KR102292255B1 - Induction heat cooking apparatus and the driving module thereof - Google Patents

Abstract

A driving module according to an embodiment of the present invention is a driving module for supplying power to a load, the driving module comprising: an inverter generating power according to a switching duty of a switching element turned on and off according to a driving frequency; and an extension unit for flowing an auxiliary current to the inverter to ensure ZVS of the switching element. Therefore, through the above solution, when a plurality of cooking utensils are included, it is possible to control the output by varying the duty while keeping the driving frequencies of the two cooking utensils the same, thereby reducing noise. In addition, by further including an extension circuit to secure the ZVS range of the switching element of the inverter, it is possible to protect the switching element and improve driving stability.

Description

Electromagnetic induction heating cooking apparatus and its driving module

The present invention relates to an electromagnetic induction heating cooker, and more particularly, to an electromagnetic induction heating cooker that reduces noise and a driving module thereof.

In recent years, the market size of electric stoves is gradually expanding. This is because, in the case of an electric stove, carbon monoxide is not generated in the combustion process, and the risk of safety accidents such as gas leakage or fire is low.

On the other hand, electric ranges include a highlight method that converts electricity into heat using a nichrome wire with high electrical resistance, and an induction method that generates a magnetic field to apply heat through electromagnetic induction heating method.

The electromagnetic induction heating cooker may mean an electric range operating according to an induction method. The operating principle of the electromagnetic induction heating cooker is described below.

In general, an electromagnetic induction heating cooker flows a high-frequency current to a working coil or a heating coil provided therein.

When a high-frequency current flows through the working coil or heating coil, a strong magnetic force line is generated. When the magnetic force line generated from the working coil or the heating coil passes through the cooking appliance, an eddy current is formed. Accordingly, heat is generated as an eddy current flows through the cooking appliance to heat the container itself, and as the container is heated, the contents in the container are heated.

Such an induction heating cooking appliance is disclosed in detail in Korean Publication No. 10-2016-0123672 and the like.

As described in the prior art, in the case of an induction heating cooking appliance generally applied at home, it often includes at least two or more cooking areas. Such household induction heating cookers control the output by applying different frequencies to the heating coils constituting a plurality of craters.

However, in this way of controlling the output, the frequency difference between adjacent craters may be close to the audible frequency, which may cause noise.

In order to eliminate such noise, a method of controlling the output by fixing the frequency of a plurality of craters to be the same and varying the duty at each frequency has been proposed.

However, due to the asymmetry of the load current, the ZVS (zero voltage switching range of the inverter is limited), which causes a problem in that the range for stably varying the output is limited.

Korean Publication No. 10-2016-0123672 (Published on October 26, 2016)

A first object of the present invention is to provide an induction heating cooker capable of controlling an output by varying a duty while an induction heating cooker includes a plurality of cookers while maintaining the same driving frequency of the two cookers. will be.

To this end, it is to provide an induction heating cooker capable of improving driving stability by further including an extension circuit to secure the ZVS range of the switching element of the inverter.

In addition, a third object of the present invention is to provide a method of driving an inverter capable of remarkably reducing noise by discharging all of the charging voltage of the snubber capacitor within a short time by an extension circuit.

A driving module according to an embodiment of the present invention is a driving module for supplying power to a load, the driving module comprising: an inverter generating power according to a switching duty of a switching element turned on and off according to a driving frequency; and an extension unit for flowing an auxiliary current to the inverter to ensure ZVS of the switching element.

The inverter includes a first switching element and a second switching element connected in series with each other, a first snubber capacitor connected in parallel with the first switching element to protect the first switching element, and in parallel with the second switching element. and a second snubber capacitor connected to the to protect the second switching element.

A contact point of the first and second switching elements may be the same as a contact point of the first and second snubber capacitors, and a load current may flow from the contact point to the load.

The extension unit includes a third switching element and a diode connected in series to both ends of the first and second switching elements connected in series, and a contact point between the third switching element and the diode and the first and second switching elements It may include an inductor connected between the contact points of the device.

The third switching element may be turned on before the first switching element is turned on to flow the auxiliary current for discharging the first snubber capacitor to the first snubber capacitor.

The first snubber capacitor may be discharged by a discharge current obtained by summing the auxiliary current and the load current before the first switching element is turned on.

The driving of the third switching element may be performed when the duty of the first switching element is 0.5 or less.

The inverter may be driven on/off by a preset driving frequency, and output power may be controlled to vary according to a switching duty of the switching element.

On the other hand, an embodiment of the present invention is a heating coil for emitting a specific level of power according to user selection; an inverter for transferring power to the heating coil according to a switching duty of a switching element turned on and off according to a driving frequency; And it provides an induction heating cooking appliance comprising an extension for flowing an auxiliary current to the inverter to ensure the ZVS of the switching element.

The inverter includes a first switching element and a second switching element connected in series with each other, a first snubber capacitor connected in parallel with the first switching element to protect the first switching element, and in parallel with the second switching element. and a second snubber capacitor connected to the to protect the second switching element.

A contact point of the first and second switching elements may be the same as a contact point of the first and second snubber capacitors, and a load current may flow from the contact point to the load.

The extension unit includes a third switching element and a diode connected in series to both ends of the first and second switching elements connected in series, and a contact point between the third switching element and the diode and the first and second switching elements It may include an inductor connected between the contact points of the device.

The third switching element may be turned on before the first switching element is turned on to flow the auxiliary current for discharging the first snubber capacitor to the first snubber capacitor.

The first snubber capacitor may be discharged by a discharge current obtained by summing the auxiliary current and the load current before the first switching element is turned on.

The driving of the third switching element may be performed when the duty of the first switching element is 0.5 or less.

The induction heating cooker may be driven on/off by a preset driving frequency, and output power may be controlled to vary according to a switching duty of the switching element.

The output power may be generated by AC voltage and AC current converted from the commercial power source.

The induction heating cooking appliance includes: a rectifying unit receiving commercial power and rectifying it; and a DC link capacitor that stores the voltage rectified from the rectifier and provides the voltage to the inverter.

The extension may be connected between the DC link capacitor and the inverter.

Through the above solution, when a plurality of cooking utensils are included, it is possible to control the output by varying the duty while maintaining the same driving frequency of the two cooking utensils, thereby reducing noise.

In addition, by further including an extension circuit to secure the ZVS range of the switching element of the inverter, it is possible to protect the switching element and improve driving stability.

In addition, by discharging all of the charging voltage of the snubber capacitor within a short time by the expansion circuit, noise can be remarkably reduced and the output can be controlled by protecting the switching element.

1 is a top perspective view of an electromagnetic induction heating cooking apparatus according to an embodiment of the present invention.
FIG. 2 is an internal perspective view of the electromagnetic induction heating cooker of FIG. 1 .
3 is a block diagram of an electromagnetic induction heating cooking apparatus according to an embodiment of the present invention.
FIG. 4 is a detailed circuit diagram of the electromagnetic induction heating and cooking apparatus of FIG. 3 .
5A and 5B are waveform diagrams showing the state of the snubber capacitor in the normal operation and the abnormal operation of the inverter.
6A and 6B are circuit diagrams and waveform diagrams when an extension unit is driven according to an embodiment of the present invention.
7A to 7C show the effect of the current and the switching signal of the inverter switching device according to the duty.

Expressions referring to directions such as “before (F) / after (R) / left (Le) / right (Ri) / up (U) / down (D)” mentioned below are defined as shown in the drawings, but , This is for the purpose of explaining the present invention to the extent that it can be clearly understood, and it goes without saying that each direction may be defined differently depending on where the reference is placed.

The use of terms such as 'first, second', etc. added before the components mentioned below is only to avoid confusion of the components referred to, and is irrelevant to the order, importance, or master-slave relationship between the components. . For example, an invention including only the second component without the first component can also be implemented.

In the drawings, the thickness or size of each component is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. In addition, the size and area of each component do not fully reflect the actual size or area.

In addition, angles and directions mentioned in the process of explaining the structure of the present invention are based on those described in the drawings. In the description of the structure in the specification, if the reference point for the angle and the positional relationship are not clearly mentioned, reference is made to the related drawings.

Hereinafter, an induction power cooker including a battery will be described as an example with reference to FIGS. 1 and 2 , but it is not necessarily limited thereto.

FIG. 1 is a top perspective view of an electromagnetic induction heating cooking appliance 1 according to an embodiment of the present invention, and FIG. 2 is an internal perspective view of the electromagnetic induction heating cooking appliance 1 of FIG. 1 .

Referring to FIG. 1 , a cooker 1 (not shown) may be positioned above the electromagnetic induction heating cooker 1 . The electromagnetic induction heating cooking appliance 1 may heat a cooking container located thereon.

Specifically, a method for the electromagnetic induction heating cooking appliance 1 to heat the cooking vessel will be described. The electromagnetic induction heating cooking appliance 1 may generate a magnetic field. Some of the magnetic field generated by the electromagnetic induction heating cooking appliance 1 may pass through the cooking container. At this time, when the material of the cooking vessel contains an electrical resistance component, the magnetic field generates an eddy current in the cooking vessel. The eddy current heats the cooking vessel itself, and this heat is conducted and transferred to the inside of the cooking vessel. Accordingly, the electromagnetic induction heating cooking appliance 1 operates in such a way that the contents of the cooking container are cooked.

On the other hand, when the material of the cooking vessel does not contain an electrical resistance component, the cooking vessel must be a stainless steel vessel or a metal vessel such as an enamel or cast iron vessel in order to be heated by the eddy current electromagnetic induction heating cooking device 1 .

As shown in FIG. 2 , the electromagnetic induction heating cooking appliance 1 may include a casing 20 including at least one upper plate glass 11 and heating coils 51 , 52 , 53 . First, each component constituting the electromagnetic induction heating cooking appliance 1 will be described in detail.

The upper glass 11 serves to protect the inside of the electromagnetic induction heating cooking appliance 1 and support the cooking container. Specifically, the upper glass 11 may be formed of tempered glass made of a ceramic material obtained by synthesizing various minerals. Accordingly, the inside of the electromagnetic induction heating cooking appliance 1 can be protected from the outside. In addition, the upper glass 11 may support the cooking vessel located thereon. Accordingly, the cooking vessel may be positioned above the upper glass 11 . The heating coils 51 , 52 , and 53 serve to generate a magnetic field for heating the cooking vessel, and at least one heating coil 51 , 52 , 53 may be included according to a design. At this time, a cooking pot for cooking is defined according to each coil 51 , 52 , 53 . A user input unit 12 for selecting the output of each crater may be disposed on one side of the upper glass 11 .

Specifically, the heating coils 51 , 52 , and 53 may be positioned under the upper glass 11 . In the heating coils 51 , 52 , and 53 , current may or may not flow according to the power on/off of the electromagnetic induction heating cooking appliance 1 . In addition, even when current flows through the heating coils 51 , 52 , and 53 , the amount of current flowing through the heating coils 51 , 52 , 53 may vary according to the heating power stage of the electromagnetic induction heating cooking appliance 1 .

When a current flows through the heating coils 51 , 52 , and 53 , the heating coils 51 , 52 , 53 may generate a magnetic field. As the current flowing through the heating coils 51 , 52 , 53 increases, a magnetic field is generated more.

On the other hand, the direction of the magnetic field generated in the heating coils (51, 52, 53) is determined by the direction of the current flowing through the heating coils (51, 52, 53). Therefore, when an alternating current flows through the heating coils 51, 52, 53, the direction of the magnetic field is converted by the frequency of the alternating current. For example, when an alternating current of 60 Hz is applied to the heating coils 51, 52, 53, the direction of the magnetic field is changed 60 times per second.

It is electrically connected to the user input unit 12 and the heating coils 51, 52, 53 in the casing 20, and receives voltage and current from commercial power and converts them to the heating coils 51, 52, 53 according to the user input. ) a driving module (not shown) for supplying power is disposed.

Such a driving module may be implemented in the form of a plurality of chips mounted on one printed circuit board, but is not limited thereto and may be implemented as one integrated chip.

The electromagnetic induction heating cooking appliance 1 may include a ferrite (not shown) therein to protect an internal driving module.

That is, the ferrite serves as a shield to block the influence of the magnetic field generated in the heating coils 51 , 52 , 53 or the electromagnetic field generated from the outside on the driving module inside the electromagnetic induction heating cooking appliance 1 .

To this end, ferrite may be formed of a material having very high permeability. The ferrite serves to induce the magnetic field flowing into the electromagnetic induction heating cooking appliance 1 to flow through the ferrite without being radiated.

1 and 2 discloses an electromagnetic induction heating cooking appliance 1 including at least one heating coil, and in general, heating coils 51 , 52 , 53 corresponding to two to four cooking zones are provided at home. It can be formed to include.

The coil size of each heating coil 51 , 52 , 53 may be formed to be different from each other, and each coil 51 , 52 , 53 is driven by an inverter according to the control of the driving module to flow a current, which is selected by the user The target power corresponding to the desired thermal power level may be generated to generate heat corresponding thereto.

To this end, each heating coil 51 , 52 , 53 can be implemented to be connected to each inverter 140 in the driving module, and a plurality of heating coils 51 , 52 , 53 are connected in series and parallel by a switch. It can also be implemented to be connected to one inverter 140 .

In the present invention, when the electromagnetic induction heating cooking appliance 1 provided in a general household includes three heating coils 51 , 52 , 53 , when the power required for each heating coil is different, each inverter is connected to each other It can be driven with different driving frequencies.

In the case of driving with such different driving frequencies, when a difference between neighboring driving frequencies enters an audible frequency, it is recognized as a very sensitive noise to the user.

In order to remove such driving noise, in the embodiment of the present invention, the driving frequency of each inverter is the same with respect to the plurality of heating coils 51, 52, 53, and by adjusting the switching duty, each heating coil 51, 52, 53) implement the driving module to determine the power of

Hereinafter, the configuration of the driving module of the electromagnetic induction heating cooking appliance 1 according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4 .

3 is a block diagram of the electromagnetic induction heating and cooking apparatus 1 according to an embodiment of the present invention, and FIG. 4 is a detailed circuit diagram of the electromagnetic induction heating and cooking apparatus 1 of FIG. 3 .

Specifically, FIG. 3 shows a configuration diagram of a driving module of the electromagnetic induction heating cooking appliance 1 corresponding to one inverter 140 and one heating coil 51 , 52 , 53 .

That is, when the electromagnetic induction heating cooking appliance 1 includes three heating coils 51 , 52 , 53 , it represents a driving module for one of the three heating coils 51 , 52 , 53 .

Hereinafter, one of the illustrated heating coils 51 , 52 , 53 is defined by reference numeral 150 .

To this end, the driving module of the heating coil 150 of FIG. 3 includes a rectifying unit 120 , a DC link capacitor 130 , an extension unit 170 , an inverter 140 , and a resonance capacitor 160 connected to commercial power as an external power source. ) is included.

The external power may be AC (Alternation Current) input power. The external power may supply AC power to the electromagnetic induction heating cooking appliance 1 . More specifically, the external power supply may supply an AC voltage to the rectifying unit 120 of the electromagnetic induction heating cooking appliance (1). The rectifier 120 (Rectifier) is an electrical device for converting alternating current to direct current. The rectifier 120 converts an AC voltage supplied through an external power source into a DC voltage. On the other hand, both ends of the DC output through the rectifier 120 (n1, n2) is referred to as a DC link, the voltage measured at both ends of the DC (n1, n2) is referred to as a DC link voltage.

If the resonance curves are the same, the output power may vary depending on the DC link voltage. The DC link capacitor 130 (C _f1 ) serves as a buffer between the external power source 110 and the inverter 140 . Specifically, the DC link capacitor 130 is used to maintain the DC link voltage converted through the rectifier 120 and supply it to the inverter 140 . The inverter 140 serves to switch the voltage applied to the heating coil 150 so that a high-frequency current flows through the heating coil 150 . The inverter 140 drives the switching elements S1 and S2 composed of an IGBT (Insulated Gate Bipolar Transistor) to allow a high-frequency current to flow in the heating coil 150, thereby forming a high-frequency magnetic field in the heating coil 150. do. In the heating coil 150 , current may or may not flow depending on whether the switching elements S1 and S2 are driven by a predetermined frequency. When a current flows through the heating coil 150, a magnetic field is generated. The heating coil 150 may heat the cooking appliance 1 by generating a magnetic field as current flows. As such, the electromagnetic induction heating cooker may heat the cooker 1 by using the heating coil 150 for electromagnetic induction. Such a switching element may include each diode, but is not limited thereto, and may include a plurality of diodes together.

In addition, each of the switching elements S1 and S2 is a snubber capacitor ( CS1 and CS2) respectively.

Each of the snubber capacitors (CS1, CS2) is connected in parallel between the collector and the emitter of each of the switching elements (S1, S2), two snubber capacitors (CS1, CS2) are the input terminal of the heating coil (150) is connected with

One side of the heating coil 150 is connected to the connection point of the switching elements S1 and S2 of the inverter 140, and the other side is connected to the resonance capacitor 160 (Cr1, Cr2). The driving of the switching elements S1 and S2 is made by a control unit (not shown), and is controlled at the switching time output from the control unit, so that the switching elements S1 and S2 operate alternately with each other while generating a high-frequency Apply voltage.

The controller (not shown) serves to control the overall operation of the electromagnetic induction heating cooking appliance 1 . That is, the control unit may control the operation of each component constituting the electromagnetic induction heating cooking appliance (1).

The resonance capacitor 160 serves as a buffer. The resonance capacitor 160 controls the saturation voltage increase ratio during the turn-off of the switching elements S1 and S2, thereby affecting energy loss during the turn-off time. The resonance capacitor 160 may include a plurality of capacitors Cr1 and Cr2 connected in series between the DC ends n1 and n2 from which the voltage is output from the rectifier 120 and the heating coil 150 . The resonance capacitor 160 may include a first resonance capacitor 160 (Cr1) and a second resonance capacitor 160 (Cr2).

Specifically, one end of the first resonant capacitor 160 (Cr1) is connected to one end n1 from which a voltage is output from the rectifier 120, and the other end is a connection point between the second resonant capacitor Cr2 and the heating coil 150. can be connected to Similarly, the second resonant capacitor 160 (Cr2) has one end connected to the other end n2 from which the low voltage is output from the rectifier 120, and the other end of the first resonant capacitor 160 Cr1) and the heating coil 150. It can be connected to a connection point. The capacitance of the first resonant capacitor 160 (Cr1) and the capacitance of the second resonant capacitor 160 (Cr2) are the same. On the other hand, the capacitance of the resonance capacitor 160 may determine the resonance frequency (resonance frequency) of the electromagnetic induction heating cooking appliance (1). Specifically, the resonance frequency of the electromagnetic induction heating cooking appliance 1 configured as a circuit diagram as shown in FIG. 3 is determined by the inductance of the heating coil 150 and the capacitance of the resonance capacitor 160 . do. In addition, a resonance curve may be formed around a resonance frequency determined by the inductance of the heating coil 150 and the capacitance of the resonance capacitor 160 . The resonance curve may represent output power according to frequency. A Q factor (quality factor) is determined according to the inductance value of the heating coil 150 included in the electromagnetic induction heating cooking appliance 1 and the capacitance value of the resonance capacitor 160 . The resonance curve is formed differently depending on the Q factor.

Accordingly, the electromagnetic induction heating cooker 1 has different output characteristics according to the inductance of the heating coil 150 and the capacitance of the resonance capacitor 160, and the frequency at which the maximum power is output is referred to as the resonance frequency f0.

In general, the electromagnetic induction heating cooking appliance 1 uses the frequency of the right region based on the resonance frequency f0 of the resonance curve. Accordingly, the electromagnetic induction heating cooking appliance 1 may increase or decrease the thermal power level by adjusting the switching duty according to the applied user input while driving by specifying one driving frequency.

As described above, the driving module of the present invention includes an extension unit to prevent a zero voltage switching (ZVS) failure that may occur when controlling the output power according to the thermal power stage while changing the duty while performing the switching driving for a specific driving frequency. (170).

In the inverter 140 including the switching elements S1 and S2, when the switching duty is controlled, the magnitude of the current decreases due to the asymmetric characteristic of the load current, so that the ZVS-limited duty occurs due to the ZVS failure, and, accordingly, the output power also limited.

That is, it does not operate at a small duty or the operation is limited, so that the corresponding output power cannot be generated.

In order to prevent such ZVS failure, in the embodiment of the present invention, an extension 170 for reinforcing a discharge current in the first snubber capacitor CS1 is further included in the front end of the inverter 140 .

Referring to FIG. 4 , the extension unit 170 is connected between the DC link capacitors 130 and Cf1 and the inverter 140 , and is connected in series to both ends n1 and n2 of the DC link capacitor 130 . It includes a third switching element (S3) and a third diode (D3), between the connection point of the third switching element (S3) and the third diode (D3) and the connection point of the first and second switching elements (S1, S2) includes an inductor (L1).

In this case, the third switching element S3 may also further include a diode between the collector and the emitter.

The third switching element S3 may be switched and driven at the same frequency as the first and second switching elements S1 and S2, and the first snubber capacitor CS1 is driven by the third switching element S3. The discharging efficiency of the first snubber capacitor CS1 may be improved by reinforcing the load current for discharging.

The description of the extension 170 will be described with reference to FIGS. 5A to 7C .

5A and 5B are waveform diagrams showing the state of the snubber capacitor in the normal operation and the abnormal operation of the inverter 140, and FIGS. 6A and 6B are diagrams for driving the expansion unit 170 according to an embodiment of the present invention. It is a circuit diagram and a waveform diagram at the time, and FIGS. 7A to 7C show the effect of the current and the switching signal of the inverter 140 switching element according to the duty.

FIG. 5A is a signal waveform diagram in a normal operation of the inverter 140 , and FIG. 5B is a signal waveform diagram in an abnormal operation of the inverter 140 .

Referring to FIG. 5A , when the two switching elements S1 and S2 of the inverter 140 operate normally at a predetermined frequency, the two switching elements S1 and S2 alternate with each other and are turned on with a predetermined duty.

At this time, there is a predetermined rest period between the two turn-on times.

This section is a discharge section of the snubber capacitors CS1 and CS2 of each of the switching elements S1 and S2. Before the corresponding switching elements S1 and S2 are turned on, the charging voltages of the snubber capacitors CS1 and CS2 are all charged. The switching elements S1 and S2 are turned on in a discharged state of 0V, that is, in a state where the voltage between the collector and the emitter of the corresponding switching elements S1 and S2 satisfies zero.

When the first switching element (S1) is mainly described, the load current (I _load ), that is, the current applied to the heating coil 150 in the period in which the first switching element (S1) is turned on, is the first switching element (S1) It passes through the first switching element S1 according to the turn-on of the first switching element S1 through the diode D1 connected to It flows through the diode D2 of S2 and passes through the second switching element S2 according to the turn-on of the second switching element S2.

At this time, the discharge period of the first snubber capacitor DS1, which is the rest period of the first switching element S1, exists before the turn-on period of the first switching element S1, and the first snubber capacitor DS1 _{In the discharge section, the discharge current I CS1} passing through the first snubber capacitor DS1 flows in a negative direction, that is, in the reverse direction of the load current I _load , so that the discharge proceeds.

As shown in FIG. 5A , when the first switching device S1 is turned on after the first snubber capacitor DS1 is sufficiently discharged to meet 0V, switching is possible without a switching loss of the switching device S1.

However, when the duty of the switching elements S1 and S2 is controlled, that is, when the duty is reduced or increased according to the output power, the first snubber capacitor DS1 is discharged before the first switching element S1 is turned on. You may not be given enough time to do it.

That is, when the first switching element S1 is turned on in a state other than 0V due to insufficient discharge time of the first snubber capacitor DS1 as shown in FIG. 5B , the slope of the _{V CE voltage instantaneously as in the second waveform.} It changes abruptly and drops to 0V.

At this time, the discharge current I _CS1 of the first snubber capacitor DS1 flows to the first switching element S1 so that hard switching of the first switching element S1 occurs, and when hard switching occurs, the first switching The first switching element S1 may be damaged due to heat generation of the element S1 .

Such discharging of the first snubber capacitor DS1 follows Equation 1 below.

At this time, T _discharge is defined as the discharge time of the corresponding snubber capacitor, Cs is the capacitance of the corresponding snubber capacitor, V is the voltage across both ends of the snubber capacitor, and I _cs1 is the discharge current flowing through the first snubber capacitor CS1 defined as a value.

Accordingly, it can be seen that the greater the value of the discharge current of the first snubber capacitor DS1, the shorter the discharge time.

In the driving module according to the embodiment of the present invention, in order to shorten the discharge time of the first snubber capacitor DS1, the current in the first snubber capacitor DS1 is reinforced in the discharge period of the first snubber capacitor DS1. It further includes an extension 170 that does.

Referring to FIGS. 6A and 6B , the expansion unit 170 according to an embodiment of the present invention is for expanding a duty region in which ZVS of the first switching element S1 is limited or failed, and mainly the first switching element ( When the duty of S1) is 0.5 or less, the effect may be further exhibited.

Accordingly, the switching driving of the third switching element S3 of the extension unit 170 may be selectively driven only when the duty is less than or equal to a predetermined duty, but is not limited thereto.

In this case, the predetermined duty may be 0.5 or less as described above.

As shown in FIG. 6B , in the idle period set before the first switching element S1 is turned on, that is, in the discharge period of the first snubber capacitor DS1 , the third switching element S3 of the extension unit 170 is turned on. .

By this turn-on, an auxiliary current flows in the reverse direction of the first snubber capacitor DS1 through the inductor L1 as shown in FIG. 6A , and in addition to the main current for discharging the first snubber capacitor DS1, Discharge current (I _cs1 ) is formed.

_{Accordingly, as the discharge current I cs1} of the first snubber capacitor DS1 in Equation 1 increases, the discharge time is shortened, so that the first snubber capacitor DS1 can be discharged for a short time.

In this way, before the first switching element S1 is turned on, the third switching element S3 of the extension unit 170 is turned on to discharge the first snubber capacitor DS1 by adding _{a discharge current I cs1 ).} By increasing the value, the first switching element S1 is turned on in a state in which the first snubber capacitor DS1 is completely discharged.

Accordingly, while device stability of the first switching device S1 is secured, the first switching device S1 is turned on/off at a desired duty to transmit output power to the heating coil 150 .

7A to 7C show the effect of the current and the switching signal of the inverter 140 switching element according to the duty.

7A is a diagram illustrating a ZVS failure state that occurs because discharge is not smoothly performed in the first snubber capacitor DS1 when the extension unit 170 according to the embodiment of the present invention is not provided.

It is set when the duty of the first switching element S1 is 0.25, and the power meets 1000W.

As shown in FIG. 7A , the current peak of the load current is asymmetrically formed, and the voltage value between the collector and the emitter of the second switching element S2 in the highlighted region (indicated by a circle), that is, the lower switching element. It is formed to have this inclination, resulting in switching loss.

At this time, as shown in FIG. 7B , when the circuit of the extension unit 170 according to the embodiment is included, the auxiliary current is induced in the first snubber capacitor DS1 before the first switching element S1 is turned on as shown in FIG. 6B . As shown in FIG. 7B , the switching loss of the lower switching element, which is the second switching element S2 , does not occur and ZVS can be normally ensured.

7c, when the duty of the first switching element S1 is reduced to 0.15, that is, when the duty of the first switching element S1 is controlled to 0.15 in order to set the output to 600W power, it is also The voltage of the second switching element S2 is formed so as not to have a slope, so that ZVS is secured even at a small duty, preferably 0.5 or less, without ZVS failure.

Therefore, even when the power control is driven by controlling the duty of the switching element of the inverter 140, the operation of the switching element is performed by introducing an auxiliary current to sufficiently discharge the first snubber capacitor DS1 of the first switching element S1. Effective power control is possible while ensuring stability.

1: Electromagnetic induction heating cooker 11: Top plate
20: case
51, 52, 53, 150: heating coil 120: rectifying unit
130: dc link capacitor 140: inverter
160: resonant capacitor 170: extension part

Claims (19)

delete delete delete delete delete delete delete delete An induction heating cooking appliance having at least two cookers and comprising at least two driving circuits corresponding to each of the cookers,
Each drive circuit
a heating coil that emits a certain level of power according to user selection;
an inverter for transferring power to the heating coil according to a switching duty of a switching element turned on and off according to a driving frequency; and
An extension unit for flowing an auxiliary current to the inverter to secure the ZVS of the switching element
includes,
Induction heating cooking appliance, characterized in that the switching elements of the at least two driving circuits have the same fixed frequency as the driving frequency. 10. The method of claim 9,
The inverter is
a first switching element and a second switching element connected in series with each other;
a first snubber capacitor connected in parallel with the first switching element to protect the first switching element;
A second snubber capacitor connected in parallel with the second switching element to protect the second switching element
Induction heating cooking appliance comprising a. 11. The method of claim 10,
A contact point of the first and second switching elements is the same as a contact point of the first and second snubber capacitors, and a load current flows from the contact point to the heating coil. 12. The method of claim 11,
the extension
A third switching element and a diode connected in series to both ends of the first and second switching elements connected in series, and
An inductor connected between a contact point between the third switching element and the diode and a contact point between the first and second switching elements
Induction heating cooking appliance comprising a. 13. The method of claim 12,
The third switching element is turned on before the first switching element is turned on to flow the auxiliary current for discharging the first snubber capacitor to the first snubber capacitor. 14. The method of claim 13,
The first snubber capacitor is an induction heating cooker, characterized in that the discharge proceeds by a discharge current that is the sum of the auxiliary current and the load current before the first switching element is turned on. 15. The method of claim 14,
Induction heating cooking appliance, characterized in that the driving of the third switching element is performed when the duty of the first switching element is 0.5 or less. 10. The method of claim 9,
The induction heating cooker performs on-off driving by a preset driving frequency, and the output power is controlled to vary according to a switching duty of the switching element. 17. The method of claim 16,
The output power is an induction heating cooking appliance, characterized in that generated by the AC voltage and AC current converted from commercial power. 10. The method of claim 9,
The induction heating cooking appliance,
a rectifying unit receiving commercial power and rectifying it; and
a DC link capacitor storing the voltage rectified from the rectifier and providing it to the inverter;
Induction heating cooking device further comprising a. 19. The method of claim 18,
The extension part is an induction heating cooking appliance, characterized in that it is connected between the DC link capacitor and the inverter.

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