A 88.6%-Efficient Multi-Input Capacitive-Based Energy Combiner with Adaptive Path Control for WSN-IoT Applications

This work introduces the integration of an adaptive path control within a capacitive-based energy combiner for Wireless Sensor Nodes (WSN) in Internet-of-Things (IoT) applications. This scheme detects available input transducers and optimally routes energy to the combiner, addressing the reduced efficiency usually observed in conventional approaches. This scheme has been shown to remain effective even when one or two of the sources is/are weak or unavailable, resulting in highly consistent combining efficiency regardless of the number and placement of sources and minimizing power loss within the circuit. Simulation results showed an average PCE of 99.4% for single sources, 88.4% for dual sources, and 81.8% for triple sources. This work is implemented using $\mathbf{6 5 n m}$ process technology and occupies a total chip area of $0.077 \mathrm{~mm}^{2}$, integrating components such as comparators, voltage reference, frequency divider, clock generator, digital control unit, and the combiner core. Furthermore, this work achieves a peak output power ($\mathrm{P}_{\text {out }}$) of up to $260.7 \mu \mathrm{~W}$.