JP2008034598A - Inverter transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transformer which will not cause production efficiency, such as an increase in the number of components to deteriorate, and which is less likely to be influenced by magnetic coupling, etc. from an environment due to iron plates, etc. coming closer, etc. <P>SOLUTION: The inverter transformer comprises a first bobbin 12, having a first through hole 11 and wound with a primary winding 10; a second bobbin 15 having a second through-hole 16 for inserting the first bobbin 12 and wound with a first and a second secondary winding 13 and 14; and a square theta-shaped magnetic core 19, consisting of middle legs 20, to be inserted into the first through hole 11, outer legs 21 arranged on both sides of the middle legs 20, and connecting legs 22 for connecting the middle legs 20 and the outer legs 21. The center of the width in the winding axis direction of the primary winding 10 and the center of the combined width of the first and second secondary windings 13 and 14, arranged in the winding axis direction, are on a plane coplanar and perpendicular to the winding axis direction of the primary winding 10. The winding width, in the winding axis direction of the primary winding 10, is not smaller than 0.80 and not larger than 1.05 in the ratio of the combined width of the first and second secondary windings 13 and 14 arranged in the winding axis direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inverter transformer used in a display lighting circuit of various electronic devices.

  A perspective view of a conventional transformer is shown in FIG.

  As shown in FIG. 8, in the conventional transformer, the primary winding 1 and the secondary winding 2 are wound around the closed magnetic circuit 3 and usually in this structure, the primary winding 1 and the secondary winding 2 are arranged. Among the magnetic fluxes generated from the windings 2, there are many leakage magnetic fluxes that are released outside without passing through the closed magnetic path 3.

  And in order to reduce this leakage magnetic flux, the method of shielding by having covered the transformer 4 with the copper foil 5 etc. was taken.

For example, Patent Document 1 is known as prior art document information relating to the invention of this application.
JP-A-11-345724

  In recent liquid crystal displays, as the screen size increases, the display housing needs to be made thinner, and accordingly, the backlight lighting inverter circuit unit is also required to be made thinner and the density of the mounted components higher.

  When thinning the backlight lighting inverter circuit unit or increasing the density of mounted parts, the distance between the circuit unit and the iron plate covering the circuit unit and the distance separating the parts used in the circuit should be reduced. It is common to take measures by doing.

  However, when measures are taken by reducing the distance between the circuit and the iron plate covering the circuit, the distance separating each part used in the circuit unit, and the distance separating the transformer and other parts here, In parts with magnetic properties such as transformers, the close proximity of objects with the magnetic properties is greatly affected by magnetic coupling, resulting in a decrease in transformer power transmission efficiency. It was a problem.

  For example, as shown in FIG. 9, the magnetic flux 7 generated in the primary winding 1 of the transformer 4 mounted on the substrate 6 passes through the closed magnetic path 3 and goes to the secondary winding 2 in parallel with FIG. As shown, a leakage magnetic flux 9 flows from the primary winding 1 through the iron plate 8 to the secondary winding 2, and an eddy current is generated in the iron plate 8 by the leakage magnetic flux 9. A loss occurs, resulting in a decrease in the power transmission efficiency of the transformer.

  And in order to make it hard to receive the magnetic influence from such an iron plate 8 etc., it is located in the method of shielding the transformer 4 with the copper foil 5 etc. as shown in FIG. 8, or above and below the transformer shown in FIG. A method of punching and removing the iron plate 8 by an amount corresponding to the dimension that the transformer 4 faces has been adopted.

  However, when such measures are taken, it cannot be denied that this leads to deterioration in production efficiency, such as an increase in the number of parts in transformer production and limitation of the shape of the iron plate.

  Therefore, the present invention aims to provide a transformer that does not deteriorate the production efficiency such as an increase in the number of parts, and is not easily affected by magnetic coupling from the surroundings due to the proximity of iron plates or the like. It is.

  In order to achieve this object, the first bobbin having the first through-hole and wound with the primary winding, and the second through-hole into which the first bobbin is inserted, A second bobbin wound with a second secondary winding, a middle leg to be inserted into the first through hole, an outer leg located on at least one side of the middle leg, and a middle leg and the outer leg. A magnetic core having connecting legs that are connected to each other, and the center of the width in the winding axis direction of the primary winding and the center of the width in which the first and second secondary windings are arranged in the winding axis direction are both The first and second secondary windings are arranged on the same plane perpendicular to the winding axis direction of the primary winding, and the winding widths in the winding axis direction of the primary winding are arranged in the winding axis direction. The ratio to the width is 0.80 or more and 1.05 or less.

  According to the present invention, since the primary winding exists at a position substantially surrounded by the two secondary windings, the secondary winding shields the leakage magnetic flux emitted from the primary winding. It is possible to obtain a transformer that has a function of shielding magnetic flux around the transformer, and that is not easily affected by magnetic coupling or the like, without performing the placement and processing associated with the mounting of the transformer.

(Embodiment)
FIG. 1 is an exploded perspective view of a transformer according to an embodiment of the present invention, in which a primary bobbin 10 is wound and a first bobbin 12 having a first through hole 11 is provided. Further, the first and second secondary windings 13 and 14 are wound symmetrically with respect to the axial center of the second through hole 16 of the second bobbin 15. The first bobbin 12 is inserted into the second through hole 16 of the second bobbin 15, and is coaxial and has the primary winding 10 on the inner peripheral side and the first and second two on the outer peripheral side. Next windings 13 and 14 are arranged.

  The second bobbin is covered with the case 17. In this case 17, openings 18 corresponding to the first through holes 11 are provided on the left and right sides, and the middle legs 20 of the E-shaped magnetic core constituting the sun-shaped magnetic core 19 are inserted into the openings 18, The second bobbin 15 is enclosed by the outer legs 21 located on both sides of the middle leg 20 and the connecting legs 22 that connect the middle leg 20 and the outer leg 21.

  The operation and effect of the transformer of this embodiment having the above configuration will be described below.

  In the transformer of the present embodiment, as shown in FIG. 2, the primary winding 10 is wound around the middle leg 20 of the sun-shaped magnetic core 19 as an axis, and the first, By winding the second secondary windings 13 and 14, the magnetic flux φ <b> 1 generated by the signal flowing through the primary winding 10 and passing through the middle leg 20 immediately becomes the first and second secondary windings. As a result, signals are excited in the first and second secondary windings 13 and 14.

  Then, when a signal flows through the primary winding 10, a leakage magnetic flux φ2 is generated simultaneously with the magnetic flux φ1 passing through the middle leg 20.

  Here, the first and second secondary windings 13 and 14 are in a positional relationship that substantially includes the primary winding 10, but the axial dimension A about the middle leg 20 of the primary winding 10 is an axis. The ratio of the first and second secondary windings 13 and 14 to the dimension B arranged in the axial direction with the middle leg 20 as an axis is 0.80 or more and 1.05 or less.

  And it arranged in the center of the dimension A of the axial direction centering on the middle leg 20 of the primary winding 10, and the axial direction centering on the middle leg 20 of the first and second secondary windings 13 and 14. The dimension B exists on the same plane that intersects perpendicularly with the axial direction of the middle leg 20.

  In short, when the primary winding 10 and the first and second secondary windings 13 and 14 are viewed from the side surface direction, the center of the dimension A and the center of the dimension B are in the same position.

  As a result, the first and second secondary windings 13 and 14 have a shielding effect on the primary winding 10 and thereby play a role of preventing the leakage flux φ2 from being released to the outside of the transformer 23. It is possible to obtain a transformer that is less susceptible to magnetic influences without the arrangement and processing associated with magnetic flux shielding around the transformer.

  Further, a magnetic gap 34 is formed in the middle leg 20 of the Japanese character-shaped magnetic core 19, and this magnetic gap 34 is also located at a position enclosed by the first and second secondary windings 13 and 14. By doing so, it is possible to prevent magnetic flux leakage from the magnetic gap 34, which is a portion where magnetic flux leakage is large, to the outside of the transformer 23. That is, the first and second secondary windings 13 and 14 also have a function for shielding magnetic flux from the leakage magnetic flux from the magnetic gap 34.

The relationship between the dimensions A and B is A / B = 0.80 to 1.05 from the characteristic diagram of the experimental results in FIG.
As a result, favorable conditions can be obtained, and it is possible to more effectively prevent leakage of the magnetic flux φ2 shown in FIG.

  As shown in FIG. 3, with the secondary load resistor 25 connected to the transformer 23, the leakage magnetic flux detection coil 26 is positioned approximately 5 (mm) above the case 17, and this leakage magnetic flux detection coil 26. The ratio between the magnetic flux released to the outside of the transformer 23 and the dimension A of the primary winding 10 and the dimension B of the secondary windings 13 and 14 shown in FIG. A relationship with A / B was obtained.

  FIG. 4 is a characteristic diagram showing the relationship between the dimensional ratio A / B and the leakage voltage VL. When the dimension ratio A / B is in the vicinity of 0.80 to 1.05, the locus of the leakage voltage VL is almost flat. By setting the dimension A and the dimension B shown in FIG. Magnetic flux leakage to the outside of the transformer 23 can be further reduced.

  Further, the characteristics shown in FIG. 4 are expected to vary slightly depending on the winding diameters of the primary winding 10 and the secondary windings 13 and 14 shown in FIG. 2, but the conditions are different from those in this experiment. Even in this case, since the local minimum value of the leakage voltage VL shown in FIG. 4 is predicted to exist in the vicinity of 0.9 in the dimension ratio A / B, the dimension ratio A / B is set to 0 from the viewpoint of preventing magnetic flux leakage. .9 is most desirable.

  Here, when the dimensional ratio A / B is a value much larger than 1.0, that is, when the primary winding 10 shown in FIG. 2 protrudes outside the secondary windings 13 and 14, the primary winding 10. Since there is no longer anything that shields the leakage flux φ2 from the leakage current, the leakage voltage VL shown in FIG. 4 increases.

  On the other hand, when the dimension ratio A / B is a value much smaller than 1.0, that is, when the primary winding 10 shown in FIG. 2 is buried inside the secondary windings 13 and 14, the primary winding. Despite the fact that there is a shield for leakage flux φ2 from 10, the value of leakage voltage VL shown in FIG. 4 increases.

  This is because the dimension A shown in FIG. 2 becomes too small, and the portion where the leakage flux φ2 is generated concentrates. Therefore, the shielding tolerance by the secondary windings 13 and 14 is exceeded, and thus the outside of the transformer 23. It is considered that the magnetic flux leakage is increased.

  And this means that the dimension A is not made too small, that is, winding the primary winding 10 with a relatively wide width and a small number of layers rather than winding the primary winding 10 over a plurality of layers with a narrow width can prevent magnetic flux leakage. It is also advantageous from the viewpoint, and it is shown that even if the transformer 23 is made thin, it does not cause any problem in terms of preventing magnetic flux leakage.

  In addition, the transformer 23 employs a form in which the first and second secondary windings 13 and 14 provide two outputs.

  This is because the sun-shaped magnetic core 19 is mainly composed of a Mn-based magnetic material having a high magnetic permeability and a high saturation magnetic flux density, and this has conductivity at the same time. Therefore, as a structure for preventing the adverse effects due to having the conductivity, the first and second secondary windings 13 and 14 are configured to have two outputs.

  For example, as shown in FIGS. 5 and 6, one secondary winding 24 is provided for the primary winding 10, one terminal 28 of the secondary winding 24 is grounded to zero potential, and the other terminal 29 is provided. It is known from experience that a voltage of about ¼ of V1 is induced in the Japanese character-shaped magnetic core 19 when the high voltage output is V1.

  On the other hand, as shown in FIG. 7, the first and second secondary windings 13 and 14 are provided for the primary winding 10, and one terminal 30 of the first secondary winding 13 and the second winding One terminal 31 of the secondary winding 14 is grounded to zero potential, and both ends of the other terminal 32 of the first secondary winding 13 and one terminal 33 of the second secondary winding 14 When the high voltage output outputted at V is V2, the voltage induced in the sun-shaped magnetic core 19 is almost zero.

  This is because the first and second secondary windings 13 and 14 are grounded at their one ends 30 and 31 in common and the other ends 32 and 33 are used as outputs, so that the first secondary winding 13 is output. And the second secondary winding 14 have opposite phase outputs, the voltages of which are + V2 × 1/2 on the first secondary winding 13 and −V2 × 1 / on the second secondary winding 14. 2 Or, conversely, the first secondary winding 13 becomes −V2 × 1/2 and the second secondary winding 14 becomes + V2 × 1/2.

  And although a voltage is induced in the sun-shaped magnetic core 19 by the output voltage of the first secondary winding 13 and the output voltage of the second secondary winding 14, these two voltages are in opposite phases. Therefore, they cancel each other, and no voltage is actually induced.

  As a result, it is possible to reduce noise emission from the Japanese character-shaped magnetic core 19 due to the charging of the Japanese character-shaped magnetic core 19.

  Since the output voltage of the first and second secondary windings 13 and 14 is V2 × 1/2 as an absolute value as described above, the first and second secondary windings 13 and 14 and the date Since it is theoretically possible to reduce the insulation withstand voltage required to the half-shaped magnetic core 19 to 1/2, it is effective in reducing the overall size of the transformer.

  Further, as shown in FIG. 1, the primary connection terminal 25 connected to the first bobbin 12 with the primary winding 10, and the secondary connected to the second bobbin 15 with the first and second secondary windings 13 and 14. By implanting the connection terminal 26, the first bobbin 12 and the second bobbin 15 are in a fitted state in a form in which the first bobbin 12 is inserted into the second through hole 16 of the second bobbin 15. However, since the primary winding connection terminal 25 and the secondary winding connection terminal 26 exist on different molded bodies, the primary winding connection terminal 25 and the secondary winding connection terminal 26 are in a close positional relationship. Even if it exists, it is possible to improve the insulation between both.

  In this embodiment, the description has been given as the day-shaped magnetic core 19 composed of the E-shaped magnetic core. However, the date is obtained by making the magnetic core, the E-shaped magnetic core and the I-shaped magnetic core (not shown) face each other. The character-shaped magnetic core 19 or the structure of the Japanese character-shaped magnetic core 19 by making a letter-shaped magnetic core (not shown) and an I-shaped magnetic core (not shown) face each other may be used.

  Further, in the case where there is a margin for the characteristics related to magnetic saturation, a U-shaped magnetic core (not shown) and an I-shaped magnetic core (not shown) are omitted. As a configuration of a square-shaped magnetic core (not shown) by facing each other, or a square-shaped magnetic core (not shown) by facing two U-shaped magnetic cores (not shown), it is small and lightweight. It does not matter even if it is made into a form.

  INDUSTRIAL APPLICABILITY The present invention has an effect of making an inverter transformer less susceptible to magnetic influence from the surroundings, and is useful in various electronic circuits.

1 is an exploded perspective view of a first embodiment of the present invention. Cross section Perspective view of the experimental circuit Characteristic diagram showing the amount of magnetic flux leakage Sectional view of the first example Circuit diagram of the first example Circuit diagram of the second example A perspective view of a conventional transformer Side view Cross section

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Primary winding 11 1st through-hole 12 1st bobbin 13 1st secondary winding 14 2nd secondary winding 15 2nd bobbin 16 2nd through-hole 19 Sun-shaped magnetic core 20 Leg 21 Outer leg 22 Connecting leg

Claims (3)

A first bobbin having a first through hole and wound with a primary winding;
A second bobbin having a second through-hole into which the first bobbin is inserted and wound with the first and second secondary windings;
A middle leg to be inserted into the first through-hole, an outer leg located on at least one side of the middle leg, and a magnetic core having a connecting leg connecting the middle leg and the outer leg,
The center of the winding axial width of the primary winding;
Together with the center of the width in which the first and second secondary windings are arranged in the winding axis direction,
On the same plane perpendicular to the winding axis direction of the primary winding,
Of the winding width in the winding axis direction of the primary winding,
The ratio to the width in which the first and second secondary windings are arranged in the winding axis direction is 0.80 or more and 1.05 or less.
Inverter transformer. The primary winding connection terminal on the first bobbin,
Secondary winding connection terminal to the second bobbin
The inverter transformer according to claim 1, wherein each inverter transformer is installed. The inverter transformer according to claim 1, further comprising a case that covers the second bobbin.

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