JP2003272931A - Boosting transformer for driving magnetron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boosting transformer wherein less frequency loss is produced and that is hardly saturated and is compact and easy to manufacture. <P>SOLUTION: A boosting transformer 20 is designed for a microwave oven, and a primary winding 21, a secondary winding 22, and a heater winding 23 surround a bar-like ferrite core 26 respectively, and they are piled up in an axial direction of the ferrite core 26. The ferrite core 26 is a square iron oxide powder resin core that an iron oxide powder is packaged with resin, and one inner diameter thereof is made larger than an outer diameter of the primary winding 21, the secondary winding 22 and the heater winding 23, and the other square inner diameter thereof is made larger than a total piling height of them. Such an iron oxide powder resin core 27 is inserted to the bar-like ferrite core 26 from the outside of the primary winding 21, the secondary winding 22 and the heater winding 23, and it is arranged opposite to the ferrite core 26 with a clearance G in-between in this state. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-frequency dielectric heating using a magnetron such as a microwave oven, and more particularly to a step-up transformer for driving the magnetron with a switching power supply.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a magnetron drive power source using a step-up transformer, which is the object of the present invention. In the figure, the alternating current from the commercial power supply 11 is rectified into a direct current by the rectifier circuit 13, smoothed by the choke coil 14 and the filter capacitor 15 on the output side of the rectifier circuit 13, and given to the input side of the inverter 16. The direct current is converted into a desired high frequency (20 to 40 kHz) by turning on and off the semiconductor switching element in the inverter 16. The inverter 16 is composed of, for example, two sets of switching element groups in which a plurality of power MOSFETs are connected in parallel for switching direct current at high speed, and a drive circuit for driving these switching element groups. The drains of the power MOSFETs that form the switching element group are connected to one end and the other end of the primary winding 182 of the step-up transformer 18, respectively, and the power MOS that forms these two switching element groups.
The sources of the FETs are connected to each other, and the gates of the power MOSFETs that form the switching element group are connected to the switching element drive circuit.
The switching element group composed of power MOSFETs is driven by the inverter control circuit 61, and the current flowing through the primary side of the step-up transformer 18 is switched on / off at high speed. The input signal of the control circuit 161 detects the primary side current of the rectifier circuit 13 at CT17, and the detected current is input to the inverter control circuit 161 and used for controlling the inverter 16.

In the step-up transformer 18, a high frequency voltage output from the inverter 16 is applied to the primary winding 181, and a high voltage according to the winding ratio is obtained in the secondary winding 182. In addition, the winding 1 having a small number of turns on the secondary side of the step-up transformer 18
83 is provided and is used for heating the filament 121 of the magnetron 12. Step-up transformer 1
The secondary winding 182 of No. 8 includes a voltage doubler half-wave rectifier circuit 19 that rectifies the output. The double voltage half-wave rectifier circuit 19 includes a high voltage capacitor 191 and two high voltage diodes 192.
193, the high voltage capacitor 191 and the high voltage diode 192 are turned on in a positive cycle (for example, the upper end of the secondary winding 182 is positive in the figure), and the electrode plate of the high voltage capacitor 191 is moved to the left side in the figure. Charge the right side plate positively and negatively. Next, in a negative cycle (the lower end of the secondary winding 182 is positive), the high voltage diode 193 conducts, and between the anode 122 and the cathode 121 of the magnetron 12, the voltage of the previously charged high voltage capacitor 191 and the secondary voltage. Winding 18
A voltage twice as large as the voltage of 2 is added.

An example of a magnetron drive power supply using a boosting transformer, which is the subject of the present invention, has been described above, but the drive power supply is not limited to this, and any drive that includes a transformer for boosting high frequencies can be used. It can be anything.

[0005]

With the need for miniaturization of microwave ovens, it is necessary to miniaturize the step-up transformer, so that high frequencies have come to be used from the low frequencies up to then. As a core of a transformer, a metal core (amorphous, silicon steel plate), which is advantageous in terms of downsizing, saturation, and cost, was used at low frequencies, but at high frequencies, the metal core is no longer used because of its large high-frequency loss. Ferrite cores have come to be used instead of.

FIG. 7 shows an example of a step-up transformer using a ferrite core. In FIG. 7, the primary winding 7
The primary winding 1, the secondary winding 72, and the heater winding 73 were placed in parallel on the same axis of the two opposing U-shaped ferrite cores 74 and 75. In the case of a magnetron driving power source that often handles a large amount of power, a zero volt switching method (hereinafter, ZVS method) based on voltage resonance is mainly used to reduce the load on the power semiconductor. In this ZVS method, the resonance voltage is changed. In order to obtain the coupling coefficient of the step-up transformer from 0.6 to 0.
It is necessary to set it to about 85, and a gap G is provided. However, in the case of the conventional step-up transformer using the two opposed U-shaped ferrite cores 74 and 75, it is necessary to further increase the peak current flowing in the primary side of the step-up transformer in order to further increase the output of the magnetron. If so, the saturation magnetic flux density characteristic of the ferrite core is poor, so that the ferrite core is easily saturated, and it is necessary to increase the size of the ferrite core to prevent saturation. This has been an obstacle to the premise of downsizing the power supply. The present invention solves these problems, and it is an object of the present invention to provide a step-up transformer that contributes to downsizing of a power supply and does not saturate even at high output.

[0007]

In order to solve the above problems, the invention of a step-up transformer for driving a magnetron according to claim 1 is a step-up transformer for supplying a drive voltage to a magnetron, wherein a primary winding and a secondary winding are provided. In a magnetron driving step-up transformer in which wires surround a rod-shaped ferrite core, a letter-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed is formed into a rod shape from the outside of the primary winding and the secondary winding. It is characterized in that it is fitted and inserted toward the ferrite core and is opposed to the rod-shaped ferrite core with a gap. The invention of a step-up transformer for driving a magnetron according to claim 2 is a step-up transformer for supplying a drive voltage to a magnetron, wherein a primary winding and a secondary winding respectively surround a rod-shaped ferrite core and the rod-shaped ferrite core. In a step-up transformer for driving a magnetron, which is stacked and juxtaposed in the axial direction of, a letter-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed, one inner diameter of which is either the primary winding or the secondary winding. Of the iron oxide powder resin core formed by forming the iron oxide powder resin core having a larger inner diameter than the outer diameter of the primary winding and a larger inner diameter of the other of the square shapes to be larger than the overlapping length of the primary winding and the secondary winding. It is characterized in that the wire is fitted and inserted from the outside of the wire toward the rod-shaped ferrite core and is opposed to the rod-shaped ferrite core with a gap. According to the above invention,
Featuring high-frequency loss, it is cheaper than a ferrite core, can be downsized, and has a saturation magnetic flux density characteristic higher than that of a ferrite core. It is small, robust, and has the effect of mechanical protection on the outside of each winding.

The invention according to claim 3 is the same as claim 1
Alternatively, in the magnetron driving step-up transformer described in 2, the rod-shaped ferrite core has a rectangular parallelepiped shape. According to the above invention, since the voids formed between the rectangular parallelepiped ferrite core and the square-shaped iron oxide powder resin core have the same width, the design of the coupling coefficient and the like becomes easy.

Further, the invention of a step-up transformer for driving a magnetron according to claim 4 is a step-up transformer for supplying a drive voltage to a magnetron, wherein a primary winding and a secondary winding respectively surround a rod-shaped ferrite core and A step-up transformer for driving a magnetron, which is formed by stacking and arranging rod-shaped ferrite cores side by side in an axial direction, and is a letter-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed, one inner diameter of which is the primary winding and the secondary winding. Inserting the rod-shaped ferrite core into a letter-shaped iron oxide powder resin core formed by forming the wire-shaped iron oxide powder resin core that is larger than any outer diameter of the wire and has the other inner diameter formed larger than the length of the rod-shaped ferrite core, and It is characterized in that the rod-shaped ferrite core is arranged so as to face each other with an air gap between the axial end portion and the letter-shaped iron oxide powder resin core. According to the above invention, the iron oxide powder resin sealing core, which has less high frequency loss, is cheaper than the ferrite core and can be miniaturized, and has a saturation magnetic flux density characteristic higher than that of the ferrite core, and has a void to prevent saturation. The provision has the advantage that it is simple to manufacture, small, robust and also serves as a mechanical protection on the outside of each winding.

According to a fifth aspect of the present invention, in the magnetron driving step-up transformer according to the fourth aspect, the rod-shaped ferrite core is columnar. According to the above invention, the rod-shaped ferrite core has a columnar shape, which has the effect of simplifying the manufacturing. Further, since the voids formed between the rod-shaped ferrite core and the metal core have the same width, it is easy to design the coupling coefficient and the like. According to the invention described in claim 6, in the step-up transformer for driving magnetron according to any one of claims 1 to 5, a rod-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed in place of the rod-shaped ferrite core is used. Is used. According to the above invention, by using the rod-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed, it is possible to manufacture the core with the same material together with the letter-shaped iron oxide powder resin core.・ Manufacturing and management work becomes easy. According to a seventh aspect of the present invention, in the magnetron driving step-up transformer according to the third or sixth aspect, a protrusion is formed on a part of a surface of the rectangular parallelepiped core that faces the letter-shaped iron oxide powder resin core. The projecting portion is brought into contact with the cup-shaped iron oxide powder resin core. According to the above invention, it is not necessary to separately prepare a spacer between the cores, and the labor for assembling it can be saved. Therefore, the step-up transformer can be easily assembled and the cost can be reduced.

The present invention of a step-up transformer for driving a magnetron is a step-up transformer for supplying a drive voltage to a magnetron, the step-up transformer for driving a magnetron comprising a primary winding and a secondary winding. In the transformer,
Two U-shaped iron oxide powder resin cores, which are resin-sealed with iron oxide powder, are arranged to face each other with U-shaped tips spaced apart from each other, and one leg of the two U-shaped iron oxide powder resin cores is arranged. It is characterized in that the primary winding and the secondary winding are provided on a core formed by abutting parts. The invention of a step-up transformer for driving a magnetron according to claim 9 is a step-up transformer for supplying a drive voltage to a magnetron, the step-up transformer for driving a magnetron comprising a primary winding and a secondary winding, Two U-shaped iron oxide powder resin cores, which are resin-sealed with iron oxide powder, are arranged to face each other with U-shaped tips spaced apart from each other, and one leg of the two U-shaped iron oxide powder resin cores is arranged. It is characterized in that the primary winding and the secondary winding are axially overlapped and juxtaposed to each other on a core formed by abutting parts. According to the above invention, there is little high frequency loss, it is cheaper and more compact than a ferrite core, and an iron oxide powder resin sealing core having a saturation magnetic flux density characteristic higher than that of a ferrite core is used. It is possible to make a compact and robust boost transformer.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A step-up transformer of the present invention will be described below with reference to the drawings. 2A and 2B are diagrams showing a step-up transformer according to the first embodiment of the present invention, where FIG. 2A is a front view, FIG. 2B is a plan view, FIG. 2C is a side view, and FIG. . In the figure, 20 is a step-up transformer according to the first embodiment, 21 is a primary winding, 22 is a secondary winding, and 23.
Is the heater winding. The primary winding 21 has a larger winding cross section and a smaller number of turns than the secondary winding 22. The heater winding 23 has an extremely small number of turns as compared with the secondary winding 22, and is not shown in the drawing. Further, since the heater winding 23 may be configured as a separate component, it is not an essential component here.
Reference numeral 26 is a rod-shaped ferrite core, which has a rectangular parallelepiped shape. A primary winding 21, a secondary winding 22, and a heater winding 23 surround the periphery of the rectangular parallelepiped-shaped ferrite core 26 and are juxtaposed side by side in the axial direction of the core.

Reference numeral 27 denotes a letter-shaped iron oxide powder resin core, which is used in the present invention and is encapsulated with iron oxide powder. One of the inner diameters of the square iron oxide powder resin core (Fig. 2 (c))
The inner diameter of the iron oxide powder resin core 27 in the left-right direction is larger than the outer diameter of any of the primary winding 21, the secondary winding 22, and the heater winding 23, and the inner diameter of the other (FIG. 2).
The inner diameter in the vertical direction of the iron oxide powder resin core 27 in (c) is formed larger than the overlapping length of the three windings of the primary winding 21, the secondary winding 22, and the heater winding 23.

The iron oxide powder used here has a particle size of 0.5 mm.
It is preferable that the surface has a film (oxide film) having a high insulating property on the surface as below. Heat resistance of resin is 1
PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PP at about 00 ° C
(Polypropylene) is suitable. By mixing iron oxide with these resins at a weight percentage of about 70% or more, saturation magnetic flux density characteristics and magnetic permeability characteristics superior to ferrite can be obtained. As described above, a magnetic path having a higher magnetic permeability and a higher saturation magnetic flux density than ferrite can be obtained by using a material having a particle size of about 0.5 mm or less, so that the magnetic circuit can be downsized even when used for high power applications. Further, since the one having the oxide film on the surface is used, it becomes difficult to form the closed circuit in which the eddy current generated by the high frequency flows, so that the high frequency loss can be reduced like the ferrite. Thus, the iron oxide powder resin core has the advantages of the ferrite core and the high saturation magnetic flux density characteristics of pure iron.

Therefore, as shown in FIG. 2 (d), the iron oxide powder resin core 27 as shown in the drawing is drawn from the outside of the primary winding 21, the secondary winding 22, and the heater winding 23 to the ferrite core 2.
6 and the spacers (not shown) are placed between the rod-shaped ferrite core 26 and the rod-shaped ferrite core 26 to secure the gap G and to face each other. Ferrite core 26 and iron oxide powder resin core 27
The void is about 0.3 to 0.8 mm.

With the above-described structure, the ferrite core 26 having a small high frequency loss is used as the main core, and the small iron oxide powder resin core 27 facing the main core 26 and hardly saturated is formed between the primary winding 21 and the secondary winding 22. Since it is arranged outside the heater winding 23 and the air gap G is provided so as not to be saturated, it contributes to a significant reduction in size as compared with the conventional step-up transformer (FIG. 7) consisting of only a ferrite core. That is,
Since the step-up transformer 20 according to the first embodiment has the iron oxide powder resin core, the cross-sectional area can be made extremely smaller than that of the ferrite core portion, and the primary winding 21, the secondary winding 22, and the heater winding 23 are It does not largely extend outside (see FIG. 2 (c)). Moreover, the iron oxide powder resin core 27 has a small high frequency loss. Further, since the ferrite core 26 of the step-up transformer has a rectangular parallelepiped shape, the ferrite core 26 and the iron oxide powder resin core 27 face each other in parallel, and the gap G formed therebetween has the same width. Designing factors such as coefficients becomes easy. Further, since the iron oxide powder resin core 27 is formed in a square shape, the manufacturing is simplified, and the square iron oxide powder resin core 27 wraps each winding 21, 22, 23 in a part from the outside. It also has the effect of providing effective protection. In the above embodiment, the primary winding 21
The secondary winding 22 and the heater winding 23 respectively surround the rod-shaped ferrite core and are arranged side by side in the axial direction of the core, but the present invention is not limited to this, and the rod-shaped The three windings centering around the ferrite core may be concentrically arranged with the second winding outside the first winding and the third winding outside the first winding.

FIG. 3 is a diagram showing a step-up transformer according to a second embodiment of the present invention. (A) is a front view, (b) is a plan view, (c) is a side view, and (d) is a perspective view. It is a figure. In the figure, 30 is a step-up transformer according to the second embodiment,
Reference numeral 1 is a primary winding, 22 is a secondary winding, and 23 is a heater winding, which are the same as those in FIG. That is, the primary winding 21
Has a larger winding cross section and a smaller number of turns than the secondary winding 22. The heater winding 23 has an extremely small number of turns as compared with the secondary winding 22, and is not shown in the drawing.

In the step-up transformer according to the second embodiment of the present invention, the cylindrical ferrite core 36 is used,
A primary winding 21, a secondary winding 22, and a heater winding 23 surround this periphery, and are arranged side by side in the axial direction of the core. Further, the iron oxide powder resin core 37 formed in a square shape is used. Of the inner diameters of the square-shaped iron oxide powder resin core, one inner diameter (the inner diameter in the left-right direction of the iron oxide powder resin core 37 in FIG. 3C) is the primary winding 21, the secondary winding 22, and the heater winding. It is formed to have a diameter larger than any of the outer diameters of 23 and an inner diameter of the other (inner diameter in the vertical direction of the iron oxide powder resin core 37 in FIG. 3C) larger than the length of the cylindrical ferrite core 36. . As shown in FIG. 3D, the columnar ferrite core 36 is fitted in the surface of the iron oxide powder resin core 37, and is arranged to face the axial end of the columnar ferrite core 36 with a gap G therebetween. There is.

With the above-described structure, the ferrite core 36 having a small high frequency loss is used as the main core, and the iron oxide powder resin core 37, which is smaller than the ferrite core and is less likely to be saturated, is placed opposite to the main core 21 and the secondary winding. The ferrite core 3 is provided outside the wire 22, the heater winding 23, and the ferrite core 36, and the gap G is provided so as not to saturate.
Compared with the conventional step-up transformer consisting of only 6 (Fig. 7), it contributes to a large size reduction. Moreover, the iron oxide powder resin core 37 has a small high frequency loss. Therefore, even under high frequency, the high frequency loss is reduced only by arranging the iron oxide powder resin core 37 having such a configuration as described above, and the ferrite core 36 and the iron oxide powder resin core 37 have the advantages. It is possible to obtain a step-up transformer. Further, since the ferrite core 36 of the step-up transformer has a cylindrical shape, it is easier to manufacture than the rectangular parallelepiped, and the gap G through which the magnetic flux passes is such that the ferrite core 36 and the iron oxide powder resin core 37 face each other in parallel. Therefore, the gaps G formed between them have the same width, which facilitates the design of the coupling coefficient and the like. Further, the square iron oxide powder resin core 37 is provided with the ferrite core 36 and the windings 21, 22,
Since 23 is partially wrapped from the outside, it also serves as a mechanical protection for these.

FIG. 4 is a diagram showing a step-up transformer according to a third embodiment of the present invention, and is a perspective view of (a) a first embodiment and (b) a second embodiment, respectively. In FIG. 4A, reference numeral 40 is a step-up transformer according to the first embodiment.
Is a primary winding, 22 is a secondary winding, and 23 is a heater winding. Reference numeral 47 is a letter-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed. The respective windings 21, 22, 23 and the letter-shaped iron oxide powder resin core 47 are the same as the corresponding parts in FIG. That is, the primary winding 21 has a larger winding cross section and a smaller number of turns than the secondary winding 22, and the heater winding 23 is the secondary winding 2
The number of turns is extremely small compared to 2. The cup-shaped iron oxide powder resin core 47 has one inner diameter of the primary winding 21, the secondary winding 22,
It is made larger than any of the outer diameters of the heater windings 23, and the inner diameter of the other is larger than the primary winding 26 and the secondary winding 22.
And the heater winding 23 are formed to be larger than the overlapping length of the three windings. Reference numeral 46 denotes a rod-shaped iron oxide powder resin core according to the third embodiment, which has a rectangular parallelepiped shape. Around the periphery of the rectangular parallelepiped iron oxide powder resin core 26, the primary winding 2
The primary winding 1, the secondary winding 22, and the heater winding 23 surround each other and are arranged side by side in the axial direction of the core. Then, the primary winding 21, the secondary winding 22, and the heater winding 23 are fitted from the outside toward the iron oxide powder resin core 46, and a spacer (not shown) is placed between the rod-shaped iron oxide powder resin core 46. A gap G is secured to face each other. Iron oxide powder resin core 46
The void of the iron oxide powder resin core 47 is about 0.3 to 0.8 mm.

With the above-mentioned structure, the main core 46 and the auxiliary core (square-shaped core) 47 are formed of an inexpensive iron oxide powder resin core which has less high frequency loss, is smaller in size than the ferrite core, and is less likely to be saturated. Therefore, it greatly contributes to miniaturization as compared with the conventional step-up transformer (FIG. 7) including only the ferrite core. Also, iron oxide powder resin core 4
Since 6 is a rectangular parallelepiped shape, iron oxide powder resin cores 46 and 4
The portions facing each other are parallel to each other, and the gap G formed therebetween has the same width, which facilitates the design of the coupling coefficient and the like. Further, since the iron oxide powder resin core 47 is formed in a square shape, the manufacturing is simplified, and the square iron oxide powder resin core 47 is formed.
Since it partially wraps each winding from the outside, it also has a secondary effect of mechanically protecting each winding.

In FIG. 4 (b), 40 'is a step-up transformer according to the second embodiment, 21 is a primary winding, 22 is a secondary winding, and 23 is a heater winding. 47 'is a letter-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed. Each winding 2
1, 22, 23 and the letter-shaped iron oxide powder resin core 47 'are the same as the corresponding parts in FIG. 46 'is a cylindrical iron oxide powder resin core according to the third embodiment. A primary winding 21, a secondary winding 22, and a heater winding 23 surround the circumference of the cylindrical iron oxide powder resin core 46 'and are juxtaposed side by side in the axial direction of the core. The character-shaped iron oxide powder resin core 47 'covers the wire 22, the heater winding 23 and the iron oxide powder resin core 46', and the iron oxide powder resin core 46 'and the character-shaped iron oxide powder resin core 47'. A gap G is secured between the space and Iron oxide powder resin core 46 '
The voids 47 and 47 'are about 0.3 to 0.8 mm.

With the above-mentioned structure, the main core 46 'and the auxiliary core (square-shaped core) 47' are formed by the iron oxide powder resin core which has less high frequency loss and is smaller in size and less likely to be saturated than the ferrite core. Therefore, compared with the conventional step-up transformer (FIG. 7) consisting only of a ferrite core, it contributes greatly to downsizing. Further, the mutually opposing portions of the iron oxide powder resin cores 46 'and 47' are parallel,
Since the gap G formed between them has the same width, the design of the coupling coefficient and the like becomes easy. Furthermore, iron oxide powder resin core 4
7'is a square shape, so the manufacturing is simple and the resin core 4
7'wraps each winding and each part from the outside of the iron oxide powder resin core 46 ', so that the mechanical protection of each winding is also effective.

FIG. 5 is a diagram showing a step-up transformer according to a fourth embodiment of the present invention. (A) is a front view, (b) is a plan view, (c) is a side view, and (d) is a perspective view. It is a figure. In the figure, 50 is a step-up transformer according to the fourth embodiment,
Reference numeral 1 is a primary winding, 22 is a secondary winding, and 23 is a heater winding, which are the same as those in FIG. Reference numeral 56 denotes a rectangular parallelepiped-shaped ferrite core, which is surrounded by a primary winding 21, a secondary winding 22, and a heater winding 23, and is arranged side by side in the axial direction of the core. 27 is an iron oxide powder resin core, which is the same as that of FIG. That is, of the inner diameters of the square iron oxide powder resin core, one of the inner diameters (the inner diameter in the left-right direction of the iron oxide powder resin core 27 in FIG. 5C) is the primary winding 21, the secondary winding 22, and the heater. It is made larger than any of the outer diameters of the windings 23, and the inner diameter of the other winding (the inner diameter in the vertical direction of the iron oxide powder resin core 27 in FIG. 5C) is the primary winding 21 and the secondary winding. It is formed larger than the overlapping length of the three windings of 22 and the heater winding 23.

According to the fourth embodiment of the present invention, the protrusion 56a is formed on a part of the surface of the rectangular parallelepiped ferrite core 56 facing the iron oxide powder resin core 27. The height of the protrusion 56a is substantially the same as that of the gap G in FIG. Since the gap G to be ensured between the rectangular parallelepiped ferrite core 56 and the iron oxide powder resin core 27 can be secured by the protruding portion 56a, it is not necessary to use the spacer described in FIG. 2, and the spacer is separately prepared. Since it is not necessary to do so, the step of assembling it can be omitted, so that the step-up transformer can be easily assembled as well as the cost reduction. Further, the projecting portion 56a is designed to be saturated with a slight magnetic flux by selecting a small cross-sectional area in the passage direction of the magnetic path so that a magnetic short circuit is not formed. Further, in FIG. 5, one protruding portion 56a is formed at the center of the side surface of the rectangular parallelepiped ferrite core 56, but one protruding portion 56a is formed at each end of the side surface of the rectangular parallelepiped ferrite core 56, and oxidation is performed at two points. Iron powder resin core 2
It is also possible to improve the stability of the assembly by contacting with 7. Also, this protruding portion 56a
2 was carried out on the rectangular parallelepiped ferrite core 26 shown in FIG. 2, but the same can be carried out on the rod-shaped iron oxide powder resin core 46 shown in FIG. 4 (a).

FIG. 6 is a diagram showing a step-up transformer according to a fifth embodiment of the present invention. (A) is a front view, (b) is a plan view, (c) is a side view, and (d) is a perspective view. It is a figure. In the figure, reference numeral 60 denotes a step-up transformer according to the fifth embodiment, which is 2
1 is a primary winding, 22 is a secondary winding, 23 is a heater winding,
Reference numerals 64 and 65 are U-shaped iron oxide powder resin cores in which iron oxide powder is resin-sealed. Each winding 21, 22, 23 is the same as the corresponding part in FIG. That is, the primary winding 21 is the secondary winding 2
The winding cross section is large and the number of turns is small as compared with 2, and the number of turns of the heater winding 23 is extremely smaller than that of the secondary winding 22.
As shown in the figure, the U-shaped iron oxide powder resin cores 64 and 65 are arranged so that their U-shaped tips are opposed to each other with a gap G therebetween.
The primary winding 21 and the secondary winding 2 are provided on the core formed by the butting of one leg of the U-shaped iron oxide powder resin cores 64, 65.
2 and the heater winding 23 are arranged side by side in the axial direction. The void G between the iron oxide powder resin cores 64 and 65 is 0.3 to
It is about 0.8 mm.

With the above-described structure, the iron oxide powder resin cores 64 and 65, which have less high-frequency loss and are smaller in size and less likely to saturate than the ferrite core, form the entire core portion of the step-up transformer. Compared with the conventional step-up transformer (FIG. 7) consisting of only one, it contributes to downsizing.

[0028]

As described above, according to the step-up transformer of the present invention,
Simplified manufacturing by using iron oxide powder resin sealed core that has less high frequency loss, is cheaper than ferrite core and can be miniaturized, and has saturation magnetic flux density characteristics higher than ferrite core, and also creates a gap to prevent saturation So small,
An inexpensive and robust step-up transformer can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetron drive power source using a step-up transformer, which is a target of the present invention.

FIG. 2 is a diagram showing a step-up transformer according to a first embodiment of the present invention, (a) is a front view, (b) is a plan view, and (c).
Is a side view, and (d) is a perspective view.

FIG. 3 is a diagram showing a step-up transformer according to a second embodiment of the present invention, (a) is a front view, (b) is a plan view, and (c).
Is a side view, and (d) is a perspective view.

FIG. 4 is a perspective view showing a step-up transformer according to a third embodiment of the present invention, where (a) is a first embodiment and (b) is a second embodiment.

5A and 5B are diagrams showing a step-up transformer according to a fourth embodiment of the present invention, where FIG. 5A is a front view, FIG. 5B is a plan view, and FIG.
Is a side view, and (d) is a perspective view.

FIG. 6 is a diagram showing a step-up transformer according to a fifth embodiment of the present invention, where (a) is a front view, (b) is a plan view, and (c).
Is a side view, and (d) is a perspective view.

FIG. 7 is a diagram showing a conventional step-up transformer using a ferrite core.

[Explanation of symbols]

11 Commercial Power Supply 12 Magnetron 122 Anode 121 Cathode 13 Rectifier Circuit 14 Choke Coil 15 Filter Capacitor 16 Inverter 161 Inverter Control Circuit 17 CT 18 Boost Transformer 181 Primary Winding 182 Secondary Winding 183 Filament Heating Winding 19 Double Voltage Half Wave Rectifier circuit 191 High-voltage capacitors 192, 193 High-voltage diode 20 Step-up transformer 21 Primary winding 22 Secondary winding 23 Heater winding 26 Rectangular parallelepiped-shaped ferrite core 27 Square-shaped iron oxide powder resin core 30 Step-up transformer 36 according to the second embodiment Cylindrical ferrite core 37 Iron oxide powder resin core 40, 40 'Step-up transformer 46 according to the third embodiment Rectangular solid iron oxide powder resin core 46' Cylindrical iron oxide powder resin Core 47, 47 'Mouth with iron oxide powder sealed with resin V-shaped iron oxide powder resin core 50 Step-up transformer 56 according to the fourth embodiment Rectangular parallelepiped-shaped ferrite core 56a Projection portion 60 Step-up transformers 64 and 65 according to the fifth embodiment U-shaped iron oxide powder resin core G Void

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Kitazumi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 3K090 AA04 BA01 BB01 EB11

Claims (9)

[Claims] 1. A step-up transformer for supplying a driving voltage to a magnetron, wherein a primary winding and a secondary winding each surround a rod-shaped ferrite core, and a step-up transformer for driving a magnetron, wherein iron oxide powder is resin-sealed. In the state in which the square-shaped iron oxide powder resin core is inserted from the outside of the primary winding and the secondary winding toward the rod-shaped ferrite core and is opposed to the rod-shaped ferrite core with a gap. A step-up transformer for driving a magnetron, which is characterized in that 2. A step-up transformer for supplying a drive voltage to a magnetron, wherein a primary winding and a secondary winding surround a rod-shaped ferrite core and are stacked side by side in the axial direction of the rod-shaped ferrite core. A step-up transformer for use in an iron oxide powder resin core sealed with iron oxide powder, the inner diameter of which is larger than the outer diameter of either the primary winding or the secondary winding Of the iron oxide powder resin core, the inner diameter of the other of which is formed larger than the overlapping length of the primary winding and the secondary winding, from the outside of the primary winding and the secondary winding toward the rod-shaped ferrite core. A step-up transformer for driving a magnetron, wherein the step-up transformer is in a state of being inserted and is opposed to the rod-shaped ferrite core with a gap. 3. The step-up transformer for driving a magnetron according to claim 1, wherein the rod-shaped ferrite core has a rectangular parallelepiped shape. 4. A step-up transformer for supplying a drive voltage to a magnetron, wherein a primary winding and a secondary winding surround a rod-shaped ferrite core and are arranged side by side in the axial direction of the rod-shaped ferrite core. A step-up transformer for use in an iron oxide powder resin core sealed with iron oxide powder, the inner diameter of which is larger than the outer diameter of either the primary winding or the secondary winding The other inner diameter of the rod-shaped ferrite core is formed to be larger than the length of the rod-shaped ferrite core, and the rod-shaped ferrite core is inserted into the resin-shaped iron oxide powder resin core. A step-up transformer for driving a magnetron, wherein the step-up transformer is opposed to the iron oxide powder resin core with a gap therebetween. 5. The step-up transformer for driving a magnetron according to claim 4, wherein the rod-shaped ferrite core has a cylindrical shape. 6. The magnetron driving booster according to claim 1, wherein a rod-shaped iron oxide powder resin core in which iron oxide powder is resin-sealed is used in place of the rod-shaped ferrite core. Trance. 7. A protrusion is formed on a part of a surface of the rectangular parallelepiped core that faces the square iron oxide powder resin core,
The step-up transformer for driving a magnetron according to claim 3 or 6, wherein the projecting portion is brought into contact with the letter-shaped iron oxide powder resin core. 8. A step-up transformer for supplying a drive voltage to a magnetron, the step-up transformer for driving a magnetron having a primary winding and a secondary winding, wherein a U-shaped resin-sealed iron oxide powder is used. The two iron oxide powder resin cores are arranged so as to face each other with U-shaped tips spaced apart from each other, and the primary member is formed on the core formed by butting one leg portion of the two U-shaped iron oxide powder resin cores. A booster transformer for driving a magnetron, comprising a winding and a secondary winding. 9. A step-up transformer for supplying a drive voltage to a magnetron, the step-up transformer for driving a magnetron comprising a primary winding and a secondary winding, wherein a U-shaped resin-sealed iron oxide powder is used. The two iron oxide powder resin cores are arranged so as to face each other with U-shaped tips spaced apart from each other, and the primary member is formed on the core formed by butting one leg portion of the two U-shaped iron oxide powder resin cores. A step-up transformer for driving a magnetron, comprising a winding and a secondary winding arranged side by side in an axial direction.