IoT Energy Harvesting Challenges: e-peas Tackles It Head-on with New PMICs
With its new PMIC, e-peas hopes to enable more performant energy harvesting for IoT devices. But to do so, what are the challenges that come with IoT energy harvesting?
Recently, battery life and charging IoT devices have been pressing issues to both companies and researchers. To maximize IoT battery life, many companies are turning to onboard energy harvesting. This could provide a solid solution; however, it could also bring challenges.
A high-level depiction of some energy harvesting sources and a general system. Image used courtesy of Techplayon
A Belgian company, e-peas (electronic portable energy autonomous systems) Semiconductor, is a firm believer in energy-harvesting and is one of many companies focused on addressing these challenges. Yesterday, it brought two new PMICs to market, both of which are focused on providing more performant energy harvesting for IoT.
This article will discuss some of the challenges of energy harvesting in IoT and highlight the two new releases from e-peas.
Challenge #1: Buck-boost for Energy Harvesting
Many of the challenges of energy harvesting for IoT are because energy harvesting is inherently non-continuous and fluctuates output greatly. This makes these sources not very reliable for continuous power, to put it more explicitly.
Taking solar as an example, variables like cloud coverage and time of the year can significantly affect what voltages get output from our solar energy harvester.
Over the typical 24 hours, a solar panel can output anything from 0V to 100% of its rated output. Naturally, this means that a device that is expected to be constantly available cannot be powered by energy harvesting alone. It will also need a battery.
Example power architecture of a solar energy harvesting device. Image used courtesy of Analog Devices
However, the variable output of an energy harvesting device is significantly juxtaposed with a battery, a device that requires a precise cell voltage to charge. This requirement is challenge #1: how to achieve this continuous cell voltage to charge a battery when the output of the harvesting unit fluctuates so wildly?
A popular solution to this problem is a buck-boost converter. This DC/DC converter can produce a stable output voltage regardless of whether the input voltage is higher or lower than the output. This converter also benefits from high efficiencies compared to linear regulators, another critical consideration for low-powered IoT.
The challenge of energy fluctuation is but one issue; a second problem concerns powering wireless communication.
Challenge #2: Supercapacitor for IoT
Challenge #2 comes from the fact that all IoT devices utilize some form of wireless communication.
The challenge is that wireless communication technology also requires non-continuous power, with heavy current spikes occurring during data transmission. These drastic spikes can often be too much for conventional Li-ion or LiPo batteries to handle, causing damage to the cells themselves.
An example of IoT current spikes. Image used courtesy of Medium
A popular solution here is a supercapacitor, a device that stores less energy than a battery but provides faster response times and a suitable charge/discharge count before becoming damaged. This way, it can act as a buffer between the battery and the RF circuitry, providing the energy needed for short current bursts during transmission.
With these challenges in mind, it's essential to see what companies create to work around them or utilize the potential solutions to said challenges.
Innovation from e-peas
Aware of these challenges above, yesterday, e-peas released two brand new energy harvesting PMICs for IoT.
The first offering, the AEM10330, is a solar-specific energy harvesting IC. Boasting an integrated buck-boost converter and allowing up to 7 solar cells as inputs, the new PMIC seems to be very versatile.
The IC can support input voltages from 100 mV-4.5V, load voltages ranging from 1.2 V to 3.3 V, and load currents up to 60 mA. This device could be well suited for the transitory nature of energy harvesting and IoT devices.
On top of this, the AEM10330 claims to offer improved supercapacitor charging and balancing circuitry, which it states is 3x faster than the competition, to enable better transitory responses to the current needs of RF transmissions.
AEM30330 block diagram. Image used courtesy of e-peas
On the other hand, the company's other offering, the AEM30330, is explicitly focused on RF and vibration energy harvesting.
This PMIC offers similar specs to its counterpart, accepting input voltages from 100 mV-4.5V and output voltages from 1.2V-3.3V maxing at 60 mA in high power mode. This PMIC also shares improved supercapacitor charging and cold starts from 275 mV input voltage and input power of 3 μW.
A Complete Solution?
From the looks of its new PMICs, e-peas appears to know its target audience and the design challenges it faces. With integrated buck-boost circuitry, improved supercapacitor charging capabilities, and support of a wide range of output voltages, the new PMICs from e-peas seem like a versatile and valuable solution to energy-harvesting IoT applications.
Interested in learning more about IoT and energy harvesting? Find out more in the articles down below.