GB2265260A - Power supply unit - Google Patents

Abstract

An input power supply unit 37 is interconnected to one or more output modules 9 via a backplane 40, the supply unit 37 being detachably connected to the backplane 40 by way of a split transformer, primary winding 38 of which is formed on unit 37 and secondary winding 42 formed on the backplane. The output module(s) 9 may be detachably connected to the backplane. To enable variation of the transformed voltage the secondary winding or the secondary winding and backplane and/or output modules may be substituted. <IMAGE>

Description

POWER SUPPLY UNIT This invention relates to power supply units which are comprised of a number of physically separable input conversion modules. Such an arrangement is extremely flexible in application, but is generally physically larger than conventional power supplies.

Conventionally, power supply units, whether modular or otherwise are comprised of one or more main printed circuit boards on which are mounted the input components, the transformer and output power components. In some instances additional plug-in "daughter" pcb's may exist, carrying low dissipation control circuitry and components.

The overall dimensions of the resulting structure are determined by the largest component(s) dimensions in each axis, resulting in a space envelope which is not optimally "filled". This particularly applies to the height (here defined as the dimension orthogonal to the main pcb) and the approach can be categorised as 2 dimensional.

This form of construction is wasteful of space and additionally places severe constraints on thermal design, it being difficult to ensure that adequate airflow is available to cool temperature sensitive components irrespective of the mounted attitude of the power unit.

It is an aim of the present invention to retain the modular aspects of the power unit while reducing the overall size of the output power modules while simultaneously optimising the coooling air flow through these modules, by employing 3 dimensional construction techniques.

According to the invention of co-pending British patent application from which this application has been divided, there is provided a power output module for a power supply unit, the output power module comprising; a pair of planar side members having apertures therein for allowing passage of cooling air; a pair of printed circuit boards respectively disposed in parallel spaced apart planes between and at least substantially perpendicular to the major plane of the planar side members; and a plurality of electrical components mounted on the printed circuit board; wherein the electrical components are disposed on the printed circuit boards and within the space between the circuit boards, a first air flow path passing through the aperture(s) of one of the side plates, the space between the printed circuit boards and subsequently the other side plate is established, and a second air flow path from one end of the printed circuit boards and into the said space is also established, the first and second paths being substantially transverse with resepect to one another and providing flow paths for the passage of cooling air around the electrical components.

In an embodiment of this arrangement, the printed circuit boards may be elongate and disposed parallel to each other and orthogonal to the side plates in their longitudinal direction.

In a preferred arrangement, connection means is provided for enabling detachable electrical connections to be established between the electrical components of the output module and an external member against which the output module is mounted. The external member may be in the form of a backplane which can provide electrical connection between the output modules and an input stage transformer of a power supply unit. The electrical connection of the connection means may be by way of screws, plug and socket connectors or a simple touch contact.

Optionally, a third printed circuit board spaced from said pair of printed circuit boards may be provided for supporting additional circuitry. The additional circuitry may be operative for performing functional tasks. In this case, the additional circuitry may be connected to a host system to which the power supply unit is connected and may be operative, for example, for providing advance warning of a power failure thereby enabling engagement of a back-up power supply unit prior to actual failure of the supply to the host.

The side plates may be of a plastics material.

The electrical connection between the pair of printed circuit boards may be by way of plug and socket connectors or by direct soldered wire connections.

Output modules having this arrangement can be made to provide different power outputs by supplying them with different voltages from the transformer of the input stage. It is simple to do this by enabling replacement of the secondary winding of the transformer to one having appropriate taps for the desired voltages. This eliminates the need to replace actual components in the output modules.

Output modules constructed in accordance with the invention of the above referenced patent application have components arranged in each of the three dimensions while prior art modules have their components distributed on a two dimensional basis. Consequently, the output modules have the advantage that they enable the components of the module to be densly packed while providing for adequate ventilation via two paths through the module, the paths being substantially transverse with respect to one another. Such modules can also be conveniently detached or added to a power supply unit according to requirements.

The construction of the output modules provides for shorter air flow paths per unit of power generation.

This provides for a more even and uniform cooling of the components of the ouput modules.

According to the present invention there is provided a power supply unit comprising an input stage for receiving a power supply, a transformer for transforming the voltage of the power supply and for providing one or a plurality of transformed voltages, one or more output modules for generating one or a plurality of power outputs, a backplane for providing electrical connection between the transformer and output module(s), and connection means for providing detachable electrical connection between the output module(s) and the backplane, wherein the transformer is in the form of a split transformer the primary winding being disposed on the input stage and a second winding for providing the one or the plurality of transformed voltages being provided on the backplane, the primary and secondary windings being detachable from one another thereby enabling variation of the transfomed voltage(s) by substitution of: a) the secondary winding or both the secondary winding and the backplane with an alternative secondary winding or alternative second winding and backplane; and/or b) the output module(s).

According to the present invention there is further provided a method of interconnecting an input power supply to one or a plurality of output modules via a backplane for providing electrical connection between the output modules and the input power supply, comprising detachably connecting the backplane to the input power supply by way of a split transformer, the primary winding of the transformer being formed on the input stage and the secondary winding of the transformer being formed on the backplane.

The method may comprise detachably connecting the output module(s) to the backplanes.

Power supply units embodying the present invention can be easily and simply adapted to provide different power outputs according to desired working conditions.

The output modules can be quickly secured by means of screws to the backplane thereby enabling a desired configuration of the desired power supply unit to be established quickly.

A consequence of this is that any special configuration desired can be established by use of an appropriate ouput module and/or secondary winding of the transformer. New secondary windings of the transformer may be wound. as appropriate so as to provide the desired output taps.

Power supply units embodying the present invention may be used as switch-mode power supplies.

The invention will now be further described by way of example with reference to the accompanying drawings, in which; Figure 1 illustrates a conventional power output module; Figure 2 is a perspective view of a power ouput module which is the subject of co-pending British patent application no. from which this application has been divided; Figure 3 is an exploded view of the module of Figure 2; Figure 4 illustrates an input stage which may be used in a power supply unit embodying the present invention; Figure 5 is an exploded perspective view of a power supply unit embodying the present invention; Figure 6 is a perspective view of the power supply unit when assembled; and Figure 7 is a perspective view of the power supply unit including an outer casing and integral cooling fan.

Figure 1 illustrates a conventional ouput module for use in a power supply unit. The module comprises a printed circuit board (pcb) 1 onto which all components are soldered as illustrated by a toroid inductor 2 and an electrolytic capacitor 4. A terminal panel 6 provides for electrical connection via screw terminals to the components of the printed circuit board. The module is.

provided with a heat sinking base 8 onto which power dissipating components can be mounted. A conventional output module of this type has been sold under the trade mark ML.

Figure 2 illustrates the perspective view of an output module which is the subject of the above referenced British patent application. This output module will be described in greater detail with reference to the exploded view illustrated in Figure 3. The output module 9 comprises a pair of plastics side plates 10 each having apertures 12 formed therein for enabling air to pass into the interior of the output module.

The module is provided with a pair of pcb's 14 and 16 respectively which house electrical components of the module. These electrical components include electrolytic capacitors 18 and toroidal inductors 20.

The precise form of circuitry would be evident to the skilled man in the art.

In this embodiment the pcb's 14, 16 are elongate and are disposed spaced apart with respect to one another so as to define a space 21 in which the electrical- components are housed. The toroidal inductors 20 may be mounted onto the side plates 10 by suitable attachment means.

The pcb's 14, 16 are provided with side lugs 22 which are received by corresponding recesses 24 provided in the side plates 10.

Modules may be of different sizes (widths) depending on the output power and pcb 14 may be implemented by rivetting copper pressings to an insulating substrate rather than by conventional etching techniques.

Output power generated by the module is delivered to a connection panel 26 having screw terminals (not shown) for connection to a host system to which power is to be applied.

Above the pcb 16, an additional printed circuit board 28 is provided on which circuitry (not shown) is provided for performing various functional operations to be connected to the host system. A socket 30 provides for electrical connection between the additional circuitry and the host system, electrical interconnections 32 being provided between the additional circuit board 28 and the pcb 16. The additional circuitry may be operative for generating signals warning the host signal of an interruption in the power supply.

Beneath the lower pcb 14 is provided an aluminium heats ink 34 on to which are mounted power dissipating devices which are electrically connected to pcb 14 and is also located by side plates 10.

Copper pressings 35 provide for electrical connection between the electrical components of the output module and a backplane to which the output module 9 can be attached. The module 9 may be secured to the backplane by way of screws (not shown) passing through holes in the copper pressings 35. Attachment of the output module 9 to a backplane will be described below in detail with reference to Figures 5 to 7.

Air for cooling and ventilating the electrical components housed in the space 21 between the pcb' s 14 and 16 can be received from substantially two orthogonal directions denoted by X, Y and Y1 in Figure 3. The construction illustrated in Figure 3 enables achievement of a compact assembly of electrical components having a high power density configuration while enabling effective and even cooling and ventilation of the components.

Figure 4 illustrates a power converter 37 for use in the input stage of a power supply unit which will be described below with reference to Figures 5 to 7. The converter 37 comprises electrolytic capacitors 36 and other components suitable for supplying mains power to the primary winding 38 of a transformer. Details of the electrical circuitry of the power supply unit and the modules are not described herein since they conform with devices known in the art.

Figure 5 illustrates an exploded view of a power supply system embodying the present invention. In Figure 5 a pair of output modules 9 corresponding to the one described with reference to Figure 2 and 3 are arranged for electrical connection to a backplane 40. The backplane is in the form of a printed circuit board having electrical connectors (not shown) thereon for providing electrical connection between the copper pressings 35 of the output modules and appropriate voltage taps (not shown) of a secondary winding 42 of the transformer. The electrical connection between the backplane and the pressings 35 may be secured by screws passing through screw holes provided in the backplane 41 and corresponding screw holes in the pressings.

The transformer is in the form of a split transformer whereby the secondary winding 42 of the transformer can be easily separated from the primary winding 38 which is attached to the converter 35.

The modules 1 can each be detachably removed from the backplane 1 as the copper pressings abut the backplane.

In an alternative arrangement, there may be a plug and socket connection between the backplane and copper pressings.

The power output from the terminals of the connection panels 26 of the respective modules 1 can be varied by adjusting the taps of the secondary winding 42. This can be readily understood from the above described example, a power supply unit having power outputs conforming to a wide variety of different desired configurations can be constructed with ease simply by interchanging an appropriate secondary winding or secondary winding and backplane. Conceivably, the secondary winding itself may be detachable from the backplane thereby making it possible to alter the output power supplies from the respective modules 1 simply by changing the secondary winding 42.

Figure 6 illustrates three output power modules 9 coupled to a converter 37 via the transformer and backplane 40. Figure 7 illustrates five of the output power modules 9 coupled to the backplane. The power modules 9 are housed within a casing 44. Ventilation can be assisted by means of a fan 46.

Claims (5)

1. A power supply unit comprising an input stage for receiving a power supply, a transformer for transforming the voltage of the power supply and for providing one or a plurality of transformed voltages, one or more output modules for generating one or a plurality of power outputs, a backplane for providing electrical connection between the transformer and output module(s), and connection means for providing detachable electrical connection between the output module(s) and the backplane, wherein the transformer is in the form of a split transformer the primary winding being disposed on the input stage and a secondary winding for providing the one or the plurality of transformed voltages being provided on the backplane, the primary and secondary windings being detachable from one another thereby enabling variation of the transformed voltage(s) by substitution of: a) the secondary winding or both the secondary winding and the backplane with an alternative secondary winding or alternative secondary winding and backplane respectively; and/or b) the output module(s).

2. A method of interconnecting an input power supply to one or a plurality of output modules via a backplane for providing electrical connection between the output modules and the input power supply, comprising detachably connecting the backplane to the input power supply by way of a split transformer, the primary winding of the transformer being formed on the input# stage and the secondary winding of the transformer being formed on the backplane.

3. A method according to claim 1, comprising detachably connecting the output module(s) to the backplane.

4. A method according to claim 1 substantially as hereinbefore described.

5. A power supply unit substantially as hereinbefore described with reference to any one of Figures 4 to 7 of the accompanying drawings.