Fairchild FAN9612 Manuals

FAIRCHILD Design Consideration for Interleaved Boundary Conduction Mode PFC Using FAN9611 FAN9612 handbook

This application note presents practical step-by-step design considerations for an interleaved Boundary-Conduction- Mode (BCM) Power-Factor-Correction (PFC) converter employing Fairchild PFC controllers FAN9611 and FAN9612. It includes designing the inductor and Zero- Current-Detection (ZCD) circuit, selecting the components, and closing the control loop. The design procedure is verified through an experimental 400W prototype converter. The FAN9611/12 interleaved dual BCM PFC controller operates two parallel-connected boost power trains 180º out of phase, extending the maximum practical power level of this control technique from 200-300W to greater than 800W. Unlike the Continuous Conduction Mode (CCM) technique often used at this power level, BCM offers inherent zero-current switching of the boost diodes (no reverse-recovery losses), which permits the use of less expensive diodes without sacrificing efficiency. Furthermore, the input and output filters can be made smaller due to ripple cancellation between the power stages and the effective doubling of the switching frequency. The advanced line feed-forward with peak detection circuit minimizes the output voltage variation during line transients. To guarantee stable operation with less switching loss at light load