Supercapacitors Support Miniature Energy Harvester ICs In Powering ULP Devices

Several individual electronic trends have come together to create low-cost, easy-to implement energy management circuits capable of total power supply control of scavenged and harvested energy supplied to small loads. These circuits can significantly extend the life of a battery powering the load or entirely replace the battery. Among the trends propelling practical, low-cost scavenged energy modules are:

• the development of ultra-low power (ULP) ICs
• the ability to create efficient ultra-low-power dc-dc converters with control logic, allowing intelligent energy measurement and management functions
• the introduction of high-capacitance storage devices in miniature sizes.

This article builds upon a previous work discussing the benefits of ULP IC technology. Here, we will discuss the performance and characteristics of a scavenging/harvesting circuit in powering the equivalent of a ULP IC and document its performance using prismatic cell supercapacitors, radial-can supercapacitors, and extended value tantalum capacitors. The energy management circuit investigated is comprised of an energy management IC (the e-peas AEM10330) and four passive components—three capacitors and one inductor. We begin by describing the capabilities of the energy management IC and the associated application circuit.

We then discuss the electrical characteristics of the three previously mentioned capacitor types, each of which may be used to store the excess energy harvested by the chip and thereby extend operation of the energy harvesting circuit. As we explain, the different capacitor types are suited to different application requirements, and voltage derating is a key consideration for ensuring capacitor reliability. Finally, we present experimental results to illustrate the performance enabled by the supercaps and tantalum capacitors, followed by a summary of key takeaways from this discussion.