This thesis is a part of collaborated project between Ericsson AB and Blekinge Institute of Technology to develop signal processing methods to be used in digital power in order to increase the functionality, performance and reliability of dc-dc converters. The task of this project work is to model a buck converter and a measurement system to sense the inductor current and output voltages of the buck converter system of Ericsson’s BMR450. Such that the measurements of inductor current and output voltage can be sampled with 5MS/s and properly calibrated for BMR450 and get connected to the PCI-6111. Different current sensing techniques are analyzed and the chosen technique is modeled and simulated. The BMR450 system with measurement circuit model is implemented in MATLAB Simulink and SimPowersystems. Three different models of the buck converter are derived, simulated and compared.