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The military market isn’t exactly keen to ride the bleeding edge when it comes to embracing new power supply and power conversion concepts. But it’s had no choice than to evolve in order to keep pace with the challenges of modern digital electronics. The newest crop of high-performance FPGAs and processors demands a lot from a power supply. They typical require low voltages, high currents, tight regulation, fast transient response and even supply voltage sequencing. Meanwhile, the typical high-performance embedded computer requires several different voltages, 5V and below. For example, each FPGA or DSP will require one voltage for the I/O circuitry and another to power the processor core.
Applications in military and aerospace call for unique and highly reliable converters with multiple independent outputs. Martek Power, for example, added two high-power, multichannel models to the 28V Input DC/DC converter family earlier this year. The new models, CB150D (Figure 1) and CB225T, are available at 2, 3.3, 5, 5.2, 12, 15, 24 and 28 VDC outputs, expanding the choice of output power of the CB series DC/DC power converter to a range of 5 to 225W.
Measuring 2.28 x 2.90 x .0.50 inch (57.9 x 73.7 x 12.7 mm) in size, the CB150D is a 150W device with two independent 75W output channels. The CB225T, measuring 2.28 x 4.35 x 0.50 inch (57.9 x 110.5 x 12.7 mm) in size, is a triple output module with three independent 75W output channels. Both DC/DC converters feature a wide input range of 16 to 40 VDC and a power density of 45W/in3. These together with full specified performance over an operating temperature range of 55° to +100°C from no load to full load make the two new models unique in the mission-critical market segment.
System Partitioning Rethink
In the past, engineers would typically place a DC/DC power converter at each output–a solution that is very expensive, very heavy and often inefficient. The challenge therefore is to improve efficiency while supplying various low-voltage requirements on a single board. Today, engineers are turning to a single high-power DC/DC converter, with several point-of-load converters to power individual devices on the board. Separating DC/DC converter functionality, especially at the point of load, provides important benefits to military application such as flexibility, size and weight reduction.
For decades, the bricks of distributed power architecture converters delivered the classic functions of the DC/DC converter–isolation, voltage transformation and regulation–to the point of load. As the number of voltages required at the board level began to proliferate, however, DPA increasingly consumed valuable real estate and unnecessarily replicated full converter functionality.
Putting a different twist on distributed power, Vicor came up with a DC/DC converter architecture with decoupled functionality called Factorized Power Architecture (FPA). FPA breaks power conversion into flexible and scalable power building blocks called V•I Chips. The Voltage Transformation Module (VTM) is a current multiplier that provides transformation and isolation. The Pre-Regulator Module (PRM) provides a regulated, non-isolated output voltage–a “factorized bus”–that is settable within the range of 26 VDC to 50 VDC from an unregulated input source.
Isolated and Regulated
The combination of the PRM and VTM creates an isolated, regulated DC/DC converter. PRMs can also be used stand-alone as non-isolated voltage regulators when the input and output returns are not common. A military PRM-VTM chip set can provide up to 100A or 115W at a system density of 172 A/in3 or 198 W/in3, and because the PRM can be located, or factorized, remotely from the point of load, these power densities can effectively be doubled.
Vicor’s latest offering in that architecture family is the VI BRICK (Figure 2). VI BRICK BCMs provide a highly efficient solution for Intermediate Bus Architecture or point-of-load (POL) designs that require multiple output voltages. They are available with nominal input voltages including 48 VDC (11 models) and high voltage up to 380 VDC (three models), and a wide array of output voltages from 1.5 to 48 VDC. The efficiency and compact size of these modules yields power density up to 390 W/in³. VI BRICK models are available in a base temperature grade of -40° to +100°C operating, and -40° to +125°C storage, with a slotted-flange baseplate and through-hole pin style.
Digital Approach Reduces Parts Count
Although power supplies are still primarily analog components, the addition of digital circuitry and interfaces offers significant benefits for military system designers–especially given the wide variation of power supply characteristics demanded across the military market. Lambda offers a range of digitally controlled modules to its innovative NV-Power (Figure 3) family of configurable AC-DC power supplies, enabling increased power output of up to 1450W peak rating for 10 seconds. The new modules enable Lambda to satisfy the increasing demand for low-profile configurable power solutions from 350W to above 1,000W.
The new digitally controlled modules incorporate many innovative design features including a new integrated magnetics transformer that allows for small size and increased efficiency. The digital control allows customizations based on the application’s requirements. NV-Power employs an 8-bit microcontroller to handle housekeeping routines, replacing the array of comparators, op amps and other discrete components used in less integrated designs. This brings a 50% parts count reduction, which in turn allows 40% more board space for power components. All units operate with an input range of 90 - 264 VAC.
Forward deployed military systems must wrestle with uncertain and unreliable power conditions. Serving that need, Calex has announced its Hold Up and Hold Up Light product offerings. The Hold Up modules (Figure 4) are designed for use with Calex DC/DC Converters to protect against brown-out and temporary power loss conditions, and provide a clean, uninterrupted source of power for downstream circuitry. The Hold Up model, part number HU-28, provides a complete turnkey solution for easy design integration. The Hold Up Light model, part number HUL-28, requires the use of an external capacitor bank in addition to the HUL module.
The HU-28 and HUL-28 have an input range of 15.5 VDC to 36 VDC. Both the HU-28 and HUL-28 offer user-programmable hold-up trip voltage. Both modules have two modes of operation: “stand-by” and “tripped.” During stand-by, the module charges the hold-up capacitors to 45V and maintains that voltage. When tripped, the module stops charging the hold-up capacitors and connects them to the Vout pins. The operating temperature range for both models is -40° to 100°C.
Unique Requirements for Space
Power conversion technology for space-based applications has its own unique challenges. What’s needed is guaranteed radiation tolerance through long-term exposure to low dose radiation. At one time, a total dose of 100 krad or more was acceptable, but over time the industry learned that continual low dose radiation is much more of a concern and typical of that encountered during the application. With that in mind, VPT rolled out a new product line in April that meets today’s updated reliability requirements for space, including the new radiation requirements, small size and light weight mandates, stringent requirements of 100% reliable operation through a wide range of space flight conditions.
This new family comprised of more than 50 DC/DC converter modules specifically designed and manufactured for space applications, is grouped into four product families. These new space DC/DC converters deliver up to 120 watts of output power and operate reliably through harsh radiation environments. VPT packages its “S” space series of DC/DC converters in miniature, hermetic, metal cases for reliable power delivery through the extreme temperature, shock, vibration and radiation environments of space travel. Specific features of the new SVSA, SVHF, SVTR and SVFL product families include 6 to 120W of output power in standard single and dual output voltages.
The devices are characterized and guaranteed to 30 krads (Si) per VPT’s RHA plan specified per MIL-PRF-38534, Appendix G, Level P with 2x margin. MIL-PRF-38534 Class H element evaluated components standard is supported. The devices are guaranteed to contain no pure tin and feature a fault tolerant design with radiation-immune magnetic isolation technology. Case temperature operation is rated at -55° to +125°C with full performance over entire temperature range.
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