Patent Application
20240251484
The present disclosure relates to an induction heating type cooktop.
Various types of cooking appliances are used to heat food at home or in restaurants. In the past, gas stoves using gas as fuel have been widely used, but recently, devices that heat cooking vessels using electricity rather than gas are becoming popular.
Methods of heating objects using electricity are largely divided into resistance heating and induction heating. Resistance heating is a method of heating by transferring the heat generated when an electric current flows through a metal resistance wire or a non-metallic heating element such as silicon carbide to the cooking vessel through radiation or conduction. The induction heating method uses the magnetic field generated around the coil when high-frequency power of a certain size is applied to the coil to generate an eddy current in a cooking container made of metal, thereby heating the cooking container itself.
In the case of the induction heating type, the inverter applies high-frequency power to the coil. The inverter is driven by applying Zero Voltage Switching (ZVS) to reduce switching loss. Recently, High-frequency driving for the extent of types of objects that can be heated, increase of output, and reduction of product volume is required to reduce.
Meanwhile, Wide Band Gab (WBG) can be used as a switching element for high-frequency driving. In this case, a negative voltage is formed at the gate-source voltage due to a high voltage change rate and rapid change in parasitic components in the transient section during switching, it is affected a negative effect on the operation of (−) low-rated switching devices (for example, SiC devices).
Additionally, since ringing may occur in the gate-source voltage due to resonance between components and parasitic components of the PCB and switching elements, a stable driver is required.
An object of the present disclosure is to provide an induction heating type cooktop that form negative voltage and minimizes ringing in an inverter to which a Wide Band Gab (WBG) element is applied.
The induction heating type cooktop according to an embodiment of the present disclosure is to vary the composite impedance of the driving unit that drives the switching element.
The induction heating type cooktop according to an embodiment of the present disclosure is to reduce the composite impedance of the driver in the switching transient section of the switching device, and increase the composite impedance of the driver when the drain-source voltage of the switching device falls and returns to the diode.
An induction heating type cooktop may include a top glass on which a cooking vessel is placed, a working coil configured to generate a magnetic field for heating the cooking vessel, and an inverter. The inverter may include at least one switching element configured to be driven to flow current to the working coil, and a driving unit configured to drive the switching element, wherein the composite impedance of the driver is variable.
The driving part is configured to reduce the composite impedance in the switching transient section of the switching element, and increase the composite impedance when the drain-source voltage of the switching element falls and returns to the diode.
The induction heating type cooktop of claim 1, wherein the driving part includes first to third impedance forming units for adjusting the composite impedance of the driving unit.
The third composite impedance formed by the third impedance forming unit is greater than the first composite impedance formed by the first impedance forming unit, and wherein the first composite impedance is greater than the second composite impedance formed by the second impedance forming unit.
The first impedance forming unit may include a first gate resistor, a first switch configured to selectively connect the first gate resistance to a gate internal resistance of the switching element, and a first switch power supply unit configured to control the first switch to operate.
The second impedance forming unit includes a second gate resistor, and wherein the first gate resistance is smaller than the second gate resistance.
The third impedance forming unit may include a second diode connected to the gate internal resistance of the switching element, a second switch connected to the second diode, and a second switch power unit configured to control the second switch to operate.
When the gate of the switching element is turned off, the first impedance forming unit is configured to form the composite impedance.
The third impedance forming unit is configured to form the composite impedance in a switching transient section of the switching element.
When the drain-source voltage of the switching element falls and returns to the diode, the second impedance forming unit is configured to form the composite impedance.
According to an embodiment of the present disclosure, increasing a size of a negative voltage is minimized and an occurrence of a ringing phenomenon is minimized, thereby improving a stability of an inverter operation.
According to an embodiment of the present disclosure, there is an advantage in that a structure in which a composite impedance of a driving unit can be varied is simplified and an increase in volume size is minimized.
According to an embodiment of the present disclosure, there is an advantage in that a cooktop using a WBG element can be stably driven at a high frequency.
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The suffixes “module” and “unit or portion” for components used in the following description are merely provided only for facilitation of preparing this specification, and thus they are not granted a specific meaning or function.
Hereinafter, an induction heating type cooktop and operating method the same according to an embodiment of the present disclosure will be described. For convenience of explanation, “induction heating type cooktop” is referred to as “cooktop.”
The cooking vessel 1 may be located at the top of the cooktop 10, and the cooktop 10 may heat the cooking vessel 1 located at the top.
First, a method by which the cooktop 10 heats the cooking vessel 1 will be described.
As shown in
On the other hand, if the material of the cooking vessel 1 does not contain the electrical resistance component, the eddy current 30 does not occur. Therefore, in this case, the cooktop 10 cannot heat the cooking vessel 1.
Accordingly, the cooking vessel 1 that can be heated by the cooktop 10 may be a stainless steel vessel or a metal vessel such as an enamel or cast iron vessel.
Next, a method by which the cooktop 10 generates the magnetic field 20 will be described.
As shown in
The top glass 11 can support the cooking vessel 1. For that, the cooking vessel 1 can be placed on the upper surface of the top glass 11. A heating area in which the cooking vessel 1 is heated may be formed in the top glass 11.
Additionally, the top glass 11 may be formed of tempered glass made of ceramic material synthesized from various minerals. Accordingly, the top glass 11 can protect the cooktop 10 from external shocks, etc.
Additionally, the top glass 11 can prevent foreign substances such as dust from entering the cooktop 10.
The working coil 12 may be located below the top glass 11. This working coil 12 may or may not be supplied with current to generate the magnetic field 20. Specifically, current may or may not flow in the working coil 12 depending on whether an internal switching element of the cooktop 10 is turned on or off.
When current flows through the working coil 12, a magnetic field 20 is generated. The magnetic field 20 may meet the electrical resistance component contained in the cooking vessel 1 to generate an eddy current 30. The eddy current heats the cooking vessel 1, so that the contents of the cooking vessel 1 can be cooked.
Additionally, a heating power of the cooktop 10 can be adjusted depending on an amount of current flowing through the working coil 12. As a specific example, the greater the current flowing through the working coil 12, the greater the magnetic field 20 is generated. As a result, the magnetic field 20 passing through the cooking vessel 1 increases, thereby increasing the heating power of the cooktop 10.
The ferrite core 13 is a component that protects an internal circuit of the cooktop 10. Specifically, the ferrite core 13 may serve as a shield to block an influence of the magnetic field 20, generated by the working coil 12 or an externally generated electromagnetic field, on the internal circuit of the cooktop 10.
To this end, the ferrite core 13 may be formed of a material with very high permeability. The ferrite core 13 may serve to guide the magnetic field flowing into the cooktop 10 to flow through the ferrite core 13 rather than being radiated. The movement of the magnetic field 20 generated in the working coil 12 by the ferrite core 13 may be as shown in
Meanwhile, the cooktop 10 may further include other components in addition to the top glass 11, working coil 12, and ferrite core 13 described above. For example, the cooktop 10 may further include an insulating material (not shown) located between the top glass 11 and the working coil 12. That is, the cooktop according to the present disclosure is not limited to the cooktop 10 shown in
Since the circuit diagram of the cooktop 10 shown in
Referring to
The power supplier 110 can receive an external power input. The external power input may be alternation current (AC) power.
The power supplier 110 may supply AC voltage to the rectifier unit 120.
The rectifier 120 may be an electrical device for converting AC to DC. The rectifier 120 may convert AC voltage supplied through the power supplier 110 into DC voltage. The rectifier 120 may supply the converted voltage to DC ends 121.
The output terminal of the rectifier 120 may be connected to DC ends 121. The DC ends 121 may output through the rectifier 120 can be referred to as a DC link. The voltage measured at both ends of DC 121 may be also referred to as a DC link voltage.
The DC link capacitor 130 may serve as a buffer between the power supplier 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 may serve to switch the voltage applied to the working coil 12 so that a high-frequency current flows in the working coil 12. The inverter 140 may include a semiconductor switch. The semiconductor switch may be an Insulated Gate Bipolar Transistor (IGBT) or a Wide Band Gab (WBG) device, but this is only an example and is not limited thereto. Meanwhile, the WBG device may be made of SiC (Silicon Carbide) or GaN (Gallium Nitride). The inverter 140 drives the semiconductor switch to cause a high-frequency current to flow in the working coil 12, thereby forming a high-frequency magnetic field in the working coil 12.
Current may or may not flow in the working coil 12 depending on whether the switching element is driven. When current flows through the working coil 12, a magnetic field is generated. The working coil 12 can heat the cooking appliance by generating a magnetic field as current flows.
One side of the working coil 12 may be connected to a connection point of a switching element of the inverter 140, and the other side of that may be connected to the resonance capacitor 160.
The switching element may be driven by a driving unit (not shown), and is controlled by the switching time output from the driving unit, so that the switching elements can operate alternately and apply a high-frequency voltage to the working coil 12. Since the on/off time of the switching element applied from the driving unit (not shown) is controlled in a gradually compensated manner, the voltage supplied to the working coil 12 may be changed from a low voltage to a high voltage.
The resonance capacitor 160 may be a component that functions as a buffer. The resonant capacitor 160 may control a saturation voltage rise rate during turn-off of the switching element, thereby affecting energy loss during that time.
The SMPS 170 may refer to a power supply device that efficiently converts power according to switching operations. The SMPS 170 may convert the DC input voltage into a square wave voltage and then obtain a controlled DC output voltage through a filter. The SMPS 170 can minimize unnecessary losses by controlling the flow of power using a switching processor.
In the case of the cooktop 10 configured with the circuit diagram shown in
Next,
First, the quality (Q) factor (quality factor) may be a value indicating the sharpness of resonance in a resonant circuit. Accordingly, in the case of the cooktop 10, the Q factor may be determined by the inductance value of the working coil 12 and the capacitance value of the resonance capacitor 160 included in the cooktop 10. The resonance curve is different in accordance with the Q factor. Accordingly, the cooktop 10 may have different output characteristics in accordance with the inductance value of the working coil 12 and the capacitance value of the resonance capacitor 160.
The horizontal axis of the resonance curve may represent frequency, and the vertical axis may represent output power. The frequency that outputs maximum power in the resonance curve is called a resonance frequency (f0).
In general, the cooktop 10 may use the frequency in the right area based on the resonance frequency (f0) of the resonance curve. Additionally, the cooktop 1 may have a minimum and maximum operating frequency set in advance.
As an example, the cooktop 10 may operate at a frequency ranging from the maximum operating frequency (fmax) to the minimum operating frequency (fmin). In other words, the operating frequency range of the cooktop 10 may be from the maximum operating frequency (fmax) to the minimum operating frequency (fmin).
As an example, the maximum operating frequency (fmax) may be a IGBT maximum switching frequency. The IGBT maximum switching frequency may refer to the maximum frequency that can be driven, considering the breakdown voltage and capacity of the IGBT switching element. For example, the maximum operating frequency (fmax) may be 75 kHz.
The minimum operating frequency (fmin) may be approximately 20 KHz. In this case, since the cooktop 10 does not operate at audible frequencies (approximately 16 Hz to 20 kHz), a noise from the cooktop 10 can be reduced.
Meanwhile, the setting values of the maximum operating frequency (fmax) and the minimum operating frequency (fmin) described above are only examples and are not limited thereto.
When the cooktop 10 receives a heating command, the operating frequency according to the heating power level set in the heating command can be determined. Specifically, the cooktop 10 can adjust the output power by lowering the operating frequency as the set heating power level becomes higher and increasing the operating frequency as the set heating power level becomes lower. In other words, when the cooktop 10 receives a heating command, a heating mode that operates in any one of the operating frequency ranges according to the set heating power can be implemented.
Meanwhile, the cooktop 10 may apply and operate Zero Voltage Switching (ZVS) to reduce switching losses. In addition, the cooktop 10 has recently expanded types of the cooking vessel 1 that can be heated, and high-frequency driving for high output and reduced product size has been required. Accordingly, the cooktop 10 may be equipped with a WBG element, thereby being driven at a high frequency.
On the other hand, when the cooktop 10 is driven at a high frequency, a negative voltage can be formed at the gate-source voltage due to the high voltage change rate (dv/dt) and rapid change in parasitic components in a transient section during switching. The formed negative voltage can be a detrimental effect on the operation of (−) low-rated WBG devices, especially SiC devices. Specifically, for IGBT devices, the allowable gate-source voltage (Vgs) is −20 to +20V, but for SiC devices, the allowable gate-source voltage (Vgs) is −10 to +20V. Since the (−) rating of SiC devices is low a reduction of the negative voltage may be required.
Additionally, when using the WBG device, ringing may occur in the gate-source voltage due to a resonance phenomenon between parasitic components of the WBG device and elements. Specifically, as the drain-source voltage (Vds) all decreases and reflux to the diode begins, a resonance phenomenon may be induced between the parasitic inductance of the PCB and the snubber capacitor. From that, since ringing occurs at the gate-source terminal, measures to reduce the ringing phenomenon may be required.
Accordingly, the present disclosure is to improve a stability of inverter operation by providing a cooktop 10 including a gate driving circuit that provides an impedance path for reducing negative voltage and ringing in the inverter 140 to which a WBG element is applied.
In order to improve a trade-off relationship between negative voltage and ringing according to gate resistance, the present disclosure may make the gate resistance small when forming a negative voltage and make the gate resistance large in the section where ringing occurs, thereby providing stable stability.
The inverter 140 of the cooktop may include at least one switching element. For a specific example, a half-bridge type inverter 140 may have two switching elements, and a full-bridge type inverter 140 may have four switching elements. In this disclosure, it is assumed that the inverter 140 is the half-bridge type.
The driving unit is connected to the switching element so that the on and off of the gate is controlled. The driving unit may include a power supply unit (Vdrv_L) for applying a signal to the gate of the switching element. The power supply may apply a signal to turn on the gate to the switching element.
Meanwhile, referring to
Accordingly, the present disclosure is to provide a driving unit that changes the impedance path to minimize the formation of negative voltage and the occurrence of ringing phenomenon.
A driving unit for driving the switching element of the inverter 140 according to an embodiment of the present disclosure may be connected to the switching element. The driving unit may be implemented as a gate driving circuit that controls on and off of the gate of the switching element.
In other words, the inverter 140 may include at least one switching element driven to flow current to the working coil 12 and a driving unit that drives the switching element, and the composite impedance of the driving unit can be varied.
The driving unit may include a first impedance forming unit 1010, a second impedance forming unit 1020, a third impedance forming unit 1030, and a power supply unit Vdrv_L.
Each of the second impedance forming unit 1020 and the power supply unit Vdrv_L may correspond to Rg and the power supply unit Vdrv_L shown in
The first impedance forming unit 1010 may form a composite impedance of the driving unit when the gate is turned off. The first impedance forming unit 1010 may include a first gate resistor Rg1, a first switch SW1 that selectively connects the first gate resistor Rg1 to the gate internal resistance Rg(in) of the switching element, and a first switch power supply unit Vdrv_1 that controls the first switch SW1.
That is, the first impedance forming unit 1010 may form a composite impedance when the gate of the switching device is turned off, and thus the first gate resistance Rg1 and the gate internal resistance Rg(in) of the switching element can be connected.
The first impedance forming unit 1010 may operate when a quick turn-off of the gate is required to reduce switching loss of the switching element.
The first impedance forming unit 1010 may include at least part or all of a first gate resistor Rg1 connected to the gate internal resistance Rg(in), a first diode D1, a first switch SW1, and a first switch power supply unit Vdrv_1.
The first gate resistance Rg1 may be smaller than the second gate resistance Rg2, which will be described later. The first gate resistor Rg1 may be selectively connected to the gate internal resistance Rg(in). The first gate resistor Rg1 may be connected in series with the gate internal resistance Rg(in) in accordance with whether the first switch SW1 is turned on or off. The first gate resistor Rg1 may be connected between the first diode D1 and the first switch SW1.
The first diode D1 may be connected between the first gate resistor Rg1 and the first switch SW1. One end of the first diode D1 may be connected to the first gate resistor Rg1, and the other end of that may be connected to a contact point between the second gate resistor Rg2 and the gate internal resistance Rg(in).
The first diode D1 may separate resistance depending on gate on/off.
The first switch SW1 may be turned on or off depending on whether power is supplied from the first switch power supply unit Vdrv_1. One end of the first switch SW1 may be connected to the first gate resistor Rg1, and the other end of that may be connected to a contact point between the second gate resistor Rg2 and the power supply unit Vdrv_L.
The first switch power supply unit Vdrv_1 can control the first switch SW1. The first switch power supply unit Vdrv_1 may control the first switch SW1 to be turned on at time t0 of
The second impedance forming unit 1020 may form a composite impedance of the driving unit in the ringing forming section.
The second impedance forming part 1020 may include a second gate resistance Rg2, and the first gate resistance Rg1 may be smaller than the second gate resistance Rg2. One end of the second gate resistor Rg2 may be connected to the contact point of the first diode D1 and the gate internal resistance Rg(in), and the other end of that may be connected to the contact point of the first switch SW1 and the power supply unit Vdrv_L.
The second gate resistor Rg2 may form a composite impedance of the driving unit when both the first switch SW1 and the second switch SW2 are turned off. That is, when both the first switch SW1 and the second switch SW2 are turned off, the second gate resistance Rg2 may be connected to the gate internal resistance Rg(in) of the switching element.
The second gate resistor Rg2 may form an impedance from time t2 to time t3 in
The third impedance forming unit 1030 may form the composite impedance of the driving unit in the negative voltage forming section. The third impedance forming unit 1030 can minimize the composite impedance of the driving unit. The third impedance forming unit 1030 may include a second diode D2 connected to the gate internal resistance Rg(in) of the switching element, a second switch SW2 connected to the second diode D2, and a second switch power unit Vdrv_2 that controls the switch SW2.
Specifically, when the third impedance forming unit 1030 is driven, the composite impedance may be formed only by the gate internal resistance Rg(in).
The third impedance forming unit 1030 may include at least part or all of the second diode D2, the second switch SW2, and the second switch power supply unit Vdrv_2.
The third impedance forming part 1030 may be connected in parallel to each of the first gate resistor Rg1 and the second gate resistor Rg2.
Also, the second diode D2 and the second switch SW2 may be connected in series.
One end of the second diode D2 may be connected to the gate internal resistance Rg(in). More specifically, one end of the second diode D2 may be connected to a contact point of the gate internal resistance Rg(in), the first diode D1, and the second gate resistor Rg2. The other end of the second diode D2 may be connected to the second switch SW2.
The drain of the second switch SW2 may be connected to the second diode D2, the gate of that may be connected to the second switch power supply unit Vdrv_2, and the source of that may be connected to the ground. One end of the second switch power supply unit Vdrv_2 may be connected to the second switch SW2 and the other end of that connected to the ground. The resistance between the second switch power supply unit Vdrv_2 and the second switch SW2 shown in
Next, a method of operating the inverter will be described based on the voltage of the switching element and the driving unit that drives it during one cycle shown in
FIG. may be a voltage change for the lower switching element assuming that the inverter 140 of the cooktop is a half-bridge type, but this is an example and is not limited thereto.
In
Referring to
That is, the first impedance forming unit 1010 can form the composite impedance of the driving unit. That is, both the gate internal resistance Rg(in) and the first gate resistance Rg1 may be connected.
When the composite impedance is the first impedance in the section from t0 to t1, the first impedance may be the first gate resistance Rg1.
The section from t1 to t2 (second mode) may be a switching transient section. That is, the switching transient section may be a section where the gate of another switching element begins to turn off. This section is a section in which a negative voltage can be formed, and the formation of the negative voltage can be minimized by forming an impedance smaller than the first impedance. Accordingly, in the second mode, the first switch SW1 may be turned off and the second switch element SW2 may be turned on. That is, the third impedance forming unit 1030 may form a composite impedance in the switching transient section of the switching element. Accordingly, the composite impedance of the driving unit can be minimized.
When the composite impedance in the section from t1 to t2 is the second impedance, the second impedance may be close to ‘0’. Accordingly, the second impedance may be smaller than the first impedance.
The section from t2 to t3 (a third mode) may be a section where feedback to the diode begins after all drain-source voltages drop. That is, this section is a dead time section after the drain-source voltage becomes 0V, and is a section in which ringing can occur. Therefore, the occurrence of ringing can be minimized by forming a relatively large impedance. Accordingly, in the third mode, the first switch SW1 may be turned off and the second switch element SW2 may also be turned off. Accordingly, the second impedance forming unit 1020, that is, the second gate voltage Rg2, may form the composite impedance of the driving unit. That is, when the drain-source voltage of the switching element falls and then returns to the diode, the second impedance forming unit 1020 can form a composite impedance.
When the composite impedance in the section from t2 to t3 is referred to as the third impedance, the third impedance may be the second gate resistance Rg2. Meanwhile, since the second gate resistance Rg2 is greater than the first gate resistance Rg1, the third impedance may be greater than the first impedance. Accordingly, since a relatively large impedance is formed in the third mode the ringing phenomenon can be reduced.
In summary, the driving unit of the switching element can reduce the composite impedance in the switching transient section and increase the composite impedance when the drain-source voltage of the switching element falls and returns to the diode. For this, the driving unit may include the first to third impedance forming units 1010, 1020, and 1030 for adjusting the composite impedance of the driving unit, and the third composite impedance formed by the third impedance forming unit 1030 is greater than the first composite impedance formed by the first impedance forming portion 1010, and the first composite impedance 1010 may be greater than the second composite impedance formed by the second impedance forming portion 1020.
In the composite impedance, the third impedance may be the largest and the second impedance may be the smallest. That is, in case the composite impedance is listed in order of size, it may be the third impedance, the first impedance, and the second impedance.
As described above, according to the embodiment of the present disclosure, the cooktop 10 can flexibly adjust the composite impedance of the driving unit, thereby lowering the composite impedance in the switching transient section and increasing the composite impedance due to the reduction of the drain-source voltage in the diode reflux start section. Accordingly, there is an advantage in minimizing negative voltage and the occurrence of ringing phenomenon. By minimizing the formation of negative voltage, the operational reliability of the cooktop 10 using the WBG element driven at a high frequency is secured, and the occurrence of ringing phenomenon is minimized, thereby improving the Rds (on) and loss of the element.
It can be seen that when the gate resistance is 2Ω, i.e., relatively small, a ringing phenomenon may occur. Also, it can be seen that when the gate resistance is 30Ω, i.e., relatively large, a large negative voltage may be formed.
On the other side,
The above description is merely an illustrative description of the technical idea of the present disclosure, and those skilled in the art may make various modifications and variations without departing from the essential characteristics of the present disclosure.
Accordingly, the embodiments disclosed in the present disclosure are not intended to limit the technical idea of the present disclosure but are for explanation, and the scope of the technical idea of the present disclosure is not limited by these embodiments.
The scope of protection of this disclosure should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0108221 | Aug 2021 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2021/012007 | 9/6/2021 | WO |
