STMicroelectronics – PFC controller keeps distortion to a minimum in high-power applications

STMicroelectronics’ L4984D is a current-mode PFC controller which offers a low-cost solution for boost PFC pre-regulators in applications which require compliance with the IEC 61000-3-2 and JEIDA-MITI standards, and which supply power in a range from a few hundred Watts to more than 1kW.

The L4984D implements ST’s proprietary line-modulated fixed-off-time control scheme which allows fixed-frequency operation in boost PFC converters as long as they are operated in continuous-conduction mode.

The highly linear multiplier includes a special circuit which is able to reduce the crossover distortion of the AC input current. This enables the device to operate over a wide mains-voltage range while maintaining a reasonably low figure for total harmonic distortion, even over a wide range of load values.

The output voltage is controlled by means of a voltage-mode error amplifier and an accurate internal voltage reference. Loop stability is optimised by the voltage feed-forward function, which also markedly improves transient response in the case of mains drops and surges.

The IC is provided with protection against feedback-loop failures or erroneous settings.


  • Energy-efficient power supplies that must comply with Blue Angel, ENERGY STAR® or Energy 2000
  • Servers
  • Web servers

  • Adjustable output over-voltage protection
  • Inductor saturation protection
  • AC brown-out detection
  • Digital leading-edge blanking on current sense
  • Soft-start
  • Disable function for remote turn-on/turn-off

The EVL4984-350W demonstration board implements a 350W PFC pre-conditioner with a wide input-voltage range. It complies with IEC 61000-3-2 and JEITA-MITI standards.

Orderable Part Number: EVL4984-350W