Electric power conversion systems – Current conversion – With conductive support mounting
Reexamination Certificate
2000-04-26
2001-03-13
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
With conductive support mounting
C323S908000, C307S147000
Reexamination Certificate
active
06201721
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to power distribution and, more specifically, to a bus holdup circuit, a method of bolstering a bus voltage associated with a distributed power system and a distributed power system employing the circuit or the method.
BACKGROUND OF THE INVENTION
Telecommunications and computer systems may be deployed in a wide variety of conditions other than an office environment. These systems are often packaged as a collection of modules or circuit boards connected to a primary power bus that distributes power to each of the individual modules or circuit boards. The primary power is generally a DC voltage of a value, such as 48 volts.
A major concern in such a distributed power system is the impact that a single module or circuit board can have on the power system if the module or circuit board were to become faulted, leading to a decrease in the voltage of the primary power bus. This, of course, would adversely affect the operation of the remaining operational modules or circuit boards. This may cause a catastrophic failure of the entire telecommunication or computer system, rather than perhaps the loss of just a single feature or function associated with the faulted module or circuit board.
Presently, distributed power systems attempt to address this problem using two basic strategies. The first strategy is directed to enhancing the transient energy delivery capability of the primary power bus by a direct addition of energy storage capability to the bus itself. This usually takes the form of adding capacitors across the primary power bus that, under a fault condition, may be used to supply energy to the circuit boards in an attempt to maintain the bus voltage.
The second strategy attempts to isolate each of the modules or circuit boards from the primary power bus in the event that the bus voltage droops. In concert with the isolation of the modules the second strategy also provides an energy storage capability associated with each module. This modularized form of energy storage attempts to maintain the voltage at the individual module despite a droop in the primary power bus.
Although the implementation of these two strategies provides some advantage over the use of a distributed power system that offers no fault isolation capability, each of the modules must basically provide a significant portion of its own energy storage capability, since sharing of energy between the modules is effectively foreclosed by the fault isolation circuitry. This modular energy storage capability is therefore used to deal with a fault on another module which may cause the voltage on the primary power bus to droop significantly, and to deal with a fault condition on the module itself. Of course, the dual role required of the energy storage capability necessitates larger capacity energy storage devices thereby adversely affecting, among other things, the overall cost and size of the distributed power system.
Accordingly, what is needed in the art is a system and method of bolstering a bus voltage associated with a distributed power system that reduces the energy storage required in each module.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides, for use with a module of a distributed power system having a backplane interface adapted to be removably coupled to a DC backplane of the distributed power system, a bus holdup circuit, method of bolstering a bus voltage associated with the distributed power system and a distributed power system employing the circuit or the method. In one embodiment, the bus holdup circuit includes: (1) an energy storage circuit, coupled across the backplane interface, adapted to store dissipate energy to bolster a voltage across the DC backplane and (2) an inrush limiting circuit, series-coupled to the energy storage circuit, adapted to limit an inrush current to the module.
The present invention, in one aspect, introduces the broad concept of providing a substantially non-dissipative and distributed bus holdup circuit located on a module of a distributed power system. The bus holdup circuit provides energy to the DC backplane during, in part, a fault-clearing transient in the distributed power system. When employing multiple modules with corresponding bus holdup circuits, each bus holdup circuit may contribute collectively to providing energy to a single module or a collection of modules that are involved with either a fault or other transient condition. Further, each bus holdup circuit may limit an inrush current to its associated module.
In one embodiment of the present invention, the energy storage circuit comprises a capacitor. Of course, more than one capacitor may be used with the module as appropriate. In an embodiment to be illustrated and described, each of a plurality of modules of the distributed power system is provided with a bus holdup circuit that contributes to providing an adequate holdup energy without requiring a central bus holdup circuit.
In one embodiment of the present invention, the inrush limiting circuit comprises a resistor. An inrush current limiting resistor allows potentially damaging inrush current to be received and suppressed in a constructive manner. Of course, other components may be used to adequately handle the energy from an inrush current and are well within the broad scope of the present invention.
In one embodiment of the present invention, the bus holdup circuit includes a switch, coupled across the inrush limiting circuit, that allows the energy storage circuit to bolster the voltage. In an embodiment to be illustrated and described, the switch is a diode. Of course, other switches or a combination of switches may be appropriately applied to allow the energy storage circuit to bolster the voltage on the DC backplane. Those skilled in the pertinent art will understand that the present invention is employable with any conventional or later-developed type of switches.
In one embodiment of the present invention, the DC backplane is free of a central bus holdup circuit. The modularized bus holdup circuit allows the central bus to be free of components that may typically have limited service life by distributing such components among the modules. The maintenance of these components may be more easily addressed at the module level rather than at the system level.
In one embodiment of the present invention, the bus holdup circuit enables the module to be hot-pluggable to the DC backplane. The ability to plug and unplug a module from the DC backplane under a powered-up condition greatly simplifies the addition or extraction of a module. This feature allows a group of modules to remain operational thereby avoiding a shutdown of the system when a single module requires service or must otherwise be removed from the system.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
REFERENCES:
patent: 5726506 (1998-03-01), Wood
patent: 5940288 (1999-08-01), Kociecki
Suranyi Gabriel G.
Thottuvelil Vijayan J.
Han Jessica
Lucent Technologies - Inc.
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