JPWO2013061595A1 - Induction heating device - Google Patents

Abstract

The induction heating device according to the present invention performs soft start control so that the power supplied to the heating coils is gradually increased from a preset minimum value to a steady power value at the start of power supply to each of the plurality of heating coils. After the power supplied to the heating coil reaches the steady power value, the inverter circuit is controlled so that the supply of the steady power value is maintained until the end of the power supply to the heating coil, and the steady power value is heated. It is set to be larger than the average power value supplied to the coil.

Description

  The present invention is an apparatus for induction heating an object to be heated using a heating coil such as an induction heating cooker or an IH rice cooker, and particularly relates to control of the induction heating apparatus.

  Conventionally, in this type of induction heating device, for example, an inverter circuit is connected to each of two heating coils, and the supply of high-frequency current from the inverter circuit to the heating coil is duty-controlled at a constant cycle and at an arbitrary ratio (For example, refer to Patent Document 1).

  In this induction heating apparatus, in order to make the instantaneous input power values to the two inverter circuits equal, when the input power amounts to the two inverter circuits are equal, the heating time by the two inverter circuits is 1: 1. Duty control is performed at the ratio. In addition, when the input power amount to one inverter circuit is made larger than the input power amount to the other inverter circuit, the heating time of one inverter circuit is lengthened. With the above control operation, the heating power by the two heating coils can be arbitrarily set.

  Patent Document 1 discloses performing normal soft start in which the power supplied to the heating coil is gradually increased to a predetermined power at the start immediately after the start of heating. Further, in Patent Document 1, when two heating coils are alternately heated by duty control, when restarting after stopping heating of one heating coil, two startup coils are reduced by shortening the rise time. It is described that the average input power is prevented from lowering when the operation of the inverter circuit is switched.

  In addition, as a conventional induction heating device having a soft start function, a switching means is connected in series to a heating coil for induction heating of an object to be heated, and the conduction of the switching means is controlled by a drive control means. There has been provided an induction heating device having a plurality of predetermined values and changing the power value to a desired power value with a time constant (see, for example, Patent Document 2).

  The induction heating device disclosed in Patent Document 2 has a low output power at which the power conversion efficiency of the inverter circuit is reduced by increasing the power value at the start of the soft start function as much as possible in accordance with the characteristics of the load. The operation is suppressed. In the induction heating device disclosed in Patent Document 2, the efficiency of the inverter circuit is increased, the output power at the time of startup is increased to shorten the soft start period, and the efficiency of the inverter circuit is further increased.

  Moreover, in the rice cooker as the conventional induction heating apparatus, the first switching means is connected in series to the first heating coil for induction heating of the pan, and the first metal plate on the inner surface side of the lid covering the pan is induction heated. There is a configuration in which the second switching means is connected in series to the two heating coils. In such a rice cooker, the first switching means and the second switching means are controlled to be turned on / off by the control means, and different minimum on-times are obtained when the first switching means is activated and when the second switching means is activated. And a rice cooker that sets an on-time at startup as an initial value has been proposed (see, for example, Patent Document 3).

  Furthermore, as a conventional induction heating apparatus, an induction heating cooker that controls the ON time of the switching means based on the turn-on voltage of the switching means has been proposed (for example, see Patent Document 4).

JP-A-5-166579 JP 2008-204884 A JP 2005-152306 A JP-A-11-111440

  However, in the conventional induction heating apparatus, in order to shorten the rise time of the soft start, it is necessary to set a large change width of the driving frequency and the on / off ratio of the switching elements constituting the inverter circuit. When such a setting is made, when a load fluctuation occurs when the operation of the inverter circuit is switched, a period for reducing or stopping the input power to the inverter circuit after detecting the load fluctuation, that is, the switching element is During the period until the drive control state is changed, the input power to the inverter circuit becomes large, and the switching element continues to be driven and controlled, and the amount of increase in the input power to the inverter circuit becomes large during that period.

  As a result, in the conventional induction heating device, there is a risk of transition to an operation state deviating from the allowable operation state of the inverter circuit determined by a load constant, etc., for example, switching is performed by applying a high voltage to the switching element. There was a problem that a serious accident that would destroy the device occurred.

  In addition, when the rise time of the soft start is short, the time for detecting the load fluctuation is also short, and there is a problem that the load fluctuation cannot be detected with high accuracy.

  Further, when the rise time of the soft start is shortened, the change ΔW per unit time of the input power to the inverter circuit is increased. If this change ΔW is large, at the end of the soft start, the input power to the inverter circuit once exceeds the steady value that is the input power to the inverter circuit after the soft start, that is, a phenomenon that approaches the steady value. Shooting is likely to occur. Switching power used in an inverter circuit because the voltage applied to the switching element and the current flowing through the switching element increase instantaneously as power exceeding the steady value is instantaneously input to the inverter circuit. There was a problem that the specification of the element had to be set to a steady value or more.

  Further, when the input power to the inverter circuit is controlled by changing the drive frequency of the switching element, when the frequency fluctuation during the soft start period is abrupt, the sound caused by the change Δf per unit time of the drive frequency Has occurred, and there has been a problem of providing an induction heating device that generates an harsh sound.

  The average input power to the inverter circuit is obtained by dividing the amount of power input during the drive period of the inverter circuit by one cycle time including the operation period and the non-operation period of the inverter circuit. For this reason, when the ratio of the heating time by the two inverter circuits is constant, if the soft start control period is long, the ratio of the soft start control period in the drive period of the inverter circuit increases, and the input power to the inverter circuit and the average power There was a problem that would be dissociated. In addition, when the period of one cycle is shortened to achieve uniform heating, the ratio of the soft start control period is further increased and the difference between the input power and the average power is increased, and the input power during the soft start control is increased. Furthermore, it could not be ignored.

  Further, in the configuration of the conventional induction heating apparatus, in order to increase the power conversion efficiency of the inverter circuit, it is necessary to lengthen the on-time when starting the switching means and shorten the soft start operation period.

  For this reason, an excessive current suddenly flows to the heating coil when the switching means is activated, and the current is suddenly induced and vibrated also in the heated object such as a pan magnetically coupled to the heating coil. There was a problem of generating abnormal noise.

  The problem that abnormal noise occurs as described above can be solved by shortening the on-time at the start-up of the switching means and reducing the current flowing to the heating coil at the start-up, but this reduces the power conversion efficiency of the inverter circuit. I was in a dilemma.

  Also, if the ON time of the switching means is shortened and the switching means is turned on while a voltage is applied to the switching means, an excessive current flows through the switching means, and large electromagnetic noise is generated. There is a possibility that the switching means is destroyed due to an increase in heat generation due to loss.

  The present invention solves various problems in the conventional induction heating device, and by performing control to gradually increase the input power by securing a predetermined time so as not to shorten the rise time of the soft start control. In addition, the switching element in the inverter circuit is prevented from being broken and abnormal noise is generated, and the average input power at the time of operation switching is set in advance by grasping the amount of decrease in the average input power at the time of switching the operation of the two inverter circuits. It is an object of the present invention to provide an induction heating device that can be controlled to a specified value.

  In this invention, while setting it as the structure which does not generate | occur | produce abnormal noise at the time of starting, it is providing the induction heating apparatus which can improve electric power conversion efficiency and can suppress generation | occurrence | production of electromagnetic noise.

In order to solve the problems in the conventional induction heating apparatus, the induction heating apparatus according to the present invention is
A plurality of heating coils for induction heating the object to be heated;
An inverter circuit for supplying power to the plurality of heating coils;
A control unit for driving and controlling the inverter circuit,
The control unit is an induction heating device that induction-heats an object to be heated by alternately supplying electric power to each heating coil from the inverter circuit,
The control unit performs soft start control so that the power supplied to the heating coils is gradually increased from a preset minimum value to a steady power value at the start of power supply to each heating coil, After the power supplied to the heating coil reaches the steady power value, the inverter circuit is controlled to maintain the supply of the steady power value until the end of power supply to the heating coil, and the steady power The value is set to be larger than the average power value supplied to the heating coil.

  The induction heating apparatus according to the present invention configured as described above sets the average power to the target value by compensating for the power decrease during the soft start control by setting the steady power to be higher than the supplied average power. can do. For this reason, the induction heating device according to the present invention eliminates the need for shortening the rise time in the soft start control, can prevent the destruction of the switching unit and the generation of abnormal noise, and at the time of switching the operation of a plurality of inverter circuits By grasping the amount of decrease in the average input power, the average value of the input power at the time of operation switching can be set as the set value.

  The induction heating device of the present invention performs control to gradually increase the input power by securing a predetermined time so as not to shorten the rise time of the soft start control, thereby destroying the switching part and abnormal noise in the inverter circuit. It is possible to prevent the occurrence, and it is possible to control the average value of the input power at the time of the operation switching to the set value by grasping the amount of decrease in the average input power at the time of the operation switching of the plurality of inverter circuits. Moreover, in this invention, while being able to comprise so that an abnormal sound may not be generated at the time of starting, power conversion efficiency can be improved and generation | occurrence | production of electromagnetic noise can be suppressed.

The figure which shows the circuit structure of the induction heating apparatus of Embodiment 1 which concerns on this invention. Time chart of input power to inverter circuit in induction heating apparatus of embodiment 1 according to the present invention Time chart of input power to inverter circuit in induction heating apparatus of embodiment 2 according to present invention Time chart of input power to inverter circuit in induction heating apparatus of embodiment 3 according to present invention The figure which shows the circuit structure of the induction heating apparatus of Embodiment 4 which concerns on this invention. The figure which shows the circuit structure of the induction heating apparatus of Embodiment 5 which concerns on this invention. Arrangement of heating coils in induction heating apparatus according to Embodiment 6 of the present invention Circuit diagram showing a part of the induction heating apparatus according to the seventh embodiment of the present invention in a block form Time chart of input power in induction heating apparatus according to embodiment 7 of the present invention shown in FIG. The wave form diagram which shows the ON time of the switching part in each area | region (area | region a, area | region b, and area | region c) of the input electric power at the time of soft start control in the induction heating apparatus of Embodiment 7 which concerns on this invention Time chart of input power in induction heating apparatus of embodiment 8 according to present invention Circuit diagram showing a part of the induction heating apparatus according to the ninth embodiment of the present invention in a block form Time chart of input power in induction heating apparatus of embodiment 9 according to the present invention The circuit diagram which shows the other structure which blocked and showed a part of induction heating apparatus of Embodiment 9 which concerns on this invention

The induction heating device according to the first aspect of the present invention includes a plurality of heating coils for induction heating an object to be heated,
An inverter circuit for supplying power to the plurality of heating coils;
A control unit for driving and controlling the inverter circuit,
The control unit is an induction heating device that induction-heats an object to be heated by alternately supplying electric power to each heating coil from the inverter circuit,
The control unit performs a soft start control so that the power supplied to the heating coils is gradually increased from a preset minimum value to a steady power value at the start of power supply to each heating coil. And after the power supplied to the heating coil reaches the steady power value, the inverter circuit is controlled to maintain the supply of the steady power value until the end of power supply to the heating coil, and The steady power value is set to be larger than the average power value supplied to the heating coil.

  The induction heating apparatus according to the first aspect of the present invention configured as described above sets the steady power so that the steady power value is equal to or higher than the average power value to be supplied. The average power can be set to the target value by compensating for the decrease. In addition, even if power is supplied by switching the on / off operation alternately to multiple heating coils, abnormal sounds (panning) can be prevented from occurring in the pan that is the object to be heated. On the other hand, an induction heating device that does not cause discomfort can be realized.

  The induction heating device according to the second aspect of the present invention is configured such that the control unit in the first aspect controls average power supplied to the heating coil by changing a steady power value. ing.

  Since the induction heating apparatus according to the second aspect of the present invention configured as described above can control the average power, the average power can be changed to a desired value. In addition, since the induction heating device of the second aspect can perform power control with a constant period during which electric power is supplied to each heating coil, it can be performed at high speed in order to avoid temperature fluctuations of the object to be heated. Even when switching is desired, power control can be performed without lengthening the period of one round.

  In the induction heating apparatus according to the third aspect of the present invention, the control unit in the first aspect or the second aspect changes the end of power supply in the soft start control period, whereby the heating coil Is configured to control the average power supplied to the.

  Since the induction heating apparatus according to the third aspect of the present invention configured as described above can control the average power, the average power can be changed to a desired value. In addition, since the induction heating device of the third aspect can control the power without changing the steady power, it supplies a large amount of power by extending the power supply end time without increasing the rated power of the device. It becomes possible.

  In the induction heating apparatus according to the fourth aspect of the present invention, the control unit according to any one of the first to third aspects includes power supplied to the heating coil during a soft start control period. It is supplied to the heating coil by grasping the amount, the amount of power supplied to the heating coil in the period for supplying steady power, and the time for the operation of supplying power to each of the heating coils to make a round. It is configured to calculate average power.

  Since the induction heating apparatus according to the fourth aspect of the present invention configured as described above can grasp the average power supplied to the inverter circuit, how much the steady power and the end of power supply are changed. It can be calculated.

An induction heating apparatus according to a fifth aspect of the present invention, in the fourth aspect, a current measurement unit that measures a current supplied from a power source to the inverter circuit;
A time measuring unit for measuring the time of the operating state of the inverter circuit,
The control unit calculates power supplied to the inverter circuit based on an output value of the current measurement unit, and includes an amount of power supplied to the inverter circuit based on a time measured by the time measuring unit, and the heating It is configured to grasp the time required for the operation of supplying power to each of the coils to complete a cycle.

  Since the induction heating apparatus according to the fifth aspect of the present invention configured as described above can control power by managing time, the operation time is controlled in the same state even in areas with different frequencies. be able to.

An induction heating device according to a sixth aspect of the present invention, in the fourth aspect, a current measurement unit that measures a current supplied from a power source to the inverter circuit,
A zero cross detector for detecting a point at which the voltage of the power source is at a zero level;
A power calculation unit for calculating the power supplied to the inverter circuit,
The power calculation unit is configured to read an output signal from the current measurement unit in synchronization with a frequency of a detection signal from the zero cross detection unit, and to output a zero cross signal to the control unit,
The control unit is configured to calculate a power value and / or an amount of power input to the inverter circuit during a period from the time when the zero cross signal is generated to the time when the next zero cross signal is generated.

  Since the induction heating apparatus according to the sixth aspect of the present invention configured as described above can perform power control in units of detection of zero-cross signals, it is possible to perform power control without providing a timekeeping unit. It becomes.

In the induction heating apparatus according to the seventh aspect of the present invention, a zero-cross detection unit that detects a point at which the voltage of the power source in the fifth aspect becomes a zero level;
A power calculation unit for calculating the power supplied to the inverter circuit,
The power calculation unit is configured to read an output signal from the current measurement unit in synchronization with a frequency of a detection signal from the zero cross detection unit, and to output a zero cross signal to the control unit,
The control unit is configured to calculate a power value and / or an amount of power input to the inverter circuit during a period from the time when the zero cross signal is generated to the time when the next zero cross signal is generated.

  Since the induction heating apparatus according to the seventh aspect of the present invention configured as described above can control power by managing time, the operation time is controlled in the same state even in areas with different frequencies. be able to.

  In the induction heating apparatus according to the eighth aspect of the present invention, each of the heating coils in any one of the first to seventh aspects is disposed substantially concentrically, and the control unit includes: The electric power supplied to the heating coil having a larger diameter is made larger than that of the heating coil having a smaller diameter.

  The induction heating apparatus according to the eighth aspect of the present invention configured as described above can approach the density of power supplied from a plurality of heating coils, and can uniformly heat the object to be heated. In addition, when the object to be heated is in the shape of a container, the heat of the object to be heated heated by the outer heating coil having a large diameter is transferred to the side surface of the container. The temperature outside tends to drop. Therefore, the density of the electric power supplied from the outer heating coil having a large diameter to the object to be heated is slightly higher than the density of the electric power supplied from the inner heating coil having a small diameter to the object to be heated to compensate for the heat transfer. The object to be heated can be heated uniformly.

  In the induction heating apparatus according to the ninth aspect of the present invention, the induction heating apparatus according to any one of the first to seventh aspects is a cooking appliance, and each of the heating coils is substantially concentric. The control unit is configured to change a ratio of electric power supplied to the heating coil having a small diameter and the heating coil having a large diameter based on the cooking sequence.

  In the induction heating apparatus according to the ninth aspect of the present invention configured as described above, the power supplied to the two heating coils is controlled and heated uniformly according to the cooking content and the cooking scene, By supplying a large amount of power to the heating coil and heating it non-uniformly, and by not supplying power to one heating coil, it is possible to obtain effects specific to cooking contents and cooking scenes. Therefore, in the induction heating apparatus according to the ninth aspect of the present invention, an arbitrary heating pattern can be realized depending on the ratio of the input power.

In the induction heating apparatus according to a tenth aspect of the present invention, in the first aspect, the power value supplied to the heating coil is a minimum value in a plurality of on-times that the switching unit in the inverter circuit can take. A minimum on-time setting section for setting a minimum on-time;
An on-time variable setting unit for setting a plurality of on-time variables of the switching unit;
A current detector for detecting an input current supplied from a power source;
A current setting unit that sets a value corresponding to the target value of the input current,
The control unit sets the minimum on-time set by the minimum on-time setting unit as an initial value of the on-time when starting the switching unit, and the current set by the current setting unit after the start-up The on-time of the switching unit is varied by the on-time variable set by the on-time variable setting unit so as to be the target power of the set value,
A plurality of on-times that the switching unit can take include a first on-time group on the low power supply side including at least the minimum on-time, and an on-time longer than the on-time included in the first on-time group. And a second on-time group on the high supply power side including the on-time that is the target power, and
The variable of the on time when the on time of the switching unit transitions from the on time included in the first on time group to the on time included in the second on time group is the first on time. The on-time variable within the group and the on-time variable within the second on-time group are set larger.

  In the induction heating apparatus according to the tenth aspect of the present invention configured as described above, the occurrence of abnormal noise from the object to be heated is prevented, and the on-time at the start-up is the minimum on-time during the soft start control period. As described above, the power conversion efficiency can be suppressed from being reduced by lowering the supplied power and shifting the on-time after startup to the on-time included in the second on-time group with the maximum variable. .

  An induction heating apparatus according to an eleventh aspect of the present invention is the tenth aspect, wherein the on-time included in the first on-time group is only the minimum on-time.

  In the induction heating apparatus according to the eleventh aspect of the present invention configured as described above, the control is such that no abnormal noise is generated from the object to be heated, and the control can maximize the power conversion efficiency. .

  In the tenth aspect or the eleventh aspect, the induction heating device according to the twelfth aspect of the present invention is in a state in which a voltage is applied to the switching unit when operating at least with the minimum on-time. It is configured to control from off to on.

  In the induction heating apparatus according to the twelfth aspect of the present invention configured as described above, the generation of abnormal noise from the object to be heated can be suppressed to an extreme level. This is because even when the switching unit is activated, even if it is turned on while a voltage is applied to the switching unit, it can be turned on in a state where no voltage is immediately applied to the switching unit by utilizing the maximum variable. Therefore, it is possible to prevent a decrease in power conversion efficiency.

  An induction heating apparatus according to a thirteenth aspect of the present invention is configured to set the start timing of the switching unit in the vicinity of a zero cross point of a power supply in any one of the tenth to twelfth aspects. ing.

  In the induction heating apparatus according to the thirteenth aspect of the present invention configured as described above, since the amount of change in the supplied power due to the change in the on-time becomes small, it is possible to reduce the occurrence of flicker in lighting or the like. . In addition, since the voltage applied to the switching unit is lower and the supplied power is smaller, the damage during the on-time switching is less, which can contribute to preventing the switching unit from being destroyed.

  The novel features of the invention are nonetheless specifically set forth in the appended claims, but the invention, both in terms of structure and content, should be read in conjunction with the drawings and in the detailed description that follows. Will be better understood and appreciated.

  Hereinafter, an induction heating apparatus having a heating coil as an embodiment of the induction heating apparatus of the present invention will be described with reference to the accompanying drawings. Note that the induction heating device of the present invention is not limited to the configuration of the induction heating device described in the following embodiments, but has a technical idea equivalent to the technical idea described in the following embodiments. It includes an induction heating device configured based on common technical knowledge in the technical field.

(Embodiment 1)
FIG. 1 is a diagram showing a circuit configuration of the induction heating apparatus according to the first embodiment of the present invention, and shows a circuit connection state from a power source to supplying a high-frequency current to a heating coil via an inverter circuit. is there. FIG. 2 is a time chart of the input power to the inverter circuit in the induction heating apparatus according to the first embodiment of the present invention, and shows control related to power supply to the object to be heated.

  In FIG. 1, a commercial power source 41 is connected to a rectifier circuit 42 that is a rectifier unit for converting an AC power source into a DC power source. In addition to the diode bridge for converting the AC power source to the DC power source, the rectifier circuit 42 smoothes the rectified power source output from the diode bridge, and electromagnetic noise generated by the operation of the induction heating device. It may be configured to include a filter inductor or capacitor so as not to propagate to the filter.

  A first inverter circuit 43 and a second inverter circuit 44 are connected to the output of the rectifier circuit 42. Each of the first inverter circuit 43 and the second inverter circuit 44 includes a switching unit composed of at least one switching element, and the frequency of the power source 41 is determined by the on / off operation of these switching units. Form a higher frequency. The frequency of the on / off operation of the switching unit is often set to several tens of kHz from the viewpoint of preventing the generation of audible sound and reducing the switching loss that occurs when the switching unit repeats the on / off operation.

  To the outputs of the first inverter circuit 43 and the second inverter circuit 44, a first heating coil 45 and a second heating coil 46 for inductively heating the object to be heated 48 are connected, respectively.

  The first inverter circuit 43 and the second inverter circuit 44 supply a high-frequency current to the first heating coil 45 and the second heating coil 46, respectively, so that the first heating coil 45 and the second heating coil 45 are supplied. A high frequency magnetic flux is generated in the coil 46. By supplying this high-frequency magnetic flux to the object to be heated 48 disposed in the vicinity of the first heating coil 45 and the second heating coil 46, an eddy current is generated in the object to be heated 48, and the eddy current and the object to be heated are heated. The heated object 48 is induction-heated based on the specific resistance of the object 48.

  A control unit 47 for driving and controlling the switching unit is provided at a control terminal (for example, a gate in the case of IGBT) of the switching unit (switching element) included in the first inverter circuit 43 and the second inverter circuit 44. It is connected. The control unit 47 drives and controls the switching unit by outputting an on / off signal with a controlled operating frequency and duty ratio to a control terminal.

  About the induction heating apparatus of Embodiment 1 comprised as mentioned above, the operation | movement and an effect | action are demonstrated, referring FIG.

  In FIG. 2, the upper part (a) of the time chart shows the input power to the first inverter circuit 43, and the lower part (b) of the time chart shows the input power to the second inverter circuit 44. Here, from the input power to the inverter circuits 43 and 44, the switching loss generated by the switching operation of the switching unit (switching element) in the inverter circuit, and the components of the induction heating apparatus including the heating coils 45 and 46 A value obtained by subtracting a loss such as a conduction loss caused by a current flowing through the current is the supply power supplied to the object to be heated 48.

  However, since the induction heating device generally has high heating efficiency and the switching loss and conduction loss with respect to the input power to the inverter circuits 43 and 44 are small, the input power to the inverter circuits 43 and 44 is supplied to the object to be heated 48. It can be regarded as substantially the same as the power.

  Electric power is alternately input to the first inverter circuit 43 and the second inverter circuit 44 in the first embodiment. Therefore, according to the configuration of the first embodiment, power is not input to the first inverter circuit 43 and the second inverter circuit 44 at the same time. It is possible to provide an induction heating device that can prevent the occurrence of beat interference sound due to the difference in the operating frequency of the inverter circuit 44 and does not give the user unpleasant feeling.

  In addition, in the input power to the first inverter circuit 43 and the input power to the second inverter circuit 44, the mutual maximum input power (steady power) does not overlap in the same time zone. The sum of the input power to a certain first inverter circuit 43 and the input power to the second inverter circuit 44 is when only one inverter circuit of the first inverter circuit 43 or the second inverter circuit 44 operates. The steady power of is not exceeded.

  Therefore, in the induction heating device of the first embodiment, it is not necessary to set the rated power of the induction heating device higher than the steady power, and the induction heating device can be operated even with the power supply 41 having a small power capacity. It becomes composition.

  The control of the first inverter circuit 43 and the second inverter circuit 44 of the induction heating apparatus of the first embodiment is performed by controlling the first inverter circuit 43 (first heating circuit) as shown in the region A and the region D in FIG. When the power supply of each of the coil 45) and the second inverter circuit 44 (second heating coil 46) is started, the power supplied to each inverter circuit 43, 44 is set from a preset minimum value (minimum power). Soft start control that gradually increases to a predetermined value (steady power) is performed. Here, the minimum value of the power supplied to the inverter circuits 43 and 44 is a value smaller than at least half of the steady power value.

  Normally, when a transition is made from a state in which no power is input to the inverter circuit to a state in which power is input, an inrush current is generated in which a large current flows momentarily in the inverter circuit due to the action of charges charged in the components of the inverter circuit. To do. In the induction heating apparatus of the first embodiment, the inrush current is reduced by performing the soft start control as described above and reducing the input power to the inverter circuits 43 and 44 at the start of the power supply start. Therefore, it is possible to safely operate the inverter circuits 43 and 44 by suppressing the destruction of the inverter circuits 43 and 44 and the generation of noise due to the inrush current.

  Also, when a large inrush current occurs, the heating coil suddenly generates a strong magnetic flux and magnetically couples with the heated object, causing the heated object to vibrate and generating an abnormal sound such as a pan Cause. For this reason, in the induction heating apparatus of the first embodiment, by performing the soft start control as described above, the input power to the inverter circuit at the start of power supply is reduced, and an abnormal sound such as a pot sound is generated. Can be reduced.

  Furthermore, in the induction heating apparatus of the first embodiment, the first heating coil 45 and the second heating coil 46 are in a soft start control period in which the power supplied to the inverter circuit is gradually increased from a preset minimum value. It can be determined whether or not an object to be heated 48 that is suitable for induction heating is disposed. If it is determined that the non-conforming heated object 48 is arranged, the input power to the inverters 43 and 44 is stopped before the input power to the inverter circuits 43 and 44 reaches the steady power. The destruction of the inverter circuits 43 and 44 can be prevented, and the inverter circuits 43 and 44 can be operated stably.

  As shown in FIG. 2A, in the first inverter circuit 43, when the input power to the first inverter circuit 43 reaches the first steady power PS1 after the soft-start control, the region A starts from the region A. The operation proceeds to B, and the first inverter circuit 43 is driven and controlled so as to maintain the first steady power PS1 for a predetermined period. On the other hand, in the second inverter circuit 44, when the input power to the second inverter circuit 44 reaches the second steady power PS2, as shown in FIG. The second inverter circuit 44 is driven and controlled so that the second steady power PS2 is maintained for a predetermined period.

  After the first stationary power PS1 is input to the first inverter circuit 43 in the region B that is the stationary power input period, the first inverter circuit 43 is stopped, thereby shifting to the region C that is the dead time period. . Similarly, after the second steady power PS2 is input to the second inverter circuit 44 in the region E that is the steady power input period, the second inverter circuit 44 is stopped, thereby entering the region F that is the dead time period. And migrate.

  If the input power to the first inverter circuit 43 and the input power to the second inverter circuit 44 are configured to overlap, the first inverter circuit 43 and the second inverter circuit 44 There is a possibility that the audible sound due to the difference in operating frequency or the induced voltage due to the interference of the magnetic field is generated in the components of the induction heating device and the induction heating device is destroyed. Therefore, in order to prevent destruction due to such a cause, in the induction heating apparatus of the first embodiment, the region C and the region F are set as dead time periods, and the operation suspension periods of the two inverter circuits 43 and 44 are set. Is provided. Note that it is not an essential condition to provide the region C and the region F as described above as long as the induction heating device can be designed so as not to be destroyed.

  In the induction heating apparatus of the first embodiment, the operation from the region A to the region F shown in FIG. 2 is set as one cycle, and power is supplied to the object to be heated 48 by repeating these operations. The first average power PA1 of the input power to the first inverter circuit 43, that is, the first average power PA1 supplied from the first heating coil 45 to the object to be heated 48 is a region A that is a soft start control period. The sum of the amount of power input to the first inverter circuit 43 and the amount of power input to the first inverter circuit 43 in the region B, which is the steady power input period, in the period from region A to region F Divided by a certain period T.

  Similarly, the second average power PA2 supplied from the second heating coil 46 to the object to be heated 48 is equal to the input power amount to the second inverter circuit 44 in the region D that is the soft start control period, and the steady state. The sum of the input power amount to the second inverter circuit 44 in the region E that is the power input period is divided by the period T that is the period from the region A to the region F.

  When the object to be heated 48 that supplies power from the first heating coil 45 and the object to be heated 48 that supplies power from the second heating coil 46 are the same object to be heated 48, the first average power PA1 The sum of the second average power PA2 is the total power supplied to the object to be heated 48. In addition, when the object to be heated 48 that supplies power from the first heating coil 45 and the object to be heated 48 that supplies power from the second heating coil 46 are separate objects to be heated 48, 48, The average power PA1 and the second average power PA2 are supplied to the respective objects to be heated.

  In the case of the heating device, the temperature change amount of the heated object itself, the temperature change amount and the evaporation amount of the contents of the container that is the heated object, and the like are determined by the average power supplied to the heated object. For this reason, in the induction heating apparatus according to the first embodiment that alternately switches the heating coils that supply the input power, it is necessary to control the first average power PA1 and the second average power PA2.

  As the time of the period T becomes longer, the time for supplying power from one heating coil to the object to be heated becomes longer, and the time for not supplying electric power from the other heating coil to the object to be heated. Becomes longer. For this reason, the temperature difference of the to-be-heated object in the vicinity of each heating coil when supplying electric power and when not supplying electric power becomes large. Therefore, in order to reduce the temperature difference of the object to be heated and heat it uniformly, the period T is preferably as short as possible.

  The region C and the region F, which are the operation suspension periods of the two inverter circuits 43 and 44, are extremely short compared to the other regions. For this reason, in order to shorten the period T, it is necessary to either shorten the soft start control period of the region A or the region D or shorten the steady power input period of the region B or the region E.

  In the case where the first steady power PS1 and the second steady power PS2 are not changed, in order to input the steady power to the inverter circuits 43 and 44 even if the region A and the region D that are the soft start control period are shortened, It is necessary to set a large change width of the drive frequency and / or the on / off ratio of the switching units constituting the inverter circuits 43 and 44. In such a case, it is determined whether the object to be heated 48 is suitable for the induction heating apparatus or not suitable for the soft start control period in which the power supplied to the inverter circuits 43 and 44 is gradually increased from the minimum value. The determination time is shortened and it is difficult to make an accurate determination.

  Further, since the change frequency of the driving frequency and / or the on / off ratio of the switching unit is large, when the non-conforming heated object 48 is disposed, the inverter circuit 43, 44 is instantaneously reached to the operating region where the inverter circuit 43, 44 is destroyed. It becomes difficult to operate the circuits 43 and 44 stably.

  Furthermore, when the input power to the inverter circuit is controlled by changing the drive frequency of the switching unit, if the frequency fluctuation in the soft start control period is abrupt, the pot caused by the change Δf per unit time of the drive frequency Abnormal sounds such as ringing may occur.

  From the above viewpoints, it is not desirable to shorten the region A and the region D, which are the soft start control period, by increasing the drive frequency of the switching unit and the change width of the on / off ratio.

  Therefore, it is ideal to shorten the period T by shortening the steady power input period of the region B and the region E. However, when the steady power input period is shortened, there is a ratio between a region where the power such as the region A and the region D in the period T is not supplied much and a region where no power is supplied such as the region C and the region F which are dead time periods. There is a problem that the first average power PA1 and the second average power PA2 increase and further decrease compared to the first steady power PS1 and the second steady power PS2.

  For example, when the first heating coil 45 and the second heating coil 46 supply power to the same object to be heated 48, and the first steady power PS1 and the second steady power PS2 are the same power If the steady power input period of the region B or region E is orders of magnitude longer than the other regions, the power supplied to the heated object 48 is substantially the same as the first average power PA1 (second average power PA2). It could be regarded as electric power. However, in the configuration of the induction heating apparatus according to the first embodiment, in which the steady power input period of the region B and the region E needs to be shortened (the time of the region B is not significantly increased with respect to the region A), In order to control the first average power PA1 and the second average power PA2 supplied to the object 48 to values suitable for the heating situation, the first average power PA1 and the second average power PA2 are set to the first steady state. It must be grasped as a value different from the power PS1 and the second steady power PS2.

  Therefore, in the induction heating device of the first embodiment, by setting the first steady power PS1 and the second steady power PS2 so as to exceed the first average power PA1 and the second average power PA2, The first average power PA1 and the second average power PA2 can be controlled to required power values even if the period T is shortened in order to uniformly heat the article 48 to be heated.

  According to the experiment results of the inventors, when the ratio of the period of the region B to the period of the region A becomes substantially the same digit (10 times or less), the difference between the steady power and the average power becomes large, and the usability of the induction heating apparatus is increased. If it is bad, it will be at a level where the user will have an adverse effect. The condition that the ratio of the period of the region B to the period of the region A is substantially the same digit is that the dead time period of the region C and the region F is zero, and the period of the region C and the region F is set to be long. The more the ratio of the period of the region B to the period of the region A is not the same digit and exceeds 10 times, the greater the difference between the steady power and the average power, and the usability of the induction heating device becomes worse It will be at a level where you will feel negative effects.

  In addition, in the induction heating apparatus of the first embodiment, in the region B and the region E that are the steady power input period, the constant power that is a constant value is continuously input to the inverter circuits 43 and 44. The present invention is not limited to such a configuration, and the power input to the inverter circuits 43 and 44 may be power that slightly fluctuates up and down in the regions B and E. In short, the effect of the present invention can be obtained if steady power equal to or higher than the target average power is input to the inverter circuits 43 and 44 in a certain period of the region B and region E.

(Embodiment 2)
FIG. 3 is a time chart of input power to the inverter circuit in the induction heating apparatus according to the second embodiment of the present invention, and shows a control method related to power supply to the object to be heated. The induction heating device of the second embodiment specifically shows a method for controlling the input power to the inverter circuit in the induction heating device of the first embodiment. In the description of the second embodiment, the same reference numerals are given to the same functions, configurations, and operations as the elements in the induction heating apparatus of the first embodiment, and the description of the first embodiment is used for the description. To do.

  FIG. 3 shows the average power (PA3) of the input power to the first inverter circuit 43 and the first power in the induction heating apparatus that supplies power to the object to be heated by the control method shown in FIG. 2 shows a control method in the case of further increasing the average power (PA4) of the input power to the second inverter circuit 44.

  As shown in FIG. 3, in the induction heating apparatus of the second embodiment, the power change rate (change rate of input power per unit time) in the soft start control period is the power change in the soft start control period in the first embodiment. The rate has not changed and is the same. For this reason, in the induction heating apparatus of the second embodiment, the slope of the input power in the soft start control period (areas A and D) in FIG. 3 showing the power change rate is the same as that shown in FIG. However, in the induction heating apparatus of the second embodiment, the steady power (PS3, PS4) input to the first inverter circuit 43 and the second inverter circuit 44 in the steady power input period (regions B, E) is increased. I am letting.

  As shown in FIG. 3, the input power to the first inverter circuit 43 in the steady power input period (region B) is the third steady power PS3 that is larger than the first steady power PS1 in the first embodiment. Further, the input power to the second inverter circuit 44 in the steady power input period (region E) is the fourth steady power PS4 that is larger than the second steady power PS2 in the first embodiment.

  As described above, in the second embodiment, the third stationary power PS3 and the fourth stationary power PS4 are set larger than the first stationary power PS1 and the second stationary power PS2, respectively. Thus, the soft start control period of the region A and the region D is long. Further, since the period T from the area A to the area F is the same as the period T in the first embodiment, the steady power input periods of the area B and the area E are shortened.

  By using the control method in the second embodiment, the amount of electric power input to the first inverter circuit 43 in both the periods of the regions A and B, and the second inverter circuit 44 in both the regions D and E. The amount of power input has increased. For this reason, the third average power PA3 and the fourth average power PA4 divided by the same period T as the period T shown in FIG. 2 also increase. Conversely, in the control method in the second embodiment, the average power supplied to the respective inverter circuits 43 and 44 is obtained by supplying the steady power smaller than the first steady power PS1 and the second steady power PS2. It is also possible to decrease. For this reason, in the control method in Embodiment 2, it becomes possible to control the electric power supplied to a to-be-heated object by controlling steady electric power.

  In the control method in the second embodiment, even when the period T is shortened in order to reduce the temperature difference in the object to be heated and uniformly heat the object to be heated, the steady power of the input power to the inverter circuit By setting a large value, it is possible to increase the average power. For this reason, by using the control method in Embodiment 2, the object to be heated can be uniformly heated with different average power.

(Embodiment 3)
FIG. 4 is a time chart of the input power to the inverter circuit in the induction heating apparatus according to the third embodiment of the present invention, and shows control related to power supply to the object to be heated. The induction heating device of the third embodiment is different in the control method of the input power to the inverter circuit in the induction heating device of the second embodiment. In the description of the third embodiment, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating device of the first and second embodiments, and the description thereof will be omitted. The description of 1 and Embodiment 2 is cited.

  FIG. 4 shows the average power PA3 of the input power to the first inverter circuit 43 and the second power in the induction heating apparatus according to the third embodiment that supplies power to the object to be heated by the control method shown in FIG. The control method in the case of increasing the average power PA4 of the input power to the inverter circuit 44 is shown.

  As shown in FIG. 4, in the induction heating apparatus of the third embodiment, the power change rate during the soft start control and the conditions of the steady power PS1 and PS2 of the input power to the inverter circuits 43 and 44 are as shown in FIG. Since the conditions in the first embodiment shown are not changed, the soft start control periods of the region A and the region D are the same. However, the steady power input periods of the regions B and E where the input power to the inverter circuits 43 and 44 maintains the steady power are longer than the periods shown in FIG. Accordingly, the period T1 that is the period from the area A to the area F is longer than the period T shown in FIG.

  As a result, the ratio of the steady power input periods of the region B and the region E occupying the period T1 increases, and the third average power PA3 and the fourth average power PA4 shown in FIG. 4 are the same as the first average power PA3 shown in FIG. The average power PA1 and the second average power PA2 are increased.

  That is, even if the steady power of the input power to the inverter circuit, which is the rated power of the induction heating device, remains set at a constant value, the power supplied to the object to be heated is increased by setting the period T1 long. Can be made.

  On the contrary, the average power supplied to the inverter circuit can be reduced by shortening the period that is the period from the area A to the area F, that is, by shortening the area B and the area E that are the steady power input periods. It is. For this reason, in the control method in the induction heating apparatus of Embodiment 3, the electric power supplied to a to-be-heated object can be controlled to a desired state by controlling a period.

  In addition, although the control method in Embodiment 2 controls steady electric power and the control method in Embodiment 3 differs in the point which controls a period, both are means to finally control average electric power. For this reason, it is also possible to configure a control method for controlling the average power by combining the control methods in the second embodiment and the third embodiment and selectively using two variables of the steady power and the cycle.

(Embodiment 4)
FIG. 5 is a diagram showing a circuit configuration of the induction heating apparatus according to the fourth embodiment of the present invention, and shows a connection state of a circuit until a high frequency current is supplied from a power supply to a heating coil via an inverter circuit. is there. In the induction heating apparatus of the fourth embodiment, there are a measuring unit that is a measuring unit for the current flowing from the power source to the inverter circuit, and a time measuring unit that is a timing unit that measures the operating time in each operation mode (operating state) of the inverter circuit. This is different from the configuration of the first to third embodiments described above. In the description of the fourth embodiment, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating device of the first to third embodiments, and the description thereof will be omitted. The description of Embodiment 3 is used from 1.

  As shown in FIG. 5, in the induction heating apparatus of the fourth embodiment, as a current measuring means for measuring the current flowing from the commercial power source 41 to the first inverter circuit 43 and the second inverter circuit 44. A current measuring unit 49 is provided. As the current measuring unit 49, for example, a current transformer (CT) using a mechanism that generates an electromotive voltage with a flowing current value can be used.

  In the induction heating apparatus according to the fourth embodiment, the two inverter circuits 43 and 44 are controlled. However, the power supply 41 is common, and power is alternately supplied from the power supply 41 to the two inverter circuits 43 and 44. Therefore, it is possible to provide one input current measuring unit on the input side of the rectifier circuit 42 and measure the current flowing through each of the inverter circuits 43 and 44.

  When the output signal formed in the current measuring unit 49 is input to the control unit 47, the control unit 47 grasps the value of the input power to the inverter circuits 43 and 44 in operation, and based on the value of the input power. Thus, by outputting the next control signal to the respective inverter circuits 43 and 44, the input power to the inverter circuits 43 and 44 is controlled. Here, since the voltage of the commercial power supply 41 is substantially constant, the input power to the inverter circuits 43 and 44 can be grasped by measuring the input current by the current measuring unit 49.

  In the induction heating apparatus of the fourth embodiment, for example, in the case of the control method shown in FIG. 2, the soft start control period of the region A and the region D where soft start control is performed, and the region B and the region E where steady power is supplied Since there is no large difference between the steady power input period and the ratio of the input power amount in the region A to the total amount of input power to the first inverter circuit 43 and the total amount of input power to the second inverter circuit 44 The ratio of the input power amount in the occupied area D is high, and the input power amount to the inverter circuits 43 and 44 in the soft start control period may be ignored in grasping the first average power PA1 and the second average power PA2. Can not.

  Therefore, in the induction heating device of the fourth embodiment, by measuring the time of the region A and the region D by the time measuring unit 50, the input electric energy to the inverter circuits 43 and 44 in the soft start control period is grasped, The average power supplied to the object to be heated 48 can be controlled to be a value set in the operation unit (not shown) or a value determined in advance in the sequence.

Next, a method for controlling the average power in the induction heating apparatus of the fourth embodiment will be described.
When the first inverter circuit 43 is performing the soft start control (region A in FIG. 2), the current measuring unit 49 measures the current value flowing from the power source 41 to the first inverter circuit 43 every moment, and is measured. A signal based on the current value is output to the control unit 47.

  The control unit 47 controls the first inverter circuit 43 so as to have a current value that flows when the first steady power PS <b> 1 is input to the first inverter circuit 43. The controller 47 receives the time of the region A measured by the time measuring unit 50 and can grasp the ratio of the region A in the period T.

  As shown in FIG. 3, when the steady power is controlled and is not changed from the period T shown in FIG. 2, the first average power PA1 of the input power to the first inverter circuit 43 is changed to the third average. In order to increase to the power PA3, the first steady power PS1 needs to be increased to the third steady power PS3.

  When the period of the region A and the region B in the period T determined based on the relationship between the input power to the first inverter circuit 43 and the input power to the second inverter circuit 44 is fixed, the time of the region A The ratio of the area A and the area B with respect to the period T can be grasped by measuring. In addition, by grasping the input power in the region A, the third steady power PS3 whose average power value becomes the set value can be obtained. Therefore, the power is set low at the start immediately after the start of heating, and the soft start control is performed. An induction heating device that supplies the set average power can be provided by performing control that brings the average power set at the final stage of the period closer to the steady power at which the average power is obtained.

  Note that, for example, if the object to be heated, such as a rice cooker, is constant, the power at the start immediately after the start of heating is set to a value close to the third steady power PS3 that is the average power value of the set value. By doing so, it is possible to reduce time loss such as gradually bringing the average power closer to the set value.

  In addition, if the target steady power of the object to be heated 48 once heated is stored, the stored steady power may be set as a target value in the subsequent control, and an easy-to-use induction heating apparatus is provided. Can be provided.

  Further, if the object to be heated 48 is constant and the operation time of the inverter circuit is determined in advance, the power supplied during the soft start control period can be calculated, and the average power and the steady power to be input to the inverter circuit are calculated. Therefore, the steady power can be set according to the average power desired to be input to the inverter circuit. Further, the average power input to the inverter circuit is set to a desired value by controlling the inverter circuit to stop when the sum of the area A and the area B becomes the operating time of the inverter circuit. It becomes possible.

  In addition, in the induction heating apparatus of the fourth embodiment, two inverter circuits are controlled, but the power source 41 is common and supplies power alternately, so the input power is measured by one current measurement unit. Thus, the configuration can be reflected in the control.

(Embodiment 5)
FIG. 6 is a diagram showing a circuit configuration of the induction heating apparatus according to the fifth embodiment of the present invention, and shows a circuit connection state from the power source to supplying a high-frequency current to the heating coil via the inverter circuit. is there. In the induction heating device of the fifth embodiment, the zero cross detection unit that is a zero cross detection unit that detects that the power supply voltage has reached zero level, and the power that grasps the momentary power input from the power source to the induction heating device. The configuration is different from that of the first to fourth embodiments described above in that a power calculation unit which is a calculation unit is provided. In the description of the fifth embodiment, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating apparatus of the first to fourth embodiments, and the description thereof will be omitted. The description of Embodiment 4 is used from 1.

  As shown in FIG. 6, in the induction heating apparatus of the fifth embodiment, a current measurement unit 49 for measuring the current flowing through the first inverter circuit 43 and the second inverter circuit 44 is provided. As the current measuring unit 49, for example, a current transformer (CT) using a mechanism that generates an electromotive voltage with a flowing current value can be used. When the output signal formed based on the current value measured by the current measuring unit 49 is input to the power calculating unit 52, the power calculating unit 52 grasps the input power to each of the inverter circuits 43 and 44.

  The control unit 47 to which the signal from the power calculation unit 52 is input controls the input power to the inverter circuits 43 and 44 by outputting the next control signal to the operating inverter circuits 43 and 44. Here, since the voltage of the commercial power supply 41 is substantially constant, the input power to the inverter circuits 43 and 44 can be grasped by measuring the input current by the current measuring unit 49.

  In the induction heating apparatus of the fifth embodiment, for example, in the case of the control method shown in FIG. 2, the soft start control periods of the regions A and D where soft start control is performed, and the regions B and E where steady power is supplied. Since there is no large difference between the steady power input period and the ratio of the input power amount in the region A to the total amount of input power to the first inverter circuit 43 and the total amount of input power to the second inverter circuit 44 The ratio of the input power amount in the occupied region D is high, and the input power to the inverter circuits 43 and 44 in the soft start control period cannot be ignored in grasping the first average power PA1 and the second average power PA2. .

  Therefore, in the induction heating apparatus of the fifth embodiment, the time of the area A and the area D is measured by the time measuring unit 50 so that the input power to the inverter circuits 43 and 44 in the soft start control period can be grasped. Control can be performed so that the average power supplied to the heated object 48 becomes a value set in an operation unit (not shown) or a value predetermined in the sequence.

Next, a method for controlling the average power in the induction heating apparatus of the fifth embodiment will be described.
When the first inverter circuit 43 is performing the soft start control (region A in FIG. 2), the current measuring unit 49 measures the current value flowing from the power source 41 to the first inverter circuit 43 every moment, and is measured. A signal based on the current value is output to the control unit 47.

  In the induction heating apparatus of the fifth embodiment, the output signal of the zero cross detection unit 51 generated when the voltage of the AC power supply 41 crosses the zero level is used as the minimum unit of the trigger, and the power calculation unit 52 detects the zero cross. The signal output from the current measurement unit 49 is detected at a timing that is synchronized with the output signal of the unit 51 and the AC voltage is not at a zero level. The power calculator 52 calculates the power input to the inverter circuits 43 and 44 during the period of the zero cross signal from the detected value. In general, even during the soft start control period, the control signal is not changed in the period from the zero cross point to the next zero cross point (half wave period). If the output signal is detected from the power, the power can be calculated.

  In the induction heating apparatus of the fifth embodiment, as described above, the calculation of the power is repeated until the input power to the inverter circuits 43 and 44 reaches a steady value, and the calculated power amount is added to the software. The amount of power input to the inverter circuits 43 and 44 during the start control period can be grasped.

  As described in the third embodiment with reference to FIG. 4, when the steady power is not changed in the power control, the first steady power PS1 is used to increase the average power input to the first inverter circuit 43. Therefore, it is necessary to lengthen the time in the region B where the inverter circuit 43 is operated.

  Since the input power amount to the first inverter circuit 43 in the region B is the input power in the steady power input period, it can be easily calculated. Further, in the region C to the region F, the power supplied to the first inverter circuit 43 is zero. For this reason, by grasping the amount of power in the region A in which the input power is changing every moment, the length of the steady power input period in the region B can be calculated so that the average power becomes the set value.

  In the fifth embodiment, power control can be performed by counting the number of zero cross signals by the ratio of the number of zero crosses included in the period T1 and the number of zero crosses included in the region A and the region B. Therefore, power control is possible without providing the time measuring unit 50 which is the time measuring means described in the fourth embodiment, but more accurate control is performed by performing power control using the time measuring unit 50 in combination. be able to.

  If the object to be heated 48 is constant and the steady power is determined in advance, the amount of power supplied during the soft start control period can be calculated, and the average power to be input to the inverter circuit and the operation of the inverter circuit Since the relationship with time can be derived, the operation time of the inverter circuit can be set according to the average power desired to be input to the inverter circuit. Further, the average power input to the inverter circuit is set to a desired value by controlling the inverter circuit to stop when the sum of the area A and the area B becomes the operating time of the inverter circuit. be able to.

  In addition, in the induction heating apparatus of the fifth embodiment, by synchronizing the calculation of electric power with the output signal of the zero-cross detection unit 51, the zero-cross period becomes the minimum calculation unit. For example, the zero-cross detection unit 51 is twice The power calculation may be performed every time the signal is changed, and the minimum calculation unit is not limited to the zero cross period by the zero cross detection unit 51 of the fifth embodiment.

(Embodiment 6)
FIG. 7 is a layout diagram of heating coils in the induction heating apparatus according to the sixth embodiment of the present invention. The induction heating apparatus of the sixth embodiment is different from the first to fifth embodiments in that the arrangement of the plurality of heating coils is specifically specified. In the description of the sixth embodiment, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating device of the first to fifth embodiments, and the description thereof will be omitted. The description of Embodiment 5 is used from 1.

  As shown in FIG. 7, in the induction heating apparatus of the sixth embodiment, the first heating coil 45 and the second heating coil 46 are arranged substantially concentrically. The first heating coil 45 has a small diameter and is disposed on the inner side, and the second heating coil 46 has a larger diameter than the first heating coil 45 and is disposed on the outer side.

  In the induction heating apparatus of the sixth embodiment, an induction heating cooker is used as the induction heating apparatus. In the induction heating cooker, a pot that is the object to be heated 48, a pot that is the object to be heated 48 in the rice cooker, or the like. In most cases, the portion that is placed on the induction heating cooker and heated is circular. For this reason, by arranging a plurality of heating coils concentrically as shown in FIG. 7, the entire bottom surface of the pot or the pot as the article to be heated 48 can be efficiently heated.

  In addition, in the induction heating device, when the diameter of the heating coil is small, the distance between the center side portion and the outer peripheral side portion of the heating coil is close, so that magnetic flux cancellation tends to occur in the heating coil. For this reason, even if the same current as a large-diameter heating coil is applied to a small-diameter heating coil in the same level as the large-diameter heating coil, coil thickness, coil wire density, and coupled state, it is supplied to the object to be heated. The electric power per unit area is smaller for the small-diameter coil.

  Therefore, when heating the object to be heated 48 uniformly, it is necessary to pass a current larger than the current flowing through the outer heating coil through the inner heating coil. In the layout diagram of the heating coils 45, 46 shown in FIG. 7, the area of the outer second heating coil 46 is larger than the area of the inner first heating coil 45. For this reason, from the viewpoint of performing uniform heating, the ratio of the input power to the inverter circuits 43 and 44 connected to the two heating coils 46 and 46 is substantially proportional to the planar view area of the heating coil. The input power to the circuits 43 and 44 is larger than the average input power to the second inverter circuit 44 connected to the outer second heating coil 46.

  In the induction heating apparatus according to the sixth embodiment, the power values supplied to the heating coils 45 and 46 are alternately switched, so that the steady power of the outer second heating coil 46 is changed to the inner first heating coil. By making it larger than the steady power of 45, the article to be heated 48 can be heated uniformly. In the induction heating apparatus according to the sixth embodiment, the stationary power input period during which the stationary power is supplied to the second outer heating coil 46 is set to the stationary power to the inner first heating coil 45. The object to be heated 48 can be uniformly heated by making it longer than the time of the steady power input period in which is supplied.

  Moreover, in order to implement | achieve the uniform heating with respect to the to-be-heated material 48 with the control method in Embodiment 6 which switches the electric power supplied to each heating coil 45,46 alternately, the cycle to switch is made early. It is necessary to reduce the fluctuation width of the temperature of the object to be heated 48 on the heating coil. In particular, when the contents to be heated 48 such as a pan are in a boiling state, if the switching cycle is slow, the bubble rise that occurs at the time of boiling occurs only when it is heated, and the bubble rise is intermittent. Since it occurs, it is considered that the user is uncomfortable during cooking or the cooking performance is affected.

  According to the results of experiments by the inventors, it has been confirmed that the difference in boiling feeling appears remarkably for the user unless the power supplied to the heating coils 45 and 46 is alternately switched for about 4 seconds or less. Yes. In addition, according to the results of experiments by the inventors, it has been found that it is desirable for the user to set the cycle to about 2 seconds or less in order to ensure that the user feels no discomfort.

  In the induction heating apparatus of the sixth embodiment, the average power is calculated by taking into account the input power at the time of soft start control, and reflected in the control of the inverter circuit. Even when the control is frequently performed, the set average power can be accurately supplied.

  In addition, since the induction heating device according to the sixth embodiment can arbitrarily adjust the electric power of the first heating coil 45 disposed inside and the second heating coil 46 disposed outside, the object to be heated The electric power supplied to the 1st heating coil 45 arrange | positioned inside is not restricted to the uniform heating with respect to 48, and the electric power supplied to the 2nd heating coil 46 arrange | positioned outside is conversely increased. It is also possible.

Furthermore, in the induction heating apparatus of the sixth embodiment, the inverter circuit connected to one of the heating coils is stopped, and only the first heating coil 45 disposed inside or the second disposed outside. In this configuration, electric power can be supplied only to the heating coil 46.

  As described above, the induction heating apparatus according to the sixth embodiment has a configuration in which an arbitrary heating pattern can be created to reliably supply power suitable for various cooking scenes and heating conditions.

  In each of the above-described embodiments according to the present invention, the control method for changing the steady power as the control method of the input power to the inverter circuit has been described. However, the rated power is determined for the electrical equipment, and the instantaneous power is used. However, it is not preferable to exceed the rated power.

  Therefore, in the induction heating apparatus of the present invention, when the desired average power is not obtained even when the steady power is increased to the rated power, the power is controlled by combining two control methods such as increasing the period T. It is also possible.

  In the first to sixth embodiments according to the present invention, the region C and the region F are also provided so that the input power to the first inverter circuit 43 and the input power to the second inverter circuit 44 do not overlap. If the inverter circuits are not destroyed, and each inverter circuit is driven and controlled at the same frequency to prevent the occurrence of beat interference noise, a plurality of It is good also as a control method which inputs electric power into an inverter circuit simultaneously.

  In the first to sixth embodiments according to the present invention, an independent inverter circuit is connected to each heating coil. However, power supplied to a plurality of heating coils by one inverter circuit is used. If the inverter circuit configuration can be adjusted, there is no need to connect an independent inverter circuit for each heating coil.

  Further, in the above-described first to sixth embodiments according to the present invention, the region B and the region E that maintain the steady power value are changed to the region C and the region F that stop the input power to the inverter circuit. Although the transition state is described, when the power input to the heating coil is extremely small, the power supply to the heating coil is stopped before the input power reaches the steady power value, that is, after the region A. There may be a control mode in which the region C starts immediately.

  However, with the induction heating device of the present invention that grasps and controls the input power and time during the soft start control, the input power is reduced even in the control mode in which the region C starts immediately after the region A. It is possible to reliably grasp the average power and control the average power to a desired set value.

  Further, in the above-described first to sixth embodiments according to the present invention, the description has been given under the condition that the power change rate in the soft start control period is not changed. As long as the configuration can be adjusted so as to reliably prevent the occurrence of this, the power change rate may be adjustable.

  Furthermore, in the above-described first to sixth embodiments according to the present invention, the case where two heating coils are used has been described, but switching is similarly performed even when three or more heating coils are used. Thus, desired average power can be supplied to the object to be heated 48.

  In the induction heating apparatus of the present invention, since the steady value is set to a value that exceeds the power set value supplied to the object to be heated, the power decrease during the soft start control is supplied with a steady value power that exceeds the set value. Thus, it is possible to control the average power supplied to the object to be heated to be a set value by compensating for the power decrease during the soft start control. In addition, in the induction heating device of the present invention, when a power is alternately supplied to a plurality of heating coils, a steady-state power exceeding the set value is also supplied with respect to a power drop during soft start control that occurs at the time of operation switching. Thus, it is possible to control the average power supplied to the object to be heated to be a set value by compensating for the power decrease during the soft start control.

  Furthermore, by using the power control method for the induction heating device of the present invention, it is possible to supply a desired average power to the object to be heated, and to uniformly heat the object to be heated, and to provide a plurality of heating coils. In the case where power is alternately supplied to the heating coil, it is possible to heat the object to be heated non-uniformly by increasing the ratio of the power supplied to one of the heating coils.

  As described above, in the first to sixth embodiments according to the present invention, power is alternately supplied to a plurality of heating coils, and desired average power is supplied to an object to be heated. That is, it is possible to realize the following three characteristics: heating the object to be heated uniformly, and increasing the ratio of the electric power supplied to one heating coil to heat it nonuniformly.

(Embodiment 7)
Hereinafter, an induction heating apparatus according to a seventh embodiment of the present invention will be described with reference to the accompanying drawings. The induction heating apparatus according to the seventh to ninth embodiments of the present invention described below is the induction heating apparatus of the present invention described in the first to sixth embodiments. The configuration of an induction heating apparatus that is configured to prevent abnormal noise from being generated at startup, improve power conversion efficiency, and suppress generation of electromagnetic noise will be described. In addition, in Embodiment 7 and Embodiment 8, although the induction heating apparatus which has one heating coil is demonstrated, it is applicable also to the induction heating apparatus which has a some heating coil.

  In the description of the seventh embodiment according to the present invention, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating apparatus according to the first to sixth embodiments, and the description will be made. The description of Embodiment 1 to Embodiment 6 is incorporated.

  FIG. 8 is a circuit diagram showing a part of the induction heating apparatus according to the seventh embodiment of the present invention. In FIG. 8, the circuit configuration from the power source to supplying the high-frequency current to the heating coil via the inverter circuit, and the on / off control signal of the switching unit composed of the switching elements as switching means included in the inverter circuit are shown. The generated configuration is shown in a block diagram.

  As shown in FIG. 8, in the induction heating apparatus of the seventh embodiment, the object to be heated 48 such as a pan is disposed in the vicinity (directly above) the heating coil 45, and the heating coil 45 and the object to be heated 48 are magnetically coupled. Thus, the object to be heated 48 is configured to be induction-heated.

  The resonance capacitor 63 is connected in parallel to the heating coil 45 and constitutes a resonance circuit with the heating coil 45. The inverter circuit 43 is connected in series to the heating coil 45, and includes a switching unit such as an IGBT and a reverse conducting diode connected in parallel to the switching unit.

  The power source 41 that is an AC power source supplies power to the induction heating device. When a commercial power source is used as the power source 41, the frequency is 50 Hz or 60 Hz.

  A rectifier circuit 42, which is a rectifier that rectifies commercial power from the power source 41 and supplies power to the heating coil 45 via the inverter circuit 43, includes a diode bridge 60, a choke coil 61, and a smoothing capacitor 62. ing.

  The current detection unit 67 that is a current detection unit detects an input current supplied from the power supply 41 and is configured using a current transformer, a shunt resistor, or the like.

  The current setting unit 68 sets a value corresponding to the target value of the input current, and a plurality of current setting values are stored in a ROM (not shown) inside the microcomputer.

  The minimum on-time setting unit 69 serving as a minimum on-time setting unit sets a minimum value (minimum on-time) of the on-time of the switching unit of the inverter circuit 43. The set minimum value of the ON time of the switching unit is stored in a ROM inside the microcomputer. The minimum value of the ON time of the switching unit of the inverter circuit 43 (minimum ON time) is the ON value at which the power value supplied to the heating coil 45 becomes the minimum value in a plurality of ON times that the switching unit of the inverter circuit 43 can take. Say time.

  The on-time variable setting unit 70, which is an on-time variable setting means, determines the on-time when shifting from the state in which the switching unit of the inverter circuit 43 is controlled at a certain on-time to an on-time longer than the on-time. Set the variable. The plurality of variable values set in this way are stored in the ROM inside the microcomputer. Here, in the on-time variable setting unit 70, a plurality of on-time variables of the switching unit are set.

  The control unit 47 performs on / off control of the switching unit of the inverter circuit 43, and all output signals of the current detection unit 67, the current setting unit 68, the minimum on-time setting unit 69, and the on-time variable setting unit 70. The on-time calculator 65 for setting the ON time of the switching unit of the inverter circuit 43 and the pulse generator 66 for outputting a high pulse of the ON time set by the ON-time calculator 65 are provided. The configuration of the control unit 47 in the seventh embodiment is an example, and the present invention is not limited to this configuration.

  FIG. 9 is a time chart of input power in the induction heating apparatus of the seventh embodiment shown in FIG. 8, and shows a time chart of input power (supplied power) supplied from the power supply 41. When the power target value (steady power) PS is supplied immediately after the start of power supply (area a), the relationship between the ON time of the switching unit and the supplied power can be grasped when the switching unit of the inverter circuit 43 is started. Absent. For this reason, it is necessary to activate the switching unit based on an on-time estimated in advance, and there is a problem that feedback control is difficult and power control becomes unstable.

  Therefore, in the induction heating apparatus of the seventh embodiment, at the time of starting the switching unit of the inverter circuit 43, the minimum on-time t (min) at which the power target value PS is not supplied in any state is set. By setting the initial value of the on-time, the minimum power is supplied to the inverter circuit at the time of startup. The minimum power due to the minimum on-time t (min) is the minimum power required to drive the heating coil 45. After starting up in this way, soft start control is performed in which the supplied power becomes the final power target value PS by adding a variable amount of on time and gradually increasing the on time.

  FIG. 10 is a waveform diagram showing the ON time of the switching unit in each region (region a, region b, and region c) of input power during soft start control in the induction heating apparatus of the seventh embodiment. In FIG. 10, in the time chart shown in FIG. 9, the ON time of the switching unit in the regions a, b, and c of the input power at the time of soft start control is shown. 10A shows a control signal for the switching unit in the region a, FIG. 10B shows a control signal for the switching unit in the region b, and FIG. 10C shows a control signal in the region c. The control signal with respect to a switching part is shown.

  As shown in FIG. 10, the on-time in the region a, the on-time in the region b, and the on-time in the region c are representatively shown, and the on-time in the region b rather than the on-time t1 in the region a. t2 is longer, and the on time t3 in the region c is longer than the on time t2 in the region b.

  By increasing the ON time of the switching unit of the inverter circuit 43, the supplied power is increased. For this reason, by gradually increasing the ON time, the supplied power can be set to the final power target value PS as shown in FIG.

About the induction heating apparatus of Embodiment 7 comprised as mentioned above, the operation | movement and an effect | action are demonstrated.
At the time of starting to start supplying power from a state in which power is not supplied to the object to be heated 48, the switching unit of the inverter circuit 43 is turned on with the minimum on-time t (min) set in the minimum on-time setting unit 69. And

  Since the ON time at this time is the minimum value of the time during which the switching unit of the inverter circuit 43 is in the ON state, the supplied power is the minimum value of the power that can be supplied to the heating coil 45. For this reason, the supply power p1 at the time of starting of the inverter circuit 43 becomes the minimum value (see FIG. 9).

  The minimum on-time t (min) is set so as not to reach the final power target value PS in any state. Therefore, by starting the inverter circuit 43 with the minimum on-time t (min) as described above, the object to be heated 48 is overheated without supplying electric power exceeding the target value to the heating coil 45. The cooking performance can be prevented from deteriorating.

  In particular, when the steady power PS, which is the target power value, is the rated power value of the induction heating device, the input power value is not allowed to exceed the rated power value. Setting so as not to exceed the target power value PS is an indispensable condition in the product specification.

  When the minimum on-time t (min) is long, an excessive current suddenly flows to the switching unit when the switching unit of the inverter circuit 43 is started, and the unstable operation such as exceeding the rated current or rated voltage of the switching unit. The switching part may be destroyed. For this reason, in consideration of specifications such as the rated current and rated voltage of the switching unit, the switching unit can be prevented from being destroyed by shortening the minimum on-time t (min).

  Further, in relation to the length of the minimum on-time t (min), an excessively large current flows to the heating coil 45 when the switching unit is activated, and the object to be heated 48 such as a pan magnetically coupled to the heating coil 45. Also, the current is steeply induced and vibrates, which may generate an abnormal sound like hitting a pot called “Katsu”. For this reason, by shortening the minimum on-time t (min), it is possible to prevent an excessively large current from flowing to the heating coil 45 and to suppress the generation of abnormal noise. Since the suppression state becomes larger as the minimum on-time t (min) is shorter, it is desirable to set the minimum on-time t (min) as short as possible.

  After the on-off control of the switching unit of the inverter circuit 43 is performed at the minimum on-time t (min) which is the first on-time t1, the on-time variable Δt1 set by the on-time variable setting unit 70 is set as the minimum on-time t (min). The power supply p <b> 2 is supplied from the power supply 41 to the heating coil 45 by performing on / off control of the switching unit with the added second on-time t <b> 2.

  In the induction heating apparatus of the seventh embodiment, the switching unit of the inverter circuit 43 is controlled to be turned on / off during the minimum on-time t (min), so that the minimum on-time t (min) of the switching unit and the supply power p1 are The control unit 47 can grasp the relationship. For this reason, the control unit 47 can compare the final target power value PS with the supplied power p1 at the minimum on-time t (min). Based on the comparison result, the control unit 47 can minimize the target power value PS. When the supply power p1 at the on-time t (min) is low, the switching unit can be controlled to be turned on / off at the on-time t2 to which the on-time variable Δt1 is added so that the supply power does not exceed the target power PS. .

  As described above, the on-time variable Δt2 set in the on-time variable setting unit 70 is set to the second after the on-off control of the switching unit at the second on-time t2 (region b), as in the on-time switching method. The on / off control of the switching unit is performed at the third on-time t3 added to the on-time t2. As a result, the supplied power p3 is supplied from the power supply 41 to the heating coil 45 in the third on-time t3 (region c). In this soft start control, after the elapse of the third on-time t3, the supply power p4 (region d) is supplied to the heating coil 45 at the fourth on-time t4 obtained by adding the on-time variable Δt3 to the third on-time t3. The same operation is repeated after the fourth on-time t4 has elapsed. By changing the setting of the on-time in this way, the power supplied to the heating coil 45 gradually increases from the minimum power supply p1 and can finally be set to the target power value PS.

  In the time chart shown in FIG. 9, the case where the input power supply period (each region) in the soft start control is set to be long is described, but the time chart in FIG. 9 is an example. For example, in the induction heating apparatus of the seventh embodiment, by shortening the supply time of each region in the soft start control period, it becomes possible to quickly reach the supply power to the target power value PS and control the input power. It becomes the structure which can improve further.

  In the induction heating apparatus according to the present invention, the maximum on-time variable Δt (max) having a plurality of on-time variables and having the largest on-time variable is changed from the minimum on-time t (min) at the start to the target power value PS. It is set in any area until it reaches. In the seventh embodiment, as shown in FIG. 9, the maximum on-time variable Δt (max) is added to the minimum on-time t (min) of the region a and set to the on-time of the region b (supply power). p2). Here, the supply power value at the minimum on-time t (min) is at least a value smaller than ½ of the target power value PS, and at least the maximum on-time variable Δt (max) is added to the minimum on-time t (min). The supply power value at the determined time is set so as not to exceed the target power value PS.

  In the induction heating apparatus according to the seventh embodiment of the present invention, the control unit 47 sets the minimum on-time t (min) set by the minimum on-time setting unit 69 as an initial value of the on-time, and the inverter circuit 43 The switching unit is activated. In addition, after the start-up, the controller 47 sets the on-time variable setting unit 69 so that the power supplied to the heating coil 45 becomes the target power (steady power) PS of the current set value set by the current setting unit 68. The on-time of the switching unit is controlled to vary according to the variable of the on-time set in.

  In the present invention described using the induction heating device of the seventh embodiment as an example, a plurality of on-times that can be taken by the switching unit of the inverter circuit 43 are set, and low supply power including at least the minimum on-time t (min) A first on-time group on the side and an on-time longer than the on-time included in the first on-time group, and the second on the high supply power side including the on-time that becomes the target power (steady power) PS It is classified into the on-time group.

  In the induction heating device of the present invention, the on-time variable when the on-time of the switching unit transitions from the on-time included in the first on-time group to the on-time included in the second on-time group is: It is set larger (longer) than the variable of the on-time within one on-time group and the variable of the on-time within the second on-time group. For example, in Embodiment 7, as shown in FIG. 9, the first on-time group on the low supply power side includes only the on-time of region a (minimum on-time t (min) at startup). In addition, the second on-time group on the high power supply side includes on-times in all regions after the region b. Therefore, when the on-time of the switching unit transitions from the minimum on-time t (min) of the first on-time group region a to the on-time (t2) of the second on-time group region b, the maximum on-time The ON time (t2) to which the variable Δt (max) is added is set.

  In the induction heating apparatus of the seventh embodiment, the minimum on-time t (min) is controllable from the viewpoint of suppressing the generation of abnormal noise from the object to be heated 48 and preventing the switching circuit etc. of the inverter circuit 43 from being destroyed. By setting the time as short as possible and switching the on-time at least once with the maximum on-time variable, the operation period in the soft start control until the target power value PS is reached even when the minimum on-time t (min) is short is shortened. It is possible to increase the power conversion efficiency of the inverter circuit.

  In the induction heating apparatus according to the seventh embodiment, the minimum on-time t that is the first on-time t1 from the viewpoint of suppressing the generation of abnormal noise from the object to be heated 48 and the destruction of the switching unit or the like in the inverter circuit 43. Although (min) is set short, the power conversion efficiency of the inverter circuit 43 is low in the operation of supplying power with low power.

  Therefore, from the viewpoint of power conversion efficiency and ease of power control, it is desirable to shorten the power supply period with low power as much as possible and to quickly bring the supplied power close to the target power value PS. For this reason, in the operation of supplying power with low power, after the switching unit is on / off controlled with the minimum on-time t (min), the maximum on-time variable set in the on-time variable setting unit 70 is set to the minimum on-time t ( By performing on / off control of the switching unit at the second on-time t2 added to (min), the power p2 supplied at the on-time t2 can be quickly brought close to the target power value PS. In the induction heating apparatus of the seventh embodiment controlled in this way, it is possible to improve the power conversion efficiency and the ease of power control.

  When the on-time of the switching unit in the inverter circuit 43 is short and the current flowing through the heating coil 45 is small, the resonance current is insufficient, so that the inverter circuit 43 may be controlled to be turned on while a voltage is applied to the switching unit. There is.

  When the soft start control is continuously performed with the on-time being short, when the inverter circuit 43 is turned on, the charge stored in the resonance capacitor 63 is short-circuited, and the power conversion efficiency of the inverter circuit 43 is reduced. Will be significantly reduced. For this reason, when soft start control is continuously performed with a short on-time, the minimum on-time is set so that the turn-on operation can be performed with no voltage applied to the switching unit during the minimum on-time t (min). It is necessary to set the time t (min).

  However, the induction heating apparatus according to the seventh embodiment of the present invention has different on-time variables, for example, an inverter with an on-time to which the maximum on-time variable is added shortly after operating at the minimum on-time t (min). In order to control the drive of the circuit 43, even if the control has a problem of turning on in a state in which a voltage is applied to the switching unit when operating with the minimum on-time t (min), the period is minimized. can do. Therefore, the induction heating device of the seventh embodiment has a configuration that can set the minimum on-time t (min) without worrying about the power conversion efficiency.

  In addition, as shown in FIG. 9, after supplying the power of the target power value PS, when the soft start control is repeatedly performed such that the power supply is temporarily stopped and then the target power starts to be supplied again, The induction heating apparatus has a problem that an abnormal sound is generated from the object to be heated 48 every time activation is started. However, since the induction heating apparatus according to the seventh embodiment of the present invention has an effect of suppressing abnormal noise generated from the article to be heated 48 during the soft start control period, such supply power is started (soft start control). In the induction heating apparatus configured to repeat the above, a further effect is obtained.

  Further, in the case of supplying a large amount of power to the object to be heated 48, when the on / off switching operation for the inverter circuit 43 is frequently performed, the period during which the supply power in one cycle of the switching operation is small (such as the region a), and the power The proportion of the switching period (area f) that is not supplied increases. As a result, the induction heating apparatus cannot supply desired power set as average power.

  Therefore, in the configuration of the induction heating apparatus of the seventh embodiment, at the time of start-up that may generate an abnormal sound such as a pot sound, the start-up is performed with the minimum on-time t (min), and then the maximum on-time variable is quickly added. The on-time is increased to increase the power supply. As a result, the induction heating device of the seventh embodiment has a configuration that can supply high average power even if the switching operation is frequently performed.

(Embodiment 8)
Hereinafter, an induction heating apparatus according to an eighth embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the eighth embodiment according to the present invention, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating device according to the first to seventh embodiments, and the description thereof will be carried out. The description of Embodiment 1 to Embodiment 7 is incorporated.

  FIG. 11 is a time chart of input power in the induction heating apparatus according to the eighth embodiment of the present invention, and is a time chart of the voltage waveform of power supply 41 and input power (supply power) supplied from power supply 41. This is different from the above-described seventh embodiment in that the supplied power has ripples (pulsations).

  The capacity of the smoothing capacitor 62 (see FIG. 8) is as small as several μF, and ripple occurs when a current is passed through the heating coil 45. In the induction heating apparatus of the eighth embodiment, the ripple voltage waveform is substantially the same as the voltage waveform of the power supply 41. In the time chart shown in FIG. 11, the supplied power causes ripples in synchronization with the frequency of the power supply 41, because the voltage of the smoothing capacitor 62 causes ripples.

  In the induction heating apparatus according to the eighth embodiment of the present invention, the zero cross point of the power supply 41 is detected, and the timing for changing the on-time is controlled using the detected point as a trigger. Since the induction heating apparatus according to the eighth embodiment is configured using the small-capacity smoothing capacitor 62, the supplied power fluctuates in synchronization with the power supply voltage. Similarly, the induction heating device can be configured such that abnormal noise is not generated when the switching unit is started, power conversion efficiency can be improved, and generation of electromagnetic noise can be suppressed.

  Further, in the induction heating apparatus of the eighth embodiment, since the ON time is changed in the vicinity of the zero cross point, the change amount of the supplied power is small immediately before and after the change of the ON time, for example, flicker in lighting etc. Can reduce the impact.

  Furthermore, in the switching part of the inverter circuit 43, the voltage applied to the switching part is low, and the smaller the supplied power, the less damage is caused when switching the on-time. Changing the on-time contributes.

  Before the switching unit of the inverter circuit 43 is started, the switching unit continues to be in an off state. Therefore, the charge charged in the smoothing capacitor 62 has no place to discharge, and even if the voltage of the power supply 41 becomes zero, the smoothing capacitor 62 is smoothed. The capacitor 62 is in a state where a voltage equal to or lower than the peak voltage of the power supply 41 is applied.

  For this reason, even if the inverter circuit 43 is started at the zero crossing point of the power supply 41, the current accompanying the voltage charged in the smoothing capacitor 62 flows to the switching unit or the like at the time of startup, and the switching unit or the like is destroyed or heated The problem that abnormal sounds from 48 occur is not solved.

  However, in the induction heating apparatus according to the eighth embodiment of the present invention, regardless of the voltage of the smoothing capacitor 62, soft switching is performed so as to prevent the switching unit from being destroyed and to suppress the generation of abnormal noise from the object to be heated 48. The induction heating device is configured to start at the minimum on-time t (min) in the start control period and to flow the current accompanying the voltage charged in the smoothing capacitor 62 to the switching unit. Is realized.

  In the induction heating apparatus of the eighth embodiment, the voltage value of the smoothing capacitor 62 at the zero cross point of the power supply 41 increases as the capacity of the smoothing capacitor 62 increases, and the detection circuit and / or The discharge conditions differ depending on the connection state of various circuits such as a noise countermeasure circuit, and the voltage value is determined according to the connection state.

(Embodiment 9)
Hereinafter, an induction heating apparatus according to a ninth embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the ninth embodiment according to the present invention, the same reference numerals are given to the same functions, configurations, and operations as those of the elements in the induction heating apparatus according to the first to eighth embodiments, and the description will be made. The description of Embodiment 1 to Embodiment 8 is incorporated.

  FIG. 12 is a circuit diagram showing a part of the induction heating apparatus according to the ninth embodiment of the present invention in a block form. In the induction heating apparatus according to the ninth embodiment, the heating coil is configured to be substantially concentric with two of the first heating coil 45 on the inner side and the second heating coil 46 on the outer side. 46 differs from the above-described seventh and eighth embodiments in that inverter circuits 43 and 44 are connected to 46.

  FIG. 13 is a time chart of input power in the induction heating apparatus of the ninth embodiment, and FIG. 13A is a time chart of input power supplied to the first heating coil 45 (inner heating coil). FIG. 13B is a time chart of the input power supplied to the second heating coil 46 (outer heating coil).

  Since the operation, action, role, effect, and the like of each element of the soft start control in the induction heating apparatus of the ninth embodiment are the same as those of the seventh embodiment, description thereof is omitted in the ninth embodiment. .

  In the induction heating apparatus according to the ninth embodiment, two heating coils 45 and 46 are provided to induction-heat one object 48, and inverter circuits 43 and 44 are connected to the heating coils 45 and 46, respectively. Thus, independent power is supplied to the first heating coil 45 that is the inner heating coil and the heating coil 46 that is the outer heating coil.

In the circuit configuration of the induction heating device of the ninth embodiment, the two inverter circuits 43 and 44 cannot be operated simultaneously from the viewpoint of detection of supplied power and interference of magnetic fields.
Therefore, for example, in order to uniformly heat the object to be heated 48, as shown in FIG. 13, the period during which power is supplied to the first heating coil 45 (inner heating coil) is the second heating coil 46 (outer side). The power supply to the heating coil) is stopped, and after a certain period of time, the power is supplied to the second heating coil 46 and the power supply to the first heating coil 45 is stopped. As described above, since the power supply and the stop are repeatedly controlled at regular intervals, the power control is performed so that the heat generation amount in the object to be heated 48 by the first heating coil 45 and the second heating coil is uniform. There is a need to.

  For this reason, in the induction heating apparatus of the ninth embodiment, as described in the induction heating apparatus of the sixth embodiment, by controlling the steady power supplied to the heating coils 45 and 46 to a desired value, And / or by controlling the steady power input period during which steady power is supplied to the heating coils 45 and 46 to a desired time, the object to be heated 48 can be uniformly heated.

  In the induction heating apparatus that needs to switch the on / off operation to a plurality of inverter circuits as described above, by using the soft start control described in the ninth embodiment, an abnormal sound (unpleasant sound) such as a pot sound is generated. Therefore, it is possible to realize an induction heating device that does not cause discomfort to the user.

  In the induction heating apparatus shown in FIG. 12, the configuration of the inverter circuit in which one switching unit for controlling the power supplied to one heating coil is connected has been described. However, the present invention has such a configuration. It is not limited. For example, as shown in FIG. 14, each inverter circuit 70, 71 is configured by a switching arm in which two switching units are connected in series, and the circuit configuration for controlling the power supplied to each heating coil 45, 46 is used. Even if it exists, the effect of this invention can be show | played.

  As described above, the induction heating device according to the present invention starts the inverter circuit with the minimum on-time t (min) at which power conversion efficiency is low but no abnormal noise is generated as an initial value for the inverter circuit, and then the on-time The power conversion efficiency can be increased by largely changing the power to change from a low power conversion efficiency state to a high state and performing on / off control of the switching unit.

  The induction heating apparatus according to the present invention described in Embodiments 7 to 9 described above includes a heating coil that induction-heats an object to be heated, a resonance capacitor that forms a resonance circuit with the heating coil, and the heating coil. A switching unit connected in series, a rectifying unit that rectifies an AC power source and supplies power to the heating coil, a minimum on-time setting unit that sets a minimum value of an on-time of the switching unit, and an on-time of the switching unit An on-time variable setting unit that sets a plurality of variables, a current detection unit that detects an input current supplied from an AC power supply, a current setting unit that sets a value corresponding to a target value of the input current, and the switching unit And a control unit that controls on / off.

  In the induction heating apparatus of the present invention, the control unit sets the minimum on-time set by the minimum on-time setting unit as the initial value of the on-time when starting the switching unit, and after the startup, The on-time of the switching unit is varied according to the on-time variable set by the on-time variable setting unit so that the target power of the current set value set by the current setting unit is obtained. The plurality of on-times that the switching unit can take include a first on-time group on the low power supply side including at least the minimum on-time, and an on-time longer than the on-time included in the first on-time group. And the second on-time group on the high supply power side including the on-time as the target power. In the control unit, a variable of the on time when the on time of the switching unit transitions from the on time included in the first on time group to the on time included in the second on time group, The variable is set larger than the variable of the on-time within the first on-time group and the variable of the on-time within the second on-time group.

  In the induction heating apparatus according to the present invention configured as described above, an abnormal sound is not generated when the switching unit is activated by setting the minimum on time, which is a minimum on-time when the switching unit is activated. be able to. In addition, the induction heating device according to the present invention rapidly increases the on-time of the switching unit at a timing close to the start-up except for the start-up, and prevents an operating state in which an excessive current flows through the switching unit at the time of turn-on, thereby converting power. It becomes the structure which can aim at the improvement of efficiency and can aim at suppression of electromagnetic noise.

  As described above, in the induction heating apparatus according to the present invention, in the soft start control for the switching unit in the inverter circuit, a plurality of on-times having different supply powers are set, and the largest on-time variable is set in the switching unit. By setting when the switching unit is in an operating state when voltage is applied to the switching unit at the time of turn-on, it is possible to prevent abnormal noise that occurs when the switching unit is started up, improve power conversion efficiency, and generate electromagnetic noise. Can be suppressed.

  Although the invention has been described in its preferred form with a certain degree of detail, the present disclosure of this preferred form should vary in the details of construction, and combinations of elements and changes in order may vary in the claimed invention. It can be realized without departing from the scope and spirit.

  As described above, the induction heating device according to the present invention supplies desired power to the object to be heated in the soft start control period, heats the object to be heated to a desired state, and is convenient for the user. A good and highly versatile heating device can be provided.

41 Power Supply 42 Rectifier Circuit 43 First Inverter Circuit 44 Second Inverter Circuit 45 First Heating Coil 46 Second Heating Coil 47 Control Unit 48 Object to be Heated 49 Current Measurement Unit 50 Timekeeping Unit 51 Zero-Cross Detection Unit 52 Power Calculation Section 60 Diode bridge 61 Choke coil 62 Smoothing capacitor 67 Current detection section 68 Current setting section 69 Minimum on-time setting section 70 On-time variable setting section 65 On-time calculator 66 Pulse generator

Claims (13)

A plurality of heating coils for induction heating the object to be heated;
An inverter circuit for supplying power to the plurality of heating coils;
A control unit for driving and controlling the inverter circuit,
The control unit is an induction heating device that induction-heats an object to be heated by alternately supplying electric power to each heating coil from the inverter circuit,
The control unit performs a soft start control so that the power supplied to the heating coils is gradually increased from a preset minimum value to a steady power value at the start of power supply to each heating coil. And after the power supplied to the heating coil reaches the steady power value, the inverter circuit is controlled to maintain the supply of the steady power value until the end of power supply to the heating coil, and An induction heating apparatus set so that a steady power value is larger than an average power value supplied to the heating coil.   The induction heating device according to claim 1, wherein the control unit is configured to control an average power supplied to the heating coil by changing a steady power value.   The induction heating apparatus according to claim 1, wherein the control unit is configured to control an average power supplied to the heating coil by changing a power supply end time in a soft start control period.   The control unit supplies electric power to the heating coil during the soft start control period, to supply electric power to the heating coil during the period during which steady power is supplied, and to the heating coil. The induction heating apparatus according to any one of claims 1 to 3, configured to calculate an average power supplied to the heating coil by grasping a time required for the operation to make a round. A current measuring unit (49) for measuring a current supplied from a power source to the inverter circuit;
A time measuring unit (50) for measuring the time of the operating state of the inverter circuit,
The control unit calculates power supplied to the inverter circuit based on an output value of the current measurement unit, and includes an amount of power supplied to the inverter circuit based on a time measured by the time measuring unit, and the heating The induction heating device according to claim 4, wherein the induction heating device is configured to grasp a time required for one cycle of supplying power to each of the coils. A current measuring unit for measuring the current supplied from the power source to the inverter circuit;
A zero cross detector for detecting a point at which the voltage of the power source is at a zero level;
A power calculation unit for calculating the power supplied to the inverter circuit,
The power calculation unit is configured to read an output signal from the current measurement unit in synchronization with a frequency of a detection signal from the zero cross detection unit, and to output a zero cross signal to the control unit,
5. The induction according to claim 4, wherein the control unit is configured to calculate a power value and / or a power amount input to the inverter circuit in a period from a time when a zero cross signal is generated to a time when a next zero cross signal is generated. Heating device. A zero-cross detector that detects a point at which the voltage of the power supply is at a zero level;
A power calculation unit for calculating the power supplied to the inverter circuit,
The power calculation unit is configured to read an output signal from the current measurement unit in synchronization with a frequency of a detection signal from the zero cross detection unit, and to output a zero cross signal to the control unit,
6. The induction according to claim 5, wherein the control unit is configured to calculate a power value and / or a power amount input to the inverter circuit in a period from a time when a zero cross signal is generated to a time when the next zero cross signal is generated. Heating device.   Each of the said heating coils is arrange | positioned substantially concentrically, The said control part is comprised so that the electric power supplied to a heating coil with a larger diameter may be larger than a heating coil with a small diameter. The induction heating apparatus according to item 1.   The induction heating device is a cooking appliance, and each of the heating coils is arranged substantially concentrically, and the control unit supplies power to a heating coil with a small diameter and a heating coil with a large diameter based on a cooking sequence. The induction heating device according to any one of claims 1 to 7, wherein the induction heating device is configured to change a ratio of the heating. A minimum on-time setting unit that sets a minimum on-time at which the power value supplied to the heating coil is a minimum value in a plurality of on-times that can be taken by the switching unit in the inverter circuit;
An on-time variable setting unit for setting a plurality of on-time variables of the switching unit;
A current detector for detecting an input current supplied from a power source;
A current setting unit that sets a value corresponding to the target value of the input current,
The control unit sets the minimum on-time set by the minimum on-time setting unit as an initial value of the on-time when starting the switching unit, and the current set by the current setting unit after the start-up The on-time of the switching unit is varied by the on-time variable set by the on-time variable setting unit so as to be the target power of the set value,
A plurality of on-times that the switching unit can take include a first on-time group on the low power supply side including at least the minimum on-time, and an on-time longer than the on-time included in the first on-time group. And a second on-time group on the high supply power side including the on-time that is the target power, and
The variable of the on time when the on time of the switching unit transitions from the on time included in the first on time group to the on time included in the second on time group is the first on time. The induction heating device according to claim 1, wherein the induction heating device is set to be larger than a variable of on-time within the group and a variable of on-time within the second on-time group.   The induction heating apparatus according to claim 10, wherein the on-time included in the first on-time group is only the minimum on-time.   The induction heating device according to claim 10 or 11, wherein the induction heating device is configured to control from off to on in a state in which a voltage is applied to the switching unit when operating at least at a minimum on-time.   The induction heating device according to any one of claims 10 to 12, configured to set a start timing of the switching unit in the vicinity of a zero cross point of a power source.

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