A Generic Power Management Circuit for Energy Harvesters With Shared Components Between the MPPT and Regulator

Abstract

This paper presents a novel power management circuit (PMC) for harvesting the energy from the ambient. The proposed PMC comprises an energy harvester, a startup, a dc–dc boost converter, and a dc–dc buck converter. The PMC is capable of working with various low-power energy harvesters and can track the maximum power point after every 4.5 s. To achieve the maximum power point tracking (MPPT), an open-circuit-voltage-based method is used to transfer the maximum power from the energy harvester to the power optimized boost converter. The proposed MPPT scheme works for a wide range of equivalent source resistance of the energy harvester in the range of $20~\Omega $ –1 $\text{M}\Omega $ . An auxiliary energy harvester is used for the startup to avoid any external supply. Regulated voltage across a load is provided by the buck converter which features sharing the switches and inductor with the boost converter. The complete circuit is designed, optimized, and simulated in 180-nm mixed-mode CMOS technology using three different types of energy harvesters, which are precisely characterized and modeled. Post-layout simulated results are presented for the input power ranging from 150 nW to $500~\mu \text{W}$ for different values of source resistances ranging from $20~\Omega $ to 1 $\text{M}\Omega $ . For a source resistance of 100 $\text{k}\Omega $ , the efficiency of the boost converter is 39.91% and 89.91% at available power of 156 nW and 2.5 $\mu \text{W}$ , respectively. The buck converter is able to regulate the load voltage to 1 V across the load resistance ranging from $100~\Omega $ to 2 $\text{k}\Omega $ .