JP4345775B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that performs cooking using induction heating by a high-frequency magnetic field.

  A conventional induction heating cooker will be described with reference to the drawings. FIG. 13 is a circuit diagram showing a configuration of an example of an induction heating cooker conventionally used.

  The power source 1 is a DC power source obtained by rectifying the commercial power source, and has a pulsating current twice as smooth as the commercial power source frequency or a smoothed voltage. The power source 1 supplies high-frequency power to the heating coil 5 through the choke coil 2 and the smoothing capacitor 3 according to the switching operation of the first switching element 6 and the second switching element 7. The high frequency power supplied to the heating coil 5 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 the aluminum pan or the like is usually excluded as being unheatable. The current flowing through the heating coil 5 is a resonance current determined by the heating coil 5 and the resonance capacitor 4. The current monitor 9 is composed of a current transformer or the like, and monitors the input current supplied from the power supply 1. The control means 10 controls the switching time of the first switching element 6 and the second switching element 7 so that the current detected by the current monitor 9 becomes a predetermined current value. Usually, the ON times of the first switching element 6 and the second switching element 7 are the same, and the switching operation is repeated alternately. The first switching element 6 and the second switching element 7 have a built-in diode for power regeneration, and a current is generated when the switching operation of the first switching element 6 and the second switching element 7 is switched. Will flow.

  FIG. 12 shows waveforms during operation of the first switching element 6 and the second switching element 7. The control means 10 inputs a drive signal to the gate of the first switching element 6 to turn on the first switching element 6 to turn it on. Then, the current Ic1 flows from the smoothing capacitor 3 through the first switching element 6, the heating coil 5, and the resonance capacitor 4 to become a resonance current. After a predetermined on-time has elapsed, the control means 10 turns off the first switching element 6, continues to input a drive signal to the gate of the second switching element 7, and turns on the second switching element 7. To. Then, the current Ic2 flows from the resonance capacitor 4 through the heating coil 5 and the second switching element 7, and becomes a resonance current.

By repeating the above operation, a resonance current is supplied to the heating coil 5. Here, the ON time of each switching element 6, 7 will be controlled in a shorter space than periodic resonant current determined by the inductance of the heating coil 5 and the capacitance of the resonant capacitor 4. In addition, the maximum power is generated when the period of the resonance current and the period of each of the switching elements 6 and 7 coincide. In addition, this system is characterized in that the maximum voltage of each switching element 6, 7 matches the voltage of the power supply 1.

  In such a conventional induction heating cooker, it has been difficult to heat an aluminum pan or a multi-layer pan in which aluminum occupies most of the pan thickness because the specific resistance of the pan itself is low.

  As methods for heating the aluminum pan, there are (1) a method for increasing the ampere turn of the heating coil, that is, a method for increasing the number of turns of the heating coil, and (2) a method for further increasing the heating frequency. When the number of turns of the coil is increased, the cooker becomes larger, and when the frequency is further increased, the loss of the switching element is increased, and it becomes difficult to cool the switching element.

  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.

In order to solve the above-mentioned problems, the present invention provides a first switching element and a second switching element connected in series and connected to a smoothing capacitor, and connected in series to each other and connected in parallel to the second switching element. Heating coil and resonant capacitor for induction heating, control means for alternately driving both switching elements, pan discriminating means for detecting the type of pan heated by the heating coil, and switching means for switching the capacity of the resonant capacitor The control means, when heating the aluminum pan, the resonance current flowing through the heating coil compared to the frequency of the drive signal for the control means to drive the first switching element and the second switching element. in so that to set the frequency of more than twice, when heating a magnetic stainless steel or iron pan is of the resonant current In so that to set the wave number lower than the frequency of the drive signal, an induction heating cooker for switching the capacitance of the resonance capacitor by controlling the switching means in response to the determined signal by the pan discriminating means.

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. Moreover, it becomes possible to effectively heat various pans with one type of heating coil, and it is possible to achieve a reduction in size compared to a conventional induction heating cooker also used for heating aluminum pans.

According to invention of Claim 1, it becomes possible to supply a high frequency electric power to a pan, without increasing the loss of a 1st switching element and a 2nd switching element, and an aluminum pan and a multilayer pan can be heated. An induction heating cooker can be realized. Moreover, it becomes possible to effectively heat various pans with one type of heating coil, and it is possible to achieve a reduction in size compared to a conventional induction heating cooker also used for heating aluminum pans.

  Further, according to the invention of claim 2, 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.

Moreover, according to invention of Claim 3 , 4 , it becomes possible to suppress only the pot floating resulting from the lightness of a pot when needed, and can improve safety | security.

The invention according to claim 1 of the present invention includes a first switching element and a second switching element connected in series to each other and connected to a smoothing capacitor, and connected in series to each other and connected in parallel to the second switching element. switching for switching a heating coil and a resonant capacitor for inductive heating, a control means for driving the front SL both switching elements alternately, a pan determination means for detecting a type of pot is heated by the heating coil, the capacitance of the resonant capacitor Means for controlling the resonance of the heating coil when the aluminum pan is heated compared to the frequency of a drive signal for driving the first switching element and the second switching element by the control means. in so that to set the frequency of the current more than doubled, when heating a magnetic stainless steel or iron pan is circumference of the resonant current In so that to set the number lower than the frequency of the drive signal, an induction heating cooker for switching the capacitance of the resonance capacitor by controlling the switching means in response to the determined signal by the pan discriminating means.

In the above embodiment, when heating an aluminum pan , high-frequency power is supplied to the pan without increasing the switching loss of the switching element, and various pans can be effectively heated with a single heating coil. It will be.

The invention according to claim 2 is the induction heating cooker according to claim 1, wherein when the aluminum pan is heated, the resonance current frequency is set to 100 kHz or more.

  In the above embodiment, even when the weight of an aluminum pan or the like is light, the pan does not easily float.

According to a third aspect of the present invention, there is provided a first switching element and a second switching element that are connected in series and connected to a smoothing capacitor, and an induction that is connected in series and connected in parallel to the second switching element. A heating coil and a resonant capacitor for heating; a control unit that alternately drives the switching elements; a switching unit that switches a capacity of the resonant capacitor; and a pan weight determination unit that detects the weight of the pan; When heating the aluminum pan, the control means makes the frequency of the resonance current flowing in the heating coil more than double the frequency of the drive signal that drives the first switching element and the second switching element. set, the pot is lighter than the set value by and the pan weight determining means a case of heating the aluminum pan If it is determined is induction heating cooker which controls so as to further increase the frequency of the resonance current switching capacity of the resonance capacitor compared to the case where the pan is not determined that the lighter than the set value.

In the above embodiment, in which it suppressed Rukoto is enabled only when needed pot floating due to lightness of the pot.

The invention according to claim 4 is the induction heating cooker according to claim 3, wherein the frequency of the resonance current is set to 100 kHz or more when the aluminum pan is heated .

  In the said embodiment, it becomes possible to suppress the pot floating resulting from the lightness of a pot only when needed.

  Hereinafter, the induction heating cooker of the present invention will be described with reference to FIGS.

( Reference form 1)
FIG. 1 is a circuit configuration diagram of an induction heating cooker showing one reference form, and FIG. 2 is a waveform diagram of each part of a circuit in the induction heating cooker. In this invention, the control means that controls the switching element doubles the frequency of the resonance current formed by the heating coil and the resonance capacitor compared to the frequency of the drive signal of the first switching element and the second switching element. The points set above are different from the induction heating cooker of the conventional example shown in FIG. 13, and other parts having the same structure and effect are given the same reference numerals as those of the conventional example, and detailed description is omitted. The explanation will focus on the different points.

  The power source 1 is a rectified commercial power source, and may be used non-smoothed or smoothed by an electrolytic capacitor or the like. The choke coil 2 connected to the positive electrode of the power source 1 and the smoothing capacitor 3 connected between the other end of the choke coil 2 and the negative electrode of the power source 1 serve as a supply source for supplying a high-frequency current. A resonance capacitor 4 and a heating coil 5 for induction heating are connected in series to each other, and a heating coil is connected to a common connection point of the first switching element 6 and the second switching element 7 connected in parallel to the smoothing capacitor 3 in series. One end of the resonance capacitor 4 is connected to the other end of the second switching element 7. The pan 8 generates heat due to the eddy current generated by receiving the high frequency magnetic field of the heating coil 5. The current monitor 9 monitors the input current supplied from the power source 1. The control means 20 inputs the drive signal shown in FIG. 2 to the gate of the first switching element 6 to turn on the first switching element 6 and turns it on. Then, the current Ic1 shown in FIG. 2 flows from the smoothing capacitor 3 to the first switching element 6, the heating coil 5, and the resonance capacitor 4 as a resonance current. Next, when the resonance current reaches zero current, the control means 20 turns off the first switching element 6 and subsequently inputs the drive signal shown in FIG. 2 to the gate of the second switching element 7 to turn it on. The second switching element 7 is turned on. Then, the current Ic2 shown in FIG. 2 flows from the resonance capacitor 4 to the heating coil 5 and the second switching element 7 as a resonance current. At this time, since the conduction time of the second switching element 7 is ½ or less of the period of the resonance current, the electric path from the resonance capacitor 4 to the heating coil 5 and the second switching element 7, and the resonance capacitor 4 Thus, the electric circuit for supplying electric power to the heating coil 5 through the diode built in the second switching element 7 is alternately repeated. The control means 20 continues this operation until the current value detected by the current monitor 9 reaches a predetermined value, and then detects the zero current of the second switching element 7 to turn off the second switching element 7. . By repeating this operation, a resonance current is supplied to the heating coil 5, and a high frequency magnetic field is supplied to the pan 8 from the heating coil 5. The control means 20 causes the first switching element 6 and the second switching element 7 to perform control according to the input power using a microcomputer or the like. Here, the drive signals of the first switching element 6 and the second switching element 7 are normally performed at 20 to 30 kHz in consideration of switching loss and the like. In contrast, the resonance frequency determined by the inductance of the heating coil 5 coupled to the pan 8 and the capacity of the resonance capacitor 4 is more than twice the operating frequency of the first switching element 6 and the second switching element 7, that is, two waveforms. The above resonance current is set to a constant such that the second switching element 7 flows in one switching operation. 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., increasing the skin resistance and increasing the switching loss. It is something that is not allowed. In addition, by using this method, the ampere turn that is normally performed, that is, by increasing the diameter of the heating coil 5, the magnetic flux entering the pan is increased, and the increase in the heating coil diameter that is a problem in the heating method is suppressed. Is also possible.

The operation in the above configuration will be described. Figure 2 is a diagram showing waveforms of each portion present reference embodiment. (A) shows the current waveform Ic1 flowing through the first switching element 6, (b) shows the current waveform Ic2 flowing through the second switching element 7, and (c) shows the gate of the first switching element 6 from the control means 20. (D) shows the waveform of the drive signal applied to the gate of the second switching element 7 from the control means 20. It can be seen from the waveform of the drive signal that the drive frequency of each switching element remains the same as before, and that the resonance current having a frequency several times the frequency of the drive signal is supplied to the heating coil 5.

According to embodiments of the present reference above, it is possible to supply high frequency power to the pan 8 without increasing the switching loss of the first switching element 6 and the second switching element 7, Ya aluminum pan An induction heating cooker capable of heating a multi-layer pan can be realized.

(Embodiment 1 )
FIG. 3 is a waveform diagram of each part of the circuit configuration in the induction heating cooker showing an embodiment corresponding to the invention of claim 2, and FIG. 4 shows the frequency of the high-frequency magnetic field supplied to the heating coil in the induction heating cooker. FIG. The present invention is different from the induction heating cooker of Reference Embodiment 1 shown in FIG. 1 in that the control means sets the frequency of the resonance current determined by the heating coil and the resonance capacitor to 100 kHz or more. The configuration and FIG. 3 are the same as FIG. 2 and will not be described in detail.

  The control means 20 sets the resonance frequency of the resonance current determined by the inductance of the heating coil 5 and the capacity of the resonance capacitor 4 to 100 kHz or more.

  In the above embodiment, since the frequency of the resonance current determined by the heating coil 5 and the resonance capacitor 4 is set to 100 kHz or more, the pot does not easily float even when the weight of the aluminum pan or the like is light. That is, 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 5, and this is a phenomenon caused by adding the lightness factor of the pan itself to FIG. As shown, the buoyancy decreases as the frequency of the high-frequency magnetic field supplied to the heating coil 5 is increased. Therefore, in this embodiment, the resonance frequency of the resonance current is set to 100 kHz or more to solve the problem of the pot floating.

  As described above, according to the present embodiment, 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.

( Reference form 2 )
FIG. 5 is a waveform diagram of each part of the circuit configuration in the induction heating cooker showing one embodiment. In the present invention, the control means controls the input power by controlling the number of resonance currents that pass when the second switching element is turned on, so that the induction power of the reference form 1 shown in FIG. 1 is controlled. Unlike the heating cooker, the circuit configuration of FIG. 1 is the same, and a detailed description is omitted, and different points are mainly described.

  The control means 20 receives a current signal that flows when the second switching element 7 is detected, which is detected by the current monitor 9, and controls the number of resonance currents that flow when the second switching element 7 is conductive to pass through the zero current. The input power is controlled.

In the above-mentioned reference form, the control means 20 receives a current signal that flows when the second switching element 7 is detected detected by the current monitor 9 and passes the zero current of the resonance current that flows when the second switching element 7 is conductive. As shown in FIG. 5 <high power> , the number of passing through the resonance current zero current is small, that is, the higher the frequency of the drive signal is, the larger the input power is. Become. Also, in this configuration, as shown in FIG. 5 <low power> , the controllability becomes better as the number of resonance currents passing through the zero current at the rated power increases, which is effective when the resonance current exceeds 100 kHz. Control method. In other words, it is possible to control to change the input power in accordance with cooking of the food.

According to this reference embodiment as described above, the range of adjustment of the input power is widened, in which the control of the superior induction heating cooker can be realized.

( Reference form 3 )
FIG. 6 is a waveform diagram of each part of the circuit configuration in the induction heating cooker showing one embodiment. In the present invention, the control means controls the input power by controlling the number of resonance currents that flow when the first switching element is turned on, so that the induction power of the reference form 1 shown in FIG. Unlike the heating cooker, the circuit configuration of FIG. 1 is the same, and a detailed description is omitted, and different points are mainly described.

  The control means 20 receives a current signal that flows when the first switching element 6 is detected, which is detected by the current monitor 9, and controls the number of resonance currents that flow when the first switching element 6 is conductive to pass through the zero current. The input power is controlled.

In the above-mentioned reference form, the control means 20 receives the current signal flowing when the first switching element 6 is turned on detected by the current monitor 9 and passes the zero current of the resonance current flowing when the first switching element 6 is turned on. As shown in FIG. 6 <high power> , the smaller the number of resonance currents due to the current flowing through the first switching element 6, that is, the drive signal of the first switching element 6 is controlled. The higher the frequency, the greater the input power. Further, in this configuration, as shown in FIG. 6 <low power> , the larger the number of resonance currents that pass through the zero current of the rated power, the smaller the input power and the better the controllability, so that the resonance current exceeds 100 kHz. This is an effective control method. In other words, it is possible to control to change the input power in accordance with cooking of the food.

According to this reference embodiment as described above, the range of adjustment of the input power is widened, in which the control of the superior induction heating cooker can be realized.

( Reference form 4 )
FIG. 7 is a waveform diagram of each part of the circuit configuration in the induction heating cooker showing one embodiment. According to the present invention, the number of resonance currents that pass through the zero current of the resonance current that flows when the first switching element and the second switching element are conducted is controlled simultaneously, and the frequency of the drive signal of the switching element is kept constant. Unlike the induction heating cooker of Reference Embodiment 1 shown in FIG. 1, the input power is controlled as it is, and the circuit configuration in FIG. 1 is the same, and detailed description is omitted, and different points are mainly described.

  The control means 20 receives a current signal that flows when the first switching element 6 and the second switching element 7 are detected, detected by the current monitor 9, and flows when the first switching element 6 and the second switching element 7 are conductive. The number of resonance currents passing through the zero current is controlled, and the input power is controlled while keeping the frequency of the drive signal of the switching element constant.

In the above-mentioned reference form, the control means 20 receives the current signal flowing when the first switching element 6 and the second switching element 7 detected by the current monitor 9 are received, and the first switching element 6 and the second switching element. 7 is controlled so that the number of resonance currents that pass through the zero current passes through and the input power is controlled while keeping the frequency of the drive signal of the switching element constant, the input power is mainly the second switching element. 7, the input power increases as the number of resonance currents that pass through the second switching element 7 decreases as shown in FIG. 7 <high power> . Further, in this configuration, as shown in FIG. 7 <low power> , the greater the number that passes through the zero current of the resonance current at the rated power, the smaller the input power and the better the controllability.

According to this reference embodiment as described above, the adjacent heating coils constant frequency input power adjustment in becomes possible, the induction heating cooker adjacent (one cooking device body of the drive signal of the switching element Thus, it is possible to suppress the generation of interference sound due to the difference in the frequency of the drive signal in the form of a parallel arrangement), and an induction heating cooker with less noise can be realized.

( Reference form 5 )
FIG. 8 is a waveform diagram of each part of the circuit configuration in the induction heating cooker showing one embodiment. The present invention in that the control means controls the input power by changing the ON time of the first switching element is different from the induction heating cooker according to the first reference shown in FIG. 1, the circuit arrangement of FIG. 1 is the same Thus, the detailed explanation will be omitted, and different points will be mainly described.

  The control means 20 is configured to control the input power by changing the ON time of the first switching element 6.

In the above reference embodiment, the control means 20 controls the input power by changing the conduction time of the first switching element 6, that is, the charge stored in the resonance capacitor 4 when the first switching element 6 is in the conduction state. By controlling the amount, the amount of power is controlled when the second switching element 7 becomes conductive. The control of the input power by this configuration is not limited when turning off the first switching element 6 as shown in FIG. 8 <low power>, and fine control of the input power is possible, and the controllability is excellent. Further, as shown in FIG. 8 <High power> , the input power increases as the conduction time of the first switching element 6 increases.

According to this reference embodiment as described above, the range of adjustment of the input power is widened, in which the control of the superior induction heating cooker can be realized.

(Embodiment 2 )
FIG. 9 is a circuit configuration diagram of an induction heating cooker showing an embodiment corresponding to the invention of claim 1 , and FIG. 10 is a waveform diagram of a current flowing through a switching element in the induction heating cooker. This invention is different from the induction heating cooker of the reference form 1 in that the capacity of the resonant capacitor connected in series with the heating coil is switched in order to change the frequency of the resonant current according to the type of the pan. Other parts having the same structure and operational effects are denoted by the same reference numerals as those in FIG. 1, detailed description thereof is omitted, and different points are mainly described.

  Three resonance capacitors 4 are connected in parallel, and a common connection point is connected to the heating coil 5. Reference numeral 11 denotes a switching means such as a switch that is connected to two of the resonance capacitors 4 and switches the capacitance. Reference numeral 12 denotes a pan discriminating means for detecting the kind of pan, and transmits the detected discrimination signal to the control means 20a. The control means 20a controls the switching means 11 according to the signal discriminated by the pan discriminating means 12 to switch the capacity of the resonance capacitor 4 and change the frequency of the resonance current to control the input power.

  In the above embodiment, when the pan 8 is made of magnetic stainless steel or iron, it is desirable that the frequency of the resonance current is lower than the frequency of the driving signal of the switching element as in the conventional example. This is because loss caused by the heating coil 5 increases due to the skin effect when a high-frequency current is passed. When the pan 8 is iron or the like, the pan is sufficiently heated by the specific resistance at the frequency of the drive signal. It is possible.

On the other hand, when the pan 8 is an aluminum pan or a multi-layer pan, as described in the reference embodiment 1, it is necessary to flow a resonance current several times as high as the frequency of the drive signal. 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. Moreover, in the case of this structure, switching of the heating coil 5 performed by heating the conventional aluminum pan is not necessary. When the pan 8 is an iron pan or the like, the resonance frequency is low, so the value of the resonance capacitor 4 is large. When the pan is an aluminum pan, the value of the resonance capacitor 4 is small. Thus, FIG. 10 <pan 1> , <pan 2> has shown the waveform of the electric current which flows into the switching element when a pan changes. The most effective resonance current can be selected by selecting the optimum resonance capacitor 4 according to the type of pan.

  In addition, various methods, such as detecting from the change of the impedance seen from the heating coil 5 of the pan, the change of the frequency of resonance current, etc. can be considered as the pan discriminating means 12 in the above embodiment, but if the initial purpose is achieved, This method is also acceptable.

  As described above, according to the present embodiment, various types of pans can be effectively heated with one type of heating coil, and the induction heating cooker is smaller than a conventional induction heating cooker for heating aluminum pans. A cooker is realized.

(Embodiment 3 )
FIG. 11 is a circuit configuration diagram of an induction heating cooker showing an embodiment corresponding to the invention of claim 3 . In the present invention, in order to change the frequency of the resonance current according to the weight of the pan, the capacity of the resonance capacitor connected in series with the heating coil is switched, which is the induction heating in Reference Embodiment 1 and Embodiment 2 . Unlike the cooking device, other parts having the same structure and effects are denoted by the same reference numerals as those in FIG. 1 and FIG.

  13 is a pan weight discriminating means for detecting the weight of the pan, and transmits the detected weight discriminating signal to the control means 20b. And the control means 20b controls the said switching means 11 according to the signal discriminate | determined by the said pan weight discrimination | determination means 13, and switches the resonant capacitor 4, and changes the frequency of a resonant current.

  In the above embodiment, when the pan 8 is an aluminum pan, a repulsive force is generated from the anti-phase magnetic field generated in the pan and the magnetic field from the heating coil 5, and the lightness factor of the pan itself is added to the pan so that the pan floating phenomenon occurs. Occurs. For this purpose, a configuration in which the buoyancy is reduced by increasing the frequency of the high-frequency magnetic field supplied to the heating coil 5 as shown in FIG. 4 is effective. However, increasing the frequency of the resonance current leads to an increase in the loss of the heating coil 5. Therefore, in the present embodiment, the weight of the pan is detected by the pan weight discriminating means 13, and only when the weight is below a certain level, the capacity of the resonant capacitor 4 is switched by the switching means 11 and the frequency of the resonant current is increased. , Prevent the pot from floating.

  The pan weight discriminating means 13 may be of various types such as a weight sensor or detection of the moment when the pan is lifted, and any type may be used as long as the initial purpose is achieved.

  As described above, according to the present embodiment, it is possible to suppress the pot floating caused by the lightness of the pot only when necessary, and realize a highly safe induction heating cooker.

The circuit block diagram of the induction heating cooking appliance which shows the reference form 1 of this invention Waveform diagram of each part of circuit configuration in the same induction heating cooker The wave form diagram of each part of the circuit structure in the induction heating cooking appliance which shows Embodiment 1 of this invention The figure which shows the frequency characteristic of the high frequency magnetic field supplied to the heating coil in the induction heating cooking appliance <Low power> Waveform diagram of current flowing through the switching element in the induction heating cooker showing Reference Embodiment 2 of the present invention <High power> Waveform diagram of current flowing through the switching element in the induction heating cooker Waveform diagram of the current flowing through the switching element in the <Power Large> waveform diagram of the current flowing through the switching device in the induction heating cooker showing a reference embodiment 3 of the present invention <power small> the induction heating cooker Waveform diagram of the current flowing through the switching element in the <power small> waveform diagram of the current flowing through the switching device in the induction heating cooker showing a reference embodiment 4 of the present invention <power Large> the induction heating cooker Waveform diagram of the current flowing through the switching element in the <Power Large> waveform diagram of the current flowing through the switching device in the induction heating cooker showing the fifth reference of the present invention <power small> the induction heating cooker The circuit block diagram in the induction heating cooking appliance which shows Embodiment 2 of this invention <Pot 1> Waveform diagram of current flowing through the switching element in the induction heating cooker <Pot 2> Waveform diagram of current flowing through the switching element in the induction heating cooker The circuit block diagram in the induction heating cooking appliance which shows Embodiment 3 of this invention Waveform diagram of each part of the circuit configuration in a conventional induction heating cooker Circuit configuration diagram showing the induction heating cooker

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Resonant capacitor 5 Heating coil 6 1st switching element 7 2nd switching element 9 Current monitor 11 Switching means 12 Pan discriminating means 13 Pan weight discriminating means 20, 20a, 20b Control means

Claims (4)

A first switching element and a second switching element connected in series to each other and connected to the smoothing capacitor; a heating coil and a resonance capacitor for induction heating connected in series to each other and connected in parallel to the second switching element; A control means for alternately driving both the switching elements, a pot discriminating means for detecting the type of pot heated by the heating coil, and a switching means for switching the capacity of the resonant capacitor, the control means comprising an aluminum pan When the heating means is heated, the control means sets the frequency of the resonance current flowing in the heating coil to be twice or more compared to the frequency of the drive signal for driving the first switching element and the second switching element. , than the low frequency of the drive signal the frequency of the resonance current when heating the magnetic stainless steel or iron pan As set, the induction heating cooker for switching the capacitance of the resonance capacitor by controlling the switching means in response to the determined signal by the pan discriminating means. The induction heating cooker according to claim 1, wherein the frequency of the resonance current is set to 100 kHz or more when the aluminum pan is heated. A first switching element and a second switching element connected in series to each other and connected to the smoothing capacitor; a heating coil and a resonance capacitor for induction heating connected in series to each other and connected in parallel to the second switching element; Control means for alternately driving both the switching elements, switching means for switching the capacity of the resonant capacitor, and pan weight determining means for detecting the weight of the pan, the control means when the aluminum pan is heated, When the control means sets the frequency of the resonance current flowing in the heating coil to be twice or more compared with the frequency of the drive signal for driving the first switching element and the second switching element, and heats the aluminum pan. the pot above when it and the pot by the pan weight determination means has determined that the lighter than the set value a Induction heating cooker which controls so as to increase the frequency of the resonance current switching capacity of the resonance capacitor compared with the case of no discrimination between lighter than value. The induction heating cooker according to claim 3, wherein the frequency of the resonance current is set to 100 kHz or more when the aluminum pan is heated .

Images