An 88% efficiency 0.1–300-μW 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 μA) and heavy ( 300 μA) 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 Vgs 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 μW and PE 60% at 100 nW