JP2019067690A - Electromagnetic induction heating device - Google Patents

Abstract

To provide an electromagnetic induction heating device of inverter type which performs induction heating by supplying a desired power to a heated object of different material.SOLUTION: An electromagnetic induction heating device supplies a high frequency current to a first resonance load circuit 50 by an inverter of half-bridge circuit system using first upper and lower arms 3, when a heated object is a nonmagnetic substance, and supplies a high frequency current to a second resonance load circuit 60 by an inverter of full-bridge circuit system using second upper and lower arms 4, when the heated object is a magnetic substance. The first resonance load circuit is a series circuit of a heating coil 11, a second resonance capacitor 13, and a first resonance capacitor 12 provided between the output terminal of the first upper and lower arms, and the second resonance load circuit is a series circuit of a heating coil, and a second resonance capacitor provided between the output terminal of the first upper and lower arms and the output terminal of the second upper and lower arms.SELECTED DRAWING: Figure 1

Description

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

  In recent years, an inverter type electromagnetic induction heating device for induction heating a metal pan without using a fire has been widely used. The electromagnetic induction heating apparatus applies a high frequency current to a heating coil, generates an eddy current in a pan bottom of a metal pan disposed closely above the heating coil, and generates heat due to the electric resistance of the pan bottom itself. Generally, it is known that magnetic materials such as iron pots having large specific resistances are easy to induction heat, but nonmagnetic materials such as copper pots and aluminum pots having small specific resistances are difficult to induction heat.

  As a prior art which solves this problem, there is an electromagnetic induction heating device of patent documents 1. This electromagnetic induction heating device determines whether the metal pan placed above the heating coil is a magnetic pan or a nonmagnetic pan. In the case of a nonmagnetic pan, the high frequency inverter is a half bridge circuit system, and in the case of a magnetic pan In the case of using a full bridge circuit system, metal pots of different materials are efficiently inductively heated.

Patent No. 4909662

  In Patent Document 1, when heating a high-resistance magnetic pan, the switch means for switching the circuit system of the high frequency inverter and the capacity of the resonance capacitor is turned on to switch the inverter to the full bridge circuit system, and The magnetic pan is inductively heated using both the capacitor (FIG. 1, reference numeral 12) and the second resonant capacitor (reference numeral 13).

  On the other hand, when heating a low resistance nonmagnetic pan, the switch means is turned off, the inverter is switched to the half bridge circuit system, and the second resonance capacitor having a large capacity is separated to make a first resonance having a small capacity. Inductively heat the nonmagnetic pan using a condenser. Therefore, when heating the nonmagnetic pan, there is a problem that the second resonance capacitor having a large capacity is not effectively used.

  Further, in the configuration of Patent Document 1, in the case of the full bridge circuit system, the series capacitance of the two resonance capacitors functions as a snubber capacitor of the second upper and lower arms (FIG. 1, reference numeral 4 of the same document). There is also a problem that the setting of is complicated.

  The object of the present invention is to address the above problems, and in particular, an inverter type electromagnetic induction heating apparatus capable of efficiently supplying desired power by using two resonant capacitors together regardless of the material of the metal pan. It is to provide.

  In order to achieve the above object, an electromagnetic induction heating apparatus according to the present invention comprises a DC power supply for supplying a DC voltage, first upper and lower arms connected between positive and negative electrodes of the DC power supply, and positive and negative electrodes of the DC power supply. A half bridge circuit system using the first upper and lower arms, and the second upper and lower arms connected between them, and a heating coil for inductively heating the object to be heated, and when the object to be heated is a nonmagnetic material The high frequency current is supplied to the first resonant load circuit by the first inverter, and when the object to be heated is a magnetic body, the second inverter is a full bridge circuit type inverter using the first upper and lower arms and the second upper and lower arms. The heating coil is supplied with a high frequency current to two resonant load circuits, and the first resonant load circuit is provided between the output terminals of the first upper and lower arms and the negative electrode of the DC power supply; First resonant capacitor and the first The heating coil is a series circuit of resonant capacitors, and the second resonant load circuit is provided between the output terminals of the first upper and lower arms and the output terminals of the second upper and lower arms. It is a series circuit of resonant capacitors.

  According to the present invention, regardless of whether the inverter is a full bridge circuit system or a half bridge circuit system, the second resonance capacitor is effectively used, so the capacity of the first resonance capacitor can be reduced. In addition to the ability to miniaturize the entire inverter circuit, desired power can be efficiently supplied regardless of the circuit system.

FIG. 1 is a circuit diagram of an electromagnetic induction heating device according to a first embodiment. The block diagram of the half bridged circuit system of the electromagnetic induction heating apparatus of FIG. The block diagram of the full bridge circuit system of the electromagnetic induction heating apparatus of FIG. State explanatory drawing of the mode 1 of the full bridge circuit system of FIG. State explanatory drawing of the mode 2 of the full bridge circuit system of FIG. State explanatory drawing of mode 3 of the full bridged circuit method of FIG. State explanatory drawing of the mode 4 of the full bridge circuit system of FIG. State explanatory drawing of mode 5 of the full bridged circuit method of FIG. State explanatory drawing of mode 6 of the full bridged circuit method of FIG. FIG. 5 is a circuit diagram of an electromagnetic induction heating device according to a second embodiment. FIG. 7 is a circuit diagram of an electromagnetic induction heating device according to a third embodiment. FIG. 7 is a circuit diagram of an electromagnetic induction heating device according to a fourth embodiment.

  Hereinafter, embodiments of the present invention will be described using the drawings. In the drawings, the same reference numerals denote the same constituent elements or constituent elements having similar functions, and redundant description will be omitted as appropriate.

  FIG. 1 is a circuit diagram of an electromagnetic induction heating apparatus according to a first embodiment. In FIG. 1, a DC power supply 1 is a power supply that rectifies an AC voltage supplied from a commercial AC power supply (not shown) and outputs a DC voltage. Between the positive electrode and the negative electrode of this DC power supply 1, a power semiconductor switching element (hereinafter simply referred to as "switching element") 5a and 5b are connected in series to a first upper and lower arm 3, a switching element 5c and A second upper and lower arm 4 in which 5d is connected in series is connected.

  Diodes 6a to 6d are connected in parallel in the reverse direction to switching elements 5a to 5d, respectively, and snubber capacitors 7a and 7b are connected in parallel to switching elements 5a and 5b, respectively. The snubber capacitors 7a and 7b are charged or discharged by a blocking current at the time of turn-off of the switching element 5a or 5b, and the change in voltage applied to both switching elements is reduced to suppress the turn-off loss.

  A first resonant load circuit 50 is connected between the output terminal of the first upper and lower arms 3 and the negative electrode of the DC power supply 1. The first resonance load circuit 50 includes a heating coil 11 whose one end is connected to the output terminal of the first upper and lower arms 3 and a second resonance capacitor 13 whose one end is connected to the other end of the heating coil 11. A series circuit in which a first resonance capacitor 12 connected to the other end of the second resonance capacitor 13 is connected in series. In the first resonant load circuit 50, the first resonant capacitor 12 and the second resonant capacitor 13 form a capacitor series 15 connected in series, and the combined capacitance functions as a resonant capacitance of the first resonant load circuit 50. .

  A series circuit of a second resonant load circuit 60 and a relay 20 is connected between the output terminal of the first upper and lower arms 3 and the output terminal of the second upper and lower arms 4. The second resonant load circuit 60 is a series circuit in which the heating coil 11 and the second resonant capacitor 13 are connected in series. The first resonant load circuit 50 and the second resonant load circuit 60 can be switched by switching the relay 20 according to the material of the metal pot and the set heating power. The heating coil 11 and the second resonance capacitor 13 may be interchanged and connected.

  Here, since the heating coil 11 and the metal pot (not shown) to be heated are magnetically coupled, when the metal pot is converted to an equivalent circuit viewed from the heating coil 11, the equivalent resistance of the metal pot is obtained. And the equivalent inductance are connected in series. The equivalent resistance and the equivalent inductance differ depending on the material of the metal pan, and in the case of a nonmagnetic material such as low resistance copper and aluminum, both the equivalent resistance and the equivalent inductance become smaller, and in the case of a magnetic material such as high resistance iron Will also grow. Below, the difference between the half bridge circuit system used at the time of nonmagnetic material heating and the full bridge circuit system at the time of magnetic material heating is explained using FIG. 2 and FIG.

When the object to be heated is a nonmagnetic material such as a copper pan or an aluminum pan, the metal pan is induction heated using a half bridge circuit type inverter. Specifically, as shown in FIG. 2, the relay 20 is turned off, and the SEPP ( S ingle E) is configured of the first upper and lower arms 3, the heating coil 11, the first resonant capacitor 12, and the second resonant capacitor 13. for heating in the inverter of nded P ush- P ull) method.

  As described above, since the low resistance nonmagnetic material has a small equivalent resistance, it is necessary to flow a large current to obtain a desired output. The skin resistance of the object to be heated is characterized by being proportional to the square root of the frequency, and it is effective to raise the frequency when heating a low resistance object such as copper or aluminum. Therefore, the combined capacitance of the capacitor series 15 is set so that the first upper and lower arms 3 can be driven at a frequency of, for example, about 90 kHz.

  In the present embodiment, the capacitor series body 15 is constituted by the first resonance capacitor 12 and the second resonance capacitor 13, but the second resonance capacitor 13 is a full bridge circuit system for heating a high resistance object to be heated. In order to double as a function as a resonant capacitor in the case of the above, setting of these capacitances will be described later. In the configuration of Patent Document 1, the voltage of the heating coil 11 is applied to the relay 20, but in the present embodiment, the voltage generated in the second resonant capacitor 13 is reduced and applied to the relay 20. The withstand voltage of the relay 20 can be reduced, and the relay 20 can be miniaturized.

  On the other hand, when the object to be heated is a magnetic material such as an iron pot, the metal pan is induction heated using an inverter of a full bridge circuit system. Specifically, as shown in FIG. 3, a full-bridge inverter configured by turning on the relay 20 and comprising the first upper and lower arms 3, the second upper and lower arms 4, the heating coil 11, and the second resonance capacitor 13. Do the heating with

  As described above, since the high resistance magnetic body has a large equivalent resistance, current hardly flows in the second resonant load circuit 60. Therefore, by switching to the full bridge circuit system, the output voltage of the inverter can be doubled to that of the half bridge circuit system to obtain a desired output. In the case of copper and aluminum described above, the inverter frequency is increased to about 90 kHz because the resistance is small, but the skin resistance is increased in the case of iron, so the first upper and lower arms 3 and 5 at a frequency of about 20 kHz The second upper and lower arms 4 are driven. For this reason, the capacity of the second resonance capacitor 13 is set in accordance with the drive frequency of about 20 kHz.

  As described above, since the combined capacitance of the capacitor series 15 is set in accordance with the drive frequency of about 90 kHz, the capacitance of the first resonance capacitor 12 is naturally small, and is sufficiently smaller than that of the second resonance capacitor 13. Become. As shown in FIG. 3, when the relay 20 is in the on state, the first resonance capacitor 12 is connected in parallel to the switching element 5 d of the upper and lower arms 4, so that it functions as a snubber capacitor of the second upper and lower arms 4. Can.

  As described above, in the present embodiment, the switching of the relay 20 can switch the capacitance of the resonant capacitor along with the switching between the full bridge circuit system and the half bridge circuit system. Therefore, the setting range of the drive frequency of the inverter can be expanded, and heating can be performed at an optimum frequency according to the material of the object to be heated.

Next, details of the operation of the full bridge circuit system of FIG. 3 will be described using operation mode explanatory diagrams shown in FIGS. 4A to 4F.
(Mode 1)
Mode 1 is shown in FIG. 4A. This is a state in which the switching elements 5a and 5d are in the on state and the current of the heating coil 11 is positive (rightward). After the switching elements 5a and 5d are turned on, the polarity of the coil current changes from negative to positive when the stored energy of the heating coil 11 becomes zero, and the DC power supply 1 to the switching element 5a, the heating coil 11, the resonance capacitor 13, the relay 20, A current starts to flow in the path of the switching element 5d.
(Mode 2)
Mode 2 is shown in FIG. 4B. After the mode 1, when the switching elements 5a and 5d are turned off, coil current having positive polarity is transmitted through the snubber capacitor 7a, the heating coil 11, the resonant capacitor 13 and the path of the resonant capacitor 12, the snubber capacitor 7b, the heating coil 11, The flow continues in the two paths of the resonant capacitor 13 and the resonant capacitor 12. During this time, since the snubber capacitor 7a is charged, the voltage of the switching element 5a gradually increases, while the snubber capacitor 7b is discharged, so the voltage of the switching element 5b gradually decreases.

Further, since the resonance capacitor 12 connected to the switching element 5d is charged by the coil current, the voltage of the switching element 5d gradually increases and the voltage of the switching element 5c decreases. That is, the resonant capacitor 12 plays the role of a snubber capacitor of the second upper and lower arms 4 in a full bridge inverter.
(Mode 3)
Mode 3 is shown in FIG. 4C. After mode 2, when a forward voltage is applied to the diodes 6b and 6c, coil current continues to flow in the path of the diode 6b, the heating coil 11, the resonant capacitor 13, the relay 20, and the diode 6c.
(Mode 4)
Mode 4 is shown in FIG. 4D. When the stored energy of the heating coil 11 becomes zero after the switching elements 5c and 5b are turned on, the polarity of the coil current changes from positive (right direction) to negative (left direction), and the switching element 5c, relay 20, resonant capacitor 13 The current starts to flow in the path of the heating coil 11 and the switching element 5b.
(Mode 5)
Mode 5 is shown in FIG. 4E. After the mode 4, when the switching elements 5b and 5c are turned off, coil current having negative polarity is generated by the resonant capacitor 12, the resonant capacitor 13, the heating coil 11, the path of the snubber capacitor 7a, the resonant capacitor 12, the resonant capacitor 13, The flow continues in the two paths of the heating coil 11 and the snubber capacitor 7b. During this time, since the snubber capacitor 7a is discharged, the voltage of the switching element 5a gradually decreases, while the snubber capacitor 7b is charged, so the voltage of the switching element 5b gradually increases.

Further, since the resonant capacitor 12 connected to the switching element 5d is discharged by the coil current, the voltage of the switching element 5d gradually decreases and the voltage of the switching element 5c increases. That is, the resonant capacitor 12 plays the role of a snubber capacitor of the second upper and lower arms 4 in a full bridge inverter.
(Mode 6)
Mode 6 is shown in FIG. 4F. After the mode 5, when a forward voltage is applied to the diodes 6a and 6d, the coil current continues to flow in the path of the diode 6d, the relay 20, the resonant capacitor 13, the heating coil 11, and the diode 6a.

  As described above, by repeating the operations of mode 1 to mode 6 described above, the high frequency current can be supplied to the heating coil 11 using the DC power supply 1 as a power supply, and the object to be heated is induced by the magnetic flux generated from the heating coil 11 It is heated.

  In the present embodiment, the current flowing through the heating coil 11 has a sine wave due to the equivalent inductance of the coupling between the heating coil 11 and the metal pan and the resonance capacitor. Such a current resonance type inverter sets and drives a drive frequency higher than a resonance frequency so that the coil current is delayed in phase from the output voltage of the inverter. As a result, since the current is in the lag phase, when each switching element is turned on, switching can be performed with the voltage of the switching element at zero volt, and no turn-on loss occurs.

  According to the electromagnetic induction heating apparatus of the present embodiment described above, the second resonance capacitor 13 is effectively utilized regardless of whether the inverter is a full bridge circuit system or a half bridge circuit system. In addition to the fact that the capacity of the resonant capacitor 12 can be made sufficiently small and the entire inverter circuit can be made compact, desired power can be efficiently supplied regardless of the circuit system.

  Further, since the characteristics of the snubber capacitors of the second upper and lower arms are determined not by the combined capacitance of the two resonant capacitors but by the capacitance of the first resonant capacitor 12, the capacitance design of the snubber capacitor is facilitated.

  Furthermore, since the voltage generated in the second resonance capacitor 13 is reduced and applied, the withstand voltage of the relay 20 can be lowered, and the relay 20 can be miniaturized.

  FIG. 5 is a circuit diagram of the electromagnetic induction heating device of the second embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, in addition to the first resonant capacitor 12 and the second resonant capacitor 13 of the first embodiment, the third resonant capacitor 14 is connected between the connection point thereof and the positive electrode of the DC power supply 1.

  When the object to be heated is a copper pot or an aluminum pot, the relay 20 is turned off, and the first upper and lower arms 3 and the heating coil 11 and the first, second and third resonance capacitors 12, 13 and 14 are formed. Heating is performed using a half bridge circuit type inverter. As described above, when heating a low resistance object, it is effective to increase the frequency, so that the first and second upper and lower arms 3 can be driven at a frequency of, for example, about 90 kHz. Second, set the capacitances of the third resonance capacitors 12, 13, 14. By providing the third resonance capacitor 14, it is possible to reduce the ripple current caused by the switching frequency flowing through the DC power supply 1 as compared with the configuration of the first embodiment.

  On the other hand, when the object to be heated is an iron pot, the relay 20 is turned on and the first and second upper and lower arms, the heating coil 11, and the first, second and third resonance capacitors 12, 13 and 14 Heating with a full-bridge inverter. As described above, the first resonance capacitor 12 plays the role of the snubber capacitor of the second upper and lower arms 4 in the full bridge type inverter, but the third resonance capacitor 14 is similarly the second upper and lower arms It plays the role of snubber capacitor of 4.

  As described above, according to the configuration of the present embodiment, in addition to the effects obtained by the configuration of the first embodiment, it is also possible to obtain the effect of further reducing the ripple current when adopting the half bridge circuit configuration.

  FIG. 6 is a circuit diagram of the electromagnetic induction heating device of the third embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The present embodiment differs from FIG. 1 in that snubber capacitors 7c and 7d are connected in parallel to the switching elements 5c and 5d of the second upper and lower arms 4, respectively. As described above, although the first resonance capacitor 12 plays the role of the snubber capacitor of the second upper and lower arms 4, when the wiring inductance between the resonance capacitor 12 and the second upper and lower arms 4 is large, the switching element 5c is used. , 5d may have a high surge voltage applied.

  Therefore, it is desirable to provide a snubber capacitor close to the switching elements 5c and 5d in parallel, so that the turn-off loss of the switching elements 5c and 5d can be suppressed.

  FIG. 7 is a circuit diagram of the electromagnetic induction heating device of the fourth embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  When the object to be heated is copper or aluminum, as described above, since the coil current is large and the frequency is high, the current flowing through the capacitor series 15 also becomes large, and the voltage also becomes high. In the present embodiment, the first and second resonant capacitors 12 and 13 are configured by connecting a plurality of capacitors in series and in parallel.

  In the present embodiment, the first resonance capacitor 12 is configured by two series and three parallel connections of 12a to 12f, and the second resonance capacitor 13 is configured by three parallel connections of 13a to 13c. In order to adjust the capacitances of the first resonance capacitor 12 and the second resonance capacitor 13, it is possible to appropriately change the number of series connection and the number of parallel connection of the capacitors. Since the increase in the withstand voltage and the increase in capacity of the ceramic capacitor are progressing, the size can be further reduced by replacing the film capacitor with the ceramic capacitor.

1 DC power supply,
3, 4 upper and lower arms,
5a to 5d switching elements,
6a-6d diodes,
7a-7d snubber capacitors,
12, 12a to 12f, 13, 13a to 13c, 14 resonant capacitors,
11 heating coils,
15 capacitor series,
20 relays,
50 first resonant load circuit,
60 Second resonant load circuit

Claims (6)

DC power supply that supplies DC voltage,
First upper and lower arms connected between positive and negative electrodes of the DC power supply;
Second upper and lower arms connected between positive and negative electrodes of the DC power supply;
A heating coil for inductively heating the object to be heated;
When the object to be heated is a nonmagnetic material, a high frequency current is supplied to the first resonant load circuit by a half bridge circuit type inverter using the first upper and lower arms;
An electromagnetic induction heating apparatus for supplying high frequency current to a second resonant load circuit by a full bridge circuit type inverter using the first upper and lower arms and the second upper and lower arms when the object to be heated is a magnetic body. There,
A series of the heating coil, a second resonant capacitor, and a first resonant capacitor, wherein the first resonant load circuit is provided between the output terminals of the first upper and lower arms and the negative electrode of the DC power supply. Circuit and
The second resonance load circuit is a series circuit of the heating coil and the second resonance capacitor, which is provided between the output terminals of the first upper and lower arms and the output terminals of the second upper and lower arms. An electromagnetic induction heating device characterized by In the electromagnetic induction heating device according to claim 1,
A relay provided between the second resonant load circuit and the output terminals of the second upper and lower arms is:
When the object to be heated is a nonmagnetic material, it is turned off
An electromagnetic induction heating device characterized in that the object to be heated is turned on when the object is a magnetic material. In the electromagnetic induction heating device according to claim 1,
In the case of using the inverter of the full bridge circuit system, the first resonance capacitor functions as a snubber capacitor when the switching elements of the second upper and lower arms are turned off. An electromagnetic induction heating apparatus comprising: a resonant load circuit; and an inverter that converts a DC voltage of a DC power source into an AC voltage to supply power to the resonant load circuit,
The inverter is
A first upper and lower arm composed of at least two switching elements connected in series and a second upper and lower arm;
Between the output terminals of the first upper and lower arms and the positive and negative electrodes of the direct current voltage, a first heating coil for inductively heating an object to be heated, a first resonance capacitor, and a second resonance capacitor Equipped with a resonant load circuit,
Between the output terminal of the first upper and lower arms and the output terminal of the second upper and lower arms, there is provided a second resonant load circuit constituted of the heating coil and the second resonant capacitor, and a relay.
When the relay is turned on,
The first resonance capacitor is connected in parallel to the switching elements of the second upper and lower arms, and the switching elements of the second upper and lower arms are turned off. An electromagnetic induction heating device characterized by having a snubber function of upper and lower arms. In the electromagnetic induction heating device according to claim 4,
An electromagnetic induction heating device characterized in that each of the switching elements of the first upper and lower arms and the second upper and lower arms comprises a snubber capacitor in parallel. In the electromagnetic induction heating device according to claim 4,
An electromagnetic induction heating apparatus, wherein the first and second resonant capacitors are formed by connecting a plurality of capacitors in series and in parallel.

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