A submodular boost converter ASIC for output energy improvements in photovoltaic applications

Photovoltaic (PV) energy harvesting suffers from output energy reduction due to shading, dirt accumulation or manufacturing variability. Typical PV modules consist of 60 solar cells connected in series. Hence, shading a single cell can cause a whole substring of 20 cells to be bypassed. To overcome these drawbacks, this paper proposes the application of boost converters on submodular level, cutting the series connection to only a few cells. System level simulations prove that this architecture features increased output energy compared to state-of-the-art approaches like power optimizers. For reducing component costs and increasing system reliability, an ASIC for this application has been developed in a 150nm CMOS technology. This paper describes the design and the implementation of a highly efficient hysteretic controlled boost converter. Its high switching frequency of more than 500 kHz enables operation on a single phase while achieving an RMS input current ripple of less than 1.5 % required in photovoltaic applications. Measurements prove a RMS current ripple of less than 1 % and a maximum switching frequnecy of 650 kHz.