A Self-Resonant Boost Converter for Photovoltaic Energy Harvesting With a Tracking Efficiency >90% Over an Ultra-Wide Source Range

Abstract

Herein, we present a self-resonant boost converter integrated circuit (IC) for ultra-wide range source tracking of a photovoltaic generator (PVG). The tracking is efficiently achieved using a self-controlled resonant frequency generator (SRFG). The SRFG, which is realized using a harmonic oscillator, defines the switching frequency of the converter by operating under three conditions: underdamping, overdamping, and critical damping. The maximum power point tracking (MPPT) controller, which synchronously operates with the SRFG, tracks the light irradiance of the PVG over a 75 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> operating range of source resistance (20–1500 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> ). The MPPT is achieved by controlling the ON-time of the power switch using a programmable delay controller (PDC). The proposed SRFG and the MPPT controller are realized using 31 and 38 nW, respectively. The zero current switching (ZCS) controller is realized using 20 nW. The total power consumption of the converter is 125 nW. The converter IC is fabricated in a 180-nm CMOS process with a 2- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thick top-metal option. Measured results show that the boost converter achieves tracking efficiencies > 90% over an ultra-wide range of source resistance (20–1500 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> ), corresponding to the illuminance range (3000–5 lux). The measured peak end-to-end efficiency is 86% at 250-mV input and 20- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> source resistance. Using a commercial PVG module, the converter delivers the maximum output power of 120 <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> with a peak conversion efficiency of 89%. The boost converter performs a self-startup at 80-mV input using an on-chip transformer-based startup circuit (OTSC).