JP4107150B2 - Induction heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating device such as an electromagnetic cooker that heats an object to be heated by using induction heating by a high frequency magnetic field.
[0002]
[Prior art]
A conventional induction heating apparatus (see, for example, Patent Document 1) will be described with reference to the drawings. FIG. 16 shows a conventional induction heating apparatus. A series circuit of a heating coil 5 and a first semiconductor switch 6 arranged in series with the power source 1, a third capacitor 10 connected in parallel with the heating coil 5, and a third capacitor 10 connected in parallel with the third capacitor 10. A series circuit of two capacitors 4 and a second semiconductor switch 7, a first reverse conducting element 26 connected in parallel to the first semiconductor switch 6, and a first circuit connected in parallel to the second semiconductor switch 7. 2 semiconductor switches 27.
[0003]
FIG. 17 is a diagram showing operation waveforms of FIG. I6 is the current flowing through the first semiconductor switch 6 and the first reverse conducting element 26, V6 is the collector-emitter voltage, and I6 is the current flowing through the second semiconductor switch 7 and the second reverse conducting element 27. V7 represents the collector-emitter voltage, and I5 represents the current flowing through the heating coil 5.
[0004]
Then, operation | movement of the conventional induction heating apparatus is demonstrated using FIG.16 and FIG.17. First, the control means 9 supplies electric power from the DC power supply 1 to the heating coil 5 by bringing the first semiconductor switch 6 into a conductive state. At this time, a current flows substantially on a straight line as indicated by I6 in FIG.
[0005]
Next, the control means 9 brings the first semiconductor switch 6 into a non-conductive state for a predetermined time. Then, the energy stored in the heating coil 5 first charges the third capacitor 10, and the collector potential of the first semiconductor switch 6 gradually rises as indicated by V6 in FIG. When the collector potential of the first semiconductor switch 6 becomes equal to the potential of the second capacitor 4, the second reverse conducting element 27 becomes conductive, and the energy of the heating coil 5 is transferred to the second capacitor 4. Stored. By keeping the second semiconductor switch 7 in a conductive state when the second reverse conducting element 27 is in a conductive state, this time, as shown by I7 in FIG. Will be supplied. The control means 9 makes the second semiconductor switch 7 non-conductive when a predetermined time has elapsed. Then, the energy stored in the heating coil 5 and the energy stored in the third capacitor 10 are regenerated to the DC power source 1 through the first reverse conducting element 26. By making the first semiconductor switch 6 conductive during this regeneration period, power is again supplied from the power source 1 to the heating coil 5. By performing this operation at about 20 to 50 kHz, a high frequency magnetic field is supplied to the load 8 by passing a current as shown in I5 through the heating coil 5, and an eddy current is generated on the surface of the load 8 to heat the load 8. It will be.
[0006]
In this way, induction heating can be performed with a simple component configuration, and the capacitance of the second capacitor 4 is made larger than that of the third capacitor 10, so that the first semiconductor switch 6 and the second semiconductor switch 7 It has features such as the use of inexpensive semiconductor switches with reduced withstand voltage. Further, the capacitance of the second capacitor 4 is set sufficiently lower than the resonance frequency of the resonance circuit formed by the heating coil 5 and the second capacitor 4 than the drive frequency of the first and second switching elements 6 and 7. Therefore, the control means 9 can reasonably control the conduction time of the first semiconductor switch 6 and the second semiconductor switch 7 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.
[0007]
In addition, an example of another circuit configuration of the conventional induction heating device (for example, see Patent Document 2) will be described with reference to the drawings. FIG. 18 shows a conventional induction heating apparatus. A series body of a first semiconductor switch 6 and a second semiconductor switch 7 is connected in parallel with the power source 1, and a series connection of a heating coil 5 and a first capacitor 3 is connected to the first semiconductor switch 6, a third capacitor. 10 and the first reverse conducting element 26 are connected, a second reverse conducting element 27 is connected to the second semiconductor switch 7, and the load 8 is arranged to be magnetically coupled to the heating coil 5. .
[0008]
Next, the operation of this conventional example will be described. When the second semiconductor switch 7 is turned on, a current determined by the voltage difference between the power source 1 and the first capacitor 3 is supplied to the heating coil 5. Next, when the second semiconductor switch 7 is turned off, the charge stored in the third capacitor 10 moves to the first capacitor 3 through the heating coil 5, and after the charge of the third capacitor 10 is lost. When the first reverse conducting element 26 is conducted, a current flows from the heating coil 5 to the first capacitor 3. The first capacitor 3 is turned on after the power of the heating coil 5 is changed to the first capacitor 3 by setting the first semiconductor switch 6 to the conductive state at the timing when the first reverse conducting element 26 is conducted. As a power source, power is supplied to the heating coil 5.
[0009]
Further, when the first semiconductor switch 6 is turned off after a predetermined time has elapsed, the electric charge stored in the heating coil 5 is supplied to the power source through the second reverse conducting element 27 after the electric charge is stored in the third capacitor. It will regenerate to 1. In this regeneration period, the second semiconductor switch 7 is turned on again to return to the initial operation.
[0010]
Here, the third capacitor 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 semiconductor switch 6 and the second semiconductor switch 7 become non-conductive. ing. In addition, the induction heating element of this embodiment cannot secure necessary power unless the capacity of the first capacitor is set in the vicinity of the resonance frequency of the resonance circuit formed with the heating coil 5. Since the resonance frequency is greatly different, the control means 9 performs control by combining the drive frequency close to the resonance frequency, that is, by changing the drive frequency.
[0011]
[Patent Document 1]
JP-A-8-262666
[Patent Document 2]
Japanese Patent Laid-Open No. 5-114474
[0012]
[Problems to be solved by the invention]
However, in such a conventional induction heating device (FIG. 16), since the current flowing through the heating coil 5 has a high frequency component superimposed on the DC component, for example, when the DC power source 1 rectifies the commercial power source For example, in addition to the high-frequency component necessary for heating the load 8, a component twice the commercial power source is supplied to the heating coil 5. Since this commercial power supply component is not absorbed by the load 8, it is radiated from the heating coil 5 to the outside. Such unnecessary electromagnetic field radiation has a problem that causes noise and the like in the surroundings.
[0013]
In the conventional example in which a direct current component does not flow into the heating coil 5 (FIG. 18), it is necessary to secure input power by changing the drive frequency when the type of the load 8 changes. This is because the input power greatly depends on the resonance frequency of the resonance circuit formed by the first capacitor 3 and the heating coil 5, so that the first switching element according to the load 8 is required to ensure stable input power. This is because it is necessary to change the driving frequency of 6 and the second switching element 7. For this reason, when an induction heating apparatus has a some burner, it has the subject that the interference sound of the frequency of the difference of a mutual drive frequency generate | occur | produces.
[0014]
The present invention solves the above-described problems, and can reduce unnecessary noise by reducing the radiation of the electromagnetic field of the commercial frequency component from the heating coil, and even when the input power or the load is different, the heating coil An object of the present invention is to provide an induction heating device that does not generate a load interference sound by keeping the frequency of the current flowing through the coil constant.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention provides a first semiconductor switch, a reverse conducting element connected in parallel to the first semiconductor switch, and a limit for limiting an input voltage during a conduction period of the first semiconductor switch. A flow means, a second semiconductor switch connected in series with the first semiconductor switch, a second reverse conducting element connected in parallel to the second semiconductor switch, and a load (object to be heated) A heating coil for induction heating, a first capacitor and a second capacitor that form a series resonance circuit with the heating coil during conduction of the first semiconductor switch or the second semiconductor switch, and the first semiconductor A third capacitor that forms a resonance circuit with the heating coil when the switch and the second semiconductor switch are non-conductive, and a conductive period of the first semiconductor switch and the second semiconductor switch A control circuit that exclusively controls each other at a constant frequency, the resonance frequency of the resonance circuit formed by the first capacitor and the heating coil, and the resonance frequency of the resonance circuit formed by the second capacitor and the heating coil, Set lower than the drive frequency of the control circuit, and set the resonance frequency of the resonance circuit formed by the third capacitor and the heating coil to be higher than the drive frequency of the control circuit. In addition, after supplying power from the power source to the first and second capacitors through the current limiting means, power is supplied from the first and second capacitors to the heating coil, and the current limiting means includes The power supply and the heating coil have an action of preventing a short circuit through the first semiconductor switch and the second semiconductor switch. It is set as the induction heating apparatus characterized by this.
[0016]
As a result, after the power supply from the power supply is performed to the first and second capacitors through the current limiting means, the power supply is performed from the first and second capacitors to the heating coil. It is not short-circuited via the switch, so that the current with the frequency component of the power supply hardly passes through the heating coil, and the magnetic field with the frequency component of the power supply is radiated from the heating coil to the outside. The resonance frequency of the resonance circuit formed by the first and second capacitors and the heating coil can be made larger than the drive frequency of the control circuit, so that the resonance frequency can be reduced by changing the load. Even if it changes, it can be controlled at a constant frequency without changing the driving frequency, and the resonance frequency of the resonance circuit formed by the third capacitor and the heating coil can be controlled. By setting the frequency lower than the dynamic frequency, the third capacitor can be charged and discharged quickly even when the input power is small. Therefore, even when the input power is changed, control can be performed at a constant frequency without changing the drive frequency. Therefore, it is possible to realize an induction heating device capable of preventing the interference sound of the load caused by the difference in driving frequency between adjacent burners.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention according to claims 1 to 7 includes a first semiconductor switch, a reverse conducting element connected in parallel to the first semiconductor switch, and a limit for limiting the input voltage during the conducting period of the first semiconductor switch. Current means, a second semiconductor switch connected in series with the first semiconductor switch, a second reverse conducting element connected in parallel with the second semiconductor switch, a heating coil, and the first A first capacitor and a second capacitor that form a series resonant circuit with the heating coil during a conduction period of the semiconductor switch or the second semiconductor switch, and non-connection of the first semiconductor switch and the second semiconductor switch. The conduction period of the third capacitor forming a resonance circuit with the heating coil and the first semiconductor switch and the second semiconductor switch when conducting is controlled mutually exclusively at a constant frequency. A resonance circuit formed by the first capacitor and the heating coil, and a resonance frequency of the resonance circuit formed by the second capacitor and the heating coil is set lower than a drive frequency of the control circuit. And setting the resonance frequency of the resonance circuit formed by the third capacitor and the heating coil to be higher than the drive frequency of the control circuit. In addition, after supplying power from the power source to the first and second capacitors through the current limiting means, power is supplied from the first and second capacitors to the heating coil, and the current limiting means includes The power supply and the heating coil have an action of preventing a short circuit through the first semiconductor switch and the second semiconductor switch. It is set as the induction heating apparatus characterized by this.
[0018]
As a result, power is supplied from the power source to the first and second capacitors through the current limiting means, and then current is supplied from the first and second capacitors to the heating coil. The current limiting means prevents the power source and the heating coil from being short-circuited via the semiconductor switch, and the current having the frequency component of the power source hardly passes through the heating coil. It is possible to greatly reduce the radiated magnetic field to the outside. In addition, by setting the resonance frequency of the resonance circuit formed by the first and second capacitors and the heating coil to be lower than the drive frequency of the control circuit, the electrical characteristics of the object to be heated change, and the heating coil electrical Even if the characteristic, for example, the L component changes, and the resonance frequency of the circuit changes, the influence on the driving frequency can be absorbed and can be controlled at a constant frequency without changing the driving frequency. By setting the resonance frequency of the resonance circuit formed by the heating coil higher than the drive frequency, the third capacitor can be charged and discharged quickly even when the input power is small. However, the influence on the drive frequency can be absorbed, and even when the input power is changed, control can be performed at a constant frequency without changing the drive frequency. As a result, it is possible to realize an induction heating apparatus that can drive adjacent burners at the same frequency and prevent the interference noise of the load caused by the difference in drive frequency between the burners.
[0019]
In addition to the above, the first semiconductor switch is configured such that the first capacitor and the heating coil form a resonance circuit when conducting in the forward direction.
[0020]
In addition to the above, the second semiconductor switch is configured such that the second capacitor and the heating coil form a resonance circuit when conducting in the forward direction.
[0021]
In the invention according to claim 4, in addition to the above, the capacity of the first capacitor is equal to or larger than the capacity of the second capacitor.
[0022]
In the invention according to claim 5, in addition to the above, a third capacitor is connected in parallel with the heating coil.
[0023]
Similarly, since the current flowing through the heating coil always passes through the capacitor, and the current having the frequency component of the power source is reduced from being applied to the heating coil, the frequency component of the power source from the heating coil is reduced. It is possible to reduce the amount of magnetic field radiated to the outside, and to realize an induction heating device that can keep the frequency of the current flowing in the heating coil constant regardless of the type of input power or load It is.
[0024]
The invention according to claim 6 is a series body of current limiting means and a first semiconductor switch connected in parallel to a DC power source, a first reverse conducting element connected in parallel with the first semiconductor switch, A series body of a heating coil and a first capacitor connected to the first semiconductor switch for induction heating of a load, and a series connection of a second semiconductor switch and a second capacitor connected in parallel to the heating coil Body, a second reverse conducting element connected in parallel to the second semiconductor switch, and a third capacitor connected in parallel to the heating coil, and formed by the first capacitor and the heating coil. The resonance frequency of the resonance circuit formed by the resonance circuit and the second capacitor and the heating coil is set lower than the drive frequency of the control circuit, and the third capacitor and the heating Set higher also than the driving frequency of the control circuit the resonance frequency of the resonant circuit formed by yl In addition, after supplying power from the power source to the first and second capacitors through the current limiting means, power is supplied from the first and second capacitors to the heating coil, and the current limiting means includes The power supply and the heating coil have an action of preventing a short circuit through the first semiconductor switch and the second semiconductor switch. It is an induction heating device.
[0025]
As a result, the current flowing through the heating coil always passes through the capacitor, and the current having the frequency component of the power supply is reduced from being applied to the heating coil. Therefore, the magnetic field having the frequency component of the power supply from the heating coil is reduced. It is possible to reduce the amount of radiation radiated to the outside and realize an induction heating device that can keep the frequency of the current flowing through the heating coil constant regardless of the type of input power or load. .
[0026]
In addition to the above, the present invention according to claim 8 is an induction heating apparatus in which a third reverse conducting element is connected in series with the current limiting means.
[0027]
As a result, in addition to the above, it is possible to prevent power from being regenerated from the second capacitor to the power source through the second semiconductor switch and the current limiting means, and it is possible to prevent unnecessary current from flowing and decrease efficiency. It is possible to realize an induction heating apparatus capable of preventing the above.
[0028]
According to a ninth aspect of the present invention, there is provided an induction heating system comprising a commercial power supply and a rectifying means for rectifying the commercial power supply, and a fourth capacitor for supplying power to the current limiting means is disposed between the commercial power supply and the rectifying means. It is a device.
[0029]
Thereby, in addition to the above, it becomes possible to prevent regeneration of electric power to an unnecessary power source without connecting a reverse conducting element in particular, and an inexpensive induction heating apparatus can be realized.
[0030]
According to a tenth aspect of the present invention, there is provided an induction heating apparatus in which switching means is provided in series with the third capacitor and the switching means is controlled according to the state of input power.
[0031]
As a result, in addition to the above, it becomes possible to prevent an increase in loss caused by the conduction of the first or second semiconductor switch in a state where electric charge remains in the third capacitor that occurs when the input power is low. It is possible to realize an induction heating device capable of reducing the input power without increasing the current.
[0032]
The present invention according to claims 11 to 12 is an induction heating apparatus that provides a certain non-conduction time when driving the first semiconductor switch and the second semiconductor switch.
[0033]
As a result, in addition to the above, it is possible to reliably prevent a failure due to the first semiconductor switch and the second semiconductor switch being simultaneously conducted simultaneously, thereby realizing a highly reliable induction heating apparatus.
[0034]
According to the thirteenth aspect of the present invention, the control means 9 compares the output of the input current detection means 21 for detecting the current of the commercial power supply 1 with the input power command value, and the conduction time of the first semiconductor switch 6 is determined by the comparison value. Induction heating device for controlling
[0035]
Thereby, in addition to the above, it is possible to realize an induction heating device that has a quick response to the input power command value and good controllability.
[0036]
The present invention according to claims 14 to 15 is provided with coil current detection means for detecting the current of the heating coil, and induction for controlling the conduction time of the first semiconductor switch so that the coil current detection means becomes a predetermined value. It is a heating device.
[0037]
As a result, in addition to the above, it is possible to control the current flowing through the heating coil, and it is possible to prevent the heating coil current from flowing more than necessary depending on the type of load, and induction heating with excellent reliability. A device can be realized.
[0038]
According to the sixteenth to seventeenth aspects of the present invention, there is provided first voltage detection means for detecting the voltage of the first semiconductor switch, and the first semiconductor switch is set so that the first voltage detection means has a predetermined value. The induction heating device controls the conduction time.
[0039]
As a result, in addition to the above, it is possible to prevent the voltage of the first semiconductor switch from rising more than necessary depending on the type of load, and a highly reliable induction heating apparatus can be realized.
[0040]
The present invention according to claims 18 to 19 includes second voltage detection means for detecting the voltage of the second semiconductor switch, and the first semiconductor switch is set so that the first voltage detection means has a predetermined value. The induction heating device controls the conduction time.
[0041]
As a result, in addition to the above, it is possible to prevent the voltage of the second semiconductor switch from rising more than necessary depending on the type of load, and a highly reliable induction heating apparatus can be realized.
[0042]
【Example】
(Example 1)
A first embodiment of the present invention will be described with reference to the drawings.
[0043]
FIG. 1 is a diagram showing a circuit configuration of the induction heating apparatus of this embodiment. The direct current power source 1 is connected to the first semiconductor switch 6 through the current limiting means 2, and the first reverse conducting element 26 is connected to the first semiconductor switch 6 in parallel. The first semiconductor switch 6 is connected to a series circuit of the heating coil 5 and the first capacitor 3. The heating coil 5 is configured so that a load 8 such as a pan is magnetically coupled to the heating coil 5. The load 8 is heated by electromagnetic induction by the high-frequency current flowing through.
[0044]
Further, a series circuit of a second semiconductor switch 7 and a second capacitor 4 is connected to the heating coil 5, and a second reverse conducting element 27 is connected to the second semiconductor switch 7. And the control means 9 is set as the structure which supplies the electric power of the DC power supply 1 to the load 8 through the heating coil 5 by making the 1st semiconductor switch 6 and the 2nd semiconductor switch 7 into a conduction | electrical_connection state alternately. At this time, the control means 9 keeps the driving frequency of the first semiconductor switch 6 and the second semiconductor switch 7 constant so that no interference sound between the pans is generated even if the heating operation is performed with the adjacent burner. ing. In this embodiment, the first and second semiconductor switches 6 and 7 are described as IGBTs conducting in the forward direction and diodes connected in reverse parallel thereto, but the diodes are configured inside the elements like MOSFETs. There is no problem even if the device is used.
[0045]
Next, the operation of this embodiment will be described. FIG. 2 is a diagram showing a current path in each section of the inverter circuit, and FIG. 3 is a waveform diagram corresponding to FIG. In FIG. 3, I6 indicates a current flowing through the first semiconductor switch 6, I26 indicates a current flowing through the first reverse conducting element 26, V6 indicates a collector-emitter voltage thereof, and I6 flows through the second semiconductor switch 7. I27 is the current flowing through the second reverse conducting element 27, V7 is the collector-emitter voltage, I5 is the current flowing through the heating coil 5, and I2 is the current flowing through the current limiting means 2. Yes.
[0046]
A description will be given from the state of FIG. The control means 9 makes the first semiconductor switch 6 conductive according to the power command value. Then, energy is stored in the current limiting means from the DC power source 1 according to the conduction time of the first switching element 6. On the other hand, the first capacitor 3 supplies power to the load 8 through the heating coil 5 using the first capacitor 3 as a power source. This is a waveform as shown by I6 in FIG.
[0047]
Next, when the control means 9 brings the first semiconductor switch 7 into a non-conducting state, the state shown in FIG. 2B is obtained, and the current of the heating coil 5 and the current limiting means 2 charges the third capacitor 10. As a result, the voltage of the first semiconductor switch 6 gradually increases. Eventually, when the potentials of the second capacitor 4 and the third capacitor 10 become equal, the second reverse conducting element 27 becomes conductive, and the state transitions to the state of FIG. In (c), the electric power stored in the current limiting means 2 can store energy in the first and second capacitors through the second reverse conducting element 27, and the energy stored in the heating coil 5 can also be stored in the second capacitor 4. Stored in For this reason, as shown in I7 of FIG. 3, a large reverse conduction current flows to the second reverse conduction element 27. The control means 9 keeps the second semiconductor switch 7 in a conducting state during the period in which the current flows through the second reverse conducting current 27, thereby completing the accumulation of energy from the heating coil 5 to the second capacitor 4. At this point, the state shown in FIG. In the state (d), power is supplied to the load 8 through the heating coil 5 using the second capacitor 4 as a power source.
[0048]
Further, the energy stored in the current limiting means 2 stores electric power in the first capacitor 3 through the heating coil 5. Then, when the control means 9 turns off the second semiconductor switch 7 for a predetermined time, the state of the second semiconductor switch 7 is gradually lowered while the state transitions to the state of FIG. The voltage of the switch 7 increases. Thereafter, when the potential of the third capacitor becomes zero, the first reverse conducting element 26 becomes conductive, and the electric power stored in the heating coil 5 passes through the first reverse conducting element 26 to the first capacitor. 3 will store energy. By bringing the first semiconductor switch 6 into a conducting state while the first reverse conducting element 26 is conducting, the state returns to the state of FIG. 2A, 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 as indicated by I5 in FIG. 3, and a high-frequency magnetic field generated by this high-frequency current is absorbed by the load 8, and the load 8 itself The load 8 itself generates heat due to the eddy current generated by the high-frequency resistance and the high-frequency magnetic field.
[0049]
With such a configuration, after the power supply from the power source 1 is supplied to the first capacitor 3 and the second capacitor 4 through the current limiting means 2, the first capacitor 3 and the second capacitor 4 Since power is supplied to the heating coil 5, the power source 1 and the heating coil 5 are not short-circuited via the first semiconductor switch 6 or the second semiconductor switch 7, and therefore the power source 1 fluctuates (pulsating flow). It is possible to greatly reduce the fact that the current having the frequency component hardly passes through the heating coil 5 and the magnetic field having the frequency component of the power source 1 is radiated from the heating coil 5 to the outside. Become. Further, by setting the resonance frequency of the resonance circuit formed by the first capacitor 3 and the second capacitor 4 and the heating coil 5 to be higher than the drive frequency of the control circuit 9, the resonance frequency is changed by changing the load 8. Even if it changes, the control means 9 can control at a constant frequency without changing the driving frequency. That is, by setting the resonance frequency of the first capacitor 3 and the second capacitor 4 and the heating coil 5 sufficiently lower than the driving frequency, the first capacitor 3 and the second capacitor 4 are heated by the change of the load 8. Even if the resonance frequency of the coil 5 changes, the input power can be secured without following the drive frequency to the resonance frequency.
[0050]
In addition, since the resonance frequency of the resonance circuit formed by the third capacitor 10 and the heating coil 5 is set higher than the drive frequency, the third capacitor 10 can be charged and discharged quickly even when the input power is small. Even when the input power is changed, the control means 9 can control at a constant frequency without changing the driving frequency. As a result, for example, when the induction heating apparatus is operated as close as between adjacent burners, it is possible to prevent the interference noise of the load caused by the difference in the driving frequency of the induction heating apparatus.
[0051]
Further, as shown in FIG. 3I2, it is desirable that the current limiting means 2 has a capacity such that the current of the current limiting means 2 is not always less than or equal to zero, and the capacity of the first capacitor 3 and the second capacitor 4 is Since it is sufficient if there is a capacity capable of supplying high-frequency power to the heating coil 5, several μF to several tens μF are sufficient, and it is desirable that the capacity of both is the same or the capacity of the first capacitor 3 is large. Here, a choke coil having a core made of a magnetic material such as sendust or a thin silicon steel plate is used as the current limiting means 2.
[0052]
In addition, when arrange | positioning in parallel with the 1st semiconductor switch 6 as shown in FIG. 4, when arrange | positioning in parallel with the 2nd semiconductor switch 7 as shown in FIG. 5, a 3rd capacitor | condenser is shown in FIG. Thus, when both are arranged, the same effect as that obtained when the heating coil 5 is placed in parallel is obtained, and the first semiconductor switch 6 and the second semiconductor switch 7 have a role of greatly reducing the loss at the time of turn-off. Will have.
[0053]
As described above, according to this embodiment, after the power supply 1 is supplied to the first capacitor 3 and the second capacitor 4 through the current limiting means 2, the first capacitor 3 and the second capacitor are supplied. Since power is supplied from 4 to the heating coil 5, the power source 1 and the heating coil 5 are not short-circuited via the first semiconductor switch 6 or the second semiconductor switch 7, and therefore the power source 1 fluctuates ( In this case, the current having the frequency component hardly passes through the heating coil 5 and the magnetic field having the frequency component of the power source 1 is radiated from the heating coil 5 to the outside. The load 8 is changed by setting the resonance frequency of the resonance circuit formed by the first capacitor 3 and the second capacitor 4 and the heating coil 5 to be lower than the drive frequency of the control circuit 9. Even if the resonance frequency changes, the control means 9 can control at a constant frequency without changing the drive frequency, and the resonance frequency of the resonance circuit formed by the third capacitor 10 and the heating coil 5 can be set to the drive frequency. By setting a higher value, the third capacitor 10 is quickly charged / discharged even when the input power is small. Therefore, even when the input power is changed, the control means 9 controls at a constant frequency without changing the drive frequency. Therefore, it is possible to realize an induction heating device capable of preventing the interference sound of the load caused by the difference in driving frequency between adjacent burners.
[0054]
(Example 2)
A second embodiment of the present invention will be described with reference to the drawings.
[0055]
The configuration of this embodiment is shown in FIG. This embodiment is different from the first embodiment in that a third reverse conducting element 13 is connected in series with the current limiting means 2.
[0056]
The operation in the above configuration will be described. FIG. 8 shows an operation diagram for the operation in this embodiment. In the case where the third reverse conducting element 13 is not provided, if the capacity of the current limiting means 2 is small, the first capacitor 3 and the second capacitor 4 are used as a power source when the second semiconductor switch 7 is in a conducting state. The power stored in the capacitor is regenerated to the DC power supply 1 through the path of 1 capacitor 3 → second capacitor 4 → second semiconductor switch 7 → current limiting means 2 → DC power supply 1. At this time, if the necessary power is supplied to the load 8, a large ripple current is required for the current limiting means 2, and the loss of the current limiting means 2 becomes large. Here, by connecting the third reverse conducting element 13 to the current limiting means 2, it becomes possible to prevent the power from being regenerated in the DC power source 1 as indicated by I2 in FIG.
[0057]
As described above, according to the present embodiment, the third reverse conducting element 13 is connected in series to the current limiting means 2, thereby allowing direct current from the second capacitor 4 through the second semiconductor switch 7 and the reverse conducting element 2. It is possible to realize an induction heating device that can prevent power from being regenerated in the power source 1, can prevent unnecessary current from coming and going, and can prevent a decrease in efficiency.
[0058]
(Example 3)
A third embodiment of the present invention will be described with reference to the drawings.
[0059]
The configuration of this example is shown in FIG. This embodiment is different from the first embodiment in that the DC power source 1 is composed of a commercial power source 16, a fourth capacitor 17, and a rectifier bridge 18, and a fourth capacitor 17 for supplying power to the current limiting means 2 is provided. The point is that it is disposed between the commercial power supply 16 and the rectifying bridge 18.
[0060]
The operation of this embodiment will be described. In the case where the fourth capacitor 17 for supplying power to the current limiting means 2 is arranged on the output side of the rectifier bridge 18, if the capacity of the current limiting means 2 is small, the second semiconductor switch 7 is in the conductive state. Using the first capacitor 3 and the second capacitor 4 as a power source, the first capacitor 3 → the second capacitor 4 → the second semiconductor switch 7 → the current limiting means 2 → the fourth capacitor 17 is stored in the capacitor. The generated electric power is regenerated in the fourth capacitor 17. At this time, if the necessary power is supplied to the load 8, a large ripple current is required for the current limiting means 2, and the loss of the current limiting means 2 becomes large. Here, by arranging the current limiting means 17 on the input side of the rectifying bridge 18, it is possible to prevent power from being regenerated in the fourth capacitor 17.
[0061]
As described above, according to the present embodiment, the fourth capacitor 17 is arranged on the input side of the rectifier bridge 18, whereby the fourth capacitor 17 is passed through the second semiconductor switch 7 and the current limiting means 2. It is possible to realize an induction heating device that can prevent the regeneration of electric power in the capacitor 17 and can prevent unnecessary current from passing and can prevent a decrease in efficiency.
[0062]
Example 4
A fourth embodiment of the present invention will be described with reference to the drawings.
[0063]
The configuration of this embodiment is shown in FIG. This embodiment is different from the second embodiment in that the switch means 20 is connected in series with the third capacitor 10 and the control means 9 turns the switch means 20 on and off according to the state of the input power. .
[0064]
The operation of this embodiment will be described. When the input power is large, the charge of the third capacitor 10 becomes zero, that is, each switch is turned on in a state where the first reverse conducting element 26 and the second reverse conducting element 27 are conducting. It is possible to operate with the loss (turn-on loss) at the moment of conduction at approximately zero.
[0065]
However, when the input power is small, there is a case where the first and second semiconductor switches 6 and 7 are turned on before the charge of the third capacitor 10 runs out, and the turn-off loss due to the effect of the third capacitor. In some cases, the turn-on loss becomes larger than the reduction of the above. Since such a tendency becomes larger as the input power becomes smaller, the control means 9 can reduce the input power to a smaller value by separating the third capacitor using the switch means 20 according to the state of the input power. Become. The switch means 20 is not particularly limited, such as a relay switch or a semiconductor switch.
[0066]
As described above, in this embodiment, by providing the switch means 20 in series with the third capacitor, the first or second in a state where electric charge remains in the third capacitor generated when the input power is small. An increase in loss caused by conduction of the semiconductor switches 6 and 7 can be prevented, and an induction heating apparatus that can reduce the input power without increasing the loss can be realized.
[0067]
(Example 5)
A fifth embodiment of the present invention will be described with reference to the drawings.
[0068]
Since the configuration of this embodiment is the same as that shown in FIG.
[0069]
The operation of this embodiment will be described. FIG. 11 shows each part waveform when performing input power control in this embodiment. FIG. 11A shows waveforms when the input power is large, and FIG. 11B shows voltage and current waveforms of the switching elements when the input power is small. Here, Vg6 and Vg7 indicate drive signals applied to the first switching element 6 and the second switching element 7, respectively. The control means 9 controls the input power by changing the conduction time of the first semiconductor switch 6 and the conduction time of the second semiconductor switch 7 simultaneously, that is, by changing the conduction ratio, with a constant frequency. Here, during the change of the conduction state of the first semiconductor switch 6 and the second semiconductor switch 7, a certain non-conduction time (td1 and td2) is given.
[0070]
Furthermore, in this embodiment, the non-conducting time (td2) when transitioning from the conducting state of the first semiconductor switch 6 to the conducting state of the second semiconductor switch 7 is different from the conducting state of the second semiconductor switch 7. The non-conducting time (td1) when the first semiconductor switch 6 transitions to the conducting state can be set long. This is because it is desirable that each reverse conducting element is in a conducting state as the timing for conducting the first and second semiconductor switches 6 and 7, and the conducting times of the reverse conducting elements are different. In this way, it is possible to prevent the first semiconductor switch 6 and the second semiconductor switch 7 from being simultaneously turned on by setting the non-conduction time to a constant value. Further, by making the non-conduction time (td 1, td 2) constant, it is possible to provide a highly reliable induction heating apparatus that can simplify the control means 9.
[0071]
As described above, according to this embodiment, when the first semiconductor switch 6 and the second semiconductor switch 7 are driven, the first semiconductor switch 6 and the second semiconductor switch 6 are surely provided by providing a certain non-conduction time. Therefore, it is possible to prevent a failure due to simultaneous conduction of the semiconductor switches 7 and to realize a highly reliable induction heating apparatus.
[0072]
(Example 6)
A sixth embodiment of the present invention will be described with reference to the drawings.
[0073]
The configuration of this embodiment is shown in FIG. This embodiment is different from the first embodiment in that the DC power source 1 is rectified from the commercial power source 16 by the rectifier bridge 18 and then made by the fourth capacitor 17, and the input current detection means 21 is connected to the rectifier bridge 18. This is a point provided on the input side.
[0074]
The operation of this embodiment will be described. As shown in FIG. 12, the control means 9 compares the current value detected by the input current detection means 21 with the command value inside the control means 9, and the first semiconductor has a power value according to the command value. The conduction time of the switch 6 is controlled. By performing such control, the followability to the command value is improved, and an induction heating apparatus having excellent controllability can be realized. Further, since the current flowing through the heating coil is operated at a constant frequency, when the conduction time of the first semiconductor switch 6 is determined, the conduction time of the second semiconductor switch 7 is also uniquely determined.
[0075]
As described above, according to the present embodiment, the control means 9 compares the output of the input current detection means 21 for detecting the current of the commercial power supply 1 with the input power command value, and the first semiconductor switch 6 is compared with the comparison value. By controlling the conduction time, it is possible to realize an induction heating device having a quick response to the input power command value and good controllability.
[0076]
(Example 7)
A seventh embodiment of the present invention will be described with reference to the drawings.
[0077]
The configuration of this example is shown in FIG. The present embodiment is different from the first embodiment in that the DC power source 1 is made of the fourth capacitor 17 after the commercial power source 16 is rectified by the rectifier bridge 18, and the coil current detecting means 22 is connected to the heating coil 5. It is a point provided in series.
[0078]
The operation of this embodiment will be described. As shown in FIG. 13, the control means 9 compares the coil current value detected by the coil current detection means 22 with the command value inside the control means 9, and the first current is obtained so that the coil current becomes the command value. The conduction time of the semiconductor switch 6 is controlled. By performing such control, it is possible to control the current flowing through the load 8, and it is possible to instantaneously detect that the load 8 fluctuates and perform control according to the fluctuation.
[0079]
Further, by limiting the coil current so as not to exceed a predetermined value, when using a load having a low high-frequency resistance such as a non-magnetic pan as the load 8, heat generation of parts due to excessive coil current flow, etc. Can be prevented from increasing.
[0080]
As described above, according to the present embodiment, the current flowing through the heating coil 5 is controlled by the coil current detecting means 22, thereby preventing the current in the heating coil 5 from flowing more than necessary depending on the type of the load 8. Therefore, an induction heating apparatus with excellent reliability can be realized.
[0081]
(Example 8)
An eighth embodiment of the present invention will be described with reference to the drawings.
[0082]
The configuration of this embodiment is shown in FIG. The present embodiment is different from the first embodiment in that the DC power source 1 is made of the fourth capacitor 17 after the commercial power source 16 is rectified by the rectifier bridge 18 and the collector-emitter of the first semiconductor switch 6. It is the point provided with the 1st voltage detection means 23 which detects a voltage between.
[0083]
The operation of this embodiment will be described. As shown in FIG. 14, the control means 9 compares the collector-emitter voltage of the first semiconductor switch 6 detected by the first voltage detection means 23 with the command value inside the control means 9, and determines the command value. The conduction time of the first semiconductor switch 6 is controlled so as to obtain the same collector-emitter voltage. By performing such control, the voltage of the first semiconductor switch 6 can be controlled, and it is possible to instantaneously detect that the load 8 has changed and to perform control according to the change.
[0084]
In addition, by limiting the collector-emitter voltage so that it does not exceed a predetermined value, it becomes possible to keep the collector-emitter voltage within a predetermined value, and it is possible to prevent component breakdown due to breakdown voltage. Become.
[0085]
As described above, according to the present embodiment, the first voltage detecting means 23 for detecting the voltage of the first semiconductor switch 6 is provided, and the first semiconductor is set so that the first voltage detecting means 23 becomes a predetermined value. By controlling the conduction time of the switch 6, it becomes possible to prevent the voltage of the first semiconductor switch 6 from rising more than necessary depending on the type of load, and a highly reliable induction heating device can be realized. It is.
[0086]
Example 9
An eleventh embodiment of the present invention will be described with reference to the drawings.
[0087]
The configuration of this embodiment is shown in FIG. The present embodiment is different from the first embodiment in that the DC power source 1 is made of the fourth capacitor 17 after the commercial power source 16 is rectified by the rectifier bridge 18 and the collector-emitter of the second semiconductor switch 7. The second voltage detecting means 24 for detecting the inter-voltage is provided.
[0088]
The operation of this embodiment will be described. As shown in FIG. 15, the control means 9 compares the collector-emitter voltage of the second semiconductor switch 7 detected by the second voltage detection means 24 with the command value inside the control means 9 and determines the command value. The conduction time of the first semiconductor switch 6 is controlled so as to obtain the same collector-emitter voltage. By performing such control, the voltage of the second semiconductor switch 7 can be controlled, and it is possible to instantaneously detect that the load 8 has changed and to perform control according to the change. In addition, by limiting the collector-emitter voltage so that it does not exceed a predetermined value, it becomes possible to keep the collector-emitter voltage within a predetermined value, and it is possible to prevent component breakdown due to breakdown voltage. Become.
[0089]
As described above, according to the present embodiment, the second voltage detecting means 24 for detecting the voltage of the second semiconductor switch 7 is provided, and the second semiconductor is set so that the second voltage detecting means 24 becomes a predetermined value. By controlling the conduction time of the switch 7, it becomes possible to prevent the voltage of the second semiconductor switch 7 from rising more than necessary depending on the type of load, and a highly reliable induction heating device can be realized. It is.
[0090]
【The invention's effect】
As a result, the current flowing through the heating coil 5 always passes through the 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 radiated magnetic field to the outside, and the frequency of the current flowing through the heating coil 5 can be kept constant regardless of the type of input power or load, and heating is performed by an adjacent burner. In this case, an induction heating apparatus that does not generate load interference sound is realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of an induction heating apparatus according to a first embodiment of the present invention.
FIG. 2A is a diagram showing an operation mode in which the first semiconductor switch 6 of the induction heating apparatus according to the first embodiment of the present invention is in a conductive state.
(B) The figure which shows the operation mode which makes the 1st semiconductor switch 6 of the induction heating apparatus of the 1st Example of this invention a non-conduction state.
(C) The figure which shows the operation mode which makes the 1st semiconductor switch 6 of the induction heating apparatus of the 1st Example of this invention the non-conduction state, and makes the 2nd reverse conduction element 27 a conduction state.
(D) The figure which shows the operation mode which the 2nd semiconductor switch 7 of the induction heating apparatus of the 1st Example of this invention makes into a conduction | electrical_connection state.
(E) The figure which shows the operation mode which turns off the 2nd semiconductor switch 7 of the induction heating apparatus of the 1st Example of this invention.
(F) The figure which shows the operation mode which makes the 2nd semiconductor switch 7 of the induction heating apparatus of the 1st Example of this invention a non-conduction state, and makes the 1st reverse conduction element 26 a conduction state.
FIG. 3 is a diagram showing operation waveforms of the induction heating apparatus according to the first embodiment of the present invention.
FIG. 4 is a diagram showing different circuit configurations of the induction heating apparatus according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a different circuit configuration of the induction heating apparatus according to the first embodiment of the present invention.
FIG. 6 is a diagram showing different circuit configurations of the induction heating apparatus according to the first embodiment of the present invention.
FIG. 7 is a diagram showing a circuit configuration of an induction heating apparatus according to a second embodiment of the present invention.
FIG. 8 is a diagram showing operation waveforms of the induction heating apparatus according to the second embodiment of the present invention.
FIG. 9 is a diagram showing a circuit configuration of an induction heating apparatus according to a third embodiment of the present invention.
FIG. 10 is a diagram showing a circuit configuration of an induction heating apparatus according to a fourth embodiment of the present invention.
FIG. 11A is a diagram showing operation waveforms when the input power is large in the induction heating apparatus of the fifth embodiment of the present invention.
(B) The figure which shows the operation | movement waveform at the time of the input power small of the induction heating apparatus of the 5th Example of this invention.
FIG. 12 is a diagram showing a circuit configuration of an induction heating apparatus according to a sixth embodiment of the present invention.
FIG. 13 is a diagram showing a circuit configuration of an induction heating apparatus according to a seventh embodiment of the present invention.
FIG. 14 is a diagram showing a circuit configuration of an induction heating apparatus according to an eighth embodiment of the present invention.
FIG. 15 is a diagram showing a circuit configuration of an induction heating apparatus according to a ninth embodiment of the present invention.
FIG. 16 is a diagram showing a circuit configuration of a conventional induction heating apparatus.
FIG. 17 shows a waveform of a conventional induction heating device
FIG. 18 is a diagram showing a circuit configuration of a conventional induction heating device.
[Explanation of symbols]
1 DC power supply
2 Current limiting means
3 First capacitor
4 Second capacitor
5 Heating coil
6 First semiconductor switch
7 Second semiconductor switch
8 Load
9 Control means
10 Third capacitor
13 Third reverse conducting element
16 Commercial power supply
17 Fourth capacitor
18 Rectifier bridge
20 Switch means
21 Input current detection means
22 Coil current detection means
23 First voltage detecting means
24 Second voltage detection means
26 First reverse conducting element
27 Second reverse conducting element

Claims (19)

A first semiconductor switch; a reverse conducting element connected in parallel to the first semiconductor switch; current limiting means for limiting an input voltage during a conduction period of the first semiconductor switch; and the first semiconductor switch. A second semiconductor switch connected in series with the second semiconductor switch, a second reverse conducting element connected in parallel to the second semiconductor switch, a heating coil for inductively heating an object to be heated, and the first semiconductor switch Alternatively, the first capacitor and the second capacitor that form a series resonance circuit with the heating coil during the conduction period of the second semiconductor switch, and the first semiconductor switch and the second semiconductor switch when the second semiconductor switch is non-conductive. The conduction period of the third capacitor that forms the resonance circuit with the heating coil and the first semiconductor switch and the second semiconductor switch are mutually controlled exclusively at a constant drive frequency. A resonance circuit formed by the first capacitor and the heating coil, and a resonance frequency of the resonance circuit formed by the second capacitor and the heating coil is lower than a drive frequency of the control circuit. And setting the resonance frequency of the resonance circuit formed by the third capacitor and the heating coil to be higher than the drive frequency of the control circuit, and supplying power from the power source through the current limiting means to the first And supplying power to the heating coil from the first and second capacitors, and the current limiting means includes a power source and a heating coil serving as the first semiconductor switch and the second semiconductor switch. An induction heating apparatus characterized by having an effect of preventing a short circuit through a wire.   The induction heating device according to claim 1, wherein the first semiconductor switch has a resonance circuit formed by the first capacitor and the heating coil when conducting in the forward direction.   The induction heating apparatus according to claim 1 or 2, wherein the second semiconductor switch is formed by a second circuit and a heating coil forming a resonance circuit when conducting in the forward direction.   The induction heating apparatus according to any one of claims 1 to 3, wherein the capacity of the first capacitor is equal to or larger than the capacity of the second capacitor.   The induction heating apparatus according to any one of claims 1 to 4, wherein a third capacitor is connected in parallel with the heating coil. A current limiting means connected in parallel to a DC power source and a series body of first semiconductor switches; a first reverse conducting element connected in parallel to the first semiconductor switch; and the first current conducting means for inductively heating a load. A series connection body of a heating coil and a first capacitor connected to one semiconductor switch, a second connection body of a second semiconductor switch and a second capacitor connected in parallel to the heating coil, and the second semiconductor A second reverse conducting element connected in parallel to the switch; and a third capacitor connected in parallel to the heating coil; a resonance circuit formed by the first capacitor and the heating coil; and the second capacitor The resonance frequency of the resonance circuit formed by the capacitor and the heating coil is set lower than the drive frequency of the control circuit, and the resonance circuit formed by the third capacitor and the heating coil is set. As well as higher than the driving frequency of the resonant frequency and the control circuit, after the power supply from the power source was performed in the first and second capacitors through said current limiting means, from said first and second capacitors An induction heating apparatus that supplies power to the heating coil and has a function of preventing a short circuit between the power source and the heating coil via the first semiconductor switch and the second semiconductor switch while the current limiting means .   The induction heating apparatus according to claim 1, wherein a third capacitor is connected to one or both of the first semiconductor switch and the second semiconductor switch.   The induction heating apparatus according to any one of claims 1 to 7, wherein a third reverse conducting element is connected in series with the current limiting means.   The rectifier that rectifies the commercial power source and the commercial power source, and a fourth capacitor that supplies power to the current limiting unit is disposed between the commercial power source and the rectifier unit. The induction heating device described in 1.   The induction heating device according to any one of claims 1 to 9, wherein the third capacitor includes switch means in series and controls the switch means according to a state of input power.   The induction heating device according to claim 1, wherein a certain non-conduction time is provided when driving the first semiconductor switch and the second semiconductor switch.   The non-conducting time is the non-conducting time when the operation is switched from the second semiconductor switch to the first semiconductor switch than the non-conducting time when the operation is switched from the first semiconductor switch to the second semiconductor switch. The induction heating device according to claim 11, wherein the induction heating device is set short.   13. The induction according to claim 1, further comprising an input current detection unit configured to detect a current of a power source, and controlling a conduction time of the first semiconductor switch so that the input current detection unit has a predetermined value. Heating device.   The coil current detection means for detecting the current of the heating coil is provided, and the conduction time of the first semiconductor switch is controlled so that the coil current detection means becomes a predetermined value. Induction heating device.   The induction heating device according to claim 14, wherein the conduction time of the first switching element is limited so that the coil current detection means does not exceed a predetermined value.   The first voltage detection means for detecting the voltage of the first semiconductor switch is provided, and the conduction time of the first semiconductor switch is controlled so that the first voltage detection means becomes a predetermined value. The induction heating apparatus according to any one of the above.   The induction heating device according to claim 16, wherein the conduction time of the first switching element is limited so that the voltage of the first voltage detection means does not exceed a predetermined value.   The second voltage detecting means for detecting the voltage of the second semiconductor switch is provided, and the conduction time of the first semiconductor switch is controlled so that the first voltage detecting means becomes a predetermined value. The induction heating apparatus according to any one of the above.   The induction heating device according to claim 18, wherein the conduction time of the first switching element is limited so that the voltage of the second voltage detection means does not exceed a predetermined value.

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