This PWM controller integrates power factor correction (PFC) and quasi−resonant flyback controllers necessary to implement a compact and highly efficient Ac-Dc LED driver for high performance, low ripple LED lighting applications. The PFC stage utilizes a proprietary multiplier architecture to achieve low harmonic distortion and near−unity power factor while operating in a Critical Conduction Mode (CrM). The quasi−resonant current−mode flyback stage features a proprietary valley−lockout circuitry, ensuring stable valley switching and works down to the 4th valley before 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 which is critical in SMART Lighting applications,