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.