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UCC25600: with or without PFC

Kaji@PAN
Mastermind 7015 points
Part Number: UCC25600
Other Parts Discussed in Thread: PMP

HI,

I asked about the startup circuit with the following thread.
e2e.ti.com/.../590291
The starting circuit refers to PMP 5141, but PFC is unnecessary.
I think about deleting as shown in the attached diagram, but are there any problems?

I am considering the following AC / DC circuit in another project.
I would like to refer to PMP 5141 for this matter as well. However, since the area of the board is narrow, I do not want to use the PFC circuit.
Is it OK to not use PFC with the following specifications? What is the problem when not using PFC?

Specification (AC / DC converter)
Input / output condition ① (initial setup)
Input: AC 80V ~ 120V
Output: DC 24V 6A

Input / output condition ② (Voltage rises to ② after a certain period from startup)
Input: AC 180V ~ 240V
Output: DC 24 V 12.5 A

Best regards,

UCC25600startupcircuit.pdf

  • 0
    TI__Expert 3200 points
    Hi Kaji,

    An AE will be responding to your question soon.
  • 0 in reply to Brian Johnson96
    TI__Mastermind 25570 points

    Hi Kaji

    Yes your modified circuit will work but there are a number of things to recognise -

    The load power is about 144W

    The power factor will be poor and will probably not meet IEC61000-3-2 harmonic current limits.

    The output voltage will be a function of the line voltage and of load. At no load it will be equal to the peak of line voltage. As the load increases there will be an increasing ripple voltage on the output.

    The input voltage range is 80V to 240V. Assuming a sinusoidal input the peak voltages are 113V to 340V -

    This is a very wide input voltage range for an LLC stage to handle and it won't work efficently across this range and of course at full load the ripple voltage on the output capacitor will reduce the minimum voltage further.

    You  might be able to use a voltage doubler input with a switch to convert between 80V/120V operation and 180/240V  operation - this would reduce the voltage range at the input to the LLC to something more manageable but at the expense and complication of having a switch that can detect when the line voltage changes.

    The first question to answer is whether you need to meet a PF standard - if you do then you will need a PFC front end

    Regards

    Colin