Enhanced power supply circuitry with long duration and high-efficiency charging for indoor photovoltaic energy harvesting internet of things end device

Abstract

Light is a popular choice as an indoor energy source for Internet of Things (IoT) end devices. However, indoor light sources are intermittent, which can disrupt the operation of IoT end devices, potentially leading to safety concerns or inaccurate data. Therefore, there is a growing need to develop a long-duration power supply for IoT end devices. The energy from ambient light is harnessed to charge a supercapacitor through an energy manager chip. This supercapacitor serves as the power source for IoT nodes when the ambient light is unavailable. Nevertheless, as the voltage of the supercapacitor drops below the operating threshold, the IoT end node will eventually shut down. This paper proposes a circuit that utilizes a Joule Thief circuit, booster converter, and capacitor stack-up circuit to extract the remaining energy from the supercapacitor and boost the voltage, thereby extending the operational lifespan of IoT end nodes. Additionally, capacitor stack-up circuits significantly enhance charging efficiency. PSpice design and simulations confirm circuit feasibility. High-efficiency charging and long-duration IoT nodes suggest replacing traditional batteries with supercapacitors, reducing environmental impact.