JP2000091063A - Electromgnetic induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating device aiming at the reduction of the cost of circuit by commonly using an arm formed of plural switching elements, a current detecting unit for heating coil and a resonance capacitor in plural inverter circuits. SOLUTION: A full-bridge type inverter circuit for converting the direct current voltage from a smoothing capacitor 3 to the high frequency voltage is formed of a first arm 15 and a second arm 16. The other full-bridge type inverter circuit is formed of the second arm 16 and a third arm 17. A control circuit 14 is provided to control the drive of each driving circuit so as to commonly use the second arm 16 in both the inverter circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating device capable of heating a plurality of cooking pots by alternately driving a plurality of inverter circuits.

[0002]

2. Description of the Related Art FIG.
No. 87, JP-A-63-45789, JP-A-Hei-8
It is a circuit diagram of the conventional electromagnetic induction heating device assumed from -78148 gazette. In FIG. 10, 1 is a commercial AC power supply, 2 is a rectifier circuit for full-wave rectification of the AC voltage of the commercial AC power supply 1, 3 is a smoothing capacitor for smoothing the full-wave rectified DC voltage obtained from the rectifier circuit 2, and 4 is Switching element 4a
Arm 5 composed of a switching element 4b and a switching element 5b
One full-bridge inverter circuit that converts the DC voltage from the smoothing capacitor 3 into a high-frequency AC voltage by the A-arm 4 and the B-arm 5 is configured as an arm.
Reference numeral 6 denotes a C-arm including a switching element 6a and a switching element 6b, and reference numeral 7 denotes a D-arm including a switching element 7a and a switching element 7b. The other full-bridge inverter circuit that converts the AC voltage is formed.

Reference numeral 8 denotes a first heating coil connected to the A arm 4, 9 denotes a first resonance capacitor connected between the first heating coil 8 and the B arm 5, and 10 denotes a first resonance capacitor connected to the C arm 6. The second heating coil 11 and the second heating coil 10
A second resonance capacitor connected to the arm 7;
Is a drive A circuit for sending a drive signal to the A arm 4 and the B arm 5, 13 is a drive B circuit for sending a drive signal to the C arm 6 and the D arm 7, and 14 is an operation of the drive A circuit 12 and the drive B circuit 13. Control circuit. 50 is a first heating coil current detector interposed between the first heating coil 8 and the first resonance capacitor 9, and 51 is a current detector between the second heating coil 10 and the second resonance capacitor 11. An intervening second heating coil current detector, 52 is a first output measuring circuit for measuring the output of the first heating coil current detector 50, and 53 is an output of the second heating coil current detector 51. Is a second output measurement circuit that measures

Next, the operation of the electromagnetic induction heating device will be described. The AC voltage from the commercial AC power supply 1 is supplied to a rectifier circuit 2
Is converted to a DC voltage via the smoothing capacitor 3.
Then, this DC voltage is converted into a rectangular wave-shaped high frequency voltage by driving one full-bridge type inverter circuit composed of the A arm 4 and the B arm 5, and the high frequency voltage is converted into the first heating coil 8 and the first Applied to the resonance capacitor 9. At the same time, a sinusoidal high-frequency current largely flows through the first heating coil 8 by a resonance circuit formed by the first heating coil 8 and the first resonance capacitor 9. As a result, an induced eddy current flows through one of the heated loads (cooking pan, not shown) magnetically coupled to the first heating coil 8, and is heated by the eddy current loss P (w) generated by the induced eddy current. The load is heated.

At this time, the high-frequency current flowing through the first heating coil 8 is detected by the first heating coil current detector 50, and the detected amount is measured by the first output measuring circuit 52. Then, the first output measurement circuit 52 simultaneously determines the suitability or unsuitability of one of the heated loads magnetically coupled to the first heating coil 8 based on the magnitude of the detected amount.
This is because, for example, when an aluminum pot is used for an electromagnetic induction heating device for an iron pot (a load to be heated), it is possible to prevent an overcurrent from flowing into the inverter circuit and break each switching element.

Also, by driving the other full-bridge type inverter circuit composed of the C arm 6 and the D arm 7,
Second heating coil 10 and second resonance capacitor 11
Is applied with a high-frequency voltage. Then, the other heated load magnetically coupled to the second heating coil 10 is heated by the same operation phenomenon as described above. At this time, the second output measurement circuit 53 performs the second
Of the other heated load magnetically coupled to the heating coil 10 is determined at the same time.

Further, one full-bridge inverter circuit and the other full-bridge inverter circuit are driven in parallel, and the first heating coil 8 and the second heating coil 1 are driven.
In the case where both high-frequency currents are simultaneously passed to 0 to heat both loads to be heated, interference noise is generated due to the difference in operating frequency between the respective full-bridge inverter circuits. This interference sound causes a very strange feeling to humans. For the purpose of solving such a problem of the interference sound, a control means for alternately driving both full-bridge inverter circuits in a time-division manner is provided in advance.

[0008]

As described above, the conventional electromagnetic induction heating apparatus has an independent inverter circuit for supplying high-frequency power to each of a plurality of heating coils, and alternately drives the inverter circuits in a time-division manner. Let me. However, when two full-bridge type inverter circuits are used, eight switching elements are required. When three full-bridge inverter circuits are required, twelve switching elements are required. Has the problem that the cost is high as a whole.

Further, since a current detector is required independently for each heating coil, two current detectors are required when there are two sets of inverter circuits, and three current detectors when three sets of inverter circuits are used.
However, there is a problem in that the number of parts is required and the cost of parts is also increased.

[0010] Further, since a resonance capacitor is independently provided for each heating coil, there is a similar problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. In an electromagnetic induction heating apparatus having a plurality of inverter circuits for alternately supplying a high-frequency current to a plurality of heating coils, an arm is provided. It is an object of the present invention to provide an electromagnetic induction heating induction for reducing the cost of the entire circuit by sharing a current detector for a heating coil, a current detector for a heating coil, and a resonance capacitor among a plurality of inverter circuits. The purpose is.

[0012]

An electromagnetic induction heating apparatus according to the present invention includes a plurality of arms each including at least two switching elements, and a plurality of full-bridge type arms formed by combining two arms. An inverter circuit is provided, a heating circuit and a resonance capacitor connected to each of the full-bridge type inverter circuits are provided as a unit, and a drive circuit for controlling the driving of a switching element provided for each arm is provided. It has a control circuit for driving and controlling the circuits in pairs.

Further, a current detector for the heating coil for detecting a current flowing through the heating coil is provided, and the current detector for the heating coil is shared by each full-bridge inverter circuit.

Further, the resonance capacitor is shared by each full-bridge type inverter circuit.

[0015] The heating coil is formed of a plurality of heating coils wound on the inside and outside, respectively.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram illustrating an embodiment of an electromagnetic induction heating apparatus according to the present invention, that is, a method of operating two heating coils while sharing one arm, and FIG. FIG. 4 shows a timing chart of the operation of the arm. In FIG. 1, the same reference numerals as those in the conventional example indicate the same or corresponding parts. Reference numeral 15 denotes a first arm including a first switching element 15a and a second switching element 15b, 16 denotes a second arm including a third switching element 16a and a fourth switching element 16b, and 17 denotes a fifth arm. And a third arm composed of the switching element 17a and the sixth switching element 17b. First arm 15 and second arm
One full-bridge type inverter circuit for converting the DC voltage from the smoothing capacitor 3 into a high-frequency voltage from the arm 16 of FIG. The other arm is constituted by the second arm 16 and the third arm 17.

Reference numeral 18 denotes a first drive circuit for sending a drive signal to the switching elements 15a and 15b forming the first arm 15, and 19 drives the switching elements 16a and 16b forming the second arm 16. A second drive circuit for sending out a signal, 20 is a fifth switching element 17a and a sixth switching element 17b constituting a third arm 17
Is a third drive circuit that sends a drive signal to the third drive circuit.

Next, the operation of the electromagnetic induction heating device according to the first embodiment will be described with reference to FIGS. FIG.
In the following, a case will be described in which only one heating coil, that is, only the second heating coil 10 is operated. Control circuit 1
4 is the second drive circuit 19 and the third drive circuit 2
0 and control signals having phases opposite to each other are transmitted.
One full-bridge inverter circuit constituted by the arm 16 and the third arm 17 is driven. At this time,
The control circuit 14 stops the operation of the first drive circuit 9a for driving the first arm 15.

Here, the switching elements (switching elements 15a to 17b) constituting the first arm 15, the second arm 16, and the third arm 17 are provided.
FIG. 2 is a timing chart of the ON / OFF operation of FIG.
(A). In FIG. 2A, the first arm 15
Of the switching element 15a and the switching element 15b maintain the off operation. The switching element 16a which is a component of the second arm 16 and the switching element 1 which is a component of the third arm 17
7b repeats the on / off operation in synchronization with each other. At this time, the switching element 16b, which is another component of the second arm 16, and the switching element 17a, which is another component of the third arm 17, are synchronized with each other, and the operation of the switching element 16a and the switching element 16b is performed. The on / off operation is repeated so that the waveform has an opposite phase.

A high frequency voltage is applied to the second heating coil 10 and the second capacitor 11 by a series of on / off operations of the switching elements 16a, 16b, 17a, and 17b. Thereby, the second heating coil 10
, An induced eddy current flows through a heated load (cooking pan, not shown) magnetically coupled to the second heating coil 10. Then, the load to be heated is heated by the eddy current loss P (w) of the induced eddy current as in the conventional example.

Next, a case where both the first heating coil 8 and the second heating coil 10 are operated will be described. The control circuit 14 sends out control signals having opposite phases to the first drive circuit 18 and the second drive circuit 19 for a predetermined period A, respectively, and the control circuit 14 comprises the first arm 15 and the second arm 16. Drive the full-bridge inverter circuit. At this time, the control circuit 14 stops the operation of the third drive circuit 20. Then, immediately after the lapse of the predetermined period A, the control circuit 14 stops the operations of the first drive circuit 18 and the second drive circuit 19 and stops the drive of one of the full-bridge inverter circuits.

Thereafter, the control circuit 14 sends control signals having opposite phases to the second drive circuit 19 and the third drive circuit 20 for a predetermined period B with a time difference, and the second arm 16 and the third The other full-bridge inverter circuit constituted by the arm 17 is driven. At this time, the control circuit 14 stops the operation of the first drive circuit 18. Here, the second arm 16 is shared across one full-bridge inverter circuit and the other full-bridge inverter circuit. Then, immediately after the elapse of the predetermined period B, the control circuit 14 stops the operations of the second drive circuit 19 and the third drive circuit 20, and stops the drive of the other full-bridge inverter circuit. The driving of the one full-bridge inverter circuit and the driving of the other full-bridge inverter circuit are alternately performed in a time-division manner.

Here, the switching elements (switching elements 15a to 17b) constituting the first arm 15, the second arm 16, and the third arm 17 are provided.
FIG. 2 is a timing chart of the ON / OFF operation of FIG.
(B). In FIG. 2B, in a period A in which one of the full-bridge inverter circuits is driven, the switching element 17a and the switching element 17b included in the third arm 17 maintain the OFF operation. The switching element 15b, which is a component of the first arm 15, and the switching element 16a, which is a component of the second arm 16, are turned on / off in synchronization with each other.
Repeat the OFF operation. At this time, the switching element 15a, which is another component of the first arm 15, and the switching element 16b, which is another component of the second arm 16, are synchronized with each other, and the operations of the switching element 15b and the switching element 16a are performed. The on / off operation is repeated so that the waveform has an opposite phase.

The series of on / off operations of the switching element 15a, the switching element 15b, the switching element 16a, and the switching element 16b perform the first operation.
A high-frequency voltage is applied to the heating coil 8 and the first capacitor 9. As a result, a high-frequency current flows through the first heating coil 8, and an induced eddy current flows through one of the loads to be heated that is magnetically coupled to the first heating coil 8. Then, one of the heated loads is heated by the same operation phenomenon as described above.

In the period B in which the other full-bridge type inverter circuit is driven in FIG. 2B, the switching elements 15a and 15b constituting the first arm 15 maintain the OFF operation. The switching element 16a as a component of the second arm 16 and the switching element 17b as a component of the third arm 17 repeat on / off operations in synchronization with each other. At this time, the switching element 16b, which is another component of the second arm 16, and the switching element 17a, which is another component of the third arm 17, are synchronized with each other, and the operation of the switching element 16a and the switching element 17b is performed. The on / off operation is repeated so that the waveform has an opposite phase.

A high frequency voltage is applied to the second heating coil 10 and the second capacitor 11 by a series of on / off operations of the switching elements 16a, 16b, 17a, and 17b. Thereby, the second heating coil 10
, A high-frequency current flows, and an induced eddy current flows to the other heated load magnetically coupled to the second heating coil 10. Then, the other heated load is heated by the same operation phenomenon as described above. Note that the time ratio between the period A and the period B is appropriately determined according to the ratio of the heat capacity (W) of the first heating coil 8 and the second heating coil 10.

FIG. 3 is a plan view showing an example of a spiral heating coil used in the electromagnetic induction heating device of the present invention. In FIG. 3, the spiral inner heating coil (A in FIG. 3) and the spiral outer heating coil (B in FIG. 3) correspond to the first heating coil 8 or the second heating coil, respectively. Equivalent to 10. When heating a heated load having a small bottom area, only the inner heating coil is operated, and when heating a heated load having a large bottom area, the inner heating coil and the outer heating coil are alternately time-divided. Execute the operation. As another example, the first heating coil 8 and the second heating coil 10 are separated from each other,
It is also possible to heat the load to be heated in each case. The same is true for Embodiments 2 to 6 described later.

As described above, in the electromagnetic induction heating apparatus having a plurality of full-bridge type inverter circuits characterized in that high-frequency currents are alternately passed through the two heating coils in a time-division manner, the arm constituting the inverter circuit is provided. Therefore, for example, in the case of the conventional example, eight switching elements are required, whereas in the case of the present invention, the circuit configuration can be realized with six switching elements. Therefore, an electromagnetic induction heating device that has a plurality of heating coils and can reduce the cost as a whole can be obtained.

Embodiment 2 FIG. 4 is a circuit diagram for explaining another embodiment of the electromagnetic induction heating apparatus according to the present invention, that is, a method for operating three heating coils by sharing an arm, and FIG. FIG. 4 shows a timing chart of the operation of the arm. 4, the same reference numerals as those in the conventional example or the first embodiment denote the same or corresponding parts. Reference numeral 21 denotes a seventh switching element 21a and an eighth switching element 21a.
Arm composed of the switching element 21b of FIG.
Reference numeral 2 denotes a fifth arm including a ninth switching element 22a and a tenth switching element 22b, and reference numeral 23 denotes an eleventh switching element.
The sixth arm 24 includes a switching element 23a and a twelfth switching element 23b, and a seventh arm 24 includes a thirteenth switching element 24a and a fourteenth switching element 24b.

The fourth arm 21 and the fifth arm 22 constitute a first full-bridge inverter circuit for converting a DC voltage from the smoothing capacitor 3 to a high-frequency voltage. The fifth arm 22 and the sixth arm 23 constitute a second full-bridge inverter circuit. Further, the sixth arm 23 and the seventh arm 24 constitute a third full-bridge inverter circuit. Reference numeral 25 denotes a third heating coil connected to the sixth arm 23, and reference numeral 26 denotes a third capacitor interposed between the third heating coil 25 and the seventh arm 24.

Reference numeral 27 denotes a fourth drive circuit for sending a drive signal to the switching elements 21a and 21b constituting the fourth arm 21, and reference numeral 28 denotes driving by the switching elements 22a and 22b constituting the fifth arm 22. A fifth drive circuit for transmitting a signal, 29 is a sixth drive circuit for transmitting a drive signal to the switching elements 23a and 23b constituting the sixth arm 23, and 30 is a switching element 24a for constituting the seventh arm 24 and This is a sixth drive circuit that sends a drive signal to the switching element 24b.

The operation of the electromagnetic induction heating apparatus according to the second embodiment will be described with reference to FIGS. FIG.
In this case, the method of operating only one of the three heating coils is the same as in the first embodiment, and a description thereof will not be repeated. Then, a case where all of the first heating coil 8, the second heating coil 10, and the third heating coil 25 are operated will be described. The control circuit 14 sends out control signals having opposite phases to the fourth drive circuit 27 and the fifth drive circuit 28 only for a predetermined period A, and the control circuit 14 includes the fourth arm 21 and the fifth arm 22. One full-bridge inverter circuit is driven. At this time, the control circuit 14 stops the operations of the sixth drive circuit 29 and the seventh drive circuit 30. Then, immediately after the predetermined period A has elapsed, the control circuit 14
The operation of the seventh and fifth drive circuits 28 is stopped, and the driving of the first full-bridge inverter circuit is stopped.

Thereafter, the control circuit 14 sends control signals having opposite phases to the fifth drive circuit 28 and the sixth drive circuit 29 for a predetermined period B with a time difference, and the fifth arm 22 and the sixth The second full-bridge inverter circuit constituted by the arm 23 is driven. At this time, the control circuit 14 stops the operations of the fourth drive circuit 27 and the seventh drive circuit 30. And
Immediately after the predetermined period B has elapsed, the control circuit 14 stops the operation of the fifth drive circuit 28 and the sixth drive circuit 29 and stops the drive of the second full-bridge inverter circuit.

Thereafter, the control circuit 14 sends control signals having opposite phases to the sixth drive circuit 29 and the seventh drive circuit 30 for a predetermined period C with a time difference, and the sixth arm 23 and the seventh The third full-bridge inverter circuit constituted by the arm 24 is driven. At this time, the control circuit 14 controls the fourth drive circuit 27
And the operation of the fifth drive circuit 28 is stopped. Here, the fifth arm 22 is shared across the first full-bridge inverter circuit and the second full-bridge inverter circuit, and the sixth arm 23 is connected to the second full-bridge inverter circuit and the third full-bridge inverter circuit. Is shared across the full-bridge type inverter circuit. Immediately after the elapse of the predetermined period C, the control circuit 14
And the operation of the seventh drive circuit 30 is stopped,
Of the full-bridge inverter circuit is stopped. The driving of the first full-bridge inverter circuit, the second full-bridge inverter circuit, and the third inverter circuit is alternately repeated in a time-division manner.

Here, the on / off operation of each switching element (switching elements 21a to 24b) constituting the fourth arm 21, the fifth arm 22, the sixth arm 23, and the seventh arm 24 is described. This will be described with reference to the timing chart shown in FIG. In FIG. 5, in a period A in which the first full-bridge inverter circuit is driven, switching elements 23a and 23b forming the sixth arm 23, and switching elements 24a and switching elements forming the seventh arm 24 are further illustrated. 24b maintain the off operation. The switching element 21a, which is a component of the fourth arm 21, and the switching element 22b, which is a component of the fifth arm 22, repeat on / off operations in synchronization with each other. At this time, the switching element 21b, which is another component of the fourth arm 21, and the fifth
Switching element 22 which is another component of arm 22 of FIG.
a and the switching element 2
The on / off operation is repeated so that the operation waveforms of 1a and the switching element 22b have opposite phases.

A high-frequency voltage is applied to the first heating coil 8 and the first capacitor 9 by a series of on / off operations of the switching elements 21a, 21b, 22a, and 22b. As a result, a high-frequency current flows through the first heating coil 8, and an induced eddy current flows through a first heated load (not shown) magnetically coupled to the first heating coil 8. Then, the first heated load is heated by the same operation phenomenon as described above.

In the period B in which the second full-bridge inverter circuit is driven in FIG.
1 and the switching element 24a and the switching element 24b that form the seventh arm 24,
The off operation is maintained for each. And the fifth arm 2
Switching element 22b, which is one component of switching arm 2, and switching element 23a, which is one component of sixth arm 23.
Repeat the on / off operation in synchronization with each other. At this time, the switching element 22a, which is another component of the fifth arm 22, and the switching element 23b, which is another component of the sixth arm 23, are synchronized with each other, and the switching element 22b and the switching element 23a
The on / off operation is repeated so that the operation waveform is in the opposite phase.

A high-frequency voltage is applied to the second heating coil 10 and the second capacitor 11 by a series of on / off operations of the switching elements 22a, 22b, 23a, and 23b. Thereby, the second heating coil 10
An induced eddy current flows through a second heated load (not shown) which is magnetically coupled with the first and second heated loads, and the heated load is heated.

In the period C in which the third full-bridge inverter circuit is driven in FIG.
1 and the switching element 22a and the switching element 22b that form the fifth arm 22.
The off operation is maintained for each. And the sixth arm 2
3 and a switching element 24a which is a component of the seventh arm 24.
Repeat the on / off operation in synchronization with each other. At this time, the switching element 23a, which is another component of the sixth arm 23, and the switching element 24b, which is another component of the seventh arm 24, are synchronized with each other, and the switching element 23b and the switching element 24a are synchronized.
The on / off operation is repeated so that the operation waveform is in the opposite phase.

A high-frequency voltage is applied to the third heating coil 25 and the third capacitor 26 by a series of on / off operations of the switching elements 23a, 23b, 24a, and 24b. Thereby, the third heating coil 25
An induced eddy current flows through a third heated load (not shown) that is magnetically coupled to the third heated load, and the heated load is heated. The time ratio of the driving periods A, B, and C is appropriately determined according to the ratio of the heat capacity (W) of each of the first heating coil 8, the second heating coil 10, and the third heating coil 25. I do. In addition to the above-mentioned heating coils being configured independently,
A spiral heating coil may be formed by a plurality of heating coils from the inside to the outside.
This is the same for the third to sixth embodiments described later.

As described above, in the electromagnetic induction heating apparatus having a plurality of full-bridge type inverter circuits characterized in that high-frequency currents are alternately supplied to the three heating coils in a time-division manner, the arms constituting the inverter circuits are provided. Therefore, for example, in the case of the conventional example, twelve switching elements are required, whereas in the case of the present invention, the circuit configuration can be realized with only eight switching elements. Therefore, an electromagnetic induction heating device that has a plurality of heating coils and can reduce the cost as a whole can be obtained.

Embodiment 3 FIG. 6 is a circuit diagram for explaining still another embodiment of the electromagnetic induction heating device having means for operating three heating coils by sharing an arm.
In FIG. 6, the same reference numerals as those in the first or second embodiment denote the same or corresponding parts. Next, the operation of the electromagnetic induction heating device according to the third embodiment will be described.
In FIG. 6, the method of operating only one of the three heating coils is the same as in the first embodiment, and a description thereof will not be repeated.

Next, a case where the first heating coil 8, the second heating coil 10, and the third heating coil 25 are operated will be described. The first full-bridge inverter circuit composed of the fourth arm 21 and the fifth arm 22 is driven for a predetermined time a to operate the first heating coil 8. Thereafter, the method of driving the second full-bridge inverter circuit composed of the fifth arm 22 and the sixth arm 23 with a time difference for a predetermined time b to operate the second heating coil 10 is described in the following. Since it is the same as the second embodiment, the description is omitted here.

A method of operating the third heating coil 25 will be described. The control circuit 14 sends out control signals having opposite phases to the fifth drive circuit 28 and the seventh drive circuit 30 for a predetermined period C, and the control circuit 14 includes the fifth arm 22 and the seventh arm 24. 3 is driven. At this time, the control circuit 14 stops the operations of the fourth drive circuit 27 and the sixth drive circuit 29. Immediately after the elapse of the predetermined period C, the control circuit 14
The operations of the eighth and seventh drive circuits 30 are stopped, and the driving of the third full-bridge inverter circuit is stopped.

Here, the fifth arm 22 is shared by the first full-bridge inverter circuit, the second full-bridge inverter circuit, and the third full-bridge inverter circuit. Such a first full-bridge inverter circuit, a second full-bridge inverter circuit,
By driving the third inverter circuit alternately in a time-sharing manner, the first heating coil 8, the second heating coil 10,
The third heating coils 25 execute the respective operations. Thereby, each heating load magnetically coupled to each heating coil can be heated.

As described above, since the arm constituting the full-bridge type inverter circuit is shared, an electromagnetic induction heating apparatus which has a plurality of heating coils and which can reduce the cost as a whole is provided. Obtainable.

Embodiment 4 FIG. 7 shows still another embodiment of the electromagnetic induction heating apparatus according to the present invention, that is, an arm and a resonance capacitor are shared, and a heating coil current detector and an output measurement circuit are shared to operate two heating coils. FIG. 4 is a circuit diagram illustrating a method for causing the image to be generated. 7, the same reference numerals as those in the conventional example or the first embodiment denote the same or corresponding parts.

The case where both the first heating coil 8 and the second heating coil 10 are operated will be described. The control circuit 14 sends out control signals having opposite phases to the first drive circuit 18 and the third drive circuit 20 for a predetermined period A, respectively, and the control circuit 14 comprises the first arm 15 and the third arm 17. Drive the full-bridge inverter circuit. At this time, the control circuit 14 stops the operation of the second drive circuit 19. This allows
A high-frequency voltage is applied to the first heating coil 8 and the first resonance capacitor 9. Then, the high-frequency current flowing through the first heating coil 8 is detected by the first heating coil current detector 50, and the detected amount is measured by the first output measurement circuit 51. Next, the first output measurement circuit 52 determines whether one of the loads to be heated, which is magnetically coupled to the first heating coil 8, is appropriate or inappropriate.

Next, immediately after the lapse of the predetermined period A, the control circuit 14 stops the operation of the first drive circuit 18 and the third drive circuit 20 and stops the drive of one of the full-bridge inverter circuits. . After this, the control circuit 1
4 sends a control signal having an opposite phase to each of the second drive circuit 19 and the third drive circuit 20 for a predetermined time b with a time difference, and the other is constituted by the second arm 16 and the third arm 17. Drive the full-bridge inverter circuit. At this time, the control circuit 14 stops the operation of the first drive circuit 18. As a result, a high-frequency voltage is applied to the second heating coil 10 and the first resonance capacitor 9. Next, a high-frequency current flowing through the second heating coil 10 is detected by the first heating coil current detector 50, and the detected amount is measured by the first output measurement circuit 52. Then, the first output measurement circuit 52 determines whether the other heated load magnetically coupled to the second heating coil 8 is appropriate or inappropriate. Here, the third arm 17, the first resonance capacitor 9, the first heating coil current detector 50,
The first output measurement circuit 52 is shared by one full-bridge type invar circuit and the other full-bridge type inverter circuit.

Next, immediately after the lapse of the predetermined period B, the control circuit 14 stops the operations of the second drive circuit 19 and the third drive circuit 20, and stops the drive of the other full-bridge inverter circuit. . The driving of the one full-bridge inverter circuit and the driving of the other full-bridge inverter circuit are alternately performed in a time-division manner.

As described above, in the electromagnetic heating device having a plurality of full-bridge type inverter circuits characterized in that a high-frequency current flows alternately in a time-division manner through two heating coils, a part of an arm, a resonance capacitor, Since the current detector for the heating coil and the output measuring circuit are shared, an electromagnetic induction heating device that can reduce the cost as a whole can be obtained in a device provided with a plurality of heating coils.

Embodiment 5 FIG. FIG. 8 is a circuit diagram illustrating a method of operating two heating coils by sharing a resonance capacitor, a heating coil current detector, and an output measurement circuit without sharing an arm. 8, the same reference numerals as those in the conventional example or the first to fourth embodiments indicate the same or corresponding parts. 31 is the fifteenth switching element 31a and the first
An eighth arm composed of six switching elements 31b;
Reference numeral 32 denotes a ninth arm including a seventeenth switching element 32a and an eighteenth switching element 32b. The eighth arm 31 constitutes one half-bridge type inverter circuit for converting the DC voltage from the smoothing capacitor 3 to a high-frequency voltage. The ninth arm 32 forms the other half-bridge type inverter circuit that converts the DC voltage into a high-frequency voltage. Reference numeral 33 denotes an eighth drive circuit for sending a drive signal to the switching elements 31a and 31b constituting the eighth arm 31, and reference numeral 34 sends a drive signal to the switching elements 32a and 32b constituting the ninth arm 32. This is a ninth drive circuit.

The operation of the electromagnetic induction heating device according to the fifth embodiment will be described. In FIG. 8, a case where only the first heating coil 8 is operated will be described. The control circuit 14 sends a control signal to the eighth drive circuit 33, whereby the switching element 31a and the switching element 31b constituting the eighth arm are alternately turned ON / OFF.
The OFF operation is repeated. Switching element 31a is ON
In the state (the switching element 31b is in the OFF state), the DC voltage from the smoothing capacitor 3 is applied to the first heating coil 8 and the first capacitor 9 through the switching element 31a.

When the switching element 31b is ON (the switching element 31a is OFF), the electric charge charged in the first capacitor 9 is discharged to the first heating coil 8 through the switching element 31b. By repeating the charge / discharge operation,
A high-frequency current flows on the first heating coil 8 side. Accordingly, one of the loads to be heated magnetically coupled to the first heating coil 8 is heated by the same operation phenomenon as described above. At the same time, the first heating coil current detector 50 detects the above-described high-frequency current, and measures the detected amount by the first output measurement circuit 52. Then, the first output measuring circuit 52 determines whether one of the loads to be heated is appropriate or inappropriate.

A case will be described in which both the first heating coil 8 and the second heating coil 10 are operated. The control circuit 14 sends a control signal to the eighth drive circuit 33 for a predetermined period A to drive one half-bridge type inverter circuit formed by the eighth arm 31. At this time, the control circuit 14 controls the ninth drive circuit 3
4 is stopped. Then, immediately after the lapse of the predetermined period A, the control circuit 14 stops the operation of the eighth drive circuit 33 and stops the drive of one half-bridge inverter circuit. Here, the operation method of the switching elements 31a and 31b is the same as described above.

Thereafter, the control circuit 14 sends a control signal to the ninth drive circuit 34 for a predetermined period B with a time lag to drive the other half-bridge type inverter circuit constituted by the ninth arm 32. At this time, the control circuit 14 stops the operation of the eighth drive circuit 33. Then, immediately after the predetermined period B has elapsed, the control circuit 14 stops the operation of the ninth drive circuit 34 and stops the drive of the other half-bridge inverter circuit.
Here, the first resonance capacitor 9, the first heating coil current detector 50, and the first output measuring circuit 52 are involved in the first heating coil 8 when one of the half-bridge inverter circuits is driven. When the other half-bridge inverter circuit is driven, the second heating coil 10
Engage with. The operation method of the switching element 32a and the switching element 32b is the same as that of the eighth arm 31.
Is the same as the ON / OFF repetition operation of the switching element 31a and the switching element 31b, and the description is omitted here.

By alternately driving one half-bridge type inverter circuit and the other half-bridge type inverter circuit in a time-sharing manner, a high-frequency current flows through the first heating coil 8 and the second heating coil 10. Flows. As a result, both heated loads that are magnetically coupled to both heating coils are heated by the same operation phenomenon as described above. At the same time, the first heating coil current detector 50
The high-frequency current flowing through the heating coil 8 or the second heating coil 10 is detected, and the first output measurement circuit 52 determines whether the load to be heated is appropriate or inappropriate based on the detected amount.

As described above, when driving both the half-bridge type inverter circuits, the resonance capacitor, the current detector for the heating coil, and the output measurement circuit are shared across both circuits. In an apparatus provided with a heating coil, it is possible to obtain an electromagnetic induction heating apparatus capable of reducing the circuit cost as a whole.

Embodiment 6 FIG. FIG. 9 is a circuit diagram illustrating a method of operating three heating coils by sharing a resonance capacitor, a heating coil current detector, and an output measurement circuit without sharing an arm. In FIG. 9, the same reference numerals as those of the conventional example or the first to fifth embodiments indicate the same or corresponding parts. 35 denotes a nineteenth switching element 35a and a second
And a third half-bridge inverter circuit configured to convert the DC voltage from the smoothing capacitor 3 into a high-frequency voltage by using the tenth arm 35. 36 is the tenth
10 is a tenth drive circuit for sending a drive signal to the switching elements 35a and 35b constituting the arm 35 of FIG.

The operation of the electromagnetic induction heating device according to the sixth embodiment will be described. In FIG. 9, the case where only the first heating coil 8 or both the first heating coil 8 and the second heating coil 10 are operated is the same as in the fifth embodiment, and the description is omitted here.

The case where all of the first heating coil 8, the second heating coil 10, and the third heating coil 25 are operated will be described. The control circuit 14 sends a control signal to the eighth drive circuit 33 for a predetermined period A,
The first half-bridge type inverter circuit constituted by the arm 31 is driven. At this time, the control circuit 14
Of the drive circuit 34 and the tenth drive circuit 36 are stopped. Then, immediately after the elapse of the predetermined period A, the control circuit 14 stops the operation of the eighth drive circuit 33 and stops the drive of the first half-bridge inverter circuit. Thereafter, the control circuit 14 sends a control signal to the ninth drive circuit 34 for a predetermined period B with a time lag to drive the second half-bridge inverter circuit formed by the ninth arm 32. At this time, the control circuit 14 stops the operation of the eighth drive circuit 33 and the tenth drive circuit 36. Then, immediately after the elapse of the predetermined period B, the control circuit 14 stops the operation of the ninth drive circuit 34 and stops the drive of the second half-bridge inverter circuit.

Further, after this, the control circuit 14 sends out a control signal to the tenth drive circuit 36 for a predetermined period C with a time difference, and the third
Drive the half-bridge type inverter circuit. At this time, the control circuit 14 stops the operation of the eighth drive circuit 33 and the ninth drive circuit 34. Then, immediately after the predetermined period C has elapsed, the control circuit 14
The operation of the 0 drive circuit 36 is stopped, and the driving of the third half-bridge inverter circuit is stopped. The operation method of the switching element 35a and the switching element 35b forming the tenth arm 35 is the same as the ON / OFF repetitive operation of each switching element forming the eighth arm 31 and the ninth arm 32. . Here, the first resonance capacitor 9, the first heating coil current detector 50, and the first output measurement circuit 52 are connected to the first heating coil 8 when the first half-bridge inverter circuit is driven. When the second half-bridge inverter circuit is driven, the second heating coil 10 is involved. Further, they are associated with the third heating coil 25 when the third half-bridge inverter circuit is driven.

By driving the first half-bridge inverter circuit to the third half-bridge inverter circuit alternately in a time-sharing manner, the first heating coil 8
A high-frequency current flows through the third heating coil 25. Thus, each heating load magnetically coupled to each heating coil is heated by the same operation phenomenon as described above. At the same time, the first
The heating coil current detector 50 of the first heating coil 8,
The high-frequency current flowing through the second heating coil 10 and the third heating coil 25 is detected, and the first output measurement circuit 52 determines whether the load to be heated is appropriate or inappropriate based on the detected amount.

As described above, when driving each of the half-bridge type inverter circuits, the resonance capacitor, the current detector for the heating coil, and the output measurement circuit are shared across the respective circuits. In the case of the apparatus provided with the coil, it is possible to obtain an electromagnetic induction heating device that can reduce the cost of the circuit as a whole.

[0065]

Since the present invention is configured as described above, it has the following effects.

The electromagnetic induction heating apparatus according to the present invention is provided with a plurality of arms composed of at least two switching elements, a plurality of full-bridge type inverter circuits formed by combining two arms, and A bridge type inverter circuit is provided as one unit, and a heating coil and a resonance capacitor connected to each circuit are provided, and a drive circuit for driving and controlling a switching element provided for each arm is provided. For example, in the case where two sets of full-bridge type inverter circuits are provided, the conventional example requires eight switching elements, whereas the present invention requires only six switching elements. Configuration can be realized. Also,
Where three sets of inverter circuits are used, the conventional example requires 12 switching elements, whereas the present invention can realize a circuit configuration using only eight switching elements.
Therefore, an electromagnetic induction heating device that has a plurality of heating coils and can reduce the cost of the circuit as a whole can be obtained.

Further, a current detector for the heating coil for detecting a current flowing in the heating coil is provided, and the current detector for the heating coil is shared by each full-bridge type inverter circuit. There is no restriction on the number of sets and it can be dealt with by only one. Thus, an electromagnetic induction heating device that can reduce the cost of the current detector can be obtained.

Further, since the resonance capacitor is shared by each full-bridge inverter circuit, the above-mentioned components can be dealt with only by one without being limited by the number of inverter circuit sets. Thus, an electromagnetic induction heating device capable of reducing the cost of the resonance capacitor can be obtained.

Further, since the heating coil is formed from a plurality of heating coils wound on the inner side and the outer side, the heating area is appropriately adjusted according to the size or shape of the cooking pot as the load to be heated. Can be adjusted. Thereby, appropriate cooking can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing Embodiment 1 of an electromagnetic induction heating device according to the present invention.

FIG. 2 is a timing chart showing ON / OFF operations of each switching element included in the inverter circuit in the first embodiment.

FIG. 3 is a plan view of a heating coil applied to the electromagnetic induction heating device of the present invention.

FIG. 4 is a circuit diagram showing an electromagnetic induction heating device according to a second embodiment.

FIG. 5 is a timing chart showing ON / OFF operations of each switching element included in the inverter circuit according to the second embodiment.

FIG. 6 is a circuit diagram showing an electromagnetic induction heating device according to a third embodiment.

FIG. 7 is a circuit diagram showing an electromagnetic induction heating device according to a fourth embodiment.

FIG. 8 is a circuit diagram showing an electromagnetic induction heating device according to a fifth embodiment.

FIG. 9 is a circuit diagram showing an electromagnetic induction heating device according to a sixth embodiment.

FIG. 10 is a circuit diagram showing a conventional electromagnetic induction heating device.

[Explanation of symbols]

1 Commercial AC power supply, 2 Rectifier circuit, 3 Smoothing capacitor, 4 A arm, 5 B arm, 6 C arm, 7 D
Arm, 8 first heating coil, 9 first resonance capacitor, 10 second heating coil, 11 second resonance capacitor, 12 drive A circuit, 13 drive B circuit,
14 control circuit, 15 first arm, 16 second arm, 17 third arm, 18 first drive circuit, 19 second drive circuit, 20 third drive circuit, 21 fourth arm, 22 5th arm, 23 6th arm, 24 7th arm, 25 3rd heating coil, 26 3rd resonance capacitor, 27 4th drive circuit, 28 5th drive circuit, 29 6th drive Circuit, 30 seventh drive circuit, 31 eighth arm, 32 ninth arm, 33 eighth drive circuit, 34 ninth drive circuit, 35 tenth arm, 36 tenth drive circuit, 50 th 1 current detector for heating coil, 51 second current detector for heating coil, 52 first output measurement circuit, 53 second output measurement circuit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Tanaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Tadashi Asano 2-3-2 Marunouchi, Chiyoda-ku, Tokyo 3 F term in Ryo Denki Co., Ltd. (reference)

Claims (4)

[Claims] 1. A plurality of arms each including at least two switching elements, a plurality of full-bridge inverter circuits formed by combining two of the arms, and the full-bridge inverter circuit as one unit. A heating coil and a resonance capacitor connected to each of the circuits, a drive circuit for controlling the driving of switching elements provided for each arm, and a control circuit for controlling the drive of the drive circuits in pairs. An electromagnetic induction heating device, characterized in that: 2. A heating coil current detector for detecting a current flowing through the heating coil, wherein the heating coil current detector is shared by the full-bridge inverter circuits. An electromagnetic induction heating device as described. 3. The electromagnetic induction heating device according to claim 1, wherein the resonance capacitor is shared by the full-bridge inverter circuits. 4. The electromagnetic induction heating apparatus according to claim 1, wherein the heating coil is formed of a plurality of heating coils wound on the inside and outside, respectively.