Patent Description:
Various types of cooking apparatuses are used at homes and restaurants to heat food items. Gas ranges that use gas as a fuel have been widely used as one of the cooking apparatuses. Apparatuses are available that heat an object to be heated, e.g., a cooking container comprising a pot, by using electricity rather than gas.

Among methods of heating an object to be heated with electricity, induction heating involves generating eddy current in an object to be heated made of metal (e.g., a cooking container) with a magnetic field that is generated around a coil when high-frequency power having predetermined magnitude is supplied to the coil, such that the object to be heated itself is heated. An induction heating apparatus to which induction heating is applied is ordinarily provided with a working coil in a heating zone (or heating region) in which an object to be heated is placed (or provided) and heated.

For the induction heating apparatus, a plurality of working coils is disposed in a single heating zone to heat an object to be heated, as disclosed in <CIT>. <CIT> relates to an induction heating cooker with one driving circuit that supplies a high-frequency current to each of a plurality of heating coils including an inner peripheral coil and an outer peripheral coil, a switching means that switches each of the heating coils to a conduction state and a non-conduction state, and a control device that determines whether an object to be heated is present or not above the inner peripheral coil when the inner peripheral coil is in the conduction state and the outer peripheral coil is in the non-conduction state, and stops the operation of the driving circuit if the object to be heated is not present above the inner peripheral coil.

As in the above document, the induction heating apparatus includes the plurality of working coils of different sizes, so that some of the plurality of working coils cannot be used depending on the size of an object to be heated. Additionally, the plurality of working coils are connected to one another in parallel. Thus, it may be difficult to adjust the outputs of the plurality of working coils differently, causing deterioration in the efficiency of a current supply circuit that supplies current to the working coils.

An object of the present disclosure is to provide an induction heating apparatus and a method for controlling the same in which a plurality of working coils is disposed in a single working coil base, thereby making it possible to use all the plurality of working coils regardless of the size of an object to be heated.

An object of the present disclosure is to provide an induction heating apparatus and a method for controlling the same in which connection relationships among a plurality of working coils are adjusted depending on the type of an object to be heated, thereby making it possible to adjust the outputs of the working coils differently.

An object of the present disclosure is to provide an induction heating apparatus and a method for controlling the same in which connection relationships among a plurality of working coils are adjusted depending on a target output value, thereby making it possible to improve the efficiency of a current conversion circuit that supplies current to working coils.

Aspects according to the present disclosure are not limited to the above ones, and other aspects and advantages that are not mentioned above can be clearly understood from the description and can be more clearly understood from the embodiments set forth herein. Additionally, the aspects and advantages in the present disclosure can be realized via means and combinations thereof that are described in the appended claims.

According to the present disclosure, an induction heating apparatus includes a working coil base that accommodates a first working coil and a second working coil, a first relay that adjusts a connection between the other end of the first working coil and a resonance capacitor, and a second relay that selectively connects one end of the second working coil to any one of the other end of the first working coil and a current conversion circuit.

In the above configurations, connection relationships among a plurality of working coils may be adjusted.

In one embodiment, the induction heating apparatus may include a current conversion circuit that converts current supplied from an external power source, a first working coil whose one end is connected to the current conversion circuit, a second working coil whose one end is connected to the current conversion circuit or the other end of the first working coil, a resonance capacitor that connects to the other end of the second working coil, a first relay that adjusts a connection between the other end of the first working coil and the resonance capacitor, a second relay that selectively connects one end of the second working coil to any one of the other end of the first working coil and the current conversion circuit, and a controller that controls the first relay and the second relay.

In one or more embodiments, a working coil base may be provided that accommodates the first working coil and the second working coil.

In one embodiment, the first working coil and the second working coil of the induction heating apparatus may be coupled to each other as a litz wire structure and/or may be accommodated in the working coil base.

In one embodiment, the first working coil of the induction heating apparatus may be accommodated in the working coil base in a way that the first working coil is disposed on or under the second working coil.

In one embodiment, the first working coil and the second working coil of the induction heating apparatus may be accommodated in the working coil base in a way that a turn of the first working coil and a turn of the second working coil are alternately placed.

The controller of the induction heating apparatus controls the first relay's and the second relay's connections. So, the controller may control whether a relay is turned off (Open) or turned on (closed) or whether a relay is connected to one or another terminal.

The control of the relay's is based on the sort an object to be heated placed on the induction heating apparatus and a target output value.

In one embodiment, when the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and when the target output value is a predetermined reference output value or greater, the controller of the induction heating apparatus may control the first relay such that the first relay connects between the other end of the first working coil and the resonance capacitor, and controls the second relay such that the second relay connects between one end of the second working coil and the current conversion circuit.

In one embodiment, when the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and when the target output value is less than the predetermined reference output value, the controller of the induction heating apparatus may control the first relay such that the first relay does not connect between the other end of the first working coil and the resonance capacitor, and controls the second relay such that the second relay connects between one end of the second working coil and the other end of the first working coil.

In one or more embodiments, the controller may control the first and second relay to connect the first and second working coil in parallel or in series.

In one embodiment, when the object to be heated placed on the induction heating apparatus is an anti-ferromagnetic object to be heated, the controller of the induction heating apparatus may control the first relay such that the first relay does not connect between the other end of the first working coil and the resonance capacitor, and controls the second relay such that the second relay connects between one end of the second working coil and the other end of the first working coil.

In another embodiment, a method for controlling an induction heating apparatus, including a current conversion circuit that converts current supplied from an external power source, a first working coil whose one end is connected to the current conversion circuit, a second working coil whose one end is connected to the current conversion circuit or the other end of the first working coil, a working coil base that accommodates the first working coil and the second working coil, a resonance capacitor that connects to the other end of the second working coil, a first relay that adjusts a connection between the other end of the first working coil and the resonance capacitor, a second relay that selectively connects one end of the second working coil to any one of the other end of the first working coil and the current conversion circuit, and a controller, may include determining the type of an object to be heated placed on the induction heating apparatus by the controller, determining a target output value by the controller, and controlling the first relay's and the second relay's connections by the controller, based on at least one of the type of the object to be heated placed on the induction heating apparatus and the target output value.

In another embodiment, controlling the first relay's and the second relay's connections in the method may include when the controller determines that the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and determines that the target output value is a predetermined reference output value or greater, controlling the first relay by the controller such that the first relay connects between the other end of the first working coil and the resonance capacitor, and when the controller determines that the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and determines that the target output value is the predetermined reference output value or greater, controlling the second relay by the controller such that the second relay connects between one end of the second working coil and the current conversion circuit.

In another embodiment, controlling the first relay's and the second relay's connections in the method may include when the controller determines that the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and determines that the target output value is less than the predetermined reference output value, controlling the first relay by the controller such that the first relay does not connect between the other end of the first working coil and the resonance capacitor, and when the controller determines that the object to be heated placed on the induction heating apparatus is a ferromagnetic object to be heated and determines that the target output value is less than the predetermined reference output value, controlling the second relay by the controller such that the second relay connects between one end of the second working coil and the other end of the first working coil.

In another embodiment, controlling the first relay's and the second relay's connections in the method may include when the controller determines that the object to be heated placed on the induction heating apparatus is an anti-ferromagnetic object to be heated, controlling the first relay by the controller such that the first relay does not connect between the other end of the first working coil and the resonance capacitor, and when the controller determines that the object to be heated placed on the induction heating apparatus is an anti-ferromagnetic object to be heated, controlling the second relay by the controller such that the second relay connects between one end of the second working coil and the other end of the first working coil.

In an induction heating apparatus and a method for controlling the same according to the present disclosure, a first working coil and a second working coil are disposed in a single working coil base, thereby making it possible to use all the working coils regardless of the size of an object to be heated.

In the induction heating apparatus and the method for controlling the same, a connection relationship between the first working coil and the second working coil can be adjusted by changing a connection relationship between a first relay and a second relay depending on the type of an object to be heated, thereby making it possible to adjust the outputs of the working coils differently.

In the induction heating apparatus and the method for controlling the same, a connection relationship between the first working coil and the second working coil is adjusted by changing a connection relationship between a first relay and a second relay depending on a target output value, thereby making it possible to improve the efficiency of a current conversion circuit.

The above-described aspects, features and advantages are specifically described hereunder with reference to the accompanying drawings such that one having ordinary skill in the art to which the present disclosure pertains can easily implement the technical idea of the disclosure. In the disclosure, detailed descriptions of known technologies in relation to the disclosure are omitted if they are deemed to make the gist of the disclosure unnecessarily vague. Below, preferred embodiments according to the disclosure are specifically described with reference to the accompanying drawings. In the drawings, identical reference numerals can denote identical or similar components.

When any one component is described as being in the "upper portion (or lower portion)" of another component or "on (or under)" another component, any one component can be disposed on the upper surface (or lower surface) of another component, and an additional component can be interposed between the two components.

When any one component is described as being "connected", "coupled" or "connected" to another component, any one component can be directly connected or connected to another component, but an additional component can be "interposed" between the two components or the two components can be "connected", "coupled" or "connected" by an additional component.

Throughput the disclosure, each component can be provided as a single one or a plurality of ones, unless explicitly indicated otherwise.

In the disclosure, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless explicitly indicated otherwise. It is to be understood that the term "comprise" or "include," when used in this disclosure, is not interpreted as necessarily including stated components or steps, but can be interpreted as including some of the stated components or steps or as further including additional components or steps.

Hereafter, an induction heating apparatus and a method for controlling the same in several embodiments are described.

<FIG> is a circuit diagram showing an induction heating apparatus of one embodiment.

Referring to <FIG>, the induction heating apparatus <NUM> of one embodiment includes a current conversion circuit <NUM>, a first working coil <NUM>, a second working coil <NUM>, a resonance capacitor <NUM>, a first relay <NUM>, a second relay <NUM> and a controller <NUM>. Thought not illustrated in <FIG>, the induction heating apparatus <NUM> of one embodiment includes a working coil base <NUM>.

The current conversion circuit <NUM> converts current supplied by an external power source <NUM>. The current conversion circuit <NUM> may convert current supplied from the external power source <NUM> to current having a target frequency, and output the current having the target frequency to the first working coil <NUM> and/or the second working coil <NUM> that are described hereafter.

The target frequency is a frequency of current that needs to be output to the first working coil <NUM> and/or the second working coil <NUM> by the current conversion circuit <NUM> such that the induction heating apparatus outputs heat corresponding to a target output value through the first working coil <NUM> and the second working coil <NUM>.

The target frequency value may correspond to an amount of heat energy to be output through the first working coil <NUM> and the second working coil <NUM>, and set through an interface (not illustrated) included in the induction heating apparatus <NUM> by a user.

The current conversion circuit <NUM> may convert current, supplied from the external power source <NUM> through a rectifying circuit, an inverted circuit, a smoothing capacitor and the like, to current of a target frequency, and output the current of the target frequency.

An object to be heated (e.g., a cooking container) is disposed at the upper side of the first working coil <NUM>. The first working coil <NUM> heats the object to be heated through resonance current generated between the first working coil <NUM> and the object to be heated, as current flows. The first working coil <NUM> may be supplied with current from the current conversion circuit <NUM>.

One end of the first working coil <NUM> connects to the current conversion circuit <NUM>. Additionally, the other end of the first working coil <NUM> may connect to the second working coil <NUM> or the resonance capacitor <NUM>.

An object to be heated is disposed at the upper side of the second working coil <NUM>. The second working coil <NUM> heats the object to be heated through resonance current generated between the second working coil <NUM> and the object to be heated, as current flows. The second working coil <NUM> may be supplied with current from the current conversion circuit <NUM>.

One end of the second working coil <NUM> connects to the other end of the current conversion circuit <NUM> or the first working coil <NUM>. Additionally, the other end of the second working coil <NUM> may connect to the resonance capacitor <NUM>.

The working coil base <NUM> is a structure that accommodates the first working coil <NUM> and the second working coil <NUM>. The working coil base <NUM> is made of a non-conductive material.

A structure in which the first working coil <NUM> and the second working coil <NUM> are accommodated in the working coil base <NUM> is specifically described with reference to <FIG>.

<FIG> is a view showing a working coil and a working coil base of the induction heating apparatus of one embodiment.

<FIG> shows the first working coil <NUM> and the second working coil <NUM> accommodated in the working coil base <NUM>. The first working coil <NUM> and the second working coil <NUM> may sit on the working coil base <NUM>, and be wound a plurality of times. That is, the first working coil <NUM> and the second working coil <NUM> may include a plurality of turns.

In this case, the first working coil <NUM> and the second working coil <NUM> may be coupled to each other as a Litz wire structure, in a first embodiment. Illustration in relation to this is provided in <FIG>.

<FIG> is an enlarged view showing portion "A" in <FIG> when a first working coil and a second working coil of the induction heating apparatus of one embodiment are coupled to each other as a Litz wire structure.

<FIG> shows a partial area of the portion in which the first working coil <NUM> and the second working coil <NUM> are accommodated in the working coil base <NUM>. In this case, a turn of the first working coil <NUM> and a turn of the second working coil <NUM> are combined and form a signal turn.

The turn of the first working coil <NUM> and the turn of the second working coil <NUM> may be coupled as a Litz wire structure. That is, the turns of the first working coil <NUM> and the second working coil <NUM> may include a plurality of wires respectively, and the outer surfaces of the plurality of wires may be coated with an insulating layer.

In a state in which the first working coil <NUM> and the second working coil <NUM> are insulated from each other, the turn of the first working coil <NUM> and the turn of the second working coil <NUM> are combined as a single turn, such that the first working coil <NUM> and the second working coil <NUM> are placed (or provided) within the same area range the working coil base <NUM>. Accordingly, the first working coil <NUM> and the second working coil <NUM> may heat an object to be heated within the same area range, and the user may use all the working coils <NUM>, <NUM>, regardless of the size of the object to be heated.

Referring back to <FIG>, the first working coil <NUM> may be accommodated in the working coil base <NUM> in a way that the first working coil <NUM> is disposed on or under the second working coil <NUM>, in a second embodiment. Illustration in relation to this is provided in <FIG>.

<FIG> is a cross-section view along line "B" in <FIG> when the first working coil is disposed on or under the second working coil in the induction heating apparatus of one embodiment.

<FIG> shows a cross section of a partial area of the portion in which the first working coil <NUM> and the second working coil <NUM> are accommodated in the working coil base <NUM>. In this example, a turn of the first working coil <NUM> may be disposed under a turn of the second working coil <NUM>.

That is, the first working coil <NUM> is accommodated in the working coil base <NUM>, and then the second working coil <NUM> is disposed on the first working coil <NUM>. In this case, the outer surfaces of the first working coil <NUM> and the second working coil <NUM> may be coated with an insulating layer.

Since the first working coil <NUM> is disposed under the second working coil <NUM> as described above, the first working coil <NUM> and the second working coil <NUM> may be placed (or provided) in the same area range of the working coil base <NUM>. Accordingly, the first working coil <NUM> and the second working coil <NUM> may heat an object to be heated in the same area range, and the user may use all the working coils <NUM>, <NUM> regardless of the size of the object to be heated.

<FIG> shows an embodiment in which the first working coil <NUM> is disposed under the second working coil <NUM>. However, in another embodiment, the second working coil <NUM> may be disposed under the first working coil <NUM>.

Referring back to <FIG>, the first working coil <NUM> and the second working coil <NUM> may be accommodated in the working coil base <NUM> such that a turn of the first working coil <NUM> and a turn of the second working oil <NUM> are alternately provided, in a third embodiment. Illustration in relation to this is provided in <FIG>.

<FIG> is a cross-sectional view along line "B" in <FIG> when the first working coil and the second working coil are accommodated in the working coil base <NUM> in a way that a turn of the first working coil and a turn of the second working coil are alternately provided, in the induction heating apparatus of one embodiment.

<FIG> shows a cross section of a partial area of the portion in which the first working coil <NUM> and the second working coil <NUM> are accommodated in the working coil base <NUM>. In this example, a turn of the first working coil <NUM> and a turn of the second working coil <NUM> may be alternately provided.

That is, a turn of the first working coil <NUM> may be disposed between turns of the second working coil <NUM>. Additionally, a turn of the second working coil <NUM> may be disposed between turns of the first working coil <NUM>.

Since a turn of the first working coil <NUM> and a turn of the second working coil <NUM> are alternately provided, the first working coil <NUM> and the second working coil <NUM> may be provided in the same area range of the working coil base <NUM>. Accordingly, the first working coil <NUM> and the second working coil <NUM> may heat an object to be heated in the same area range, and the user may use all the working coils <NUM>, <NUM> regardless of the size of the object to be heated.

Referring back to <FIG>, the resonance capacitor <NUM> connects to the other end of the second working coil <NUM>. The resonance capacitor <NUM> forms a resonance circuit together with at least one of the first working coil <NUM> and the second working coil <NUM>. Thus, resonance current is generated among the first working coil <NUM>, the second working coil <NUM>, and the object to be heated, and the object to be heated is heated.

The first relay <NUM> (or first relay circuit) is disposed between the first working coil <NUM> and the resonance capacitor <NUM>. The first relay <NUM> adjusts a connection between the other end of the first working coil <NUM> and the resonance capacitor <NUM>. As the first relay <NUM> is turned on or turned off, the first relay <NUM> connects between the first working coil <NUM> and the resonance capacitor <NUM> or disconnects the first working coil <NUM> from the resonance capacitor <NUM>. The first relay <NUM> may be a Single Pole Single Throw (SPST) relay that has two contact point for one switch. The first relay <NUM>'s connection is controlled by the controller <NUM> that is described below.

The second relay <NUM> (or second relay circuit) selectively connects one end of the second working coil <NUM> to any one of the other end of the first working coil <NUM>, and the current conversion circuit <NUM>. That is, the second relay <NUM> adjusts an object to which the second working coil <NUM> is to connect. In this example, the second relay <NUM> connects to contact point A or contact point B, and connects one end of the second working coil <NUM> to the other end of the first working coil <NUM> or the current conversion circuit <NUM>. The second relay <NUM> may be a Single Pole Double Throw (SPDT) relay that has three contact points for one switch. The second relay <NUM>'s connection is controlled by the controller <NUM> as will be described below.

The controller <NUM> controls entire operation of the induction heating apparatus <NUM>. The controller <NUM> may be implemented to include a physical element including at least one of ASICs(Application Specific Integrated Circuits), DSPs(Digital Signal Processors), DSPDs(Digital Signal Processing Devices), PLDs(Programmable Logic Devices), FPGAs(Field Programmable Gate Arrays), controllers, micro-controllers, and microprocessors.

The controller <NUM> controls the first relay <NUM>'s and the second relay <NUM>'s connections. In this example, the controller <NUM> controls the first relay <NUM>'s and the second relay <NUM>'s connections such that the second working coil <NUM> only operates, the first working coil <NUM> and the second working coil <NUM> connect and operate in parallel, or the first working coil <NUM> and the second working coil <NUM> connect and operate in series. Detailed Description in relation to this is provided with reference to <FIG>.

<FIG> is a circuit diagram showing a first relay's and a second relay's connections for operating the second working only in the induction heating apparatus of one embodiment.

Referring to <FIG>, the controller <NUM> controls the first relay <NUM> such that the first relay <NUM> does not connect between the other end of the first working coil <NUM>, and the resonance capacitor <NUM>. Then the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM>, and the current conversion circuit <NUM>. Accordingly, the current conversion circuit <NUM> and the resonance capacitor <NUM> may connect to each other only through the second working coil <NUM>.

That is, the controller <NUM> turns off the first relay <NUM> and controls the second relay <NUM> such that the second relay <NUM> connects to contact point B, thereby making it possible to operate the second working coil <NUM> only.

The above-described control of operating the second working coil <NUM> only is similar to below-described control of connecting and operating the first working coil <NUM> and the second working coil <NUM> in parallel, but likely generates heat. Thus, the control of operating the second working coil <NUM> only may not be used.

<FIG> is a circuit diagram showing the first relay's and the second relay's connections for connecting and operating the first working coil and the second working coil in parallel in the induction heating apparatus of one embodiment.

Referring to <FIG>, the controller <NUM> controls the first relay <NUM> such that the first relay <NUM> connects between the other end of the first working coil <NUM>, and the resonance capacitor <NUM>. Then the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM>, and the current conversion circuit <NUM>. Accordingly, the current conversion circuit <NUM> and the resonance capacitor <NUM> may connect to each other through the first working coil <NUM> and the second working coil <NUM>. In this example, the first working coil <NUM> and the second working coil <NUM> connect in parallel between the current conversion circuit <NUM> and the resonance capacitor <NUM>.

That is, the controller <NUM> turns on the first relay <NUM> and controls the second relay <NUM> such that the second relay <NUM> connects to contact point B, thereby making it possible to connect and operate the first working coil <NUM> and the second working coil <NUM> in parallel.

As the first working coil <NUM> and the second working coil <NUM> connect and operate in parallel, the resistance and inductance of all the working coils decrease. Accordingly, the output of the induction heating apparatus <NUM> increases. That is, the control of a parallel connection between the first working coil <NUM> and the second working coil <NUM> can be useful when a high output is required.

<FIG> is a circuit diagram showing the first relay's and the second relay's connections for connecting and operating the first working coil and the second working coil in series in the induction heating apparatus of one embodiment.

Referring to <FIG>, the controller <NUM> controls the first relay <NUM> such that the first relay <NUM> does not connect between the other end of the first working coil <NUM>, and the resonance capacitor <NUM>. Then the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the other end of the first working coil <NUM>. Accordingly, the current conversion circuit <NUM> and the resonance capacitor <NUM> may connect to each other through the first working coil <NUM> and the second working coil <NUM>. In this example, the first working coil <NUM> and the second working coil <NUM> connect in series between the current conversion circuit <NUM> and the resonance capacitor <NUM>.

That is, the controller <NUM> turns off the first relay <NUM> and controls the second relay <NUM> such that the second relay <NUM> connects to contact point A, thereby making it possible to connect and operate the first working coil <NUM> and the second working coil <NUM> in series.

As the first working coil <NUM> and the second working coil <NUM> connect and operate in series, the resistance and inductance of all the working coils increase. Accordingly, the output of the induction heating apparatus <NUM> decreases. However, since a range of driving frequencies supplied through the current conversion circuit <NUM> may increase, the output may be controlled more precisely. Thus, the control of a series connection between the first working coil <NUM> and the second working coil <NUM> can be useful when a low output is required.

Referring back to <FIG>, the controller <NUM> may control the first relay <NUM>'s and the second relay <NUM>'s connections, based on at least one of the type of an object to be heated placed on the induction heating apparatus <NUM> and a target output value.

In one embodiment, the controller <NUM> may receive an input corresponding to the type of the object to be heated from the user through the interface (or interface unit) disposed at the induction heating apparatus <NUM>, and determine the type of the object to be heated based on the received input. In another embodiment, the controller <NUM> may supply current of a specific frequency to the first working coil <NUM> and the second working coil <NUM> through the current conversion circuit <NUM>, and analyze the output of the first working coil1 <NUM> and the second working coil <NUM>, to determine the type of the object to be heated.

Additionally, the controller <NUM> may receive an input corresponding to a target output value from the user through the interface disposed at the induction heating apparatus <NUM>, and determine the target output value based on the received input.

The controller <NUM> may control the first relay <NUM> such that the first relay <NUM> connects between the other end of the first working coil <NUM> and the resonance capacitor <NUM>, and control the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the current conversion circuit <NUM>, when the object to be heated provided on the induction heating apparatus <NUM> is made of a ferromagnetic material and when the target output value is a predetermined reference output value or greater. That is, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in parallel, when the object to be heated provided on the induction heating apparatus <NUM> is made of a ferromagnetic material and when the target output value is the reference output value or greater.

Additionally, the controller <NUM> may control the first relay <NUM> such that the first relay <NUM> does not connect between the other end of the first working coil <NUM> and the resonance capacitor <NUM>, and control the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the other end of the first working coil <NUM> when the object to be heated provided on the induction heating apparatus <NUM> is made of a ferromagnetic material and when the target output value is less than the reference output value. That is, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in series when the object to be heated provided on the induction heating apparatus <NUM> is made of a ferromagnetic material and when the target output value is less than the reference output value.

Further, the controller <NUM> may control the first relay <NUM> such that the first relay <NUM> does not connect between the other end of the first working coil <NUM> and the resonance capacitor <NUM>, and control the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the other end of the first working coil <NUM> when the object to be heated provided on the induction heating apparatus <NUM> is made of a non-ferromagnetic material. That is, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in series when the object to be heated provided on the induction heating apparatus <NUM> is made of an anti-ferromagnetic material.

The reason for the above-described control is given with reference to <FIG> and <FIG>.

<FIG> is a graph showing outputs of the induction heating apparatus based on frequencies of currents supplied through a current conversion circuit when an object to be heated provided on the induction heating apparatus of one embodiment is made of a ferromagnetic material.

<FIG> shows a graph of outputs of the induction heating apparatus <NUM>, based on frequencies of currents supplied through the current conversion circuit <NUM> when a ferromagnetic object to be heated is provided on the induction heating apparatus <NUM>. In the graph, the solid line shows outputs of the induction heating apparatus <NUM> when the first working coil <NUM> and the second working coil <NUM> connect and operate in parallel, and the dashed line shows outputs of the induction heating apparatus <NUM> when the first working coil <NUM> and the second working <NUM> connect and operate in series.

Referring to the graph, when the first working coil <NUM> and the second working coil <NUM> connect and operate in series, a maximum output of the induction heating apparatus <NUM> is about <NUM> W, and when the first working coil <NUM> and the second working coil <NUM> connect and operate in parallel, a maximum output of the induction heating apparatus <NUM> is about <NUM> W. Thus, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in parallel, when the target output value is <NUM> W or greater in the case of a ferromagnetic object to be heated. In the embodiment of <FIG>, the reference output value may be <NUM> W.

Additionally, the controller <NUM> may output the target output value regardless of the state in which the first working coil <NUM> and the second working coil <NUM> connect in parallel or in series, when the target output value is less than <NUM> W in the case of a ferromagnetic object to be heated. When the first working coil <NUM> and the second working coil <NUM> connect and operate in series, the output may be adjusted within a wider range of frequencies, thereby making it possible to control the output more precisely. Further, the series connection between the first working coil <NUM> and the second working coil <NUM> may result in the same output as the parallel connection between the first working coil <NUM> and the second working coil <NUM>, at currents of lower frequencies, thereby ensuring improvement in the efficiency of the current conversion circuit <NUM>.

Thus, when the target output value is less than <NUM> W in the case of a ferromagnetic object to be heated, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in series.

<FIG> is a graph showing outputs of the induction heating apparatus based on frequencies of currents supplied through a current conversion circuit when an anti-ferromagnetic object to be heated is provided on the induction heating apparatus of one embodiment.

<FIG> shows a graph of outputs of the induction heating apparatus <NUM>, based on frequencies of currents supplied through the current conversion circuit <NUM> when an anti-ferromagnetic object to be heated is provided on the induction heating apparatus <NUM>. In the graph, the solid line shows outputs of the induction heating apparatus <NUM> when the first working coil <NUM> and the second working coil <NUM> connect and operate in parallel, and the dashed line shows outputs of the induction heating apparatus <NUM> when the first working coil <NUM> and the second working <NUM> connect and operate in series.

Referring to the graph, a maximum output in the series connection between the first working coil <NUM> and the second working coil <NUM> may be greater than in the parallel connection between the first working coil <NUM> and the second working coil <NUM>. Further, the series connection may result in the same output as the parallel connection, at currents of lower frequencies, thereby ensuring improvement in the efficiency of the current conversion circuit <NUM>.

Thus, in the case of an anti-ferromagnetic object to be heated, the controller <NUM> may connect and operate the first working coil <NUM> and the second working coil <NUM> in series.

Since the connection between the first working coil <NUM> and the second working coil <NUM> is adjusted depending on the type of an object to be heated, as described above, the induction heating apparatus <NUM> may adjust outputs differently and help to improve the efficiency of the current conversion circuit <NUM>.

<FIG> is a flow chart showing a method for controlling the induction heating apparatus of one embodiment.

Referring to <FIG>, the controller <NUM> determines the type of an object to be heated provided on the induction heating apparatus <NUM> (S1110). In one embodiment, the controller <NUM> may receive an input corresponding to the type of the object to be heated through the interface disposed at the induction heating apparatus <NUM> from the user, and based on the received input, determine the type of the object to be heated. In another embodiment, the controller <NUM> may supply current of a specific frequency to the first working coil <NUM> and the second working coil <NUM> through the current conversion circuit <NUM>, and analyze the output of the first working coil <NUM> and the second working coil <NUM>, to determine the type of the object to be heated.

Then the controller <NUM> may determine a target output value (S1120). In this case, the controller <NUM> may receive an input corresponding to the target output value through the interface disposed at the induction heating apparatus <NUM> from the user, and based on the received input, determine the target output value.

Then the controller <NUM> determines whether the object to be heated provided on the induction heating apparatus <NUM> is a ferromagnetic object to be heated (S1130).

When the object to be heated provided on the induction heating apparatus <NUM> is a ferromagnetic object to be heated, the controller <NUM> determines whether the target output value is the reference output value or greater (S1140).

When the target output value is the reference output value or greater, the controller <NUM> turns on the first relay <NUM> (S1150). That is, the first controller <NUM> controls the first relay <NUM> such that the first relay <NUM> connects between the first working coil <NUM> and the resonance capacitor <NUM>.

Additionally, when the target output value is the reference output value or greater, the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects to contact point B (S1160). That is, the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the current conversion circuit <NUM>.

That is, when the object to be heated provided on the induction heating apparatus <NUM> is a ferromagnetic object to be heated and when the target output value is the reference output value or greater, the controller <NUM> connects and operates the first working coil <NUM> and the second working coil <NUM> in parallel.

When determining that the object to be heated provided on the induction heating apparatus <NUM> is not a ferromagnetic object to be heated in step <NUM> (S1130) or when determining that the target output value is not the reference output value or greater in step <NUM> (S1140), the controller <NUM> turns off the first relay <NUM> (S1170). That is, the controller <NUM> controls the first relay <NUM> such that the first relay <NUM> does not connect between the first working coil <NUM> and the resonance capacitor <NUM>.

When determining that the object to be heated provided on the induction heating apparatus <NUM> is not a ferromagnetic object to be heated in step <NUM> (S1130) or when determining that the target output value is not the reference output value or greater in step <NUM> (S1140), the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects to contact point A (S1180). That is, the controller <NUM> controls the second relay <NUM> such that the second relay <NUM> connects between one end of the second working coil <NUM> and the other end of the first working coil <NUM>.

That is, when the object to be heated provided on the induction heating apparatus <NUM> is an anti-ferromagnetic object, the controller <NUM> connects and operates the first working coil <NUM> and the second working coil <NUM> in series.

In the induction heating apparatus <NUM> and the method for controlling the same <NUM> according to the disclosure, since the first working coil <NUM> and the second working coil <NUM> are accommodated in a single working coil base <NUM>, as described above, all the working coils <NUM>, <NUM> can be used regardless of the size of an object to be heated. Further, the first relay <NUM>'s and the second relay <NUM>'s connections can change based on at least one of the type of an object to be heated and a target output value, to change a connection relationship between the first working coil <NUM> and the second working coil <NUM>, thereby making it possible to adjust the outputs of the first working coil and the second working coil differently and ensure improvement in the current conversion circuit's efficiency.

Claim 1:
An induction heating apparatus (<NUM>), comprising:
a current conversion circuit (<NUM>) configured to convert current supplied from an external power source (<NUM>);
a first working coil (<NUM>), one end thereof is connected to the current conversion circuit (<NUM>);
a second working coil (<NUM>), one end thereof is connectable to the current conversion circuit (<NUM>) or the other end of the first working coil (<NUM>);
a resonance capacitor (<NUM>) being connected to the other end of the second working coil (<NUM>);
a first relay (<NUM>) for connecting the other end of the first working coil (<NUM>) and the resonance capacitor (<NUM>);
a second relay (<NUM>) for selectively connecting one end of the second working coil (<NUM>) to any one of the other end of the first working coil (<NUM>) and the current conversion circuit (<NUM>);
characterized by
a controller (<NUM>) configured to control the first relay's (<NUM>) and/or the second relay's (<NUM>) connections based on the type of an object to be heated provided on the induction heating apparatus (<NUM>) and a target output value.