Multiple-Input Energy Harvesting DC Adder Combiner for Internet of Things (IoT) Wireless Sensor Nodes (WSN) Applications in 65nm CMOS Technology

Wireless technology has its inherent need for battery to power-up a system. One way to overcome this challenge is to extract power from ambient sources. Ambient energy harvesting is a way to utilize the energy from the surroundings as this energy is considered "free-energy." Different ambient sources are available and among the commonly utilized sources are solar energy, thermal energy and RF signals. This paper presents a DC adder combiner with a cross-coupled charge pump structure that provides concurrent addition utilizing the DC outputs from photovoltaic (PV), radio frequency (RF) and thermoelectric generator (TEG) sources. First-level gate controls are added to the conventional cross-coupled structure to provide a higher power conversion efficiency. The circuit is composed of two stages of the modified cross-coupled charge pump structure with bypass transmission gates that will bypass the charge pump structure whenever some sources are weak or are not available. Different availabilities of the three inputs are tested. The proposed DC adder combiner circuit has a maximum power conversion efficiency of 76.10% when three inputs are available. The highest maximum power conversion efficiency obtained is 98.1% when only one source is available. The DC adder combiner covers a chip area of 290 um x 297 um