Transformer-Free, Off-the-Shelf Electrical Interface for Low-Voltage DC Energy Harvesting

Energy harvesting from various ambient energy sources keeps gaining interest to deal with the challenges arising from more and more widespread Internet of Things applications in consumer electronics and industrial applications such as remote sensing. However, available energy is scarce and designers must comply with small size package and thermal dissipation that inevitably lead to compromises. This paper presents a transformer-free and self-powered oscillator that can be directly powered from a very low dc voltage source such as a thermoelectric module and able to deliver dc bias output. Using off-the-shelves parts, such a design is less cumbersome and gives more freedom to designers while tailoring their circuits with respect to their applications. The oscillator consists of a modified Hartley oscillator including a supplementary capacitor that provides a bias voltage in its output. Theoretical analysis is validated through experimental measurements showing that the proposed solution could be deployed in buildings and/or wearable devices as small and cheap complete microgenerators using for example thermoelectric elements or microbial fuel cells.