JPH01266704A - Transformer - Google Patents

Abstract

PURPOSE:To reduce leakage inductance while suppressing stray capacitance by forming a first winding with open-looped, conductive tubular paths and by winding other windings so that they pass through the interior of the conductive tubular paths. CONSTITUTION:A secondary winding N2 is formed of open-looped, conductive tubular paths 1a, 1b and a first winding N1 is arranged so that it passes through these paths. More specifically, it is of such structure that the secondary coil N2 neighbors an iron core 5 thereof in all the four surfaces to allow a good magnetic coupling. Thus, an N2 voltage and current induced by the flux of the first winding N1 is increased, which, in turn, reduces leakage inductance correspondingly. Thus, the neighboring surface area of the first and second windings N1, N2 is decreased, thereby allowing leakage inductance to be reduced without increasing the stray capacitance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transformer, particularly a high frequency transformer suitable as an output transformer for a switching power supply device.

(Prior art and its problems) As a switching power supply device, for example, as shown in FIG. 8, the primary windings N,
Apply voltage to diode D and smoothing circuit CH
Products that are rectified and smoothed using methods such as those used to supply power to loads are widely used as power supplies for electronic computing devices and other devices. By the way, in such a switching power supply device, the switching frequency of the semiconductor inverter circuit λ is being increased to a higher frequency due to demands such as power transfer efficiency, but in this case, if the leakage inductance of the output transformer T is large, the inverter circuit This leads to an increase in the surge voltage level that occurs when the switching elements constituting the switch are turned off, and to deterioration of the power transfer characteristics. In addition, if the stray capacitance between the primary and secondary windings N I and N Z is large, noise generated when the switching element is turned off and external noise from the power supply etc. will be easily transmitted to the output side via the output transformer T. Therefore, there is a drawback that this increases the risk of causing damage or malfunction to the load circuit elements.

By the way, conventionally used transformers, for example, Fig. 9(a)
First wind the secondary winding N2 around the iron core C, and then
In a transformer having a conventional structure in which the next winding N is wound, it is difficult to reduce the shedding inductance.

Therefore, as shown in FIG. 9(b), the primary and secondary windings Nl
, N2 are alternately laminated to achieve a tight coupling between the primary and secondary windings N r and N z , thereby reducing leakage inductance. ing. However, with this method, 1
This has the drawback of increasing stray capacitance between the next and secondary windings N, , N, and increasing the amount of noise transmitted to the output side.

(Objective of the Invention) An object of the present invention is to provide a high-frequency transformer with reduced leakage inductance while reducing stray capacitance.

(Means of the present invention for solving the problem) The number of turns of an output transformer used in a switching power supply device is generally small, and in the case of a device with a high switching frequency, the number of turns of the primary winding ranges from several turns to 10 turns. The winding has several turns, and the secondary winding has one to several turns. The present invention has been developed with this in mind, and is characterized by the fact that the secondary winding is formed by an open loop conductive conduit body, and the primary winding is provided so as to penetrate through the inside of the secondary winding. This structure reduces leakage inductance without increasing stray capacitance. Next, the present invention will be explained with reference to drawings of an embodiment.

(Embodiment) FIG. 1 is a perspective view of an embodiment of the present invention in which the secondary winding has one turn, and FIG. 2 is an exploded perspective view thereof.

In FIG. 1, Nz is a secondary winding, which is formed from the following parts. (la) and (lb) are conductive pipe bodies, respectively, which are made as shown in (la) and (lb) in FIG. (2) is a connection terminal board, (3) is a connection board,
The connection terminal board (2) is an insulating board (2a) with two pipe body insertion holes (2al), as shown in (2) in Fig. 2.
) is formed by depositing a metal film using sputtering or vapor deposition technology, and is arranged in two parallel openings (2b).
(2c). Also, the connection plate (3) is the second
As shown in (3) in the figure, a common connection part is formed by applying metal in a horizontal shape to an insulating substrate (3a) having a conduit body insertion hole (3a,) using the same technique as above. (3b)
has. And the opening-shaped connection part (2) of the connection terminal board (2)
b) Connect one end of the conductive pipe bodies (la) and (lb) to (2c), for example, by soldering, and connect the other end to the connecting plate (
By soldering to the common connection part (3b) of 3), a one-turn open loop secondary winding N2 having a core insertion interval (4) at the center is formed.

Next, N is the primary winding, first of all, the first conductive pipe body (
1a), then fold back and insert the second conductive pipe body (1b
), a primary winding N having the required number of turns is formed. (5) is a three-leg iron core, and (5) in Fig. 2 is a three-leg iron core.
a) As in (5b), the first. Consisting of the second core forming part, each central leg (5a +) (5b r
) is inserted into the space (4) provided between the secondary winding conductive conduit bodies, and the respective legs are butted together. In this case, in order to maintain the overlapping state of the iron cores, an appropriate bond maintaining material (not shown) is provided.

(Function) Each part of the present invention having the above structure has a relative position as shown in the front view of FIG. 3, and the primary winding N is surrounded by the secondary winding N2 on the entire circumference. Therefore, if a current in the direction shown by ■■ in Figure 3 is passed through the primary winding N, the primary winding N.

The magnetic flux generated in the iron core (5) interlinks with the secondary winding N2.
Only the magnetic flux Φ entering therein and the magnetic flux Φ1□ leaking out of the iron core (5) after interlinking with N2, all of the generated magnetic flux of N interlinks with the secondary winding N2.

On the other hand, in the conventional transformer shown in FIG. 9(a), the above-mentioned Φ, 1. In addition to Φ1□, magnetic flux Φ, which does not interlink with the secondary winding N2 but flows into the iron core, is a waste that leaks into the secondary winding without interlinking with the iron core or flowing into the iron core. It has a magnetic flux ΦI4. Therefore, in the case of the present invention, the amount of magnetic flux interlinking with the secondary winding N2 is larger compared to the conventional one, and furthermore, in the present invention, the secondary coil N2 is adjacent to each other in the four circumferential directions of the iron core, so the magnetic flux is Better bonding.

Therefore, the induced voltage and current amount in N2 due to the magnetic flux of the primary winding N are larger than in the conventional case, and the leakage inductance can be reduced accordingly.

Furthermore, the present invention does not use sand inch winding (to reduce leakage inductance), so the adjacent area between the primary and secondary windings N, , N, , etc. is small.

Therefore, the leakage inductance can be reduced without increasing the stray capacitance unlike the sandwich-wound transformer shown in FIG. 9(g) above, and as a result, the leakage inductance is lower than that of the conventional transformer shown in FIG. Small, Figure 9(b)
This makes it possible to realize a high-frequency transformer with smaller stray capacitance than the conventional transformer shown in .

(Other Embodiments) In the above, a conductive conduit body forming the secondary winding N2 has a rectangular cross section, but it goes without saying that it may be circular or other shapes. Moreover, in the above, a plurality of conductive conduit bodies (la) are formed by the connection terminal plate (2) and the connection plate (3).
Although the secondary winding N2 is formed by connecting (lb), it can be formed by bending a single conductive pipe, for example, as shown in the perspective view of FIG. In addition, although the above description has been about a one-turn secondary winding, the connecting terminal plate (2) and the connecting plate (3) are used to connect four or more conductive conduit bodies as shown in Figure 5.
, the secondary winding N with the number of turns of 2 tangs or more
You can make 2.

Further, in the above, the secondary winding was formed by connecting the conductive pipe bodies with the connecting plates (2) and (3), but for example, by bending one conductive pipe as shown in FIG. A secondary winding having multiple turns can be formed.

However, in this case, winding the primary winding N becomes a little complicated.

Furthermore, although the transformer using an iron core has been described above, it goes without saying that an air core transformer may also be used. Furthermore, as shown in Fig. 7, in the switching power supply shown in Fig. 8, the rectifying diode D can be connected to the connection terminal plate (2) to which the secondary winding N2 is connected and fixed. From the wire Nz to the diode D via the lead wire
Since the L%m impedance of the high frequency circuit between the secondary winding and the diode can be made smaller than that in which the secondary winding and the diode are connected, the voltage fluctuation rate can be reduced. Furthermore, although the transformer has been described above, it goes without saying that it can also be used as a current transformer. It goes without saying that it can also be used in general high frequency circuits other than output transformers of switching power supplies. Moreover, although the transformer consisting of the primary and secondary windings has been described above, the tertiary and quaternary windings can also be wound in the same manner as the primary winding N.

(Effects of the Invention) As is clear from the above, the present invention provides a high frequency transformer with low leakage inductance and low stray capacitance, and therefore includes a semiconductor switching circuit that is particularly prone to generating surge voltage. The effect is great when used in high frequency circuits. Figure 7 shows the present invention (curve A) and the conventional transformer (curve 8).
These are the results of an experiment in which the relationship between leakage inductance and stray capacitance was determined using the curve (curve) as a parameter, and it can be seen that the present invention continues to be superior.

[Brief explanation of the drawing]

FIG. 8 is a circuit diagram showing an example of a switching power supply device, FIGS. 9(a) and (b) are schematic structural diagrams of a conventional transformer, and FIG.
FIG. 2 is a perspective view showing an embodiment of the present invention and an exploded perspective view thereof, FIG. 3 is a front view of the present invention, FIGS. 4 and 5,
FIG. 6 shows a modification of the present invention, and FIG. 7 shows experimental results. X...Semiconductor inverter circuit, ■...Constant voltage control circuit, T...Output transformer, N...Primary winding,
N2... Secondary winding, D... Rectifier diode, C
H...Smoothing circuit, L...Load, C...Iron core,
(la) (lb)... Conductive pipe body, (2)...
・Connection terminal board, (2a)...Insulating board, (2b)
(2c)...mouth-shaped connection part, (3)...connection plate,
(3a)... Insulating substrate, (3b)... Common connection part, (4)... Core insertion interval, (5)... Iron core, (5a) (5b) - Core forming part, ( 5a+)
(5t++) Central leg. yI? ! Figure 1 弗 2 Figure 8 <CI+ (b) @4!
・) Honmohe・hK Engineering・・−3

Claims (2)

[Claims] (1) A transformer characterized in that the first winding is formed of an open-loop conductive conduit body, and other required windings are wound so as to pass through the open-loop conductive conduit body. . (2) Both ends of a plurality of conductive conduit bodies are connected in series while being positioned in parallel with a connecting terminal plate and a connecting plate to form a first winding made of open loop conductive conduit bodies. A transformer according to claim 1, characterized in that: