Abstract:
An arrangement of an isolating support board having conductive surfaces between busbars, the support board having a portion projecting beyond the busbars in the transverse direction, and filter capacitors connected to the conductive surfaces being fastened on the projecting portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The arrangement relates to the mounting of filter capacitors in power supplies using busbars. 
     2. Description of the Prior Art 
     In the case of data processing systems having a relatively high power consumption, in particular, the operating voltage is fed via busbars to a backplane. Filter capacitors are arranged on the backplane, which is designed as a printed circuit board. The filter capacitors occupy valuable space on the backplane due to their large capacitance and the large value necessitated thereby. In order to avoid this, filter capacitors have previously been screwed to the chassis and connected to the backplane by short additional connecting lines. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to arrange filter capacitors with a low mounting expense and space requirement. 
     The invention contains the insight that when supplying the backplane using busbars, the insulating layer between the busbars can be replaced by a printed circuit board whose surfaces make good contact with the busbars due to the mechanical interconnection of the busbars which exists in any case. The printed circuit board projects laterally beyond the busbars, that is to say in the transverse direction with respect to the running direction of the busbars. Capacitors which are connected to the surfaces are arranged on the projecting part. These printed circuit boards with the filter capacitors are easy to produce and can be mounted virtually with no additional expense since they are mounted instead of the insulating layer used to date. In this way, the filter capacitors neither occupy space on the backplane nor do they have to be mounted and connected in a separate work operation. The arrangement along the busbars additionally enables a large number of relatively small filter capacitors to be used, which leads to a small series resistance and thus to an excellent filter effect. As a result of the distribution of the filter capacitance over a considerable part of the busbar, the inductance of the latter also becomes less effective, with the result that the power supply unit becomes simpler and more stable during operation. 
     A busbar assembly designed in this way can also be used on the backplane for distributing the supply voltages, since connection lugs are integrally formed on the busbars, on the side facing away from the capacitors, which lugs are then each connected to feeding points on the backplane. This connection can be effected by short cables, a plug connection or a soldered joint. 
     If the intention is to supply two voltages at the same ground potential, then three busbars are used in a preferred development, the middle busbar carrying ground potential and a support board with filter capacitors are arranged in each case between the middle busbar and an edge busbar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a busbar assembly as a section in the running direction of the busbars, 
     FIG. 2 shows the arrangement according to FIG. 1 in a side view, and 
     FIG. 3 shows the same arrangement in a plan view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates two busbars 10a, 10b, which carry a different potential. The busbars are connected to one another by a fastening, which is symbolically illustrated in the drawing by a screw 14 and nut 16. This fastening must, of course, be embodied in an insulated manner. 
     The busbars are electrically isolated by a printed circuit board 11, which is embodied, in a known two-sided design, by an insulating support layer 12 and two conductive layers 13, 13b which are applied to the surfaces and are usually made of copper with a surface refinement. 
     The printed circuit board 11 is wider on one side than the busbars and thus extends beyond the busbars transversely with respect to the main direction of the busbars. Filter capacitors 15 are fastened in a known manner on this projecting area, which filter capacitors are illustrated here as can capacitors, one pole of which is connected to the conductive layer 13a and the other pole of which is connected to the conductive layer 13b, usually by soldering. A relatively large number of these capacitors are present along the busbar, as symbolized in FIG. 3. The number of capacitors depends on the length of the busbar and their capacitance is then the corresponding fraction of the total required capacitance. 
     Holes are provided in the printed circuit board 11 for the fastenings 14, 16 (not emphasized in the figures). These holes can be designed as elongated holes 17 (shown only once in FIG. 3) which extend to the edge of the printed circuit board, so that the printed circuit board together with the capacitors can be withdrawn, following the release of the connections, on the side carrying the capacitors, and be replaced by another specimen. This simplifies disassembly and permits simple repair after delivery. 
     Connection points 18 can be integrally formed on the busbars. The connection points either make contact with direct connectors or, if provided with holes, are screwed directly to a backplane, for example. In this case, the busbar assembly can run transversely across the backplane and provide a buffered DC voltage at a plurality of points, without space for the buffer capacitors being required on the backplane. To give a better overall view, FIG. 3 shows such a connection 18 only once for the upper busbar; the same applies correspondingly to the lower busbar (not visible). 
     Not shown in the figures is the expansion to more than two busbars, in which case a busbar and a printed circuit board are placed alternately one on top of the other. A busbar for ground then preferably lies in the center. The lower printed circuit board is then designed to be wider, with the result that the capacitors are not hindered by the upper printed circuit board. 
     Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that my wish is to include within the claims of the patent warranted hereon all such changes and modifications as reasonably come within my contribution to the art.