6 Switch-mode supply power factor improvement via harmonic elimination methods

The authors present power factor improvement methods, for switched-mode power supplies, by using harmonics elimination. Three methods were valuated: a series connected resonant filter, a parallel connected resonant filter, and an active boost converter. The two passive filters are commercial products, and the boost converter is an in-house design using a power MOSFET as the switching device and a dedicated commercial IC for the control circuit. An off-the-shelf PC power supply along with the two passive filters and a boost converter were used as the test specimen. The experimental results show input power factor, distortion factor, crest factor, total harmonic distortion, and harmonic components. Also identified are the power system impacts of nonlinear current, the relative cost of harmonic elimination, and the motivation that may come from new power quality standards