Compaq DL590 - HP ProLiant - 1 GB RAM Technology Brief page 8

TC020702TB
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ECHNOLOGY RIEF
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Figure 6: Compaq designed the ProLiant DL590/64 server's I/O board.
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Distributed Power System
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Historically, most ProLiant servers have been powered by one or more AC-to-DC, multiple output
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power supplies. Power from the power supplies is cabled or routed to all components of the
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server. This is known as centralized power distribution. This approach works well at moderate
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power levels. But as server performance has increased, so has the demand for more power.
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To manage the increased power, the ProLiant DL590/64 server uses a hot-pluggable distributed
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power system that is fully redundant, including the high-line AC line feeds. In a distributed power
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system, a primary power supply converts power from the AC mains to an intermediate DC voltage
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that is easy to distribute throughout a server system. A common value is +48 volts DC, which is a
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level high enough to keep the currents low but within the safe voltage limits. At the load, a second
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power supply converts the high voltage to the required lower voltage. In the ProLiant DL590/64
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server, these local power converters are known as system power modules. Throughout the
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industry, they are also known as point of load converters or voltage regulator modules (VRMs).
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. . Since the system power modules are located next to the loads, the large cables and wires typical
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with high currents are no longer required. This allows a significant cost saving and a simpler
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design. System power modules are typically more reliable than the power supplies they replace.
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Three 1250-watt primary power supplies in the front of the ProLiant DL590/64 server take in
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AC power. Each of these distributes 48 volts DC at up to 1200 watts (see Figure 7). These
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48-volt supplies provide power to the processor power modules and to the memory boards. They
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also provide 48 volts to the three system power modules that convert the power into the 3.3 and
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5-volts needed for PCI slots and logic and into the 12 volts needed for the server's fans and hard
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drives.
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