JP2000133526A - Boosting transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boosting transformer which has a closed magnetic circuit structure which can be constituted into an ultra thin type. SOLUTION: This device is provided with a core 20 with an E-type section, having a central leg 22, on outer leg 23 and a plate part 21, coils 40 and 50 which are wound around the central leg 22 and a printed board 30, on which insulating thin plate having through-holes a plurality of electrodes are formed. The printed board 30 is fixed on the plate part 21 by the central leg 22 inserted into the through-holes, and leads 41 and 51 are connected to the electrodes by the coils 40 and 50 mounted on the printed board 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a step-up transformer incorporated in a piezoelectric inverter unit for lighting a cold cathode discharge tube or the like in a digital electronic still camera or a notebook personal computer. .

[0002]

2. Description of the Related Art FIG. 5 shows a main part of a piezoelectric inverter unit, wherein 1 is a step-up transformer, 2 is a piezoelectric transformer,
Is a cold cathode discharge tube for illuminating the back of the liquid crystal display screen,
Reference numeral 4 denotes an FET driven by a control circuit (not shown) connected to the gate 4a. The step-up transformer 1 operates as a transformer by connecting a tap of a coil having one end connected to the power supply Vcc and the other end to the primary drive electrode of the piezoelectric transformer 2 to the FET 4 to operate as a transformer. To make up for the shortage.

As a conventional step-up transformer, a coil 7 is mounted on a drum-shaped core 6 fixed on a base 5 as shown in FIG.
Is wound and covered with a cylindrical core 8. As shown in FIG. 7, a combination of a bobbin 11 wound with a coil 10 and an E-shaped core 12 and an I-shaped core 13 is also used.

[0004]

However, the former step-up transformer having a base has a problem that it is difficult to reduce the height and magnetic flux leakage easily occurs, and the latter using a bobbin is not only difficult to reduce the height similarly. There was a disadvantage that the cost was high. Therefore, an object of the present invention is to provide a step-up transformer having a closed magnetic circuit structure that can be configured to be ultrathin.

[0005]

SUMMARY OF THE INVENTION A step-up transformer according to the present invention comprises a first core having an E-shaped section having a flat plate portion having a central leg provided at the center and outer legs formed at both ends, and wound around the central leg. A coil, a second core of a flat plate shape forming a closed magnetic path by abutting against the first core, and a printed board in which a plurality of electrodes are formed on an insulating thin plate having a through hole in the center. The center leg of the first core is inserted into the through hole, the printed board is fixed on the flat plate portion, the coil is placed on the printed board, and the lead wire is connected to the electrode.

[0006]

1 is a front sectional view showing an embodiment of a booster coil according to the present invention, FIG. 2 is a plan view, FIG. 3 is a side sectional view, and FIG. 4 is an exploded perspective view. 20 and 60 are a pair of cores made of an insulating magnetic material. As is clear from FIG. 4, a columnar central leg 22 is provided at the center of the flat plate portion 21 of the core 20, and outer legs 23 are formed at both ends of the flat plate portion 21, respectively. A plate-shaped core 60 is abutted against such a core 20 having an E-shaped cross section to form a closed magnetic circuit.

Reference numeral 30 denotes a printed board in which a plurality of electrodes 32 are formed on an insulating thin plate having a through hole 31 at the center. Printed board
In 30, the center leg 22 of the core 20 is inserted into the through hole 31 and fixed on the flat plate portion 21. On the opposite side of the printed board 30,
Four projecting pieces 33 projecting outside the butted cores 20 and 60 are provided. The protruding piece 33 is wider at the distal end than at the base, and the electrode 32 is formed from the distal end of the protruding piece 33 to the base. Four electrodes 32
The two electrodes 32a and 32b are electrically connected by a narrow printed conductor. Further, a projection 35 is formed on one side surface of the printed board 30 on the side where the protruding piece 33 is provided, so that the direction of the step-up transformer can be identified.

[0008] Two coils 4 located on the printed board 30
0 and 50 are wound on the central leg 22 of the core 20 adjacent vertically, and after each lead wire 41 and 51 is wound on the protruding piece 33,
Each electrode 33 is soldered. The protruding piece 33 has a wider tip, so the wound lead wire 4
1, 51 do not come off from the protruding piece 33. The lead wires 41 and 51 connected to the electrodes 32a and 32b which are conducted by the printed conductor 34 correspond to the tap portion of the transformer 1 connected to the FET 4 in FIG.

To assemble the step-up transformer, first, the center leg 22 is inserted into the through hole 31, and the printed board 30 is placed and fixed on the flat plate portion 21 of the core 20. Next, the coil 40 and the coil 50 that have been previously hardened are sequentially fitted into the center leg 22, and the lead wires 41 and 51 are soldered to the electrode 33. Then, it is only necessary to bond and fix the core 60 to the core 20. This transformer is used in a state where the flat plate portion 21 of the core 20 is dropped into a through hole formed in a printed circuit board of the inverter unit. In that case, each protruding piece 33 of the printed board 30
Will adhere to the upper surface of the printed circuit board.

In the above embodiment, two coils 40 and 50 are used, but a single coil with taps drawn out with lead wires at both ends may be used. Also, instead of providing the printed conductor 34 on the printed board 30, two electrodes 32a, 32
b may be changed so as to conduct.

[0011]

According to the present invention, an ultra-thin step-up transformer having a closed magnetic circuit structure can be obtained. Therefore, there is an effect that an inverter unit having a thickness of about 2 mm can be formed by combining with a thin piezoelectric transformer.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing one embodiment of the present invention.

FIG. 2 is a plan view of the transformer.

FIG. 3 is a side sectional view of the transformer.

FIG. 4 is an exploded perspective view of the transformer.

FIG. 5 is a circuit diagram showing a main part of the piezoelectric inverter unit.

FIG. 6 is a front sectional view showing a conventional example of a transformer.

FIG. 7 is a front sectional view showing another conventional example of a transformer.

[Explanation of symbols]

 20, 60 Core 21 Flat plate 22 Center leg 23 Outer leg 30 Printed board 32 Electrode 33 Projecting piece 40, 50 Coil

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Claims (3)

[Claims] 1. A first core having an E-shaped cross section having a flat plate portion provided with a central leg at the center and outer legs formed at both ends, a coil wound around the central leg, and a first core A second core of a flat plate shape forming a closed magnetic path by abutting the first core, and a printed board in which a plurality of electrodes are formed on an insulating thin plate having a through hole in the center, and penetrating through a central leg of the first core. A step-up transformer characterized in that a printed board is fixed on a flat plate portion by inserting into a hole, a coil is mounted on the printed board, and a lead wire is connected to an electrode. 2. The step-up transformer according to claim 1, wherein said coil comprises two coils stacked one above the other. 3. The step-up transformer according to claim 1, wherein protruding pieces protruding outside the butted first and second cores are respectively formed on opposing side surfaces of the printed board, and electrodes are formed on the protruding pieces.