GaN based high gain non-isolated DC-DC stage of microinverter with extended-duty-ratio boost

Microinverter is attracting more attention due to its compact size, plug and play concept, easy installation, and higher power yield under partial shading condition. This paper explores a converter for the DC-DC stage of a non-isolated microinverter. The topology termed as extended-duty-ratio (EDR) boost, is a hybrid of the interleaved boost and switched capacitor concept which has the advantage of providing high gain but simultaneously maintaining reduced voltage and current stress on most of the switches. The inductor current is interleaved, reducing the equivalent ripple on the converter input current and the inductor power loss. The converter operation is identified to be divided into different zones depending on the duty ratio of the phases. The operating principles along with the details of the component design and loss analysis as a function of converter phases has been studied. A 250 W GaN based 3-level EDR prototype with input from 20 V-40 V and 225 V output and operating at switching frequency of 200 kHz has been developed to validate converter's operation in hardware.