An Improved OCV-Based MPPT Method Targeting Higher Average Efficiency in Thermal/Solar Energy Harvesters

This paper presents an improved open-circuit voltage (OCV)-based maximum power point tracking (MPPT) method which is able to achieve MPPT within a shorter sampling time compared to traditional architectures, and thus provides a higher average conversion efficiency from thermal/solar energy harvesters. The proposed OCV-based MPPT method employs separate control signals for the converter and MPPT blocks. A short time delay between disabling the converter and enabling the MPPT blocks eliminates the long charging time required to compensate for the voltage drop in the sampled signal, and thus reduces the sampling time. The prototype chip fabricated in 0.18-μm has a 0.58 mm×0.33 mm total area, delivers a 1.8 V DC voltage at an input voltage of 0.28 V. Measurement results confirm a sampling time of 26ms every 16s with an improved average efficiency of 82.2%.