JP7045295B2 - Electromagnetic induction heating device - Google Patents

Description

The present invention relates to an inverter type electromagnetic induction heating device that supplies desired electric power to an object to be heated to perform induction heating.

In recent years, an inverter type electromagnetic induction heating device that induces and heats a metal pot without using fire has been widely used. In the electromagnetic induction heating device, a high-frequency current is passed through a heating coil, an eddy current is generated in a pot bottom of a metal pot arranged close to the heating coil, and heat is generated by the electric resistance of the pot bottom itself. As a conventional example of an electromagnetic induction heating device, there is an induction heating cooker as disclosed in Patent Document 1.

According to claim 1 of this Patent Document 1, "having first and second upper and lower arms which are a series of two main switching elements, DC voltage is converted into DC / AC and AC voltage is supplied to the load. A first inverter control means for operating the inverter as a half-bridge type inverter by driving the switching element of the first upper and lower arms, and the switching element of the first and second upper and lower arms. In a power conversion device provided with a second inverter control means for operating the inverter as a full-bridge type inverter by driving, a chopper that converts a DC power supply voltage into DC / DC and applies it to the inverter as the DC voltage. A full bridge comprising a circuit, a first load circuit connected between the output terminals of the half-bridge inverter including the first upper and lower arms, and the first and second upper and lower arms. A second load circuit connected between the output terminals of the method inverter and including at least a part of the first load circuit, and a switch means for connecting and disconnecting the second load circuit from the inverter are provided. A power conversion device characterized in that one of the switching elements of the upper and lower arms of No. 2 is also used as a switching element for boosting or raising / lowering the pressure of the chopper circuit "is disclosed.

That is, as shown in FIG. 1 and the like of the same document, the method of Patent Document 1 is provided with a chopper circuit in front of the inverter, and when the inverter becomes a full bridge method, a part of the switching element of the inverter is a chopper circuit. It is also used as a switching element of.

Japanese Unexamined Patent Publication No. 2009-136104

In Patent Document 1, when the switching element for both the full-bridge type inverter and the chopper is in the off state, the path for directly charging the smoothing capacitor from the input power supply is cut off when the voltage of the smoothing capacitor is lower than the input power supply voltage. In order to do so, a switching element is separately provided to perform step-down operation. Therefore, the number of switching elements to be controlled increases, and it is necessary to add a drive circuit and a control circuit. Further, since the switching element is turned on and off, there is a problem that the switching loss increases in addition to the conduction loss.

An object of the present invention is to address the above problems, and it is generated from a pan by smoothing the DC link voltage applied to the inverter without adding a switching element other than the inverter and suppressing the pulsation of the heating coil current. It is an object of the present invention to provide an inverter type electromagnetic induction heating device that prevents an exciting noise.

In order to achieve the above object, the electromagnetic induction heating device of the present invention includes a heating coil for inductively heating an object to be heated, a smoothing DC voltage of a smoothing capacitor is converted into an AC voltage, and the heating coil and a resonance capacitor are included. It includes an inverter that supplies high-frequency power to the resonance load circuit and a chopper circuit that converts the rectified voltage obtained by rectifying the AC voltage of a commercial AC power supply into the smoothed DC voltage and applies it to the inverter. It has a first upper and lower arm composed of a switching element for an AC, a series circuit of one diode, and antiparallel diodes provided in each of the upper arm and the lower arm, and the chopper circuit is an inductor. A recirculation diode that allows a recirculation current flowing due to the stored energy of the inductor to flow through the smoothing capacitor and a switching element for a buck-boost chopper, and one of the switching elements for the inverter is also used as the switching element for the buck-boost chopper. When the combined switching element is in the off state, the diode of the inverter cuts off the path for directly charging the smoothing capacitor from the rectified voltage obtained by rectifying the AC voltage of the commercial AC power supply.

According to the inverter type electromagnetic induction heating device of the present invention, the excitation sound generated from the pan by smoothing the DC link voltage applied to the inverter without adding a switching element other than the inverter and suppressing the pulsation of the heating coil current. Can be prevented.

The circuit block diagram of the electromagnetic induction heating apparatus of Example 1. FIG. The operating waveform of the electromagnetic induction heating device of FIG. The operating waveform of the electromagnetic induction heating device of FIG. The power control characteristic diagram of the electromagnetic induction heating apparatus of FIG. 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. The operating waveform of the electromagnetic induction heating device of FIG. The operating waveform of the electromagnetic induction heating device of FIG. The circuit block diagram of the electromagnetic induction heating apparatus of Example 6. The operating waveform of the electromagnetic induction heating device of FIG. The operating waveform of the electromagnetic induction heating device of FIG. The operating waveform of the electromagnetic induction heating device of FIG.

Hereinafter, examples of the electromagnetic induction heating device of the present invention will be described with reference to the drawings. In each figure, reference numbers having the same reference number indicate the same configuration requirements or configuration requirements having similar functions, and duplicate explanations are omitted as appropriate.

FIG. 1 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the first embodiment. As shown here, the commercial AC power supply 1 is connected to the input terminal of the rectifier circuit 2 composed of the diodes 2a to 2d via the inductor 8 and the capacitor 9 constituting the normal filter. The rectifier circuit 2 outputs a rectified DC voltage obtained by rectifying a commercial AC voltage, and the output terminal of the rectifier circuit 2 is a chopper inductor 41 and a power semiconductor switching element (hereinafter, simply referred to as "switching element"). ) 5b are connected in series.

Further, a smoothing capacitor 44 is connected to both ends of the inductor 41 via a recirculation diode 6h and an antiparallel diode 6a. An upper and lower arm including a switching element 5a constituting an upper arm and a series of a switching element 5b and a diode 10b constituting a lower arm are connected in parallel to both ends of the smoothing capacitor 44. A reverse parallel diode 6a is connected in parallel to the upper arm (switching element 5a) of the upper and lower arms in the opposite direction, and a reverse parallel diode 6b is connected in parallel to the lower arm (switching element 5b and the diode 10b). ing.

By connecting a snubber capacitor (not shown) in parallel to the upper arm and the lower arm, the snubber capacitor is charged or discharged by the breaking current at the turn-off of the switching element 5a or 5b, and the change in the voltage applied to both switching elements is reduced. It is possible to suppress the turn-off loss.

One end of the heating coil 11 is connected to the output terminals of the upper and lower arms, and resonance capacitors 13a and 13b are connected between the other end of the heating coil 11 and the positive and negative electrodes of the smoothing capacitor 44, respectively, and a half-bridge type inverter circuit is used. Consists of.

In the electromagnetic induction heating device 100 of the present embodiment having the above configuration, the switching element 5b is used as a switching element for an inverter and also as a switching element for a buck-boost chopper using the inductor 41 as an inductor for a chopper. .. In this case, the diode 10b is smoothed from the commercial AC power supply 1 via the inductor 41 and the antiparallel diode 6a when the switching element 5b is in the off state and the voltage of the smoothing capacitor 44 is lower than the commercial AC voltage. It serves to block the path for directly charging the capacitor 44.

FIG. 2 is an operation waveform for one commercial frequency cycle in this embodiment. From the top, the waveforms in the figure are the voltage v (44) of the smoothing capacitor 44, the voltage v (1) of the commercial AC power supply 1, the input current i (1), the current i (41) of the inductor 41, and the heating coil 11. Current i (11).

The voltage v (44) of the smoothing capacitor 44 is pulsating at a frequency twice the commercial frequency, but is sufficiently smoothed, and the pulsation of the current i (11) of the heating coil 11 is suppressed. Since the current i (41) of the inductor 41 is intermittent (repeated on / off), it is shown in black in the figure. In this embodiment, by operating the inverter under the condition that the current i (41) of the inductor 41 is intermittent, the input current i (1) can be made into a sinusoidal waveform without adding the power factor improvement control. Is. That is, if the on-time duty of the switching element 5b for both the chopper and the inverter is fixed during one cycle of the commercial frequency, the inductor 41 responds to the instantaneous voltage of the voltage v (1) of the commercial AC power supply 1. Since the current flows, the input current i (1) passed through the normal filter naturally becomes a sinusoidal shape. Even under the condition that the smoothing voltage v (44) is lower than the commercial AC voltage, the phenomenon that the input current i (1) increases does not occur, and the achievement of the direct charging path cutoff function by the diode 10b can be confirmed.

FIG. 3 is an operating waveform near the peak of the commercial AC power supply voltage. The waveforms in the figure are, from the top, the voltage v (44) of the smoothing capacitor 44, the gate signals vg (5a) and vg (5b) of the switching elements 5a and 5b, the current i (41) of the inductor 41, and the heating coil 11. The currents i (11) and the currents i (5a), i (6a), i (5b), i (6b), and i (10b) of each element.

When the switching element 5b is turned on (vg (5b) is turned on), a current starts to flow in the inductor 41 and the current i (41) increases. On the other hand, the current i (11) of the heating coil 11 flows through the antiparallel diode 6b and recirculates, and then the polarity of the current is reversed. The combined current of (11) flows. Further, only the current i (11) of the heating coil 11 flows through the diode 10b.

On the other hand, when the switching element 5b is turned off (vg (5b) is turned off), the energy stored in the inductor 41 causes a circulating current to flow through the smoothing capacitor 44 via the antiparallel diode 6a and the recirculation diode 6h, and the inductor 41 The current i (41) decreases. By turning on the switching element 5a while the current is flowing through the antiparallel diode 6a, the zero voltage zero current turn-on operation is performed, so that no turn-on loss occurs in the switching element 5a.

Further, while the switching element 5a is on (vg (5a) is on), the current i (41) of the inductor 41 becomes zero, and the current i (11) of the heating coil 11 is switched when the current i (11) of the heating coil 11 is flowing through the switching element 5a. When the element 5a is turned off, the current i (11) of the heating coil 11 flows through the antiparallel diode 6b and recirculates. By turning on the switching element 5b during that time, the zero voltage zero current turn-on operation is performed, so that the turn-on loss in the switching element 5b does not occur.

As described above, in this embodiment, by operating both switching elements under the condition that the current i (41) of the inductor 41 is intermittent, a turn-on loss occurs in the switching element 5b used for both the buck-boost chopper and the inverter. do not do. Further, it is possible to make the input current i (1) into a sinusoidal waveform without newly adding a power factor improvement control.

FIG. 4 is a power control characteristic diagram showing the relationship between the on-time duty of the switching element 5b (the ratio of the conduction period of the switching element 5b to the switching cycle shown by vg (5b) in FIG. 3) and the power. By utilizing the relationship shown in this figure, in the electromagnetic induction heating device 100 of this embodiment, the power is controlled according to the thermal power set by the user by controlling the on-time duty of the switching element 5b. Is possible. As described above, since the switching element 5b also functions as a switching element for the buck-boost chopper, the energy stored in the inductor 41 is adjusted by controlling the on-time duty of the switching element 5b, and the voltage of the smoothing capacitor 44 is adjusted. It is possible to control. In addition, since it also functions as a switching element for an inverter, it is possible to control the current flowing through the heating coil 11, and by utilizing both of these actions, the electric power can be the desired thermal power set by the user. Can be controlled to.

According to the electromagnetic induction heating device of the present embodiment described above, the power factor of the input current is improved and the DC link voltage is smoothed without newly providing a switching element other than the switching element necessary for realizing the inverter. It is possible to prevent the generation of excitation noise and control the power of the inverter. Further, since a switching element is not required other than the switching element required for realizing the inverter, it is possible to suppress the scale-up of the control circuit of the switching element.

FIG. 5 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the second embodiment. It should be noted that duplicate explanations will be omitted for the common points with the first embodiment.

In this embodiment, the chopper inductor 41 and the switching element 5a are connected in series to the output terminal of the rectifier circuit 2. A smoothing capacitor 44 is connected to both ends of the inductor 41 via a recirculation diode 6 g and an antiparallel diode 6b. An upper and lower arm including a series of a switching element 5a constituting an upper arm and a diode 10a and a switching element 5b constituting a lower arm are connected in parallel to both ends of the smoothing capacitor 44. A reverse parallel diode 6a is connected in parallel to the upper arm (switching element 5a and a diode 10a) of the upper and lower arms, and a reverse parallel diode 6b is connected in parallel to the lower arm (switching element 5b). ing.

In the first embodiment, the switching element 5b is also used as the switching element for the buck-boost chopper and the inverter, but in the present embodiment, the switching element 5a plays a role. In this case, the diode 10a is used for smoothing from the commercial AC power supply 1 via the antiparallel diode 6b and the inductor 41 when the switching element 5a is in the off state and the voltage of the smoothing capacitor 44 is lower than the commercial AC voltage. It serves to block the path for directly charging the capacitor 44.

The electromagnetic induction heating device of the present embodiment described above can also obtain the same effect as that of the first embodiment.

FIG. 6 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the third embodiment. It should be noted that duplicate explanations will be omitted for the common points with the above embodiments.

In this embodiment, a second upper and lower arm composed of a switching element 5c of the upper arm and a switching element 5d of the lower arm are connected in parallel to both ends of the smoothing capacitor 44. Antiparallel diodes 6c and 6d are connected in parallel to the switching elements 5c and 5d, respectively, in opposite directions. A heating coil 11 and a resonance capacitor 13 are connected between the output terminals of the two upper and lower arms to form a full-bridge type inverter.

The full bridge method of the present embodiment can increase the number of turns of the heating coil 11 as compared with the half bridge method of the first and second embodiments, and even if the current i (11) of the heating coil 11 is reduced. The magnetomotive force can be maintained. This has the effect of reducing the current flowing through the switching element and reducing the loss.

FIG. 7 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the fourth embodiment. It should be noted that duplicate explanations will be omitted for the common points with the third embodiment.

The difference from the third embodiment is that a relay 20 for disconnecting the resonance load circuit including the heating coil 11 and the resonance capacitor 13 from the upper and lower arms including the switching elements 5a and 5b and the diode 10b is provided, and the heating coil 11 and the resonance load circuit are provided. Resonant capacitors 12a and 12b are connected between the connection point of the resonance capacitor 13 and the positive and negative electrodes of the smoothing capacitor 44, respectively.

In this embodiment, the inverter method is switched between the full bridge method and the half bridge method by switching the relay 20 according to the material (magnetic material or non-magnetic material) of the object to be heated and the magnitude of the set thermal power, and the resonance capacitor is used. The resonance frequency can be changed by switching the capacitance.

Here, since the heating coil 11 and the object to be heated (not shown) are magnetically coupled, when the object to be heated is converted into an equivalent circuit viewed from the heating coil 11 side, the equivalent resistance and the equivalent inductance of the object to be heated are in series. It becomes a configuration connected to. Equivalent resistance and equivalent inductance differ depending on the material of the object to be heated. In the case of non-magnetic material with low resistance copper or aluminum, both the equivalent resistance and equivalent inductance are small, and in the case of magnetic material with high resistance iron, which one. Will also grow.

In FIG. 7, when the object to be heated is a non-magnetic material such as copper or aluminum, the relay 20 is turned off, and a half-bridge type inverter composed of a second upper and lower arm, a heating coil 11, and resonance capacitors 12a and 12b. Heat with. As described above, since the non-magnetic material and the object to be heated with low resistance 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 capacitances of the resonance capacitors 12a and 12b are set so that the second upper and lower arms can be driven at a frequency of, for example, about 90 kHz. The first upper and lower arms are disconnected from the resonant load circuit because the relay 20 is in the off state. Therefore, the switching element 5b operates only as a switching element for a buck-boost chopper using the inductor 41 as an inductor for the chopper.

On the other hand, when the object to be heated is a magnetic material such as iron or stainless steel, the relay 20 is turned on, and the full bridge method is composed of the first and second upper and lower arms, the heating coil 11, and the resonance capacitors 12a, 12b, and 13. Heat with the inverter of. As described above, since the magnetic material and the object to be heated having high resistance has a large equivalent resistance, it is difficult for current to flow in the resonance load circuit. Therefore, by switching to the full bridge method, the output voltage of the inverter is doubled to obtain the desired output. In the case of copper and aluminum mentioned above, the resistance is small, so the frequency of the inverter was set to about 90 kHz to increase the skin resistance, but in the case of iron, the resistance is originally large, so the first and second upper and lower arms are used at a frequency of about 20 kHz. Drive. As described above, the capacitance of the resonance capacitors 12a and 12b is set according to the drive frequency of about 90 kHz, but the capacitance of the resonance capacitor 13 is set according to the drive frequency of about 20 kHz. Since the drive frequencies are significantly different, the capacitance of the resonance capacitor 13 is sufficiently larger than that of the resonance capacitors 12a and 12b. Therefore, the resonance frequency of the full bridge type inverter is mainly set by the resonance capacitor 13. Further, even in the full bridge type inverter operation, since the current flowing through the resonance capacitor 13 is large, there is no problem in the inverter operation even when the resonance capacitors 12a and 12b are connected.

In this embodiment, the capacitance of the resonance capacitor can also be switched by switching the relay 20. Therefore, the setting range of the drive frequency of the inverter can be widened, and heating can be performed at an optimum frequency according to the material of the object to be heated.

FIG. 8 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the fifth embodiment. It should be noted that duplicate explanations will be omitted for the common points with the above embodiments.

In this embodiment, for example, a configuration in which a plurality of inverters of the first embodiment are used is shown, and a normal filter composed of an inductor 8 and a capacitor 9 is commonly used. Here, the first to third inverters are 20A, 20B, and 20C, respectively. The inverters 20B and 20C have the same configuration as the inverter 20A, and the heating coil 11 of each inverter may be arranged in a three-burner stove shape corresponding to the heating of different objects to be heated, or one cover. The arrangement of the bite-sized stoves corresponding to the heating of the heated object (for example, the coils are arranged concentrically) may be used.

FIG. 9 is an example of an operating waveform when two inverters are used. When two inverters are used, the gate signals of the switching elements 5a and 5b of the inverter 20B are shifted by 180 ° with respect to the gate signals of the switching elements 5a and 5b of the inverter 20A. As a result, the phase of the current flowing through the inductor 41 of the inverter 20A and the phase of the current flowing through the inductor 41 of the inverter 20B are shifted by 180 °, so that the ripple of the combined current of the inductor 41 is reduced. As a result, the values of the inductor 8 and the capacitor 9 of the normal filter of each inverter can be reduced, and the normal filter can be miniaturized.

On the other hand, FIG. 10 is an example of an operating waveform when three inverters are used. When three inverters are used, the gate signal of the switching elements 5a and 5b of the inverter 20B is shifted by 120 ° with respect to the gate signal of the switching elements 5a and 5b of the inverter 20A, and the gate of the switching elements 5a and 5b of the inverter 20B is used. The gate signal of the switching elements 5a and 5b of the inverter 20C is shifted by 120 ° with respect to the signal. As a result, the phase of the current flowing from the inverter 20A to the inductor 41 of the 20C is shifted by 120 °, so that the ripple of the combined current of the inductor 41 is reduced.

As described above, in this embodiment, the inductor and the capacitor of the normal filter can be miniaturized by operating the plurality of inverters with the phases shifted.

FIG. 11 is a circuit configuration diagram of the electromagnetic induction heating device 100 of the sixth embodiment. It should be noted that duplicate explanations will be omitted for the common points with the above embodiments.

In this embodiment, when the voltage of the commercial AC power supply 1 is positive, the switching element 5a and the inductor 41 are connected in series via the diode 2a. A smoothing capacitor 44 is connected to both ends of the inductor 41 via a recirculation diode 6 g and an antiparallel diode 6b. On the other hand, when the voltage of the commercial AC power supply 1 is negative, the switching element 5b and the inductor 41 are connected in series via the diode 2b. A smoothing capacitor 44 is connected to both ends of the inductor 41 via a recirculation diode 6h and an antiparallel diode 6a.

At both ends of the smoothing capacitor 44, an upper and lower arm in which a series body of a switching element 5a and a diode 10a constituting an upper arm and a series body of a switching element 5b and a diode 10b constituting a lower arm are connected in series. Are connected in parallel.

FIG. 12 is an operation waveform for one commercial frequency cycle in this embodiment. From the top, the waveforms in the figure are the voltage v (44) of the smoothing capacitor 44, the voltage v (1) of the commercial AC power supply 1, the input current i (1), the current i (41) of the inductor 41, and the heating coil 11. Current i (11).

The voltage v (44) of the smoothing capacitor 44 is pulsating at a frequency twice the commercial frequency, but is sufficiently smoothed, and the pulsation of the current i (11) of the heating coil 11 is suppressed. Since the current i (41) of the inductor 41 is intermittent (repeated on / off), it is shown in black in the figure. In this embodiment, by operating the inverter under the condition that the current i (41) of the inductor 41 is intermittent, the input current i (1) can be made into a sinusoidal waveform without adding the power factor improvement control. Is. That is, if the on-time duty of the switching elements 5a and 5b for both the chopper and the inverter is fixed in one cycle of the commercial frequency, the inductor 41 has the instantaneous voltage of the voltage v (1) of the commercial AC power supply 1. Since the current corresponding to the current flows, the input current i (1) via the normal filter naturally becomes a sinusoidal shape.

FIG. 13 is an operating waveform near the positive peak of the commercial AC power supply voltage, and FIG. 14 is an operating waveform near the negative peak of the commercial AC power supply voltage. The waveforms in the figure are, from the top, the voltage v (44) of the smoothing capacitor 44, the gate signals vg (5a) and vg (5b) of the switching elements 5a and 5b, the current i (41) of the inductor 41, and the heating coil 11. The currents i (11) and the currents i (5a), i (6a), i (5b), i (6b), and i (10b) of each element.

From FIG. 13, when the voltage v (1) of the commercial AC power supply 1 is positive, when the switching element 5a is turned on (vg (5a) is turned on), a current starts to flow in the inductor 41 and the current i (41) increases. On the other hand, the current i (11) of the heating coil 11 flows through the antiparallel diode 6a and recirculates, and then the polarity of the current is reversed. The combined current of (11) flows. Further, only the current i (11) of the heating coil 11 flows through the diode 10a.

On the other hand, when the switching element 5a is turned off (vg (5a) is turned off), the energy stored in the inductor 41 causes a recirculation current to flow in the smoothing capacitor 44 via the antiparallel diode 6b and the recirculation diode 6g, and the inductor 41 The current i (41) decreases. By turning on the switching element 5b while the current is flowing through the antiparallel diode 6b, the zero voltage zero current turn-on operation is performed, so that no turn-on loss occurs in the switching element 5b.

Further, the current of the inductor 41 becomes zero while the switching element 5b is on (vg (5b) is on), and the switching element 5b is turned off when the current i (11) of the heating coil 11 is flowing through the switching element 5b. Then, the current i (11) of the heating coil 11 flows through the antiparallel diode 6a and recirculates. By turning on the switching element 5a in the meantime, the zero voltage zero current turn-on operation is performed, so that the turn-on loss in the switching element 5a does not occur.

From FIG. 14, when the voltage v (1) of the commercial AC power supply 1 is negative and the switching element 5b is turned on (vg (5b) is turned on), a current starts to flow in the inductor 41 and the current i (41) increases. Here, since the direction in which the current of the inductor 41 flows from the left to the right in FIG. 11 is positive, the waveform increases in the negative direction. After the current i (11) of the heating coil 11 flows through the antiparallel diode 6b and recirculates, the polarity of the current is reversed, and the current i (41) of the inductor 41 and the current i (11) of the heating coil 11 are connected to the switching element 5b. ) Combined current flows. Further, only the current i (11) of the heating coil 11 flows through the diode 10b.

On the other hand, when the switching element 5b is turned off (vg (5b) is turned off), the energy stored in the inductor 41 causes a circulating current to flow through the smoothing capacitor 44 via the antiparallel diode 6a and the recirculation diode 6h, and the inductor 41 The current i (41) decreases. By turning on the switching element 5a while the current is flowing through the antiparallel diode 6a, the zero voltage zero current turn-on operation is performed, so that no turn-on loss occurs in the switching element 5a.

Further, the current of the inductor 41 becomes zero while the switching element 5a is on (vg (5a) is on), and the switching element 5a is turned off when the current i (11) of the heating coil 11 is flowing through the switching element 5a. Then, the current i (11) of the heating coil 11 flows through the antiparallel diode 6b and recirculates. By turning on the switching element 5b during that time, the zero voltage zero current turn-on operation is performed, so that the turn-on loss in the switching element 5b does not occur.

In Examples 1 to 5, regardless of the voltage polarity of the commercial AC power supply 1, only one of the upper arm and the lower arm is configured to be used as a switching element for the buck-boost chopper and the inverter. Therefore, the burden on the switching element and the diode that are also used becomes large. In this embodiment, since the switching element to be shared is switched between 5a and 5b according to the positive and negative polarities of the commercial AC power supply voltage, the burden on the semiconductor elements including the antiparallel diodes 6a and 6b is reduced.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, or replace other configurations with respect to the configurations of each embodiment.

100 electromagnetic induction heating device,
1 Commercial AC power supply,
2 Rectifier circuit,
2a-2d, 10a, 10b diodes,
6a-6d antiparallel diode,
6g, 6h recirculation diode,
5a-5d switching element,
8 inductor,
9 capacitors,
12a, 12b, 13, 13a, 13b resonant capacitors,
11 heating coil,
20 relays,
41 inductor,
44 Smoothing capacitor

Claims (7)

A heating coil that induces and heats the object to be heated,
An inverter that converts the smoothing DC voltage of the smoothing capacitor into an AC voltage and supplies high-frequency power to the resonance load circuit including the heating coil and the resonance capacitor.
A chopper circuit that converts the rectified voltage obtained by rectifying the AC voltage of a commercial AC power supply into the smoothed DC voltage and applies it to the inverter.
It is an electromagnetic induction heating device equipped with
The inverter has a first upper and lower arm composed of a series circuit of two inverter switching elements and one diode, and a reverse parallel diode provided in each of the upper arm and the lower arm.
The chopper circuit includes an inductor, a recirculation diode that causes a recirculation current flowing due to the stored energy of the inductor to flow through the smoothing capacitor, and a switching element for a buck-boost chopper.
One of the switching elements for the inverter is also used as the switching element for the buck-boost chopper.
When the dual-purpose switching element is in the off state, the diode of the inverter cuts off the path for directly charging the smoothing capacitor from the rectified voltage obtained by rectifying the AC voltage of the commercial AC power supply. Device. A heating coil that induces and heats the object to be heated,
An inverter that converts the smoothing DC voltage of the smoothing capacitor into an AC voltage and supplies high-frequency power to the resonance load circuit including the heating coil and the resonance capacitor.
A chopper circuit that converts the AC voltage of a commercial AC power supply into the smooth DC voltage and applies it to the inverter.
It is an electromagnetic induction heating device equipped with
The inverter includes an upper arm consisting of a series circuit of an inverter switching element and a diode, a lower arm consisting of a series circuit of an inverter switching element and a diode, and an antiparallel diode provided in each of the upper arm and the lower arm. Has a first upper and lower arm composed of,
The chopper circuit includes an inductor, a recirculation diode that causes a recirculation current flowing due to the stored energy of the inductor to flow through the smoothing capacitor, and a switching element for a buck-boost chopper.
The inverter switching element is also used as the buck-boost chopper switching element.
An electromagnetic induction heating device characterized in that when a switching element also used is in an off state, the diode included in the arm cuts off a path for directly charging the smoothing capacitor from the AC voltage of the commercial AC power supply. In the electromagnetic induction heating device according to claim 1 or 2.
The inverter further has a second upper and lower arm composed of a series circuit of two inverter switching elements.
An electromagnetic induction heating device, characterized in that the resonance load circuit is connected between the output terminals of the first upper and lower arms and the second upper and lower arms. In the electromagnetic induction heating device according to claim 3,
An electromagnetic induction heating device comprising a switch between the output terminal of the first upper and lower arm and the resonance load circuit to disconnect the resonance load circuit from the output terminal of the first upper and lower arm. In the electromagnetic induction heating device according to any one of claims 1 to 4.
An electromagnetic induction heating device characterized in that an electric current flows intermittently through the inductor of the chopper circuit. In the electromagnetic induction heating device according to any one of claims 1 to 5.
When driving a plurality of the inverters, the electromagnetic induction heating device is characterized in that the current flowing in each of the inverters is driven by shifting the phase. In the electromagnetic induction heating device according to any one of claims 1 to 5.
An electromagnetic induction heating device characterized in that the larger the set thermal power, the larger the on-time duty of the switching element that is also used.

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