Electronic Design

AC-DC Power-Supply Maker Aims To Increase Power Densities

In space-restricted designs, a power supply's capabilities can be a limiting factor in determining system-level performance. This is particularly true in the telecom and datacom areas, where demand for power is growing and power-supply manufacturers are being pressed to build units with greater power density. To date, many applications that require 300 W or more of power have been limited to ac-dc switching supplies that offer just a few watts per cubic inch.

But one power-supply vendor says it has the technology to move the power density of high-power ac-dc switching supplies beyond the single-digit range. Online Power Supply, Englewood, Colo., has developed a technology that achieves nearly 20 W/in.3

Consider that value in light of current and projected industry-wide performance. In a road map issued last year, the Power Sources Manufacturers Association assessed power-supply requirements for 1000-W ac-dc converters—a category that would encompass many space-sensitive applications. According to PSMA's projections, demands for power density should rise from a 2- to 4-W/in.3 range in 2000 to a 3.5- to 6- W/in.3 range in 2005. These numbers reflect expectations of performance gains that can be achieved using current approaches to power-supply design. With its spin on ac-dc converter design, Online Power Supply plans to offer significantly greater power density.

The company has already demonstrated this capability with its first product, the OPS-U-500-385, introduced last fall (see the figure). This unit is a power-factor-corrected (PFC) front-end module that generates 500 W of 385-V dc output in a 2.9- by 1.6- by 5.7-in. package. That translates to 18.9 W/in.3

Under high-line conditions (240-V ac input), efficiency for this supply is specified at 97.4%. The company says its closest competitor achieves just 94% efficiency in a design that's significantly larger. Much of the difference in size between Online's PFC front end and rival units stems from the addition of external hold-up capacitors and EMI filters. These elements have been integrated within Online's PFC front-end module.

The technology deployed in the PFC front end will be the basis for a planned portfolio of other high-power-density supplies. For example, the company plans to release a version with a 48-V dc output some time late in the second quarter. This product will deliver 1000 W in a 1.6- by 4- by 7.25-in. package, for a power density just above 21 W/in.3 (By the way, that 1000-W specification is said to be a conservative rating.) Online Power Supply plans to expand its product line further by developing units with dc outputs of 24 V and lower, as well as by increasing the level of available output power.

When asked about the underlying technology of its supply, the company was reluctant to give details. CEO Kris Budinger noted only that in power-supply design, "Most of the core problems relate to magnetics—the strategies and the way they are done." Budinger went on to state that Online Power uses a different approach to magnetics design to boost supply performance.

The company's achievements with the PFC front-end module were validated recently with a design win at a "large wireless telecommunications pro-vider." According to Budinger, the customer, whose name has not yet been disclosed, had previously ordered 800 units for testing and evaluation, and expects to place an initial volume purchase shortly.

For details, call (800) 445-4824, or visit www.onlinepowersupply.com.

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