Recent advancements in renewable energy has created a need for both high step-up and high efficiency dc-dc converters. These needs have typically been addressed with converters using high frequency transformers to achieve the desired gain. The transformer design, however, is challenging. This paper presents a high step-up current fed converter based on the classical Cockcroft-Walton (CW) multiplier. The capacitor ladder allows for high voltage gains without the need of a transformer. The cascaded structure limits the voltage stresses in the converter stages, even for high gains. The converter (unlike traditional CW multipliers) allows the output voltage to be efficiently controlled. In addition, the converter supports multiple input operation without modifying the topology. This makes the converter especially suitable for PV applications where high gain, high efficiency, small converter size and MPPT are required. Design equations and possible control algorithms are presented in this paper. The converter operation was verified using digital simulation and a 450 W prototype converter.