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UCC28063: DC and Square waveform input

Mason Noh
Expert 2490 points
Part Number: UCC28063

Hi TI,

My customer has a question about input source.

If PFC input source is square waveform not sinusoidal, There is no issue? How about only DC input?

They already tested under this condition, and it is working well.

But they want to be sure there are no other problems at the IC level.

Input source

1. 90Vac~264Vac, Square waveform

2. DC100V

3. DC300V

  • 0
    TI__Mastermind 26840 points

    Hello Mason,

    Thank you for your application of the UCC28063 with a DC/square-wave input. 

    The UCC28063 uses constant-on-time control with on-time set by the COMP level. With DC or square-wave input, there should be very little ripple in the COMP voltage so on-time over a "cycle" should be quite stable.  There should be no issues with the controller with these inputs.

    For the PFC system, extended operation at high DC voltage might incur higher switching losses than expected from the normal sinusoidal AC input for the same output power. This is because the switching frequency will always be high, instead of varying with the instantaneous line voltage.  Even though the peak currents may be quite low, capacitive discharge losses will be significant. 

    A similar concern of higher conduction loss exists during sustained operation at low DC input.  Switching frequency and capacitive losses are low of course, but peak currents are always high.  A review of the power stage thermal performance at highest and lowest lines is a good idea.

    Regards,
    Ulrich