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PMP21366: Efficiency of AC230V input condition

Toshihiro Watanabe
Genius 10235 points
Part Number: PMP21366
Other Parts Discussed in Thread: UCC28064A,

Hello,

We are wondering the reason the efficiency in lighter load becomes higher and lower repeatedly.

38.5W, 98%.

76.4W 96%

153W 97.3%

229.7W 96.7%

306.2W 97.2%

Would you let us know why the efficiency goes high and low like this?

Best regards,

Toshihiro Watanabe

  • 0
    TI__Expert 4830 points
    Toshihiro san,

    It is because of phase and light load management functions of UCC28064A. When the load decreases, the PFC operation will move from 2-phase to 1-phase. With 1-phase operation, you will see the efficiency going up. Then we further reduce the load and efficiency will reduce under the same 1-phase operation. When we reduce the load furthermore, PFC will enter burst-mode operation to reduce the power consumption. Under burst mode operation, we can have higher efficiency then 1-phase operation. That is why you observe another efficiency up at very light load.

    Regards,
    Sheng-Yang Yu
  • 0 in reply to Sheng-yang Yu1
    TI__Genius 10235 points

    Hello Sheng-Yang-san,

    Thank you for your answer.Please let me ask about AC115V operation.

    The efficiency is reduced from 40W increasing power until 150W. What mode does UCC28084A working? Is this area single phase mode without burst?

    If it thinks so, above area would be interleave mode.

    If 40W to 150W is burst mode, would you let us know where the mode is changed from burst, single and interleave mode?

    Best regards,

    Toshihiro Watanabe 

  • 0 in reply to Toshihiro Watanabe
    TI__Expert 4830 points
    Toshihiro san,

    I double checked my PMP21366 design. I am actually disable the burst mode function of UCC28064A - there is no upper resistor on BRST pin. So from 40W to 150W at 115VAC, the board should be in 1 phase operation. Sorry for the confusion.

    Regards,
    Sheng-Yang Yu