Among the properties of the DC-to-DC converter, one is specific and not mentioned so far. That is the ability to increase the output voltage at will. In the “jargon” of conversion, the decrease action is usually referred to “buck” operation while the increase is referred to “boost” operation. The necessity of these capabilities is obvious. Namely, one gets the voltage produced by the filter, by the linear regulator, or from any voltage source (e.g., solar panel) and needs to accommodate its value to a proper application. In DC power processing and distribution, more frequently, one needs to boost the input DC voltage while in low power (e.g., integrated electronic circuit) application, one would more frequently need the buck operation. In any case, the efficiency stays as a paramount requirement. It was found in the earlier research that these properties may be achieved by special processing procedure in which the input DC signal is first “chopped” into a sequence of pulses and then integrated to produce a DC voltage of the required value. In addition, since the switching frequency is much higher than 100 Hz (as it was in the rectifier), the filtering of the resulting waveform to recover the DC component is much easier. This kind of circuits was named switch-mode (switching) DC-to-DC converters. To them is devoted this chapter. Two main categories of switching converters are in use: the non-isolated and the isolated. The former are most frequently in use when the grid is not involved in the conversion (e.g., when the primary energy source is of renewable nature), while the second allows for DC isolation of the energy source and the load. Almost all solutions of the switching DC-to-DC converters have both variants and will be visited in this chapter. What is special to this text is the attention given to the dependence of the output voltage on the load resistance since our primary interest is to supply power to electronics. To complete the study, implementation of modern high-power electronic components will be analyzed from the efficiency of implementation point of view considering power, frequency of switching, or loading capabilities.