JP2007287600A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device with noise in the surroundings suppressed, and without interference noise of loads generated among a plurality of burners. <P>SOLUTION: A control means 8 controls conduction time of a first and a second semiconductor switches 5, 4 so as an input current detection means 16 to be a given value, and, on the other hand, emits energy of an auxiliary resonance means 9 before the semiconductor switches 5, 4 turn to a conduction state and passes current to a first or a second inverse conduction elements 15, 14 to keep the semiconductor switches 5, 4 connected in parallel with the inverse conduction elements in a conductive state during a period when a current flows in the latter. With this, a magnetic field is restrained from emission outside, leading to suppression of noise in the surroundings. Further, by controlling the conduction time of the semiconductor switches 5, 4 and passing current to the inverse conduction elements 15, 14 by the auxiliary resonance means 9, switching loss at on-off times in the semiconductor switches 5, 4 can be restrained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating apparatus that heats an object to be heated using induction heating by a high-frequency magnetic field.

  Conventionally, as this type of induction heating apparatus, one shown in FIG. 6 is known (for example, see Patent Document 1).

  As shown in the figure, this induction heating device includes a heating coil 3 and a first semiconductor switch 5 that are magnetically coupled to a load 6 such as a pan arranged in series with the DC power source 1, and a heating coil. 3 in parallel with the first capacitor 23, the second capacitor 24 connected in parallel with the first capacitor 23, and the second semiconductor switch 4, and in parallel with the first semiconductor switch 5. The first reverse conducting element 15 connected to the second semiconductor switch 4, the second reverse conducting element 14 connected in parallel to the second semiconductor switch 4, and the first semiconductor switch 5 and the second semiconductor switch 4 alternately It is comprised with the control means 8 to operate | move.

  FIG. 7 shows operation waveforms of the induction heating apparatus shown in FIG. I5 and I15 are currents flowing through the first semiconductor switch 5 and the first reverse conducting element 15, V6 is the collector-emitter voltage, I4 and I14 are the second semiconductor switch 4 and the second reverse conducting element. 14, V 4 indicates the collector-emitter voltage, and I 3 indicates the current flowing through the heating coil 3.

  In this induction heating device, first, the control means 8 supplies power from the DC power source 1 to the heating coil 3 by setting the first semiconductor switch 5 in a conductive state. At this time, a current flows substantially linearly as indicated by I5 in FIG.

  Next, the control means 8 brings the first semiconductor switch 5 into a non-conductive state for a predetermined time. Then, the energy stored in the heating coil 3 first charges the first capacitor 23, and gradually increases the collector potential of the first semiconductor switch 5 as indicated by V6 in FIG. When the collector potential of the first semiconductor switch 5 becomes equal to the potential of the second capacitor 24, the second reverse conducting element 14 becomes conductive, and the energy of the heating coil 3 is stored in the second capacitor 24. It is done. By keeping the second semiconductor switch 4 in a conductive state when the second reverse conducting element 24 is in a conductive state, this time, as shown by I4 in FIG. Power will be supplied.

  The control means 8 puts the second semiconductor switch 4 in a non-conductive state when a predetermined time has elapsed. Then, the energy stored in the heating coil 3 and the energy stored in the first capacitor 23 are regenerated to the DC power source 1 through the first reverse conducting element 15. By making the first semiconductor switch 5 conductive during this regeneration period, power is again supplied from the DC power source 1 to the heating coil 3. By performing this operation at about 20 to 50 kHz, a high frequency magnetic field is supplied to the load 6 by passing a current as shown in I3 through the heating coil 3, and an eddy current is generated on the surface of the load 6 so that the load 6 is inductively heated. Will be.

  As described above, this induction heating apparatus can perform induction heating with a simple component configuration, and the capacity of the second capacitor 24 is made larger than that of the first capacitor 23, whereby the first and second semiconductors are formed. The switches 5 and 4 are characterized in that the withstand voltage is suppressed and inexpensive semiconductor switches can be used. Further, the capacitance of the second capacitor 24 is sufficiently lower than the resonance frequency of the resonance circuit formed by the heating coil 3 and the second capacitor 24 than the drive frequency of the first and second switching elements 5 and 4. Therefore, the control unit 8 can control the conduction time of the first and second semiconductor switches 5 and 4 under a constant frequency condition regardless of the input power and the type of load. Thus, even when two types of loads are heated adjacent to each other, there is a feature that no interference sound is generated due to a difference in driving frequency between the loads.

  Moreover, as an induction heating apparatus, what is shown in FIG. 8 is also known (for example, refer patent document 2).

  As shown in the figure, a series body of a first semiconductor switch 5 and a second semiconductor switch 4 is connected in parallel with the DC power source 1, and the first semiconductor switch 5 is connected to the heating coil 3 and the resonant capacitor 2. The series connection body, the snubber capacitor 7 and the first reverse conducting element 15 are connected, the second reverse conducting element 14 is connected to the second semiconductor switch 4, and the load 6 such as a pan is connected to the heating coil 3. Are arranged directly above the heating coil 3 so as to be magnetically coupled to each other.

  Here, when the second semiconductor switch 4 is turned on, a current determined by the difference in voltage between the DC power source 1 and the resonant capacitor 2 is supplied to the heating coil 3. Next, when the second semiconductor switch 4 is turned off, the charge stored in the snubber capacitor 7 moves to the resonance capacitor 2 through the heating coil 3, and after the snubber capacitor 7 has been depleted, the first reverse conduction is established. When the element 15 becomes conductive, a current flows from the heating coil 3 to the resonance capacitor 2. By setting the first semiconductor switch 5 in the conductive state at the timing when the first reverse conducting element 15 is conducted, the power of the heating coil 3 is transferred to the resonant capacitor 2 and then the resonant capacitor 2 is used as a power source. Electric power is supplied to the heating coil 3. Further, when the first semiconductor switch 5 is turned off after a predetermined time has elapsed, electric charge is stored in the snubber capacitor 7 and then the electric power stored in the heating coil 3 through the second reverse conducting element 14 is converted into direct current. The power source 1 will be regenerated. In this regeneration period, the second semiconductor switch 4 is again turned on to return to the initial operation.

The snubber capacitor 7 plays a role of reducing a loss when the semiconductor switch is turned off by gradually increasing the voltage when the first and second semiconductor switches 5 and 4 are in a non-conductive state. In addition, in this induction heating device, if the capacity of the resonance capacitor 2 is not set near the resonance frequency of the resonance circuit formed by the heating coil 3 and the resonance capacitor 2, the necessary electric power cannot be secured, while the load 6 Since the resonance frequency varies greatly depending on the type, the control means 8 performs control to bring the drive frequency close to the resonance frequency, that is, control by changing the drive frequency.
JP-A-8-262666 Japanese Patent Laid-Open No. 5-114474

  However, in the conventional induction heating device referred to Patent Document 1, the current flowing through the heating coil 3 has a shape in which a high frequency component is superimposed around a DC component, and thus, for example, when the DC power source 1 rectifies a commercial power source. In addition to the high-frequency component necessary for heating the load 6, a component twice the commercial power supply is supplied to the heating coil 3. Since this commercial power source component is not absorbed by the load 6, it is radiated from the heating coil 3 to the outside. Such unnecessary electromagnetic field radiation has a problem that causes noise and the like in the surroundings.

  Moreover, in the conventional induction heating apparatus of patent document 2, it is necessary to ensure input power by changing the drive frequency when the type of the load 6 changes. Therefore, since the input power largely depends on the resonance frequency of the resonance circuit formed by the resonance capacitor 2 and the heating coil 3, the control means 8 has a first function corresponding to the load 6 in order to ensure stable input power. It is necessary to change the driving frequency of the switching element 5 and the second switching element 4. For this reason, when an induction heating apparatus has a some burner, it has the subject that the interference sound of the frequency in the difference of a mutual drive frequency generate | occur | produces.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an induction heating device that suppresses the generation of noise and the like to the surroundings and that does not have a load interference sound generated between a plurality of burners.

  In order to solve the above-described conventional problems, an induction heating apparatus according to the present invention includes a DC power source, a series body of first and second semiconductor switches connected in parallel to the DC power source, and first and second semiconductors. First and second reverse conducting elements connected in reverse parallel to the switch; a series circuit of a heating coil and a resonant capacitor connected between a connection point of the first and second semiconductor switches and a DC power supply; Control means for controlling the conduction time of the first and second semiconductor switches, input current detection means for detecting the input current, and auxiliary resonance means having a resonance circuit connected in parallel with the first or second semiconductor switch The control means controls the conduction time of the first and second semiconductor switches so that the input current detected by the input current detection means becomes a predetermined value, and the first or second semiconductor Switch is on The energy stored in the auxiliary resonance means is released before the current flows, the current flows through the first or second reverse conducting element, and the first or second connected in parallel during the period when the current flows through the reverse conducting element. The semiconductor switch is turned on.

  As a result, the current flowing through the heating coil always passes through the resonant capacitor, and the current having the frequency component of the DC power supply is reduced from being applied to the heating coil. It is possible to reduce the radiated magnetic field to the outside, and the generation of noise and the like to the surroundings can be suppressed. Further, the conduction time of the first and second semiconductor switches is changed in accordance with the input power so that the input power is controlled to a predetermined value and the auxiliary resonance means performs the first operation immediately before the first or second semiconductor switch is turned on. By passing a current through the first or second reverse conducting element, it is possible to suppress a switching loss when the first or second semiconductor switch is turned on. For this reason, even if the input power is changed, the frequency of the current flowing through the heating coil can be kept constant, and there is no load interference sound generated between a plurality of burners.

  The induction heating device of the present invention can provide an induction heating device that suppresses the generation of noise and the like to the surroundings and that does not have a load interference sound generated between a plurality of burners.

  A first aspect of the present invention is a DC power supply, a series body of first and second semiconductor switches connected in parallel to the DC power supply, and first and second connected in antiparallel to the first and second semiconductor switches, respectively. The second reverse conducting element, the series circuit of the heating coil and the resonant capacitor connected between the connection point of the first and second semiconductor switches and the DC power source, and the conduction time of the first and second semiconductor switches A control means for controlling, an input current detection means for detecting an input current, and an auxiliary resonance means connected in parallel to the first or second semiconductor switch and provided with a resonance circuit. The conduction time of the first and second semiconductor switches is controlled so that the input current detected by the means becomes a predetermined value, and before the first or second semiconductor switch becomes conductive, the auxiliary resonance means Stored energy An induction heating device that discharges a current to the first or second reverse conducting element and makes the first or second semiconductor switch connected in parallel during a period in which the current flows through the reverse conducting element, It is a thing. As a result, the current flowing through the heating coil always passes through the resonant capacitor, and the current having the frequency component of the DC power supply is reduced from being applied to the heating coil. It is possible to reduce the radiated magnetic field to the outside, and the generation of noise and the like to the surroundings can be suppressed. Further, the conduction time of the first and second semiconductor switches is changed in accordance with the input power so that the input power is controlled to a predetermined value and the auxiliary resonance means performs the first operation immediately before the first or second semiconductor switch is turned on. By passing a current through the first or second reverse conducting element, it is possible to suppress a switching loss when the first or second semiconductor switch is turned on. For this reason, even if the input power is changed, the frequency of the current flowing through the heating coil can be kept constant, and there is no load interference sound generated between a plurality of burners.

  As a result, the current flowing through the heating coil always passes through the resonant capacitor, and the current having the frequency component of the DC power supply is reduced from being applied to the heating coil. It is possible to reduce the radiated magnetic field to the outside, and the generation of noise and the like to the surroundings can be suppressed. Further, the conduction time of the first and second semiconductor switches is changed in accordance with the input power so that the input power is controlled to a predetermined value and the auxiliary resonance means performs the first operation immediately before the first or second semiconductor switch is turned on. By passing a current through the first or second reverse conducting element, it is possible to suppress a switching loss when the first or second semiconductor switch is turned on. For this reason, even if the input power is changed, the frequency of the current flowing through the heating coil can be kept constant, and there is no load interference sound generated between a plurality of burners.

  In particular, according to a second invention, in the first invention, there is provided a coil current detecting means for detecting a current of the heating coil, and the control means is configured so that the output value of the coil current detecting means is a predetermined value. The conduction time of the second semiconductor switch is controlled, and the energy stored in the auxiliary resonance means is released before the first or second semiconductor switch becomes conductive, and the current flows to the first or second reverse conduction element. And the first or second semiconductor switch connected in parallel during the period in which the current flows through the reverse conducting element is brought into a conducting state. As a result, the current flowing through the heating coil always passes through the resonant capacitor, and the current having the frequency component of the DC power supply is reduced from being applied to the heating coil. It is possible to reduce the radiated magnetic field to the outside, and the generation of noise and the like to the surroundings can be suppressed. Further, by changing the conduction time of the first and second semiconductor switches according to the current flowing through the heating coil, it becomes possible to control the power by the current of the heating coil, and the first or second semiconductor switch is in the conduction state. By flowing current through the first or second reverse conducting element by the auxiliary resonance means immediately before becoming, switching loss at the time of turn-on in the first or second semiconductor switch can be suppressed. For this reason, even if the input power is changed, the frequency of the current flowing through the heating coil can be kept constant, and there is no load interference sound generated between a plurality of burners.

  In particular, according to a third aspect of the present invention, in the first or second aspect of the invention, there is provided resonance voltage detection means for detecting a voltage at a connection point between the resonance capacitor and the heating coil, and the control means has a predetermined output value of the resonance voltage detection means The conduction time of the first and second semiconductor switches is controlled so that the value of the first and second semiconductor switches becomes equal, and the energy stored in the auxiliary resonance means is released before the first or second semiconductor switch becomes conductive. Alternatively, a current is passed through the second reverse conducting element, and the first or second semiconductor switch connected in parallel during the period in which the current flows through the reverse conducting element is brought into conduction. As a result, the DC current flowing through the heating coil always passes through the resonant capacitor, and the frequency component of the DC power supply from the heating coil is reduced because the current having the frequency component of the DC power supply is reduced. It is possible to reduce the external emission of a magnetic field having In addition, by changing the conduction time of the first and second semiconductor switches according to the resonance voltage, power control by the resonance voltage becomes possible, and auxiliary is performed immediately before the first or second semiconductor switch is turned on. By causing a current to flow through the first or second reverse conducting element by the resonance means, it is possible to suppress a switching loss when the first or second semiconductor switch is turned on. For this reason, even if the input power is changed, the frequency of the current flowing through the heating coil can be kept constant, and there is no load interference sound generated between a plurality of burners.

  According to a fourth invention, in particular, in any one of the first to third inventions, a snubber capacitor is connected to one or both of the first or second semiconductor switches, whereby the first and second semiconductor switches are provided. Since the steep rise of the collector-emitter voltage at the turn-off time can be suppressed by the snubber capacitor, the turn-off loss can be greatly reduced. For this reason, a simple cooling structure can be taken, and a small and low noise induction heating apparatus can be realized.

  According to a fifth aspect of the invention, in particular, in any one of the first to fourth aspects of the invention, the control means fixes the non-conduction state time that occurs when the first and second semiconductor switches are switched to each other. By making the other non-conduction time variable, the auxiliary resonance means operates with respect to the state transition of either the first semiconductor switch to the second semiconductor switch or the second semiconductor switch to the first semiconductor switch. Therefore, a simple circuit configuration can be taken. Therefore, the switching loss at the time of turning on the first or second semiconductor switch can be suppressed by the circuit means at low cost. Therefore, an induction heating apparatus that can keep the frequency of the current flowing through the heating coil constant regardless of the input power or the type of load is realized.

  In particular, according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the first and second semiconductor switches have substantially the same conduction time, and the first and second semiconductor switches correspond to the input power. In addition, the induction heating apparatus that can control the electric power with a simple circuit configuration is realized by changing the conduction time and operating one of the non-conduction states at a constant frequency.

  In a seventh aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, a series circuit of a third semiconductor switch, an auxiliary resonance coil, and an auxiliary resonance capacitor is provided in parallel with the first or second semiconductor switch. Auxiliary resonance means comprising a reverse conducting element connected in antiparallel with the third semiconductor switch is provided, and the energy stored in the auxiliary resonance capacitor at a predetermined timing is used for the first or second energy using the third semiconductor switch. By supplying to the reverse conducting element, the auxiliary resonant circuit can be realized with a simple configuration of the auxiliary resonant coil, the auxiliary resonant capacitor, and the semiconductor switch, so that the first or second semiconductor switch can be turned on with inexpensive circuit means. Switching loss at the time can be suppressed. For this reason, the induction heating apparatus which can keep constant the frequency of the electric current which flows into a heating coil irrespective of the kind of input electric power or load is implement | achieved.

  In an eighth aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, the third semiconductor switch has a variable non-conducting time, and the first or second semiconductor switch becomes conductive. Switching loss at the time of turn-on of the first or second semiconductor switch by causing the semiconductor switch to be in a conductive state before being operated so as to be in a non-conductive state before being in a non-conductive state. And the loss of the third semiconductor switch can be suppressed, and an induction heating device that can keep the frequency of the current flowing in the heating coil constant regardless of the input power or the load type is realized. To do.

  In the ninth invention, in particular, in any one of the first to eighth inventions, the capacitance of the auxiliary resonant capacitor is made larger than the capacitance of the snubber capacitor, so that the first and second semiconductor switches are turned off. Since the operation to suppress steep rises depends only on the snubber capacitor, the loss of the semiconductor switch can be suppressed with a simple design, a simple cooling configuration can be taken, and the induction heating device is small and has low noise. Can be realized.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 to 3 show an induction heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the induction heating apparatus in the present embodiment includes a DC power source 1, a series body of first and second semiconductor switches 5 and 4 connected in parallel to the DC power source 1, and first, Between the first and second reverse conducting elements 15 and 14 connected in antiparallel to the second semiconductor switches 5 and 4, and the connection point between the first and second semiconductor switches 5 and 4 and the DC power supply 1. A series circuit of the heating coil 3 and the resonant capacitor 2 connected to the control circuit 8, control means 8 for controlling the conduction time of the first and second semiconductor switches 5 and 4, and input current detection for detecting the input current of the DC power source 1. Means 16 and auxiliary resonance means 9 having a resonance circuit connected in parallel with the first or second semiconductor switch 5 or 4 are provided.

  The control means 8 controls the conduction time of the first and second semiconductor switches 5 and 4 so that the input current detected by the input current detection means 16 becomes a predetermined value, and the first or second The energy stored in the auxiliary resonance means 9 is released before the second semiconductor switches 5 and 4 are turned on, current flows through the first or second reverse conducting elements 15 and 14, and current flows through the reverse conducting elements. During this period, the first or second semiconductor switch 5 or 4 connected in parallel is made conductive.

  Here, a load 6 such as a pan is arranged to be magnetically coupled to the heating coil 3. A snubber capacitor 7 is connected to both ends of one or both of the first semiconductor switch 5 and the second semiconductor switch 4. The auxiliary resonance means 9 includes a series circuit of a third semiconductor switch 12, an auxiliary resonance coil 11, and an auxiliary resonance capacitor 10, and a third reverse conducting element 22 connected in antiparallel to the third semiconductor switch 12. It is configured.

  In the present embodiment, the first semiconductor switch 5, the second semiconductor switch 4, and the third semiconductor switch 12 include the IGBT that conducts in the forward direction and the reverse conducting elements 15 and 14 connected in reverse parallel thereto. However, there is no problem even if an element in which a reverse conducting element is formed inside the element, such as a MOSFET, is used. In the present embodiment, the auxiliary resonance means 9 is constituted by a series resonance circuit of the third semiconductor switch 12, the auxiliary resonance coil 11, and the auxiliary resonance capacitor 10. The resonance current is not particularly limited as long as the current flows through the first reverse conducting element 15 and / or the second reverse conducting element 14. The means for detecting the input current may use a current transformer, a resistor, or the like, but is not particularly limited thereto.

  Next, the operation in this embodiment will be described.

  FIG. 2 shows a current path in each section of the inverter circuit, and FIG. 3 shows a waveform corresponding to FIG.

  A description will be given from the state of FIG. When the control means 8 brings the second semiconductor switch 4 into a conducting state (Vge 4 in FIG. 3, the same applies hereinafter), the heating coil 3 and the resonant capacitor 2 are connected according to the conduction time of the second switching element 4 from the DC power source 1. A current flows (Ic4), and power is supplied to the heating coil 3. A load 6 such as a pan is magnetically coupled to the heating coil 3, and a high frequency magnetic field is generated in the heating coil 3 in response to a high frequency current flowing through the heating coil 3, and the high frequency magnetic field is supplied to the load 6. The load 6 is inductively heated by the eddy current generated in the surface layer portion of the load 6 in response to the high-frequency magnetic field.

  Next, after the conduction time determined in accordance with the input current has elapsed, the control means 8 enters the state shown in FIG. 2B when the second semiconductor switch 4 is turned off, and is stored in the snubber capacitor 7. When the energy is released through the path of the heating coil 3 → resonance capacitor 2 and the snubber capacitor 7 is no longer charged, the first reverse conducting element 15 becomes conductive, and the heating coil 3 → resonance capacitor 2 → first reverse conduction. A current flows in the loop of the element 15. When the first semiconductor switch 5 is kept in the conducting state when the first reverse conducting element 15 is in the conducting state (Vge5), the state shifts to the state of FIG. 2C, and the resonance capacitor 2 is used as the power source. When one semiconductor switch 5 is turned on, a current flows through the heating coil 2 (Ic5) and power is supplied. Thereafter, when a predetermined conduction time determined according to the input current elapses, the control means 8 makes the first semiconductor switch 5 non-conductive and shifts to the state shown in FIG. When the snubber capacitor 7 is charged through the path of the coil 3 → snubber capacitor 7 and the potential of the snubber capacitor 7 becomes the same as that of the DC power source 1, the second reverse conducting element 15 becomes conductive, and the resonance capacitor 2 → heating coil 3 → A current flows through the path from the second reverse conducting element 14 to the DC power source 1.

  Thereafter, the current of the heating coil 3 flows out in the opposite direction, transitions to the state shown in FIG. 2E, the current flows through the path of the heating coil 3, the resonance capacitor 2, and the snubber capacitor 7, and then the heating coil 3 → the resonance capacitor Current flows through the path of 2 → first reverse conducting element 15. Thereafter, the control means 8 turns on the third semiconductor switch 12 at a predetermined timing, and shifts to the state of FIG. In this state, the electric charge stored in the auxiliary resonance capacitor 10 charges the snubber capacitor 7 through the auxiliary resonance coil 11 and the third semiconductor switch 12, and then a current flows through the second reverse conducting element 14. When the second reverse conducting element 14 is turned on, the second semiconductor switch 4 is turned on to return to the state of FIG. 2A, and this operation is repeated thereafter. By continuously repeating this operation at a frequency of about 20 to 50 kHz, a high frequency current flows through the heating coil 3 as shown by I3 in FIG. 3, and a high frequency magnetic field generated by this high frequency current is absorbed by the load 6. The load 6 itself generates heat due to an eddy current generated by the high-frequency resistance and high-frequency magnetic field of the load 6 itself.

  By adopting such a configuration, the direct current component (low frequency component) does not flow through the heating coil 3, and only the high frequency component required for heating is supplied to the heating coil 3, and unnecessary frequency components are externally supplied. Can be prevented from being emitted. Furthermore, in the present embodiment, when the types of loads 6 are different or when the input power is changed, the conduction frequencies of the first semiconductor switch 5 and the second semiconductor switch 4 are kept constant while the driving frequencies of the first semiconductor switch 5 and the second semiconductor switch 4 are kept constant. By changing the time and the non-conduction time, the input power can be set to a set value without greatly increasing the loss of each semiconductor switch. Thereby, the interference sound between the loads 6 generated between adjacent burners can be prevented.

  In addition, the conduction time of the first semiconductor switch 5 and the second semiconductor switch 4 is made substantially the same, and the control means 8 controls the first semiconductor switch 5 according to the input power so that the output of the input current detection means 16 becomes a predetermined value. The conduction time of the semiconductor switch 5 and the second semiconductor switch 4 can be changed, and one of the non-conduction times can be varied to operate at a constant frequency.

  Further, the control means 8 assists by fixing one of the non-conduction state times that occur when the first and second semiconductor switches 5 and 4 are switched to each other and making the other non-conduction time variable. The resonance means 9 only needs to cope with one of the switching operations, and the circuit can be simplified.

  On the other hand, the control means 8 makes the third semiconductor switch 12 conductive immediately before the predetermined non-conduction time between the first semiconductor switch 5 and the second semiconductor switch 4 ends (about 2 μsec before the end), and next The first semiconductor switch 5 or the second semiconductor switch 4 is turned on. After that, the control means 8 turns off the third semiconductor switch 12 at the timing when the current flows through the third reverse conducting element 22, and then the first semiconductor switch 5 or the first semiconductor switch 5 that is in the conducting state at a predetermined timing. 2 semiconductor switch 4 is operated to be in a non-conductive state. By operating at such timing, the third semiconductor switch 12 does not generate a turn-off loss, so that the switching loss can be suppressed.

  Furthermore, by making the capacity of the auxiliary resonant capacitor 10 larger than the capacity of the snubber capacitor 7, the current from the auxiliary resonant capacitor 10 can flow sufficiently to the second reverse conducting element 14 after charging the snubber capacitor 7. It becomes possible.

  As described above, according to the present embodiment, immediately before the first or second semiconductor switch 5 or 4 is turned on, the auxiliary resonance means 9 causes the first or second reverse conducting element 15 or 14 to be turned on. By passing a current, it is possible to suppress a switching loss when the first or second semiconductor switch 5 or 4 is turned on. For this reason, the frequency of the current flowing through the heating coil 3 can be kept constant regardless of the type of input power or load, and the resonance capacitor 2 is connected in series to the heating coil 3, so that it has a frequency component of the power source. Since the current applied to the heating coil 3 is reduced, an induction heating device that can reduce the magnetic field having the frequency component of the DC power supply 1 from the heating coil 3 to the outside is realized. Is.

(Embodiment 2)
FIG. 4 shows an induction heating apparatus according to Embodiment 2 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in the figure, in the induction heating apparatus according to the present embodiment, coil current detection means 17 for detecting the current of the heating coil 3 is connected to the current path of the series circuit of the heating coil 3 and the resonant capacitor 2, so that the coil current is The output of the detection means 17 is connected to the control means 8. Other configurations are the same as those of the first embodiment.

  Next, the operation in this embodiment will be described.

  The operation of the present embodiment is substantially the same as that of the first embodiment, but the control means 8 has the first semiconductor switch 5 and the second semiconductor switch 4 so that the coil current detection means 17 has a predetermined value. The third embodiment is different from the first embodiment in that the third semiconductor switch 12 is controlled. Further, common non-conduction is performed so that the conduction time of the first and second semiconductor switches 5 and 4 is changed so that the coil current detection means 17 has a predetermined value and the frequency of the current flowing through the heating coil 3 is constant. By controlling the time, the interference sound of the pot between adjacent burners can be prevented.

  The control means 8 can reduce the burden on the circuit by deciding which of the outputs of the input current detection means 16 and the coil current detection means 17 is to be preferentially controlled according to the type of the load 6. A highly efficient induction heating device can be realized.

  As described above, according to the present embodiment, immediately before the first or second semiconductor switch 5 or 4 is turned on, the auxiliary resonance means 9 causes the first or second reverse conducting element 15 or 14 to be turned on. By passing the current, it is possible to suppress the switching loss when the first or second semiconductor switch 5, 4 is turned on. Therefore, the frequency of the current flowing through the heating coil 3 is independent of the input power and the type of the load 6. While being able to keep constant, since the resonant capacitor 2 is connected in series with the heating coil 3, it is reduced that the electric current with the frequency component of the DC power supply 1 is applied to the heating coil 3. For this reason, the induction heating apparatus which can reduce that the magnetic field with the frequency component of DC power supply 1 is radiated | emitted outside from the heating coil 3 is implement | achieved.

(Embodiment 3)
FIG. 5 shows an induction heating apparatus according to Embodiment 3 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in the figure, in the induction heating apparatus according to the present embodiment, a resonance voltage detection unit 18 that detects a resonance voltage is connected to a connection point of a series circuit of the heating coil 3 and the resonance capacitor 2. The output is connected to the control means 8. Other configurations are the same as those of the first embodiment.

  Next, the operation in this embodiment will be described.

  The operation of the present embodiment is substantially the same as that of the first embodiment, but the control means 8 controls the first semiconductor switch 5 and the second semiconductor switch 4 so that the resonance voltage detection means 18 has a predetermined value. The third embodiment is different from the first embodiment in that the third semiconductor switch 12 is controlled. Further, a common time is set so that the conduction frequency of the first semiconductor switch 5 and the second semiconductor switch 4 is changed and the frequency of the current flowing through the heating coil 3 is constant so that the resonance voltage detection means 18 has a predetermined value. By controlling the non-conduction time, the interference sound of the pan between adjacent burners can be prevented.

  The control means 8 can reduce the burden on the circuit by deciding which one of the outputs of the input current detection means 16 and the resonance voltage detection means 18 is to be preferentially controlled according to the type of the load 6. A highly efficient induction heating device can be realized.

  As described above, according to the present embodiment, immediately before the first or second semiconductor switch 5 or 4 is turned on, the auxiliary resonance means 9 causes the first or second reverse conducting element 15 or 14 to be turned on. By passing the current, it is possible to suppress the switching loss when the first or second semiconductor switch 5, 4 is turned on. Therefore, the frequency of the current flowing through the heating coil 3 is independent of the input power and the type of the load 6. While being able to keep constant, since the resonant capacitor 2 is connected in series with the heating coil 3, it is reduced that the electric current with the frequency component of the DC power supply 1 is applied to the heating coil 3. For this reason, the induction heating apparatus which can reduce that the magnetic field with the frequency component of DC power supply 1 is radiated | emitted outside from the heating coil 3 is implement | achieved.

  The configurations of the first to third embodiments described above can be appropriately combined as necessary, and are not limited to the embodiments themselves.

  As described above, since the induction heating device according to the present invention can provide an induction heating device that suppresses the generation of noise to the surroundings and does not have a load interference sound generated between a plurality of burners. Of course, it can be applied as various induction heating devices.

The circuit block diagram of the induction heating apparatus in Embodiment 1 of this invention (A) The figure which shows the operation mode which makes the 1st semiconductor switch of the same induction heating apparatus into a conduction | electrical_connection state (b) The figure which shows the operation mode which makes the said 1st semiconductor switch non-conduction state (c) The same induction heating apparatus The figure which shows the operation mode which makes the 2nd semiconductor switch of this conductive state (d) The figure which shows the operation mode which makes the 2nd semiconductor switch non-conducting state (e) Both the 1st, 2nd semiconductor switches are the same The figure which shows the operation mode made into an OFF state (f) The figure which shows the operation mode in which the auxiliary | assistant resonance means of the same induction heating apparatus operate | moves Operation waveform diagram of induction heating apparatus corresponding to (a) to (f) of FIG. The circuit block diagram of the induction heating apparatus in Embodiment 2 of this invention The circuit block diagram of the induction heating apparatus in Embodiment 3 of this invention Circuit diagram of a conventional induction heating device Waveform diagram of the induction heating device Circuit diagram of another conventional induction heating device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Resonance capacitor 3 Heating coil 4 2nd semiconductor switch 5 1st semiconductor switch 6 Load 7 Snubber capacitor 8 Control means 9 Auxiliary resonance means 10 Auxiliary resonance capacitor 11 Auxiliary resonance coil 12 3rd semiconductor switch 14 2nd Reverse conducting element 15 First reverse conducting element 16 Input current detecting means 17 Coil current detecting means 18 Resonant voltage detecting means 22 Third reverse conducting element

Claims (9)

DC power supply, first and second semiconductor switches connected in parallel to DC power supply, and first and second reverse conducting elements connected in antiparallel to first and second semiconductor switches, respectively A series circuit of a heating coil and a resonant capacitor connected between the connection point of the first and second semiconductor switches and the DC power supply, and control means for controlling the conduction time of the first and second semiconductor switches; Input current detection means for detecting an input current and auxiliary resonance means having a resonance circuit connected in parallel with the first or second semiconductor switch, wherein the control means has an input detected by the input current detection means. The conduction time of the first and second semiconductor switches is controlled so that the current becomes a predetermined value, and the energy stored in the auxiliary resonance means is released before the first or second semiconductor switch is turned on. First Other current flows in the second reverse conducting device, induction heating device for a conductive state the first or second semiconductor switches connected in parallel to the period in which current is flowing in the reverse conducting device. Coil current detection means for detecting the current of the heating coil is provided, and the control means controls the conduction time of the first and second semiconductor switches so that the output value of the coil current detection means becomes a predetermined value, and the first The energy stored in the auxiliary resonance means is released before the first or second semiconductor switch is turned on, the current is passed through the first or second reverse conducting element, and the current is flowing through the reverse conducting element. The induction heating device according to claim 1, wherein the first or second semiconductor switch connected in parallel is turned on. Resonance voltage detection means for detecting the voltage at the connection point of the resonance capacitor and the heating coil is provided, and the control means is a conduction time of the first and second semiconductor switches so that the output value of the resonance voltage detection means becomes a predetermined value. And the energy stored in the auxiliary resonance means is discharged before the first or second semiconductor switch is turned on, and the current is passed through the first or second reverse conducting element, and the current flows through the reverse conducting element. 3. The induction heating device according to claim 1, wherein the first or second semiconductor switch connected in parallel is in a conductive state during a period in which the gas flows. The induction heating apparatus according to any one of claims 1 to 3, wherein a snubber capacitor is connected to one or both of the first or second semiconductor switches. 5. The control device according to claim 1, wherein one of the non-conduction state times generated when the first and second semiconductor switches are switched is fixed, and the other non-conduction time is variable. The induction heating device described in 1. The conduction times of the first and second semiconductor switches are substantially the same, the conduction times of the first and second semiconductor switches are changed according to the input power, and one of the non-conduction states is changed to operate at a constant frequency. The induction heating device according to any one of claims 1 to 5. Auxiliary resonance means comprising a series circuit of a third semiconductor switch, an auxiliary resonance coil, and an auxiliary resonance capacitor in parallel with the first or second semiconductor switch, and a reverse conducting element connected in antiparallel with the third semiconductor switch. The induction heating according to claim 1, wherein energy stored in the auxiliary resonant capacitor is supplied to the first or second reverse conducting element using a third semiconductor switch at a predetermined timing. apparatus. The third semiconductor switch is turned on before the variable non-conduction time ends, and the first or second semiconductor switch is turned on, and before the semiconductor switch that is turned on is turned off. The induction heating device according to claim 1, wherein the induction heating device is operated so as to be in a non-conduction state. The induction heating apparatus according to any one of claims 1 to 8, wherein a capacity of the auxiliary resonance capacitor is larger than a capacity of the snubber capacitor.