KR20210054479A - Induction heating apparatus - Google Patents

Abstract

The present invention relates to an induction heating device which can ensure safety. The induction heating device comprises: a coil; an inverter configured to provide a drive current to the coil; a current sensor measuring a driving current of the coil; and a control unit controlling the inverter so that the driving current follows a target current based on a user input. The control unit maintains switching operation of the inverter based on that a time, at which the driving current smaller than a reference current is sensed, is smaller than a reference time, and operation of the inverter can be stopped based on that a time, at which the driving current smaller than the reference current is sensed, is equal to or longer than the reference time.

Description

Induction heating device {INDUCTION HEATING APPARATUS}

The disclosed invention relates to an induction heating device using a heating coil.

It is known that the resonance frequency of the circuit changes when the cooking method of shaking cookware (pan): pushing forward and drawing back cookware (pan) is performed in an induction heating cooker. In this case, in order to keep the heating power constant in the cooking utensil shake recipe, either (1) the operating frequency of the high-frequency current flowing through the heating coil is immediately lowered, or (2) the output voltage is increased. However, any countermeasure among the above (1) and (2) may cause heating to be stopped due to an increase in the voltage of the resonant capacitor. Therefore, in general, the conventional induction heating cooker responds by stopping heating or lowering the heating power rather than maintaining a constant heating power.

For example, the induction heating cooker of Patent Document 1 does not stop the inverter circuit when it is judged that the object to be heated is not placed on the top plate or the object to be heated is not suitable for heating. It is configured to continue the operation for a certain period of time in a state in which the output is suppressed.

[Patent Literature]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2012-89433

However, in the prior art disclosed in Patent Document 1, output is suppressed by the output restraining means even when the object to be heated is not temporarily placed on the top plate when the cookware is shaken. In this case, in the prior art, there is a problem in that it takes time to reheat until the set output when the cookware is returned to the top plate.

The disclosed invention has been made in view of such a point, and an object thereof is to configure the state of disengagement of an object to be heated at low cost.

In addition, it is an object of the present invention to heat the cookware at a set heat faster than before, without consuming power unnecessarily, and when the cookware is returned to its original position in the case of temporary separation of the cookware such as shaking the cookware.

Induction heating apparatus according to the disclosed invention, the coil; An inverter configured to provide a drive current to the coil; A current sensor measuring the driving current of the coil; And a control unit for controlling the inverter so that the driving current follows a target current based on a user input. The control unit maintains the switching operation of the inverter based on the detection time of the driving current smaller than the reference current is less than the reference time, and the detection time of the driving current smaller than the reference current is greater than or equal to the reference time. Thus, the operation of the inverter can be stopped.

The control unit may identify whether a time when a driving current smaller than the reference current is sensed is greater than or equal to the reference time based on detection of a driving current smaller than the reference current.

The control unit, based on the detection of a driving current greater than the reference current before a time when a driving current smaller than the reference current is sensed reaches the reference time, the inverter so that the driving current follows the target current. Can be controlled.

The control unit may reduce the switching frequency of the inverter to a first speed based on the detection of a driving current smaller than the reference current.

The controller may increase the switching frequency of the inverter to a second speed greater than the first speed based on the detection of a driving current greater than the reference current while reducing the switching frequency of the inverter to the first speed. have.

The controller may increase the switching frequency of the inverter to a third speed based on the detection of a driving current smaller than the reference current.

The control unit may reduce the switching frequency of the inverter to a fourth speed greater than the third speed based on the detection of a driving current greater than the reference current while increasing the switching frequency of the inverter to the third speed. have.

In accordance with the disclosed invention, a method for controlling an induction heating device including a coil includes: providing a driving current to the coil; Measuring the driving current of the coil; And adjusting the frequency of the driving current so that the driving current follows a target current based on a user input. Adjusting the frequency of the driving current is based on the detection time of the driving current smaller than the reference current is less than the reference time, maintaining the frequency of the driving current, and the time when the driving current smaller than the reference current is detected It may include stopping providing the driving current based on being equal to or greater than the reference time.

According to the disclosed invention, it is possible to configure the detection of the separation state of the object to be heated at low cost.

In addition, since the control is stabilized, in the case of temporary separation of the cookware such as shaking of the cookware, the impedance of the heating coil increases compared to the stable arrangement state of the cookware, so unnecessary power consumption does not occur. In addition, when the cookware returns to the stable arrangement state from the temporary separation of the cookware, it can be immediately operated under the control state before shaking the cookware, so that heating with a set heat power can be achieved faster than in the prior art.

1 is a diagram showing a configuration example of an induction heating device according to a first embodiment.
2 is a diagram showing a relationship between an operating point and a change in impedance according to a position of an object to be heated.
3 is a diagram showing an example of time changes in set power, detected power, and inverter output current in power control of an induction heating device.
4 is a flowchart showing an example of the flow of power control for the installation state of the cookware.
5A is a view for explaining the operation of the induction heating device in the power control flow of FIG. 4.
5B is a view for explaining the operation of the induction heating device in the power control flow of FIG. 4.
5C is a view for explaining the operation of the induction heating device in the power control flow of FIG. 4.
5D is a view for explaining the operation of the induction heating device in the power control flow of FIG. 4.
6 is a view for explaining another example of the power control method of the induction heating device.
7 is a view for explaining another example of the power control method of the induction heating device.
8 is a diagram for explaining the operation of the induction heating device, and is a diagram showing changes in driving power and driving frequency.
FIG. 9 is an enlarged view of a partial time range of FIG. 8, and is a diagram illustrating a change in a driving frequency and an impedance of a series resonance circuit.
FIG. 10 is an enlarged view of a partial time range of FIG. 8 and is a diagram illustrating a change in driving frequency and impedance of a series resonant circuit.
11 is a diagram for explaining the operation of the induction heating device, and is a diagram showing changes in driving power and execution voltage.

The same reference numerals refer to the same elements throughout the specification. This specification does not describe all elements of the embodiments, and general content in the technical field to which the disclosed invention belongs or content overlapping between the embodiments will be omitted. The term'unit, module, member, block' used in the specification may be implemented in software or hardware, and according to embodiments, a plurality of'units, modules, members, blocks' may be implemented as one component, It is also possible for one'unit, module, member, block' to include a plurality of components.

Throughout the specification, when a part is said to be "connected" with another part, this includes not only the case of being directly connected, but also the case of indirect connection, and the indirect connection includes connection through a wireless communication network. do.

In addition, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Throughout the specification, when a member is said to be positioned "on" another member, this includes not only the case where a member is in contact with the other member, but also the case where another member exists between the two members.

Terms such as first and second are used to distinguish one component from other components, and the component is not limited by the above-described terms.

Singular expressions include plural expressions, unless the context clearly makes exceptions.

In each step, the identification code is used for convenience of explanation, and the identification code does not describe the order of each step, and each step may be performed differently from the specified order unless a specific order is clearly stated in the context. have.

Hereinafter, embodiments of the disclosed invention will be described with reference to the drawings. Here, the description of the following preferred embodiments is essentially merely an illustration, and is not intended to limit the disclosed invention, its applications, or its use.

<First Example>

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

In the example of Fig. 1, the power supplied from the AC power supply 10 is rectified in the rectifying circuit 11, boosted in the PFC circuit 12, and charged in the output capacitor 13. The PFC circuit 12 can use a conventionally known configuration, and includes, for example, a choke coil 14, a switching element 15, and a rectifier diode 16. The AC power supply 10 is provided with a voltage sensor 17 for measuring a power supply voltage and a current sensor 18 for measuring a power current.

The induction heating device (A) is a series including an inverter (30) that converts DC power received from the output condenser (13) into AC power and outputs it, and a heating coil (41) that receives and heats power supplied from the inverter (30). It includes a resonance circuit 40 and a control unit 50.

The circuit configuration of the inverter 30 is not particularly limited, and a conventionally known configuration can be applied. For example, FIG. 1 shows an inverter 30 of a bridge configuration in which two pairs of arms 31 and 32 are connected in parallel. In Fig. 1, in two pairs of arms 31 and 32, two switching elements 33 are connected in series, respectively. In addition, each switching element 33 is composed of a parallel circuit of a transistor and a diode connected to the transistor in parallel and reverse directions. Accordingly, in the inverter 30, each switching element 33 performs a switching operation under the control of the controller 50, so that DC power is converted into AC power, and the converted AC power is output. In the following description, a connection node between the two switching elements 33 on one arm 31 is referred to as a first node N1, and a connection node between the two switching elements 33 on the other arm 32 is first. It will be referred to as a 2 node (N2).

The series resonance circuit 40 includes a heating coil 41 and a resonance capacitor 42 provided in series between the first node N1 and the second node N2. The shape of the heating coil 41 is not particularly limited, but may be, for example, an annular coil wound in a spiral shape along a predetermined one direction. In addition, a current sensor 43 for measuring a current flowing through the series resonance circuit 40 is provided between the first node N1 and the second node N2.

The control unit 50 includes an input voltage detection unit 51, an input current detection unit 52, an output current detection unit 53, and a drive processing unit 54. The input voltage detection unit 51 is for detecting the input voltage to the induction heating device A, that is, the inverter 30, and detects the input voltage to the inverter 30 based on the output of the voltage sensor 17, for example. do. The input current detection unit 52 is for detecting the input current to the induction heating device A, that is, the inverter 30, for example, detects the input current to the inverter 30 based on the output of the current sensor 18. do. The output current detection unit 53 is for detecting the output current of the inverter 30, that is, the current flowing through the heating coil 41, for example, the output power of the inverter 30 based on the output of the current sensor 43 Is detected.

The drive processing unit 54 has a power calculation function, a switching control function, a responsiveness change function, and a stop delay function.

The power calculation function is a function of calculating the input power or output power of the inverter 30. Specifically, the drive processing unit 54 calculates the input power of the inverter 30 based on the detection result of the input current detection unit 52 and the detection result of the input voltage detection unit 51. Further, the drive processing unit 54 calculates the output power of the inverter 30 based on the detection result of the output current detection unit 53. The power calculation function of the input current detection unit 52, the input voltage detection unit 51, and the drive processing unit 54 is an example of a power detection unit that detects the input power of the inverter 30. The power calculation function of the output current detection unit 53 and the drive processing unit 54 is an example of a power detection unit that detects the output power of the inverter 30. Here, the configuration of FIG. 1 exemplifies an example in which both the input power and the output power of the inverter 30 can be detected, but either input power or output power may be detected.

The switching control function turns on the switching element 15 of the inverter 30 based on the set power set for heating the heating coil and the power calculated by the power calculation function (hereinafter referred to as inverter power (Pinv)). This is a function to control /off. The set electric power is, for example, electric power set according to the amount of heating required to realize a target heat power (hereinafter, referred to as a target heat power), such as a heat power set by a user. Inverter power Pinv is an example of detection power. Here, the power output from the inverter 30 and the power detected by the controller 50 are substantially the same. Therefore, in the present embodiment, the power output from the inverter 30 is sometimes referred to as inverter power Pinv.

The responsiveness change function is a function that changes the control responsiveness to changes in the state of the object to be heated, for example. The stop delay function is a function of delaying the timing of stopping or suppressing the output of the inverter 30 when the inverter power Pinv is less than the cooking appliance departure detection value, which will be described later. Here, the contents of the switching control function, the responsiveness change function, and the stop delay function will be described in detail in the description of the operation of the induction heating device A to be described later. Responsiveness changes include changes in control response speed.

FIG. 2 is a diagram showing a relationship between an operating point and a change in impedance according to a position of a cookware that is an object to be heated.

In FIG. 2, the thick solid line indicates between the operating frequency of the inverter 30 and the impedance of the heating coil 41 when the cookware is placed in the center of the heating coil 41 (hereinafter referred to as “the center of the cooker”). Represents the relationship. The thin solid line represents the relationship between the operating frequency of the inverter 30 and the impedance of the heating coil 41 in a state in which the cooking utensil is separated from the heating coil 41 by about half. The dotted line shows the relationship between the operating frequency of the inverter 30 and the impedance of the heating coil 41 in a detached state in which the cooking appliance is completely shifted from the heating coil 41. In addition, in FIG. 2, a triangle mark indicates a movement trajectory of an operating point in a control method (hereinafter referred to as a comparative example) in which the operating frequency is followed so as to operate at a resonant frequency that has been generally performed in the prior art, and the circle mark is in the present embodiment. The movement trajectory of the operating point in the induction heating device A is shown. As shown in FIG. 2, in the disclosed invention, the inverter 30 supplies driving power of a frequency higher than the resonance frequency of the series resonance circuit 40 to the series resonance circuit 40.

As shown in Fig. 2, when the cooking appliance is horizontally separated from the center of the cooking appliance from the top plate (not shown) in the induction heating device A, the resonance frequency is lowered and the series resonance circuit 40 The impedance at the resonance point of is decreased.

In the induction heating apparatus according to the comparative example, since the heating coil is controlled to operate near the resonance frequency as described above, the operating frequency of the heating coil decreases as the cookware is separated, and the impedance of the heating coil decreases ( See the triangular mark in Fig. 2). In this case, the voltage of the resonant capacitor increases and the current flowing through the series resonant circuit (heating coil) increases. Here, since the voltage of the resonant capacitor cannot be directly monitored, in the induction heating apparatus according to the comparative example, as shown in the bottom of Fig. 3, when the current flowing through the heating coil exceeds a predetermined threshold (Fig. 3 Refer to t11 at the bottom), it is determined that cooking utensils are separated. After that, the induction heating device according to the comparative example can stop the output current of the inverter. Here, in the induction heating apparatus according to the comparative example, when the cookware returns to the center, the heating operation is performed again, but since the output of the inverter is suppressed or stopped, it takes time to reach the target thermal power.

On the contrary, the induction heating device A of the present embodiment can maintain the operating state before that even when a change in the resonance frequency occurs, such as caused by the separation of cookware, in the normal operating state of the induction heating device A. . Specifically, for example, the induction heating device (A) lowers the response speed of the control unit 50 to lower the frequency followability to the fluctuation of the resonance frequency, so that the inverter 30 maintains the operating state up to that point. Can be controlled. In other words, the induction heating device (A) of the present embodiment, even when the cookware is separated, the control unit 50 can be such that there is no substantial change in the driving frequency for driving the inverter 30 and the output voltage of the inverter. . Here, "control so that there is no change" means not only controlling so that there is no change at all, but also the output power is constant power for gentle changes in impedance such as slight changes in the installation position of the heated object or temperature changes. In the case of performing a follow-up control by (constant power), the control includes a slight change in the driving frequency or the output voltage of the inverter due to a change in the response speed in the range operated by this control.

As indicated by the circle mark in Fig. 2, the impedance of the series resonance circuit 40 increases as the cooking utensils are shifted and separated. As a result, as shown at the top of FIG. 3, the output power of the inverter 30 is reduced, so that unnecessary power is not consumed. In addition, since the induction heating device A of the present embodiment maintains the operating state in the normal operation state even when the cooking appliance is separated, the target heat power is immediately obtained when the cooking appliance returns to the center of the heating coil 41. Can reach you. Comparing the upper end (Example) and the lower end (Comparative Example) of FIG. 3, the return time Tu2 of the comparative example is significantly larger than the return time Tu1 of the embodiment. Here, in the above description, "there is no substantial change in the driving frequency" includes not only a case where there is no change in the driving frequency, but also a slight change or fluctuation in the driving frequency under the influence of a circuit or a control system. For example, the amount of frequency fluctuation included in the case of "there is no substantial change in the driving frequency" is a frequency that is greater than the fluctuation of the resonance frequency due to the temperature change of the cookware, for example, 100 Hz/sec or more and 1 kHz/sec or less. Is the frequency of the degree. At this time, the operation in this section is an example of the operation realized by using the above-described responsiveness change function.

Hereinafter, a specific operation of the induction heating apparatus A will be described with reference to the flowchart of FIG. 4 and the waveform diagrams of FIGS. 5 and 8 to 11. 8 shows the change in driving power and driving frequency of the inverter 30 with time change. In addition, FIG. 9 shows, for example, a change in the driving frequency and impedance of the inverter 30 with respect to the time change by enlarging a part of the time period between the times t10 to t12 in FIG. 8.

When the operation of the induction heating device A is started at time t1 in FIG. 8, the control unit 50 lowers the driving frequency of the inverter 30 so that the frequency control amount becomes a predetermined control amount per unit time (hereinafter, a normal control amount). The normal control amount of the driving frequency can be set arbitrarily. Then, at time t2, when the driving frequency of the inverter 30 reaches a predetermined frequency, the control unit 50 operates the induction heating device A in a normal operation mode. The driving frequency at this time is set to a frequency higher than the resonance frequency fq of the series resonance circuit 40.

Fig. 4 is a diagram for explaining the operation after entering the normal operation mode (after the normal operation mode). Here, "normal operation" refers to a state in which the control of the inverter 30 for heating is stabilized by reaching a target thermal power set by a user or an internal program.

In step S1 of Fig. 4, it is determined whether or not the output current of the inverter 30 (hereinafter referred to as inverter current Iinv) exceeds the foreign matter detection value. The foreign matter detection value is a threshold value set to determine a case where an excessive current flows in the event of an abnormality such as a foreign matter being placed in the heating coil 41. In addition, in the following description, it will be described that the object to be heated is a cooking utensil. The foreign matter detection value is an example of a predetermined threshold current.

In step S1, when the inverter current Iinv exceeds the foreign matter detection value (Yes in step S1), the control unit 50 stops the operation of the inverter 30 and enters a standby (standby) state (Fig. 5D). See t22 ~ t50). On the other hand, in step S1, when the inverter current Iinv is less than or equal to the foreign matter detection value (No in step S1), the flow advances to the next step S2.

In step S2, it is determined whether the input power or output power (hereinafter referred to as inverter power Pinv) of the inverter 30 detected by the control unit 50 is less than a predetermined cookware departure detection value. The cooking appliance departure detection value may be set to a value capable of detecting a state in which the cooking appliance is deviated from the heating coil 41 (hereinafter referred to as “cooking appliance separation”), and can be set arbitrarily. For example, the cooking utensil departure detection value is set to a value that prevents detection of the cooking utensil departure when the cooking utensil is off by about half (hereinafter, referred to as "half departure"). For example, the cooking appliance departure detection value may be a fixed value, or may be changed according to a set power or target heating power.

In step S2, when the inverter power Pinv is equal to or greater than the cookware departure detection value (No in step S2), the flow returns to step S1. FIG. 5A shows an example of a waveform showing a time change of the inverter current Iinv and the inverter power Pinv when the cookware is half-departed from the normal operation at time t10. As shown in FIG. 5A, the inverter power Pinv temporarily decreases as the cookware is halved at time t10, but normal operation continues without decreasing until the level at which the cookware deviation is detected. Accordingly, the inverter power Pinv returns to the set power after a certain period of time has elapsed (see time t12).

When the cookware is in a state of half deviation from the normal operation at time t10, the control unit 50 lowers the frequency response or voltage response to the detected power detected by the power detection unit, thereby reducing the frequency response of the inverter 30 to the detected power. It reduces the control responsiveness of the drive power.

More specifically, for example, when a person shakes the cookware by hand, the position of the cookware is expected to change at a speed of 50 [mm/sec] or more. Then, in the conventional inverter, the resonance frequency is expected to fluctuate, for example, about -10 [kHz/sec] (refer to the solid line in Fig. 9). On the other hand, in the present embodiment, for example, as the frequency control amount when reducing the frequency response, it is set so as to have a control fluctuation width smaller than -5 [kHz/sec]. Fig. 9 shows an example of a frequency control amount of -0.2 [kHz/sec] by a dotted line when reducing the frequency response.

In this way, by delaying control by lowering the control responsiveness, for example, when the cookware is shaken, power is reduced, so that it is possible to detect that the cookware is shaken by a human hand or that the cookware is temporarily moved.

In addition, the frequency control amount when lowering the responsiveness may be a value larger than the fluctuation value when boiling water by heating the cooking utensil. For example, when boiling water by heating a cookware, the resonance frequency fq of the series resonance circuit 40 fluctuates about -0.1 [kHz/sec]. Therefore, the frequency control amount when reducing the frequency response can be set between -5 [kHz/sec] and -0.1 [kHz/sec].

In FIG. 10, when the cookware is shaken by a human hand, the position of the cookware is changed at a speed of 5 [mm/sec], and the frequency control amount of the driving frequency of the inverter 30 is -0.2 [kHz/sec] An example of setting to is displayed. Even when the shaking speed of the cookware is slow as shown in FIG. 10, since the impedance varies greatly by applying the control of the present embodiment, the deviation of the cookware can be sufficiently detected.

In addition, although FIG. 8, FIG. 9, and FIG. 10 showed examples of reducing the frequency response to the detected power, it is not limited to this. For example, as shown in FIG. 11, the voltage response to the detected power detected by the power detection unit may be lowered. Specifically, when the position of the cookware is moved at a speed of 50 [mm/sec], the impedance at the same frequency is expected to fluctuate by about 1.7 [times/sec]. Then, the conventional inverter is expected to have a control fluctuation width of +30 [%/sec] as an effective voltage value (also referred to as an execution voltage). On the other hand, in the present embodiment, for example, the voltage effective value at the time of lowering the voltage responsiveness is set so that the control variation width is smaller than +10 [%/sec]. In this case, as in the case of the frequency control amount, it may be a value larger than the control fluctuation width of the effective voltage when the cookware is heated to boil water. For example, in the case of boiling water by heating a cookware, the impedance of the series resonance circuit 40 fluctuates about 1.005 [times/sec], resulting in a control fluctuation range of +0.3 [%/sec] as the effective voltage value. It is expected. Therefore, the control fluctuation width of the effective voltage when reducing the voltage responsiveness can be set between +0.3 [%/sec] +10 [%/sec]. More specifically, for example, the control variation width of the effective voltage may be set to + 0.6 [%/sec].

On the other hand, in step S2, when the inverter power Pinv is less than the cookware departure detection value (Yes in step S2), the flow proceeds to the next step S3.

In step S3, it is determined whether or not the state in which the inverter power Pinv is less than the cookware departure detection value is maintained for a predetermined cookware departure detection time Td. The cooking utensil departure detection time Td may be arbitrarily set, but is not particularly limited, for example, a time (for example, about several seconds) in which the cooking appliance shaking state and the cooking appliance separation state can be determined.

In step S3, if the state in which the inverter power Pinv is less than the cookware departure detection value is maintained for the cookware departure detection time Td (Yes in step S3), the flow proceeds to step S4, and the control unit ( 50) detects the departure state of the cookware, stops the operation of the inverter, and may enter the standby state. That is, when the control unit 50 detects that the input power and/or the output power of the inverter 30 is less than the predetermined cooking appliance separation detection value for a predetermined time, the heating object is separated from the state (here, the cooking appliance separation It has a function as a means for detecting separation of an object to be heated to detect as a state).

FIG. 5B shows that when the cookware departure state is in a normal operation at time t10 and the inverter power Pinv is less than the cookware departure detection value is maintained at the cookware departure detection time Td, the inverter current ( Iinv) and an example of a waveform representing the time change of the inverter power Pinv are shown. Time t10 of FIG. 5B corresponds to time t14 of FIGS. 8 and 11, and time t50 of FIG. 5B corresponds to time t16 of FIGS. 8 and 11.

As mentioned above, the induction heating apparatus A of the present embodiment is configured to maintain the operating state in the normal state even when the cooking appliance is separated from the normal state. More specifically, the induction heating device A lowers the frequency response or voltage response to the detected power detected by the power detection unit, thereby reducing the control responsiveness of the drive power of the inverter 30 to the detected power. I can make it.

Then, even when the cookware is separated from the normal state, there is substantially no frequency fluctuation, so that the impedance of the series resonance circuit 40 may increase (see FIG. 2 ). As such, when the impedance of the series resonance circuit 40 increases, the inverter current Iinv decreases, and as a result, the inverter power Pinv can be quickly lowered to less than the cookware departure detection value (time t10 ~ see t13). Since the control unit 50 controls to maintain the operating state in the normal state, the inverter power Pinv may not be returned to a value higher than the cookware departure detection value unless the cookware position is returned. And, in the example of FIG. 5B, since the cooking appliance separation state is maintained for the cooking appliance separation detection time Td, the control unit 50 controls the inverter 30 to stop the output of the inverter current Iinv or suppress the output. can do. Accordingly, even when the cookware is separated, the control unit 50 can safely stop the output of the inverter 30.

5C shows the inverter current Iinv in the case where the inverter power Pinv is less than the cookware departure detection time Td in step S3 is not maintained (No in step S3), and An example of a waveform representing the time change of the inverter power Pinv is shown. In Fig. 5C, as in Fig. 5B, the cooking appliance is separated from the normal operation at time t10. Then, at time t21 after the passage of time Td1 (Td1 < Td) from time t13, the cookware is returned to its original position. As mentioned above, the control unit 50 may maintain the operating state in the normal state until the cooking appliance detachment detection time Td elapses even after the cookware is released from the normal operation. That is, since the control unit 50 maintains the operating state in the normal state at the elapse of time Td1, the inverter power Pinv immediately returns to the power state for achieving the target thermal power, and required heating is resumed. Therefore, the induction heating device A can quickly reach the target thermal power compared to the prior art. In addition, when the cookware is separated, that is, when the cookware is shaken, since the impedance increases significantly and the inverter power Pinv decreases, unnecessary power is not supplied to the heating coil 41 and no overcurrent occurs. . In the flow of Fig. 4, when the cookware is returned in step S3 (No in step S3), the process returns to step S1.

FIG. 5D shows the inverter current Iinv and the inverter power Pinv when the cookware is separated from the normal operation at time t10 and the cookware is not returned and a foreign substance is placed at time t21 after the lapse of time Td2 from time t13. An example of a waveform representing a change in time is shown. In Fig. 5D, the operation from time t10 to time t21 is the same as that of Fig. 5C. However, in FIG. 5D, since a foreign material is placed on the heating coil 41, the inverter current Iinv reaches the above-described foreign material detection value. That is, the determination of Yes is made in step S1 of FIG. 4, and the control unit 50 quickly stops the inverter 30 so that the induction heating device A enters the standby state.

As described above, according to the present embodiment, the control unit 50 is configured to maintain the operation in the normal state for a predetermined period (cookware departure detection time Td) even when the cooking appliance is separated from the normal state. That is, when the inverter power Pinv is smaller than the cookware departure detection value in the normal operation state, the control unit 50 makes the increase amount of the inverter power Pinv output from the inverter 30 smaller than a predetermined reference power amount. The inverter 30 can be controlled. Therefore, the induction heating device (A) can stop the output when the cookware is separated for a predetermined period of time or more, and quickly restore the cookware to its original position in the case of shaking the cookware without consuming unnecessary power. It can be heated with a set firepower.

<Other Examples>

In the above embodiment, the control unit 50 may control a case in which the power is decreased so that the response speed is faster than when the power is increased toward the set power.

This embodiment will be described in detail using the waveforms of Fig. 6. Here, the configuration of the induction heating device (A) may be the same as in the above embodiment, and the flow chart of the operation may be the same as that of FIG. 4, so a description thereof will be omitted here. The same applies to Fig. 7 described below.

6 is an example of a waveform showing the time change of the inverter current (Iinv) and the inverter power (Pinv) when the cookware is returned to the center at time t61 after the cookware is half-departed from the normal operation at time t10. Show. In FIG. 6, as in the case of FIG. 5A, the inverter power Pinv temporarily decreases as the cookware is removed by half at time t10, but the normal operation is continued because it does not decrease to the level at which the departure of the cookware is detected. Accordingly, the inverter power Pinv may return to the set power after a certain period of time has elapsed (see time t12). Subsequently, when the cookware returns to the center at time t61, an overshoot may occur in which the power temporarily increases. Here, since the control unit 50 controls the response speed to be faster when the power is lowered than when the power is raised toward the set power, the inverter power Pinv can be quickly returned to the set power as shown in FIG. have.

At this time, as shown by a dotted line in FIG. 6, an upper limit power (upper limit power> set power) for determining whether to change the response speed of the control may be provided. Accordingly, when the inverter power Pinv exceeds the upper limit power, the control unit 50 speeds up the response speed of the control than when the inverter power Pinv is less than the upper limit power. As a result, overshoot of the inverter power Pinv can be suppressed when the cookware is returned in a state in which the cookware is temporarily detached (including half detached). The upper limit power is an example of the determination power.

In addition, in the above embodiment, when the inverter power Pinv is less than the set power and greater than the cookware departure detection value continues for a predetermined time or longer, the power fluctuation amount of the inverter power Pinv per unit time You can also make this larger.

This embodiment will be described in detail using the waveforms of Fig. 7. In FIG. 7, the power increase amount of the inverter per unit time is controlled to increase at a time t71 in which a predetermined time Tp has elapsed after the cooking appliance is half-departed from the normal operation at time t10. 7 shows an example in which the amount of power increase of the inverter per unit time is not changed by a dotted line. As shown in FIG. 7, the effect of shortening the return time can be obtained by increasing the amount of power increase of the inverter per unit time (refer to the time Tq in FIG. 7 ).

In addition, in the above embodiment, the induction heating device A may include a temperature measuring unit that measures the temperature of the cookware. Although a specific illustration is omitted, for example, the temperature measuring unit may include a thermistor known in the art or a temperature sensor using infrared rays. Accordingly, the induction heating device A is driven to be supplied from the inverter 30 to the series resonance circuit 40 according to the temperature measured by the temperature measuring unit when the inverter power is smaller than the set power set for heating the heating coil. It is also possible to change the response speed of power control.

As a result, since it is possible to discern the change in impedance of the non-heated material due to heating and the change in impedance due to the separation of the non-heated material, heating can be performed without erroneously detecting that the non-heating material has been separated from the output decrease due to the increase in impedance due to heating. Can be controlled.

The induction heating device according to the first embodiment of the disclosed invention includes a series resonance circuit including a heating coil and a condenser provided in series, and an inverter that supplies driving power of a frequency higher than the resonance frequency of the series resonance circuit to the series resonance circuit. And, a power detection unit that detects the input power or output power of the inverter, and when it is detected that the input power and/or output power of the inverter detected by the power detection unit is less than a predetermined set power value for a certain period of time It characterized in that it comprises a detachment detection means for the object to be heated to detect the detached state of water.

According to the present embodiment, since it is possible to detect the departure of cookware based on the detection result of the input power or the output power, it is possible to configure inexpensively without the need to install a sensor such as an infrared sensor or a weight sensor.

In a second embodiment of the disclosed invention, in the first embodiment, a control unit for controlling the inverter based on a set power set for heating of the heating coil and a detected power detected by the power detection unit is provided, and the control unit Is characterized in that when it is sensed that the object to be separated from the normal operation state is detected, the response speed of the inverter control to the change of the detected power is lowered compared to before the normal operation state is reached.

Here, the response speed is a concept including the control frequency of the inverter, the pulse width of the inverter output voltage, and/or the control speed of the voltage peak value of the output voltage.

According to the above example, since the response speed is lowered as the object to be heated leaves the heating coil, that is, the driving frequency and the inverter output voltage are not substantially changed, the impedance of the series resonance circuit increases as a result. As a result, the output power of the inverter is reduced and unnecessary power is not consumed. In addition, in the induction heating apparatus of the present embodiment, even when the object to be heated deviates from the heating coil, the operating state in the normal operation state is maintained. Therefore, when the object to be heated returns to the heating coil, the operation state of the set thermal power is quickly restored. It can be operated.

In the third embodiment of the disclosed invention, in the first embodiment, the control unit reduces the control responsiveness of the driving power to the detection power by lowering the frequency response or voltage response to the detection power. It is characterized.

In the fourth embodiment of the disclosed invention, in the second embodiment, when the detection power side is higher than the set power by a predetermined or more, the control unit controls the driving power for the detection power compared with the normal operation state. It is characterized in that it increases the response speed of.

In a fifth embodiment of the disclosed invention, in the first embodiment, a control unit for controlling the inverter based on a set power set for heating of the heating coil and a detected power detected by the power detection unit is provided, and the control unit In the normal operation state, when the detected power becomes smaller than the predetermined power, the inverter maintains the operating state so far until a predetermined period elapses, and when the predetermined period elapses, the output of the inverter It characterized in that the control to stop or suppress.

Therefore, even when the cookware is separated, the output of the inverter can be safely stopped.

In a sixth embodiment of the disclosed invention, in a fifth embodiment, the control unit stops the output of the inverter when a state in which the detected power is less than the predetermined power is maintained for a predetermined time.

According to the above example, since the output is stopped after a predetermined time elapses after the cooking appliance is released, unnecessary power consumption can be prevented.

In the seventh embodiment of the disclosed invention, in the fifth embodiment, the control unit controls the power fluctuation amount per unit time when the driving power is lowered to be greater than the power fluctuation amount per unit time when the driving power is increased. do.

Accordingly, overshoot of the driving power output from the inverter can be suppressed.

In the eighth embodiment of the disclosed invention, in the fifth embodiment, the control unit is the response speed of the drive power control to suppress overshoot of the detection power when the determination power provided to a value higher than the set power is exceeded. It is characterized in that to change.

Accordingly, overshoot of the driving power output from the inverter can be suppressed.

In the ninth embodiment of the disclosed invention, in the fifth embodiment, a current measurement unit for measuring the output current of the inverter is provided, and the control unit is configured such that the current measured by the current measurement unit exceeds a predetermined threshold current. In this case, the inverter is controlled to stop or suppress the output of the inverter.

Therefore, when a foreign substance or the like is installed, heating can be quickly stopped, thereby ensuring safety.

In a tenth embodiment of the disclosed invention, in the fifth embodiment, a temperature measuring unit for measuring a temperature of an object to be heated is provided, and when the detection power side is smaller than the set power, the temperature measured by the temperature measuring unit It is characterized in that the response speed of the driving power control is changed on the basis of.

Therefore, it is possible to discriminate the impedance change of the non-heated material due to heating and the impedance change due to the separation of the non-heated material, so that the decrease in output due to the increase in the impedance due to heating does not erroneously detect that the non-heated material is leaving, and heating can be controlled.

In the eleventh embodiment of the disclosed invention, in the fifth embodiment, the control unit increases the amount of power of the inverter per unit time when the detected power is less than the set power and greater than the predetermined power continues for a predetermined time or longer. It is characterized in that it is controlled so as to increase.

Accordingly, it is possible to increase the speed of power recovery when the cookware is not in a detached state.

In the twelfth embodiment of the disclosed invention, in the third embodiment, the control unit controls the inverter at a frequency higher than the resonant frequency of the series resonant circuit in a normal operation state, and decreases the frequency response. It is characterized in that the frequency control amount is set so that the control fluctuation width is smaller than -5 [kHz/sec].

In the thirteenth embodiment of the disclosed invention, in the third embodiment, the control unit controls the inverter at a frequency higher than the resonant frequency of the series resonant circuit in a normal operation state, and decreases the voltage responsiveness. It is characterized in that it is set such that the effective voltage value is less than +10 [% / sec].

As in the twelfth and thirteenth embodiments, when the frequency control amount is set to a value less than -5 [kHz/sec] or the voltage responsiveness is lowered, the effective voltage value is less than +10 [%/sec]. As a result, when the object to be heated temporarily moves, for example, when the cooking utensil is shaken, power is reduced, so that it is possible to detect that the cooking utensil as the object to be heated is shaken or moved by a human hand. .

As described above, in the induction heating apparatus using a heating coil, the disclosed invention stops output when the cookware is separated, does not consume unnecessary power in the case of shaking the cookware, and when the cookware returns to its original position. Since it can be quickly heated with a set thermal power, it is very useful and has high industrial applicability.

The disclosed invention is not limited to the above embodiments, and may be appropriately changed without departing from the spirit. For example, a P-type MOS transistor can be used as an N-type MOS transistor, or an N-type MOS transistor can be used as a P-type MOS transistor. It is not limited to MOS transistors, and other transistors can also be used.

A induction heating device
30 inverter
40 series resonant circuit
41 heating coil
42 resonant capacitor
50 control unit

Claims (14)

coil;
An inverter configured to provide a drive current to the coil;
A current sensor measuring the driving current of the coil;
And a control unit for controlling the inverter so that the driving current follows a target current based on a user input,
The control unit,
Maintaining the switching operation of the inverter based on the detection time of the driving current less than the reference current is less than the reference time,
An induction heating device for stopping the operation of the inverter based on the detection time of the driving current smaller than the reference current being greater than or equal to the reference time. The method of claim 1, wherein the control unit,
An induction heating device for identifying whether or not a time when a driving current smaller than the reference current is sensed is greater than or equal to the reference time, based on detection of a driving current smaller than a reference current. The method of claim 1, wherein the control unit,
Induction heating for controlling the inverter so that the driving current follows the target current based on the detection of a driving current greater than the reference current before a time when a driving current less than the reference current is sensed reaches the reference time Device. The method of claim 1, wherein the control unit,
An induction heating device for reducing a switching frequency of the inverter to a first speed based on the detection of a driving current smaller than the reference current. The method of claim 4, wherein the control unit,
An induction heating device for increasing the switching frequency of the inverter to a second speed greater than the first speed based on the detection of a driving current greater than the reference current while reducing the switching frequency of the inverter to a first speed. The method of claim 1, wherein the control unit,
An induction heating device for increasing the switching frequency of the inverter at a third speed based on the detection of a driving current smaller than the reference current. The method of claim 6, wherein the control unit,
An induction heating device for reducing the switching frequency of the inverter to a fourth speed greater than the third speed based on the detection of a driving current greater than the reference current while increasing the switching frequency of the inverter to a third speed. In the control method of an induction heating device comprising a coil,
Providing a driving current to the coil;
Measuring the driving current of the coil;
And adjusting the frequency of the driving current so that the driving current follows a target current based on a user input,
Adjusting the frequency of the driving current,
Maintaining the frequency of the driving current based on the detection time of the driving current less than the reference current is less than the reference time,
And stopping providing the driving current based on the sensed time that the driving current smaller than the reference current is greater than or equal to the reference time. The method of claim 8, wherein adjusting the frequency of the driving current,
The control method of an induction heating apparatus further comprising identifying whether a time when a drive current less than the reference current is sensed is greater than or equal to the reference time based on the sensed driving current less than the reference current. The method of claim 8, wherein adjusting the frequency of the driving current,
The frequency of the driving current is adjusted so that the driving current follows the target current based on the detection of a driving current greater than the reference current before the detected time of the driving current less than the reference current reaches the reference time. Control method of an induction heating device further comprising: The method of claim 8, wherein adjusting the frequency of the driving current,
The control method of an induction heating apparatus further comprising reducing the frequency of the driving current to a first speed based on the detection of a driving current smaller than the reference current. The method of claim 11, wherein adjusting the frequency of the driving current,
Induction further comprising increasing the frequency of the driving current to a second speed greater than the first speed based on the detection of a drive current greater than the reference current while reducing the frequency of the drive current to a first speed. How to control the heating device. The method of claim 8, wherein adjusting the frequency of the driving current,
The control method of the induction heating apparatus further comprising increasing the frequency of the driving current at a third speed based on the detection of a driving current smaller than the reference current. The method of claim 13, wherein adjusting the frequency of the driving current,
Induction further comprising reducing the frequency of the driving current to a fourth speed greater than the third speed based on the detection of a driving current greater than the reference current while increasing the frequency of the driving current to a third speed. Control method of the heating device.

Images