JP2003338358A - Induction heating apparatus and induction heating cooking device and rice cooker by use of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating apparatus, an induction cooking device, and a rice cooker having low loss, high efficiency, and a simple configuration. <P>SOLUTION: This induction heating apparatus is provided with two bidirectional switching elements 21, 22, a drive circuit 24, a load circuit 28 having a heating coil 25 and resonance capacitors 26, 27, and an AC power supply 29 to perform induction heating without causing loss rectified to a direct current. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker, an induction heating type rice cooker, which is used in general households and businesses.
The present invention relates to an induction heating device such as an induction heating processing machine and an induction heating snow melting device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 17, an induction heating apparatus disclosed in Japanese Patent Laid-Open No. 11-111441 has an AC power source 1, a heating coil 2, and a commercial power source of 100V 50Hz or 60Hz. IG connected to heating coil 2
A switching element 3 realized by incorporating a BT (insulated gate bipolar transistor) and a diode, and a drive circuit 4 for turning on / off the switching element 3 are provided.

Further, the resonance capacitor 5 is connected to the heating coil 2
And a full-wave diode bridge 10 composed of four diodes 6, 7, 8, and 9, and a smoothing capacitor 11 connected in parallel between the output terminals of the diode bridge 10. Has become.

The load pan 12 is magnetically coupled to the heating coil 5.

In the above configuration, the AC power supply 1 generates a voltage converted to DC including ripple by the diode bridge 10 between the terminals of the smoothing capacitor 11, and the drive circuit 4 turns on / off the switching element 3 at high frequency. Then, by supplying a high-frequency current to the heating coil 2, an induction current is generated in the load pan 12 magnetically coupled to the heating coil 2 to cause iron loss and heating.

[0006]

In such a conventional technique, since the output voltage of the AC power supply 1 is once converted into DC by the diode bridge 10, a voltage drop occurs in the diode bridge 10. , The voltage value is diode bridge 10 in all phases of AC power supply 1.
2 of the diodes 6, 7, 8 and 9 constituting the above-mentioned structure work, so that the efficiency of the induction heating device decreases and the diode bridge 10 generates a large amount of heat. In some cases, it is necessary to provide a radiator or a cooling fan, and the first problem is that the device becomes complicated.

[0007]

In order to solve the above-mentioned first problem, the present invention provides two bidirectional switching elements connected in series and a drive circuit for turning on and off the two bidirectional switching elements. A load circuit having a heating coil and a resonance capacitor, and an AC power supply, one terminal of the load circuit being connected to a connection point between the two bidirectional switching elements, and the AC power supply being the bidirectional switching. By connecting to the element and the load circuit, the loss in the diode bridge is eliminated, the efficiency is increased, and the induction heating device having a simple structure is realized.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention turns on and off two bidirectional switching elements connected in series and the two bidirectional switching elements. Drive circuit, a load circuit having a heating coil and a resonance capacitor, and an AC power supply, one terminal of the load circuit is connected to a connection point between the two bidirectional switching elements, and the AC power supply is the By being configured to be connected to the bidirectional switching element and the load circuit, it is possible to use the AC as it is without generating a large loss due to rectification from the AC power source, and the bidirectional switching element can be freely used. Since the high frequency current is supplied to the heating coil, an induction heating device having a high efficiency and a simple structure can be realized.

According to a second aspect of the present invention, the induction heating device according to the first aspect has a choke coil, the choke coil is connected in series with an AC power source, and both ends of one bidirectional switching element are connected. With the configuration in which the choke coil is connected, the step-up operation is performed, the current rating of the bidirectional switching element is small, and a small device can be realized.

According to a third aspect of the present invention, the induction heating device according to the second aspect is configured such that the choke coil has a sendust core, so that the choke coil can be realized at a low cost and with a simple structure. It provides a cost device.

According to a fourth aspect of the present invention, there is provided a partial resonance capacitor in which the induction heating device according to any one of the first to third aspects is connected from a connection point of two bidirectional switching elements. With the configuration, the overvoltage is prevented when two switching elements are alternately turned on, the switching loss is reduced, and the allowable value of the switching timing deviation is widened, so that the configuration is simple and reliable. This is to realize a high-performance device.

According to a fifth aspect of the present invention, the induction heating device according to any one of the first to fourth aspects is configured so that the bidirectional switching element is made of a SiC semiconductor. The ON loss and switching loss of the switching element are effectively suppressed to achieve high efficiency.

According to a sixth aspect of the present invention, an induction heating cooker having a simple structure and a high efficiency is provided by including the induction heating device according to any one of the first to fifth aspects. It will be realized.

According to a seventh aspect of the invention, a rice cooker having a simple structure and high efficiency is realized by adopting the structure having the induction heating device according to any one of the first to fifth aspects. It is a thing.

[0015]

EXAMPLES Next, specific examples of the present invention will be described.

(Embodiment 1) FIG. 1 is a circuit diagram of an induction heating apparatus for heating a pot according to the first embodiment of the present invention.

In FIG. 1, a series circuit 23 of two bidirectional switching elements 21 and 22 using a SiC semiconductor,
A driving circuit 24 for alternately turning on / off the bidirectional switching elements 21, 22 and a heating coil 25 formed by winding a litz wire made up of 35 enameled wires having a diameter of 0.35 mm in a flat spiral shape, and a film type resonance capacitor. 26, 2
It has a load circuit 28 including an AC power supply 29 and an AC power supply 29.

Heating coil 2 serving as one terminal of the load circuit 28
5 has one terminal connected to the bidirectional switching elements 21 and 22.
Is connected to the connection point of.

Each of the bidirectional switching elements 21 and 22 is a switching element capable of freely turning on and off a current of both positive and negative polarities, just like an electrode type switch.

The AC power supply 29 is composed of a 100 V 60 Hz commercial power supply 30 and a filter circuit 31, and the filter circuit 31 is composed of a choke coil 32 and a smoothing capacitor 33. The bidirectional switching elements 21 and 22 are connected in series. Both ends of the circuit 23 and the load circuit 2
It is also connected to the terminals of the eight resonance capacitors 26 and 27.

The load 34 is a pan or the like that is induction-heated.

FIG. 2 shows an operation waveform diagram of this embodiment, in which a enamel pot having a diameter of 22 cm is placed as a load 34 and the apparatus is operated by receiving an input power of 1000 W. It is in. (A) shows the waveform of the output voltage VAC of the commercial power supply 30, (A) shows the waveform of the current ISW1 flowing through the bidirectional switching element 21, and (C) shows the waveform of the current ISW2 flowing through the bidirectional switching element 22.

The VAC waveform has an effective value of 100 V at 60 Hz.
Of the sine wave of which the absolute value of the peak is 141 V corresponding to twice the root of the effective value.

The ISW1 and ISW2 waveforms also have a sine wave envelope (envelope) on both the positive and negative sides, and are current waveforms filled with high frequencies of the switching frequencies of the bidirectional switching elements 21 and 22. Cage, 50
It is the peak current value of A.

In this state, the output current waveform of the commercial power supply 30 is the same sine wave as the voltage VAC, the phases are the same, the power factor is almost 1, and the efficiency of the transmission and distribution system is minimized. It has become.

In the present embodiment, the relationship between the operating frequency of the drive circuit 24 and the resonance frequency of the load circuit 28 is that the electric power input from the AC power supply 29 to the device becomes maximum when the two are the same. The power with which the load 34 is induction heated is also maximized.

If there is a slight difference between the two frequencies, the operation waveform will be as described below.

First, the frequency of the drive circuit 24 is set to the load circuit 2
The operation when the resonance frequency is slightly higher than 8 will be described.

FIG. 3 shows an operation waveform diagram in which the phase in the vicinity of t1 in FIG. 2 is enlarged in the time direction, and in this period, VAC becomes approximately + 141V. (A) is the on / off signal Sg1 from the drive circuit 24, and (A) is the drive circuit 24.
Is a current ISW1 flowing in the bidirectional switching element 21, (d) is a current ISW2 flowing in the bidirectional switching element 22, and (e) is a voltage VSW2 applied to the bidirectional switching element 22. The waveform is shown.

At t3, the bidirectional switching element 22 is turned off by the drive circuit 24, and at the same time,
When the bidirectional switching element 21 is turned on, VS
W2 is almost equal to the instantaneous value of the output voltage of the AC power supply 29+
The voltage becomes 141 V, and the resonant operation of the load circuit 28 causes a current to flow in the bidirectional switching element 21.

During the period from t3 to t4, I
The operation in which SW1 becomes negative is performed, the period from t4 to t5 becomes positive, and a current having an absolute value of maximum 50 A flows during this period.

At t5, the bidirectional switching element 21 is turned off by the drive circuit 24, and at the same time,
When the bidirectional switching element 22 is turned on, V
SW2 becomes almost zero, and the resonant operation of the load circuit 28 causes a current to flow in the bidirectional switching element 22.

During the period from t5 to t6, I
The operation in which SW2 is negative is performed, and the period thereafter is positive, and a current having an absolute value of maximum 50 A flows.

By repeating such operations, the high frequency current is supplied to the heating coil 25.

FIG. 4 shows an operation waveform diagram in which the phase in the vicinity of t2 in FIG. 2 is enlarged in the time direction, and in this period, VAC becomes approximately -141V. (A) is the on / off signal Sg1 from the drive circuit 24, and (A) is the drive circuit 24.
Is a current ISW1 flowing in the bidirectional switching element 21, (d) is a current ISW2 flowing in the bidirectional switching element 22, and (e) is a voltage VSW2 applied to the bidirectional switching element 22. The waveform is shown.

At t7, the bidirectional switching element 22 is turned off by the drive circuit 24, and at the same time,
When the bidirectional switching element 21 is turned on, VS
W2 is almost equal to the instantaneous value of the output voltage of the AC power supply 29-
The voltage becomes 141 V, and the resonant operation of the load circuit 28 causes a current to flow in the bidirectional switching element 21.

During the period from t7 to t8, I
The operation in which SW1 is positive is performed, the period from t8 to t9 is negative, and a current having an absolute value of maximum 50 A flows during this period.

At t9, the bidirectional switching element 21 is turned off by the drive circuit 24, and at the same time,
When the bidirectional switching element 22 is turned on, V
SW2 becomes almost zero, and the resonant operation of the load circuit 28 causes a current to flow in the bidirectional switching element 22.

In the period from t9 to t10,
The operation in which ISW2 becomes negative is performed, and the subsequent period becomes positive, and a current having an absolute value of maximum 50 A flows.

By repeating such operations, the high frequency current is supplied to the heating coil 25.

As described above, the output voltage V of the AC power supply 29
Regardless of whether the instantaneous value of AC is positive or negative, a high-frequency current of 25 kHz flows to the bottom of the enamel pan, which is the load 34, by supplying a high-frequency current to the heating coil 25.
Induction heating of 0 W will be performed.

Next, the operation when the frequency of the drive circuit 24 is somewhat lower than the resonance frequency of the load circuit 28 will be described.

FIG. 5 shows an operation waveform diagram in which the phase in the vicinity of t1 in FIG. 2 is enlarged in the time direction, and in this period, VAC becomes approximately + 141V. (A) is the on / off signal Sg1 from the drive circuit 24, and (A) is the drive circuit 24.
Is a current ISW1 flowing in the bidirectional switching element 21, (d) is a current ISW2 flowing in the bidirectional switching element 22, and (e) is a voltage VSW2 applied to the bidirectional switching element 22. The waveform is shown.

At t11, the drive circuit 24 turns off the bidirectional switching element 22 and at the same time turns on the bidirectional switching element 21,
VSW2 becomes +141 V, which is almost equal to the instantaneous value of the output voltage of the AC power supply 29, and due to the resonance operation of the load circuit 28,
A current will flow through the bidirectional switching element 21.

During the period from t11 to t12, IS
W1 is positive, the absolute value reaches a maximum of 50 A, and the resonance action is effective in the period from t12 to t13 and becomes negative.

At t13, when the drive circuit 24 turns off the bidirectional switching element 21 and at the same time turns on the bidirectional switching element 22, VSW2 becomes substantially zero, and a current flows through the bidirectional switching element 22 this time. It will be.

Here, in the period from t13 to t14, ISW2 is positive and the absolute value reaches 50 A at maximum,
In the period after t14, the resonance effect becomes effective and becomes negative.

By repeating such an operation, the high frequency current is supplied to the heating coil 25.

FIG. 6 shows an operation waveform diagram in which the phase in the vicinity of t2 in FIG. 2 is enlarged in the time direction. In this period, VAC becomes approximately -141V. (A) is the on / off signal Sg1 from the drive circuit 24, and (A) is the drive circuit 24.
Is a current ISW1 flowing in the bidirectional switching element 21, (d) is a current ISW2 flowing in the bidirectional switching element 22, and (e) is a voltage VSW2 applied to the bidirectional switching element 22. The waveform is shown.

At t15, the bidirectional switching element 22 is turned off by the drive circuit 24, and at the same time, the bidirectional switching element 21 is turned on.
VSW2 becomes -141V which is almost equal to the instantaneous value of the output voltage of the AC power supply 29, and due to the resonance operation of the load circuit 28,
A current will flow through the bidirectional switching element 21.

During the period from t15 to t16, IS
W1 is negative, the absolute value reaches a maximum of 50 A, and the resonance action is effective in the period from t16 to t17, which is positive.

At t17, when the bidirectional switching element 21 is turned off by the drive circuit 24 and at the same time the bidirectional switching element 22 is turned on, VSW2 becomes almost zero, and a current flows through the bidirectional switching element 22 this time. It will be.

Here, in the period from t17 to t18, ISW2 is negative and the absolute value reaches 50A at maximum,
In the period from t18 onward, the resonance effect works and becomes positive.

By repeating such operations, the high frequency current is supplied to the heating coil 25.

As described above, even when the frequency of the drive circuit 24 is lower than the resonance frequency of the load circuit 28, the high frequency current is applied to the heating coil 25 regardless of whether the instantaneous value of the output voltage VAC of the AC power supply 29 is positive or negative. Is supplied, a high-frequency current of 25 kHz flows to the bottom of the enamel pan serving as the load 34, and induction heating of 1000 W is performed.

Although the two resonance capacitors 26 and 27 are provided in the present embodiment, any one of them may be used, and the capacitance may be doubled instead. Although the transient voltages applied to the elements 21 and 22 are different and the current paths are slightly different, the induction heating operations are almost the same.

For example, when only the resonance capacitor 27 is used, the load circuit 28 is a series circuit of the heating coil 25 and the resonance capacitor 27, so that the order of connecting the heating coil 25 and the resonance capacitor 27 is free, and both of them can be connected. The connection point side of the switching elements 21 and 22 is connected to the resonance capacitor 27.
May be connected.

(Embodiment 2) FIG. 7 is a circuit diagram of an induction heating apparatus according to the second embodiment of the present invention.

In FIG. 7, at the connection point between the bidirectional switching elements 21 and 22, that is, the connection point between the bidirectional switching elements, a 0.05 microfarad film type partial resonance capacitor 4 is connected.
0 and 41 are connected to the two output terminals of the AC power supply 29, and the drive circuit 42 has two bidirectional switching elements at a frequency slightly higher than the resonance frequency of the load circuit 28. 21 and 22 are alternately used, and both of the elements are turned off for a predetermined period when the on-periods of both elements are switched, and a drive with a dead time is used. For the configuration of other parts,
The same one as in the first embodiment is used.

FIG. 8 shows an operation waveform diagram in which a period in which the instantaneous value of the output voltage VAC of the AC power supply 29 is + 141V is enlarged. (A) is an on / off signal S from the drive circuit 24.
g1 and (a) are on / off signals Sg from the drive circuit 24.
2, (c) is the current ISW1 flowing through the bidirectional switching element 21, (d) is the current ISW2 flowing through the bidirectional switching element 22, and (e) is the bidirectional switching element 22.
The waveform of the voltage VSW2 applied to is shown.

At t19, when the bidirectional switching element 22 is turned off by the drive circuit 42, t1
9 flows into the partial resonance capacitors 40 and 41, the absolute value of VSW2 starts to increase, and at t20, V
When SW2 reaches the voltage VAC of the AC power supply 29, the drive circuit 42 turns on the bidirectional switching element 21.

Therefore, VSW2 is maintained at +141 V, which is almost equal to the instantaneous value of the output voltage of the AC power supply 29, and the resonant operation of the load circuit 28 causes a negative current to flow in the bidirectional switching element 21.

At t21, ISW1 becomes zero at one end, but positive ISW then flows, and the maximum absolute value is 50 A.
Reach up to.

The operating frequency of the drive circuit 42 depends on the load circuit 2
Since the resonance frequency is set to be slightly higher than the resonance frequency of 8, the turn-off timing t22 of the bidirectional switching element 21 by the drive circuit 42 comes before the ISW decreases to zero due to the resonance action.

Therefore, the absolute value of VSW2 decreases with time due to the current flowing through the partial resonance capacitors 40 and 41, and becomes zero at t23. At this time, the drive circuit 42 turns on the bidirectional switching element 22. And

When the bidirectional switching element 22 is turned on, VSW2 enters a substantially zero period, and a current flows through the bidirectional switching element 22 this time.

The ISW2 waveform is still t23 to t24.
Is a negative value up to, but turns positive after t24, and the absolute value reaches a maximum of 50A.

By repeating such an operation, the high frequency current is supplied to the heating coil 25.

FIG. 9 shows an operation waveform diagram in which the period in which the instantaneous value of the output voltage VAC of the AC power supply 29 is -141V is enlarged. (A) is an on / off signal S from the drive circuit 24.
g1 and (a) are on / off signals Sg from the drive circuit 24.
2, (c) is the current ISW1 flowing through the bidirectional switching element 21, (d) is the current ISW2 flowing through the bidirectional switching element 22, and (e) is the bidirectional switching element 22.
The waveform of the voltage VSW2 applied to is shown.

At t25, when the bidirectional switching element 22 is turned off by the drive circuit 42, t2
The current at 5 flows through the partial resonance capacitors 40 and 41, the absolute value of VSW2 starts to increase, and at t26, V
When SW2 reaches the voltage VAC of the AC power supply 29, the drive circuit 42 turns on the bidirectional switching element 21.

Therefore, VSW2 is maintained at -141 V, which is approximately equal to the instantaneous value of the output voltage of the AC power supply 29, and the resonant operation of the load circuit 28 causes a positive current to flow in the bidirectional switching element 21.

At t27, the ISW1 becomes zero at one end, but then the negative ISW flows, and the maximum absolute value is 50 A.
Reach up to.

The operating frequency of the drive circuit 42 is the load circuit 2
Since the resonance frequency is set to be slightly higher than the resonance frequency of 8, the turn-off timing t28 of the bidirectional switching element 21 by the drive circuit 42 comes before the ISW decreases due to the resonance action and becomes zero.

Therefore, the absolute value of VSW2 decreases with time due to the current flowing through the partial resonance capacitors 40 and 41, and becomes zero at t29. At this time, the drive circuit 42 turns on the bidirectional switching element 22. And

When the bidirectional switching element 22 is turned on, VSW2 enters a substantially zero period, and a current flows through the bidirectional switching element 22 this time.

The ISW2 waveform is still t23 to t24.
Is a positive value up to, but becomes negative after t24, and the absolute value reaches a maximum of 50A.

By repeating such an operation, the high frequency current is supplied to the heating coil 25.

As described above, in this embodiment, since the partial resonance capacitors 40 and 41 are provided in particular, when the two bidirectional switching elements 21 and 22 are switched, the dead time period in which both elements are turned off is set. Since it can be provided, even if the response time of the bidirectional switching element or the response speed of the drive circuit is slightly slow, or if it changes slightly depending on the condition or temperature, it is Since the resonance capacitor acts to suppress the temporal change of the voltage applied to the bidirectional switching elements 21 and 22, it becomes easy to match the timing of the next turn-on.

In particular, in the circuit of this embodiment using the bidirectional switching elements 21 and 22, two unidirectional switching elements having a direct current input, which is conventionally called a SEPP inverter, are provided, and each unidirectional switching element is provided. There is no operation such that the reverse diode automatically turns on even if there is a turn-on timing deviation, as in the case of the configuration in which the reverse diode is connected in parallel to the switching element, and the drive circuit 42 turns on. Since it is necessary, the effect of providing the partial resonance capacitors 40 and 41 becomes great.

At the same time, the sudden absolute value of dV / dt (voltage change rate) is suppressed to prevent switching loss of the bidirectional switching elements 21 and 22 at the time of turn-off, and also to prevent electromagnetic noise from being dissipated. It has become possible.

When the turn-on timing is deviated, a steep current flows through the resonance capacitors 40 and 41, but the partial resonance capacitors 40 and 41.
It is possible to considerably suppress the error of the voltage of VSW2 with respect to the time lag of the turn-on timing by designing the value of V to be an appropriate value, and as a result, it often becomes advantageous.

In addition, in the present embodiment, the drive circuit 4
2, the two bidirectional switching elements 21 and 22 have the same on-time, but different on-times may be set. For example, the heating power is changed by changing the ratio of the on-time of the two switching elements 21 and 22. It is also possible to control.

Therefore, the operating frequency is, for example, 25 kHz.
While keeping z constant, the heating power can be adjusted, and even if the type of the load 34, for example, the diameter or material of the pot or the thickness of the bottom changes, the heating operation can be performed with a predetermined power. Therefore, even if two or more induction heating devices are operated close to each other, the heating power of each load can be freely adjusted at the same operating frequency, and different types of loads can be heated. It becomes possible.

In this case, since two or more induction heating devices have the same operating frequency, it is possible to prevent the generation of annoying interference sound and realize a device with extremely low noise. .

In this embodiment, the two partial resonance capacitors 40 and 41 are replaced by the two bidirectional switching elements 2.
Since the capacitors 1 and 22 are connected in parallel with each other, it is possible to make the voltage jump due to the inductance of the wiring very small. It is also possible to use only one, in which case the remaining partial resonance capacitor is
By setting the sum of the electrostatic capacities of the partial resonance capacitors 40 and 41 of this embodiment, almost the same operation can be performed.

(Embodiment 3) FIG. 10 is a circuit diagram of an induction heating device for heating a pot according to a third embodiment of the present invention.

In FIG. 10, a series circuit 53 of two bidirectional switching elements 51 and 52, a drive circuit 54 for alternately turning on and off the bidirectional switching elements 51 and 52, and 35 enamel wires having a diameter of 0.35 mm are used. A load circuit 57 having a heating coil 55 and a film type resonance capacitor 56, which are formed by winding a litz wire into a flat spiral shape.
And an AC power supply 60.

Heating coil 5 serving as one terminal of load circuit 57
One terminal of 5 is connected to the bidirectional switching elements 51, 52.
Is connected to the connection point of.

The partial resonance capacitor 59 also has one end connected to the connection point of the bidirectional switching elements 51 and 52.

Further, the capacitor 58 is connected to both ends of the series circuit 53 of the two bidirectional switching elements 51 and 52 and has a function of stabilizing this voltage.

Also in this embodiment, the AC power supply 60 is 20
It is composed of a 0V60Hz commercial power supply 61 and a filter circuit 62, and the filter circuit 62 includes a choke coil 63.
And a smoothing capacitor 64.

The choke coil 65 is connected in series with the AC power supply 60 and then connected to both ends of the bidirectional switching element 52.

The choke coil 65 has a sufficiently large reactance for a high frequency of 25 kHz, stabilizes the current, and suppresses the reverse flow of the high frequency current to the AC power supply 60. There is.

The load 34 is, for example, a pan that is induction-heated.

FIG. 11 is an external view of the choke coil 65.

In FIG. 11, the toroidal core is
The sendust core 67 is used, and the enamel wire 6
It is configured by winding eight.

By using the sendust core 67,
It is not necessary to provide a gap (air gap) in the magnetic path like a silicon steel plate, the manufacturing is simple, the leakage magnetic flux is suppressed, the loss at a high frequency such as 25 kHz is small, and the inductance is good even at a large current. The characteristics can be obtained.

FIG. 12 shows a detailed circuit diagram of the bidirectional switching element 51 and a drive circuit 54. The bidirectional switching element 52 is also constructed with an equivalent circuit configuration and driven by the drive circuit 54. ing.

In FIG. 12, M of silicon semiconductor is used.
A switching element 73 composed of an OSFET 71 and a diode 72 connected in parallel, a switching element 76 composed of a MOSFET 74 made of a silicon semiconductor and a diode 75 connected in parallel are used. The gate terminal G and the source terminal S are both commonly connected and then connected to the drive circuit 54.

The drain terminal D of the switching element 73 is the terminal A, and the drain terminal D of the switching element 76 is the terminal B, which are both terminals of the bidirectional switching element 51.

The output voltage VGS from the drive circuit 54 is 15
When the voltage becomes volt, both MOSFETs 71 and 74 are turned on, and when VGS becomes 0 volt, both are turned off.

When on, when the potential of the A terminal is high, a current flows from the drain D to the source S of the MOSFET 71.
When the potential of the B terminal is high, a current flows from the drain D of the MOSFET 74 to the source S of the MOSFET 74, passes through the diode 72 and A
It will reach the terminal.

When it is off, when the A terminal has a high potential, a forward blocking voltage is applied between the drain D and the source S of the MOSFET 71, and when the B terminal has a high potential, the drain of the MOSFET 74 is high. A forward blocking voltage is applied between D and the source S.

Therefore, it operates as a bidirectional switching element.

FIG. 13 shows the output voltage VAC of the AC power supply 60.
The operation waveform diagram which expanded the period when the instantaneous value of is + 141V is shown. (A) is the output voltage VGS of the drive circuit 54
1, (a) is the output voltage VGS2 of the drive circuit 54, (c)
Is a current ISW1 flowing through the bidirectional switching element 51,
(D) is the current IS flowing in the bidirectional switching element 52
W2 and (e) show the waveform of the voltage VSW2 applied to the bidirectional switching element 52.

At t31, when the bidirectional switching element 52 is turned off by the drive circuit 54, at t3.
The current at 1 flows into the partial resonance capacitor 59 and is charged, the absolute value of VSW2 starts to increase, and at t32, V
When SW2 reaches the voltage of the capacitor 58 (about +600 V), the drive circuit 54 turns on the bidirectional switching element 51.

Therefore, VSW2 is maintained at +600 V, which is almost equal to the voltage value of the capacitor 58, and the resonant operation of the load circuit 57 causes a negative current to flow in the bidirectional switching element 51.

At t33, the ISW1 becomes zero at one end, but thereafter the positive ISW1 flows.

The operating frequency of the drive circuit 54 is equal to that of the load circuit 5.
Since the resonance frequency is set slightly higher than the resonance frequency of 7, the turn-off timing t34 of the bidirectional switching element 51 by the drive circuit 54 comes before the ISW1 decreases due to the resonance action and becomes zero.

Therefore, as the partial resonance capacitor 59 is discharged, the absolute value of VSW2 decreases with time and becomes zero at t35. At this time, the drive circuit 54 turns on the bidirectional switching element 52. To do.

When the bidirectional switching element 52 is turned on, VSW2 enters a substantially zero period, and a current flows through the bidirectional switching element 52 this time.

The ISW2 waveform is still t35 to t36.
Is a negative value up to, but becomes positive after t36.

By repeating such an operation, the high frequency current is supplied to the heating coil 55.

FIG. 14 shows the output voltage VAC of the AC power supply 60.
The operation waveform diagram which expanded the period when the instantaneous value of -141V is shown. (A) is the output voltage VGS of the drive circuit 54
1, (a) is the output voltage VGS2 of the drive circuit 54, (c)
Is a current ISW1 flowing through the bidirectional switching element 51,
(D) is the current IS flowing in the bidirectional switching element 52
W2 and (e) show the waveform of the voltage VSW2 applied to the bidirectional switching element 52.

At t37, when the bidirectional switching element 52 is turned off by the drive circuit 54, t3
The current at 7 flows into the partial resonance capacitor 59 and is charged, and the absolute value of VSW2 starts to increase, and at t38, V
When SW2 reaches the voltage of the capacitor 58 (about -600V), the drive circuit 54 turns on the bidirectional switching element 51.

Therefore, VSW2 is maintained at -600V which is almost equal to the voltage value of the capacitor 58, and the resonance operation of the load circuit 57 causes a positive current to flow in the bidirectional switching element 51.

At t39, the ISW1 becomes zero at one end, but thereafter the negative ISW1 flows.

The operating frequency of the drive circuit 54 is the load circuit 5
Since the resonance frequency is set to be slightly higher than the resonance frequency of 7, the timing t40 for turning off the bidirectional switching element 51 by the drive circuit 54 comes before the ISW1 decreases due to the resonance action and becomes zero.

Therefore, this time, the partial resonance capacitor 59 is discharged, so that the absolute value of VSW2 decreases with time and becomes zero at t41. At this time, the drive circuit 54 turns on the bidirectional switching element 52. To do.

When the bidirectional switching element 52 is turned on, VSW2 enters a substantially zero period, and a current flows through the bidirectional switching element 52 this time.

The ISW2 waveform is still t41 to t42.
Is a positive value up to, but becomes negative after t42.

By repeating such an operation, the high frequency current is supplied to the heating coil 55.

As described above, the induction heating device of this embodiment is
In particular, since the AC power supply 60 and the choke coil 65 are connected in series and then connected between the terminals of the bidirectional switching element 52, the bidirectional switching element 52 is boosted by the boosting action, that is, the output voltage of the AC power supply 60. During the period, the choke coil 65 absorbs the magnetic energy as the magnetic energy, and the energy is stored in the capacitor 58 through the bidirectional switching element 51 during the ON period of the bidirectional switching element 51 and used as a high voltage. The voltage applied to the directional switching elements 51 and 52 is about 600 V, and a high rating is required in terms of withstand voltage, but a reduced element occurs in terms of current rating, resulting in a small chip size. Since an induction heating device with the same power can be configured, a compact and lightweight device is realized. It becomes shall.

In this embodiment, one partial resonance capacitor 59 is connected between both terminals of the bidirectional switching element 52.
It may be provided between both terminals of 1 and may be respectively connected to both of the bidirectional switching elements 51 and 52 by using two partial resonance capacitors.

Regarding the constitution of the bidirectional switching elements 51 and 52, in this embodiment, two silicon type MOSFETs 71 and 74 are used, but as shown in the first and second embodiments. It does not matter even if a SiC semiconductor is used.

In this embodiment, sendust core 67 is used.
Since the choke coil 65 is configured without using a gap, the manufacturing is simplified, the inductance is easily ensured under a high current condition even at a low cost, and the power is supplied from the AC power supply 60. Since a bipolar current flows, a DC choke coil (DC
As shown in L), one side portion of the current-inductance characteristic in the opposite direction is not used and is not wasted, and it can be utilized 100%, so that a device that effectively uses a magnetic material can be realized. Therefore, the effect that the shape and weight of the device can be suppressed by that much is also improved.

(Embodiment 4) FIG. 15 is a sectional view of an induction heating cooker according to a fourth embodiment of the present invention.

In FIG. 15, in order to take an AC power supply of 100 V 60 Hz, the power plug 101 is connected to the power cord 10.
2 is connected to the induction heating device 103.

In this embodiment, the induction heating device 103 is used.
Has exactly the same configuration as that of the second embodiment, except that only the heating coil 25 shown in FIG. 7 is omitted, and the heating coil 104 of FIG. 15 is connected instead. There is.

Eight ferrite cores 105 are provided radially below the heating coil 104.

An operation unit 106 for operating and stopping the induction heating device 103 and changing the heating power is connected.

A ceramic top plate is provided on the upper side of the heating coil 104 and induction heats the load 108 which is a pot of iron, stainless steel or the like.

With the above structure, the load 108 is induction-heated. In this embodiment, in particular, the bidirectional switching element 23 is used without rectifying the AC power source led from the power source plug with a diode bridge or the like. Since the heating coil 104 performs the induction heating operation by the direct conversion into the high frequency current, the effect of high efficiency is obtained.

(Fifth Embodiment) FIG. 16 is a block diagram showing the essential parts of a rice cooker according to a fifth embodiment of the present invention.

In FIG. 16, the outer coil 201 and the inner coil 202 are each formed by winding a litz wire in 9 turns, and the outer coil 201 and the inner coil 202 are connected in series to form a heating coil 203.

In particular, the outer coil 201 is not flat,
In particular, the outside has a raised shape.

The ferrite core 204 is the heating coil 20.
Eight radially provided below the heating coil 3
The magnetic field of 03 is effectively used to perform a highly efficient induction heating operation.

The load 205 is a magnetic stainless layer on the outside.
It has an aluminum layer inside, and rice can be cooked by putting rice and water in appropriate amounts and heating.

Further, such a heating coil 203 structure,
With the arrangement of the ferrite core 204 and the shape of the load 205, the distribution of the heating power of the load 205 is improved, the convection of water due to heating is moderately obtained, and very delicious rice can be cooked. Become.

The heating coil 203 is connected, for example, in place of the heating coil 25 of the induction heating apparatus of the second embodiment shown in FIG. Since the heating coil 203 performs an induction heating operation by converting into the high frequency current, the effect of high efficiency is obtained.

[0141]

As described above, according to the present invention, by providing two bidirectional switching elements connected in series, a drive circuit, a load circuit having a heating coil and a resonance capacitor, and an AC power source, high efficiency can be achieved. Thus, an induction heating device having a simple structure can be realized.

Further, it is possible to realize an induction heating cooker and a rice cooker with high efficiency and simple structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an induction heating device according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram when the drive circuit is driven at a frequency higher than the resonance frequency of the load circuit.

FIG. 3 is an enlarged operation waveform diagram in the vicinity of t1 when driven at a frequency higher than the resonance frequency of the load circuit.

FIG. 4 is an enlarged operation waveform diagram in the vicinity of t2 when driven at a frequency higher than the resonance frequency of the load circuit.

FIG. 5 is an enlarged operation waveform diagram in the vicinity of t1 when driven at a frequency lower than the resonance frequency of the load circuit.

FIG. 6 is an enlarged operation waveform diagram in the vicinity of t2 when driven at a frequency lower than the resonance frequency of the load circuit.

FIG. 7 is a circuit diagram of an induction heating device according to a second embodiment of the present invention.

FIG. 8 is an operation waveform diagram enlarging the vicinity of VAC = + 141V.

FIG. 9 is an enlarged operation waveform diagram in the vicinity of VAC = -141V.

FIG. 10 is a circuit diagram of an induction heating device according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram of the same choke coil.

FIG. 12 is a circuit diagram of the main part of the same.

FIG. 13 is an enlarged operation waveform diagram in the vicinity of VAC = + 141V.

FIG. 14 is an enlarged operation waveform diagram in the vicinity of VAC = -141V.

FIG. 15 is a sectional view of an induction heating cooker according to a fifth embodiment of the present invention.

FIG. 16 is a configuration diagram of main parts of a rice cooker according to a sixth embodiment of the present invention.

FIG. 17 is a circuit diagram of an induction heating device according to a conventional technique.

[Explanation of symbols]

21, 22, 51, 52 Bidirectional switching element 24, 42, 54 drive circuit 25, 55, 104, 203 Heating coil 26, 27, 56 Resonant capacitors 28, 57 load circuit 29, 60 AC power supply 65 choke coil 67 Sendust Core 40, 41, 59 partial resonance capacitors 103 Induction heating device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // A47J 27/00 103 A47J 27/00 103A (72) Inventor Hidekazu Yamashita 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masanori Ogawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Makoto Kitahata 1006 Kadoma, Kadoma City, Osaka (72) ) Inventor Nobuyoshi Nagagata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Tetsuya Tahara Osaka Prefecture Kadoma City 1006 Kadoma Matsushita Electric Industrial Co., Ltd. (72) Inventor Toichihiro Osaka 1006 Kadoma, Kadoma-shi, Matsushita Electric Industrial Co., Ltd. F-term (reference) 3K051 AA02 AB08 CD44 3K059 AA03 AA06 AD07 AD1 2 4B055 AA03 AA09 BA22 BA28 5H007 AA01 AA08 BB04 BB11 CA06 CB04 CB12 CB17 CC07

Claims (7)

[Claims] 1. An electric power is input from an AC power supply, and two bidirectional switching elements connected in series,
A drive circuit for turning on / off the two bidirectional switching elements, a load circuit having a heating coil and a resonance capacitor, and one terminal of the load circuit is connected to a connection point between the two bidirectional switching elements, An induction heating device in which an AC power source is connected to the bidirectional switching element and the load circuit. 2. The induction heating device according to claim 1, further comprising a choke coil, wherein the choke coil is connected in series with an AC power source and then connected to both ends of one bidirectional switching element. 3. The induction heating device according to claim 2, wherein the choke coil has a sendust core. 4. A partial resonance capacitor connected from a connection point between two bidirectional switching elements.
The induction heating device according to any one of 1 to 3. 5. The induction heating device according to claim 1, wherein the bidirectional switching element uses a SiC semiconductor. 6. An induction heating cooker comprising the induction heating device according to any one of claims 1 to 5. 7. A rice cooker having the induction heating device according to claim 1. Description: