An improved control scheme for buck PFC converter for high efficiency adapter application

Buck Power Factor Correction (PFC) converter has attracted a lot of research interesting for its high efficiency at low input, low output voltage and cost reduction due to low voltage rating of bulky electrolytic capacitor, especially for high power density adapter application with stringent thermal constraints and efficiency requirement. However, the conventional CRM buck PFC converter usually suffers low PF and high peak current compared to the boost PFC because of the inherent dead angle of the input current. In order to meet the harmonics requirement and further improve its efficiency, this paper proposes an improved control scheme for CRM buck PFC converter. By optimizing the reference for the peak current, higher Power Factor and higher efficiency can be achieved at the same time. Experimental results from a 100W CRM Buck front-end PFC prototype verified the effectiveness of the proposed control scheme. The efficiency of Buck PFC exceeds 95.8% across the entire line input range (90~265Vac) at full load, and the line current harmonics content can also meet the harmonic requirement.