JPH06295824A - Transformer - Google Patents

Abstract

PURPOSE:To provide a highly reliable miniature transformer having low profile being employed in various lighting fixtures in which dielectric breakdown due to high frequency high voltage is eliminated. CONSTITUTION:In the miniature low profile transformer excellent in safety, the electric insulation distance is ensured between pin terminals 25, 30 and a lead wire passing through a lead out groove 27 by partially employing a high resistance ferrite core 29 and a bobbin structure, e.g. insulating protrusions, is eliminated while decreasing the embedding depth of the pin terminals 25, 30 by enhancing safety against high voltage corona discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer used in an electronic device such as an inverter lighting which generates a high voltage of a relatively high frequency.

[0002]

2. Description of the Related Art In recent years, display devices using electronic devices have been rapidly growing because they consume less power than conventional cathode ray tubes and can be made thinner in electronic equipment. In particular, liquid crystal panels have shown particularly great growth because they are easy to colorize.

However, since the liquid crystal itself has no light emitting capability, a light source using a small fluorescent lamp is attached to the back of the liquid crystal panel, and light is applied from the back side of the liquid crystal panel to improve the display quality. Since this compact fluorescent lamp requires higher brightness than general fluorescent lamps, the gas pressure in the tube is high, and the tube length is long compared to the tube diameter, and a high voltage is required for discharge. Requires a high voltage of 1-2 KV.

A step-up transformer is used as the unit for generating the high voltage, and there is a demand for a transformer which is highly safe against the high voltage and can be made compact and low in height.

The conventional transformer will be described below.
A conventional transformer is composed of a coil bobbin / ferrite core shown in FIG. That is, in FIG. 5, the primary winding 1 and the secondary winding 2 are wound around the coil bobbin 3 so as to be separated into the collar 6 provided on the coil bobbin 3. Further, the secondary winding 2 is divided into multiple layers by the collar 6 in order to prevent a short circuit inside the winding.

Reference numeral 5 is a pin terminal for the primary winding, which is planted in the coil bobbin 3 for wiring the primary winding 1.
Similarly, reference numeral 10 is a secondary winding pin terminal that is embedded in the coil bobbin 3 for wiring the secondary winding 2.

A ferrite core 4 is inserted into the coil bobbin 3 constructed as described above to form a transformer.

FIG. 6 is a perspective view of the conventional transformer shown in FIG. 5 as seen from the secondary winding pin terminal 10 side.

Reference numeral 7 in the drawing is a drawing groove for drawing the secondary winding 2 and is provided so as to cut the coil bobbin 3. The secondary winding 2 is drawn out along the drawing groove 7, is hooked by the guide protrusion 8 and is wired to the pin terminal 10. Further, reference numeral 9 is an insulating projection for securing an insulating distance between the wiring portion of the winding and the ferrite core 4.

[0010]

Since the high voltage unit generates a high voltage of 1 to 2 KV on the secondary side, it is necessary to secure the safety against dielectric breakdown at a high voltage, that is, corona discharge. Corona discharges are difficult to detect with ordinary measuring instruments, and problems cannot often be detected by short-term evaluation.

However, when electric discharge occurs, heat concentrates at one point where the electric discharge occurs, so that it tends to cause thermal breakdown of the insulator and cause dielectric breakdown in the medium to long term.

That is, the transformer is required to have an insulating structure that does not withstand the heat of corona discharge but does not generate corona discharge itself. For that purpose, it is necessary to electrically separate the part that generates the high voltage from the other part.

In order to use the transformer having the conventional structure in the high voltage unit, it is necessary to pay attention not only to the discharge due to the dielectric breakdown of the primary winding 1 and the secondary winding 2, but also to the discharge through the ferrite core 4. is there.

That is, the conventional transformer has a pin terminal 5
In 10 as well, since the insulation thickness with the ferrite core 4 via the coil bobbin 3 is required, the embedded dimension of the pin terminals 5 and 10 cannot be deepened, and as a countermeasure against discharge between the lead portion and the ferrite core 4. However, there is a problem that the dimension of the insulating projection 9 for securing the insulating distance needs to be increased, which is one of the causes of hindering the miniaturization of the transformer.

The present invention solves the above-mentioned conventional problems, and secures an electrical insulation distance by using a plurality of ferrite cores and using a material having a high electric resistance for the ferrite cores close to the pin terminals. However, it is an object of the present invention to provide a small and low-profile transformer by preventing discharge from the terminal or the lead wire to the ferrite core.

[0016]

To achieve this object, the transformer of the present invention has a structure in which a material having high electric resistance is used for a ferrite core on the side close to the terminal portion.

[0017]

With this structure, it is possible to prevent discharge between the ferrite core and the terminals, so that it is possible to omit useless insulating protrusions, and also to make it possible to take a large number of embedded pins and terminals, which is small and low in size. A back trance can be provided.

[0018]

First Embodiment A first embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a transformer according to the first embodiment of the present invention. FIG. 2 is a perspective view of an essential part of the transformer seen from the bottom.

In FIG. 1, 21 is a primary winding, 22 is a secondary winding, 23 is a split type coil bobbin having a plurality of collars 26, 24 is an E-shaped low resistance ferrite core having a low electric resistance, Reference numeral 29 is a high resistance ferrite core which is also formed in an E shape and has a high electric resistance, 25 is a pin terminal for the primary winding planted in the collar 26 at one end of the coil bobbin 23, and 30 is a collar 26 at the other end of the coil bobbin 23. It is a secondary winding pin terminal that is implanted. Further, as shown in FIG. 2, the coil bobbin 23 is provided with a plurality of lead-out grooves 27 for drawing out the winding so as to cut the flanges 26 at both ends of the coil bobbin 23.
The lead wire of the winding passes through the lead groove 27 and the guide protrusion 28.
And is wired to the secondary winding pin terminal 30.

In the present invention, as shown in FIG.
The high resistance ferrite core 29 is inserted from both ends of the coil bobbin 23 on the side opposite to 5 and 30, and the low resistance ferrite core 24 is also inserted from both ends at the opposite positions to form a transformer.

As described above, the high resistance ferrite core 29 is arranged in the position close to the pin terminals 25 and 30, and the low resistance ferrite core 24 is inserted in the position opposed to the pin terminals 25 and 30, so that the pin terminals 25 and 30 with respect to the ferrite core. Since the discharge can be prevented, not only the insulating projection is unnecessary, but also the embedded size of the pin terminals 25 and 30 can be deepened, so that a small and low-profile transformer can be realized.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 is a sectional view of a transformer according to a second embodiment of the present invention, and FIG. 4 is a perspective view of a main part as seen from the bottom surface thereof.
In the figure, reference numeral 31 is an E-shaped high resistance ferrite core in which magnetic legs are extended until they penetrate the coil bobbin 23. Similarly, 32 is an E-shaped low resistance ferrite core in which the magnetic legs are extended. The difference from the first embodiment is that the magnetic leg dimensions of the high resistance ferrite core 31 and the low resistance ferrite core 32 are made longer, and
The high-resistance ferrite core 31 is inserted from the lead-out portion of the secondary winding 22, and the low-resistance ferrite core 32 is inserted from the lead-out side of the primary winding 21.

With the structure of the ferrite core as described above, the number of parts of the ferrite core can be reduced to half as compared with the first embodiment. Further, since the number of working steps can be reduced, the manufacturing cost of the transformer can be reduced.

Although the high resistance ferrite core is inserted from both ends of the coil bobbin in the first embodiment, it may be provided only on the secondary terminal side. The dimensions of the magnetic legs may not be the same on the primary side and the secondary side.

[0027]

As described above, according to the present invention, by combining a high-resistance ferrite core and a low-resistance ferrite core in the magnetic core, it is possible to secure discharge strength without impairing the magnetic characteristics of the magnetic core, and It is possible to provide a transformer with a low profile and excellent safety.

[Brief description of drawings]

FIG. 1 is a sectional view of a transformer according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an essential part seen from the bottom of the transformer according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a transformer according to a second embodiment of the present invention.

FIG. 4 is a perspective view of an essential part seen from the bottom of the transformer according to the second embodiment of the present invention.

FIG. 5 is a sectional view of a conventional transformer.

FIG. 6 is a perspective view of a main part as seen from the bottom of a conventional transformer.

[Explanation of symbols]

 21 primary winding 22 secondary winding 23 coil bobbin 24 low resistance ferrite core 25 primary winding pin terminal 26 collar 27 lead-out groove 28 guide protrusion 29 high resistance ferrite core 30 secondary winding pin terminal 31 high resistance ferrite core 32 Low resistance ferrite core

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 27/32 B

Claims (2)

[Claims] 1. A ferrite core having a high electric resistance is provided at a position close to a planted portion of a pin terminal of a coil bobbin wound with a primary winding and a secondary winding and a lead-out groove of the winding, and an electric resistance is provided at other portions. A transformer with a low ferrite core mounted on a coil bobbin. 2. An E type having a long magnetic leg is used as a ferrite core having a high electric resistance and a ferrite core having a low electric resistance,
2. The transformer according to claim 1, wherein the high resistance ferrite core is incorporated into the coil bobbin from the secondary winding lead-out side, and the low resistance ferrite core is incorporated into the primary winding lead-out side.