An AC-DC or wide-range DC-DC converter using single-active-stage, isolated modules in an input-series and output-parallel stack is presented. Individual modules are operated with a fixed input/output transfer ratio, which is known to provide better efficiency. A varying portion of the modules are either inserted or bypassed to provide an overall transfer ratio adjustment based on the input voltage variation. The novelty of the method is in the self-bypassing of modules without the need for external switches. This is done with a loss-free discharge of their input dc links followed by placing their switches in a cross-conduction mode. Simulation and experimental results are presented. The approach can be particularly useful for medium voltage AC- DC or DC-DC conversion in applications such as EV fast chargers.
