Induction heating device and program for induction heating device

Abstract

To provide an induction heating device capable of reducing switching loss when heating an object to be heated using a plurality of heating coils.SOLUTION: A first heating coil and a second heating coil, a first half-bridge circuit connected to one end side of the first heating coil, a second half-bridge circuit connected to one end side of the second heating coil, a third half-bridge circuit connected to the other end side of the first heating coil and the second heating coil, and a control device configured to drive the first half-bridge circuit and the second half-bridge circuit with a phase shift, the control device alternately executes, at a predetermined time ratio, a first mode in which the second half-bridge circuit and the third half-bridge circuit are controlled to be driven in the same phase, and a second mode in which the first half-bridge circuit and the third half-bridge circuit are controlled to be driven in the same phase.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an induction heating device and a program for the induction heating device. [Background technology]

[0002] Patent Document 1 describes an induction heating device that includes four heating coils, two auxiliary half-bridge circuits, and one reference half-bridge circuit, with one end of each heating coil selectively connected to one of the two auxiliary half-bridge circuits and the other end connected to the reference half-bridge circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6881958 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when multiple heating coils are used simultaneously in this induction heating device, a large current, the sum of the currents flowing through the multiple heating coils, flows through a single reference half-bridge circuit, resulting in a problem of large switching losses in this reference half-bridge circuit.

[0005] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide an induction heating device that can reduce switching loss when heating an object to be heated using multiple heating coils. [Means for solving the problem]

[0006] That is, the induction heating device of the present invention comprises a first heating coil and a second heating coil, a first half-bridge circuit connected to one end of the first heating coil, a second half-bridge circuit connected to one end of the second heating coil, a third half-bridge circuit connected to the other end of the first heating coil and the second heating coil, and a control device that drives the first half-bridge circuit and the second half-bridge circuit with a phase shift, and the control device alternates between a first mode in which the second half-bridge circuit and the third half-bridge circuit are controlled to be driven in the same phase, and a second mode in which the first half-bridge circuit and the third half-bridge circuit are controlled to be driven in the same phase, at a predetermined time ratio.

[0007] The induction heating device configured in this way alternates between a first mode in which the second heating coil is not driven and a second mode in which the first heating coil is not driven in a time-division manner to heat the object to be heated using two heating coils, so that the current flowing through the third half-bridge circuit can be made smaller than when these two heating coils are driven simultaneously, thereby reducing switching loss.In addition, because the first heating coil and the second heating coil are not driven simultaneously, there is no need to consider the generation of interference noise due to the frequency difference between these two heating coils, allowing for more freedom in designing the control mode.

[0008] It is desirable that the inverter further includes a third heating coil, one end of which is connected to the second half-bridge circuit, and a fourth half-bridge circuit, the other end of which is connected to the third heating coil, and the control device drives the third half-bridge circuit and the fourth half-bridge circuit with a phase shift, and the second mode controls the first half-bridge circuit and the third half-bridge circuit to be driven in the same phase, and controls the second half-bridge circuit and the fourth half-bridge circuit to be driven in the same phase. In an induction heating device configured in this manner, the second and third heating coils connected to the second half-bridge circuit are driven alternately, so the current flowing through the second half-bridge circuit is smaller than when they are driven simultaneously, thereby reducing switching loss. Also, because the third heating coil is provided between the second and fourth half-bridge circuits, the current flowing through each half-bridge circuit can be made more uniform than when the third heating coil is provided between the third and fourth half-bridge circuits (i.e., in parallel with the first and second heating coils), thereby reducing switching loss.

[0009] It is desirable that the power supply further includes a fourth heating coil, one end of which is connected to the first half-bridge circuit and the other end of which is connected to the fourth half-bridge circuit, and that the first mode controls the second half-bridge circuit and the third half-bridge circuit to operate in the same phase, and controls the first half-bridge circuit and the fourth half-bridge circuit to operate in the same phase. In an induction heating device configured in this manner, each half-bridge circuit is connected to one heating coil that operates in the first mode and one heating coil that operates in the second mode, so the current flowing through each half-bridge circuit can be made smaller and switching loss can be reduced compared to when two heating coils that are driven simultaneously are connected. Furthermore, by equalizing the power supplied to the two heating coils in each mode, the current flowing through the four half-bridge circuits can be made uniform, and the switching loss in each half-bridge circuit can also be made uniform.

[0010] As a control method for individually adjusting the power supplied from the first heating coil and the second heating coil to the heated object, it is desirable that the control device executes the first mode and the second mode at equal time ratios, and controls the power supplied to the first heating coil in the first mode and the power supplied to the second heating coil in the second mode to twice the target power supplied to each heating coil. Since the first mode and the second mode are executed in a time-division manner, even if powers of different drive frequencies are supplied to the heating coil 1 in each of these modes, the generation of resonance noise due to this can be prevented.

[0011] As another control method, it is desirable that the control device controls the power supplied to the first heating coil in the first mode and the power supplied to the second heating coil in the second mode to be the same, and executes the first mode and the second mode at a time ratio based on the ratio between the target power supplied to the first heating coil and the target power supplied to the second heating coil. In this case, for example, by setting the power supplied in each of the first and second modes to a constant value close to the maximum power limited by a breaker or the like, even if different target supply powers are supplied to each heating coil, the power supplied to each heating coil in both modes combined can be maximized within the power limit.

[0012] It is desirable that the control device controls the time ratio between the first mode and the second mode and the power supplied to each of the heating coils in each of the modes so that the amount of power input to the first heating coil and the amount of power input to the second heating coil are equal throughout the first mode and the second mode. In this case, the power supplied to the object to be heated from the first heating coil and the second heating coil can be made uniform, so that uneven heating is less likely to occur when, for example, one object to be heated is heated using these two heating coils.

[0013] It is preferable that the heating device further includes a connection switching unit that switches the half-bridge circuits connected to the heating coils. In this way, by switching the relay according to the position of the object to be heated, it is possible to equalize the current flowing through each half-bridge circuit regardless of the combination of multiple heating coils, thereby reducing overall switching losses.

[0014] It is desirable that the control device switches between the first mode and the second mode in accordance with the cycle of the voltage of the AC power supply connected to each of the half-bridge circuits. This can reduce the load on the semiconductor elements of each half-bridge circuit when switching modes.

[0015] The induction heating device program of the present invention is a program used in an induction heating device that includes a first heating coil and a second heating coil, a first half-bridge circuit connected to one end of the first heating coil, a second half-bridge circuit connected to one end of the second heating coil, a third half-bridge circuit connected to the other end of the first heating coil and the second heating coil, and a control device, and causes the control device to perform the function of alternately executing, at a predetermined time ratio, a first mode in which the first half-bridge circuit and the second half-bridge circuit are driven with a phase shift and the second half-bridge circuit is controlled to be driven in phase with the third half-bridge circuit, and a second mode in which the first half-bridge circuit and the third half-bridge circuit are controlled to be driven in phase with the first half-bridge circuit. According to such a program for an induction heating device, it is possible to achieve the same effects as those of the induction heating device described above. [Effects of the Invention]

[0016] According to the present invention configured as described above, it is possible to provide an induction heating device that can reduce switching loss when heating an object to be heated using a plurality of heating coils. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a usage mode of an induction heating device according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the overall configuration of the induction heating device according to the embodiment. [Figure 3] FIG. 2 is a schematic diagram showing the configuration of a half-bridge circuit in the embodiment. [Figure 4]FIG. 4 is an explanatory diagram illustrating a heating operation of the control device in the embodiment. [Figure 5] FIG. 2 is an explanatory diagram illustrating thermal power control of the control device in the embodiment. [Figure 6] 10A and 10B are explanatory diagrams illustrating other heating operations of the control device in the embodiment. [Figure 7] FIG. 10 is an explanatory diagram illustrating thermal power control of a control device in a second embodiment. [Figure 8] FIG. 10 is a schematic diagram showing the configuration of an inverter device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a first embodiment of an induction heating device according to the present invention will be described with reference to the drawings.

[0019] [First embodiment] 1. Overview The induction heating device according to this embodiment uses a plurality of heating coils to induction heat an object to be heated, such as a cooking pot, placed on a top plate.

[0020] 2.Device configuration 2-1. Overall structure Specifically, as shown in Figures 1 and 2, the induction heating device 100 includes a top plate P on which an object to be heated Q is placed, a plurality of heating coils 1 that induction heat the object to be heated Q, an inverter device 2 that supplies power to the heating coils 1, and a control device 3 that controls the inverter device 2.

[0021] Furthermore, the induction heating device 100 is equipped with a position detection sensor (not shown) that detects the position of the object to be heated Q placed on the top plate P, a current detection unit (not shown) that detects the current supplied to the inverter device 2, and a voltage detection unit (not shown) that detects the voltage supplied to the inverter device 2 from a commercial power source.

[0022] 2-2.Top plate P As shown in FIG. 1, the top plate P has a flat mounting surface on which an object to be heated Q is placed, and is a flat plate made of an electrically insulating material such as glass or ceramic.

[0023] 2-3. Heating coil 1 As shown in Figures 1 and 2, the heating coil 1 consists of one or more heating coils 1 provided on the back side of the top plate P. Herein, four heating coils 1 are provided. Hereinafter, when distinguishing between the four heating coils 1, they will be referred to as a first heating coil 11, a second heating coil 12, a third heating coil 13, and a fourth heating coil 14, respectively.

[0024] Here, four heating coils 1 are arranged in a row in the order of the first heating coil 11, the third heating coil 13, the second heating coil 12, and the fourth heating coil 14. Note that the number of heating coils 1 may be plural, and they may be arranged in a two-dimensional array or the like.

[0025] The heating coil 1 is in the form of a sheet provided on a substrate, specifically formed as a printed circuit board made of photoresist or the like. Here, each of the multiple heating coils 1 has the same shape and size, but the shape and size may be changed as appropriate. The heating coil 1 may also be formed by winding a litz wire.

[0026] 2-4. Inverter device 2 The inverter device 2 converts the voltage supplied from a commercial power source into high-frequency power and supplies high-frequency power to each heating coil 1. The inverter device 2 here includes four half-bridge circuits HB, two of which are combined to form a full-bridge inverter circuit.

[0027] As shown in Fig. 3, the half-bridge circuit HB is configured using two switching elements, such as IGBTs or MOS-FETs. A snubber capacitor is provided between the drain and source of each switching element to prevent damage to these switching elements due to the large current generated when the elements are off due to parasitic inductance. One end or the other end of the heating coil 1 is connected to an AC terminal provided between the two switching elements in the half-bridge circuit HB.

[0028] Of the four half-bridge circuits HB, the first half-bridge circuit HB1 and the second half-bridge circuit HB2 are connected to one end of the heating coil 1, and the third half-bridge circuit HB3 and the fourth half-bridge circuit HB4 are connected to the other end of the heating coil 1.

[0029] Each half-bridge circuit HB is connected to two heating coils 1. Specifically, as shown in Fig. 2, the first half-bridge circuit HB1 is connected to one end of the first heating coil 11 and the fourth heating coil 14, the second half-bridge circuit HB2 is connected to one end of the second heating coil 12 and the third heating coil 13, the third half-bridge circuit HB3 is connected to the other end of the first heating coil 11 and the second heating coil 12, and the fourth half-bridge circuit HB4 is connected to the other end of the third heating coil 13 and the fourth heating coil 14.

[0030] In this manner, in this embodiment, four different types of full-bridge inverter circuits are configured by combining two half-bridge circuits HB that sandwich each of the four heating coils 1. For example, one full-bridge inverter circuit is configured by the first half-bridge circuit HB1 and the third half-bridge circuit HB3 that sandwich the first heating coil 11.

[0031] Furthermore, the inverter device 2 has a connection switching unit 21 that switches between connection and disconnection between each heating coil 1 and the full-bridge inverter circuit corresponding to that heating coil 1. The connection switching unit 21 is provided for each heating coil 1.

[0032] 2-5.Control equipment 3 The control device 3 physically comprises a CPU, memory, input means, etc., and functionally controls each half-bridge circuit HB1 to HB4 and the connection switching unit 21 by the CPU and its peripheral devices working together in accordance with the program stored in the memory.

[0033] The control device 3 controls the power (supply power) supplied to each heating coil from the inverter device 2. More specifically, the control device 3 controls the power supply to each heating coil by transmitting a control signal that controls the on / off of a switching element in each half-bridge circuit to the inverter device 2 and controlling the driving of a full-bridge inverter circuit corresponding to each heating coil.

[0034] The control device 3 controls the drive frequency of the supplied power by, for example, a PFM (Pulse Frequency Modulation) control method. Note that the specific control method is not limited to the PFM control method, and may be a PWM (Pulse Width Modulation) control method or the like.

[0035] 3. Control by control device 3 The heating operation and heat power control executed by the control device 3 when the object to be heated is heated using four heating coils 1 will be described below.

[0036] 3-1.Heating operation 2, a case will be described in which two objects to be heated Q1 and Q2 are heated using the first heating coil 11 to the fourth heating coil 14. In this case, the control device 3 alternately executes, at a predetermined time ratio, a first mode in which power is supplied to the first heating coil 11 and the third heating coil 13 corresponding to the object to be heated Q1, and a second mode in which power is supplied to the second heating coil 12 and the fourth heating coil 14 corresponding to the object to be heated Q2.

[0037] The first and second modes will be described in more detail below. 5(1)(2), the control device 3 drives the first half-bridge circuit HB1 and the second half-bridge circuit HB2 with a phase shift, and drives the third half-bridge circuit HB3 and the fourth half-bridge circuit HB4 with a phase shift throughout the first and second modes. Here, phase shift means that there is a shift between the timing at which two switching elements included in one half-bridge circuit alternate between on and off and the timing at which two switching elements included in the other half-bridge circuit alternate between on and off.

[0038] Here, two half-bridge circuits (e.g., HB1 and HB2) are driven out of phase with each other (phase difference of approximately 180 degrees). The magnitude of the phase difference is not limited to this, as long as there is a phase difference. Furthermore, the phase difference between the first half-bridge circuit HB1 and the second half-bridge circuit HB2 may be different between the first mode and the second mode.

[0039] Then, in the first mode, the control device 3 controls the two half-bridge circuits HB2 and HB3 connected to the second heating coil 12 to operate in the same phase, and also controls the two half-bridge circuits HB1 and HB4 connected to the fourth heating coil 14 to operate in the same phase. In addition, in the second mode, the control device 3 controls the two half-bridge circuits HB1 and HB3 connected to the first heating coil 11 to operate in the same phase, and also controls the two half-bridge circuits HB2 and HB4 connected to the third heating coil 13 to operate in the same phase.

[0040] In each mode, the two half-bridge circuits HB connected to a specified heating coil 1 are driven in the same phase (phase difference = 0 degrees) so as not to generate a potential difference, thereby controlling so that no power is supplied to the specified heating coil 1.

[0041] In this way, when the object to be heated is heated using the first heating coil 11 to the fourth heating coil 14, in the first mode, power is supplied only to the first heating coil 11 and the third heating coil 13 out of the four heating coils 1, and in the second mode, power is supplied only to the second heating coil 12 and the fourth heating coil 14.

[0042] In order to reduce the load on the switching element due to mode switching, the switching between the first mode and the second mode is performed in accordance with the cycle of the voltage of the AC power supply.

[0043] 3-2. Fire control Next, the heat power control when performing the above-mentioned heating operation will be explained using an example in which two heated objects are placed as shown in Figure 2, one of which, Q1, is heated at 1500 W and the other, Q2, is heated at 1000 W (see setting condition 1 in Figure 5). In this case, the target supply power of the first heating coil 11 and the third heating coil 13 that heat the object to be heated Q1 is set to 750 W, respectively, so that the object to be heated Q1 can be heated evenly, and similarly, the target supply power of the second heating coil 12 and the fourth heating coil 14 that heat the object to be heated Q2 is set to 500 W, respectively. Here, the target supply power means the power to be supplied to each heating coil 1, which is set according to the heating power set for the object to be heated.

[0044] In order to supply the target supply power set in this manner, the control device 3 of this embodiment executes the first mode and the second mode at an equal time ratio (1:1), and supplies twice the target supply power to each heating coil 1 to the first heating coil 11 and the third heating coil 13 in the first mode, and to the second heating coil 12 and the fourth heating coil 14 in the second mode.

[0045] Here, as shown in FIG. 5, the first mode and the second mode are alternately executed at intervals of 50 msec, and the target supply power is supplied to each heating coil 1 by supplying 1500 W to each of the first heating coil 11 and the third heating coil 13 in the first mode, and 1000 W to each of the second heating coil 12 and the fourth heating coil 14 in the second mode.

[0046] In addition, when two heated objects Q1 and Q2 are heated with the same heating power, or when one heated object is heated using four heating coils 11 to 14, the control device 3 may control the time ratio between the first mode and the second mode and the power supplied to each heating coil 1 in each mode so that the amount of power input to each heating coil 1 is uniform throughout the first mode and the second mode.

[0047] 4. Evaluation of switching losses Here, in order to evaluate the magnitude of the switching loss of the inverter device 2 of the induction heating device 100 according to the present invention, the current flowing through each half-bridge circuit when the object to be heated is heated using four heating coils 1 under the above-described heating operation and set heating power (setting condition 1 in Figure 5) is calculated.

[0048] When heating an object using multiple heating coils, the total power supply Pin [W] is the sum of the power supplied to the multiple heating coils. If we assume that the impedance of each heating coil is the same, the following equation holds: Pin=n×I×R n: number of heating coils I: Square of (current flowing through each heating coil [A]) R: Coil resistance including the heated object [Ω]

[0049] Assuming that the total power supply Pin supplied to the heating coils through the first and second modes is 2500 W, the number of heating coils n is 4, and the coil resistance is 10 Ω, the current flowing through each heating coil 1 is calculated to be 7.9 A on average using the above formula. Since each half-bridge circuit is connected to both the heating coil driven in the first mode and the heating coil driven in the second mode, the current flowing through them is equally 15.8 A.

[0050] Also, even if the set heating power for each heated object is changed as in setting condition 2 in Figure 5, if the total supply power Pin is the same (here 2500 W), the current flowing to each half-bridge circuit will be the same (here 15.8 A).

[0051] 5.Effects In the induction heating device 100 configured in this manner, each half-bridge circuit HB1 to HB4 is connected to one heating coil 11, 13 driven in the first mode and one heating coil 12, 14 driven in the second mode, so the current flowing through each half-bridge circuit HB1 to HB4 can be made smaller than when two heating coils driven simultaneously are connected, thereby reducing switching losses.

[0052] Furthermore, because the power supplied to the two heating coils 1 is controlled uniformly in each mode, the current flowing through the four half-bridge circuits HB is uniform, and the switching loss in each half-bridge circuit HB is also uniform. This results in a uniform load on each half-bridge circuit HB, stabilizing the product lifespan.

[0053] Since the first mode and the second mode are executed in a time-division manner, even if powers of different drive frequencies are supplied to the heating coil 1 in each of these modes, the generation of resonance noise due to this can be prevented.

[0054] 6.Other heating operations The heating operation of the control device 3 when heating an object to be heated using three or less heating coils will be described below.

[0055] 6-1. Using three heating coils 6(i), a description will be given of a case where objects to be heated Q1 and Q2 are heated using the first heating coil 11 to the third heating coil 13. In this case, the control device 3 alternately executes a first mode in which power is supplied to the first heating coil 11 and the third heating coil 13 and a second mode in which power is supplied to the second heating coil 12 at a predetermined time ratio.

[0056] Specifically, the control device 3 controls the connection switching unit 21 to disconnect the first half-bridge circuit HB1 or the fourth half-bridge circuit HB4 from the fourth heating coil 14, and drives each half-bridge circuit in the same way as in the case where four heating coils are used as described above. As a result, the control device 3 supplies power only to the first heating coil 11 and the third heating coil 13 of the three heating coils 1 in the first mode, and supplies power only to the second heating coil 12 in the second mode.

[0057] By performing this heating operation, the two heating coils connected to the second half-bridge circuit HB2 and the third half-bridge circuit HB3 are driven alternately, so that the current flowing through the two half-bridge circuits is smaller than when they are driven simultaneously, thereby reducing switching losses.

[0058] 6-2. When using two heating coils 6(ii), a case will be described in which objects to be heated Q1 and Q2 are heated using a first heating coil 11 and a second heating coil 12. In this case, the control device 3 alternately executes a first mode in which power is supplied to the first heating coil 11 and a second mode in which power is supplied to the second heating coil 12 at a predetermined time ratio.

[0059] The control device 3 controls the connection switching unit 21 to disconnect the corresponding half-bridge circuits from the third heating coil 13 and the fourth heating coil 14, and drives the two half-bridge circuits HB1 and HB2 with a phase shift throughout the first and second modes. Furthermore, the control device 3 controls the two half-bridge circuits HB2 and HB3 to drive in phase in the first mode, and controls the two half-bridge circuits HB1 and HB3 to drive in phase in the second mode. As a result, the control device 3 supplies power only to the first heating coil 11 of the two heating coils 1 in the first mode, and only to the second heating coil 12 in the second mode.

[0060] By performing such a heating operation, the current flowing through the third half-bridge circuit HB3 can be made smaller than when the first heating coil 11 and the second heating coil 12 are driven simultaneously, thereby reducing switching loss.

[0061] [Second embodiment] The control device 3 of the second embodiment executes the first mode and the second mode described above at different time ratios. Specifically, the control device 3 here uniformly controls the power supplied to each heating coil 1 in each mode, and executes the first mode and the second mode at a predetermined time ratio based on the ratio between the target power supply to the heating coil in the first mode and the target power supply to the heating coil in the second mode.

[0062] When two heated objects are placed as shown in FIG. 2, one heated object Q1 is heated at 1500 W and the other heated object Q2 is heated at 1000 W (see setting condition 3 in FIG. 7), for example, the control device 3 controls the power supplied to each heating coil 1 in each mode to 1250 W, and executes the first mode and the second mode at a time ratio of 6:4.

[0063] Even when controlling the thermal power by adjusting the time ratio of each mode in this way, if the total power supply Pin is the same, the current flowing to each half-bridge circuit HB will be the same.

[0064] In this way, the total power supply Pin, which is the average of the two modes, can be maximized within the power limitations imposed by breakers, etc. For example, in the case where there is a power limit such that the breaker will trip if the total power supply Pin to the induction heating device 100 exceeds 2500 W, if an attempt is made to achieve the target power shown in setting condition 1 in Fig. 5 using the control method of the first embodiment, the total power supply Pin will exceed 3000 W in the first mode, causing the breaker to trip. In contrast, if the control method of the second embodiment is used to achieve the same target power (see setting condition 3 in Fig. 7), the total power supply Pin in each mode will not exceed 2500 W, and the breaker will not trip.

[0065] [Third embodiment] The connection switching unit 21 of the inverter device 2 according to the third embodiment switches the half-bridge circuits HB connected to each heating coil, as shown in Fig. 8. The control device 3 according to this embodiment identifies the position and size of the object to be heated placed on the top plate based on the output of the position detection sensor, and controls the connection switching unit 21 based on the position to switch the connection mode of the half-bridge circuits HB so that the object to be heated Q can be heated.

[0066] Specifically, when the control device 3 determines that two or more heating coils need to be used based on the position or size of the object to be heated, it switches the connection mode of the half-bridge circuit HB so that the object to be heated Q can be heated by the above-mentioned heating operation. As a result, several half-bridge circuits are each connected to two heating coils.

[0067] In this case, when a plurality of heating coils 1 are used, the current flowing through each half-bridge circuit can be made uniform regardless of the combination of the heating coils 1, thereby reducing the overall switching loss.

[0068] [Other embodiments]

[0069] The control device in each of the above embodiments controls the driving of the four half-bridge circuits to control the power supplied to the four heating coils, but the number of heating coils and the number of half-bridge circuits controlled by the control device are not limited to those described above. The control device may be one that controls the driving of at least three half-bridge circuits and controls the power supplied to the two heating coils. Specifically, when an object to be heated is heated using two heating coils connected to one half-bridge circuit, the control device may be one that alternately executes, at a predetermined time ratio, a first mode in which the two half-bridge circuits connected to one heating coil are driven in phase with each other, and a second mode in which the two half-bridge circuits connected to the other heating coil are driven in phase with each other.

[0070] The control device may execute a third mode between the first and second modes, in which the driving manner of each half-bridge circuit differs from the first and second modes. In the third mode, the control device may, for example, stop driving all half-bridge circuits or drive all half-bridge circuits with a phase shift.

[0071] The present invention may also be applied to a contactless power supply device that includes a power supply coil instead of a heating coil. In this case, too, it is sufficient that the drive of at least three half-bridge circuits is controlled and the power supplied to the two power supply coils is controlled in a time-division manner.

[0072] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0073] 100...Induction heating device 1. Heating coil 2. Inverter device HB: Half-bridge circuit 21 Connection switching unit 3. Control equipment P···Top plate Q ···The object being heated

Claims

1. a first heating coil and a second heating coil; a first half-bridge circuit connected to one end of the first heating coil; a second half-bridge circuit connected to one end of the second heating coil; a third half-bridge circuit connected to the other end of the first heating coil and the other end of the second heating coil; a control device that drives the first half-bridge circuit and the second half-bridge circuit with a phase difference, The control device alternately executes, at a predetermined time ratio, a first mode in which the second half-bridge circuit and the third half-bridge circuit are controlled to operate in the same phase, and a second mode in which the first half-bridge circuit and the third half-bridge circuit are controlled to operate in the same phase.

2. a third heating coil, one end of which is connected to the second half-bridge circuit; a fourth half-bridge circuit connected to the other end of the third heating coil, the control device drives the third half-bridge circuit and the fourth half-bridge circuit with a phase shift; 2. The induction heating device according to claim 1, wherein the second mode controls the first half-bridge circuit and the third half-bridge circuit to be driven in the same phase, and controls the second half-bridge circuit and the fourth half-bridge circuit to be driven in the same phase.

3. a fourth heating coil having one end connected to the first half-bridge circuit and the other end connected to the fourth half-bridge circuit; 3. The induction heating device according to claim 2, wherein the first mode controls the second half-bridge circuit and the third half-bridge circuit to be driven in the same phase, and controls the first half-bridge circuit and the fourth half-bridge circuit to be driven in the same phase.

4. 4. The induction heating device according to claim 1, wherein the control device executes the first mode and the second mode at equal time ratios, and controls the power supplied to the first heating coil in the first mode and the power supplied to the second heating coil in the second mode to be twice the target power supplied to each heating coil.

5. 4. The induction heating device according to claim 1, wherein the control device controls the power supplied to the first heating coil in the first mode and the power supplied to the second heating coil in the second mode to be the same, and executes the first mode and the second mode at a time ratio based on a ratio between a target power supply to the first heating coil and a target power supply to the second heating coil.

6. 4. The induction heating device according to claim 1, wherein the control device controls the time ratio between the first mode and the second mode and the power supplied to each of the heating coils in each of the modes so that the amount of power input to the first heating coil and the amount of power input to the second heating coil are equal throughout the first mode and the second mode.

7. The induction heating device according to claim 1 , further comprising a connection switching unit that switches half-bridge circuits connected to the heating coils.

8. The induction heating device according to claim 1 , wherein the control device switches between the first mode and the second mode in accordance with a cycle of a voltage of an AC power supply connected to each of the half-bridge circuits.

9. a first heating coil and a second heating coil; a first half-bridge circuit connected to one end of the first heating coil; a second half-bridge circuit connected to one end of the second heating coil; a third half-bridge circuit connected to the other end of the first heating coil and the other end of the second heating coil; A program used in an induction heating apparatus including a control device, A program for an induction heating device that causes the control device to perform the function of alternately executing, at a predetermined time ratio, a first mode in which the first half-bridge circuit and the second half-bridge circuit are driven with a phase shift and the second half-bridge circuit is controlled to be driven in the same phase, and a second mode in which the first half-bridge circuit and the third half-bridge circuit are controlled to be driven in the same phase.

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