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WEBENCH Tools/UCC2813-3-Q1: soft start vs slope compensation

Part Number: UCC2813-3-Q1

Tool/software: WEBENCHRegistered Design Tools


I am using UCC2813-3-Q1 for a simple forward converter. I find that the soft-start is not working. The first output pulse appears as COMP pin is around 1V. But the duty cycle is high. This IC comes with internal soft-start. I do not have anything external for soft-start. I also do not have any slope compensations since my application does not require above 45% duty. 

Is there a correlation between the slope compensation and the soft-start circuitry?



  • Hi,

    You may refer to 8.3.14 for adding slope compensation to see any help to your application.

    The internal soft start is fixed so if you want to make better soft start you may need to add external soft start with an external op-amp, if your design cannot accept the existing internal soft start performance.