An optimal peak current mode control scheme for critical conduction mode (CRM) Buck PFC converter

Buck Power Factor Correction (PFC) converter has attracted a lot of research interests for its high efficiency at low input condition. The low output voltage also facilitates the design of the cascade power stage. However, the conventional CRM buck PFC converter usually suffers low power factor (PF) or poor harmonic performance. And the output voltage is the only parameter to adjust the PF and harmonic performance, which is not flexible for circuit design and optimization. This paper proposes a peak current mode control scheme with optimized current reference for CRM Buck PFC converter. The proposed control scheme can provide an extra control parameter to adjust the PF and harmonics besides the output voltage. And a higher PF and efficiency can be achieved compared with conventional CRM Buck PFC. Furthermore, the inductor size can also be reduced due to lower peak current. Experimental results from a 100W CRM Buck PFC prototype verify the effectiveness of the proposed control scheme. The full load efficiency is higher than 95.4% across the entire input ranges. And the PF is above 0.95 at 115Vac input with 84Vdc output.