An 88% Efficiency 0.1–300- $\mu$ W Energy Harvesting System With 3-D MPPT Using Switch Width Modulation for IoT Smart Nodes.

This paper presents a novel 3-D maximum power point tracking (3-D MPPT) system for energy harvesting systems (EHS) within Internet of Things (IoT) smart nodes. The proposed 3-D MPPT utilizes a switch width modulation (SWM) technique for improving power efficiency (PE) at idle (<1 $\mu \text{A}$) and heavy (>300 $\mu \text{A}$) load modes. The SWM eliminates the gate driver/conduction loss tradeoff in a reconfigurable switched capacitor charge pump (SCCP). The proposed SWM technique modulates the SCCP switch resistance in proportion to the load condition, input voltage, and $V_{\mathrm {gs}}$ applied. A cold startup technique is incorporated in the proposed EHS with an energy-aware algorithm for input harvester select purpose. The fabricated test chip in 65-nm CMOS technology can harvest solar and thermal energy from 0.35 V and provides a regulated output voltage at 1 V with the peak efficiency of 88% at 200 $\mu \text{W}$ and PE >60% at 100 nW. [ABSTRACT FROM AUTHOR]