This paper proposes a novel zero voltage transition (ZVT) auxiliary circuit applied to a bidirectional converter for interface circuit between ultracapacitors or batteries with DC bus in electric vehicle (EV), fuel cell electric vehicle (FCEV) and hybrid electric vehicle (HEV). This auxiliary circuit provides almost soft switching condition for all switching elements while the control circuit remains PWM. So, the energy conversion through the converter is highly efficient. The proposed converter acts as a ZVT Buck to charge ultracapacitor or battery. On the other hand, it acts as a ZVT Boost to discharge ultracapacitor or battery. Buck operation of the proposed bidirectional converter is analyzed and its operating modes are discussed. The simulation has been done using PSPICE software and its results verify aforementioned capabilities of this converter.
