High Step-Up Boost-Cuk-Forward Converter with Reduced Switch Voltage Stress and Ripple-Free Input Current

A new combined boost-Cuk-forward (CBCF) converter with ripple-free input current and low switch voltage stress is proposed for high step-up applications. Two coupled inductors are applied to achieve low switch voltage stress as well as balanced dc-link voltages, wherein the former is placed in series with the boost diode, and the latter is formed as a forward converter. Because these inductors are coupled with the output Cuk inductor, a ripple-free input current is also attained. The proposed converter is run at discontinuous conduction mode (DCM) by applying a low output-side Cuk inductance to reduce the switching loss by providing a ZCS turn-on of MOSFET and removing the diode reverse recovery current. In addition, the proposed converter does not have a problem with ground leakage current. The practical results verify the performance and effectiveness of the proposed CBCF high step-up converter.