This paper presents a DC-DC buck converter through duality approach. In switched mode power supply (SMPS), buck converters are predominant parts. To control output quantity at output end, these converters are attached after rectifiers. There are some applications in which current source is available and there is need of output current control as most of SMPS applications have low current ratings. So to meet this requirement the dual of voltage buck converter i.e. current buck converter is proposed. The converter also finds applications to power up current-based loads such as light-emitting diode. In this paper, the steps required for formation of dual network of buck converter are also discussed. The mathematical analysis of the conversion ratio is also discussed. The simulation of the proposed converter is done using MATLAB. The results provide the verification of the mathematical equations of current buck converter and duality principle.