Digitally-controlled H-bridge DC-DC converter for micropower PV energy harvesting system

This paper presents a micro-power photovoltaic (PV) harvesting system. A H-bridge configuration DC-DC converter is designed to harvest PV energy and deliver energy to applications of Internet of Thing (IOT). The main converter consists of a single inductor with two inputs and two outputs. It regulates a constant 1V output voltage for several applications such as sensors and signal transmitters. The surplus energy is stored in a rechargeable battery. The battery also serves as a secondary input source to provide energy to the output load in heavy-load condition. Due to the limited energy of the system, the power consumption of the power system is optimized by several techniques. A perturb-and-observe maximum power point tracker (MPPT) is implemented to maximize the power extracted from the PV harvester. Pulse-width modulation (PWM) and pulse-frequency modulation (PFM) are used to regulate the output voltage. The controller is designed mainly in digital and free of power-hungry circuits. The proposed converter occupies an area of 1.44mm2. The estimated peak power efficiency is 84% while driving 3-10μA load current.Agency for Science, Technology and Research (A*STAR)The authors would like to acknowledge the funding support from NTU-A*STAR Silicon Technologies Centre of Excellence under the program grant No. 11235100003.The authors would like to acknowledge the valuable support from Broadcom Singapore, Nanyang Technological University and VIRTUS IC Design of Excellence with the Joint Industry Postgraduate (JIP) programme