New PMICs take advantage of peak power point tracking for energy recovery
In the emerging field of IoT, designing for maximum battery life is a top priority for engineers. One popular way to accomplish this is to take advantage of the energy harvesting on the device through solar or RF power sources. While improvements in the efficiency of harvesting devices usually get the most coverage, these systems are just as important to these systems: the power management integrated circuits (PMICs) that are used.
An example of an energy recovery system. Image of Mouser
The past month has seen activity in the energy recovery PMIC market, with new ones from both e-peas and Nowi. This article discusses some attributes of PMICs for energy harvesting applications and discusses developments in the field.
PMICs for energy recovery
Energy harvesting systems place unique demands on the underlying power management circuits, creating a demand for Specialized PMICs explicitly designed for the application.
A unique aspect of energy harvesting is that they generally operate at very low voltage. A photovoltaic (PV) cell, for example, has a standard output of 0.8 V. In contrast, a Li-ion battery tends to have a cell voltage of 4.2 V. As such, an essential measurement for energy recovery.
Another unique attribute is the ability of the PMIC to cleanly and efficiently boost low voltages and how high they can start, called cold start.
A design challenge for energy harvesting PMICs is the highly nonlinear output of sources such as solar cells. Image of Digi-Key
The second complexity of energy recovery is the fact that they are dealing with inconsistent energy sources. While many standard PMICs are designed to operate with constant sources, such as a battery, the output of a recuperator fluctuates widely throughout the day. For this reason, one measure of energy harvesting PMICs is Maximum Power Point Tracking (MPPT).
MPPT is a technique in which the PMIC dynamically adapts based on its current inputs to ensure maximum average output power to the storage device over time. Its efficiency is usually measured by how quickly the MPPT algorithm responds to input changes. A good PMIC could adjust in seconds, with some being able to adjust in a fraction of a second.
E-peas newest PMIC
Now that a certain context has been established for energy harvesting devices, e-peas is a company shaking up the field with its PMICs. Recently, e-peas released three new PMICs, the AEM10900, AEM10300, and AEM30300.
These PMICs have impressive operational characteristics; Notably, all three claim to draw no quiescent current from the battery, ensuring that the precious stored energy is not wasted on the PMIC. Whether they have true “zero” quiescent current or have such a small draft that it is considered negligible remains to be seen, but it is an impressive achievement.
A typical application diagram for the AEM10900. Image of e-peas
The AEM10900, more focused on solar harvesting, operates with a cold start voltage of 250 mV, an incredibly low number. The AEM10300 and AEM30300, both of which appear to focus on RF recovery, offer extremely low-power DC / DC converters with the ability to boost voltages in a range of 100mV to 4.5V.
All three devices have MPPT functionality and can draw input power in single-digit microwatts depending on the configuration.
While e-peas has been quite active with its energy harvesting PMICs, Nowi is another company trying to make waves with its technology.
Nowi partners with a remote solution
The companies say this collaboration is a sustainability effort, where Remote Solution wants to bring energy harvesting to its devices to minimize battery-related discharges. For this, the company has chosen to work with Nowi for its NH2 PMICs.
According to Nowi, the NH2 provides remote solutions with a reduced nomenclature and footprint, requiring only one external capacitor to operate and having a footprint of 12mm2. Additionally, Nowi boasts of the MPPT capabilities of its NH2, which is said to have a 1 second response time to changes in its environment.
Nowi and e-peas both seem to have a clear understanding of their target audience and apps, as their products tick all the right boxes and focus on all the right metrics. As the progression towards sustainable energy and battery-less IoT applications continues to grow, the number of new PMICs and energy harvesting as a whole are sure to increase.
Interested in other IoT news? Find out more in the articles below.
From security to design simplification: IoT design takes another leap forward
Spotlight on energy recovery: Maxim claims the “smallest solar recovery solution”
The Immortal IoT: How Energy Harvesting PMICs and Low Power MCUs Enable ‘Infinite Battery’