JP4617855B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating device used in general homes, offices, restaurants, factories, and the like, and can suppress interference noise.

Conventionally, in this type of induction heating apparatus, when a plurality of induction heating means are installed close to each other, an interference sound is generated when the heating coils of the induction heating means are driven at different frequencies. In order to suppress this, a technique for driving a plurality of heating coils at the same frequency (for example, refer to Patent Document 1), or setting so that the driving frequency difference between the plurality of heating coils is equal to or lower than the audible frequency. A technique (for example, see Patent Document 2) is known.
Japanese Patent Laid-Open No. 2002-8840 JP 2004-37775 A

  However, in each of the conventional configurations, when performing high-frequency power control by an inverter circuit or a booster circuit in an induction heating device and harmonic current suppression by a power factor correction circuit at the same time, the magnetic body incorporated in each circuit When a current having a frequency based on the operating frequency of each circuit flows through a plurality of inductors having a plurality of inductors, that is, inductors installed in the vicinity of a plurality of heating coils or a magnetic-shielding core material, the current is generated based on a driving frequency difference between the plurality of inductors There was a problem that interference sound could not be suppressed.

  The present invention solves the above-described conventional problems, and suppresses or eliminates the interference sound generated based on the drive frequency difference of a plurality of inductors built in the inverter circuit, the booster circuit, and the power factor correction circuit. It is an object of the present invention to provide an induction heating apparatus that makes it possible.

In order to solve the above-described conventional problems, an induction heating apparatus of the present invention is connected after commercial power rectification, and improves the power factor by turning on and off the switching element, and the output of the power factor correction circuit And a booster circuit that boosts the voltage above the output of the power factor correction circuit by turning on and off the switching element, and an inverter that is connected to the output of the booster circuit and generates a high-frequency current by turning on and off the switching element Circuit, and an inductor having a magnetic body incorporated in each of the power factor correction circuit, the booster circuit, and the inverter circuit, and the switching element of the inverter circuit has an operation cycle number N ₁ times in an operation cycle T _1. , after operating, times _'operation period the number N _{1 in'} operation period T _1, by operating, driving of inductors built in the inverter circuit It repeats the operation to change the frequency, the switching element of the boost circuit, after operating in the operation cycle T _3, by operating the operating periodic T _{3 ',} changing the driving frequency of the inductor built in the boosting circuit repeating an operation of, the switching element of the power factor correction circuit, after operating in the operation cycle T _4, is operated in operating periodic T _{4 ',} the driving frequency of the inductor built in the power factor correction circuit By repeating the changing operation, the switching element of the inverter circuit and the switching of the booster circuit are performed every predetermined period Ta (however, Ta = T ₁ · N ₁ + T ₁ ′ · N ₁ ′) less than the audible period. The gate voltage phases of the elements and the switching elements of the power factor correction circuit are made substantially the same.

Thereby, interference sound can be suppressed.

  The induction heating apparatus according to the present invention suppresses or prevents the interference sound generated due to the drive frequency difference Δf of a plurality of inductors having magnetic bodies built in an inverter circuit, a booster circuit, and a power factor correction circuit. Is possible.

A first invention is connected after rectification of a commercial power source and is connected to an output of the power factor correction circuit that improves the power factor by turning on and off the switching element, and is connected to the output of the power factor improvement circuit, and A booster circuit that boosts the voltage to a voltage higher than the output of the power factor correction circuit, an inverter circuit that is connected to the output of the booster circuit and generates a high-frequency current by turning on / off a switching element, the power factor correction circuit, and the booster circuit and comprising an inductor having a magnetic substance incorporated respectively to the inverter circuit, the switching elements of the inverter circuit, the operation cycle number N ₁ times the operation cycle T _1, after operating in the operation cycle T _{1 '} operation period the number N _{1 'times,} is operated, repeats the operation of changing the driving frequency of the inductor built in the inverter circuit, the temperature After the switching elements of the circuit, it is operated at an operating period T _3, by operating the operating periodic T _{3 ',} repeating the operation of changing the driving frequency of the inductor built in the boosting circuit, the power factor correction circuit of the switching element, after operating in the operation cycle T _4, it is operated in operating periodic T _{4 ',} by repeating the operation of changing the driving frequency of the inductor built in the power factor correction circuit, audible period The switching element of the inverter circuit, the switching element of the booster circuit, and the switching of the power factor correction circuit at every predetermined period Ta (where Ta = T ₁ · N ₁ + T ₁ ′ · N ₁ ′) By using an induction heating device in which the gate voltage phases of the elements are substantially the same, interference noise can be suppressed.

  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)
FIG. 1 shows an induction heating cooker as an induction heating device in an embodiment of the present invention.

  As shown in the figure, the commercial power source 1 is a 200 V commercial power source that is a low-frequency AC power source, and is connected to the input terminal of a rectifier circuit that is a bridge diode and a low-frequency filter (hereinafter, rectifier circuit) 2. The power factor correction circuit 33 is connected after rectification of the commercial power supply and improves the power factor by turning on / off the switching element. The power factor correction circuit is connected to the output of the power factor improvement circuit 33 by turning on / off the switching element. Is provided with a booster circuit 10 that boosts the voltage to a voltage equal to or higher than the output, and an inverter circuit 11 that is connected to the output of the booster circuit 10 and generates a high-frequency current by turning on and off the switching element.

  The power factor correction circuit 33 improves the power factor by turning on / off the fourth switching element 31, the booster circuit 10 boosts the voltage to an arbitrary voltage by turning on / off the third switching element 5, and the inverter circuit 11 A high-frequency current is generated by turning on and off the first switching element 12 and the second switching element 13, and the pan 19 disposed opposite to the heating coil 17 is heated.

The second choke coil 30 used for power factor improvement is connected to the cathode side output terminal of the rectifier circuit 2. Further, a parallel connection body of the third snubber capacitor 39 and the fourth switching element 31 is connected between the second choke coil 30 and the anode side output terminal of the rectifier circuit 2. The fourth diode 32 is arranged to be connected to the high potential side terminal (collector) of the fourth switching element 31. The second choke coil 30, the fourth switching element 31, the fourth diode 32, and the third snubber capacitor 39 constitute a power factor correction circuit 33.

  The first first smoothing capacitor 3 is connected between the output terminal of the power factor correction circuit 33, that is, between the cathode side terminal of the fourth diode 32 and the low potential side terminal (emitter) of the fourth switching element 31. The first smoothing capacitor 3 smoothes the input voltage and supplies energy to the booster circuit 10.

  A first choke coil 4 is connected between the high-potential side output terminals of the first smoothing capacitor 3. A parallel connection body of the first snubber capacitor 8, the fourth diode 7, and the third switching element 5 is connected between the output terminal of the first choke coil 4 and the low potential side terminal of the first smoothing capacitor 3. . Further, the third diode 6 is arranged to be connected to the high potential side terminal (collector) of the third switching element 5. Further, a second smoothing capacitor 9 is connected between the cathode side terminal of the third diode 6 and the low potential side terminal (emitter) of the third switching element 5. The first choke coil 4, the third switching element 5, the third diode 6, the fourth diode 7, the first snubber capacitor 8, and the second smoothing capacitor 9 constitute a booster circuit 10. The second smoothing capacitor 9 supplies a voltage obtained by boosting the voltage of the first smoothing capacitor 3 to the inverter circuit 11.

  The inverter circuit 11 is connected to the output terminal of the booster circuit 10, that is, both ends of the second smoothing capacitor 9. Connected to both ends of the second smoothing capacitor 9 are a first switching element 12 and a second switching element 13 connected in series. A first diode (reverse conducting element) 14 and a second diode (reverse conducting element) 15 are anti-parallel to the first switching element 12 and the second switching element 13 (the high potential side terminal of the switching element ( The collector) and the cathode of the diode are connected). A second snubber capacitor 16 is connected in parallel to the second switching element 13 (which may be the first switching element 12). Furthermore, a series connection body of the heating coil 17 and the resonance capacitor 18 is connected in parallel to the second switching element 13 (which may be the first switching element 12). The heating coil 17 is disposed to face the pan 19 as a load.

  Moreover, the input detection unit 20 that detects the input current of the inverter circuit 11 and the input setting unit 42 that outputs a current reference value according to the input setting based on the operation by the user are compared by the first comparison unit 22. A signal output from the first comparison unit 22 and the first oscillation unit (microcomputer) 21 that outputs a transmission frequency signal corresponding to the input setting is output to the first variable conduction ratio setting unit 23. The first variable conduction ratio setting unit 23 sets the conduction ratio between the first switching element 12 and the second switching element 13 at the driving frequency based on the first oscillation unit 21, and the first switching element 12. And the second switching element 13 is exclusively controlled. The first control circuit 24 includes the input detection unit 20, the first oscillation unit 21, the first comparison unit 22, the first variable conduction ratio setting unit 23, and the input setting unit 42.

  The signal output from the voltage detection unit 25 that detects the voltage of the second smoothing capacitor 9 as the input voltage of the inverter circuit 11 is compared by the reference voltage 26 and the second comparison unit 27, and the second comparison unit. 27 outputs a signal to the second variable conduction ratio setting unit 28 so as to obtain a predetermined input voltage of the inverter circuit 11. The second variable conduction ratio setting unit 28 sets the conduction ratio of the third switching element 5 at a drive frequency based on the reference oscillation by the second oscillation unit (microcomputer) 41, and Conduct conduction control. The second control circuit 29 includes the voltage detection unit 25, the second comparison unit 27, the second variable conduction ratio setting unit 28, and the second oscillation unit 41.

The third control circuit 40 that controls the fourth switching element 31 of the power factor correction circuit 33 includes an input current detector 35 that detects an input current of the induction heating device, and the input current detector 35.
And the output of the reference sine wave generating circuit 34 are compared by a third comparison unit 36, and a third variable conduction ratio setting unit is provided so that an input current equivalent to that of the reference sine wave can be obtained from the third comparison unit 36. A signal is output to 38. The third variable conduction ratio setting unit 38 sets the conduction ratio of the fourth switching element 31 at a drive frequency based on the reference oscillation by the third oscillator (microcomputer) 37, and controls the conduction of the fourth switching element 31. I do. At this time, the oscillation frequency of the third oscillation unit 37 is set to be higher than the operating frequencies of the booster circuit 10 and the inverter circuit 11. As a result, as shown in FIG. 2, the number of switching times of the power factor correction circuit 33 at which the voltage value corresponding to the input of each circuit is the lowest increases, and the increase in switching loss can be minimized. . The third control circuit 40 includes the reference sine wave generation circuit 34, the input current detector 35, the third comparison unit 36, the third oscillation unit 37, and the third variable conduction ratio setting unit 38.

  Further, the first, second, and third oscillating units 21, 37, and 41 are electrically wired and connected so as to recognize each other's oscillating frequency, and have a predetermined period Ta based on the oscillating frequencies of the other oscillating units. A drive frequency of a plurality of inductors having magnetic bodies built in the power factor correction circuit 33, the booster circuit 10 and the inverter circuit 11 in the period, that is, a plurality of heating coils or inductors installed in the vicinity of the magnetic-shielding core material is set. It is.

  The operation of the induction cooking device configured as described above will be described below.

  First, the commercial power supply 1 is full-wave rectified by the rectifier circuit 2 and supplied to the power factor correction circuit 33 connected to the output terminal of the rectifier circuit 2, and the first smoothing capacitor 3 is connected to the output terminal of the power factor correction circuit 33. Is connected. Since the first smoothing capacitor 3 is set to a very large capacity, the envelope (envelope) of the voltage of the first smoothing capacitor 3 is smoothed and supplied to the booster circuit 10.

  When the commercial power source 1 is smaller than the voltage of the first smoothing capacitor 3, the power factor improvement circuit 33 is unable to turn on the fourth diode 32 included in the power factor improvement circuit 33, and the input current waveform is distorted. The fourth switching is performed by the third control circuit 40 that changes the output of the third variable conduction ratio setting unit 38 so that the input current detector 35 becomes equal to the output of the reference sine wave generation circuit 34 when it becomes significantly low. Element 31 is turned on. As a result, an input current flows from the commercial power source 1 through the second choke coil 30 and a distorted input current is prevented from flowing to the commercial power source 1 side.

  When the fourth switching element 31 is turned on, the diode bridge of the rectifier circuit 2 is turned on, so that the current flowing through the commercial power supply 1 suddenly flows to the fourth switching element 31. Hard switching operation will be performed. When the switching element 31 is turned off after the ON time set by the third variable conduction ratio setting unit 38 has elapsed, the third snubber capacitor 39 is connected in parallel to the fourth switching element 31, so that the fourth The ZVS operation in which the voltage applied to the switching element 31 rises at a gradual rate of change with time (depending on the capacity of the third snubber capacitor 39) is performed. When one period determined by the reference oscillation frequency of the third oscillation unit 37 elapses, the fourth switching element 31 is turned on again. The above is the operation of the power factor correction circuit 33 in one cycle, and the operation waveforms of the respective parts of the power factor correction circuit 33 are as shown in FIG.

  The voltage of the first smoothing capacitor 3 is boosted to an arbitrary voltage by the boosting circuit 10 and supplied to the inverter circuit 11 via the second smoothing capacitor 9.

The booster circuit 10 stores energy in the first choke coil 4 during the period in which the third switching element 5 is turned on as shown in the operation waveform of FIG. The energy stored in the first choke coil 4 charges the second smoothing capacitor 9 via the third diode 6 to perform a boosting operation. That By setting a longer third conduction period of the switching element 5, it is possible to output a higher voltage. In addition, since the third switching element 5 has the fourth diode 7 and the first snubber capacitor 8 connected in parallel, when the third switching element 5 is turned off, the first snubber capacitor 8 has an inclination. Charging starts, and the third switching element 5 realizes ZVS turn-off operation. During the period in which the third switching element 5 is off, the first snubber capacitor 8 starts discharging after charging, and when the first snubber capacitor 8 is completely discharged, the fourth diode 7 is turned on. If an ON signal is input to the gate of the third switching element 5 during the period in which the fourth diode 7 is ON, the fourth diode 7 is turned OFF and a current is supplied to the third switching element 5. The third switching element 5 realizes a ZVS & ZCS turn-on operation and stores energy in the choke coil 4 again. The above is the operation of one cycle of the booster circuit 10. The first smoothing capacitor 3 corresponding to the output of the power factor correction circuit 33 is boosted by the boosting circuit 10 as shown in FIG. 2D and output to the second smoothing capacitor 9.

  The voltage of the second smoothing capacitor 9 boosted by the booster circuit 10 is supplied to the inverter circuit 11. As shown in FIG. 5, the inverter circuit 11 operates the pan 19 by causing the heating coil 17 to generate a high-frequency current having a predetermined frequency by turning on and off the first switching element 12 and the second switching element 13. Heat. Since the second snubber capacitor 16 discharges with a slope when the first switching element 12 is turned off from the on state, the first switching element 12 realizes the ZVS turn-off operation. When the second snubber capacitor 16 is fully discharged, the second diode 15 is turned on. When an on signal is applied to the gate of the second switching element 13 during the period in which the second diode 15 is on, The diode 15 is turned off and a current is commutated to the second switching element 13, and the second switching element 13 realizes a ZVS & ZCS turn-off operation. When the second switching element 13 is turned off from the on state, the second snubber capacitor 16 is charged with an inclination, so that the second switching element 13 realizes a ZVS turn-off operation. When the second snubber capacitor 16 is charged to the same voltage as that of the commercial power supply 1, the first diode 14 is turned on, and the gate of the first switching element 12 is turned on while the first diode 14 is turned on. When the ON signal is applied, the first diode 14 is turned off and current is commutated to the first switching element 12, and the first switching element 12 realizes the ZVS & ZCS turn-on operation. The above is the operation of one cycle of the inverter circuit 11.

  Here, based on FIG. 7, the knowledge about the interference sound which the inventors obtained from experiment is demonstrated. Interference sound is generated when two or more sound waves having different frequencies interfere with each other.

FIG. 7 shows the state of interference at a point where two sound waves having different frequencies are present (a point where the phase difference is k). As shown in the figure, the synthesized wave y (t) 45 of the sound wave y ₁ (t) 43 having the frequency f1 = 20 kHz and the sound wave y ₂ (t) 44 having the frequency f2 = 22 kHz is expressed by the superposition theorem (Equation 1). It is expressed as

  It can be seen that the composite wave y (t) 45 has an envelope waveform from (Equation 3), and the frequency is given by (Equation 2).

  As shown in FIG. 7, the sound pressure level of the synthesized wave y (t) 45 changes from small → large → small → large → small during one cycle of the envelope 46 and presses the human eardrum twice. Become. That is, humans can hear an interference sound in which the half period of the envelope 46 of the synthesized wave y (t) 45 is one period, and the frequency is expressed by (Equation 3).

  Eventually, a sound corresponding to the frequency difference between the two sound waves can be heard by the human ear as an interference sound.

In other words, a plurality of sound waves depending on the frequency of the current flowing in the heating coil and inductor generated from the material that causes vibration such as the magnetic shielding core material installed near the heating coil and inductor of each induction heating device interfere with each other in the figure. A synthetic wave y (t) 45 as shown is generated, and an interference sound corresponding to a half cycle of the envelope 46 of the synthetic wave y (t) 45, that is, a frequency difference between a plurality of sound waves is generated.

  In the present embodiment, a period obtained by multiplying a drive cycle of a plurality of inductors each having a magnetic body incorporated in each of the power factor correction circuit 33, the booster circuit 10, and the inverter circuit 11 by a predetermined integer is set to be equal to or less than the audible cycle. The drive frequencies of the plurality of inductors are periodically changed so as to be substantially the same every predetermined cycle.

That is, in the first control circuit 24, the second control circuit 29, and the third control circuit 40, the first switching element 12, the second switching element 13, the third switching element 5, and the fourth switching element. When setting each switching timing of 31, for example, a gate voltage signal as shown in FIG. 6 is set. As a result, the first switching element 12 and the second switching element 13 are operated for two periods at T ₁ within a predetermined period Ta, and then changed to T ₁ ′ for one period. The operation period of the switching element 5 is operated for ₃ periods at T ₃ , then changed to T ₃ ′ for 1 period operation, and further, the operation period of the fourth switching element 31 is operated for 8 periods at T ₄ , and then T Change to ₄ 'to operate for one cycle. Then, as shown in FIG. 6, after the predetermined period Ta has elapsed, the phase difference of the gate voltage signal in the first switching element 12, the second switching element 13, the third switching element 5, and the fourth switching element 31 is It becomes possible to make substantially the same, and the interference sound of the sound wave which generate | occur | produces from the several inductor which has a magnetic body each incorporated in the power factor improvement circuit 33, the booster circuit 10, and the inverter circuit 11 can be suppressed.

  However, FIG. 6 shows that the first switching element 12 and the second switching element 13 represented by (Equation 4), (Equation 5), and (Equation 6) in (Equation 4) have an on / off time ratio of 1, 3 shows that the time ratio 3 of the switching element 5 is 3 and the time ratio 4 of the fourth switching element 31 is 0.5, it goes without saying that there is no problem even if each time ratio is other than 0.5. .

Further, T ₁ ′ and T ₃ ′ and their operation cycle numbers N ₁ ′ and N ₂ ′ in FIG. 6 satisfy (Equation 7), assuming that the operation cycle numbers of T ₁ and T ₃ are N ₁ and N _2. Is selected as follows.

T ₁ · N ₁ + T ₁ '· N ₁ ' = T ₃ · N ₂ + T ₃ '· N ₂ ' = Ta Equation 7
The predetermined cycle Ta is longer than the operation cycle T ₁ of the inverter circuit 11, the operation cycle T _{3 of} the booster circuit 10 _, and the operation cycle T ₄ of the power factor correction circuit 33 _, and shorter than the cycle Tb corresponding to the audible frequency. This is a set period and is selected so as to satisfy (Equation 8).

T ₁ <Ta∩T ₃ <Ta∩Ta <Tb Equation 8
By satisfying (Equation 7) and (Equation 8), the first switching element 12, the second switching element 13, and the third switching element for each predetermined period Ta shorter than the period Tb corresponding to the audible frequency. 5. The phase difference of the gate voltage signal in the fourth switching element 31 can be corrected to be substantially the same, and the half cycle of the envelope waveform of the synthesized wave of the sound wave caused by the inverter operating frequency corresponds to the audible frequency. Since it is shorter than the period Tb, the interference sound becomes higher than the audible frequency, and the interference sound can be suppressed. Furthermore, by changing T ₁ , N ₁ , T ₁ ′, N ₁ ′, T ₃ , N ₂ , T ₃ ′, N ₂ ′, Ta so as to satisfy (Equation 7) and (Equation 8), When the operating frequency of the inverter circuit 11 is changed, the high-frequency power generated in the heating coil 17 is changed, and the power can be controlled by the PFM method that changes the operating frequency of the inverter circuit 11.

  As described above, the induction heating apparatus according to the present embodiment has a period obtained by multiplying the drive cycle of the plurality of inductors each having a magnetic body incorporated in the power factor correction circuit 33, the booster circuit 10 and the inverter circuit 11 by a predetermined integer. Since the frequency difference of the plurality of sound waves becomes greater than or equal to the audible frequency region by periodically changing the drive frequency of the plurality of inductors so that they are substantially the same for each predetermined period set below the audible period, the composite wave However, the frequency at which the human eardrum is pressed becomes higher than the audible frequency, and the interference sound can be suppressed.

Further, the predetermined period Ta is determined so as to be equal to or less than the audible period within a range equal to or greater than the drive period of the plurality of inductors and equal to or less than the least common multiple of the drive period. For each short period, the phase differences of sound waves having different frequencies generated from a plurality of inductors incorporated in the power factor correction circuit 33, the booster circuit 10, and the inverter circuit 11 are corrected to be substantially the same, and the frequency differences of the plurality of sound waves are corrected. It becomes possible to set it to an audible frequency or higher, and it is possible to suppress interference sound generated by interference of sound waves generated from a plurality of inductors.

  In addition, by operating the drive frequencies of the inductors having magnetic materials included in the power factor correction circuit 33, the booster circuit 10, and the inverter circuit 11 at two or more different drive frequencies within a predetermined period, respectively, a predetermined period is obtained. It is possible to correct the phase difference of the synthesized wave at a point where sound waves with different frequencies generated from a plurality of induction heating devices each time are substantially the same, and interference sound generated by interference of sound waves generated from a plurality of inductors Can be suppressed.

  In addition, the high frequency power control is performed by changing the drive frequency of the inductor having the magnetic material included in each of the booster circuit 10 and the inverter circuit 11, thereby allowing the power factor correction circuit 33, the booster circuit 10, and the inverter circuit 11 to be controlled. The power of a plurality of induction heating devices can be controlled while suppressing the interference sound by using the PFM method that changes the operating frequency.

  In addition, by controlling the high frequency power control by changing the predetermined period Ta, the number of patterns for switching the drive frequencies of the plurality of inductors can be increased. The power of a plurality of induction heating devices can be controlled while suppressing the interference sound by using the PFM method that changes the operating frequency of the circuit and the inverter circuit.

  Further, by setting the drive frequency of the inductor having the magnetic substance included in the power factor correction circuit 33 higher than the drive frequency of the inductor having the magnetic substance included in the booster circuit 10 and the inverter circuit 11, the booster circuit 10 and the inverter The number of switching times of the power factor correction circuit 33 whose input power is lower than that of the circuit 11 is increased, and an increase in switching loss accompanying an increase in the operating frequency of each circuit can be minimized.

  Furthermore, the power factor correction circuit 33, the booster circuit 10, and the inverter circuit 11 are fixed to a driving frequency corresponding to a predetermined output when the driving frequency difference of the inductor having the magnetic material included in each circuit is equal to or lower than the audible frequency. In addition, since the drive frequency of the inductor having the magnetic material included in each circuit is not changed within a predetermined period, the supplied high frequency power is stably changed without changing periodically within the predetermined period. High frequency power can be supplied, and the drive frequency of multiple inductors in the range where the drive frequency difference of multiple inductors is less than or equal to the audible frequency, that is, the operation of the power factor correction circuit, booster circuit and inverter circuit A plurality of induction heating devices using the PFM method that changes the frequency according to a predetermined output while suppressing interference sound It is possible to control the power.

  As described above, the induction heating device according to the present invention suppresses the interference sound generated due to the drive frequency difference Δf of a plurality of inductors having magnetic bodies built in the inverter circuit, the booster circuit, and the power factor correction circuit. As an induction heating cooker, of course, induction heating copy roller, induction heating melting furnace, induction heating jar rice cooker, or other induction heating type It can also be applied as a heating device.

Circuit diagram of induction heating apparatus in an embodiment of the present invention Voltage waveform diagram of each circuit in the same induction heating device Current / voltage waveform diagram of power factor correction circuit in the same induction heating device Current / voltage waveform diagram of booster circuit in the same induction heating device Current / voltage waveform diagram of inverter circuit in the same induction heating device The figure which shows the control signal of each switching element in the same induction heating apparatus The figure which shows the mode of the interference of the sound wave from which the frequency in an induction heating apparatus differs

DESCRIPTION OF SYMBOLS 1 Commercial power supply 10 Booster circuit 11 Inverter circuit 17 Heating coil 19 Pan 24 1st control circuit 29 2nd control circuit 40 3rd control circuit

Claims (1)

Connected after commercial power supply rectification and connected to the output of the power factor correction circuit and the power factor correction circuit for improving the power factor by switching on and off of the switching element, and output of the power factor correction circuit by switching on and off of the switching element A booster circuit that boosts the voltage to the above voltage; an inverter circuit that is connected to the output of the booster circuit and generates a high-frequency current by turning on and off the switching element;
An inductor having a magnetic body incorporated in each of the power factor correction circuit, the booster circuit, and the inverter circuit;
The switching element of the inverter circuit;
Operation period T ₁ in the operation cycle number N ₁ times, after operating, times _'operation period the number N _{1 in'} operation period T _1, by operating, the operation of changing the driving frequency of the inductor built in the inverter circuit repetition,
The switching element of the boost circuit, the operation after operating in a cycle T _3, by operating the operating periodic T _{3 ',} repeating the operation of changing the driving frequency of the inductor built in the boosting circuit,
The switching element of the power factor correction circuit, after operating in the operation cycle T _4, is operated in operating periodic T _{4 ',} repeats an operation of changing the driving frequency of the inductor built in the power factor correction circuit By
The switching element of the inverter circuit, the switching element of the booster circuit, and the power factor correction circuit for each predetermined period Ta (where Ta = T ₁ · N ₁ + T ₁ ′ · N ₁ ′) less than the audible period An induction heating apparatus in which the gate voltage phases of the switching elements are substantially the same.

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