KR101852609B1 - A induction heating cooker - Google Patents

Abstract

The present invention discloses an induction heating apparatus. Specifically, in the induction heating apparatus according to the embodiment of the present invention, the alternating current is applied to the heating target to be heated by the user, and the resonance frequency of the eddy current flowing through the magnetic field generated by the alternating current, And an inverter unit for heating the object to be heated by flowing an eddy current corresponding to the identified material of the object to be heated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a heating apparatus using induction heating, and more particularly, to an induction heating apparatus capable of heating both a magnetic body and a non-magnetic body.

Generally, induction heating is a method in which a resistance component of an induction coil in a heating device and a resistance component of a heating target react with each other to heat only the heating target. When a current flows through the induction coil, a magnetic field is formed around the induction coil. The eddy current flows through the heating target body by the resistance component and only the heating target is heated.

The energy efficiency of the electromagnetic induction heating apparatus using the induction heating method is about 90%, and the energy efficiency is 30 to 40% in the gas range, the high-light range and the hot plate. And it is spreading around large restaurants, hotels and the like because it is considerably superior to fire, has no danger of fire, and does not emit harmful gas.

However, there is a problem that such an induction heating apparatus is limited in heating depending on the material of the container used. Specifically, the direction of the swirling current generated by the induction heating device on the heating target when heating the heating target is opposite to the direction of the current flowing through the heating coil. Because of this, a repulsive force by magnetic force is generated between the pot and the heating coil. On the other hand, since the electromagnetic force also acts between the heating coil and the pot, when the pot is a magnetic body such as iron, a magnetic attractive force is generated between the heating coil and the pot. In a pot of a magnetic body, the attraction is larger than the repulsive force, so that the pot is attracted to the heating coil.

However, in the case of a non-magnetic body to be heated body made of aluminum, copper or the like, the attractive force does not work but only the repulsive force is applied. At this time, when the gravitational force of the adhered object becomes smaller than the repulsive force, there is a problem that the non-magnetic object to be heated has a pan float which is separated from the heating coil.

In addition, in the case of the induction heating apparatus for both the magnetic body and the non-magnetic body, there is a problem that the efficiency when heating the non-magnetic body is significantly lowered to 70% or less as compared with the magnetic body.

Further, at the time of power control of 600 W or less for the heating of the nonmagnetic material by using the heating device, the frequency for switching the inverter power device of the heating device becomes close to the resonance frequency, and the load is short-circuited so that the overcurrent flows, There is a problem that continuous control is impossible.

Korean Registered Patent No. 10-1472747 (December, 2014)

An embodiment of the present invention is to provide an induction heating device and an electromagnetic induction heating method for easily heating a magnetic body heating object and a non-magnetic body heating object using a resonance inverter provided with a plurality of resonance inverters.

An induction heating apparatus according to an embodiment of the present invention is characterized in that an alternating current is applied to a heating target to be heated by a user and a resonance frequency of an eddy current flowing through a magnetic field generated by the alternating current A container identifying unit for identifying the material of the object to be heated by checking; And an inverter unit for heating an object to be heated by flowing an eddy current corresponding to the identified material of the heating target.

The container discriminating unit can discriminate the material of the heating target by changing the minute current flowing in the heating target to a frequency form.

And the eddy current flowing in a bridging manner with the heating target is combined with an electrical impedance possessed by the heating target to generate a magnetic field having a specific resonant frequency. The container discriminating unit confirms the magnitude of the specific resonant frequency, Can be determined.

The container discriminating unit can discriminate the material of the heating target by showing that the resonance frequency of the material to be heated of the nonmagnetic material is higher than the resonance frequency of the heating target of the magnetic material by two times or more.

The inverter unit includes a first resonant inverter and a second resonant inverter connected in parallel with a power supply, wherein in the first resonant inverter and the second resonant inverter, a first loss reduction smoothing capacitor (Cs1) and a second loss reduction smoothing capacitor The loss reduction spanner capacitor Cs2 may be connected in parallel.

The inverter unit includes a first link resonance capacitor (C1) connected in series between the first resonance inverter and the second resonance inverter by varying the value of the series compensation capacitor according to the container material identified by the container discrimination unit, The phase angle of the current flowing through the two-link resonant capacitor C2 can be deformed.

The inverter unit controls the phase angle of the current flowing through the first link resonant capacitor C1 and the second link resonant capacitor C2 to a phase angle that flows a resonance current corresponding to twice the switching frequency, The heating body can be heated.

The inverter unit can continuously heat the non-magnetic body of the heating target body after heating the heating target body by changing the resonance frequency by replacing the series compensation capacitor.

According to the embodiment of the present invention, it is possible to easily confirm whether the object to be heated is a magnetic body or a non-magnetic body through the container discrimination unit of the induction heating apparatus. Further, by controlling the electric power to be heated according to the property of the heating target through the structure of the resonant inverter, the heating target can be efficiently heated.

1 is a schematic diagram of an induction heating apparatus according to an embodiment of the present invention
2 is a block diagram of a container identifying unit according to an embodiment of the present invention.
3 is a circuit diagram of the inverter unit according to the first embodiment of the present invention.
4 is a circuit diagram of the inverter unit according to the second embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described with reference to FIGS. 1 to 4. FIG. However, this is an exemplary embodiment only and the present invention is not limited thereto.

In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intention or custom of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

The technical idea of the present invention is determined by the claims, and the following embodiments are merely a means for effectively explaining the technical idea of the present invention to a person having ordinary skill in the art to which the present invention belongs.

In the following description, terms such as " transmission ", "transmission "," transmission ", "reception ", and the like, of a signal or information refer not only to the direct transmission of signals or information from one component to another But also through other components. In particular, "transmitting" or "transmitting" a signal or information to an element is indicative of the final destination of the signal or information and not a direct destination. This is the same for "reception" of a signal or information. Also, in this specification, the fact that two or more pieces of data or information are "related" means that when one piece of data (or information) is acquired, at least a part of the other data (or information) can be obtained based thereon.

1 is a configuration diagram of an induction heating apparatus according to an embodiment of the present invention.

Referring to FIG. 1, an induction heating apparatus 100 according to an embodiment of the present invention may include a power supply unit 102, a container determination unit 104, an inverter unit 106, and a switching driver unit 108.

The power supply unit 102 can supply power to the induction heating apparatus 100. Specifically, the power supply unit 102 may include a line filter for preventing malfunction of the induction heating apparatus 100 from external noise. The power supply unit 102 includes a low-pass filter. When the DC voltage is supplied from the power supply unit 102 to the induction heating apparatus 100, unnecessary portions are removed through low-pass filtering to the supplied DC voltage, .

The container discriminating unit 104 can confirm the material of the heating target to be heated in the induction heating apparatus 100. [ Specifically, the container identifying unit 104 can confirm the material of the target to be heated by checking the minute frequency of the signal that is output in response to the material of the target.

2 (a), the container determination unit 104 includes a sensor unit 112, a current generation unit 114, a micro current sensing unit 116, and a determination unit 118 .

The sensor unit 112 can confirm whether or not the object to be heated is placed on the induction heating apparatus 100. [ Specifically, the sensor unit 112 can confirm whether or not the heating target is placed in a heated position. The sensor unit 112 may include various sensors that can detect whether an object is placed, such as a sensing sensor, an ultrasonic sensor, an infrared sensor, a laser sensor, or the like.

The current generating unit 114 can generate a current to the heated body detected by the sensor unit 112. [ Specifically, the current generating unit 114 generates an eddy current after determining whether the detected heated object is a magnetic substance container or a non-magnetic substance container. For example, the current generating unit 114 may be formed of an exciting coil (exciting coil for generating a primary H field). The current generating unit 114 can generate a first magnetic field when an alternating current having a specific frequency is applied. Here, the alternating current is a current whose direction of current flow changes periodically with time, for example, a current having a waveform of a sine wave. That is, the current generating unit 114 generates the first magnetic field by applying the alternating current, and the generated first magnetic field is bridged with the heating target and the eddy current flows to the heating target. At this time, the eddy current flowing through the heating target is combined with the electrical impedance possessed by the heating target to generate a second magnetic field having a specific resonant frequency.

The micro-current sensing unit 116 may sense a micro-current flowing by the second magnetic field generated by the current generating unit 114. [ Specifically, the micro-current sensing unit 116 can flow a micro alternating current having a specific frequency in the micro-current sensing unit 116 while bridging the magnetic field generated by the current generating unit 114 and the heating target. For example, the microcurrent sensing unit 116 may be formed of a pickup coil.

Here, FIG. 2 (b) is an exemplary view showing the structure of the current generating unit 114 and the fine current sensing unit 116. Referring to Fig. 2 (b), the current generating unit 114 can generate an eddy current in the heating target. Specifically, the current generating section 114 generates a first magnetic field generated by applying an alternating current, and the generated first magnetic field can be linked with the heating target to generate an eddy current in the heating target. At this time, the micro-current sensing unit 116 can sense the micro-current of the second magnetic field generated through the eddy current generated in the heating target and the impedance of the heating target.

The determination unit 118 can determine the material of the heating target through the minute current flowing in the minute current sensing unit 116. Specifically, the determination unit 118 can determine the material of the heating target by checking the frequency of the minute current sensed by the minute current sensing unit 116. The determining unit 118 can determine whether the heated body is a magnetic body or a non-magnetic body according to the frequency of the micro current. For example, when the material to be heated is a non-magnetic material, the discrimination unit 118 uses the fact that the frequency is two to three times higher than that of the material of the object to be heated, Or not. This is because the resonance frequency of the magnetic body is slightly different from that of the nonmagnetic body so that even if the resonance frequency of the magnetic body and the nonmagnetic body are affected by the design of the current generation unit 114 and the microcurrent sensing unit 116, The material of the material to be heated can be accurately discriminated by using the property of the frequency to be checked according to the material of the material to be inspected.

The inverter unit 106 can heat the heating target by causing an eddy current to flow through the heating target. Specifically, the inverter unit 106 is provided with a working coil so that an eddy current matching the material can be flowed according to the material of the heating target determined by the container discriminating unit 104, thereby heating the heating target. A specific method by which the inverter unit 106 heats the heating target will be described later with reference to FIG. 3 and FIG.

The switching driver 108 can control the switching of the inverter unit 106. [ Specifically, the switching driver 108 can control the alternating operation of zero voltage switching (ZVS) provided in the inverter unit 106 through the switching control signal.

3 is a circuit diagram of an inverter unit according to an embodiment of the present invention.

As shown in FIG. 3, the inverter unit 106 according to an embodiment of the present invention includes a first resonant inverter INV1 and a second resonant inverter INV2. The first resonance inverter INV1 and the second resonance inverter INV2 may be connected in parallel with the power supply E. [

Specifically, the inverter unit 106 includes a first inductor L1, a first switching unit Q1, a first link resonance capacitor C1, and a first loss reduction snubber capacitor Cs1. The second inductor L2, the second switching unit Q2, the second link resonant capacitor C2 and the second loss reduction snubber capacitor Cs2, the series compensation capacitor Cc and the working coil L ). At this time, the first switching unit Q1 is composed of the first switch S1 and the first diode D1, and the second switching unit Q2 is composed of the second switch S2 and the second diode D2 . That is, the inverter unit 106 is formed of a time division high-frequency multi-resonance type soft switching inverter circuit.

The first resonator inverter INV1 includes a first inductor L1 and a first switching unit Q1 connected in series and a first inductor L1 and a first switching unit Q1, Resonant capacitors C1 are connected in parallel.

The second resonant inverter INV2 is formed by connecting a second inductor L2 and a second switching unit Q2 in series and a second inductor L2 and a second switching unit Q2 between the second inductor L2 and the second switching unit Q2, The resonance capacitor C2 is connected in parallel.

At this time, the first link resonant capacitor C1 of the first resonant inverter INV1 and the second link resonant capacitor C2 of the second resonant inverter INV2 are connected in series. The series compensation capacitor Cc and the working coil L are connected in series and connected between the first link resonant capacitor C1 and the second link resonant capacitor C2, 2 switching unit Q2 in parallel.

That is, the inverter unit 106 includes two inverters (specifically, the first resonance inverter INV1 and the second resonance inverter INV2) in the resonance type inverter, and each switching unit (specifically, the first switching unit The loss reduction snubber capacitors Cs1 and Cs2 are connected in parallel to the first switching unit Q1 and the second switching unit Q2 so that the heat loss can be reduced when the zero voltage soft switch is operated. The inverter unit 106 may be implemented with a phase shift PWM (pulse width modulation) technique through the above circuit configuration. Here, PWM technology refers to a technique of controlling the time when the switch is turned on and off. The inverter unit 106 is connected to a series compensation capacitor C 1 through a configuration in which a series compensation capacitor Cc and a working coil L are connected between a first link resonance capacitor C 1 and a second link resonance capacitor C 2 connected in series Cc) can be easily controlled according to the material (magnetic body or non-magnetic body) of the heating target.

The operation of the inverter unit 106 configured by the above circuit will be described in detail with reference to FIG.

4 is an exemplary diagram illustrating an operation of the inverter unit according to an embodiment of the present invention.

4, the inverter unit 106 varies the value of the series compensation capacitor Cc according to the material of the heating target, so that the first and second link resonant capacitors C1, And the phase angle of the current flowing through the capacitor C2 is changed. FIG. 4 (b) is a graph showing the operation waveform for each mode.

The inverter unit 106 can operate in a time division manner with the two resonance inverters INV1 and INV2 using the six modes shown in Fig. 4A as basic operations. The inverter unit 106 controls the phases of the currents flowing through the first link resonant capacitor C1 and the second link resonant capacitor C2 through the respective inverters to provide a resonance frequency corresponding to twice the switching frequency Current can flow. As a result, the inverter unit 106 can heat the heating target which is a non-magnetic material.

In the first mode of FIG. 4A, current flows in the direction of the DC power source as the series compensation capacitor Cc connected to the load is discharged before the gate signal of the first switching unit Q1 is applied.

In the second mode, the gate signal is applied and the first diode D1 of the first switching unit Q1 conducts, and the series compensation capacitor Cc starts to be charged by the load resonance current. As the series compensation capacitor Cc is charged, the inductor current iL is gradually reduced.

After the load resonance current is charged in the series compensation capacitor Cc, the current flowing in the first inductor L1 in the third mode is changed in the opposite direction to the current direction flowing in the first mode, and the first switch S1 is switched to the low Is turned on according to the control signal at zero voltage switching (ZVS) and zero current switching (ZCS) with switching loss. At this time, the series compensation capacitor Cc discharges.

In the fourth mode, the first switch unit Q1 is turned off according to the control signal, a current flows along the first loss reduction snubber capacitor Cs1, and the energy stored in the first inductor L1 decreases, And charged into the capacitor Cc. The voltage VQ1 across the switch gradually increases.

In the fifth mode, the discharge of the loss reduction snubber capacitor Cs1 is started and charges the series compensation capacitor Cc to the maximum.

In the sixth mode, the series compensation capacitor Cc and the first loss reduction snubber capacitor Cs1 are discharged. At this time, when the collector-emitter voltage (VQ1) of the switch is 0, it returns to the first mode. The second inverter INV2 also operates in the same mode as the first inverter INV1.

Referring to FIG. 4B, the gate voltage VG1 of the switch means one period from t1 to t6. That is, this period means the switching frequency.

In the waveform of the resonant load current (iR) below, t1 to t3 correspond to 1/2 of the t1 to t6 periods and signify the resonant frequency, which means twice the switching frequency. That is, the resonant frequency operates in a mode twice as high as the switching frequency. Soft switching is performed in mode 3 and mode 4, and the operation of the inverter cell in the frequency doubling mode in this condition suppresses the switching surge and reduces the switching loss in the high switching operation of the switch unit Q1. Zero voltage switching is achieved and the switching noise is suppressed and the EMI noise level can be lowered.

In Mode 3, the current through the first inductor L1 is changed in the opposite direction, so that the first switch S1 is switched between the zero voltage switching (ZVS) where the voltage across the switch is zero and the zero current switching (ZCS) The switching power loss of the switch is reduced.

In mode 4, the gate signal of the switch unit Q1 is turned off, and zero voltage switching (ZVS) is realized when the voltage across the switch VQ1 is zero. It can be seen that a total of three soft switching operations are performed with two ZVS and one ZCS.

The resonant frequency is changed according to the resistance value of the heating target and the resonant frequency is set to twice the switching frequency by selecting the series resonant capacitor Cc as a low value for the low resistance metal load. The phase angle can be adjusted from 90 to 180 degrees and the output can be adjusted up to 2.5 [kW].

For a metal load with a high resistance, a series resonant capacitor (Cc) having a high value is selected and the resonance frequency is set equal to the switching frequency. The phase angle can be adjusted from 0 to 180 degrees and the output can be adjusted up to 5 [kW]. This allows for wider frequency power regulation in two modes of operation that change the resonant frequency.

The inverter unit 106 can control the phase angle of the current through the above operation. Specifically, when the heating target is a magnetic body, the relationship between the resonant frequency f _r and the switching frequency f _sw can be confirmed through the following mathematical equations (1) to (5).

I _{R (Q1)} and i _{R (Q2)} flowing through the link resonant capacitors C1 and C2 are sinusoidal waves, respectively, and can be expressed by the following equations ₍₁₎ and ₍₂₎ , respectively.

[Equation 1]

&Quot; (2) "

는

과

의 위상각을 의미한다.here,

The

and

.

At this time, the resonance load current i _R can be expressed by the following equation (3).

&Quot; (3) "

At this _{time, f r = f out = f} sw, w = 2πf can, using the above equations (1) through (3) expressed by Equation (4) to the equation (3) because it is _sw.

&Quot; (4) "

에 대하여 정리하면, 하기의 수학식 5와 같이 나타낼 수 있다. Equation (4)

The following equation (5) can be obtained.

&Quot; (5) "

The resonance frequency f _r is designed to be equal to the switching frequency f _sw in the magnetic metal container having a high resistance value as shown in Equation (4). That is, the switching frequency is set equal to the resonance frequency (w = 2πf _sw ) where the value of the series compensation capacitor Cc is set higher than the non-magnetic body.

If the object to be heated is a non-magnetic material, the relationship between the resonance frequency f _r and the switching frequency f _sw can be confirmed by the following mathematical equations (6) to (10).

&Quot; (6) "

&Quot; (7) "

는

과

의 위상각을 의미한다.here,

The

and

.

At this time, the resonance load current i _R can be expressed by the following equation (8).

&Quot; (8) "

At this _{time, f r = f out = f} sw, w = 2πf can, using the equation (6) to 8 represented by the equation (9) to the equation (8), so _sw.

&Quot; (9) "

에 대하여 정리하면, 하기의 수학식 10과 같이 나타낼 수 있다. Equation (9)

The following equation (10) can be obtained.

&Quot; (10) "

A low-resistance non-magnetic metal container such as aluminum or copper has a resonance frequency f _r designed to be twice the switching frequency f _sw . The resonant frequency (w = 2πf _r ) is designed by setting the series compensation capacitor Cc lower than the magnetic body and set to a value twice the switching frequency (w = 2πf _sw ).

The inverter unit 106 changes the value of the series compensation capacitor Cc in the inverter unit 106 to change the resonance frequency when heating the heating target body which is a magnetic body and then heating the heating target body which is a nonmagnetic body . For example, in a case where the inverter unit 106 operates at 50 kHz (in this case, a series compensation capacitor Cc = 800 nF) in order to heat a heating target body as a magnetic body and then heats the heating target body which is a nonmagnetic body, The resonance frequency can be changed by changing the series compensation capacitor Cc, which is a variable capacitor, to 17 nF. The inverter unit 106 is operated by varying the series compensation capacitor Cc, thereby facilitating heating according to the material of the heating target.

In this way, the inverter unit 106 can reduce the switching power loss, increase the energy saving efficiency, and have a high power density. In addition, zero voltage switching is achieved, switching surge is suppressed, the EMI noise level is lowered in both modes of operation, and wider radio frequency power regulation is enabled.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. I will understand. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by equivalents to the appended claims, as well as the appended claims.

100: Induction heating device
102:
104:
106: Inverter section
108:
112:
114:
116: Micro current sensor
118:

Claims (8)

A container discrimination for confirming the material of the heating target body by applying an alternating current to a heating target to be heated by a user and confirming a resonant frequency of an eddy current flowing through a magnetic field generated by the alternating current, part; And
And an inverter unit for heating an object to be heated by flowing an eddy current corresponding to the identified material of the heating target,
Wherein the inverter unit includes a first resonant inverter and a second resonant inverter connected in parallel to a power source, the first resonant inverter and the second resonant inverter operate in a time-
The first resonant inverter includes a first inductor connected in parallel to the power source, a first inductor connected in series with the first inductor and connected in parallel with the power source, and a second inductor connected in parallel to both ends of the first inductor. 1 diode, a first loss reduction snubber capacitor connected in parallel at both ends of the first switching unit, and a first link resonance capacitor connected between the first inductor and the first switching unit, Including,
The second resonant inverter includes a second inductor connected in parallel to the power source, a second inductor connected in series with the second inductor and connected in parallel with the power source, and a second inductor connected in parallel at both ends of the second inductor. 2 diode, a second loss reduction snubber capacitor connected in parallel at both ends of the second switching unit, and a second loss reducing snubber capacitor connected between the second inductor and the second switching unit, And a second link resonant capacitor connected in series with the capacitor,
Wherein the inverter section further comprises a series compensation capacitor connected between the first link resonant capacitor and the second link resonant capacitor and a working coil connected in series with the series compensation capacitor.
The method according to claim 1,
The container determination unit may determine,
And changes the minute current flowing in the heating target body into a frequency form to discriminate the material of the heating target.
The method of claim 2,
An eddy current flowing in a state of being bridged with the object to be heated is combined with an electrical impedance possessed by the heating target to generate a magnetic field having a specific resonant frequency,
The container determination unit may determine,
And confirms the size of the specific resonance frequency to discriminate the material of the heating target.
The method of claim 3,
The container determination unit may determine,
Wherein the resonance frequency of the non-magnetic material body is higher than the resonance frequency of the material to be heated of the magnetic material by two or more times, thereby discriminating the material of the object to be heated.
delete The method according to claim 1,
The inverter unit includes:
A first link resonance capacitor (C1) and a second link resonance capacitor (C1) connected in series between the first resonance inverter and the second resonance inverter by varying a value of the series compensation capacitor according to the container material determined by the container discrimination unit To deform the phase angle of the current flowing in the second capacitor (C2).
The method of claim 6,
The inverter unit includes:
The phase of the current flowing through the first link resonant capacitor C1 and the second link resonant capacitor C2 is controlled to be a phase angle that flows a resonance current corresponding to twice the switching frequency to heat the object to be heated, Lt; / RTI >
The method of claim 6,
The inverter unit includes:
And the resonance frequency is changed by replacing the series compensation capacitor to continuously heat the heating target body which is a nonmagnetic body after heating the heating target body which is a magnetic body.

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