Fairchild Semiconductor – PFC and current-mode PWM controller FL7921R provides integrated solution for driving LEDs

Fairchild’s FL7921R combines a combines a Power Factor Correction (PFC) controller and a quasi-resonant PWM controller to provide a complete power-control solution for driving LEDs.

For PFC control, the FL7921R uses a controlled on-time technique to provide a regulated DC output voltage. Innovative technology in the device reduces input-current distortion at the zero-crossing point to reduce harmonic distortion. The PFC function is always on regardless of the PWM stage’s status, ensuring that a high power factor is maintained even in light-load conditions.

For PWM operation, the FL7921R provides several functions to enhance performance, including valley detection, green-mode operation and high-/low-line over-power  compensation.

The FL7921R is featured in a Fairchild reference design, RD-570, for a 100W smart LED lamp, which operates from a universal input-voltage range of 90V to 305V AC, and has an output of 50V/2A. The design achieves efficiency of 91.56% at an output voltage of 47V when operating from a 50Hz mains input at 230V AC.


Fairchild’s FL7921R: high power factor in full- and low-load conditions


  • Brown-out protection
  • Over-current protection
  • Open-loop protection
  • Over-temperature protection
  • Adjustable over-temperature threshold using external temperature sensor


  • Medium- to high-power LED lighting drivers


Orderable Part Number
: FEBFL7921RMX_L65U100A