GB2271888A

GB2271888A - Component transformer housing, winding and terminal arrangement

Info

Publication number: GB2271888A
Application number: GB9321647A
Authority: GB
Inventors: George Brune; Wilfried Krug; Eckhard Sander
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 1992-10-20
Filing date: 1993-10-20
Publication date: 1994-04-27
Also published as: FR2697942A1; DE4235314A1; FR2697942B1; GB9321647D0

Abstract

A transformer component suitable for use on a printed circuit board with at least two separate windings (W1, W2 contained in a housing in which the ends of one winding (W1) are connected to terminals (A5, A6) Protruding on one side of the housing and the ends of a second winding (W2) are connected to terminals (A1, A4) protruding on the opposite side of the housing. The component may be used for electrical isolation and level adaptation in an ISDN communications system. <IMAGE>

Description

2271888 COMPONENT WITH TRANSFORMER FUNCTION The invention relates to a

component which consists of a housing and a transformer contained therein which has at least two separate windings, the winding ends of which, in the interior of the housing, are connected with terminals which protrude from the housing, and which is used beside other components as an assembly element for printed circuit boards.

Such transformers which are enclosed in a housing are known, for example, as wired component parts. They are used in transmission and communications systems inter alia for electrically isolating, for example, the line side terminal of system components. When used on printed circuit boards, it is necessary to ensure that no arcing due to static charges can occur between the printed conductors leading to the input and output sides of such a transformer. Quite specific regulations must therefore be observed with regard to electrical safety. These regulations can differ in individual countries, for example in view of the voltage values to be considered. Furthermore, when considering the conductor routing for the terminals of such a transformer, coupling of the transmitted information should not be allowed to develop, in order to guarantee trouble-free functioning. This is particularly important during the transmission of information at high data rates. Special precautions are necessary in order to be able to meet the specifications which exist, for example, with regard to creepage distance and clearance problems when using the known transformers for assembly on printed circuit boards, on account of their given terminal diagrams. Thus, for example, additional paths also having directional change must be provided for the individual printed conductors. This results in additional space being required for the accommodation of the respective 1 component, and the functioning of the component can also be impaired as a result. In Figure 1, a terminal diagram for a transformer which is already commercially available is represented, in which cross-overs are required for the windings because of the position and assignment of the terminals. Additional problems then arise when preparing the layout for such a printed circuit board as a result of the necessary change of the printed circuit board side. The maximum creepage distance and clearance which can be attained is small. In order thus to be able to satisfy the regulations in each case, starting from the respective terminal pin a detour towards the outside is to be provided. Although such transformer-components are realized internally so as to be extremely resistant with regard to high voltage, this benefit is wasted as a result of the "pinout" and the printed conductor routing necessary therewith. In certain countries, limiting values with regard to functional reliability and with regard to electrical safety are fixed which are higher than in other countries. In order to meet these values, comparatively large housings are then to be provided for the transformers to be used in these countries. The provision of such differing housing sizes is, however, also disadvantageous in so far as in such a case no common layout applicable to all countries is possible for one printed circuit board. It is not possible to use the same component either if subsequently more stringent requirements are issued with regard to the values to be considered.

The invention seeks to optimize a component, which has a transformer function, for very different cases of use. At the same time, the problems on account of existing regulations for the layout of a printed circuit board are to be reduced to a minimum.

According the invention there is provided a component which consists of a housing and a transformer contained therein which has at least two separate windings, the ends of which windings, in the interior of the housing, are connected with terminals which protrude from the housing, and which component is used beside other components as an assembly element for printed circuit boards, wherein the ends of the first winding are connected with terminal pins which are at the furthest possible distance from those terminal pins with which the ends of the second winding are connected, given the preset housing form.

Accordingly for the smallest possible housing, the greatest possible distance between the terminal pins is achieved, that is, the optimum isolation in terms of safety. At the same time, the material expenditure for the production of such a housing is then thereby diminished. Exact isolation between the two transformer sides takes place towards the outside. As a result, the transformer winding in the interior of the housing can be arranged separately likewise in a simple manner.

In particular the windings may be arranged within the component housing such that the windings are arranged within the component housing such that each end of the windings is connected to the respective terminal pin without crossing another winding.

Furthermore the winding may be arranged within the housing such that their core or cores are parallel to an end face of the housing containing the associated terminal pins.

Maximum creepage distances and clearances can be achieved on the printed circuit board, with which clearances even those regulations which are determined on the basis of comparatively high limiting values, can be observed. One and the same printed circuit board can thus be employed for use in different countries.

In particular in the case of rectangular housing shapes, the regulations which exist with regard to electrical safety and with regard to functioning can also be met in particular in that the terminal diagram according to the invention and the coordination of the transformer windings permit non-crossing, linear and substantially parallel, short line routing. This is advantageous in particular when the rate of data transmission is high. No detours for the printed conductor are thus enforced so that an adverse influence as a result of earth lines or as a result of other data lines can be avoided in a simple manner. As a result of the choice of assignment of the terminal pins of the transformer according to the invention, integration of the transformer into an assembly on a printed circuit board can also be carried out in an optimum manner in consideration of the valid regulations.

According to the invention, the component can be used as an SMD-component (Surface Mounted Device) so that the advantages connected therewith, such as, Inter alia, inexpensive construction, can be exploited.

The optimum integration mentioned is possible in particular if according to the invention the terminal pins are arranged, in the case of a housing which in the plan view is rectangular, exclusively on two opposing housing faces or in the region of two opposing boundary edges of the base area and each end of the first winding is exclusively connected with, in each case, one of the terminal pins provided on the first housing side or in the region of the boundary edge, and each end of the other winding is exclusively connected with, in each case, one of the terminal pins provided on the other housing side lying opposite the first housing side or on the opposing region of the boundary edge.

1 The terminal pins respectively associated with the winding ends of each winding can be at the furthest possible distance from each other, which distance is defined, for example, by a preset grid. As a result, according to a further development of the invention it then becomes possible to provide, furthermore, two additional terminal pins at least relative to the terminal pins of one winding, which additional pins lie between the terminal pins present for the ends of this winding mentioned. As a result, there is an unequal number of terminal pins on the two sides, whereby assembly with protection against polarity reversal is also guaranteed. A component which has been used incorrectly can thus be recognized immediately by means of a visual examination.

According to a further development of the invention, this first winding is subdivided into two part windings. The first end of each part winding is connected with respectively one of the external terminal pins, the second end of each part winding being connected respectively with one of these additional terminal pins. The connection of these free ends of the part windings is effected in an advantageous manner in such a way that this second end of each part winding is connected with that free additional terminal pin which lies next to the terminal pin associated with its first winding end. In addition to spatial isolation of primary and secondary side of the transformer, a symmetrical terminal assignment therefore also results. This is of significance in particular for a component which can be surface-mounted in order to make savings in respect of throughconnections.

A transformer with the two part windings associated with one side is employed in use in communications systems, for example, if remote feed of -6 connected telephone terminal units has to take place.

According to the invention, the two additional terminal pins of the first outer side, which pins protrude f rom the housing in an insulated manner, are connected with each other by means of a printed circuit board-printed conductor. As a result, there is basically the possibility of using transformers with two part windings for the first transformer side even if merely one transformer which has just one part winding relative to each terminal side is required for the respective case of application. This can be sensible in certain cases if, for example, the one or the other type of transformer can be provided more cheaply. These two types of transformer are then to be used in each case as a "second source" in a pincompatible manner.

The housing for the component can be selected according to the invention such that in its plan view it has a substantially square form or boundary surface.

The smallest possible cornered housing can thus be used relative to the shape of the transformer windings contained therein. The choice of an almost square housing also renders possible the horizontal structural form and thus little overall height.

The pinout of the transformer can be used selectively for transformers with one and with two part windings on one side, for example on the primary side, in which case, as already mentioned, the transformer with two part windings with downward compatibility can be inserted into a printed circuit board for the transformer with just one winding on this corresponding side.

The advantages of the component according to the invention with transformer function have an optimum effect in their entirety in particular when this component is provided on a printed circuit board which pertains to a digital interface for the transmission of voice information and of data information with a high transmission rate. The layout of the printed circuit board can be created in an optimum manner with the component according to the invention with regard to the specifications of certain standards (for example ETS300.012) for the ISDN-layer 1 of an SO- interface and the standard EN60950-U1003 which relates to electrical safety. The high data transmission rate of such a four-wire-usable standardized interface SO or the interface S2 of an ISDNcommunications system requires that the conductor connections on the printed circuit board be run so as to be as short as possible, as parallel as possible and in a straight line. These requirements can be met in an optimum manner by means of the component according to the invention on the basis of the outlined spatial isolation of primary and secondary side and on the basis of the symmetrical terminal assignment. With this use, for the sake of the requirements which exist in total, the advantages presented by this component can be exploited to the full. Given the substantially square embodiment of the housing parallelepiped block, the optimum creepage distance and clearance between the primary and secondary terminals is also attained. Thus all European safety requirements according to this standard which has been mentioned can be covered. The requirement, which exists for such digital ISDN-Sinterfaces, that namely for the purpose of obtaining symmetry of the impedance to earth the information communicated on the printed conductor may not be affected electromagnetically by other adjacent conductor routes, can easily be met. The interface must namely correspond to quite specific physical parameters so that ISDN-terminal units of the various manufacturers can be connected to ihe bus of the interface. As a result of the coordination of the transformer windings according to the invention with quite specific terminal pins, as a result of this selection there is a practical solution which has the outlined, extremely positive features for the conductor routing with respect to the transformer used in an ISDN-S-interface.

The terminal points (PAD-pattern) of the terminal pins on the printed circuit board substantially represent the layout of the position of the terminal pins actually present in total, in each case, on opposing sides. The transformer component is designed with regard to its terminal pins in such a way that to a certain extent the latter is basically congruent with the conductor feeds contained in the circuit diagram. Accordingly the specifications of the circuit diagram can be used directly for the production of the relevant layout of the printed circuit board. Thus there follows from this a linkage of the transformer, which linkage is free of change-overs and thus inexpensive and problem-free with regard to the ISDN-requirements.

Further advantageous developments can be inferred from the remaining claims.

For a better understanding of the present invention, and to show how it may be brought into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a terminal diagram of a commercially available transformer. 30 Figure 2 shows part of the circuit diagram of a port of an SO-interface. Figures 3 and 4 show, as an exemplary embodiment, in each case a diagrammatic representation of the outline of a transformer in accordance with the invention, with the windings which are accommodated therein being indicated diagrammatically.

-g- Figure 5 shows the soldering pattern (PAD-pattern) on the printed circuit board for a transformer in accordance with the invention.

The terminal diagram of a commercially available transformer element which, for example, represents a wired component part (PTH-component, pin to hole) has already been explained. This component requires crossovers for its connection on the printed circuit board and "detours" are made in the conductor routing so that, for example, when used in an S-interface of a communications system, the electrical safety and the functionality specifications can be met. The maximum creepage distance and clearance which can be attained is denoted by the letter a; it amounts, f or example, to approximately 4 mm.

Figure 2 shows, in part of the circuit diagram of an SO-port, the use of the transformer according to the invention in the digital interface SO. This digital interface is used for level adaptation and for electrical isolation between line and ISDNtelecommunications system or between line and ISDNterminal units. A respective transformer component Uel and Ue2 is present for the input and output signal direction. This component is not formed as a pluggable wire component, but represents a component which can be surface-mounted, a so-called SMD-component (Surface Mounted Devices). The terminals or terminal pins can, for example, be realized as metal caps and also as soldering ends which are angular or hook-shaped. In particular they may be used advantageously for the transmission of digital information, in particular of high rates of information, due to the reduction of parasitic capacitance and inductance at the terminals achieved thereby.

The terminal points 1 to 4 represent the terminals for the assembly plug. Drl to Dr4 denote current- compensated annular-core reactors which are used for the suppression of disturbance signals. The diodes denoted by Gl to G9 represent a protective circuit arrangement for the module IC which is connected by way of the series resistors Rl to R4 to a respective transformer winding Wl. A conversion of information in respect of downstream, system-specific components is effected by means of this telecommunications module IC. For example, for the purposes of synchronization this module IC effects the conversion of the incoming clock pulse edges to the clock pulse edges supplied on the system side. Furthermore, it also performs logging functions. This means that in those cases in which "jobs" are to be communicated, it inserts the corresponding bits into the data stream. Such jobs are retransmitted by way of a bit word which is introduced again and again into the data stream. Furthermore, conversions are effected by this module, for example the conversion of data with a code of a so-called three-level logic to a normal TTL-level.

In the exemplary embodiment, the transformer winding of the one side is subdivided into two part windings, namely the part winding W21 and the part winding W22. In the case of an SO-interface near to the device, such part windings are necessary if an ISDN-terminal device in a so-called phantom feed has to be supplied with power by way of an installation line or, for example, a line of the German Bundespost (Federal Postal Administration). This would also apply to terminal devices with which no special plug-in power supply unit is associated and which do not therefore have their own power supply. The terminals of the part windings W21 and W22 which do not belong to the line are connected, in the exemplary embodiment, by means of a bridge. The transformer variant having two part windings can thus be used in this manner even in cases when a transformer is required with, in each case, just one single winding for each side. If therefore, for example, the demand for SO- terminal devices which have to be fed remotely by way of a line in the absence of their own plug-in power supply unit should be reduced, existing surviving components of transformers with twopart windings could be used instead of the transformers with, in each case, one-part windings. This could of course also be the case if for quite specific reasons this kind of transformer can be obtained more cheaply. The advantages in the case of the application of the component according to the invention are thus not only of a technical nature, but also of a logistic nature. If this connection at the terminal pins of the component is made, in cases without remote feed, transformers of one-part winding type and also transformers of the other two-part winding type can thus be used in a pin-compatible manner, possibly resulting in economic advantages. The choice of transformer can be made to depend upon the costs.

In Figures 3 and 4, the component according to the invention is represented in each case in a diagrammatic manner with the transformer windings. Figure 3 shows the embodiment with, in each case, a secondary and a primary winding. A certain transformation ratio exists for these windings, as different voltage levels from those on the line side are used in the system. Thus not only is electrical isolation effected, but in addition a level adaptation is effected in order to obtain a required level ratio.

The windings of the transformer are accommodated in a parallelepiped block-shaped housing, for example a plastics housing, in which case the housing has a substantially square upper or lower boundary surface.

Compared with the side length of the boundary surface, the height dimension of the parallelepiped block is small. The terminals are brought out for the component exclusively on two opposing side faces, namely on the side face 9P1 and M. The arrangement of these terminals can follow a certain preset grid. It is assumed, for example, for the exemplary embodiment that in total ten terminal possibilities can basically be provided within the preset grid. Of these terminal possibilities in total four terminals, namely the terminals Al to A4, are provided on the side face SF2 and two terminals, namely the terminals A5 and A6 in the form of terminal pins shaped in a certain manner, are provided on the opposing side face. The winding ends of one winding are exclusively connected with two terminal pins which are present on, in each case, one side face. For the winding Wl these are the terminal pins A5 and A6 and for the other winding W2 these are the terminal pins Al and A4. Those terminal pins which lie furthest outside are selected. On account of the presence of extra terminal pins A2 and A3, which are not connected in the case of the component according to Figure 3, when the component is applied to a printed circuit board, protection against reversal of the device during assembly is provided. By means of a visual examination it is possible to recognize immediately whether correct assembly has occurred.

In the case of the component according to Figure 4 which has a housing which corresponds with Figure 3, the winding W2 is divided into two part windings, namely the part windings W21 and W22. The winding ends of the part windings are likewise run exclusively to terminal pins which are located on one side face, namely the side face SF2, whilst the winding Wl is connected with its winding ends to the terminal pins A5 and A6 present on the diametrically opposed line side. The terminal pins A2 and A3 correspond with the terminal pins of Figure 3 denoted in like manner. In the exemplary embodiment according to the Figure they are, however, connected in the manner shown. The first part winding W21 is thus associated with the terminal pins A4 and A3 by way of its winding ends. The association with the terminal pins Al and A2 is effected for the second part winding W22. As a result of the unequal number of terminal pins on the two opposing side faces, assembly with protection against polarity reversal is additionally guaranteed. The variant of the embodiment according to Figure 4 with a two-part winding is used, as already mentioned, if a remote feed is required. If the terminal pins A2 and A3 are connected with each other by means of a corresponding printed conductor, this embodiment corresponds in terms of its effect to the embodiment according to Figure 3. Reference has already been made to this in the explanation of Figure 2.

In Figure 5 the soldering pattern on the printed circuit board is represented, which pattern basically corresponds with the position of the terminal pins Al to A6. In the case of these pads, the solder terminals relative to the terminal pins lie apart at the greatest possible distance from each other. This distance corresponds to the distance between the primary and the secondary side of the transformer. Given a certain distance between the outer edges and a given length of the soldering points this distance then amounts to, for example, approximately 12 mm and thus forms an optimum creepage distance and clearance between the primary and secondary terminals. All the safety requirements of the European countries according to standard EN 60950 can thus be covered.

In the real embodiment, the transformer windings shown can be applied to an annular core. In this case, these windings can be laid one upon the other for the purpose of reducing the magnetic field leakage.

As a result of the position and the assignment of the terminal pins and the selected arrangement of the transformer windings a situation is reached where given a printed circuit board assembly with this component the conductor routing can be effected so as to be as short as pssible, to be as linear as possible and to be as parallel as possible. This then, in particular with regard to the application as an SO-transformer, provides the optimum solution to the problems which 10 exist in such cases of application.

Claims

1. Component which consists of a housing and a transformer contained therein which has at least two separate windings, the ends of which windings, in the interior of the housing, are connected with terminals which protrude from the housing, and which component is used beside other components as an assembly element for printed circuit boards, wherein the ends of the first winding are connected with terminal pins which are at the furthest possible distance from those terminal pins with which the ends of the second winding are connected, given the preset housing form.

2. Component according to claim 1, wherein the housing represents a surface-mounted housing.

3. Component according to claim 1 or 2, wherein the terminal pins are arranged, in the case of a housing which in the plan view is rectangular, exclusively on two opposing housing faces which are preferably furthest away from each other or in the region of two opposing boundary edges of the base area, and each end of the first winding is exclusively connected with, in each case, one of the terminal pins provided on the first housing side or boundary edge, and each end of the second winding is exclusively connected with, in each case, one of the terminal pins provided on the other housing side lying opposite the first housing side or on the other opposing boundary edge.

4. Component according to claim 3, wherein the terminal pins in the region of the outer lateral boundary of the housing faces, which pins are respectively associated with the ends of one of the windings have the greatest possible interspace which is defined by a preset grid.

5. Component according to one of the claims 1 4, wherein one of the housing faces or boundary edges has, furthermore, two additional terminal pins which lie between the terminal pins provided for the ends of the first winding.

6. Component according to claim 5, wherein this first winding is subdivided into two part windings and a first end of each part winding is connected with respectively one of the external terminal pins in that the second end of each part winding is connected respectively with one of the additional terminal pins.

7. Component according to claim 6, wherein the second end of each part winding is connected with that free additional terminal pin which lies next to the terminal pin associated with its first end so that a symmetrical terminal assignment results.

8. Component according to claim 5, wherein the two additional terminal pins which protrude from the housing are connected with each other on the outside by means of a printed circuit board-printed conductor.

9. Component according to one of the claims 1 to 8, wherein the housing forms a parallelepiped block shape which has a substantially square upper or lower boundary surface.

10. Component according to one of the preceding claims 1 - 9, wherein it is used for the purposes of electrical isolation and for level adaptation as an isolating element between system elements and/or between various line and transmission sides of a transmission or communications system, in particular an ISDN- communications system, and can be applied to a printed circuit board, which also forms a certain functional unit of such a system, in addition to other components, and wherein this functional unit represents a digital interface for the transmission of voice information and of data information with a high transmission rate.

11. Component used according to claim 10, wherein the interface, in which it is used, represents a 4wire-usable standardized interface SO of an ISDNcommunications system.

12. Component used according to claim 10, wherein the interface, in which it is used, represents the standardized interface S2 of an ISDN-communications system.

13. Component according to one of the claims 1 to 9, wherein the position of the solder-terminal points (PAD-pattern) for the terminal pins on the printed circuit board substantially corresponds with the layout of the position of the terminal pins actually present altogether in each case, on the opposing sides.

14. Component according to claim 9, wherein it is set upon the printed circuit board (horizontal use) with the substantially square boundary surface.

15. Component according to claim 9, wherein the housing (H) surrounds the wound cores of the transformer in consideration of the grid for possible terminal pins with the least possible interspace (lateral and vertical interspace).

16. Component according to claim 15, wherein the windings are applied to an annular core.

17. Component according to any preceding claim wherein the windings are arranged within the component housing such that each end of the windings is connected to the respective terminal pin without crossing another winding.

18. Component according to any preceding claim wherein the windings are arranged within the housing such that their core or cores are parallel to an end face of the housing containing the associated terminal pins.

19. Component as claimed in any preceding claim, wherein the terminal pins are arranged on the housing in such a way that simple and technically trouble-free routing can be provided for the printed conductor towards the outside.

20. Component substantially as herein described with reference to Figures 2, 3 and 5 of the 5 accompanying drawings.

21. Component substantially as herein described with reference to Figures 2, 4 and 5 of the accompanying drawings.

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