JP2022034221A - Electromagnetic induction heating device - Google Patents

Abstract

To realize an electromagnetic induction heating device of an inverter system which supplies desired power to heating target objects made of different materials to conduct an induction heating, without using a relay for switching an inverter circuit.SOLUTION: A first upper-lower arm 51 with switching elements 5a and 5b serially connected to each other and a second upper-lower arm 52 with switching elements 5c and 5d serially connected to each other are serially connected to each other between a positive electrode P and a negative electrode N of a DC power source 1 for rectifying an AC voltage supplied from a 200-V commercial AC power supply or from a 100-V commercial AC power supply and outputting a DC voltage.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inverter type electromagnetic induction heating device that supplies desired electric power to an object to be heated, which is a magnetic material or a non-magnetic material, to perform induction heating.

In recent years, an inverter type electromagnetic induction heating device that heats an object to be heated such as a pot without using fire has been widely used. The electromagnetic induction heating device applies a high-frequency current to the heating coil, generates an eddy current in a metal object to be heated (such as a pot) placed close to the heating coil, and generates heat by the electric resistance of the object to be heated. It is a thing. Generally, when the object to be heated is a magnetic material such as iron having a large intrinsic resistance, it is easy to heat, and when the object to be heated is a non-magnetic material such as copper or aluminum having a small intrinsic resistance, it is difficult to heat it.

As a conventional example that can appropriately heat an object to be heated regardless of whether it is a magnetic material or a non-magnetic material, there is an electromagnetic induction heating device disclosed in Patent Document 1. This electromagnetic induction heating device discriminates whether the cooking pot is a magnetic pot or a non-magnetic pot, and switches a relay (FIG. 1, reference numeral 20 in the same document) according to the discriminating result to obtain a circuit system for a high frequency inverter. The half-bridge method is used when heating the non-magnetic pot, and the full-bridge method is used when heating the magnetic pot, and the capacity of the resonance capacitor is also switched at the same time to induce and heat objects to be heated of different materials.

Japanese Patent No. 4909966

In Patent Document 1, when heating a high-resistance magnetic pot, the switch (relay) that switches between the circuit method of the high-frequency inverter and the capacity of the resonance capacitor is turned on, the inverter is switched to the full bridge circuit method, and the first The magnetic pot is induced and heated by using the resonance capacitor (FIG. 1, reference numeral 12 of the same document), the second resonance capacitor (the same, reference numeral 15), and the third resonance capacitor (the same, reference numeral 13).

On the other hand, when heating a low-resistance non-magnetic pot, the switch (relay) is turned off, the inverter is switched to the half-bridge circuit method, and the third resonance capacitor with a large capacity is completely disconnected to have a small capacity. The non-magnetic pot is induced and heated using the first resonance capacitor and the second resonance capacitor.

By doing so, in the electromagnetic induction heating device of Patent Document 1, a magnetic pot and a non-magnetic pot can be purchased and heated, but a switch (relay) is used to switch the circuit method of the high-frequency inverter and the capacity of the resonance capacitor. Was required, which hindered miniaturization.

An object of the present invention is to address the above problems, and in particular, to efficiently transfer desired power to objects to be heated of different materials without using an inverter method or a switch (relay) for switching a resonant capacitor. It is to provide an inverter type electromagnetic induction heating device that can be supplied well.

In order to achieve the above object, the electromagnetic induction heating device of the present invention has a plurality of heating coils for inductively heating one object to be heated, and the plurality of heatings by converting the DC voltage output by the DC power supply into an AC voltage. An electromagnetic induction heating device including an inverter circuit that supplies a coil, wherein the inverter circuit has an upper and lower arm that is a series of two switching elements between a positive electrode and a negative electrode of the DC power supply. A plurality of units are connected in series, and the heating coil and the non-magnetic are connected between the output terminal of the inverter circuit and the connection point between the upper and lower arms, or between the output terminal of the inverter circuit and the electrode of the DC power supply. It is assumed that a series of resonance capacitors for body heating is connected, and a series of the heating coil and the resonance capacitor for heating the magnetic material are connected between the output terminals of the inverter circuit.

According to the present invention, it is possible to efficiently supply desired electric power to objects to be heated of different materials without using an inverter method or a switch (relay) for switching a resonance capacitor.

The circuit block diagram of the electromagnetic induction heating apparatus of Example 1. FIG. The circuit block diagram of the DC power supply of Example 1. FIG. Operation waveform when the non-magnetic material of Example 1 is heated. Operation waveform when the magnetic material of Example 1 is heated. The circuit block diagram of the electromagnetic induction heating apparatus of Example 2. The circuit block diagram of the electromagnetic induction heating apparatus of Example 3. FIG. The circuit block diagram of the electromagnetic induction heating apparatus of Example 4. FIG. The circuit block diagram of the electromagnetic induction heating apparatus of Example 5.

Hereinafter, the electromagnetic induction heating device according to the embodiment of the present invention will be described with reference to the drawings. In each figure, those having the same reference numerals indicate the same constituent elements or the constituent elements having similar functions, and duplicate explanations are omitted as appropriate.

FIG. 1 is a circuit configuration diagram of the electromagnetic induction heating device of the first embodiment. In the electromagnetic induction heating device of this embodiment, a heat-resistant glass top plate is installed on the upper part of the metal housing, and a high-frequency current is supplied to a heating coil arranged below the top plate to supply a high-frequency current to the upper surface of the top plate. A metal object to be heated placed in a predetermined position is induced and heated, but the description of such a well-known configuration will be omitted below.

In FIG. 1, the DC power supply 1 is a power supply that rectifies an AC voltage supplied from a commercial AC power supply of 200 V or 100 V and outputs a DC voltage. A first upper and lower arm 51 in which power semiconductor switching elements (hereinafter, simply referred to as “switching elements”) 5a and 5b are connected in series between the positive electrode P and the negative electrode N of the DC power supply 1 The second upper and lower arms 52 to which the switching elements 5c and 5d are connected in series are connected in series. In the following, the connection points of the switching elements 5a and 5b will be referred to as an output terminal O _A , the connection points of the switching elements 5b and 5c will be referred to as a connection point _OB , and the connection points of the switching elements 5c and 5d will be referred to as an output terminal _OC . do.

Diodes 6a to 6d are connected in parallel to each of the switching elements 5a to 5d in the opposite direction, and capacitors 7a to 7d are connected in parallel to each of the switching elements 5a to 5d. The capacitors 7a to 7d are charged or discharged by the breaking current at the turn-off of the switching elements 5a to 5d, and the change in the voltage applied to each switching element is reduced to suppress the turn-off loss. It also has the role of balancing the voltage applied to the off switching elements of the switching elements 5a to 5d.

As shown in FIG. 1, one end of the first heating coil 11 is connected to the output terminal _OA of the first upper and lower arm 51, the other end of the first heating coil 11, the first upper and lower arm 51, and the first one. _A first resonance capacitor 21b is connected between the connection points OB of the second upper and lower arms 52. Similarly, one end of the second heating coil 12 is connected to the output terminal _OC of the second upper and lower arm 52, and is between the other end of the second heating coil 12 and the negative electrode N of the DC power supply 1. Is connected to the second resonant capacitor 22b. Further, a fifth resonance capacitor 30 is connected between the other end of the first heating coil 11 and the other end of the second heating coil 12.

Both the first heating coil 11 and the second heating coil 12 are heating coils used for heating one object to be heated, and both may be arranged concentrically, or each of them may be arranged concentrically. May be wound in a semicircular shape and combined to form an annular heating coil. Further, although the details will be described later, the first resonance capacitor 21b and the second resonance capacitor 22b function as resonance capacitors when the non-magnetic material is heated, and the fifth resonance capacitor 30 resonates when the magnetic material is heated. It functions as a capacitor.

Here, the DC power supply 1 rectifies the AC voltage supplied from the commercial AC power supply 100 as shown in FIG. 2, for example, by the diodes 101a to 101d, and after passing through a normal filter composed of the inductor 102a and the capacitor 103a, It is a power supply that outputs a DC voltage by a boost chopper including an inductor 102b for boosting, a switching element 105, a diode 106a, and a capacitor 103b for smoothing.

Since the heating coils 11 and 12 and the metal pot (not shown) that is the object to be heated are magnetically coupled, if the metal pot is converted into an equivalent circuit seen from the heating coils 11 and 12 side, it is equivalent to the metal pot. A resistor and an equivalent inductance are connected in series. The equivalent resistance and the equivalent inductance differ depending on the material of the metal pot. In the case of a low resistance non-magnetic material, both the equivalent resistance and the equivalent inductance become small, and in the case of a high resistance magnetic material, both become large.

In the electromagnetic induction heating device of this embodiment, the object to be heated is heated by changing the driving method of the first upper and lower arms 51 and the second upper and lower arms 52 according to the material of the object to be heated and the set thermal power. In the following, the difference in control between heating a non-magnetic material typified by aluminum and heating a magnetic material typified by iron will be described.

<Control when heating non-magnetic material>
First, control during heating of a non-magnetic material will be described with reference to FIG.

FIG. 3 shows an operation waveform when the object to be heated is a non-magnetic material such as an aluminum pan. The waveforms shown here are, in order from the top, (a) the gate drive signals vg _5a to vg _5d of the switching elements 5a to 5d, (b) the voltages v _5b , v _5d , and the heating coil 11 applied to the switching elements 5b and 5d. , 12 currents i ₁₁ , i ₁₂ , (c) Voltages v _21b , v _22b of the resonance capacitors 21b, 22b, (d) Currents of each element of the upper and lower arms 51, 52 i _5a to i _5d , i _6a to i _6d . Is. The directions of the currents i ₁₁ and i ₁₂ flowing through the heating coils 11 and 12 are positive in the direction of the arrow of the alternate long and short dash line shown in FIG.

In this embodiment, when the object to be heated is a non-magnetic material such as a copper pan or an aluminum pan, the upper arms of the first upper and lower arms 51 and the second upper and lower arms 52 (switching elements 5a and 5c) are turned on at the same time. A period during which the lower arms are turned on and a period during which the lower arms (switching elements 5b and 5d) are turned on at the same time are provided. As a result, the series resonance of the first resonance load circuit including the first heating coil 11 and the first resonance capacitor 21b and the second resonance load circuit including the second heating coil 12 and the second resonance capacitor 22b. It functions as a modified half-bridge type inverter circuit that uses the circuit as a load circuit.

During the period when the switching elements 5a and 5c are on at the same time, the series resonance load circuit of the first heating coil 11, the first resonance capacitor 21b, the second heating coil 12 and the second resonance capacitor 22b is DC. The voltage V1 of the power supply ₁ is applied. At this time, if the capacities of the capacitors 7b and 7d are the same, a voltage of about _1/2 of the voltage V1 of the DC power supply 1 is applied to the switching elements 5b and 5d, respectively. Similarly, if the capacities of the capacitors 7a and 7c are the same, the voltage applied to the switching elements 5a and 5c while the switching elements 5b and 5d are on at the same time is about _1/1 of the voltage V1 of the DC power supply 1. It becomes 2. The directions of the currents of the heating coil 11 and the heating coil 12 are both positive.

In FIG. 3, the switching elements 5a to 5d can be turned on during the period in which the current is flowing through the diodes 6a to 6d, and the soft switching operation with less switching loss is possible.

As described above, since the low resistance non-magnetic material has a small equivalent resistance, it is necessary to pass a large current in order to obtain a desired output. The skin resistance of the object to be heated has a characteristic of being proportional to the square root of the frequency, and when heating a low-resistance object to be heated such as copper or aluminum, it is effective to increase the frequency. Therefore, the capacities of the first and second resonance capacitors 21b and 22b are set so that the upper and lower arms 51 and 52 can be driven at a frequency of, for example, about 90 kHz.

Since the low resistance non-magnetic material has a small equivalent resistance, the ratio of the current change to the frequency change is large, and the current easily flows. Therefore, it is desirable to control the voltage applied to the resonance load circuit at a low level. In this embodiment, when the non-magnetic material is heated, the heating coil current is controlled by varying the voltage of the smoothing capacitor 103b, that is, the voltage of the DC power supply 1 applied to the inverter 2 by the boost chopper shown in FIG. Since the upper and lower arms 51 and the upper and lower arms 52 are connected in series to the DC power supply 1, the voltage applied to the first resonance load circuit including the first heating coil 11 and the first resonance capacitor 21b is a DC power supply. The voltage of 1 is 1/2 of the voltage V ₁ , and the voltage applied to the second resonance load circuit including the second heating coil 12 and the second resonance capacitor 22b is also 1 / of the voltage V ₁ of the DC power supply 1. It becomes 2, and the voltage applied to the resonance load circuit can be suppressed low.

In Patent Document 1 described above, since the voltage of the DC power supply is directly applied to the first resonance load circuit and the second resonance load circuit, it is necessary to lower the voltage of the DC power supply 1 itself. Therefore, it is necessary to provide a step-down function in the power supply circuit of Patent Document 1, and the power supply circuit has become large in size.

On the other hand, in this embodiment, the non-magnetic material can be heated while the voltage of the DC power supply 1 remains high and the voltage of the resonance load circuit is kept low. Further, since the voltage applied to the switching elements 5a to 5d is about _½ of the voltage V1 of the DC power supply 1, the withstand voltage of the element can be lowered, and the switching element having a low on-resistance can be applied, resulting in low loss. It is effective for.

<Control when heating magnetic material>
Next, control during heating of the magnetic material will be described with reference to FIG.

FIG. 4 shows an operation waveform when the object to be heated is a magnetic material such as an iron pan. The meaning of vg _5a and the like in FIG. 4 is the same as that in FIG.

In this embodiment, when the object to be heated is a magnetic material such as an iron pan, the upper arm 5a of the first upper and lower arm 51 and the lower arm 5d of the second upper and lower arm 52 are turned on and off at the same time as shown in FIG. , The lower arm 5b of the first upper and lower arm 51 and the upper arm 5c of the second upper and lower arm 52 are turned on and off at the same time. As a result, it functions as a modified half-bridge type inverter circuit in which the series resonance circuit of the first heating coil 11, the fifth resonance capacitor 30, and the second heating coil 12 is used as a load circuit.

While the switching elements 5a and 5d are on at the same time, the voltage V1 of the DC power supply ₁ is applied to the series resonance load circuit of the first heating coil 11, the fifth resonance capacitor 30, and the second heating coil 12. Resonance. At this time, if the capacities of the capacitors 7b and 7c are the same, a voltage of about _1/2 of the voltage V1 of the DC power supply 1 is applied to the switching elements 5b and 5c, respectively. Similarly, if the capacities of the capacitors 7a and 7d are the same, the voltage applied to the switching elements 5a and 5d while the switching elements 5b and 5c are on at the same time is about _1/1 of the voltage V1 of the DC power supply 1. It becomes 2. The direction of the current of the heating coil 11 is in the forward direction, and the direction of the current of the heating coil 12 is in the opposite direction.

Also in FIG. 4, the switching elements 5a to 5d can be turned on during the period when the current is flowing through the diodes 6a to 6d, and the soft switching operation with less switching loss is possible.

When the object to be heated is iron, the resistance is originally large, so the first upper and lower arms 51 and the second upper and lower arms 52 are driven at a frequency of about 20 kHz. Therefore, the capacity of the fifth resonance capacitor 30 is set according to the drive frequency of about 20 kHz, which is sufficiently larger than the capacities of the first and second resonance capacitors 21b and 22b. Therefore, even if the first resonance capacitor 21b and the second resonance capacitor 22b are connected on the circuit, the capacitances of the first and second resonance capacitors 21b and 22b are sufficiently larger than the capacitance of the fifth resonance capacitor 30. Because it is small, almost no current flows and there is no effect on operation.

As described above, since the high resistance magnetic material has a large equivalent resistance, the ratio of the current change to the change in the switching frequency is small, and the heating coil current can be easily controlled by the frequency control of the inverter circuit. The heating coil current may be controlled by varying the voltage of the DC power supply 1 applied to the inverter as in the case of heating a non-magnetic material.

By properly using the control described above according to the type of the object to be heated, the electromagnetic induction heating device of this embodiment does not provide a switch (relay) or a step-down circuit which is indispensable in the circuit configuration of Patent Document 1. The desired electric power required to realize the set thermal power can be supplied to the object to be heated both when the magnetic material is heated and when the non-magnetic material is heated.

FIG. 5 is a circuit configuration diagram of the electromagnetic induction heating device of the second embodiment. Duplicate explanations will be omitted for the common points with the first embodiment.

In this embodiment, the first resonance capacitor 21a is added between the other end of the first heating coil 11 and the positive electrode P of the DC power supply 1 to the circuit configuration of the first embodiment shown in FIG. , _A second resonance capacitor 22a is added between the other end of the second heating coil 12 and the connection point OB.

In the first embodiment, the current flows from the DC power supply 1 only when the switching elements 5a and 5c are turned on at the same time when the non-magnetic material is heated, but in this embodiment, the DC power supply 1 is also turned on when the switching elements 5b and 5d are turned on. Since it is a half-bridge circuit type inverter in which a current flows from the inverter, it is possible to reduce the ripple current of the DC power supply 1.

According to this embodiment, when the converter as shown in FIG. 2 is connected to the front stage of the inverter circuit, the capacitor 103b is connected between the inverter circuit and the converter, so that the ripple current becomes smaller and the ripple current becomes smaller. The size of the capacitor can be reduced. Moreover, since the amount of heat generated by the internal resistance of each capacitor can be reduced, reliability can be improved.

FIG. 6 is a circuit configuration diagram of the electromagnetic induction heating device of the third embodiment. Duplicate explanations will be omitted for the common points with the second embodiment.

In this embodiment, a fifth resonance capacitor 31 is added between the output terminal _OA and one end of the first heating coil 11 to the circuit configuration of the second embodiment shown in FIG. 5, and the output terminal _OC is added. A fifth resonance capacitor 32 is added between the second heating coil 12 and the second heating coil 12. Further, the fifth resonance capacitor 30 of the second embodiment is omitted, and the other ends of the first heating coil 11 and the second heating coil 12 are short-circuited. The positions of the fifth resonance capacitor 31 and the first heating coil 11 or the positions of the fifth resonance capacitor 32 and the second heating coil 12 shown in FIG. 6 may be interchanged.

As a result, the series circuit of the fifth resonance capacitor 31 and the first heating coil 11 is connected between the output terminal _OA of the first upper and lower arm 51 and the connection points of the second resonance capacitors 21a and 21b. _A series circuit of the fifth resonance capacitor 32 and the second heating coil 12 is connected between the output terminal OC of the second upper and lower arm 52 and the connection point of the second resonance capacitors 22a and 22b. ..

As described above, in this embodiment, the inverter unit provided with the resonance load circuit including the fifth resonance capacitors 31 and 32 is connected in series, and the connection points of the first resonance capacitors 21a and 21b and the second resonance capacitor are connected. Since the structure has a simple structure in which the connection points of 22a and 22b are short-circuited, it can be easily mounted on an electromagnetic induction heating device.

<Control when heating non-magnetic material>
In this embodiment, when the object to be heated is a non-magnetic material such as a copper pan or an aluminum pan, as in the above embodiment, the upper arms of the first upper and lower arms 51 and the second upper and lower arms 52 (switching elements). A period in which the lower arms (5a and 5c) are turned on at the same time and a period in which the lower arms (switching elements 5b and 5d) are turned on at the same time are provided. As a result, the first resonance load circuit including the first heating coil 11, the first resonance capacitors 21a and 21b, and the fifth resonance capacitor 31, and the second heating coil 12 and the second resonance capacitors 22a and 22b An inverter circuit is configured in which the series resonance circuit of the second resonance load circuit composed of the fifth resonance capacitor 32 and the fifth resonance capacitor 32 is used as the load circuit.

As described above, when heating a low-resistance object to be heated such as copper or aluminum, it is effective to increase the frequency so that the upper and lower arms 51 and 52 can be driven at a frequency of, for example, about 90 kHz. The capacitances of the first resonance capacitors 21a and 21b and the second resonance capacitors 22a and 22b are set. Here, in this embodiment, the fifth resonance capacitor 31 is connected in series to the first resonance capacitors 21a and 21b, and the fifth resonance capacitor 32 is connected in series to the second resonance capacitors 22a and 22b. It becomes a composition. As will be described later, since the capacitances of the fifth resonance capacitors 31 and 32 are sufficiently larger than those of the first resonance capacitors 21a and 21b and the second resonance capacitors 22a and 22b, the resonance frequencies are mainly the first and second resonance capacitors. It is determined by the second resonance capacitor.
<Control when heating magnetic material>
In this embodiment, when the object to be heated is a magnetic material such as an iron pan, the upper arm 5a of the first upper and lower arm 51 and the lower arm 5d of the second upper and lower arm 52 are turned on and off at the same time as in the above embodiment. Then, the lower arm 5b of the first upper and lower arm 51 and the upper arm 5c of the second upper and lower arm 52 are turned on and off at the same time. As a result, an inverter circuit having a series resonance circuit of the first heating coil 11, the second heating coil 12, and the fifth resonance capacitors 31 and 32 as a load circuit is configured.

As described above, when the object to be heated is iron, the resistance is originally large, so that the first upper and lower arms 51 and the second upper and lower arms 52 are driven at a frequency of about 20 kHz. Therefore, the capacitances of the fifth resonant capacitors 31 and 32 are set according to the drive frequency of about 20 kHz, which is larger than the capacitances of the first resonant capacitors 21a and 21b and the second resonant capacitors 22a and 22b. It will be a large enough value.

Up to this point, an electromagnetic induction heating device that uses two heating coils to heat one object to be heated has been shown, but since a high resonance voltage is generated in the heating coil, it is necessary to suppress the voltage.

FIG. 7 is a circuit configuration diagram of the electromagnetic induction heating device of the fourth embodiment. Duplicate explanations will be omitted for the common points with the second embodiment.

To outline, the circuit configuration of the present embodiment shown in FIG. 7 is the circuit configuration of the second embodiment shown in FIG. 5 with a circuit configuration that is a mirror image of the circuit configuration added. Therefore, the electromagnetic induction heating device of this embodiment uses four heating coils to heat one object to be heated. Since there are some configurations that are inconsistent with this outline, the circuit configuration of this embodiment will be specifically described below.

In this embodiment, the power semiconductor switching elements 5e and 5f are connected in series between the positive electrode P and the negative electrode N of the DC power supply 1 with respect to the circuit configuration of the second embodiment shown in FIG. The upper and lower arms 53 and the fourth upper and lower arms 54 to which the switching elements 5g and 5h are connected in series are connected in series. In the following, the connection points of the switching elements 5e and 5f will be referred to as output terminals OE, the connection points of the switching elements _5f and 5g will be referred to as connection points OF, and the connection points of the switching elements _5g and _5h will be referred to as output terminals OG. do.

Further, diodes 6e to 6h are connected in parallel to each of the added switching elements 5e to 5h in the opposite direction, and capacitors 7e to 7h are connected to each of the switching elements 5e to 5h in parallel. The capacitors 7e to 7h are charged or discharged by the breaking current at the turn-off of the switching elements 5e to 5h, and the change in the voltage applied to each switching element is reduced to suppress the turn-off loss. It also has the role of balancing the voltage applied to the off switching elements of the switching elements 5e to 5h.

One end of the third heating coil 13 is connected to the output terminal _OE of the third upper and lower arm 53, the other end of the third heating coil 13, the positive electrode _P of the DC power supply 1, and the connection point OF. Third resonance capacitors 23a and 23b are connected between them, respectively. Similarly, one end of the fourth heating coil 14 is connected to the output terminal _OG of the fourth upper and lower arm 54, and the other end of the fourth heating coil 14, the connection point _OF , and the DC power supply 1 are connected. Fourth resonance capacitors 24a and 24b are connected between the negative electrodes N, respectively. Further, a fifth resonance capacitor 35 is connected between the other end of the first heating coil 11 and the other end of the third heating coil 13, and the other end of the second heating coil 12 and the fourth end. A fifth resonance capacitor 36 is connected between the other ends of the heating coil 14 of the above. Further, the connection point OB and the connection point OF are short _{- circuited} .
<Control when heating non-magnetic material>
In this embodiment, when the object to be heated is a non-magnetic material such as a copper pan or an aluminum pan, the period during which the upper arms (switching elements 5a, 5c, 5e, 5g) of the upper and lower arms 51 to 54 are turned on at the same time. And, a period is provided in which the lower arms (switching elements 5b, 5d, 5f, 5h) are on at the same time. As a result, the first resonance load circuit including the first heating coil 11 and the first resonance capacitors 21a and 21b, and the second resonance load including the second heating coil 12 and the second resonance capacitors 22a and 22b. A half-bridge circuit type inverter having a series resonance circuit of the circuit as a load circuit, a third resonance load circuit including a third heating coil 13 and third resonance capacitors 23a and 23b, a fourth heating coil 14 and a fourth It functions as a half-bridge circuit type inverter having a series resonance circuit of a fourth resonance load circuit composed of four resonance capacitors 24a and 24b as a load circuit. The direction of the current flowing through the heating coils 11 to 14 is the positive direction when the arrow direction of the alternate long and short dash line shown in FIG. 7 is the positive direction.

As described above, when heating a low-resistance object to be heated such as copper or aluminum, it is effective to increase the frequency so that the upper and lower arms 51 to 54 can be driven at a frequency of, for example, about 90 kHz. The capacitances of the first resonance capacitors 21a and 21b, the second resonance capacitors 22a and 22b, the third resonance capacitors 23a and 23b and the fourth resonance capacitors 24a and 24b are set.
<Control when heating magnetic material>
In this embodiment, when the object to be heated is a magnetic material such as an iron pan, the period during which the upper arms of the upper and lower arms 51 and 52 (switching elements 5a and 5c) are simultaneously on and the lower of the upper and lower arms 53 and 54. A period in which the arms (switching elements 5f and 5h) are on at the same time is provided, or a period in which the upper arms of the upper and lower arms 51 and 54 (switching elements 5a and 5g) are on at the same time and the upper and lower arms 52 and 53 are turned on. A period is provided in which the lower arms (switching elements 5f and 5d) are on at the same time. As a result, it functions as a full-fridge circuit type inverter using the series resonance circuit of the heating coils 11 to 14 and the fifth resonance capacitors 35 and 36 as the load circuit.

A period during which the upper arms 51 and 52 (switching elements 5a and 5c) are simultaneously turned on and a period during which the lower arms 53 and 54 (switching elements 5f and 5h) are simultaneously turned on are provided. In this case, the directions of the currents of the heating coils 11 and 12 are in the forward direction, and the directions of the currents of the heating coils 13 and 14 are in the opposite directions.

On the other hand, the period during which the upper arms of the upper and lower arms 51 and 54 (switching elements 5a and 5g) are turned on at the same time and the period during which the lower arms of the upper and lower arms 52 and 53 (switching elements 5f and 5d) are turned on at the same time. When provided, the directions of the currents of the heating coils 11 and 14 are in the forward direction, and the directions of the currents of the heating coils 12 and 13 are in the opposite directions.

Since a magnetic material with high resistance has a large equivalent resistance, it is difficult for current to flow in the resonant load circuit. Therefore, by changing to the full bridge circuit system as in the circuit configuration of this embodiment, the output voltage of the inverter circuit can be doubled as in the half bridge circuit system to obtain a desired output.

FIG. 8 is a circuit configuration diagram of the electromagnetic induction heating device of the fifth embodiment. Duplicate explanations will be omitted for the common points with the fourth embodiment.

In FIG. 8, with respect to the circuit configuration of the fourth embodiment shown in FIG. 7, the fifth resonance capacitors 31 to 34 are connected in series to each of the heating coils 11 to 14, respectively. Further, as a result of omitting the fifth resonance capacitors 35 and 36 of the second embodiment, the connection points of the first resonance capacitors 21a and 21b and the connection points of the third resonance capacitors 23a and 23b are short-circuited, and the second resonance occurs. The connection point between the capacitors 22a and 22b and the connection point between the fourth resonance capacitors 24a and 24b are short-circuited.

<Control when heating non-magnetic material>
Also in this embodiment, when the object to be heated is a non-magnetic material such as a copper pan or an aluminum pan, the upper arms of the upper and lower arms 51 to 54 (switching elements 5a, 5c, 5e, 5g) are turned on at the same time. A period and a period during which the lower arms (switching elements 5b, 5d, 5f, 5h) are on at the same time are provided. Here, the resonance capacitors 21a and 23a, 21b and 23b are connected in parallel, and the first heating coil 11 and the third heating coil 13 share the resonance capacitors 21a, 21b, 23a and 23b. It becomes. Similarly, the resonance capacitors 22a and 24a, 22b and 24b are connected in parallel, and the second heating coil 12 and the fourth heating coil 14 share the resonance capacitors 22a, 22b, 24a and 24b. It becomes. The direction of the current flowing from the heating coils 11 to 14 is the positive direction when the arrow direction of the alternate long and short dash line shown in FIG. 8 is the positive direction.

As described above, when heating a low-resistance object to be heated such as copper or aluminum, it is effective to increase the frequency, and the upper and lower arms 51 to 54 resonate so as to be driven at a frequency of, for example, about 90 kHz. The capacities of the capacitors 21a, 21b, 23a, 23b and the resonance capacitors 22a, 22b, 24a, 24b are set.

As described above, in this embodiment, the resonance capacitors 21a, 21b, 23a, 23b can be shared by the first heating coil 11 and the third heating coil 13, and the resonance capacitors 22a, 22b, 24a, 24b can be used for the second heating. Since it can be shared by the coil 12 and the fourth heating coil 14, the number of parts can be reduced.

<Control when heating magnetic material>
Also in this embodiment, when the object to be heated is a magnetic material such as an iron pan, the period during which the upper arms 51 and 52 (switching elements 5a and 5c) are simultaneously on and the upper and lower arms 53 and 54 are A period during which the lower arms (switching elements 5f and 5h) are simultaneously on, or a period during which the upper arms 51 and 54 (switching elements 5a and 5g) are simultaneously on and the upper and lower arms 52 and 53 are provided. A period is provided in which the lower arms (switching elements 5f and 5d) are on at the same time. As a result, it functions as a full-fridge circuit type inverter using the series resonance circuit of the heating coils 11 to 14 and the fifth resonance capacitors 31 to 34 as the load circuit.

When the upper arms 51 and 52 (switching elements 5a and 5c) are on and the lower arms 53 and 54 (switching elements 5f and 5h) are on. The directions of the currents of the heating coils 11 and 12 are in the forward direction, and the directions of the currents of the heating coils 13 and 14 are in the opposite directions.

When the upper arms 51 and 54 (switching elements 5a and 5g) are on and the lower arms 52 and 53 (switching elements 5f and 5d) are on. The directions of the currents of the heating coils 11 and 14 are in the forward direction, and the directions of the currents of the heating coils 12 and 13 are in the opposite directions.

1 DC power supply,
2 Inverters 5a-5h, 105 switching elements,
6a-6h, 101a-101d, 106a, 106b diodes,
7a-7h, 103a, 103b capacitors,
11 First heating coil,
12 Second heating coil,
13 Third heating coil,
14 Fourth heating coil,
21a, 21b first resonant capacitor,
22a, 22b Second resonant capacitor,
23a, 23b Third resonant capacitor,
24a, 24b Fourth resonant capacitor,
30, 31-34 Fifth resonant capacitor,
51 First upper and lower arms,
52 Second upper and lower arm,
53 Third upper and lower arm,
54 Fourth upper and lower arm,
100 commercial AC power supply,
102a, 102b inductor

Claims (11)

Multiple heating coils that induce and heat one object to be heated,
An inverter circuit that converts the DC voltage output by the DC power supply into an AC voltage and supplies it to the plurality of heating coils.
It is an electromagnetic induction heating device equipped with
The inverter circuit is
A plurality of upper and lower arms, which are a series of two switching elements, are connected in series between the positive electrode and the negative electrode of the DC power supply.
A heating coil and a resonance capacitor for heating a non-magnetic material are connected in series between the output terminal of the inverter circuit and the connection point between the upper and lower arms, or between the output terminal of the inverter circuit and the electrode of the DC power supply. The body is connected and
An electromagnetic induction heating device characterized in that a series of a heating coil and a resonance capacitor for heating a magnetic material are connected between the output terminals of the inverter circuit. In the electromagnetic induction heating device according to claim 1,
The inverter circuit is
The first upper and lower arms, which are a series of two switching elements,
A series of second upper and lower arms, which is a series of two switching elements,
A third upper and lower arm, which is a series of two switching elements,
A series of fourth upper and lower arms, which is a series of two switching elements,
The first inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
A second inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the third and fourth upper and lower arms, and
A third inverter circuit that operates as a full-bridge inverter by driving the switching elements of the first to fourth upper and lower arms, and
Consists of
A first heating coil, a first resonance capacitor, a second heating coil, and a second resonance capacitor are connected between the output terminals of the first inverter circuit.
A third heating coil, a third resonance capacitor, a fourth heating coil, and a fourth resonance capacitor are connected between the output terminals of the second inverter circuit.
The first to fourth heating coils and the fifth resonance capacitor are connected between the output terminals of the third inverter circuit.
An electromagnetic induction heating device characterized in that a snubber capacitor and a voltage balancing capacitor are connected in parallel to the switching element. In the electromagnetic induction heating device according to claim 1,
The inverter circuit is
The first upper and lower arms, which are a series of two switching elements,
A series of second upper and lower arms, which is a series of two switching elements,
A third upper and lower arm, which is a series of two switching elements,
A series of fourth upper and lower arms, which is a series of two switching elements,
The first inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
A second inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the third and fourth upper and lower arms, and
A third inverter circuit that operates as a full-bridge inverter by driving the switching elements of the first to fourth upper and lower arms, and
Consists of
A first heating coil, a first resonance capacitor, a second heating coil, a second resonance capacitor, and a fifth resonance capacitor are connected between the output terminals of the first inverter circuit.
A third heating coil, a third resonance capacitor, a fourth heating coil, a fourth resonance capacitor, and a fifth resonance capacitor are connected between the output terminals of the second inverter circuit.
The first to fourth heating coils and the fifth resonance capacitor are connected between the output terminals of the third inverter circuit.
An electromagnetic induction heating device characterized in that a snubber capacitor and a voltage balancing capacitor are connected in parallel to the switching element. In the electromagnetic induction heating device according to claim 1,
The inverter circuit is
The first upper and lower arms, which are a series of two switching elements,
A series of second upper and lower arms, which is a series of two switching elements,
The first inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
A third inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
Consists of
A first heating coil, a first resonance capacitor, a second heating coil, and a second resonance capacitor are connected between the output terminals of the first inverter circuit.
The first and second heating coils and the fifth resonance capacitor are connected between the output terminals of the third inverter circuit.
An electromagnetic induction heating device characterized in that a snubber capacitor and a voltage balancing capacitor are connected in parallel to the switching element. In the electromagnetic induction heating device according to claim 1,
The inverter circuit is
The first upper and lower arms, which are a series of two switching elements,
A series of second upper and lower arms, which is a series of two switching elements,
The first inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
A third inverter circuit that operates as a half-bridge type inverter by driving the switching elements of the first and second upper and lower arms, and
Consists of
A first heating coil, a first resonance capacitor, a second heating coil, a second resonance capacitor, and a fifth resonance capacitor are connected between the output terminals of the first inverter circuit.
The first and second heating coils and the fifth resonance capacitor are connected between the output terminals of the third inverter circuit.
An electromagnetic induction heating device characterized in that a snubber capacitor and a voltage balancing capacitor are connected in parallel to the switching element. In the electromagnetic induction heating device according to claim 2,
The first to fourth resonance capacitors are electromagnetic induction heating devices having a smaller capacitance than the fifth resonance capacitor. In the electromagnetic induction heating device according to any one of claims 3 to 5.
The first and second resonance capacitors are electromagnetic induction heating devices having a smaller capacitance than the fifth resonance capacitor. In the electromagnetic induction heating device according to any one of claims 2 and 3.
When the object to be heated is a non-magnetic material, the first and second inverter circuits are characterized in that a high frequency current is supplied to the first to fourth heating coils to heat the object to be heated. Electromagnetic induction heating device. In the electromagnetic induction heating device according to any one of claims 2 and 3.
When the object to be heated is a magnetic material, the third inverter circuit supplies a high frequency current to the first to fourth heating coils to heat the object to be heated. Heating device. In the electromagnetic induction heating device according to claims 4 and 5.
When the object to be heated is a non-magnetic material, the first inverter circuit supplies a high frequency current to the first and second heating coils to heat the object to be heated. Induction heating device. In the electromagnetic induction heating device according to claims 4 and 5.
When the object to be heated is a magnetic material, the third inverter circuit is characterized by supplying a high frequency current to the first and second heating coils to heat the object to be heated. Heating device.

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