A Switched Capacitor Energy Harvester Based on a Single-Cycle Criterion for MPPT to Eliminate Storage Capacitor

A single-cycle criterion maximum power point tracking (MPPT) technique is proposed to eliminate the need for bulky on-chip capacitors in the energy harvesting system for Internet of Everything (IoE). The conventional time-domain MPPT features ultra-low power consumption; however, it also requires a nanofarad-level capacitor for fine time resolution. The proposed maximum power monitoring does not rely on the time-domain, but on logic criterion that can be simply determined by a finite-state machine where the maximum photovoltaic (PV) power occurs at minimum conversion ratio and maximum switching frequency. Single-cycle is used as the criterion to determine the magnitude of the output power. Practical concerns, such as self-startup and self-sustaining capabilities are here addressed by proper design of the reconfigurable switched capacitor power converter. A hysteretic control not only regulates the output, but also avoids the loading condition in IoE applications. This harvester simultaneously addresses the challenges including self-startup, self-sustaining capability, and regulated output without using a storage capacitor. Compared with various PV cells, the power conversion efficiency has a peak value of 72%, which remains above 60% for a wide harvesting voltage and power range. The chip area is as small as 0.552 mm(2).