Using zero-current-switched quasiresonant converters as power factor preregulator

Th use of zero-current-switched quasiresonant power converters (ZCS-QRCs) as power factor preregulators (PFPs) is studied. The study is applicable to boost, buck-boost, flyback, SEPIC, and Cuk topologies. The main conclusion obtained is that the switching frequency variation range using a half-wave resonant switch is lower than that using a full-wave resonant switch if the load connected to the output is almost constant. Moreover, using topologies with power transformers (flyback, SEPIC, or Cuk), this variation range can be minimized by choosing an adequate value of the normalized switching frequency at the peak of the sinusoidal input voltage. However, this range increases greatly when the load changes in the same manner. In this case, a smaller switching frequency variation range is obtained using the full-wave switch. However, this type of resonant switch decreases the efficiency because it handles reactive energy and then a tradeoff between switching frequency variation range and efficiency must be considered