JP4345151B2 - Induction heating cooker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating cooker that performs cooking using induction heating by a high-frequency magnetic field.
[0002]
[Prior art]
Hereinafter, a conventional induction cooking device will be described with reference to the drawings. FIG. 13 is a block diagram showing a configuration of an example of an induction heating cooker conventionally used.
[0003]
The power source 1 is a DC power source obtained by rectifying a commercial power source, and has a pulsating current twice as smooth as a commercial frequency or a smoothed voltage. The power source 1 is connected to the smoothing capacitor 2 and the choke coil 3 and supplies high-frequency power to the heating coil 6 in accordance with the switching operation of the switching element 4. The high frequency power supplied to the heating coil 6 is supplied to the pan 8 as a high frequency magnetic field, and the pan itself generates heat due to the eddy current generated by the high frequency magnetic field. Here, the pan 8 is usually made of a material having a large specific resistance, such as magnetic stainless steel or iron, and an aluminum pan or the like is usually excluded as being unheatable. Here, the current of the heating coil 6 is a resonance current determined by the heating coil 6 and the resonance capacitor 7 that are magnetically coupled to the pan 8 when the switching element 4 is in the ON state, and the control means 15 causes the resonance current to become zero current again. Until the current flows through the diode 5. The control means 15 turns off the switching element 4 for an off time determined according to the set input power, and then turns on the switching element 4 again.
[0004]
FIG. 12 shows waveforms during operation of the switching element 4. When the gate VGE of the switching element 4 enters an on operation, the resonance current Ic becomes zero again, and remains on until the current flows through the diode 5. Further, when the switching element 4 is turned off, the resonance voltage Vce is generated at both ends of the switching element 4. However, the switching element 4 enters the on state again after a predetermined off time has elapsed.
[0005]
[Problems to be solved by the invention]
In such a conventional induction heating cooker, it is difficult to heat an aluminum pan or a multi-layer pan in which the aluminum material has many components within the thickness of the bottom of the pan because the specific resistance of the pan itself is low.
[0006]
The first effective method for induction heating of the aluminum pan is to increase the ampere turn of the heating coil, that is, to increase the number of turns of the heating coil. As the second method, the heating frequency is increased. Further, the frequency is increased. However, when the number of turns of the heating coil is increased, the cooker becomes larger, and when the frequency is further increased, the loss of the switching element increases, and the secondary problem such as the cooling of the switching element becomes difficult. Will occur.
[0007]
This invention solves said subject and it aims at providing the induction heating cooking appliance which can heat an aluminum pan and a multilayer pan.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a smoothing capacitor connected in parallel to a power supply, a choke coil connected to a positive electrode of the power supply, a switching connected to a reverse end of the choke coil and a negative electrode of the power supply. An element, a diode that is connected in parallel to the switching element and circulates current when the current flows in a direction opposite to the switching element, a heating coil that is arranged in parallel to the switching element and connected in series to each other, and a resonance capacitor A high-frequency inverter and a control means for controlling the switching element, when heating a multi-layer pan in which an aluminum pan or aluminum material shows many components of the thickness of the pan bottom , compared to the driving frequency of the switching element, Resonance current generated in the heating coil and the resonant capacitor when the switching element is on Wavenumbers high rather possible more than twice the induction heating cooker inductance and resonant current capacity determined two or more waveforms of the resonant capacitor of the heating coil coupled with the pot flows at a switching operation once.
[0009]
Thereby, it becomes possible to supply high frequency power to the pan without increasing the switching loss of the switching element, and an induction heating cooker capable of heating an aluminum pan or a multi-layer pan can be realized.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention according to claim 1 includes a smoothing capacitor connected in parallel to a power source, a choke coil connected to the positive electrode of the power source, a switching element connected to the reverse end of the choke coil and the negative electrode of the power source. A high-frequency inverter comprising a diode connected in parallel to the switching element and circulating a current when the current flows in a direction opposite to the switching element; a heating coil arranged in parallel to the switching element and connected in series to each other; And a control means for controlling the switching element, and when heating a multi-layer pan in which an aluminum pan or an aluminum material shows a large amount of components in the thickness of the bottom of the pan, the switching frequency is compared with the driving frequency of the switching element. The frequency of the resonance current generated by the heating coil and the resonance capacitor when the element is on is More than doubled high rather as possible, an induction heating cooker inductance and resonant current capacity determined two or more waveforms of the resonant capacitor of the heating coil coupled with the pot flows at a switching operation once.
[0011]
Thereby, it becomes possible to supply high frequency power to the pan without increasing the switching loss of the switching element, and an induction heating cooker capable of heating an aluminum pan or a multi-layer pan can be realized.
[0012]
In the present invention according to claim 2, when heating an aluminum pan or a multi-layer pan in which the aluminum material has many components in the thickness of the bottom of the pan, the resonance determined by the inductance of the heating coil coupled to the pan and the capacity of the resonant capacitor. It is an induction heating cooking appliance of Claim 1 which makes an electric current frequency 100 kHz or more.
[0013]
Thereby, even when the weight of an aluminum pan or the like is light, the pan does not easily float, and a highly safe induction heating cooker can be realized.
[0014]
The present invention according to claim 3 detects the zero current at the moment when the resonance current changes from positive to negative when heating an aluminum pan or a multilayer pan in which the aluminum material has many components in the thickness of the bottom of the pan. The induction heating cooker according to claim 1 or 2, further comprising a zero current detecting means and a counter for counting the number of times the zero current passes, wherein the switching element is turned off at a predetermined number of times of zero current.
[0015]
As a result, the switching operation can be performed with the number of necessary resonance currents and zero current, and a highly reliable induction heating cooker with little switching loss can be realized.
[0016]
The present invention according to claim 4 controls the input power in the off time of the switching element when heating the aluminum pan or the multi-layer pan in which the aluminum material has many components in the thickness of the bottom of the pan. 2. The induction heating cooker according to 2.
[0017]
As a result, the power can be adjusted while maintaining the number of resonance currents, and an induction heating cooker excellent in controllability can be realized.
[0018]
The present invention according to claim 5 changes the number of times the zero current of the resonance current is passed when heating the aluminum pan or the multi-layer pan in which the aluminum material has many components within the thickness of the bottom of the pan, thereby changing the input power. It is an induction heating cooking appliance of Claim 3 which controls.
[0019]
Thereby, the range of power adjustment becomes wide and the induction heating cooking appliance excellent in controllability can be implement | achieved.
[0020]
The present invention according to claim 6 is the induction according to claim 5, wherein the driving frequency of the switching element is made constant when heating the aluminum pan or the multi-layer pan in which the aluminum material has many components in the thickness of the bottom of the pan. It is a heating cooker.
[0021]
This makes it possible to adjust the power at a certain frequency, to suppress the generation of interference sound due to the difference in drive frequency between adjacent induction heating cookers, and to realize an induction heating cooker with less noise It is possible to adjust the power at a certain frequency, to suppress the generation of interference sound due to the difference in driving frequency of adjacent induction heating cookers, and to realize an induction heating cooker with less noise is there.
[0022]
The present invention according to claim 7 has a pan discriminating means for detecting the kind of pan, a plurality of resonant capacitors, and a switching means for switching the resonant capacitor, wherein the pan discriminated by the pan discriminating means is made of magnetic stainless steel or The resonance capacitor is switched to change the frequency of the resonance current so that the value of the resonance capacitor is increased in the case of iron, and the resonance capacitor is decreased in the case where the pan determined by the pan determination means is aluminum. It is an induction heating cooking appliance as described in any one of 6.
[0023]
Thereby, it becomes possible to heat various pots effectively with one kind of heating coil, and a small induction heating cooker can be provided compared with the conventional induction heating cooker combined with aluminum pot heating.
[0024]
【Example】
Example 1
A first embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 1.
[0025]
FIG. 1 is a diagram illustrating a circuit configuration of an induction heating cooker according to the present embodiment. This embodiment differs from the conventional example in that the control method of the control means 9 that controls the switching element 4 is different. The power source 1 is a rectified commercial power source, and may be used non-smooth or in a form smoothed by an electrolytic capacitor or the like. The smoothing capacitor 2 is connected in parallel with the power source 1 and functions as a supply source for supplying a high-frequency current. The choke coil 3 is connected to the positive electrode of the power supply 1 and is used to perform zero current switching when the switching element 4 is turned off. A diode 5 is connected to the switching element 4 in parallel, and is used to circulate the current when the current flows in the opposite direction to the switching element 4. The switching element 4 generates a resonance current that resonates at the resonance frequency of the heating coil 6 and the resonance capacitor 7 when in the ON state, and supplies a high-frequency magnetic field to the pan 8. The control means 9 causes the switching element 4 to perform control according to the input power using a microcomputer or the like. Here, the driving of the switching element 4 is normally performed at 20 to 30 kHz in consideration of switching loss and the like. On the other hand, the resonance frequency determined by the inductance of the heating coil 6 coupled to the pan 8 and the capacity of the resonance capacitor is more than twice the operation frequency of the switching element 4, that is, the resonance current having two or more waveforms is a single switching operation. It is a constant that flows. This is intended to generate heat using the feature that the skin resistance of the pan is proportional to the square root of the frequency when heating an aluminum pan, etc., and does not increase the skin resistance and increase the switching loss. Is. Also, by using this method, it is possible to increase the magnetic flux entering the pot by increasing the ampere turn that is normally performed, that is, the diameter of the heating coil, and to suppress the increase of the heating coil diameter that is a problem in the method of heating. become.
[0026]
The operation in the above configuration will be described. FIG. 2 is a diagram showing waveforms at various parts in the present embodiment. Waveform (a) shows current waveform Ic flowing through switching element 4 and diode 5, waveform (b) shows voltage Vce generated between the collector and emitter of switching element 4, and waveform (c) shows current flowing through heating coil 6. IL shows a waveform (d) shows a drive waveform VGE given from the control means 9 to the switching element 4. When a gate signal is given to the switching element 4 by the control means 9, the switching element 4 is turned on. At this time, the resonance current generated by the heating coil 6 and the resonance capacitor 7 flows through the switching element 4. Here, since the frequency of the resonance current is at least twice as high as the drive frequency, the resonance current eventually becomes zero, and this time the current flows through the diode 5 in the opposite direction. During this time, since a resonance current continues to flow through the heating coil 6, a high frequency magnetic field determined by the resonance frequency is supplied to the pan 8. That is, the same effect as that in the state of driving at a frequency that is twice or more the normal frequency can be obtained. Thereafter, after supplying the necessary power, the switching element 4 is turned off at the timing when the current flows through the diode 5, and after a certain period, the switching element is turned on again, and this is repeated.
[0027]
As described above, according to the present embodiment, high frequency power can be supplied to the pan 8 without increasing the switching loss of the switching element 4, and the induction heating cooker capable of heating an aluminum pan or a multi-layer pan. Can be realized.
[0028]
(Example 2)
A second embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 2.
[0029]
FIG. 3 is a waveform diagram showing the operation of this embodiment. Since the overall configuration of the present embodiment is the same as that of the first embodiment, a description thereof will be omitted.
[0030]
The operation in the above configuration will be described. In this embodiment, the frequency of the resonance current determined by the heating coil 6 and the resonance capacitor 7 is set to 100 kHz or more. Here, when heating an aluminum pan or the like, a repulsive force is generated from an antiphase magnetic field generated in the pan and a magnetic field from the heating coil 6, and this is a phenomenon that occurs due to the lightness factor of the pan itself. As shown, the buoyancy decreases as the frequency of the high-frequency magnetic field supplied to the heating coil 6 is increased. Here, the problem of pot floating is solved by setting the resonance frequency of the resonance current to 100 kHz or more.
[0031]
As described above, according to this embodiment, even when the weight of an aluminum pan or the like is light, it is difficult for the pan to float, and a highly safe induction heating cooker can be realized.
[0032]
(Example 3)
A third embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 3.
[0033]
FIG. 5 is a diagram showing a circuit configuration of this embodiment. The circuit configuration used in the present embodiment is different from that in the first embodiment in order to detect the turn-off timing of the switching element 4, so that the zero current detection means 10 that detects the zero current of the switching element 4 and the counter that counts the number of resonance currents. 11, the control means 9 controls the switching element 4.
[0034]
The operation in the above configuration will be described. The zero current detection means 10 comprises current detection means such as a current transformer and a flip-flop, and detects the moment when the current changes from positive to negative and outputs it to a logic circuit such as a counter 11 and an AND circuit. The counter 11 counts up to a preset number of resonance currents, and outputs when the set value is reached. The control means 9 receives the output from the counter 11 and the output from the zero current detection means 10 and turns off the switching element 4.
[0035]
As described above, according to this embodiment, it is possible to reliably perform a switching operation with zero current and the number of necessary resonance currents, and to realize a highly reliable induction heating cooker with little switching loss. .
[0036]
(Example 4)
A fourth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 1.
[0037]
FIG. 6 is a waveform diagram showing the operation of this embodiment. Since the overall configuration of the present embodiment is the same as that of the first embodiment, a description thereof will be omitted.
[0038]
The operation in the above configuration will be described. In this embodiment, the supply of the high-frequency current to the heating coil 6 is stopped during the off time, that is, the power is adjusted with the length of the off time using the fact that no power is applied. By using this method, it is possible to perform control with a substantially constant on-time, and it is possible to perform power adjustment only by zero current detection without counting the number of resonance currents. In the method of this embodiment, the input power increases as the off time is shorter, that is, the frequency is higher.
[0039]
As described above, according to the present embodiment, it is possible to adjust the power while maintaining the number of resonance currents, and it is possible to realize an induction heating cooker excellent in controllability.
[0040]
(Example 5)
A fifth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 5.
[0041]
FIG. 7 is a waveform diagram showing the operation of this embodiment. Since the overall configuration of the present embodiment is the same as that of the fifth embodiment, a description thereof will be omitted.
[0042]
The operation in the above operation will be described. In this embodiment, the input power is controlled by controlling the number of resonance currents. In this method, the smaller the number of resonance currents, that is, the lower the frequency, the larger the input power. This method is effective when the resonance current exceeds 100 kHz because the controllability improves as the number of resonance currents at full power increases.
[0043]
As described above, according to this embodiment, the range of power adjustment is widened, and an induction heating cooker with excellent controllability can be realized.
[0044]
(Example 6)
A sixth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 6.
[0045]
FIG. 8 is a waveform diagram showing the operation of this embodiment. Since the overall configuration of the present embodiment is the same as that of the sixth embodiment, a description thereof will be omitted.
[0046]
The operation in the above operation will be described. In this embodiment, the driving frequency is made constant by controlling the number of resonance currents and changing the off time. In this method, since the off time is also determined by the number of resonance currents, the control frequency is inferior, but the driving frequency is constant, so that the interference sound between the pans generated when there are two burners is prevented. It becomes possible.
[0047]
As described above, according to the present embodiment, it is possible to adjust power at a constant frequency, and it is possible to suppress the generation of interference sound due to the difference in driving frequency between adjacent induction heating cookers, and there is little noise. It is possible to adjust the power at a certain frequency that can realize an induction heating cooker, it is possible to suppress the generation of interference sound due to the difference in driving frequency of adjacent induction heating cookers, and induction with less noise A cooking device can be realized.
[0048]
(Example 7)
A seventh embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 7.
[0049]
FIG. 9 is a diagram showing a circuit configuration of the present embodiment. The circuit configuration used in the present embodiment is different from that of the first embodiment in that the pot discriminating means 13 discriminates the kind of the pot and the switching for switching the capacity of the resonant capacitor 7 according to the kind of the pot discriminated by the pot discriminating means 13. It is the point which has the means 12.
[0050]
The operation in the above configuration will be described. When the pan 8 is made of magnetic stainless steel or iron, the frequency of the resonance current is desired to be lower than the driving frequency as in the conventional example. This is because the loss generated in the heating coil 6 increases due to the skin effect when a high-frequency current is passed, so that the pan can be heated sufficiently with the specific resistance at the driving frequency when the pan 8 is iron or the like. It is. On the other hand, when the pan 8 is an aluminum pan or a multi-layer pan, it is necessary to flow a resonance current several times as large as the driving frequency as described in the first embodiment. Therefore, it is effective to change the frequency of the resonance current depending on the material of the pan to create a resonance current corresponding to the pan 8. In the case of this method, it is not necessary to switch the heating coil 6 which is performed by the conventional aluminum pan heating. When the pan 8 is an iron pan or the like, the resonance frequency is low, so the value of the resonance capacitor 7 is large, and when the pan 8 is an aluminum pan, the value of the resonance capacitor 7 is small. FIG. 10 shows an operation waveform when the pan is changed. The most effective resonance current can be selected by selecting the optimum resonance capacitor 7 according to the type of pan. Here, various methods are conceivable, such as detecting the pan discriminating means 13 from the impedance seen from the heating coil 6 of the pan or the change in the frequency of the resonance current.
[0051]
As described above, according to the present embodiment, it becomes possible to effectively heat various pots with one type of heating coil, and a small induction heating cooker as compared with the conventional induction heating cooker combined with aluminum pot heating. Is realized.
[0052]
(Example 8)
An eighth embodiment of the present invention will be described with reference to the drawings .
[0053]
FIG. 11 is a diagram showing a circuit configuration of this embodiment. The circuit configuration used in the present embodiment is different from that of the first embodiment in that the pan weight discriminating means 14 for detecting the weight of the pan and the capacity of the resonant capacitor 7 are switched according to the pan weight detected by the pan discriminating means 14. It is the point which has the switching means 12.
[0054]
The operation in the above configuration will be described. When the pan 8 is an aluminum pan, a repulsive force is generated from the reverse phase magnetic field generated in the pan and the magnetic field from the heating coil 6, and the lightness factor of the pan itself is added to the pan so that the pan floating phenomenon occurs. For this purpose, as shown in FIG. 4, a method of increasing the frequency of the high-frequency magnetic field supplied to the heating coil 6 to reduce the buoyancy is effective. However, increasing the frequency of the resonance current leads to an increase in the loss of the heating coil 6. Therefore, the pot weight discriminating means 14 detects the weight of the pot, and only when the weight is below a certain value, the capacity of the resonant capacitor 7 is changed by the switching means 12 and the frequency of the resonance current is increased to prevent the pot from being lifted. It is effective to do. Here, as the pan weight discriminating means, various methods such as a weight sensor and detection of the moment when the pan is lifted can be considered.
[0055]
As described above, according to the present embodiment, it is possible to suppress the phenomenon that the pan is lifted when the pan is light, and a highly safe induction heating cooker is realized.
[0056]
【The invention's effect】
As is apparent from the above examples, according to the first aspect of the invention, it is possible to supply high frequency power to the pan 8 without increasing the switching loss of the switching element 4, an aluminum pan and an aluminum material It is possible to realize an induction heating cooker capable of heating a multi-layer pot that has many components within the thickness of the pot bottom .
[0057]
Further, according to the present invention of claim 2, even when the weight of an aluminum pan or the like is light, the pan does not easily float, and an induction heating cooker with high safety can be realized.
[0058]
Further, according to the present invention of claim 3, it is possible to realize a highly reliable induction heating cooker with a small number of switching currents and a switching operation with zero current, which can be surely performed with zero switching current. is there.
[0059]
According to the fourth aspect of the present invention, the power can be adjusted while maintaining the number of resonance currents, and an induction heating cooker excellent in controllability can be realized.
[0060]
Moreover, according to the present invention of claim 5, the range of power adjustment is widened, and an induction heating cooker with excellent controllability can be realized.
[0061]
Further, according to the present invention of claim 6, it is possible to adjust the power at a constant frequency, it is possible to suppress the generation of interference sound due to the difference in the driving frequency of the adjacent induction heating cookers, It is possible to adjust the power at a certain frequency, which can realize a small induction heating cooker, and it is possible to suppress the generation of interference sound due to the difference in driving frequency of adjacent induction heating cookers, and there is little noise An induction heating cooker can be realized.
[0062]
In addition, according to the present invention of claim 7, it becomes possible to effectively heat various pans with a single type of heating coil, and the induction heating cooking is smaller than the conventional induction heating cooker also used for heating aluminum pans. Implements the vessel.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of an induction heating cooker according to a first embodiment of the present invention. FIG. 2 is a waveform diagram showing an operation of each part of the induction heating cooker according to the first embodiment of the present invention. 3 is a waveform diagram showing the operation of each part of the induction heating cooker according to the second embodiment of the present invention. FIG. 4 is a diagram showing the characteristics of the second embodiment of the present invention. The figure which shows the circuit structure of the induction heating cooking appliance of an Example. [FIG. 6] (a) The wave form diagram which shows the operation | movement of each part when the input electric power of the induction heating cooking appliance of the 4th Example of this invention is large. The wave form diagram which shows the operation | movement of each part when the input electric power of the induction heating cooking appliance of the 4th Example of this invention is small. (A) Input power of the induction heating cooking appliance of the 5th Example of this invention (B) The operation of each part when the input power of the induction heating cooker of the fifth embodiment of the present invention is small Waveform diagram [FIG. 8] (a) Waveform diagram showing the operation of each part when the input power of the induction heating cooker of the sixth embodiment of the present invention is large. (B) Induction of the sixth embodiment of the present invention. FIG. 9 is a waveform diagram showing the operation of each part when the input power of the cooking device is small. FIG. 9 is a diagram showing the circuit configuration of the induction cooking device of the seventh embodiment of the present invention. The wave form diagram which shows the operation | movement of each part at the time of using the 1st pan of the induction heating cooking appliance of 7th Example (b) Use the 2nd pan of the induction heating cooking appliance of 7th Example of this invention. FIG. 11 is a diagram showing the circuit configuration of the induction heating cooker according to the eighth embodiment of the present invention. FIG. 12 is a diagram showing the waveforms of each part of the conventional induction heating cooker. FIG. 13 is a diagram showing an example of a circuit configuration of a conventional induction heating cooker.
DESCRIPTION OF SYMBOLS 1 Power supply 2 Smoothing capacitor 3 Choke coil 4 Switching element 5 Diode 6 Heating coil 7 Resonance capacitor 8 Pan 9 Control means 10 Zero current detection means 11 Counter 12 Switching means 13 Pan discrimination interruption means 14 Pan weight discrimination means 15 Control means

Claims (7)

A smoothing capacitor connected in parallel to the power supply, a choke coil connected to the positive electrode of the power supply, a switching element connected to the opposite end of the choke coil and the negative electrode of the power supply, and connected in parallel to the switching element A diode that circulates the current when current flows in the opposite direction to the switching element, a high-frequency inverter that is arranged in parallel with the switching element and connected in series with each other, and a control that controls the switching element The heating coil when the switching element is in an on-state compared to the driving frequency of the switching element when heating the aluminum pan or the multi-layer pan in which the aluminum material has many components in the thickness of the bottom of the pan. said generated at the resonant capacitor resonant frequency of the current is 2 times or more higher rather as possible, and the pot Induction heating cooker combined inductance and resonant current capacity defining two or more waveforms of the resonant capacitor of the heating coil flows in the switching operation of one. When heating an aluminum pan or a multilayer pan in which an aluminum material has many components within the thickness of the pan bottom, the resonance current frequency determined by the inductance of the heating coil coupled to the pan and the capacity of the resonant capacitor is 100 kHz or more. The induction heating cooker according to 1. When heating an aluminum pan or a multi-layer pan in which the aluminum material has many components of the thickness of the bottom of the pan, zero current detection means that detects the zero current at the moment when the resonance current changes from positive to negative and zero current passing The induction heating cooker according to claim 1 or 2, further comprising a counter for counting the number of times, wherein the switching element is turned off at a predetermined number of times of zero current. The induction heating cooker according to claim 1 or 2, wherein when an aluminum pan or an aluminum material heats a multi-layer pan in which many ingredients are included in the thickness of the bottom of the pan, the input power is controlled by the switching element off time. The input power is controlled by changing the number of times that the zero current of the resonance current is passed when heating an aluminum pan or a multilayer pan in which an aluminum material has many components in the thickness of the bottom of the pan . Induction heating cooker. The induction heating cooker according to claim 5 , wherein the driving frequency of the switching element is constant when the aluminum pan or the multi-layer pan in which the aluminum material has many components within the thickness of the bottom of the pan is heated .   A pan discriminating means for detecting the type of pan, a plurality of resonant capacitors, and a switching means for switching the resonant capacitor. When the pan discriminated by the pan discriminating means is magnetic stainless steel or iron, the value of the resonant capacitor is The frequency of the resonance current is changed according to any one of claims 1 to 6, wherein the resonance capacitor is switched so that the value of the resonance capacitor is reduced when the pot determined by the pot determination means is aluminum. Induction heating cooker.

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