A Generic Power Management Circuit for Energy Harvesters With Shared Components Between the MPPT and Regulator (2019)

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~\Omega $ </tex-math></inline-formula> –1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> . 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$500~\mu \text{W}$ </tex-math></inline-formula> for different values of source resistances ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~\Omega $ </tex-math></inline-formula> to 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> . For a source resistance of 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> , the efficiency of the boost converter is 39.91% and 89.91% at available power of 156 nW and 2.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> , respectively. The buck converter is able to regulate the load voltage to 1 V across the load resistance ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\Omega $ </tex-math></inline-formula> to 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> .