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This paper proposes a high step-up dc-dc converter based on Cockcroft-Walton (CW) voltage multiplier without step-up transformer. Providing high step-up rate, the proposed converter is quite suitable for applying to low-input level dc generation systems. The proposed converter improves the impractical operation of the conventional boost dc-dc converter at high duty ratio due to non-ideal characteristics of the circuit components, such as the equivalent series resistance of the inductor. For easy design, a commercial average-current-control continuous conduction mode (CCM) integrated circuit (ICE1PCS01) and a complex programmable logic device (CPLD) LC4256V are used to implement the control strategy of the proposed converter. A modified switching function, which is built in CPLD, controls the switches to generate an alternating source to the CW voltage multiplier. Under CCM operation, the output voltage ripple of the proposed converter can be limited by the flexibly adjustable frequency. A 200W laboratory prototype is built for test and the experimental results demonstrate the validity of the proposed converter.