This paper presents a self balanced modular multilevel dc-dc converter (MMDC) based on the conventional buck converter topology, where both switches are replaced by capacitor clamped submodules (SMs). This converter achieves a significant reduction in input voltage through a high-voltage step-down ratio, which is determined by the number of SMs. The phase shifted carrier pulse width modulation (PSC-PWM) technique is used to control the switching state of SMs such that there is a constant number of SMs supporting the input voltage at any time. The converter exhibits an inherent capability to balance the voltages of the SM capacitors without the need for additional complex balancing control techniques. The structure of the two level high step down ratio (5:1) MMDC, along with its operating mode analysis and parameter design, are presented in this paper. The effectiveness of the MMDC is validated through the simulation and experimental results.