Electromagnetic induction heating device

Abstract

To provide an inverter system electromagnetic induction heating device, capable of efficiently supplying a desired power to a heated material.SOLUTION: An electromagnetic induction heating device comprises: a plurality of heating coils for conducting and heating a heated material; a DC power supply that outputs a DC voltage; and an inverter circuit that converts the DC voltage output by the DC power supply into an AC voltage and is supplied to the plurality of heating coils. The inverter circuit is that legs as a serial body of three switching elements are connected in parallel between a positive electrode and a negative electrode of the DC power supply, and each serial body of each heating coil and a resonance capacitor is connected between an output terminal of one leg and an output terminal of the other leg, and each serial body of each heating coil and the resonance capacitor is connected between the two output terminals of the same legs.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inverter type electromagnetic induction heating device that supplies a desired amount of power to an object to be heated, such as a metal pot, to perform induction heating. [Background technology]

[0002] In recent years, inverter-type electromagnetic induction heating devices that heat objects such as metal pots without using fire have come into widespread use. An electromagnetic induction heating device passes a high-frequency current through a heating coil, generating eddy currents in a metal object (such as a pot) placed close to the heating coil, causing the object to generate heat through its own electrical resistance.

[0003] As a conventional technique for inductively heating an object to be heated by using multiple heating coils in combination, there is an induction heating cooking device disclosed in Patent Document 1. As shown in Fig. 2 of the same document, this induction heating cooking device has a series body of three switching elements (Q11, Q12, Q13), in which a series body of a first working coil L11 (heating coil) and a first main resonance capacitor C14 (resonance capacitor) is connected in parallel to the first switching element Q11, and a series body of a second working coil L12 (heating coil) and a second main resonance capacitor C15 (resonance capacitor) is connected in parallel to the third switching element Q13, and auxiliary diodes D14 and D15 that limit the voltage of the resonance capacitor to the input voltage are connected between the connection points of each heating coil and the resonance capacitor and the positive or negative pole of the input voltage.

[0004] In this conventional example, a series circuit of switching elements is shared to form multiple half-bridge inverters, and each of the half-bridge inverters is controlled in a time-division manner to supply the desired power to each heating coil and inductively heat the object to be heated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2828967 Summary of the Invention [Problem to be solved by the invention]

[0006] In the induction heating cooking device of Patent Document 1, the period during which the input voltage can be applied to the series combination of the heating coil and the resonant capacitor is only half the switching period, so in order to obtain the desired power, it is necessary to set the number of turns of the heating coil so that the current required during that period flows. Therefore, when trying to increase the output of the induction heating cooking device, it is difficult to increase the magnetomotive force even if the number of turns of the heating coil is increased, and it is necessary to reduce the number of turns to increase the current, which causes a problem of reduced heating efficiency due to increased copper loss and switching loss. In addition, since the frequency of the resonant load circuit cannot be changed depending on the material of the pan, it is not possible to heat at an appropriate frequency, which causes a problem of reduced heating efficiency.

[0007] An object of the present invention is to address the above-mentioned problems and to provide an inverter-type electromagnetic induction heating device that can efficiently supply the desired power to an object to be heated when multiple heating coils are used in combination to inductively heat the object to be heated. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the electromagnetic induction heating device of the present invention is an electromagnetic induction heating device comprising a plurality of heating coils for induction heating an object to be heated, a DC power supply that outputs a DC voltage, and an inverter circuit that converts the DC voltage output by the DC power supply into an AC voltage and supplies it to the plurality of heating coils, wherein the inverter circuit is configured by connecting legs, each of which is a series arrangement of three switching elements, in parallel between the positive and negative electrodes of the DC power supply, and a series arrangement of a heating coil and a resonant capacitor is connected between the output terminal of one leg and the output terminal of the other leg, and a series arrangement of a heating coil and a resonant capacitor is connected between the two output terminals of the same leg. Effect of the Invention

[0009] According to the electromagnetic induction heating device of the present invention, when multiple heating coils are used in combination to induction heat an object to be heated, the desired power can be efficiently supplied to the object to be heated by controlling the current flowing through the multiple heating coils depending on the heated area of ​​the bottom of the pot and the presence or absence of a pot on the heating coil. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a circuit diagram of an electromagnetic induction heating device according to a first embodiment. [Diagram 2] FIG. 2 is a circuit diagram of a DC power supply according to the first embodiment. [Figure 3A] The first pattern of gate drive signal. [Figure 3B] Operation waveform of the first pattern. [Figure 4A] The second pattern of gate drive signal. [Figure 4B] Operation waveform of the second pattern. [Figure 5A] The third pattern of gate drive signal. [Figure 5B] Operation waveform of the third pattern. [Figure 6A] 4 is the fourth pattern of gate drive signal. [Figure 6B] Operation waveform of the fourth pattern. [Figure 7A] The fifth pattern of gate drive signal. [Figure 7B] Operation waveform of the fifth pattern. [Figure 8A] The sixth pattern of gate drive signal. [Figure 8B] Operation waveform of the sixth pattern. [Figure 9A] The seventh pattern of gate drive signal. [Figure 9B] Operation waveform of the seventh pattern. [Figure 10A] 8 shows the gate drive signal of the eighth pattern. [Figure 10B] Operating waveform of the eighth pattern. [Figure 11A] The ninth pattern of gate drive signal. [Figure 11B] Operation waveform of the ninth pattern. [Figure 12A] The tenth pattern of gate drive signal. [Figure 12B] Operating waveform of the tenth pattern. [Figure 13A] 11. The gate drive signal of the eleventh pattern. [Figure 13B] Operating waveform of the eleventh pattern. [Figure 14] Connection diagram of the heating coil and upper, middle and lower arms when the coil currents are all in phase. [Figure 15] This is a connection diagram of the heating coils and the upper, middle, and lower arms when the currents in heating coils 12 and 13 are in opposite phase to the currents in heating coils 11 and 14. [Figure 16] FIG. 11 is a circuit diagram of an electromagnetic induction heating device according to a second embodiment. [Figure 17] FIG. 1 is a diagram showing a configuration in which six sets of heating coils according to an embodiment are arranged side by side. [Figure 18A] FIG. 18 is a diagram showing the relative positions of the configuration of FIG. 17 and the object to be heated. [Figure 18B] FIG. 18 is a diagram showing the relative positions of the configuration of FIG. 17 and the object to be heated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the electromagnetic induction heating device of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same components or components having similar functions, and duplicated explanations will be omitted as appropriate. EXAMPLES

[0012] 1 is a circuit diagram of an electromagnetic induction heating device according to a first embodiment of the present invention. In the electromagnetic induction heating device of this embodiment, a heat-resistant glass top plate is placed on top of a metal housing, and a high-frequency current is supplied to a heating coil placed below the top plate to induction heat a metal object to be heated (such as a pot) placed at a predetermined position on the top surface of the top plate, but a description of this well-known configuration will be omitted below.

[0013] 1, DC power supply 1 is a power supply that rectifies AC voltage supplied from a commercial AC power supply of 200V or 100V and outputs a DC voltage. Fig. 2 shows an example of a specific configuration of DC power supply 1. DC power supply 1 illustrated here is a non-smooth DC power supply obtained by rectifying AC voltage supplied from commercial AC power supply 100 with diodes 101a to 101d and passing it through a normal filter composed of inductor 102 and capacitor 103.

[0014] As shown in FIG. 1, a first upper, middle, and lower arm 51 (first leg) in which power semiconductor switching elements (hereinafter simply referred to as "switching elements") 5a, 5b, and 5c are connected in series, and a second upper, middle, and lower arm 52 (second leg) in which switching elements 5d, 5e, and 5f are connected in series are connected in parallel between the positive electrode P and negative electrode N of such a DC power supply 1.

[0015] Diodes 6a-6f are connected in parallel in the opposite direction to the switching elements 5a-5f, and snubber capacitors 7a-7f are connected in parallel to the switching elements 5a-5f, respectively. The snubber capacitors 7a-7f are charged or discharged by the interruption current when the switching elements 5a-5f are turned off, and the change in voltage applied to each switching element is reduced, thereby suppressing turn-off loss.

[0016] Here, the connection point of the switching elements 5a, 5b of the first upper, middle, and lower arm 51 is the output terminal O A The connection point of the switching elements 5b and 5c is the output terminal O B The connection point between the switching elements 5d and 5e of the second upper, middle and lower arm 52 is called the output terminal O. D The connection point of the switching elements 5e and 5f is the output terminal O E In the electromagnetic induction heating device shown in FIG. A One end of the first heating coil 11 is connected to the output terminal O D One end of the second heating coil 12 is connected to the first heating coil 11 , and a first resonant capacitor 21 is connected between the other end of the first heating coil 11 and the other end of the second heating coil 12 .

[0017] Also, the output terminal O B One end of the third heating coil 13 is connected to the output terminal O E One end of the fourth heating coil 14 is connected to the first heating coil 11, and a second resonant capacitor 22 is connected between the other end of the third heating coil 13 and the other end of the fourth heating coil 14. A third resonant capacitor 23 is connected between the other end of the first heating coil 11 and the other end of the third heating coil 13, and a fourth resonant capacitor 24 is connected between the other end of the second heating coil 12 and the other end of the fourth heating coil 14.

[0018] Therefore, in the electromagnetic induction heating device of the present embodiment, by changing the driving method of the first upper, middle, and lower arm 51 and the second upper, middle, and lower arm 52, not only can the first resonant load circuit (the resonant load circuit including the first heating coil 11, the second heating coil 12, and the first resonant capacitor 21) and the second resonant load circuit (the resonant load circuit including the third heating coil 13, the fourth heating coil 14, and the second resonant capacitor 22) be switched between a parallel connection or a series connection state, but the phase of the current flowing through the heating coils can be changed to be in phase or opposite phase to heat the object to be heated.

[0019] Similarly, by appropriately setting the driving method of each upper, middle, and lower arm and changing the capacitance of the third and fourth resonant capacitors 23, 24 relative to the capacitance of the first and second resonant capacitors 21, 22, it is possible to configure a third resonant load circuit (a resonant load circuit including the first heating coil 11, the third heating coil 13, and the third resonant capacitor 23) and a fourth resonant load circuit (a resonant load circuit including the second heating coil 12, the fourth heating coil 14, and the fourth resonant capacitor 24) having resonant frequency characteristics different from the resonant frequencies of the first and second resonant load circuits. Any one of the first to fourth resonant load circuits can be selected and energized to heat the object to be heated, or the inverter method can be switched to a full-bridge method or a half-bridge method, and the driving frequency can also be changed to heat the object to be heated. Below, the features of the action and effect of the energization control of the 11 patterns shown in Table 1, which can be realized by the electromagnetic induction heating device of this embodiment, will be sequentially described in detail. In the following, the direction of the dashed arrow in FIG. 1 indicates the direction of the current i flowing from the heating coils 11 to 14. 11 From i 14 The positive direction is defined as the

[0020] [Table 1]

[0021] <First pattern> First, a first pattern of control in which first and second resonant load circuits are connected in parallel in a full-bridge system and currents of the same phase are passed through heating coils 11 to 14 will be described with reference to Figs. 3A and 3B.

[0022] FIG. 3A shows the gate drive signals vg of the switching elements 5a to 5f during the first pattern control. 5a ~vg 5f FIG. 3B shows operational waveforms when currents of the same phase flow through the heating coils 11 to 14 due to the gate drive control of FIG. 3A. The waveforms shown in FIG. 3B are, from the top, (a) the gate drive signals vg of the switching elements 5a to 5f, 5a ~vg 5f, (b) voltage v1 applied to the first resonant load circuit (heating coils 11, 12, resonant capacitor 21), voltage v2 applied to the second resonant load circuit (heating coils 13, 14, resonant capacitor 22), current i 11 , i 12 , i 13 , i 14、 (c) Current i of each element of upper, middle and lower arms 51 and 52 5a ~i 5f , i 6a ~i 6f It is.

[0023] The inverter system is a full-bridge system, and the first and second resonant load circuits are connected in parallel to supply the same phase current i to the heating coils 11 to 14. 11 , i 12、 i 13 , i 14 3A, the middle arms (switching elements 5b, 5e) of the first upper-middle-lower arm 51 and the second upper-middle-lower arm 52 are always on, and periods in which the upper arm of the first upper-middle-lower arm 51 and the lower arm (switching elements 5a, 5f) of the second upper-middle-lower arm 52 are simultaneously on are alternated with periods in which the lower arm of the first upper-middle-lower arm 51 and the upper arm (switching elements 5c, 5d) of the second upper-middle-lower arm 52 are simultaneously on. Note that a predetermined time interval is provided before and after each period so that the two periods do not overlap.

[0024] As a result, when the switching elements 5a and 5f are on at the same time, a current flows from the DC power supply 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, the switching element 5e, and the switching element 5f, and from the DC power supply 1 through the switching element 5a, the switching element 5b, the heating coil 13, the resonant capacitor 22, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 3B(b), the current i 11 , i 12 , i 13 , i 14As a result, the switching elements 5a to 5f can be turned on during the period when current flows through the diodes 6a to 6f, enabling a soft switching operation with little switching loss.

[0025] 3B(b), the voltage v1 of the first resonant load circuit (heating coils 11, 12, resonant capacitor 21) and the voltage v2 of the second resonant load circuit (heating coils 13, 14, resonant capacitor 22) can be applied over the entire switching period, and it is possible to apply to the resonant circuits a voltage twice as high as that of Patent Document 1, which can apply a voltage only over a half period of the switching period. Therefore, it is possible to obtain a magnetomotive force by increasing the number of turns of the heating coil compared to Patent Document 1, and the increase in current can be reduced, which is effective in increasing efficiency.

[0026] <Second pattern> Next, using Figures 4A and 4B, a second pattern of control will be described in which the first and second resonant load circuits are connected in series in a full-bridge system and opposite-phase currents are passed through heating coils 11, 12 and heating coils 13, 14.

[0027] FIG. 4A shows the gate drive signals vg of the switching elements 5a to 5f during the second pattern control. 5a ~vg 5f FIG. 4B shows the operation waveforms when currents of opposite phases flow through the heating coils 11 and 12 and the heating coils 13 and 14 due to the gate drive control of FIG. 4A. 5a etc. have the same meaning as in Figure 3B.

[0028] The inverter system is a full-bridge system, and the first and second resonant load circuits are connected in series to supply currents i in opposite phases to the heating coils 11 and 12 and the heating coils 13 and 14. 11 , i 12 , i 13 , i 14When current is applied, as shown in FIG. 4A , a period in which the upper and lower arms of the first upper-middle-lower arm 51 and the middle arm of the second upper-middle-lower arm 52 (switching elements 5a, 5c, 5e) are turned on simultaneously is alternated with a period in which the middle arm of the first upper-middle-lower arm 51 and the upper and lower arms of the second upper-middle-lower arm 52 (switching elements 5b, 5d, 5f) are turned on simultaneously.

[0029] As a result, when the switching elements 5a, 5c, and 5e are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, the switching element 5e, the heating coil 14, the resonant capacitor 22, the heating coil 13, and the switching element 5c. Therefore, as shown in FIG. 4B(b), the current i 11 , i 12 and the current i of the heating coils 13 and 14 13 , i 14 As a result, the switching elements 5a to 5f can be turned on during the period in which current flows through the diodes 6a to 6f, enabling a soft switching operation with little switching loss.

[0030] Here, as shown in FIG. 4B(b), the voltage v1 of the first resonant load circuit (heating coils 11, 12, resonant capacitor 21) and the voltage v2 of the second resonant load circuit (heating coils 13, 14, resonant capacitor 22) can be applied throughout the entire switching period, and it is possible to apply to the resonant circuits a voltage that is twice as high as that of Patent Document 1, in which a voltage can only be applied during half the switching period.

[0031] In this manner, this embodiment functions as a full-bridge inverter circuit with the series resonant circuits of the first and second heating coils 11, 12 and the first resonant capacitor 21, and the third and fourth heating coils 13, 14 and the second resonant capacitor 22 as load circuits.

[0032] <Third Pattern> Next, a third pattern of control in which the first and second resonant load circuits are connected in parallel in a half-bridge manner and currents of the same phase are passed through the heating coils 11 to 14 will be described with reference to Figs. 5A and 5B.

[0033] FIG. 5A shows the gate drive signals vg of the switching elements 5a to 5f during the third pattern control. 5a ~vg 5f FIG. 5B shows the operation waveforms when currents of the same phase flow through the heating coils 11 to 14 due to the gate drive control of FIG. 5A. 5a etc. have the same meaning as in Figure 3B.

[0034] The inverter system is a half-bridge system, and the first and second resonant load circuits are connected in parallel to supply the same phase current i to the heating coils 11 to 14. 11 , i 12 , i 13 , i 14 When a current is to flow, as shown in FIG. 5A, the middle arm of the first upper-middle-lower arm 51 and the middle-lower arm of the second upper-middle-lower arm 52 (switching elements 5b, 5e, 5f) are always on, the upper arm (switching element 5d) of the second upper-middle-lower arm 52 is always off, and the upper and lower arms of the first upper-middle-lower arm 51 (switching elements 5a, 5c) are turned on and off complementarily.

[0035] As a result, when the switching element 5a is on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, the switching elements 5e and 5f, and from the DC power source 1 through the switching element 5a, the switching element 5b, the heating coil 13, the resonant capacitor 22, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 5B(b), the current i 11 , i 12 , i 13 , i 14 As a result, the switching elements 5a and 5c can be turned on during the period when current flows through the diodes 6a and 6c, enabling soft switching operation with little switching loss.

[0036] Here, as shown in FIG. 5B(b), the voltage v1 of the first resonant load circuit (heating coils 11 and 12, resonant capacitor 21) and the voltage v2 of the second resonant load circuit (heating coils 13 and 14, resonant capacitor 22) are applied only during a half cycle of the switching period, and the current i 11 From i 14 The amplitude of the output can be reduced to 1 / 2 compared to Fig. 3B(b). If the impedance of the first and second resonant load circuits is the same, the power can be reduced to 1 / 4, and by combining it with frequency control, a wide output power range can be covered, which is effective in improving output controllability.

[0037] The lower arm (switching element 5f) of the second upper, middle, and lower arm 52 may be constantly off, and the upper arm (switching element 5d) of the second upper, middle, and lower arm 52 may be constantly on. Also, the drive signals of the switching elements of the upper, middle, and lower arms 51, 52 may be interchanged.

[0038] <Fourth pattern> Next, using Figures 6A and 6B, a fourth pattern of control will be described in which the first and second resonant load circuits are connected in series in a half-bridge system and opposite-phase currents are passed through heating coils 11, 12 and heating coils 13, 14.

[0039] FIG. 6A shows the gate drive signals vg of the switching elements 5a to 5f during the fourth pattern control. 5a ~vg 5f FIG. 6B shows the operation waveforms when currents of opposite phases flow through the heating coils 11 and 12 and the heating coils 13 and 14 due to the gate drive control of FIG. 6A. 5a etc. have the same meaning as in Figure 3B.

[0040] The inverter system is a half-bridge system, and the first and second resonant load circuits are connected in series to supply currents i in opposite phases to the heating coils 11 and 12 and the heating coils 13 and 14. 11 , i 12 , i 13 , i 14When current is to flow, as shown in FIG. 6A , the middle arm (switching element 5e) of the second upper-middle-lower arm 52 is always on and the upper and lower arms (switching elements 5d, 5f) of the second upper-middle-lower arm 52 are always off, and a period in which the upper and lower arms (switching elements 5a, 5c) of the first upper-middle-lower arm 51 are simultaneously on and a period in which the middle arm (switching element 5b) of the first upper-middle-lower arm 51 is on are alternately provided.

[0041] As a result, when the switching elements 5a and 5c are on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, the switching element 5e, the heating coil 14, the resonant capacitor 22, the heating coil 13, and the switching element 5c. Therefore, as shown in FIG. 6B(b), the current i 11 , i 12 and the current i of the heating coils 13 and 14 13 , i 14 As a result, the switching elements 5a to 5c can be turned on during the period when current flows through the diodes 6a to 6c, enabling soft switching operation with little switching loss.

[0042] Here, as shown in FIG. 6B(b), the voltage v1 of the first resonant load circuit (heating coils 11 and 12, resonant capacitor 21) and the voltage v2 of the second resonant load circuit (heating coils 13 and 14, resonant capacitor 22) are applied only during a half cycle of the switching period, and the current i 11 From i 14 The amplitude of the amplitude can be reduced to half compared to Figure 4B(b).

[0043] The drive signals for the switching elements of the upper, middle and lower arms 51 and 52 may be interchanged.

[0044] In this manner, this embodiment functions as a half-bridge type inverter circuit with the series resonant circuits of the first heating coil 11, the first resonant capacitor 21, the second heating coil 12, and the third heating coil 13, the second resonant capacitor 22, and the fourth heating coil 14 as load circuits.

[0045] <Fifth pattern> Next, a fifth pattern of control in which current is passed through heating coils 11 and 12 in a full-bridge system will be described with reference to Figs. 7A and 7B.

[0046] FIG. 7A shows the gate drive signals vg of the switching elements 5a to 5f during the fifth pattern control. 5a ~vg 5f FIG. 7B shows the operation waveforms when current flows through the heating coils 11 and 12 due to the gate drive control of FIG. 7A. 5a etc. have the same meaning as in Figure 3B.

[0047] The inverter system is a full-bridge system, and the heating coils 11 and 12 are supplied with a current i 11 , i 12 When current is to flow, as shown in FIG. 7A , the lower arms (switching elements 5c, 5f) of the first upper-middle-lower arm 51 and the second upper-middle-lower arm 52 are always on, and periods in which the upper arm of the first upper-middle-lower arm 51 and the middle arm of the second upper-middle-lower arm 52 (switching elements 5a, 5e) are simultaneously on are alternated with periods in which the middle arm of the first upper-middle-lower arm 51 and the upper arm of the second upper-middle-lower arm 52 (switching elements 5b, 5d) are simultaneously on.

[0048] As a result, when the switching elements 5a and 5e are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, and the switching elements 5e and 5f. Therefore, as shown in FIG. 7B(b), a current i 11 , i 12As a result, the switching elements 5a, 5b, 5d, and 5e can be turned on during the period when current flows through the diodes 6a, 6b, 6d, and 6e, enabling soft switching operation with little switching loss.

[0049] 7B(b), the voltage v1 of the first resonant load circuit (heating coils 11, 12 and resonant capacitor 21) can be applied over the entire switching period, and a voltage twice as high as that of Patent Document 1, which can apply a voltage only over a half period of the switching period, can be applied to the resonant circuit. Therefore, it is possible to obtain a magnetomotive force by increasing the number of turns of the heating coil compared to Patent Document 1, and the increase in current can be reduced, which is effective in increasing efficiency.

[0050] <Sixth Pattern> Next, a sixth pattern of control in which current flows through heating coils 13 and 14 in a full-bridge system will be described with reference to Figs. 8A and 8B.

[0051] FIG. 8A shows the gate drive signals vg of the switching elements 5a to 5f during the sixth pattern control. 5a ~vg 5f FIG. 8B shows the operation waveforms when current flows through the heating coils 13 and 14 due to the gate drive control of FIG. 8A. 5a etc. have the same meaning as in Figure 3B.

[0052] The inverter system is a full-bridge system, and the heating coils 13 and 14 are supplied with a current i 13 , i 14 When current is to flow, as shown in FIG. 8A , the upper arms (switching elements 5a, 5d) of the first upper-middle-lower arm 51 and the second upper-middle-lower arm 52 are always on, and periods in which the middle arm of the first upper-middle-lower arm 51 and the lower arm (switching elements 5b, 5f) of the second upper-middle-lower arm 52 are simultaneously on are alternated with periods in which the lower arm of the first upper-middle-lower arm 51 and the middle arm of the second upper-middle-lower arm 52 (switching elements 5c, 5e) are simultaneously on.

[0053] As a result, when the switching elements 5b and 5f are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5a, the switching element 5b, the heating coil 13, the resonant capacitor 22, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 8B(b), a current i 13 , i 14 As a result, the switching elements 5b, 5c, 5e, and 5f can be turned on during the period when current flows through the diodes 6b, 6c, 6e, and 6f, enabling soft switching operation with little switching loss.

[0054] Here, as shown in FIG. 8B(b), the voltage v2 of the second resonant load circuit (heating coils 13, 14 and resonant capacitor 22) can be applied for the entire switching period, and a voltage twice as high as that of Patent Document 1, in which a voltage can be applied only for half a switching period, can be applied to the resonant circuit.

[0055] In this manner, this embodiment functions as a full-bridge inverter circuit with a series resonant circuit of the first heating coil 11, the first resonant capacitor 21, and the second heating coil 12, or the third heating coil 13, the second resonant capacitor 22, and the fourth heating coil 14, as a load circuit.

[0056] <Seventh Pattern> Next, a seventh pattern of control in which current is passed through heating coils 11 and 12 in a half-bridge manner will be described with reference to Figs. 9A and 9B.

[0057] FIG. 9A shows the gate drive signals vg of the switching elements 5a to 5f during the seventh pattern control. 5a ~vg 5f FIG. 9B shows an operational waveform when a current flows only through the heating coil 11 by the gate drive control of FIG. 9A. 5a etc. have the same meaning as in Figure 3B.

[0058] The inverter system is a half-bridge system, and the heating coils 11 and 12 are supplied with a current i 11, i 12 When a current is to flow, as shown in FIG. 9A , the lower arm of the first upper-middle-lower arm 51 and the middle-lower arm of the second upper-middle-lower arm 52 (switching elements 5c, 5e, 5f) are always on, the upper arm (switching element 5d) of the second upper-middle-lower arm 52 is always off, and the upper-middle arm (switching elements 5a, 5b) of the first upper-middle-lower arm 51 are turned on and off complementarily.

[0059] As a result, when the switching element 5a is on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 21, the heating coil 12, and the switching elements 5e and 5f. Therefore, as shown in FIG. 9B(b), a current i 11 , i 12 As a result, the switching elements 5a and 5b can be turned on during the period when current flows through the diodes 6a and 6b, enabling soft switching operation with little switching loss.

[0060] Here, as shown in FIG. 9B(b), the voltage v1 of the first resonant load circuit (heating coils 11, 12, resonant capacitor 21) is applied only during a half cycle of the switching period, and the current i 11 The amplitude of the output can be reduced to 1 / 2 compared to Figure 7B(b). If the impedance of the resonant load circuit is the same, the power can be reduced to 1 / 4, and by combining it with frequency control, a wide output power range can be covered, which is effective in improving output controllability.

[0061] The upper arm (switching element 5d) of the second upper, middle, and lower arm 52 may be always on, and the middle arm (switching element 5e) of the second upper, middle, and lower arm 52 may be always off. Also, the drive signals of the switching elements of the upper, middle, and lower arms 51 and 52 may be interchanged.

[0062] <Eighth Pattern> Next, an eighth pattern of control in which current is passed through heating coils 13 and 14 in a half-bridge manner will be described with reference to Figs. 10A and 10B.

[0063] FIG. 10A shows the gate drive signals vg of the switching elements 5a to 5f during the eighth pattern control. 5a ~vg 5f FIG. 10B shows the operation waveforms when current flows through the heating coils 13 and 14 due to the gate drive control of FIG. 10A. 5a etc. have the same meaning as in Figure 3B.

[0064] The inverter system is a half-bridge system, and the heating coils 13 and 14 are supplied with a current i 13 , i 14 When a current is to flow, as shown in FIG. 10A , the upper arm of the first upper-middle-lower arm 51 and the upper and lower arms of the second upper-middle-lower arm 52 (switching elements 5a, 5d, 5f) are always on, the middle arm (switching element 5e) of the second upper-middle-lower arm 52 is always off, and the middle-lower arm (switching elements 5b, 5c) of the first upper-middle-lower arm 51 are turned on and off complementarily.

[0065] As a result, when the switching element 5b is on, a current flows from the DC power source 1 through the switching element 5a, the switching element 5b, the heating coil 13, the resonant capacitor 22, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 10B(b), a current i 13 , i 14 As a result, the switching elements 5b and 5c can be turned on during the period when current flows through the diodes 6b and 6c, enabling soft switching operation with little switching loss.

[0066] Here, as shown in FIG. 10B(b), the voltage v2 of the second resonant load circuit (heating coils 13, 14, resonant capacitor 22) is applied only during a half cycle of the switching period, and the current i 12 The amplitude of the amplitude can be reduced to half compared to FIG. 8B(b).

[0067] The middle arm (switching element 5e) of the second upper, middle, and lower arm 52 may be always on, and the lower arm (switching element 5f) of the second upper, middle, and lower arm 52 may be always off. Also, the drive signals of the switching elements of the upper, middle, and lower arms 51, 52 may be interchanged.

[0068] In this manner, this embodiment functions as a half-bridge type inverter circuit with a series resonant circuit of the first heating coil 11, the first resonant capacitor 21, and the second heating coil 12, or the third heating coil 13, the second resonant capacitor 22, and the fourth heating coil 14 as a load circuit.

[0069] <Ninth Pattern> Next, a ninth pattern of control in which currents of opposite phases are passed through heating coils 11, 14 and heating coils 12, 13 of the third and fourth resonant load circuits in a half-bridge system will be described with reference to Figs. 11A and 11B.

[0070] FIG. 11A shows the gate drive signals vg of the switching elements 5a to 5f during the ninth pattern control. 5a ~vg 5f FIG. 11B shows the operation waveforms when currents of opposite phases flow through the heating coils 11 and 14 and the heating coils 12 and 13 due to the gate drive control of FIG. 11A. 5a etc. have the same meaning as in Figure 3B.

[0071] The inverter system is a half-bridge system, and the current i of the opposite phase is supplied to the heating coils 11, 14 and the heating coils 12, 13 of the third and fourth resonant load circuits. 11 , i 12 , i 13 , i 14 When current is applied, as shown in FIG. 11A , a period in which the upper and lower arms of the first upper-middle-lower arm 51 and the upper and lower arms of the second upper-middle-lower arm 52 (switching elements 5a, 5c, 5d, 5f) are turned on simultaneously is alternated with a period in which the middle arm of the first upper-middle-lower arm 51 and the middle arm of the second upper-middle-lower arm 52 (switching elements 5b, 5e) are turned on simultaneously.

[0072] As a result, when the switching elements 5a, 5c, 5d, and 5f are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 23, the heating coil 13, and the switching element 5c, and from the DC power source 1 through the switching element 5d, the heating coil 12, the resonant capacitor 24, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 11B(b), the current i 11 , i 14 and the current i of the heating coils 12 and 13 12 , i 13 As a result, the switching elements 5a to 5f can be turned on during the period in which current flows through the diodes 6a to 6f, enabling a soft switching operation with little switching loss.

[0073] Here, as shown in FIG. 11B(b), voltage v3 of the third resonant load circuit (heating coils 11, 13, resonant capacitor 23) and voltage v4 of the fourth resonant load circuit (heating coils 12, 14, resonant capacitor 24) are applied for only half a switching period.

[0074] <Tenth Pattern> Next, a tenth pattern of control in which currents of opposite phases are passed through the heating coils 11, 13 of the third resonant load circuit in a half-bridge system will be described with reference to Figs. 12A and 12B.

[0075] FIG. 12A shows the gate drive signals vg of the switching elements 5a to 5f during the tenth pattern control. 5a ~vg 5f FIG. 12B shows the operation waveforms when currents of opposite phases flow through the heating coils 11 and 13 due to the gate drive control of FIG. 12A. 5a etc. have the same meaning as in Figure 3B.

[0076] The inverter system is a half-bridge system, and the heating coils 11 and 13 of the third resonant load circuit are supplied with currents i 11 , i13 When current is to flow, as shown in FIG. 12A , the upper, middle, and lower arm (switching elements 5d, 5e, 5f) of the second upper, middle, and lower arm 52 is always off, and a period in which the upper and lower arms (switching elements 5a, 5c) of the first upper, middle, and lower arm 51 are simultaneously on and a period in which the middle arm (switching element 5c) of the first upper, middle, and lower arm 51 is on are alternately provided.

[0077] As a result, when the switching elements 5a and 5c are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5a, the heating coil 11, the resonant capacitor 23, the heating coil 13, and the switching element 5c. Therefore, as shown in FIG. 12B(b), the current i 11 and the current i of the heating coil 13 13 are in opposite phase. As a result, the switching elements 5a to 5c can be turned on during the period when current flows through the diodes 6a to 6c, enabling soft switching operation with little switching loss. Furthermore, according to the tenth pattern control, a third resonant load circuit can be configured that has resonant frequency characteristics different from the resonant frequencies of the first and second resonant load circuits, so that a metal pot can be efficiently heated at an appropriate frequency according to the material of the pot.

[0078] Here, as shown in FIG. 12B(b), the voltage v3 of the third resonant load circuit (heating coils 11, 13, resonant capacitor 23) is applied for only half a switching period.

[0079] <Eleventh Pattern> Next, an eleventh pattern of control in which currents of opposite phases are passed through the heating coils 12, 14 of the fourth resonant load circuit in a half-bridge system will be described with reference to Figs. 13A and 13B.

[0080] FIG. 13A shows the gate drive signals vg of the switching elements 5a to 5f during the eleventh pattern control. 5a ~vg 5fFIG. 13B shows the operation waveforms when currents of opposite phases flow through the heating coils 12 and 14 due to the gate drive control of FIG. 13A. 5a etc. have the same meaning as in Figure 3B.

[0081] The inverter system is a half-bridge system, and the heating coils 12 and 14 of the fourth resonant load circuit are supplied with currents i 12 , i 14 When current is to flow, as shown in FIG. 13A , the upper, middle, and lower arm (switching elements 5a, 5b, 5c) of the first upper, middle, and lower arm 51 is always off, and a period in which the upper and lower arms (switching elements 5d, 5f) of the second upper, middle, and lower arm 52 are simultaneously on and a period in which the middle arm (switching element 5e) of the first upper, middle, and lower arm 52 is on are alternately provided.

[0082] As a result, when the switching elements 5d and 5f are simultaneously turned on, a current flows from the DC power source 1 through the switching element 5d, the heating coil 12, the resonant capacitor 24, the heating coil 14, and the switching element 5f. Therefore, as shown in FIG. 13B(b), the current i 12 and the current i of the heating coil 14 14 are in opposite phase. As a result, the switching elements 5d-5f can be turned on during the period when current flows through the diodes 6d-6f, enabling soft switching operation with little switching loss. In addition, according to the eleventh pattern control, a fourth resonant load circuit can be configured that has resonant frequency characteristics different from the resonant frequencies of the first and second resonant load circuits, so that a metal pot can be efficiently heated at an appropriate frequency according to the material of the pot.

[0083] Here, as shown in FIG. 13B(b), the voltage v4 of the fourth resonant load circuit (heating coils 12, 14, resonant capacitor 24) is applied for only half a switching period.

[0084] In this manner, this embodiment functions as a half-bridge type inverter circuit with a series resonant circuit of the first heating coil 11, the third resonant capacitor 23, and the third heating coil 13, or the second heating coil 12, the fourth resonant capacitor 24, and the fourth heating coil 14 as a load circuit.

[0085] By using the above-described control appropriately depending on the heating location of the bottom of the pot and whether or not there is a pot on the heating coil, the electromagnetic induction heating device can supply the desired power required to achieve the set heating power to the heated object.

[0086] <An example of a specific arrangement of heating coils> Fig. 14 is a configuration diagram showing a method of connecting the heating coils 11 to 14 and the upper, middle, and lower arms 51, 52 shown in Fig. 1, together with a specific arrangement of the first to fourth heating coils 11 to 14 in the electromagnetic induction heating device. In this electromagnetic induction heating device, one annular heating coil for induction heating one object to be heated (such as a metal pot) is formed by combining the first to fourth heating coils 11 to 14 wound in a roughly fan shape, and this heating coil is connected to each of the upper, middle, and lower arms as shown in the figure.

[0087] In this embodiment, the first heating coil 11 and the second heating coil 12 are disposed on the rear side of the electromagnetic induction heating device, and the third heating coil 13 and the fourth heating coil 14 are disposed on the front side of the electromagnetic induction heating device. A one end of the first resonant capacitor 21 is connected to the outer periphery of the first heating coil 11, one end of the first resonant capacitor 22 is connected to the inner periphery of the first heating coil 11, and the output terminal O of the upper, middle, and lower arms 52 is connected to the D The other end of the first resonant capacitor 21 is connected to the outer periphery of the second heating coil 12, and the other end of the first resonant capacitor 21 is connected to the inner periphery of the second heating coil 12. B one end of the second resonant capacitor 22 is connected to the outer periphery of the third heating coil 13, one end of the second resonant capacitor 23 is connected to the inner periphery of the third heating coil 13, and the output terminal O of the upper, middle, and lower arms 52 is connected to the EThe other end of the second resonant capacitor 22 is connected to the outer periphery of the fourth heating coil 14, and the other end of the second resonant capacitor 22 is connected to the inner periphery of the fourth heating coil 14. The third resonant capacitor 23 is connected between the inner periphery of the first heating coil 11 and the inner periphery of the third heating coil 13, and the fourth resonant capacitor 24 is connected between the inner periphery of the second heating coil 12 and the inner periphery of the fourth heating coil 14. Note that, although a configuration in which the first heating coil 11 and the second heating coil 12 are arranged on the rear side and the third heating coil 13 and the fourth heating coil 14 are arranged on the front side is illustrated here, the installation direction of each heating coil is not limited to the above example as long as the straight portions of each heating coil are arranged to face each other and the arc portions of each heating coil form one circumference.

[0088] As shown in FIG. 14, when the first heating coil 11 is wound clockwise from the outer circumference to the inner circumference, the second heating coil 12 is wound counterclockwise from the outer circumference to the inner circumference, the third heating coil 13 is wound clockwise from the outer circumference to the inner circumference, and the fourth heating coil 14 is wound counterclockwise from the outer circumference to the inner circumference, as in the first pattern (FIG. 3B) or the third pattern (FIG. 5B), when currents of the same phase are passed through the heating coils 11 to 14 for heating, as shown by the dashed arrow in FIG. 14, the current i 11 and current i 12 and the current i in the straight section where the first heating coil 11 and the third heating coil 13 face each other 11 and current i 13 and the current i in the straight section where the second heating coil 12 and the fourth heating coil 14 face each other 12 and current i 14 The current i in the straight section where the third heating coil 13 and the fourth heating coil 14 face each other is 13 and current i 14 As a result, the magnetic flux is cancelled out, suppressing the amount of heat generated by the pan located in the straight portion of each heating coil, and a desired amount of heat can be obtained on the outer periphery of the pan.

[0089] On the other hand, as in the ninth pattern (FIG. 11B), the current i 11 , i14 With respect to the current i of the heating coils 12 and 13, 12 , i 13 When the currents are out of phase with each other, the currents in the straight sections where the heating coils face each other will be in phase, as shown by the dashed arrows in Figure 15. Therefore, the large magnetic flux created by each heating coil causes large eddy currents to flow in the pan located in the straight section of each heating coil in a direction that cancels out the large magnetic flux, thereby obtaining the desired amount of heat.

[0090] In this way, by controlling the phase of the current in the heating coil, the heat generating location on the bottom of the pot can be changed, making it possible to perform appropriate heating control according to the material, size, etc. of the pot.

[0091] Furthermore, the method of connecting the upper, middle, and lower arms 51, 52 and the heating coils 11 to 14 in this embodiment can suppress the potential difference in the areas where the heating coils are close to each other, so that even if the gap between the heating coils is narrowed, a sufficient insulation distance can be ensured.

[0092] Furthermore, by changing the winding method of each heating coil and the connections between the upper, middle and lower arms and the resonant capacitor, it is easy to change the heat generating location in the bottom of the pot. EXAMPLES

[0093] Fig. 16 is a circuit diagram of an electromagnetic induction heating device of Example 2. The same parts as in Fig. 1 are given the same reference numerals and repeated explanations will be omitted.

[0094] In FIG. 16, the output terminal O A One end of the first resonant capacitor 31 is connected to the output terminal O. The other end of the first resonant capacitor 31 is connected to one end of the first heating coil 11. D One end of the second resonant capacitor 32 is connected to the output terminal O1, the other end of the second resonant capacitor 32 is connected to one end of the second heating coil 12, and the other ends of the first heating coil 11 and the second heating coil 12 are connected to each other. BOne end of the third resonant capacitor 33 is connected to the output terminal O. The other end of the third resonant capacitor 33 is connected to one end of the third heating coil 13. E One end of a fourth resonant capacitor 34 is connected to the first heating coil 11, the other end of the fourth resonant capacitor 34 is connected to one end of the fourth heating coil 14, and the other ends of the third heating coil 13 and the fourth heating coil 14 are connected to each other. In addition, a fifth resonant capacitor 35 is connected between the connection point of the first heating coil 11 and the second heating coil 12 and the connection point of the third heating coil 13 and the fourth heating coil 14.

[0095] Therefore, in the electromagnetic induction heating device of the present embodiment, by changing the driving method of the first upper, middle, and lower arm 51 and the second upper, middle, and lower arm 52, not only can the first resonant load circuit including the first heating coil 11, the second heating coil 12, the first resonant capacitor 31, and the second resonant capacitor 32, and the second resonant load circuit including the third heating coil 13, the fourth heating coil 14, the third resonant capacitor 33, and the fourth resonant capacitor 34 be switched between a parallel connection or a series connection state, but the phase of the current flowing through the heating coils can be changed to be the same phase or opposite phase to heat the object to be heated.

[0096] Similarly, by appropriately setting the driving method of each upper, middle, and lower arm and changing the capacitance of the fifth resonant capacitor 35 relative to the capacitances of the first to fourth resonant capacitors 31 to 34, it is also possible to configure a third resonant load circuit including the first heating coil 11, the third heating coil 13, the first resonant capacitor 31, the third resonant capacitor 33, and the fifth resonant capacitor 35 having resonant frequency characteristics different from the resonant frequencies of the first and second resonant load circuits, and a fourth resonant load circuit including the second heating coil 12, the fourth heating coil 14, the second resonant capacitor 32, the fourth resonant capacitor 34, and the fifth resonant capacitor 35.It is possible to select one of the first to fourth resonant load circuits and pass current through it to heat the object to be heated, or to switch the inverter method between a full-bridge method and a half-bridge method and change the driving frequency to heat the object to be heated.

[0097] In this embodiment, the first resonant load circuit has the first resonant capacitor 31 and the second resonant capacitor 32 connected in series, so that the withstand voltage of the first and second resonant capacitors can be reduced. Similarly, the second resonant load circuit has the third resonant capacitor 33 and the fourth resonant capacitor 34 connected in series, so that the withstand voltage of the third and fourth resonant capacitors can be reduced. Furthermore, the third resonant load circuit has the first resonant capacitor 31, the third resonant capacitor 33 and the fifth resonant capacitor 35 connected in series, and the fourth resonant load circuit has the second resonant capacitor 32, the fourth resonant capacitor 34 and the fifth resonant capacitor 35 connected in series, so that the withstand voltage of the fifth resonant capacitor can also be reduced.

[0098] <Other examples of specific heating coil arrangements> The electromagnetic induction heating device of this embodiment may be configured to have a plurality of inverter circuits, and each inverter circuit may supply current only to the heating coil facing the object to be heated placed on the top plate. For example, Fig. 17 is a plan view from above of an electromagnetic induction heating device equipped with six inverters (2A, 2B, 2C, 2D, 2E, 2F) illustrated in Fig. 1 or Fig. 16, and is a configuration diagram in which heating coils 11 to 14 wound concentrically are arranged as one set, two vertically and three horizontally, and are arranged under the top plate 110. In the following, the heating coils 11 to 14 of the circuit configurations 2A to 2F are referred to as 11A to 14F, respectively.

[0099] When the object to be heated 200 (such as a metal pan) is placed in the position shown in Fig. 18A, only inverters 2E and 2F are driven. Specifically, inverter 2E passes current through heating coils 13E and 14E in either the sixth pattern (Fig. 8B) or the eighth pattern (Fig. 10B), and inverter 2F passes current through all of heating coils 11F to 14F in either the first pattern (Fig. 3B) to the fourth pattern (Fig. 6B) or the ninth pattern (Fig. 11B), thereby obtaining the desired amount of heat.

[0100] On the other hand, when two objects to be heated 200A and 200B are placed at the positions shown in Fig. 18B, only inverters 2B, 2D, and 2E are driven. Specifically, inverter 2B passes current to heating coils 12B and 14B according to the eleventh pattern (Fig. 13B), inverter 2D passes current to heating coils 11D and 13D according to the tenth pattern (Fig. 12B), and inverter 2E passes current to all of heating coils 11E to 14E according to any of the first pattern (Fig. 3B) to the fourth pattern (Fig. 6B) and the ninth pattern (Fig. 11B), thereby obtaining a desired amount of heat.

[0101] In this way, in this embodiment, the heating coil to which current is applied is determined depending on whether a pot is placed on the heating coil, the inverter type is switched between full-bridge type and half-bridge type, and the drive frequency is also changed and controlled, making it possible to perform appropriate heating control according to the material, size, etc. of the pot. [Explanation of symbols]

[0102] 1 DC power supply, 2. 2A~2F inverter, 5a to 5f switching elements, 6a to 6f, 101a to 101d Diodes, 7a~7f, 103 capacitors, 11, 11A to 11F: first heating coil; 12, 12A~12F second heating coil; 13, 13A~13F third heating coil; 14, 14A~14F fourth heating coil; 21, 31 first resonant capacitor, 22, 32 second resonant capacitor; 23, 33 third resonant capacitor, 24 34 Fourth resonant capacitor, 35 Fifth Resonant Capacitor 51 First upper, middle and lower arms, 52 Second upper, middle and lower arms, 100 Commercial AC power supply, 102 inductor, 110 top plate, 200, 200A, 200B Heated object

Claims

1. A plurality of heating coils for induction heating an object to be heated; A DC power supply that outputs a DC voltage; an inverter circuit that converts a DC voltage output by the DC power supply into an AC voltage and supplies the AC voltage to the plurality of heating coils; An electromagnetic induction heating device comprising: The inverter circuit includes: A leg, which is a series body of three switching elements, is connected in parallel between a positive electrode and a negative electrode of the DC power supply, A series circuit of a heating coil and a resonant capacitor is connected between the output terminal of one leg and the output terminal of the other leg.

1. An electromagnetic induction heating device, comprising: a heating coil and a resonant capacitor connected in series between two output terminals of the same leg.

2. 2. The electromagnetic induction heating device according to claim 1, The plurality of heating coils is four heating coils, The inverter circuit includes: a first leg which is a series body of three switching elements and a second leg which is a series body of three switching elements are provided in parallel between a positive electrode and a negative electrode of the DC power supply, a first resonant load circuit, which is a series circuit of a first heating coil, a first resonant capacitor, and a second heating coil, is connected between a first output terminal of the first leg and a first output terminal of the second leg; a second resonant load circuit, which is a series circuit of a third heating coil, a second resonant capacitor, and a fourth heating coil, is connected between the second output terminal of the first leg and the second output terminal of the second leg; a third resonant load circuit, which is a series circuit of the first heating coil, a third resonant capacitor, and the third heating coil, is connected between the first output terminal and the second output terminal of the first leg; An electromagnetic induction heating device characterized in that a fourth resonant load circuit, which is a series circuit of the second heating coil, a fourth resonant capacitor, and the fourth heating coil, is connected between the first output terminal and the second output terminal of the second leg.

3. 2. The electromagnetic induction heating device according to claim 1, The plurality of heating coils is four heating coils, The inverter circuit includes: a first leg which is a series body of three switching elements and a second leg which is a series body of three switching elements are provided in parallel between a positive electrode and a negative electrode of the DC power supply, a first resonant load circuit, which is a series circuit of a first heating coil, a first resonant capacitor, a second heating coil, and a second resonant capacitor, is connected between a first output terminal of the first leg and a first output terminal of the second leg; a second resonant load circuit, which is a series circuit of a third heating coil, a third resonant capacitor, a fourth heating coil, and a fourth resonant capacitor, is connected between the second output terminal of the first leg and the second output terminal of the second leg; a third resonant load circuit, which is a series circuit of the first heating coil, the first resonant capacitor, the fifth resonant capacitor, the third heating coil, and the third resonant capacitor, is connected between the first output terminal and the second output terminal of the first leg; An electromagnetic induction heating device characterized in that a fourth resonant load circuit which is a series circuit of the second heating coil, the second resonant capacitor, the fifth resonant capacitor, the fourth heating coil, and the fourth resonant capacitor is connected between the first output terminal and the second output terminal of the second leg.

4. 4. The electromagnetic induction heating device according to claim 2, The electromagnetic induction heating device is characterized in that the inverter circuit operates as a full-bridge inverter or a half-bridge inverter by changing the drive of each switching element.

5. 4. The electromagnetic induction heating device according to claim 2, An electromagnetic induction heating device characterized in that the inverter circuit connects the first resonant load circuit and the second resonant load circuit in parallel or in series by changing the drive of each switching element.

6. 4. The electromagnetic induction heating device according to claim 2, An electromagnetic induction heating device characterized in that the inverter circuit changes the drive of each switching element to pass currents of the same phase or opposite phase to the first resonant load circuit and the second resonant load circuit.

7. 4. The electromagnetic induction heating device according to claim 2, The electromagnetic induction heating device, characterized in that the inverter circuit changes the drive of each switching element to pass a current through only one of the first resonant load circuit or the second resonant load circuit.

8. 4. The electromagnetic induction heating device according to claim 2, The electromagnetic induction heating device, characterized in that the inverter circuit changes the drive of each switching element to pass a current through only one of the third resonant load circuit or the fourth resonant load circuit.

9. 4. The electromagnetic induction heating device according to claim 2, The four heating coils are all wound in a substantially fan-like shape, An electromagnetic induction heating device, characterized in that the straight portions of the four heating coils are arranged so as to face each other.

10. 10. The electromagnetic induction heating device according to claim 9, The electromagnetic induction heating device is characterized in that the inverter circuit supplies currents of the same phase to the straight portions of the four heating coils.

11. 10. The electromagnetic induction heating device according to claim 9, The electromagnetic induction heating device is characterized in that the inverter circuit supplies currents of opposite phases to the straight portions of the four heating coils.

12. 4. The electromagnetic induction heating device according to claim 2, The electromagnetic induction heating device, wherein the first resonant load circuit and the third resonant load circuit have different resonant frequencies.

13. 4. The electromagnetic induction heating device according to claim 2, The electromagnetic induction heating device, wherein the second resonant load circuit and the fourth resonant load circuit have different resonant frequencies.

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