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Can you feed DC into PFC circuit

Other Parts Discussed in Thread: UCC29950, UCC28180

I would like to feed 300V DC into a power supply with a PFC circuit.  This will be for about an hour during AC power outage.

Normally the input would be AC.  Will the PFC circuit still operated and will it damage or reduce the lifetime or reliability of the components?

  • Hi Michael,

    It depends on the PFC controller used in the design in many cases there will be no issue. Can you specify the TI part number used in the design?

    Regards

    Peter
  • no specific TI part.  this was a question about PFC circuits in general.  not sure exactly how the PFC chips work and why they would depend on (i assume halfwave) AC waveform. 

    am assuming a switching supply w/o PFC would not be affected if it was fed 300V DC instead of AC if its input is a FW bridge followed by a large filter cap.

    thanks

  • Hello Michael

    As Peter said, it depends on the specific controller. Some controllers need to see a zero crossing at the AC input in order to detect a 'loss of input power' condition. If they don't see the zero crossing, they time out and eventually stop on the assumption that the line has failed. The UCC29950 for example does this. Other controllers - the UCC28180 - don't care and will happily run from DC.

    There is no inherent reason for DC operation to damage or reduce product lifetime more than AC operation
    providing of course that the product is designed correctly.

    Regards
    Colin
  • if the circuit wants to see a zero crossing - or a zero level since the controller sees the output of the bridge

    would a positive square wave or better yet DC with a 99% or so duty cycle satisfy it?