JP2007080700A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device having a small number of frequency components of a commercial power supply which are emitted from a heating coil, and generating a small quantity of noise because no interference noise between loads is generated between adjacent burners. <P>SOLUTION: Energy stored in an auxiliary resonance means 9 is discharged before a first or second semiconductor switch 5, 4 is switched on to pass a current in a first or second reverse conducting element 15, 14, and the parallel-connected first or second semiconductor switch 5, 4 is brought into a conducting state during a time period when the current is being passed through the reverse conducting element. Thereby, a current passing through the heating coil 3 always passes through a resonance capacitor 2, and since it becomes possible to reduce the chances where a magnetic field having the frequency components of the power supply is emitted to the outside from the heating coil 3, and switching loss can be suppressed when the first or second semiconductor switch 5, 4 is turned on, the induction heating device generating a small quantity of noise can be obtained because no interference noise between loads is generated between the adjacent burners. <P>COPYRIGHT: (C)2007,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, induction heating apparatuses having various circuit configurations are known (see, for example, Patent Document 1).

  As shown in FIG. 6, 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 heating coil 3 and the resonant capacitor are connected to the first semiconductor switch 5. 2 connected in series, a snubber capacitor 7 and a first reverse conducting element 15, a second reverse conducting element 14 is connected to the second semiconductor switch 4, and a load 6 such as a pan is a heating coil 3 is arranged immediately above the heating coil 3 so as to be magnetically coupled to the heating coil 3.

  When the second semiconductor switch 4 is turned on, a current determined by the voltage difference 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 charge of the snubber capacitor 7 is exhausted, the first reverse When the conduction element 15 is conducted, 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.

Here, the snubber capacitor 7 plays a role of reducing the loss at the time of turn-off of the semiconductor switch by gradually increasing the voltage when the first and second semiconductor switches 5 and 4 become non-conductive. Yes. In addition, this induction heating device cannot secure necessary power unless the capacity of the resonance capacitor 2 is set in the vicinity of the resonance frequency of the resonance circuit formed by the heating coil 3 and the resonance capacitor 2. 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.
Japanese Patent Laid-Open No. 5-114474

  However, in the conventional configuration, it is necessary to secure input power by changing the drive frequency when the type of the load 6 changes. On the other hand, 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 semiconductor switch 5 and the second semiconductor switch 4. For this reason, when an induction heating apparatus has a some burner, it has the subject that the interference sound by the frequency of a mutual drive frequency difference generate | occur | produces.

  The present invention solves the above-described conventional problems, and provides an induction heating device that has a low frequency component of a commercial power source radiated from a heating coil and that has no interference noise between loads generated between adjacent burners. For the purpose.

  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. A first circuit and a second reverse conducting element connected in reverse parallel to the switch, and 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 source; , Control means for controlling the conduction time of the first and second semiconductor switches, and auxiliary resonance means connected in parallel with the first or second semiconductor switch and provided with a resonance circuit, the first or second The energy stored in the auxiliary resonance means is released before the semiconductor switch of the first switch is turned on, the current flows through the first or second reverse conducting element, and the current is passed through the reverse conducting element in parallel. First or second semiconductor switch In which the switch conductive.

  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 power supply is reduced from being applied to the heating coil. It is possible to reduce the radiation of the magnetic field to the outside, and to allow a current to flow to the first or second reverse conducting element by the auxiliary resonance means immediately before the first or second semiconductor switch becomes conductive. Therefore, since the switching loss at the time of turn-on of the first or second semiconductor switch can be suppressed, the frequency of the current flowing through the heating coil can be kept constant regardless of the type of input power or load, It is possible to reduce noise without interference sound between loads generated between burners.

  The induction heating device of the present invention can be one that has a small frequency component of the commercial power source radiated from the heating coil and a low noise without interference sound between loads generated between adjacent 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 And a control means for controlling the power supply, and an auxiliary resonance means connected in parallel with the first or second semiconductor switch and provided with a resonance circuit, before the first or second semiconductor switch is turned on. The energy stored in the means is discharged, the current flows through the first or 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 in a conductive state. By heating coil The flowing current always passes through the resonant capacitor, and the current with the frequency component of the power supply is reduced from being applied to the heating coil, so the magnetic field with the frequency component of the power supply is radiated from the heating coil to the outside. And the first or second semiconductor switch is made to flow in the first or second reverse conducting element by the auxiliary resonance means immediately before the first or second semiconductor switch is turned on. Since the switching loss at the time of turn-on of the second semiconductor switch can be suppressed, the frequency of the current flowing through the heating coil can be kept constant regardless of the type of input power or load, and the load generated between adjacent burners There can be little noise without interfering sound.

  In particular, the second invention is the collector-emitter at the time of turn-off of the first and second semiconductor switches by connecting a snubber capacitor to one or both of the first and second semiconductor switches in the first invention. Since the sudden rise of the voltage between the two 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 third aspect of the invention, in particular, in the first or second aspect of the invention, the control means fixes one of the non-conduction times that occurs when the first and second semiconductor switches are switched, and varies the other non-conduction time. As a result, the auxiliary resonance means only needs to operate 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. In addition, it is possible to suppress a switching loss when the first or second semiconductor switch is turned on with an inexpensive circuit means. For this reason, the induction heating apparatus which can keep the frequency of the electric current which flows into a heating coil constant irrespective of the kind of input electric power or load is implement | achieved.

  In particular, according to a fourth invention, in any one of the first to third inventions, the first and second semiconductor switches have substantially the same conduction time, and the first and second semiconductor switches correspond to the input power. By changing one of the non-conduction times and operating at a constant frequency by varying one of the non-conduction times, it becomes possible to control the power with the non-conduction time of the first and second semiconductor switches, so that a simple circuit configuration An induction heating apparatus capable of controlling electric power with is realized.

  According to a fifth aspect of the invention, in particular, in any one of the first to fourth aspects of the invention, the auxiliary resonance means includes a third semiconductor switch, a series circuit of an auxiliary resonance coil and an auxiliary resonance capacitor, and a third semiconductor switch. A third reverse conducting element connected in antiparallel, and supplying the energy stored in the auxiliary resonant capacitor to the first or second reverse conducting element using a third semiconductor switch at a predetermined timing. Thus, the auxiliary resonant circuit can be realized with a simple configuration of a coil, a capacitor, and a semiconductor switch, and the switching loss at the time of turning on the first or second semiconductor switch can be suppressed by an inexpensive circuit means. 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 a sixth aspect of the invention, in particular, in any one of the first to fifth aspects, the third semiconductor switch has a variable non-conducting time, and the first or second semiconductor switch is turned on. When the first or second semiconductor switch is turned on by operating so that the first or second semiconductor switch that has been made conductive before becomes non-conductive before the first or second semiconductor switch made conductive becomes non-conductive. Induction heating that can keep the frequency of the current flowing in the heating coil constant regardless of the type of input power or load, because the switching loss in the power supply can be suppressed and the loss of the third semiconductor switch can be suppressed. The device is realized.

  In the seventh aspect of the invention, in particular, in the fifth or sixth aspect of the present invention, 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 have a steep rise at the turn-off time. Since the suppression operation 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 a compact and low noise induction heating device can be realized. It is.

  In the eighth invention, in particular, in any one of the first to seventh inventions, when the resonance frequency of the resonance circuit including the heating coil and the resonance capacitor is lower than the operating frequency, the non-conduction time is fixed and the conduction time is set. By controlling the input power by the ratio, the frequency of the current flowing through the heating coil is kept constant with a simple control method when the resonance frequency of the heating coil and the resonant capacitor is low, that is, when the load is a magnetic material such as magnetic stainless steel. As a result, it is possible to perform optimal power control according to the load while maintaining the above, and thus an induction heating device having excellent controllability is realized.

  In the ninth invention, in particular, in any one of the first to eighth inventions, when the resonance frequency of the resonance circuit including the heating coil and the resonance capacitor is lower than the operation frequency, the auxiliary resonance means is not operated. When the resonance frequency of the heating coil and the resonance capacitor is low, that is, when the load of magnetic material such as magnetic stainless steel is used, the optimum power according to the load is maintained with the frequency of the current flowing through the heating coil being kept constant with a simple control method. Since the control can be performed, an induction heating device having excellent controllability is realized.

  According to a tenth aspect of the invention, in particular, in the eighth aspect of the invention, when the resonance frequency of the resonance circuit including the heating coil and the resonance capacitor is lower than the operation frequency, the operation of the first or second semiconductor switch to the non-conduction state By making the transition and the operation transition to the conductive state of the third semiconductor switch almost simultaneous, optimal power control corresponding to the load can be performed with a simple control circuit while keeping the frequency of the current flowing in the heating coil constant. Therefore, an induction heating device with excellent controllability is realized.

  Hereinafter, embodiments of the present invention will be described 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 device of 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, 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 control circuit 8 for controlling the conduction time of the first and second semiconductor switches 5, 4, and the first or second semiconductor switch 5, 4. And auxiliary resonance means 9 connected in parallel with each other and having a resonance circuit. Then, the energy stored in the auxiliary resonance means 9 is released before the first or second semiconductor switch 5 or 4 is turned on, and a current is passed through the first or second reverse conducting element 15 or 14, and the reverse The first or second semiconductor switch 5 or 4 connected in parallel during a period in which a current flows through the conductive element is set in a conductive state.

  Further, a load 6 such as a pan is disposed on the heating coil 3 so as to be magnetically coupled to the heating coil 3, and a snubber capacitor 7 is provided at one or both ends of the first semiconductor switch 5 or the second semiconductor switch 4. Is connected.

  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 13 connected in parallel to the third semiconductor switch 12. The The first semiconductor switch 5, the second semiconductor switch 4, and the third semiconductor switch 12 generate a high-frequency magnetic field in the heating coil 3 according to a command from the control unit 8 and inductively heat the load 6 with this high-frequency magnetic field.

  When the load 6 is inductively heated, the control means 8 keeps the drive frequency of the first semiconductor switch 5 and the second semiconductor switch 4 constant, so that even if the heating operation is performed with the adjacent burner, the interference sound between the pans Is prevented from occurring. In the present embodiment, the first semiconductor switch 5, the second semiconductor switch 4, and the third semiconductor switch 12 are described as IGBTs that conduct in the forward direction and diodes connected in reverse parallel thereto. There is no problem even if an element in which a diode is formed inside the element, such as a MOSFET, is used. Further, 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 it is configured to flow through the first reverse conducting element 15 and / or the second reverse conducting element 14.

  Next, the operation of the induction heating apparatus in the present embodiment will be described based on FIGS.

  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. The control means 8 brings the second semiconductor switch 4 into a conductive state (Vge4 in FIG. 3) according to the power command value. Then, a current flows from the DC power source 1 to the heating coil 3 and the resonant capacitor 2 (Ic4 in FIG. 3) according to the conduction time of the second semiconductor switch 4, and power is supplied. A load 6 such as a pan is magnetically coupled to the heating coil 3, and a high frequency magnetic field generated by the heating coil 3 is supplied to the load 6, and an eddy current due to the high frequency magnetic field flows through the load 6 to heat the load 6.

  Next, when the control means 8 brings the second semiconductor switch 4 into a non-conducting state, the state shown in FIG. 2 (b) is reached, and the energy stored in the snubber capacitor 7 is released through the path of the heating coil 3 → resonance capacitor 2. When the electric charge of the snubber capacitor 7 is exhausted, the first reverse conducting element 15 becomes conductive, and a current flows through the loop of the heating coil 3 → the resonant capacitor 2 → the first reverse conducting element 15. When the first reverse conducting element 15 is in the conducting state, the first semiconductor switch 5 is kept in the conducting state (Vge5 in FIG. 3), the state shifts to the state in FIG. When the first semiconductor switch 5 is turned on as a power source, a current flows through the heating coil 3 (Ic5 in FIG. 3), and power is supplied. Thereafter, when the control means 8 brings the first semiconductor switch 5 into a non-conducting state, the control means 8 shifts to the state shown in FIG. 2D and charges the snubber capacitor 7 through the path of the resonance capacitor 2 → the heating coil 3 → the snubber capacitor 7. When the potential of the snubber capacitor 7 becomes the same as that of the DC power source 1, the second reverse conducting element 14 becomes conductive, and the current flows through the path of the resonant capacitor 2 → the heating coil 3 → the second reverse conducting element 14 → the DC power source 1. Flows.

  Thereafter, the current of the heating coil 3 flows out in the opposite direction, transitions to the state of FIG. 2 (e), 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 2 → Current flows through the path of the first reverse conducting element 15. Thereafter, the control means 8 makes the third semiconductor switch 12 conductive at a predetermined timing, and shifts to the state of FIG. In this state, the electric charge stored in the third 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. Become. 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.

  In FIG. 3, Vge12 is a control signal that the control means 8 gives to the third semiconductor switch 12, Ic14 is a current flowing through the first reverse conducting element 14, and Ic15 is a current flowing through the first reverse conducting element 15. , I12 indicates a current flowing through the third semiconductor switch 12, and I13 indicates a current flowing through the third reverse conducting element 13.

  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 the set value without greatly increasing the loss of each semiconductor switch. As a result, it is possible to prevent the interference sound between the loads 6 generated between adjacent burners.

  Further, the control means 8 makes the conduction time of the first semiconductor switch 5 and the second semiconductor switch 4 the same and adjusts the common non-conduction time to make the driving frequency constant, thereby simplifying the input power control. It can be carried out. Further, the non-conduction time that occurs when switching the semiconductor switch is always a fixed value, and the other switching time is made variable so that the auxiliary resonance means 9 only needs to respond to the switching of one of the switches, thereby simplifying the circuit. be able to.

  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. Thereafter, the control means 8 makes the third semiconductor switch 12 non-conductive at the timing when the current flows through the third reverse conducting element 13, and then the first semiconductor switch 5 or the first semiconductor switch 5 which is in the conductive state at the predetermined timing. 2 semiconductor switch 4 is operated so as 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.

  Further, 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 is sufficiently passed through the second reverse conducting element 14 after charging the snubber capacitor 7. Is possible.

  As described above, according to the present embodiment, the current is supplied to the first or second reverse conducting element 15 or 14 by the auxiliary resonance means 9 immediately before the first or second semiconductor switch 5 or 4 is turned on. Since the switching loss at the turn-on time of the first or second semiconductor switch 5 or 4 can be suppressed by flowing the current, the frequency of the current flowing through the heating coil 3 is kept constant regardless of the type of input power or load. In addition, since the resonance capacitor 2 is connected in series to the heating coil 3, the current having the frequency component of the power supply is reduced from being applied to the heating coil 3. An induction heating apparatus that can reduce the external emission of a magnetic field having a component is realized.

(Embodiment 2)
Next, the induction heating apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. Since the basic configuration is the same as that of the first embodiment, the description thereof is omitted.

  FIG. 4 shows a current path in each section of the inverter circuit, and FIG. 5 shows a waveform corresponding to FIG.

  In the present embodiment, the resonance frequency of the resonance circuit composed of the heating coil 3 and the resonance capacitor 2 in a state where the load 6 is magnetically coupled is determined by the driving frequency of the first semiconductor switch 5 and the second semiconductor switch 4. In other words, it is assumed that the load 6 is made of a magnetic material such as magnetic stainless steel.

  The description starts from the state of FIG. The control means 8 brings the second semiconductor switch 4 into a conducting state (Vge4 in FIG. 5) according to the power command value. Then, a current flows from the DC power source 1 to the heating coil 3 and the resonance capacitor 2 according to the conduction time of the second semiconductor switch 4 (Ic4 in FIG. 5), and power is supplied. A load 6 such as a pan is magnetically coupled to the heating coil 3, and a high frequency magnetic field generated by the heating coil 3 is supplied to the load 6, and an eddy current due to the high frequency magnetic field flows through the load 6 to heat the load 6.

  Next, when the control means 8 brings the second semiconductor switch 4 into a non-conducting state, the state shown in FIG. 4B is obtained, and the energy stored in the snubber capacitor 7 is released through the path of the heating coil 3 → the resonance capacitor 2. When the electric charge of the snubber capacitor 7 runs out, the first reverse conducting element 15 becomes conductive, and a current flows through the loop of the heating coil 3 → the resonant capacitor 2 → the first reverse conducting element 15. When the first reverse conducting element 15 is in the conducting state, the first semiconductor switch 5 is kept in the conducting state (Vge5 in FIG. 5), the state shifts to the state in FIG. When the first semiconductor switch 5 is turned on as a power source, a current flows through the heating coil 3 (Ic5 in FIG. 5), and power is supplied. Thereafter, when the first semiconductor switch 5 is turned off, the control means 8 shifts to the state shown in FIG. 4D and charges the snubber capacitor 7 through the path of the resonance capacitor 2 → the heating coil 3 → the snubber capacitor 7. When the potential of the snubber capacitor 7 becomes the same as that of the DC power source 1, the second reverse conducting element 14 becomes conductive, and the current flows through the path of the resonant capacitor 2 → the heating coil 3 → the second reverse conducting element 14 → the DC power source 1. Flows. 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. 4A, and this operation is repeated thereafter. By repeating this operation continuously 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. 5, 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.

  Note that Vge12, Ic14, Ic15, I12, and I13 in FIG. 5 are as described in the first embodiment.

  In the above operation, since the resonance frequency of the resonance circuit composed of the heating coil 3 magnetically coupled to the load 6 and the resonance capacitor 2 is lower than the drive frequency, the non-conduction time can be varied as in the first embodiment. Without this, the input power can be adjusted by the conduction time ratio of the first and second semiconductor switches 5 and 4. At this time, it is desirable to fix the non-conduction time because the control circuit is simplified.

  Further, the third semiconductor switch 12 is turned on for a certain period of time at the time of transition from the first semiconductor switch 5 to the second semiconductor switch 4 or almost simultaneously with the first semiconductor switch 5 from the second semiconductor switch 4. By providing time, it becomes easier for a current to flow through the reverse conducting element at the time of transition of the state of the semiconductor switch, so that it is possible to prevent the turn-on loss of the semiconductor switch.

  When the resonance frequency of the resonance circuit composed of the heating coil 3 and the resonance capacitor 2 in a state where the load 6 is magnetically coupled is lower than the drive frequency of the first semiconductor switch 5 and the second semiconductor switch 4, That is, when the load 6 is made of a magnetic material such as magnetic stainless steel, the third semiconductor switch 12 need not be operated.

  As described above, according to the present embodiment, when the resonance frequency of the resonance circuit composed of the heating coil 3 and the resonance capacitor 2 is lower than the operating frequency, the non-conduction time is fixed and the input power control is performed with the conduction time ratio. By doing so, when the resonance frequency of the heating coil 3 and the resonant capacitor 2 is low, that is, when the load is made of a magnetic material such as magnetic stainless steel, the load is kept constant with the frequency of the current flowing through the heating coil 3 by a simple control method. It is possible to perform optimal power control according to the above.

  As described above, the induction heating device according to the present invention has a small frequency component of the commercial power source radiated from the heating coil, and can reduce noise without interference sound between loads generated between adjacent burners. Therefore, it can be applied as various heating devices as well as cooking appliances.

The circuit diagram of the induction heating apparatus in Embodiment 1 of this invention The figure which shows the electric current path in each area of the inverter circuit of the induction heating apparatus Each operation waveform diagram corresponding to FIG. 2 of the induction heating apparatus The figure which shows the current pathway in each area of the inverter circuit of the induction heating apparatus in Embodiment 2 of this invention. Each operation waveform diagram corresponding to FIG. 4 of the induction heating apparatus Circuit diagram of a 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 13 3rd Reverse conducting element 14 second reverse conducting element 15 first reverse conducting element

Claims (10)

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 source, and a control means for controlling the conduction time of the first and second semiconductor switches. And an auxiliary resonance means connected in parallel with the first or second semiconductor switch and provided with a resonance circuit, and energy stored in the auxiliary resonance means before the first or second semiconductor switch is turned on. Inductive heating device that discharges the first and second reverse conducting elements and causes the first or second semiconductor switch connected in parallel during the period in which the current flows through the reverse conducting element. The induction heating apparatus according to claim 1, wherein a snubber capacitor is connected to one or both of the first and second semiconductor switches. The induction heating apparatus according to claim 1 or 2, wherein the control means fixes one of the non-conduction times generated when the first and second semiconductor switches are switched and makes the other non-conduction time variable. 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 times is varied to operate at a constant frequency. The induction heating device according to any one of claims 1 to 3. The auxiliary resonance means has a series circuit of a third semiconductor switch, an auxiliary resonance coil, and an auxiliary resonance capacitor, and a third reverse conducting element in which the third semiconductor switch is connected in antiparallel, and at a predetermined timing. The induction heating device according to any one of claims 1 to 4, wherein the energy stored in the auxiliary resonant capacitor is supplied to the first or second reverse conducting element using a third semiconductor switch. 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 the first or second semiconductor switch that is turned on is turned off. The induction heating device according to any one of claims 1 to 5, wherein the induction heating device is operated so as to be in a non-conductive state before being in a conductive state. The induction heating apparatus according to claim 5 or 6, wherein the capacity of the auxiliary resonant capacitor is larger than that of the snubber capacitor. The induction according to any one of claims 1 to 7, wherein when the resonance frequency of the resonance circuit including the heating coil and the resonance capacitor is lower than the operating frequency, the non-conduction time is fixed and the input power control is performed based on the conduction time ratio. Heating device. The induction heating apparatus according to any one of claims 1 to 8, wherein the auxiliary resonance means is not operated when a resonance frequency of a resonance circuit including a heating coil and a resonance capacitor is lower than an operation frequency. When the resonance frequency of the resonance circuit including the heating coil and the resonance capacitor is lower than the operation frequency, the operation of the first or second semiconductor switch to the non-conduction state and the operation of the third semiconductor switch to the conduction state The induction heating apparatus according to claim 8, wherein the time of transition is substantially simultaneous.