A Comparative Study on Si-SJ-MOSFETs vs. GaN-HEMTs Used for LLC-Single-Stage Battery Charger

It is a common practice to charge batteries with a pure DC current. For this purpose, a bank of fast-aging electrolytic capacitors is usually used in single-phase battery chargers to suppress the low frequency input power from entering into the battery. Single-stage chargers permit to eliminate this electrolytic capacitor bank by transferring the input power to the battery directly. This paper covers the design of a single-stage charger based on a LLC resonant converter. A comparative design is presented for two transistor types: GaN-HEMTs and Si-SJ-MOSFETs. Theoretical and experimental results show that GaN-HEMTs allow higher switching frequencies and also give a higher total efficiency due to their lower parasitic output capacitance.