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UCC28070A: How to solve output ripple

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Prodigy 90 points
Part Number: UCC28070A

Tool/software:

Hi team,

I want to ask how to solve the output voltage ripple, this is my waveform  .

Orange waveform is my output voltage, red waveform is the current of inductor. 

You can see the ripple is about 7V. And that is too big for me.

And last I want to ask when I raise the output power,but the output voltage would decrease .How can I solve these two problem?

  • 0
    TI__Mastermind 32500 points

    Hello, 

    The only way to reduce the amplitude of the ripple on the output voltage is to increase the value of the output capacitance.  This relationship is inversely proportional (with a given output current), so if you want to cut the ripple in half, you must double the capacitance.  

    For the dropping voltage problem, more information is needed, but it sounds like you are operating at a power limit.  
    Attempts to increase Pout by reducing load resistance causes Vout to drop, because Pout has hit a design limit. 
    To increase this limit, the simplest way is to reduce the resistance on the IMO pin, but all other aspects of the PFC power stage design must be able to accommodate the higher power.  

    Regards,
    Ulrich