With more and more computing stuffed into smaller spaces, power has direct implications on the size, cooling and mobility of a system. Selecting power supplies and power conversion electronics rank as make or break technical choices in embedded military computer systems. Factor in the hurdles of multi-voltage electronics and the complexity of distributed system architectures, and it’s clear to see why military system designers are hungry for solutions that untangle those challenges. Fortunately, military power conversion vendors are easing the burden with more efficient products, new partitioning strategies and increased ruggedization.

Taking aim at aircraft distributed power and similar applications, V•I Chip, a subsidiary of Vicor, offers a MIL-COTS BCM bus converter. This high-efficiency (more than 95 percent), Sine Amplitude Converter (SAC) operates from MIL-STD704E/F 270 VDC and delivers an isolated 30.0 to 41.3 VDC. This voltage is suitable as an input to the MIL-COTS PRM regulator and VTM current multiplier. The MIL-COTS BCM achieves a power density of 829W per cubic inch in a V•I Chip package compatible with standard pick-and-place and surface mount assembly processes. The package provides flexible thermal management through its low junction-to-case and junction-to-board thermal resistance. Owing to its high conversion efficiency and safe operating temperature range, the BCM may not require a discrete heat sink in typical applications. Low junction-to-case and junction-to-lead thermal impedances assure low junction temperatures and long life in the harshest environments.

Aircraft Distributed Power

Another bus converter solution targeting aircraft needs, the VPTHVM-270 Series (Figure 1) from VPT offers a bus converter module that offers wide input voltage ranges—a high priority in avionics systems. With up to 200W of output power, this regulated bus converter module operates from a 270V bus to step down the power to create a regulated 28V bus for avionics power systems. A wide input voltage range accommodates MIL-STD-704 input power requirements for avionics and other applications. The high-efficiency design reduces input power requirements and eases thermal management, thereby increasing the overall system reliability.

With a footprint of just 2.35 inches (59.69 mm) by 1.550 inches (39.37 mm) and weighing in at 85 grams, the VPTHVM-270 Series saves valuable space and weight in a power system. Output power is up to 200W, with an efficiency up to 91 percent. Input voltage range is from 160 to 500 volts per MIL-STD-704. The unit is tested to JESD22, MIL-STD-810 and MIL-STD-883. A rugged six-sided all metal package improves performance reliability through the harsh environments of vibration, shock and temperature cycling.

Saving Board Space

Compact electronics are the norm these days, and high-power AC-DC conversion always comes down to a question of board space. With that in mind, TDK-Lambda has expanded its PFE series (Figure 2) of AC-DC power bricks with the introduction of the new PFE1000F modules. These modules provide a convenient AC-DC pcb-mounted solution with an output power of up to 1008W. Up to now, using bricks in an AC to DC conversion application required two modules. One module was needed to handle the AC input rectification and power factor correction (PFC), and a second for the DC-DC isolation and low voltage conversion. The PFE series combines these two functions into a single brick.

All PFE1000F models accept a wide AC input from 85V to 265V at 47-63 Hz, have active power factor correction (PFC), an input to output isolation of 3 kVAC, and an input to baseplate rating of 2.5 kVAC with application circuitry. In addition, over-voltage, over-current and over-temperature protections are included. The PFE1000F comes in a compact 3.94 x 0.53 x 6.3-inch package and can be conduction-cooled with a cold-plate or forced air-cooled with a heatsink. 

Reliable Power Factor Correction

Power factor correction is another piece of the power conversion puzzle where highly reliable commercial off- the-shelf solutions are vital to military and aerospace applications. Serving such needs, Martek Power provides an active power factor correction and harmonic attenuation module with 100W output power, extending the power range offered by the PFC family to 100 to 1000W. The PF100 (Figure 3) is intended for use with Martek Power’s 100-watt 270 VDC input DC-DC converters; this front end rectifier provides a full 100W of output power from a universal single phase input from 85V to 265 VAC.

Packaged in a five-sided continuous aluminum case with dimensions of only 2.4 x 2.3 x 0.5 inch, the new unit meets CE101 and CE102 of MIL-STD-461 for conducted EMI without requiring any external filtering. Meeting MIL-STD-704E, ABD0100.1.8.1 and MIL-STD1399, it also delivers full performance over a wide, -40° to +100°C, operating temperature range, and boost efficiencies and power factor up to 93 percent and 0.99 respectively.

Getting the Heat Out

In harsh environment military applications, managing heat—in the form of dissipate power—is a tricky challenge. RECOM power attacks that problem with its PowerlinePlus Series of 20W to 50W power range DC-DC converters. These are the first modules to incorporate RECOM’s innovative ICE Technology—a combination of techniques to minimize internal heat dissipation and maximize the heat transfer to ambient to create a new converter series, which offers high-end performance at a price that is significantly lower than conventional specialist converters.

PowerlinePlus converters boast a case temperature operating range of -45° to +120°C, built-in Class B EMC filters and fully protected outputs. PowerlinePlus converters combine a high-efficiency design with a revolutionary integrated heat sink case to deliver more power over a wider temperature range while requiring less space and cost than equivalent solutions previously offered for these demanding applications. The PowerlinePlus Converter Series consists of six module offerings. An example is the RPP20-S-D, which provides 20W of power with 2:1 input voltage range, single or dual output options, 2 kVDC isolation, built-in EMC filter and operates at efficiencies of up to 90% to offer an ambient operating temperature range from -45° up to +100°C without derating, in a case size of only 2 x 1.2 inches.

Board-Level Power Supplies

Not to be left out, rugged board-level power supplies provide system designers with a complete modular solution for slot-card military systems. An example is Aitech Defense Systems’ P230 (Figure 4), a rugged, 3U, conduction-cooled, high-

efficiency power supply that operates over a continuous input voltage range of 18 VDC to 36 VDC. The P230 provides four industry-standard isolated voltage levels of +3.3V, +5V, +12V and -12V at up to 10A, 20A, 9A and 1 A respectively, or a combined total power capacity output of up to 150W, with an efficiency of better than 85%. This makes the P230 suited for use in a number of small form factor, robust and rugged VME-, CompactPCI- and VPX-based subsystems for high-reliability, embedded computing applications.

The DC to DC converters are equipped with internal thermal shutdown circuitry to protect them from damage due to potential system overheating. Mechanical and thermal construction includes a protective aluminum housing for mechanical ruggedization, EMI/RFI shielding and thermal conduction of heat to the system enclosure. A chemical conversion coating provides maximum heat transfer and corrosion resistance on thermal interface surfaces. Wedge-locks hold the P230 in place and clamp it to the enclosure’s thermal rails for optimum heat transfer, and extractors are included on the P230’s top panel for easy removal. Military-rated models operate at temperatures from -55° to +85°C (at the heat sink) when running at 85% of maximum rated power, and up to +75°C when operating at full rated power.  

Aitech Defense Systems 

Chatsworth, CA.

(888) 248-3248.

[www.rugged.com].

Calex

Concord, CA.

(925) 687-4411.

[www.calex.com].

Lambda Americas

San Diego, CA.

(619) 575-4400.

[www.lambdapower.com].

Martek Power

Torrance, CA.

(310) 202-8820.

[www.martekpower.com].

Pico Electronics

Pelham, NY,

(914) 738-1400.

[www.picoelectronics.com].

RECOM Power

Brooklyn, NY.

(718) 855-9710.

[www.recom-power.com].

TDK-Lambda Americas

San Diego, CA.

(619) 575-4400.

[www.lambdapower.com].

Vicor

Andover, MA.

(978) 749-8359.

[www.vicorpower.com].

VPT

Blacksburg, VA.

(425) 353-3010.

[www.vpt-inc.com].