JPS61129806A - Pulse transformer - Google Patents

Abstract

PURPOSE:To decrease the unnecessary radiation for whole frequency band width by connecting a shield plate positioned on the primary side to the case of the unit and connecting a shield plate positioned on the secondary side to the outside conductor of a transmission cable through a shield material. CONSTITUTION:A shield plate 11 and a shield plate 12 are provided electrically insulated and facing each other in a specified interval. A core material 19 is positioned at the specified position on the these shield plates 11 and 12 passing through the plates. Windings 17 and 18 are wound on the positions of the core material 19 facing each other so as to be positioned on the sides of the shield plates 11 and 12. The shield material is provided so as to surround the shield plate 12, and the shield plate 11 is connected on the case 15 of the unit, and then, the shield plate 12 is connected through the shield material 20 on the outside conductor 23a of the transmission cable 23 whose core wire is connected to the winding 18. Whereby, the noise source is confined in the shield for both primary and secondary sides of the windings 17 and 18, providing the DC insulation for the primary and secondary sides. An unnecessary radiation is decreased for whole frequency band width, with inexpensive construction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulse transformer suitable for use, for example, in data transmission of digital equipment.

[Conventional technology]

Pulse transformers are generally used when transmitting and receiving data in digital equipment, especially when DC isolation is required on the transmitting side. This DC isolation is required to prevent digital equipment from malfunctioning due to noise introduced into a large loop formed through the AC line. This pulse transformer is also used for the purpose of transmitting pulses between devices with completely different DC levels.

However, this DC insulation using a pulse transformer has a drawback in that it causes a large amount of so-called unnecessary radiation.

That is, as shown in FIG. 4, a conventional pulse transformer (1) includes a ring-shaped core member (2) and a primary winding ( 3) and a secondary winding (4), the signal source (5) of the digital equipment is provided on the primary winding (3) side, and the secondary winding (4) is connected to the transmission table (6) side. case (7)
) is stored within. and the transmission data from the signal source (5).

- The motor generally has a wide band noise component, and this noise component is coupled to the secondary side via the stray capacitance Csx that exists between the primary winding (3) and the secondary winding (4). This is because it is radiated using the outer sheath (outer conductor) of the transmission cable (6) as an antenna.

In addition, signals from various noise sources (8) within the device may be affected by stray capacitance C existing between the noise source (8) and the secondary winding (4).
This is because it is coupled to the secondary side via sy and is radiated at the same time.

[Problem that the invention seeks to solve]

In order to solve these drawbacks, conventional methods have been to narrow the radiation band by connecting an appropriate small-capacity capacitor to the outer sheath of the transmission cable and the equipment case, or to give up insulation using a pulse transformer and use an optical transmission cable, etc. However, in the former case, unnecessary radiation in the low frequency band still remains and a high frequency loop remains, which causes problems such as deterioration of sound quality, and in the latter case, the cost is extremely high. It has disadvantages such as being expensive.

The present invention has been made in view of these points, and it is an object of the present invention to provide an inexpensive pulse transformer that can reduce unnecessary radiation over the entire frequency band.

[Means for solving problems]

This invention provides first and second shield plates (11
) (12) and a core member (19) of a predetermined shape disposed at a predetermined position of these shield plates so as to pass through them.
), and the above-mentioned first and second
A plurality of windings (17) and (18) are wound so as to be located on the side of the second shield plate, respectively, and a shield member (2o) is provided to surround the second shield plate.
), and the first shield plate is attached to the device case (1
5), and the second shield plate is connected via the shield member to the outer conductor of a transmission cable (23) whose inner conductor is connected to one of the windings.

[Effect]

First shield plate (11) and second shield plate (12)
are provided facing each other and electrically insulated at a predetermined interval, and a core member (19) of a predetermined shape is disposed at a predetermined position of these shield plates so as to penetrate through the shield plates. A plurality of windings (17) (1B
) is wound, a shield member (20) is provided so as to surround the second shield plate, the first shield plate is connected to the device case (15), and the second shield plate is wound around the winding. The outer sheath or outer conductor of the transmission cable (23) whose inner conductor or core wire is connected to (18) is connected via a shield member. This results in 1 of the winding.
Noise sources are confined within the shield on both the primary and secondary sides, and DC insulation between the primary and secondary sides is obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 3.

Figure 1 shows the overall configuration of this embodiment. In the figure, α1 is an insulating substrate, (11) is a copper foil formed on one main surface of the insulating substrate α1, and (12) is an insulating substrate. Board a・
This is a copper foil formed on the other main surface of the.

That is, the insulating substrate Ql and the copper foil (11), (12
) constitutes a so-called double-sided substrate.

As shown in FIG. 2, the copper foil (12) is formed with a groove (13) in a predetermined shape, for example, a rectangular shape, by a common method such as etching, and is formed on the inner circumference (12a) and the outer circumference (12b). be divided. Then, copper foil (11) is placed on the four corners of the outer periphery (12b).
A screw hole (13') is provided that penetrates through the screw hole (13'), and the board Ql, which has copper foils (11) and (12) formed on both sides, is connected to the device case by screw (14) through this screw hole (13'). (Chassis) Attached to (15). As a result, the copper foil (11) is substantially grounded by contact with the case (15), and the outer periphery (12) of the copper foil (12)
b) is grounded by screw (14). Therefore, here, the outer periphery (12b) of the copper foil (1 work) and the copper foil (12) are shown.
) is the first shield plate (primary side), and the inner peripheral part (12a) of the copper foil (12) is the second shield plate (secondary side).By grounding this first shield plate, 2 from the primary side
Noise components that try to jump to the next side are almost completely dropped, are substantially shielded, and are not transmitted to the secondary side.

Further, a hole (1) having a predetermined shape, for example, a rectangular shape, penetrating up to the copper foil (11) is provided in the center of the inner circumference (12a) of the copper foil (12).
6) is drilled. The primary winding (17) and the secondary winding (
18) is inserted. At this time, the primary winding (17) is located on the first shield plate side, and the
The next winding (18) is located on the second shield plate side. This core member (19) is fixed to the substrate (to) side by adhesive or the like.

Further, a case-shaped shield member (2o) is provided to cover a portion of the secondary winding (18) that protrudes toward the inner peripheral portion (12a) of the copper foil (12) serving as the second shield plate. The bottom part of this shield member (2o) is fixed to the inner peripheral part (12a) of the copper foil (work 2) by solder (21). The top of the shield member (20) has a receiving part (22) for the connector (22).
22a), and opposite to this, one end of a coaxial cable (23) serving as a transmission cable is provided with an insertion portion (
22b) is provided, and this insertion part (22b) is connected to the receiving part (
22a), substantially the second shield plate is connected to the outer conductor (sheath) (23a) of the coaxial cable via the shield member (20); The conductor (core wire) (23b) is connected to one end of a secondary winding (18) via a matching resistor (24), and the other end of this secondary winding (18) is connected to a shield member (20). be done. In addition, the other end of this secondary winding (18) is the inner peripheral part (12a) of the l17I foil (12) II
It is also possible to connect it to I.

In this way, the inner peripheral part (12a) of the copper foil (12) serving as the second shield plate located between the secondary winding (18) and the first shield plate is connected to the coaxial cable (12a) through the shield member (2o). 23), the secondary winding (18) is substantially completely surrounded by the outer conductor (23a) of the secondary side coaxial cable (23), Unnecessary radiation noise is prevented from being generated from the voltage source itself generated in the secondary winding (18).

Note that the core member (19) is fitted into the hole (16) and held on the substrate αQ as described above, and therefore, in this state, the shielding effect does not extend to the inside of the core member (19). Therefore, as shown in FIG. 3, a copper piece (25) having a predetermined shape, for example, a V-shape, is placed between a part of the inner wall of the core member (19) and the copper foil (11) or (12). (
Volatize into part 26). One end of this copper piece (25) is attached to the copper foil (11) or (12) with a shaft (27).
The other end should be left a little space or insulated so that it does not come into contact with the copper foil (11) or (12) on the opposite side. This makes it possible to provide a shielding effect even to the inside of the core member (19).

This copper piece (25) may be inserted into both the primary side and the secondary side, or only on one side.It is optional whether the copper piece (25) is inserted into either the primary side or the secondary side, and unnecessary radiation is smaller than before even if the copper piece (25) is not inserted into either the primary side or the secondary side.

For example, the diameter of the core member (19) is set to about φ8, 1
When the number of turns of the secondary winding (17) was 167 and the number of turns of the secondary winding (18) was 4T, the following results were obtained when comparing the conventional pulse transformer and the pulse transformer according to this embodiment. . That is, in the conventional pulse transformer, the stray capacitance between the primary winding and the secondary winding was 1 pF, but in the pulse transformer according to this embodiment, the stray capacitance between the primary winding and the secondary winding was 1 pF. The stray capacitance between the next winding (17) and the second shield plate was 0.1 pF. This reduced unnecessary radiation by approximately 20dB.

〔Effect of the invention〕

As described above, according to the present invention, the first shield plate located on the primary side is connected to the case (chassis) of the equipment, and the second shield plate located on the secondary side is connected to the external conductor of the transmission cable. Since the connection is made through a shielding member that surrounds the secondary winding of the transformer, DC insulation between the primary and secondary sides of the pulse transformer is ensured, and unnecessary radiation is reduced over the entire frequency band. Moreover, there is no possibility that a high frequency loop remains and the sound quality is deteriorated as in the conventional case, and the cost is also low.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention, FIG. 2 is a plan view for explaining the invention in detail, and FIG. 3 is a partial sectional view for explaining the invention. , FIG. 4 is a configuration diagram for explaining a conventional example. . (to) is an insulating board, (11) and (12) are copper/foil, (15) is a case, (16) is a hole, (17) is a primary winding, (18) is a secondary winding, ( 19) is a core member, (20
) is the shield member, (23) is the coaxial cable, (25)
is a piece of copper. Figure 1

Claims (1)

[Claims] first and second shield plates that are electrically insulated and provided to face each other at a predetermined interval; a core member of a predetermined shape that is disposed at a predetermined position of the shield plate so as to penetrate therethrough; , a plurality of windings are wound around opposing portions of the core member so as to be located on the side of the first and second shield plates, respectively; and a plurality of windings are provided so as to surround a portion of the second shield plate. the first shield plate is connected to a device case, and the second shield plate is connected to an outer conductor of a transmission cable having an inner conductor connected to one of the windings, and the shield member A pulse transformer characterized by being connected through.