KR101515026B1 - Induction heater having multiple working coil - Google Patents

Abstract

An induction heater having multiple working coils of the invention includes a switch to turn on/off the power; a relay to connect respectively or simultaneously connect the input of switch to multiple outputs; a first working coil and a second working coil in parallel; and a control to determine the induction heating operation state of the first and second working coils in order to maintain induction heat only for a working coil performing normal induction heating by controlling the relay.

Description

TECHNICAL FIELD [0001] The present invention relates to an induction heating apparatus having a plurality of working coils,

The present invention relates to an induction heating apparatus having a plurality of working coils. More specifically, the present invention relates to an induction heating apparatus including a plurality of working coils selectively coupled to a line, And an induction heating apparatus configured to allow an induction heating operation by allowing connection.

The induction heating apparatus generates an eddy current in a container that flows a high-frequency current through a working coil to generate a high-frequency magnetic field in the working coil and magnetically couples with the working coil through the magnetic field. As a result, And heat the food to heat the food.

On the other hand, a recent induction heating apparatus evolves into a multiple-output type having a plurality of working coils. This will be described with reference to Fig. 1, the circuit and operation of a conventional multi-output induction heating cooker.

A plurality of inverters 10-1, 10-2, ... are connected in parallel to an AC power source.

The inverters 10-1, 10-2, ... have a bridge rectifier circuit 11 for rectifying input AC power to a DC power source, a filter inductor 12 for smoothing the DC power rectified rectified through the bridge rectifier circuit 11, An LC smoothing circuit 12 composed of a resonance capacitor Lf and a filter capacitor Cf and an LC resonance circuit 13 composed of an induction heating coil Lr and a resonance capacitor Cr for resonating an output voltage of the LC smoothing circuit 12 And first and second switches S1 and S2 that are switched according to a control signal input from the outside to supply power to the induction heating coil Lr so that the induction heating coil Lr can perform a heating operation.

The AC source of the conventional multi-output induction heating cooker having the above structure is connected to an AC source through a bridge rectifier circuit 11 provided in each of a plurality of inverters 10-1, 10-2, Is smoothed uniformly through the LC smoothing circuit 12 composed of the post-filter inductor Lf and the filter capacitor Cf.

At this time, when the second switch S2 is turned on according to the control signal and the output voltage of the LC smoothing circuit 12 is inputted to the LC resonance circuit 13, the current flowing in the induction heating coil Lr is resonated And the resonance capacitor Cr is charged.

When the second switch S2 is turned off according to the control signal and the first switch S1 is turned on at the same time, the charging energy of the resonant capacitor Cr is discharged and the induction heating coil Lr) in the opposite direction.

Therefore, if the charging / discharging operation is repeated at a frequency higher than the audible frequency, the electromagnetic induction effect due to the magnetic field generated from the induction heating coil Lr causes the heating container (not shown) on the heating plate Lt; / RTI >

However, in the induction heating cooker in this prior art, since the first and second switches are separately configured for each induction heating coil and the control operation is separately controlled by controlling the switching operation, a large load .

In addition, the inverter must be individually configured for each induction heating coil, so that the circuit design is complicated, costly, and requires a lot of space.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an induction heating apparatus capable of operating working coils using a minimum number of switching elements and a control unit even if a plurality of working coils are provided.

In addition, in a state in which a plurality of working coils are arranged adjacent to each other, it is automatically determined which of the working coils is located, and by selectively operating only the working coils, an optimum heating effect is obtained using a plurality of working coils I will.

In addition, even if an inexpensive switching element having a low withstand voltage is used, a high output heating operation exceeding the breakdown voltage of the switching element is desired.

According to an aspect of the present invention, there is provided an induction heating apparatus including a plurality of working coils, each of the plurality of working coils including a switching unit for turning on and off the application of current, a relay for connecting the input side connected to the switching unit, A first working coil and a second working coil each having one end connected to each output side of the relay unit and the other end connected to each other in parallel, and a switching unit for generating a high frequency current by turning the switching unit on and off at a high frequency, A high frequency current is separately applied to the first working coil and the second working coil to determine the induction heating operation state of each of the first working coil and the second working coil, The control unit controls the relay unit to maintain the induction heating.

The relay unit may include a first relay for selectively turning on and off the first working coil to the line, and a second relay for selectively turning on and off the second working coil to the line.

The apparatus may further include a sensing unit for outputting a measurement value corresponding to a current value flowing through the first working coil or the second working coil, wherein when the first working coil or the second working coil is driven, The induction heating operation state of the first working coil or the second working coil can be determined based on the measurement value output from the sensing unit.

The switching unit may further include a first capacitor and a second capacitor arranged in series between the power supply unit side and the GND side, wherein the switching unit includes a first switching device and a second switching device connected in series between the power supply side and the GND side, Wherein the relay unit is coupled to the connection point of the first switching device and the second switching device and the connection point of the first working coil and the second working coil is connected to the connection point of the first capacitor and the second capacitor, And the control unit may alternately turn on and off the first switching device and the second switching device.

A second relay unit connected to the switching unit and the input side in common to connect the input side connected to the switching unit to a plurality of output sides respectively, A first sensing unit connected to each output side of the first and second working coils and configured to output a measured value corresponding to a current value flowing through the third working coil and the fourth working coil and the first working coil or the second working coil, And a second sensing unit for outputting a measured value corresponding to a current value flowing through the second working coil or the fourth working coil, wherein the control unit switches the switching unit and the second switching unit independently or simultaneously to a high frequency, To 4 < th > relays are selectively turned on, and at this time, based on measured values from the first sensing unit or the second sensing unit, the induction of each of the first to fourth working coils The induction heating can be maintained by judging the heating operation state and controlling the relay unit or the second relay unit only with respect to the working coil in which induction heating is normally performed.

Also, the connection point of the switching unit and the relay unit and the connection point of the second switching unit and the second relay unit may be coupled to each other, and the controller may switch the switching unit and the second switching unit on and off at the same time.

The control unit may further include a third relay unit for interrupting a connection between the switching unit and the relay unit and the connection point between the second switching unit and the second relay unit, (1) when one or both of the first working coil and the second working coil are driven, or (2) when the third working coil and the fourth working coil are to be driven, The high frequency current through the switching unit and the high frequency current through the second switching unit may be coupled to a specific working coil.

The induction heating apparatus having a plurality of working coils according to the present invention can operate the working coils using a minimum number of switching elements and a control unit even if a plurality of working coils are provided.

Further, in a state in which a plurality of working coils are arranged adjacent to each other, it is automatically determined which of the working coils is located, and an optimum heating effect can be obtained by selectively operating only the working coils.

Further, even if an inexpensive switching element having a low withstand voltage is used, a high output heating operation exceeding the breakdown voltage of the switching element can be achieved.

1 is a view for explaining a circuit and an operation of a conventional multi-output induction heating cooker.
2 is a view showing an arrangement of a working coil in an induction heating apparatus having a plurality of working coils according to an embodiment of the present invention.
3 is a block diagram for explaining a configuration of an induction heating apparatus having a plurality of working coils according to an embodiment of the present invention.
4 shows a circuit diagram implementing an induction heating apparatus according to an embodiment of the present invention.
5 is a block diagram for explaining a configuration of an induction heating apparatus having a plurality of working coils according to another embodiment of the present invention.
Fig. 6 shows a circuit diagram implementing the induction heating apparatus shown in Fig.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of an induction heating apparatus having a plurality of working coils according to the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the technical scope of the present invention. Will be.

2 is a view showing an arrangement of a working coil in an induction heating apparatus having a plurality of working coils according to an embodiment of the present invention. The figure conceptually shows a top view of the arrangement of induction heating coils (i.e., working coils) in an induction heating apparatus A having a plurality of working coils.

That is, the large working coil WC5 on the right side of the drawing can operate alone, and the container will be located inside the circular shape of the working coil WC5.

On the other hand, four working coils (WC1, WC2, WC3 and WC4) are disposed adjacent to the left side of the drawing, and are hereinafter referred to as a freezone (F). In this freezone, when a container of any size is placed, the container is placed on one or more working coils, and a working coil located at the bottom of the container is automatically configured to sense and operate the container to heat the container. That is, the container can be inductively heated at any position in the freezer.

If the user performs the heating operation of the freezer in a state where the container is placed so as to cover the working coil WC2 and the working coil WC3, only the working coils WC2 and WC3 on which the container is placed will be operated to perform induction heating, The other two working coils without the container will not operate.

Fig. 3 illustrates a configuration of an induction heating apparatus according to an embodiment of the present invention, which includes a plurality of working coils as described with reference to Fig. 2 and can selectively operate a working coil on which the container is placed Fig.

Referring to the drawings, an induction heating apparatus having a plurality of working coils according to an embodiment of the present invention includes a power source unit 10, a switching unit 20, a relay unit 30, a first working coil 41, a second working coil 42, a sensing unit 50, and a control unit 60.

The power supply unit 10 receives the AC power supplied from the commercial power supply, rectifies the generated AC power, and generates DC power. The generated DC power may be supplied to coils (for example, first and / or second working coils) that perform induction heating by intermittent operation of the switching unit 20. [

The switching unit 20 includes a switching element that is turned on and off corresponding to an input switching signal. The switching element may include an IGBT having a high withstand voltage and a high operating speed so that the DC power from the power supply section 10 can be applied to the working coil by turning on and off with a high frequency equal to or higher than an audible frequency.

The switching element may operate in response to a high-frequency switching signal provided by the control unit 60, which will be described later, but the switching unit 20 may include a special high-frequency switching element (not shown) The switching element may be controlled to have high frequency on-off.

The relay unit 30 may include one input side and a plurality of output sides and is configured to connect the input side to one or a plurality of output sides corresponding to input control signals.

If the relay unit 30 turns on the output side of the first working coil 41 and turns off the output side of the second working coil 42 the high frequency current from the switching unit 20 flows through the first working coil 41, Will only be authorized for. If the relay part simultaneously connects the two output lines to the input side, the high frequency current will be divided and applied to the first working coil and the second working coil simultaneously.

One end of each of the first and second working coils 41 and 42 is connected to the relay unit 30 and the other ends of the first and second working coils 41 and 42 are connected in parallel.

The first working coil 41 and the second working coil 42 may have the same size so as to have the same output, but may have different sizes.

The sensing unit 50 is disposed between the connection point of the other end of the first and second working coils and the ground, and senses a resonant current flowing by an arbitrary working coil. The sensing unit 50 may sense a current to output a specific measured value, and the measured value may be input to the controller 60. [

By arranging the sensing unit 50 between the connection point of the first working coil 41 and the second working coil 42 and the ground, it is possible to detect the current flowing through each of the two working coils with only one sensing unit .

The sensing unit 50 generates a small current proportional to the resonance current of the working coil which is a large value, inputs the generated small current directly to the control unit, or generates another signal corresponding to the value of the generated current (for example, A voltage value or a digital level) to the control unit 60.

The control unit 60 turns on and off a specific switching element of the switching unit 20 with a high frequency to apply a high frequency current to the working coil side. Further, when the switching unit 20 includes a high-frequency switching device, the operation of the high-frequency switching device is controlled.

The control unit 60 may control the relay unit 30 to selectively turn on either or both of the first and second working coils 41 and 42. [

In this configuration, when an operation of the induction heating device is requested by the user, the control unit 60 applies a high-frequency current to one of the working coils, refers to the measurement values provided by the sensing unit 50, Check the heating operation status. The working coil in which induction heating normally occurs can be regarded as having a container. The control unit 60 selectively controls the relays connected to the working coil in which the current resonance occurs normally and induction heating is performed so that the high frequency current is applied only by the corresponding working coil to perform induction heating. At this time, the working coil where the container is placed may be one or plural.

In the induction heating apparatus having a plurality of working coils having such a configuration, the first working coil 41 and the second working coil 42 are arranged adjacent to each other to constitute the freezer zone F, The control unit 60 can automatically select the working coil corresponding to the position where the container is placed and can heat the container by driving only the working coil.

If the number of working coils connected in parallel to the relay unit 30 is not more than two but three or more are connected in parallel and the coupling of each working coil is controlled, There will be. Further, when the size of each working coil is downsized and arranged closely in four directions, the freezer can be configured in various forms, and heating can be efficiently performed without being restricted by the bottom shape of the container.

4 is a schematic circuit diagram of an induction heating apparatus according to an embodiment of the present invention configured to operate in a current resonance manner.

The induction heating apparatus according to the present invention can drive each working coil by a half bridge current resonance method by connecting two switching elements in series. To this end, a first switching device 21 and a second switching device 22 are arranged in series between the power supply section 10 side providing the driving current and the ground (or GND) A first capacitor 81 and a second capacitor 82 which are arranged in series between the ground and the ground are disposed and the input side of the relay unit 30 is connected to the connection point of the first switching device 21 and the second switching device 22 And the other end side of the working coils is coupled to the connection point of the first capacitor 81 and the second capacitor 82. The sensing unit 50 may be disposed between the working coil and the connection point of the capacitors.

When the control unit 60 alternately turns on and off the first switching device 21 and the second switching device 22, current resonance occurs in the working coils.

The relay unit 30 includes a first relay 31 for turning on and off the first working coil 41 to a line (a line connected to the switch unit), and a second relay 31 for turning on and off the second working coil 42 to the line And a second relay 32 which turns on and off.

The first relay 31 and the second relay 32 may have one input side connected to the switching unit 20 and one output side connected to one end of the working coil and the other one connected to the switching unit 20 .

The commercial AC power (AC) is input to the power supply unit (10).

The DC power that is rectified and output by the power supply unit 10 is grounded via the first switching device 21 and the second switching device 22 and is also connected to the first capacitor 81 and the second capacitor 82 To ground.

A connection point of the input ends of the first relay 31 and the second relay 32 is coupled to a connection point of the first switching device 21 and the second switching device 22. [ A first working coil 41 is connected in series to the first relay 31 and a second working coil 42 is connected in series to the second relay 32. [

The connection point of the other ends of the first and second working coils 41 and 42 is coupled to one end of the sensing unit 50 and the other end of the sensing unit 50 is connected to the first capacitor 81 and the second And is coupled to the connection point of the capacitor 82.

In this configuration, when the control section 60 turns on the first relay 31 and / or the second relay 32 and alternately switches the first switching device 21 and the second switching device 22 at high speed, High frequency direct current is alternately applied in forward and reverse directions to the selected working coil to perform induction heating.

That is, when the first relay 31 is turned on and the second relay 32 is turned off, when the first switching element 21 is turned on, the current flows through the first switching element to the first relay 31 When the second switching device 22 is turned on, the current flows through the first capacitor → the sensing part → the first working coil → the first relay → the second switching device To the ground.

The measured value of the sensing unit 50 is provided to the controller so that the controller 60 can sense which working coil is normally heating the vessel.

5 is a block diagram for explaining a configuration of an induction heating apparatus having a plurality of working coils according to another embodiment of the present invention. A first switching unit 210 for applying a high frequency current to the first working coil unit 410 and a second switching unit 220 for applying a high frequency current to the second working coil unit 420 So that the current applied from the first switching unit 210 and the current applied from the second switching unit 220 can be added together.

The DC power generated by the power supply unit 10 may be simultaneously supplied to the first switching unit 210 and the second switching unit 220 configured in parallel.

The first switching unit 210 turns on and off according to the high-frequency switching signal provided by the controller 60 to convert the DC power into a high-frequency current.

The first relay unit 310 can control the application of the high frequency current to the first working coil unit 410 by controlling ON or OFF of the line of the first working coil unit 410.

The first working coil portion 410 may include one or more working coils. That is, as shown in FIG. 3, the first relay unit 310 may include a plurality of output terminals that can be connected to an input terminal, and one end of one or more working coils may be coupled to each output terminal.

The other end of one or more working coils of the first working coil part 410 is connected to the ground through the first sensing part 510.

The first sensing unit 510 senses a resonant current flowing through the first working coil part 410. At this time, since the resonance current is a current having a very large value, the first sensing unit 510 may generate a small current proportional to the resonance current and transmit it to the control unit, or may output a voltage value proportional to the resonance current.

The second switching unit 220, the second relay unit 320, the second working coil unit 420, and the second sensing unit 520 are the same as those described above.

Here, the first working coil portion 410 and the second working coil portion 420 may be disposed adjacent to each other to form a freeze zone F.

The third relay unit 70 selectively connects the output terminal of the first switching unit 210 and the output terminal of the second switching unit 220. When the third relay unit 70 connects the output terminal of the first switching unit 210 and the output terminal of the second switching unit 220, the first switching unit 210 and the second switching unit 220 Connected in parallel.

The control unit 60 can control the first switching unit 210 and the second switching unit 220 on and off at the same timing. In this configuration, when execution of the induction heating by the user is requested, the control unit first performs a procedure for checking which working coil the container is located.

First, the first relaying unit 310 is controlled to connect the first working coil unit 410 to the line, and the first switching unit 210 is operated to apply a high-frequency current to the first working coil unit 410 . At this time, the resonance current is checked through the first sensing unit 510 to determine whether induction heating is normally performed.

Subsequently, the first relay unit 310 is turned off, the second relay unit 320 is controlled to connect the second working coil unit 420 to the line, and the second switching unit 220 is operated, A high frequency current is applied to the coil portion 420. Then, the resonance current is checked through the second sensing unit 520 to determine whether induction heating is normally performed.

After checking whether all of the working coils are operated, the control unit 60 applies induction heating by applying a high frequency current only to the working coils normally undergoing induction heating.

On the other hand, when the container is located in only one of the first walking coil portion 410 and the second walking coil portion 420 and only one of the working coils is operated, the third relay portion 70 is turned on, 1 switching unit 210 and the second switching unit 220 are configured in parallel. At this time, the relay part of the part of the working coil not operated is controlled to be OFF.

When the first switching unit 210 and the second switching unit 220 are configured in parallel, the high-frequency current generated by the first switching unit 210 and the high-frequency current generated by the second switching unit 220 are supplied to either one of the working coils, Frequency currents are applied in combination with each other, so that a maximum of twice as much current can be applied as compared with the case of using one switching unit. This has the effect of improving the output of the working coil part. Such an operation method is hereinafter referred to as a " power boost ".

6 is a circuit diagram illustrating the induction heating apparatus shown in Fig. The illustrated circuit diagram is constituted by a first switching device 21 and a second switching device 22 which are connected in series between a side of a power supply unit 10 providing a current and a ground GND side of the first switching unit 210 And the second switching unit 220 includes the third switching device 23 and the fourth switching device 24 connected in series between the power source 10 side and the ground side.

A first capacitor 81 and a second capacitor 82 and a third capacitor 83 and a fourth capacitor 84 are disposed in series between the power source 10 side and the ground side.

The pair of the first relay 31 and the first working coil 41 and the pair of the second relay 32 and the second working coil 42 are connected in parallel to each other, 2 switching element 22 and the connection point of the first capacitor 81 and the second capacitor 82. In addition,

The first sensing unit 510 may be disposed between a connection point of the other ends of the first and second working coils and a connection point of the first capacitor 81 and the second capacitor 82.

The second switching unit 220, the second relay unit 320, the second working coil unit 420, the second sensing unit 520, the third capacitor 83 and the fourth capacitor 84, May be configured to be symmetrical with the above configuration.

The third relay unit 70 includes a fifth relay 75 that interrupts the connection between the first switching unit 210 and the first relay unit 310 and a fifth relay unit 75 that interrupts the connection between the second switching unit 220 and the second relay unit 310. [ And a sixth relay (76) for interrupting the connection of the part (320).

The contacts of the fifth relay 75 and the contacts of the sixth relay 76 can be connected to each other as shown in FIG. In this configuration, when the first working coil 41 and / or the second working coil 42 are to be driven by controlling the fifth relay and the sixth relay, The high frequency driving current and the high frequency driving current applied through the second switching unit 220 can be simultaneously applied to the first working coil and / or the second working coil.

That is, when the contacts of the fifth relay 75 and the sixth relay 76 are selected in the manner shown in FIG. 6, the power boost does not operate. If any one of the contacts is moved, the power boost operates State.

The detailed operation is as follows. The control unit 60 selects the contact point a of the fifth relay 75 and selects the contact point a of the first relay point 31 in order to drive only the first working coil 41 And selects the contact (b) of the second relay (32). Further, the contact (a) of the third relay 33 and the fourth relay 34 is selected.

In this connection, the first working coil 41 is subjected to induction heating by the high-frequency driving current through the first switching device 21 and the second switching device 22.

At this time, when the contact b of the sixth relay 76 is selected, the high-frequency driving current by the third switching device 23 and the fourth switching device 24 is transmitted through the fifth relay 75 to the first So that it can be applied to the working coil 41.

That is, when the first switching device 21 is turned on, the driving current from the third switching device 23 is superimposed on the working coil. When the second switching device 22 is turned on, the fourth switching device 24, The driving current from the driving coil will be superimposed on the working coil.

When the driving currents are simultaneously supplied from the two switching elements, the first working coil 41 is boosted to perform stronger induction heating.

Such a power boost is possible because the induction heating system according to the present invention is a current resonance system. That is, since the voltage is maintained and induction heating is generated by switching the current, the amount of current can be improved as the switching elements are connected in parallel.

Further, even if a switching device having a low withstand voltage against an applicable high-frequency driving current is used, a driving current higher than the breakdown voltage of each switching device can be applied to a specific working coil by configuring the switching devices in parallel.

The operation of the induction heating apparatus according to the present invention is as follows.

The first to fourth working coils may be arranged in various ways to constitute a freezone. For example, they may be arranged in a row as shown in FIG. 1, or may be arranged in a concentrated manner in all directions. First, the user puts an arbitrary container in an arbitrary position of the freezer and executes the operation of the induction heating apparatus.

Then, the control unit controls the relays to apply the driving current only to the first working coil, and judges whether induction heating is normally performed through the sensing unit.

Subsequently, the control unit drives only the second working coil and judges whether or not the induction heating is normally operated. In addition, the control unit sequentially monitors the operation of the third working coil and the fourth working coil. At this time, it is preferable to control the fifth relay and the sixth relay so that the power boost does not operate in the above determination operation.

After determining whether or not the induction heating operation is performed on all the working coils, it is possible to recognize which of the working coils the container is located. If the container is located in the first working coil and / or the second working coil (case 1), it is possible to drive the corresponding one or both of the working coils to control the heating of the container. In this case, the fifth relay and the sixth relay can be controlled to activate the power boost. That is, by controlling the fifth relay and the sixth relay to implement the state in which the first and second switching elements and the third and fourth switching elements are connected in parallel, a specific working coil (the first working coil and / It is possible to apply the boosted driving current to the working coil.

If the container is positioned over the second working coil and the third working coil (Case 2), the second working coil is driven by the driving current by the first and second switching elements, The third working coil is driven by the driving current by the fourth switching element, so that the induction heating can be performed with the same output as the case 1 described above.

When the container is placed in the third and / or fourth working coils (Case 3), as in Case 1, one or both of the third and fourth working coils can be driven There will be.

The embodiments of the present invention described above are merely illustrative of the technical idea of the present invention, and the scope of protection of the present invention should be interpreted according to the claims. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. It should be interpreted that it is included in the scope of right.

Claims (7)

A switching unit including a first switching device and a second switching device connected in series between the power supply part and the GND,
A first capacitor and a second capacitor arranged in series between the power supply unit and the GND,
A first working coil and a second working coil connected in parallel to each other so that one end thereof is connected to a connection point of the first capacitor and the second capacitor,
And a second relay whose output side is connected to the connection point of the first switching element and the second switching element and whose output side is connected to the other end of the first working coil and whose output side is connected to the other end of the second working coil, part,
The switching unit is turned on and off at a high frequency to generate a high frequency current and the relay unit is controlled to apply a high frequency current individually to the first and second working coils, And a control unit for judging respective induction heating operation states of the coils and controlling the relay unit only for working coils normally performing induction heating to maintain induction heating. delete The method according to claim 1,
And a sensing unit for outputting a measurement value corresponding to a current value flowing through the first working coil or the second working coil,
The control unit determines the induction heating operation state of the first working coil or the second working coil based on the measured value output from the sensing unit when the first working coil or the second working coil is driven And a plurality of working coils. delete A first switching unit that is connected to the power supply unit on the input side to receive the current and turns on and off the output of the current on the output side,
A first relay unit having an input side connected to the output side of the first switching unit and connecting the currents applied from the first switching unit to a plurality of output sides, respectively,
A first working coil and a second working coil, each having one end connected to each output side of the first relay unit and the other end commonly connected and configured in parallel,
A first sensing unit for outputting a measurement value corresponding to a current value flowing through the first working coil or the second working coil,
A second switching unit connected in common with the first switching unit to receive an electric current from the power source unit and to turn on and off the output of the electric current at the output side,
A second relay unit connected to an output side of the second switching unit to connect the current applied from the second switching unit to a plurality of output sides, respectively,
A third working coil and a fourth working coil having one ends connected to the respective output sides of the second relay unit and the other ends connected in common,
A second sensing unit for outputting a measurement value corresponding to a current value flowing through the third working coil or the fourth working coil,
Wherein the first switching unit and the second switching unit are switched independently or simultaneously at a high frequency and a high frequency switching current is selectively applied to the first to fourth working coils, Heating operation state of each of the first to fourth working coils based on the measured values from the first and second working units, and controls the first relay unit or the second relay unit only for the working coil in which induction heating is normally performed And a control unit for maintaining the induction heating. 6. The method of claim 5,
A connection point between the first switching unit and the first relay unit and a connection point between the second switching unit and the second relay unit,
Wherein the controller controls the first switching unit and the second switching unit on and off at the same time. The method according to claim 6,
Further comprising a third relay unit for interrupting a connection between a connection point of the first switching unit and the first relay unit and a connection point of the second switching unit and the second relay unit,
The control unit is configured to (1) drive one or both of the first working coil and the second working coil and not drive the remaining working coils, or (2) operate either one of the third working coil and the fourth working coil The first relay is turned on and the high-frequency current through the first switching unit and the high-frequency current through the second switching unit are coupled to the working coil to drive the second relay, And a plurality of working coils for applying the working coils.

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