Page 54 - EE Times Europe Magazine | April2019

54 EE|Times EUROPE — Boards & Solutions Insert

Thermal and Vibration Energy Powers IoT Devices

Design considerations for thermoelec-
tric-energy–harvesting systems “include
electrical and thermal requirements, ther-
moelectric materials, application-specific
considerations, durability targets, selling price,
and engineering budget,” said Piggott.
Vibrations are a ubiquitous energy source.
Every car on the road creates vibrations on the
asphalt and in the cab. Given the number of
cars on the world’s motorways, the appeal of
Figure 2: Equivalent circuit of piezoelectric effect (Image: “A piezoelectric vibration based gener- deriving energy from vibrations is clear.
ator for wireless electronics.” Smart Materials and Structures 13 (2004) 1131–1142) Maxim Integrated’s MAX17710 PMIC is a
complete system for charging and protecting
micropower-storage cells and can manage
Figure 3: poorly regulated sources such as energy-
Simplified operat- harvesting devices with output levels ranging
ing circuit of the from 1 µW to 100 mW (Figure 3).
MAX17710 The AEM30940 integrated energy man-
(Image: Maxim agement subsystem from e-peas extracts DC
Integrated) power from a TEG, piezo generator, micro-
turbine generator, or high-frequency RF
inputs to simultaneously store energy in a
rechargeable element and supply the system
with two independent regulated voltages. The
PMIC integrates an ultra-low-power boost
converter to charge a storage element, such as
a lithium-ion battery, a thin-film battery, or a
super- or conventional capacitor. It can start
operating with empty storage elements at an
input voltage as low as 380 mV and an input
power of just 3 µW (Figure 4).
The LTC3588-1 integrated circuit shown
in Figure 5 offers a complete energy storage
solution, optimized for high-impedance
generators such as piezoelectric transducers.
The Analog Devices circuit features a low-
loss full-wave rectifier and a high-efficiency
synchronous buck converter that transfers
energy from a storage device at the input to a
regulated voltage output capable of supplying
loads up to 100 mA. It is available in a
3 × 3-mm DFN or 10-conductor MSE package.
To design a fully autonomous wireless
sensor system effectively, you need low-
power-consumption microcontrollers and
transducers that consume a minimum amount
of electricity using low-energy environments.
Figure 4: Typical application circuit for the AEM30940 (Image: e-peas) A power solution for such systems may
consist of storing mechanical, thermal, or
Figure 5: electromagnetic energy available in the local
Complete energy environment of the sensors themselves.
storage solution, Supercapacitors are the technological
optimized for prerequisite to energy harvesting. They have
high-impedance the functional characteristics of electrolytic
generators such capacitors and rechargeable batteries but can
as piezoelectric store 10× to 100× more energy per unit volume
transducers or mass than an electrolytic capacitor. They
(Image: Analog Devices) can accumulate charge at far higher speeds and
withstand far more charge-discharge cycles
than typical rechargeable batteries. ■
Maurizio Di Paolo Emilio is a staff
correspondent at AspenCore, editor of Power
Electronics News, and editor-in-chief of EEWeb.

APRIL 2020 | www.eetimes.eu