JP2022048403A - Electromagnetic induction heating device - Google Patents

Abstract

To provide an electromagnetic induction heating device capable of suppressing uneven heating due to the size and arrangement of a pot and also capable of cooking without worrying about the arrangement of the pot.SOLUTION: In an electromagnetic induction heating device, an object to be heated placed on a top plate is inductively heated, using a plurality of heating coils arranged in a distributed manner under the top plate. The electromagnetic induction heating device includes a rectifier circuit converting AC voltage to DC voltage, an inverter pair comprising a pair of inverters, and a control circuit controlling the inverter pair. Each inverter comprising the inverter pair includes: an inverter circuit converting the DC voltage to high frequency AC voltage; a resonant circuit in which two series circuits each including a heating coil and a resonant capacitor are connected in series; and a switch connected in series to the resonant circuit. The inverter pair is configured to connect between a midpoint connecting series circuits of one inverter and a midpoint connecting series circuits of the other inverter.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electromagnetic induction heating cooker (IH cooking heater) that heats a pan using a plurality of heating coils.

In recent years, an inverter type electromagnetic induction heating cooker (IH cooking heater) that heats an object to be heated such as a pot without using a fire has been widely used. The IH cooking heater applies a high-frequency current to a heating coil, generates an eddy current in a pot made of a material such as iron or stainless steel, which is arranged close to the coil, and generates heat by the electric resistance of the pot itself. As described above, the IH cooking heater can be cooked without using a fire, and has high safety and comfort in the cooking environment. Therefore, the IH cooking heater is rapidly becoming popular as an alternative to the gas range.

In the conventional IH cooking heater, a heating coil is arranged under the glass top plate, and an inverter for supplying a high frequency current is connected to the heating coil. The pot placed on the top plate is heated using one heating coil.

However, in the method of heating the pot using one heating coil, there is a problem that only a part of the bottom of the pan is heated depending on the size and arrangement of the pot, and uneven heating occurs. Therefore, an induction heating device has been proposed that appropriately heats pots of various sizes and arrangements by using a plurality of heating coils.

For example, in Patent Document 1, a circular heating coil and a circular heating coil are arranged so as to surround the circumference, and the radial size of the circular heating coil is the circumferential direction of the circular heating coil. Power to the surrounding heating coil group that is smaller than the size of the circle and whose minimum outer diameter is smaller than the outer diameter of the circular heating coil, the first inverter that supplies power to the circular heating coil, and the surrounding heating coil group. A large pot having a bottom size larger than the outer diameter size of the circular heating coil, which is equipped with a second inverter for supplying the above and a control means for controlling the first and second inverters, has a bias in the heating distribution. It does not occur and can be heated without impairing the cooking performance.

JP 2013-140815

However, in the configuration of Patent Document 1, since the shapes of the first heating coil and the surrounding heating coil group are different, the load impedance of each heating coil differs depending on the mounting position of the pot. Therefore, since the electric power supplied to the first heating coil and the surrounding heating coil group is different, there is a problem that the heating power of the pot is different and uneven heating occurs.

Therefore, in the present invention, in an electromagnetic induction heating cooker provided with a plurality of heating coils for inducing and heating an object to be heated (pot, etc.) placed on a top plate and a plurality of inverters, heating unevenness due to the size and arrangement of the pot It is an object of the present invention to provide an object that can be cooked without worrying about the size and arrangement of the object to be heated (pot, etc.).

In order to solve the above problems, the electromagnetic induction heating device of the present invention uses electromagnetic induction heating for inductively heating an object to be heated placed on the top plate by using a plurality of heating coils dispersedly arranged below the top plate. A device including a rectifying circuit that converts an AC voltage into a DC voltage, an inverter pair composed of a pair of inverters, and a control circuit that controls the inverter pair, and each inverter constituting the inverter pair. Includes an inverter circuit that converts the DC voltage into a high-frequency AC voltage, a resonance circuit in which two series circuits including the heating coil and a resonance capacitor are connected in series, and a switch connected in series to the resonance circuit. The inverter pair is configured by connecting an intermediate point connecting the series circuits of one inverter and an intermediate point connecting the series circuits of the other inverter.

According to the electromagnetic induction heating device of the present invention, in an electromagnetic induction heating cooker provided with a plurality of heating coils for inducing and heating an object to be heated (pot, etc.) placed on a top plate and a plurality of inverters, the object to be heated is provided. It is possible to suppress uneven heating due to the size and arrangement of (pots, etc.), and it is possible to cook without worrying about the arrangement of pots.

It is a perspective view of the top plate of the electromagnetic induction heating apparatus of Example 1. FIG. The block diagram of the electromagnetic induction heating apparatus of Example 1. FIG. The inverter circuit block diagram of the electromagnetic induction heating apparatus of Example 1. FIG. Inverter operation waveform of the electromagnetic induction heating device of the first embodiment. The figure which shows the resistance value of each object to be heated and the inductance ratio with respect to iron. Frequency characteristics of the input power of the electromagnetic induction heating device of the first embodiment. Duty characteristics of the input power of the electromagnetic induction heating device of the first embodiment. It is a figure which shows the heating region of the electromagnetic induction heating apparatus of Example 1. FIG. This is an operation mode of the IGBT and the switch in the heating region of the electromagnetic induction heating device of the first embodiment. It is a circuit block diagram which shows the modification of the electromagnetic induction heating apparatus of Example 1. FIG. It is a figure which shows the heating coil arrangement drawing and the heating area of the electromagnetic induction heating apparatus of Example 2. FIG. It is a circuit block diagram of the electromagnetic induction heating apparatus of Example 2. FIG. It is a block diagram of the resonance circuit of the electromagnetic induction heating apparatus of Example 3. FIG. It is a graph of the voltage generated in the resonance circuit of the electromagnetic induction heating apparatus of Example 3. It is a block diagram of the resonance circuit of the electromagnetic induction heating apparatus of Example 4. FIG. It is a graph of the voltage generated in the resonance circuit of the electromagnetic induction heating apparatus of Example 4.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the electromagnetic induction heating device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 9.

FIG. 1 is a perspective view of the top plate 1 of the electromagnetic induction heating device of the present invention as viewed from above. As shown here, 12 heating coils Lr are dispersedly arranged below the top plate 1. A plurality of inverter pairs are connected to these heating coils Lr, and a high-frequency AC voltage is applied by selecting the heating coil Lr below the object to be heated (pot, etc.) placed at an arbitrary position on the top plate 1. It can be supplied. The electromagnetic induction heating device of this embodiment includes three inverter pairs and three heating coil regions 2 to 4. For example, the heating coils Lr1 to Lr4 are arranged in the heating coil region 2, and _four heating coils Lr are also arranged in the heating coil regions 3 and ₄ as in the heating coil region 2. Although the heating coil region configured by arranging the four heating coils Lr in the vertical direction is illustrated here, the heating coil region may be configured by arranging the four heating coils Lr in the horizontal direction. Further, the number of heating coils is not limited to four, and more heating coils may be arranged. Further, although the shape of the heating coil is elliptical here, it may be circular.

FIG. 2 is a block diagram of the electromagnetic induction heating device of the first embodiment. As shown here, the electromagnetic induction heating device of this embodiment has a rectifying circuit 6 that converts an AC voltage from a commercial power source 5 and outputs a DC voltage, a filter circuit 7, an input current detector 8, and 6. Two inverters 10 (10a, 10b, 10c, 10d, 10e, 10f), a control circuit 50, an input current detection circuit 51, a drive circuit 52, a resonance current detection circuit 53, a switch control circuit 54, and an input power. It is provided with a setting unit 55. The inverters 10a and 10b form a first inverter pair corresponding to the heating coil region 2 by connecting the intermediate points described later, and the inverters 10c and 10d connect the intermediate points to each other to form a heating coil region. The second inverter pair corresponding to No. 3 is configured, and the inverters 10e and 10f form a third inverter pair corresponding to the heating coil region 4 by connecting the intermediate points to each other. Since the configurations of the inverters 10 are the same, the details of the present embodiment will be described below using the inverters 10a and 10b constituting the first inverter pair.

The inverter 10a is composed of an inverter circuit 20a, a resonance current detector 30a, a resonance circuit 40a, and a switch SW ₁ . The inverter circuit 20a is connected between the positive electrode p point and the negative electrode n point of the filter circuit 7, and power is supplied from the commercial power source 5 via the rectifier circuit 6 and the filter circuit 7. The resonance circuit 40a connected to the inverter circuit 20a is configured by arranging the series circuit 41a of the resonance capacitor Cr ₁ and the heating coil _{Lr1 and the series circuit 42a of the heating coil Lr 2 and the resonance capacitor Cr 2 in series} . On the other hand, the inverter 10b is composed of an inverter circuit 20b, a resonance current detector 30b, a resonance circuit 40b, and a switch SW ₂ . The inverter circuit 20b is connected between the positive electrode p point and the negative electrode n point of the filter circuit 7, and power is supplied from the commercial power source 5 via the rectifier circuit 6 and the filter circuit 7. The resonance circuit 40b connected to the inverter circuit 20b is configured by arranging a series circuit 41b of the resonance capacitor Cr ₃ and the heating coil Lr ₃ and a series circuit 42b of the heating coil Lr ₄ and the resonance capacitor Cr ₄ in series. Further, the connection point (intermediate point) of the series circuits 41a and 42a of the resonance circuit 40a and the connection point (intermediate point) of the series circuits 41b and 42b of the resonance circuit 40b are connected.

Next, the operation of each inverter in the first inverter pair will be described. Since the operations of the inverters 10a and 10b are the same, the inverter 10a will be described below. Generally, in the IH cooking heater, a resonance type inverter is used. In the resonance type inverter, the drive frequency fs of the inverter circuit 20a> the resonance frequency fr of the resonance circuit 40a is set, and the characteristic of the resonance load is made inductive, so that the current flowing through the resonance circuit 40a becomes the output voltage of the inverter circuit 20a. It is an inverter that controls so that the phase is delayed. As a result, an increase in loss in the inverter circuit 20a is suppressed. That is, in FIG. 2, the resonance current IL ₁ flowing through the resonance circuit 40a is controlled so as to be in a delayed phase with respect to the voltage at the output terminal t, which is the connection point between the inverter circuit 20a and the resonance circuit 40a. The loss of 20a can be suppressed.

However, if power control (PWM control) is performed by changing the conduction period of the inverter circuit 20a while the drive frequency fs of the inverter circuit 20a is fixed, the polarity of the resonance current IL is reversed during the conduction period of the inverter circuit 20a. In some cases, the resonance current IL ₁ advances to the phase advance mode in which the phase advances from the output voltage of the inverter circuit 20a. Since the phase advance mode causes an increase in the loss of the inverter circuit 20, it is a mode that must be avoided in the resonance type inverter.

FIG. 3 is a more specific circuit configuration of the electromagnetic induction heating device of the first embodiment. In FIG. 3, a rectifying circuit 6 for rectifying an AC voltage from a commercial power supply 5 to a DC voltage and a filter circuit 7 composed of an inverter Lf and a filter capacitor Cf are connected, and a positive electrode p point and a negative electrode of the filter capacitor Cf are connected. The inverter circuit 20a of the inverter 10a and the inverter circuit 20b of the inverter 10b are connected between the n points.

The inverter circuit 20a of the inverter 10a is a power semiconductor switching element in which an IGBT 60 and an IGBT 61 are connected in series. Diodes D (D ₁ and D ₂ ) are connected in parallel to each IGBT in opposite directions, and the cathode terminal of the diode D is connected to the collector terminal of the IGBT and the anode terminal is connected to the emitter terminal. Hereinafter, the circuit composed of the IGBT 60 and the diode D ₁ is referred to as a first upper arm, and the circuit composed of the IGBT 61 and the diode D ₂ is referred to as a first lower arm. Further, snubber capacitors Cs (Cs ₁ , Cs ₂ ) are connected in parallel to each IGBT. The snubber capacitors Cs ₁ and Cs ₂ are charged or discharged by the breaking current at the turn-off of the IGBT 60 or the IGBT 61. Since the capacitances of the snubber capacitors Cs ₁ and Cs ₂ are sufficiently larger than the output capacitance between the collector and the emitter of the IGBTs 60 and 61, the change in the voltage applied to both IGBTs at the time of turn-off is reduced and the turn-off loss is suppressed. _A series circuit of the resonance circuit 40a and the switch SW1 is connected to the output terminal t point and the negative electrode n point, which are the connection points of the IGBTs 60 and 61. The resonance circuit 40a has a configuration in which the series circuit 41a of the resonance capacitor Cr ₁ and the heating coil Lr1 and the series circuit 42a of the heating coil Lr ₂ and the resonance capacitor Cr _{2 are} connected in series.

The inverter circuit 20b of the inverter 10b is a power semiconductor switching element in which an IGBT 62 and an IGBT 63 are connected in series. Diodes D (D ₃ and D ₄ ) are connected in parallel to each IGBT in opposite directions, and the cathode terminal of the diode D is connected to the collector terminal of the IGBT and the anode terminal is connected to the emitter terminal. Hereinafter, the circuit composed of the IGBT 62 and the diode D ₃ is referred to as a second upper arm, and the circuit composed of the IGBT 63 and the diode D ₄ is referred to as a second lower arm. Further, snubber capacitors Cs (Cs ₃ , Cs ₄ ) are connected in parallel to each IGBT. The snubber capacitors Cs ₃ and Cs ₄ are charged or discharged by the breaking current at the turn-off of the IGBT 62 or the IGBT 63. Since the capacitance of the snubber capacitors Cs ₃ and Cs ₄ is sufficiently larger than the output capacitance between the collector and the emitter of the IGBTs 62 and 63, the change in the voltage applied to both IGBTs at the time of turn-off is reduced and the turn-off loss is suppressed. A series circuit of the resonance circuit 40b and the switch SW ₂ is connected to the output terminal w point and the negative electrode n point, which are the connection points of the IGBTs 62 and 63. The resonance circuit 40b has a configuration in which a series circuit 41b of the resonance capacitor Cr ₃ and the heating coil Lr ₃ and a series circuit 42b of the heating coil Lr ₃ and the resonance capacitor Cr ₄ are connected in series.

Then, the intermediate point in the resonance circuit 40a of the inverter 10a (the connection point of the series circuits 41a and 42a) and the intermediate point in the resonance circuit 40b of the inverter 10b (the connection point of the series circuits 41b and 42b) are connected to each other. Since the series circuits 41a, 41b, 42a, 42b to be energized can be arbitrarily selected by forming an inverter pair and switching the inverter circuits 20a, 20b, SW ₁ and SW ₂ , the top plate 1 is heated. The heating region can be changed according to the placement position of the object.

The input current detector 8 detects the current input from the commercial power source 5. The input current detection circuit 51 converts the output signal level of the input current detector 8 into a signal suitable for the input level of the control circuit 50. The control circuit 50 determines the material and state of the object to be heated from the relationship between the input current detected by the input current detection circuit 51 and the resonance current IL ₁ or IL ₂ detected by the resonance current detection circuit 53, and determines the material and state of the object to be heated, and operates the heating operation. Start or stop.

Next, the specific operation of each inverter will be described using the inverter 10a. Here, as shown in FIG. 3, the current flowing through the first upper arm of the inverter circuit 20a is Ic ₁ , the current flowing through the first lower arm is Ic ₂ , and the resonance current is IL ₁ . Further, the voltage between the collector and the emitter of the IGBT 60 of the first upper arm is Vc ₁ , the voltage between the collector and the emitter of the IGBT 61 of the first lower arm is Vc ₂ , and the power supply voltage of the inverter is Vp.

Next, the operation will be described. FIG. 4 shows the operation waveforms of the inverters 10a from modes 1 to 4. In any mode, the IGBT 60 and the IGBT 61 are driven complementarily by providing a dead time period, the switch SW ₁ is in the on state, and the IGBT 62 and the IGBT 63 and the switch SW ₂ are in the off state.

The detailed operation in the mode 1 to the mode 4 will be described below.

(Mode 1)
It is assumed that mode 1 starts from the timing when the current of the current Ic ₁ of the IGBT 60 increases from negative to 0 A. No current is flowing through the IGBT 60 at the start of mode 1, but since the IGBT 60 is already on, the current Ic ₁ starts flowing through the IGBT 60 immediately after the start of mode 1. At this time, since the voltage across the IGBT 60 (voltage between the collector terminal and the emitter terminal Vc ₁ ) is 0V, the IGBT 60 is turned on with ZVZCS without any loss.

(Mode 2)
When the IGBT 60 is cut off and the mode 2 is set, the resonance current IL ₁ becomes the path of the filter capacitor Cf, the snubber capacitor Cs ₁ , the resonance capacitor Cr ₁ , the heating coil Lr ₁ , the heating coil Lr ₂ , the resonance capacitor Cr ₂ , and the switch SW ₁ . , Snubber capacitor Cs ₂ , resonance capacitor Cr ₁ , heating coil Lr ₁ , heating coil Lr ₂ , resonance capacitor Cr ₂ , and switch SW ₁ . At this time, the snubber capacitor Cs ₁ is charged and the snubber capacitor Cs ₂ is discharged. As a result, the voltage across the IGBT 60 gradually rises, ZVS turn-off occurs, and the switching loss can be reduced.

When the voltage Vc ₁ of the snubber capacitor Cs ₁ becomes equal to or higher than the power supply voltage (voltage between pn), the voltage Vc ₂ of the snubber capacitor Cs ₂ becomes 0V, the diode D ₂ is turned on, and the resonance current IL ₁ continues to flow. An on signal is input to the IGBT 61 while a current is flowing through the diode D ₂ .

(Mode 3)
It is assumed that the mode 3 starts from the timing when the current of the current Ic ₂ of the IGBT 61 increases from negative to 0 A. No current is flowing through the IGBT 61 at the start of mode 3, but since the IGBT 61 is already on, the current Ic ₂ starts to flow through the IGBT 61 immediately after the start of mode 3. At this time, since the voltage across the IGBT 61 (voltage between the collector terminal and the emitter terminal Vc ₂ ) is 0V, the IGBT 61 is turned on with ZVZCS without any loss.

(Mode 4)
When the IGBT 61 is cut off and the mode 4 is set, the resonance current IL ₁ flows in the path of the heating coil Lr ₂ , the heating coil Lr ₁ , the resonance capacitor Cr ₁ , the snubber capacitor Cs ₂ , the switch SW ₁ , and the resonance capacitor Cr ₂ . At this time, the snubber capacitor Cs ₂ is charged and the snubber capacitor Cs ₁ is discharged. As a result, the voltage across the IGBT 61 gradually rises, ZVS turn-off occurs, and the switching loss can be reduced.

When the voltage Vc ₂ of the snubber capacitor Cs ₂ becomes equal to or higher than the power supply voltage (voltage between pn), the voltage Vc ₁ of the snubber capacitor Cs ₁ becomes 0V, the diode D ₁ is turned on, and the resonance current IL ₁ continues to flow. An on signal is input to the IGBT 60 while _a current is flowing through the diode D1.

By repeating the above operations from modes 1 to 4 and passing a high frequency current through the heating coils Lr ₁ and Lr ₂ , magnetic flux is generated from the heating coils Lr ₁ and Lr ₂ . Due to this magnetic flux, an eddy current flows in the pot arranged _on the heating coils _Lr1 and Lr2, and the pot itself generates heat by induction heating.

Next, the method of detecting the material of the pot will be described. The object to be heated is discriminated into a magnetic substance and a non-magnetic substance. As a method of distinguishing, energization is performed with low power (about 300 W) before heating. The resonance current IL ₁ or IL ₂ at that time is detected, and the material of the object to be heated is determined from the detected current value. When the current value is small, it is determined to be a heated object of a magnetic material such as iron, and when the current value is large, it is determined to be a non-magnetic material to be heated such as non-magnetic stainless steel, aluminum, or copper. FIG. 5 shows the resistance value of each object to be heated at a frequency of 20 kHz. As shown here, the resistance value of non-magnetic stainless steel is 1/3 of iron, that of aluminum is 1/20, and that of copper is about 1/25.

Further, the control circuit 50 sets the conduction period of each IGBT of the inverter circuits 20a and 20b according to the signal from the input power setting unit 55 via the drive circuit 52, and controls the input power by PFM control or PWM control. Material detection needs to be performed with low power and in a short time in order to prevent the occurrence of overcurrent and overvoltage.

Next, the power control method will be described. FIG. 6 shows the relationship between frequency and input power. The IH cooking heater uses a resonance phenomenon to pass a large high-frequency current through the heating coil. Therefore, the frequency characteristic of the input power shows the resonance characteristic. As shown in FIG. 5, since the resistance of the iron pan is large, the resonance Q becomes small, and a gentle resonance characteristic is exhibited. On the other hand, low-resistance materials such as aluminum and copper have a large resonance Q, so they exhibit steep resonance characteristics. For iron pans with a small resonance Q, power control by frequency is possible by utilizing the gentle resonance characteristics.

Further, FIG. 7 shows the relationship between the Duty of the IGBT 60 and the input power. In an iron pan with a small resonance Q, power control by Duty is also possible.

Next, a method of switching the heating coil Lr used for heating the object to be heated in the heating coil region 2 will be described with reference to FIGS. 8 and 9.

FIG. 8 shows a variable pattern of the heating region, in which the pattern P ₁ is the heating coils Lr ₁ and Lr ₂ , the pattern P ₂ is the heating coils Lr ₁ and Lr ₃ , and the pattern P ₃ is the heating coils Lr ₃ and Lr ₄ . The pattern P ₄ is a pattern in which electric power is supplied to the heating coils Lr ₁ to Lr ₄ to heat the object to be heated on the heating coil.

Further, FIG. 9 shows a method of driving the IGBT and the switch in each heating pattern shown in FIG. In addition, "SW" described in FIG. 9 represents an operation of switching complementarily between the IGBT 60 and the IGBT 61 of the inverter circuit 20a or the IGBT 62 and the IGBT 63 of the inverter circuit 20b. Since the drive pattern of the pattern P1 for heating the object to be heated by using the heating coils _Lr1 and Lr2 has already been described in _FIG . ₄ and the like, the drive patterns of the patterns _P2 to _P4 will be described below. ..

_In the pattern P2, the IGBT 60 and the IGBT 61 of the inverter circuit 20a are switched, the IGBT 63 of the inverter circuit 20b is turned on, and the IGBT 62 and the switches SW ₁ and SW ₂ are turned off. As a result, between the output point t of the inverter circuit 20a and the output point w of the inverter circuit 20b, the series circuit 41a (resonant capacitor Cr ₁ , heating coil Lr ₁ ) and the series circuit 41b (heating coil Lr ₃ , resonance capacitor Cr ₃ ) A series circuit is connected. The IGBT 63 is in the ON state, and the w point and the n point are short-circuited. Therefore, the resonance circuit configuration seen from the output point t of the inverter circuit 20a is a series circuit of the _two sets of resonance capacitors and the heating coil, and is the same as the resonance circuit configuration described in the pattern P1, so that the inverter operation is the same.

In the pattern P3 _, the IGBTs 60 and 61 of the inverter 10a and the switch SW ₁ are turned off, the IGBTs 62 and 63 of the inverter 10b are switched, and the switch SW ₂ is turned on. Regarding the inverter operation in this case, the inverter 10b has the same circuit configuration as the inverter 10a, and has the same operation.

_In the pattern P4, the inverters 10a and 10b are switched and the switches SW ₁ and SW ₂ are turned on. At this time, the inverter 10a and the inverter 10b are operated in synchronization with each other. That is, the first upper arm of the inverter 10a and the second upper arm of the inverter 10b operate in synchronization, and the first lower arm of the inverter 10a and the second lower arm of the inverter 10b operate in synchronization. Since the operation of the inverter in this case is the same as the operation of the pattern P ₁ , the description thereof is omitted.

By controlling the above drive pattern, the heating region can be changed, and even if the size or position of the pot changes, it is possible to efficiently heat the pan.

FIG. 10 shows a modified example of the first embodiment. The difference from the first embodiment is that the switch is an IGBT or MOSFET which is a semiconductor element. FIG. 10 is described as an IGBT. By using a semiconductor element, it is possible to switch on and off at high speed, so the heating region can be changed at high speed, which leads to improvement in cookability. Further, since the voltage applied to the switch in the off state is about ½ of the voltage generated at the inverter output point t or the inverter output point w, a semiconductor element having a low withstand voltage of about 200 V can be used. When the withstand voltage of a MOSFET is lowered, the on-resistance becomes smaller. Therefore, by using a MOSFET with a low withstand voltage, the loss during energization can be reduced and the efficiency can be improved.

According to the electromagnetic induction heating device of the present embodiment described above, an electromagnetic induction heating cooker equipped with a plurality of heating coils for inductively heating an object to be heated (pot, etc.) placed on a top plate and a plurality of inverters. In the above, it is possible to suppress uneven heating due to the size and arrangement of the object to be heated (pot or the like), and it is possible to cook without worrying about the arrangement of the pot.

Next, the electromagnetic induction heating device of the second embodiment of the present invention will be described with reference to FIGS. 11 and 12. It should be noted that the common points with the above-mentioned examples are omitted. FIG. 11 shows an arrangement diagram of the heating coils and a heating region, and the difference from the first embodiment is that eight heating coils Lr are arranged in the heating coil region under the control of one inverter pair, and four heating coils are arranged. The point is that the heating region can be switched each time. By increasing the number of heating coils in this way, uneven heating can be further reduced as compared with the configuration of the first embodiment.

FIG. 12 is an inverter circuit diagram in the heating coil arrangement of FIG. As shown here, in the inverter 10a of the present embodiment, the resonance circuit 40a includes a series circuit 41a including a resonance capacitor Cr ₁₁ and two heating coils Lr ₁₁ and Lr ₁₂ , and two heating coils Lr ₁₃ and Lr ₁₄ . It is composed of a series circuit 42b composed of a resonance capacitor Cr ₁₃ . Similarly, in the inverter 10b, the resonance circuit 40b is a series circuit 41b consisting of a resonance capacitor Cr ₁₅ and two heating coils Lr ₁₅ and Lr ₁₆ , and a series including two heating coils Lr ₁₇ , Lr ₁₈ and a resonance capacitor Cr ₁₆ . It is composed of a circuit 42b. Further, the structure is such that the intermediate point of the resonance circuit 40a and the intermediate point of the resonance circuit 40b are connected.

Also in this embodiment, as in the first embodiment, the series circuits 41a, 41b, 42a, 42b to be energized can be selected by switching the inverter circuits 20a, 20b, the switches SW ₁ and SW ₂ , and the heating region. Can be changed. The switching operation of the heating region is the same as that of the _first embodiment, and the patterns P1 to P4 shown in FIG. ₁₁ can be switched from the operation pattern of FIG.

In FIG. 12, the resonance circuit 40 is configured by a series circuit in which four heating coils Lr are arranged and two resonance capacitors Cr are arranged in one inverter 10, but more heating coils and resonance capacitors are used. The same effect can be obtained even if a resonance circuit is configured, and the number of heating coils and resonance capacitors is not limited.

Next, the electromagnetic induction heating device of the third embodiment of the present invention will be described with reference to FIGS. 13 and 14. It should be noted that the common points with the above-mentioned examples are omitted. FIG. 13 shows the configuration pattern of the resonant circuit. Here, since the resonance circuit 40 connected to each inverter circuit 20 has the same configuration, the resonance circuit 40a will be described as a representative.

FIG. 13A is a configuration of the resonant circuit 40a according to the first embodiment.

The resonance circuit 40a of FIG. 13B has _a configuration in which the series circuit 41a of the resonance capacitor Cr ₁ and the heating coil Lr1 and the series circuit 42a of the resonance capacitor Cr ₂ and the heating coil Lr2 _are connected in series. That is, the internal arrangement of the series circuit 42a is the opposite of that of the first embodiment.

The resonance circuit 40a of FIG. 13C has a configuration in which the series circuit 41a of the heating coil Lr ₁ and the resonance capacitor Cr ₁ and the series circuit 42a of the heating coil Lr ₂ and the resonance capacitor Cr ₂ are connected in series. That is, the internal arrangement of the series circuit 41a is the opposite of that of the first embodiment.

The resonance circuit 40a of FIG. 13D has a configuration in which the series circuit 41a of the heating coil Lr ₁ and the resonance capacitor Cr ₁ and the series circuit 42b of the resonance capacitor Cr ₂ and the heating coil Lr ₂ are connected in series. That is, the internal arrangements of the series circuits 41a and 42a are both opposite to those of the first embodiment.

FIG. 14 shows the peak voltage at the connection points V1 to _V3 of _each resonant circuit of FIG. The heating coil current at this time is about 20 Arms. As shown in FIG. 14, in (A) and (B), a maximum peak voltage of about 450 V is generated. On the other hand, in (C) and (D), the voltage is about 320V, and the voltage can be reduced by 100V or more. By the method of connecting the heating coil and the resonance capacitor in this way, the voltage between the heating coil or the resonance capacitor and the ground can be lowered, so that the failure due to dielectric breakdown can be reduced. Alternatively, the space distance can be reduced, which contributes to miniaturization.

Next, the electromagnetic induction heating device of the fourth embodiment of the present invention will be described with reference to FIGS. 15 and 16. It should be noted that the common points with the above-mentioned examples are omitted. FIG. 15 shows the configuration pattern of the resonant circuit. Here, since the resonance circuit 40 connected to each inverter circuit 20 has the same configuration, the resonance circuit 40a will be described as a representative.

FIG. 15A is a configuration of the resonant circuit 40a of the second embodiment. Hereinafter, the common configuration with FIG. 15A will be omitted, and different configurations will be described.

In the resonance circuit 40a of FIG. 15B, the series circuit 42a has a configuration in which the heating coil Lr ₁₃ , the resonance capacitor Cr ₁₂ and the heating coil Lr ₁₄ are connected in series.

In the resonance circuit 40a of FIG. 15C, the series circuit 42a has a configuration in which the resonance capacitor Cr ₁₂ and the heating coils Lr ₁₃ and Lr ₁₄ are connected in series.

In the resonance circuit 40a of FIG. 15D, the series circuit 41a has a configuration in which the heating coil Lr ₁₁ , the resonance capacitor Cr ₁₁ and the heating coil Lr ₁₂ are connected in series.

In the resonance circuit 40a of FIG. 15 (E), the series circuit 41a has a configuration in which the heating coil Lr ₁₁ and the resonance capacitor Cr ₁₁ and the heating coil Lr ₁₂ are connected in series, and the series circuit 42a resonates with the heating coil Lr ₁₃ . The capacitor Cr ₁₂ and the heating coil Lr ₁₄ are connected in series.

In the resonance circuit 40a of FIG. 15F, the series circuit 41a has a configuration in which the heating coil Lr ₁₁ and the resonance capacitor Cr ₁₁ and the heating coil Lr ₁₂ are connected in series, and the series circuit 42a heats the resonance capacitor Cr ₁₂ . The coils Lr ₁₃ and Lr ₁₄ are connected in series.

In the resonance circuit 40a of FIG. 15 (G), the series circuit 41a has a configuration in which the heating coils Lr ₁₁ and Lr ₁₂ and the resonance capacitor Cr ₁₁ are connected in series.

In the resonance circuit 40a of FIG. 15 (H), the series circuit 41a has a configuration in which the heating coils Lr ₁₁ and Lr ₁₂ and the resonance capacitor Cr ₁₁ are connected in series, and the series circuit 42a has the heating coil Lr ₁₃ and the resonance capacitor Cr. ₁₂ and the heating coil Lr ₁₄ are connected in series.

In the resonance circuit 40a of FIG. 15 (I), the series circuit 41a has a configuration in which the heating coils Lr ₁₁ and Lr ₁₂ and the resonance capacitor Cr ₁₁ are connected in series, and the series circuit 42a has the resonance capacitor Cr ₁₂ and the heating coil Lr. ₁₃ and Lr ₁₄ are connected in series.

FIG. 16 shows the peak voltage at the connection _points V1 to V5 of _each resonant circuit of FIG. The heating coil current at this time is about 17 Arms. As shown in FIG. 16, in (A) to (C), a maximum peak voltage of about 420 V is generated. On the other hand, in (C) and (D), the voltage is about 280V, and the voltage can be reduced by 100V or more. By the method of connecting the heating coil and the resonance capacitor in this way, the voltage between the heating coil or the resonance capacitor and the ground can be lowered, so that the failure due to dielectric breakdown can be reduced. Alternatively, the space distance can be reduced, which contributes to miniaturization. In FIG. 15, two heating coils Lr and one resonance capacitor Cr are arranged in each series circuit, but one heating coil Lr and two resonance capacitors Cr are arranged in each series circuit. Can also obtain the same effect.

1 Top plate 2, 3, 4 Heating coil region 5 Commercial power supply 6 Rectifier circuit 7 Filter circuit 8 Input current detector 10 Inverter 20 Inverter circuit 30 Resonance current detector 40 Resonance circuit 41, 42 Series circuit 50 Control circuit 51 Input current detection Circuit 52 Drive circuit 53 Resonant current detection circuit 54 Switch control circuit 55 Input power setting unit Cr Resonant capacitor Lr Heating coil SW switch Lf Inverter Cf Filter capacitor 60, 61, 62, 63, 64, 65 IGBT
D diode

Claims (6)

An electromagnetic induction heating device that induces and heats an object to be heated placed on a top plate by using a plurality of heating coils dispersedly arranged under the top plate.
A rectifier circuit that converts AC voltage to DC voltage,
An inverter pair consisting of a pair of inverters and
A control circuit for controlling the inverter pair is provided.
Each inverter constituting the inverter pair is
An inverter circuit that converts the DC voltage into a high-frequency AC voltage,
A resonance circuit in which two series circuits including the heating coil and the resonance capacitor are connected in series,
A switch connected in series to the resonant circuit is provided.
The inverter pair is configured by connecting an intermediate point in which the series circuits of one inverter are connected to each other and an intermediate point in which the series circuits of the other inverter are connected to each other. Device. In the electromagnetic induction heating device according to claim 1,
The plurality of heating coils are dispersedly arranged in the plurality of heating coil regions.
An electromagnetic induction heating device characterized in that the inverter pair is provided for each heating coil region. In the electromagnetic induction heating device according to claim 1 or 2.
The switch is an electromagnetic induction heating device characterized in that it is composed of an IGBT or MOSFET which is a power semiconductor element. The electromagnetic induction heating device according to any one of claims 1 to 3.
An electromagnetic induction heating device characterized in that a plurality of heating coils for supplying electric power are selected and a heating region is switched by a combination of a switching operation of an inverter circuit of each inverter and a switch on / off of each inverter. In the electromagnetic induction heating device according to claim 1,
The electromagnetic induction heating device, characterized in that the series circuit includes a plurality of heating coils. In the electromagnetic induction heating device according to claim 1,
The electromagnetic induction heating device, characterized in that the series circuit includes a plurality of resonant capacitors.

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