More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC–DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

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Micropower energy harvesting

More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC-DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

Energy harvesting: State-of-the-art

Energy harvesting is an emerging technology with applications to handheld, portable and implantable electronics. Harvesting ambient heat energy using thermoelectric generators (TEG's) [1] is a convenient means to supply power to body-worn electronics and industrial sensors. Using TEG's for body-wearable applications limits the output voltage to 50mV for temperature differences of 1–2K usually found between the body and ambience. Several existing systems [2, 3] use a battery or an initial high voltage energy input to kick-start operation of the system from this low voltage. Further, changing external conditions cause the voltage and power generated by the TEG to vary, necessitating efficient control circuits that can adapt and extract the maximum possible power out of these systems. In this paper, a battery-less thermoelectric energy harvesting interface circuit which uses a mechanically assisted startup circuit to operate from 35mV input is presented. An efficient control circuit that performs maximal end-to-end transfer of the extracted energy to a storage capacitor and regulates the output voltage at 1.8V is demonstrated.

/pdf/a-battery-less-thermoelectric-energy-harvesting-interface-2f2stxta6c.pdf

A Battery-Less Thermoelectric Energy Harvesting Interface Circuit With 35 mV Startup Voltage

A platform architecture combining energy from solar, thermal, and vibration sources is presented. A dual-path architecture for energy harvesting is employed that has a peak efficiency improvement of 11%-13% over the traditional two-stage approach. The system implemented consists of a reconfigurable multi-input, multi-output switch matrix that combines energy from three distinct energy-harvesting sources-photovoltaic, thermoelectric, and piezoelectric. The system can handle input voltages from 20 mV to 5 V and is capable of extracting maximum power from individual harvesters all at the same time utilizing a single inductor. A proposed time-based power monitor is used for achieving maximum power point tracking for the photovoltaic harvester. This has a peak tracking efficiency of 96%. The peak efficiencies achieved with inductor sharing are 83%, 58%, and 79% for photovoltaic boost, thermoelectric boost, and piezoelectric buck-boost converters, respectively. The switch matrix and the control circuits are implemented on a 0.35-μm CMOS process.

Platform Architecture for Solar, Thermal, and Vibration Energy Combining With MPPT and Single Inductor

An autonomous power generator unit including two micropower sources and their management IC has been fabricated: a RF power receiver and a 1 V miniature thermogenerator combined with a micropower DC/DC up-converter are combined with a 78% efficiency manager and charger, and a 5 nW discharge monitor to manage and store the harvested energy in a 30 above-IC deposited microbattery.

Efficient Power Management Circuit: From Thermal Energy Harvesting to Above-IC Microbattery Energy Storage

An autonomous power generator unit includes 2 micropower sources and their associated management IC; a 1V miniature thermogenerator and RF power receiver are combined with a micropower DC-DC upconverter, power supply manager and microbattery charger, and a 5nW discharge monitor, to manage and store the harvested energy in a 30mm2 above-IC deposited microbattery.

Efficient Power Management Circuit: Thermal Energy Harvesting to Above-IC Microbattery Energy Storage

The proposed microsystem architecture comprises two power sources, and a microbattery used as a storage unit ; a complete integrated circuit transforms and manages the harvested energy and interfaces the microbattery. The first source is a RF power receiver combined with a classical RF converter. The second micropower source is a 1V miniature thermogenerator based on sintered bismuth telluride thermoelements, combined with a micropower DC/DC up converter. The converter architecture includes an innovative power switch control designed for better power efficiency, and improved supply noise performance. The microbattery is a lithium, solid-state, battery post-processed on the integrated circuit. A discharge monitor with 5nW power consumption, along with a 78% efficiency charge unit interfaces the battery. These harvesting and power storage devices are foreseen as a way to provide power on a chip, allowing either permanent active security for smart card applications or sensors supply for monitoring applications for example.

M. Plissonnier

Papers

Efficient Power Management Circuit: From Thermal Energy Harvesting to Above-IC Microbattery Energy Storage

Efficient Power Management Circuit: Thermal Energy Harvesting to Above-IC Microbattery Energy Storage

On chip post-processed microbattery powered with RF and thermal energy through a power management circuit