The highly integrated FAN6921MR combines Power Factor Correction (PFC) controller and Quasi-Resonant PWM controller. Integration provides cost effect design and allows for fewer external components. For PFC, FAN6921MR 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, FAN6921MR can reduce input current distortion at zero-crossing duration to improve THD performance. For PWM, FAN6921MR provides several functions to enhance the power system performance: valley detection, green-mode operation, high / low line over power compensation. FAN6921MR provides many protection functions as well: secondary-side open-loop and over-current with auto recovery 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 brown-in / out for AC input voltage UVP. The FAN6921MR controller is available in a 16-pin small outline package (SOP).