KR20220095900A - Induction heat cooking apparatus providing low-noise container detection and operating method for the same - Google Patents

Abstract

An induction heating apparatus for providing a low-noise container detection function according to an embodiment of the present disclosure includes: a power supply unit which supplies power; a DC link capacitor which is connected in parallel with the power supply unit, to be charged with the power supplied from the power supply unit; a working coil which generates an induced magnetic field when current flows; a resonant capacitor which is connected to the working coil, to form a resonant circuit; an inverter of which switching is controlled so that a DC voltage of the DC link capacitor is applied to the working coil; and a processor which charges the working coil with free resonance energy through PWM control, controls the inverter so that the current flowing through the working coil and the resonance capacitor freely resonates, and determines whether a cooking container is present on the working coil based on the current flowing through the working coil.

Description

INDUCTION HEAT COOKING APPARATUS PROVIDING LOW-NOISE CONTAINER DETECTION AND OPERATING METHOD FOR THE SAME

The present disclosure relates to an induction heating device that provides a quiet container detection function and a method of operating the same.

Recently, 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 applies heat through electromagnetic induction heating by generating a magnetic field.

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

In general, an induction cooker allows a high-frequency current to flow through 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 vessel, an eddy current is formed. Accordingly, as an eddy current flows in the cooking vessel, heat is generated to heat the cooking vessel itself, and as the cooking vessel is heated, the contents in the vessel are heated.

As described above, the induction heating cooker is an electric cooking device that heats the contents by inducing heat to the cooking vessel itself. By using an induction cooker, it is possible to reduce indoor air pollution by not consuming oxygen and discharging waste gas. In addition, the induction cooker has high energy efficiency and stability, and the risk of burns is low because the container itself is heated.

On the other hand, in an induction cooker, the object to be heated can be heated by applying a high-output high-frequency current to the working coil. The DC link capacitor may be included in the induction heating cooker for heating such an object to be heated. Such a DC link capacitor is a smoothing capacitor that can charge an electric charge based on the voltage from the power supply unit, and thus can serve as a buffer that maintains the voltage when converting power from the power supply unit to provide a relatively constant voltage. have. The induction cooker starts driving after charging the DC link capacitor by rectifying the AC input power.

When the driving of the induction heating device is started while the DC link capacitor included in the induction heating device of the present disclosure is charged, the current may be instantaneously introduced due to the charged voltage of the DC link capacitor (eg, about 344V). This current may flow into/out of the induction heating device, causing a starting noise and damaging the components included.

The present disclosure is an invention for gradually applying electric charges charged in a DC link capacitor included in an induction heating device to a working coil.

The present disclosure is an invention for solving a problem in which noise is generated when a container sensing function using a resonance current of a working coil is used after applying a charging charge of a DC link capacitor to a working coil.

Induction heating device providing a low-noise container detection function according to an embodiment included in the present disclosure is a power supply unit for supplying power, a DC link capacitor connected in parallel with the power supply unit to charge the power supplied from the power supply unit, an induced magnetic field when current flows Free resonance energy is charged to the working coil through the switching-controlled inverter and PWM control so that the working coil that generates It may include a processor that controls the inverter so that the current flowing through the working coil and the resonance capacitor resonates freely, and determines whether the cooking container is present on the working coil based on the current flowing through the working coil.

The induction heating apparatus according to an embodiment included in the present disclosure may further include a container detection noise reduction unit for reducing the storage voltage of the resonance capacitor before the start of free resonance.

The container sensing noise reduction unit may turn off and then turn on the switching element of the inverter included in the resonance circuit during free resonance for a predetermined time before starting the free resonance in order to reduce the storage voltage of the resonance capacitor.

In order to prevent an instantaneous change in current when the inverter starts driving through various embodiments included in the present disclosure, the instantaneous change in the current flowing through the working coil is prevented through PWM control, thereby eliminating the starting noise.

Through various embodiments included in the present disclosure, it is possible to secure stability in driving the inverter by preventing an instantaneous change in current when driving the inverter is started.

Through various embodiments included in the present disclosure, it is possible to remove the operation noise of the container detection function provided in the induction heating device.

1 is a circuit diagram showing the configuration of an induction heating device according to an embodiment.
2 is a diagram illustrating a flow of current when charging free resonance energy according to an embodiment of the present disclosure.
3 is a diagram illustrating a flow of current during free resonance according to an embodiment of the present disclosure.
4 is a view showing operation signals of each element when the induction heating device of the present disclosure operates in a container sensing mode.
5 is a flowchart illustrating a control method for operating the induction heating device of the present disclosure in a low noise container detection mode.
6 is a view showing a gate signal of each switching element according to PWM control of the induction heating device of the present disclosure.
7 is a diagram illustrating an energy relationship between elements included in the induction heating device when the induction heating device of the present disclosure starts sensing the container without reducing the energy stored in the resonance capacitor.
8 is a view for explaining a method of operating the container detection noise reduction unit according to an embodiment of the present disclosure.
9 is a diagram illustrating an energy relationship between elements included in the induction heating device when the induction heating device of the present disclosure starts sensing the container after reducing the stored energy of the resonance capacitor.

Hereinafter, the embodiments will be described in detail with reference to the drawings so that those of ordinary skill in the art can easily carry out the embodiments. The following embodiments may be implemented in various different forms and are not limited to the embodiments described herein.

For clear explanation, parts not related to the description are omitted, and the same reference numerals are given to the same or similar elements throughout the specification. Further, some embodiments will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the present disclosure, if it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the embodiments, the detailed description may be omitted.

In describing the components of the embodiments, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the nature, order, order, or number of the elements are not limited by the terms. When it is described as “connected”, “coupled” or “connected” between any components, any components may be directly connected or connected, and other components may be “interposed” between each component or each component It will be understood that may be “connected”, “coupled” or “connected” through other components.

In the present disclosure, terms such as “comprises”, “consisting of” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one It should be understood that it does not preclude the possibility of the presence or addition of or more other features or numbers, steps, operations, components, parts, or combinations thereof.

In addition, in implementing the present disclosure, components may be subdivided for convenience of description, but these components may be implemented in one device or module, or one component may include a plurality of devices or modules It may be implemented by being divided into .

Hereinafter, an induction heating device according to an embodiment will be described.

1 is a circuit diagram showing the configuration of an induction heating device according to an embodiment.

The induction heating device 100 of the present disclosure includes a power supply unit 110 , a DC link capacitor 120 , a resonance capacitor 160 , a working coil WC, an inverter 130 , an inverter driving unit 135 , and a comparison unit 170 ). , the processor 180 , and at least some or all of the container detection noise reduction unit 190 may be included.

The power supply unit 110 may include an AC power source 113 and a rectifier 115 for converting alternating current into direct current, and supplies power to the induction heating device 100 .

The DC link capacitor 120 may be connected in parallel with the power supply unit 110 to charge power supplied from the power supply unit 110 .

The inverter 130 may switch the voltage applied to the working coil WC so that a high-frequency current flows through the working coil WC. Specifically, the inverter 130 may include a first switching element 131 and a second switching element 132 , and the first switching element 131 and the second switching element 132 are alternately turned on/off. may be repeated to drive the working coil WC. That is, in the first state, the first switching element 131 is turned on, the second switching element 132 is turned off, and in the second state, the first switching element 131 is turned off, and the second switching element 132 is turned off. can be turned on. The inverter 130 may be controlled to repeat the first state and the second state at a predetermined cycle. When switching is controlled so that the first switching element 131 and the second switching element 132 are alternately turned on, the DC voltage from the rectifier 115 may be alternately applied to the working coil WC. The working coil WC may be driven as a DC voltage is alternately applied.

The first switching device 131 and the second switching device 132 may be switching devices made of an insulated gate bipolar transistor (IGBT), but this is only an example, and the switching device may mean a semiconductor device capable of high-speed switching. . As the first switching element 131 and the second switching element 132 are alternately turned on, a high-frequency current flows in the working coil WC, and accordingly, a high-frequency magnetic field may be formed in the working coil WC.

In the working coil WC, current may flow as a DC voltage is alternately applied by the inverter 130, and the working coil WC may generate an induced magnetic field by the high-frequency current to heat the cooking vessel.

One side of the working coil WC is connected to the node 130a between the first and second switching elements 131 and 132 , and the other side of the working coil WC is connected to the node between the first and second resonant capacitors 161 and 162 . may be connected to 160a.

The inverter 130 may be driven by the inverter driving unit 135 .

The inverter driving unit 135 may control switching of the first and second switching elements 131 and 132 constituting the inverter 130 . The inverter driving unit 135 may apply a high-frequency voltage to the working coil WC by controlling the first and second switching elements 131 and 132 to alternately operate with each other. Although the inverter driver 135 and the processor 180 are separately illustrated in this specification, the inverter driver 135 may be included in the processor 180 .

The resonance capacitor 160 may include a plurality of resonance capacitors 161 and 162 connected in series between the DC link capacitor 120 and the working coil WC.

The resonance capacitor 160 may include a first resonance capacitor 161 and a second resonance capacitor 162 . Specifically, one end of the first resonant capacitor 161 is connected to one end 121a from which a voltage is output from the rectifying unit 115 , and the other end is a connection point 160a between the second resonant capacitor 162 and the working coil WC. can be connected to Similarly, the second resonant capacitor 162 has one end connected to the other end 121b from which the voltage is output from the rectifier 115 and the other end connected to the connection point 160a between the first resonant capacitor 161 and the working coil WC. can be connected

The capacitance of the first resonance capacitor 161 and the capacitance of the second resonance capacitor 162 may be the same.

The capacitance of the resonance capacitor 160 may determine the resonance frequency of the induction heating device 100 (resonance frequency). Specifically, the resonance frequency of the induction heating device 100 configured in the circuit diagram as shown in FIG. 1 is determined by the inductance of the working coil WC and the capacitance of the resonance capacitor 160 .

The comparator 170 may compare the current flowing through the working coil WC with a preset reference value. Specifically, the comparator 170 may be a device that senses a current flowing through the working coil WC and outputs the sensed current in the form of a voltage. The comparator 170 may output a pulse by comparing the output voltage with a preset reference value. This will be described later in detail with reference to FIG. 4 .

The processor 180 may control the overall operation of the induction heating apparatus 100 .

The processor 180 may determine whether the cooking vessel is present on the working coil WC based on the output pulse transmitted from the comparator 170 .

The processor 180 may control the switching timing at which the inverter driver 135 drives the first switching element 131 and the second switching element 132 .

In addition, the processor 180 may control the operation of the induction heating apparatus 100 according to the presence or absence of the cooking vessel.

The vessel detection noise reduction unit 190 may include at least some or all of the sink circuit 181 , the delay circuit 183 , and the comparator circuit 185 . The container detection noise reduction unit 190 may be a circuit for reducing energy stored in the resonance capacitor 160 to be described later. More details on this will be provided later.

The induction heating apparatus 100 of the present disclosure may operate in a container detection mode.

The container detection mode means a mode for detecting the presence or absence of a cooking container on the working coil WC of the induction heating apparatus 100 . When the induction heating apparatus 100 is driven to produce a set output despite the absence of a cooking container on the working coil WC, there is a risk that the internal elements may be damaged. Accordingly, the induction heating apparatus 100 of the present disclosure may operate in the container sensing mode for the first time during operation or periodically during operation.

The processor 180 supplies energy to the working coil WC by turning on/off the switching elements constituting the inverter 130 a predetermined number of times or more when operating in the container detection mode, and controls the inverter driving unit 135 to perform walking. Energy supplied to the coil WC may be free-resonant.

When the induction heating device 100 operates in the container sensing mode, free resonance energy is charged to the circuit of the induction heating device 100 including the working coil WC, and the working coil WC free resonates a current, The existence of the cooking vessel is determined by analyzing the waveform of the resonance current flowing through the working coil (WC). In more detail, the induction heating apparatus 100 further includes an element for converting the resonance current of the working coil WC into a pulse voltage, and whether or not the cooking container exists based on the width of the output pulse or the counted number of pulses to detect

In this regard, a method of determining the presence of a cooking vessel on the working coil WC by the induction heating apparatus 100 of the present disclosure operating in the vessel detection mode will be described in detail with reference to FIGS. 2 to 4 .

2 is a diagram illustrating a flow of current when charging free resonance energy according to an embodiment of the present disclosure; 3 is a diagram illustrating a flow of current during free resonance according to an embodiment of the present disclosure. Figure 4 is a view showing the operation signal of each element when the induction heating device of the present disclosure free resonance.

First, referring to FIGS. 2 and 3 , the processor 180 controls to repeatedly turn on/off the first switching element 131 and turn off/on the second switching element 132 as shown in FIG. 2 . Thus, energy can be supplied to the working coil WC. That is, the processor 180 may supply energy to the working coil WC by alternately operating the first switching element 131 and the second switching element 132 .

Thereafter, as shown in FIG. 3 , the processor 180 may turn off the first switching element 131 and turn on the second switching element 132 to free resonance with energy stored in the working coil WC. Conversely, the processor 180 may turn on the first switching element 131 and turn off the second switching element 132 to free-resonate the energy supplied to the working coil WC. That is, the processor 180 may turn on any one of the first and second switching elements 131 and 132 and turn off the other to free-resonate the energy supplied to the working coil WC.

In FIG. 3, the working coil WC, the second switching element 132, and the second capacitor 162 are illustrated as forming a resonance circuit, but this is only an example, and the working coil WC and the first switching element ( 131 and the first capacitor 161 may form a resonance circuit.

Hereinafter, for convenience of description, a case in which the processor 180 turns off the first switching element 131 and turns on the second switching element 132 will be described as an example.

4 is a diagram illustrating operation signals of each element when free resonance occurs according to an embodiment of the present disclosure. The first graph 401 is a gate signal of the first switching device 131 , and the second graph 403 is a gate signal of the second switching device 132 . The third graph 405 is a resonance current flowing through the working coil WC, and the fourth graph 407 is an output signal of the comparator 170 .

The comparator 170 may output a pulse by comparing the current 405 flowing through the working coil WC with a preset reference value in a state where only the second switching element 132 is turned on. The processor 180 may determine whether the cooking vessel is present on the working coil WC based on the pulse 407 output from the comparator 170 .

This is because the magnitude of the current flowing through the working coil WC when the cooking container is positioned on the working coil WC is different from the magnitude of the current flowing through the working coil WC when the cooking container is not positioned on the cooking container. This is because the pulse output from the comparator 170 varies depending on the presence or absence.

For example, when the cooking container is positioned on the working coil WC, the magnitude of the current flowing through the working coil WC may be smaller than the magnitude of the current flowing through the working coil WC when the cooking container is not positioned.

According to an embodiment, the processor 180 may measure the width of the waveform 407 output from the comparator 170 while the second switching element 132 is on and determine whether the cooking container exists, and the processor Reference numeral 180 counts the number of pulse repetitions of the waveform 407 output from the comparator 170 while the second switching element 132 is turned on to determine whether the cooking container exists.

For example, when there is no load on the working coil WC, the width of the waveform 407 output from the comparator 170 may be the longest. When a load exists on the working coil WC, the width of the waveform 407 output from the comparator 170 may be shortened.

If the width of the waveform 407 output from the comparator 170 is equal to or less than the preset reference time, the processor 180 may determine that the cooking vessel exists, and the processor 180 outputs the output from the comparator 170 . When the width of the waveform 407 exceeds a preset reference time, it may be determined that the cooking container does not exist.

According to another embodiment, the processor 180 may count the pulses of the waveform 407 output from the comparator 170 during a time during which the second switching element 132 maintains an on state. Here, counting the pulses of the waveform 407 may mean counting the output from low to high and then output again as low as one pulse.

The processor 180 may determine whether the counted number of pulses is less than or equal to a preset reference number. The processor 180 may determine that the cooking container exists when the counted number of pulses is less than or equal to a preset reference number, and the processor 180 determines that the cooking container exists when the counted number of pulses exceeds the preset reference number. can be judged not to be.

Through this, the induction heating apparatus 100 of the present disclosure may operate in a container detection mode.

On the other hand, the induction heating apparatus 100 may charge the working coil (WC) with the charging voltage of the DC link capacitor 120 connected in parallel with the power supply unit 110 . The DC link capacitor 120 may be in a state of being charged by a predetermined voltage based on the rectified voltage being applied from the power supply unit 110 . For example, even if an AC input voltage of 220V is rectified in the power supply unit 110 and applied to the DC link capacitor 120 , the instantaneous maximum voltage of the input voltage has a value of about 220/0.707 V, so the DC link capacitor 120 . may be in a state of being charged to a voltage of about 311V. Accordingly, when the induction heating device 100 is driven in a state in which the charged DC link capacitor 120 is not discharged, a high current instantly flows in the working coil WC. In this way, when the voltage charged in the DC link capacitor 120 is inputted to the working coil WC at once, noise may be generated and elements included therein may be damaged.

In addition, noise is generated even when a resonance current flows to the working coil WC to operate in the above-described container sensing mode.

Hereinafter, for convenience of description, the noise generated by the DC link capacitor 120 is named as starting noise, and the noise when operating in the vessel detection mode is named as vessel detection noise.

Such starting noise and vessel detection noise not only cause inconvenience to users, but also cause misunderstanding due to malfunction of the device.

Therefore, the present disclosure is to prevent the instantaneous current flow of the induction heating device 100, and to provide a method for operating in a low noise container detection mode that reduces both the starting noise and the container detection noise.

Next, FIG. 5 is a flowchart illustrating a control method for operating the induction heating device of the present disclosure in a low noise container detection mode.

Referring to FIG. 5 , the induction heating device 100 of the present disclosure may charge free resonance energy for container detection through PWM control ( S501 ). The processor 180 may charge the free resonance energy for container detection by controlling the PWM (Pulse Width Modulation) switching element of the inverter 130 .

Next, with reference to FIG. 6 , a method for the processor 180 to charge free resonance energy for container detection through PWM control will be described.

6 is a view showing a gate signal of each switching element according to PWM control of the induction heating device of the present disclosure.

6 (a) shows the gate signal 601 of the first switching element 131 and the gate signal 603 of the second switching element 132 in the first section of resonant current energy charging through PWM control, 6 (b) shows the gate signal 605 of the first switching element 131 and the gate signal 607 of the second switching element 132 in the second section of resonant current energy charging through PWM control, FIG. 6C shows the gate signal 609 of the first switching element 131 and the gate signal 611 of the second switching element 132 in the third period of resonant current energy charging through PWM control.

The processor 180 may PWM control the switching element of the inverter 130 to charge the resonance current energy. In more detail, the processor 180 adjusts the operating frequency and duty cycle of the first switching element 131 and the second switching element 132 from a high frequency low Duty to a low frequency high Duty in order to gradually charge the resonance current energy. can be controlled with

For example, in the processor 180 , as shown in FIG. 6A , in the first section, the duty cycle of the first switching element 131 is 0%, and the duty cycle of the second switching element 132 is 0%. It can be controlled with a high frequency operating frequency (eg, 85 kHz) at 33%, and in the second section after the first section, as shown in FIG. 6 ( b ), the operating duty cycle of the first switching element 131 is 5 %, the operating duty cycle of the second switching element 132 is 57%, which can be controlled at a high frequency operating frequency (eg, 85 kHz), and in the third section after the second section (c) and Likewise, the operation duty cycle of the first switching element 131 is 30%, and the operation duty cycle of the second switching element 132 is 45%, so that the low frequency operation frequency (eg, 65 kHz) can be controlled. The above-described duty cycle and operating frequency are merely examples and are not limited thereto.

According to the above-described example, when starting the startup, the processor 180 of the present disclosure may control the operating frequency of each switching element of the inverter 130 from a high frequency and a low duty to a low frequency and a high duty.

Through this, since the charging voltage of the DC link capacitor 120 does not instantaneously flow into the working coil WC, there is an advantage in that starting noise can be reduced.

Returning to FIG. 5 again, the induction heating device 100 may reduce the energy stored in the resonance capacitor 160 before the free resonance starts ( S503 ). Step S503 may be a step performed to reduce container detection noise generated when operating in the container detection mode.

The container detection noise may be generated due to energy stored in the resonance capacitor 160 during free resonance for container detection. This will be described in detail with reference to FIG. 7 .

7 is a diagram illustrating an energy relationship between elements included in the induction heating device when the induction heating device of the present disclosure starts sensing the container without reducing the stored energy of the resonance capacitor.

Referring to FIG. 7 , the first waveform 1301 represents the current flowing through the working coil WC, the second waveform 1303 represents the gate signal of the first switching element 131 , and the third waveform 1305 . may represent the gate signal of the second switching element 132 . The fourth waveform 1307 may represent the voltage of the first resonant capacitor 161 , and the fifth waveform 1309 may represent the voltage of the second resonant capacitor 162 .

The first period T1 is a period in which energy is charged to the working coil WC for free resonance, and the first switching element 131 and the second switching element 132 operate on/off through the above-described duty control. is a repeating section. At this time, the current 1301 flowing through the working coil WC repeatedly increases and decreases to a predetermined size, and free resonance energy is charged. The voltages 1307 and 1309 of the first and second resonant capacitors 161 and 162 also repeatedly increase and decrease to a predetermined level.

The second section T2 is a section in which free resonance occurs in the resonance circuit including the working coil WC and the second resonance capacitor 162 , and the gate signal 1303 of the first switching element 131 is kept off and , the gate signal 1305 of the second switching element 132 is maintained on. At this time, it can be seen that the current 1301 flowing through the working coil WC gradually decreases while performing free resonance.

On the other hand, the magnitude of the current 1301 flowing through the working coil WC at the start point of the second section T2 is the maximum value 1310 of the current 1301 flowing through the working coil WC in the first section T1. It can be seen that exceeding This is because free resonance starts when the storage voltage of the second resonance capacitor 162 is high.

Accordingly, it can be seen that the container detection noise is generated due to the storage voltage of the resonance capacitor 160 included in the free resonance circuit for container detection.

Next, a control method for reducing the vessel detection noise generated when the induction heating apparatus 100 of the present disclosure operates in the vessel sensing mode will be described with reference to FIG. 8 .

Fig. 8 (a) is a diagram showing a circuit diagram of the vessel sensing noise reducing unit, and Fig. 8 (b) is a diagram showing an output signal according to the operation of the vessel sensing noise reducing unit.

Referring to (a) of FIG. 8 , the processor 180 provides an enable signal to the sink circuit 181 and the delay circuit 183 of the container detection noise reduction unit 190 to reduce the energy stored in the resonance capacitor 160 . can be transmitted. When it is determined that free resonance energy is stored through the above-described PWM control, the processor 180 applies an Enable signal to the sink circuit 181 and the delay circuit 183 of the vessel detection noise reduction unit 190 to start free resonance. can be transmitted

The sink circuit 181 may be a circuit for turning off signals of all switching elements of the inverter 130 . For example, when the enable signal is input to the sink circuit 181 , both the first switching element 131 not included in the free resonance circuit for container detection and the second switching element 132 included in the free resonance circuit are activated. A signal for turning off may be transmitted to the inverter driving unit 135 .

The delay circuit 183 may be a circuit for delaying the time it takes for the switching element included in the free resonance circuit for container detection to turn on again for a predetermined time. For example, the delay circuit 183 may output a voltage gradually increasing in magnitude when an enable signal is input. According to an embodiment, the Delay circuit 183 may be composed of an RC circuit, and according to the time constant of the Delay circuit 183, a predetermined time it takes for the switching element included in the free resonance circuit for container detection to turn on again. This can be adjusted.

The comparator circuit 185 may be a circuit that compares a reference voltage and an input voltage, and outputs an ON signal when the reference voltage and the input voltage match. For example, when the reference voltage of the comparator circuit 185 is 3.3 V, when the voltage input from the delay circuit 183 becomes 3.3 V, the comparator circuit 185 may output a high value.

Although the delay circuit 183 and the comparator circuit 185 are separately shown in FIG. 8(a), the two circuits are combined to turn off the switching element of the inverter included in the resonance circuit at the time of free resonance for a predetermined time before the start of free resonance. It can be composed of one circuit that turns on.

In FIG. 8B , a first graph 801 indicates an enable signal transmitted from the processor 180 , a second graph 802 indicates a reference voltage of the comparator circuit 185 , and a third graph 803 . ) represents the input voltage of the comparator circuit 185 (that is, the output voltage of the Delay circuit 183), the fourth graph 804 represents the output voltage of the comparator circuit 185, and the fifth graph 805 is A gate signal of the first switching device 131 (a switching device not included in the resonance circuit) is shown, and a sixth graph 806 is a gate signal of the second switching device (132, a switching device included in the resonance circuit). In FIG. 8 , t1 and t2 refer to time points different from those of T1 and T2 in FIGS. 7 and 9 .

When the enable signal 801 of the processor 180 is turned on at time t1 of FIG. 8B , both the first switching element 131 and the second switching element 132 are turned off by the sink circuit 181 . . At this time, the output voltage 803 of the delay circuit 183 is gradually increased. At time t2, the reference voltage 802 of the comparator circuit 185 and the output voltage 803 of the delay circuit 183 coincide, and the comparator circuit 185 turns on the second switching element 132 with an output signal ( 804) is transmitted to the inverter driving unit 135 . In this specification, the time difference Δt between t2 and t1 may be defined as a predetermined time for reducing the storage voltage of the resonance capacitor 160 . The predetermined time may be 4 us, but this is only an example.

According to the above-described embodiment, the inverter driving unit 135 performs the first switching element 131 and the second switching according to the signal output from the container detection noise reduction unit 190 based on the enable signal output from the processor 180 . By controlling the on/off operation of the element 132 , it is possible to control the timing of flowing the resonance current in the working coil WC and the reduction of the stored energy of the resonance capacitor 160 .

The sink circuit 181, the delay circuit 183, and the comparator circuit 185 included in the container detection noise reduction unit 190 may include a logic circuit in which a boolean algebra is implemented in a physical device, It may be pre-designed. According to an embodiment, the logic circuits included in the sink circuit 181 , the delay circuit 183 , and the comparator circuit 185 are AND, OR, NOR, NOT, NAND, XOR, XNOR, flip-flops, and latches. It can be implemented as various combinational logic circuits or sequential logic circuits such as latches and buffers, and further includes various logic elements that perform complex logic functions combining basic Boolean algebra. can

9 is a diagram illustrating an energy relationship between elements included in the induction heating device when the induction heating device of the present disclosure starts sensing the container after reducing the stored energy of the resonance capacitor.

Referring to FIG. 9 , a first waveform 1501 indicates a current flowing through the working coil WC, a second waveform 1503 indicates a gate signal of the first switching element 131 , and a third waveform 1505 . may represent the gate signal of the second switching element 132 . The fourth waveform 1507 may represent the voltage of the first resonant capacitor 161 , and the fifth waveform 1509 may represent the voltage of the second resonant capacitor 162 .

The first period T1 is a period in which energy is charged to the working coil WC for free resonance, and the first switching element 131 and the second switching element 132 operate on/off through the above-described duty control. is a repeating section. At this time, the current 1501 flowing through the working coil WC is repeatedly increased and decreased to a predetermined size, and the free resonance energy is charged. The voltages 1507 and 1509 of the first and second resonant capacitors 161 and 162 also repeatedly increase and decrease to a predetermined level.

The second period T2 is a period in which free resonance occurs in the resonance circuit including the working coil WC and the second resonance capacitor 162 , and the gate signal 1503 of the first switching element 131 is kept off and , the gate signal 1505 of the second switching element 132 is maintained on.

Meanwhile, before the start of the second period T2 , that is, before the start of free resonance, the second switching element 132 preset to maintain an on state during free resonance turns off for a predetermined time t and then turns on again. will keep

At this time, it can be seen that the storage voltage 1509 of the second resonance capacitor 162 is in a low state unlike in FIG. 7 . In addition, it can be seen that the resonance current 1501 of the working coil WC also does not exceed the maximum value of the current 1501 flowing through the working coil WC in the first section.

Therefore, through the above-described control method, the induction heating apparatus 100 of the present disclosure reduces the stored energy of the resonance capacitor 160 and then operates in the container sensing mode, there is an advantage in that the operation noise can be reduced.

Returning to FIG. 5 again, the induction heating apparatus 100 may start free resonance to detect a container (S505).

The present disclosure can reduce the starting noise of the induction heating device 100 itself through the aforementioned PWM control, and also when the induction heating device 100 operates in the container detection mode through the inverter 130 control, the container detection noise is also Since it can be reduced, there is an advantage that it can provide a container detection function with low noise.

Induction heating apparatus 100 according to an embodiment may further include a computer-readable recording medium or memory (not shown) for recording a program for performing the above-described various methods. The method for the present disclosure described above may be provided by being recorded in a computer-readable recording medium as a program for execution by a computer.

The method of the present disclosure may be executed through software. When executed as software, the constituent means of the present disclosure are code segments that perform necessary tasks. The program or code segments may be stored on a processor-readable medium.

The computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored. Examples of the computer-readable recording device include ROM, RAM, CD-ROM, DVD±ROM, DVD-RAM, magnetic tape, floppy disk, hard disk, and optical data storage device. In addition, the computer-readable recording medium is distributed in network-connected computer devices so that the computer-readable code can be stored and executed in a distributed manner.

The present disclosure described above is capable of various substitutions, modifications and changes within the scope that does not depart from the technical spirit of the present invention for those of ordinary skill in the art to which the present disclosure pertains. It is not limited by the drawings.

180: processor
190: vessel detection noise reduction unit

Claims (13)

In the induction heating device for providing a quiet container detection function,
a power supply unit for supplying power;
a DC link capacitor connected in parallel with the power supply unit to charge power supplied from the power supply unit;
a working coil that generates an induced magnetic field when an electric current flows;
a resonance capacitor connected to the working coil to form a resonance circuit;
an inverter controlling switching so that the DC voltage of the DC link capacitor is applied to the working coil; and
Free resonance energy is charged in the working coil through PWM control, and the inverter is controlled so that the current flowing through the working coil and the resonance capacitor has free resonance, and based on the current flowing in the working coil, cooking is performed on the working coil. and a processor for determining if a vessel is present. The method according to claim 1,
The processor is
changing an operating frequency of the inverter from a first frequency to a second frequency less than a first frequency, and changing a duty cycle of the inverter from a first duty cycle to a second duty cycle greater than the first duty cycle The method according to claim 1,
Further comprising a container sensing noise reduction unit for reducing the storage voltage of the resonance capacitor before the start of the free resonance, induction heating device. 4. The method according to claim 3,
The container detection noise reduction unit,
In order to reduce the storage voltage of the resonance capacitor, the switching element of the inverter included in the resonance circuit at the time of free resonance is turned off for a predetermined time before the free resonance starts and then turned on, an induction heating device. 5. The method according to claim 4,
The container detection noise reduction unit,
Induction including a sink circuit that turns off all the switching elements of the inverter, a delay circuit and a comparator circuit that turns on and off the switching elements of the inverter included in the resonance circuit during free resonance for a predetermined time before starting the free resonance heating device. 5. The method according to claim 4,
The container detection noise reduction unit,
When the switching element included in the resonance circuit at the time of the free resonance is a first switching element, the induction heating device for turning the first switching element off and on for a predetermined time before starting the free resonance. 5. The method according to claim 4,
The container detection noise reduction unit,
When the switching element included in the resonance circuit at the time of the free resonance is a second switching element, the induction heating device turns on and off the second switching element for a predetermined time before starting the free resonance. The method according to claim 1,
When the cooking vessel is present on the working coil, the magnitude of the current flowing through the working coil during the free resonance is smaller than the magnitude of the current flowing when the cooking vessel does not exist, the induction heating apparatus. A method of operating an induction heating device, comprising:
charging free resonance energy to the working coil through PWM control;
reducing the storage voltage of the resonant capacitor;
controlling an inverter so that a current flowing through the working coil and the resonance capacitor resonates freely; and
and determining whether a cooking vessel is present on the working coil based on the current of the working coil. 10. The method of claim 9,
The step of charging free resonance energy to the working coil through the PWM control is,
changing an operating frequency of the inverter from a first frequency to a second frequency less than the first frequency and changing a duty cycle of the inverter from a first duty cycle to a second duty cycle greater than the first duty cycle. 10. The method of claim 9,
Reducing the storage voltage of the resonant capacitor comprises:
When the current flowing through the working coil and the resonance capacitor free resonance, if the switching device included in the resonance circuit is the first switching device, turning the first switching device off and on for a predetermined time before the free resonance starts A method comprising 10. The method of claim 9,
Reducing the storage voltage of the resonant capacitor comprises:
When the current flowing through the working coil and the resonance capacitor free resonance, if the switching element included in the resonance circuit is the second switching element, turning off the second switching element for a predetermined time before starting the free resonance and then turning on the second switching element A method comprising In a recording medium recording a method of operating an induction heating device, the method comprises:
charging free resonance energy to the working coil through PWM duty control;
reducing the storage voltage of the resonant capacitor;
controlling an inverter so that a current flowing through the working coil and the resonance capacitor resonates freely; and
and determining whether a cooking vessel is present on the working coil based on the current of the working coil.

Images