Fully Soft Switched Bidirectional Buck–Boost Converter With Improved Voltage Conversion Ratio and Single Auxiliary Switch

In this article, a fully soft-switched bidirectional buck/boost converter with improved voltage conversion ratio (VCR) and minimum semiconductor devices is proposed. An auxiliary circuit which employs only one active switch along with coupled inductors technique is utilized to increase VCR and provide soft switching condition for all semiconductor devices. Soft switching condition is provided at a wide power range while the leakage inductance energy of coupled inductors is absorbed in both power flow directions. The main switches are turned
on
at zero voltage-zero current switching and turn
off
at zero voltage switching, while the switches body diodes used as the converter diodes turn
off
at zero current switching, which alleviates the diodes reverse recovery problem. Soft switching operation and low component count especially the active switches have contributed to realize a proper converter efficiency. Moreover, the converter has maintained continuous current at low voltage side, common ground between the high and low voltage sides and switches voltage stress similar to the basic bidirectional buck/boost topology. A converter prototype at 300 W and 100 kHz is implemented to confirm the converter theoretical operation and analysis.