JP2005223125A - Step-up transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a step-up transformer of which insulation of a secondary coil is assured while a low profile at mounting is possible with ease of assembly. <P>SOLUTION: Since the direction of a winding axis of a primary coil and a secondary coil wound on magnetic legs 2C-2F is parallel to a mounting plane, a step-up transformer 1 becomes a low profile. The secondary coil is wound on the magnetic leg independent of the primary coil, so the length required for divided winding is assured. A main core 2 can employ the core of simple form such as U-shape and I-shape, and the primary coil wound on the main core 2 can employ a thin wire material, resulting in an easy assembly work. Further, since the lower part of an I-type core 3 is a low potential side at the output on the secondary side, wiring is allowed also at the lower part of the I-type core 3, improving flexibility in wiring with a substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a step-up transformer, and more particularly to a step-up transformer capable of multiple outputs.

  In recent years, a liquid crystal display device with a backlight is often used as a display device. A cold cathode tube is used for a backlight which is a light source of a liquid crystal display device. In order to drive the cold cathode tube, it is necessary to apply a high-voltage AC voltage to the cold cathode tube. In order to apply a high-voltage AC voltage to the cold cathode tube, an inverter (DC / AC converter) that converts a low-voltage DC voltage supplied from an input power source into a high-voltage AC voltage is required. One of the electronic components constituting the inverter is a step-up transformer that outputs a high voltage to be applied to a cold cathode tube.

As the display device becomes larger, it is necessary to simultaneously turn on the cold cathode tubes by applying a high voltage to a plurality of cold cathode tubes. If a step-up transformer is provided for each cold cathode tube, the area of the circuit board increases, so a step-up transformer capable of multiple outputs is employed. As an example of a step-up transformer capable of multiple outputs, in Japanese Patent Laid-Open No. 2001-126937 (Patent Document 1), two magnetic legs for secondary winding are provided on a core, and 2 wound around each magnetic leg. An example of a step-up transformer in which a high voltage is taken from the next winding is disclosed.
JP 2001-126937 A

  As display devices become thinner, electronic components mounted on a circuit board are required to have a low profile. Since a high voltage is output from the secondary winding, it is necessary to ensure electrical insulation between the high-voltage portion and the low-voltage portion in the secondary winding. As a method for ensuring electrical insulation, there is a method in which the secondary winding is divided into a plurality of winding portions via a partition portion so that the distance between the winding portions is as large as possible. Such a winding method is hereinafter referred to as divided winding.

  Although it is possible to ensure the electrical insulation of the secondary winding by a winding method other than split winding, the winding method in this case is more complicated than split winding. A complicated winding method is a factor that reduces workability. Therefore, split winding is excellent both in terms of securing electrical insulation and in winding work.

  A bobbin for dividing and winding the secondary winding needs to have a partition for dividing the winding. The thickness of the partition portion of the bobbin is set so as to ensure electrical insulation, and the number is set so as to minimize the potential difference between the winding portions. Since the bobbin is lengthened by providing the partition portion on the bobbin, it is necessary to lengthen the magnetic leg on which the bobbin is mounted according to the length of the bobbin. Therefore, the step-up transformer disclosed in Patent Document 1 has a problem that it is difficult to cope with a reduction in height if split winding is employed.

  Moreover, the step-up transformer disclosed in Patent Document 1 includes one primary winding corresponding to two secondary windings. In order to supply power to the two secondary windings, a wire having a large wire diameter is used for the primary winding so that a large amount of current flows. However, when the wire diameter is increased, winding work becomes difficult and productivity is lowered.

  Furthermore, the step-up transformer disclosed in Patent Document 1 includes a core having a complicated shape. In order to cope with the reduction in height and size, a thin portion of the core is generated. Therefore, the step-up transformer disclosed in Patent Document 1 has a problem that it is weak against stress during thermal shock and mechanical stress. Moreover, productivity is reduced due to the complicated shape of the core.

  Furthermore, in the step-up transformer disclosed in Patent Document 1, the core is close to or in contact with the board mounting surface. In the case of a wiring pattern in which the substrate wiring passes through the lower part of the core, there is a possibility that electric discharge occurs between the core that is at a high potential during operation and the lower wiring. Therefore, in the step-up transformer disclosed in Patent Document 1, since the substrate wiring cannot be passed under the core, the substrate area increases.

  In summary, the present invention is a step-up transformer having a core that forms a first closed magnetic circuit and a second closed magnetic circuit that overlaps a part of the first closed magnetic circuit in a plane parallel to the mounting surface. Prepare.

  The core forms a first magnetic leg forming a first closed magnetic path, a second magnetic leg forming a first closed magnetic path and parallel to the first magnetic leg, and forming a second closed magnetic circuit. A third magnetic leg disposed coaxially with the central axis of one magnetic leg, and a fourth magnetic leg forming a second closed magnetic path and disposed coaxially with the central axis of the second magnetic leg; , And a central magnetic leg forming an overlapping portion of the first closed magnetic path and the second closed magnetic path.

  The step-up transformer further includes a first winding portion attached to the core so that the first closed magnetic circuit passes therethrough. The first winding part includes a first primary winding part wound around the first magnetic leg and a first secondary winding part wound around the second magnetic leg.

  The step-up transformer further includes a second winding portion attached to the core so that the second closed magnetic circuit passes therethrough. The second winding part includes a second primary winding part wound around the third magnetic leg and a second secondary winding part wound around the fourth magnetic leg.

  Preferably, the first secondary winding portion has a terminal to which a low potential is applied to the central magnetic leg side, and the second secondary winding portion has a terminal to which a low potential is applied to the central magnetic leg side. Have.

  Preferably, the first secondary winding portion includes a first bobbin having a partition portion that divides the first secondary winding portion, and the second secondary winding portion includes the second 2 It has the 2nd bobbin which has a partition part which divides the next winding part.

  Preferably, the core is an I-type core sandwiched between a pair of U-type cores and a pair of U-type cores whose openings are opposed to each other.

  Preferably, the core has a first auxiliary magnetic leg that lowers the magnetic coupling between the first magnetic leg and the second magnetic leg by generating a leakage magnetic flux in a space having one end portion opposed to the central magnetic leg. And a second auxiliary magnetic leg whose one end portion generates a leakage magnetic flux in a space facing the central magnetic leg to reduce the magnetic coupling between the third magnetic leg and the fourth magnetic leg.

  Preferably, the first primary winding portion has a first primary winding that generates magnetic flux in a first direction, and the second primary winding portion is opposite to the first direction. A second primary winding for generating magnetic flux in the second direction;

  The step-up transformer of the present invention enables a reduction in mounting height while ensuring the insulation of the secondary winding. Further, the step-up transformer of the present invention can be easily assembled. Furthermore, the step-up transformer of the present invention can increase the degree of freedom of wiring on the circuit board.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a three-view diagram of the step-up transformer according to the first embodiment. FIG. 1A is a plan view of the step-up transformer 1. FIG. 1B is a right side view of the step-up transformer 1. FIG. 1C is a bottom view of the step-up transformer 1.

  FIG. 2 is a diagram showing the plane and front of the main core 2 in FIG. FIG. 2A is a diagram showing a plane of the main core 2, and FIG. 2B is a diagram showing the front of the main core 2.

  The main core 2 includes U-shaped cores 2 </ b> A and 2 </ b> B and an I-shaped core 3. The U-type cores 2A and 2B are joined to both side surfaces of the I-type core 3 and fixed with an adhesive or varnish.

  FIG. 3 is a view of the U-shaped core 2A viewed from the X direction and the Y direction in FIG. FIG. 3A shows the U-shaped core 2A viewed from the X direction in FIG. FIG. 3B shows the U-shaped core 2A viewed from the Y direction in FIG.

  As shown in FIG. 1, the step-up transformer 1 includes a main core 2. The main core 2 includes a U-shaped core 2A that forms the main part of the first closed magnetic circuit, a U-shaped core 2B that forms the main part of the second closed magnetic circuit, the first closed magnetic circuit, and the second closed magnetic circuit. And an I-type core 3 forming an overlapping portion.

  The U-shaped core 2 </ b> A and the U-shaped core 2 </ b> B are arranged so as to face the opening and sandwich the I-shaped core 3. The U-type core 2A and the I-type core 3 form a first closed magnetic circuit, and the U-type core 2B and the I-type core 3 form a second closed magnetic circuit.

  The U-shaped core 2A includes a magnetic leg 2C around which the secondary winding is wound and a magnetic leg 2D around which the primary winding is wound. The magnetic leg 2C has a length sufficient to split the secondary winding.

  Further, when the step-up transformer 1 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. Therefore, the magnetic leg 2C and the magnetic leg 2D are arranged so as to be parallel to each other.

  The U-shaped core 2B includes a magnetic leg 2E around which the secondary winding is wound and a magnetic leg 2F around which the primary winding is wound. The magnetic leg 2E has a length sufficient to split the secondary winding.

  Similarly to the magnetic legs 2C and 2D, when the step-up transformer 1 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. And the magnetic legs 2F are arranged in parallel to each other.

  In the U-shaped core 2A, the magnetic leg 2C and the magnetic leg 2E are arranged on the X1-X2 axis in FIG. In the U-shaped core 2B, the magnetic leg 2D and the magnetic leg 2F are disposed on the X3-X4 axis in FIG.

  The step-up transformer 1 further includes a primary side bobbin 4 attached to the main core 2 and wound with a primary winding, and a secondary side bobbin 5 attached to the main core 2 and wound with a secondary winding. .

  The primary-side bobbin 4 includes a first primary winding bobbin 4A mounted on the magnetic leg 2D and a second primary winding bobbin 4B mounted on the magnetic leg 2F.

  The secondary bobbin 5 includes a first secondary winding bobbin 5A mounted on the magnetic leg 2C, a second secondary winding bobbin 5B mounted on the magnetic leg 2E, and a secondary winding. And a partition 5C for split winding.

  Note that one step-up transformer is constituted by the first primary winding wound around the first primary winding bobbin 4A and the first secondary winding wound around the first secondary winding bobbin 5A. The Similarly, another step-up transformer is formed by the second primary winding wound around the second primary winding bobbin 4B and the second secondary winding wound around the second secondary winding bobbin 5B. Composed.

  For convenience of explanation, hereinafter, the first primary winding bobbin 4A, the first primary winding, the first secondary winding bobbin 5A, and the first secondary winding are combined to form the first. This is called the winding part. The second primary winding bobbin 4B, the second primary winding, the second secondary winding bobbin 5B, and the second secondary winding are combined to form a second winding portion. Called.

  The primary side bobbin 4 further includes primary side terminals 6A to 6F. A terminal connected to the winding is selected from the primary side terminals 6A to 6F according to the winding method of the primary winding. For example, if the winding start position and the winding end position are the same, in the first winding portion, the primary terminals 6A and 6B are connected to the first primary winding, and the second winding portion. Then, the primary side terminals 6E and 6F are connected to the second primary winding. If the winding start position and winding end position are different, the primary side terminals 6B and 6C are connected to the first primary winding in the first winding section, and the second winding section is used in the second winding section. Primary side terminals 6E and 6D are connected to the second primary winding.

  Note that, in order to enhance the mounting stability, the primary side terminals 6A to 6F are all soldered on the circuit board regardless of the winding start and winding end positions.

  Secondary bobbin 5 further includes secondary terminals 7A to 7D. The secondary side terminal 7A is a terminal on the high potential side of the secondary voltage taken out from the first winding part, and the secondary side terminal 7B is a low potential of the secondary voltage taken out from the first winding part. This is the terminal on the side. Similarly, the secondary side terminal 7D is a terminal on the high potential side of the secondary voltage taken out from the second winding part, and the secondary side terminal 7C is the secondary voltage taken out from the second winding part. This is a terminal on the low potential side.

  The “high potential side” indicates the side where the absolute value of the secondary voltage is high, that is, the side where the secondary voltage is amplified. The “low potential side” indicates the side where the absolute value of the secondary voltage is low, that is, the side serving as a reference for the amplitude of the secondary voltage.

  The step-up transformer 1 is provided with a gap 8A for preventing discharge between the secondary terminal 7A and the core 2A. Similarly, the step-up transformer 1 includes a gap 8B that prevents discharge between the secondary terminal 7D and the core 2B, a gap 8C that prevents discharge between the primary terminal 6A and the core 2A, and 1 A gap 8D is provided to prevent discharge between the secondary terminal 6F and the core 2B.

  The step-up transformer of the first embodiment will be described in more detail. Since the winding axis directions of the primary winding and the secondary winding wound around the magnetic legs 2C to 2F are parallel to the mounting surface, the step-up transformer 1 is reduced in height. Since the secondary winding is wound around a magnetic leg independent of the primary winding, the length necessary for the split winding is ensured. A simple core such as U-type or I-type can be used for the main core 2, and a thin wire can be used for the primary winding wound around the main core 2, so that assembly work is facilitated. Further, since the lower part of the I-type core 3 is on the low potential side in the output on the secondary side, wiring is possible also in the lower part of the I-type core 3 and the degree of freedom of wiring on the substrate can be increased.

  Furthermore, in the step-up transformer according to the first embodiment, it is possible to eliminate interference between magnetic fluxes intersecting with two secondary windings by generating synchronized magnetic fluxes in opposite directions by the two primary windings. It is. By eliminating the interference, the first winding portion and the second winding portion can output a high voltage without affecting each other.

  Furthermore, in the step-up transformer of the first embodiment, terminals are provided on each of the primary bobbin 4 and the secondary bobbin 5. Compared with the case where all the terminals are provided on one bobbin, the positioning accuracy between the terminals and the wiring is more gradual in the mounting, which facilitates the mounting operation.

  In FIG. 2, U-type cores 2 </ b> A and 2 </ b> B and an I-type core 3 are shown as examples of the main core 2. However, the main core 2 is not limited to the configuration shown in FIG. For example, although not shown, the main core 2 may include one E-type core and one I-type core. In this case, the opening of the E-type core and the side surface of the I-type core are joined.

  As shown in FIGS. 2 and 3, the U-shaped core 2A includes magnetic legs 2C and 2D. The magnetic leg 2C includes peripheral portions 2G to 2J that are curved.

  A secondary winding is wound around the magnetic leg 2 </ b> C via the secondary bobbin 5. When a current flows through the secondary winding, a high voltage portion and a low voltage portion are generated in the secondary winding. Since the potential of the core is in a floating state, a discharge may occur between the high voltage portion of the winding and the core. In particular, when the magnetic leg has a pointed portion, the electric field concentrates on the pointed portion and discharge tends to occur. Accordingly, the peripheral portions 2G to 2J are subjected to curved surface processing for preventing electric discharge. In addition, the curvature radius of the peripheral parts 2G-2J is set to 0.5-0.7 millimeters as an example.

  A primary winding is wound around the magnetic leg 2 </ b> D through a primary bobbin 5. When a current flows through the primary winding, a high-voltage portion is generated in the primary winding as well as the secondary winding, but since the voltage is lower than the high-voltage portion of the secondary winding, discharge between the core and the core is difficult to occur. . The peripheral portions 2K to 2N are subjected to curved surface processing as necessary.

  In addition, curved surface processing similar to that of the U-shaped core 2A is also performed on the magnetic legs 2E and 2F of the U-shaped core 2B.

  4 is a cross-sectional view taken along IV-IV of the step-up transformer 1 of FIG. The secondary bobbin 5 is attached to the U-type cores 2 </ b> A and 2 </ b> B and the I-type core 3. Gaps 8E and 8F are provided between the U-shaped core 2A and the secondary bobbin 5. Further, gaps 8G and 8H are provided between the U-shaped core 2B and the secondary bobbin 5. The gaps 8E to 8H are provided in order to prevent discharge between the secondary winding and the main core 2 like the gaps 8A to 8D.

  FIG. 5 is a schematic diagram showing the magnetic flux generated in the main core 2. In the main core 2, a magnetic flux 10A is generated by the primary winding 9A, and a magnetic flux 10B is generated by the primary winding 9B. An induced electromotive force is generated in the secondary winding 9C by electromagnetic induction of the magnetic flux 10A, and an induced electromotive force is generated in the secondary winding 9D by electromagnetic induction of the magnetic flux 10B.

  The direction of the current flowing through the primary winding 9A (direction A1 to A2 in the figure) and the direction of the current flowing through the primary winding 9B (direction B1 to B2 in the figure) are opposite to each other. . Therefore, the magnetic flux 10A and the magnetic flux 10B are opposite to each other in the magnetic legs 2D and 2F. A part of the magnetic fluxes 10A and 10B leaks from the main core 2 as leakage magnetic flux, but the remaining magnetic flux passes through the I-type core 3 and returns through the magnetic legs 2C and 2E, respectively. Therefore, the output taken out from the secondary windings 9C and 9D is stabilized.

  The magnetic leg 2C and the magnetic leg 2E are arranged on the same axis, and the magnetic leg 2D and the magnetic leg 2F are arranged on the same axis so that the effect of eliminating the interference can be exhibited most.

  In FIG. 5, the secondary windings 9C and 9D both have a low potential on the I-type core 3 side. Therefore, even if there is a substrate wiring at the bottom of the I-type core, it is difficult for a discharge to occur between the core and the wiring.

[Embodiment 2]
FIG. 6 is a three-side view of the step-up transformer according to the second embodiment. FIG. 6A is a plan view of the step-up transformer 11. FIG. 6B is a right side view of the step-up transformer 11. FIG. 6C is a bottom view of the step-up transformer 11.

  The step-up transformer 11 includes a main core 12. The main core 12 includes a U-shaped core 12A that forms the main part of the first closed magnetic circuit, a U-shaped core 12B that forms the main part of the second closed magnetic circuit, the first closed magnetic circuit, and the second closed magnetic circuit. And an I-type core 13 forming an overlapping portion.

  The U-shaped core 12A includes a magnetic leg 12C around which the secondary winding is wound and a magnetic leg 12D around which the primary winding is wound. The magnetic leg 12C has a length sufficient to split the secondary winding.

  When the step-up transformer 11 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. Therefore, the magnetic leg 12C and the magnetic leg 12D are arranged so as to be parallel to each other.

  The U-shaped core 12B includes a magnetic leg 12E around which the secondary winding is wound and a magnetic leg 12F around which the primary winding is wound. The magnetic leg 12E has a length sufficient to split the secondary winding.

  Similarly to the magnetic legs 12C and 12D, when the step-up transformer 11 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. The legs 12F are arranged so as to be parallel to each other.

  In the U-shaped core 12A, the magnetic leg 12C and the magnetic leg 12E are arranged on the X1-X2 axis in FIG. In the U-shaped core 12B, the magnetic leg 12D and the magnetic leg 12F are arranged on the X3-X4 axis in FIG.

  The step-up transformer 11 further includes a primary side bobbin 14 attached to the main core 12 and wound with a primary winding, and a secondary side bobbin 15 attached to the main core 12 and wound with a secondary winding. .

  The primary side bobbin 14 and the secondary side bobbin 15 are fitted by the fitting portions 20A to 20C, and their positions are fixed.

  The primary-side bobbin 14 includes a first primary winding bobbin 14A mounted on the magnetic leg 12D and a second primary winding bobbin 14B mounted on the magnetic leg 12F.

  Primary side bobbin 14 further includes primary side terminals 16A to 16F. As with the primary side terminals 6A to 6F in FIG. 1, the terminals connected to the windings are selected for the primary side terminals 16A to 16F in accordance with how the primary windings are wound.

  The secondary bobbin 15 includes a first secondary winding bobbin 15A mounted on the magnetic leg 12C, a second secondary winding bobbin 15B mounted on the magnetic leg 12E, and a secondary winding. And a partition 15C for split winding.

  Secondary bobbin 15 further includes secondary terminals 17A to 17D. As in the secondary terminals 7A to 7D in FIG. 1, the secondary terminals 17A and 17D are set as high potential terminals, and the secondary terminals 17B and 17C are set as low potential terminals.

  The step-up transformer 11 is further provided with gaps 18A to 18D. Like the gaps 8A to 8D in FIG. 1, the gaps 18A to 18D are provided to prevent discharge between the secondary terminals 17A and 17D or the primary terminals 16A and 16F and the U-shaped cores 12A and 12B.

  The step-up transformer according to the second embodiment will be described in more detail. In the step-up transformer 1 of FIG. 1, the main core 2 is fitted into the primary bobbin 4 and the secondary bobbin 5, and further, in the gap between the primary bobbin 4, the secondary bobbin 5, and the main core 2. The positional relationship between the primary bobbin 4 and the secondary bobbin 5 is determined by injecting the adhesive. However, the positional relationship between the primary side bobbin 4 and the secondary side bobbin 5 is not precisely determined, and the positional relationship between the terminals may be shifted.

  On the other hand, in the step-up transformer 11 of the second embodiment, the primary bobbin 14 and the secondary bobbin 15 that are configured separately are fitted to each other. Therefore, even if the main core 12 is not fitted, the positional relationship between the primary bobbin 14 and the secondary bobbin 15 is stabilized. The positional relationship between the terminals provided on each bobbin is stable and is superior to the step-up transformer 1 in terms of mounting. Further, since the primary bobbin 14 and the secondary bobbin 15 are integrated, the mechanical stress received by the core is distributed to the bobbin.

[Embodiment 3]
FIG. 7 is a three-side view of the step-up transformer according to the third embodiment. FIG. 7A is a plan view of the step-up transformer 21. FIG. 7B is a right side view of the step-up transformer 21. FIG. 7C is a bottom view of the step-up transformer 21.

  The step-up transformer 21 includes a main core 22. The main core 22 includes a U-shaped core 22A that forms the main part of the first closed magnetic circuit, a U-shaped core 22B that forms the main part of the second closed magnetic circuit, the first closed magnetic circuit, and the second closed magnetic circuit. And an I-type core 23 forming an overlapping portion.

  As will be described in detail later, the I-type core 23 is chamfered larger than the I-type core 3 so as to effectively inject an adhesive for fixing the main core 22.

  The U-shaped core 22A includes a magnetic leg 22C around which the secondary winding is wound and a magnetic leg 22D around which the primary winding is wound. The magnetic leg 22C has a length sufficient to split the secondary winding.

  When the step-up transformer 21 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. Therefore, the magnetic leg 22C and the magnetic leg 22D are arranged so as to be parallel to each other.

  The U-shaped core 22B includes a magnetic leg 22E around which the secondary winding is wound and a magnetic leg 22F around which the primary winding is wound. The magnetic leg 22E has a length sufficient to split the secondary winding.

  Similarly to the magnetic legs 22C and 22D, when the step-up transformer 21 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. The legs 22F are arranged so as to be parallel to each other.

  In the U-shaped core 22A, the magnetic leg 22C and the magnetic leg 22E are arranged on the X1-X2 axis in FIG. In the U-shaped core 22B, the magnetic leg 22D and the magnetic leg 22F are arranged on the X3-X4 axis in FIG.

  The step-up transformer 21 further includes a primary side bobbin 24 attached to the main core 22 and wound with a primary winding, and a secondary side bobbin 25 attached to the main core 22 and wound with a secondary winding. .

  The primary bobbin 24 includes a first primary winding bobbin 24A mounted on the magnetic leg 22D and a second primary winding bobbin 24B mounted on the magnetic leg 22F.

  The primary side bobbin 24 further includes primary side terminals 26A to 26F. As for the primary side terminals 26A to 26F, as with the primary side terminals 6A to 6F in FIG. 1, the terminals connected to the windings are selected according to the winding method of the primary windings.

  The secondary bobbin 25 includes a first secondary winding bobbin 25A mounted on the magnetic leg 22C, a second secondary winding bobbin 25B mounted on the magnetic leg 22E, and a secondary winding. And a partition 25C for split winding.

  The secondary bobbin 25 further includes secondary terminals 27A to 27D. Similar to the secondary side terminals 7A to 7D in FIG. 1, the secondary side terminals 27A and 27D are set as high potential side terminals, and the secondary side terminals 27B and 27C are set as low potential side terminals.

  The step-up transformer 21 is further provided with gaps 28A to 28D. Like the gaps 8A to 8D in FIG. 1, the gaps 28A to 28D are provided to prevent discharge between the secondary side terminals 27A and 27D or the primary side terminals 26A and 26F and the U-shaped cores 22A and 22B.

  The step-up transformer according to the third embodiment will be described in more detail. When fixing the main core 22, the primary side bobbin 24, and the secondary side bobbin 25, after assembling these, the clearance between the I-type core 23 and the primary-side bobbin 24, and the I-type core 23 and the secondary side bobbin 25 An adhesive is injected into the gap with the bobbin 25. In particular, since the U-type cores 22A and 22B and the I-type core 23 are reliably joined, conduction of the joint surfaces is ensured. By ensuring the conduction of the joint surfaces, the potentials of the U-type cores 22A and 22B and the I-type core 23 become the same, and discharge at the joint surfaces is prevented.

  FIG. 8 is a diagram illustrating a plane and a front surface of the I-type core 23. FIG. 8A is a diagram showing a plane of the I-type core 23, and FIG. 8B is a diagram showing the front of the I-type core 23.

  The I-type core 23 includes peripheral portions 23A and 23B that are obliquely chamfered (C surface treatment). The peripheral portions 23A and 23B are chamfered so that a gap sufficient to inject a sufficient amount of adhesive to fix the main core 22, the primary bobbin 24, and the secondary bobbin 25 is generated. Made.

  FIG. 9 is a cross-sectional view taken along the line IX-IX of the step-up transformer 21 of FIG. Adhesive is injected from the gap formed by the peripheral portions 23A and 23B of the I-type core 23 and the secondary bobbin 25. The U-type cores 22A and 22B, the I-type core 23, and the secondary bobbin 25 are fixed by an adhesive.

[Embodiment 4]
FIG. 10 is a diagram illustrating a plane and a right side of the step-up transformer according to the fourth embodiment. Referring to FIG. 10, FIG. 10A is a plan view of the step-up transformer 31. FIG. 10B is a right side view of the step-up transformer 31.

  FIG. 11 is a plan view of the main core 32. The main core 32 includes an E-type core 32 </ b> A, an E-type core 32 </ b> B, and an I-type core 33. The E-type core 32A includes an auxiliary magnetic leg 32G. Similarly, the E-type core 32B includes an auxiliary magnetic leg 32H.

  12 is a view of the E-type core 32A viewed from the X direction and the Y direction in FIG. FIG. 12A shows the E-type core 32A viewed from the X direction of FIG. FIG. 12B shows the E-type core 32A viewed from the Y direction in FIG.

  The auxiliary magnetic legs 32G are provided higher in the vertical direction than the magnetic legs 32C and 32D. The amount of magnetic flux leaking from the auxiliary magnetic leg 32G depends on the cross-sectional area of the auxiliary magnetic leg 32G. Therefore, if the auxiliary magnetic leg 32G is expanded in the width direction, the mounting area is increased, so that the auxiliary magnetic leg 32G is extended in the vertical direction. However, the height of the auxiliary magnetic leg 32G is equal to or lower than the height of the E-type core 32A for the purpose of reducing the height.

  As shown in FIG. 10, the step-up transformer 31 includes a main core 32. The main core 32 includes an E-type core 32A that forms the main part of the first closed magnetic circuit, an E-type core 32B that forms the main part of the second closed magnetic circuit, the first closed magnetic circuit, and the second closed magnetic circuit. And an I-type core 33 forming an overlapping portion.

  The E-type core 32A has a magnetic leg 32C around which the secondary winding is wound, a magnetic leg 32D around which the primary winding is wound, one end facing the substantially central portion of the I-type core 33, and one end and the I-type. An auxiliary magnetic leg 32G for generating leakage magnetic flux between the core 33 and the core 33 is included. The magnetic leg 32C has a length sufficient to split the secondary winding.

  When the step-up transformer 31 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. Therefore, the magnetic leg 32C and the magnetic leg 32D are arranged so as to be parallel to each other.

  The E-type core 32A is different from the U-type core 2A shown in FIG. 1 in that it includes an auxiliary magnetic leg 32G. In order to generate a leakage magnetic flux between the I-type core 33 and the auxiliary magnetic leg 32G, the auxiliary magnetic leg 32G is not joined to the I-type core 33, that is, shorter than the magnetic legs 32C and 32D.

  The E-type core 32B has a magnetic leg 32E around which the secondary winding is wound, a magnetic leg 32F around which the primary winding is wound, one end facing the substantially central portion of the I-type core 33, and one end and the I-type. An auxiliary magnetic leg 32H for generating a leakage magnetic flux between the core 33 and the core 33 is included. The magnetic leg 32E has a length sufficient to split the secondary winding.

  Similarly to the magnetic legs 32C and 32D, when the step-up transformer 31 is driven, it is necessary to ensure electrical insulation between the primary winding and the secondary winding. The legs 32F are arranged so as to be parallel to each other.

  Similarly to the auxiliary magnetic legs 32G, the auxiliary magnetic legs 32H are shorter than the magnetic legs 32E and 32F so as not to be joined to the I-type core 33.

  In the E-type core 32A, the magnetic legs 32C and the magnetic legs 32E are arranged on the X1-X2 axes in FIG. In the U-shaped core 32B, the magnetic legs 32D and the magnetic legs 32F are arranged on the X3-X4 axes in FIG.

  The step-up transformer 31 further includes a primary-side bobbin 34 attached to the main core 32 and wound with a primary winding, and a secondary-side bobbin 35 attached to the main core 32 and wound with a secondary winding. .

  The primary side bobbin 34 includes a first primary winding bobbin 34A mounted on the magnetic leg 32D, and a second primary winding bobbin 34B mounted on the magnetic leg 32F.

  Primary side bobbin 34 further includes primary side terminals 36 </ b> A to 36 </ b> F. As for the primary side terminals 36A to 36F, similarly to the primary side terminals 6A to 6F in FIG. 1, the terminals connected to the windings are selected according to the winding method of the primary windings.

  The secondary bobbin 35 includes a first secondary winding bobbin 35A mounted on the magnetic leg 32C, a second secondary winding bobbin 35B mounted on the magnetic leg 32E, and a secondary winding. And a partition part 35C for split winding.

  Secondary bobbin 35 further includes secondary terminals 37A to 37D. As in the secondary side terminals 7A to 7D in FIG. 1, the secondary side terminals 37A and 37D are set as high potential side terminals, and the secondary side terminals 37B and 37C are set as low potential side terminals.

  The step-up transformer 31 is further provided with gaps 38A to 38D. Like the gaps 8A to 8D in FIG. 1, the gaps 38A to 38D are provided to prevent discharge between the secondary side terminals 37A and 37D or the primary side terminals 36A and 36F and the E-type cores 32A and 32B.

  The step-up transformer according to the fourth embodiment will be described in more detail. Part of the magnetic flux generated by the primary winding bobbin 34 </ b> A leaks from between the auxiliary magnetic leg 32 </ b> G and the I-type core 33. Similarly, part of the magnetic flux generated by the primary winding bobbin 34 </ b> B leaks from between the auxiliary magnetic leg 32 </ b> H and the I-type core 33. The amount of leakage magnetic flux, that is, the amount of leakage magnetic flux, can be adjusted by the cross-sectional area of the auxiliary magnetic legs 32G and 32H and the size of the gap between the auxiliary magnetic legs 32G and the I-type core 33. The leakage inductance is closely related to the leakage magnetic flux amount, and the leakage inductance can be increased by increasing the leakage magnetic flux amount. Therefore, it is not necessary to increase the number of windings more than necessary in order to increase the leakage inductance.

  FIG. 13 is a diagram of a circuit example to which the step-up transformer of the present invention is applied. Referring to FIG. 13, lighting circuit 40 forms a resonant circuit in combination with step-up transformer 41, inverter 42 that converts a DC voltage into an AC voltage, cold cathode tubes 43A and 43B, and cold cathode tube 43A. Capacitor 44A, capacitor 44B that forms a resonance circuit in combination with cold cathode tube 43B, terminals 45A to 45D that couple boost transformer 41 and inverter 42, and boost transformer 41 and cold cathode tubes 43A and 43B are coupled. Terminals 46A to 46D. The step-up transformer 41 may be any of the above-described step-up transformers 1, 11, 21, 31.

  The voltage applied to the cold cathode tube 43A has a high potential on the terminal 46A side and a low potential on the terminal 46B side. Similarly, the voltage applied to the cold cathode tube 43B has a high potential on the terminal 46D side and a low potential on the terminal 46C side.

  In a general cold cathode tube lighting operation, an AC voltage having the same phase is applied to the cold cathode tubes 43A and 43B. However, U-shaped and W-shaped cold cathode tubes have been proposed along with recent progress in cold cathode tube manufacturing technology. When lighting a U-shaped or W-shaped cold cathode tube, voltages in opposite phases are often applied to one electrode and the other electrode of the cold cathode tube, respectively. As a method for applying a voltage having an opposite phase, for example, there is a method in which the winding directions of the secondary winding of the step-up transformer 41 are opposite to each other.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

FIG. 3 is a three-side view of the step-up transformer according to the first embodiment. It is a figure which shows the plane and front of the main core. It is the figure which looked at the U-type core 2A from the X direction and Y direction of FIG. It is sectional drawing between IV-IV of the step-up transformer 1 of FIG. 3 is a schematic diagram showing magnetic flux flowing through the main core 2. FIG. FIG. 6 is a three-side view of the step-up transformer according to the second embodiment. FIG. 6 is a three-side view of the step-up transformer according to the third embodiment. 2 is a diagram showing a plane and a front surface of an I-type core 23. FIG. FIG. 8 is a cross-sectional view taken along the line IX-IX of the step-up transformer 21 in FIG. 7. It is a figure which shows the plane and right side surface of a step-up transformer of Embodiment 4. 3 is a plan view of a main core 32. FIG. It is the figure which looked at the E type | mold core 32A from the X direction and Y direction of FIG. It is a figure of the circuit example to which the step-up transformer of this invention is applied.

Explanation of symbols

  1, 11, 21, 31 Step-up transformer, 2, 12, 22, 32 Main core, 2A, 2B, 12A, 12B, 22A, 22B U-type core, 2C-2F, 12C-12F, 22C-22F, 32C-32F Magnetic leg, 2G-2N, 23A, 23B peripheral part, 3, 13, 23, 33 I-type core, 4, 14, 24, 34 Primary side bobbin, 4A, 14A, 24A, 34A First primary winding Bobbin, 4B, 14B, 24B, 34B Second primary winding bobbin, 5, 15, 25, 35 Secondary bobbin, 5A, 15A, 25A, 35A First secondary winding bobbin, 5B, 15B, 25B, 35B second secondary winding bobbin, 5C, 15C, 25C, 35C partition, 6A-6F, 16A-16F, 26A-26F, 36A-36F primary side terminals, 7A-7D, 17A-17D, 27 A-27D, 37A-37D secondary terminal, 8A-8H, 18A-18D, 28A-28D, 38A-38D gap, 9A, 9B primary winding, 9C, 9D secondary winding, 10A, 10B magnetic flux, 20A-20C fitting part, 32A, 32B E type core, 32G, 32H auxiliary magnetic leg, 40 lighting circuit, 42 inverter, 43A, 43B cold cathode tube, 44A, 44B capacitor, 45A-45D, 46A-46D terminals.

Claims (6)

A core that forms a first closed magnetic path and a second closed magnetic path that overlaps a part of the first closed magnetic path in a plane parallel to the mounting surface;
The core is
A first magnetic leg forming the first closed magnetic path;
A second magnetic leg that forms the first closed magnetic path and is parallel to the first magnetic leg;
A third magnetic leg that forms the second closed magnetic path and is arranged coaxially with a central axis of the first magnetic leg;
A fourth magnetic leg that forms the second closed magnetic path and is arranged coaxially with a central axis of the second magnetic leg;
A central magnetic leg that forms an overlapping portion of the first closed magnetic path and the second closed magnetic path;
A first winding portion mounted on the core so that the first closed magnetic path passes therethrough,
The first winding portion is
A first primary winding wound around the first magnetic leg;
Including a first secondary winding portion wound around the second magnetic leg,
A second winding part mounted on the core so that the second closed magnetic path passes therethrough,
The second winding part is
A second primary winding wound around the third magnetic leg;
A step-up transformer including a second secondary winding portion wound around the fourth magnetic leg. The first secondary winding portion has a terminal to which a low potential is applied to the central magnetic leg side,
2. The step-up transformer according to claim 1, wherein the second secondary winding portion has a terminal to which a low potential is applied to the central magnetic leg side. The first secondary winding portion has a first bobbin having a partition portion that divides the first secondary winding portion,
2. The step-up transformer according to claim 1, wherein the second secondary winding portion includes a second bobbin having a partition portion that divides the second secondary winding portion.   2. The step-up transformer according to claim 1, wherein the core is an I-type core sandwiched between a pair of U-type cores whose openings are opposed to each other and the pair of U-type cores. The core is
A first auxiliary magnetic leg that lowers the magnetic coupling between the first magnetic leg and the second magnetic leg by causing leakage magnetic flux in a space having one end portion opposed to the central magnetic leg;
One end includes a second auxiliary magnetic leg that generates a leakage magnetic flux in a space opposed to the central magnetic leg to reduce magnetic coupling between the third magnetic leg and the fourth magnetic leg. The step-up transformer according to claim 1. The first primary winding portion has a first primary winding that generates magnetic flux in a first direction;
2. The step-up transformer according to claim 1, wherein the second primary winding section includes a second primary winding that generates a magnetic flux in a second direction opposite to the first direction.

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