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Powering energy-efficient embedded systems in a cluttered environment

Embedded systems are everywhere on the battlefield-in unmanned vehicles, ground vehicles, on the backs and hands of warfighters-sitting in the field gathering data, and everywhere in-between. All these systems rely on one thing in common, and that's power.

As demands on embedded systems grow, and the need for decreasing size, weight, and power become more clear, power supplies are making the leap to increased efficiency, lighter weight, and smaller size.

Energy-efficient embedded systems often must function in environ- ments where power is at a premium, and run at low power.

Having an efficient power supply is important. Power supplies are one of the largest factors in the efficiency of a system, particularly when they are converting electricity from AC to DC power (and vice versa), or changing the voltage. "One big place you can achieve efficiency [in a system] is in power supply design," says Martin Sweeney, lead project engineer at Parvus Corp. in Salt Lake City."

Power supplies must be able to convert power while protecting the system they serve from surges and electromagnetic interference.
Power supplies must be able to convert power while protecting the system they serve from surges and electromagnetic interference.

Efficiency is key

Efficient power supplies are important in systems where power is limited. A vehicle may have several systems running inside of it, and that means each system is running on shared power. Having more efficient systems means being able to fit more on a single vehicle, making it more valuable and useful to the mission. "One way to reduce the power budget of a system is to have a more efficient power supply," Sweeney says.

An efficient power supply not only is important for running electronics, but also means less wasted power and less waste heat. "The better the efficiency, the less heat is produced by the power supply," Sweeney says.

One way to achieve enhance efficiency in a power supply is to have zero-crossover on switching. There are many different approaches to achieving zero-crossover, but the primary objective involves converting power by turning the switch from on to off at zero volts.

Ruggedization and interference

Where power efficiency is key, power supplies need to guard against several kinds of threats.

It's important that power supplies be able to withstand power surges and guarantee system safety. The technology to protect against surges remains largely unchanged, with diodes that clamp off voltages once they reach a certain point, and circuits that prevent overvoltage from occurring.

Power supplies in these systems need to protect themselves, particularly in the cluttered environment of a combat vehicle, but they also must prevent their own functions from interfering with other systems. "They try to cover it from both ends, prevent stuff from emitting and bulletproof the other boxes from the emissions," Sweeney says. "For the emissions, you're talking about a passive filter of semiconductors, common mode choke. Generally, the noise comes out in a common mode noise present in both lines: positive and ground. Once it gets onto your power line, it also radiates. It will interfere with other boxes and cables, causing them to malfunction. With interference, many different defects can happen. That's why they try to avoid that by putting radiation limits and susceptibility limits on the box."

Preventing emissions to reduce interference with other systems is commonly performed by using electromagnetic interference (EMI) shielding or by using smaller current loops, filters, and wide traces.

COMPANY INFO

Absopulse Electronics Ltd
absopulse.com
Aeroflex Inc.
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AJ's Power Source Inc.
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Analytic Systems
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Behlman Electronics Inc.
behlmanpower.com
Comdel Inc.
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ConTech
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DRS Pivotal Power 902-835-7268
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Energy Technologies Inc.
ruggedsystems.com
Falcon Electric Inc.
falconups.com
Gaia Converter Inc.
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