JPH11329698A - Resonance preventing device for electromagnetic induction heater cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device, outputting desired power and capable of preventing a resonance phenomenon of a heated container even if the characteristic frequency of the heated pot agrees with the oscillation frequency of an inverter circuit, by solving an existing problem that a resonance phenomenon of a heated container arises when the characteristic frequency of the heated container agrees with the oscillation frequency of an inverter circuit in the event of fructuation of power or variation of an alternating-current power supply. SOLUTION: This resonance preventing device is mainly composed of a control circuit 10 for controlling an inverter circuit 9, a detection circuit 11 for detecting the oscillation frequency of the inverter circuit 9, a memory circuit 12 having stored the characteristic frequency of a heated container 8, a comparison circuit 13 for comparing the characteristic frequency of the heated container 8 with the oscillation frequency of the inverter circuit 9, and an adjusting circuit 14 for adjusting the control circuit 10 based on a result of the comparison circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing resonance of an electromagnetic induction heating cooker.

[0002]

2. Description of the Related Art A circuit configuration of a conventional electromagnetic induction heating system will be described with reference to FIG. In FIG. 4, 101 is an AC power supply, and 102 is a rectifier. The inverter circuit 103 is connected to the output of the rectifier 102. The inverter circuit 103 includes a smoothing capacitor 104, a resonance capacitor 105, a switching element 106, and a heating coil 107 connected in parallel to the resonance capacitor 105. A heating container 108 is provided near the heating coil 107, and the heating coil 107 is heated by electromagnetic induction by supplying a high-frequency current to the heating coil 107. The control circuit 109 is connected to the switching element 106.

The control circuit 109 includes a switching element 1
An on-time setting circuit 111 for setting an on-time of 06;
An on-time switching unit 112 for switching the on-time of the switching element 106 is provided, and the input power at the time of keeping the temperature is controlled by the on-time switching unit 112. With this configuration, when the temperature is kept warm, the oscillation frequency of the inverter circuit 103 is constant with respect to the voltage fluctuation of the AC power supply 101, and the design for shifting the natural frequency of the container 108 to be heated and the oscillation frequency of the inverter circuit 103 is facilitated. ing.

[0004]

However, in the above-mentioned conventional configuration, the natural frequency of the inverter circuit does not match the natural frequency of the container to be heated when the power is changed other than the heat retention or when the AC power source fluctuates. Sometimes, when the natural frequency of the inverter circuit coincides with the natural frequency of the heated container, a resonance phenomenon of the heated container occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to prevent the resonance phenomenon of the container to be heated even when the power is changed other than the heat retention or when the AC power supply is changed.

[0006]

SUMMARY OF THE INVENTION In order to solve this problem, a resonance preventing device for an electromagnetic induction heating cooker according to the present invention is provided.
A heated container installed in the main body, a heating coil provided in the main body, an inverter circuit for supplying a high-frequency current to the heating coil, a control circuit for controlling the inverter circuit, and an oscillation frequency of the inverter circuit And a storage circuit that stores the natural frequency of the container to be heated in advance, and a comparison circuit that compares the oscillation frequency detected by the detection circuit with the natural frequency stored in the storage circuit. And an apparatus having an adjustment circuit for adjusting the oscillation frequency of the inverter circuit based on the result of the comparison circuit so as not to match the natural frequency of the heated container stored in the storage circuit. .

According to the configuration of the present invention, when the oscillation frequency of the inverter circuit fluctuates due to the variable power or the fluctuation of the AC power supply when heating the container to be heated by electromagnetic induction, the oscillation frequency of the inverter circuit at that time is detected. The circuit detects and compares the natural frequency of the container to be heated, which is stored in advance, with the detected oscillation frequency of the inverter circuit by the comparison circuit. If the two coincide, the adjustment circuit increases the oscillation frequency of the inverter circuit by heating. By adjusting so as not to match the natural frequency of the container, a device that does not resonate the heated container can be obtained.

Further, the temperature of the heated container is measured by a temperature sensor, and the natural frequency of the heated container stored in the storage circuit is corrected by the temperature correction circuit. An apparatus that does not resonate the container to be heated with higher accuracy than in the case where there is no correction by the temperature sensor corresponding to the change in the number can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a heating container provided in a main body, a heating coil provided in the main body, and an inverter for supplying a high-frequency current to the heating coil. A circuit, a control circuit for controlling the inverter circuit, a detection circuit for detecting an oscillation frequency of the inverter circuit, a storage circuit for storing a natural frequency of the container to be heated in advance, and a detection circuit for detecting the oscillation frequency. A comparison circuit that compares the oscillation frequency with the natural frequency stored in the storage circuit; and a natural frequency of the heated container in which the oscillation frequency of the inverter circuit is stored in the storage circuit based on a result of the comparison circuit. This is a device that is configured with an adjustment circuit that adjusts so that it does not match the frequency. When the oscillation frequency of the inverter circuit matches the natural frequency of the heated container when outputting power, the adjustment is performed. The circuit outputs higher power than the target power, then outputs lower power than the target power, and repeats this operation to generate the target power on average, and the oscillation frequency of the inverter circuit. And the eigenfrequency of the heated container can be made not to coincide with each other, and the resonance phenomenon of the heated container can be prevented.

According to a second aspect of the present invention, there is provided a heating container provided in a main body, a heating coil provided in the main body, an inverter circuit for supplying a high-frequency current to the heating coil, A control circuit that controls an inverter circuit, a detection circuit that detects an oscillation frequency of the inverter circuit, a storage circuit that stores a natural frequency of the container to be heated in advance, an oscillation frequency detected by the detection circuit, A comparison circuit that compares the natural frequency stored in the storage circuit, a temperature sensor that detects the temperature of the container to be heated, and a natural frequency stored in the storage circuit based on the temperature detected by the temperature sensor. A correction circuit that corrects the oscillation frequency of the inverter circuit based on a result of the comparison circuit so that the oscillation frequency does not match a natural frequency of the heated container stored in the storage circuit. This device is composed of an adjustment circuit for adjusting the temperature of the heated container and correcting the natural frequency of the heated container with a temperature sensor and a temperature correction circuit to prevent the resonance phenomenon of the heated container even when the temperature of the heated container changes. Has the effect of being able to

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a basic circuit diagram of an electromagnetic induction heating cooker according to Embodiment 1 of the present invention. In FIG. 1, 1 is an AC power supply, 2 is a rectifier, 3 is a choke coil,
4 is a smoothing capacitor, 5 is a heating coil, 6 is a resonance capacitor, 7 is a switching element, 8 is a container to be heated, 9
Is an inverter circuit, 10 is a control circuit, 11 is a detection circuit,
12 is a storage circuit, 13 is a comparison circuit, and 14 is an adjustment circuit. The inverter circuit 9 includes a choke coil 3, a smoothing capacitor 4, a heating coil 5, a resonance capacitor 6, and a switching element 7.

The operation of the embodiment will be described below with reference to FIGS. When the container 8 to be heated is subjected to electromagnetic induction heating with electric power P1, the ON time of the switching element 7 is controlled by the control circuit 10, and the container 8 to be heated is heated by an alternating magnetic field generated by a high-frequency current supplied to the heating coil 5. I do. At this time, the oscillation frequency of the inverter circuit 9 is detected by the detection circuit 11 and compared with the natural frequency of the container 8 to be heated previously stored in the storage circuit 12 using the comparison circuit 13. The circuit 9 maintains the oscillation. If the comparison results in a match, the adjusting circuit 14 adjusts the on-time of the switching element 7 so that the natural frequency of the container 8 to be heated does not match the oscillation frequency of the inverter circuit 9.

As shown in FIG. 2, the adjusting method is as follows.
(P1 <P2), and then P3 (P1> P
The power of 3) is generated. At this time, the power of each of P2 and P3 is set so that the natural frequency of the oscillation frequency of the heated container 8 and the inverter circuit 9 does not match, and the time for generating P2 and P3 is adjusted to output P1 on average. The device obtained in this way can generate the indicated power P1 on average, and can prevent the resonance phenomenon because the natural frequency of the container 8 to be heated does not match the oscillation frequency of the inverter circuit 9. Effects can be obtained.

If the natural frequencies of the plurality of containers 8 to be heated are stored in advance, the same effect can be obtained by using a plurality of containers 8 to be heated.

Further, when incorporating in a device that does not require the accuracy with respect to the indicated power P1, the power P2 (P1 <P2) or P3 (P1 <P3) that does not make the natural frequency of the heated container 8 coincide with the oscillation frequency of the inverter circuit 9 The same effect can be obtained by setting the power of the device.

When a plurality of multiple values of the natural frequency of the container 8 to be heated are stored in the storage circuit 12, the oscillation frequency of the inverter circuit 9 matches the multiple of the natural frequency of the container 8 to be heated. Then, the effect of suppressing the occurrence of the resonance phenomenon can be obtained.

(Embodiment 2) FIG. 3 is a basic circuit diagram of electromagnetic induction heating according to Embodiment 2 of the present invention. In FIG. 3, reference numeral 15 denotes a temperature sensor, and 16 denotes a temperature correction circuit. Otherwise, follow FIG.

The operation of the embodiment will be described below with reference to FIG. A temperature sensor 15 and a temperature correction circuit 16 are added to the first embodiment. The temperature of the heated container 8 is measured by the temperature sensor 15, the temperature change of the natural frequency of the heated container 8 is corrected by the temperature correction circuit 16, and the natural frequency of the heated container 8 after the temperature change is stored in advance. Circuit 1
2 and the oscillation frequency of the inverter circuit 9 is controlled so that the natural frequency of the heated container 8 does not match the temperature change of the heated container 8. This has the advantageous effect that the resonance phenomenon can be prevented.

If the natural frequencies of the plurality of containers 8 to be heated are stored in advance, the same effect can be obtained by using a plurality of containers 8 to be heated.

Further, when incorporating into a device that does not require the accuracy with respect to the indicated power P1, the power P2 (P1 <P2) or P3 (P1 <P3) that does not make the natural frequency of the heated container 8 coincide with the oscillation frequency of the inverter circuit 9 The same effect can be obtained by setting the power of the device.

When a plurality of multiple values of the natural frequency of the container 8 to be heated are stored in the storage circuit 12, the oscillation frequency of the inverter circuit 9 matches the multiple of the natural frequency of the container 8 to be heated. Then, the effect of suppressing the occurrence of the resonance phenomenon can be obtained.

[0022]

As described above, the resonance preventing apparatus for an electromagnetic induction heating cooker according to the present invention controls the resonance frequency of the heated container by controlling the natural frequency of the heated container and the oscillation frequency of the inverter circuit so as not to coincide with each other. And the desired power can be output.

Further, according to the present invention, even when the natural frequency of the heated container changes due to a temperature change, control is performed so that the natural frequency of the heated container does not coincide with the oscillation frequency of the inverter circuit. It can prevent the resonance phenomenon of the container,
In addition, an advantageous effect that a desired power can be output can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an inverter circuit according to a first embodiment of the present invention and a device for preventing resonance of an electromagnetic induction heating cooker using the inverter circuit.

FIG. 2 is a diagram showing generation of inverter power for preventing resonance according to the first embodiment;

FIG. 3 is a configuration diagram showing a resonance prevention device for an electromagnetic induction heating cooker in which a temperature sensor and a temperature correction circuit are added to Embodiment 2 of the present invention.

FIG. 4 is a configuration diagram showing a conventional inverter circuit and a resonance preventing device for an electromagnetic induction heating cooker using the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier 3 Choke coil 4 Smoothing capacitor 5 Heating coil 6 Resonant capacitor 7 Switching element 8 Heated container 9 Inverter circuit 10 Control circuit 11 Detection circuit 12 Storage circuit 13 Comparison circuit 14 Adjustment circuit 15 Temperature sensor 16 Temperature correction circuit

Claims (2)

[Claims] A heating container provided in the main body, a heating coil provided in the main body, an inverter circuit for supplying a high-frequency current to the heating coil, a control circuit for controlling the inverter circuit, A detection circuit for detecting the oscillation frequency of the inverter circuit, a storage circuit in which the natural frequency of the container to be heated is stored in advance, and the oscillation frequency detected by the detection circuit and the natural frequency stored in the storage circuit. An electromagnetic induction having a comparison circuit for comparison and an adjustment circuit for adjusting the oscillation frequency of the inverter circuit based on the result of the comparison circuit so as not to match the natural frequency of the container to be heated stored in the storage circuit. Resonance prevention device of cooking device. 2. A container to be heated installed in a main body, a heating coil provided in the main body, an inverter circuit for supplying a high-frequency current to the heating coil, a control circuit for controlling the inverter circuit, A detection circuit for detecting the oscillation frequency of the inverter circuit, a storage circuit in which the natural frequency of the container to be heated is stored in advance, and the oscillation frequency detected by the detection circuit and the natural frequency stored in the storage circuit. A comparison circuit for comparing, a temperature sensor for detecting the temperature of the container to be heated, a correction circuit for correcting the natural frequency stored in the storage circuit based on the temperature detected by the temperature sensor, and a correction circuit for the comparison circuit. An electromagnetic induction device having an adjustment circuit for adjusting the oscillation frequency of the inverter circuit based on the result so as not to match the natural frequency of the heated container stored in the storage circuit. Resonance prevention device for induction heating cooker.