DESIGN PLUS POWER MANAGEMENT ARCHITECTURES
approach).
These oscillating circuits operate
alongside the main boost converter -
so that when the power output gets to
a level that is high enough, the boost
converter takes over (thereby enabling
more ef cient operational performance
to be achieved).
The setup means that energy
can be drawn ef ciently from the
environment across a much more
extensive range of input voltages
- starting off at very low levels and
carrying on all the way up to several
orders of magnitude above this.
For instance, in a solar context an
e-Peas IC can work with a photovoltaic
cell that is generating a mere 3μW,
but will also support multiple cells
pumping out as much as 500mW of
power.
In order that the system can
respond to variations occurring in the
environmental conditions, maximum
power point tracking (MPPT) is applied
on a continuous basis (usually at
5s intervals). This feature is easily
con gurable though, so that the end
user can adjust the regularity to t the
particular system requirements.
NOWI Energy is a venture-backed
enterprise that is focusing its attention
on body-worn and IoT-driven solutions
for scavenging minuscule amounts
of energy, through incorporation into
consumer and medical monitoring
products.
It offers a comprehensive ICbased
intelligent power management
subsystem that is applicable to RF
(including use of Wi-Fi signals), solar
or thermal deployment.
This highly integrated subsystem
takes up only a small amount of
board space (12 square mm in total)
as it doesn’t require inclusion of any
inductor components (which also
lowers the bill-of-materials costs)
and calls for the addition of just one
external capacitor.
The company estimates that it can
reduce the board real estate that a
conventional solution would occupy
by a factor of at least 10 (often 20).
The quick-acting MPPT has a settling
time of less than 1s, and the ef ciency
of the boost converter is up to 90%. As
well as selling hardware, NOWI is also
licensing its IP to several companies in
the consumer sector.
Mechanical vibrations
Anthony Quelen, Senior Analogue
Designer at CEA-LETI, has been
leading a research project that
involves the conversion of on-going
mechanical vibrations into electricity
using an oscillating magnet placed
within a coil, alongside a proprietary IC
that features a real-time optimal input
impedance generator and a unique
boost architecture with no off-chip
components needed.
Applicable for deployment on trains,
industrial motors etc., the harvester
setup requires low output impedance
and low voltage characteristics (due to
the boost architecture), relying on high
currents to augment power ef ciencies
over a large output power range.
As the continuous vibrations need
to correspond to the natural frequency
of the harvester coil, they must be of
a steady and predicable nature - with
the harvester parameters being set
accordingly inside the IC (so that they
exactly match requirements).
The complete solution is
streamlined - comprising of just
the harvester coil (which has
approximately the same diameter
as a 2 Euro coin), an energy storage
reserve (namely a battery cell or
supercapacitor) and the power
management IC (which is fabricated
using a standard CMOS process).
The need for external capacitor or
inductor components has been totally
removed.
“By working with partners, we
now have a very effective prototype
solution,” said Quelen. “The IC
achieves more than twice the energy
extraction gures from periodic
vibrations that a full-bridge recti er
would and quadruples what can be
taken from mechanical shocks.”
This equates to as much as 50mW
of power generation, with overall
ef ciency levels climbing to 95.9%.
“The next phase is for us to
license this technology to a power
semiconductor manufacturer, so that
it can get true commercial uptake.”
There is certainly a growing number
of different ways via which energy
can be drawn from the world that
surrounds us - with each having its
own innate merits, depending on the
application scenario.
Likewise, numerous
tactics are now being
explored regarding how best
to ensure wastage remains
negligible and that every
precious mW of available
power is fully exploited.
Research institutes,
Figure 2: An e-Peas
AEM10941 power
management IC for
photovoltaic use
cases
Figure 3: NOWI
Energy’s compact
power management
solution aimed
at IoT/wearable
deployment
university spin-outs and
edgling rms are all coming
up with ingenious power
management topologies that
may well challenge what the
established IDMs can offer.
www.newelectronics.co.uk 28 April 2020 21
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