JP4845432B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker used in general households.

In a general induction heating cooker, an electric resistance value R of a heated load viewed from a heating coil is expressed by the following equation.
N ² √ (ρfμ) (1)
(In the above formula, N: number of heating coil turns, ρ: resistivity, f: current frequency, μ: relative permeability)
Accordingly, the electric resistance value R is a value proportional to the square of the heating coil turns N, the square root of the resistivity ρ, the square root of the current frequency f, and the square root of the relative permeability μ.
Since the electrical resistivity and relative permeability of iron, magnetic SUS, nonmagnetic SUS, and aluminum are the values shown in Table 1 below, the nonmagnetic SUS pan is approximately compared to the aluminum pan (hereinafter referred to as aluminum pan). 5 times, iron pans and magnetic SUS pans have a resistance value ratio of about 20 times.

  Therefore, assuming that the same current is supplied to the heating coil, the aluminum pan can obtain only 1/20 of the heating output of an iron pan or the like. On the other hand, if the number of turns N of the heating coil is adjusted so that a desired heating output can be obtained with a predetermined heating coil current in the aluminum pan, the current flows only 1/20 when the iron pan or the like is driven under the same driving conditions. The heating output becomes 1/400 and a sufficient heating output cannot be obtained.

Therefore, the following conventional induction heating cookers have been proposed as those capable of heating both an iron pan and an aluminum pan having a large difference in skin resistance.
Such a conventional induction heating cooker includes a heating coil capable of selecting a plurality of turns so that both a pan having a high skin resistance such as iron or magnetic stainless steel and a pan having a low resistance made of aluminum or copper can be heated. A load circuit consisting of a resonance capacitor that can select multiple capacitances, a switching device such as a relay that switches the connection of the heating coil and resonance capacitor of the load circuit, and a high-frequency output of a frequency corresponding to the resonance frequency of the load circuit By providing an inverter to be supplied, detecting the material of the object to be heated based on the operating state of the load circuit, and controlling the connection of the resonance circuit by the switching device and the frequency of the high frequency output of the inverter, the material of the object to be heated Even when the skin resistance due to the difference is large or small, it can be heated to the same extent (see, for example, Patent Document 1).

JP 2000-48945

  However, in such a conventional induction heating cooker, in order to be able to heat both an iron pan and an aluminum pan having a large difference in skin resistance, a plurality of switching devices such as relays are used depending on the material of the object to be heated. By switching the connection of the heating coil, the load resistance value seen from the heating coil is adjusted, but if the connection state of the heating coil is not appropriate for the characteristics of the heated load, the inverter outputs a high frequency signal. Is temporarily stopped, the connection by the relay which is a switching device is switched and then restarted, and there is a problem that smooth thermal power adjustment cannot be performed. Further, when a relay is used as a switching device for switching the heating coil, there is a problem that the circuit life is shortened compared to a switching device that does not use a relay due to its contact life.

  This invention was made in order to solve the above-mentioned problems, and its purpose is not between contact connection switching by a relay or the like which is a switching device, but between an iron pan and an aluminum pan having a large difference in skin resistance. It aims at obtaining the induction heating cooking appliance which can heat both.

In the induction heating cooker according to the present invention, a DC power supply circuit that converts an AC power supply into a DC power supply, a plurality of magnetically coupled heating coils, and an output voltage of the DC power supply circuit are converted into a high-frequency voltage, High-frequency output control means for controlling the phase difference at the same frequency and applying the high-frequency voltage to the plurality of heating coils, and the high-frequency output control means is configured to apply a high-frequency voltage to each heating coil. An inverter circuit including two switching elements is provided for each heating coil, and the detected output current value is compared with a limit value for switching element protection. If the output current value is less than the limit value, the input power When the set power is compared, and the input power is smaller than the set power, the drive frequency of the switching element of each inverter circuit is adjusted to bring the input power closer to the set power Therefore, when the detected output current value exceeds the limit value and when the input power is larger than the set power, the phase of the drive signal to the switching element of each inverter circuit is adjusted and heated. This is a phase control mode for lowering the output.

  In this invention, the high frequency output control means converts the output voltage of the DC power supply circuit into a high frequency voltage to a plurality of magnetically coupled heating coils, and the high frequency voltage is phase-differed to the plurality of heating coils at the same frequency. Since the load impedance is adjusted using the mutual inductance between multiple heating coils, it can be applied to a heated pan with a large skin resistance such as an iron pan and an aluminum pan. It can be heated to the same extent.

Embodiment 1 FIG.
Figure 1 is a circuit diagram showing the overall configuration of the induction heating cooker according to Embodiment 1 of implementation, FIG. 2 is a plan view showing the size and the positional relationship of the inner and outer heating coils of the same induction heating cooker, 3 the It is a side view which shows the positional relationship of the internal / external heating coil of an induction heating cooking appliance, and a to-be-heated load.
In FIG. 1, a high frequency output means 3 is connected to the output side of a DC power supply circuit 2 that converts an AC power supply 1 into a DC power supply, and the high frequency output control means 3 applies a high frequency voltage to a plurality of heating coils 4 and 5. It has become.
As shown in FIG. 2 and FIG. 3, the heating coil 4 is a heating coil having a small outer shape (hereinafter referred to as an inner heating coil) that is wound in a substantially circular shape among the plurality of heating coils. The heating coil 5 (hereinafter referred to as the outer heating coil) is wound, and the center positions of the inner heating coil 4 and the outer heating coil 5 are arranged so as to substantially coincide with each other. Below the inner / outer heating coils 4, 5, a ferrite 6 that shields magnetic flux is arranged, and a heated pan 7 that is a heated load is placed on the inner / outer heating coils 4, 5 via a top plate 8. Has been.

Next, the magnetic flux generated by the current flowing through the inner / outer heating coils 4 and 5 will be described with reference to FIGS.
FIG. 4 is a waveform diagram showing voltage waveforms applied to the inner / outer heating coils 4, 5, and FIG. 5 is an explanatory diagram showing the direction of magnetic flux generated by the current flowing through the inner / outer heating coils 4, 5.
In FIG. 5, the direction of the magnetic flux due to the current flowing through the inner heating coil 4 at a certain time is indicated by alternate long and short dashed arrows 9a and 9b, and the direction of the magnetic flux due to the current flowing through the outer heating coil 5 is indicated by two-dot chain arrows 10a and 10b. .
First, FIG. 4A shows that a high frequency voltage is applied to the inner heating coil 4 and the outer heating coil 5 in the same phase. At this time, the currents flowing through the inner heating coil 4 and the outer heating coil 5 are also substantially in phase. In addition, an induced eddy current flows in a direction opposite to the heating coil current through a heated pan 7 that is a heated load placed on the inner and outer heating coils 4 and 5.

The direction of the magnetic flux generated by the current flowing through the inner / outer heating coils 4 and 5 is generated in the clockwise direction with respect to the direction of current flow. Inverts as it inverts.
In the case of FIG. 4 (a), the currents flowing through the inner heating coil 4 and the outer heating coil 5 are substantially in phase, so the direction of the magnetic flux generated by the current in the inner heating coil 4 as shown in FIG. The direction of the magnetic flux generated by the current of the outer heating coil 5 is the same direction.
In FIG. 5A, a part 9 b of the magnetic flux generated by the current of the inner heating coil 4 is linked to the outer heating coil 5, and a part of the magnetic flux 10 b generated by the current of the outer heating coil 5 is also the inner heating coil 4. Since the magnetic flux generated around the inner and outer heating coils 4 and 5 increases in an overlapping manner with each other, the mutual inductance between the inner and outer heating coils 4 and 5 acts positively. The effective inductance of the heating coils 4 and 5 is increased, and the current flowing through the inner and outer heating coils 4 and 5 is suppressed.

On the other hand, as shown in FIG. 4B, when a high frequency voltage is applied to the inner heating coil 4 and the outer heating coil 5 in opposite phases, the currents flowing in the inner heating coil 4 and the outer heating coil 5 are also almost opposite in phase. It becomes. The direction of the magnetic flux generated by the current flowing through the inner / outer heating coils 4 and 5 is opposite as shown in FIG.
At that time, a part 9 b ′ of the magnetic flux generated by the current of the inner heating coil 4 is linked to the outer heating coil 5, and a part of the magnetic flux 10 b ′ generated by the current of the outer heating coil 5 is also linked to the inner heating coil 4. In addition, since the magnetic flux generated around the inner and outer heating coils 4 and 5 cancel each other, the mutual inductance between the inner and outer heating coils 4 and 5 acts negatively, and the inner and outer heating coils 4 The effective inductance of 5 is reduced, and the current easily flows through the inner and outer heating coils 4 and 5.

  In the first embodiment, when the heated pan 7 is a low resistance pan such as an aluminum pan, the high frequency output control means 3 drives the inner heating coil 4 and the outer heating coil 5 in the same phase, The current flowing in the inner / outer heating coils 4 and 5 is suppressed, and the inner heating coil 4 and the outer heating coil 5 are in reverse phase when the heated pan 7 is a high resistance pan such as an iron pan or a magnetic SUS pan. Induction heating cooking that makes it easy to flow current through the inner and outer heating coils 4 and 5 by driving and can be used for a heated pan 7 made of a material having a large electric resistance, such as an aluminum pan and an iron pan. Can be obtained.

Embodiment 2. FIG.
Figure 6 is a plan view showing the size and the positional relationship of the upper and lower heating coil of the induction heating cooker according to Embodiment 2 of implementation, FIG. 7 is the same induction heating cooker upper and lower heating coil and the object to be heated load FIG. 8 is a waveform diagram of the voltage applied to the upper and lower heating coils, FIG. 9 is an explanatory diagram showing the direction of the magnetic flux generated by the current flowing through the upper and lower heating coils, and FIG. 10 is the same induction. It is a side view which shows the positional relationship of another upper and lower heating coil of a heating cooker, and a to-be-heated load.
In the first embodiment, a plurality of heating coils are arranged in the form of an inner heating coil and an outer heating coil on the same plane. In the second embodiment, the plurality of heating coils are arranged vertically, and the upper heating coil and the lower heating coil are arranged in the vertical direction. It is a stacked arrangement in the form of a heating coil.
The circuit configuration of the induction heating cooker according to the second embodiment is the same as that of FIG. 1 according to the first embodiment.

  As shown in FIG. 7, the plurality of heating coils stacked in the vertical direction in the second embodiment are the upper heating coil 4 ′ (hereinafter referred to as the upper heating coil) disposed near the top plate 8 and the pan 7 to be heated. And a heating coil 5 ′ (hereinafter referred to as a lower heating coil) disposed away from the top plate 8 and the heated pan 7 and below the upper heating coil 4 ′. In FIG. 9, the direction of the magnetic flux due to the current flowing through the upper heating coil 4 'is indicated by a one-dot chain arrow, and the direction of the magnetic flux due to the current flowing through the outer heating coil 5' is indicated by a two-dot chain arrow.

FIG. 8 shows voltages applied to the upper heating coil 4 ′ and the lower heating coil 5 ′. In the case of FIG. 8A, the phases of the currents flowing through the upper heating coil and the lower heating coil are substantially the same. . In this case, the direction of the magnetic flux generated by the current flowing through the upper heating coil 4 ′ and the direction of the magnetic flux generated by the current flowing through the lower heating coil 5 ′ are the same as shown in FIG. In addition, an induced eddy current in a direction opposite to the heating coil current flows through the heated pan 7 placed on the upper and lower heating coils 4 ′ and 5 ′.
At this time, as in the first embodiment, the magnetic flux due to the coil current is linked between the upper and lower heating coils 4 ′ and 5 ′, and the mutual inductance between the upper and lower heating coils 4 ′ and 5 ′ is increased. Acting positively, the effective inductance of the upper and lower heating coils 4 'and 5' is increased, and the current flowing through the upper and lower heating coils 4 'and 5' is suppressed.

On the other hand, as shown in FIG. 8B, when a high-frequency voltage is applied to the upper heating coil 4 ′ and the lower heating coil 5 ′ in the opposite phase, the current flowing through the upper heating coil 4 ′ and the lower heating coil 5 ′. The phase of the magnetic flux generated by the current flowing through the upper and lower heating coils 4 ′ and 5 ′ is also reversed as shown in FIG. 9B.
At that time, a part 9′b of the magnetic flux generated by the current of the upper heating coil 4 ′ is linked to the lower heating coil 5 ′, and a part of the magnetic flux 10′b generated by the current of the lower heating coil 5 ′ is also upper. Since the magnetic flux generated around the upper and lower heating coils 4 'and 5' cancels each other by interlinking with the heating coil 4 ', the mutual inductance between the upper and lower heating coils 4' and 5 'is negative. , The effective inductance of the upper and lower heating coils 4 ′ and 5 ′ becomes small, and current easily flows through the upper and lower heating coils 4 ′ and 5 ′.

  In the second embodiment, the high-frequency output control means 3 drives the upper heating coil 4 'and the lower heating coil 5' in the same phase when the heated pan 7 is a low resistance pan such as an aluminum pan. To suppress the current flowing in the heating chamber, and when the heated pan 7 is a high resistance pan such as an iron pan or a magnetic SUS pan, the upper heating coil 4 'and the lower heating coil 5' are driven in opposite phases. Thus, it is possible to obtain an induction heating cooker that can be used even for the heated pan 7 having greatly different electrical resistances by allowing current to easily flow through the upper and lower heating coils 4 ′ and 5 ′.

  In addition, since the magnetic flux due to the induced eddy current flowing through the heated pan 7 is more linked to the upper heating coil 4 ′ than the lower heating coil 5 ′, the inductance of the upper heating coil 4 ′ becomes smaller, and the lower heating Since a larger coil current flows than the coil 5 ′, the lower heating coil 5 ′ and the upper heating coil are reduced by reducing the number of turns of the lower heating coil 5 ′ from the upper heating coil 4 ′ as shown in FIG. 4 'inductance can be balanced, and therefore the current balance of the upper and lower heating coils 4' and 5 'can be balanced. Therefore, the upper and lower heating coils 4' and 5 'and switching elements caused by current imbalance The concentration of heat generation can be reduced.

Embodiment 3 FIG.
Figure 11 is a circuit diagram showing a configuration of an induction heating cooker according to the third implementation, FIG. 12 is a waveform diagram of a drive signal for the low-resistance pots of the same induction heating cooker 13 of the induction heating cooker It is a wave form diagram of the drive signal for high resistance pans.
In FIG. 11, the alternating current supplied from the alternating current power supply 1 is converted into direct current by the direct current power supply circuit 2. The DC power supply circuit 2 includes a rectifier diode bridge 11 that rectifies AC power, a reactor 12, and a smoothing capacitor 13.
The input current input to the DC power supply circuit 2 is detected by the input current detection circuit 14.

Inverter circuits 3 and 3 ′ are connected to the output DC bus of the DC power supply circuit 2. The inverter circuit 3 is a high-frequency output means for the inner heating coil 4, and is composed of two switching elements (IGBT) 15 (hereinafter referred to as upper switches) and 16 (hereinafter referred to as lower switches) connected in series between the DC buses. ), And diodes 17 and 18 connected to the switching elements 15 and 16 in antiparallel, respectively.
The inverter drive circuit 19 outputs a drive signal for alternately turning on and off the upper switch 15 and the lower switch 16 of the inverter circuit 3, and the output current detection means 20 has an output flowing through a series circuit of the inner heating coil 4 and the resonance capacitor 21. The current is detected.

The inverter circuit 3 ′ for the outer heating coil 5 has the same configuration as the inverter circuit 3 for the inner heating coil 4. The upper switch 15 ′ and the lower switch 16 ′ and the upper and lower switches 15 ′ and 16 ′ are respectively provided. It consists of diodes 17 'and 18' connected in antiparallel.
The inverter drive circuit 19 ′ outputs a drive signal for alternately turning on and off the upper switch 15 ′ and the lower switch 16 ′ of the inverter circuit 3 ′, and the output current detection means 20 ′ includes the external heating coil 5 and the resonance capacitor 21 ′. The output current flowing in the series circuit is detected.

The output control means 22 controls the inverter drive circuits 19 and 19 ′ from the detection value of the input current detection circuit 14 and the detection values of the output current detection means 20 and 20 ′.
In the third embodiment, the high-frequency output control means for controlling and applying the high-frequency voltage to the inner and heating coils 4 and 5 includes inverter circuits 3 and 3 ′, inverter drive circuits 19 and 19 ′, and output control means 22. It consists of
When using a heated pan 7 having a low electrical resistance such as an aluminum pan, the input current detected by the input current detecting means 14 is the same as when using a pan having a high electrical resistance such as an iron pan. For the same input current, the coil current detected by the output current detection means 20 and 20 ′ increases for the same input current.
Moreover, when using the to-be-heated pan 7 with large electrical resistance like an iron pan, it becomes a reverse relationship with the above-mentioned.
Therefore, the material of the heated pan 7 is determined based on the input / output current value detected by the output control means 22 which is the heated pot material determining means, and the phase of the drive signal to the inverter circuits 3 and 3 ′ is the same phase. Select whether to use reverse phase.

FIG. 12 shows an example of a drive signal for a low-resistance pan such as an aluminum pan where the heated pan 7 is an aluminum pan, and heating output control is performed by frequency control. FIG. 12A shows the drive frequency of the heating coil 4. , 5 and the resonant frequency of the resonant capacitors 21 and 21 'is used.
In the driving frequency range, the current flowing through the load circuit is delayed from the applied voltage, and the switching element of the inverter circuit is turned on when the diode connected in antiparallel with the switching element to be turned on is conducting. Since this is a state, the switching loss is suppressed by zero voltage switching. 12A shows a drive signal with a high heating output, and FIG. 12B shows a drive signal with a low heating output in which the heating frequency is increased to suppress the heating output.
FIG. 13 shows an example of a drive signal for a high-resistance pan such as the heated pan 7 being an iron pan or a magnetic SUS pan, and FIG. 13A shows a drive signal waveform of a high heating output, (b ) Is a drive signal waveform with a low heating output in which the driving frequency is increased to suppress the heating output.

In FIG. 12A, the upper switches 15 and 15 ′ of the inverter circuits 3 and 3 ′ are in a conductive state during the period I. At this time, a clockwise current flows through the inner heating coil 4 and the outer heating coil 5. Further, during the period II, the lower switches 16 and 16 ′ of the inverter circuits 3 and 3 ′ are conductive, and a counterclockwise current flows through the inner heating coil 4 and the outer heating coil 5. Thus, in the case of the drive signal of FIG. 12A, currents in the same circumferential direction flow through the inner and outer heating coils 4 and 5, and the magnetic fluxes generated by the currents overlap and strengthen each other. The back electromotive force generated in each of the inner and outer heating coils 4 and 5 is increased, and the current flowing through the inner and outer heating coils 4 and 5 is suppressed and decreased.
Therefore, even in the case where an aluminum pan having a small electrical resistance and a large current easily flows through the heating coil in the heated pan 7, the current flows in the same direction in the inner and outer heating coils 4 and 5, respectively. Since the current flowing through the outer heating coils 4 and 5 can be suppressed, it is possible to prevent an overcurrent from flowing through the switching elements 15, 16, 15 ′ and 16 ′.

On the other hand, in FIG. 13A, the inverter circuit 3 upper switch 15 and the inverter circuit 3 ′ lower switch 16 ′ are in a conductive state during the period III. At this time, a clockwise current flows through the inner heating coil 4, and a counterclockwise current flows through the outer heating coil 5. In FIG. 13B, during the period IV, the lower switch 16 of the inverter circuit 3 and the upper switch 15 ′ of the 3 ′ are in a conductive state, a counterclockwise current flows through the inner heating coil 4, and the outer heating coil 5 A counterclockwise current flows in
Thus, in the case of the drive signal of FIG. 13, since the current in the reverse circulation direction flows through the inner and outer heating coils 4 and 5, the magnetic fluxes generated by the current cancel each other and weaken each other. The back electromotive force generated in the inner / outer heating coils 4 and 5 is reduced, and the current flowing through the inner and outer heating coils 4 and 5 is increased.
Therefore, even when heating an iron pan or a magnetic SUS pan in which the electric resistance is large in the heated pan 7 and the current hardly flows to the heating coil, by applying a voltage in the reverse direction to the inner and outer heating coils 4 and 5, By increasing the currents flowing through the inner and outer heating coils 4 and 5, respectively, large input power can be obtained.

  In this third embodiment, the output control means 22 determines the material of the heated pan 7 based on the input current value detected by the input current detection circuit 14 and the output current detection means 20, 20 ′, and the output current value. The phase of the drive signal of the inverter circuit 3 for the internal heating coil 4 and the phase of the drive signal of the inverter circuit 3 'for the external heating coil 5 are the same or By selecting one of the reverse phases, and the inverter drive circuits 19 and 19 ′ drive the inverter circuits 3 and 3 ′ at the selected phase, the influence of the difference in electric resistance in the heated pan 7 is reduced and further driven. Adjustment of the high heating output and low heating output of the pan 7 to which the phase of the signal is selected can be obtained by controlling the driving frequency.

In addition, in the said Embodiment 3, although the structure which wound the inner heating coil 4 and the outer heating coil 5 in the same circumference direction was shown, when winding in the reverse direction, it is the same when heating a high resistance pan. The same effect can be obtained by driving in the phase and driving in the opposite phase when heating the low resistance pan.
Moreover, in said Embodiment 3, the phase relationship of the heating current or the applied voltage of the internal heating coil 4 and the external heating coil 5 is selectively fixed by the material of the to-be-heated pan 7, and the heating power is adjusted by frequency control. However, the heating power may be adjusted by switching between frequency control and phase control.

Embodiment 4 FIG.
FIG. 14 is a waveform diagram of various drive signals of the induction heating cooker according to Embodiment 3 of the present invention, and FIG. 15 is a flowchart of the heating output control process of the induction heating cooker.
In the fourth embodiment, the applied voltage to the inner / outer heating coils 4 and 5 is driven by frequency control regardless of the material of the heated pan 7, and the desired heating power is obtained even at the lowest frequency in the control frequency range. If it is less than this, the phase difference of the voltage applied to the inner and outer heating coils 4 and 5 is controlled. The circuit configuration of the induction heating cooker according to the fourth embodiment is the same as that of FIG. 10 according to the third embodiment.

14A to 14E, the upper waveform is a drive signal to the upper switch 15 of the inverter circuit 3 for the inner heating coil 4, and the lower waveform is the upper signal of the inverter circuit 3 ′ for the outer heating coil 5. This is a drive signal to the switch 15 '.
The drive signals to the lower switches 16 and 16 ′ of the inverter circuits 3 and 3 ′ are not shown. However, as shown in FIG. Turns on and off with time.
14A to 14C are drive signals in the frequency control mode, FIG. 14A is an example of an upper limit frequency drive signal, FIG. 14B is an example of an intermediate frequency drive signal, and FIG. 14C is an example of a lower limit frequency drive signal. is there. Further, (d) to (e) are drive signals in the phase difference control mode, (d) is an example of an intermediate phase difference drive signal, and (e) is a maximum phase difference drive signal. Note that the maximum phase difference is not necessarily 180 °.

Next, the heating power control process of this Embodiment 4 is demonstrated based on the flowchart of FIG.
First, the output current value detected by the output control means 22 using the output current detection means 20 and 20 ′ is a limit value for protecting the switching elements 15, 16, 15 ′, 16 ′ of the inverter circuits 3, 3 ′. When the comparison is made (step 1) and the limit value is not satisfied, the input power calculated based on the detection value of the input current detection means 14 is compared with the set power (step 2).
If the input power is smaller than the set power, the output control means 22 determines whether the frequency of the drive signal is higher than the lower limit frequency (step 3). If the frequency is higher than the lower limit frequency, the frequency control mode The drive signal waveform is assumed to be in the states of (a) and (b) of FIG. In this case, the drive frequency is lowered (step 4) to bring the input power closer to the set power.

When the drive frequency is the lower limit frequency, the drive frequency cannot be lowered anymore, so the phase difference control mode is set. The drive signals to the inverter circuits 3 and 3 ′ in this phase difference control mode are in the states shown in FIGS. Then, the output control means 22 compares the phase difference of the drive signal being output with the maximum phase difference (180 °) (step 5), and if smaller than the maximum phase difference, increases the phase difference and increases the heating output. (Step 6).
If the output current is greater than the limit value in step 1 or if the input power is greater than the set power in step 2, the coil current needs to be reduced, and the output control means 22 It is determined whether or not the phase difference is larger than the minimum phase difference (0 °) (step 7). If it is larger, the phase difference control mode is set, and the phase difference of the drive signal is reduced so as to reduce the output current and input power. (Step 8).
Further, when the phase difference of the drive signal is the minimum phase difference (0 °), the frequency control mode is set, and the output control means 22 compares the frequency of the drive signal with the upper limit frequency (step 9). If it is lower, the driving frequency is increased and the heating output is decreased (step 10).

  In the fourth embodiment, the output control means 22 protects the output current value detected by the output current detection means 20, 20 ′ and the switching elements 15, 16, 15 ′, 16 ′ of the inverter circuits 3, 3 ′. When the detected output current value is less than the limit value, the input power and the set power are compared. When the input power is smaller than the set power, the drive signal to the inverter circuits 3 and 3 ′ is compared. Is set to a frequency control mode in which the heating output is increased in order to bring the input power closer to the set power, and when the detected output current value exceeds the limit value or when the input power is greater than the set power, the control is performed to the inverter circuits 3 and 3 ′. The inverter drive circuits 19 and 19 ′ drive the inverter circuits 3 and 3 ′ in the phase difference control mode in which the drive signal is controlled to lower the heating output, and the control mode is thus switched. Thus, it is possible to obtain an induction heating cooker that can be used regardless of the material of the electric resistance of the heated pan 7, and it is not necessary to determine the material of the heated pan 7 at the start of heating. .

Embodiment 5 FIG.
Figure 16 is a circuit diagram showing a configuration of an induction heating cooker according to the fifth implementation, FIG. 17 is a waveform diagram of a drive signal for the low-resistance pots of the same induction heating cooker 18 of the induction heating cooker FIG. 19 is a waveform diagram of a drive signal for a pan having an intermediate electric resistance of the induction heating cooker.
In FIG. 16, the same or corresponding parts as those in FIG. 11 of the third embodiment are denoted by the same reference numerals, and description thereof is omitted.
Reference numeral 23 denotes a clamp diode connected in parallel to the resonance capacitor 21 on the inner heating coil 4 side, and reference numeral 23 ′ denotes a clamp diode connected in parallel to the resonance capacitor 21 ′ on the outer heating coil 5 side.

In the fifth embodiment, when the connection point potential of the inner heating coil 4 and the resonance capacitor 21 is lower than the negative bus potential of the DC power supply circuit 2 while the lower switch 16 of the inverter circuit 3 for the inner heating coil 4 is in conduction. A semi-resonant inverter circuit is used in which the clamp diode 23 is turned on and a circulating current flows to prevent commutation due to series resonance between the heating coil 4 and the resonant capacitor 21, and the conduction ratio control of the upper switch 15 and the lower switch 16. The heating output control is performed equivalently to the frequency control by adjusting the applied voltage.
As for the inverter circuit 3 ′ for the outer heating coil 5, the frequency control is performed by adjusting the applied voltage by the conduction ratio control of the upper switch 15 ′ and the lower switch 16 ′, similarly to the inverter circuit 3 for the inner heating coil 4. Equivalent to the heating output control.
The conduction ratio control refers to control in which the ratio of the on-time of the upper switch 15 ′ and the lower switch 16 ′ is different, and is performed for the purpose of substantially reducing the applied voltage.

  Further, in the fifth embodiment, similarly to the third embodiment, the output control means 22 is based on the input current value detected by the input current detection circuit 14 and the output current detection means 20, 20 ′ based on the output current value. The material of the heated pan 7 is determined, and the drive signal of the inverter circuit 3 for the inner heating coil 4 and the inverter circuit 3 for the outer heating coil 5 are determined according to the electrical resistance characteristics of the determined material of the heated pan 7. The phase of the drive signal of 'is selected from either the same phase or the opposite phase.

FIG. 17 shows a drive signal for a low resistance pan, (a) shows a drive signal waveform at a high heating output, (b) shows a drive signal waveform at a low heating output, and the upper row shows an inverter for the inner heating coil 4. The drive signal waveforms to the upper switch 15 and the lower switch 16 of the circuit 3, and the lower stage are the drive signal waveforms to the upper switch 15 ′ and the lower switch 16 ′ of the inverter circuit 3 ′ for the external heating coil 5.
FIG. 18 shows a drive signal for a high resistance pan, (a) shows a drive signal waveform at high heating output, and (b) shows a drive signal waveform at low heating output.
Also in the fifth embodiment, in the case of FIG. 17 in which voltages of the same phase are applied to the inner heating coil 4 and the outer heating coil 5, the magnetic flux generated by the currents flowing in the inner and outer heating coils 4, 5 respectively. Since they overlap each other, the back electromotive force generated in the inner / outer heating coils 4, 5 is increased, and as a result, the current flowing in the inner / outer heating coils 4, 5 is suppressed.
In the case of FIG. 18 in which reverse phase voltages are applied to the inner and outer heating coils 4 and 5, the magnetic fluxes generated by the currents flowing through the inner and outer heating coils 4 and 5 cancel each other. The back electromotive force generated in the outer heating coils 4 and 5 is reduced, and as a result, the current flowing through the inner and outer heating coils 4 and 5 can be increased, and the output power can be increased.

In the fifth embodiment, the material of the heated pan 7 is determined based on the input current value and the output current value detected by the output control means 22, and the electric resistance characteristic of the determined material of the heated pan 7 is obtained. Accordingly, the phase of the drive signal of the semi-resonant inverter circuit 3 for the internal heating coil 4 and the phase of the drive signal of the semi-resonant inverter circuit 3 'for the external heating coil 5 is selected from the same phase or the opposite phase. In this way, the inverter drive circuits 19 and 19 ′ drive the inverter circuits 3 and 3 ′, and the adjustment of the low heating output of the pan 7 to which the phase of the drive signal is selected is adjusted by the semi-resonant inverter circuits 3 and 3 ′. By using and controlling the conduction ratio of the upper switches 15 and 15 ′ and the lower switches 16 and 16 ′, it is possible to obtain an induction heating cooker in which the influence of the difference in electric resistance due to the material of the heated pan 7 is reduced.
Moreover, since the semi-resonant inverter circuits 3 and 3 'can be driven at a constant frequency, problems such as resonance sound between pans do not occur even when applied to a cooker having a plurality of heating ports.

  Note that the voltage applied to the inner heating coil 4 and the outer heating coil 5 or the phase difference of the current flowing through the inner heating coil 4 and the outer heating coil 5 has an intermediate electric resistance from the detected input current and output current. The intermediate phase difference as shown in FIG. 19 may be determined by determining the electrical resistance of the heated pan 7 that is a non-magnetic sus pan. Also in FIG. 19, (a) shows the drive signal waveform at the time of high heating output, and (b) shows the drive signal waveform at the time of low heating output in which the drive frequency is increased to suppress the heating output.

Embodiment 6 FIG.
Figure 20 is a circuit diagram showing a configuration of an induction heating cooker according to the sixth implementation, FIG. 21 is a waveform diagram of a drive signal for the low-resistance pots of the same induction heating cooker 22 of the induction heating cooker It is a wave form diagram of the drive signal for high resistance pans.
In the sixth embodiment, a single-stone resonant inverter circuit is used as the high-frequency conversion means. 20, the same or corresponding parts as those in FIG. 11 or 16 are denoted by the same reference numerals.
In the sixth embodiment, on the output side of the DC power supply circuit 2, a parallel load circuit 24 of the inner heating coil 4 and its resonance capacitor 21 and a parallel load circuit 24 ′ of the outer heating coil 5 and its resonance capacitor 21 ′ are connected. The switching element 25 and the anti-parallel diode 26 are connected in series with the parallel load circuit 24, and the switching element 25 'and the anti-parallel diode 26' are connected in series with the parallel load circuit 24 '. The circuit is configured.
The applied voltage is adjusted by the conduction time control of the switching elements 25 and 25 ′ of this one-stone resonant inverter circuit, and the heating output control is performed equivalent to the frequency control.
The conduction time control refers to control for changing the on-time while the off-time of the drive signals of the switching elements 25 and 25 ′ does not change, and is performed for the purpose of substantially reducing the applied voltage.

  FIGS. 21 and 22 show drive signals for the switching elements 25 and 25 ′ of the one-stone resonant inverter circuit. FIG. 21 shows the ON state at the same phase (timing), and FIG. 22 shows the reverse phase (drive cycle). At a timing shifted by half a cycle). In FIGS. 21 and 22, (a) is a driving signal for high heating output with a longer on-time of the switching element, and (b) is a driving signal for low heating output with a shorter on-time of the switching element. Yes, the conduction time is controlled.

Next, the operation of the induction heating cooker according to the sixth embodiment will be described.
In the monolithic resonance inverter circuit, when the switching elements 25 and 25 ′ are in the ON state, the DC power source voltage is applied to the resonance capacitors 21 and 21 ′ and the inner and outer heating coils 4 and 5, and the heating coil current is proportional to the conduction time. To increase.
Then, when the switching elements 25 and 25 ′ are turned off, the inner and outer heating coils 4 and 5 and the resonance capacitors 21 and 21 ′ are in the resonance mode, and the heating coil current is charged with the charges charged in the parallel resonance capacitors 21 and 21 ′. After that, the heating coil current is commutated to charge the resonant capacitors 21 and 21 ′, and the charging causes the connection point potential between the parallel load circuits 24 and 24 ′ and the switching elements 25 and 25 ′ to become a negative DC bus potential. If it falls below, the anti-parallel diodes 26 and 26 ′ become conductive and a regenerative current flows through the smoothing capacitor 13. While the antiparallel diodes 26 and 26 'are conducting, the switching elements 25 and 25' are turned on to perform zero voltage switching.

  Even in the form using this one-stone resonant inverter circuit, as shown in FIG. 21, the switching element 25 of the internal heating coil inverter circuit and the switching element 25 ′ of the external heating coil inverter circuit are turned on. If they are the same, the direction of the current flowing in the inner heating coil 4 and the direction of the current flowing in the outer heating coil 5 are the same in the same circumferential direction, and the magnetic fluxes generated by the current flowing in the inner and outer heating coils 4 and 5 are superimposed on each other. Therefore, the counter electromotive force generated in the inner / outer heating coils 4 and 5 is increased, and as a result, the current flowing through the inner / outer heating coils 4 and 5 is suppressed.

  Further, as shown in FIG. 22, when the switching element 25 of the inner heating coil inverter circuit and the switching element 25 ′ of the outer heating coil inverter circuit are turned on, the timing is shifted by a half cycle of the driving cycle. Since the direction of the current flowing through the heating coil 4 and the direction of the current flowing through the outer heating coil 5 are almost opposite to each other, the magnetic fluxes generated by the currents flowing through the inner and outer heating coils 4 and 5 cancel each other. The back electromotive force generated in the outer heating coils 4 and 5 is reduced, and as a result, the current flowing through the inner and outer heating coils 4 and 5 can be increased, and the input power can be increased.

When the winding directions of the inner heating coil 4 and the outer heating coil 5 are reversed, driving the switching elements 25 and 25 ′ of the inverter circuit with the same phase causes the inner and outer heating coils 4 and 5 to move in the reverse winding direction. Since the current flows and the magnetic fluxes generated by the heating coil current cancel each other, the heating coil current can be increased even if the heated pan 7 has a high electrical resistance.
In addition, when the switching elements 25 and 25 ′ of the inverter circuit are driven in the opposite phase, the current in the same circulation direction flows through the inner and outer heating coils 4 and 5 and the magnetic flux generated by the heating coil current is superimposed. Even if the pan 7 has a low electrical resistance, the heating coil current can be suppressed.

  In the sixth embodiment, the material of the heated pan 7 is determined based on the input current value and the output current value detected by the output control means 22, and the electric resistance characteristic of the determined material of the heated pan 7 is obtained. Accordingly, the phase of the drive signal of the switching element 25 of the monolithic resonance inverter for the inner heating coil and the driving signal of the switching element 25 ′ of the monolithic resonance inverter for the outer heating coil is selected from the same phase or the opposite phase The inverter drive circuits 19 and 19 ′ drive the switching elements 25 and 25 ′ of the inverter circuit with the phase thus adjusted, and the adjustment of the low heating output of the heating pan 7 in which the phase of the drive signal is selected is the switching element of the one-stone resonant inverter By controlling the conduction time of 25, 25 ', an induction heating cooker can be obtained in which the influence of the difference in electrical resistance due to the material of the pan 7 is reduced. .

Embodiment 7 FIG.
Figure 23 is a circuit diagram showing a configuration of an induction heating cooker according to the seventh implementation, FIG. 24 is a side view showing the positional relationship between the heating load and the inner and outer heating coils of the same induction heating cooker.
In FIG. 23, the same or corresponding parts as those in FIG. 11, FIG. 16, or FIG.
In the seventh embodiment, two switching elements (upper switch and lower switch) connected in series between the DC buses on the output side of the DC power supply circuit 2 and diodes connected in reverse parallel to the switching elements ( There are three sets of arms (hereinafter, the three sets of arms are referred to as a U-phase arm 3U, a V-phase arm 3V, and a W-phase arm 3W) composed of an upper diode and a lower diode.
The upper switch, lower switch, upper diode and lower diode of the U-phase arm 3U are 15U, 16U, 17U, 18U, and the upper switch, lower switch, upper diode and lower diode of the V-phase arm 3V are 15V, 16V, 17, 18V. The upper switch, lower switch, upper diode, and lower diode of the W-phase arm 3W are 15 W, 16 W, 17 W, and 18 W.

  Between the output point of the U-phase arm 3U and the output point of the V-phase arm 3V, a load circuit composed of the inner heating coil 4 and the resonance capacitor 21 is connected, and the output point of the U-phase arm 3U and the output of the W-phase arm 3W Between the points, a load circuit composed of the external heating coil 5 and its resonant capacitor 21 'is connected. The switching element of each arm is operated by a drive signal from the drive circuits 19U, 19V, 19W controlled by the output control means 22, and a difference in output potential of each arm is applied to each load circuit.

FIGS. 25 to 27 are waveform diagrams of drive signals when performing heating output control by frequency control. FIG. 25 is a three-arm full bridge mode, FIG. 26 is a two-arm full bridge mode, and FIG. 27 is a half-bridge mode. This is a drive signal. In FIGS. 25 to 27, (a) is a drive signal at the time of high heating output, and (b) is a drive signal at the time of low heating output.
Here, the 3-arm full bridge mode means that the switching elements of the three sets of arms (U-phase arm, V-phase arm, W-phase arm) are driven at the same frequency, and the output potential of the U-phase arm 3U and the V-phase arm 3V. Is applied to the load circuit of the inner heating coil 4 and the resonance capacitor 20, and the difference between the output potential of the U-phase arm 3U and the output potential of the W-phase arm 3W is the load of the outer heating coil 5 and the resonance capacitor 20 '. Applied to the circuit.
In this case, since a voltage is applied to the inner heating coil 4 and the outer heating coil 5 in the reverse phase in the reverse circulation direction, and the heating coil current flows, the magnetic fluxes generated by the heating coil current cancel each other, and the load Since the impedance of the circuit is reduced, the current flowing through the heating coil can be increased, and a large heating output can be obtained even for the heated pan 7 having a high electrical resistance such as an iron pan.

The two-arm full bridge mode is a mode in which the switching elements of the V-phase arm 3V and the W-phase arm 3W are driven at high frequency without driving the switching elements of the U-phase arm 3U. A difference between the output potential of the V-phase arm 3V and the output potential of the W-phase arm 3W is applied to the series circuit of the outer heating coil 5 and the resonance capacitor 21 '.
In this case, a voltage is applied to the inner heating coil 4 and the outer heating coil 5 with the same phase in the same circulation direction, and the heating coil current flows. Therefore, the magnetic flux generated by the heating coil current is superimposed on each other. And since the impedance of a load circuit is enlarged, a heating coil electric current can be suppressed and a suitable heating output can be obtained with respect to the to-be-heated pan 7 of middle electric resistance like a nonmagnetic SUS pan.

  Further, the half-bridge mode is one in which the switching element of the U-phase arm 3U is not driven, one of the V-phase arm 3V and the W-phase arm 3W is driven at high frequency, and the other is fixedly driven. In FIG. 27, the switching element of the V-phase arm 3V is driven at high frequency, and the switching element of the W-phase arm 3W is fixedly driven (upper switch 15W: off, lower switch 16W: on).

In this case as well, the difference between the output potential of the V-phase arm 3V and the output potential of the W-phase arm 3W is applied to the series circuit of the inner heating coil 4, the resonance capacitor 21, the outer heating coil 5, and the resonance capacitor 21 '. Since the W-phase arm output potential is fixed to the DC bus negative side potential, the high-frequency voltage applied to the series circuit is half that of the 2-arm full bridge mode.
Further, as in the two-arm full bridge mode, a voltage is applied to the inner heating coil 4 and the outer heating coil 5 with the same phase in the same circulation direction, and the heating coil current flows. Since the generated magnetic flux is superimposed on each other to increase the impedance of the load circuit, the heating coil current is suppressed. Therefore, the heating coil current is also suppressed for the heated pan 7 having a low electrical resistance such as an aluminum pan. Can do.

Next, a method for determining the operation mode (3-arm full bridge mode, 2-arm full bridge mode, half bridge mode) of the inverter circuit will be described.
FIG. 28 is a flowchart of the heating pot determination process for determining the operation mode of the induction heating cooker, and FIG. 29 is a graph showing the relationship between the input current and the output current for determining the heating pot of the induction heating cooker.
28, the inverter circuit is first driven with a drive signal for load determination (step 11), and the detected values of the input current detection circuit 14 and the output current detection circuits 20, 20 ′ are set to various modes shown in the graph of FIG. By applying, input / output current determination processing is performed (step 12).
If the input current is smaller than the predetermined value, there is no load to be heated, or since it is a small object, heating is stopped (step 13). If the input current is greater than the predetermined value, the determination is made based on the detected output current.
When the output current is small, a three-arm full-bridge drive is performed as a high resistance pan such as an iron pan or a magnetic SUS pan (step 14). When the output current is medium, a medium resistance pan such as a non-magnetic SUS pan is used. Two-arm full-bridge driving is performed (step 15), and when the output current is large, half-bridge driving is performed as a low resistance pan such as an aluminum pan (step 16).

  In the seventh embodiment, three sets of arms 3U each composed of two switching elements connected in series between the DC buses on the output side of the DC power supply circuit 2 and diodes connected in antiparallel to the switching elements, respectively. 3V and 3W, a load circuit composed of the inner heating coil 4 and its resonance capacitor 21 is connected between the output point of the U-phase arm 3U and the output point of the V-phase arm 3V, and the output of the U-phase arm 3U A load circuit comprising the external heating coil 5 and its resonant capacitor 21 'is connected between the point and the output point of the W-phase arm 3W, and is based on the input current value and the output current value detected by the output control means 22 The material of the heated pan 7 is determined and the phase of the drive signals of the arms for the inner and outer heating coils 4 and 5 is the same or opposite depending on the electrical resistance characteristics of the determined material of the heated pan 7. either And an induction heating cooker in which the drive circuits 19V, 19U, and 19W drive the arms 3U, 3V, and 3W at the selected phase so that the output potential difference of each arm is applied to each load circuit. By selecting the driving mode of 3 arm full bridge, 2 arm full bridge or half bridge for 3 sets of arms 3U, 3V, 3W respectively, An induction heating cooker that can be used for the heated pan 7 that can be reversed in the reverse rotation direction, the same phase in the same rotation direction, or the applied voltage can be halved and greatly different in electric resistance. Obtainable.

Embodiment 8 FIG.
Figure 30 is a waveform diagram of a driving signal of the conduction ratio control of 3 arms full bridge mode of the induction heating cooker according to the eighth implementation, Figure 31 is a second conduction ratio control arms full bridge mode the induction heating cooker Fig. 32 is a waveform diagram of the drive signal, Fig. 32 is a waveform diagram of a drive signal for half-bridge mode conduction ratio control of the induction heating cooker, and Fig. 33 is a drive signal for phase difference control of the three-arm full bridge mode of the induction heating cooker. FIG. 34 is a waveform diagram of a drive signal for phase difference control in the two-arm full bridge mode of the induction heating cooker.

  In the induction heating cooker according to the seventh embodiment, the heating output is adjusted by controlling the drive frequency of the up / down switch of the inverter circuit. In the eighth embodiment, the heating output is shown in FIGS. As described above, the heating output is adjusted by controlling the conduction ratio of the upper and lower switches of each arm. 30 to 32, (a) is a drive signal waveform of high heating output, (b) is a drive signal waveform of low heating output, and the U-phase arm upper switch and U-phase from the top to the bottom, respectively. The ON / OFF state of the arm lower switch, the V phase arm upper switch, the V phase arm lower switch, the W phase arm upper switch, and the W phase arm lower switch is shown.

FIG. 30 shows a drive signal waveform in the three-arm full-bridge mode, and the difference between the output potential of the U-phase arm 3U and the output potential of the V-phase arm 3V is applied to the series circuit of the inner heating coil 4 and the resonant capacitor 20, The difference between the output potential of the arm 3U and the output potential of the W-phase arm 3W is applied to the series circuit of the outer heating coil 5 and the resonance capacitor 20 ′.
In this case, a high-frequency voltage proportional to the conduction ratio of the upper switches 15U, 15V, and 15W is applied to the inner heating coil 4 and the outer heating coil 5 in opposite phases in the reverse rotation direction. Since the magnetic fluxes generated by 5 cancel each other, the current flowing through the heating coil can be increased, and a large heating output can be controlled for the heated pan 7 of the high resistance pan.

FIG. 31 shows a two-arm full bridge mode drive signal waveform. The U-phase arm 3U is not driven (both the U-phase arm upper switch 15U and the lower switch 16U are off), and the V-phase arm 3V and the W-phase arm 3W. The upper switches 15V and 15W and the lower switches 16V and 16W are driven at a high frequency, and the difference between the output potential of the V-phase arm 3V and the output potential of the W-phase arm 3W is determined by the inner heating coil 4, the resonance capacitor 20, It is applied to the outer heating coil 5 and the resonant capacitor 20 '.
In this case, since the voltage is applied in series to the inner heating coil 4 and the outer heating coil 5 in the same phase in the same circumferential direction, the magnetic fluxes generated by the currents flowing in the inner and outer heating coils 4 and 5 overlap each other. Therefore, the heating output is controlled by the conduction ratio of the upper switches 15V and 15W while the current flowing through the inner and outer heating coils 4 and 5 is suppressed.

Further, FIG. 32 shows a drive signal in the half-bridge mode, the U-phase arm 3U is not driven, the V-phase arm 3V is driven at high frequency, the W-phase arm 3W is fixedly driven (the upper switch 15W of the W-phase arm is off, The lower switch 16W is turned on).
In this case, as in the two-arm full bridge mode, the difference between the output potential of the V-phase arm 3V and the output potential of the W-phase arm 3W is determined by the internal heating coil 4, the resonance capacitor 20, the external heating coil 5 connected in series, Since the voltage is applied to the resonance capacitor 20 ′, a voltage is applied in series to the inner heating coil 4 and the outer heating coil 5 in the same circumferential direction, and the magnetic fluxes generated by the currents flowing through the inner and outer heating coils 4, 5 are mutually In addition to the superposition, the high-frequency applied voltage is lower than that in the two-arm full bridge mode, so that the heating current can be controlled while suppressing the output current for the heated pan 7 of the low resistance pan.

  In the eighth embodiment, three sets of arms 3U each composed of two switching elements connected in series between the DC buses on the output side of the DC power supply circuit 2 and diodes connected in antiparallel to the switching elements, respectively. 3V and 3W, a load circuit composed of the inner heating coil 4 and its resonance capacitor 21 is connected between the output point of the U-phase arm 3U and the output point of the V-phase arm 3V, and the output of the U-phase arm 3U A load circuit comprising the external heating coil 5 and its resonant capacitor 21 'is connected between the point and the output point of the W-phase arm 3W, and is based on the input current value and the output current value detected by the output control means 22 The material of the heated pan 7 is determined and the phase of the drive signals of the arms for the inner and outer heating coils 4 and 5 is the same or opposite depending on the electrical resistance characteristics of the determined material of the heated pan 7. either And an induction heating cooker in which the drive circuits 19V, 19U, and 19W drive the arms 3U, 3V, and 3W at the selected phase so that the output potential difference of each arm is applied to each load circuit. By selecting the driving mode of 3 arm full bridge, 2 arm full bridge or half bridge for 3 sets of arms 3U, 3V, 3W respectively, It was possible to set the opposite phase in the reverse rotation direction to each other, the same phase in the same rotation direction, or to halve the applied voltage. The adjustment of the low heating output of the heated pan 7 in the drive mode can be controlled by controlling the conduction ratio of the upper and lower switches of each arm, so Hesi induction heating cooker can be obtained.

In the case of driving in the 3-arm full bridge mode or the 2-arm full bridge mode, the phase difference control shown in FIGS. 33 and 34 may be used in place of the conductivity ratio control shown in FIGS.
Also in this method, in the three-arm full bridge mode (FIG. 33), the difference between the output potential of the U-phase arm 3U and the output potential of the V-phase arm 3V and the W-phase arm 3W is determined by the inner heating coil 4, the resonance capacitor 20, and the outer. This is applied to the heating coil 5 and the resonant capacitor 20 ′. In the two-arm full bridge mode (FIG. 34), the difference between the output potential of the V-phase arm 3V and the output potential of the W-phase arm 3W is determined by the inner heating coil 4, This is applied to the series circuit of the resonance capacitor 20, the external heating coil 5, and the resonance capacitor 20 ', and heating control equivalent to conduction ratio control can be performed. Further, since the conduction ratio of the upper switch and the lower switch of each arm can be made the same as compared with the conduction ratio control, the heat generation variation between the upper and lower switching elements can be reduced.

Embodiment 9 FIG.
Figure 35 is a circuit diagram showing a configuration of an induction heating cooker according to the ninth implementation, FIG. 36 is a side view showing the positional relationship between the upper and lower heating coils of the same induction heating cooker heated load. 35 and 36, the same or corresponding portions as those in FIGS. 23 and 24 are denoted by the same reference numerals.
In the ninth embodiment, the inner heating coil 4 and the outer heating coil 5 in the seventh embodiment are replaced with an upper heating coil 4 ′ and a lower heating coil 5 ′ in which a plurality of heating coils are stacked.
Therefore, the ninth embodiment also has three inverter circuits 3V, 3U, and 3W, and the upper heating coil 4 ′ and the lower heating coil 5 ′ are in the three-arm full bridge mode, as in the seventh embodiment. It is driven in three operation modes: arm full bridge mode and half bridge mode.

In the case of the three-arm full bridge mode, a voltage is applied to the upper heating coil 4 ′ and the lower heating coil 5 ′ in the reverse phase in the reverse circulation direction to flow the heating coil current, so that the magnetic flux generated by the heating coil current Cancel each other and reduce the impedance of the load circuit, so that the current flowing through the heating coil can be increased, and a large heating output can be obtained even for a heated pan 7 having a high electrical resistance such as an iron pan. it can.
Further, in the case of the 2-arm full bridge mode, a voltage is applied to the upper heating coil 4 ′ and the lower heating coil 5 ′ in the same circulation direction, and a heating coil current flows. Therefore, the heating coil current is generated. Since the magnetic fluxes are superimposed on each other to increase the impedance of the load circuit, the heating coil current can be suppressed.
Further, in the half bridge mode, the high frequency voltage applied to the upper heating coil 4 ′ and the lower heating coil 5 ′ is half that of the two-arm full bridge mode, but the voltage is applied with the same phase in the same circulation direction. Because the heating coil current flows, the magnetic flux generated by the heating coil current is superimposed on each other to increase the impedance of the load circuit, so the heating coil current is suppressed, so that the low electrical resistance like an aluminum pan The heating coil current can be suppressed for the heated pan 7.

  In the ninth embodiment, three sets of arms 3U each composed of two switching elements connected in series between the DC buses on the output side of the DC power supply circuit 2 and diodes connected in reverse parallel to the switching elements, respectively. 3V and 3W, a load circuit composed of the inner heating coil 4 and its resonance capacitor 21 is connected between the output point of the U-phase arm 3U and the output point of the V-phase arm 3V, and the output of the U-phase arm 3U A load circuit comprising the external heating coil 5 and its resonant capacitor 21 'is connected between the point and the output point of the W-phase arm 3W, and is based on the input current value and the output current value detected by the output control means 22 The material of the heated pan 7 is determined and the phase of the drive signals of the arms for the inner and outer heating coils 4 and 5 is the same or opposite depending on the electrical resistance characteristics of the determined material of the heated pan 7. either And an induction heating cooker in which the drive circuits 19V, 19U, and 19W drive the arms 3U, 3V, and 3W at the selected phase so that the output potential difference of each arm is applied to each load circuit. By selecting the drive mode of 3 arm full bridge, 2 arm full bridge or half bridge for 3 sets of arms 3U, 3V, 3W, respectively, the voltage applied to the upper and lower heating coils 4 ', 5' Induction cooking that can be used for heated pans 7 that have different electrical resistances and can have directions opposite to each other in the reverse rotation direction, the same phase in the same rotation direction, or half the applied voltage. Can be obtained.

  Note that the upper heating coil 4 ′ is disposed closer to the heated pan 7 than the lower heating coil 5 ′, and the magnetic flux generated by the induced eddy current flowing in the heated pan 7 is lower than that of the lower heating coil 5 ′. Since the upper heating coil 4 'is more interlinked with the upper heating coil 4', the inductance of the upper heating coil 4 'becomes smaller, and a larger coil current flows through the lower heating coil 5'. Therefore, as shown in FIG. Further, by reducing the number of turns of the lower heating coil 5 ′ from that of the upper heating coil 4 ′, the difference in inductance between the lower heating coil 5 ′ and the upper heating coil 4 ′ is compensated, and the upper heating coil 4 ′ and the lower heating coil 5 ′. Therefore, the concentration of heat generation of the heating coil and the switching element due to the current imbalance can be reduced.

Circuit diagram showing a configuration of an induction heating cooker according to Embodiment 1 of implementation. The top view which shows the magnitude | size and positional relationship of the internal / external heating coil of the induction heating cooking appliance. The side view which shows the positional relationship of the internal / external heating coil of the same induction heating cooking appliance, and a to-be-heated load. The wave form diagram of the voltage applied to an inner / outer heating coil. Explanatory drawing which shows the direction of the magnetic flux which generate | occur | produces with the electric current which flows into an inner / outer heating coil. Plan view illustrating the sizes and the arrangement relationships of the upper and lower heating coil of the induction heating cooker according to Embodiment 2 of implementation. The side view which shows the positional relationship of the upper / lower heating coil of the same induction heating cooking appliance, and a to-be-heated load. The wave form diagram of the voltage applied to an upper and lower heating coil. Explanatory drawing which shows the direction of the magnetic flux which generate | occur | produces with the electric current which flows into an upper and lower heating coil. The side view which shows the positional relationship of another upper and lower heating coil of the same induction heating cooking appliance, and a to-be-heated load. Circuit diagram showing a configuration of an induction heating cooker according to Embodiment 3 of implementation. The wave form diagram of the drive signal for the low resistance pan of the same induction heating cooker. The wave form diagram of the drive signal for the high resistance pan of the induction heating cooking appliance. The wave form diagram of the various drive signals of the induction heating cooking appliance which concerns on Embodiment 4 of this invention. The flowchart of the heating output control process of the induction heating cooking appliance. Circuit diagram showing a configuration of an induction heating cooker according to the fifth implementation. The wave form diagram of the drive signal for the low resistance pan of the same induction heating cooker. The wave form diagram of the drive signal for the high resistance pan of the induction heating cooking appliance. The wave form diagram of the drive signal for the pots having an intermediate electric resistance of the induction heating cooker. Circuit diagram showing a configuration of an induction heating cooker according to the sixth implementation. The wave form diagram of the drive signal for the low resistance pan of the same induction heating cooker. The wave form diagram of the drive signal for the high resistance pan of the induction heating cooking appliance. Circuit diagram showing a configuration of an induction heating cooker according to the seventh implementation. The side view which shows the positional relationship of the internal / external heating coil of the same induction heating cooking appliance, and a to-be-heated load. The wave form diagram of the drive signal of the frequency control of 3 arm full bridge mode of the same induction heating cooking appliance. The wave form diagram of the drive signal of the frequency control of 2 arm full bridge mode of the induction heating cooking appliance. The wave form diagram of the drive signal of the frequency control of the half bridge mode of the induction heating cooking appliance. The flowchart of the to-be-heated pot determination process which determines the operation mode of the induction heating cooking appliance. The graph which shows the relationship between the input current and output current for the to-be-heated pot determination of the induction heating cooking appliance. Waveform diagram of driving signals for three conduction ratio control arms full bridge mode of the induction heating cooker according to the eighth implementation. The wave form diagram of the drive signal of conduction ratio control of 2 arm full bridge mode of the induction heating cooking appliance. The wave form diagram of the drive signal of the conduction ratio control of the half bridge mode of the induction heating cooking appliance. The wave form diagram of the drive signal of phase difference control of 3 arm full bridge mode of the same induction heating cooking appliance. The wave form diagram of the drive signal of phase difference control of 2 arm full bridge mode of the induction heating cooking appliance. Circuit diagram showing a configuration of an induction heating cooker according to the ninth implementation. The side view which shows the positional relationship of the upper / lower heating coil of the same induction heating cooking appliance, and a to-be-heated load.

Explanation of symbols

1 AC power supply, 2 DC power supply circuit, 3 high frequency output control means, 4 internal heating coil, 5 external heating coil, 6 ferrite.

Claims (3)

A DC power supply circuit that converts AC power into DC power;
A plurality of magnetically coupled heating coils;
High-frequency output control means for converting the output voltage of the DC power supply circuit into a high-frequency voltage, and applying the high-frequency voltage to the plurality of heating coils by controlling the phase difference at the same frequency, respectively ;
With
The high-frequency output control means has an inverter circuit that includes two switching elements for each heating coil to apply a high-frequency voltage to each heating coil,
The detected output current value is compared with the switching element protection limit value. When the output current value is less than the limit value, the input power and the set power are compared. When the input power is smaller than the set power, the inverters In the frequency control mode that increases the heating output to adjust the drive frequency of the switching element of the circuit to bring the input power closer to the set power, and when the detected output current value exceeds the limit value and the input power is greater than the set power An induction heating cooker characterized by having a phase control mode in which the phase of the drive signal to the switching element of each inverter circuit is adjusted to lower the heating output.   The induction heating cooker according to claim 1, wherein the plurality of heating coils are configured by arranging heating coils having different inner and outer diameters on the same plane.   The induction heating cooker according to claim 1, wherein the plurality of heating coils are heating coils arranged in a stacked state.

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