CN111341541A

CN111341541A - Step-up transformer and microwave cooking appliance with same

Info

Publication number: CN111341541A
Application number: CN202010247511.9A
Authority: CN
Inventors: 増田愼一
Original assignee: Midea Group Co Ltd; Guangdong Midea Kitchen Appliances Manufacturing Co Ltd
Current assignee: Midea Group Co Ltd; Guangdong Midea Kitchen Appliances Manufacturing Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2020-06-26

Abstract

The invention discloses a step-up transformer and a microwave cooking appliance with the same, comprising: an insulated bobbin, a winding assembly, and a magnetic core. The bobbin is annular to surround the center hole, and an insulating partition plate is arranged in a tube cavity of the bobbin, so that a primary winding groove, a heating winding groove and a secondary winding groove are sequentially defined in the bobbin along the axial direction of the center hole. The winding assembly comprises a primary winding, a secondary winding and a heating winding, wherein the primary winding and the secondary winding are respectively wound in a primary winding groove and a secondary winding groove to form a whole block, the winding width of the primary winding is larger than the overlapping thickness of the primary winding, the winding width of the secondary winding is not more than 2/3 of the winding width of the primary winding, the heating winding is wound in the heating winding groove, and the mutual coupling coefficient of the primary winding and the secondary winding is 0.6-0.8. Magnetic gaps are formed in the central hole and the radial outer side of the bobbin for the two magnetic cores inserted on the bobbin. According to the booster transformer disclosed by the invention, the size can be reduced, and the production efficiency is improved.

Description

Step-up transformer and microwave cooking appliance with same

Technical Field

The invention belongs to the technical field of household appliances, and particularly relates to a step-up transformer and a microwave cooking appliance with the same.

Background

In general microwave cooking appliances, a step-up transformer is often used to perform step-up. However, the size of some step-up transformers is larger than the height and thickness thereof, which limits the application of the step-up transformer, and thus it is difficult to adapt to microwave cooking appliances with complicated internal structures. In some step-up transformers, the secondary winding is divided into 2-3 pieces, so that the width of the divided winding is shortened, large steps are not generated, but the assembly process is time-consuming, the production efficiency is low, and the winding management difficulty is high.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a step-up transformer to reduce the size and improve the production efficiency.

The invention also aims to provide a microwave cooking appliance with the step-up transformer.

The step-up transformer according to the embodiment of the present invention includes: the coil comprises an insulating bobbin, a first winding groove, a heating winding groove and a second winding groove, wherein the bobbin is annular to surround a central hole, an insulating partition plate is arranged in a tube cavity of the bobbin, so that a primary winding groove, the heating winding groove and the second winding groove are sequentially defined in the bobbin along the axial direction of the central hole, and the insulating partition plate separates the primary winding groove from the heating winding groove and the heating winding groove from the second winding groove; a winding assembly including a primary winding, a secondary winding and a heating winding for connecting a heater, wherein the primary winding is wound in the primary winding slot to form a whole block, the winding width of the primary winding is larger than the overlapping thickness of the primary winding, the secondary winding is wound in the secondary winding slot to form a whole block, the winding width of the secondary winding is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding is not more than 2/3 of the winding width of the primary winding, the heating winding is wound in the heating winding slot, and the mutual coupling coefficient of the primary winding and the secondary winding is 0.6-0.8; for two magnetic cores inserted on the bobbin, magnetic gaps are formed in the central hole and on the radial outer side of the bobbin by the two magnetic cores.

According to the boosting transformer of the embodiment of the invention, the primary winding is wound in the primary winding groove to form a whole block, the winding width of the primary winding is larger than the overlapping thickness of the primary winding, the secondary winding is wound in the secondary winding groove to form a whole block, the winding width of the secondary winding is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding does not exceed 2/3 of the winding width of the primary winding, the heating winding is wound in the heating winding groove, and the mutual coupling coefficient of the primary winding and the secondary winding is 0.6-0.8. Therefore, the winding width of the secondary winding, which has a large influence on the height of the step-up transformer, is reduced, and the high-voltage line is wired by eliminating the lead-in groove of the secondary winding and the winding groove dedicated for the heating winding, so that the total width of the step-up transformer can be reduced, and the application range of the step-up transformer can be expanded. In addition, only the secondary winding is set to a flat structure with a height of overlap larger than the width of the winding, so that the area of the primary winding and the secondary winding facing each other is not increased, and the magnetic coupling between the windings is mainly determined by the influence of the magnetic core, so that the coupling ratio between the windings can be easily adjusted, the structural design of the step-up transformer is easy, and the long development period can be eliminated.

In some embodiments, the core is U-shaped in cross-section in the plane of the axis.

Specifically, the magnetic gaps at both ends of the magnetic core are located between the axial ends of the primary winding.

In some embodiments, the two cores are equal in size.

In some embodiments, an inner spacer is disposed on the bobbin within the central bore, and one end of each of the two magnetic cores abuts against the inner spacer.

In some embodiments, the bobbin is open radially outward for winding wire, the step-up transformer further comprising a cover at least partially covering a lumen of the bobbin.

Specifically, an outer spacer is arranged on the cover part and positioned outside the tube cavity, and the other ends of the two magnetic cores are abutted to the outer spacer.

In some embodiments, two of the magnetic cores are fixedly connected by an adhesive.

In some embodiments, the primary winding slot and the heating winding slot are separated by only one layer of the insulating partition, and the heating winding slot and the secondary winding slot are separated by only one layer of the insulating partition.

The microwave cooking appliance comprises the boosting transformer and the microwave generator, wherein the boosting transformer is connected with the microwave generator, and the microwave generator is connected with the boosting transformer.

According to the microwave cooking appliance, the primary winding is wound in the primary winding groove to form a whole block, the winding width of the primary winding is larger than the overlapping thickness of the primary winding, the secondary winding is wound in the secondary winding groove to form a whole block, the winding width of the secondary winding is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding does not exceed 2/3 of the winding width of the primary winding, the heating winding is wound in the heating winding groove, and the mutual coupling coefficient of the primary winding and the secondary winding is 0.6-0.8. Therefore, the winding width of the secondary winding which has great influence on the height of the step-up transformer is reduced, and the high-voltage wire distribution is performed by eliminating the leading-in groove of the secondary winding and the winding groove special for the heating winding, thereby improving the convenience of being installed on the microwave cooking appliance. In addition, only the secondary winding is set to be a flat structure with a larger overlapping height than winding width, the area of the primary winding and the secondary winding facing each other is not increased, the magnetic coupling between the windings is mainly determined by the influence of the magnetic core, so that the coupling ratio between the windings can be easily adjusted, the structural design of the microwave cooking appliance is easy, and the long development period can be eliminated.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural diagram of a step-up transformer according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a step-up transformer according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a step-up transformer according to the related art;

FIG. 4 is a schematic diagram of another step-up transformer in the related art;

FIG. 5 is a schematic diagram of a structure of a further step-up transformer in the related art;

FIG. 6 is a schematic diagram of the overlapping state of the secondary windings in the embodiment of the present invention;

FIG. 7 is a circuit diagram of a microwave cooking appliance in an embodiment of the present invention;

FIG. 8 is an equivalent circuit diagram of a microwave cooking appliance in an embodiment of the present invention;

fig. 9 is a graph showing a change in current (Ib) -voltage (Eb) characteristics of the magnetron in the embodiment of the present invention.

Reference numerals:

microwave cooking appliance 1000,

A step-up transformer 100,

A primary winding 1, a secondary winding 2, a heating winding 3, a magnetic core 4, a first magnetic core 4A, a second magnetic core 4B, a magnetic gap 5, a bobbin 6, an insulating partition 61, a center hole 62, a cover 7, a secondary winding introduction groove 8,

A power supply unit 10, a power conversion unit 11, a double voltage rectifier circuit 13, a commercial power supply 20, a rectifier 21, an inductor 22, a capacitor 23, a capacitor 24, a semiconductor device 25, a diode 26, a current detection device 27, a control unit 28, and a magnetron 29.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "inner", "outer", "vertical", "horizontal", "axial", "radial", and the like, indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, are used only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The step-up transformer 100 according to the embodiment of the present invention is described below with reference to the drawings.

As shown in fig. 1 and 2, the step-up transformer 100 according to the embodiment of the present invention includes: an insulated bobbin 6, a winding assembly and a magnetic core 4. The bobbin 6 is annular to surround the central hole 62, and an insulating partition 61 is arranged in the cavity of the bobbin 6, so that a primary winding groove, a heating winding groove and a secondary winding groove are defined in the bobbin 6 in sequence along the axial direction of the central hole 62, and the insulating partition 61 separates the primary winding groove from the heating winding groove and the heating winding groove from the secondary winding groove. The winding assembly comprises a primary winding 1, a secondary winding 2 and a heating winding 3 for connecting a heater, wherein the primary winding 1 is wound in a primary winding groove to form a whole block, the winding width of the primary winding 1 is larger than the overlapping thickness of the primary winding, the secondary winding 2 is wound in a secondary winding groove to form a whole block, the winding width of the secondary winding 2 is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding 2 is not more than 2/3 of the winding width of the primary winding 1, the heating winding 3 is wound in a heating winding groove, and the mutual coupling coefficient of the primary winding 1 and the secondary winding 2 is 0.6-0.8. For the two cores 4 inserted into the bobbin 6, the magnetic gaps 5 are formed in the center hole 62 and radially outside the bobbin 6 of the two cores 4.

In a specific example, the booster transformer 100 is used in a high-frequency heating apparatus having a structure in which a dc voltage obtained by rectifying a commercial ac power supply by a flyback circuit is converted into a high-frequency voltage, boosted by the booster transformer 100, and then supplied to a magnetron.

As shown in the drawing, the winding width and the overlapping thickness of the primary winding 1 are denoted by W1 and H1, respectively, and the winding width and the overlapping thickness of the secondary winding 2 are denoted by W2 and H2, respectively. In the step-up transformer 100, the respective winding groups and the magnetic bodies need to be insulated from each other, and in order to perform such insulation, the insulating bobbin 6 and the insulating spacer 61 are provided as shown in fig. 1 and 2. That is, the insulating bobbin 6 and the insulating partition 61 insulate the primary winding 1, the secondary winding 2, and the heating winding 3 from each other. The magnetic gap 5 is arranged to be easily adjustable so that the magnetic permeability is consistent with the operating state of the circuit.

The general step-up transformer has a structure as shown in fig. 3 to 5. For example, in the step-up transformer shown in fig. 3, the winding assembly includes a primary winding 1, a secondary winding 2, and a heating winding 3, and two magnetic cores 4 sandwich a magnetic gap 5 to constitute a magnetic body for a magnetic circuit in which these windings are combined. The respective windings are arranged on an insulated bobbin 6. The relationship between the width (W1) of the primary winding 1 and the overlap height (H1) of the primary winding 1 is W1 ≧ H1, and the secondary winding 2 has the same relationship. Therefore, the size of the step-up transformer 100 is larger than the height and thickness, which limits the application range of the step-up transformer 100, and the step-up transformer shown in fig. 3 is a key for determining the mounting position on the high-frequency heating apparatus because the high-frequency heating apparatus is complicated, high-voltage wiring is required, and the internal structure is complicated.

In addition, in the related art, the secondary winding 2 generating a high voltage is generally divided into 2 to 3 blocks by the insulating partition 61, and as shown in fig. 3, the secondary winding 2 is divided into 3 blocks by the insulating partition 61, which is a factor causing an increase in the height of the step-up transformer. In addition, in the process of assembling the step-up transformer, the secondary winding 2 is divided into 2 to 3 pieces in the secondary winding 2, so that the rotation of the winding machine needs to be stopped temporarily when the winding moves. In addition, when the winding wire is guided to another position, the winding wire is slowly operated without damaging the winding wire, which results in a large loss in processing time.

However, when the winding width of the secondary winding 2 is large and is not divided, the following problem occurs. In general, the secondary winding 2 is applied with a high voltage, and the maximum instantaneous voltage applied from the start of winding to the completion of winding is 6KV to 10 KV. When the secondary winding 2 is assembled, as shown in fig. 6, the secondary winding 2 is wound around the bobbin 6 in the direction of the arrow, is gradually overlapped, and is wound for a predetermined number of windings. When the secondary winding 2 is formed by this method, the secondary winding 2 cannot be formed in an aligned state without necessity in terms of processing, and a stepped portion may occur.

When the secondary winding 2 is formed in this way, as shown in fig. 6, first, it is assumed that the winding start time is L1, the turn-back points of the winding are set to L2 and L3 in this order, and the winding end point is L9. In this case, when the secondary winding 2 is formed in the aligned state, the winding at the L10 position is connected to the winding at the L8 position. However, when the winding at the winding end point L10 produces a step, the stepped winding is processed so as to be adjacent to the winding at the L6 or L4 position. The step is generated by adding a voltage 2 to 3 times the number of steps to be generated in proportion to the number of steps to be generated, as compared with the voltage applied when the entire array is formed.

That is, the secondary winding 2 is divided into 2 to 3 pieces to form the winding, and the winding width (W2) after division is shortened so that a large step is not generated, thereby reducing the voltage applied when the step is generated. However, the assembly process is time-consuming and the production efficiency is low. If the insulating spacer may be a resin plate, the inclination of the plate wall during molding makes it difficult to arrange the windings in order. If cut apart into the polylith, the slope of siding wall is always corrected with the tool, is difficult to carry out wire winding processing, and the width in groove is narrower, is difficult to control the wire winding position, and the equipment degree of difficulty is high.

In the step-up transformer 100 according to the embodiment of the present invention, the primary winding 1 is wound in the primary winding slot to form a whole block, the winding width of the primary winding 1 is larger than the overlapping thickness thereof, the secondary winding 2 is wound in the secondary winding slot to form a whole block, the winding width of the secondary winding 2 is smaller than the overlapping thickness thereof, and the heating winding 3 is wound in the heating winding slot. Thereby, the winding width W2 of the secondary winding 2 is reduced, the overlapping thickness H2 of the secondary winding 2 is increased, the winding shape becomes a flat shape, and the width of the booster transformer 100 is reduced without changing the total cross-sectional area of the windings, so that the range of use of the booster transformer 100 can be expanded, which is easy to be mounted on other equipment such as the inside of a high-frequency heating apparatus. In addition, since the thickness of the secondary winding 2 is reduced, even if the secondary winding 2 is not divided, the voltage applied to each layer of the winding is further reduced, and the management of the winding process becomes easy, for example, the winding process can be performed while mounting the correction jig on the outer surfaces of the plate walls on both sides. When the secondary winding 2 of high voltage is applied to the winding, the potential difference generated between the windings can be reduced. In addition, the management of preventing the winding damage is easy to be carried out through the simplification of the processing technology. As a result, insulation breakdown between the windings is less likely to occur, and the cause of breakdown in the insulation of the windings due to the step of the windings in the winding process of step-up transformer 100, which is caused by the application of a high voltage to the stepped windings, can be reduced, thereby making it possible to improve the reliability of step-up transformer 100.

In the step-up transformer 100 shown in fig. 4, the winding assembly includes a primary winding 1, a secondary winding 2, and a heating winding 3, and the magnetic gap 5 is sandwiched between two magnetic cores 4 to constitute a magnetic body for a magnetic circuit in which these windings are combined. The respective windings are also arranged on the insulating bobbin 6. The relationship between the width (W1) of the primary winding 1 and the overlap height (H1) of the primary winding 1 is W1 < H1, and the secondary winding 2 has the same relationship. The secondary winding 2 is formed in one piece as 1, and the loss in processing time is reduced, but the relative area between the primary winding 1 and the secondary winding 2 is increased, and therefore, the coupling ratio, which is an important characteristic in designing the magnetic flux leakage type insulation transformer, has a structural influence larger than the influence of the magnetic core 4. The distance adjustment of the magnetic gap 5 causes little change in the coupling ratio, and the distance between the blocks of the primary winding 1 and the secondary winding 2 mainly affects the coupling ratio, so that the design is difficult, and the development cycle is likely to be long.

The step-up transformer 100 according to the embodiment of the present invention has the above advantages of being compact and reducing the magnetic coupling without passing through the magnetic core 4 between the windings, so that the degree of magnetic coupling between the windings can be easily adjusted by the distance of the magnetic gap 5 of the magnetic core 4, and the coupling coefficient between the primary winding 1 and the secondary winding 2 can be controlled to be 0.6 to 0.8, for example. This simplifies the structural design of the step-up transformer 100, and improves the efficiency during development. The degree of magnetic coupling is an important characteristic of the step-up/step-up transformer 100 for a high-frequency heating apparatus using a magnetron as a load.

In the step-up transformer 100 shown in fig. 5, the relationship between the width W1 of the primary winding 1 and the overlapping thickness H1 of the primary winding 1 is set to W1 > H1, and the relationship between the winding width W2 and the overlapping thickness H2 of the secondary winding 2 is set to W2 < H2, whereby the width of the step-up transformer 100 is reduced, the degree of coupling between the primary winding 1 and the secondary winding 2 can be easily designed, and the winding process of the secondary winding 2 can be simplified. However, the width of the step-up transformer 100 is increased, and the application range of the step-up transformer 100 is also easily limited, and for example, the high-frequency heating apparatus is complicated, high-voltage wiring is required, and the internal structure is complicated.

In the step-up transformer 100 according to the embodiment of the present invention, the heating winding 3 is disposed between the primary winding 1 and the secondary winding 2, and the secondary winding introduction slot is omitted, whereby the width of the step-up transformer 100 is further reduced, and the relationship between the width W1 of the primary winding 1 and the width W2 of the secondary winding 2 is set to W1 ≦ 2/3 × W1, whereby the position of the magnetic gap 5 of the core 4 can be easily disposed.

According to the step-up transformer 100 of the embodiment of the invention, the primary winding 1 is wound in the primary winding groove to form a whole block, the winding width of the primary winding 1 is larger than the overlapping thickness, the secondary winding 2 is wound in the secondary winding groove to form a whole block, the winding width of the secondary winding 2 is smaller than the overlapping thickness, the winding width of the secondary winding 2 is not more than 2/3 of the winding width of the primary winding 1, the heating winding 3 is wound in the heating winding groove, and the mutual coupling coefficient of the primary winding 1 and the secondary winding 2 is 0.6-0.8. Accordingly, the winding width of the secondary winding 2, which greatly affects the height of the step-up transformer 100, is reduced, and the application range of the step-up transformer 100 can be expanded by eliminating the lead-in groove of the secondary winding 2 and the winding groove dedicated to the heating winding 3 and performing high voltage wire wiring, and thus, the step-up transformer 100 can be applied to a high frequency heating apparatus having a complicated structure. Further, only by setting the secondary winding 2 to have a flat structure in which the overlapping height is larger than the winding width, the area of the primary winding 1 facing the secondary winding 2 is not increased, and the magnetic coupling between the windings is mainly determined by the influence of the core 4, so that the coupling ratio between the windings can be easily adjusted, the structural design of the step-up transformer 100 is easy, and the long development period can be eliminated.

In some embodiments, as shown in fig. 1 and 2, the core 4 has a U-shaped cross-section in the plane of the axis. Thus, the magnetic core 4 has the advantages of small impedance deviation, large output current, capability of suppressing higher harmonics and the like, and is beneficial to improving the performance of the step-up transformer 100. Optionally, the core 4 is a ferrite core.

Of course, in other embodiments, the magnetic core 4 may be another type of magnetic core 4, and the type of the magnetic core 4 is not particularly limited.

Specifically, as shown in fig. 1 and 2, the magnetic gap 5 at both ends of the magnetic core 4 is located between both ends in the axial direction of the primary winding 1, that is, the magnetic gap 5 is located at a position not exceeding the range of the winding width W1 of the primary winding 1. Therefore, the leakage inductance of the secondary winding 2 can be reduced, the leakage inductance of the primary winding 1 is increased, and the optimal design is facilitated.

In some embodiments, as shown in fig. 1, the two magnetic cores 4 have the same size, so that the two magnetic cores 4 are completely symmetrical to each other by being inserted into the bobbin 6, and the magnetic gap 5 is approximately located at a middle position in the width direction (i.e. axial direction) of the entire bobbin 6, thereby facilitating the universal production of the magnetic cores 4, and facilitating the improvement of efficiency and the reduction of cost.

As shown in the characteristic example of fig. 9, the current-voltage characteristic of the magnetron is that the current fluctuates drastically due to the voltage fluctuation. For stabilization of the magnetron current, it is necessary to have a large leakage inductance on the secondary side of the booster transformer 100. In this case, the primary side leakage inductance is minimized due to the relationship of the primary side resonance voltage control, but is optimized. As shown in an equivalent circuit of the step-up transformer 100 of the high-frequency heating apparatus of fig. 8, L12 is a leakage inductance of the secondary side, and L11 is a leakage inductance of the primary side.

Thus, in order to optimize the leakage inductance design of step-up transformer 100, two types of cores 4 having different sizes can be used in common to form two cores 4 having the same size, which contributes to improvement in production efficiency, component management, and cost reduction.

Alternatively, as shown in fig. 2, the magnetic core 4 may include a first magnetic core 4A and a second magnetic core 4B, and the sizes of the first magnetic core 4A and the second magnetic core 4B may also be different, in which case, the first magnetic core 4A and the second magnetic core 4B may be of one kind. I.e. for optimizing the leakage inductance design, two sizes of cores 4 may be required, but one kind of correspondence may be used.

In the configuration shown in fig. 4, when the two cores are made to have the same size, the magnetic gap 5 of the core 4 cannot be set within the winding width of the primary winding 1, and therefore the leakage inductance on the primary winding 1 side increases. Therefore, the leakage inductance of the secondary winding 2 is increased and the leakage inductance of the primary winding 1 is decreased, resulting in failure to optimize the design. To optimize the design, two types of cores 4 may be used. To optimize the leakage inductance design, 2 sizes of cores 4 are required, but 1 type correspondence may be used.

In some embodiments, as shown in fig. 1 and 2, an internal spacer is provided on the bobbin 6 within the central bore 62, against which one end of each of the two cores 4 rests. It should be noted that, the two magnetic cores 4 generate eddy current loss during the process of alternating magnetization, and the magnetic gap 5 is beneficial to reduce the eddy current loss. In the present embodiment, since the two magnetic cores 4 of the present embodiment are stopped against the inner spacer to form the magnetic gap 5 at a spacing, it is advantageous to reduce the eddy current loss.

In some embodiments, as shown in fig. 1 and 2, the bobbin 6 is open on the radially outer side for winding, and the booster transformer 100 further includes a cover 7, the cover 7 at least partially covering the lumen of the bobbin 6. The provision of the cover portion 7 thereby contributes to the improvement of the mounting stability of the two magnetic cores 4. In addition, the cover 7 at least partially covers the lumen of the bobbin 6, also contributing to the cleanliness of the riser lumen.

Specifically, as shown in fig. 1 and 2, an outer spacer is provided on the cover 7 outside the lumen, and the other ends of the two magnetic cores 4 are stopped against the outer spacer. Whereby the other ends of both magnetic cores 4 are stopped against the outer spacer to form the magnetic gap 5 at a spacing, which is advantageous in reducing eddy current loss.

In some embodiments, the two magnetic cores 4 are fixedly connected by an adhesive. This improves the stability of mounting the two cores 4 and improves the stability of the operation of the step-up transformer 100.

In some embodiments, as shown in fig. 1 and 2, the primary winding slot and the heating winding slot are separated by only one layer of insulating barrier 61, and the heating winding slot and the secondary winding slot are separated by only one layer of insulating barrier 61. This is advantageous in further reducing the width of the booster transformer 100, thereby facilitating the assembly of the booster transformer 100, as the booster transformer 100 can be easily adapted to a high-frequency heating apparatus or the like.

A step-up transformer 100 in one embodiment of the invention is described below with reference to fig. 1.

The booster transformer 100 according to the embodiment of the present invention includes: an insulating bobbin 6, a winding assembly, a magnetic core 4 and a cover 7.

The bobbin 6 is annular to surround the central hole 62, and an insulating partition 61 is arranged in the cavity of the bobbin 6, so that a primary winding groove, a heating winding groove and a secondary winding groove are defined in the bobbin 6 in sequence along the axial direction of the central hole 62, the primary winding groove and the heating winding groove are separated by only one layer of insulating partition 61, and the heating winding groove and the secondary winding groove are separated by only one layer of insulating partition 61. An internal spacer is provided on the bobbin 6 within the central bore 62 and one end of each of the two cores 4 rests against the internal spacer.

The winding assembly comprises a primary winding 1, a secondary winding 2 and a heating winding 3 for connecting a heater, wherein the primary winding 1 is wound in a primary winding groove to form a whole block, the winding width of the primary winding 1 is larger than the overlapping thickness of the primary winding, the secondary winding 2 is wound in a secondary winding groove to form a whole block, the winding width of the secondary winding 2 is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding 2 is not more than 2/3 of the winding width of the primary winding 1, the heating winding 3 is wound in a heating winding groove, and the mutual coupling coefficient of the primary winding 1 and the secondary winding 2 is 0.6-0.8.

For the two cores 4 inserted into the bobbin 6, the magnetic gaps 5 are formed in the center hole 62 and radially outside the bobbin 6 of the two cores 4. The two magnetic cores 4 are fixedly connected by the adhesive, and the two magnetic cores 4 are equal in size. The magnetic core 4 has a U-shaped cross section on the plane of the axis, and the magnetic gaps 5 at both ends of the magnetic core 4 are located between the two axial ends of the primary winding 1.

The cap 7 at least partially covers the lumen of the bobbin 6. An outer spacing piece is arranged on the cover part 7 and positioned outside the tube cavity, and the other ends of the two magnetic cores 4 are abutted against the outer spacing piece.

A microwave cooking appliance 1000 in an embodiment of the present invention is described below with reference to the accompanying drawings.

The microwave cooking appliance 1000 according to the embodiment of the present invention includes the step-up transformer 100 according to the above-described embodiment of the present invention and a microwave generator connected to the step-up transformer 100.

According to the microwave cooking appliance 1000 of the embodiment of the invention, the primary winding 1 is wound in the primary winding groove to form a whole block, the winding width of the primary winding 1 is larger than the overlapping thickness of the primary winding 1, the secondary winding 2 is wound in the secondary winding groove to form a whole block, the winding width of the secondary winding 2 is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding 2 is not more than 2/3 of the winding width of the primary winding 1, the heating winding 3 is wound in the heating winding groove, and the mutual coupling coefficient of the primary winding 1 and the secondary winding 2 is 0.6-0.8. Accordingly, the winding width of the secondary winding 2, which greatly affects the height of the step-up transformer 100, is reduced, and the convenience of installation in the microwave cooking appliance can be improved by eliminating the introduction groove of the secondary winding 2 and the winding groove dedicated to the heating winding 3 and performing high-voltage wire distribution. In addition, only the secondary winding 2 is set to a flat structure with a larger overlapping height than winding width, the area of the primary winding 1 and the secondary winding 2 facing each other is not increased, and the magnetic coupling between the windings is mainly determined by the influence of the magnetic core 4, so that the coupling ratio between the windings can be easily adjusted, the structural design of the microwave cooking appliance is easy, and the long-term development period can be eliminated.

Optionally, the heating winding 3 of the step-up transformer 100 is connected to the microwave generator, so that power can be supplied to the microwave generator.

Specifically, the microwave generator may be a magnetron. A magnetron is an electric vacuum device used to generate microwave energy. Electrons in the magnetron interact with a high-frequency electromagnetic field under the control of a constant magnetic field and a constant electric field which are vertical to each other, and energy obtained from the output power of the transformer is converted into microwave energy, so that the aim of generating the microwave energy is fulfilled.

Alternatively, fig. 7 shows an example of a circuit diagram of a microwave cooking appliance 1000 using the step-up transformer of the present invention. Fig. 7 shows a power supply portion 10 of the circuit, which rectifies a commercial power supply 20 by a rectifier 21 and smoothes the power supply by a coil 22 and a capacitor 23. The power conversion unit 11 is constituted by: a frequency conversion circuit including a semiconductor device 25 for converting the power supplied from the power supply unit 10 into high-frequency power, a diode 26, a step-up transformer 100, and a capacitor 24; a voltage doubling rectifying circuit, which is composed of a boosting transformer 100, a capacitor and a diode; a magnetron 29 for converting the high-voltage rectified power into a high frequency; and a control unit 28 for controlling the entire microwave cooking appliance while ON/OFF-controlling the semiconductor component 25.

Other constructions, such as circuit boards, etc., and operations of the microwave cooking appliance according to the embodiments of the present invention are known to those skilled in the art and will not be described in detail herein.

In the description herein, references to the description of the terms "embodiment," "example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A step-up transformer, comprising:

the coil comprises an insulating bobbin, a first winding groove, a heating winding groove and a second winding groove, wherein the bobbin is annular to surround a central hole, an insulating partition plate is arranged in a tube cavity of the bobbin, so that a primary winding groove, the heating winding groove and the second winding groove are sequentially defined in the bobbin along the axial direction of the central hole, and the insulating partition plate separates the primary winding groove from the heating winding groove and the heating winding groove from the second winding groove;

a winding assembly including a primary winding, a secondary winding and a heating winding for connecting a heater, wherein the primary winding is wound in the primary winding slot to form a whole block, the winding width of the primary winding is larger than the overlapping thickness of the primary winding, the secondary winding is wound in the secondary winding slot to form a whole block, the winding width of the secondary winding is smaller than the overlapping thickness of the secondary winding, the winding width of the secondary winding is not more than 2/3 of the winding width of the primary winding, the heating winding is wound in the heating winding slot, and the mutual coupling coefficient of the primary winding and the secondary winding is 0.6-0.8;

for two magnetic cores inserted on the bobbin, magnetic gaps are formed in the central hole and on the radial outer side of the bobbin by the two magnetic cores.

2. A step-up transformer according to claim 1, wherein said core has a U-shaped cross section in a plane of said axis.

3. A step-up transformer according to claim 2, wherein said magnetic gaps at both ends of said magnetic core are located between both axial ends of said primary winding.

4. A step-up transformer according to claim 1, characterised in that the two cores are of equal size.

5. A step-up transformer according to claim 1, wherein an inner spacer is provided on said bobbin in said central hole, and one end of each of said two cores abuts against said inner spacer.

6. A step-up transformer according to claim 1, wherein said bobbin is open on a radially outer side for winding a wire, said step-up transformer further comprising a cover portion at least partially covering a lumen of said bobbin.

7. A step-up transformer according to claim 6, characterised in that an outer spacer is provided on the cover outside the tube cavity, and the other ends of the two cores are stopped against the outer spacer.

8. A step-up transformer according to claim 1, characterised in that said two magnetic cores are fixedly connected by an adhesive.

9. A step-up transformer according to any one of claims 1 to 8, characterised in that the primary winding slot and the heating winding slot are separated by only one layer of said insulating barrier, and the heating winding slot and the secondary winding slot are separated by only one layer of said insulating barrier.

10. Microwave cooking appliance, characterized in that it comprises a step-up transformer according to any of claims 1 to 9 and a microwave generator connected to said step-up transformer.