Evaluation of silicon MOSFETs and GaN HEMTs in soft-switched and hard-switched DC-DC boost converters for domestic PV applications

Abstract

Hard-switched high-gain DC-DC converters such as the boost converter play an important role in renewable energy systems. Research to increase their efficiency is important and can be achieved using soft-switching techniques; however, that approach requires an auxiliary circuit. The auxiliary circuit decreases power density and reliability while increasing the cost. Moreover, soft-switching topologies usually cannot improve the efficiency for all power and voltage ranges. Wide bandgap (WBG) devices, such as gallium nitride (GaN), result in lower switching losses than silicon (Si), can be used while retaining the simple structure of a hard-switched topology. However, the high cost of these devices is problematic for their frequently cost-sensitive applications. To quantify the cost and efficiency, this study compares soft-switching techniques and WBG-based switches in DC-DC boost converters for a photovoltaic (PV) energy application. The performance of four prototypes including the soft-switched and hard-switched DC-DC converters with both state-of-the-art Si and GaN switches are evaluated in terms of cost, power density, efficiency, and reliability using theoretical analysis, simulation and experimental results. It is shown that the GaN-based hard-switched converter provides higher efficiency and power density; it is more expensive than its Si-based counterpart, yet is cheaper than soft-switched converters.