Electromagnetic induction heating device

Abstract

To provide an inverter type electromagnetic induction heating device which can efficiently supply the desired power to a heating object.SOLUTION: An electromagnetic induction heating device comprises: a plurality of heating coils for induction-heating a heating object; a DC power source which outputs DC voltage; and an inverter circuit which converts the DC voltage output from the DC power source into AC voltage and supplies the AC voltage to the plurality of heating coils. The inverter circuit is obtained by parallelly connecting, between the positive electrode and the negative electrode of the DC power source, legs being series bodies of three or more switching elements. The series bodies of the heating coil and a resonance capacitor are connected between output terminals of the 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 that can be controlled independently, 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 attempting to increase the output of the induction heating cooking device, it is difficult to increase the magnetomotive force even by increasing the number of turns of the heating coil, 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.

[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 independently controllable heating coils are used in combination to inductively heat a single object to be heated. [Means for solving the problem]

[0008] In order to achieve the above 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 has three or more legs, each of which is a series body of switching elements, connected in parallel between the positive and negative electrodes of the DC power supply, and a series body of the heating coil and a resonant capacitor is connected between the output terminals of each of the legs. Effect of the Invention

[0009] According to the electromagnetic induction heating device of the present invention, when multiple independently controllable heating coils are used in combination to induction heat a single heated object, the desired power can be efficiently supplied to the heated object 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. 2 is a circuit diagram of an electromagnetic induction heating device according to an embodiment. [Diagram 2] FIG. 2 is a circuit diagram of a DC power supply according to an 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 11] Connection diagram of the heating coil and upper, middle and lower arms when the coil currents are in phase. [Figure 12]Connection diagram of the heating coil and upper, middle and lower arms when the coil current is in opposite phase. [Figure 13] FIG. 2 is a diagram showing a configuration in which three heating coil pairs are arranged side by side according to an embodiment. [Figure 14A] FIG. 14 is a diagram showing the positional relationship between the configuration of FIG. 13 and the object to be heated. [Figure 14B] FIG. 14 is a diagram showing the positional relationship between the configuration of FIG. 13 and the object to be heated. [Figure 14C] FIG. 14 is a diagram showing the positional relationship between the configuration of FIG. 13 and the object to be heated. [Figure 14D] FIG. 14 is a diagram showing the positional relationship between the configuration of FIG. 13 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.

[0012] Fig. 1 is a circuit diagram of an electromagnetic induction heating device according to an embodiment of the present invention. Note that the electromagnetic induction heating device of this embodiment has a heat-resistant glass top plate installed on top of a metal housing, and a high-frequency current is supplied to a heating coil arranged 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] Between the positive electrode P and negative electrode N of such a DC power supply 1, a first upper, middle, and lower arm 51 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 in which switching elements 5d, 5e, and 5f are connected in series are connected in parallel.

[0015] Diodes 6a to 6f are connected in parallel in the opposite direction to the switching elements 5a to 5f, and capacitors 7a to 7f are connected in parallel to the switching elements 5a to 5f, respectively. The capacitors 7a to 7f are charged or discharged by the interruption current when the switching elements 5a to 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 set to 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 and output terminal O D A series circuit of a first heating coil 11 and a first resonant capacitor 21 is connected between the output terminals O B and output terminal O E A series circuit of a second heating coil 12 and a second resonant capacitor 22 is connected between the first and second resonant capacitors 22 and 24.

[0017] Therefore, in the electromagnetic induction heating device of this 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 and the second resonant load circuit including the second heating coil 12 be switched between parallel connection and series connection, but also the phase of the current flowing through the heating coils can be changed to the same phase or the opposite phase to heat the object to be heated. Similarly, by appropriately setting the driving method of each upper, middle, and lower arm, it is possible to select one of the heating coils 11 and 12 to energize and heat the object to be heated, or to switch the inverter method to the full bridge method or the half bridge method to heat the object to be heated. Below, the features such as the action and effect of the eight patterns of energization control shown in Table 1 that can be realized by the electromagnetic induction heating device of this embodiment will be sequentially described in detail. Note that, below, the direction of the dashed arrow in FIG. 1 indicates the direction of the current i flowing through the heating coils 11 and 12. 11 , i 12 The positive direction is defined as the

[0018] [Table 1]

[0019] <First pattern> First, a first pattern of control in which resonant load circuits are connected in parallel in a full-bridge system and currents of the same phase are passed through heating coils 11 and 12 will be described with reference to Figs. 3A and 3B.

[0020] 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 and 12 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 v applied to the heating coils 11 and 12 and the resonant capacitors 21 and 22 11,12,21,22 , the current i of the heating coils 11 and 12 11 , i 12, (c) Current i of each element of upper, middle and lower arms 51, 52 5a ~i 5f , i 6a ~i 6f It is.

[0021] The inverter system is a full-bridge system, and the resonant load circuits are connected in parallel to supply the same phase current i to the heating coils 11 and 12. 11 , i 12 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.

[0022] As a result, when the switching elements 5a and 5f are on at the same time, a current flows from the DC power source 1 through the path of the switching element 5a, the heating coil 11, the resonant capacitor 21, the switching element 5e, and the switching element 5f, and from the DC power source 1 through the path of the switching element 5a, the switching element 5b, the heating coil 12, the resonant capacitor 22, and the switching element 5f. Therefore, as shown in FIG. 3B(b), the current i 11 , i 12 As 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.

[0023] Here, as shown in FIG. 3B(b), the voltages v of the heating coils 11 and 12 and the resonant capacitors 21 and 22 are 11,12,21,22can apply a voltage over the entire switching period, and can apply twice the voltage to the resonant circuit as in Patent Document 1, which can apply a voltage only during 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.

[0024] <Second pattern> Next, a second pattern of control in which resonant load circuits are connected in series in a full-bridge system and currents of opposite phases are passed through heating coils 11 and 12 will be described with reference to Figs. 4A and 4B.

[0025] 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 due to the gate drive control of FIG. 4A. 5a etc. have the same meaning as in Figure 3B.

[0026] The inverter system is a full-bridge system, and the resonant load circuits are connected in series to supply currents i in opposite phases to the heating coils 11 and 12. 11 , i 12 When 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.

[0027] 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 switching element 5e, the resonant capacitor 22, the heating coil 12, and the switching element 5c. Therefore, as shown in FIG. 4B(b), the current i 11 , i 12As 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.

[0028] Here, as shown in FIG. 4B(b), the voltages v of the heating coils 11 and 12 and the resonant capacitors 21 and 22 are 11,12,21,22 can apply a voltage for the entire switching period, and can apply to the resonant circuit a voltage that is twice as high as that of Patent Document 1, which can apply a voltage only for a half period of the switching period.

[0029] In this manner, this embodiment functions as a full-bridge type inverter circuit in which the series resonant circuits of the first heating coil 11, the first resonant capacitor 21, and the second heating coil 12 and the second resonant capacitor 22 serve as load circuits.

[0030] <Third Pattern> Next, a third pattern of control in which resonant load circuits are connected in parallel in a half-bridge manner and currents of the same phase are passed through heating coils 11 and 12 will be described with reference to Figs. 5A and 5B.

[0031] 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 and 12 due to the gate drive control of FIG. 5A. 5a etc. have the same meaning as in Figure 3B.

[0032] The inverter system is a half-bridge system, and the resonant load circuits are connected in parallel to supply the same phase current i to the heating coils 11 and 12. 11 , i 12When 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.

[0033] 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 switching elements 5e and 5f, and from the DC power source 1 through the switching element 5a, the switching element 5b, the heating coil 12, the resonant capacitor 22, and the switching element 5f. Therefore, as shown in FIG. 5B(b), the current i 11 , i 12 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.

[0034] Here, as shown in FIG. 5B(b), the voltages v of the heating coils 11 and 12 and the resonant capacitors 21 and 22 are 11,12,21,22 is applied only for half a switching period, and the current i 11 , i 12 The amplitude of the output can be reduced to 1 / 2 compared to Figure 3B(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.

[0035] 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.

[0036] <Fourth pattern> Next, a fourth pattern of control in which resonant load circuits are connected in series in a half-bridge system and currents of opposite phases are passed through heating coils 11 and 12 will be described with reference to Figs. 6A and 6B.

[0037] 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 due to the gate drive control of FIG. 6A. 5a etc. have the same meaning as in Figure 3B.

[0038] The inverter system is a half-bridge system, and the resonant load circuits are connected in series to supply currents i in opposite phases to the heating coils 11 and 12. 11 , i 12 When 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.

[0039] 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 switching element 5e, the resonant capacitor 22, the heating coil 12, and the switching element 5c. Therefore, as shown in FIG. 6B(b), the current i 11 , i 12 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.

[0040] Here, as shown in FIG. 6B(b), the voltages v of the heating coils 11 and 12 and the resonant capacitors 21 and 22 are11,12,21,22 is applied only for half a switching period, and the current i 11 , i 12 The amplitude of the amplitude can be reduced to half compared to Figure 4B(b).

[0041] The drive signals for the switching elements of the upper, middle and lower arms 51 and 52 may be interchanged.

[0042] In this manner, this embodiment functions as a half-bridge type inverter circuit in which the series resonant circuits of the first heating coil 11, the first resonant capacitor 21, and the second heating coil 12 and the second resonant capacitor 22 serve as load circuits.

[0043] <Fifth pattern> Next, a fifth pattern of control in which a current flows only through heating coil 11 in a full-bridge system will be described with reference to Figs. 7A and 7B.

[0044] 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 an operational waveform when a current flows only through the heating coil 11 by the gate drive control of FIG. 7A. 5a etc. have the same meaning as in Figure 3B.

[0045] The inverter system is a full-bridge system, and the current i 11 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.

[0046] 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, and the switching elements 5e and 5f. Therefore, as shown in FIG. 7B(b), a current i 11 As 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.

[0047] Here, as shown in FIG. 7B(b), the voltage v of the heating coil 11 and the resonant capacitor 21 11,21 can apply a voltage over the entire switching period, and can apply twice the voltage to the resonant circuit as in Patent Document 1, which can apply a voltage only during 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.

[0048] <Sixth Pattern> Next, a sixth pattern of control in which a current flows only through heating coil 12 in a full-bridge system will be described with reference to Figs. 8A and 8B.

[0049] 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 an operational waveform when a current flows only through the heating coil 12 due to the gate drive control of FIG. 8A. 5a etc. have the same meaning as in Figure 3B.

[0050] The inverter system is a full-bridge system, and the current i 12When 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.

[0051] 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 12, the resonant capacitor 22, and the switching element 5f. Therefore, as shown in FIG. 8B(b), a current i 12 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.

[0052] Here, as shown in FIG. 8B(b), the voltage v of the heating coil 12 and the resonant capacitor 22 12, v 22 can apply a voltage for the entire switching period, and can apply to the resonant circuit a voltage that is twice as high as that of Patent Document 1, which can apply a voltage only for a half period of the switching period.

[0053] In this manner, this embodiment functions as a full-bridge inverter circuit with the series resonant circuit of the first heating coil 11 and the first resonant capacitor 21, or the series resonant circuit of the second heating coil 12 and the second resonant capacitor 22, as a load circuit.

[0054] <Seventh Pattern> Next, a seventh pattern of control in which a current flows only through heating coil 11 in a half-bridge system will be described with reference to Figs. 9A and 9B.

[0055] 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.

[0056] The inverter system is a half-bridge system, and the current i 11 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.

[0057] 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, and the switching elements 5e and 5f. Therefore, as shown in FIG. 9B(b), a current i 11 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.

[0058] Here, as shown in FIG. 9B(b), the voltage v of the heating coil 11 and the resonant capacitor 21 11,21 is applied only for half a 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.

[0059] 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.

[0060] <Eighth Pattern> Next, an eighth pattern of control in which a current flows only through heating coil 12 in a half-bridge system will be described with reference to Figs. 10A and 10B.

[0061] 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 an operational waveform when a current flows only through the heating coil 12 by the gate drive control of FIG. 10A. 5a etc. have the same meaning as in Figure 3B.

[0062] The inverter system is a half-bridge system, and the current i 12 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.

[0063] 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 12, the resonant capacitor 22, and the switching element 5f. Therefore, as shown in FIG. 10B(b), a current i 12 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.

[0064] Here, as shown in FIG. 10B(b), the voltage v of the heating coil 12 and the resonant capacitor 22 12, v 22 is applied only for half a switching period, and the current i 12 The amplitude of the amplitude can be reduced to half compared to FIG. 8B(b).

[0065] 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.

[0066] In this manner, this embodiment functions as a half-bridge type inverter circuit with the series resonant circuit of the first heating coil 11 and the first resonant capacitor 21, or the series resonant circuit of the second heating coil 12 and the second resonant capacitor 22, as a load circuit.

[0067] 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.

[0068] In Fig. 1, an electromagnetic induction heating device is described that has two upper, middle and lower arms with three switching elements connected in series and uses two heating coils to heat an object to be heated, but an electromagnetic induction heating device may also be configured that has two legs (assembly of arms) with four or more switching elements connected in series and uses three or more heating coils to heat an object to be heated. In this case, too, by driving appropriate switching elements based on the same concept as above, it is possible to switch the heating coil to which current flows from three or more heating coils, switch the current direction of each heating coil to the same phase or opposite phase when current flows through multiple heating coils, and switch the inverter type between full bridge type and half bridge type.

[0069] <An example of a specific arrangement of heating coils> Fig. 11 is a configuration diagram showing a method of connecting the heating coils 11, 12 and the upper, middle, and lower arms 51, 52 shown in Fig. 1, together with a specific arrangement of the first and second heating coils 11, 12 in the electromagnetic induction heating device. In this electromagnetic induction heating device, one annular heating coil for induction heating one heated object (such as a metal pot) is formed by combining the first heating coil 11 and the second heating coil 12 wound in a semicircular shape (approximately D-shaped) like the outline of a half moon, and this heating coil is connected to each of the upper, middle, and lower arms as shown in the figure.

[0070] In this embodiment, the first heating coil 11 is disposed at the rear side of the electromagnetic induction heating device, and the second heating coil 12 is disposed at 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 21 is connected to the inner periphery of the first heating coil 11, and the other end of the first resonant capacitor 21 is connected to the output terminal O of the second upper-middle-lower arm 52. D and the output terminal O of the upper, middle and lower arms 51 B one end of the second resonant capacitor 22 is connected to the outer periphery of the second heating coil 12, one end of the second resonant capacitor 22 is connected to the inner periphery of the second heating coil 12, and the other end of the second resonant capacitor 22 is connected to the output terminal O of the second upper-middle-lower arm 52. E In this embodiment, the first heating coil 11 is disposed at the rear side and the second heating coil 12 is disposed at the front side, but the installation direction of the two heating coils is not limited to the above example as long as the straight portions of the two heating coils face each other and the arc portions of the two heating coils form one circumference.

[0071] As shown in FIG. 11, when the first heating coil 11 is wound clockwise from the outer circumference to the inner circumference and the second heating coil 12 is wound counterclockwise from the outer circumference to the inner circumference, when heating is performed by passing currents of the same phase through the heating coils 11 and 12 as in the first pattern (FIG. 3B) or the third pattern (FIG. 5B), the current i of the first heating coil 11 in the straight portion where the heating coils face each other is as shown by the dashed arrow in FIG. 11 and the current i of the second heating coil 12 12Therefore, the large magnetic flux created by the two heating coils causes large eddy currents to flow in the center of the pot in a direction that cancels out the large magnetic flux, resulting in the desired amount of heat.

[0072] On the other hand, when heating is performed by passing currents of opposite phases through the heating coils 11 and 12 as in the second pattern (FIG. 4B) or the fourth pattern (FIG. 6B), the current i of the first heating coil 11 in the straight portion where the heating coils face each other is as shown by the dashed arrow in FIG. 11 and the current i of the second heating coil 12 12 As a result, the magnetic flux is cancelled out, suppressing the amount of heat generated in the center of the pot and allowing the desired amount of heat to be generated in the outer periphery of the pot.

[0073] 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.

[0074] In this embodiment, when the currents in heating coils 11 and 12 are in phase, the amount of heat generated in the center of the bottom of the pot is increased, and when the currents are in opposite phase, the amount of heat generated in the outer periphery of the bottom of the pot is increased. However, it is easy to change the heat generating location of the bottom of the pot by changing the winding direction of heating coils 11 and 12 and the connections to the upper, middle and lower arms and the resonant capacitor.

[0075] <Other examples of specific arrangements of heating coils> The electromagnetic induction heating device of this embodiment may be configured to include multiple 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. 13 is a plan view of an electromagnetic induction heating device including three sets of the circuit configuration illustrated in Fig. 1, viewed from above, and is a configuration diagram in which heating coils 11 and 12 wound concentrically are arranged in three rows, one above the other, below the top plate 110. In the following, the heating coils arranged on the left side are referred to as heating coils 11L and 12L, the heating coils arranged in the center are referred to as heating coils 11C and 12C, and the heating coils arranged on the right side are referred to as heating coils 11R and 12R.

[0076] When the object to be heated 200 (such as a metal pan) is placed in the position shown in Fig. 14A, only the inverter for the right coil is driven. Specifically, a desired amount of heat can be obtained by applying a current to both heating coils 11R and 12R by any one of the first pattern (Fig. 3B) to the fourth pattern (Fig. 6B).

[0077] When the object to be heated 200 is placed in the position shown in Fig. 14B, the inverters for the center row coils and the right row coils are driven. Specifically, the inverter for the center row coils passes a current only to the heating coil 12C according to either the sixth pattern (Fig. 8B) or the eighth pattern (Fig. 10B), and the inverter for the right row coils passes a current only to the heating coil 11R according to either the fifth pattern (Fig. 7B) or the seventh pattern (Fig. 9B), thereby generating a desired amount of heat.

[0078] When a large object to be heated 200 is placed at the position shown in Fig. 14C, the inverters for the left row coils and the center row coils are driven. Specifically, the inverter for the left row coils passes current to both heating coils 11L and 12L using any one of the first pattern (Fig. 3B) to fourth pattern (Fig. 6B), and the inverter for the center row coils passes current only to heating coil 12C using any one of the sixth pattern (Fig. 8B) or eighth pattern (Fig. 10B), thereby obtaining the desired amount of heat.

[0079] When a small heated object 200 is placed in the position shown in Figure 14D, the desired amount of heat can be obtained by driving only the inverter for the left row coils and passing current only through the heating coil 12L using either the sixth pattern (Figure 8B) or the eighth pattern (Figure 10B).

[0080] 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 or not, and the inverter type is switched between full-bridge type and half-bridge type, making it possible to perform appropriate heating control according to the material, size, etc. of the pot. [Explanation of symbols]

[0081] 1 DC power supply, 2 Inverter 5a to 5f switching elements, 6a to 6f, 101a to 101d Diodes, 7a~7f, 103 capacitors, 11 first heating coil; 12 a second heating coil; 21 first resonant capacitor; 22 second 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 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: Three or more legs each being a series body of switching elements are connected in parallel between a positive electrode and a negative electrode of the DC power source, A series circuit of the heating coil and a resonant capacitor is connected between output terminals of each of the legs, The plurality of heating coils is two 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 series circuit including a first heating coil and a first resonant capacitor is connected between the first output terminal of the first leg and the first output terminal of the second leg; a series circuit including a second heating coil and a second resonant capacitor is connected between the second output terminal of the first leg and the second output terminal of the second leg; A snubber capacitor is connected in parallel to each switching element. The electromagnetic induction heating device is characterized in that the inverter circuit connects the two heating coils in parallel or in series by changing the drive of each switching element.

2. 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: Three or more legs each being a series body of switching elements are connected in parallel between a positive electrode and a negative electrode of the DC power source, A series circuit of the heating coil and a resonant capacitor is connected between output terminals of each of the legs, The plurality of heating coils is two 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 series circuit including a first heating coil and a first resonant capacitor is connected between the first output terminal of the first leg and the first output terminal of the second leg; a series circuit including a second heating coil and a second resonant capacitor is connected between the second output terminal of the first leg and the second output terminal of the second leg; A snubber capacitor is connected in parallel to each switching element. The electromagnetic induction heating device is 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 two heating coils.

3. 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: Three or more legs each being a series body of switching elements are connected in parallel between a positive electrode and a negative electrode of the DC power source, A series circuit of the heating coil and a resonant capacitor is connected between output terminals of each of the legs, The plurality of heating coils is two 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 series circuit including a first heating coil and a first resonant capacitor is connected between the first output terminal of the first leg and the first output terminal of the second leg; a series circuit including a second heating coil and a second resonant capacitor is connected between the second output terminal of the first leg and the second output terminal of the second leg; A snubber capacitor is connected in parallel to each switching element. The two heating coils are both wound in a substantially D-shape, The straight portions of both heating coils are arranged to face each other. The electromagnetic induction heating device is characterized in that the inverter circuit passes currents of the same phase through the straight portions of both heating coils.

4. 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: Three or more legs each being a series body of switching elements are connected in parallel between a positive electrode and a negative electrode of the DC power source, A series circuit of the heating coil and a resonant capacitor is connected between output terminals of each of the legs, The plurality of heating coils is two 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 series circuit including a first heating coil and a first resonant capacitor is connected between the first output terminal of the first leg and the first output terminal of the second leg; a series circuit including a second heating coil and a second resonant capacitor is connected between the second output terminal of the first leg and the second output terminal of the second leg; A snubber capacitor is connected in parallel to each switching element. The two heating coils are both wound in a substantially D-shape, The straight portions of both heating coils are arranged to face each other. The electromagnetic induction heating device is characterized in that the inverter circuit passes currents of opposite phases through the straight portions of both heating coils.

5. The electromagnetic induction heating device according to any one of claims 1 to 4, 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.

6. The electromagnetic induction heating device according to any one of claims 1 to 4, The electromagnetic induction heating device is characterized in that the inverter circuit changes the drive of each switching element to pass a current through only one of the two heating coils.

7. The electromagnetic induction heating device according to any one of claims 1 to 4, The inverter circuit includes a plurality of inverter circuits, An electromagnetic induction heating device, characterized in that each inverter circuit supplies current only to a heating coil facing the object to be heated.

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