In this article, different autotransformer structures are discussed, demonstrating their connection and voltage gain characteristics. In this sense, an autotransformer structure was chosen that presents a high voltage gain with a low transformation ratio (N), thus seeking to reduce the leakage inductance and volume. From there, this structure is integrated into the isolated boost converter, thus generating a new high step-up DC-DC topology. The proposed converter presents as main characteristics: high voltage gain, low voltage stress on the components, continuous input current, low number of components, simplicity of operation and control, and high efficiency. To validate the theoretical evaluations, a 200 W, 30 V/400 V prototype was built in the laboratory, achieving a maximum efficiency of 96.25%.