Design of Switched-Inductor Charging Regulator for Resistive On-Chip Thermoelectric Generators

On-chip thermoelectric generators (TEGs), unlike bulky off-chip TEGs, are easy to integrate and tiny. A CMOS switched-inductor charging regulator (SLCR) both harvests TEG power & draws battery power to supply Internet-of-Things (IoT) wireless microsensors. However, on-chip TEGs output millivolts, carry
$\text{M}\boldsymbol{\Omega }$
source resistance R
_S
, and produce nW power, which demand SLCR to boost low voltage, manage leakage, & maintain high efficiency. Design of such CMOS SLCR power stage often needs prolonged exhaustive tweaking & trial-and-error process. To tackle these challenges, this brief proposes a fundamental theory on the design of nW CMOS SLCR for low-voltage high-R
_S
applications. With closed-form equations, this theory predicts the optimal power switch, optimal inductor, and optimal current profile, such that SLCR can harvest from the lowest voltage with highest efficiency. This brief provides experimental results with a 180-nm CMOS SLCR power stage prototype. With the theory, an optimal CMOS SLCR power stage can be designed with closed-form equations, without extensive trial-and-error efforts.