An Incremental Step Sensing MPPT Based SI-SIDO Energy Harvester With >99% Peak MPPT Efficiency for an Input Power Range of 30 μW to 33 mW

An energy harvesting (EH) system with incremental step sensing (ISS) maximum power point tracking (MPPT) algorithm is presented in this work. The ISS-MPPT algorithm is generic for any discontinuous conduction mode (DCM) based converter independent of the type, topology, and control of the converter and converter parameters. The problem in implementing a successive approximation register (SAR) inspired algorithm for MPP hill climbing is rectified by our proposed adaptive step-size-based approach for fast-tracking. A resistor or current-sensor less, time-based, input current sensing technique is proposed to generate a voltage inversely proportional to the input current. The chip-prototype is fabricated in a standard 180 nm CMOS technology occupying 1.17 mm2 of silicon area. The fabricated chip is a single inductor-single input dual output boost converter (SI-SIDO) which caters to an input power range of 30
$\mu \text{W}$
to 33 mW and an input voltage range of 150 mV to 1.8 V. The proposed system is compatible with photo-voltaic (PV) and dc output (like thermal transducers, bio-fuel cells)-type sources achieving up to 99.5% MPPT efficiency. The chip achieves an MPPT efficiency of not less than 95% in the case of a dc input source with 300 mV to 0.8 V open circuit voltage (
$V_{\mathrm{ OC}}$
) and 25–
$500 \Omega $
of input resistance (
$R_{\mathrm{ IN}}$
) in measurements. A peak converter efficiency of 88% is achieved with a quiescent power consumption of 1.8
$\mu \text{W}$
with the MPP module consuming 440 nA of current.