I've been researching how to design power factor correction into an agricultural LED lighting system. My client requires at least a 0.95 power factor. I'm planning to use PWM controlled buck converters (e.g. TI LM3404 or similar) to supply constant current to the LEDs.

In my research one simple thing I've turned up is a Valley Fill circuit.

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My questions are:

  1. I could use some help understanding the design process behind component selection for the six components C1, C2, R1, D1, D2, and D3.

  2. The Wikipedia page seems to indicate that it's a mediocre power factor correction circuit (total harmonic distortion of ~35%), what should I be looking into given a requirement of at least 0.95 power factor?

  3. This is in reference to an LED lighting project I'm working on. Should I have a PFC circuit in place per LED driver? Where do these types of circuits belong in the topology of a lighting system.

  • 6
    \$\begingroup\$ Why don't you use a free sim like LTSpice and check it out yourself? \$\endgroup\$
    – Andy aka
    Commented Jun 14, 2017 at 17:49
  • \$\begingroup\$ As long as you can accept a very high AC ripple on Vout, 0.95 PF is not a problem. What power level are we talking about? At high power, the R1 losses do become a problem. \$\endgroup\$
    – winny
    Commented Nov 2, 2017 at 11:27

1 Answer 1


All of the major chip suppliers have PWM/PFC combo devices in their lineups. You can easily find these by doing a web search for the combined initialisms. Most will have much better PFC than the circuit you referenced.


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