ON Semiconductor NCP1937 PFC
& QR Flyback Controller
ON Semiconductor NCP1937 PFC & QR Flyback Controller integrates power factor correction (PFC) and quasi−resonant flyback functionality necessary to implement a compact and highly efficient Switched Mode Power Supply for an adapter application. The PFC stage exhibits near−unity power factor while operating in a Critical Conduction Mode (CrM) with a maximum frequency clamp. The circuit incorporates all the features necessary for building a robust and compact PFC stage while minimizing the number of external components. The quasi−resonant current−mode flyback stage features a proprietary valley−lockout circuitry, ensuring stable valley switching. This system works down to the 4th valley and toggles to a frequency foldback mode with a minimum frequency clamp beyond the 4th valley to eliminate audible noise. Skip mode operation allows excellent efficiency in light load conditions while consuming very low standby power consumption.