Comparison study of LLC resonant circuit and two quasi dual active bridge circuits

This paper presents a comparison study of three isolated DC/DC circuit topologies, LLC resonant circuit, phase shift bridge circuit and phase shift quasi switched capacitor (QSC) circuit. The device stress of three circuits is compared using total switching device power (SDP) which can be used as an indicator of circuit efficiency, device cooling requirement, device packaging requirement and cost of the power electronics converter. Transformer is the main passive component in the circuit that affects significantly the converter power density. The transformer area products (AP) of three circuits are thus calculated and compared. Device loss oriented circuit design is carried out on the three circuit topologies for 1 kW, 400 V to 48 V telecomm power supply application using commercially available GaN devices. Basing on the circuit design results, the device loss of three circuits is calculated and compared at various switching frequencies and load conditions. In the end, a 1 kW, 0.5 MHz, 400-48 V GaN device based phase shift QSC converter prototype is built and tested to verify the analysis and showcase the circuit performance.