Navy

Zero power startup switch

Improves vibrational energy harvesting systems by only triggering power conversion when it doesn’t pose a risk for battery drain

Energy Electronics Sensors

The military is exploring several energy harvesting devices and this new ZPSS will further their utility by better managing the available energy. Image: US Army

Navy scientists have developed a more efficient, power-conserving energy harvesting system that gates the power converter from the battery. The patented technology is available via license agreement to companies that would make, use, or sell it commercially.

For wireless and distributed sensor systems, vibrational energy harvesting provides a way to extend the operational lifetime beyond what a chemical battery alone can provide. By converting mechanical vibrations from a pump, vehicle, or structural frame into electrical energy, vibrational energy harvesting can be used to either supplement or replace chemical batteries.

For energy harvesting systems to be efficient, a power converter circuit is typically required to efficiently deliver the harvested energy from the transducer (the device that converts one form of energy to electrical energy) to the battery for storage. The power converter is comprised of active circuit elements (transistors) and therefore requires a certain amount of overhead power to operate. This overhead power typically comes from the battery being recharged. While the power consumption of the power converter is relatively small, it can be detrimental to the system if insufficient energy is harvested to replace it. For systems where the applied energy source is not consistently available or only present for irregular intervals, the consumption of the power converter will dominate, and more energy will flow out of the battery than into it.

Navy scientists have addressed these issues by introducing a Zero power startup switch (ZPSS) into the energy harvesting system to gate the power converter from the battery when the energy harvested is insufficient to compensate for the power converter’s overhead power requirements. This circuit measures the output from the transducer, determines if enough energy is present to merit the operation of the power converter, and either connects or disconnects the power converter from the battery as appropriate, preventing unwanted battery drain.

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