JPH11135344A - Compact transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact transformer with high performance and less loss which is suitable for a transformer in use for a chopper type DC-DC converter power supply circuit. SOLUTION: A primary coil, functioning as a largel-current choke coil, is wound as a sprial spring by a welded flat insulation wire, and it is welded by heating to form a bobbinless coil 1. Further, a secondary coil is wound as a spiral spring by a welded flat insulation wire having a width of one second or less of conductor as to form a two-layer coil, consisting of first layer coil and second layer coil, in such a way that the welded flat insulation wire on the most central side of the first layer coil is connected with that on the most central side of the second layer coil, and it is welded by heating to form a two-layer boibbinless coil 2, and then the primary and secondary coils are incorporated in a small-pot type core 3 having a closed magnetic circuit structure, thereby forming a compact transformer T1 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small transformer having a large current choke coil function for use in a DC-DC converter power supply.

[0002]

2. Description of the Related Art DC-DC mounted on portable electronic devices and the like
Converter power supply, size of the power supply, for the purpose of improving the weight and input-output conversion efficiency, in the direction of operating the switching frequency is 100kH _Z ~1MH _Z and higher frequency.
Under such circumstances, the transformer used for the DC-DC converter power supply is suitable for high-frequency operation.
There is a need for a small, high-performance transformer with little loss.

A conventional transformer will be described with reference to FIGS. First, in the chopper type DC-DC converter power supply circuit shown in FIG.
Transformer, as shown in FIG. 4, the transformer T ₂ which is wound the drum-type core 30 directly primary coil 10 and secondary coil 20 using a ferrite material used in circuits operating at H _Z frequencies above, Alternatively, as shown in FIGS. 5 and 6, the primary coil 10 and the secondary coil 20 are wound on the bobbin 40, and then assembled by an EE type core 31 or an EI type core 32 using a ferrite material. Transformers T ₃ or T ₄ are used.

[0004]

In a conventional transformer using a drum type core, as shown in FIG.
Since the core 30 has an open magnetic path structure, the effective magnetic permeability among the core magnetic characteristics is very low as compared with the core having the closed magnetic path structure. Therefore, when compared with the same number of turns, the result is that the inductance L shows a value that is as small as a fraction.

This means that in order to obtain the same inductance L in a transformer using a drum-type core as compared with a transformer using a core having a closed magnetic circuit structure, the number of turns must be increased. ing.
However, an increase in the number of turns causes an increase in the DC resistance R, resulting in a decrease in L / R, which is one of the important characteristics of the coil, resulting in deterioration of the transformer characteristics. Also L
A decrease in / R means that the DC loss of the coil increases. When this is used as a transformer, the power loss increases as compared with a transformer using a core having a closed magnetic circuit structure, so that there is a drawback that the conversion efficiency is poor, and a DC-DC converter of low power (several W or less) is used. There is a problem that it can only be used for a power supply.

Further, in a transformer having an open magnetic circuit structure using a drum-type core, since all magnetic flux goes out, it adversely affects other electronic circuits or components due to electromagnetic induction, and malfunctions of the electronic circuits may occur. It has the disadvantage that it is very likely to be the cause. For this reason, there is a problem that not only is there a great restriction on the arrangement of the components of the transformer, but also it cannot be used depending on the electronic circuit.

Transformers using an EE type core or an EI type core have cores 31 and
Since the structure of 32 is a closed magnetic circuit structure, it does not have the drawbacks of a transformer using a drum-type core, and is widely used for a DC-DC converter power supply from small power to large power.

However, the transformer using the EE type core or the EI type core has a structure in which a primary coil and a secondary coil are wound on a bobbin which becomes a winding core of a coil winding, and then these cores are wound. And a structure assembled as a transformer is a general structure. For this reason, the space factor is degraded by the amount of the bobbin, and it is necessary to increase the window area of the core. However, in this case, there is a problem that the outer diameter of the core is inevitably increased, and at the same time, the outer diameter of the assembled transformer is increased. In addition, the use of a bobbin has the disadvantage that the cost is higher than that of a transformer using a bobbinless coil.

[0009] As described above, DC-DC converter power source to be mounted on a portable electronic device, miniaturization of the power supply, for the purpose of improving the weight and input-output conversion efficiency, operating switching frequency and 100kH _Z ~1MH _Z In the direction of higher frequencies. In such a situation, the chopper method D
There is also a demand for a small-sized, low-loss, high-performance transformer that improves the disadvantages and problems of the above-described conventional transformer suitable for high-frequency operation in a transformer used for a C-DC converter power supply.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned various problems of the prior art.
-An object of the present invention is to provide a compact, low-loss, high-performance transformer suitable for use in a DC converter power supply circuit.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a high-current choke coil which also functions as a high-current choke coil.
A bobbinless coil (hereinafter abbreviated as a spiral wound coil) in which a fused flat rectangular insulated wire having a large conductor cross-sectional area capable of permitting an output current of an output voltage is wound in a spiral shape and heated and fused to the next coil n _1. And the secondary coil n ₂
A two-layer coil formed by winding a flat rectangular insulated electric wire having a width equal to or less than の of the conductor width of the primary coil n _{1 in} a spiral manner to form a first-layer coil body and a second-layer coil body. Winding (hereinafter abbreviated as "alpha winding") such that the most central fused flat insulated wire of the first layer coil body is connected to the most central fused flat insulated wire of the second layer coil body. 2-layer bobbin-less coils heat sealing after (hereinafter, abbreviated as alpha-turn coil) used, the primary coil n ₁ and 2
Built next coil n ₂ small pot core of closed magnetic circuit structure, in miniaturized small transformers. The large current is, for example, 3 to 10 A. The structure of the alpha winding coil itself is known as disclosed in FIG. 1 of Japanese Utility Model Laid-Open No. 61-114946. This alpha-wound coil is shown in FIG. In FIG. 7, 2a
Is a flat wire.

Further, according to the present invention, the small pot-shaped core having the closed magnetic circuit structure comprises a pot portion and a lid portion provided with a groove at the upper four corners, and the primary coil n ₁ and the secondary coil n ₂ are provided in the groove. The small transformer has a structure in which a total of four terminals are inserted and pulled out as leads outside the core.

This will be described in more detail. First, the chopper type DC-DC converter power supply circuit shown in the circuit diagram of FIG. 3 will be described. In this Figure 3, small transformers of the present invention is shown by the symbol T _1, n ₁ is the primary coil, n ₂ denotes the secondary coil. N also indicates the number of turns. here,
n ₁ : n ₂ operates as a transformer, and n ₁ also operates as a coil for a large current choke function. Also,
C ₁ and C ₂ are capacitors, D ₁ and D ₂ are diodes, T
R ₁ is a transistor, V _IN is an input voltage, and V ₁ and V ₂ are output voltages. Also, the output voltage V ₂ = n ₂ / n ₁ × V ₁
It is.

In the transformer T ₁ used in the circuit of FIG. 3, as a specific means for solving the above-mentioned conventional problems, a primary conductor n ₁ is provided with a large conductor cross-sectional area (depending on an output current capacity). The flattened insulated electric wire having a winding is wound in a spiral form by a winding machine, and a heated spirally wound winding coil, a secondary coil n ₂ , and a primary coil n
_A flat rectangular insulated electric wire having a width equal to or less than 1/2 of the conductor width of _{No. 1} is wound by an alpha coil winding machine, and the heat-sealed alpha wound coil is closed by a Ni-Zn ferrite material. The above-mentioned conventional problem is solved by incorporating a small pot type core having a structure into a small transformer.

[0015]

[Action] small transformers T ₁ of the present invention, as shown in FIG. 1, a closed magnetic path mainspring wound coil 1 of the primary coil n ₁ in a small pot core 3 structures the secondary coil n ₂ alpha-turn It has a transformer structure in which the coil 2 is completely covered with a core. For this reason, when compared with a transformer using a drum core with the same number of coil turns, the pot type core has a large effective magnetic permeability, so that a value about four times larger in inductance can be obtained. EE type, E
Even when compared with a transformer using an I-type core, a value approximately twice as large can be obtained. As a result, in the transformer using the pot-type core, the number of coil turns that obtains the same inductance as the transformer using the drum-type core can be obtained with half the number of coil turns of the transformer using the drum-type core. The sectional area of the coil can be reduced to half.

Also, in comparison with a transformer using an EE type or EI type core, the same inductance can be obtained with a coil turn of 1 / 1.4, and a bobbin is used as a winding frame. Therefore, the cross-sectional area occupied by the coil portion can be reduced to about 1/2 as a whole.

Further, in a coil having the same coil inner diameter, it is possible to reduce the coil outer diameter by an amount corresponding to halving the sectional area occupied by the coil portion. As a result, the outer diameter of the core accommodating the coil can be reduced in proportion to the coil size, and the transformer can be reduced in size.

Further, the small transformer according to the present invention is characterized in that the small pot-shaped core having the closed magnetic circuit structure has a groove formed in the upper four corners thereof.
A total of four terminals of the secondary coil n ₁ and the secondary coil n ₂ can be inserted and pulled out as leads outside the core.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. First, in FIG. 1, reference numeral 1 is a primary coil n ₁ that operates as a high current choke coil. The primary coil n ₁ is formed by welding a flat rectangular insulated electric wire (having a conductor width equal to or less than the core inner height) having a large conductor cross-sectional area that can tolerate an output current of the output voltage V ₁ by an air-core coil winding machine. This is a spirally wound coil in which a bobbin-less coil that has been cooled and hardened is taken out from a winding machine after the coil is wound in a spiral shape, and then heated and fused by hot air or energization or the like.

Reference numeral 2 denotes a secondary coil n ₂ functioning as a transformer. The secondary coil n ₂ has a conductor width of １ ／ or less of the conductor width of the fused rectangular insulated wire used for the primary coil n ₁ and has a conductor rectangular cross section of 1/10 to 1/50. heating the insulated wire at the alpha coil winding machine, after alpha winding turns calculated by the following equation 1 on a slightly larger winding axis than the primary coil outer diameter of the coil n _1, with hot air or current, etc. This is an alpha-wound coil in which a bobbin-less coil that has been fused and then hardened by cooling is removed from a winding machine.

[0021]

[Equation 1] Number of turns of secondary coil n ₂ = V ₂ / V ₁ × n ₁
(N is the number of turns)

Next, the primary coil n
₁ 1 and the secondary coil n ₂ 2 at the winding start, after cutting a total of four winding end terminals need line length, performs terminal processing of the preliminary solder.
The primary coil n ₁ 1 and the secondary coil n ₂ having completed the above operations
2 is incorporated into the pot-shaped core shown in FIG. 2A and 2B are schematic diagrams showing the structure of the pot-shaped core. FIG. 2A is a front view of the pot portion, FIG. 2B is a cross-sectional view of FIG. () Is a front view of a lid portion, and (d) is a cross-sectional view of (b) in FIG. In FIG. 2, 3a is a pot portion, 3b is a lid portion, and m is a groove.

Further, although not shown, the pot core for insulation between the primary coil n ₁ and the secondary coil n ₂ to incorporation during, was a thin film in a cylindrical insulating tube primary coil n ₁ When inserted between the secondary coil n _2. Next, the four terminal-processed terminals are inserted into grooves m at the four corners of the pot portion 3a, and pulled out of the core. Next, a lid 3b, which is a disc-shaped core, is fitted and inserted into the pot 3a. Next, an adhesive is applied to the fitting portion, cured and fixed, and integrated as a pot-shaped core 3.

Next, although not shown, the pot core 3
A metal such as silver (Ni-Zn ferrite material has a specific resistance of 10 ¹⁰ ohms or more) is provided on the outer periphery of the four corners to provide four electrodes, and then the four electrodes are provided on these electrodes. the terminal processed terminal was completed as a small transformer T ₁ of the fixed and the surface mounting type soldering.

The electrode structure of the transformer is such that the pre-soldered primary coil n ₁ and secondary coil n ₂ are wound at the beginning and end of winding, and the flat insulated wires at the ends are wound on the pot-shaped core 4.
It is also possible to use a method of directly bonding and fixing the outer periphery of the corner to form a transformer electrode.

Although the miniature transformer of the present invention has a structure using a fused rectangular insulated wire as an embodiment, a current capacity and high frequency characteristics can be obtained even with a bobbinless coil wound with a round fused insulated wire. Although it is inferior, it can be manufactured with the same structure.

As an embodiment of the transformer of the present invention,
Although the non-insulated chopper type DC-DC converter power supply of FIG. 3 has been described, it goes without saying that the transformer of the present invention can be used as a transformer of an isolated DC-DC converter power supply.

[0028]

According to the transformer of the present invention, not only the outer diameter of the transformer can be reduced by downsizing the coil, but also the amount of electric wire used and the ferrite material can be reduced by downsizing the core, thereby reducing the weight of the transformer. Can be
Since the total length of the electric wire used for the coil is reduced by 30 to 50%, the effective resistance is reduced accordingly, the AC loss and the DC loss can be reduced, and the conversion efficiency can be improved. Further, heat generation due to loss can be improved by 30 to 50%. Since the core has a completely closed magnetic circuit structure, the leakage magnetic flux is very small, and the adverse effect of the magnetic flux on other circuits or components can be greatly reduced. The structure is suitable for miniaturization and high density mounting required for parts of portable information equipment. As described above, the transformer of the present invention
Practical effects are extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a small transformer using a small pot-shaped core having a closed magnetic circuit structure according to the present invention.

FIG. 2 is a schematic view showing a configuration of a small pot type core having a closed magnetic circuit structure used in the small transformer of the present invention. (A) is a front view of a pot part. (B) is (a) sectional drawing of the aa part of FIG. (C) is a front view of a lid part. (D)
(C) is a sectional view taken along the line bb in FIG.

FIG. 3 is a circuit diagram showing a DC-DC converter power supply circuit using the small transformer of the present invention. (Also used for conventional technology)

FIG. 4 is a schematic sectional view showing the structure of a conventional transformer using a drum core.

FIG. 5 is a schematic sectional view showing the structure of a conventional transformer using an EE type core.

FIG. 6 is a schematic sectional view showing the structure of a conventional transformer using an EI type core.

FIG. 7 is a perspective view showing a structure of an alpha-winding coil.

[Explanation of symbols]

1 the primary coil n ₁ (a mainspring wound coils) 2 secondary coil n ₂ (alpha-turn coil) 3 pot core 3a pot portion 3b lid portion C _1, C ₂ capacitors D _1, D ₂ diode T ₁ small transformers TR ₁ Transistor V _IN input voltage V ₁ , V ₂ output voltage

Claims (2)

[Claims] 1. A primary coil n ₁ that also functions as a large-current choke coil, fused rectangular insulated wire was wound on spirally to thermal bonding with a large conductor cross-sectional area that can tolerate the output current of the output voltage to use the bobbin-less coil and a secondary coil n _2, 1 1 layer coil body below half fusion Chakutaira angle insulated wire was wound in spirally the primary conductor width of the coil n ₁ and 2 In the two-layer coil forming the coil body of the first layer, the fused flat rectangular insulated wire at the most central side of the first layer coil body is connected to the fused rectangular flat insulated wire at the most central side of the second layer coil body. The primary coil n ₁ and the secondary coil n ₂ are assembled in a small pot-type core having a closed magnetic circuit structure by using a two-layer bobbinless coil that is heat-sealed and then heat-sealed. Small transformer. 2. A small pot-shaped core having a closed magnetic circuit structure comprising a pot portion and a lid portion provided with grooves in upper four corners, and a total of terminals of a primary coil n ₁ and a secondary coil n _{2 in} the grooves. 2. The small transformer according to claim 1, wherein four small wires are inserted into the core and are drawn out of the core as leads.