Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
1999-02-19
2001-11-13
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C307S058000
Reexamination Certificate
active
06317345
ABSTRACT:
BACKGROUND OF THE INVENTION
Contemporary electronic systems utilize electronic backplanes, also referred to as motherboards, that serve as a communication medium for the exchange of electronic signals between a plurality of daughter cards. These same backplanes also serve as a vehicle for providing electrical power to the daughter cards. Power is generated at one or more power supplies and is distributed to the daughter cards via the backplane at a mating set of connectors.
Modern systems utilizing backplane designs such as VME 64 Extension and Compact PCI require a plurality of power supply voltages with application-specific tailoring of power supply current requirements for each of the plurality of power supply voltages. A typical embodiment utilizes one or more free-standing, separately housed power supplies that are mounted within the enclosure and connected to the backplane via bundles of high-current capacity wires. These free-standing power supplies are typically self-contained power supply systems, having their own enclosures. This configuration yields several undesirable performance problems. The power supply enclosure adds to the physical weight, cost, and size of the power supply. This configuration typically includes a cooling fan that must be integrated into the airflow management design of the enclosure further adding cost and addition acoustic noise. Since current drawn from the power supply is application dependent, the current capacity of the power supply often must change with application, necessitating a change in the power supply configuration. As free-standing units, the power supplies are coupled to the backplane via bundles of high-current wires. The size, quantity, and configuration of these wires is application dependent and therefore must be reconfigured according to the application and current capacity thereof. Because the power rating of the power supply is driven by the worst case requirement of any single direct current (DC) voltage, the power supply selected for an application is typically larger than required. These power supplies tend to be available in standard sizes that offer limited choices, for example such that a need for increased current at 5 Volts will result in more current being generated at the other voltages as well, even if not required for the application.
Contemporary system applications demand fault-tolerant operation. This demand drives a need for fault-tolerant, redundant power supplies having current sharing and hot swap capability. A typical embodiment employs filly redundant power supplies, significantly increasing physical space, weight, and cost. Assuming that each unit is a free-standing power supply with multiple output voltages and high-current capacity, a small number, for example 3, power supplies are commonly employed in redundant systems. This requires significantly more power capacity, for example 50%, than a non-redundant system, such that the system will continue to perform with uninterrupted operation if one of the power supplies fails. Battery backup, if required, is expensive and bulky, requiring a separate battery-powered AC generator and associated charging circuit. Power supplies designed to accept battery backup are expensive and require significant additional circuitry for the battery backup system.
Another conventional power supply distribution system employs redundant front-end power supplies that convert alternating current (AC) power to a DC voltage, which is then distributed to redundant DC input power supplies, typically located on the daughter cards to which they are providing power. However, in this configuration the DC-input power supplies consume valuable daughter card space and create electrical noise and heat on the daughter cards. Because each daughter card requires separate DC-input power supplies, the system level cost is significantly increased. Furthermore, redundancy for DC-input power supply fault tolerance requires duplication on each daughter card, greatly increasing cost and occupation of space.
A further embodiment employs redundant front plug-in power supplies that plug into the backplane in a manner similar to a daughter card, typically along side the daughter cards in adjacent slots at one or both ends of the backplane. As each plug-in unit is a power supply with multiple output voltages and consumes valuable daughter card slot space, a small number (typically 2) power supplies are used in redundant systems. This requires significantly more power capacity (typically 100%) than a non-redundant system. Furthermore, the cost, weight, and physical space are significantly higher (typically 100%) for the redundant system.
SUMMARY OF THE INVENTION
The present invention is directed to a method and apparatus for partitioning and packaging a power generation and distribution system in a manner which overcomes the limitations of the prior art.
The present invention provides a means for eliminating the bundles of cables between power supplies and the backplane. This is accomplished by providing a small DC input power supply configured to plug directly into the backplane.
The present invention further provides a means for plugging a plurality of these small DC input power supply modules into the backplane in such a manner that they are distributed along the length of the backplane such that backplane voltage drops are minimized and such that power supply currents flow essentially orthogonal to the signal connections between the backplane slots. This minimizes signal interference and reduces or eliminates the need for bus bars on the backplane.
The present invention further provides a means for built-in redundancy that minimizes excess power supply capacity and cost. This is accomplished by providing a low-cost, non-isolated, current-sharing DC-to-DC converter sub-circuit with a relatively modest power output, for example less than 50 Watts. Each plug-in DC input power supply module may include a plurality of DC-to-DC converter sub-circuits for each output voltage, thereby providing redundancy on each plug-in DC input power supply module. With multiple plug-in DC input power supply modules distributed across the backplane, excess capacity to allow for a single fault requires only one additional DC-to-DC converter sub-circuit for each voltage level.
The present invention further reduces the cost of the individual plug-in DC input power supply modules by utililizing a common ground connection to the backplane. This common ground connection is effected through individual plug-in DC input power supply modules that plug directly into the backplane without intervening cables. This dramatically reduces the inductance and resistance of backplane connections. This is accomplished by providing a non-isolated, DC-to-DC converter sub-circuit operating at a high switching frequency with a common low-impedance ground connection to the backplane. This permits the DC-to-DC converters to use small, planar inductors in the printed circuit board rather than transformers, significantly reducing cost.
In a first aspect, the present invention is directed to a redundant power supply for a backplane. A plurality of independent voltage converter units are distributed in parallel between a voltage input and a voltage output. The voltage converter units are adapted for maintaining current sharing between multiple units. Means for monitoring the status of each voltage converter unit are included to identify a fault. Means for selectively activating at least one of said multiple units is further included so as to redundantly supply power to the backplane.
In a preferred embodiment, the voltage converter units comprise non-isolated back-end DC-to-DC converters. One or more redundant isolated front ends may be further included for supplying the voltage input to the voltage converter units.
The redundant power supply may be configured in a modular form adapted for removably coupling with a backplane.
In a preferred embodiment, one or more of said modules may be used for a backplane application and a spare empty location i
Hayward C. Michael
Rehlander Richard N.
Sullivan Robert C.
Hybricon Corporation
Laxton Gary L.
Mills & Onello LLP
Wong Peter S.
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