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.