Triple-mode photovoltaic power management: Achieving high efficiency against harvesting and load variability

We present a triple-mode energy-harvesting power management unit (PMU) that interfaces a photovoltaic (PV) cell and delivers a regulated supply (VLoad) of 0.45V while storing remaining energy in a 3V rechargeable battery. The objective is to maximize the end-to-end conversion efficiency of the PMU against the variabilities of harvested energy and load power dissipation. Specifically, it uses an intermediate energy-storage capacitor to minimize the involvement (charging or discharging) of a battery in the conversion process over time. The experiments show that the proposed PMU can achieve 2.2× higher end-to-end conversion efficiency than the conventional dual-mode architectures when faced with typical variabilities in harvested energy and load power dissipation.