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UCC28180: The difference of power loss between CCM and CrCM PFC system..

Ernest Cho
Expert 3191 points
Part Number: UCC28180
Other Parts Discussed in Thread: UCC28065, UCC28056

Tool/software:

Hello team,

I assume CCM PFC has better in power loss(power dissipation) than CrCM PFC when overall conditions are the same(or similar) like : MOSFET Rds(on), Diode Vf, similar switching frequency (or on-time), Output power is around 300W.

My assumption is because CrCM shows much larger peak inductor currents than CCM so conduction loss(SW on time = I^2*Rds(on)) and diode Vf loss(SW off time = I*Vf) would be larger. (Switching loss would be similar.)

But I don't know numerical rate between CrCM and CCM. 

Do you have some experimental or calculational results for power loss of these two PFCs?

Best regards, 
Ernest Cho

  • 0
    TI__Genius 12795 points

    The efficiency is more than just conduction loss. CrCM has higher peak current than CCM at the same power stage but it is a soft switching so the switching loss is lower. Especially if you also care about low load efficiency like 100W, CrCM is better than CCM. 

    There are other factors to consider which PFC to select. Please read this selection guide.

    www.ti.com/.../sluaao8.pdf

  • 0 in reply to Ning Tan
    TI__Expert 3191 points

    Hi Ning,

    Thank you for your explanation.

    Customer is checking competitor's CrCM device which integrated HV FET and HV diode(Sanken), they evaluated power loss and found ~10W even at a lower power(~100W), is it reasonable power loss for CrCM? And can CCM device show lower power loss than CrCM?
    If so, I'd like to promote our CCM device for them even UCC28180 is not integrated HV components.

    Bests,
    Ernest

  • 0 in reply to Ernest Cho
    TI__Genius 12795 points

    Can you share their part number? Is the system designed at 100W full power? If 100W is the full power, 10W loss is high.

  • 0 in reply to Ning Tan
    TI__Expert 3191 points

    The part name is SSC2016S. Their system is Refrigerator and it is designed 300W in max. 

  • +1 in reply to Ernest Cho
    TI__Genius 12795 points

    Ernest,

    You can see their block diagram. The HV FET and diode are located outside of the IC. 

    I'd recommend to consider CrCM PFC like UCC28056 or UCC28065 for this power range. It can offer better efficiency.

  • +1 in reply to Ning Tan
    TI__Expert 3191 points

    Thank you Ning, 

    I've worked with them to show UCC28180 EVM and had demo with them.

    UCC28180 EVM showed ~30% lesser loss so they are satisfied. (They just measured their system idle powers so 10W is their system's power.)

    Also double checked to identify SSC2016S do not included FET, Diode, etc. (Prior meeting they mentioned Sanken device included FET,.. ).

    Thank you your answers helps for me.

    Best Regards, 
    Ernest