UCC28060: CALCULATION OR MATHCAD

Hello Andy,

The benefits for interleaved CRM and CCM PFC in regards to input and output ripple current cancelation and bulk capacitance RMS current reduction, reduced conduction losses and totol magnetic volume are similar. The link below will take you to an application note that discusses these benefits and is worth reading if you want to understand this better.

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slua746&fileType=pdf

CrM critical conduction mode PFC only turns on the boost FET in a zero current condition and turns of the peak current based on PF needs. Turing on into zero current means that there is no boost diode recovery current and a cheaper diode can be used.  The following application note is for a single stage PFC CrM.  This application note is good reference.  Please note that because the peak current are so high in CrM PFC they are generally designed for 300W or less per phase (600W total).

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=sluu138&fileType=pdf

CCM PFC is generally fixed frequency and ultra-fast boost diodes are used or even SiC. These are generally designed for the 600W to kWs range.  The following application note reviews how to design a CCM interleaved PFC boost using the UCC28070.

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slua479&fileType=pdf

Regards,

Mike