The topic of my Final Project was to model, simulate, design and test a bidirectional DC/DC converter. The goal was to design a power converter circuit which is capable of producing 5V and 20V from a 3-cell LiPo accumulator supply, moreover this accumulator can be charged-up by plugging an outer 20V supply to the output. Another aim was to go through a step-by-step design process which will be utilizable and can be a basis of any future power converter design. A converter consisting of all the three operation modes may spread widely, thanks to the newest USB Type-C receptacle and the Power Delivery Specification that allows both the 20V voltage level with higher current rating (3-5A) and the bidirectional power flow as well. Due to a detailed technical literature study that was made about the new USB specification and about the different converter topologies, a proper configuration was selected. This was followed by the analysis of the converter, where both the large and the small signal models were derived and examined. All the three operations were simulated open-loop in LTSpice. For an optimal operation, feedback loops with additional regulators are needed, thus three possible controller approaches were investigated and designed for the buck and the boost modes. Simulations were made in the MATLAB Simulink Environment. After that, the schematic and PCB design was managed by Altium Designer. Before finalizing the panel an extra beta-version board was created to test the electrical components. After this the final converter board was manufactured, soldered and all the three operations were tested in open-loop configuration.