Electronic Design

Configurable Power Systems Reshape Standard Supply Landscape

Modular architecture, high-efficiency dc-dc converters, and versatile packaging produce highly customized power supplies off-the-shelf.

When selecting modular power-supply components, designers have traditionally been forced to choose between two paths—standard, off-the-shelf solutions, or custom, application-specific solutions. In many cases, designers would like to specify a custom supply to obtain the optimum performance in the most compact package. That isn't always feasible, though.

Order quantities may not be high enough to justify the NRE costs associated with a custom solution. In addition, product development cycles might not allow sufficient time to develop and qualify a custom product. On the other hand, standard product offerings don't always provide the desired level of performance or the right combination of options.

But now, Vicor Corp. is striving to raise the level of customization achievable in standard, off-the-shelf products. Through its introduction of the VIPAC Power System, a family of configurable power-supply products, the power-supply manufacturer has increased the range of options and the level of performance that designers can attain in a standard supply. VIPAC exploits a cleverly partitioned power architecture, modular front ends, high-efficiency dc-dc converters, and versatile packaging design to permit a high degree of customization and industry-leading power density (see the figure).

Breadth will be the hallmark of Vicor's new power system. VIPAC will allow designers to specify operation from either a 48-V dc or a 115-/230-V ac input with one to three regulated voltage outputs between 1.8 and 48 V at power levels ranging from 50 to 900 W (Table 1).

A VIPAC supply consists of several configurable elements. These include an application-specific power processing unit (PPU), a number of chassis options, and remotely located holdup capacitors. To specify the PPU, users will select from one of three modular front ends. These are the filter input attenuator module (FIAM), which operates from dc; the filter autoranging rectifier module (FARM), an ac input unit; and the filter harmonic attenuation module (FHAM). Within these modules, a microprocessor-based front-end controller incorporates a multimode user interface that allows programming of power-up and power-down output sequencing and real-time control of outputs.

The front-end modules offer EMI filtering, transient protection, autoranging bridge rectification, and power-factor correction options as required. Users select the appropriate front end and combine it with one or more of the company's second-generation dc-dc converters to obtain the desired voltage outputs, current, and power levels.

The list of available output voltages includes the popular values between 1.8 and 48 V. But these values generally can be trimmed over a range that's 10% to 110% of nominal value. On the low end of the voltage spectrum, VIPAC permits outputs to be trimmed down to 500 mV.

The front-end and dc-dc converter modules interconnect via a "snake" interface board that's sized in accordance with the number and size of the modules selected. The three front-end modules share the same footprint and only one is used per supply, fixing the amount of real estate required by the front end. Therefore, the dc-dc converter section determines the length and width of the supply depending on the number and size of the converters needed. Vicor's dc-dc converters come in standard quarter-, half-, and full-brick package styles.

Initially, the num-ber and combination of dc-dc converters, which the user specifies, will be limited to one of six coldplate styles. These provide a standard set of footprints from which a variety of power supplies may be configured (see the tables for footprint dimensions). These coldplate options allow for power-supply configurations of one to three outputs with varying levels of current and power output, depending on the heatsink.

For each of these coldplate options, however, users will have five heatsinks from which to select. They may specify the power supply with coldplate only, or with 0.5- or 1.0-in. tall heatsinks in either a transverse or longitudinal orientation. These options provide the designer with three alternatives for cooling. They can select either conduction, convection, or forced convection (fan cooling). The conduction-cooled versions with just the coldplate may be mounted into the user's existing chassis, heatpipe, or heatsink.

Designers may additionally specify one of four output-termination styles: a threaded stud, a multipin connector for quick connect, a pinned version for direct attachment, and a cable mate or a flat cable connector.

Despite this level of configurability, VIPAC power supplies offer high levels of current and power density by volume (Table 2). Although these values vary with module and heatsink selection, essentially, power density for this product line varies from 6 to 23 W/in.3 According to Vicor, competitive power-supply series from other vendors offer power densities below this range.

But power density is only one piece of the equation. VIPAC's main claims to greatness are configurability and time-to-market. These distinctions reflect not only the wide range of input and output voltage, current, and power options available to designers, but also faster design prototyping and some special functions that competitive units might not offer. Among these special features are output sequencing, overvoltage protection on all outputs, independent load regulation, and no minimum load requirement.

The partitioned architecture em-ployed by VIPAC permits the use of remotely located holdup capacitors. In some cases, this flexibility allows the PPU to be placed close to the load and permits the optimization of capacitor selection for the application. In all cases, reliability is enhanced by thermally decoupling the capacitors from the converters and coldplate. Users may either supply their own capacitors or order a prepackaged holdup box from Vicor.

Perhaps even more interesting than the current list of options is the company's plan to increase VIPAC's level of configurability in the future. Using a Web-based power-supply selection tool named VCAD, Vicor customers will be able to configure their power supplies online. Initially, in the first-phase rollout of VIPAC, customers will have to specify their power-supply designs using the finite number of mechanical packages described previously.

In the planned phase two of the VIPAC introduction, however, designers will be able to take any of the allowed electrical configurations and create custom mechanical packages to house them. To enable this step, Vicor will offer an advanced version of the VCAD mechanical design tool at the company Web site. Phase two of VIPAC and VCAD is supposedly about a year away.

Also planned is the future expansion of voltage output options. Furthermore, the initial introduction of VIPAC doesn't include the FHAM option, which the company expects to release later this year.

Price & Availability
Pricing for the VIPAC power systems starts at $0.55/W in quantities of 500. Beginning in March, the lead time for prototype units will be two weeks for popular configurations.

Vicor Corp., 25 Frontage Rd., Andover, MA 01810; (978) 470-2900; fax (978) 475-6715; www.vicr.com.

TAGS: Vicor
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