As MIT’s Larry Hardesty notes, the rapidly evolving Internet of Things (IoT) is expected to boast extremely low-power sensors capable of running for months on a single charge using various energy harvesting techniques.
Indeed, MIT researchers have designed a power converter chip designed to both power a device and charge a battery that’s more than 80 percent efficient, even at the extremely low and variable power levels characteristic of tiny solar cells. Previous iterations, says Hardesty, had efficiencies of only 40 or 50 percent.
Image Credit: MIT
The new MIT chip also offers additional features, including the ability to directly charge both a battery and a device. All operations share a single inductor, effectively saving on circuit board space.
“We still want to have battery-charging capability, and we still want to provide a regulated output voltage,” explained Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on a new paper describing the chip. “We need to regulate the input to extract the maximum power, and we really want to do all these tasks with inductor sharing and see which operational mode is the best. And we want to do it without compromising the performance, at very limited input power levels – 10 nanowatts to 1 microwatt – for the Internet of Things.”
Brett Miwa, who leads a power conversion development project as a fellow at Maxim Integrated, says the current trend is to lower efficiency as the power drops due to a fixed amount of energy.
“[However, El-Damak’s] design is unusually efficient for how low a power level she’s at. One of the things that are most notable about it is that it’s really a fairly complete system. It’s really kind of a full system-on-a chip for power management,” said Miwa. “And that makes it a little more complicated, a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature. So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy.”
Commenting on this, Patrick Gill, a Principal Research Scientist at Rambus, noted that recent advances in energy harvesting technology would help accelerate the development and deployment of next-gen smart sensors.
“Many IoT devices will have a tiny sensor, a tiny battery, and be charged by a photovoltaic with intermittent access to light. El-Damak’s techniques nearly double the efficiency of photovoltaic power harvesting systems, and could make energy-harvesting more practical,” added Gill. “What’s particularly interesting is that as energy management innovations deliver increasing power, the energy needed for sensing, computation and wireless transmission continues to decrease. Since it’s the product of power available times power efficiency that dictates the capability of an autonomous sensing node, we can expect to see a quickly-expanding range of digital interactions in IoT widgets that do not need to be plugged in.”
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