Power Management Unit for Solar Energy Harvester Assisted Batteryless Wireless Sensor Node

Abstract

This work describes an energy-efficient monolithic Power Management Unit (PMU) that includes a charge pump adapted to photovoltaic cells with the capability of charging a large supply capacitor and managing the stored energy efficiently to provide the required supply voltage and power to low energy consumption wireless sensor nodes such as RFID sensor tags. The proposed system starts-up self-sufficiently with a light source luminosity equal to or higher than 500 lux using only a 1.42 cm2 solar cell and integrating an energy monitor that gives the ability to supply autonomous sensor nodes with discontinuous operation modes. The system occupies an area of 0.97 mm2 with a standard 180 nm CMOS technology. The half-floating architecture avoids losses of charging the top/button plate of the stray capacitors in each clock cycle. Measurements’ results on a fabricated IC exhibit an efficiency above 60% delivering 13.14 μW over 1.8 V. The harvested energy is enough to reach the communication range of a standard UHF RFID sensor tag up to 21 m.

On Search for Unconventional Energy Sources for Harvesting

“…Ubiquitous electromagnetic energy is an important source used in harvesters. The basic form of energy here is light converted into electric current in photovoltaic cells [15]. The photovoltaic phenomenon, which involves the excitation of electrons in solids by light, is currently used on a large scale in photovoltaic panels to produce electricity.…”

Earliest Deadline First Scheduling for Real-Time Computing in Sustainable Sensors

“…When designing and developing standalone sensor systems, engineers have to address a lot of design issues relative to the performance characteristics of the sensor, the capacity of the energy storage unit, the processing performance of the microcontroller, etc. The implementation of energy-harvesting systems is rapidly changing as better power management chips are introduced and harvesters are improved [23,24]. Electronic engineers gain application experience with EH technology.…”

Development of a low-power solar energy harvester PMU integrated circuit optimized for indoor environments.

“…The output power provided by the energy harvester is enough to power continuously the aforementioned wireless sensor node in Section 4.2 under indoor light conditions in sleep mode while the remnant power can be stored in the supply capacitor to provide energy to the sporadic operation of the microcontroller during the active mode. In order to increase the available current and therefore the external capacitor charging, it would be possible also to arrange two photocells in parallel as it is explained in our work When using the smaller storage capacitor selected in Section 5.3.4, 0.555 µF instead of 47 µF , the charging process of the storage capacitor is reduced from 16.5 s to only 140ms, as depicted in the Figures 5.51 and 5.50 respectivelly [115]. Fig.…”