In comparison with linear power supplies switching power supplies (switching converters) provide higher efficiency, smaller dimensions, and less-expensive implementation. Mentioned advantages are just some of the reasons that made their use predominant in almost all applications.

Operation of a switching converter is based on the use of semiconductor devices operating as switches. These switches usually change configuration of a circuit and through an inductor-capacitor network change the properties of the input variables.

Due to the different modes of work, which change fast, modeling and control of switching converters is complex and requires special attention. Traditionally, the control of switching power supplies has been implemented using analog controllers.

Although the analog controlled systems have proven successful there are several reasons that make digital control attractive. The digital controllers are less sensitive to external influences, they are more flexible and allow implementation of more sophisticated control laws. These advantages of digital control have been recognized and fast development of microprocessors has been followed by the wider use of digital systems in medium to high power applications.

Unlike in the medium to high power applications, the use of digital controllers in low to medium power applications (a fraction of watt to several hundreds of watts) is rare. At lower power levels the analog control is still dominant.

This thesis investigates problems of digital controller implementation at lower power levels, gives detailed guidelines for digital controller design and hardware selection, and proposes new hardware solutions for the main functional digital controller blocks.

The new functional blocks are implemented on a specially designed digital controller IC set for DC-to-DC converters. It was shown that efficient digital control at lower power levels is also possible.

This thesis also investigates problems of sporadic use of the digital controllers and slow voltage loop in single phase, rectifiers with power factor correction (PFC-s). It shows a way to design completely digitally controlled, high-switching frequencу PFC with relatively simple hardware and proposes two new digital methods for the voltage loop dynamics improvement. Additionally, a new method for modeling, control, and stability analysis of the wide-bandwidth PFC's voltage loop is presented.