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Although microsensors nowadays can save money, energy, and lives, highly functional devices can exhaust a tiny battery very quickly. Harvesting ambient energy can help replenish the battery, but only when an ambient source is available. Unfortunately, many embedded microsensors are small, stationary, and enclosed, so thermal gradients, motion, and light are absent. Wireless power in these cases is...
When supplied well and with little power losses, multifunctional microsystems can add life- and cost-saving intelligence to hospitals, factories, and cars. Unfortunately, fitting the multiple power supplies that diverse subsystems require into millimeters is challenging. One reason for this is, although efficient and therefore necessary, inductors are bulky. And supplying several outputs with one...
A fundamental challenge wireless microsystems face is size, and in consequence, lifetime because tiny batteries exhaust quickly. Although small fuel cells and atomic sources store more energy than lithium-ion batteries and super capacitors, they source less power, so they cannot power as many functions. Small batteries and capacitors, however, cannot sustain life for long. Thankfully, the environment...
Wireless microsensors can sense and share data that can save lives, energy, and money. Recharging or replacing thousands of tiny, easily exhaustible batteries, however, is too costly. Fortunately, photovoltaic (PV) cells can generate 100x more power from sunlight than other transducers can from motion, heat, or radiation. But since PV cells cannot supply the milliwatts that microsystems can at times...
The main challenge with microsensors is limited space, because tiny batteries store little energy. Harvesting energy helps, but only when ambient energy is available. And even then, power is low because miniaturized transducers harness little power. This is why managing how and when to schedule functional tasks is so important. This paper proposes a schedule that requires the battery to hold only...
Although microsystems today require less power than ever before, they still cannot fit large enough batteries to sustain them for months or years at a time. Ambient energy is appealing, but only when available, which is often not the case for embedded sensors. Transmitting power wirelessly is more practical in these applications. Tiny receivers, however, capture a small fraction of the power that...
Wireless microsensors in factories, hospitals, cars, and so on process information that can save money, energy, and lives. Unfortunately, tiny batteries exhaust quickly, and replacing so many of them frequently is impractical. This is why recharging them with ambient energy is so appealing, especially when vibrations, for example, are abundant and steady. Still, tiny piezoelectric transducers draw...
This chapter focuses on how to most efficiently transfer and condition harvested energy and power with emphasis on the imposed requirements of microscale dimensions. The driving objective is to maximize operational life by reducing all relevant power losses. The chapter therefore briefly reviewes the electrical characteristics and needs of available harvesting sources and the operational implications...
Wireless microsensors and other miniaturized electronics cannot only monitor and better-manage power consumption in emerging small- and large-scale applications (for space, military, medical, agricultural, and consumer markets) but also add energy-saving and performance-enhancing intelligence to old, expensive, and difficult-to-replace infrastructures and tiny contraptions in difficult-to-reach places...
Piezoelectric harvesters are popular today because they typically draw more power from kinetic energy in motion than electrostatic and electromagnetic systems. Still, tiny transducers only derive a small fraction of what is available. Thankfully, raising the damping force with which transducers draw power increases that fraction, except overinvesting battery energy for that purpose can overdamp the...
Although energy in vibrations is often vast, the electrostatic force with which tiny variable capacitors draw power from motion is miniscule, so output power is low. Thankfully, extracting energy at higher voltages generates more power because the electrical damping force that impedes motion to draw power is stronger. Clamping the transducer to a battery is convenient in this respect, but limiting...
Wireless microsystems can add performance-enhancing, energy-saving, and networked intelligence to inaccessible places like the human body and large infrastructures like factories, hospitals, and farms. For this, they require an onboard source and a power-conditioning circuit that supply microwatts about a prescribed dc voltage. And since tiny dc batteries store little energy, switched-inductor dc-dc...
A major challenge with emerging microsensors, biomedical implants, and other portable devices is operational life, because tiny batteries exhaust quickly. And even though 1g fuel cells store 5 to 10× more energy than 1g Li-ion batteries, fuel cells supply 10 to 20× less power [1]. This means fuel cells last longer with light loads and Li-ion batteries output more power across shorter periods. Therefore,...
Battery-supplied systems demand fast, power efficient, and compact power supplies. Although linear regulators are quick and small, tiny batteries cannot sustain their losses for long. Pulse-width-modulated (PWM) switchers are considerably more efficient, but also slower. Luckily, hysteretic converters can respond within one switching cycle. Stabilizing the system for maximum speed with a hysteretic...
Wireless microsensors add intelligence to otherwise inaccessible locations and large infrastructures, such as tiny crevices in hospitals, factories, and farms. These small devices, however, store little energy, so functionality is low or lifetime is short, or both. Luckily, harnessing ambient energy can replenish these microsystems, and because solar light generates considerably higher power density...
Portable microsystems, which typically incorporate transceivers, analog/digital converters, microprocessors, and others, require several fast on-chip supplies to both function and save energy. Linear regulators are fast and compact, but also lossy, and although switched inductors are efficient, power inductors are bulky, which is why supplying several functions with one inductor is often an optimal...
Because wireless microsystems can only incorporate tiny batteries, they typically exhaust stored on-board energy quickly. Fortunately, harvesting ambient energy is a viable means of extending their operational lifetimes, except starting and re-starting miniaturized microwatt harvesters from nocharge conditions is difficult. The challenge is drawing usable energy from millivolt signals under micro-scale...
A challenge wireless microsensors and other microsystems face is short lifetime, because tiny batteries store little energy. Fortunately, the environment holds vast amounts of energy, and of available sources, like light, motion, temperature, and radiation, solar light produces the highest power density. Still, micro-scale photovoltaic (PV) cells harness a diminutive fraction of light and artificial...
Energy and power in tiny batteries are often insufficient to sustain the demands of a wireless microsystem for extended periods. Piezoelectric transducers are viable alternatives because they draw power from a vast tank-free supply of ambient kinetic energy in vibrations. Unfortunately, small devices alone seldom dampen vibrations enough to fully harness what is available, which is why investing energy...
Because small batteries store little energy, micro-scale systems often trade functionality or lifetime, or both, for integration. Harnessing ambient energy can abate the sacrifice, but only to the extent transducer and circuit efficiencies allow. Optimally adjusting the electrical damping force in the transducer is therefore as important as lowering power losses in the circuit. In kinetic electrostatic...
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