MHz GaN-based interleaved CRM bi-directional buck/boost converter with coupled inductor

This paper presents a high frequency high efficiency GaN device based interleaved critical current mode (CRM) bi-directional buck/boost converter with a coupled inductor. The switching frequency is continually driven to MHz range with GaN devices due to their small switching loss and driving loss, which greatly reduce the size of the passive components. The coupled inductor further reduces the core volume due to certain DC flux reductions. The equivalent inductance and the impact of the coupled inductor on the CRM buck-boost converter are analyzed in detail. The resonant period at CRM is less with a coupled inductor than with a non-coupled inductor, which is beneficial for high frequency operation. The soft-switching range and the circulating energy are both improved using a coupled inductor at CRM. Experimental results validate the theoretical analysis, and the coupled inductor prototype efficiency is 98.5% at 1MHz, which is 0.3% higher than a prototype with a non-coupled inductor.