This whitepaper explores the basic operation of three different types of non-isolated (shared ground) DC-DC converters: Buck, Boost and Buck-Boost. The input-output relationship will be derived for each converter in continuous conduction mode (CCM) by using volt-second balance. In addition, effects of the parasitic series resistance of the inductor (RL), also known as DCR, on the output of each topology is illustrated mathematically and experimentally.