JPH0410382A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To prevent the heat generation of a resistor by connecting a half-wave rectification circuit comprising a semiconductor switching element capacitor, to a coil for lowering the output voltage of an inverter circuit, and electrically energizing the semiconductor switching element of the half-wave rectification circuit while the semiconductor switching element of the inverter circuit is live. CONSTITUTION:Half-wave rectification circuits 10 and 11 comprising a diode and a capacitor are respectively connected to transformer coils 8 and 9, and electric power necessary for actuating a control circuit 6 is supplied from DC voltage rectified with a rectifier 2 via a resistor 16. At the time of startup, drive current applied from the control circuit 6 to the semiconductor switching element of an inverter circuit 3 may be small. In other words, when drive electric power is small, a resistance component at the time of startup increases. Actually, however, a small amount of current flows to the semiconductor switching element at the startup and, therefore, a current loss due to the resistance component is small, thereby enabling the use of the resistor 16 having small capacity. According to the aforesaid construction, the heat generation of the resistor 16 can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency heating device used in homes and the like, and more specifically, to a high frequency heating device using an inverter circuit as its power source.

Conventional technology The conventional technology will be explained below with reference to the drawings.

FIG. 8 is a circuit diagram showing the configuration of a conventional high-frequency heating device. In the figure, a commercial power source 31 is rectified by a rectifier 32 and converted to a DC voltage of about 100V.

The DC voltage generated by the rectifier 32 is applied to an inverter circuit 33. The inverter circuit 33 converts the DC voltage into a high frequency AC voltage, and its output is applied to the transformer 34. The transformer 34 has a primary winding for applying a high-frequency voltage outputted by the inverter circuit 33, a secondary winding for generating a high voltage, and a secondary winding for generating a low voltage to supply power to the filament of the magnetron 35. It consists of a tertiary winding. The high frequency high voltage generated by the secondary winding is rectified into a DC high voltage by a rectifier including a diode and a capacitor. When the DC high voltage is applied between the anode and cathode of the magnetron 35, and the low voltage generated by the tertiary winding is supplied to the filament of the magnetron 35, and the temperature of the filament rises sufficiently, the magnetron 35 oscillates. and generate microwaves.

The microwaves generated by the magnetron are guided into an opening containing non-heated items such as food, and are irradiated onto the non-heated items to cook them.

Control circuit 36 controls semiconductor switching elements within inverter circuit 33 .

The fan 37 is driven by a DC motor 38 and cools the inverter circuit 33, transformer 34, magnetron 35, and the like.

Power for driving the control circuit 36 and the DC motor 38 is supplied via a resistor 39 from the DC output of a rectifier 32 that rectifies the commercial power supply 31.

Invention tries to solve! IN A DC power source obtained by rectifying a battery or commercial power source, an inverter circuit having a semiconductor switching element that converts the DC power source into a high-frequency AC power source, and a control circuit that controls the semiconductor switching element of the inverter circuit. a transformer including a plurality of windings that step up or step down the output of the inverter circuit; and a magnetron that is energized by the output of the transformer and generates microwaves.
A conventional high-frequency heating device equipped with a DC motor for driving a fan for forced cooling uses a DC voltage obtained by rectifying the commercial power source to drive the DC motor and the control circuit. That is, the structure was such that a voltage of about 100 volts DC was supplied by dropping the voltage through a resistor.

With such a configuration, there were problems as described below.

A low DC voltage of about 15 volts is required to drive the control circuit and DC motor. Therefore, in order to obtain power from the output of a rectifier that rectifies the commercial power supply, that is, the 100 volt DC voltage, it is necessary to lower the voltage with a resistor.

Therefore, the resistor needs to drop the voltage from 100 volts DC to 15 volts and supply 15 watts of power to the control circuit and DC motor.
The tm loss becomes very large. For this reason, a large cement resistor was used as the resistor in order to withstand large losses, but due to the large amount of heat generated, the printed circuit board on which the resistor was placed could burn out, and the large resistor also increased its weight. There were issues such as cracks appearing in the printed circuit board.

Means for Solving the Problems (1) A single-stone resonant inverter circuit that includes a DC power source obtained by rectifying a battery or a commercial power source, and a semiconductor switching element that converts the DC power source into a high-frequency AC power source. A high-frequency heating device comprising a transformer having a plurality of windings that step up or step down the output of the inverter circuit, and a magnetron that is energized by the output of the transformer and generates microwaves, the plurality of windings of the transformer A half-wave rectifier circuit consisting of a semiconductor switching element such as a diode and a capacitor is connected to the winding that steps down the output of the inverter circuit, and a forced cooling fan is connected from the half-wave rectifier circuit. or a control circuit that controls the inverter circuit, and the polarity of the winding of the transformer to which the half-wave rectifier circuit is connected is the same as that of the inverter circuit. The semiconductor switching element such as the diode of the half-wave rectifier circuit is configured to be conductive during the period when the semiconductor switching element such as the transistor is conductive.

(2) an impark circuit having a DC power source obtained by rectifying a battery or a commercial power source, and a semiconductor switching element that converts the DC power source into a high-frequency AC power source;
a control circuit that controls semiconductor switching elements of the inverter circuit; a transformer that includes a plurality of windings that step up or step down the output of the inverter circuit; and a magnetron that is energized by the output of the transformer and generates microwaves. , a high-frequency heating device equipped with a DC motor for driving a fan for forced cooling, in which power for driving the DC motor and the control circuit is provided in a transformer, and the output of the inverter circuit is stepped down. The windings are supplied from the same winding.

(3) A DC motor that obtains a DC voltage by connecting multiple rectifiers to one winding installed in a transformer to step down the output of the inverter circuit, and drives a forced cooling fan using the DC voltage. Also, the inverter circuit is configured to drive a control circuit that controls semiconductor switching elements in the inverter circuit, and each of the plurality of rectifiers is connected in parallel.

(4) In a transformer that steps up or steps down the output of an inverter circuit, the primary winding applies the output of the inverter circuit, the secondary winding that generates high voltage to energize the magnetron, and the filament of the magnetron. A transformer is equipped with a tertiary winding that supplies power to the DC motor and control circuit, and a quaternary winding that steps down the output of the inverter circuit and supplies power to the DC motor and control circuit. magnetic coupling between the quaternary winding for supplying the output of the inverter circuit and the primary winding for applying the output of the inverter circuit; magnetic coupling between the quaternary winding and the secondary winding for energizing the magnetron; The structure will be made stronger.

Effect (1) Among the windings of a transformer equipped with a plurality of windings that boost or step down the output of the inverter circuit,
A half-wave rectifier circuit consisting of a semiconductor switching element such as a diode and a capacitor is connected to the winding that steps down and outputs the output of the inverter circuit, and from the half-wave rectifier circuit, a DC motor or , the polarity of the winding of the transformer, which obtains power for driving a control circuit etc. that controls the inverter circuit, and to which the half-wave rectifier circuit is connected, is a semiconductor switching element such as a transistor in the inverter circuit. By configuring the semiconductor switching element such as the diode of the half-wave rectifier circuit to be conductive during the period in which the half-wave rectifier circuit is conductive, the following effects can be obtained.

First, by adopting a configuration in which power for driving the control circuit or the DC motor is obtained from a winding provided in the transformer, the DC motor or the inverter circuit that drives a fan for forced cooling has conventionally been used. This has the effect of eliminating the need to use large resistors such as cement resistors, which were necessary to obtain electric power to drive the control circuits that control the.

Second, the polarity of the winding of the transformer to which the half-wave rectifier circuit is connected is such that the polarity of the half-wave rectifier circuit's diode or By configuring the semiconductor switching element to be conductive, power can be effectively taken out from the winding, so that the number of turns of the winding of the transformer can be reduced.

(2) An inverter circuit having a semiconductor switching element, a transformer having a plurality of windings that step up or step down the output of the inverter circuit, a control circuit that controls the semiconductor switching element of the inverter circuit, and a forced cooling circuit. In a high-frequency heating device comprising a plurality of circuit elements that require DC low-voltage power, such as a DC motor for driving a fan of the To obtain the power necessary to drive a plurality of circuit elements such as a DC motor and the control circuit, and connect a plurality of rectifiers to the same winding, and use the DC voltage obtained from each rectifier, By supplying power to the circuit elements, one winding can supply power to a plurality of circuit elements, and the winding structure of the transformer can be simplified.

(3) Connect multiple rectifiers to one winding installed in a transformer to step down the output of the inverter circuit to obtain a low DC voltage, and use the low DC voltage to activate a fan for forced cooling. Drives circuit elements that require low DC voltage power, such as a DC motor to be driven and a control circuit that controls semiconductor switching elements in the inverter circuit, and connects each of the plurality of rectifiers in parallel. This configuration has the effect of reducing the time required for the plurality of rectifiers to receive power from the windings of the transformer and output the rated DC low voltage.

(4) A transformer that boosts or steps down the output of the inverter circuit, a primary winding for applying the output of the inverter circuit, a secondary winding that generates high voltage to energize the magnetron, and a filament of the magnetron. The tertiary winding supplies power to the tertiary winding, and the output of the inverter circuit is stepped down, and DC low-voltage power is supplied to circuit elements such as the DC motor and control circuit via multiple rectifiers made of diodes and capacitors. a quaternary winding, and the magnetic coupling between the quaternary winding and the quaternary winding is such that the magnetic coupling between the quaternary winding and the secondary winding is By configuring it in a position where the magnetic coupling is stronger, it is possible to very stably supply the low DC voltage generated by multiple rectifiers connected to the quaternary winding and consisting of diodes and capacitors to the circuit elements. It has this effect.

Example Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

(1) FIG. 1 is a circuit diagram showing the configuration of a high-frequency heating device according to an embodiment of the present invention.

In the figure, a commercial power supply 1 is rectified by a rectifier 2 and
It is converted to a DC voltage of about Porto voltage. The DC voltage is
In addition to the impark circuit 3, the inverter circuit 3 converts the DC voltage into a high frequency AC voltage and outputs it. The output of the inverter circuit 3 is applied to a transformer 4.

The transformer 4 includes a primary winding that applies the output of the inverter circuit 3, a secondary winding that generates a high voltage to boost the output of the inverter circuit 3 and energize the magnetron 5, and a filament of the magnetron 5. In order to supply power, it cools the tertiary winding that steps down the output of the inverter circuit 3, the control circuit 6 that controls semiconductor switching elements such as transistors in the inverter circuit 3, the magnetron 5, the inverter circuit 3, and the transformer 4. Circuit elements 1 that require low DC voltage, such as a DC motor 7 to drive a fan
It consists of a winding 8 or 9 which supplies power to the winding 5.

Half-wave rectifier circuits 10 and 11 each consisting of a diode and a capacitor are connected to the windings 7 and 8 of the transformer.
, 8 and outputs a DC low voltage to supply power to circuit elements 15 such as the DC motor 7 and the control circuit 6.

The power necessary for starting the control circuit 6 is supplied from the DC voltage rectified by the rectifier 2 via the resistor 16. At startup, the drive power applied from the control circuit 6 to the semiconductor switching elements of the impark circuit 3 may be small.

That is, IGBT or MOS is used as the semiconductor switching element.
When using an FET, when the drive power is small, the resistance component when turned on increases, but since the current flowing through the semiconductor switching element at startup is small, the loss due to the resistance component is small.Therefore, the resistor 16 should be small. That's fine.

The circuit configuration inside the inverter circuit 3 is shown in FIG.

The figure shows a one-sided resonant circuit consisting of one main semiconductor switching element 12, such as a transformer, a capacitor, an inductor, and the like. The diode is for transistor protection.

During steady operation of the inverter circuit, the ratio of on and off times of the semiconductor switching element 12 such as the transistor, that is, the duty, is about 60%, and the on period of the semiconductor switching element 12 is longer than the off period. Therefore, during the ON period of the semiconductor switching element 12, the half-wave rectifier circuit 10 shown in FIG. Each die of II
The polarities of the primary winding of the transformer 4 and the winding 8.9 are determined so that the odes are conductive and charge is accumulated in each capacitor. By doing this, the on period of the semiconductor switching element 12 is longer than the off period, so more charges are transferred to each capacitor of the half-wave rectifier circuit 10 in one cycle when the semiconductor switching element 12 turns on and off. Can be accumulated.

(2) FIG. 3 is a circuit diagram showing the configuration of a high frequency heating device according to another embodiment of the present invention. In the figure, the circuit operations and symbols are the same as in (1), so detailed explanations will be omitted.

The transformer 4 includes a control circuit 6 that controls semiconductor switching elements such as transistors in the inverter circuit 3,
One winding 8 that supplies power to circuit elements that require low DC voltage, such as the magnetron 5, the inverter circuit 3, and the DC motor 7 for driving the fan that cools the transformer 4.
is provided. A plurality of rectifiers 10 are connected to the winding 8 in order to supply low DC voltage to the control circuit 6 and the DC motor 7.
11 is provided. In order to supply power to multiple circuit elements that require low DC voltage in this way, by providing multiple rectifier circuits in one winding, the number of windings installed in the transformer can be reduced, and the configuration of the transformer can be reduced. can be easily done.

(3) FIG. 4 is a circuit diagram showing the configuration of a high frequency heating device according to another embodiment of the present invention.

In the figure, the circuit operations and symbols are the same as in (1), so detailed explanations will be omitted.

The transformer 4 includes a control circuit 6 that controls semiconductor switching elements such as transistors in the inverter circuit 3,
One winding 8 that supplies power to circuit elements that require low DC voltage, such as the magnetron 5, the inverter circuit 3, and the DC motor 7 for driving the fan that cools the transformer 4.
is provided. A plurality of rectifiers 10 are connected to the winding 8 in order to supply low DC voltage to the control circuit 6 and the DC motor 7.
11 are provided in parallel. By providing the rectifiers 10.11 in parallel to the winding 8 in this way, the rectifiers 10.11 receive power from the transformer winding 8, and the time it takes to output the rated DC voltage is increased. It can save time.

FIG. 5 is a diagram showing this situation. The figure shows that the output voltage of the rectifier 11 receives power from the winding 8 of the transformer and outputs a low DC voltage, and the output voltage of the rectifier 11, which supplies power to the control circuit 6, starts from the time when it receives power from the winding 8 of the transformer. It is a diagram in which the times TI and T2 until reaching the rated output voltage v1 were measured. In the same figure (A), the rectifier 11 and the rectifier 10 are connected to the winding 8.
In this figure, it takes time T1 to reach the rated output voltage ■1. Further, FIG. 2B shows a case where the rectifier 11 and the rectifier 10 are connected in series with the winding 8, and it takes time T2 until the rated output voltage ■1 is reached. As you can see in this diagram, Akira is 4, mT1
<72, so the rectifier 11 and the rectifier FilO are connected to the winding 8
It is better to connect the rectifier in parallel to the rated output voltage V1.
The time required to reach the goal is reduced.

(4) FIG. 6 is a sectional view showing the configuration of a transformer for boosting or voltage-boosting the output of an inverter circuit, which is used in a high-frequency heating device according to another embodiment of the present invention.

In the figure, the transformer has a primary winding 13 that applies the output of the inverter circuit, a secondary winding 14 that generates a high voltage to boost the output of the inverter circuit and energize the magnetron, and a transformer that supplies power to the filament of the magnetron. In order to supply voltage, there is a three o'clock winding that voltages the output of the inverter circuit, a control circuit that controls semiconductor switching elements such as transistors in the inverter circuit, and a fan that drives the magnetron, inverter circuit, and transformer. The winding 8 is provided with a winding 8 that supplies power to a circuit element that requires low DC voltage such as a DC motor, and the winding 8 has a secondary winding f! so that the magnetic coupling with the primary winding 13 is strong. It is provided at a position closer to the primary cotton 13 than the cotton 14.

A magnetron is powered by a high voltage applied between its anode and cathode, supplying sufficient power to its filament.
When the filament temperature increases, it can oscillate and generate microwaves, and when it oscillates, the voltage between the anode and cathode is clipped to about 4 kilovolts.

In the startup state, sufficient power is supplied to the magnetron filament to increase its temperature quickly, so a high voltage of 7 to 8 kilovolts is applied between the anode and cathode of the magnetron, and when it oscillates, the anode and cathode The voltage between the cathodes is about 4 kilovolts. 7th
Figure (A) shows this situation. Since the voltage generated in the secondary winding of the transformer is also affected by this, it becomes as shown in the same figure (B). However, the secondary winding voltage is voltage doubled and rectified and applied to the anode and cathode of the magnetron.

On the other hand, as shown in FIG. The secondary winding 1 is arranged such that the coupling is stronger than the magnetic coupling with the secondary winding 14.
By providing the lever closer to the primary winding 13 than the winding wA8, a more stable voltage can be output from the winding wA8.

Effects of the Invention According to the present invention, the following effects are achieved. The output of the inverter circuit is converted into a voltage as a means of providing power to circuit elements that require low DC voltage power, such as semiconductor switching elements in the inverter circuit and DC motors used to drive cooling fans. By providing a winding in the transformer and obtaining power from this winding,
Conventionally, the loss of the resistor for the voltage layer, which was necessary to supply power to the circuit elements from a DC voltage of about 100 volts, can be significantly reduced, the heat generation of the resistor can be suppressed, and a small and light resistor can be used. This has the effect of preventing the printed circuit board on which the resistor is placed from burning or cracking, and realizing a high-frequency heating device with improved reliability.

[Brief explanation of drawings]

Figures 1 to 4 are circuit diagrams showing the configuration of a high-frequency heating device according to an embodiment of the present invention, and Figure 5 is a circuit diagram showing the time required for the output voltage of the rectifier of the same device to reach the rated output. 6 is a sectional view showing the configuration of the transformer of the same device, FIG. 7 is an operational waveform diagram of the voltage applied to the anode and cathode of the magnet of the device and the voltage generated in each winding of the transformer, FIG. 8 is a circuit diagram showing the configuration of a conventional high-frequency heating device. 3... Inverter circuit, 4... Transformer, 89... Winding wire, 10.11... Rectifier, I2... Semiconductor switching element , 13
......-Secondary winding, 14...Secondary first winding,
15...Circuit element. Name of agent: Patent attorney Shigetaka Awano (1 person) 1% 4 ・-Trace/4-- >;Kanjiju t5-ri:Ie:#,) Fig. 1Fl 脣回 Bath Otsu Fig. Fig. Fig. Fig. Fig. Fig. Time Fig. %

Claims (4)

[Claims] (1) An inverter circuit having a DC power source obtained by rectifying a battery or commercial power source, a semiconductor switching element that converts the DC power source into a high-frequency AC power source, and a plurality of windings that step up or step down the output of the inverter circuit. a magnetron that is energized by the output of the transformer to generate microwaves, and a diode connected to a winding that steps down and outputs the output of the inverter circuit among the plurality of windings of the transformer. The half-wave rectifier circuit consists of a half-wave rectifier circuit consisting of a semiconductor switching element and a capacitor, and a control circuit that controls the inverter circuit or a DC motor that drives a forced cooling fan that receives power from the half-wave rectifier circuit. A high frequency heating device in which the polarity of the winding of the transformer to which the rectifier circuit is connected makes the semiconductor switching element of the half-wave rectifier circuit conductive while the semiconductor switching element of the inverter circuit is conductive. (2) an inverter circuit having a DC power source obtained by rectifying a battery or a commercial power source, and a semiconductor switching element that converts the DC power source into a high-frequency AC power source;
a control circuit that controls semiconductor switching elements of the inverter circuit; a transformer that includes a plurality of windings that step up or step down the output of the inverter circuit; and a magnetron that is energized by the output of the transformer and generates microwaves. and a DC motor for driving a fan for forced cooling, and power for driving the DC motor and the control circuit is supplied from the same winding among a plurality of windings provided in the transformer. High frequency heating equipment. (3) A plurality of rectifiers that rectify the output obtained from one winding provided in a transformer, a DC motor that receives power from the rectifier, and a control circuit that controls semiconductor switching elements of an inverter circuit, 3. The high frequency heating device according to claim 2, wherein a rectifier is connected in parallel to one winding provided in the transformer. (4) A transformer that includes a winding for applying the output of an inverter circuit, a winding for supplying power to a DC motor and a control circuit, and a winding for energizing a magnetron. Magnetic coupling between the winding for supplying power to circuits, etc. and the winding for applying the output of the inverter circuit is achieved by adding a magnetron to the winding for supplying power to the DC motor and control circuit, etc. The high-frequency heating device according to claim 1 or 2, wherein the magnetic coupling between the high-frequency heating device and the winding wire is stronger than the magnetic coupling between the high-frequency heating device and the winding.