JP2003257608A - Induction cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction cooker capable of inducing and heating load of an aluminum pot having low magnetic permeability and low resistance and suppressing pot interference sound when heating a plurality of burners simultaneously. <P>SOLUTION: When a load detection means 6 detects that the pot made of a material having low resistance and low magnetic permeability is heated, a first inverter circuit 1 supplies a high frequency current in which at least one of high harmonic wave components higher than primary high harmonic wave component becomes large in size of high harmonic wave component of a high frequency current supplied to a first load coil 3. A second inverter circuit 2 supplies a high frequency current in which the primary high harmonic wave component becomes the maximum in size of high harmonic wave component of a high frequency current supplied to a second load coil 4 for induction heating. Consequently, even if these two inverter circuits operate simultaneously, interference sound can be sufficiently reduced, although the sound occurs in an audible region. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having a plurality of heating ports using an inverter circuit used at home or business.

[0002]

2. Description of the Related Art In recent years, an induction heating cooker using an inverter circuit has been equipped with a temperature detecting element or the like in the vicinity of a pot or the like, which is a load, by taking advantage of its good heating response and controllability. Place it in place, detect the pot temperature, etc., and adjust the heating power and cooking time accordingly to achieve fine cooking, and without using flames, because it has high thermal efficiency, it pollutes the indoor air. In particular, the characteristics of being safe and clean have attracted attention, and the demand for them has been growing rapidly.

The operation of the conventional induction heating cooker will be described below with reference to the drawings. FIG. 12 is a block diagram showing a configuration of a conventional example. In FIG. 12, reference numeral 21 is a first switching means 21a and a second switching means 21b.
A second inverter circuit having a third switching means 22a and a fourth switching means 22b, and 23 being supplied with a high-frequency current from the first inverter circuit 21. A first load coil for applying induction heating by applying a high frequency alternating magnetic field to a load such as a pan, and 24 is supplied with a high frequency current from the second inverter circuit 22 to apply a high frequency alternating magnetic field to the load such as a pan. The second load coil 25 for induction heating by means of induction heating is a housing that houses these.

The operation of the above configuration will be described. The first inverter circuit 21 rectifies and smoothes a commercial power source (not shown) to convert direct current into high frequency alternating current, and the first load coil 2
A high-frequency current is passed through 3 to generate an eddy current in a load pan (not shown) magnetically coupled to the first load coil 23, and the Joule heat causes the load pan to be induction-heated. Similarly, the second inverter circuit 22 rectifies and smoothes a commercial power source (not shown), converts the smoothed direct current into a high frequency alternating current, and causes a high frequency current to flow through the second load coil 24. An eddy current is generated in a magnetically coupled load pan (not shown), and the Joule heat heats the load pan inductively.

At this time, the first inverter circuit 21 changes the drive frequency and drive time of the first switching means 21a and the second switching means 21b so that the induction heating output to the load pan becomes a desired value. By alternately driving them, the magnitude and frequency of the high frequency current supplied to the first load coil 23 are changed. Similarly, the second inverter circuit 22 is driven alternately by varying the drive frequency and drive time of the third switching means 22a and the fourth switching means 22b so that the induction heating output to the load pan becomes a desired value. By doing so, the magnitude and frequency of the high frequency current supplied to the second load coil 24 are changed.

In this case, the load pan produces mechanical vibration due to the high-frequency current being applied. Generally, however, the load loss is higher than the audible frequency at which the user cannot hear the vibration sound and the switching loss of the switching means. For example, the frequency is set to a frequency at which the loss of power components does not increase beyond the cooling capacity of the equipment, usually about 20 kHz to 30 kHz.

[0007]

However, in the conventional induction heating cooker as described above, the first inverter circuit 21 and the second inverter circuit 22 have different induction heating outputs or different materials. In most of the cases where the load pans are heated at the same time, such as when they are operating at the same time, the drive frequencies are different, so the difference in the drive frequencies causes interference noise, which is not useful to the user. There was a problem that it gave a pleasant feeling.

In order to improve the above problems, an induction heating cooker has been devised in which the frequencies of the high-frequency currents supplied to the corresponding load coils by the respective inverter circuits are always almost the same, but they are the same. Since the frequency is about 20 to 30 kHz at most, in order to induction-heat a pot made of a material with low resistance and low permeability such as aluminum,
Sufficient skin resistance cannot be obtained, and sufficient induction heating output cannot be obtained unless a large high-frequency magnetic field is applied, so excessive electrical and thermal stress is applied to power components such as load coils and switching elements that make up inverter circuits. Therefore, there is a problem that a large increase in cost due to cooling measures, EMC measures, etc., and an increase in the size of parts and equipment, and a large pot easily floats due to its large buoyancy, so that it cannot be used in actual use. Was.

The present invention is intended to solve the above-mentioned problems. Even if a plurality of inverter circuits and load coils are housed in the same housing and they are operated with different induction heating outputs, the occurrence of interference noise is suppressed, It is another object of the present invention to provide an induction heating cooker which is easy to use by allowing induction heating even for a pot made of a material having low resistance and low magnetic permeability.

[0010]

In order to solve the above problems, the present invention has a plurality of inverter circuits for supplying a high frequency current having a frequency higher than an audible frequency to a load coil, and at least one of the plurality of inverter circuits. One is to supply a corresponding load coil with a high-frequency current having a frequency that is at least twice the frequency of the high-frequency current supplied to the corresponding load coil by another inverter circuit, so that a plurality of inverter circuits operate simultaneously. However, in addition to suppressing the interfering noise between the induction cooked load pans, an inverter circuit that supplies a high frequency current with a frequency more than twice the high frequency current supplied to the corresponding load coil by another inverter circuit is low. Induction heating of pots with low resistance and low magnetic permeability is possible.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The object of the present invention can be achieved by adopting the configurations described in each claim as an embodiment, and therefore, the action will be described together with the features characterized in each claim. Then, the significance of the embodiment will be explained in an easy-to-understand manner.

According to the first aspect of the present invention, a plurality of sets of inverter circuits including a load coil for converting direct current into high frequency alternating current and supplying a high frequency current in an audible range or more to the load coil are provided. At least one of the circuits is
The corresponding load coil is supplied with a high-frequency current having a frequency that is at least twice as high as the high-frequency current supplied to the corresponding load coil by the other inverter circuit, and the other inverter circuit corresponds to the high-frequency current. Input detection means for detecting an input current of the first inverter circuit supplying a high frequency current that is at least twice the frequency of the high frequency current supplied to the load coil, and a load coil corresponding to the output of the input detection means. Is configured to include an input current control unit that controls the input current of the first inverter circuit so that the frequency of the high frequency current supplied to the input circuit is varied so as to obtain a predetermined input. By supplying a high-frequency current of a frequency above the audible range to the corresponding load coil, induction heating of a load such as a pan by the high-frequency magnetic flux generated from the load coil Rukoto can, mechanical vibration sound of the pot at the time of independent operation is that you do not hear the user. Further, a specific inverter circuit supplies a corresponding load coil with a high-frequency current having a frequency that is at least twice as high as the high-frequency current supplied to the corresponding load coil by another inverter circuit, for example, 21k inverter circuit
Hz, when a specific inverter circuit supplies a high frequency current of 42 kHz, which is double this frequency, the first harmonic component (fundamental wave) of this high frequency current is the high frequency current supplied by another inverter circuit. Since the frequency of the second harmonic component of 2 substantially matches, no interference sound is generated, and
When a high frequency current frequency of 52.5 kHz, which is five times higher, is supplied, the first harmonic component (fundamental wave) of this high frequency current is the second harmonic component of the high frequency current supplied by the other inverter circuit. The frequency difference between the wave component (42 kHz) and the third harmonic component (63 kHz) is 10.5 kHz,
Although the interference sound in the audible range is generated, the magnitude of the frequency component of the latter is sufficiently smaller than that of the former, and the sound pressure of the interference sound is reduced.

Further, since a high frequency current is supplied as needed at a frequency twice or more that of other inverter circuits which are usually heated at a high frequency current frequency in the audible range of 20 kHz to 30 kHz, low resistance and low magnetic permeability. Even if the pot is made of the same material, sufficient skin resistance can be obtained and buoyancy can be reduced, so that the load can be stably induction-heated and other inverter circuits can be supplied to specific inverter circuits. Since a high frequency current with a frequency more than twice that of the existing high frequency current is supplied, it suffices to take measures to improve the cooling capacity of the limited inverter circuit and EMC strengthening measures. It has the effect of being able to. Further, an input detection unit that detects an input current of the first inverter circuit that supplies a high frequency current that is at least twice the frequency of the high frequency current that another inverter circuit supplies to the corresponding load coil, and the input detection unit. The frequency of the high-frequency current supplied to the corresponding load coil is changed according to the output of the
And an input current control means for controlling the input current of the inverter circuit, the input current of the first inverter circuit is varied to obtain a desired induction heating output, and at this time, it is supplied to the corresponding load coil. The frequency of the high-frequency current to be generated is varied within the range of twice or more the frequency of the high-frequency current supplied to the other load coil, so it is generated between the load and the induction-heated other inverter circuit. The sound pressure of the interfering sound being generated can be reduced.

For example, in the case where the first inverter circuit supplies the high frequency current frequency at about 2.5 times the frequency of the high frequency current supplied to the corresponding load coil by the other inverter circuit, this high frequency current is supplied. The first harmonic component (fundamental wave) of the current causes a frequency difference in the audible region between the second harmonic component and the third harmonic component of the high frequency current supplied by another inverter circuit, and causes interference. Although the sound is generated, since the magnitude of the frequency component of the latter is sufficiently smaller than that of the former, a load that is induction-heated in the first inverter circuit and a load that is induction-heated in another inverter circuit This has the effect of reducing the sound pressure of the interfering sound generated between the two. Further, since the frequency is varied, the turn-on / turn-off timing of the switching element can be easily set so as to reduce switching loss or switching noise.

According to a second aspect of the present invention, in addition to the structure of the first aspect, a cooling fan that cools the inverter circuit and can change the air flow rate is provided, and the load coil corresponding to another inverter circuit is supplied. Change the air flow rate of the cooling fan or the change condition of the air flow rate depending on whether the first inverter circuit supplying the high frequency current more than twice the frequency of the high frequency current is cooled or the other inverter circuits are cooled. By doing so, the noise and wind noise of the cooling fan can be reduced without unnecessarily increasing the air volume of the cooling fan to operate.

According to a third aspect of the present invention, in addition to the configuration of the first aspect, there is provided load detection means for determining the material of the load to be heated for at least one of the plurality of sets of inverter circuits. If the load material determined by the load detection means is a predetermined material, the inverter circuit whose heating target is this load is at least twice the frequency of the high frequency current supplied to the load coil corresponding to the other inverter circuit. Since the high-frequency current of the load is supplied to the corresponding load coil, the load detection means discriminates the material of the load, and when the load of the predetermined material is detected, this inverter is the heating target of this load. It is possible to supply the load coil corresponding to the circuit with a high-frequency current that is at least twice the frequency of the high-frequency current supplied to the load coil corresponding to the other inverter circuit, In addition, if the material is not a predetermined material, the inverter circuit whose load is to be heated does not exceed the frequency of the high-frequency current supplied to the corresponding load coil by another inverter circuit more than twice. Accordingly, the frequency of the high frequency current supplied to the corresponding load coil can be switched. As a result, sufficient skin resistance can be obtained even with a pot made of a material having low resistance and low magnetic permeability. Also,
Generally, when the frequency of high frequency current increases, the electrical or thermal stress of power components such as load coils and switching elements that make up the inverter circuit and the wiring that connects them also increases, but it can be used with loads other than specified materials. If it is not necessary to pass a high-frequency high-frequency current to the load coil to be used, the frequency of the high-frequency current supplied by the other inverter circuit to the corresponding load coil should not be set to more than twice the frequency. The power flow of the cooling fan at this time can be reduced because it is possible to reduce the electrical stress or the thermal stress of the power components such as the load coil and switching elements that make up the inverter circuit when heating the load except This has the effect of reducing wind noise of the cooling fan.

The invention according to claim 4 is the invention according to claim 1 or 3.
In addition to the high frequency current having a configuration as described in 1, a cooling fan capable of cooling the first inverter circuit and changing the air volume is provided, and the frequency of the high frequency current supplied to the load coil corresponding to another inverter circuit is twice or more. Is supplied by the first inverter circuit, and when the first inverter circuit supplies a high frequency current lower than twice the frequency of the high frequency current supplied to the corresponding load coil by the other inverter circuit. In this case, by changing the air volume of the cooling fan or changing conditions of the air volume, the air volume is increased / decreased according to the heat generation amount of the first inverter circuit, and the air volume of the cooling fan is unnecessarily increased to operate. Without this, it is possible to reduce the noise and wind noise of the cooling fan. For example, when the same heating output is obtained, the case where the first inverter circuit supplies a high frequency current that is at least twice the frequency of the high frequency current supplied to the corresponding load coil by another inverter circuit, Since the amount of heat generated in the inverter circuit is larger than that in the case where the first inverter circuit supplies a high frequency current that is lower than twice the frequency of the high frequency current supplied to the corresponding load coil by the other inverter circuit, By cooling by increasing the air flow rate, it is possible to reduce the air flow rate of the cooling fan and the noise generated by the cooling fan when the high frequency current is supplied to the load coil corresponding to the other inverter circuit.

According to a fifth aspect of the present invention, there is provided the configuration according to any one of the first to fourth aspects, the first inverter circuit has a switching means, and the input current control means has an input detection. Since the conduction time or the driving cycle of the corresponding switching means is varied according to the output of the means to control the input current of the first inverter circuit so as to obtain a predetermined input, this means is used. Since the frequency or the magnitude of the high frequency current supplied to the corresponding load coil can be controlled by changing the conduction time or the driving cycle of the switching means, it can be easily realized by a program programmed in an integrated circuit such as a microcomputer. This has the effect of reducing the size and cost of the device.

According to a sixth aspect of the present invention, in addition to the configuration according to any one of the first to fifth aspects, one of a plurality of sets of inverter circuits has a load coil corresponding to another inverter circuit. When not supplying a high frequency current having a frequency more than twice as high as the supplied high frequency current, all inverter circuits are configured to supply a high frequency current having substantially the same frequency to the corresponding load coil. Therefore, when one of the plurality of sets of inverter circuits does not supply a high frequency current having a frequency more than twice the high frequency current supplied to the corresponding load coil by the other inverter circuit, all the inverter circuits support the corresponding load. The frequencies of the high-frequency currents supplied to the coils can be made substantially the same, and even when a plurality of inverter circuits are operating at the same time, the high-frequency currents of substantially the same frequency are supplied to each other. Because it is providing a response to the load coil, has the effect of interference sound does not occur at the load with each other are inductively heated thereto.

The invention according to claim 7 is the invention according to claim 5 or 6.
In addition to the above configuration, all inverter circuits are configured to supply a high-frequency current with a constant frequency to the corresponding load coil, so the material, size, shape, or induction heating output of the load to be heated. Induction heating can always be performed with a high frequency current of a constant frequency, regardless of the size of the load. Since it is supplied to the coils, there is an effect that no interference sound is generated between the loads that are induction-heated in these coils.

According to an eighth aspect of the present invention, in addition to the configuration of the seventh aspect, each of the other inverter circuits has a switching means, and the other inverter circuit keeps the driving frequency of the switching means constant. Since it is configured to supply high frequency current by changing the conduction time,
By this means, other inverter circuits can control the frequency or magnitude of the high-frequency current supplied to the corresponding load coil by varying the conduction time of the switching means, and can be easily programmed by a program programmed in an integrated circuit such as a microcomputer. Therefore, there is an effect that the size and cost of the device can be reduced.

According to a ninth aspect of the present invention, the high frequency current supplied from one inverter circuit to the load coil corresponding to the other inverter circuit is the same as the configuration according to any one of the third to eighth aspects. When a high-frequency current having a frequency more than twice that of the above is supplied to the corresponding load coil, if the load to be heated by the other inverter circuit is a predetermined material, the inverter circuit to be heated by this load does not operate. With this configuration, the plurality of inverter circuits simultaneously supply the corresponding load coil with a high-frequency current having a frequency twice or more the high-frequency current supplied by the other inverter circuit to the corresponding load coil. Because there is no
At the same time, the plurality of inverter circuits have an effect that it is possible to eliminate a chance of generating an interference sound by supplying a high frequency current having a frequency twice or more the high frequency current supplied to the corresponding load coil by another inverter circuit. .

According to the tenth aspect of the present invention, in addition to the structure of the ninth aspect, there is provided notifying means, and the notifying means does not operate because the load to be heated by another inverter circuit is a predetermined material. Since this is configured to notify the user, this means can allow the user to recognize that he is trying to operate multiple inverter circuits with a load of a predetermined material, and the user can deal with it without confusion. It has the effect that

The invention as set forth in claim 11 has a plurality of sets each having an inverter circuit including a load coil and supplying a high-frequency current to the load coil, wherein a predetermined inverter circuit in the configuration is the corresponding load circuit. The magnitude of the harmonic component of the high-frequency current supplied to the coil is such that at least one of the higher-order harmonic components higher than the first-order harmonic component thereof is supplied as necessary, and another inverter is supplied. The circuit is configured to supply the high-frequency current having the maximum first-order harmonic component in the magnitude of the harmonic component of the high-frequency current supplied to the corresponding load coil. The inverter circuit can supply high-frequency current to the corresponding load coil to inductively heat a load such as a pan with the high-frequency magnetic flux generated from the load coil.

Further, the predetermined inverter circuit supplies the corresponding load coil with a high-frequency current in which at least one higher harmonic component higher than the first harmonic component is large, as required. , The other inverter circuit has the maximum first harmonic component, the frequency is 21 kHz, and the predetermined inverter circuit has the maximum second harmonic component, and the high frequency current is 42 kHz. In this case, the frequency of the second harmonic component of the high frequency current supplied by the predetermined inverter circuit is substantially the same as the frequency of the second harmonic component of the high frequency current supplied by the other inverter circuit. No sound is produced,
In the case where the predetermined inverter circuit supplies the high frequency current such that the second harmonic component becomes maximum and its frequency is 52.5 kHz, the second harmonic component of this high frequency current is Although the frequency difference between the second harmonic component (42 kHz) and the third harmonic component (63 kHz) of the high-frequency current supplied by the inverter circuit is 10.5 kHz, the audible interference sound is generated. Since the magnitude of the latter frequency component is sufficiently smaller than that of the former, the sound pressure of the interference sound is reduced.

Further, the other inverter circuit is usually 20 k
A high frequency current having a frequency of about 30 kHz as a first harmonic component and having a magnitude larger than that of a higher harmonic component is applied for induction heating, and a predetermined inverter circuit supplies a high frequency current. The frequency of the first harmonic component of the same as the frequency of the first harmonic component of the high frequency current supplied by the other inverter circuit, and the magnitude of the higher harmonic component is large. If a harmonic current that is to be supplied is supplied as required, it has the effect that even a pot made of a material having low resistance and low magnetic permeability can perform induction heating that can obtain sufficient skin resistance.

According to a twelfth aspect of the present invention, in addition to the configuration of the eleventh aspect, a high-order harmonic component having a frequency higher than the first-order harmonic component of the high-frequency current supplied by the predetermined inverter circuit. Since the difference between the frequency of the component and the frequency of the first harmonic component of the high-frequency current supplied by the other inverter circuit is set to be larger than the audible range, this means allows, for example, another inverter circuit. , The first harmonic component becomes maximum, the frequency thereof is 21 kHz, and the predetermined inverter circuit supplies the high frequency current such that the second harmonic component becomes maximum and the frequency thereof is 50 kHz. The second-order harmonic component of the high-frequency current supplied by the predetermined inverter circuit has a frequency difference of 2 from the first-order harmonic component of the high-frequency current supplied by another inverter circuit.
Since it is 9 kHz, which is above the audible range, the user cannot hear the interference sound between the load pans in this part, and the second harmonic component (42 kHz) of the high frequency current supplied by other inverter circuits and the second Third harmonic component (63 kHz)
And the frequency difference of 8 kHz and 13 kHz respectively, and the interference sound in the audible range is generated, but the magnitude of the frequency component of the latter is sufficiently smaller than that of the former, and the sound pressure of the interference sound is reduced. Have.

According to a thirteenth aspect of the present invention, in addition to the configuration of the eleventh or twelfth aspect, a load detecting means for discriminating a material of a load to be heated is provided for a predetermined inverter circuit. If the load material determined by the load detection means is a predetermined material, the predetermined inverter circuit,
The harmonic component of the high-frequency current supplied to the corresponding load coil is configured to supply the high-frequency current in which at least one higher harmonic component is higher than the first-order harmonic component. Therefore, when the load detecting means determines the material of the load and detects the load of a predetermined material, the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil by the inverter circuit that is heating this load is detected. In addition, it is possible to supply a high-frequency current in which at least one of higher harmonic components higher than the first harmonic component is large, and if the material is not a predetermined material, the load is to be heated. In the inverter circuit, in the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil, at least one higher harmonic component than the first harmonic component is large. To the corresponding load coil by supplying a high-frequency current that maximizes the first harmonic component similar to the high-frequency currents supplied by other inverter circuits, without supplying a high-frequency current. The type of high-frequency current supplied can be switched. As a result, even if the pot is made of a material having a low resistance and a low magnetic permeability, it is possible to perform induction heating with sufficient skin resistance.

Further, generally, when the frequency of the high frequency current increases, the electrical or thermal stress of the power components such as the load coil and the switching element forming the inverter circuit and the wiring connecting them increases, but the predetermined material is used. If it is not necessary to pass a high-frequency current with a higher magnitude of higher-order harmonic components to the corresponding load coil for loads other than the above, the same as the high-frequency current supplied to the corresponding load coil by another inverter circuit. By selecting to supply a high-frequency current that maximizes the first harmonic component of, power components such as a load coil and a switching element that constitute an inverter circuit when heating a load other than a predetermined material, or Since the electrical or thermal stress of the wiring that connects them can be reduced, the air volume of the cooling fan at this time can be reduced to cut off the cooling fan wind. It has the effect of suppressing the sound.

The invention as defined in claim 14 is based on claims 11 to 11.
13. In addition to the configuration described in any one of 13 above, an input detection means for detecting an input current of a predetermined inverter circuit, and a primary of a high-frequency current supplied to a corresponding load coil according to an output of the input detection means. An input current control means for controlling the input current of the predetermined inverter circuit so as to obtain a predetermined input by varying the frequency or magnitude of the harmonic component is provided. Desired input of induction heating is obtained by varying the input current of the inverter circuit, and at this time, the high frequency current supplied to the corresponding load coil is a higher harmonic component than the first harmonic component. Since at least one of them is made large and varied, for example, the other inverter circuit has the maximum first-order harmonic component, the frequency thereof is 21 kHz, and the predetermined inverter circuit is Frequency of the first harmonic component 21k
When the high-frequency current is supplied by changing the frequency around Hz to maximize the second harmonic component and changing the frequency around 42 kHz, the high-frequency current supplied by the predetermined inverter circuit The frequency of the second harmonic component is slightly different from the frequency of the second harmonic component of the high frequency current supplied by the other inverter circuit, and the interference sound of the frequency difference is generated. Is sufficiently larger than the latter, the sound pressure of the interference sound can be small.

Similarly, in the predetermined inverter circuit, the second harmonic component becomes maximum and its frequency is 52.5k.
When a high frequency current is supplied by varying its magnitude at a constant Hz, the second harmonic component of this high frequency current is the second harmonic component of the high frequency current supplied by another inverter circuit. Although the frequency difference between the wave component (42 kHz) and the third harmonic component (63 kHz) is 10.5 kHz, and the audible interference sound is generated, the magnitude of the latter frequency component is sufficiently smaller than that of the former. , The sound pressure of the interference sound is reduced.

In this way, the sound pressure of the interference sound generated between the load that is induction-heated in a predetermined inverter circuit and the load that is induction-heated in another inverter circuit can be reduced. Have.

According to a fifteenth aspect of the present invention, in addition to the structure of the fourteenth aspect, the predetermined inverter circuit has a switching means, and the input current control means corresponds to the output of the input detection means. Since the conduction time or the driving cycle of the switching means is varied to control the input current of the predetermined inverter circuit so as to obtain the predetermined input, the high frequency supplied to the corresponding load coil by this means. The magnitude of the current or the frequency of the first harmonic component can be controlled by varying the conduction time of the switching means or the drive cycle, and can be easily realized by a program programmed in an integrated circuit such as a microcomputer. This has the effect of enabling downsizing and cost reduction.

The invention as defined in claim 16 is based on claims 11 to 11.
15. In addition to the configuration according to any one of 15 above, in a magnitude of a harmonic component of a high frequency current supplied to a corresponding load coil by a predetermined inverter circuit, a higher order than a first harmonic component thereof When not supplying the high frequency current in which at least one of the higher harmonic components is large, all inverter circuits maximize the first harmonic component in the corresponding load coil, Since it is configured to supply the high-frequency current, one of the plurality of sets of inverter circuits does not supply the high-frequency current in which at least one of the higher-order harmonic components is higher than the first-order harmonic component. In this case, the frequency of the first harmonic component of the high frequency current supplied to the load coils corresponding to all the inverter circuits can be made substantially the same, and when the inverter circuits are operating simultaneously, But, since the supply to each corresponding load coil a high-frequency current of approximately the same frequency to each other, has the effect of interference sound does not occur at the load with each other are inductively heated thereto.

According to a seventeenth aspect of the present invention, in addition to the configuration of the fifteenth or sixteenth aspect, all inverter circuits have a high frequency in which the frequencies of the first harmonic components are substantially the same in the corresponding load coils. Since it is configured to supply an electric current, the material, size, shape, and
Alternatively, regardless of the size of the induction heating output, induction heating can always be performed with a high-frequency current of a constant frequency, so control is simple and high-frequency currents of a constant frequency can be generated even when multiple inverter circuits are operating simultaneously. Since they are supplied to the corresponding load coils, there is an effect that no interference sound is generated between the loads that are induction-heated by these.

According to an eighteenth aspect of the present invention, in addition to the structure of the seventeenth aspect, each of the other inverter circuits has a switching means, and the other inverter circuit keeps the driving frequency of the switching means constant. Since the conduction time is varied to supply the high-frequency current, this means allows the other inverter circuits to vary the frequency or magnitude of the high-frequency current supplied to the corresponding load coil to change the conduction time of the switching means. By doing so, it can be controlled and can be easily realized by a program programmed in an integrated circuit such as a microcomputer, so that there is an effect that the size and cost of the device can be reduced.

The invention described in claim 19 is from claim 13 to
In addition to the configuration according to any one of 18 above, the predetermined inverter circuit has a higher harmonic component than the first harmonic component in the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil. When a high-frequency current in which at least one of the harmonic components is large is being supplied while varying the frequency of the first-order harmonic component, if the load to be heated of another inverter circuit is a predetermined material, this load Since the inverter circuit whose heating target is to be heated does not operate, by this means, a plurality of inverter circuits can simultaneously use the first harmonic voltage component of the magnitude of the harmonic component of the high-frequency current supplied to the corresponding load coils. Interference sound by supplying a high-frequency current in which at least one higher harmonic component is higher than the second harmonic component while varying the frequency of the first harmonic component It has the effect that it is possible to eliminate the opportunity to occur.

According to a twentieth aspect of the present invention, in addition to the configuration of the nineteenth aspect, there is provided an informing means, and when the informing means is a predetermined material for a load to be heated by another inverter circuit, Since it is configured to notify that it does not operate, this means allows the user to recognize that he is trying to operate multiple inverter circuits with a load of a predetermined material, and the user does not get confused. It has the action of being able to deal with it.

According to a twenty-first aspect of the present invention, a predetermined inverter circuit has a switching element, a reverse conducting element connected in parallel with the switching element, a load coil, and a resonance capacitor, and inputs a DC voltage. And a control circuit for generating a resonance current in the load coil by conduction of the switching element and controlling the conduction period of the switching element, wherein the magnetic field generated by the load coil has high conductivity and low magnetic permeability. When induction heating is performed, the resonance current flowing through the switching element or the reverse conducting element resonates in a cycle shorter than the driving period of the switching element, and the resonance current resonates with an amplitude of a predetermined magnitude or more in the driving period. The DC voltage is boosted and smoothed by the boosting smoothing means to maintain the An induction heating cooker according to any one of claims 11 to 20 comprising been.

According to the present invention, the driving frequency of the switching element is lowered to suppress the switching loss of the switching element, and the load coil is supplied with a resonance current having a frequency higher than the driving frequency of the switching element to achieve high conductivity of aluminum or the like. It has the effect of realizing an induction heating cooker that heats a high-load, low-permeability load with high output. When heating a load with high conductivity and low magnetic permeability, boost the DC voltage input to the inverter circuit so that the peak value of the resonance current does not decay to zero during the driving period of the switching element. Since the step-up smoothing means for smoothing is provided, the drive period of the switching element is changed to stably control the output while the resonance current is generated for one cycle or more during the drive period, or the duty of the switching element ( It becomes possible to control so as not to increase the turn-on loss).

According to a twenty-second aspect of the present invention, the predetermined inverter circuit includes a series connection body of a low potential side first switching element and a high potential side second switching element, and the first switching element. A first reverse conducting element connected in parallel, a second reverse conducting element connected in parallel to the second switching element, and a first reverse conducting element connected in parallel to the first switching element or the second switching element And a resonance circuit including a resonance capacitor, a DC voltage is input between both ends of the series connection body to resonate due to conduction of the first switching element and the second switching element, A control circuit for exclusively controlling conduction between the first switching element and the second switching element is provided, and the first switching element or the first reverse conducting element is provided. The generated resonance current resonates in a cycle shorter than the driving period of the first switching element when the magnetic field generated by the load coil inductively heats a load having high conductivity and low magnetic permeability, and the resonance current in the driving period changes. 21. The DC voltage is boosted and smoothed by a boosting smoothing means to maintain resonance at an amplitude of a predetermined magnitude or more, and the DC voltage is supplied to the inverter circuit.
The induction heating cooker according to any one of 1.

According to the present invention, since the switching element has a plurality of switching elements as compared with the case where one switching element is used, the duty thereof is reduced, and the output control is performed according to the load by changing the driving time ratio or the driving frequency. It has the function of realizing an induction heating cooker that can be performed finely. When heating a load with high conductivity and low magnetic permeability, boost the DC voltage input to the inverter circuit so that the peak value of the resonance current does not decay to zero during the driving period of the switching element. Further, since the step-up smoothing means for smoothing is provided, the driving period of the switching element is changed to stably control the output while the resonance current is generated for one cycle or more during the driving period of the switching element, or the switching element is stable. It becomes possible to control so as not to increase the responsibility of (the occurrence of turn-on loss).

According to a twenty-third aspect of the present invention, a plurality of inverter circuits each including a load coil for supplying a high frequency current to the load coil, and a predetermined load coil among the plurality of load coils have a high conductivity and a low conductivity. The maximum order of the frequency components of the current flowing through the predetermined load coil when heating a load of permeability is the other order when heating an iron-based or non-magnetic stainless steel-based load by another load coil. A load for operating the inverter circuit to which each of the load coils belongs so as to have a higher order than the maximum order of the frequency components of the current flowing through the load coil and heating the load having the high conductivity and the low magnetic permeability. An induction heating cooker in which the frequency of the load coil current flowing in the coil is changed to change the heating output. According to the present invention, the frequency component of a predetermined load coil current that heats a load having high conductivity and low magnetic permeability is higher and higher than the frequency component of another load coil current that heats an iron-based or non-magnetic stainless steel load. Therefore, if the primary frequency components of both are approximately the same (for example, about 20 kHz) at frequencies exceeding the audible frequency, the frequency difference between the frequency components that maximize the current components of both load coil currents is an integer of the primary frequency. Can be secured twice.

In this state, since the heating output is changed by changing the frequency of the predetermined load coil current, the lower limit of the change range of the frequency of the predetermined load coil current is set to the order at which the frequency components of both coils are maximum. The variation of the frequency of the other load coil current is limited so that the frequency difference between the two is larger than the audible frequency, and the predetermined load coil current frequency is changed to suppress mutual interference noise and vary the heating output. It becomes possible to do. The method of changing the heating output by changing the frequency can easily optimize the switching timing of the switching element and prevent the increase of switching loss and switching noise. As a method of changing the output of the predetermined load coil which tends to occur, a great practical effect is achieved. Here, the frequencies of the other load coils may be fixed, or the frequency difference between the frequency components that maximize the above components may be changed so as to exceed the audible frequency. However, since the frequency of the maximum frequency component of the current components of other load coils is low, the switching loss of other load coils and the responsibility of applying it to other inverter components are those of a certain load coil current. It is relatively loose, and it is relatively easy to control the heating output at a constant frequency by control such as the drive time ratio.

The invention as set forth in claim 24 is the induction heating cooker as set forth in claim 23, wherein the heating output is varied while the frequency of the current flowing through the other load coil is kept substantially constant. According to the present invention, when the heating output is varied while keeping the frequency of the current flowing through the other load coil substantially constant, a high conductivity and low magnetic permeability load and an iron-based or non-magnetic stainless steel load are simultaneously heated. In any of the cases where the iron-based load and the stainless-based load are simultaneously heated, it is possible to suppress the generation of the interference sound due to the frequency difference of the mutual magnetic fields and vary the heating output.

According to a twenty-fifth aspect of the present invention, the step-up smoothing means has a choke coil connected to a DC power input terminal pair and a series connection body of a third switching element, and a smoothing capacitor serving as a power supply for high frequency current. Then, during the conduction period of the third switching element, magnetic energy is accumulated in the choke coil, and during the cutoff period of the third switching element, the choke coil releases the magnetic energy to the smoothing capacitor through the diode. The induction heating cooker according to claim 21, wherein:

According to the present invention, the drive frequency of the switching element is lowered to suppress the switching loss of the switching element, and the load coil is supplied with a resonance current having a frequency higher than the drive frequency of the switching element to achieve high conductivity of aluminum or the like. It has the effect of realizing an induction heating cooker that heats a high-load, low-permeability load with high output. Also, when heating a load with high conductivity and low magnetic permeability, the DC voltage input by the inverter is set by a choke coil so that the peak value of the resonance current does not decay to zero during the driving period of the switching element. Since the DC power is boosted by discharging energy to the smoothing capacitor through the diode and boosted, the driving period of the switching element is changed while the resonant current is generated for one cycle or more, and the output is output. It becomes possible to perform stable control or control so that the duty of the switching element (generation of turn-on loss) is not increased.

In the twenty-sixth aspect of the present invention, the step-up smoothing means comprises a second smoothing capacitor connected in parallel to the series connection body of the first switching element and the second switching element, and the first switching element. A choke coil connected in series with the element, the energy is stored in the choke coil by conduction of the first switching element, and the energy is stored in the second reverse conduction by shutting off the first switching element. The induction heating cooker according to claim 22, wherein the induction heating cooker is moved to the second smoothing capacitor via an element. The present invention, without newly providing a switching element and a choke coil exclusively for boosting,
The voltage boosted by the first switching element and the choke coil is smoothed by the second capacitor. This prevents the peak value of the resonance current from being attenuated to zero during the driving period of the switching element. Further, the ripple of the envelope of the current flowing through the load coil is reduced, and the beat caused by the ripple of the envelope is prevented.

According to a twenty-seventh aspect of the present invention, in the predetermined inverter circuit, when the magnetic field generated by the load coil heats a load having high conductivity and low permeability, the first switching element and the second switching element are provided. Driving the switching elements in substantially the same driving period, and the resonance current flowing through the first switching element and the first reverse conducting element resonates in a cycle of approximately 2/3 times the driving period, The first switching element changes the driving period by stopping the driving when the resonance current is after the second cycle after the driving is started and the current of the first switching element is zero or more, and the load coil is changed. 27. The induction heating cooker according to claim 22 or 26, wherein the heating output is changed by changing the frequency of the electric current.

According to the present invention, the driving frequency of the switching element is reduced to suppress the switching loss of the switching element, and the load coil is supplied with a resonance current having a frequency higher than the driving frequency of the switching element to achieve high conductivity of aluminum or the like. It has the effect of realizing an induction heating cooker that heats a high-load, low-permeability load with high output. The resonance frequency changes according to the change of the drive period, and the phases of the drive period and the resonance current are deviated, but the relationship of resonating at a cycle of about ⅔ times the drive period does not change. Also, the current of the first switching element is biased in the negative direction due to the energy emitted from the choke coil. On the other hand, the first switching element is ON / OFF controlled so that the driving is stopped at the time when the resonance current is after the second cycle after the driving is started and the first switching element is flowing. The second switching element is turned on and off at the same timing as the first switching element, but is positively biased by the current flowing through the choke coil, so that a larger current than that of the first switching element flows. The drive is stopped at that point. As described above, since the frequency of both the first switching element and the second switching element is changed and the output control is performed so that the driving is stopped when the current becomes larger than zero, the other switching element No voltage is applied in the forward direction at the time of driving, that is, the turn-on mode does not occur or even if it occurs, the level can be small.

The invention described in Item 28 is defined by Items 11 to 11.
27. The structure according to any one of 27 above, further comprising a cooling fan capable of cooling a predetermined inverter circuit and changing the air volume, wherein the predetermined inverter circuit has a first harmonic component in its corresponding load coil. When a high frequency current in which at least one of higher harmonic components is large is supplied, and when the predetermined inverter circuit or another inverter circuit supplies a high frequency current in which the first harmonic component is maximum In this case, by changing the air volume of the cooling fan or the changing condition of the air volume, the air volume is increased / decreased according to the heat generation amount of the predetermined inverter circuit, and the air volume of the cooling fan is increased unnecessarily to operate. Without this, it is possible to reduce the noise and wind noise of the cooling fan. For example, when the same heating output is obtained, the predetermined inverter circuit
The case where the high-frequency current in which at least one of the higher-order harmonic components is larger than the second-order harmonic component is supplied is the first
Since the amount of heat generated by the inverter circuit will be larger than when the high-frequency current that maximizes the second harmonic component is being supplied by the specified inverter circuit or other inverter circuits, it is possible to increase the air volume of the cooling fan to cool it. It is possible to reduce the air volume of the cooling fan and reduce the noise generated by the cooling fan when a predetermined inverter circuit or another inverter circuit supplies a high frequency current that maximizes the first harmonic component.

[0052]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment showing the best mode for carrying out the present invention will be described below with reference to the drawings.

Example 1 An induction heating cooker of Example 1 of the present invention will be described with reference to FIGS. First Embodiment FIG. 1 is a block diagram showing the entire configuration of a first embodiment of the present invention. In FIG. 1, 1 is a first inverter circuit including a first switching means 1a and a second switching means 1b, and 2 is a second inverter circuit including a third switching means 2a and a fourth switching means 2b. A circuit 3 is a first load coil which is included in the first inverter circuit 1 and which is supplied with a high frequency current having a frequency higher than the audible range to apply a high frequency alternating magnetic field to a load such as a pot for induction heating. Is included in the second inverter circuit 2 and is supplied with a high-frequency current having a frequency higher than the audible range to apply a high-frequency alternating magnetic field to a load such as a pan to perform induction heating. A housing housing, 6 is load detecting means for determining the material of a load such as a pot to be heated by the first inverter circuit 1 or the second inverter circuit 2, and 7 is the first inverter circuit 1 or Input detecting means for detecting an input current of 2 to the inverter circuit 2, 8 the first inverter circuit 1 or the second based on the output of the input detecting means 7 inverter circuit 2
The input current control means for controlling the induction heating output to the load to a desired value by varying the input current of (3), and 9 is a notification means.

In the notifying means 9 of the first embodiment, any one of the first and second inverter circuits 1 and 2 determines the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil. A high-frequency current in which at least one higher harmonic component than the first harmonic component is large is supplied to the corresponding load coil while varying the frequency of the first harmonic component, and another inverter If the load to be heated in the circuit is made of a predetermined material, the user is informed that the other inverter circuit whose heating target is this load does not operate. The cooling fan drive means 100 includes a motor for rotating a cooling fan (not shown) for cooling the first inverter circuit 1 and the second inverter circuit 2, a drive circuit for the motor, and the like. The cooling fan drive means 100 changes the air volume of the cooling fan based on the detection result of the load detection means.

The operation of the above configuration will be described. The first inverter circuit 1 rectifies and smoothes a commercial power source (not shown) to generate a direct current for the first and second switching means 1a and 1b.
Are alternately turned on and off to be converted into a high frequency alternating current, and a high frequency current having a frequency higher than the audible range is passed through the first load coil 3, so that a load pan magnetically coupled to the first load coil 3 (not shown). An eddy current is generated in and the Joule heat heats the load pan by induction. Similarly, the second inverter circuit 2
Is a third and a fourth switching means 2a, which rectifies and smoothes a commercial power source (not shown) and converts direct current into high frequency alternating current.
By turning on and off 2b alternately, it is converted into a high frequency alternating current, a high frequency current having a frequency higher than the audible range is passed through the second load coil 4, and a load pan (not shown) magnetically coupled to the second load coil 4 is supplied. An eddy current is generated, and the Joule heat heats the load pan inductively.

At this time, the input current control means 8 sets the first input current of the first inverter circuit 1 or the second inverter circuit 2 detected by the input detection means 7 to a desired value.
And the second switching means 1a, 1b or the third and fourth switching means 2a, 2b are supplied to the first or second load coil 3, 4 by varying the conduction time and the conduction time ratio or the drive cycle. By changing the magnitude or frequency of the high-frequency current (the magnitude and the frequency may be varied), the induction heating output to each heating target load is adjusted.

Further, the load detecting means 6 determines whether or not the load to be heated is a pot made of a predetermined material when each of the first and second inverter circuits 1 and 2 starts operating. ing. In this embodiment, the predetermined material is a material having low resistance (resistivity of about 50 × 10 −8 Ωm or less) and low magnetic permeability (relative magnetic permeability = 1), such as aluminum,
Material such as copper is assumed.

FIG. 2 shows the circuit configuration of the induction heating cooker according to the first embodiment (first inverter circuit 1 including the first load coil 3).
And the second inverter circuit 2 including the second load coil 4 have the same configuration. ) Is a figure which shows. The power supply 51 is a 200 V commercial power supply which is a low frequency AC power supply, and is connected to the input end of a rectifier circuit 52 which is a bridge diode.
The first smoothing capacitor 53 is connected between the output terminals of the rectifier circuit 52. A series connection body of the choke coil 54 and the first switching element 57 is further connected between the output terminals of the rectifier circuit 52. The load coil 59 is arranged so as to face a pan 61 made of aluminum which is an object to be heated.

Reference numeral 50 denotes an inverter, the low potential side terminal of the second smoothing capacitor 62 is connected to the negative terminal of the rectifier circuit 52, and the high potential side terminal of the second smoothing capacitor 62 is the second switching element (IGBT). , Insulated Gate B
It is connected to the high-potential side terminal (collector) of the apolar transistor 55, and is connected to the second switching element (IGB).
The low potential side terminal (emitter) of T) 55 is connected to the connection point between the choke coil 54 and the high potential side terminal (collector) of the first switching element (IGBT) 57. A series connection body of the load coil 59 and the resonance capacitor 60 is connected in parallel to the first switching element 57.

The second diode 56 (second reverse conducting element) is connected in antiparallel to the second switching element 55 (the cathode of the second diode 56 and the collector of the second switching element 55 are connected). , The first diode 5
8 (first reverse conducting element) is the first switching element 57.
In reverse parallel (the second switching element 55 and the first switching element 57 correspond to the first switching means 1a and the second switching means 1b in FIG. 1). The snubber capacitor 64 is connected in parallel with the first switching element 57. Correction resonance capacitor 6
The series connection body of 5 and the relay 66 is connected in parallel to the resonance capacitor 60. The control circuit 63 inputs the detection signals of the current transformer 67 that detects the input current from the power supply 51 and the current transformer 68 that detects the current of the load coil 59, and also receives the second switching element 55 and the first switching element. A signal is output to the gate of 57 and the drive coil (not shown) of the relay 66.

The operation of the induction heating cooker configured as above will be described below. The power supply 51 is a rectifier circuit 52
Is full-wave rectified by and is supplied to the first smoothing capacitor 53 connected to the output end of the rectifying circuit 52. The first smoothing capacitor 53 works as a supply source for supplying a high frequency current to the inverter.

FIG. 3 is a diagram showing waveforms at various portions in the above circuit, and FIG. 3 (A) shows a case where the output is a large output of 2 kW. FIG. 3A shows the second switching element 55.
And the current waveform Ic2 flowing through the second diode 56,
The figure (b) shows the current waveform Ic1 flowing through the first switching element 57 and the first diode 58, and the figure (c) shows the voltage Vce1 generated between the collector and the emitter of the first switching element 57. (D) shows the drive voltage Vg2 applied to the gate of the second switching element 55, (e) shows the drive voltage Vg1 applied to the gate of the first switching element 57, and (f) shows the load coil 59. Each of the flowing currents IL is shown.

When the output is 2 kW (FIG. 3 (A)), the control circuit 63 causes the gate of the first switching element 57 to have a driving period T for the period from time t0 to time t1 as shown in (e).
_The ON signal which is ₁ (about 24 μsec) is output. During the driving period T ₁ , the first switching element 57 and the first switching element 57
Of the diode 58, the load coil 59, and the resonance capacitor 60 resonates, and the resonance period (1 / f) when the pot 61 is an aluminum pot is about 2 / of the driving period T _1. The number of turns of the load coil 59 (40T), the capacitance of the resonant capacitor 60 (0.04 μF), and the driving period T ₁ are set so as to triple (about 16 μsec).
The choke coil 54 is the first switching element 57.
In the driving period T ₁ of, the electrostatic energy of the smoothing capacitor 53 is stored as magnetic energy. Resonance period (1
/ F) is the drive cycle T _{3 of} the first switching element 57.
(= About 2 × T ₁ = about 50 μsec).

Next, at time t1 which is the timing between the second peak of the resonance current flowing through the first switching element 57 and the resonance current next becoming zero, that is, in the forward direction of the first switching element 57. The driving of the first switching element 57 is stopped when the collector current flows.

Then, since the first switching element 57 is turned off, the potential of the terminal of the choke coil 54 connected to the collector of the first switching element 57 rises, and this potential becomes the potential of the second smoothing capacitor 62. When it exceeds, the second smoothing capacitor 62 is charged through the second diode 56, and the magnetic energy stored in the choke coil 54 is released. The voltage of the second smoothing capacitor 62 is the peak value (2) of the DC output voltage Vdc of the rectifier circuit 52.
The voltage is increased to be higher than 83 V (500 V in this embodiment). The boosted level depends on the conduction time of the first switching element 57, and the longer the conduction time, the higher the voltage generated in the second smoothing capacitor 62 tends to be.

In this way, the second smoothing capacitor 62-
By boosting the voltage level of the second smoothing capacitor 62 that functions as a DC power source when resonating in the closed circuit formed by the second switching element 55 or the second diode 56-the load coil 59-the resonance capacitor 60. ,
Second switching element 55 shown in (a) of FIG.
The peak value (peak value) of the resonance current flowing in the first switching element 57 and the peak value of the resonance current flowing in the first switching element 57 of FIG. In addition, the pan made of aluminum can be induction-heated at a high output and the output can be continuously increased or decreased so as not to become small.

Then, as shown in (d) and (e) of FIG. 3A, the control circuit 63 is provided with a dwell period (d1) for preventing simultaneous conduction of both switching elements from time t1. ) At a later time point t2, the drive signal is output to the gate of the second switching element 55. As a result, as shown in FIG. 7A, the path is changed to a closed circuit composed of the load coil 59, the resonance capacitor 60, the second switching element 55 or the second diode 56, and the second smoothing capacitor 62, and the resonance current is changed. Will flow. Since the driving period T ₂ of this driving signal is set to the substantially same period as T _{1 in} this case, the first switching element 5
As in the case where 7 is conducting, about 2 / of the driving period T ₂
A resonance current having a period of 3 flows.

Therefore, the current IL flowing through the load coil 59
Has a waveform as shown in (f) of FIG.
And the driving cycle of the second switching element (the sum of T ₁ and T ₂ and the rest period) is about three times the cycle of the resonance current.
If the second drive frequency is about 20 kHz, the frequency of the resonance current flowing through the load coil 59 is about 60 kHz.

FIG. 4 shows the waveform of each part in the induction heating cooker of the first embodiment. FIG. 4A shows the voltage waveform of the commercial power supply 51, and FIG. 4B shows the load coil 59 and the resonance capacitor 6.
The voltage Vce1 applied to the series connection body of 0s, and FIG. 4C shows the current IL flowing through the load coil 59. FIG.
Shows the waveform of each part in the conventional induction heating cooker. FIG. 13A is a voltage waveform of the commercial power supply 51, and FIG.
13B shows the voltage applied to the series connection body of the load coil and the resonance capacitor, and FIG. 13C shows the current flowing through the load coil. In the conventional example, as shown in FIG. 13C, the envelope of the load coil current has a ripple with a frequency twice the commercial power frequency. There was a problem that this ripple caused a pot noise. In the first embodiment, the output voltage of the rectifier circuit 52 is changed by the second smoothing capacitor 62.
While the commercial power supply shown in FIG. 4A has a pulsating waveform obtained by full-wave rectification, the envelope of the current flowing through the load coil 59 is smoothed as shown in FIG. The ripple of the current envelope is greatly reduced, and the noise of the pot is suppressed.

The waveform of FIG. 3B has a low output 4
It is for 50W. 3 (B) (a ')-
(E ′) is a waveform corresponding to (a) to (e) of FIG. The output power is controlled as shown in FIG.
Driving time of the second switching element 55 _{(T 2} ') and the drive time of the first switching element 57 _{(T 1')} 2
This is performed by making each drive time T ₂ and T ₁ at the time of kW output shorter than each drive time.

In FIG. 3A, the second diode 5
When the first switching element 57 is turned on at the time when the current flowing in 6 reaches its peak (time t5 in FIG. 3A), the output power becomes the minimum output power or a value close to it. On the other hand, the second switching element 55 has two
When the second switching element 55 is turned off and the first switching element 57 is turned on at the time point (not shown) at which the resonance value becomes zero again after starting to flow (the time point shown by t6 in the figure). Maximum output power can be obtained (resonance point power control).

When the output setting is 450 W, which is a low output, the driving time (T ₂ ′) is set to the maximum output setting of 2 kW as shown in (a ′) of FIG. Although it is made shorter than the case of, the second switching element 55 is turned off at the time (t3 ′) when the forward current is flowing in the second switching element 55. By doing this, even when setting the maximum output,
Even when the output is set low, the energy accumulated in the load coil 59 causes the snubber capacitor 64 to resonate with the turn-off of the second switching element 55 to lower the collector potential of the second switching element 55 and Switching loss can be reduced by gradually increasing the voltage rise between the collector and the emitter.

As a result, the voltage is not applied in the forward direction at the time of turning on the first switching element 57 which is to be turned on continuously, or the level thereof is made small even if it is applied to suppress the turn-on loss or at the time of turning on. Noise can be prevented, and the turn-off loss of the second switching element 55 can be reduced.

Next, at the time of start-up, the control circuit 63 turns off the relay 66 and sets the constant frequency (about 21 kHz).
In z), the second switching element 55 and the first switching element 57 are alternately driven. The drive period of the second switching element 55 is driven in a mode shorter than the resonance cycle of the resonance current, the drive time ratio is minimized, and the drive time ratio is gradually increased after the output is minimized. 63
Detects the material of the load pan 61 from the detection output of the current transformer 67 and the detection output of the current transformer 68. When the control circuit 63 determines that the material of the load pan 61 is iron-based, it stops heating and then turns on the relay 66,
Start heating again at low power. At this time, the control circuit 63
Causes the second switching element 55 and the first switching element 57 to start again from a minimum output at a constant frequency (about 21 kHz) with a minimum drive time ratio and gradually increase to a predetermined output.

On the other hand, when it is not detected that the load is iron-based, when the predetermined drive time ratio is reached, the resonance current of the resonance current is changed from the drive period of the second switching element 55 as shown in FIG. 3B. Move to short cycle mode. At this time, the driving period is set so that the output is in the low output state.

FIG. 5 shows the second switching element 55 and the first switching element 55.
The drive frequency of the switching element 57 of is constant (20 kHz
It is a figure which shows the ON time of the 1st switching element 57 at the time of z), and the relationship of input electric power. As shown in this figure, in the present embodiment, about 2 kW is around ½ of the cycle.
Heating output is obtained, and the output can be linearly reduced by shortening the driving period of the first switching element from the peak in the vicinity thereof. Therefore, as shown in FIG. 5, the lower limit Tonmi of the limiter of the drive time or the drive time ratio is
If n and the upper limit Tonmax are set, stable control can be performed.

As described above, according to the present embodiment, when a load of high conductivity and low magnetic permeability such as aluminum or copper is heated by the magnetic field generated by the load coil 59, the second switching element 55 and the first diode are heated. Since the resonance current due to the load coil 59 and the resonance capacitor 60 flowing through 56 resonates in a cycle shorter than the drive period (T ₁ , T ₂ ) of both switching elements, the second switching element 55
Of a frequency higher than the driving frequency of (3 times in this embodiment) can be supplied to the load coil 59 for heating.
Further, a choke coil 54 which is a boosting means and a second smoothing capacitor 62 which is a smoothing means are provided to boost and smooth the voltage of the smoothing capacitor 62 which is a high frequency power source, and in each driving period (T and T ′). Since the amplitude of the resonance current is increased, the first cycle ends after the resonance current starts to flow after the drive starts, and the resonance current with a sufficiently large amplitude is continued after the first cycle reaches the second cycle. A large output variable range can be obtained by changing the drive stop timing of each switching element after the eye.

Further, the choke coil 54 which is a step-up means.
Is obtained by changing the magnitude of boosting in association with the drive period of the first switching element 57, that is, the first
When the conduction time of the switching element 57 becomes long, for example, the boosting action of the choke coil 54 becomes large and the voltage of the smoothing capacitor 62 as the smoothing means becomes high, so that it can be used for output control.

Further, the boosting means 54 moves the energy accumulated in the choke coil 54 due to the conduction of the first switching element 57 to the second smoothing capacitor 62 via the second diode 56. With a simple configuration, a pulsating input DC voltage can be smoothed into a high-voltage power supply. Based on this power supply, a high-frequency current with a smoothed envelope is converted and supplied to the load coil 59. The sound can be suppressed.

The resonance current flowing through the first switching element 57 or the first diode 58 is the load coil 5
When a load having high conductivity and low magnetic permeability, such as aluminum or copper, is heated by the magnetic field generated by 9, magnetic resonance occurs at a cycle shorter than the driving period (T ₁ ) of the first switching element 57, and the second switching element 57 resonates. In addition to the resonance current flowing through the switching element 55 or the second diode 56, the wave number of the resonance frequency within the driving cycle of the first and second switching elements can be increased.

Further, when the first switching element 57 is turned on, the first choke coil 54 is energized with the first energy.
By having the smoothing capacitor 53, it is possible to suppress the high frequency component from leaking to the power supply 51 when the energy is stored in the choke coil 54.

Further, when the maximum output is set, the control circuit 63 causes the second switching element 55 to have a resonance current after the second cycle after the driving of the second switching element 55 is started.
The signal that cuts off the conduction of the second switching element 55 is output within the period flowing in the first switching element 57, or the resonance current after the driving of the first switching element 57 has started after the second cycle and the first Since the signal that cuts off the conduction of the first switching element is output within the period when the current flows through the switching element 57, the first switching element 5 at the maximum output
7 or the increase of the turn-on loss of the second switching element 55 can be suppressed.

Further, when the maximum output is set, the control circuit 63 causes the resonance current of the second switching element 55 after the driving is started to pass through the peak phase after the second cycle and reach the zero point. 55 is output, or the second switching element 55 is turned on until the resonance current after the driving of the first switching element 57 starts to pass the peak phase after the second cycle and reaches the zero point. By outputting a signal to cut off, the generation of turn-on loss of the first switching element 57 or the second switching element 55 at the time of maximum output is suppressed, and the output is reduced if the driving period thereof is shortened. In addition, even if the output is low, the turn-on mode of each switching element hardly occurs and the turn-on loss hardly occurs.

Further, the second switching element 55 and the first switching element 55
When the ratio of the conduction periods T ₁ and T ₂ of the switching element 57 is set to approximately 1 and a load having high conductivity and low magnetic permeability is heated by the magnetic field generated by the load coil 59, the second switching element 55 and the second switching element 55 The resonance current flowing through the second diode 56 is the driving period T of the second switching element 55.
By becoming resonates at approximately 2/3 of the period of _2, a second
Switching element 55 and first switching element 57
Of the three resonance currents can be generated during the driving periods T ₁ and T _{2 of 1,} and the high frequency current of about 3 times the driving frequency can be supplied to the load coil 59, and the second switching element 55 is driven by the second diode 5
6 can be started at a timing when a current is flowing through 6, and driving can be stopped at a timing when a current is flowing in the forward direction through the second switching element 55. The first switching element 57 and the first diode 58 Can be the same, and the control becomes stable.

At the time of startup, the second switching element 5
5, the driving frequency of the first switching element 57 is kept constant, the driving time ratio is changed to increase the heating output, and the driving frequency is changed from the middle to increase the heating output.
The load can be easily detected. That is,
By changing the driving time ratio while keeping the driving frequency constant, the output can be monotonously changed in a low output state even with a load of a material such as aluminum having high conductivity and low magnetic permeability or a load of iron system. The load can be detected accurately and in a low output state. Further, after reaching a predetermined drive time ratio, drive time or heating output, the drive time ratio is kept constant so that the switching element can be driven and cut off in a specific phase range in the case of a load having high conductivity and low magnetic permeability. By changing the cut-off phase and changing the drive frequency, it is possible to suppress a sudden increase in the loss of the switching element and change the output.

At the time of startup, the second switching element 5
The driving period T _{2 of} 5 is shorter than the resonance cycle of the resonance current so that the driving time ratio between the second switching element 55 and the first switching element 57 is changed to increase the heating output.
When the predetermined drive time or the predetermined drive time ratio is reached, the drive period T ₂ of the second switching element 55 is discretely changed to be longer than the cycle of the resonance current and low output, and then the drive period is changed. By gradually shortening and increasing the heating output from the low output value to the predetermined output value,
It is possible to accurately and stably determine whether the load 61 has a high conductivity and a low magnetic permeability by a predetermined driving time or a predetermined driving time ratio, and the load 61 has a high conductivity and a low magnetic permeability. In such a case, the drive period can be discretely lengthened to shift to a low output state, and from there, it is possible to stably increase and reach a predetermined value.

When the iron-based load or the non-magnetic stainless steel load 61 is heated by the magnetic field generated by the load coil 59, the resonance current is changed to the second switching element 55 and the first switching element 55.
When the iron-based load or the load 61 made of non-magnetic stainless steel is heated to the maximum output by resonating at a period longer than the conduction periods T ₂ and T ₁ of the switching element 57 of FIG. Of the resonance element 65 for correction so that the switching element can be shut off at the timing when the current flows in the forward direction in the switching element 57.
Is connected in parallel to the resonance capacitor 60 and switched to a larger capacity than when heating a load having high conductivity and low magnetic permeability, the resonance capacitor 60 and the correction capacitor 64 are connected in series with the load coil 59. In addition, the capacity can be switched, and when the iron-based load or the load made of non-magnetic stainless steel is heated, the resonance capacitor 60 is switched to a larger capacity than when a load having high conductivity and low magnetic permeability is heated. As a result, the resonance frequency becomes longer and the current increases, and since the DC voltage Vdc is boosted by the choke coil 54, the amplitude of the resonance current becomes large, so that the current flows in the forward direction in the switching element. Switch when turning on the switching element by setting the maximum output in the range that can interrupt the switching element at the timing When trying to suppress an increase in the grayed loss may be greater than that of the conventional configuration the maximum output. Further, when an aluminum-based pot and an iron-based pot are to be heated by the same inverter, conventionally, the number of turns of the load coil 59 and the resonance capacitor are simultaneously switched so that the resonance frequency and the magnetic field emitted to the object to be heated 61 are radiated. Was changing the strength (ampere turn) of the choke coil 5
The operation of switching the number of coil turns can be replaced by the boosting action of the first and second switching means 57, and the resonance capacitor 60 can be switched by the same load coil 59, so that the objects to be heated of a wide range of materials can be heated. There is an effect that can be heated.

Further, the correction resonance capacitor 65 is started without being connected to the resonance capacitor 60, that is, it is started by the resonance capacitor 60 having a small capacity, and the output is gradually increased. If it is determined that the load is iron-based, it is determined that the load is iron-based, and after driving is stopped, the relay 60 is turned on and the correction resonance capacitor 65 is connected in parallel. That is, since the resonance capacitor 60 is switched to have a large capacity and the drive frequency is re-driven at a low frequency, the resonance frequency becomes longer and the current increases, and further, the choke coil 54 and the second smoothing capacitor as the boosting means. Since the DC power supply voltage is boosted by 62, the resonance current value increases.
In order to suppress an increase in switching loss at the time of turning on the switching element 57 by setting the maximum output within a range in which the switching element can be interrupted at the timing when the current flows in the switching element 55 and the forward direction,
The maximum output can be made larger than that of the conventional configuration. If it is determined that the load has high conductivity and low magnetic permeability, the output is continuously increased to a predetermined drive time ratio or a predetermined output, and then the drive time ratio is fixed and the conduction time is changed. Since the output reaches the specified output, so-called soft-start operation is possible to start at a low output for any load, judge the load, and stably reach the specified output value or limit value. Becomes

Note that, in FIG. 2, the ratio of the capacities of the first smoothing capacitor 53 and the second smoothing capacitor 62 may be appropriately determined depending on the case. For example, if the former is 1000 microfarads and the latter is 15 microfarads, the smoothness of the envelope of the load coil current will be high. In this case, a choke coil may be inserted in the power supply line on the input side of the first smoothing capacitor 53. On the contrary, if the former is set to about 10 microfarads and the latter is set to about 100 microfarads, the reduction of the power factor can be suppressed, but the latter may be expensive since it requires a large withstand voltage.

Further, in FIG. 2, the second smoothing capacitor 62 may connect the low potential side to the positive electrode of the rectifier circuit 52, and the snubber capacitor 64 may be connected in parallel to the second switching element 55. However, the same effect can be obtained.

Further, the low potential side terminal of the resonance capacitor 60 may be connected to the high potential side terminal (collector) of the second switching element 55, and the capacitance is divided so that the high potential side of the second switching element 55. And the first switching element 5
The same operation is performed even when simultaneously connected to the low potential side terminal (emitter) of 7. The resonant circuit connected in parallel to the second switching element 55 or the first switching element 57 is not limited to that of this embodiment, and the technique of this embodiment can be applied as appropriate.

FIG. 6 and FIG. 7 are frequency spectrum diagrams of the high frequency current supplied to the load coil by the inverter circuit of the induction heating cooker according to the first embodiment of the present invention. When the load detection means 6 determines that the load material to be heated by the first inverter circuit 1 is not a material having a low resistance and a low magnetic permeability such as aluminum, the first high frequency current of the high frequency current supplied to the first load coil 3 is determined. The first harmonic component is maximized and the frequency is set to 21 kHz to perform induction heating (hereinafter referred to as "normal heating operation"). At this time, the frequency spectrum of the high-frequency current supplied to the first load coil 3 has a maximum first-order harmonic component (21 kHz) as shown in FIG. 6, and subsequent higher-order harmonic components are the first-order harmonic components. Small compared to harmonic components. When it is determined that the load material to be heated is a material having low resistance and low magnetic permeability, such as aluminum, it is higher than the first harmonic component (frequency 22 kHz) of the high frequency current supplied to the first load coil 3. Induction heating is performed by setting a high frequency current with a large (maximum) magnitude of the third harmonic component (frequency 66 kHz) (hereinafter referred to as "high frequency heating operation"). At this time, the frequency spectrum of the high frequency current supplied to the first load coil 3 maximizes the third harmonic component (66 kHz) as shown in FIG. 7, and the other harmonic components are the third harmonic components. Small compared to. Therefore, even with a load made of a material having low resistance and low magnetic permeability, it is possible to obtain a skin resistance on the surface of the load, reduce the buoyancy of the load, and obtain an induction heating output sufficient for cooking.

The load detecting means 6 is the second inverter circuit 2
When it is determined that the load material to be heated of is not a material having a low resistance and a low magnetic permeability such as aluminum, the “normal heating operation” is performed, and the first high frequency current supplied to the second load coil 4 is determined.
The second harmonic component is maximized and its frequency is set to 21 kHz for induction heating. At this time, the second load coil 4
As shown in FIG. 6, the frequency spectrum of the high-frequency current supplied to the maximum of the first-order harmonic component (21 kHz) is maximum, and subsequent higher-order harmonic components are smaller than the first-order harmonic component. When it is judged that the load material to be heated is a material with low resistance and low magnetic permeability such as aluminum, "high frequency heating operation"
As a high frequency current in which the size of the third harmonic component (frequency 66 kHz) is larger (maximum) than the first harmonic component (frequency 22 kHz) of the high frequency current supplied to the second load coil 4. Then induction heating is performed. At this time, the second
As shown in FIG. 7, the frequency spectrum of the high frequency current supplied to the load coil 4 of the third harmonic component (66 kHz)
Is the maximum, and the other harmonic components are smaller than the third harmonic component. Therefore, even with a load made of a material having low resistance and low magnetic permeability, it is possible to obtain a skin resistance on the surface of the load, reduce the buoyancy of the load, and obtain an induction heating output sufficient for cooking.

As a result, the load material to be heated of the first inverter circuit 1 is a material having low resistance and low magnetic permeability, and the load material to be heated of the second inverter circuit 2 is
If the load material to be heated by the first inverter circuit 1 is not a low resistance and low magnetic permeability material, or vice versa, the second inverter circuit 2 is not a low resistance and low magnetic permeability material.
If the load material to be heated of is a material with low resistance and low magnetic permeability, the third-order high-frequency current on the side supplying the high-frequency current that maximizes the third-order harmonic component (frequency 66 kHz) The harmonic component is the first harmonic component (frequency 21k
The frequency difference between the first harmonic component of the high frequency current of the inverter circuit on the side supplying the high frequency current is 45 kHz, and the interference sound due to the maximum value of each harmonic component is It is out of the audible range, and the first harmonic component (frequency: 22 kHz) of the high frequency current supplied by the inverter circuit operating in high frequency heating and the first harmonic component of the high frequency current supplied by the inverter circuit operating in high frequency heating. 1
The frequency difference with the second harmonic component (frequency 21kHz) is 1k
Although the interference sound is generated at Hz, the sound pressure of the interference sound is reduced because the size of the former is sufficiently smaller than that of the latter. The same applies to harmonic components of other orders.

Further, at this time, when the induction heating output of the inverter circuit operating as the high frequency heating operation is controlled by changing the conduction time ratio and the driving cycle of the corresponding switching means, for example, the first inverter is used. The circuit 1 is a high frequency heating operation, the second inverter circuit 2 is a normal heating operation, and the second inverter circuit 2 has a maximum first harmonic component (frequency 21 kHz) in the second load coil 4 and its frequency is constant. In the case of supplying the high-frequency current of
A frequency higher than Hz (in the embodiment, the lower limit is 52.5 kHz, which is 2.5 times 21 kHz), is varied with the frequency whose lower limit is the frequency of the third harmonic component, and a high frequency is applied to the first load coil 3. Since the current is supplied, the third harmonic component of the high frequency current is the second harmonic component (42 kHz) of the high frequency current supplied by the second inverter circuit 2.
And the third-order harmonic component (63 kHz) causes a frequency difference in the audible range, and although an interference sound is generated, since the magnitude of the latter frequency component is sufficiently smaller than that of the former,
A load that is induction-heated in the inverter circuit 1 of
It is possible to reduce the sound pressure of the interfering sound generated between the inverter circuit 2 and the load that is induction-heated.

In addition, the first and second inverter circuits 1,
If the load material to be heated of No. 2 is not a material having low resistance and low magnetic permeability, the first and second inverter circuits 1 and 2 are connected to the corresponding first and second load coils 3 and 4, respectively. Since the high-frequency current whose magnitude of the first-order harmonic component (frequency 21 kHz) is maximum is supplied, no interference sound is generated when the first and second inverter circuits 1 and 2 operate simultaneously.
In this case, one of the inverter circuits changes the conduction time ratio and the drive frequency of the corresponding switching means to change the magnitude and frequency of the high frequency current supplied to the corresponding load coil to change the induction heating output to the load. If so, the other inverter circuit also follows this and changes the conduction time ratio and drive frequency of the corresponding switching means to change the magnitude and frequency of the high-frequency current supplied to the corresponding load coil. Vary the induction heating output to the load.

Further, if it is inconvenient to change the other induction heating output by doing so, each inverter circuit has a corresponding load coil regardless of the material and shape of the load and the size of the induction heating output. This can be easily avoided by changing the induction heating output to the load to be heated by keeping the frequency of the high frequency current constant and changing only the conduction time ratio of each switching means at 21 kHz fixed in this embodiment. At the same time, the simple control of changing only the conduction time ratio of the switching means can be easily realized by a program programmed in an integrated circuit such as a microcomputer, so that the device can be downsized and the cost can be reduced. In the cooling fan drive means 100, based on the detection result of the load detection means 6, both the first inverter circuit 1 and the second inverter circuit 2 perform a heating operation by using a material having low resistance and low magnetic permeability as a heating target. If not, the rotation speed of the cooling fan is set to a low speed to reduce the air volume, which is the ability to blow the air. Cooling fan drive means 100
On the basis of the detection result of the load detection means 6, only one of the first inverter circuit 1 and the second inverter circuit 2 performs heating operation with a low resistance and low magnetic permeability material as a heating target. If the cooling fan is rotating, the rotation speed of the cooling fan is set to a medium speed, and the air volume, which is the ability to blow the cooling fan, is set to a medium. Further, in the cooling fan driving means 100, both the first inverter circuit 1 and the second inverter circuit 2 are heating based on the detection result of the load detecting means 6, and the load material to be heated is the load material. If the material has a low resistance and a low magnetic permeability, the rotation speed of the cooling fan is set to a high speed to increase the air volume, which is the ability to blow the air.

The induction heating cooker of the embodiment has a heating output of 4
It has an operating unit that can be switched in stages (minimum output level 1 to maximum output level 4). Cooling fan drive means 10
0 means that the air volume of the cooling fan can be switched in five stages (minimum air volume level 1 to maximum air volume level 5). If neither the first inverter circuit 1 nor the second inverter circuit 2 is heating a low resistance, low magnetic permeability material based on the detection result of the load detection means 6, the inverter At the output level 1, the cooling fan drive means 100 sets the air volume of the cooling fan to the air volume level 1, and at the output levels 2 to 4, sets the air volume of the cooling fan to the air volume level 2. Based on the detection result of the load detection means 6, the first
In the case where only one of the inverter circuit 1 or the second inverter circuit 2 of No. 1 is heating for a material having a low resistance and a low magnetic permeability, the cooling is performed at the output levels 1 and 2 of the inverter. The fan drive unit 100 sets the air volume of the cooling fan to the air volume level 3, and sets the air volume of the cooling fan to the air volume level 4 at the output levels 3 and 4. Based on the detection result of the load detection means 6, both the first inverter circuit 1 and the second inverter circuit 2 are heating, and the load material to be heated is a material having low resistance and low magnetic permeability. In the case of the output levels 1 to 3 of the inverter, the cooling fan driving means 100 sets the air volume of the cooling fan to the air volume level 4, and at the output level 4, the air volume of the cooling fan is the air volume level 5.
And As described above, in the induction heating cooker according to the embodiment, the changing condition of the air volume is optimally changed according to the combination of the driving conditions of the plurality of inverters.

Generally, when the frequency of the high-frequency current increases, the electrical or thermal stress of the power components such as the load coil and the switching element forming the inverter circuit and the wiring connecting them increases, but the specified materials are excluded. Since it is possible to reduce the electrical or thermal stress of the power components such as the load coil and the switching element forming the inverter circuit when heating the load, or the wiring connecting them, as described above, the load detection means 6 detects the load. According to the result, the cooling fan driving means 100 enhances the cooling capacity of the cooling fan when the frequency of the high frequency current increases, and conversely, cooling in the case of a load other than a predetermined material in which the frequency of the high frequency current does not increase. The wind noise of the cooling fan can be suppressed by reducing the air volume of the fan. In the above example, the cooling fan drive means 100 determines the air volume of the cooling fan based on the detection result of the load detection means 6, but the first inverter circuit 1 or the second inverter circuit 2 heats the predetermined material. The method of obtaining the information as to whether or not the object is operating is not limited to the detection result of the load detection means 6, and it can be identified by using the input setting information of the user, the output information of another detection circuit, or the like. You can

Further, in the present embodiment, when the load materials of the first and second inverter circuits 1 and 2 are simultaneously heated to have a low resistance and a low magnetic permeability, one of the inverter circuits has a high frequency. As the heating operation, the conduction time ratio and drive frequency of the corresponding switching means (22 k in this embodiment).
If the induction heating output to the load is varied by varying the magnitude of the high frequency current supplied to the corresponding load coil and the frequency of the maximum third harmonic component, The other inverter circuit also follows the high frequency heating operation to change the conduction time ratio of the corresponding switching means and the drive frequency (about 22 kHz in this embodiment) to increase the magnitude of the high frequency current supplied to the corresponding load coil. And the frequency of the maximum third harmonic component is varied to vary the induction heating output to the load. Also, if there is a problem in that the other induction heating output changes by doing so, each inverter circuit has a high-frequency current of the corresponding load coil regardless of the load material, shape, and induction heating output size. In this embodiment, the frequency of the third harmonic component is kept constant, and in this embodiment, the induction heating output to the load to be heated is changed by fixing only 66 kHz and changing only the conduction time ratio of each switching means. This can be avoided, or it is possible to prevent the occurrence of interference sound by preventing a plurality of high-frequency operations from being performed at the same time by not operating the inverter circuit that was intended to be operated later in time series. At this time, in the present embodiment, when one of the first or second inverter circuits 1 and 2 is performing high-frequency heating operation in the notification means 9, the load to be heated by the other inverter circuit is predetermined. If the material, aluminum or the like is used, the user is informed that the inverter circuit whose heating target is this load does not operate, so that the user can take measures without confusion.

Further, generally, when the frequency at which the magnitude of the harmonic component of the high frequency current becomes large increases, the power components such as the load coil and the switching element which constitute the inverter circuit and the electrical or heat of the wiring connecting them. Dynamic stress increases, and the harmonic component that maximizes the emitted noise level is in the high frequency band, so it is necessary to enhance the EMC performance as well, but it is necessary to perform high frequency heating operation with a load other than a predetermined material. If not, select another inverter circuit to perform normal heating operation, or perform high-frequency heating operation for a specific inverter circuit. Reduces electrical or thermal stress in power components such as load coils and switching elements that make up inverter circuits, or in the wiring that connects them. Kill to the cooling capacity improvement measures limited inverter circuit, it is only subjected to EMC strengthening measures, it is possible to suppress the cost, size of the apparatus by these measures.

Although the present embodiment has been described as having a configuration including two inverter circuits, the same applies to a configuration having three or more inverter circuits. For example, one inverter circuit operates by high frequency heating operation and the remaining two inverter circuits operate. When one inverter circuit is operating normally, the other two inverter circuits are operating in high frequency heating. The inverter circuit outputs the induction heating output of the load to be heated to the frequency of the third harmonic component of the high frequency current. If the control is made variable, the frequency of the first-order harmonic component of the high-frequency current supplied by itself can be changed to change the frequency of the third-order harmonic component. Alternatively, the remaining two inverter circuits that are normally heating are operating at a constant frequency regardless of the load material, shape, and induction heating output (the frequency of the first harmonic component is 21 k
The frequency of the third harmonic component of the high-frequency current supplied to the corresponding load coil by the inverter circuit operating at a fixed frequency (Hz) and operating at a high frequency is doubled from 21 kHz to 42
By changing the frequency higher than kHz as the lower limit (in the embodiment, the lower limit is 52.5 kHz, which is 2.5 times 21 kHz), and controlling the induction heating output thereof, it becomes 3
Even if two inverter circuits operate simultaneously, it is possible to induction heat a load made of a material having low resistance and low magnetic permeability while reducing interference noise.

In this embodiment, each inverter circuit is described as including two switching means.
As long as a desired high frequency current can be supplied to the corresponding load coil, the same effect can be obtained no matter how many load coils are included. Further, in the high-frequency heating operation, the case where the magnitude of the third-order harmonic component is maximum has been described. Is obtained.

21 kHz third harmonic component and 66 kHz
Since the power level of the former is small with respect to the frequency of z, the interference sound cannot be heard by the user. In the present embodiment, when the load detecting means 6 determines that the load material to be heated is a material having a low resistance and a low magnetic permeability such as aluminum, a high frequency current is supplied as a high frequency heating operation to the corresponding load coil. The frequency is set to 66 kHz, which is three times that of the normal heating operation. Instead of this, for example, in 2.
In the case where the load coil is supplied with a high frequency current of 52.5 kHz which is five times higher, this high frequency current is the high frequency current (fundamental wave 21) supplied by another inverter circuit.
second harmonic component (42 kHz) and third
Frequency difference with 1st harmonic component (63kHz) is 10.5kHz
However, the magnitude of the frequency component of the latter is sufficiently smaller than that of the former, and the sound pressure of the interference sound is reduced.

The load detecting means determines that
Although it is explained that it is the material, not only the material,
The shape, size, etc. may be selected as necessary.

Further, the frequencies when the respective inverter circuits are supplying the high frequency currents of the same frequency to the corresponding load coils do not have to be completely the same, as long as they are differences in the range of variations such as circuit constants. no problem.

Although the predetermined material has been described as aluminum, the resistivity is about 50 × 10 −8 Ωm or less, and the relative permeability is 1
The same effect can be obtained even if the material is a multi-layer pan or the multi-layer pan contains this material in a configuration mainly affecting induction heating.

Example 2 An induction heating cooker according to Example 2 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the induction heating cooker of the second embodiment. FIG. 1 has already been described. FIG. 8 is a diagram showing the circuit configuration of the inverter circuit of the second embodiment. The present embodiment differs from the configuration of the first embodiment in that the first smoothing capacitor 71 and the choke coil 72 are arranged between the power supply 51 and the rectifier circuit 52.

The operation of this embodiment will be described. Reference numeral 50 denotes an inverter, and the operation of the control circuit 63 is turned on alternately to secure the required input power for the second switching element 55 and the first switching element 57 as in the first embodiment.
Turn off. At this time, the second switching element 55
When the switch is turned on, in the first embodiment, a current flows through the load coil 59, and a part of the current is regenerated from the choke coil 72 to the first smoothing capacitor 71.
Therefore, by adopting the configuration of this embodiment, the rectifier circuit 5
Since 2 works so as to block the regenerative current, the current is not regenerated in the first smoothing capacitor 71, and the input power can be transmitted to the load coil 59 and the pan 61.
Since a high frequency current passes through the diode used in the rectifier circuit 52, a high speed diode is desirable.

As described above, according to the present embodiment, since the current is not regenerated in the first smoothing capacitor 71, the input power is supplied to the circuit without waste, so that the aluminum pan can be efficiently heated. It is possible to realize an induction heating cooker.

Example 3 Example 3 of the induction heating cooker of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the induction heating cooker according to the third embodiment. FIG. 1 has already been described. FIG. 9 is a diagram showing the circuit configuration of the inverter circuit according to the third embodiment. The power supply 51 is a commercial power supply, is rectified by the rectification circuit 52, and is applied to the series circuit of the choke coil 80 and the transistor 87 (switching element). The collector of the transistor 87 is connected to the anode of the diode 82, and the cathode of the diode 82 is connected to the high potential side of the smoothing capacitor 81. The low potential side of the smoothing capacitor 81 is connected to the negative side of the rectifier circuit 52.

Reference numeral 79 is an inverter, and the series connection body of the choke coil 83 and the transistor 88 is connected to both ends of the smoothing capacitor 81. A series connection body of the load coil 89 and the resonance capacitor 91 is connected to both ends of the transistor 88, and a series connection body of the resonance capacitor 92 and the relay 93 is connected to the resonance capacitor 91 in parallel. Control circuit 85
Loads the detection signal from the current transformer 67 that detects the input current from the power supply 51 and the current transformer 94 that detects the current in the load coil 89 while driving the transistor 88, and determines the material of the load pan 90. Have a function. Then, the control circuit 85, in accordance with the detection result of the load detection function, the boost control circuit 86, the relay 93,
And outputs a control signal or a drive signal to the transistor 88. The boost control circuit 86 outputs a drive signal for the transistor 87 based on the control signal from the control circuit 85.

The operation of the above configuration will be described. The control circuit 85 controls on / off of the transistor 87 so that the choke coil 80 functions as a step-up chopper. As a result, the output Vdc of the rectifier circuit 52 is boosted and a smoothed voltage is applied across the smoothing capacitor 81 via the diode 82. This smoothed voltage acts as a supply source for supplying the high frequency current of the inverter. The choke coil 83 is connected to the positive electrode of the rectifier circuit 52, and is used to perform zero current switching when the transistor 88 is turned off.

The transistor 88 has a diode 8
4 are connected in anti-parallel and are used to circulate the resonant current when it flows in the opposite direction of transistor 88. The transistor 88 generates a resonance current that resonates at a resonance frequency determined by the load coil 89 and the resonance capacitor 91 when in the ON state, and supplies a high frequency magnetic field to the pan 90.

The control circuit 85 uses a microcomputer or the like to control the transistor 88 according to the input power. When the control circuit 85 determines that the pot 90 heated by the load coil 89 by the load detection function is made of a material such as aluminum having high conductivity and low permeability, the relay 93 is used.
11 is performed with the drive control as shown in FIG. 10 performed with the power off, and when it is determined that the pan 90 is an iron-based pan, the relay 93 is turned on and the capacity of the resonance capacitor 91 is increased. The maximum output is obtained by performing such drive control.

FIG. 10 is a diagram showing waveforms at various points in this embodiment. A waveform (a) shows a current waveform Ic flowing through the transistor 88 and the diode 84, and a waveform (b) shows a voltage Vce generated between the collector and the emitter of the transistor 88.
The waveform (c) shows the current IL flowing in the load coil 89.
The waveform (d) shows the drive waveform VGE given to the transistor 88 by the control circuit 85.

The control circuit 85 supplies a gate signal to the transistor 88 to make the transistor 88 conductive. At this time, the resonance current generated in the load coil 89 and the resonance capacitor 91 flows through the transistor 88. Here, since the frequency of the resonance current is more than twice as high as the drive frequency, the resonance current eventually becomes zero, and this time the diode 84
Through, the current will flow in the opposite direction. During this time, the resonance current continues to flow in the load coil 89, so that the pan 90 is supplied with the high-frequency magnetic field determined by the resonance frequency determination. That is, the same effect as in the case of driving at a frequency twice or more the normal frequency can be obtained.

Then, after supplying the necessary power, the control circuit 85 turns off the transistor 88 at the timing when the current is flowing through the diode 84, and after a certain period of time shifts to the on state again, and this is repeated.

As shown in FIG. 11, when the material is an iron-based pot, the driving period (T ') of the transistor 88 is the same as the inductance of the load coil 89 and the capacitance of the resonance capacitor 91, and the capacitance of the resonance capacitor 92. The sum of the resonance period (T ₂ ') and the rest period (T ₁ ') determined by the added capacitance is the frequency (1 /
T ') is usually set to 20 to 30 kHz.

On the other hand, when the control circuit 85 determines that the pot 90 is made of a material such as aluminum, the resonance capacitor 92 is not added, the resonance frequency is increased, and the transistor 86 and the choke coil 80 are used. Increase boost level.

This is because the oscillation of Ic in FIG. 10A is not reduced by the attenuation so that the resonance current as shown in FIG. 10 is generated during the driving period (T) of the transistor 88 when the maximum output is set. Is continued at a predetermined amplitude or more for the required wave number, and the rest period T ₂ is shortened to obtain the maximum output.

At this time, the load coil 8 combined with the pan 90
The resonance frequency determined by the inductance of 9 and the capacitance of the resonance capacitor 91 is the operating frequency of the transistor 88 (1 /
T ') is twice or more, that is, a constant such that two or more resonance currents flow in one switching operation.
This is intended to generate heat by using the characteristic 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. This makes it possible to heat aluminum pans and multi-layer pans in this way.

As described above, according to the present embodiment, when the load 90 having high conductivity and low magnetic permeability is heated by the magnetic field generated by the load coil 89, the resonance current flowing through the switching element 88 and the diode 84 is switched. A choke coil 80, a switching element 87, a diode 82, and a booster, which is a booster for boosting the DC voltage Vdc so that the resonance current resonates in a cycle shorter than the drive period of the element 88 and the resonance current continues for the drive period, and the booster. Smoothing capacitor 8 which is a smoothing means for smoothing the voltage boosted by the means.
By providing 1, the resonance current can be zero-current switched, the drive frequency of the switching element 88 can be lower than the resonance frequency, and the zero-current switching can be performed to reduce the switching loss. , It is possible to prevent the noise of the pot and heat the aluminum pot.

The following induction heating cooker is included in the present application. That is, a rectifier circuit connected in parallel to a power source, a first smoothing capacitor connected in parallel to a DC output end of the rectifier circuit, and one end of which is connected to the positive electrode side of the DC output end of the rectifier circuit. A choke coil, and a first one whose emitter is connected to the other end of the choke coil
In parallel with the first semiconductor switching element, and the second semiconductor switching element whose collector is connected to the other end of the choke coil and whose emitter is connected to the negative electrode side of the DC end. A first coil connected, a second diode connected in parallel with the second semiconductor switching element, and a load coil connected in parallel with the second semiconductor switching element and connected in series with each other. And a resonance capacitor series circuit, a second smoothing capacitor connected to the collector of the first semiconductor switching element and the emitter of the second semiconductor switching element, and the first and the second smoothing capacitors so as to obtain a predetermined output. An induction heating cooker comprising: a control unit that controls the second semiconductor switching element;
Is included.

Further, a filter capacitor connected in parallel to the power supply, a choke coil connected in series to the power supply, a rectifier circuit connected to the choke coil, and a DC output end of the rectifier circuit on the positive electrode side. A first semiconductor switching element having its emitter connected, and a second semiconductor switching element having its collector connected to the positive electrode side of the DC output end of the rectifier circuit and its emitter connected to the negative electrode side of the DC end. A first diode connected in parallel to the first semiconductor switching element, a second diode connected in parallel to the second semiconductor switching element, and a second diode connected in parallel to the second semiconductor switching element. The series connection of the load coil and the resonance capacitor series circuit, and the core of the first semiconductor switching element. And a second smoothing capacitor connected to the emitter of the second semiconductor switching element, and control means for controlling the first and second semiconductor switching elements so as to obtain a predetermined output. A heating cooker is included.

In the induction heating cooker of the above embodiment, the third harmonic component of the oscillation frequency is maximized during the high frequency heating operation (when heating a load having high conductivity and low magnetic permeability such as aluminum). The following high-frequency current was applied to the load coil. Instead of this, during the high frequency heating operation, a high frequency current having a frequency (for example, a fundamental frequency of 50 kHz) higher than the frequency (for example, 20 kHz) during the normal heating operation (when heating the iron-based load or the non-magnetic stainless steel load) is used. You may make it the structure which flows into a load coil. For example, Japanese Patent Publication No. 2-37076 discloses an induction heating cooker (inverter circuit) in which a high-frequency current having a basic frequency of 50 kHz is passed through a load coil during high-frequency heating operation. In an induction heating cooker having a plurality of such inverter circuits, one inverter is 5
When a high frequency current of 0 kHz is applied to the load coil,
Other inverters are prohibited from passing a high frequency current of 50 kHz through the load coil. Or other inverter is 50kH
No function for high-power heating with z is provided. This allows
It is possible to prevent the occurrence of interference sound. Alternatively, the air volume of the cooling fan or the change condition of the air volume is changed depending on whether each of the plurality of inverters is in the normal heating operation or the high frequency heating operation. As a result, noise and wind noise of the cooling fan can be reduced without unnecessarily increasing the air volume of the cooling fan.

[0127]

According to the first aspect of the present invention, one inverter circuit supplies the corresponding load coil with a high-frequency current having a frequency twice or more the high-frequency current supplied by the other inverter circuit to the corresponding load coil. The induction heating output is controlled by varying the frequency of the high-frequency current during operation, so that it is possible to suppress the generation of switching loss and noise during switching, and to control the load between induction heating of other inverter circuits. It is possible to reduce the sound pressure of the interference sound generated at.

According to the second aspect of the invention, the noise and wind noise of the cooling fan can be reduced without unnecessarily increasing the air volume of the cooling fan to operate it.

According to the third aspect of the present invention, by discriminating the material of the load to be heated, the high frequency current supplied to the corresponding load coil by another inverter circuit can be selectively applied to the desired load. It is possible to supply high-frequency current of more than twice the frequency to the corresponding load coil, and connect power components such as load coils and switching elements that compose an inverter circuit when heating loads other than specified materials. Since it is possible to reduce the electrical or thermal stress of the wiring, the air volume of the cooling fan at this time can be reduced and the wind noise of the cooling fan can be suppressed.

According to the fourth aspect of the present invention, the noise and wind noise of the cooling fan can be reduced without unnecessarily increasing the air volume of the cooling fan to operate it.

According to the fifth aspect of the present invention, an inverter circuit supplying a corresponding load coil with a high frequency current having a frequency of at least twice the high frequency current supplied to the corresponding load coil by another inverter circuit, The frequency or magnitude of the high-frequency current supplied to the corresponding load coil can be controlled by varying the conduction time of the switching means or the drive cycle, and can be easily realized by a program programmed in an integrated circuit such as a microcomputer. It is possible to reduce the size and cost.

According to the sixth aspect of the invention, when the load to be heated is made of a material other than a predetermined material, even if a plurality of inverter circuits operate simultaneously, high frequency currents having substantially the same frequency are applied to the corresponding load coils. Since they are supplied, no interference sound is generated between the loads that are induction-heated in them.

According to the invention described in claim 7, when the load to be heated is other than a predetermined material, even if a plurality of inverter circuits operate simultaneously, the high frequency current frequency supplied by each inverter circuit is the material of the load. , The interference sound is not generated because it is constant regardless of the shape, size, and induction heating output.

According to the eighth aspect of the present invention, when the load to be heated is made of a material other than a predetermined material, the inverter circuit determines the frequency or the magnitude of the high frequency current supplied to the corresponding load coil to determine the conduction time of the switching means. Since it can be controlled by changing it, and can be easily realized by a program programmed in an integrated circuit such as a microcomputer, the size and cost of the device can be reduced.

According to the ninth aspect of the present invention, the interference noise caused by the plurality of inverter circuits simultaneously supplying a high frequency current having a frequency twice or more the high frequency current supplied by the other inverter circuit to the corresponding load coil. The chance of occurrence of can be eliminated.

According to the tenth aspect of the invention, the user can be made aware that he is trying to operate a plurality of inverter circuits with a load of a predetermined material, and the user can deal with it without confusion. .

According to the eleventh aspect of the invention, the specific inverter circuit has a higher harmonic component than the first harmonic component in the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil. When supplying a high-frequency current in which at least one of the wave components becomes large, the sound pressure level of the interference sound caused by the operation of another inverter circuit can be suppressed, and the specific inverter circuit has a low resistance and a low magnetic permeability. Induction heating can be performed even with a material load, and only limited inverter circuit cooling capacity improvement measures and EMC strengthening measures need to be taken, and these measures can reduce costs and increase the size of equipment. it can.

According to the twelfth aspect of the present invention, the frequency of the higher harmonic component higher than the first harmonic component of the high frequency current supplied by the specific inverter circuit and another inverter circuit are By making the difference from the frequency of the first harmonic component of the supplied high-frequency current larger than the audible range, the frequency component in which the magnitude of the harmonic component of the high-frequency current supplied to the corresponding load coil is maximum. It is possible to prevent the interference sound in the audible range from being generated by each other.

According to the thirteenth aspect of the present invention, by discriminating the material of the load to be heated, the high frequency current supplied to the corresponding load coil by the predetermined inverter circuit selectively with respect to the desired load. In the magnitude of the harmonic component of
It is possible to supply a high frequency current in which at least one of higher harmonic components higher than the first harmonic component is large,
It is possible to reduce the electrical or thermal stress of load coils, switching elements, and other power components that make up the inverter circuit when heating loads other than specified materials, or the wiring that connects these components. The wind noise of the cooling fan can be suppressed by reducing the air volume.

According to the fourteenth aspect of the present invention, an inverter circuit has a higher harmonic component than the first harmonic component in the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil. Even when controlling the induction heating output by varying the frequency of the high-frequency current when supplying a high-frequency current in which at least one of the components is large, the induction heating output is connected to the load being induction-heated in another inverter circuit. The sound pressure of the generated interference sound can be reduced.

According to the fifteenth aspect of the invention, in the magnitude of the harmonic component of the high frequency current supplied to the corresponding load coil, at least one higher harmonic component than the first harmonic component is present. An inverter circuit supplying a large high frequency current changes the magnitude or frequency of the maximum harmonic component of the high frequency current supplied to the corresponding load coil, the conduction time of the switching means or the drive cycle. Therefore, it can be controlled and can be easily realized by a program programmed in an integrated circuit such as a microcomputer, so that downsizing and cost reduction of the device can be achieved.

According to the sixteenth aspect of the present invention, when the load to be heated is made of a material other than a predetermined material, even if a plurality of inverter circuits operate simultaneously, the first harmonic component is maximized and the frequency thereof is substantially the same. Since the same high-frequency current is supplied to the corresponding load coils, no interference sound is generated between the loads that are induction-heated in these coils.

According to the seventeenth aspect of the present invention, when the load to be heated is made of a material other than a predetermined material, even if a plurality of inverter circuits operate simultaneously, the first harmonics of the high frequency current supplied by each inverter circuit. Since the frequency of the wave component is constant regardless of the material, shape, size of the load and the induction heating output, no interference sound is generated.

According to the eighteenth aspect of the present invention, when the load to be heated is made of a material other than a predetermined material, the inverter circuit causes the frequency or magnitude of the first harmonic component of the high frequency current supplied to the corresponding load coil. Can be controlled by changing the conduction time of the switching means, and can be easily realized by a program programmed in an integrated circuit such as a microcomputer, so that downsizing and cost reduction of the device can be achieved.

According to the nineteenth aspect of the present invention, the plurality of inverter circuits simultaneously have higher harmonic components than the first harmonic component in the magnitude of the harmonic components of the high frequency current supplied to the corresponding load coils. It is possible to eliminate an opportunity to generate an interference sound by supplying a high-frequency current in which at least one of the harmonic components is large while varying the frequency of the first-order harmonic component.

According to the twentieth aspect of the present invention, the user can be made aware that he or she is trying to operate a plurality of inverter circuits with a load of a predetermined material, and the user can take measures without confusion. .

According to the twenty-first aspect of the invention, the driving frequency of the switching element is lowered to suppress the switching loss of the switching element, and the resonance current having a frequency higher than the driving frequency of the switching element is supplied to the load coil. It is possible to realize an induction heating cooker that heats a high-conductivity and low-permeability load such as aluminum and aluminum with high output.

According to the twenty-second aspect of the present invention, the present invention has a plurality of switching elements as compared with a switching element having a single switching element, so that the duty is reduced and the driving time ratio is changed or the driving frequency is changed. By changing the value, it is possible to realize an induction heating cooker capable of finely controlling the output according to the load.

According to the twenty-third aspect of the present invention, it is possible to suppress mutual interference sounds and to suppress the occurrence of loss and noise when varying the heating output of a load having high conductivity and low magnetic permeability. Becomes

According to the twenty-fourth aspect of the present invention, when a high conductivity and low magnetic permeability load and an iron-based or non-magnetic stainless steel load are simultaneously heated, and an iron-based load and a stainless steel-based load are simultaneously heated. In any case of heating, it is possible to suppress the generation of interference sound due to the frequency difference of mutual magnetic fields and vary the heating output.

According to the twenty-fifth to twenty-seventh aspects of the present invention, at least one higher harmonic component than the first higher harmonic component is included.
In addition to providing a large inverter circuit, the drive frequency of the switching element is lowered to suppress the switching loss of the switching element, and the load coil is supplied with a resonance current having a frequency higher than the drive frequency of the switching element. And the like, it is possible to realize an induction heating cooker that heats a load having high conductivity and low magnetic permeability with high output.

According to the twenty-eighth aspect of the present invention, it is possible to operate by increasing the air flow of the cooling fan unnecessarily.
The noise and wind noise of the cooling fan can be reduced.
As described above, according to the present invention, it is possible to heat an aluminum pot with a high heating efficiency by supplying a current with a small amplitude change to a load coil to reduce a noise of a pot noise and a loss of a switching element. An induction heating cooker can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an induction heating cooker according to first to third embodiments of the present invention.

FIG. 2 is a diagram showing a circuit configuration of the induction heating cooker according to the first embodiment of the present invention.

FIG. 3 is a waveform chart showing the operation of each part of the induction heating cooker according to the first embodiment of the present invention.

FIG. 4 is another waveform diagram showing the operation of each part of the induction heating cooker according to the first embodiment of the present invention.

FIG. 5 is a diagram showing input power control characteristics of the induction heating cooker according to the first embodiment of the present invention.

FIG. 6 is a frequency spectrum diagram at the time of normal heating operation of the high frequency current supplied by the load coil by the inverter circuit of the induction heating cooker according to the first embodiment of the present invention.

FIG. 7 is a frequency spectrum diagram during high frequency heating operation of the high frequency current supplied from the load coil by the inverter circuit of the induction heating cooker according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a circuit configuration of an induction heating cooker according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a circuit configuration of an induction heating cooker according to a third embodiment of the present invention.

FIG. 10 is a waveform diagram showing the operation of each part of the induction heating cooker according to the third embodiment of the present invention.

FIG. 11 is another waveform diagram showing the operation of each part of the induction heating cooker according to the third embodiment of the present invention.

FIG. 12 is a block diagram showing the configuration of a conventional induction heating cooker.

FIG. 13 is a waveform diagram showing the operation of each part of the conventional induction heating cooker.

[Explanation of symbols]

1 First inverter circuit 2 Second inverter circuit 3 First load coil 4 Second load coil 6 Load detection means 7 Input detection means 8 Input current control means 9 Notification means 50, 79 inverter 51 AC power supply 52 Rectifier circuit 53 First Smoothing Capacitor 54, 72, 80, 83 Choke coil 55 Second switching element 56 Second diode (second reverse conducting element) 57 First switching element 58 First diode (first reverse conducting element) 59, 89 load coil 60, 91 Resonant capacitor 61 pan (load) 62 Second smoothing capacitor (smoothing means) 63 control circuit 65,92 Correction resonance capacitor 71 First Smoothing Capacitor 81 Smoothing capacitor 84 Diode (rectifying element) 85 Control circuit 87, 88 switching element 90 pans (load) 100 cooling fan drive means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 6/12 323 H05B 6/12 323 327 327 (72) Inventor Takahiro Miyauchi 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Atsushi Fujita 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Koji Niiyama, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) ) Inventor Takeshi Kitazumi 1006, Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 3K051 AA02 AA03 AA06 AA07 AA08 AB04 AB10 AB14 AC07 AC12 AC23 AC52 AC53 AD23 CD02 CD23 CD23

Claims (28)

[Claims] 1. A plurality of inverter circuits including a load coil for converting direct current into high frequency alternating current and supplying a high frequency current in an audible range or more to the load coil, wherein at least one of the plurality of inverter circuits comprises: The corresponding load coil is supplied with a high-frequency current having a frequency that is at least twice as high as the high-frequency current supplied to the corresponding load coil by the other inverter circuit, and the other inverter circuit corresponds to the high-frequency current. Input detection means for detecting an input current of the first inverter circuit supplying a high frequency current that is at least twice the frequency of the high frequency current supplied to the load coil, and a load coil corresponding to the output of the input detection means. And an input current control means for controlling the input current of the first inverter circuit so that the frequency of the high frequency current supplied to the circuit is varied so as to obtain a predetermined input. An induction heating cooker provided. 2. A cooling fan capable of cooling the first inverter circuit or another inverter circuit and having a variable air flow rate, and having a frequency equal to or more than twice the frequency of the high frequency current supplied to the corresponding load coil by the other inverter circuit. The air volume of the cooling fan depending on the combination of the case where the high frequency current is supplied by the first inverter circuit and the case where the high frequency current is supplied to the corresponding load coil by the other inverter circuit. Alternatively, the induction heating cooker according to claim 1, wherein the changing condition of the air volume is changed. 3. At least one of a plurality of sets of inverter circuits
On the other hand, a load detection means for determining the material of the load to be heated is provided, and if the load material determined by the load detection means is a predetermined material, the inverter circuit for which this load is to be heated is 2. A high-frequency current, which is at least twice the frequency of the high-frequency current supplied to the corresponding load coil by the inverter circuit, is supplied to the corresponding load coil.
Or the induction heating cooker according to 2. 4. A cooling fan capable of cooling the first inverter circuit and changing the air volume is provided, and a high-frequency current that is at least twice the frequency of the high-frequency current supplied to the corresponding load coil by another inverter circuit is supplied to the first inverter circuit. 1 is supplied by the inverter circuit and 2 by the frequency of the high frequency current supplied to the load coil corresponding to the other inverter circuit.
The induction heating cooker according to claim 1 or 3, wherein the air flow rate of the cooling fan or the changing condition of the air flow rate is changed when the first inverter circuit supplies a high frequency current that is lower than twice the high frequency current. 5. The first inverter circuit has a switching means, and the input current control means varies a conduction time or a driving cycle of the corresponding switching means in accordance with an output of the input detection means so that a predetermined input is provided. The induction heating cooker according to claim 1, wherein the input current of the first inverter circuit is controlled so that the above. 6. All the inverter circuits when one of the plurality of sets of inverter circuits does not supply a high frequency current having a frequency twice or more the high frequency current supplied to the corresponding load coil by another inverter circuit. A high-frequency current of substantially the same frequency is supplied to the corresponding load coil.
The induction heating cooker according to any one of 5. 7. An inverter circuit in which all of the inverter circuits supply high-frequency current of a constant frequency to corresponding load coils.
Or the induction heating cooker according to 6. 8. The other inverter circuit has a switching means, and the other inverter circuit supplies a high frequency current by varying the conduction time of the switching means with a constant drive frequency. The induction heating cooker described. 9. One of the high-frequency currents supplied from one inverter circuit to the corresponding load coil of the other inverter circuit.
When supplying a high-frequency current having a frequency more than double to the corresponding load coil, if the load to be heated of another inverter circuit is a predetermined material, the inverter circuit to be heated by this load will not operate. The induction heating cooker according to any one of 3 to 8. 10. A notification means is provided, wherein the notification means is such that a load to be heated by another inverter circuit is a predetermined material,
The induction heating cooker according to claim 9, which informs that the other inverter circuit is not operated. 11. A plurality of sets having a configuration including an inverter circuit including a load coil and supplying a high-frequency current to the load coil, wherein a predetermined inverter circuit in the configuration is provided with a high-frequency current supplied to the corresponding load coil. As needed, a high-frequency current in which at least one of the higher-order harmonic components is greater than the first-order harmonic component in the magnitude of the higher-order harmonic component is supplied as necessary, and the other inverter circuit is configured to supply the corresponding load to the corresponding load. An induction heating cooker that supplies a high-frequency current that maximizes the first-order harmonic component in the magnitude of the harmonic component of the high-frequency current supplied to the coil. 12. A frequency of a higher harmonic component higher than a first harmonic component of a high frequency current supplied by a predetermined inverter circuit, and a first harmonic of a high frequency current supplied by another inverter circuit. The induction heating cooker according to claim 11, wherein the difference from the frequency of the harmonic component is larger than the audible range. 13. A load detecting means for determining a material of a load to be heated for a predetermined inverter circuit,
If the load material discriminated by the load detection means is a predetermined material, the predetermined inverter circuit outputs a higher harmonic component of the high frequency current supplied to the corresponding load coil than the first harmonic component thereof. The induction heating cooker according to claim 11 or 12, wherein at least one of the higher harmonic components is supplied with a high frequency current. 14. An input detecting means for detecting an input current of a predetermined inverter circuit, and a frequency or magnitude of a first harmonic component of a high frequency current supplied to a corresponding load coil according to an output of the input detecting means. And input current control means for controlling the input current of the predetermined inverter circuit so as to obtain a predetermined input.
The induction heating cooker according to any one of 1. 15. The predetermined inverter circuit has a switching means, and the input current control means changes the conduction time or the drive cycle of the switching means according to the output of the input detection means so that the predetermined input is obtained. 15. The induction heating cooker according to claim 14, wherein the input current of the predetermined inverter circuit is controlled to the above. 16. A magnitude of a harmonic component of a high frequency current supplied to a corresponding load coil by a predetermined inverter circuit is such that at least one of the higher harmonic components is higher than the first harmonic component. 16. When not supplying the high frequency current which becomes, all the inverter circuits supply the corresponding load coil with the maximum first harmonic component and supply the high frequency current having substantially the same frequency. The induction heating cooker according to any one of 1. 17. The induction heating cooker according to claim 15 or 16, wherein all the inverter circuits supply corresponding load coils with a constant high frequency current having substantially the same first harmonic component frequency. 18. The inverter circuit according to claim 17, wherein each of the other inverter circuits has a switching means, and the other inverter circuit supplies a high frequency current with a constant drive frequency of the switching means and a variable conduction time thereof. The induction heating cooker described. 19. The magnitude of a harmonic component of a high frequency current supplied to a corresponding load coil by a predetermined inverter circuit is such that at least one of the higher harmonic components is higher than the first harmonic component. When a high-frequency current is supplied while varying the frequency of the first-order harmonic component, if the load to be heated by another inverter circuit is of a specified material, the inverter circuit that heats this load will operate. The induction heating cooker according to any one of claims 13 to 18, which is not provided. 20. A notification means is provided, wherein the notification means uses a predetermined material as a load to be heated by another inverter circuit,
20. The induction heating cooker according to claim 19, which informs that the other inverter circuit is not operated. 21. A predetermined inverter circuit has a switching element, a reverse conducting element connected in parallel with the switching element, a load coil, and a resonance capacitor, and a DC voltage is input to conduct the switching element. A resonance circuit is generated by the load coil, and a control circuit for controlling the conduction period of the switching element is provided, and when the magnetic field generated by the load coil induces heating of a load having high conductivity and low magnetic permeability, the switching is performed. The resonance current flowing through the element or the reverse conducting element resonates in a cycle shorter than the driving period of the switching element, and the DC voltage is used to maintain the resonance current at a predetermined amplitude or more during the driving period. And boosted and smoothed by the boosting smoothing means and supplied to the inverter circuit. The induction heating cooker according to any one of 0. 22. The predetermined inverter circuit includes a series connection body of a first switching element on the low potential side and a second switching element on the high potential side, and a first connection element connected in parallel to the first switching element. A reverse conducting element, and a second reverse conducting element connected in parallel to the second switching element,
A resonance circuit including a resonance coil and a load coil connected in parallel to the first switching element or the second switching element, and a direct current voltage is input between both ends of the series connection body; While resonating due to conduction between the switching element and the second switching element,
A control circuit for exclusively controlling conduction between the first switching element and the second switching element;
Of the switching element or the first reverse conducting element has a cycle shorter than the driving period of the first switching element when the magnetic field generated by the load coil inductively heats a load having high conductivity and low magnetic permeability. 12. The direct current voltage is boosted and smoothed by a boosting smoothing means so as to maintain resonance at an amplitude equal to or larger than a predetermined magnitude during the driving period while being resonated with the direct current voltage and supplied to the inverter circuit. An induction heating cooker according to any one of 20 to 20. 23. A plurality of inverter circuits each including a load coil for supplying a high frequency current to the load coil, and a predetermined load coil among the plurality of load coils heat a load having high conductivity and low magnetic permeability. In this case, the maximum order of the frequency components of the current flowing through the predetermined load coil is the frequency of the current flowing through the other load coil when the iron-based or non-magnetic stainless steel-based load is heated by the other load coil. In order to make the order higher than the maximum order of the components, the inverter circuit to which each load coil belongs is operated, and the load coil current flowing in the load coil that heats the load having high conductivity and low magnetic permeability. An induction heating cooker in which the heating output is changed by changing the frequency. 24. The heating output is varied while keeping the frequency of the current flowing through the other load coil substantially constant.
Induction heating cooker according to. 25. The step-up smoothing means includes a series connection body of a choke coil and a third switching element connected to a DC power supply input terminal pair, and a smoothing capacitor serving as a power supply of high frequency current, and the third switching device. During the conduction period of the element, magnetic energy is accumulated in the choke coil,
22. The induction heating cooker according to claim 21, wherein the choke coil radiates magnetic energy to the smoothing capacitor via a diode during a cutoff period of the switching element. 26. The step-up smoothing means includes a second smoothing capacitor connected in parallel to the series connection body of a first switching element and a second switching element, and a choke connected in series to the first switching element. A coil, and stores energy in the choke coil by conduction of the first switching element.
23. The induction heating cooker according to claim 22, wherein the energy is transferred to the second smoothing capacitor via the second reverse conducting element by shutting off the switching element of. 27. A predetermined inverter circuit drives the first switching element and the second switching element substantially equally when the magnetic field generated by the load coil heats a load having high conductivity and low magnetic permeability. Driving in the period, the first
The resonance current flowing through the switching element and the first reverse conducting element resonates in a cycle of approximately 2/3 times the driving period, and the first switching element has The heating output is changed by changing the driving period and changing the frequency of the load coil current so that the driving of the first switching element is stopped when the current of the first switching element is zero or more after the second cycle. 27. The induction heating cooker according to claim 22 or 26. 28. A cooling fan capable of cooling a predetermined inverter circuit and changing the air volume is provided, and the predetermined inverter circuit supplies a corresponding load coil with a higher harmonic component than a first harmonic component. The air volume of the cooling fan when at least one of the high frequency currents is large and when the predetermined inverter circuit or another inverter circuit is supplying the high frequency current having the maximum first harmonic component. Or the induction heating cooker according to any one of claims 11 to 27, wherein the change condition of the air volume is changed.