JP2002246164A - High-frequency thawing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency thawing apparatus. SOLUTION: The high-frequency thawing apparatus is provided with an electrode 101 and an inverter circuit 102 for supplying high-frequency power to the electrode 101. The inverter circuit 102 is provided with semiconductor devices 103, 104 and a drive circuit 105 driven at a predetermined frequency. As a result, low-loss operation which requires no power supply for heater can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency thawing apparatus for thawing frozen foods or the like using a high-frequency electric field, which is used for home or business use.

[0002]

2. Description of the Related Art Conventionally used high-frequency decompression devices are:
As shown in JP-A-8-255682 shown in FIG. 9, a high-frequency power supply 5 and a high-frequency power supply 6 supply a high-frequency high voltage between the upper electrode plate 2 and the lower electrode plate 3 in the heating chamber 1. By generating a high-frequency electric field between the electrode plates, dielectric heating of the object to be thawed is performed.

Further, as an impedance matching circuit,
The configuration of a series resonance circuit in which a resonance capacitor 51 and a resonance variable coil 52 shown in FIG. 10 as a conventional technique are connected in series is also used in the embodiment. The effect of reducing the loss of the coil 52 has been described as an effect.

[0004]

The high-frequency power source, which is a component of the high-frequency decompression device having the above-mentioned conventional configuration, does not describe the specific configuration of the inside, but uses an amplifier using a vacuum tube or the like. The ones used are common,
In addition to the necessity of a heater power source, the operation is performed with a large loss, such as class A amplification, and has a first problem that high efficiency cannot be expected in principle.

[0005]

SUMMARY OF THE INVENTION The present invention solves the first problem of a conventional high-frequency decompression device, which comprises an electrode and an inverter circuit for supplying high-frequency power to the electrode. The inverter circuit has a configuration including a semiconductor element and a drive circuit for driving the semiconductor element at a predetermined frequency, thereby eliminating the need for a heater power supply and performing high-frequency high-frequency decompression by performing low-loss operation. This makes it possible to realize the device.

[0006]

The invention as set forth in claim 1 includes an electrode, and an inverter circuit for supplying high-frequency power to the electrode, wherein the inverter circuit operates a semiconductor element and the semiconductor element at a predetermined frequency. With a configuration having a driving circuit for driving, a heater power supply is unnecessary, and a high-efficiency high-frequency decompression device can be realized by performing a low-loss operation such as a switching operation.

[0007] The invention described in claim 2 is the first invention.
The inverter circuit described above has a DC power supply and two semiconductor elements, and a series circuit of the two semiconductor elements is connected between output terminals of the DC power supply, and a drive circuit connects the two semiconductor elements. By adopting a configuration in which the switching operation of turning on alternately is performed, power loss in the semiconductor element is suppressed as much as possible, and a high-efficiency high-frequency decompression device is realized.

[0008] The invention described in claim 3 is based on claim 1.
An impedance matching circuit provided between an output and an electrode of the inverter circuit described above, and a DC power supply having a variable output voltage, wherein the impedance matching circuit performs a matching operation that maximizes a power factor of the output of the inverter circuit. The DC power supply is configured to output a DC voltage adjusted so that the power in the device becomes a predetermined value, thereby controlling the decompression power to a predetermined value while keeping the loss of the semiconductor element small. The present invention realizes a high-frequency decompression device capable of performing the above-mentioned operations.

The invention described in claim 4 is the first invention.
In the DC power supply described above, a switching element and an insulating transformer are provided, and one terminal of the electrode is configured to be connected to one terminal of the output of the DC power supply and a metal part of the housing, so that a high frequency high voltage is prevented. An electrode to be applied can be electrically insulated from a DC power supply, and an extremely safe high-frequency decompression device is realized.

The invention described in claim 5 is the first invention.
The electrode described above is configured with two electrode plates opposed to each other, and one of the electrode plates is configured to have substantially the same potential as one terminal of the DC power supply. It is low or unnecessary, is easy to insulate, and enables the realization of a high-frequency decompression device with a reduced size.

The invention described in claim 6 is the first invention.
In addition to the configuration described above, a cable having a first conductor provided at the center, a second conductor provided outside the first conductor, and a choke coil connected in series with one electrode plate are provided. The first conductor is connected between the other terminal of the choke coil and the semiconductor element, and the second conductor is connected to the other electrode plate and one terminal of the DC power supply. In addition to suppressing the leakage of high-frequency radio waves used for thawing by the cable configuration, the choke coil acts to cancel a considerable amount of the negative reactance component of the electrode, thereby lowering the insulation withstand voltage required for the cable. It is intended to realize a compact and low-cost high-frequency decompression device.

Further, the invention described in claim 7 is the same as claim 6.
By using a configuration having a through-type capacitor at the connection part on the choke coil side of the cable described above, the degree of impedance matching with the characteristic impedance of the cable is improved while suppressing high-frequency radio wave leakage. This is to enable the realization of a high-efficiency high-frequency decompression device with reduced power loss.

The invention described in claim 8 is the first invention.
A first choke coil having a fixed inductance value, one end of which is connected to an electrode plate constituting the electrode described above, a cable, and a first choke coil connected to a terminal of the cable on the inverter circuit side and having a variable inductance value. With the configuration including the impedance matching circuit having the two choke coils, the positive reactance of the first choke coil cancels the negative reactance of the electrode, and as a result, the withstand voltage of the cable is reduced. In addition to the fact that a compact and inexpensive high-frequency decompression device can be realized, impedance matching with the inverter circuit by the second choke coil is performed, and loss of the inverter circuit can be suppressed. Mounting of the second choke coil, which can be a high-efficiency high-frequency decompression device and is slightly complicated Even respect, since it can be in a state located in the vicinity of the inverter circuit, a simple structure as a result, a high efficiency and that the performance of high frequency decompressor at low cost can be realized.

[0014]

(Embodiment 1) An embodiment of the present invention will be described below.

FIG. 1 is a circuit diagram of a high-frequency decompression device according to a first embodiment.

The high-frequency decompression apparatus shown in FIG.
Inverter circuit 10 for supplying high frequency power to electrode 101
2 and the inverter circuit 102 has a power MO
Semiconductor elements 103, 104 constituted by SFETs,
A driving circuit 105 is provided for driving the semiconductor elements 103 and 104 at a frequency of 13.56 MHz.

In this embodiment, the inverter circuit 10
2 has a DC power supply 106 whose output voltage can be varied in the range of 0 to 200 volts. A series circuit of two semiconductor elements 103 and 104 is connected between output terminals of the DC power supply 106; , Two semiconductor elements 103, 10
4 to perform a switching operation of alternately turning on.

Further, in this embodiment, the inverter circuit 10
An impedance matching circuit 107 is provided between the output of the second electrode and the electrode 101.

The electrode 101 is constituted by facing two electrode plates 108 and 109, both of which use 18-8 stainless steel plate, and one of the lower electrode plates 109 is a DC power supply. The terminal 106 is connected to a negative terminal, which is one terminal, and has substantially the same potential.

The electrode 101 is provided in a heating chamber 110 made of an iron plate, and has a completely electrostatically shielded configuration.

In this embodiment, the impedance matching circuit 107 includes a variable capacitor 111 having a variable capacitance, a variable choke coil 112 having a variable inductance value, and a coaxial cable 113. .

The variable capacitor has a configuration in which the facing area changes by rotation. The variable choke coil has a configuration in which a ferrite core is inserted into and removed from an air-core coil. , And operates electrically.

In the inverter circuit 102, a capacitor 114 provided for stabilizing the voltage across the two semiconductor elements 103 and 104 connected in series is connected in parallel with the output of the DC power supply 106. I have.

In this embodiment, a power detection circuit 115 for detecting the output power of the DC power supply 106 is provided, a current detection circuit 116 for detecting the output current of the DC power supply 106 using a resistor, and an output terminal of the DC power supply 106. The voltage detecting circuit 117 includes a voltage detecting circuit 117 for detecting a voltage between the two, and a current detecting circuit 116 and a multiplying circuit for multiplying the output of the voltage detecting circuit 117.

Further, in this embodiment, a control circuit 119 is provided, which receives signals from the power detection circuit 115 and the power factor detection circuit 140 and supplies the signals to the DC power supply 106, the variable capacitor 111, and the variable choke coil 112. A signal is output, and an operation of adjusting the capacitance of the variable capacitor 111 and an operation of adjusting the inductance value of the variable choke coil are performed.

The power factor detection circuit 140 includes the inverter circuit 1
02, and is provided between the impedance matching circuit 107 and outputs an analog value corresponding to the power factor from the output voltage and current of the inverter circuit 105.

In this embodiment, the electrode plate 109 of the electrode 101 is used.
The terminal on the side is connected to the minus terminal of the output of the DC power supply 106, and is also connected to a casing 120 manufactured by pressing an iron plate.

FIG. 2 is a detailed circuit diagram of the DC power supply 106.

In the first embodiment, the DC power supply 106
It has a switching element 200 and an insulating transformer 201 constituted by GBT.

Further, the DC power supply 106 includes a plug 202 for connecting to an AC power supply, a full-wave rectifier circuit 203 constituted by connecting four diodes to a bridge, and a rectifier circuit 2.
03, a capacitor 205 for stabilizing the output of the switching element 200, and a capacitor 2 for absorbing an excessive jump voltage of the switching element 200 when the switching element 200 is turned off.
06, a series circuit of a resistor 207, a diode 208 connected to the secondary side of the insulating transformer 201, a capacitor 209 for stabilizing the output DC voltage, and a switching element 200 which is turned on and off at a constant frequency of 20 kHz, and its on time. Is provided with a pulse width modulation circuit 210 that makes the ratio (duty value) according to the input signal Sd.

The value of signal Sd input from control circuit 119 to DC power supply 106 is output after being adjusted so that the signal from power detection circuit 115, that is, the output power value from DC power supply 106, becomes a predetermined value. Things.

That is, when the signal from the power detection circuit 115 is smaller than a predetermined value, the Sd value is increased to increase the ON time ratio of the switching element 200, and the output voltage value of the DC power supply 106 is increased. When the signal from the power detection circuit 115 is larger than a predetermined value, the Sd value is increased and the switching element 200
Of the DC power supply 106, thereby reducing the output voltage value of the DC power supply 106.
Outputs a DC voltage having a value adjusted so that the power becomes substantially a predetermined value.

Further, in the present embodiment, the impedance matching circuit 107 performs a matching operation for maximizing the power factor of the output of the inverter circuit 102 by the following operation.

The electrode 101 has an impedance having a resistance component and a negative reactance component when the object to be defrosted 121 is present therebetween. It depends on the size, shape, temperature, etc.

The variable choke coil 112 is connected to the electrode 101
The main purpose is to cancel the negative reactance component of the variable choke coil 11.
2 makes the reactance component at the output of the inverter circuit 102 almost zero by setting the power factor to the high frequency (13.56 MHz) to a maximum value, that is, a value close to 1 by making the inverter circuit 102 operate with high efficiency. And a high-efficiency high-frequency decompression device.

However, the variable choke coil 1 of this embodiment
Numeral 12 changes the inductance value by inserting and removing a ferrite core into and from an air-core coil.
The range that can be changed is about twice and a half.
The positive reactance of the variable choke coil 112 may become larger depending on the fluctuation of the variable choke coil 112. Also, since the coaxial cable 113 is used with impedance mismatch, its length If the reactance at the output of the inverter circuit 102 cannot be reduced to almost zero as a result, the control circuit 119 may adjust the capacitance of the variable capacitor 111. The power factor at the output of the inverter circuit 102 with respect to a substantially high frequency is always kept at a maximum, that is, a value substantially close to 1.

In this embodiment, the power is controlled by controlling the output voltage of the DC power supply 106. However, the capacitance of the variable capacitor 111 and the variable choke coil 11 are controlled.
By making the combination of the two inductance values appropriate, the reactance component at the output of the inverter circuit 102 is reduced to almost zero, the power factor is maximized for high frequencies, that is, approximately 1, and the impedance at the output of the inverter circuit 102 is adjusted. Since the absolute value of (substantially only the real part) can be adjusted, the power may be controlled by this. In this case, even if the output of the DC power supply 106 is a constant voltage, Often, it may be configured with a fixed output voltage.

FIG. 3 is a detailed circuit diagram of the drive circuit 105 of the high-frequency decompression apparatus according to the first embodiment.

An oscillation circuit 301 using a 13.56 MHz crystal oscillator, a MOSFET 302 driven by the output of the oscillation circuit 301, a choke coil 303 for resonance, a capacitor 304, a drive transformer 305, and a drive transformer 305 A capacitor 306 and a trimmer capacitor 307 for impedance matching are provided.

The drive transformer 305 is formed by winding coils 308, 309, and 310 around a toroidal ferrite core and magnetically coupling them. In the present embodiment, in particular, in view of power as a high-frequency decompression device, a current capacity is reduced. In order to drive the large semiconductor elements 103 and 104 with high efficiency, it is constructed by a method called trifilar winding in which three enamel wires are wound around a core while being in close contact with each other, and a device having a high coupling coefficient is used. ing.

The DC power supply 311 has an output voltage of 24 volts and a current capacity of 0.5 amp.

The trimmer capacitor 307 absorbs variations in the drive transformer 305 and other components, sets the gate-source voltages of the semiconductor elements 103 and 104 to a predetermined value, and drives the semiconductor elements 103 and 104 with high efficiency in a production line. It will be adjusted.

FIG. 4 shows an output voltage waveform of the drive circuit 105 in a state where the semiconductor elements 103 and 104 are connected and a decompression operation is performed. Gate-source voltage Vg of the semiconductor element 103
1, (a) is a semiconductor element 104 located on the lower potential side
3 shows a waveform of the gate-source voltage Vg2 of FIG.

Since the secondary windings 309 and 310 are connected with opposite polarities, (a) and (a) have voltage waveforms of opposite phases to each other, and the semiconductor elements 103 and 104
Are turned on alternately.

In addition, since the voltage between the gate and the source of each semiconductor element is applied up to a maximum of 15 volts, the voltage between the drain and the source is reduced to almost zero volt, that is, to a state where the switch is almost conductive. A conduction effect is achieved, whereby a high efficiency of 80 to 90%, which cannot be obtained with a class-A amplifier using a vacuum tube or the like, can be achieved, and a high-efficiency high-frequency decompression device can be realized.

In addition, the high-frequency thawing apparatus of this embodiment has an insulating transformer 201 in the DC power supply 106,
1 is connected to the terminal on the side of the electrode plate 109 below the DC power source 1.
The electrode plate 1 that constitutes the electrode 101 to which a high-frequency high voltage is applied by being connected to the negative terminal of the output 06 and to the case 120 made of metal.
08 and 109 are both electrically insulated from the DC power supply 106, and can be insulated from any terminal of the plug 202.

Therefore, even if one terminal of the plug 202 is grounded to the ground, an electric shock or the like does not occur and an extremely safe high-frequency decompression device can be realized.

The two electrode plates 10 provided opposite to each other
One of the electrode plates 109 is a DC power supply 10.
6 has substantially the same potential as that of the negative terminal 6, so that the lower electrode plate 109 has the same potential as the heating chamber 110 and the housing 120, so that insulation is not required. There is no need to provide space for Therefore, a high-frequency decompression device with a reduced size can be realized.

(Embodiment 2) FIG. 5 is a circuit diagram of a high-frequency decompression device according to Embodiment 2.

Also in this embodiment, the configurations of the electrode 101, the inverter circuit 102, the power detection circuit 115, and the power factor detection circuit 140 are the same as those of the first embodiment.

In FIG. 5, electrode plates 108 and 109 made of 18-8 stainless steel and provided in parallel to constitute the electrode 101.
A choke coil 501 connected in series is provided on the electrode plate 108 located on the upper side.

In this embodiment, the choke coil 50
Reference numeral 1 denotes a drum-type ferrite core having an inductance of 11.7 microhenry by winding an enamel wire for 10 turns.
The reactance value at 3.56 MHz is approximately 1
Kiloohms.

On the other hand, when the size of the electrode 101 is 22 cm square, the imaginary part of the impedance of the electrode 101, that is, the reactance value is about -1 kohm in a state where the object to be thawed 121 such as frozen meat is contained. Since the choke coil 501 is connected to the electrode 101 in series, the electrode 101 and the choke coil 50 are connected.
The reactance value of the series circuit of 1 is a small value close to 0 and almost close to the state of only the resistance.

The cable 113 is of the coaxial type used in the first embodiment. In this embodiment, a cable of a standard called 3C-2V is used for a length of 1 meter. The value of the impedance is 75 ohms, a relatively inexpensive one commonly used for connections between televisions and television antennas.

A motor-operated variable capacitor 111 is connected to the end of the cable 113 on the side of the inverter circuit 102, and the capacitance can be adjusted by a control circuit 502.

The impedance matching circuit 503 is connected to the electrode 1
With the impedance at a high frequency of 13.01 MHz (13.56 MHz), the reactance component at the output point of the inverter circuit 102 is set to almost zero, and the maximum power factor, that is, 1
This is to make the value close to.

FIG. 6 is a diagram illustrating the configuration of the cable 113 in detail.

In FIG. 6, a first conductor 601 made of a copper wire is provided at the center, and a second conductor 6 made of a thin copper wire in the form of a mesh is provided outside the first conductor 601.
02, the first conductor 601 and the second conductor 60
2, a dielectric layer 603 using a foamed polyethylene material is provided.

An insulating outer layer 604 is provided outside the second conductor to prevent a short circuit when the second conductor 602 comes into contact with an electric component and to protect the second conductor 602. It is what fulfills the function.

In this embodiment, the coaxial cable 113 having the above configuration is used, and the first conductor 601 is connected to the terminal of the choke coil 501 on the side opposite to the electrode plate 108 and the semiconductor elements 103 and 104. Are connected between the connection points.

The second conductor 602 is connected between the other electrode plate 109 and the negative terminal of the DC power supply 106.

In this embodiment, the power factor detection circuit 140 is inserted between the connection between the inverter circuit 102 and the first conductor 601 of the cable 113, as in the first embodiment. This is for detecting a power factor related to a high frequency of the output of 102.

With the above configuration, the high-frequency decompression apparatus of the present embodiment does not require a power supply for a heater such as a vacuum tube by the same operation as in Embodiment 1 in which the semiconductor elements 103 are alternately turned on. Gate-source voltage is 15
The conduction loss is reduced by driving up to V and high-efficiency operation is enabled. The power factor detection circuit 140 detects a high-frequency power factor at the output of the inverter 102, and Since the variable capacitor 111 adjusts the variable capacitor 111 so that the power factor value becomes maximum, the loss of the semiconductor elements 103 and 104 can be minimized.

The power detection circuit 115 is connected to the DC power supply 106
The operation of detecting the output power from the DC power supply and automatically controlling the output voltage value of the DC power supply 106 to a predetermined value of 250 watts is also performed in the same manner as in the first embodiment.

In particular, in this embodiment, the leakage of the radio wave of 13.56 MHz used at the time of thawing is controlled by the structure of the cable 113, that is, the first conductor 601 to which the high frequency of the high frequency is applied to the housing 120. To the second conductor 60
By completely enclosing by 2, the effect of suppressing is obtained.

In line with the choke coil 501,
Since a considerable amount of the negative reactance component of the electrode 101 can be canceled or canceled out, the cable 11
3 can reduce the withstand voltage of the insulation required.

The 3C-2V used in this embodiment has a withstand voltage of 1 kilovolt, but there is no problem in terms of voltage due to the canceling effect of the reactance of the choke coil 501.

In general, when a load having an impedance deviating from the characteristic impedance is connected to the cable, the voltage and the current change depending on the portion of the cable, and the electrode 10
When a device having a large negative reactance such as 1 is connected, a portion to which an extremely high voltage is applied is generated due to a standing wave depending on the length of the cable 113, and a portion to which a large current flows is generated. May occur, causing a phenomenon that the loss becomes extremely large.

Therefore, by connecting the choke coil 501 in series with the electrode 101 as in this embodiment, the reactance at the electrode-side end of the cable 113 is reduced, and the magnitude of the standing wave is reduced. Can be suppressed,
A large current or the like in the cable 113 can be prevented, and loss can be suppressed.

By the action of the choke coil 501, even a coaxial cable having a small diameter and a low price can be used satisfactorily, thereby realizing a compact and low-cost high-frequency decompression device. is there.

The cable 113 used in this embodiment is
Is a coaxial type, but the axes of the first conductor 601 and the second conductor 602 do not necessarily have to be coaxial and may be shifted, and the cross section is not a circle but a square. In other words, if it is surrounded by the second conductor 602 provided outside the first conductor 601, leakage of radio waves can be eliminated.

(Embodiment 3) FIG. 7 is a circuit diagram of a high-frequency decompression device according to Embodiment 3.

In FIG. 7, a connection portion of the cable 113 on the choke coil 501 side is provided with a feedthrough capacitor 701.
Are connected, and are one of the components of the impedance matching circuit 702.

In this embodiment, the feedthrough capacitor 701
Are connected such that the center electrode penetrates through the first coil 601 of the choke coil 501 and the choke coil 133, and the outer electrode is connected to the second conductor 602, the iron heating chamber 110, and the housing. The second conductor 602 is also connected to the negative terminal of the DC power supply 106 on the opposite side of the cable 113. The other configuration is the same as that of the second embodiment.

With the above-described configuration, the high-frequency decompression apparatus of this embodiment also supplies high-frequency power from the inverter circuit 102 to the electrode 101 and suppresses radio wave leakage, The electric field is applied to perform the operation of thawing by dielectric heating.

However, in this embodiment, the feedthrough capacitor 701 is particularly connected to the choke coil 5 of the cable 113.
Since the configuration is provided at the connection portion on the 01 side, the impedance matching with the characteristic impedance of the cable 113 can be further improved.

For example, in the case of the second embodiment,
When the size of the electrode 21 is as small as about 60 mm in diameter, the real part of the impedance of the electrode 101 becomes a small value such as several ohms, and the choke coil 501 completely removes the reactance component as the imaginary part. The standing wave ratio (SWR) for the cable 113 having a characteristic impedance of 75 ohms
Is about 10 and a considerable impedance mismatching state results.

On the other hand, when the feedthrough capacitor 701 of the third embodiment is used, the reactance component can be reduced by appropriately setting the inductance value of the choke coil 501 and the capacitance value of the feedthrough capacitor 701. It is possible to make the impedance close to zero and to make the impedance at the end of the cable 113 closer to 75 ohms.

As described above, by improving the degree of impedance matching with the characteristic impedance of the cable 113, the magnitude of the standing wave generated in the cable 113 is suppressed, and the high-frequency wave caused by the reduction of the power loss in the cable 113 is reduced. Increase the efficiency of the thawing equipment, or more cables 11
By making 3 thin or low-priced,
The purpose of this is to reduce the price of the apparatus, especially the heating chamber 1
When the length of the cable 113 is long due to the arrangement such as the distance between the inverter 10 and the inverter circuit 102 being long, the effect is more pronounced.

As an effect of the fact that the cable 113 can be formed as a thin cable, even when the electrode 108 is moved up and down in accordance with, for example, the height of the object 121 to be thawed, it is moved. This also effectively works as an effect that the means can be easily configured.

(Embodiment 4) FIG. 8 is a circuit diagram of a high-frequency decompression device according to Embodiment 4.

In FIG. 8, a first choke coil 801 having a fixed inductance value of 7.4 microhenry and having one end connected to the electrode plate 108 of the electrode plates 108 and 109 constituting the electrode 101 is shown. Provided.

Further, an impedance matching circuit 803 having a second choke coil 802 which is electrically driven and has a variable inductance value is provided at a terminal of the coaxial cable 113 on the side of the inverter circuit 102.

The control circuit 804 controls the DC power supply 10
6, a signal for controlling the output voltage is output so that the output of the power detection circuit 115 becomes a predetermined value of 250 watts, and the variable capacitor 111 and the second choke coil 802 are output to the variable capacitor 111 and the second choke coil 802. The control signal is output so that the signal from the power factor detection circuit 140 becomes almost maximum.

In this embodiment, as in the third embodiment, a through-type capacitor 701 is connected to the end of the cable 113.
Are connected, and this is also the impedance matching circuit 80.
It is one of the three components.

The other configuration is described in the second embodiment.
Is equivalent to

With the above-described configuration, the high-frequency decompression apparatus of this embodiment also supplies high-frequency power from the inverter circuit 102 to the electrode 101 and suppresses radio-wave leakage, The electric field is applied to perform the operation of thawing by dielectric heating.

However, in this embodiment, the first choke coil 801 is provided at both ends of the cable 113, respectively.
And the second choke coil 802 are connected to each other.
The negative reactance component 1 has a large offset to suppress the voltage applied to the cable 113, and has a low withstand voltage, a low price, a thin thickness, and easy wiring.
No. 3 can be used.

Alternatively, if the cables 113 have the same specifications, a high-efficiency high-frequency decompression device can be realized by reducing the power loss in the cables 113.

Here, the imaginary part of the impedance of the electrode 101, that is, the reactance, changes depending on the type, temperature, size, etc. of the material 121 to be thawed. The coil can be changed by changing its inductance value to reduce the power loss of the cable 113 and reduce the power consumption of the semiconductor element 10.
3, 104 is effective in reducing the loss.

In this embodiment, the first choke coil 80
1 provides a reactance of 800 ohms corresponding to about 80% of the negative reactance of the electrode 101, so that the degree of impedance matching with the cable 113 is somewhat improved, and It has the effect of suppressing power loss.

Then, the remaining negative reactance is canceled by the second choke coil 802, and as a result, the reactance at the output of the inverter circuit 102 is made almost zero, and the power factor for high frequencies is made maximum, that is, almost 1. Shall be close.

Since the cable 113 is used in a state where the cable deviated from the characteristic impedance is connected to the terminal, the impedance conversion is further performed depending on the length of the cable 113. Minutes, the inverter circuit 10
Control is performed so that the power factor at two outputs is maximized.

Therefore, in this embodiment, the reduction of the standing wave in the cable 113 is not perfect, but the
01 has a considerable standing wave suppression effect as compared with the case where a cable is directly connected to the power supply circuit 01, whereby the power loss of the cable 113 is reduced, and the output part of the inverter circuit 102 has almost completely zero reactance. so,
This is a favorable condition with the maximum power factor.

In general, the semiconductor elements 103 and 104 are expensive, and those having a high current rating require an expensive and complicated drive circuit.
This is very effective in that the power factor at the output of the inverter circuit 102 can be almost maximized.

The second choke coil 802, whose inductance value can be varied, has a slightly complicated structure such as an electric type and requires wiring for control. It is more preferable to provide the device near the inverter circuit 102 in terms of the configuration of the device, but from this viewpoint, the configuration of the present embodiment is very excellent.

In the present embodiment, the second choke coil 802 has a structure in which the ferrite core enters and exits through the air-core coil by means of a geared motor. However, it is necessary to adopt such a structure. Rather, the one that puts a conductive material such as aluminum in and out of the air-core coil has a structure that changes the magnetic resistance of the magnetic path in the middle of the magnetic path provided with ferrite, etc. It is also possible to provide a coil in which another DC current flows through the core around which the coil is wound, change the saturation of the core with the DC current, and change the inductance of the coil on the high-frequency circuit side. In short, any configuration may be used as long as the inductance value can be adjusted.

In this embodiment, the inverter circuit 102
The variable capacitor 111 is provided to adjust the power factor at the output unit to the maximum, but this is not always necessary, and the first choke coil 801, the second choke coil 802, the cable 113 In the case where a sufficient impedance matching effect can be obtained only by the constituent elements such as the above, the configuration without the variable capacitor 111 may be used, and even if the third choke coil is provided instead of the variable capacitor 111, The power factor at the output of the inverter circuit 102 can be sufficiently increased by a constant combination with other components.

In this embodiment, the feedthrough capacitor 70
1, the effect of improving the degree of impedance matching with the cable 113 and suppressing the loss of the cable 113 as described in the third embodiment is obtained. It is not always necessary when the length is short.

In this embodiment, the power is controlled by making the output voltage of the DC power supply 106 variable, but as in the first embodiment, the DC power supply 106 having a constant voltage is used as an inverter circuit. The real part (the imaginary part is almost zero) of the impedance at the output of 102 can be changed by the impedance matching circuit 803 to control the power, and such a configuration may be employed.

The power detection circuit 115 provided in each of the embodiments uses the multiplier 118. For example, the power detection circuit 115 has a frequency of 50 Hz or 60 Hz at 100 volts as shown in FIG. When a DC power supply 106 obtained by rectifying an AC power supply is configured, 100
If the voltage stability in volts is enough,
Since the input power to the device is almost proportional to the magnitude of the output current of the AC power supply, the output current of the AC power supply can be reduced by using, for example, a current transformer and a rectifier circuit and a smoothing circuit provided on its secondary side. , Power may be detected.

[0102]

The present invention particularly has an electrode and an inverter circuit for supplying high-frequency power to the electrode, the inverter circuit having a semiconductor element and a drive circuit for driving the semiconductor element at a predetermined frequency. By configuring
This eliminates the need for a heater power supply and makes it possible to realize a high-efficiency high-frequency decompression device by performing a low-loss operation such as a switching operation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency decompression device according to a first embodiment.

FIG. 2 is a detailed circuit diagram of a DC power supply 106 of the high-frequency thawing apparatus.

FIG. 3 is a detailed circuit diagram of a drive circuit 105 of the high-frequency decompression device.

FIG. 4 is an operation waveform diagram of the driving circuit 105 of the high-frequency decompression device.

FIG. 5 is a circuit diagram of a high-frequency decompression device according to a second embodiment.

FIG. 6 is a configuration diagram of a cable 113 of the high-frequency decompression device.

FIG. 7 is a circuit diagram of a high-frequency decompression device according to a third embodiment.

FIG. 8 is a circuit diagram of a high-frequency decompression device according to a fourth embodiment.

FIG. 9 is a configuration diagram of a high-frequency decompression device according to a conventional technique.

FIG. 10 is a diagram showing a matching circuit of the high-frequency decompression device.

[Explanation of symbols]

Reference Signs List 101 electrode 102 inverter circuit 103, 104 semiconductor element 105 drive circuit 106 DC power supply 107, 503, 702, 803 impedance matching circuit 200 switching element 201 insulating transformer 120 housing 108, 109 electrode plate 601 first conductor 602 second conductor 113 Cable 501 Choke coil 701 Feed-through capacitor 801 First choke coil 802 Second choke coil

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsunori Zaimae 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 3K086 AA03 BA09 DB03 DB11 FA05 3K090 AA03 AB03 BA05 EB12 4B022 LB01 LQ08 LT07

Claims (8)

[Claims] 1. A high-frequency decompression device comprising: an electrode; and an inverter circuit for supplying high-frequency power to the electrode, wherein the inverter circuit includes a semiconductor element and a drive circuit for driving the semiconductor element at a predetermined frequency. 2. An inverter circuit having a DC power supply and two semiconductor elements, wherein a series circuit of the two semiconductor elements is connected between output terminals of the DC power supply, and a drive circuit comprises the two semiconductor elements. The high-frequency decompression device according to claim 1, wherein a switching operation for alternately turning on the elements is performed. 3. An impedance matching circuit provided between an output of an inverter circuit and an electrode, and a DC power supply having a variable output voltage, wherein the impedance matching circuit maximizes a power factor of an output of the inverter circuit. 2. The high-frequency decompression device according to claim 1, wherein a matching operation is performed, and the DC power supply outputs a DC voltage adjusted so that the power in the device becomes a predetermined value. 4. The high-frequency decompression device according to claim 1, wherein the DC power supply has a switching element and an insulating transformer, and one terminal of the electrode is connected to one terminal of the output of the DC power supply and a metal part of the housing. . 5. The high-frequency decompression apparatus according to claim 1, wherein the electrode comprises two electrode plates facing each other, and one of the electrode plates has substantially the same potential as one terminal of the DC power supply. 6. A first conductor provided at a center portion, wherein said first conductor is
A cable having a second conductor provided outside the conductor of
It has a choke coil connected in series with one of the electrode plates,
2. The high-frequency defroster according to claim 1, wherein the first conductor is connected between the other terminal of the choke coil and the semiconductor element, and the second conductor is connected to the other electrode plate and one terminal of the DC power supply. apparatus. 7. The high-frequency decompression device according to claim 6, wherein a through-type capacitor is provided at a connection portion of the cable on the choke coil side. 8. A first choke coil having a fixed inductance value, one end of which is connected to an electrode plate forming an electrode, a cable, and a variable inductance value connected to a terminal of the cable on an inverter circuit side. 2. The high frequency decompression device according to claim 1, further comprising an impedance matching circuit having a second choke coil having the following.