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May I use DC source instead AC source to test a PFC?

Sam Guo
Intellectual 380 points
Other Parts Discussed in Thread: UCC28070

I would like to use DC source to replace AC source to test PFC converter using UCC28070.  In this case, I can fixed Vin to a DC level such as 100V.  The output should be a regulated 400V no matter Vin is 100V or 200V because PFC is a boost converter.

 I am not sure Vout is still regulated when the input is a fixed DC, considering a multiplier is involved in the loop.

             My question is:

 May I use DC source instead AC source to test a PFC?

 Thank you in advance for your answer.

 

Sam Guo

  • 0
    TI__Genius 9790 points

    Hi, Sam

    DC source input for PFC based on UCC28070 is not recommended, because a multiplier is involve in the loop as you mentioned. It will cause output power limited issue in low RMS input voltage.

  • 0 in reply to Yunsheng Qu
    Intellectual 380 points

    Thank you very much for your message. I want to use a DC source to test PFC stage temporarily.  During PFC stage debug, it is better to frozen the input voltage to see the circuit behavior at different Vins, such as 50V, 100V, 200V, etc.  If AC source is used, Vin changes all the time, it is hard to see. The circuit property such as I-L slope, rising time, falling time, ringing etc at different instantaneous Vin(t).

     

    If the multiplier does not screw up the control loop when Vin(t) ≡ such as 100VDC, it is safe to do this test.  If the multiplier makes the voltage control loop go wild (means duty cycle swings form low to high wildly) when Vin is a DC.

     

    PFC is a boost converter, for Vin(t) ≡ 200VDC, if Vout is regulated to 400V, Duty cycle should be fixed 50%.  At a fixed D, it is easy to change Rg to adjust ringing time, falling time etc.  If I want see D = 75%, I just need to twist Vin = 100VDC.  All test will be in less than half output power.  

     

    Since the multiplier is inserted in the voltage loop.  I am not sure it is safe to do the Vin = DC test.

     

    In the normal running, Vin will be AC

     

    Sam

  • 0 in reply to Sam Guo
    TI__Genius 9790 points

    hi, Sam

    I think it would be safe to operate under Vin=DC though there is power limit issue.

  • 0 in reply to Yunsheng Qu
    Intellectual 380 points

    Thank you very much.

    Sam Guo