to the induction coil  130  may be regulated by a control signal generated by the controller  150 . 
     The power supply  140  may be charged by the electric power received through the induction coil  130 . The power supply  140  may include, for example, a nickel cadmium (Ni—Cd) rechargeable battery, an alkaline rechargeable battery, a nickel hydrogen (Ni—H) rechargeable battery, a sealed lead acid (SLA) rechargeable battery, a lithium ion (Li-ion) rechargeable battery, a lithium polymer (Li-polymer) rechargeable battery, and the like. 
     According to one or more embodiments of the present disclosure, the power supply  140  may include a battery for supplying a direct current and a converter for converting the direct current supplied by the battery into an alternating current supplied to the induction coil  130 , or for converting an alternating current received through the transmission coil  220  into the direct current. 
     According to one or more embodiments, the power supply  140  may include a regulator that is disposed between the battery and the controller  150  to maintain a voltage of the battery constant. 
     The controller  150  of the aerosol generating device  100  may generate and transmit a control signal to control the overall components such as the induction coil  130 , the power supply  140 , the susceptor  110 , and the like included within the aerosol generating device  100 . For example, the controller  150  may use electric power from the power supply  140  to apply current to the induction coil  130 , or may use the electric power received through the induction coil  130  to charge the power supply  140 . 
     The controller  150  may operate a heating mode for heating the susceptor  110  and a charging mode for charging the power supply  140 . The heating mode and the charging mode may be selectively operated. The heating mode and the charging mode will be described later in greater detail with reference to  FIG. 4 . 
     The controller  150  may be implemented with an array of multiple logic gates, or may be implemented with a combination of a memory in which a general-purpose microprocessor and a program capable of being executed in the microprocessor are stored. Alternatively, the controller  150  may include a plurality of processing elements. 
     Although not shown, the controller  150  may further include an input receiver for receiving a user&#39;s button input or touch input, a communication unit capable of communicating with an external communication device such as a user terminal, a display for displaying information on the state of the aerosol generating device  100 , and a pulse width modulation processer for controlling pulse width of the electric power applied to the induction coil  130 . 
     A controller  260  of the charging device  200  may control the overall operation of components such the transmission coil  220 , a power supply  280 , and the like. For example, the controller  260  may transform an external power source into an appropriate form to apply an alternating current to the transmission coil  220 . In addition, the controller  260  may store the external power source in the power supply  280 , and may apply current from the power supply  280  to the transmission coil  220 , if necessary. 
     The controller  260  may be implemented with various numbers of hardware and/or software configurations that execute functions. Alternatively, the controller  260  may be implemented by microprocessors, or by circuit configurations for a certain function. For example, the controller  260  may be implemented in various programming or scripting languages. 
     The power supply  280  of the charging device  200  may supply electric power to the induction coil  220 , if necessary. According to an embodiment, the power supply  280  may include a battery for storing electric power to be transmitted to the aerosol generating device  100 . According to another embodiment, the power supply  280  may receive electric power from the external power source such as an outlet and supply the electric power to the transmission coil  220 . In that case, the power supply  280  may include electronic devices such as a converter, an adapter, and a rectifier to receive electric power from the external power source such as the outlet and supply the electric power to the transmission coil  220  in an appropriate form. 
     The power supply  280  may further include a power receiver (not shown) that receives electric power from an external power source (not shown). The power receiver may receive electric power in a wireless charging method or a wired charging method. In the case of the wireless charging method, the power receiver may be in the form of a coil. In the case of the wired charging method, the power receiver may be combined with the external power source. The power supply may receive electric power from the external power source through the power receiver and charge a battery. An operation of charging the power supply  280  of the charging device  200  will be described later in greater detail with reference to  FIG. 18 . 
     According to an embodiment, the charging device  200  may be in the form of a cradle to which the aerosol generating device  100  may be coupled. When the aerosol generating device  100  is mounted on the cradle, electrodes of the aerosol generating device  100  and electrodes of the cradle are connected to each other, and electric power may be supplied to the power supply  140  of the aerosol generating device  100  through the power supply  280 . 
     When the charging device  200  is in the form of a cradle, a cavity in which the aerosol generating device  100  is accommodated may be formed in the charging device  200 . Coupling of the charging device  200  and the aerosol generating device  100  will be described later in greater detail with reference to  FIGS. 13 to 17 . 
     According to another embodiment, the charging device  200  may be a portable device that is not restricted by the location of the external power source. The power supply  280  may include a battery built into the charging device  200 . The power supply  280  may include a rechargeable battery. 
     Although not shown, the charging device  200  may include an input unit for receiving an input related to operations such as on-off, setting of charging intensity, and the like from the user, and an LED or a display for displaying information on remaining capacity of the battery, charging intensity, and the like of the charging device  200 . 
     Although not shown, the aerosol generating system may further include an external power source for supplying electric power to the charging device  200 . The external power source may supply electric power to the charging device  200  in a wireless charging method or a wired charging method. 
     The external power source may include an external power transmitter for transmitting electric power. In the case of the wireless charging method, the external power transmitter may be in the form of a coil. In the case of the wired charging method, the external power transmitter may be combined with the charging device  200 . The power supply  280  may receive electric power from the external power source through a power receiver and charge the battery. The external power source will be described later in greater detail with reference to  FIG. 18 . 
       FIGS. 2 and 3  are diagrams illustrating an aerosol generating device, according to another embodiment. Referring to  FIG. 2 , the aerosol generating device  100  may include an impedance matching portion  160  for receiving electric power from the transmission coil  220  through the induction coil  130 , or for transmitting electric power to the induction coil  130  for the susceptor  110  to be heated. In other words, the impedance matching portion  160  may be a power receiver and also a power transmitter. One end of the impedance matching portion  160  may be connected to the induction coil  130 , and the other end of the impedance matching portion  160  may be connected to the controller  150  or to the power supply  140 . 
     The impedance matching portion  160  may include a variety of electronic devices including resistors, coils, capacitors, and the like. Alternatively, the impedance matching portion  160  may include a conductor including a quarter-wave transformer or a stub. 
     An impedance value of the impedance matching portion  160  may be appropriately set such that a charging operation for receiving electric power from the transmission coil  220  and a heating operation for transmitting electric power to the susceptor  110  are efficiently performed. 
     In particular, the impedance value of the impedance matching portion  160  may be set such that the susceptor  110  is prevented from being heated by the electric power transmitted by the transmission coil  220  during the charging operation. 
     More specifically, the charging device  200  may include an impedance matching portion  250 . An impedance value of the impedance matching portion  250  and the impedance value of the impedance matching portion  160  may be set such that transmission and reception of electric power between the impedance matching portion  250  and the impedance matching portion  160  may be efficiently performed. 
     The susceptor  110  has its own impedance value. Here, the impedance value of the susceptor  110  refers to an impedance value that is determined by the susceptor  110  and electronic devices connected to the susceptor  110  to perform the heating operation. 
     If the impedance value of the impedance matching portion  250  of the charging device  200  and the impedance value of the susceptor  110  are similar to each other, electric power transmitted by the charging device  200  may also be transmitted to the susceptor  110 . As a result, the charging operation and the heating operation may occur simultaneously. In order to prevent such a case, the impedance value of the impedance matching portion  250  and the impedance value of the susceptor  110  are adopted to be different from each other. 
     The more the impedance value of the impedance matching portion  160  and the impedance value of the impedance matching portion  250  are similar to each other, the higher efficiency of power transfer between the impedance matching portion  160  and the impedance matching portion  250  may be achieved. On the other hand, the more the impedance value of the impedance matching portion  160  and the impedance value of the susceptor  110  are similar to each other, the higher electromagnetic induction efficiency and heating efficiency may be achieved. 
     The impedance value of the impedance matching portion  160  may be between the impedance value of the impedance matching portion  250  and the impedance value of the susceptor  110  such that electric power transfer between the impedance matching portion  250  and the susceptor  110  is prevented while achieving satisfactory power transfer efficiency with respect to the impedance matching portion  250  and electromagnetic induction efficiency with respect to the susceptor  110 . In other words, the impedance value of the impedance matching portion  160  may be a value between the impedance value of the susceptor  110  and an impedance value of the charging device  200 . 
     Referring to  FIG. 3 , the aerosol generating device  100  may be provided with a heating impedance matching portion  162  for applying a magnetic field to the susceptor  110 , and a reception impedance matching portion  164  for receiving electric power from the transmission coil  220 . A first impedance value of the heating impedance matching portion  162  and a second impedance value of the reception impedance matching portion  164  may be different from each other. 
     The first impedance value of the heating impedance matching portion  162  may be similar or equal to the impedance value of the susceptor  110 . Thus, the transmission and reception of electric power between the induction coil  130  and the susceptor  110 , and the corresponding heating operation may be efficiently performed through the heating impedance matching portion  162 . 
     The second impedance value of the reception impedance matching portion  164  may be similar or equal to the impedance value of the impedance matching portion  250  within the charging device  200 . Therefore, the transmission and reception of electric power between the induction coil  130  and the transmission coil  220 , and the corresponding charging operation may be efficiently performed through the reception impedance matching portion  164 . 
     Depending on the configuration and arrangement of RLC elements constituting each of the heating impedance matching portion  162  and the reception impedance matching portion  164 , or a value of the conductor such as the stub, the heating impedance matching portion  162  and the reception impedance matching portion  164  may have impedance values different from each other. 
     The aerosol generating device  100  may include a switch (not shown) capable of selectively choosing an impedance matching portion connected to the induction coil  130 . The aerosol generating device  100  may operate the switch to selectively connect any one of the heating impedance matching portion  162  and the reception impedance matching portion  164  to the induction coil  130 , and the heating impedance matching portion  162  or the reception impedance matching portion  164  that is not connected to the induction coil  130  may be electrically disconnected from the induction coil  130 . 
     Thus, an impedance value of the impedance matching portion connected to the induction coil  130  may be adjusted to a different value. Accordingly, the aerosol generating device  100  may selectively perform the heating operation and the charging operation according to the operation of the switch. 
     Since the first impedance value of the susceptor  110  and the second impedance value of the impedance matching portion  250  within the charging device  200  are different from each other, the susceptor  110  may be prevented from being heated by the charging device  200 . 
     For example, the switch may include a field-effect transistor (FET). The switch may also include a P channel FET or an N channel FET. As another example, the switch may include a bipolar junction transistor (BJT), an insulated gate bipolar transistor (IGBT), or a thyristor. However, embodiments of the present disclosure are not limited thereto. The switch may be a single electronic element, or a circuit including multiple electronic elements. 
       FIG. 4  is a flowchart of a method of operation of an aerosol generating device, according to an embodiment. Referring to  FIG. 4 , the aerosol generating device  100  may select any one of a charging mode and a heating mode, in S 1100 . 
     The charging mode is a mode in which electric power is supplied by the charging device  200  through the induction coil  130  to charge electric power of the power supply  140 , and the heating mode is a mode in which the susceptor  110  is heated through the induction coil  130  to vaporize an aerosol generating material. 
     Descriptions given with reference to  FIGS. 1 to 3  may apply to the charging mode and the heating mode. Descriptions to be given later with reference to  FIGS. 5 to 12  may also apply to the charging mode and the heating mode. 
     Each mode may include an algorithm, code, or a program for the aerosol generating device  100  to execute a specific function, and a mode may be operated by executing the algorithm, code, program, and the like. 
     The charging mode and the heating mode are merely examples of modes that the aerosol generating device  100  may select and operate, and the operation modes of the aerosol generating device  100  are not limited thereto. 
     According to an embodiment, the aerosol generating device  100  may select a mode that operates according to a user input received through an input unit. The aerosol generating device  100  may select the heating mode when receiving the user input for heating the cigarette  300  to smoke. The aerosol generating device  100  may also select the charging mode when receiving the user input for charging the power supply  140 . 
     In addition, the aerosol generating device  100  may select an operation mode according to a signal detected by a sensor. For example, the sensor may detect whether the cigarette  300  is inserted into the cigarette insertion portion  120  or not. The sensor may include a proximity sensor arranged in the cigarette insertion portion  120 , a touch sensor, a limit switch, a sensor for detecting a change in capacitance, an optical sensor, and the like. 
     The sensor may also detect whether the aerosol generating device  100  and the charging device  200  are coupled to each other or not. In that case, the sensor may include a proximity sensor arranged at a coupling portion between the aerosol generating device  100  and the charging device  200 , a touch sensor, a limit switch, a sensor for detecting a change in capacitance, an optical sensor, an energizing sensor for detecting connection of electrodes, and the like. 
     The aerosol generating device  100  may receive electric power through the induction coil  130  or heat the susceptor  110  through the induction coil  130  according to a selected mode, in S 1200 . 
     The descriptions given with reference to  FIGS. 1 to 3  and descriptions to be given later with reference to  FIGS. 5 to 12  may apply to the aerosol generating device  100  performing the charging operation and the heating operation. 
     To perform the selected mode, the aerosol generating device  100  may restrict operation of the mode that is not selected. For example, as described above with reference to  FIG. 3 , the aerosol generating device  100  may operate a switch to connect the induction coil  130  to only one of the heating impedance matching portion  162  and the reception impedance matching portion  164 . 
       FIG. 5  is a diagram illustrating the aerosol generating device  100  into which a cigarette is inserted. Referring to  FIG. 5 , the aerosol generating device  100  may include the cigarette insertion portion  120  into which the cigarette  300  including an aerosol generating material may be inserted. The susceptor  110  may be arranged in the cigarette insertion portion  120 . 
     When the cigarette  300  is inserted into the aerosol generating device  100 , the cigarette  300  may contact the susceptor  110  or be arranged proximate to the susceptor  110 . The aerosol generating device  100  may heat the susceptor  110  through the induction coil  130 , and heat from the susceptor  110  may be transferred to the cigarette  300  to generate an aerosol. The aerosol passes through the cigarette  300  to be delivered to a user. 
     The susceptor  110  may be arranged on a bottom surface formed at an inner end portion of the cigarette insertion portion  120 . The susceptor  110  may be in a rod shape protruding from a bottom surface of an empty space. The cigarette  300  may be inserted into the susceptor  110  from an upper end portion of the susceptor  110 , and accommodated to the bottom surface of the cigarette insertion portion  120 . 
     The induction coil  130  may be wound along a side surface of the cigarette insertion portion  120  and arranged at a position corresponding to the susceptor  110 . The induction coil  130  may be supplied with electric power by the power supply  140 . 
     As the susceptor  110  is provided in the aerosol generating device  100 , there may be various advantages compared to the case where the susceptor  110  is provided in the cigarette  300 . For example, when the susceptor  110  material is not uniformly distributed inside the cigarette  300 , the aerosol and flavor are generated non-uniformly. This problem may be solved if the susceptor  110  is provided in the aerosol generating device  100 . In addition, since the aerosol generating device  100  is provided with the susceptor  110 , a temperature of the susceptor  110  that generates heat through induction heating may be directly measured and provided to the aerosol generating device  100 . Accordingly, the temperature of the susceptor  110  may be precisely controlled. 
     The cigarette insertion portion  120  may be located at a proximal end of the aerosol generating device  100  facing the user when smoking. The cigarette insertion portion  120  may include an empty space that extends toward a distal end from the proximal end of the aerosol generating device  100 . The cigarette insertion portion  120  may include an opening that opens to the outside of the cigarette insertion portion  120 . The cigarette  300  may be inserted into the empty space through the opening of the cigarette insertion portion  120 . The empty space may include a hollow. 
     According to one or more embodiments of the present disclosure, the cigarette insertion portion  120  may be the proximal end of the aerosol generating device  100  including the empty space, or may be the empty space itself formed at the proximal end of the aerosol generating device  100 . 
     The empty space of the cigarette insertion portion  120  may include a cross section that corresponds to a shape of the cigarette  300 . For example, the cross section of the empty space of the cigarette insertion portion  120  may be in a circular shape. A diameter of the empty space of the cigarette insertion portion  120  may have a value similar to a diameter of the cigarette  300 . 
     According to one or more embodiments, a vaporizer including a liquid storage, a liquid delivery means, and a heating element may be included in the aerosol generating device  100  as an independent module. 
     The liquid storage may store a liquid composition. For example, the liquid composition may include a liquid containing a tobacco-containing substance containing a volatile tobacco flavor ingredient, or a liquid containing a non-tobacco substance. The liquid storage may be manufactured to be detachably attached to a vaporizer  18 , or may be manufactured to be integral with the vaporizer  18 . 
     For example, the vaporizer  18  may be referred to as a cartomizer or atomizer. However, embodiments of the present disclosure are not limited thereto. 
     A portion of the cigarette  300  may be inserted into the aerosol generating device  100 , and the rest portions may be exposed to the outside. The user may inhale the aerosol by biting a portion exposed to the outside. The aerosol is generated as air from the outside passes through an end portion of the cigarette  300  inserted into the aerosol generating device  100 , and the generated aerosol passes through the other end portion of the cigarette  300  to be delivered to the user. 
     For example, the external air may flow into at least one air passage formed in the aerosol generating device  100 . For example, opening and closing of the air passage and/or a size of the air passage may be adjusted by the user. Accordingly, the amount and quality of the aerosol may be adjusted by the user. As another example, the external air may flow into the cigarette  300  through at least one hole formed in a surface of the cigarette  300 . 
       FIG. 6  shows a view showing an example of a cigarette. Referring to  FIG. 6 , the cigarette  300  includes a tobacco rod  310  and a filter rod  320 . The filter rod  320  illustrated in  FIG. 6  is illustrated as a single segment, but is not limited thereto, and the filter rod  320  may include a plurality of segments. For example, the filter rod  320  may include a first segment configured to cool an aerosol and a second segment configured to filter a certain component included in the aerosol. Also, the filter rod  320  may further include at least one segment configured to perform other functions. 
     The cigarette  300  may be packaged by at least one wrapper  340 . The wrapper  340  may have at least one hole through which external air may be introduced or internal air may be discharged. For example, the cigarette  300  may be packaged by one wrapper  340 . As another example, the cigarette  300  may be double-packaged by at least two wrappers  340 . More specifically, the tobacco rod  310  may be packaged by a first wrapper, and the filter rod  320  may be packaged by a second wrapper. The tobacco rod  310  and the filter rod  320 , which are respectively packaged by wrappers, may be coupled to each other, and the entire cigarette  300  may be packaged by a third wrapper. 
     The tobacco rod  310  may include an aerosol generating material. For example, the aerosol generating material may include at least one of glycerin, propylene glycol, ethylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and oleyl alcohol, but it is not limited thereto. the tobacco rod  310  may include other additives, such as flavors, a wetting agent, and/or organic acid. Also, the tobacco rod  310  may include a flavored liquid, such as menthol or a moisturizer, which is injected to the tobacco rod  310 . 
     The tobacco rod  310  may be manufactured in various forms. For example, the tobacco rod  310  may be formed using a sheet or strands. Also, the tobacco rod  310  may be formed as a pipe tobacco, which is formed of tiny bits cut from a tobacco sheet. 
     Also, the tobacco rod  310  may be surrounded by a heat conductive material. For example, the heat-conducting material may be, but is not limited to, a metal foil such as aluminum foil. The heat conductive material surrounding the tobacco rod  310  may uniformly distribute heat transmitted to the tobacco rod  310 . As such, the heat conductivity of the tobacco rod may be increased, and flavors of aerosol generated from the tobacco rod  310  may be improved. 
     The filter rod  320  may include a cellulose acetate filter. A shape of the filter rod  320  is not limited. For example, the filter rod  320  may include a cylinder-type rod or a tube-type rod having a hollow inside. Also, the filter rod  320  may include a recess-type rod including a cavity therein. When the filter rod  320  includes a plurality of segments, the plurality of segments may have a different shape each other. 
     The filter rod  320  may be formed to generate flavors. For example, a flavoring liquid may be injected onto the filter rod  320 , or an additional fiber coated with a flavoring liquid may be inserted into the filter rod  320 . 
     The filter rod  320  may include at least one capsule  330 . The capsule  330  may generate a flavor or an aerosol. For example, the capsule  330  may have a configuration in which a liquid containing a flavoring material is wrapped with a film. For example, the capsule  330  may have a spherical or cylindrical shape, but is not limited thereto. 
     Although not shown, the cigarette  300  may further include a front end plug. The front end plug may be located on one side of a tobacco rod  21  opposite the filter rod  310 . The front end plug may prevent the tobacco rod  320  from falling out of the cigarette  300 , and may also prevent the liquefied aerosol from leaking into the aerosol generating device  100  from the tobacco rod  320  during smoking. 
       FIG. 7  is a diagram illustrating a charging device, according to an embodiment. Referring to  FIG. 7 , the charging device  200  may further include a protrusion portion  230  around which the transmission coil  220  is wound. 
     The protrusion portion  230  may protrude outward from one end of the charging device  200  in one direction. The protrusion portion  230  may provide a space around which the transmission coil  220  is wound. The transmission coil  220  may be wound along a circumference of the protrusion portion  230 . The transmission coil  220  may be wound around an outer surface of the protrusion portion  230 . Alternatively, when the protrusion portion  230  includes an empty space  290 , the transmission coil  220  may be wound along an inner surface of the empty space  290 . 
     The protrusion portion  230  may protrude by a certain length so that the transmission coil  220  has a certain number of windings extending by a certain distance. The greater the number of windings is, the greater magnitude of electromotive force is induced in the induction coil  130 . 
     According to an embodiment, the protrusion portion  230  may include a metal object or a magnetic object having a certain magnetic permeability to amplify the effect of electromagnetic induction. Accordingly, the transmission coil  220  may be in the form of a solenoid including a metal object or a magnetic object therein. 
     The charging device  200  may be coupled to the aerosol generating device  100  to charge the aerosol generating device  100 . In that case, the charging device  200  may be arranged such that the protrusion portion  2230  faces the cigarette insertion portion  120 . 
     According to one or more embodiments, the transmission coil  220  may be inserted into the induction coil  130 . Alternatively, the induction coil  130  may be inserted into the transmission coil  220 . The induction coil  130  and the transmission coil  220  may be separated by a certain distance from each other in an axial direction. According to one or more embodiments in which the charging device  200  and the aerosol generating device  100  are coupled to each other, a length and diameter of the protrusion portion  230  may be different. Embodiments in which the charging device  200  and the aerosol generating device  100  are coupled to each other will be described later in detail with reference to  FIGS. 5 to 9 . 
     Hereinafter, embodiments in which the charging device  200  and the aerosol generating device  100  are coupled to each other will be described with reference to  FIGS. 8 to 12 . Embodiments show in common that when the charging device  200  and the aerosol generating device  100  are coupled to each other, a central axis of the induction coil  130  and a central axis of the transmission coil  220  may be in parallel with each other. The central axis of the induction coil  130  and the central axis of the transmission coil  220  may be aligned to be located on the same line. Thus, the induction coil  130  may efficiently receive electric power transmitted by the transmission coil  220 , and power loss may be minimized, accordingly. 
       FIG. 8  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to an embodiment. Referring to  FIG. 8 , the protrusion portion  230  of the charging device  200  may be inserted into the cigarette insertion portion  120  of the aerosol generating device  100  to be coupled thereto. 
     In that case, the transmission coil  220  may be located inside the induction coil  130 . A diameter of the induction coil  130  may be greater than a diameter of the transmission coil  220 , and the induction coil  130  may surround the transmission coil  220 . 
     A length in an axial direction of the induction coil  130  and a length in an axial direction of the transmission coil  220  may be similar or equal to each other. When the protrusion portion  230  is inserted into the cigarette insertion portion  120 , the induction coil  130  and the transmission coil  220  may overlap partially or completely when viewed from a side. The greater the overlapping portions are, the more efficiently the induction coil  130  receives electric power transmitted by the transmission coil  220 . 
     The empty space  290  extending in an axial direction may be formed in the protrusion portion  230 . The empty space  290  may be a hollow. When the protrusion portion  230  is inserted into the cigarette insertion portion  120 , the susceptor  110  may be inserted into the empty space  280  to be accommodated therein. In that case, the protrusion portion  230  may be inserted into an empty space of the cigarette insertion portion  120 . 
     A length in an axial direction of the empty space  290  may be greater than or equal to a length of the susceptor  110  such that the susceptor  110  is mounted on a bottom surface. A diameter of the empty space  290  may be greater than or equal to a diameter of the susceptor  110 . Since residual substances of a cigarette may remain on the susceptor  110  after smoking, the diameter of the empty space  290  may be greater than the diameter of the susceptor  110  by a certain difference value, accordingly. 
       FIG. 9  is a diagram illustrating a shield member formed in a charging device coupled in the manner according to  FIG. 8 . Referring to  FIG. 9 , a shield member  242  may be arranged on an inner surface of the empty space  290  along a circumference of the empty space  290 . When the protrusion portion  230  is inserted into the cigarette insertion portion  120 , the susceptor  110  may be inserted into the shield member  242  to be accommodated therein. In that case, the shield member  242  may prevent a magnetic field generated from the transmission coil  220  from being transferred into the empty space  290 . Accordingly, the magnetic field generated from the transmission coil  220  may be prevented from affecting the susceptor  110 . As such, the susceptor  110  may be prevented from being heated. 
     The shield member  242  may include, for example, a conductor such as aluminum and copper. Alternatively, the shield member  242  may include a carbon material such as carbon fiber, carbon nanotube (CNT), carbon black, graphene, and the like. Alternatively, the shield member  242  may include a polymer composite material or a combination of the polymer composite material and carbon, ceramic, a metal, or the like. 
     The shield member  242  may be, for example, in the form of a sheet metal, mesh, or ionized gas. The shield member  242  may be attached to an inner surface of the empty space  290  by, for example, sputtering, plating, or spray coating. 
       FIG. 10  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to another embodiment. Referring to  FIG. 10 , the cigarette insertion portion  120  of the aerosol generating device  100  may be inserted into the empty space  290  formed in the protrusion portion  230  of the charging device  200  to be coupled thereto. A diameter of the empty space  290  may be greater than or equal to a diameter of the cigarette insertion portion  120 . 
     In that case, the induction coil  130  may be located inside the transmission coil  220 . A diameter of the transmission coil  220  may be greater than a diameter of the induction coil  130 , and the transmission coil  220  may surround the induction coil  130 . A length in an axial direction of the transmission coil  220  and a length in an axial direction of the induction coil  130  may be similar or equal to each other. Thus, electric power may be efficiently transmitted from the transmission coil  220  to the induction coil  130 . 
     Residual substances of a cigarette may remain on the susceptor  110  after smoking. If the cigarette insertion portion  120  is inserted into the protrusion portion  230  as illustrated in  FIG. 10 , a possibility of contamination of the charging device  200  due to the residual substances of a cigarette attached to the susceptor  110  may be reduced. 
       FIG. 11  is a diagram illustrating a state in which an aerosol generating device and a charging device are coupled to each other for a charging operation, according to another embodiment. Referring to  FIG. 11 , while the aerosol generating device  100  and the charging device  200  may be coupled to each other for a charging operation, the cigarette insertion portion  120  and the protrusion portion  230  may be aligned side by side in an axial direction, separated by a certain distance from each other in the axial direction. Accordingly, the induction coil  130  and the transmission coil  220  may be separated by a certain distance from each other in an axial direction. Thus, a possibility of contamination of the charging device  200  due to residual substances of a cigarette remaining in the cigarette insertion portion  120  may be reduced. 
     The charging device  200  may include a support  270  to secure a certain distance between the protrusion portion  230  and the cigarette insertion portion  120 . When the aerosol generating device  100  and the charging device  200  are coupled to each other, the support  270  may support the cigarette insertion portion  120  to prevent the cigarette insertion portion  120  and the protrusion portion  230  from being disposed within a certain distance from each other. A length of the support  170  may be the sum of a length of the protrusion portion  230 , a length of the cigarette insertion portion  120 , and the certain distance. 
     Although not shown, according to another embodiment, the aerosol generating device  100  may include the support  270  that supports the protrusion portion  230  to secure a certain distance between the protrusion portion  230  and the cigarette insertion portion  120 . 
     A diameter of the cigarette insertion portion  120  and a diameter of the protrusion portion  230  may be similar or equal to each other. Accordingly, a diameter of the induction coil  130  and a diameter of the transmission coil  220  may be similar or equal to each other. The more equal the diameter of the induction coil  130  and the diameter of the transmission coil  220  aligned side by side in an axial direction, the more efficiently the induction coil  130  receives electric power transmitted by the transmission coil  220 . 
       FIG. 12  is a diagram illustrating a shield member formed in a charging device coupled to the aerosol generating device in the manner according to  FIG. 11 . Referring to  FIG. 12 , the charging device  200  may include a shield member  244  that surrounds the transmission coil  220 . The shield member  244  may be in a cylindrical shape that surrounds the transmission coil  220 . 
     Thus, the shield member  244  may prevent electric power from being radiated in a radial direction of the transmission coil  220 , and may increase directivity of electric power such that the electric power is transmitted in an axial direction of the induction coil  130 . As a result, the induction coil  130  may efficiently receive electric power transmitted by the transmission coil  220 . 
     The shield member  244  may include, for example, a conductor such as aluminum and copper. Alternatively, the shield member  244  may include a carbon material such as carbon fiber, carbon nanotube (CNT), carbon black, graphene, and the like. Alternatively, the shield member  244  may be made of a polymer composite material or a combination of a polymer composite material and carbon, ceramic, a metal, or the like. 
     In addition, the shield member  244  may be, for example, in the form of a sheet metal, mesh, or ionized gas. The shield member  244  may be applied to a shield structure surrounding the transmission coil  220  by sputtering, plating, or spray coating. 
       FIG. 13  is a diagram illustrating an operation of charging an aerosol generating device through a charging device, according to an embodiment. 
     Referring to  FIG. 13 , the aerosol generating device  100  may be a holder  10  that holds an aerosol generating material inserted therein. The charging device  200  may be a cradle  20  including a cavity in which the aerosol generating device  100  may be accommodated. Descriptions on the aerosol generating device  100  given with reference to  FIGS. 1 to 12  may apply to the holder  10 , and descriptions on the charging device  200  given with reference to  FIGS. 1 to 12  may apply to the cradle  20 . In addition, descriptions on the holder  10  to be given with reference to  FIGS. 13 to 18  may apply to the aerosol generating device  100 , and descriptions on the cradle  20  to be given with reference to  FIGS. 13 to 18  may apply to the charging device  200 . 
     The holder  10  may include a holder battery  11 , a holder controller  12 , a heater  13 , and a power receiver  14 . Descriptions on the power supply  140  of the aerosol generating device  100  given with reference to  FIGS. 1 to 12  may apply to the holder battery  11 , descriptions on the controller  150  of the aerosol generating device  100  given with reference to  FIGS. 1 to 12  may apply to the holder controller  12 , and descriptions on the susceptor  110  given with reference to  FIGS. 1 to 12  may apply to the heater  13 . In addition, descriptions on the holder battery  11  to be given with reference to  FIGS. 13 to 18  may apply to the power supply  140  of the aerosol generating device  100 , descriptions on the holder controller  12  to be given with reference to  FIGS. 13 to 18  may apply to the controller  150  of the aerosol generating device  100 , and descriptions on the heater  13  to be given with reference to  FIGS. 13 to 18  may apply to the susceptor  110 . 
     The cradle  20  may include a cradle battery  21 , a cradle controller  22 , and a power transmitter  24 . Descriptions on the power supply  280  of the charging device  200  given with reference to  FIGS. 1 to 12  may apply to the cradle battery  21 , descriptions on the controller  260  given with reference to  FIGS. 1 to 12  may apply to the cradle controller  22 , and descriptions on the transmission coil  220  given with reference to  FIGS. 1 to 12  may apply to the power transmitter  24 . In addition, descriptions on the cradle battery  21  to be given with reference to  FIGS. 13 to 18  may apply to the power supply  280  of the charging device  200 , descriptions on the cradle controller  22  to be given with reference to  FIGS. 13 to 18  may apply to the controller  260 , and descriptions on the power transmitter  24  to be given with reference to  FIGS. 13 to 18  may apply to the transmission coil  220 . 
     Internal structure of the holder  10  and the cradle  20  is not limited to the illustration of  FIG. 13 . Those skilled in the art may understand that depending on the design of the holder  10  and the cradle  20 , some of the hardware components illustrated in  FIG. 13  may be omitted, or a new component may be added thereto. 
     An inner space may be formed around the heater  13  of the holder  10 , and a cigarette may be inserted into the inner space. When the cigarette is inserted into the holder  10 , the holder  10  controls an output voltage of the holder battery  11  so that a temperature of the heater  13  rises. As an aerosol generating material in the cigarette is heated by the heater  13 , an aerosol is generated. 
     A cavity  23  for accommodating the holder  10  may be formed in the cradle  20 . The cavity  23  may be formed in a lengthwise direction of the cradle  20 , and the holder  10  may be accommodated in the cavity  23  in a direction perpendicular to the lengthwise direction of the cradle  20 , as illustrated in  FIG. 1 . Alternatively, the holder  10  may be accommodated in the cavity  23  in a direction parallel to the lengthwise direction of the cradle  20 . 
     The holder battery  11  supplies electric power needed for the holder  10  to operate. For example, the holder battery  11  may supply electric power for the heater  13  to be heated. The holder battery  11  may also supply electric power needed for other hardware components provided within the holder  10  such as a sensor, user interface, memory, the holder controller  12 , and the like to operate. 
     The cradle battery  21  supplies electric power needed for the cradle  20  to operate. For example, the cradle battery  21  may supply electric power to the holder battery  11  to charge the holder battery  11 . When the holder  10  and the cradle  20  are coupled to each other, the cradle battery  21  may supply electric power needed for the holder  10  to operate. For example, when a terminal of the holder  10  and a terminal of the cradle  20  are coupled to each other, regardless of whether the holder battery  11  has discharged or not, the holder  10  may use electric power supplied by the cradle battery  21  to operate. 
     The holder battery  11  and the cradle battery  21  may include a rechargeable battery or a disposable battery. For example, the holder battery  11  and the cradle battery  21  may include a lithium iron phosphate (LiFePO4) battery, a lithium cobalt oxide (LiCoO2) battery, a lithium titanate battery, and a lithium polymer (LiPoly) battery. However, embodiments of the present disclosure are not limited thereto. 
     The heater  13  is supplied with electric power by the holder battery  11  under the control of the holder controller  12 . The heater  13  may be supplied with electric power by the holder battery  11  to heat the cigarette inserted into the holder  10 . 
     The heater  13  may be formed of any suitable electrically resistive material. For example, the suitable electrically resistive material may include a metal such as titanium, zirconium, tantalum, platinum, nickel, cobalt, chromium, hafnium, niobium, molybdenum, tungsten, tin, gallium, manganese, iron, copper, stainless steel, and nichrome, or an alloy thereof, but is not limited thereto. In addition, the heater  13  may be implemented with a metal wire, a metal plate on which an electrically conductive track is disposed, a ceramic heating element, and the like. However, embodiments of the present disclosure are not limited thereto. 
     According to an embodiment, the heater  13  may heat the cigarette inserted into an accommodation space of the holder  10 . As the cigarette is accommodated in the accommodation space of the holder  10 , the heater  13  may be located inside and/or outside the cigarette. Thus, the heater  13  may heat the aerosol generating material in the cigarette to generate the aerosol. 
     For example, the heater  13  may have a shape of a cylinder and a cone combined with each other. The heater  13  may be in a cylindrical shape having a diameter of about 2 mm and a length of about 23 mm, and an end of the heater  13  may have an acute angle. However, embodiments of the present disclosure are not limited thereto. 
     The heater  13  may include an induction heating-type heater. The heater  13  may include an electrically resistive coil for heating the cigarette through induction heating, and the cigarette may include a susceptor capable of being heated by the induction heating-type heater. 
     The holder  10  may include at least one sensor. A result sensed by the at least one sensor may be transmitted to the holder controller  12 , and according to the sensed result, the holder controller  12  may control the holder  10  to execute a variety of functions such as control of the operation of the heater, restriction of smoking, determining of whether the cigarette is inserted or not, display of notification, and the like. 
     For example, the at least one sensor may include a puff detection sensor. The puff detection sensor may detect a user&#39;s puff based on any one of a temperature change, a flow change, a voltage change, and a pressure change. 
     The at least one sensor may also include a temperature detection sensor. The temperature detection sensor may detect a temperature at which the heater  13  (or, the aerosol generating material) is heated. The holder  10  may include a separate temperature detection sensor for detecting the temperature of the heater  13 , or instead of the holder  10  including a separate temperature detection sensor, the heater  13  may serve as a temperature detection sensor. Alternatively, the holder  10  may further include a separate temperature detection sensor even if the heater  13  is able to serve as a temperature detection sensor. 
     The holder  10  may include a user interface. The user interface may provide a user with information on the state of the holder  10 . 
     The user interface may include various interfacing means such as a display or lamp for outputting visual information, a motor for outputting tactile information, a speaker for outputting sound information, an input/output (I/O) interfacing means (e.g., button or touch screen) for receiving information input from the user or outputting information to the user, terminals for data communication or for receiving charging power, a communication interfacing module for performing wireless communication with an external device (e.g., Wi-Fi (wireless fidelity), Wi-Fi direct, blue-tooth, NFC (near-field communication)), and the like. 
     However, only some of the various user interface examples described above may be selected and implemented in the holder  10 . 
     The holder controller  12  is hardware for controlling the overall operation of the holder  10 . The holder controller  12  includes at least one processor. The processor may be implemented with an array of a plurality of logic gates, or may be implemented with a combination of a general-purpose microprocessor and a memory in which a program executable in the microprocessor is stored. In addition, those skilled in the art may understand that the processor may also be implemented with other types of hardware. 
     The holder controller  12  analyzes the result sensed by the at least one sensor and controls processes to be subsequently executed. 
     The holder controller  12  may control electric power supplied to the heater  13  such that the heater  13  starts or terminates operation, based on the result sensed by the at least one sensor. The holder controller  12  may control an amount of electric power supplied to the heater  13  and a period of time for which electric power is supplied to the heater  13  such that the heater  13  is heated to a certain temperature or maintains an appropriate temperature, based on the result sensed by the at least one sensor. 
     The holder controller  12  may control the user interface, based on the result sensed by the at least one sensor. For example, when the number of puffs is counted by the puff detection sensor reaches a preset number, the holder controller  12  may use at least any one of the lamp, motor, and speaker to notify the user that the holder  10  will be terminated soon. 
     The cradle controller  22  is hardware for controlling the overall operation of the cradle  20 . The cradle  22  includes at least one processor. The processor may be implemented with an array of a plurality of logic gates, or may be implemented with a combination of a general-purpose microprocessor and a memory in which a program executable in the microprocessor is stored. In addition, those skilled in the art to which the present embodiment belongs may understand that the processor may also be implemented with other types of hardware. 
     The cradle controller  22  may control operation of all components of the cradle  20 . In addition, the cradle controller  22  may determine whether the holder  10  and the cradle  20  are coupled to each other or not, and may control operation of the cradle  20  according to coupling or separation of the cradle  20  and the holder  10 . 
     For example, when the holder  10  and the cradle  20  are coupled to each other, the cradle controller  22  may supply electric power of the cradle battery  21  to the holder  10  to charge the holder battery  11  or supply the electric power to the heater  13 . Therefore, even when remaining capacity of the holder battery  11  is little, the user may couple the holder  10  to the cradle  20  to continue smoking. 
     The cradle  20  may include a display capable of outputting visual information. In this case, the cradle controller  22  may generate a signal to be displayed on the display to provide the user with information related to the cradle battery  21  (e.g., remaining capacity, availability, and the like of the cradle battery  21 ), information related to resetting of the cradle  20  (e.g., timing for resetting, progress of resetting, completion of resetting, and the like), information related to cleaning of the holder  10  (e.g., timing for cleaning, need of cleaning, progress of cleaning, completion of cleaning, and the like), information related to charging of the cradle  20  (e.g., need of charging, progress of charging, completion of charging, and the like), and the like. 
     In addition, the cradle  20  may include at least one input device (for example, a button) which allows the user to control functions of the cradle  20 , a terminal for coupling with the holder  10 , and/or an interface (for example, a universal serial bus (USB) port, etc.) for charging the cradle battery  21 . 
     For example, the user may use the input device to execute various functions. The user may regulate a frequency of pressing the input device or a period of time for which the input device is pressed to execute desired functions of a plurality of functions of the cradle  20 . As the user operates the input device, the cradle  20  may perform a function of preheating the heater  13  of the holder  10 , a function of regulating the temperature of the heater  13  of the holder  10 , a function of cleaning a space within the holder  10  into which the cigarette is inserted, and a function of checking whether the cradle  20  is operable or not. In addition, a function of displaying the remaining capacity (available power) of the cradle battery  21 , a function of resetting the cradle  20 , and the like may be executed. However, the functions of the cradle  20  are not limited thereto. 
     The holder  10  may include the power receiver  14 , and the cradle  20  may include the power transmitter  24 . The power transmitter  24  of the cradle  20  may use one or more wireless power transmission methods to wirelessly transmit electric power to the power receiver  14  of the holder  10  without any mutual contact. Examples of the wireless power transmission methods include, but are not limited to, inductive coupling and magnetic resonance coupling. 
     The power receiver  14  of the holder  10  is connected to the holder battery  11 , and the power transmitter  24  of the cradle  20  is connected to the cradle battery  21 . The power transmitter  24  of the cradle  20  wirelessly transmits electric power to the power receiver  14  of the holder  10 , so that the holder battery  11  is charged. 
     According to one or more embodiments of the present disclosure, the location of the power transmitter  24  may be changed according to whether the holder  10  is accommodated in the cavity  23  of the cradle  20  or not. This will be described later with reference to  FIGS. 16 and 17 . 
       FIG. 14  is a conceptual diagram of a power transmitter and a power receiver used for wireless charging, according to an embodiment. 
     A power transmitter  2100  may use one or more wireless power transmission methods to wirelessly transmit electric power to a power receiver  2200  without any mutual contact. 
     According to an embodiment, the power transmitter  2100  may transmit electric power to the power receiver  2200  by one or more methods from among inductive coupling based on magnetic induction by a wireless power signal and magnetic resonance coupling based on electromagnetic resonance by a wireless power signal of a specific frequency. 
     The wireless power transmission through the inductive coupling is a technique of wirelessly transmitting electric power using a primary coil and a secondary coil. In this case, a current is induced in a coil according to magnetic induction by an alternating magnetic field applied by the other coil, such that electric power is transferred. 
     The wireless power transmission through the magnetic resonance coupling refers to a method in which resonance occurs in the power receiver  2200  by the wireless power signal transmitted by the power transmitter  2100 , and electric power is transmitted from the power transmitter  2100  to the power receiver  2200  by the resonance. 
       FIG. 14  illustrates that electric power is transmitted from the power transmitter  2100  to the power receiver  220  by using the inductive coupling. The power transmitter  2100  includes a transmission coil (i.e., Tx coil)  2110  that operates as the primary coil in the magnetic induction, and the power receiver  2200  includes a reception coil (i.e., Rx coil)  2210  that operates as the secondary coil in the magnetic induction. 
     When the intensity of a current flowing through the transmission coil  2110  of the power transmitter  2100  changes, a magnetic field passing through the transmission coil  2110  changes. The change of the magnetic field passing through the transmission coil  2110  generates an induced electromotive force on the reception coil  2210  of the power receiver  220 . The electromotive force induced to the reception coil  2210  may be used to charge a battery of the power receiver  2200 . 
       FIG. 15  is a diagram illustrating an example of an aerosol generating system before a holder is accommodated in a cradle, according to an embodiment. 
     The cradle  20  includes a first side  3210  in parallel with a lengthwise direction of the cradle  20 , and a second side  3220  perpendicular to the first side  3210 . When the holder  10  is not accommodated in the cavity  23  of the cradle  20 , the power transmitter  24  of the cradle  20  may be located to face the second side  3220 . 
     The holder  10  may include a third side  3100  on which the power receiver  14  is located. For example, when the holder  10  is in a rectangular parallelepiped shape, the third side  3100  may include a rectangular cross section. Alternatively, when a cross section of the holder  10  is in a cylindrical shape, the third side  3100  may include a portion of a circumferential surface of the holder  10 . 
     When the third side  3100  of the holder  10  is placed on the second side  3220  of the cradle  20 , the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  may face each other. If the power receiver  14  receives electric power wirelessly from the power transmitter  24  while the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  are arranged to face each other, the charging efficiency of the holder battery  11  may be enhanced. 
     According to an embodiment, a first seating groove  3230  in which the holder  10  is able to be seated may be formed on the second side  3220  of the cradle  20 . The first seating groove  3230  may prevent the holder  10  from being separated from the cradle  20 . Even when the holder  10  is not accommodated in the cavity  23  of the cradle  20 , the holder  10  may be seated in the first seating groove  3230 , so that the power receiver  14  receives electric power wirelessly from the power transmitter  24 . 
     Although not shown in  FIG. 15 , magnetic materials may be present inside the third side  3100  where the power receiver  14  is located and inside the first seating groove  3230 . The power receiver  14  may be seated on the first seating groove  3230  to face the inside of the first seating groove  3230 , by electromagnetic force of the magnetic materials. In addition, the holder  10  may be seated firmly in the first seating groove  3230  by the electromagnetic force of the magnetic materials. The magnetic materials may include materials such as permanent magnets, iron, nickel, cobalt, an alloy thereof, or the like. However, embodiments of the present disclosure are not limited thereto. 
     When the holder  10  is in a cylindrical shape, the first seating groove  3230  may be formed to correspond to the curvature of the circumferential surface of the holder  10 . Alternatively, when the holder  10  is in a rectangular parallelepiped shape, the first seating groove  3230  may be formed to correspond to a rectangular cross section of the holder  10 . In other words, a shape of the first seating groove  3230  may be determined according to the shape of the holder  10 . 
     The power receiver  14  and the power transmitter  24  may include a flexible printed circuit board (FPCB), and a coil on the FPCB. For example, the FPCB may include polyimide. As the power receiver  14  and the power transmitter  24  include FPCBs, the power receiver  14  and the power transmitter  24  may maintain a flat shape or may be curved flexibly. 
     When the holder  10  is in a cylindrical shape, the power receiver  14  of the holder  10  may be in a curved shape to correspond to the curvature of the third side  3100 . When the first seating groove  3230  is formed on the second side  3220  of the cradle  20 , the power transmitter  24  of the cradle  20  may be in a curved shape to correspond to the curvature of the first seating groove  3230 . In that case, as the first seating groove  3230  is formed to correspond to the curvature of the third side  3100 , the curvature of the power receiver  14  of the holder  10  and the curvature of the power transmitter  24  of the cradle  20  may correspond to each other. Accordingly, a corresponding area between the power receiver  14  and the power transmitter  24  is maximized. Therefore, when the power receiver  14  receives electric power wirelessly from the power transmitter  24 , charging efficiency of the holder battery  11  may be enhanced. 
       FIGS. 16 and 17  are diagrams illustrating examples of an aerosol generating system before and after a holder is accommodated in a cradle, according to an embodiment. 
       FIG. 16  illustrates an aerosol generating system before the holder  10  is accommodated in the cavity  23  of the cradle  20 . 
     The cradle  20  includes the first side  3210  in parallel with a lengthwise direction of the cradle  20 , and the second side  3220  perpendicular to the first side  3210 . The holder  10  may include the third side  3100  on which the power receiver  14  is located. For example, when the holder  10  is in a rectangular parallelepiped shape, the third side  3100  may include a rectangular cross section. Alternatively, when a cross section of the holder  10  is in a cylindrical shape, the third side  3100  may include a portion of a circumferential surface of the holder  10 . 
     When the holder  10  is not accommodated in the cavity  23  of the cradle  20 , the power transmitter  24  of the cradle  20  may be located to face the second side  3220  (hereinafter referred to as the second position) as illustrated in  FIG. 16 . 
     As such, even when the holder  10  is not accommodated in the cavity  23  of the cradle  20 , the power receiver  14  and the power transmitter  24  located on the second position may be arranged to face each other by placing the third side  3100  of the holder  10  on the second side  3220  of the cradle  20 . Since the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  are arranged to face each other, when the power receiver  14  receives electric power wirelessly from the power transmitter  24 , charging efficiency of the holder battery  11  may be enhanced. 
     Although not shown in  FIG. 16 , the first seating groove in which the holder  10  is able to be seated may be formed on the second side  3220  of the cradle  20 . The first seating groove  3230  may prevent the holder  10  from being separated from the cradle  20 . 
     The cradle  20  may include a holder accommodation detection sensor  3300  for detecting whether or not the holder  10  is accommodated in the cavity  23 . When the holder accommodation detection sensor  3300  detects that the holder  10  has been accommodated in the cavity  23 , the location of the power transmitter  24  of the cradle  20  may be changed. 
     For example, if the holder accommodation detection sensor  3300  includes a push-type switch, when the holder  10  is inserted into the cavity  23 , the holder accommodation detection sensor  3300  may be pushed into the cradle  20 . In this case, the cradle  20  may detect that the holder  10  is accommodated in the cavity  23 , and change the location of the power transmitter  24 . 
     The holder accommodation detection sensor  3300  may include a capacitance detection sensor, a hall-effect sensor, a magneto-resistor, or the like. However, embodiments of the present disclosure are not limited thereto. 
       FIG. 17  illustrates an aerosol generating system after the holder  10  is accommodated in the cavity  23  of the cradle  20 . 
     When the holder  10  is accommodated in the cavity  23  of the cradle  20 , the power transmitter  24  of the cradle  20  may be located to face the first side  3210  (hereinafter referred to as the first position), as illustrated in  FIG. 17 . 
     That is, when the holder  10  is accommodated in the cavity  23  of the cradle  20 , the third side  3100  of the holder  10  may be located on the first side  3210  of the cradle  20 , such that the power receiver  14  and the power transmitter  24  at the first position are arranged to face each other. Since the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  are arranged to face each other, when the power receiver  14  receives electric power wirelessly from the power transmitter  24 , charging efficiency of the holder battery  11  may be enhanced. 
     Although not illustrated in  FIGS. 16 and 17 , magnetic materials may be present inside the third side  3100  on which the power receiver  14  is located and inside the first side  3210  of the cavity  23 . The power receiver  14  may be accommodated in the cavity  23  to face the inside of the first side  3210 , by electromagnetic force of the magnetic materials. In addition, the holder  10  may be accommodated firmly in the cavity  23  by the electromagnetic force of the magnetic materials. The magnetic materials may include materials such as permanent magnets, iron, nickel, cobalt, an alloy thereof, or the like. However, embodiments of the present disclosure are not limited thereto. 
     The power transmitter  24  of the cradle  20  may be movable between the first position where the power transmitter  24  faces the first side  3210  inside the cradle  20  and the second position where the power transmitter  24  faces the second side  3220  inside the cradle  20 . As the power transmitter  24  is moved between the first position and the second position, a shape of the power transmitter  24  may be changed. 
     According to an embodiment, the power receiver  14  and the power transmitter  24  may include a FPCB and a coil on the FPCB. As the power receiver  14  and the power transmitter  24  include FPCBs, the power receiver  14  and the power transmitter  24  may maintain a flat shape, or may be curved flexibly. 
     When the second side  3220  is flat, the power transmitter  24  at the second position may be in a flat shape. As the holder  10  is accommodated in the cavity  23  of the cradle  20 , the power transmitter  24  may be moved from the second position to the first position, and the power transmitter  24  may be in a curved shape to correspond to the curvature of the first side  3210 . In other words, as the power transmitter  24  is moved from the second position to the first position, the power transmitter  24  may be changed from the flat shape to the curved shape. 
     Alternatively, if the first seating groove  3230  is formed on the second side  3220  as illustrated in  FIG. 15 , the power transmitter  24  at the second position may be in a curved shape to correspond to the curvature of the first seating groove  3230 . As the holder  10  is accommodated in the cavity  23  of the cradle  20 , the power transmitter  24  may be moved from the second position to the first position, and the power transmitter  24  may be in a curved shape to correspond to the curvature of the first side  3210 . In that case, depending on the difference between the curvature of the first seating groove  3230  and the curvature of the first side  3210 , a degree to which the power transmitter  24  is curved may be changed, or may remain the same. 
     According to the present embodiment, the location of the power transmitter  24  of the cradle  20  may be changed according to whether or not the holder  10  is accommodated in the cavity  23  of the cradle  20 . As such, the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  may be arranged to face each other, whether or not the holder  10  is accommodated in the cavity  23 . Thus, when the power receiver  14  receives electric power wirelessly from the power transmitter  24 , charging efficiency of the holder battery  11  may be enhanced. 
     In addition, according to the present embodiment, the power receiver  14  of the holder  10  and the power transmitter  24  of the cradle  20  may include FPCBs, so that a degree to which the power receiver  14  and the power transmitter  24  are curved is changed to increase the corresponding area. Therefore, when the power receiver  14  receives electric power wirelessly from the power transmitter  24 , charging efficiency of the holder battery  11  may be enhanced. 
       FIG. 18  is a diagram illustrating an example in which a cradle is seated on a wireless charging pad, according to an embodiment. 
     Referring to  FIG. 18 , an external power source may include a wireless charging pad  30 , according to an embodiment. However, the external power source is not limited to the wireless charging pad  30 , and may include various power storage devices such as a rechargeable battery that may be recharged by a wire. 
     The cradle  20  includes the first side  3210  in parallel with a lengthwise direction of the cradle  20 , and the second side  3220  and a fourth side  3240  that are perpendicular to the first side  3210 . In other words, the second side  3220  and the fourth side  3240  are located to face each other. 
     The cradle  20  includes the cradle battery  21 , the cradle controller  22 , the power transmitter  24 , and a power receiver  25 . However, internal configuration of the cradle  20  is not limited to the illustration of  FIG. 18 . 
     The power transmitter  24  of the cradle  20  may be located to face the second side  3220 , and the power receiver  25  of the cradle  20  may be located to face the fourth side  3240 . As illustrated in  FIG. 18 , the power receiver  25  and the power transmitter  24  may be located practically in parallel with each other within the cradle  20 . 
     As described above with reference to  FIGS. 16 and 17 , the power transmitter  24  of the cradle  20  may transmit electric power wirelessly to the power receiver  14  of the holder  10  to charge the holder battery  11 . 
     The power receiver  25  of the cradle  20  may receive electric power wirelessly from an external power transmitter to charge the cradle battery  21 . The external power transmitter may be a power transmitter  31  included within the wireless charging pad  30 . 
     The power receiver  25  of the cradle  20  may receive electric power wirelessly from the wireless charging pad  30  including the power transmitter  31 . When the fourth side  3240  of the cradle  20  is located on one side of the wireless charging pad  30 , the power receiver  25  of the cradle  20  and the power transmitter  31  of the wireless charging pad  30  may be arranged to face each other. 
     According to an embodiment, a second seating groove  32  in which the cradle  20  is able to be seated may be formed on one side of the wireless charging pad  30 . The second seating groove  32  may prevent the cradle  20  from being separated from the wireless charging pad  30 . 
     When the cradle  20  is in a cylindrical shape, the second seating groove  32  may be formed to correspond to the curvature of a circumferential surface of the cradle  20 . Alternatively, when the cradle  20  is in a rectangular parallelepiped shape, the second seating groove  32  may be formed to correspond to a rectangular cross section of the cradle  20 . In other words, depending on the shape of the cradle  20 , a shape of the second seating groove  32  may be determined. 
     Although not illustrated in  FIG. 18 , magnetic materials may be present inside the fourth side  3240  on which the power receiver  25  of the cradle  20  is located, and inside the second seating groove  32 . The power receiver  25  of the cradle  20  may be seated in the second seating groove  32  to face the inside of the second seating groove  32 , by electromagnetic force of the magnetic materials. In addition, the cradle  20  may be seated firmly in the second seating groove  32  by the electromagnetic force of the magnetic materials. The magnetic materials may include materials such as permanent magnets, iron, nickel, cobalt, an alloy thereof, or the like. However, embodiments of the present disclosure are not limited thereto. 
     The power receiver  25  of the cradle  20  and the power transmitter  31  of the wireless charging pad  30  may include a FPCB, and a coil on the FPCB. For example, the FPCB may include polyimide. As the power receiver  25  of the cradle  20  and the power transmitter  31  of the wireless charging pad  30  include FPCBs, the power receiver  25  and the power transmitter  31  may maintain a flat shape, or may be curved flexibly. 
     According to an embodiment, when the cradle  20  is in a cylindrical shape, the power receiver  25  of the cradle  20  may be in a curved shape to correspond to the curvature of the fourth side  3240 . In addition, the power transmitter  31  of the wireless charging pad  30  may be in a curved shape to correspond to the curvature of the second seating groove  32 . If the second seating groove  32  is formed to correspond to the curvature of the fourth side  3240 , the curvature of the power receiver  25  of the cradle  20  and the curvature of the power transmitter  31  of the wireless charging pad  30  may correspond to each other. Accordingly, a corresponding area between the power receiver  25  and the power transmitter  31  is maximized. Thus, when the power receiver  25  receives electric power wirelessly from the power transmitter  31 , charging efficiency of the cradle battery  21  may be enhanced. 
     Although not illustrated in  FIG. 18 , while the holder  10  is accommodated in the cradle  20 , the cradle  20  and the holder  10  may be placed on one side of the wireless charging pad  30 . 
     In that case, the power receiver  25  of the cradle  20  may receive electric power wirelessly from the power transmitter  31  of the wireless charging pad  30  to charge the cradle battery  21 . 
     In addition, as described above with reference to  FIG. 17 , as the holder  10  is accommodated in the cradle  20 , the location of the power transmitter  24  of the cradle  20  is changed to face the power receiver  14 . As such, the power receiver  14  of the holder  10  may receive electric power wirelessly from the power transmitter  24  of the cradle  20 . As a result, the holder battery  11  may be charged. 
     The descriptions of the above-described embodiments are merely examples, and it will be understood by one of ordinary skill in the art that various changes and equivalents thereof may be made. Therefore, the scope of the disclosure should be defined by the appended claims, and all differences within the scope equivalent to those described in the claims will be construed as being included in the scope of protection defined by the claims.