JP2006331964A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating device of an inverter system capable of efficiently supplying desired power to object to be heated different in materials. <P>SOLUTION: The induction heating device is provided with a resonant load circuit containing an object to be heated and an inverter inverting a direct current voltage into an alternate current voltage and supplying power to the resonant load circuit. The inverter is provided with two top and bottom arms constituted of at least two switching elements connected in series, an inductor connected to a direct current power source and a switch changing over the other connecting point of the inductor, which is changed over depending on the material of the object to be heated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter type electromagnetic induction heating apparatus that performs induction heating by supplying desired power to an object to be heated of different materials.

  In recent years, an inverter type electromagnetic induction heating apparatus that heats an object to be heated such as a pot without using a fire is widely used. The electromagnetic induction heating device applies a high-frequency current to the heating coil, generates an eddy current in a heated object made of a material such as iron or stainless steel, which is disposed in the vicinity of the coil, and the electric resistance of the heated object itself. Cause heat. It is recognized as a new heat source because it can control the temperature of the object to be heated and is highly safe. Conventionally, electric cookers incorporated in system kitchens and the like have used resistors such as sheathed heaters, plate heaters, and halogen heaters as heat sources, but in recent years, some of them have been replaced with induction heating cookers. It is being replaced by one that has been used as an induction heating cooker. As an example of such an electromagnetic induction heating apparatus, there is an induction heating cooker as disclosed in Patent Document 1. In Patent Document 1, a commercial AC power supply is rectified and smoothed, converted into a DC voltage, a high-frequency current is supplied to a heating coil by a half-bridge inverter, and an object to be heated arranged near the coil is induction-heated.

Japanese Patent Laid-Open No. 2001-126853 (Description of FIG. 1 and paragraphs (0013) to (0021))

  In Patent Document 1, it is necessary to pass a large current through the heating coil in order to supply sufficient power to the low-resistance object to be heated, which causes heating of the heating coil and increased loss of the switching element, resulting in a decrease in heating efficiency. To do. FIG. 16 shows the equivalent impedance of the coil and the object to be magnetically coupled as seen from the heating coil side, with the horizontal axis representing the equivalent inductance and the vertical axis representing the equivalent resistance. The equivalent impedance varies greatly depending on the material of the object to be heated. The material to be heated made of iron is (1) in FIG. 16, the object to be heated made of nonmagnetic stainless steel is (2), and the object to be heated made of copper or aluminum is The characteristic as shown in (3) is shown. In general, a high-resistance object to be heated such as (1) in FIG. 16 is suitable for induction heating. FIG. 17 shows the relationship between the input power and the resonance current of the object to be heated having the equivalent impedance characteristic shown in FIG. When the target input power is 2 kW, a resonance current of about 40 A may be passed through the heating coil in the iron heated object (1), but the resistance is small in the nonmagnetic stainless steel heated object (2). It is necessary to pass a current of about 55 A, and in the object to be heated (3) made of copper or aluminum, it is necessary to pass a current of about 140 A because the resistance is smaller.

  An object of the present invention is to provide an inverter type electromagnetic induction heating device that can efficiently supply desired power to an object to be heated of different materials.

  The induction heating apparatus of the present invention includes a resonant load circuit including an object to be heated, and an inverter that converts a DC voltage into an AC voltage and supplies power to the resonant load circuit, and the inverter is connected in series. It has an upper and lower arm composed of two switching elements, includes an inductor connected to a DC power source and a switch for switching the other connection point of the inductor, and switches the switch according to the material of the object to be heated.

  According to the induction heating device of the present invention, desired power can be efficiently supplied from an inverter to an object to be heated of different materials.

  Details of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram of the induction heating apparatus of this embodiment. In FIG. 1, assuming that the positive electrode side of the smoothing capacitor 115 is p point and the negative electrode side is o point, the upper and lower arms in which IGBT 103 and IGBT 104 which are power semiconductor switching elements are connected in series between the p point and the o point. 10 is connected. Diodes 105 and 106 are respectively connected in parallel to the IGBTs 103 and 104 in the reverse direction, and snubber capacitors 109 and 110 are connected to each IGBT. The snubber capacitors 109 and 110 are charged or discharged by a cutoff current when the IGBT 103 and the IGBT 104 are turned off. Since the capacitances of the snubber capacitors 109 and 110 are sufficiently larger than the output capacitance between the collectors and emitters of the IGBTs 103 and 104, the change in voltage applied to both IGBTs at the time of turn-off is reduced, and turn-off loss is suppressed.

  When the connection point of the IGBTs 103 and 104, that is, the output terminal of the upper and lower arms 10 is a point d, the heating coil 111, the first resonance capacitor 112, the second resonance capacitor 113 and the relay 114 are connected between the points d and o. Has been. A smoothing capacitor 115 is connected between the points p and o.

  In this embodiment of FIG. 1, the relays 107, 108, and 114 are selected according to the material of the object to be heated, and the half-bridge inverter method and the one-converter method are switched, or the capacitance of the resonant capacitor is switched.

  FIG. 2 shows the frequency characteristics of the equivalent resistance in the material of the object to be heated, and FIG. 3 shows the frequency characteristics of the equivalent inductance. The equivalent inductance is a magnetic heated object such as iron as shown in the graph (1) in FIG. 2 and a nonmagnetic heated object such as nonmagnetic stainless steel as shown in the graph (2) or copper or aluminum as shown in the graph (3). For non-magnetic objects, the non-magnetic object to be heated is about ½ smaller, and the resonance frequency changes if the same resonance capacitor is used.

  On the other hand, when the equivalent resistance is the same frequency, the magnetic object to be heated is approximately 10 to 20 larger in the magnetic object to be heated as in (1) and the non-magnetic object to be heated as in (3). Does not flow and power cannot be turned on. Therefore, the frequency is set low for a magnetic object to be heated, and is set to a high frequency for a non-magnetic object. However, since the magnetic object to be heated has a large equivalent resistance even in a low frequency range, the inverter is powered up by increasing the power supply voltage of the inverter as a one-converter system having a boosting function. On the other hand, since the non-magnetic object to be heated has a low equivalent resistance, the half-bridge inverter supplies desired power to heat it.

  In FIG. 1, when heating an object to be heated made of copper or aluminum, the relays 108 and 114 are turned off, and the relay 107 is turned on to operate in a half-bridge inverter system.

Next, the operation mode of the induction heating apparatus of the present embodiment will be described using the timing chart shown in FIG. Here, the voltage at point a in FIG. 1 is Va, the voltage at point d is Vd, the current flowing through the IGBT ₁₀₃ and the diode 105 is Ic ₁₀₃ , and the current flowing through the IGBT ₁₀₄ and the diode 106 is Ic ₁₀₄ . Further, the current flowing through the choke coil 102 is defined as IL ₁₀₂ , the resonance current flowing through the heating coil 111 is defined as IL _111, and the direction from the point d to the point c in FIG. 1 is defined as positive.

(Mode 1)
When the IGBT 103 is turned on and the accumulated energy of the heating coil 111 becomes zero, the polarity of the resonance current IL changes from negative to positive, and the resonance current IL ₁₁₁ flows from the smoothing capacitor 115 through the path of the IGBT 103, the heating coil 111, and the resonance capacitor 112.

(Mode 2)
Next, when the IGBT 103 is turned off, the resonance current IL ₁₁₁ has a positive polarity, and this current charges the upper arm snubber capacitor 109, discharges the lower arm snubber capacitor 110, and the voltage Vd at the point d gradually increases. To drop. Thereafter, when a forward voltage is applied to the diode 106, the resonance current IL ₁₁₁ continues to flow as a circulating current through the path of the heating coil 111, the resonance capacitor 112, and the diode 106.

(Mode 3)
Next, when the IGBT 104 is turned on and the accumulated energy of the heating coil 111 becomes zero, the polarity of the resonance current IL ₁₁₁ changes from positive to negative, and the resonance current IL ₁₁₁ flows through the path of the resonance capacitor 112, the heating coil 111, and the IGBT 104. At this time, since the IGBT 104 keeps the gate voltage on during the period in which the current flows through the diode 106, ZCS (zero current switching) and ZVS (zero volt switching) turn-on without switching loss are realized.

(Mode 4)
Next, when the IGBT 104 is turned off, the resonance current IL ₁₁₁ has a negative polarity. This current charges the lower arm snubber capacitor 110, discharges the upper arm snubber capacitor 109, and the voltage Vd at the point d gradually increases. To rise. Thereafter, when a forward voltage is applied to the diode 105, the resonance current IL ₁₁₁ continues to flow as a circulating current through the path of the heating coil 111, the diode 105, and the smoothing capacitor 115.

  As described above, by repeating the above operation, a high frequency current can be supplied to the heating coil 111 and the resonance capacitor 112 using the power supply circuit 101 and the smoothing capacitor 115 as power sources, and the object to be heated is a magnetic flux generated from the heating coil 111. Is heated by induction.

  When the magnetic object to be heated is heated by the induction heating apparatus of this embodiment, the relays 108 and 114 in FIG. 1 are turned on and the relay 107 is turned off, and the one converter method is used. Here, the one-converter system is an inverter system that also serves as a boost converter. The operation mode will be described with reference to the timing chart shown in FIG.

(Mode 1)
When the IGBT 103 is turned on and the accumulated energy of the heating coil 111 becomes zero, the polarity of the resonance current IL ₁₁₁ changes from negative to positive, and the resonance current passes from the smoothing capacitor 115 to the IGBT 103, the heating coil 111, the resonance capacitors 112 and 113, and the relay 114. IL ₁₁₁ flows.

(Mode 2)
Next, when the IGBT 103 is turned off, the resonance current IL ₁₁₁ has a positive polarity, and this current charges the upper arm snubber capacitor 109, discharges the lower arm snubber capacitor 110, and the voltage Vd at the point d gradually increases. To drop. Thereafter, when a forward voltage is applied to the diode 106, the resonance current IL ₁₁₁ continues to flow as a circulating current through the path of the heating coil 111, the resonance capacitors 112 and 113, the relay 114, and the diode 106.

(Mode 3)
Next, when the IGBT 104 is turned on and the stored energy of the heating coil 111 becomes zero, the polarity of the resonance current IL ₁₁₁ changes from positive to negative, and the resonance current IL passes through the resonance capacitors 112 and 113, the relay 114, the heating coil 111, and the IGBT 104. ₁₁₁ flows. Further, a current IL ₁₀₂ flows from the power supply circuit 101 to the IGBT 104 via the choke coil 102 and the relay 108, and energy is stored in the choke coil 102. For this reason, a current obtained by adding the resonance current IL and the input current flows to the IGBT 104. At this time, since the IGBT 104 keeps the gate voltage on during the period in which the current flows through the diode 106, ZCS and ZVS turn-on without switching loss are realized.

(Mode 4)
Next, when the IGBT 104 is turned off, the resonance current IL ₁₁₁ has a negative polarity. This current charges the lower arm snubber capacitor 110, discharges the upper arm snubber capacitor 109, and the voltage Vd at the point d gradually increases. To rise. Thereafter, when a forward voltage is applied to the diode 105, the resonance current IL ₁₁₁ continues to flow as a circulating current through the path of the heating coil 111, the resonance capacitors 112 and 113, the relay 114, and the smoothing capacitor 115. Further, the accumulated energy of the choke coil 102 flows through the path of the diode 105, the smoothing capacitor 115, and the power supply circuit 101, and the voltage of the smoothing capacitor 115 rises from the voltage of the power supply circuit 101. The boosted voltage at this time is determined by the duty of the IGBT 104 and is expressed by the following equation (1).

  By repeating the operation as described above, an inverter also serves as an operation of a boost converter, and the voltage of the smoothing capacitor 115 can be made higher than the power supply voltage. A desired material can be used for a material having a high equivalent resistance such as a magnetic object to be heated. It can be heated by applying power.

  The power supplied to the object to be heated can be adjusted by controlling the driving frequency of the upper and lower arms 10. As in this embodiment, the current flowing in the resonance circuit becomes a sine wave due to the inductance of the heating coil and the resonance capacitor, and the resonance current is delayed in phase from the voltage at point d, that is, the output voltage of the inverter. Therefore, when the IGBT is turned on, switching is performed in a state where the voltage between the collector and the emitter is zero volts (hereinafter referred to as ZVS), so that no turn-on loss occurs.

  However, when the power supplied to the object to be heated is reduced, the cut-off current of the upper and lower arms 10 is reduced, and the IGBT 103 or IGBT 104 is turned on before the charging / discharging of the snubber capacitors 109 and 110 is completed, so that ZVS is not satisfied. A condition occurs. In such a case, since turn-on loss occurs, as shown in FIG. 6, for example, an IGBT 601 is connected in series with the lower arm snubber capacitor 110, and a diode 602 is connected in reverse parallel to the IGBT 601, so that the IGBT 601 is connected. It is desirable to disconnect the snubber capacitor 110 from the upper and lower arms 10 by turning it off. Thereby, ZVS can always be realized, and even when the cutoff current is small, the turn-on loss can be eliminated.

  The skin resistance of the object to be heated is proportional to the square root of the frequency, and it is effective to increase the frequency when heating an object with low resistance such as copper or aluminum among non-magnetic objects to be heated. is there. Therefore, it is desirable to set the capacity of the first resonant capacitor 112 so that the upper and lower arms 10 can be driven at a frequency of about 90 kHz, for example. On the other hand, in the case of an object to be heated such as iron, if the frequency is high, the equivalent resistance becomes too large, so that no current flows and no power is input. Therefore, it is desirable to set the capacity of the second resonance capacitor 113 so that the upper and lower arms 10 can be driven at about 20 kHz.

  Thus, by switching the resonance capacitor capacity and the driving frequency to be driven according to the material of the object to be heated, the loss of the coil and the switching element can be suppressed, and highly efficient induction heating can be realized. In addition, even a high-resistance object such as iron can be boosted by switching to the one-converter system, so that a desired power can be input and heated. Moreover, since the number of turns can be increased, highly efficient heating can be performed.

  FIG. 7 shows a modification of FIG. The point changed in FIG. 7 is that a diode 701 is arranged instead of the relay 107. The operation is the same as in the first embodiment. By adopting this modified example, a power source for driving the relay is not required, so that miniaturization and high efficiency can be achieved.

  FIG. 8 is a circuit configuration diagram of the electromagnetic induction heating apparatus of this embodiment, and shows details of the power supply circuit 101 of FIG. In FIG. 8, a commercial AC power supply 801 is applied to a diode rectifier circuit 802 and full-wave rectified, and then an IGBT 804 is connected via an inductor 803, and a diode 805 and a capacitor 806 are connected.

  In magnetic heated objects such as iron, as shown in FIG. 9, even when a voltage varying from 0 V to the voltage peak value of a commercial AC power supply is applied to the inverter, the beat sound is heavy because the heated object is heavy. Does not occur. On the other hand, when heating an object to be heated made of copper or aluminum, if induction heating is performed with a high-frequency current that varies from 0 V to the peak as described above, a beat sound caused by the commercial frequency is generated from the object to be heated.

  Therefore, in order to prevent this, the DC voltage is smoothed as shown in FIG. A generally used capacitor input type smoothing circuit is insufficient because the input current includes many harmonics, and a power supply circuit that satisfies both voltage smoothing and harmonic suppression is required.

  In this embodiment, since the input current of the commercial AC power supply 801 needs to be close to a sine wave to reduce the harmonics, as shown in FIG. 7, a step-up chopper comprising an inductor 803, an IGBT 804, a diode 805, and a capacitor 806 is used. A circuit 80 is arranged. In the step-up chopper circuit 80, the commercial AC power supply voltage is applied to the inductor 803 during the ON period of the IGBT 804 to accumulate energy, and the energy is released to the capacitor 806 via the diode 805 during the OFF period. Therefore, the harmonics are reduced by controlling the ON period of the IGBT 804 so that the input current of the commercial AC power supply 801 becomes a sine wave, and the DC voltage is smoothed by the capacitor 806. In this embodiment, the step-up chopper circuit 80 is switched over the entire region so that the input current of the commercial AC power supply 801 becomes a sine wave.

  FIG. 11 is a timing chart of the power supply circuit of the induction heating apparatus of this example. In this embodiment, the boost chopper circuit 80 shown in FIG. 8 is operated only for a specific period as shown in the timing chart of FIG. The IGBT 804 performs a chopping operation with a desired delay time from the zero cross of the commercial AC power supply voltage, and sucks current from the commercial AC power supply 801. The harmonics can be reduced by controlling the chopping time and the ON period of the IGBT 804 according to the size of the load, that is, the desired output power. Since the induction heating apparatus of this embodiment operates as described above, the loss in the boost chopper circuit 80 can be further reduced while suppressing harmonics.

  FIG. 12 is a circuit configuration diagram of the electromagnetic induction heating device of the present embodiment, and the configuration of the power supply circuit 101 is different from FIG. 12, the step-down chopper circuit 1200 including the choke coil 102 and the capacitor 116 is added by adding the IGBT 1201 and the diode 1202 to the circuit of FIG. When heating an object to be heated, such as copper or aluminum, since the equivalent resistance is small as described above, the equivalent resistance is increased by increasing the number of turns of the heating coil or increasing the frequency. However, there are limitations due to restrictions on the shape of the device and the frequency band that can be used. As shown in FIG. 1, in the series resonance circuit composed of the heating coil 111 and the resonance capacitors 112 and 113, the Q of the circuit showing the sharpness of resonance changes due to the equivalent resistance, and when the equivalent resistance is small, the Q is large and the resonance The current flowing through the circuit also increases.

  In the current resonance type inverter in which the current flowing through the resonance circuit is sinusoidal as in this embodiment, the resonance current can be limited by increasing the drive frequency higher than the resonance frequency. However, if the difference between the resonance frequency and the drive frequency is large, the phase difference between the output voltage of the inverter and the resonance current is large, and the cutoff current of the upper and lower arms is large, so that the switching loss is increased. Therefore, it is desirable to drive the inverter at a frequency close to the resonance frequency to reduce the cut-off current, and limit the resonance current by lowering the DC voltage.

  In this embodiment, the step-up chopper circuit 80 as described above is provided in order to reduce harmonics of the input current, and the voltage lower limit value of the capacitor 806 is higher than the voltage peak value of the commercial AC power supply 801. Therefore, as shown in FIG. 12, by adding an IGBT 1201 and a diode 1202, a step-down chopper circuit 1200 including a choke coil 102 and a capacitor 116 can be provided to lower the DC voltage, thereby limiting the resonance current. Further, the step-down chopper circuit 1200 can change the voltage of the capacitor 116 by controlling the on-time duty of the IGBT 1201, and thus can perform power control by this voltage change.

  A present Example is described using FIG. 13 and FIG. In this embodiment, the diode 805 and the diode 1202 in FIGS. 8 and 12 are diodes of a silicon carbide device (hereinafter, SiC device). FIG. 13 shows the relationship between the breakdown voltage and on-resistance of a silicon device (hereinafter referred to as Si device) and a silicon carbide device (hereinafter referred to as SiC device). In general, it is known that a SiC device can significantly improve a trade-off between breakdown voltage and on-resistance compared to a Si device. As shown in FIG. 13, when comparing the Si device and the SiC device with 600V elements, the on-resistance of the SiC device is 1/1000 of that of the Si device, which can be greatly reduced. In current induction heating devices using Si devices, cooling devices and heat radiation fins are essential, but using such SiC devices can greatly reduce element loss, and cooling devices and heat radiation fins can be reduced or eliminated. Can do.

  As described above, diodes and semiconductor switching elements (IGBTs, junction FETs, MOSFETs) are changed from Si devices to SiC devices, which makes it possible to significantly reduce loss and eliminate the need for cooling devices and heat radiation fins. Cost can be reduced. Thereby, a structure in which the roaster 1402 is arranged on the entire lower surface of the top plate 1401 of the electromagnetic induction heating device as shown in FIGS. 14 and 15 is possible. In the present embodiment, the SiC device has been described as an example. However, it will be understood by those skilled in the art that the present invention is the same if wide band gap semiconductor devices such as diamond and gallium nitride (GaN) are used in addition to SiC. it is obvious.

  In the first to fifth embodiments described above, the case where the IGBT is used has been described. However, the induction heating device of the present invention is not limited to the IGBT, and may be a power MOSFET, another insulated gate semiconductor device, or a bipolar transistor. It will be apparent to those skilled in the art that the same is true.

It is a circuit block diagram of the induction heating apparatus of Example 1. It is a graph showing the relationship between the number of turns of the heating coil of the electromagnetic induction heating device of Example 1 and the equivalent resistance. It is a graph showing the relationship between the number of turns of the heating coil of the electromagnetic induction heating device of Example 1 and the equivalent inductance. It is a time chart which shows operation | movement of the aluminum and copper to-be-heated material of the electromagnetic induction heating apparatus of Example 1. FIG. 3 is a time chart showing the operation of the iron object to be heated of the electromagnetic induction heating device of Example 1. It is a circuit block diagram of the modification of the electromagnetic induction heating apparatus of Example 1. FIG. It is a circuit block diagram of another modification of the electromagnetic induction heating apparatus of Example 1. It is a circuit block diagram of the induction heating apparatus of Example 2. It is explanatory drawing of the waveform of DC voltage and a resonance current. It is explanatory drawing of the waveform of DC voltage and a resonance current. It is an operation | movement time chart of the power supply circuit of the induction heating apparatus of Example 3. FIG. It is a circuit block diagram of the induction heating apparatus of Example 4. It is explanatory drawing of the pressure | voltage resistance and on-resistance of the SiC device used in Example 5. FIG. 6 is a schematic front view of an induction heating device of Example 5. FIG. It is explanatory drawing of the induction heating apparatus of Example 5. It is explanatory drawing of the equivalent impedance of a to-be-heated object. It is explanatory drawing of the relationship between the input electric power of an induction heating apparatus, and a resonance current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Upper / lower arm, 80 ... Boost chopper circuit, 101 ... Power supply circuit, 102 ... Choke coil, 103, 104, 601, 804, 1201 ... IGBT, 105, 106, 602, 701, 805, 1202 ... Diode, 107, 108 114, relay, 109, 110 ... snubber capacitor, 111 ... heating coil, 112, 113 ... resonant capacitor, 115 ... smoothing capacitor, 116, 806 ... capacitor, 801 ... commercial AC power supply, 802 ... diode rectifier circuit, 803 ... inductor 1200 ... Step-down chopper circuit, 1401 ... Top plate, 1402 ... Roaster, 1403 ... Window, 1404 ... Handle, 1501 ... Net, 1502 ... Rail.

Claims (9)

A resonance load circuit including an object to be heated; and an inverter for converting a DC voltage of a DC power source into an AC voltage to supply electric power to the resonance load circuit, wherein the inverter is connected in series. In an induction heating apparatus having upper and lower arms composed of elements,
A first inductor connected in series to the DC power supply, the first inductor having one end connected to the DC power supply side and the other end connected to the inverter via a switch for switching a connection point; An induction heating apparatus, wherein the switch is switched according to the material of an object. The induction heating apparatus according to claim 1,
At least two or more of the switches connected to the other end of the first inductor are provided, one of the switches is connected to the upper arm of the upper and lower arms, and the other of the switches is connected to the lower arm of the upper and lower arms. ,
The switching element of the upper and lower arms is a power semiconductor switching element in which a diode is connected in antiparallel,
A first resonant load circuit comprising a heating coil and a first resonant capacitor is connected to the output terminals of the upper and lower arms;
An induction heating apparatus, wherein a series circuit of a second resonance capacitor and a switch is connected in parallel with the first resonance capacitor. In the induction heating apparatus according to claim 2,
One of the switches connected to the upper arm is a first diode. In the electromagnetic induction heating device according to any one of claims 1 to 3,
The induction heating device includes a rectifier circuit that rectifies a commercial AC power supply, and a first power supply circuit that generates an arbitrary DC voltage based on an output from the rectifier circuit,
The first power supply circuit includes a semiconductor switching element, a second inductor, a capacitor, and a second diode, and generates an arbitrary DC voltage by changing an on-time duty of the semiconductor switching element. A feature of the electromagnetic induction heating device. In the electromagnetic induction heating device according to any one of claims 1 to 4,
A second power supply circuit configured to generate an arbitrary DC voltage based on an output from the first power supply circuit, the second power supply circuit including a semiconductor switching element, a capacitor, an inductor, and a diode; 2. An electromagnetic induction heating apparatus, wherein an arbitrary DC voltage is generated by changing an on-time duty of a semiconductor switching element of the power supply circuit 2. In the induction heating apparatus according to any one of claims 2 to 5,
The induction heating apparatus, wherein the diode and the semiconductor switching element are wide band gap semiconductor devices. In the induction heating apparatus according to any one of claims 1 to 6,
The induction heating apparatus, wherein the upper and lower arm semiconductor switching elements include snubber capacitors connected in parallel. The induction heating device according to claim 7,
An electromagnetic induction heating apparatus comprising switch means for separating the snubber capacitor from the upper and lower arms. The induction heating apparatus according to claim 6,
An induction heating apparatus, wherein a roaster is disposed below a top plate of the induction heating apparatus.

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