A tutorial revisiting of the traditional sliding mode control of DC-to-DC power supplies, or power converters, of the 'buck', 'boost' and 'buck-boost' types is presented. The limitations of the traditional indirect sliding mode controller schemes are critically evaluated. These refer to the availability of the converter inductor current variable and a lack of robustness with respect to unmodelled load resistance variations. These limitations are overcome thanks to recent developments addressed as 'Generalized PI controllers' which are based on integral reconstructors of the unmeasured observable state variables and utilize only available input and output signals.