Current-sensing scheme improves PFC on/off sequences

摘要

PFC (power-factor-correction) preconverters typically use the step- up, or boost, configuration, because this type of converter is relatively easy to implement (Figure 1). However, this topology requires the output voltage to be higher than the input voltage. When this condition is not the case-for example, with on/off sequences or under load conditions-some inrush current flows through the boost inductor and diode to abruptly charge the output capacitor. For instance, before start-up, the output capacitor discharges. When you plug in the PFC stage, the output capacitor attempts to charge resonantly to twice V_(IN).