Patent Publication Number: US-2020288542-A1

Title: Induction heating-type cooktop having improved usability

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0025435, filed on Mar. 5, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an induction heating-type cooktop having improved usability. 
     BACKGROUND 
     Various types of cooking apparatuses are used to heat food at homes and restaurants. For example, gas stoves may use gas as fuel. In some cases, cooking apparatuses may use electricity for heating an object subject such as a cooking container including a pot. 
     Methods for heating an object using electricity may be classified as a resistance heating method and an induction heating method. In the resistance heating method, an object may be heated by heat that is generated when electric current flows through a metallic resistance wire or a non-metallic heating element such as silicon carbide, and the heat is delivered to the object (e.g., a cooking container) through radiation or conduction. In the induction heating method, an object itself may be heated by eddy currents that are generated in the object made of metallic ingredients based on a magnetic field generated around a coil when a predetermined magnitude of high-frequency power is supplied to the coil. 
     The induction heating method may be applied to cooktops. 
     In some cases, where a cooktop uses the induction heating method, only magnetic objects may be heated. That is, when a non-magnetic object (e.g., thermal resistant glass, earthenware, and the like) is placed on the cooktop, the cooktop may not heat the object. 
     In some cases, a cooktop may include a heating plate to heat a non-magnetic object. 
     In some cases, efficient heating may not be ensured, and a time for boiling water may be longer than usual. For instance, where the heating plate has a communication hole, a cooking container made of metal may be heated in an electro inductive manner using magnetic lines of force that passes through the communication hole while the heating plate is heated using a heating coil. 
     In some cases, a hybrid cooktop may heat a non-magnetic object through a radiant heater using an electric resistance method, and a magnetic object through a working coil by an induction heating method. 
     In some cases, a high output from the radiant heater and efficient heating may not be ensured. In some cases, when placing an object at a heating area, a user may need to consider a material of the object. 
     In some cases, a cooktop for metallic objects may heat various metallic objects (i.e., a non-magnetic metallic object and a magnetic object). 
     The cooktop for metallic object may not heat a non-magnetic non-metallic object. In some cases, when a non-magnetic metallic object is heated, the cooktop for metallic objects may be less efficient in heating and incur more material costs than a radiant heater. 
     SUMMARY 
     The present disclosure describes an induction heating-type cooktop that can heat an object regardless of the type of the object and that can ensure enhanced heating efficiency. 
     For example, the induction heating-type cooktop can heat both of a magnetic object and a non-magnetic object, where a user may not consider a material of an object to be heated. 
     The present disclosure describes an induction heating-type cooktop that can heat an object directly and indirectly using the same heat source. 
     The present disclosure describes an induction heating-type cooktop in which, when an object is a magnetic object, most of the eddy currents may be supplied to the magnetic object, and a working coil may directly heat the object. When an object is a non-magnetic object, the working coil can indirectly heat the object. 
     The present disclosure describes an induction heating-type cooktop in which coating equipment can be scaled down and manufacturing costs can be reduced. 
     Aspects of the present disclosure are not limited to the above-described ones. Additionally, other aspects and advantages that have not been mentioned may be clearly understood from the following description and may be more clearly understood from implementations. Further, it will be understood that the aspects and advantages of the present disclosure may be realized via means and combinations thereof that are described in the appended claims. 
     According to one aspect of the subject matter described in this application, an induction heating-type cooktop include a case, a cover plate including an upper plate that is coupled to an upper end of the case and that is configured to seat an object to be heated on an upper surface of the upper plate, a working coil disposed in the case and configured to heat the object, a module base that is disposed at a lower surface of the upper plate and that includes a thin layer attached to a surface of the module base, and a thermal insulation material disposed between the module base and the working coil. 
     Implementations according to this aspect may include one or more of the following features. For example, the thin layer may be coated on an upper surface of the module base or a lower surface of the module base. In some examples, the thin layer may be made of a conductive material and has a magnetic property. In the same or other examples, the thin layer may be made of a conductive material and has a non-magnetic property. 
     In some implementations, a skin depth of the thin layer may be greater than a thickness of the thin layer. In some examples, the thickness of the thin layer is between 0.1 μm and 1,000 μm, and the thin layer may be configured to, based on a resistance value of the thin layer, be heated by the working coil. 
     In some implementations, the module base may be made of a material different from a material of the thin layer. In some examples, the module base may be configured to, based a resistance value of the module base, not be heated by the working coil. In some examples, the module base has a diameter less than a width of the upper plate. 
     In some implementations, the working coil may be configured to, based on a magnetic object being placed on the upper surface of the upper plate, be driven to heat the magnetic object, and the thin layer and the magnetic object may be configured to define an equivalent circuit based on the magnetic object being placed on the upper surface of the upper plate. For example, the equivalent circuit may include a first current path including a resistance component of the magnetic object and an inductance component of the magnetic object, and a second current path including a resistance component of the thin layer and an inductance component of the thin layer, where the second current path is electrically connected in parallel to the first current path. 
     In some examples, an electrical impedance defined by the resistance component and the inductance component of the magnetic object in the equivalent circuit is less than an electrical impedance defined by the resistance component and the inductance component of the thin layer in the equivalent circuit. 
     In some implementations, the working coil may be configured to, based on a magnetic object being placed on the upper surface of the upper plate, be driven to generate an eddy current in at least one of the magnetic object or the thin layer to thereby heat the magnetic object, and a magnitude of the eddy current in the magnetic object is greater than a magnitude of the eddy current in the thin layer. 
     In some implementations, the working coil may be configured to, based on a non-magnetic object being placed on the upper surface of the upper plate, be driven to heat the non-magnetic object through the thin layer, and the thin layer and the non-magnetic object may be configured to, based on the non-magnetic object being placed on the upper surface of the upper plate, define an equivalent circuit including a resistance component of the thin layer and an inductance component of the thin layer. In some cases, the equivalent circuit may not include the resistance component of the thin layer and the inductance component of the non-magnetic object. 
     In some implementations, the working coil may be configured to, based on a non-magnetic object being placed on the upper surface of the upper plate, be driven to heat the non-magnetic object through an eddy current carried by the thin layer, and the eddy current is not applied to the non-magnetic object. 
     In some implementations, the working coil may be configured to, based on a magnetic object being placed on the upper surface of the upper plate, directly heat the magnetic object by induction and, based on a non-magnetic object being placed on the upper surface of the upper plate, heat the thin layer by induction to thereby heat the non-magnetic object. In some examples, the module base may be configured to receive a part of heat generated in the thin layer. 
     In some implementations, the induction heating-type cooktop may further include a shield plate that is disposed on a lower surface of the working coil and that is configured to block a magnetic field generated vertically below the working coil based on the working coil being driven, a supporter that is disposed between a lower surface of the shield plate and a lower surface of the case and that supports the shield plate upward, and a cooling fan disposed in the case and configured to cool the working coil. 
     In some examples, the supporter may include an elastic object that supports the shield plate upward. In some examples, the cooling fan may be configured to, draw external air from an outside of the case and blow the drawn external air to the working coil, or draw internal air from an inside the case and discharge the drawn internal air to the outside of the case. The thermal insulation material may be configured to block heat transfer from the object or the thin layer to the working coil. In some implementations, the working coil may be disposed between the thermal insulation material and the shield plate. 
     In some implementations, an induction heating-type cooktop may include a working for heating a magnetic object and a thin layer for heating a non-magnetic object, thereby making it possible to heat both of the magnetic object and non-magnetic object. 
     In some implementations, the induction heating-type cooktop may include the working coil and the thin layer provided to overlap with each other vertically, where the thin layer may be coated on an upper surface or a lower surface of a module base, may be made of a conductive material, may have at least one of a magnetic property and a non-magnetic property, and may be inductively heated by eddy currents induced by the working coil. 
     In some implementations, when the induction heating-type cooktop heats a magnetic object, a magnetic field generated by the working coil may pass through the thin layer and may be delivered to the object because skin depth of the thin layer is greater than thickness of the thin layer, thereby allowing eddy current to be induced to the object. 
     In some implementations, when the induction heating-type cooktop heats a non-magnetic object, eddy currents may be induced to the thin layer by a magnetic field generated by the working coil. 
     In some implementations, the induction heating-type cooktop may include a module base in which the thin layer is coated on one surface of the module base. The module base has a smaller size than an upper plate, and the module base and the upper plate are individually manufactured, thereby ensuring a size of coating equipment of the induction heating-type cooktop and costs incurred to manufacture the induction heating-type cooktop that are less than those of a cooktop in which a thin layer is directly coated on an upper plate. 
     In some implementations, the induction heating-type top allows a user to place an object to be heated on any heating area on an upper plate without causing the user to find out whether the object is a magnetic object or a non-magnetic object, which may improve usability of the cooktop. 
     In some implementations, the induction heating-type cooktop may heat an object using the same heat source directly and indirectly without an additional heating plate or an additional radiant heater, thereby ensuring more efficient heating and reducing material costs. 
     In some implementations, a reduced size of coating equipment and cost reduction to manufacture the induction heating-type cooktop may improve productivity of the induction heating-type cooktop in mass production. 
     Detailed effects of the present disclosure are described together with the above-described effects in the detailed description of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating an example of an induction heating-type cooktop. 
         FIG. 2  is a view illustrating example components in an example case of the induction heating-type cooktop in  FIG. 1 . 
         FIGS. 3 and 4  are views illustrating an example of a relation between a thickness and a skin depth of a thin layer. 
         FIGS. 5 and 6  are views illustrating examples of equivalent circuits and an electrical impedance change between a thin layer and an object based on types of objects to be heated. 
         FIG. 7  is a view illustrating another example induction heating-type cooktop. 
         FIG. 8  is a view illustrating example components in an example case of the induction heating-type cooktop in  FIG. 7 . 
         FIG. 9  is a view illustrating example objects to be heated on the induction heating-type cooktop in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     The above-described aspects, features and advantages are specifically described with reference to the attached drawings hereunder such that one having ordinary skill in the art to which the present disclosure pertains may easily implement the technical spirit of the disclosure. In describing the disclosure, detailed description of known technologies in relation to the disclosure is omitted if it is deemed to make the gist of the present disclosure unnecessarily vague. Below, one or more implementations of the present disclosure are specifically described with reference to the accompanying drawings. Throughout the drawings, identical reference numerals denote identical or similar components. 
       FIG. 1  illustrates an example induction heating-type cooktop.  FIG. 2  illustrates example components disposed in an example case of the induction heating-type cooktop in  FIG. 1 .  FIGS. 3 and 4  illustrates features of a skin depth of a thin layer based on a relative permeability of the thin layer.  FIGS. 5 and 6  illustrate example equivalent circuits and an example of an impedance change between a thin layer and an object based on types of the objects. 
     Referring to  FIG. 1 , the induction heating-type cooktop  1  may include a case  25 , a cover plate  20 , working coils including a first working coil (WC 1 ) and a second working coil (WC 2 ), module bases including a first module based (MB 1 ) and a second module base (MB 2 ), thin layers including a first thin layer (TL 1 ) and a second thin layer (TL 2 ). 
     The working coils WC 1  and WC 2  may be installed in the case  25 . 
     In some implementations, the case  25  may include various devices in relation to driving of the working coil (e.g., a power supplier that supplies alternating current (AC) power, a rectifier that rectifies AC power of the power supplier into direct current (DC) power, an inverter that converts DC power rectified by the rectifier into resonance currents through switching operations and that supplies the resonance currents to the working coil, a control module (including a control module for an inverter, which controls switching operations of the inverter, and a control module for an input interface, which controls an input interface) that controls operations of various devices in the induction heating-type cooktop  1 , and a relay or a semiconductor switch that turns on or off the working coil), in addition to the working coils WC 1  and WC 2 . However, detailed description in relation to this is omitted. 
     The cover plate  20  may include an upper plate  15  which is coupled to an upper end of the case  25 , and where an object is placed on an upper surface of the upper plate. 
     Specifically, the cover plate  20  may include an upper plate  15  on which an object such as a cooking container is placed. 
     The upper plate  15 , for example, may be made of a glass material (e.g., ceramics glass). 
     In some implementations, the upper plate  15  may include an input interface that receives an input from a user and that delivers the input to the above-described control module. In some examples, the input interface may also be provided at another position not at the upper plate  15 . 
     The input interface, which is a module for inputting heating intensity desired by a user or a driving period of the induction heating-type cooktop  1  and the like, may be implemented in various different forms such as a physical button or a touch panel and the like. The input interface, for example, may include a power button, a lock button, a power-level adjusting button (+, and −), a timer adjusting button (+, and −), a charge-mode button and the like. Additionally, the input interface may deliver an input received from the user to a control module for an input interface, and the control module for an input interface may deliver the input to a control module for an inverter. The control module for an inverter may control operations of various devices (e.g., the working coil) based on the input (the input from the user) received from the control module for an input interface. Detailed description in relation to this is omitted. 
     Whether the working coil (e.g., the first and second working coils WC 1  and WC 2  is driven, and heating intensity (i.e., thermal power) may be displayed visually on the upper plate  15  in a burner shape. The burner shape may be displayed by an indicator made of a plurality of light-emitting elements (e.g., light emitting diodes (LEDs)) provided in the case  25 . 
     The first and second working coils WC 1  and WC 2  may be installed in the case  25  to heat an object. 
     Specifically, driving of the first and second working coils WC 1  and WC 2  may be controlled by the control module for an inverter, and, when an object is placed on the upper plate  15 , the first and second working coils WC 1  and WC 2  may be driven by the control module for an inverter. 
     The first and second working coils WC 1  and WC 2  may directly heat a magnetic object, and may indirectly heat a non-magnetic object through the below-described first and second thin layers TL 1  and TL 2 . 
     The first and second working coils WC 1  and WC 2  may heat an object through the method of induction heating, and may be placed to respectively overlap with the first and second module bases MB 1  and MB 2  coated respectively with the first and second thin layers TL 1  and TL 2  in a vertical direction (e.g., a perpendicular direction, or an up-down direction). 
     Although  FIG. 1  illustrates two working coils WC 1  and WC 2  installed in the case  25 , the present disclosure is not limited. That is, a single working coil, or three or more working coils may be installed in the case  25 . In  FIG. 1 , for convenience of description, two working coils WC 1  and WC 2  installed in the case  25  is described as an example. 
     The module base may include first and second module bases MB 1  and MB 2 . The first and second module bases MB 1  and MB 2  may be spaced apart from each other on a lower surface of the upper plate  15 , respectively. 
     One surface (e.g., an upper surface or a lower surface) of the first module base MB 1  is coated with the first thin layer TL 1 , and one surface (i.e., an upper surface or a lower surface) of the second module base MB 2  may be coated with the second thin layer TL 2 . 
     The first and second module bases MB 1  and MB 2  may be provided to overlap respectively with the first and second working coils WC 1  and WC 2  in the vertical direction (the perpendicular direction, or the up-down direction). 
     The first and second thin layers TL 1  and TL 2  may also be provided to overlap respectively with the first and second working coils WC 1  and WC 2  in the vertical direction (the perpendicular direction, or the up-down direction). Accordingly, regardless of the position of and the type of an object, the object may be heated. 
     The first and second thin layers TL 1  and TL 2  may respectively coat the first and second module bases MB 1  and MB 2  to heat a non-magnetic object among objects. 
     The first and second thin layers TL 1  and TL 2  may have at least one of a magnetic property and a non-magnetic property (i.e., a magnetic property, a non-magnetic property or both of them). 
     The first and second thin layers TL 1  and TL 2 , for example, may be made of an conductive material (e.g., aluminum), and, as illustrated in the drawings, may respectively coat one surface of the first and second module bases MB 1  and MB 2  in a form in which a plurality of rings having different diameters are repeated. However, the present disclosure is not limited. 
     That is, the first and second thin layers TL 1  and TL 2  may be made of another material instead of a conductive material and may respectively coat the first and second module bases MB 1  and MB 2  in different forms. For convenience of description, in some examples, the first and second thin layers TL 1  and TL 2 , made of a conductive material and respectively coating one surface of the first and second module bases MB 1  and MB 2  in the form that a plurality of rings having different diameters are repeated, are described as an example. 
     The first and second module bases MB 1  and MB 2  may be made of a material different from a material of the first and second thin layers TL 1  and TL 2 . 
     The first and second module bases MB 1  and MB 2  may be made of a material that may not be inductively heated by the working coil, and may have thermal resistance and thermal conductivity of a specific level or higher. 
     For example, the first and second module bases MB 1  and MB 2  may be made of any one of an organic material, an inorganic material, and a metallic material. 
     In some implementations, inorganic materials used for the first and second module bases MB 1  and MB 2  include ceramics, glass and the like, organic materials used for the first and second module bases MB 1  and MB 2  include high-temperature heat resistant plastics and the like, and metallic materials used for the first and second module bases MB 1  and MB 2  include a metallic material thick enough (e.g., 1 mm thick aluminum) so that the metallic material is not inductively heated by the working coil. 
     Unlike the first and second module bases MB 1  and MB 2 , the first and second thin layers TL 1  and TL 2  may be made of a material that can be inductively heated by the working coil, and may have a thickness to the extent that the first and second thin layers TL 1  and TL 2  are inductively heated by the working coil. Detailed description in relation to this is provided below. 
     A diameter (i.e., a size) of each of the first and second module bases MB 1  and MB 2  may be smaller than a diameter of the upper plate  15 . 
     In the case of a cooktop in which the first and second thin layers TL 1  and TL 2  coat the upper plate  15 , when the cooktop is actually manufactured, the upper plate  15  of the cooktop  1  may be offered during the process of coating. Accordingly, although a cook zone of a diameter of 8 inches (an exemplary diameter), in which an object (i.e., a container) is placed, is actually coated, an approximately 24-inch-size upper plate  15  (e.g., (W; width)  575 ×(D; thickness)  515 ×(H; height) 4 mm) is offered during the process of coating. Accordingly, coating equipment may be scaled up, and a plurality of cooktops may not be manufactured at a time, thereby pushing up manufacturing costs. 
     In some implementations, the module base (MB 1 , MB 2 ) having a size corresponding to a size of a cookzone (e.g., the module bases MB 1  and MB 2  having a diameter the same as or similar to an 8-inch diameter of a cookzone) may be coated with a thin layer. Accordingly, coating equipment may be scaled down and manufacturing costs may be reduced. With a reduction in manufacturing costs, productivity may be enhanced and mass production may be ensured. 
     In some examples, each of the first and second module bases MB 1  and MB 2 , for example, may have resistance against temperatures of 600° C. or higher and thermal conductivity of 1.0 W/mk or more, and may diffuse part of heat generated in the first and second thin layers TL 1  and TL 2  (i.e., may serve as a heat diffusion layer). Description in relation to this is provided hereunder. 
       FIG. 1  illustrates two module bases MB 1  and MB 2  and two thin layers TL 1  and TL 2 . However, the present disclosure is not limited. That is, a single module base and thin layer, or three or more module bases and thin layers may be provided. For convenience of description, in some implementations, two module bases MB 1  and MB 2  and two thin layers TL 1  and TL 2  are described as an example. 
     Referring to  FIG. 2 , the induction heating-type cooktop  1  may further include a thermal insulation material  35 , a shield plate  45 , a supporter  50 , and a cooling fan  55 . 
     Components placed near the first working coil WC 1  are the same as components placed near the second working coil (WC 2  in  FIG. 1 ). Below, for convenience of description, components (a first module base MB 1 , a first thin layer TL 1 , a thermal insulation material  35 , a shield plate  45 , a supporter  50 , and a cooling fan  55 ) around the first working coil WC 1  are described. 
     The thermal insulation material  35  may be provided between the first module base MB 1  and the first working coil WC 1 . 
     The thermal insulation material  35  may prevent or block heat generated while the first thin layer TL 1  or an object to be heated (a heating object or “HO”) is heated through driving of the first working coil WC 1 , from being delivered to the first working coil WC 1 . 
     That is, when the first thin layer TL 1  or an object HO is heated by electromagnetic induction of the first working coil WC 1 , heat of the first thin layer TL 1  or the object HO is delivered to the upper plate  15 , and heat of the upper plate  15  is delivered to the first working coil WC 1  again. Then the first working coil WC 1  may be damaged. 
     The thermal insulation material  35 , as described above, may cut off heat delivered to the first working coil WC 1 , thereby preventing damage caused by heat to the first working coil WC 1  and preventing deterioration of heating performance of the first working coil WC 1 . 
     In some implementations, a spacer may be installed between the first working coil WC 1  and the thermal insulation material  35 . 
     The spacer may be inserted between the first working coil WC 1  and the thermal insulation material  35  such that the first working coil WC 1  does not directly contact the thermal insulation material  35 . Accordingly, the spacer may prevent heat, which is generated while the first thin layer TL 1  or an object HO is heated by driving of the first working coil WC 1 , from being delivered to the first working coil WC 1  through the thermal insulation material  35 . 
     That is, the spacer may partially serve as a thermal insulation material  35 . Accordingly, a thickness of the thermal insulation material  35  may be minimized. By doing so, a gap between the object HO and the first working coil WC 1  may be minimized. 
     Additionally, a plurality of spacers may be provided, and the plurality of spacers may be spaced apart from each other between the first working coil WC 1  and the thermal insulation material  35 . As a result, air, suctioned into the case  25  by the below-described cooling fan  55 , may be guided to the first working coil WC 1  by the spacer. 
     That is, the spacer guides the air introduced into the case  25  by the cooling fan  55  such that the air is delivered properly to the first working coil WC 1 . Accordingly, efficiency of cooling of the first working coil WC 1  may be enhanced. 
     The shield plate  45  may be provided on a lower surface of the first working coil WC 1  and may shield a magnetic field that is generated downwards when the first working coil WC 1  is driven. 
     The shield plate  45  may shield a magnetic field that is generated downwards when the first working coil WC 1  is driven, and may be supported upwards by a supporter  50 . 
     The supporter  50  may be installed between a lower surface of the shield plate  45  and a lower surface of the case  25  and may support the shield plate  45  upwards. 
     The supporter  50  may indirectly support the first working coil WC 1 , the thermal insulation material  35 , and the first module base MB 1  upwards by supporting the shield plate  45  upwards. By doing so, the supporter  50  may keep the gap between the first working coil WC 1  and the object HO constant. 
     The supporter  50 , for example, may include an elastic object (e.g., a spring) for supporting the shield plate  45  upwards, and the elastic object is not limited. In some examples, the supporter  50  may also be omitted from the induction heating-type cooktop  1 . 
     The cooling fan  55  may be installed in the case  25  to cool the first working coil WC 1 . 
     Operations of the cooling fan  55  may be controlled by the above-described control module and may be installed on a lateral wall of the case  25 . The cooling fan  55  may also be installed at another position except a lateral wall of the case  25 . In some implementations, for convenience of description, the cooling fan  55  installed on a lateral wall of the case  25  is described as an example. 
     Additionally, the cooling fan  55 , as illustrated in  FIG. 2 , may suction air outside of the case  25  and may deliver the suctioned air to the first working coil WC 1  or may suction air (particularly, hot air) inside the case  25  and may discharge the sectioned air out of the case  25 . 
     Accordingly, components (particularly, the first working coil WC 1  inside the case  25  may be efficiently cooled. 
     As described above, air outside of the case  25 , delivered to the first working coil WC 1  by the cooling fan  55 , may be guided to the first working coil WC 1  by the spacer. Accordingly, the first working coil WC 1  may be cooled directly and efficiently, thereby ensuring improved durability (i.e., improved durability through the prevention of damage caused by heat) of the first working coil WC 1 . 
     The induction heating-type cooktop  1  may have the above-described features and configurations. Below, features and configurations of the above-described thin layer are described with reference to  FIGS. 3 to 6 . 
     For convenience of description, a thickness of each of the components in  FIGS. 3 and 4  is schematically illustrated regardless of actual measurements, and a relative difference in thicknesses of the components is also are schematically illustrated regardless of actual measurements. 
       FIGS. 3 and 4  are views illustrating a relation between thickness and skin depth of the thin layer.  FIGS. 5 and 6  are views illustrating an impedance change between the thin layer and an object based on the type of the object. In some examples, the skin depth may refer to a depth or a distance to which current penetrates from a surface made of a material, and the relative permeability of the material may be inversely proportional to the skin depth. 
     The first thin layer TL 1  and the second thin layer TL 2  may have the same technical features, and may be coated on an upper surface or a lower surface of each of the first module base MB 1  and the second module base MB 2 . Below, for convenience of description, the first thin layer TL 1  coating the lower surface of the first module base MB 1  is described as an example. 
     Features of the first thin layer TL 1  are described as follows. 
     The first thin layer TL 1  may be made of a material having low relative permeability. 
     Specifically, as the first thin layer TL 1  has a low relative permeability, the first thin layer TL 1  may have a deep skin depth. The skin depth denotes a depth to which electric currents permeate a material from the surface of the material, and the relative permeability may be inversely proportional to the skin depth. Accordingly, as the first thin layer TL 1  has a lower relative permeability, the first thin layer TL 1  has a deeper skin depth. In some examples, the skin depth may be greater than 0.1 μm. In some examples, the skin depth may be greater than 1 mm. For example, a copper layer may have a skin depth of about 8.5 mm at 60 Hz. 
     The skin depth of the first thin layer TL 1  may be greater than the thickness of the first thin layer TL 1 . That is, the first thin layer TL 1  has a small thickness (e.g., 0.1 μm to 1,000 μm), and, as the skin depth of the first thin layer TL 1  is greater than the thickness of the first thin layer TL 1 , a magnetic field, generated by the first working coil WC 1 , may pass through the first thin layer TL 1  and be delivered to the object HO, and eddy currents may be induced to the object HO. 
     As illustrated in  FIG. 3 , when the skin depth of the first thin layer TL 1  is smaller than the thickness of the first thin layer TL 1 , a magnetic field, generated by the first working coil WC 1 , is hardly delivered to the object HO. 
     When the skin depth of the first thin layer TL 1  is greater than the thickness of the first thin layer TL 1  as in some examples (as in  FIG. 4 ), most of the magnetic field generated by the first working coil WC 1  is delivered to the object HO. That is, in some implementations, as the skin depth of the first thin layer TL 1  is greater than the thickness of the first thin layer TL 1 , a magnetic field generated by the first working coil WC 1  may pass through the first thin layer TL 1  and may be mostly used up at the object HO. By doing so, the object HO may be mostly heated. 
     Because the first thin layer TL 1 , as described above, has a small thickness, the first thin layer TL 1  has a resistance value to the extent that the first thin layer TL 1  can be heated by the first working coil WC 1 . 
     The thickness of the first thin layer TL 1  may be inversely proportional to the resistance value (i.e., a surface resistance value) of the first thin layer TL 1 . As the first thin layer TL 1  coating the first module base MB 1  has a smaller thickness, the first thin layer TL 1  has a greater resistance value (i.e., surface resistance). In some examples, when the first thin layer TL 1  thinly is coated on the first module base MB 1 , properties of the first thin layer TL 1  may be changed into properties of a heatable load. 
     The first thin layer TL 1 , for example, may have a thickness of 0.1 μm to 1,000 μm but is not limited. 
     The first module base MB 1 , as described above, has a thickness to the extent that the first module base MB 1  is not inductively heated by a working coil. For instance, the first module base MB 1  may have a thickness (e.g., 1 mm) greater than that of the first thin layer TL 1 , and may be a non-heatable load (i.e., a thickness and a resistance value to the extent to which the first module base MB 1  may not be heated). 
     As the first thin layer TL 1  with the features is to heat a non-magnetic object, impedance properties between the first thin layer TL 1  and the object HO may be changed based on whether the object HO is a magnetic object or a non-magnetic object. 
     Referring to  FIGS. 2 and 5 , when a magnetic object HO is placed on an upper surface of the upper plate  15 , and the first working coil WC 1  is driven, a resistance (R 1 ) and an inductance (L 1 ) of the magnetic object HO, and a resistance (R 2 ) and an inductance (L 2 ) of the first thin layer TL 1  may form an equivalent circuit. That is, the first thin layer TL 1  and the magnetic object HO may be represented by the equivalent circuit in which the resistance (R 1 ) and the inductance (L 1 ) of the magnetic object are connected in parallel with the resistance (R 2 ) and the inductance (L 2 ) of the first thin layer. 
     In this case, impedance (i.e., impedance made of R 1  and L 1 ) of the object HO that has magnetic properties in the equivalent circuit may be lower than impedance (i.e., impedance made of R 2  and L 2 ) of the first thin layer TL 1 . 
     Accordingly, when the above-described equivalent circuit is formed, magnitude of eddy currents ( 11 ) supplied to the magnetic object HO may be greater than magnitude of eddy currents ( 12 ) supplied to the first thin layer TL 1 . Most of the eddy currents may be supplied to the object HO and the object HO may be heated. 
     That is, when the object HO is a magnetic object, the above-described equivalent circuit is formed, and most of the eddy currents are supplied to the object HO. Accordingly, the first working coil WC 1  may directly heat the object HO. 
     In some examples, some of the eddy currents may also be supplied to the first thin layer TL 1  and the first thin layer TL 1  is slightly heated. Accordingly, the object HO may be slightly heated by the first thin layer TL 1  indirectly. Comparing between the degree to which the object HO is directly heated by the first working coil WC 1  and the degree to which the object HO is indirectly heated by the first thin layer TL 1 , the degree to which the object HO is indirectly heated by the first thin layer TL 1  may be less than the degree to which the object HO is directly heated by the first working coil WC 1 . 
     In relation to an object that is a non-magnetic object, description is provided as follows. 
     Referring to  FIGS. 2 and 6 , a non-magnetic object HO is placed on the upper surface of the upper plate  15 , and the first working coil WC 1  is driven, the non-magnetic object HO may have no impedance, and the first thin layer TL 1  may have impedance. For example, the first thin layer TL 1  only may have a resistance (R) and an inductance (L). In some examples, the first thin layer TL 1  and the non-magnetic object HO may be represented by the equivalent circuit including only the resistance (R 2 ) and the inductance (L 2 ) of the first thin layer. 
     Accordingly, eddy currents (I) may be supplied only to the first thin layer TL 1 , and eddy currents (I) may not be supplied to the non-magnetic object HO. Specifically, eddy currents (I) may be supplied only to the first thin layer TL 1  and the first thin layer TL 1  may be heated. 
     That is, when the object HO is a non-magnetic object, eddy currents (I) are supplied to the first thin layer TL 1  and the first thin layer TL 1  is heated, as described above. Thus, the non-magnetic object HO may be indirectly heated by the first thin layer TL 1  heated by the first working coil WC 1 . 
     In this case, heat may be concentratedly generated in the first thin layer TL 1 , and the generated heat is concentratedly delivered to a partial area (i.e., an area adjacent to the first thin layer TL 1  of the upper plate  15 . Accordingly, a temperature of the upper plate  15  reaches a self-configured protection temperature rapidly, and a temperature sensor mounted onto the upper plate  15  senses that the temperature of the upper plate  15  has reached the protection temperature. The temperature sensor supplies sensed temperature information to the above-described control module, and the control module controls an output from the first working coil WC 1  based on the supplied temperature information (i.e., when the temperature of the upper plate  15  reaches the protection temperature, the control module reduces an output from the first working coil WC 1 ). 
     That is, when the temperature of the upper plate  15  reaches the protection temperature rapidly, output performance from the cooktop  1  is reduced while an output from the working coil is reduced suddenly. 
     In some implementations, the first thin layer TL 1  may be coated on the first module base MB 1 , not on the upper plate  15 , and the first module base MB 1  has thermal resistance and thermal conductivity of a specific level or higher. Accordingly, part of the heat generated in the first thin layer TL 1  may diffused through the first module base MB 1 . 
     That is, a rapid increase in temperatures of the upper plate  15  may be prevented, and a heat flow in the cooktop  1  may be efficiently dispersed, through the role of spreading or diffusing heat played by the first module base MB 1 . By doing so, improved output performance and improved security of the cooktop  1  may be ensured. 
     The protection temperature of the upper plate  15  may be set by a manufacturer of an upper plate or a manufacturer of a cooktop. That is, a manufacturer of an upper plate supplies information on lifespans based on temperatures to a manufacturer of a cooktop, and the manufacturer of a cooktop calculates a lifespan of a product considering time spent using a cooktop and may set a protection temperature of the upper plate  15 . 
     The temperature sensor may be provided in one area of the upper plate  15 , may sense changes in temperatures of the upper plate  15 , and may supply sensed temperature information to the above-described control module. 
     In summary, regardless of whether an object HO is a magnetic object or a non-magnetic object, the object HO may be directly and indirectly heated by the first working coil WC 1  that is a single heat source. That is, when the object HO is a magnetic object, the first working coil WC 1  may directly heat the object HO, and, when the object HO is a non-magnetic object, the first thin layer TL 1  heated by the first working coil WC 1  may indirectly heat the object HO. 
     The induction heating-type cooktop  1 , as described above, may heat both the magnetic object and non-magnetic object. Accordingly, the induction heating-type cooktop may heat an object regardless of the position and type of the object and may allow a user to place the object at any heating area on the upper plate without causing the user to find out whether the object is a magnetic object or a non-magnetic object, thereby ensuring improved usability. 
     The induction heating-type cooktop  1  may directly and indirectly heat an object using the same heat source without an additional heating plate or an additional radiant heater, thereby ensuring more efficient heating and reducing material costs. 
     A size of coating equipment of the induction heating-type cooktop  1  and costs incurred to manufacture the induction heating-type cooktop  1  may be smaller than those of a cooktop in which a thin layer is directly coated on an upper plate, thereby ensuring improved productivity and mass production. 
     Below, another exemplary induction heating-type cooktop is described. 
       FIG. 7  is a view illustrating another exemplary induction heating-type cooktop.  FIG. 8  is a view illustrating components provided in a case of the induction heating-type cooktop in  FIG. 7 .  FIG. 9  is a view illustrating an object placed at the induction heating-type cooktop in  FIG. 7 . 
     The induction heating-type cooktop  2  is the same as the induction heating-type cooktop  1  in  FIG. 1  except some components and effects. Accordingly, differences are described hereunder. 
     Referring to  FIGS. 7 and 8 , unlike the induction heating-type cooktop  1  in  FIG. 1 , the induction heating-type cooktop  2  may be a zone free cooktop. 
     The induction heating-type cooktop  2  may include a case  25 , a cover plate  20 , a plurality of module bases (MBG), a plurality of thin layers (TLG), a thermal insulation material  35 , a plurality of working coils (WCG), a shield plate  45 , a supporter  50 , a cooling fan, a spacer and a control module. 
     In some implementations, the plurality of thin layers TLG may be coated on each of the plurality of module bases MBG. The plurality of thin layers TLG and the plurality of working coils WCG may overlap with each other vertically, and each of the plurality of thin layers TLG and each of the plurality of working coils WCG may be placed to correspond on a one-to-one basis. 
     In some examples, the plurality of thin layers TLG may include TL 1  and TL 2  described above with regard to  FIG. 1 . For example, the plurality of thin layers TLG may be a group of thin layers that are disposed side by side. In some examples, the plurality of module bases MBG may include MB 1  and MB 2  described above with regard to  FIG. 1 . For example, the plurality of module bases MBG may be a group of module bases that are disposed side-by-side corresponding to the group of thin layers. 
     In some implementations, the plurality of thin layers TLG and the plurality of working coils WCG may correspond on a many-to-many basis instead of a one-to-one basis. For convenience of description, in another implementation, the plurality of thin layers TLG and the plurality of working coils WCG, placed on a one-to-one basis, are described as an example. 
     That is, the induction heating-type cooktop  2 , which is a zone free cooktop including a plurality of thin layers TLG and a plurality of working coils WCG, may heat a single object HO simultaneously with all or part of the plurality of working coils WCG or with all or part of the plurality of thin layers TLG. In some examples, the induction heating-type cooktop  2  may heat an object HO by using both all or part of the plurality of working coils WCG and all or part of the plurality of thin layers TLG. 
     In some implementations, the induction heating-type cooktop  2 , as illustrated in  FIG. 9 , may heat objects to be heated (HO 1  and HO 2 ) regardless of the size, position and type of the objects (HO 1  and HO 2 ) in an area (e.g., an area of the upper plate  15 ) in which the plurality of working coils WCG (in  FIG. 8 ) and the plurality of thin layers TLG are provided. 
     The present disclosure has been described with reference to the implementations illustrated in the drawings. However, the disclosure is not limited to the implementations and the drawings set forth herein. Further, various modifications may be made by one having ordinary skill in the art within the scope of the technical spirit of the disclosure. Furthermore, though not explicitly described during description of the implementations of the disclosure, effects and predictable effects according to the configuration of the disclosure should be included in the scope of the disclosure.