JP2000243544A - Induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the manufacturing cost simplifying the structure by supplying power from an inverter circuit with time division to two or more heating coils provided inside two or more resonance circuit to heat an object. SOLUTION: A high frequency inverter circuit 10 controls transition of frequency of the gate driving signal of transistors TrA, TrB from the start frequency to the operating frequency while using a voltage controlled oscillator 12. Output control of the power from the high frequency inverter circuit 10 is performed by the frequency transition control, and power is supplied to a first resonance circuit 100 or a second resonance circuit 102 each other with time division. With this structure, a first heating coil L1 and a second heating coil L2 carry a current, and the object is heated by the first heating coil L1 and the second heating coil L2. Since the power is supplied to the first resonance circuit 100 and the second resonance circuit 102 by a pair of transistors TrA, TrB, generation of wrong operation of the circuit due to the interference can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device, and more particularly to an induction heating device having two or more heating coils which are energized alternately.

[0002]

2. Description of the Related Art Conventionally, various induction heating devices have been proposed. As one type of such induction heating devices, an induction heating device having two or more heating coils that are energized alternately is known. .

In the induction heating apparatus having two or more heating coils which are energized alternately, for example, two heating coils are arranged in a double winding of an inner side and an outer side. It is applied to an electromagnetic cooker or the like which heats cooking utensils such as pots and pots as objects to be heated by alternately energizing two provided heating coils (Japanese Patent Application Laid-Open No. 8-78148). reference).

FIG. 1 is a main circuit diagram showing an example of an induction heating device having two heating coils which are alternately energized as described above. This induction heating device is energized alternately. As two heating coils, a first heating coil L1
And a second heating coil L2.

[0005] The first heating coil L1 and the first capacitor C1 together form a first resonance circuit 100,
The second heating coil L2, together with the second condenser C2,
The resonance circuit 102 is configured.

Further, power is supplied to the first resonance circuit 100 and the second resonance circuit 102 from the commercial power supply 200 via the high-frequency inverter circuit 104 connected to the AC commercial power supply 200.

Here, the above-described high-frequency inverter circuit 1
04 is a forward converter 106, capacitors C3 and C4,
A pair of transistors Tr1-1 and Tr1-2 for supplying power to the first resonance circuit 100;
2 for supplying power to the second transistor Tr2-
1 and Tr2-2.

In the above configuration, the transistors Tr1-1 and Tr1-2 of the high-frequency inverter circuit 104 and the transistors Tr2-1 and Tr2-2 are alternately driven, so that the transistors Tr1-1 and Tr1-2 are driven. When the power is supplied, power is supplied to the first resonance circuit 100, the object to be heated is heated by the first heating coil L1, and when the transistors Tr2-1 and Tr2-2 are driven, power is supplied to the second resonance circuit 102. The supplied second heating coil L
2, the object to be heated is heated.

However, in the above-described induction heating apparatus, electric power is supplied to the first resonance circuit 100 and the second resonance circuit 102 in order to alternately energize the first heating coil L1 and the second heating coil L2. In the high frequency inverter circuit 104 for performing the operation, the transistors Tr1 and Tr2 corresponding to the first resonance circuit 100 and the second resonance circuit 102, respectively.
-1, Tr1-2 and transistors Tr2-1, Tr2-
However, there is a problem that the configuration is complicated and the manufacturing cost is high.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a simple configuration, which has two objects as in the prior art. The above-mentioned heating coils are alternately energized,
An object of the present invention is to provide an induction heating device which can alternately heat an object to be heated by one or more heating coils, thereby simplifying the configuration and reducing the manufacturing cost.

[0011]

In order to achieve the above object, an induction heating apparatus according to the present invention sets the resonance frequencies of two or more resonance circuits each having a heating coil to be different from each other. By driving the inverter circuit at the resonance frequency of the resonance circuit having the heating coil to which power is to be supplied, power is alternately supplied from the inverter circuit to two or more resonance circuits in the same manner as in the related art. The above-described heating coils are alternately energized, and the object to be heated can be alternately heated by the two or more heating coils.

In order to drive the inverter circuit at the resonance frequency of a resonance circuit having a heating coil to which power is to be supplied, the pair of transistors may be gate-driven at the resonance frequency.

That is, the invention according to claim 1 of the present invention is an induction heating apparatus for supplying power to a heating coil provided in a resonance circuit to heat an object to be heated, and is connected to a power supply. An induction heating device having an inverter circuit and two or more resonance circuits connected in parallel to the inverter circuit, each set to a different resonance frequency, and each provided with a heating coil, wherein the inverter circuit is Driving means for driving the two or more resonance circuits in a time-division manner at frequencies corresponding to different resonance frequencies, wherein the inverter circuit is driven by the driving means to different resonance frequencies of the two or more resonance circuits. By being driven in a time-division manner at the corresponding frequency, power is supplied from the inverter circuit to the two or more resonance circuits in a time-division manner, Division in which the power to the heating coil provided respectively on the power supplied the two or more resonant circuit was adapted to heat the heating object by supplying at.

According to a second aspect of the present invention, in the first aspect of the present invention, the driving means includes a voltage-controlled oscillator, and the inverter circuit includes a voltage-controlled oscillator. The voltage control oscillator controls a frequency shift from a start frequency near the resonance frequency of the resonance circuit to an operating frequency, and controls the power output by the frequency shift.

According to a third aspect of the present invention, in the first aspect of the present invention, the inverter circuit is configured to reduce a starting frequency by a separately excited frequency near a resonance frequency of the resonance circuit. This is a self-excited inverter circuit that switches to self-excited oscillation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an induction heating apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an essential part of an embodiment of an induction heating apparatus according to the present invention, as described above, which is an example of an induction heating apparatus having two heating coils which are energized alternately as described above. A circuit diagram is shown.

In FIG. 2, components that are the same as or correspond to those in FIG. 1 are given the same reference numerals as in FIG.

The induction heating apparatus shown in FIG. 2 includes a first heating coil L1 and a second heating coil L2 as two heating coils which are alternately energized.

The first heating coil L1 and the first capacitor C1 together form a first resonance circuit 100.
The second heating coil L2, together with the second condenser C2,
The resonance circuit 102 is configured.

Further, electric power is supplied to the first resonance circuit 100 and the second resonance circuit 102 from the commercial power supply 200 via the high-frequency inverter circuit 10 connected to the AC commercial power supply 200.

The first resonance circuit 100 and the second resonance circuit 102 are connected in parallel to the high-frequency inverter circuit 10.

The high-frequency inverter circuit 10 described above
Is a forward converter 106, capacitors C3 and C4, and a first
The circuit includes a pair of transistors TrA and TrB for supplying power to the resonance circuit 100 and the second resonance circuit 102, and a voltage controlled oscillator (VCO) 12.

Here, assuming that the resonance frequency of the first resonance circuit 100 is "f1" and the resonance frequency of the second resonance circuit 102 is "f2", the resonance frequency f1 and the resonance frequency f2 are different from each other. As shown in FIG. 3, the frequency of the resonance frequency f2 is set to be higher than the frequency of the resonance frequency f1 so that the two are greatly shifted.

The operation of the induction heating apparatus in the above configuration will be described. The resonance frequency f1 of the first resonance circuit 100 and the resonance frequency f2 of the second resonance circuit 102 are:
It is assumed that the settings are as shown in FIG.

First, when power is to be supplied to the first resonance circuit 100, the transistors TrA and TrB of the high-frequency inverter circuit 10 are
Is gradually lowered from a frequency f1 ′ (start frequency) higher than the resonance frequency f1 so as to match the resonance frequency f1 (operating frequency).

When the frequency of the gate drive signal of the transistors TrA and TrB of the high-frequency inverter circuit 10 matches the resonance frequency f1, the high-frequency inverter circuit 1
0 switches from the starting frequency to the self-excited oscillation, power is supplied from the high-frequency inverter circuit 10 to the first resonance circuit 100, and the first heating coil L1 is energized to heat the object to be heated.

On the other hand, when power is to be supplied to the second resonance circuit 102, the transistors TrA and TrB of the high-frequency inverter circuit 10 are
Is gradually lowered from a frequency f2 '(start frequency) higher than the resonance frequency f2 so as to match the resonance frequency f2 (operation frequency).

When the frequency of the gate drive signal of the transistors TrA and TrB of the high-frequency inverter circuit 10 matches the resonance frequency f2, the high-frequency inverter circuit 1
0 switches from the starting frequency to the self-excited oscillation, power is supplied from the high-frequency inverter circuit 10 to the second resonance circuit 102, and the second heating coil L2 is energized to heat the object to be heated.

That is, the high-frequency inverter circuit 10 controls the shift of the frequency of the gate drive signal of the transistors TrA and TrB from the start frequency to the operating frequency by using the voltage controlled oscillator 12, and the gate drive of the transistors TrA and TrB is controlled. The power output from the high-frequency inverter circuit 10 is controlled by frequency shift control from the start frequency of the signal frequency to the operating frequency, and the first resonance circuit 100 or the second resonance circuit 1 is time-divisionally controlled.
02 will be supplied with power alternately.

As a result, the first heating coil L1 and the second heating coil L2 are energized alternately in a time-sharing manner, and the object to be heated is alternately heated by the first heating coil L1 and the second heating coil L2. It will be heated.

That is, the above-described induction heating device is different from the conventional induction heating device in that a first transistor TrA and a transistor TrB provided in the high-frequency inverter circuit 10 are used for the first heating.
Since power can be alternately supplied to the resonance circuit 100 and the second resonance circuit 102, the first heating coil L1 and the second heating coil L2 can be alternately energized as in the related art by a simple configuration. In addition, the object to be heated can be alternately heated by the two or more heating coils, so that the configuration can be simplified and the manufacturing cost can be reduced.

In the above induction heating apparatus,
By driving a pair of transistors TrA and TrB provided in the high-frequency inverter circuit 10, the first resonance circuit 10
0 and the power is supplied to the second resonance circuit 102,
The circuit is less likely to malfunction due to interference.

In the above embodiment, the case where two heating coils, the first heating coil L1 and the second heating coil L2, are used, but the number of heating coils is not limited to this. Of course, there is no
One or more heating coils may be provided.

In this case, for example, the first heating coil L1
When the third heating coil L3 is provided in addition to the first heating circuit L2 and the third heating circuit L3, the third resonance circuit including the third heating coil L3 is provided together with the first resonance circuit 100 and the second resonance circuit 102. What is necessary is just to connect in parallel with the high frequency inverter circuit 10. Then, the resonance frequency of the third resonance circuit may be set to be different from the resonance frequency f1 of the first resonance circuit 100 and the resonance frequency f2 of the second resonance circuit 102.

In the above-described embodiment, when power is to be supplied to the first resonance circuit 100, a start frequency (frequency f1 ') higher than the resonance frequency f1 is used.
From the start frequency (frequency f2 ') higher than the resonance frequency f2 when power is to be supplied to the second resonance circuit 102, but is not limited to this. Of course, it is not something that can be done.

That is, when power is to be supplied to the first resonance circuit 100, the start frequency of the gate drive signal of the transistors TrA and TrB of the high-frequency inverter circuit 10 is made to match the resonance frequency f2, and gradually from this start frequency. In order to match the resonance frequency f1 and to supply power to the second resonance circuit 102, the start frequency of the gate drive signal of the transistors TrA and TrB of the high-frequency inverter circuit 10 is set to the resonance frequency. The frequency f1 may be matched, and the frequency may be gradually increased from the start frequency to match the resonance frequency f2.

In this way, the switching of the power supply to the first resonance circuit 100 and the second resonance circuit 102 is performed continuously and smoothly.

[0039]

As described above, the present invention is configured as described above, so that a simple configuration alternately energizes two or more heating coils as in the prior art, and alternately energizes the two or more heating coils. Thus, the object to be heated can be heated quickly, and an excellent effect that the structure can be simplified and the manufacturing cost can be reduced can be achieved.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram illustrating an example of an induction heating device including two heating coils that are alternately energized.

FIG. 2 is a main part circuit diagram of an induction heating device provided with two heating coils that are alternately energized, as an example of an embodiment of the induction heating device according to the present invention.

FIG. 3 is a frequency characteristic diagram of a first resonance circuit and a second resonance circuit.

[Explanation of symbols]

10, 104 high frequency inverter circuit 12 voltage controlled oscillator (VCO) 100 first resonance circuit 102 second resonance circuit 106 forward converter 200 commercial power supply L1 first heating coil L2 second heating coil C1 first capacitor C2 second capacitor C3, C4 Capacitor Tr1-1, Tr1-2, Tr2-1, Tr2-2, T
rA, TrB transistor

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[Procedure amendment]

[Submission date] March 2, 1999 (1999.3.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Deleted

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Deleted

Claims (3)

[Claims] 1. An induction heating device for heating an object to be heated by supplying electric power to a heating coil provided in a resonance circuit, wherein an inverter circuit connected to a power supply is connected in parallel to the inverter circuit. An induction heating device having two or more resonance circuits each set to a different resonance frequency and having a heating coil, wherein the inverter circuit has different resonance frequencies of the two or more resonance circuits. A driving unit that is driven in a time-division manner at a frequency corresponding to the above, wherein the inverter circuit is driven by the driving unit in a time-division manner at frequencies corresponding to different resonance frequencies of the two or more resonance circuits, The power is supplied from the inverter circuit to the two or more resonance circuits in a time-division manner, and the two or more resonance circuits are supplied with the power in a time-division manner. A heating coil provided respectively in the oscillating circuit is intended to heat the heating object by the electric power is supplied induction heating device. 2. The induction heating apparatus according to claim 1, wherein the driving unit includes a voltage-controlled oscillator, and the inverter circuit is controlled by the voltage-controlled oscillator from a start frequency near a resonance frequency of the resonance circuit. An induction heating device for controlling a frequency shift to an operating frequency and controlling an output of electric power by the frequency shift. 3. The induction heating device according to claim 1, wherein the inverter circuit is a self-excited inverter circuit that switches from a separately excited starting frequency near a resonance frequency of the resonance circuit to self-excited oscillation.