KR101659000B1 - Indution Heating Cooktop with a single inverter and Control Method thereof - Google Patents

Abstract

The present invention relates to an induction heating electric cooker having a single inverter, and more particularly, to a single inverter having at least two heating parts connected in series and regulating the resonance current supplied to the heating part using a single inverter This is about the induction heating electric cooker equipped.

A single inverter, a plurality of heating units, a series connection structure

Description

[0001] The present invention relates to an induction heating cooker having a single inverter,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating electric cooker having an inverter, and more particularly, to an induction heating electric cooker having a single inverter controlling a resonance current supplied to two or more heating parts using a single inverter .

Generally, an induction heating electric cooker causes a high frequency current to flow through a working coil or a heating coil, and when a strong magnetic force line generated by the induction heating coil passes through a cooking vessel, eddy current flows, Thereby performing the cooking function.

The basic heating principle of the induction heating electric cooker will be described as follows. When a current is applied to the heating coil, the cooking container, which is a magnetic body, generates heat by induction heating and the cooking container itself is heated by the generated heat, .

The inverter used in the induction heating electric cooker serves to switch the voltage applied to the heating coil so that a high frequency current flows through the heating coil. The inverter drives a switching element, typically an IGBT (Insulated Gate Bipolar Transistor), so that a high frequency current flows through the heating coil to form a high frequency magnetic field in the heating coil.

An inverter is connected in series with a switching element for switching an input power source, and a heating coil driven by an output voltage of the switching element is connected to a connection point of a switching element connected in series. The other side of the heating coil is connected to the resonance capacitor.

The driving of the switching element is performed by a driving unit, and the switching elements are alternately operated by the switching time outputted from the driving unit to apply a high frequency voltage to the heating coil. Since the on / off time of the switching element to be applied to the driving unit rotor is controlled to be gradually compensated, the voltage supplied to the heating coil changes from a low voltage to a high voltage.

When such induction heating electric cookers include two heating coils, two inverters are provided for switching a voltage applied to each coil to a high frequency so as to allow a high frequency current to flow through the respective heating coils.

As described above, the induction heating electric cooker according to the related art requires an inverter including an expensive semiconductor switching device, a high-powered passive device, and a driving circuit depending on the number of heating coils heating the cooking container. The unit price increases.

Further, in the conventional induction heating electric cooker having two or more inverters, when the two inverters are driven at different frequencies, the difference in output frequency is generally within the audible frequency, and the noise caused by the difference in frequency This makes the user uncomfortable.

The induction heating electric cooker having a single inverter according to the present invention is designed to provide a structure of a new heating coil for supplying a high frequency current to at least two heating coils by using a single inverter, We want to reduce the unit price.

In addition, the induction heating electric cooker having a single inverter according to the present invention provides a high frequency current to at least two heating coils by using a single inverter so as to prevent generation of noise due to difference in high frequency.

According to an aspect of the present invention, there is provided an induction heating type electric cooker having a single inverter, comprising: a power unit for converting an AC power into a DC power and outputting the DC power; An inverter unit for switching the DC power supply to provide an AC voltage; A plurality of heating units each having a series connection structure for heating a cooking vessel by receiving a high frequency current by the AC voltage to induce a vortex current; A current detector for detecting a DC link current outputted from the power supply unit and a resonance current supplied to the heating unit; And a control unit for outputting a control signal for controlling the heating unit and the inverter unit according to the set input and the detected current.

Wherein the induction heating electric cooker comprises: an inverter driving unit for controlling switching of the inverter according to the control signal; And a relay driver for controlling supply of current to the heating unit according to the control signal.

The heating unit includes: a relay for interrupting the supply of the high-frequency current according to the control signal; A heating coil connected in series to one end of the relay to form a high-frequency magnetic field by the high-frequency current; And a resonance capacitor connected in series with the heating coil to flow a resonance current to the heating coil.

The heating unit includes a first heating unit including a first relay, a first heating coil, and a first capacitor, and a second heating unit including a second relay, a second heating coil, and a second capacitor, And the second heating unit are connected in series.

Wherein the current detector comprises: a DC current detector for detecting a DC link current through a first current transformer formed between the power source and the inverter; And a resonance current detector for detecting a resonance current through a second current transformer formed between the inverter and the heating unit.

And the controller compares the detected DC link current with a reference current to control the inverter driver so that the DC link current does not exceed the reference current.

The controller compares the detected resonance current with the set input and controls the relay driver such that the DC link current does not exceed the reference current so that the resonance current does not exceed the set input.

8. The apparatus of claim 7, wherein the controller controls the relays so that the on / off frequencies of the first and second relays are the same when the setting inputs to the first and second heating units are identical.

Wherein the control unit controls the relay to control the on / off frequency of the first and second relays differently according to the respective setting inputs when the setting inputs to the first and second heating units are different from each other do.

The control unit controls the frequency of the output power of the single inverter to be higher than the resonance frequency determined by the heating coil and the resonance capacitor and the resonance frequency determined by the heating coil and the capacitor is higher than the audible frequency Do.

According to the above-described structure, the induction heating electric cooker having a single inverter according to the present invention has a coil structure capable of heating the heating coil by using a single inverter even though the heating coil has two or more heating coils. The manufacturing cost of the cooker can be reduced.

Further, since the induction heating electric cooker having a single inverter according to the present invention uses a single inverter, even when two or more heating coils are supplied with different high-frequency currents, noise caused by frequency differences is prevented.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a configuration and operation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 illustrates a configuration of an induction heating electric cooker having two heating units connected in series with a single inverter according to an embodiment of the present invention.

Referring to FIG. 1, an induction heating electric cooker having a single inverter according to an embodiment of the present invention includes a power supply unit 20 for converting AC power to DC power and outputting the AC power; A single inverter unit 30 for switching the DC power supply to provide an AC voltage; A plurality of heating units (100, 200) each having a series connection structure for heating a cooking vessel by receiving a high frequency current by the AC voltage to induce a vortex current; A current detector (500) for detecting a DC link current output from the power supply unit and a resonance current supplied to the heating unit; And a control unit 800 for outputting a control signal for controlling the heating unit and the inverter unit according to the set input and the detected current.

The induction heating electric cooker includes an inverter driving part (600) for controlling the switching of the inverter according to the control signal; And a relay driver 700 for controlling the supply of current to the heating unit according to the control signal.

The plurality of heating units include: relays (110, 210) for interrupting supply of the high-frequency current according to the control signal; A heating coil (120, 220) connected in series to one end of the relay to form a high-frequency magnetic field by the high-frequency current; And resonance capacitors 130 and 230 connected in series with the heating coil to flow a resonance current to the heating coil.

The heating unit includes a first heating unit 100 including a first relay 110, a first heating coil 120 and a first capacitor 130, a second heating unit 100 including a second relay 210, And a second heating unit 200 including a first capacitor 220 and a second capacitor 230. The first heating unit and the second heating unit may be formed in a series connection structure.

The current detector 500 includes: a DC current detector 510 for detecting a DC link current through a first current transformer CT1 formed between the power source and the inverter; And a resonance current detector 520 for detecting a resonance current through a second current transformer CT2 formed between the inverter and the heating unit.

The control unit 800 compares the detected DC link current with a reference current to control the inverter driving unit such that the DC link current does not exceed the reference current and also compares the detected resonance current with the setting input And controls the relay driver 700 such that the DC link current does not exceed the reference current so that the resonance current does not exceed the set input.

When the first and second heating units are simultaneously operated, the control unit 500 controls the relays so that the first and second relays have the same on / off frequency when the setting inputs for the first and second heating units are identical, The control unit controls the relays so that the on / off frequency of the first and second relays differs according to the respective setting inputs.

Here, when the first and second relays are in an off state, the first and second heating units may not supply the high-frequency current to the first and second heating coils, 1,2 Let it flow through detour.

The controller preferably has a higher output power frequency of the single inverter and a resonant frequency determined by the heating coil and the capacitor is higher than an audible frequency.

Fig. 2 is an equivalent circuit diagram of the inverter of the electric cooking apparatus of Fig. 1 in which the upper switching element is closed and the lower switching element is opened. Fig. 3 shows the upper switching element of the inverter of the electric cooker of Fig. Is an equivalent circuit diagram in a closed state.

Fig. 4 is a circuit diagram showing a state in which a high-frequency current is supplied only to the left first heating portion of two heating portions connected in series in the induction heating electric cooker of Fig. FIG. 6 is a circuit diagram showing a state in which a high-frequency current is supplied only to the second heating section on the right-hand side of FIG. Is supplied.

2 to 6, the operation of the induction heating electric cooker will be described in detail.

The inverter 30 is connected to the output terminal of the power supply unit 20 and includes two switching devices 31 and 32 connected in series and two capacitors 33 and 34 connected in parallel with each of the two switching devices . Generally, an IGBT (Insulated Gate Bipolar Transistor) is used as the switching element.

The induction heating electric cooker according to the present invention receives the AC power, and the power supply unit 30 rectifies and smoothes the received AC power to output DC power.

The inverter 30 controls the supply of the high frequency current to the first and second heating units 100 and 200 alternately through the upper and lower switching elements 31 and 32 in accordance with the driving signal of the inverter driving unit 600.

2, when the first and second heating units 100 and 200 are all operating and the upper switching unit 31 is turned on, the DC current output from the power unit is supplied to the upper switching unit 31, And flows sequentially through the first heating part 100 on the left side and the second heating part 200 on the right side. In this case, the lower switching element 32 is turned off.

4, when the upper switching element 31 is in the off state and the lower switching element 32 is in the on state, the lower switching element 32, the first relay 110, A first heating unit 100 composed of a heating coil 120 and a first resonant capacitor 130 and a second heating unit 100 composed of a second relay 210, a second heating coil 220 and a second resonant capacitor 230, The circuit formed by connecting the heating unit 200 in series forms an LC resonance tank circuit.

In this case, the first and second heating units 100 and 200 do not receive DC current from the power supply unit 20 but use the energy stored in the LC resonance circuit.

That is, the circuit formed by the first heating unit 100 and the second heating unit 200 connected in series with the upper switching element 31 turned on and the lower switching element 32 turned off has LC resonance The tank circuit receives the DC power supplied from the power supply unit 20 and stores the energy.

As described above, as the speeds at which the upper and lower switching elements 31 and 32 of the inverter alternately operate, the high frequency current flows to the first and second heating coils 120 and 220, and a high frequency magnetic flux is generated. The generated high frequency magnetic flux forms a swirling current in the cooking vessel to supply energy to the food inside the cooking vessel.

The capacitors 33 and 34 connected in parallel to the upper and lower switching elements 31 and 32 reduce the switching loss caused by the switching operation of the upper and lower switching elements.

The current detector 500 detects an input current using the current detector CT1 according to a control signal of the controller 800 and compares the input current with a preset reference current. Here, the reference current is determined such that the product of the reference voltage and the input voltage does not exceed the rated power.

The controller 800 performs overall control.

The controller 800 controls the inverter driving unit 600 to operate only one of the upper and lower switching elements 31 and 32 according to the detected current value and the cooking command, And outputs a switching control signal for controlling the first and second relays.

For example, as shown in FIG. 4, when only the first heating unit 100 is operated, the second relay 210 maintains the off state and the second current detection unit CT2 detects And controls the on-off switching of the first relay 110 according to the resonance current and the cooking command.

5, when only the second heating unit 200 is operated, the first relay 110 maintains the off state, and the resonance current detected by the second current detection element CT2 and the resonance current And controls on-off switching of the second relay 210 according to the cooking instruction.

6, when all of the first and second heating units 100 and 200 are operated, the resonance current detected by the second current detection device CT2 and the first and second relays 110, 210).

In this case, for example, when the heating degree of the first heating section 100 is different from that of the second heating section 200, that is, for example, the heating value of the first heating section is 1 [KW] 500 [W], the duty ratio of the control signals of the first and second relays may be controlled to be 2: 1. That is, the second heating unit 200 consumes 500 [W] of energy in the second heating coil 220, and the remaining 500 [W] of energy is returned to the power source through the second bypass.

The present invention as described above provides a structure of a heating coil so that two coils can be operated by one inverter. That is, the present invention proposes a topology in which two coils are operated by a single inverter to reduce the price of an inverter module in an induction heating (cooktop) cooker.

In the induction heating electric cooker according to the present invention, a method of driving two burners using one inverter is to control coil wiring according to conditions through relay switching. When only one heating coil is to be operated, it is possible to select any one of the heating coils to be operated by using the two first and second relays. When two heating coils are simultaneously operated, the first and second relays are turned on so that the first heating coil and the second heating coil are connected in parallel.

Each of the resonant circuits of the first and second heating units can maintain the impedance of each resonant circuit at a time when only one heating coil operates and when the two heating coils operate. If the impedance of the resonance circuit is similar, the frequency range to be controlled is reduced because the resonance frequency is similar during the vessel operation. Also, it is possible to reduce noise caused by sudden change. And since the two coils operate at the same frequency, no noise is produced in the coils.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the following claims And can be changed. However, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

1 shows a configuration of an induction heating electric cooker according to an embodiment of the present invention.

Fig. 2 is an equivalent circuit diagram in which the upper switching element of the inverter of the electric cooking appliance of Fig. 1 is closed and the lower switching element is opened. Fig.

Fig. 3 is an equivalent circuit diagram of an inverter of the electric cooker of Fig. 1 in which the upper switching element of the inverter is opened and the lower switching element is closed.

FIG. 4 is a circuit diagram showing a state in which a high-frequency current is supplied only to the left heating portion of the two heating portions connected in series in the induction heating electric cooker of FIG.

FIG. 5 is a circuit diagram of a state in which a high-frequency current is supplied to only the right heating unit of two heating units connected in series in the induction heating electric cooker of FIG.

FIG. 6 is a circuit diagram in which a high frequency current is supplied to each of two heating portions connected in series in the induction heating electric cooker of FIG. 1; FIG.

Claims (11)

A power supply unit for converting AC power into DC power and outputting the AC power; An inverter unit for switching the DC power supply to provide an AC voltage; A plurality of heating units each having a series connection structure for heating a cooking vessel by receiving a high frequency current by the AC voltage to induce a vortex current; A current detector for detecting a DC link current outputted from the power supply unit and a resonance current supplied to the heating unit; And a control unit for outputting a control signal for controlling the heating unit and the inverter unit according to the set input and the detected current, The heating unit includes: A relay for interrupting supply of the high-frequency current according to the control signal; A heating coil connected in series to one end of the relay to form a high-frequency magnetic field by the high-frequency current; And a resonance capacitor connected in series with the heating coil to flow a resonance current to the heating coil. The method according to claim 1, An inverter driving unit for controlling switching of the inverter unit according to the control signal; Further comprising a relay driver for controlling supply of current to the heating unit according to the control signal. delete The method according to claim 1, The heating unit includes: A first heating unit including a first relay, a first heating coil and a first capacitor, and a second heating unit including a second relay, a second heating coil and a second capacitor, wherein the first heating unit and the second heating Characterized in that the windings are connected in series. ≪ RTI ID = 0.0 > 1, < / RTI > The method according to claim 1, Wherein the current detector comprises: A DC current detector for detecting a DC link current through a first current transformer formed between the power unit and the inverter unit; And a resonant current detector for detecting a resonant current through a second current transformer formed between the inverter unit and the heating unit. 3. The method of claim 2, Wherein the controller compares the detected DC link current with a reference current to control the inverter driver so that the DC link current does not exceed the reference current. 5. The method of claim 4, Wherein the controller compares the detected resonance current with the set input to control the relay driver so that the DC link current does not exceed the reference current so that the resonance current does not exceed the set input. And an induction heating electric cooker. 8. The method of claim 7, Wherein the control unit controls the relays so that the on / off frequencies of the first and second relays are the same when the set inputs to the first and second heating units are identical. Electric cooker. 8. The method of claim 7, The control unit controls the relay to control the on / off frequency of the first and second relays differently according to the input set for each of the first and second heating units, And a single inverter connected to the induction heating cooker. The method according to claim 1, Wherein the control unit controls the frequency of the output power of the single inverter to be higher than a resonance frequency determined by the heating coil and the resonance capacitor. The method according to claim 1, Wherein the resonance frequency determined by the heating coil and the capacitor is higher than the audible frequency.

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