JP2003100438A - High-frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and portable high-frequency heating device at a low cost. SOLUTION: Because an inverter circuit can be manufactured as this has a built in battery 1 and an inductance L1 of the primary winding wire of a step-up transformer 6 provided at the inverter circuit and the voltage VIN of the battery are made to have relationships shown as L1 (μH)<0.01×VIN (V)<2> -0.09×VIN (V)+13.5, VIN (V)>30, and L1 (μH)<70, preparation of the portable high-frequency heating device can be realized without making the high-frequency heating device large-sized, or with a high price.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating device for dielectrically heating foods or the like by microwaves.

[0002]

2. Description of the Related Art In a conventional household high-frequency heating device, an AC commercial power source is once converted into a DC voltage by a rectifier circuit, and this DC power is turned on and off by a semiconductor switching element to generate a high-frequency power of 20 kHz or more in an inverter circuit 2. Has been converted to. Further, the inverter circuit 2 boosts this high-frequency power to a high-frequency high voltage by the step-up transformer 6 and applies it to the magnetron 3 via the high-voltage rectifier circuit 9.
The magnetron 3 is driven by this DC high voltage and is 2.45.
The object to be heated is heated by a high frequency electric field by radiating a radio wave of GHz to the heating chamber. FIG. 10 is a block diagram showing this. The magnetron 3 is a vacuum tube oscillator, and its voltage-current characteristic has a Zener characteristic. That is, when the voltage applied between the anode and cathode of the magnetron 3 is equal to or lower than a predetermined value, the impedance is almost infinite, no current flows, and no radio wave is generated. However, when a voltage equal to or higher than a predetermined voltage is applied, the impedance sharply decreases, a current flows, and radio waves are generated. Therefore, the step-up ratio of the step-up transformer 6 in an inverter circuit having an input voltage of 100 V as in a household microwave oven is designed to be about 20.

In addition, 1000 high-frequency heating devices for household use
In order to handle the converted power of W or more, it is an important technology to improve the efficiency of the inverter circuit.

A conventional household high-frequency heating device has a circuit configuration as shown in FIG. The inverter circuit 2 has a rectifying / smoothing circuit including a rectifying diode for rectifying the commercial power supply, an inductor, and a capacitor, and converts the commercial power supply into a pulsating DC voltage. High frequency power is generated in the primary winding of the step-up transformer 6 by turning on / off the first semiconductor switching element 4 at a high frequency of 20 kHz or higher. The step-up transformer 6 is excited by this high-frequency power, generates a step-up output in the secondary winding, and applies a high-frequency high voltage to the high-voltage rectifier circuit 9. The high voltage rectifier circuit 9 is configured to rectify the output voltage of the step-up transformer 6 and apply a high DC voltage to the magnetron 3.

The inverter circuit 2 forms a resonance circuit by the capacitor 7 and the primary winding of the step-up transformer 6, and the resonance phenomenon of this resonance circuit is used to turn off or turn on the semiconductor switching elements 4 and 5. Has a gentle slope. As a result, when the semiconductor switching elements 4 and 5 are turned on, switching is performed with zero current and zero voltage, and there is no period in which the voltage and the current overlap. Further, when turning off, the voltage gradually rises from zero voltage, so that the area where the voltage and the current overlap becomes very small. Therefore, the switching loss of the semiconductor switching elements 4 and 5 is reduced, and the efficiency of the inverter circuit is increased.

Further, the operation of the inverter circuit 2 will be described in detail with reference to FIG. For convenience of description, the first semiconductor switching element 4 starts from the ON state. The operation waveform of the semiconductor switching element 4 at this time becomes a triangular wave as shown in FIG. In the period 1, the first semiconductor switching element 4 is in the ON state, and a triangular wave current flows through the primary winding of the step-up transformer 6. When the first semiconductor switching element 4 is turned off after a predetermined time, the period shifts to the period 2, and the voltage of the first semiconductor switching element 4 becomes gentle due to the resonance phenomenon by the first winding of the first capacitor 7 and the step-up transformer 6. On the other hand, the voltage of the second semiconductor switching element 5 starts to rise, while gradually decreasing.

When the voltage of the first capacitor 7 becomes equal to the voltage stored in the second capacitor 8, the diode of the second semiconductor switching element 5 becomes conductive and the period 3 starts. In this period 3, the resonance circuit is configured such that the one-time winding of the step-up transformer 6, the first capacitor 7 and the second capacitor 8 change, and the resonance frequency changes. Since the second capacitor 8 has a capacitance value that is one digit larger than that of the first capacitor 7, the resonance frequency sharply decreases and the voltage rise moderates. By giving an ON signal to the second semiconductor switching element 5 during this period 3, the resonance phenomenon continues and the voltages of the first and second capacitors begin to drop (period 4).

When the second semiconductor switching element 5 is turned off after a predetermined time, the first capacitor 7 and the primary winding of the step-up transformer 6 resonate again, and the voltage of the first semiconductor switching element 4 becomes zero. The voltage of the second semiconductor switching element 5 starts to rise, while the voltage of the second semiconductor switching element 5 starts to rise. When the voltage applied to the first semiconductor switching element 4 reaches zero, the diode forming the first semiconductor switching element 4 becomes conductive and the period 6 starts. During the period, the ON signal is given to the first semiconductor switching element 4 again to repeat the above operation.

This operation is called zero-voltage switching. In order to realize this operation, the voltage of the first capacitor 7 is equal to the voltage stored in the second capacitor 8 in the period 2. Need to be In the period 5, the voltage 7 of the first capacitor needs to be equal to the DC voltage. Therefore, the constants of the first capacitor 7 are 0.18 μF, the second capacitor 8 is 4.5 μF, and the primary winding of the step-up transformer 6 is 4 μF.
It is 5 μH.

[0010]

The household microwave oven has one
It is a cooker that receives electric power of about 1000 W to 1500 W from a commercial power source of 00 V and heats food with microwaves. Since a large amount of electric power is handled, it is necessary to receive electric power from a commercial power source, but there is a great demand from users who want to use it on a table or outdoors. In order to realize this, it is necessary to mount a power supply source on the microwave oven itself so as to have a cordless structure that can be used without power supply from the outside.

In recent years, the development of rechargeable secondary batteries has advanced in applications such as mobile phones, notebook computers, electric vehicles, etc.
New batteries such as NiCd storage batteries, NiMH storage batteries, and lithium-ion storage batteries have been put to practical use. Along with this, the storage batteries have been made higher in capacity, and at the same time have been made smaller and lighter. Against this background, even for electric devices such as microwave ovens that handle a large amount of electric power, it is becoming practical to use such a secondary battery for a certain short time. is there.

One rechargeable battery (single unit) is called a cell.
The voltage per cell is a low voltage of 1.2 V nominally for nickel-cadmium storage batteries and nickel-hydrogen storage batteries and 3.7 V nominal for lithium-ion storage batteries. When supplying a large amount of power at such a low voltage, a very large amount of current must be passed. However, when the current becomes large, the semiconductor switching elements, inductors, capacitors, etc. used in the inverter circuit that performs power conversion become large in size and expensive in order to reduce the element loss. For example, in the case of performing power conversion of 1000 W, if the power source is a commercial power source of 100 V, it becomes 10 A when the power factor of the circuit is 100%.
If the power source is 50V, a current of 20A flows. Therefore, the current value handled by the inverter circuit also increases accordingly. As a result, if electric losses such as semiconductor switching elements of an inverter circuit, inductors, and capacitors are increased, it is necessary to increase the element size in order to achieve the same level of loss.

On the other hand, considering the production of the inverter circuit in the manufacturing plant, if the size of the electric parts is changed, it is necessary to partially or completely change the existing production equipment, and a large investment is imposed in any case. Therefore, it is necessary not to make a large change in the component size. This is the first issue.

Further, in order to alleviate this problem to some extent, it is necessary to connect a plurality of cells in series and to supply the voltage to a certain voltage or more before supplying the voltage to the inverter circuit. Since the voltage becomes high, it is necessary to take measures against electric shock when the device is assembled or the battery is replaced.

[0015]

The present invention has been made to solve the above problems, and a high frequency heating device has a built-in battery in which a plurality of cells are connected in series, and the inverter circuit supplies power to the inverter circuit. It receives the magnetron and excites it to generate microwaves, and the inductance value L _{1 of the} primary winding of the step-up transformer provided in the inverter circuit is 70 μH or less, and the voltage V _IN of the battery is 30 V or more. With

[0016]

[Equation 2] It is what

According to the above invention, since the battery is built in the high-frequency heating device, the high-frequency heating device can be carried and used on the table or outdoors, and the inverter circuit can be produced using the existing production equipment. It is possible to suppress the price increase of the high frequency heating device.

By connecting a switch near the middle point of the battery composed of a plurality of cells, the voltage of the battery is divided, so that it is possible to prevent electric shock when assembling the device or replacing the battery.

[0019]

A high frequency heating apparatus according to claim 1 of the present invention comprises a battery, an inverter for converting the electric power of the battery, and a magnetron energized by the inverter, the inverter being a first inverter. A parallel resonance circuit including a resonance capacitor and a step-up transformer; a first semiconductor switching element for exciting the parallel resonance circuit; a second capacitor connected in parallel to the parallel resonance circuit; and a second semiconductor switching element. It is composed of a series connection body and a high-voltage rectifier circuit that rectifies the output of the step-up transformer and outputs a high DC voltage. The inductance L ₁ of the primary winding of the step-up transformer is 70 μH or less, and the voltage V _IN of the battery is With 30V or more,

[0020]

[Equation 3] It is what

Then, the primary winding of the step-up transformer is designed so that the equipment of the existing manufacturing plant can be used according to the voltage of the battery, and the zero voltage switching operation of the inverter circuit can be secured. For,
It is possible to realize a portable high-frequency heating device without requiring investment in equipment.

In the high frequency heating apparatus according to claim 2 of the present invention, the battery generates a voltage of 30 V or more by connecting a plurality of cells in series, and a switch is provided near the midpoint of the connection. is there.

Since the switch divides the voltage of the battery and the output voltage of each battery can be halved, for example, if the switch is turned off when the device is assembled or the battery is replaced, It is possible to prevent electric shock in such a case.

A high frequency heating apparatus according to a third aspect of the present invention is a door switch in which the switch is opened / closed by a door for loading / unloading an object to be heated into / from the storage of the high frequency heating apparatus.

Since the switch divides and connects the voltage of the battery by opening and closing the door, it is possible to protect the electric shock when the device is assembled and the battery is replaced.

In the high frequency heating apparatus according to claim 4 of the present invention, the switch is constituted by a relay or a semiconductor device driven by a command unit, so that the switch is turned on when the inverter is operating or charging, and other than that. By turning the switch on and off as necessary, such as turning it off at the time, the voltage of the battery can be divided at the time of assembly or battery replacement, and protection against electric shock can be achieved.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram showing a circuit configuration of a first embodiment of the present invention. Reference numeral 1 is a battery, 2 is an inverter circuit, 3 is a magnetron, 10 is an external DC power source such as a storage battery installed in a vehicle, 11 is a charging section, 16
Is a command unit, 17 is an operation unit, and 18 is a display unit. The battery 1 is built in the high frequency heating device and supplies electric power to the inverter circuit 2. The inverter circuit 2 is composed of semiconductor switching elements 4 and 5, capacitors 7 and 8, a step-up transformer 6 and a high-voltage rectifier circuit 9, and boosts the DC power of the battery 1 to supply a DC high voltage to the magnetron 3. The magnetron 3 is energized by this high DC voltage and radiates a radio wave to a heating chamber (not shown) to dielectrically heat the object to be heated. Further, 10 is an external DC power source such as a storage battery mounted in the vehicle, which supplies power to the charging unit 11. The charging unit 11 includes a smoothing filter circuit 12, an inductor 13, a semiconductor switching element 14, and a rectifier 15, and supplies power to the battery 1 to charge the battery 1. The command unit 16 gives an operation / stop command to the charging unit 11 and the inverter circuit 2, and commands the operation of each circuit. Further, the operation unit 17 gives an operation instruction to the command unit 16 when the user operates it from the outside. Display 18
Is configured to display the operating state of the command unit 16 and inform the user of the operating state of the high frequency heating device.

Next, the operation and action will be described with reference to FIG. First, the operation of the inverter circuit 2 will be described. By turning on the first semiconductor switching device 4, the battery 1 is connected to the primary winding of the step-up transformer 6.
Current flows through the smoothing circuit. When the first semiconductor switching element 4 is turned off after a predetermined time, a resonance phenomenon occurs due to the primary winding of the step-up transformer 6 and the first capacitor 7, the voltage of the first capacitor 7 rises, and The voltage of the semiconductor switching element 4 also rises.

When the voltage of the first capacitor 7 becomes equal to the voltage stored in the second capacitor 8, the diode which constitutes the second semiconductor switching element 5 becomes conductive, and the resonance circuit causes the primary transformer of the step-up transformer 6 to operate. Since it is composed of the winding wire and the first and second capacitors, the inclination becomes steep. Further, by turning on the second semiconductor switching element 5, this resonance state continues, and when the second semiconductor switching element 5 is turned off after a predetermined time, the first capacitor 7 and the step-up transformer 6 are turned on again. Only the next winding is in a resonance state, and the voltages of the first semiconductor switching element 4 and the first capacitor 7 have steep slopes and decrease as shown in FIG.

When the voltage of the first semiconductor switching element 4 becomes zero, the diode becomes conductive and the operation is repeated by giving an ON signal to the first semiconductor switching element 4 again. During this time, a current flows through the primary winding of the step-up transformer 6 as shown in the figure, and the step-up transformer 6 is excited by this current and a step-up output is generated in the secondary winding. The step-up output of the step-up transformer 6 is rectified by the high-voltage rectifier circuit 9 and a high DC voltage is applied to the magnetron 3.

As described above, in this embodiment, since the battery is built in the high-frequency heating device, it is possible to generate electric waves from the magnetron and heat the object to be heated without receiving power from the outside.

Next, the charging section 11 will be described. When the semiconductor switching element 14 is turned on, a current flows through the inductor 13 as shown in FIG. The current at this time is represented by (Equation 4).

[0034]

[Equation 4] When turned off after a predetermined on-time, the current of the inductor 13 is supplied to the battery 1 through the diode 15. At this time, assuming that the output voltage of the charging unit 11 is V _O , the inductor 1
The current flowing through 3 is (Equation 5)

[0035]

[Equation 5] Becomes

When the semiconductor switching element 14 is turned on again when I13 becomes zero, the inductor 13
The electric current of starts to increase and the operation can be continued. Here, the ON time of the semiconductor switching element 14 is TON,
If the off time is TOFF, (Equation 6) holds.

[0037]

[Equation 6] Therefore, when this equation is modified, (Equation 7) is derived.

[0038]

[Equation 7] Therefore, by setting the on / off ratio of the semiconductor switching element 14, it is possible to obtain an arbitrary output voltage and charge the battery 1. Therefore, for example, it becomes possible to charge the battery 1 by generating a voltage required to charge the battery 1 from a 12V storage battery mounted in a vehicle.

Conventionally, a commercial power source was required as a power supply source, and it was not possible to carry a high-frequency heating device and use it, for example, outdoors. However, according to the high frequency heating apparatus of the present embodiment, the high frequency heating apparatus can be carried and used outdoors by incorporating the power supply source for supplying power to the inverter circuit 2, that is, the battery 1.
Further, by providing the charging unit 11 that charges the battery 1, for example, the high frequency heating device can be repeatedly used by charging from the storage battery mounted on the vehicle.

(Embodiment 2) FIG. 4 is a circuit diagram showing a second embodiment of the present invention. The same reference numerals as those in the first embodiment are the same components, and the description thereof will be omitted. As described in the conventional example, the step-up transformer 6 provided in the inverter circuit 2 is designed to have a winding ratio of about 20 when a commercial power source is used as an input source for household use.

However, when the voltage of the battery 1 is less than the effective voltage of the commercial power source, the boost output of the boost transformer 6 is insufficient and the cutoff voltage of the magnetron 3 is not reached, so that oscillation cannot be performed. Alternatively, a predetermined output cannot be obtained. To avoid this, it is conceivable to connect a storage battery of 1.2V or 3.7V per single cell in series to raise the output voltage of the battery 1. However, in order to raise it to a voltage equivalent to that of a commercial power source, for example, A nickel cadmium battery or a nickel-hydrogen battery would require as many as 83 batteries. To increase the number of storage batteries unnecessarily increases the cost and size of the high-frequency heating device.

Therefore, in order to cope with the shortage of the input voltage in the inverter circuit 2, it becomes necessary to increase the turn ratio of the step-up transformer 6 according to the voltage of the battery 1. However, as shown in FIG. 5, the step-up transformer 6 coaxially comprises a primary winding 6a, a secondary winding 6c, and a heater winding on the same bobbin 6b, and the bobbin 6b has a U-shaped ferrite core or the like. Since the above magnetic material 6d is fitted, there is naturally a limit to the number of additional windings. In addition, the secondary winding 6c is 2K in order to supply voltage to the magnetron 3.
Since it is a component that generates a high voltage of V or more, it may cause an inconvenient phenomenon such as discharge on the circuit unless the insulation distance is sufficient for the ferrite core 6d and other components with different potentials. turn into.

Therefore, using the existing production equipment,
To increase the turn ratio of the step-up transformer 6, the number of turns of the primary winding 6a must be reduced. However, simply reducing the inductance of the primary winding 6a causes a large current increase in the first semiconductor switching element 4 and a failure of the zero voltage operation of the semiconductor switching element 4.
As a result, the switching loss of the semiconductor switching elements 4 and 5 will increase. Therefore, there is a problem that a large-scale device is required to cool the semiconductor switching elements 4 and 5.

FIG. 6 shows a range of constants for realizing zero voltage switching in the relationship between the voltage V _{IN of the} battery 1 and the inductance L _{1 of the} primary winding 6a of the step-up transformer 6 and selecting a predetermined conversion power. It is what I asked for.

For example, when heating food that has been kept cold in a refrigerator or the like, if the microwave output is 500 w, a heating time of about 2 minutes is required. The microwave output efficiency of the high frequency heating device is about 56% from the conversion efficiency of the inverter circuit 2 and the magnetron 3, so the microwave output is 500w.
To obtain the above, about 900 w is required as the input power of the inverter circuit 2.

Therefore, in the present embodiment, the operating frequency of the inverter circuit 2 is set to 25 kHz and the predetermined conversion power is set to 900 W, and this is supplied from the battery 1. Further, since the step-up transformer 6 is configured with the existing equipment and configuration, the inductance of the primary winding 6a is 7
The upper limit is 0 μH. In this case, the relationship between the inductance L _{1 of the} primary winding 6a of the step-up transformer 6 and the battery voltage V _IN is

[0047]

[Equation 8] Becomes

For example, when the battery 1 is composed of a plurality of storage batteries (for example, a nickel-cadmium storage battery or a nickel-hydrogen storage battery), the nickel-cadmium storage battery or the nickel-hydrogen storage battery has a voltage of 1.2 V, so 40 batteries are used. In that case, a rated output voltage of 48 V is obtained. At this time, according to the above-mentioned (Equation 8), the inductance L _{1 of the} primary winding 6a may be 32.2 μH.

However, the output voltage of the nickel-cadmium storage battery or the nickel-hydrogen storage battery tends to decrease at the end of discharge, and the voltage per storage battery is 0.
It drops to 8V. Therefore, in order to maintain a predetermined converted power until this time, the inductance of the primary winding 6a must be 20.9 μH or less. By setting such a constant, even if the voltage of the battery 1 drops at the end of discharge, predetermined power conversion can be performed and the zero-voltage switching operation can be reliably performed.

Therefore, in the high frequency heating apparatus of this embodiment, the primary winding 6a of the step-up transformer 6 of the inverter circuit 2 is

[0051]

[Equation 9] By designing to satisfy the relations of V _IN (V)> 30 and L ₁ <70 (μH), it is possible to share production equipment with an inverter circuit of an existing household high-frequency heating device, Moreover, the zero voltage switching operation of the inverter circuit can be ensured. Therefore, it is possible to prevent unnecessary increase in size and cost of the step-up transformer and the inverter circuit.

(Embodiment 3) FIG. 7 is a circuit diagram showing a high-frequency heating apparatus according to a third embodiment of the present invention, in which the same reference numerals as those in the above-mentioned embodiment are the same components, and the description thereof is omitted. To do. The switch 19 is provided near the midpoint of the battery 1 composed of a plurality of storage batteries. Generally, if the AC voltage is 30 V or more and the DC voltage is 45 V or more, there is a possibility of electric shock, and a charging part (for example, a terminal part of a battery) that may be exposed must be below this voltage.

With the configuration as in this embodiment, the voltage between the terminals which may be exposed due to the disconnection of the voltage of the battery 1 by the switch 19 when assembling the high frequency heating device is the same as the voltage of the battery 1. About 1/2
And no electric shock.

Further, since the nickel-cadmium storage battery and the nickel-hydrogen storage battery are legally required to be recycled, the battery 1 must be replaced. Therefore, replacement work of the battery 1 occurs. At this time as well, the terminal portion may be touched by the user as in the case of assembly, but the switch 19 divides the voltage between the terminals at the middle point of the battery 1 to prevent electric shock to the user during battery replacement. can do.

(Embodiment 4) FIG. 8 is a circuit diagram showing a high-frequency heating apparatus according to a fourth embodiment of the present invention, in which the same reference numerals as those in the above-mentioned embodiment are the same constituent elements and the description thereof will be omitted. . The switch 19 is configured so that the switch 19 is turned off when the door of the high frequency heating device is opened, and is mounted near the door of the high frequency heating device. The voltage of the battery 1 is cut off when the door of the high-frequency heating device is opened by the switch 19. Therefore, there is no place where the entire voltage of the battery 1 is applied inside the high frequency heating device.

Further, at the same time, the battery 1 can be taken out only when the door of the high-frequency heating device is opened, so that it is possible to further reduce the possibility that the user will get an electric shock when the battery is replaced. It is convenient.

(Embodiment 5) FIG. 9 is a circuit diagram showing a high frequency heating apparatus according to a fifth embodiment of the present invention. The same reference numerals as those in the above-mentioned embodiments are the same constituent elements, and the description thereof will be omitted. . Reference numeral 19 denotes a relay switch, which is configured to turn on / off based on a signal from the command unit 16.

Next, the operation and action will be described. When the command unit 16 receives an inverter operation signal from the operation unit 17, it closes the relay switch 19 and supplies a voltage to the inverter circuit 2. Further, the instruction unit 16 also instructs the operation of the inverter circuit 2, so that the high-frequency heating device can generate radio waves to heat the object to be heated. When the operation of the inverter circuit 2 ends, the command unit 16 turns off the relay switch 19 again to prevent the standby power of the inverter circuit 2 from exhausting the battery 1.

When a command for charging operation is issued from the command unit 16, the relay switch 19 is turned on to start charging the battery 1. When the charging operation is completed, the command unit 1
6, the relay switch 19 is turned off again. With such a configuration, the voltage between the terminals of the battery 1 is always divided by the relay switch 19 when the operation of the inverter circuit 2 or the charging operation of the charging unit 11 is not performed.

Therefore, it is possible to eliminate the possibility of electric shock from the battery during assembly, and to eliminate the possibility of electric shock from the user to the battery when replacing the battery.

In the present embodiment, an example using a relay switch has been described, but the switch 19 may be a semiconductor device such as a triac.

[0062]

As described above, according to the invention described in claim 1 of the present invention, a high frequency cordless high frequency heating device is realized which does not require power supply from a commercial power source and can be used on a table or outdoors. Since the heating device can be realized and the battery can be charged by the charging unit, the high frequency heating device can be used repeatedly by charging the battery, and the inverter circuit can be produced with the existing production equipment, which makes the high frequency heating device more expensive. At the same time, there is an effect that the zero voltage switching operation is surely realized and the high efficiency operation of the inverter circuit is not impaired.

Further, according to the second aspect of the invention, since the voltage of the battery is divided by turning off the switch, the assembly worker against electric shock at the time of assembling the high frequency heating device or replacing the battery, This has the effect of protecting the user.

According to the third aspect of the invention, by opening the door, the voltage of the battery is divided, and the assembling operator and the user against electric shock when assembling the high frequency heating device or replacing the battery. There is an effect that can be protected.

Further, according to the invention described in claim 4, the command section opens the switch and the battery voltage is changed except when the high frequency heating device is operating or when the charging operation is performed on the charging section. Since the parts can be divided, there is an effect that the assembling operator and the user can be protected against electric shock when assembling the high frequency heating device and replacing the battery.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high-frequency heating device according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of an inverter circuit 2 of the same high-frequency heating device.

FIG. 3 is an operation waveform diagram of a charging unit of the high-frequency heating device.

FIG. 4 is a circuit diagram of a high-frequency heating device according to a second embodiment of the present invention.

FIG. 5A is an external view of a step-up transformer provided in an inverter circuit of the high-frequency heating device, and FIG. 5B is a sectional view of the same.

FIG. 6 shows the inductance L _{1 of the} primary winding of the step-up transformer 6 of the inverter circuit of the high-frequency heating device and the battery 1
Diagram showing the relationship of the voltage V _IN

FIG. 7 is a circuit diagram of a high frequency heating device according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a high frequency heating device according to a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram of a high frequency heating device according to a fifth embodiment of the present invention.

FIG. 10 is a block diagram showing a conventional high-frequency heating device.

FIG. 11 is a circuit diagram showing the high-frequency heating device.

FIG. 12 is an operation waveform diagram of the inverter circuit 2 of the high-frequency heating device.

[Explanation of symbols]

1 battery 2 Inverter circuit 3 magnetron 4 First semiconductor switching element 5 Second semiconductor switching element 6 step-up transformer 7 First capacitor 8 Second capacitor 9 High voltage rectifier circuit 10 External power supply 11 Charging section 12 Smoothing circuit 13 inductor 14 Semiconductor switching elements 15 diode 16 Command unit 17 Operation part 18 Display

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K086 AA10 BA08 CA20 CB20 CC20                       DB03 EA03 FA02 FA03 FA04                       FA05 FA08                 3K090 AA20 BA01 EB11 EB12 EB13                       EB32                 3L086 CC22 DA01

Claims (4)

[Claims] 1. A battery, a inverter for converting electric power of the battery, and a magnetron energized by the inverter, the inverter including a parallel resonant circuit including a first resonant capacitor and a step-up transformer. A first semiconductor switching element that excites the parallel resonant circuit, a series connection body of a second capacitor and a second semiconductor switching element that are connected in parallel to the parallel resonant circuit, and rectifies the output of the step-up transformer, A high-voltage rectifier circuit that outputs a direct current high voltage, the inductance L ₁ (μH) of the primary winding of the step-up transformer is 70 or less, the voltage V _IN (V) of the battery is 30 or more, and 1] High frequency heating device. 2. The high-frequency heating device according to claim 1, wherein the battery comprises a plurality of cells connected in series, and a switch is provided near the midpoint of the connection. 3. The high-frequency heating apparatus according to claim 2, wherein the switch also serves as a door switch which is opened and closed by a door for taking in and out an object to be heated in and out of the chamber of the high-frequency heating apparatus. 4. The high-frequency heating apparatus according to claim 2, wherein the switch comprises a relay driven by a command unit or a semiconductor device.