A Fibonacci-based Switched-Capacitor DC/DC Converter with Dynamically Adjustable Conversion Ratio for Harvesting Applications

Wireless Sensor Networks offer significant advancement in real-time data collection and analysis in various application scenarios. Sometimes their nodes are placed in difficult-to-reach areas making the replacement of their battery impossible. Therefore, the node is usually equipped with a harvesting system based on PV cells and a lithium-ion battery. A switched-capacitor DC/DC converter is proposed in this paper to optimize the power produced by a single PV cell and maximize the battery charge power. The proposed converter is based on a classic Fibonacci architecture whose control system is improved to make its input/output conversion ratio dynamically adjustable. The simulation results show that the proposed converter allows the usage of more than 90 % of the maximum available PV power to charge the battery of the node. It is important to note that this result is achieved by leveraging the wireless sensor network characteristics to keep the converter as simple as possible.