The highly integrated FAN6921ML combines a Power Factor Correction (PFC) controller and a Quasi-Resonant PWM controller. Integration provides cost-effect design and allows for fewer external components. For PFC, FAN6921ML uses a controlled on-time technique to provide a regulated DC output voltage and to perform natural power factor correction. With an innovative THD optimizer, FAN6921ML can reduce input current distortion at zero-crossing duration to improve THD performance. For PWM, FAN6921ML enhances the power system performance through valley detection, green-mode operation, and high / low line over power compensation. FAN6921ML provides: secondary-side open-loop and over-current protection, external latch triggering, adjustable over-temperature protection by RT pin and external NTC resistor, internal over-temperature shutdown, VDD pin OVP, and DET pin over-voltage for output OVP, and brownin/out for AC input voltage under-voltage protection (UVP). The FAN6921ML controller is available in a 16-pin small outline package (SOP).