This article focuses on a nonisolated dc-dc converter with main and auxiliary converters intended for railway applications. The conventional auxiliary converter is composed of multiple chopper circuits and it can effectively reduce the inductance value and ripple current simultaneously, which is beneficial for power converters utilized in onboard moving train cars. Meanwhile, it suffers from high costs, large losses, and low reliability due to many power devices used in the auxiliary converter. To solve this problem, this article proposes a nonisolated dc-dc converter with a single auxiliary chopper circuit with a focus on control, power/efficiency analysis, and performance. The validity of control and analysis is verified using a downscaled experimental setup under both steady and transient states. Further, comparisons with existing circuits in terms of losses, efficiency, and peak inductor current are carried out to show the superiority of the proposed converter.