Abstract:
An induction cooking apparatus that includes a plate that is configured to accommodate a cooking vessel; a first coil that is located under the plate; a second coil that is located under the plate and adjacent to the first coil; and a temperature detector that is located on the plate and that includes: a resistor element having a resistance value that is changed based on a temperature of the cooking vessel that is inductively heated by the second coil is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority benefit of Korean Patent Application No. 10-2016-0011705, filed on 29 Jan. 2016 in the Korean Intellectual Property Office, the entire contents of which is hereby incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    The present application generally relates to technologies about an induction cooking apparatus. 
       BACKGROUND 
       [0003]    As cooking apparatuses, various products such as a microwave oven using microwaves, an oven using a heater and a cooktop are widely used. 
         [0004]    A microwave oven radiates microwaves generated by a magnetron in an enclosed cooking chamber and vibrates water molecules of food put into the cooking chamber to heat food, and the oven heats an enclosed cooking chamber using the heater to heat food put into the cooking chamber. 
         [0005]    The cooktop heats a vessel laid thereon to heat food contained in the vessel and a representative example thereof includes a gas cooktop using gas as a heating source. In the gas cooktop, since heat loss is high due to flame, thermal efficiency deteriorates. Therefore, recently, a cooktop using electricity is attracting attention. 
       SUMMARY 
       [0006]    The present disclosure is related to an induction cooking apparatus. 
         [0007]    In general, one innovative aspect of the subject matter described in this specification can be embodied in an induction cooking apparatus including a plate that is configured to accommodate a cooking vessel; a first coil that is located under the plate; a second coil that is located under the plate and adjacent to the first coil; and a temperature detector that is located on the plate and that includes: a resistor element having a resistance value that is changed based on a temperature of the cooking vessel that is inductively heated by the second coil. 
         [0008]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The induction cooking apparatus further includes a metal member that is located on the plate and that is electrically coupled to the resistor element. The resistor element is located at a position of the plate corresponding to the first coil. The resistor element includes a negative temperature coefficient (NTC) thermistor. The induction cooking apparatus further includes a controller that is configured to control current flow in the first coil or the second coil. The induction cooking apparatus further includes a display, wherein the controller is configured to receive temperature information detected by the temperature detector and provide the temperature information to the display. The controller is configured to receive temperature information detected by the temperature detector and control the second coil based on the temperature information. The temperature detector includes: a filter that is coupled to the resistor element and that is configured to filter current flow in the resistor element, and a converter that is configured to convert a current value of the current flow filtered by the filter into a digital signal, and wherein the temperature information includes the digital signal. The controller is configured to: apply a pulse signal to the first coil, and in response to the pulse signal, detect the temperature of the cooking vessel based on current flow in the resistor element. The controller is configured to: operate the second coil continuously, and apply a pulse signal to the first coil repeatedly after the second coil begins to heat the cooking vessel. The controller is configured to: based on an operation time of the second coil or the temperature of the cooking vessel, change (i) a pulse width of the pulse signal that is applied to the first coil or (ii) a time to apply the pulse signal to the first coil. 
         [0009]    In general, another innovative aspect of the subject matter described in this specification can be embodied in an induction cooking apparatus including a plate that is configured to accommodate a cooking vessel; a first coil that is located under the plate; a second coil that is located under the plate and adjacent to the first coil; a metal member that is located in the plate; and a temperature detector that is located in the metal member and that includes: a resistor element having a resistance value that is changed based on a temperature of the cooking vessel that is inductively heated by the second coil. 
         [0010]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The resistor element includes a NTC thermistor. The induction cooking apparatus further includes: a controller that is configured to control current flow in the first coil or the second coil. The induction cooking apparatus further includes a display, wherein the controller is configured to receive temperature information detected by the temperature detector and provide the temperature information to the display. The controller is configured to receive temperature information detected by the temperature detector and control the second coil based on the temperature information. The temperature detector includes: a filter that is coupled to the resistor element and that is configured to filter current flow in the resistor element, and a converter that is configured to convert a current value of the current flow filtered by the filter into a digital signal, and wherein the temperature information includes the digital signal. The controller is configured to: apply a pulse signal to the first coil, and in response to the pulse signal, detect the temperature of the cooking vessel based on current flow in the resistor element. The controller is configured to: operate the second coil continuously, and apply a pulse signal to the first coil repeatedly after the second coil begins to heat the cooking vessel. The controller is configured to: based on an operation time of the second coil or the temperature of the cooking vessel, change (i) a pulse width of the pulse signal that is applied to the first coil or (ii) a time to apply the pulse signal to the first coil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating an example induction cooking apparatus. 
           [0012]      FIG. 2  is a diagram illustrating the example induction cooking apparatus of  FIG. 1 . 
           [0013]      FIG. 3  is a diagram illustrating an example power supply to the example induction cooking apparatus of  FIG. 1 . 
           [0014]      FIG. 4  is a diagram illustrating an example circuit of the example induction cooking apparatus of  FIG. 3 . 
           [0015]      FIG. 5  is a diagram illustrating an example induction cooking apparatus. 
           [0016]      FIGS. 6A to 8B  are diagrams illustrating example operations of the example induction cooking apparatus of FIG.  5 . 
           [0017]      FIG. 9  is a diagram illustrating an example induction cooking apparatus. 
       
    
    
       [0018]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0019]      FIG. 1  illustrates an example induction cooking apparatus. 
         [0020]    Referring to  FIG. 1 , the induction cooking apparatus  100  includes a heating plate  110 , a first heater  130 , a second heater  132 , a third heater  134 , an input unit  125  and a display  180 . 
         [0021]    The heating plate  110  is a casing of the induction cooking apparatus  100  and is disposed on the heaters. The heating plate  110  may be made of various materials such as ceramic or tempered glass. 
         [0022]    A cooking vessel is disposed on the heating plate  110  and the cooking vessel  195  is placed on at least one of the heaters  130 ,  132  and  134  and is heated by the principle of induction heating. 
         [0023]    The first heater  130  includes a plurality of induction heating coils and a resonance capacitor. 
         [0024]    In the figure, the first heater  130  includes a first coil L r1  and a second coil L r2 . 
         [0025]    The first coil L r1  may be an induction heating coil used to detect the temperature of the cooking vessel and the second induction heating coil L r2  may be used to heat the cooking vessel. 
         [0026]    In the figure, the second induction heating coil L r2  is disposed at the outer circumference of the first induction heating coil L r1 . 
         [0027]    When AC current, more particularly, high-frequency AC current, flows in the second induction heating coil L r2  in a state in which the cooking vessel  195  is placed on the first heater  130 , more particularly, the second induction heating coil L r2 , a magnetic field is generated in the second induction heating coil L r2  by resonance by the resonance capacitor and the second induction heating coil L r2  and eddy current is induced in the cooking vessel  195  due to electromagnetic induction effect of the magnetic field. By the eddy current, Joule heat is generated in a resistance component of the cooking vessel  195 , thereby heating the cooking vessel. 
         [0028]    The second heater  132  includes a third induction heating coil L r3  and a resonance capacitor. When high-frequency AC current flows in the third induction heating coil L r3  in a state in which the cooking vessel  195  is placed on the second heater  132 , more particularly, the third induction heating coil L r3 , the cooking vessel  195  is heated by eddy current as described above. 
         [0029]    The third heater  134  includes a fourth induction heating coil L r4  and a resonance capacitor. When high-frequency AC current flows in the fourth induction heating coil L r4  in a state in which the cooking vessel  195  is placed on the third heater  134 , more particularly, the fourth induction heating coil L r   4 , the cooking vessel  195  is heated by eddy current as described above. 
         [0030]    The input unit  125  receives user input so as to operate the induction cooking apparatus  100 . For example, whether at least one of the first heater  130 , the second heater  132  and the third heater  134  is heated or to which of the first induction heating coil L r1  and the second induction heating coil L r2  of the first heater  130  current is supplied is determined or the operation time or temperature of each heater is selected by user input. 
         [0031]    The input unit  125  is disposed in each of the heaters  130 ,  132  and  134  as shown in the figure. 
         [0032]    The display  180  displays the operation state of the induction cooking apparatus  100 . Whether each of the heaters  130 ,  132  and  134  operates or the temperature of the cooking vessel  195  which is being heated is displayed. 
         [0033]    In addition to the induction heat cooking apparatus  100 , since a radiant heat cooking apparatus uses a heater under a heating plate  110  similarly to the induction cooking apparatus  100 , flame is not generated and thus stability is high. However, since the temperature of the heater increases by radiant heat, on/off control is necessary to protect the heater. 
         [0034]    However, since the induction cooking apparatus  100  uses the principle of high-frequency induction heating, the heater, more particularly, the induction heating coil, is not directly heated. Since high-frequency current may be continuously supplied, high energy efficiency can be obtained and a heating time can be reduced. 
         [0035]    Since the induction cooking apparatus  100  efficiently performs induction heating even in a cooking vessel made of a magnetic material including a metal component, an electrothermal heater may be further included in order to heat a cooking vessel made of a non-magnetic material. The electrothermal heater may be placed in at least one of the heaters  130 ,  132  and  134 . The induction cooking apparatus  100  may further include a load detector for detecting the type of the cooking vessel. 
         [0036]      FIG. 2  illustrates an example induction cooking apparatus of  FIG. 1 . 
         [0037]    Referring to  FIG. 2 , the induction cooking apparatus  100  may include a first power supply  210 , a second power supply  220 , an input unit  125 , a display  180  and a temperature detector  400 . 
         [0038]    The first power supply  210  and the second power supply  220  may supply power to the plurality of induction heating coils of the cooking apparatus  100 . 
         [0039]    In  FIG. 3 , the first power supply  210  supplies power to a second induction heating coil L r2 , a third induction heating coil L r3  and a fourth induction heating coil L r4  and the second power supply  220  supplies power to a first induction heating coil L r1 . 
         [0040]    The input unit  125  may include buttons and a touchscreen related to operation of the cooking apparatus  100  and a signal input through the input unit  125  may be transmitted to the controller  170 . 
         [0041]    The display  180  may display information related to the operation state of the cooking apparatus  100 . For example, a cooking time, a residual time, cooking type information and the temperature of a cooking vessel related to cooking may be displayed. 
         [0042]    The temperature detector  400  may detect the temperature of the cooking vessel  195 . For temperature detection, an IR sensor is generally used. In this specification, a method of using a resistor element having a resistance value changed based on temperature is described. The method can increase user convenience and reduce manufacturing costs. Arrangement of a resistor element will be described with reference to  FIG. 5  and the subsequent figures. 
         [0043]    The controller  170  controls overall operation of the cooking apparatus  100 . 
         [0044]    For example, the controller  170  may control operations of the first power supply  210 , the second power supply  220 , the input unit  125 , the display  180  and the temperature detector  400 . 
         [0045]    More specifically, the controller may control the first power supply  210  or the second power supply  220  in order to cook food based on a temperature signal input through the input unit  125 . 
         [0046]    The controller  170  may receive temperature information detected by the temperature detector  400  and perform control to display the temperature information on the display  180 . 
         [0047]    The controller  170  performs control to apply a pulse signal to the first coil L r1  and detects the temperature of the cooking vessel  195  based on current flowing in the resistor element in correspondence with the pulse signal. 
         [0048]    The controller  170  performs control to continuously operate the second coil L r2  and to repeatedly apply the pulse signal to the first coil L r1 , upon heating the cooking vessel  195 . 
         [0049]    The controller  170  may perform control to change the width of the pulse signal of the first coil L r1  or the time for applying the pulse signal based on the operation time of the second coil L r2  or temperature of the cooking vessel  195 . 
         [0050]      FIG. 3  illustrates an example power supply to the example induction cooking apparatus of  FIG. 1 . 
         [0051]    Referring to  FIG. 3 , the induction cooking apparatus  100  may further include a first power supply  210  and a second power supply  220 . 
         [0052]    The first power supply  210  may supply power to a second induction heating coil L r2  of the first heater  130 , a third induction heating coil L r3  of the second heater  132  and a fourth induction heating coil L r4  of the third header  134 . Here, power may be high-frequency AC power. 
         [0053]    The second power supply  220  may supply power to the first induction heating coil L r1  of the first heater  130 . 
         [0054]    Power is supplied from different power supplies to the induction heating coils of the first heater  130 , in which the plurality of induction heating coils is disposed, such that the induction cooking apparatus using the high-frequency AC current can be efficiently and stably driven without power reduction. 
         [0055]      FIG. 4  illustrates an example circuit of the example induction cooking apparatus of  FIG. 3 . 
         [0056]    Referring to the figure, the first power supply  210  may include a first converter  310 , a second converter  312 , a first reactor L 1 , a second reactor L 2 , a first smoothing capacitor C 1 , a second smoothing capacitor C 2 , a first inverter  320 , a second inverter  322 , a power selector  330  and second to fourth switching elements S 2  to S 4 . 
         [0057]    The second power supply  220  may include a third converter  314 , a third reactor L 3 , a third smoothing capacitor C 3 , a third inverter  324  and a first switching element S 1 . 
         [0058]    The first converter  310  and the second converter  312  receive and convert voltages from a commercial AC power source  305  into DC voltages, respectively. For example, the first converter  310  and the second converter  312  may respectively include diodes to output the DC voltages rectified by the diodes. 
         [0059]    The first converter  310  and the second converter  312  may respectively include diodes and switching elements and output DC voltages converted based on the rectification characteristics of the diodes and the switching operations of the switching elements. 
         [0060]    In some implementations, the first converter  310  and the second converter  312  respectively include the diodes without the switching elements. 
         [0061]    The commercial AC power source  305  may be a single-phase AC power source or a three-phase AC power source. In a single-phase AC power source, the first converter  310  and the second converter  312  may include four diodes in the form of a bridge. In a three-phase AC power source, the first converter  310  and the second converter  312  may include six diodes. 
         [0062]    The third converter  314  receives and converts the commercial AC voltage into a DC voltage, as in the first converter  310  and the second converter  312 . In order to prevent power reduction, the third converter  314  may receive a voltage from a separate commercial AC power  307 . 
         [0063]    The first reactor L 1  and the second reactor L 2  are respectively connected to one end of each of the first converter  310  and the second converter  312  to serve to accumulate energy of an AC component to eliminate a harmonic current component or a noise component. 
         [0064]    The third reactor L 3  is connected to one end of the third converter  314  to serve to accumulate energy of an AC component to eliminate a harmonic current component or a noise component. 
         [0065]    The first smoothing capacitor C 1  and the second smoothing capacitor C 2  are respectively connected to output terminals of the first converter  310  and the second converter  312 . In the figure, the reactors L 1  and L 2  are disposed between the capacitors and the converters  310  and  315 . 
         [0066]    The first smoothing capacitor C 1  and the second smoothing capacitor C 2  smooth the rectified voltages output from the first converter  310  and the second converter  312  into DC voltages. In some implementations, the output terminals of the first converter  310  and the second converter  312  are referred to as first and second dc ends, respectively. The smoothed DC voltages of the first and second dc ends are applied to the first converter  310  and the second converter  312 , respectively. 
         [0067]    The third capacitor C 3  is connected to the output terminal of the third converter  314  and smooths the rectified voltage output from the third converter  312  into a DC voltage. The output terminal of the third converter is referred to as a third dc end. 
         [0068]    Each of the first inverter  320 , the second inverter  322  and the third inverter  324  includes a plurality of switching elements and converts the smoothed DC voltage into an AC voltage having a predetermined frequency by on/off operation of the switching elements. 
         [0069]    The first inverter  320  includes an upper arm switching element Sa and a lower arm switching element S′a connected in series. A diode is connected in anti-parallel to each switching element Sb or S′b. In addition, a snubber capacitor is connected to each switching element Sa or S′a in parallel. 
         [0070]    The switching elements Sa and S′a of the first inverter  320  perform on/off operation based on a first switching control signal from a controller. At this time, the switching elements Sa and S′a may complementarily operate. 
         [0071]    The second inverter  322  includes an upper arm switching element Sb and a lower arm switching element S′b connected in series, similarly to the first inverter  320 . A diode is connected in anti-parallel to each switching elements Sb or S′b. In addition, a snubber capacitor is connected to each switching element Sb or S′b in parallel. 
         [0072]    The switching elements Sb and S′b of the first inverter  320  perform on/off operation based on a second switching control signal from the controller. 
         [0073]    The first inverter  320  and the second inverter  322  may separately perform operation. That is, the first and second inverter may generate and output first and second high-frequency AC voltages, respectively. 
         [0074]    The third inverter  324  includes an upper arm switching element Sc and a lower arm switching element S′c connected in series, similarly to the first inverter  320 . In addition, a diode and a snubber capacitor are further connected. 
         [0075]    The fourth resonance capacitor C r4  may be connected to the second induction heating coil L r2 , for resonance. The high-frequency AC voltage may be supplied to the second induction heating coil L r2  to induce heating according to the principle of induction heating. At this time, a switching element S 4  for determining operation of the second induction heating coil L r2  may be connected to the second induction heating coil L r2 . 
         [0076]    A first AC voltage is supplied from the first inverter  320  to the second induction heating coil L r2 . 
         [0077]    The third induction heating coil L r3  and the fourth induction heating coil L r4  are connected in parallel to form a pair. A second resonance capacitor C r2  and a third resonance capacitor C r3  may be connected to the third induction heating coil L r3  and the fourth induction heating coil L r4 , for resonance. High-frequency AC voltages may be supplied to the induction heating coils L r2  and L r3  to induce heating according to the principle of induction heating. At this time, switching elements S 2  and S 3  for determining operation of the induction heating coils L r2  and L r3  may be connected to the third induction heating coil L r3  and the fourth induction heating coil L r4 , respectively. 
         [0078]    A first AC voltage from the first inverter  320  or a second AC voltage from the second inverter is supplied to the third induction heating coil L r3  and the fourth induction heating coil L r4 . To this end, the power selector  330  performs switching operation. 
         [0079]    The voltage selector  330  selects and supplies any one of the first AC voltage from the first inverter  320  and the second AC voltage from the second inverter  322  to the third induction heating coil L r3  and supplies the other to the fourth induction heating coil L r4 , when both the third induction heating coil L r3  and the second induction heating coil L r2  operate. 
         [0080]    For example, the second AC voltage may be supplied to the third induction heating coil L r3  and the first AC voltage may be supplied to the fourth induction heating coil L r4 . 
         [0081]    When three or more of the plurality of induction heating coils connected to the same inverter in parallel are turned on, the AC voltages applied to the induction heating coils may be separated. That is, AC voltages may be supplied from different inverters. Therefore, since the same inverter does not supply the same AC voltage, power reduction does not occur and the AC voltages can be stably supplied. 
         [0082]    To this end, the power selector  330  may include a relay element. In the figure, the relay element R is included. 
         [0083]    The relay element R is disposed between the inverters  320  and  322  and the fourth induction heating coil L r4  to perform relay operation, such that the fourth induction heating coil L r4  is connected to any one of the first inverter  320  and the second inverter  322 . 
         [0084]    Relay operation of the relay element R may be controlled by a control signal of a controller. 
         [0085]    The first resonance capacitor C r1  may be connected to the first induction heating coil L r1 , for resonance. A high-frequency AC voltage may be supplied to the first induction heating coil L r1  to induce heating according to the principle of induction heating. At this time, the switching element S 1  for determining operation of the first induction heating coil L r1  may be connected to first induction heating coil L r1 . 
         [0086]    A third AC voltage from the third inverter  324  is supplied to the first induction heating coil L r1 . 
         [0087]    The controller may control operation of the switching elements Sa and S′a of the first inverter  320 , the switching elements Sb and S′b of the second inverter  322 , the switching elements Sc and S′c of the third inverter  324 , the relay element R of the power selector  330  and the first to fourth switching elements S 1  to S 4  for operation of the induction heating coils. 
         [0088]    In particular, for control of the first inverter  320 , the second inverter  322  and the third inverter  324 , a pulse width modulation (PWM) switching control signal may be output. When the switching elements of the first inverter  320 , the second inverter  322  and the third inverter  324  are insulated gate bipolar transistors (IGBTs), PWM gate drive control signals may be output. 
         [0089]    The controller may receive respective values from a temperature sensor for sensing the temperature of the vicinity of each induction heating coil and an input current detector for detecting input current from the commercial AC voltage, and stop overall operation of the induction cooking apparatus  100  upon abnormal operation. 
         [0090]      FIG. 5  illustrates an example induction cooking apparatus.  FIGS. 6A to 8B  illustrate example operations of the example induction cooking apparatus of  FIG. 5 . 
         [0091]    Referring to  FIG. 5 , the induction cooking apparatus  100  may include a plate  110 , a first coil L r1  disposed under the plate  110 , a second coil L r2  disposed under the plate  110  and around the first coil L r1 , and a temperature detector  400  disposed on the plate  110  and including a resistor element  420  having a resistance value changed based on the temperature of the cooking vessel  195  inductively heated by the second coil L r2  . 
         [0092]    The induction cooking apparatus  100  may further include a metal member  410  disposed on the plate  110 . 
         [0093]    The resistor element  420  or R v  may be electrically connected to the metal member  410 . 
         [0094]    The resistor element  420  or R v  may be disposed at a position corresponding to the first coil L r1 . 
         [0095]    The resistor element  420  or R v  may include an element having a resistance value changed based on temperature. For example, the resistor element  420  or R v  may include a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor. 
         [0096]    In some implementations, the resistor element  420  or R v  includes the NTC thermistor. 
         [0097]    The plate  110  may be an insulation plate and the metal member  410  may be an AL plate. 
         [0098]    The resistor element  420  or R v  may be disposed between two metal members  410  and the cooking vessel  195  may be disposed on the resistor element  420  or R v . 
         [0099]    For temperature detection using the resistor element  420  or R v , conductive lines  432  and  433  may be connected to both ends of the two metal members  410  to be electrically connected to a filter  442  shown in  FIG. 6A . 
         [0100]    Referring to  FIG. 5 , the cooking vessel is actually heated by the second coil L r2  disposed at the outer circumference of the first coil L r1  and the first coil L r1  may intermittently operate in order to sense the temperature of the cooking vessel  195 . 
         [0101]    The size of the first coil L r1  may be similar to that of the cooking vessel. 
         [0102]    At this time, both the first coil L r1  and the second coil L r2  are insulated from the cooking vessel  195  by the plate  110  but operate by induction current. 
         [0103]      FIGS. 6A to 6B  show an equivalent circuit formed by the first coil L r1  when induction current is generated by the first coil L r1 . 
         [0104]    First, referring to  FIG. 6A , when induction current is generated by the first coil L r1 , the first coil L r1  may be expressed by LN 1  and LN 2  and both ends (nodes a and b) of a secondary coil LN 2  may be connected to the resistor element  420  or R v  of the temperature detector  400 . 
         [0105]    The temperature detector  400  may include a resistor element  420  or Rv, a filter  442  and a converter  444 . 
         [0106]    The filter  442  may be electrically connected to the resistor element  420  or Rv to filter current flowing in the resistor element  420  or Rv. 
         [0107]    Current flowing in the resistor element  420  or Rv may correspond to current flowing in the first coil Lr 1 . 
         [0108]    The converter  444  is an analog/digital (A/D) converter to convert the current value filtered by the filter  442  into a digital signal. 
         [0109]    The current value converted into the digital signal is transmitted to the controller  170  and the controller  170  may calculate the temperature of the cooking vessel  195  based on the current value converted into the digital signal. 
         [0110]      FIG. 6B  shows T-shaped inductors LX, LY and LZ which are equivalent to the primary coil LN 1  and the secondary coil LN 2  of  FIG. 6A . 
         [0111]    Hereinafter, current flow when a pulse signal is applied to the first coil Lr 1  based on the circuit of  FIG. 6B  will be described. 
         [0112]    In  FIG. 7A , when a pulse signal Vp is applied to the first coil Lr 1 , current i may flow through the inductors LX and LZ and the resistor element  420  or Rv. 
         [0113]    The temperature detector  400  may detect temperature information based on current i flowing in the resistor element  420  or Rv. 
         [0114]    (a) of  FIG. 7B  shows current waveforms i 1  and i 2  flowing in the resistor element  420  or Rv when the pulse signal Vp is applied to the first coil Lr 1 . 
         [0115]    When the filter  442  filters out a threshold Th or less, a digital signal Sd 1  shown in (b) of  FIG. 7B  may be generated in correspondence with the first current waveform i 1  and a digital signal Sd 2  shown in (c) of  FIG. 7B  may be generated in correspondence with the second current waveform i 2 . 
         [0116]    Since the resistor element  420  or Rv is an NTC thermistor, a resistance value decreases as a temperature increases. Thus, a current level increases. 
         [0117]    Accordingly, in case of the first current waveform i 1 , the temperature is higher as compared to the second current waveform i 2 . 
         [0118]    The controller  170  may receive the digital signal Sd 1  shown in (b) of  FIG. 7B  or the digital signal Sd 2  shown in (c) of  FIG. 7B  and sense the temperature based on the pulse width of the digital signal. 
         [0119]    That is, the controller  170  may sense a temperature which increases as the pulse width of the digital signal from the temperature detector  400  increases. 
         [0120]    The controller  170  may approximately sense the temperature based on the pulse width of the digital signal from the temperature detector  400 . 
         [0121]    The controller  170  may perform control to continuously operate the second coil Lr 2  and to repeatedly apply the pulse signal to the first coil Lr 1 , upon heating the cooking vessel  195 . 
         [0122]    The controller  170  may perform control to change the width of the pulse signal of the first coil Lr 1  or to change the time for applying the pulse signal based on the operation time of the second coil Lr 2  or the temperature of the cooking vessel  195 . This will be described with reference to  FIGS. 8A to 8B . 
         [0123]      FIGS. 8A to 8B  show the state in which a high-level signal is applied such that the second coil Lr 2  continuously operates and a pulse signal is repeatedly applied to the first coil Lr 1  after operation of the second coil Lr 2 , under control of the controller  170 . 
         [0124]    The controller  170  controls to automatically sense a temperature at a predetermined time after a heating time or upon manipulation of the input unit  125 . 
         [0125]    The controller  170  may perform control to increase the pulse width of the pulse signal for sensing the temperature as the heating time increases. 
         [0126]    That is, as shown in  FIG. 8B , when a pulse signal for sensing the temperature is applied later as compared to  FIG. 8A , the controller may perform control to further increase the pulse width of the pulse signal for sensing the temperature in consideration of increase in pulse width. Accordingly, the temperature can be accurately sensed. 
         [0127]    The controller  170  may perform control to sequentially increase the pulse width upon repeatedly applying the pulse for sensing the temperature to the first coil Lr 1 . 
         [0128]    The controller  170  may change the pulse width of the pulse signal applied to the first coil Lr 1  in consideration of the sensed temperature, after sensing the temperature. 
         [0129]    For example, when the sensed temperature increases, the controller may perform control to increase the pulse width. 
         [0130]      FIG. 9  illustrates an example induction cooking apparatus. 
         [0131]    Referring to the figure, the cooking apparatus  100  of  FIG. 9  may include a plate  110 , a first coil Lr 1  disposed under the plate  110 , a second coil Lr 2  disposed under the plate  110  and around the first coil Lr 1 , a metal member  410  disposed in the plate  110 , and a temperature detector  400  disposed in the metal member  410  and including a resistor element  420  or Rv having a resistance value changed based on the temperature of the cooking vessel  195  inductively heated by the second coil Lr 2 . 
         [0132]    The cooking apparatus of  FIG. 9  is similar to that of  FIG. 5  but is different therefrom in that the metal member  410  is not disposed on the plate  110  but is disposed in the plate  110  and the resistor element  420  or Rv is disposed in the metal member  410 . 
         [0133]    The height h 4  of the resistor element  420  or Rv is greater than a distance h 3  between the surface of the metal member  410  and the resistor element  420  or Rv. 
         [0134]    The conductive lines  432  and  433  may be electrically connected to both ends of the metal member  410 . 
         [0135]    Through the resistor element  420  or Rv of the structure of  FIG. 9 , temperature sensing described with reference to  FIGS. 6A to 8B  may be performed. 
         [0136]    An induction cooking apparatus includes a plate, a first coil disposed under the plate, a second coil disposed under the plate and around the first coil, and a temperature detector disposed on the plate and including a resistor element having a resistance value changed based on a temperature of a cooking vessel inductively heated by the second coil. Therefore, the induction cooking apparatus can accurately detect the temperature of the cooking vessel. 
         [0137]    By displaying the temperature information detected by the temperature detector on the display, a user can conveniently check the temperature. 
         [0138]    By receiving temperature information detected by the temperature detector and performing control to operate the second coil based on the temperature information, it is possible to cook food based on the temperature of the cooking vessel. 
         [0139]    In some implementations, an induction cooking apparatus includes a plate, a first coil disposed under the plate, a second coil disposed under the plate and around the first coil, a metal member disposed in the plate, and a temperature detector disposed in the metal member and including a resistor element having a resistance value changed based on a temperature of a cooking vessel inductively heated by the second coil. Therefore, it is possible to conveniently detect the temperature of the cooking vessel in the induction cooking apparatus. 
         [0140]    In the induction cooking apparatus, since the heater disposed under the plate is used, flame is not generated and thus stability is high. 
         [0141]    In addition, since the heater, more particularly, the induction heating coil, is not directly heated, it is possible to continuously supply high-frequency current. Therefore, high energy efficiency can be obtained and a heating time can be reduced. 
         [0142]    The motor driving apparatus and the home appliance should not be limited to configurations and methods described above, and all or some of the examples may be selectively combined with one another to achieve various alterations. 
         [0143]    The method of driving the motor or the method of operating the home appliance may be implemented as computer programming code that can be written to a processor-readable recording medium and can thus be read by a processor. The processor-readable recording medium may be any type of recording device in which data can be stored in a processor-readable manner.