An Integrated 50 V Boost Controller With Digitally-Assisted MPPT for Submodule PV Applications

Abstract

This work introduces an integrated maximum power point tracking boost controller for photovoltaic submodule applications. The IC offers a wide input voltage range from 7 V to 24 V, whereas the output voltage is actively limited to 50 V. The presented design utilizes discrete, low-ohmic MOSFETs for the output stage and thus supports input power levels up to 144 W. The converter operates with peak-current-mode control at 300 kHz switching frequency in continuous conduction mode. During light load operation, the control transitions to direct input voltage sensing pulse-frequency-modulation (PFM) with input and output voltage dependent peak inductor current. Moreover, the low-side resistive current sense is explained in detail together with an inductor current replication circuit for precise high-side turn-off. The maximum power point tracker (MPPT) is based on an adjustable resistive sense element and a delta modulator and achieves 99.9% tracking efficiency, omitting any need for a high resolution analog-to-digital converter (ADC). In addition, the series connection of multiple DC/DC converters is examined. The peak system efficiency measures 98.4%. The application-specific integrated circuit (ASIC) is manufactured in an 0.18 µm HV-BCD process and occupies 6.25 mm2 of silicon area.

Keywords

• Boost controller
• Boost converter
• DC/DC converter
• light load efficiency
• mode switching
• MPPT