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Original question:

UC3843: How to sense the current ramp of UC3843

UC3843: High inrush current

Danilo A.
Mastermind 28580 points
Part Number: UC3843

Hi Team,

Our customer has follow up inquiry related to the other thread below. 

e2e.ti.com/.../uc3843-how-to-sense-the-current-ramp-of-uc3843

Another question I have based on my simulation is that I have a high inrush current at start up yet I have soft start implemented. What I am doing at startup is using a linear regulator which I implemented using a Darlington pair to provide vcc to the ic for a short time then tapping the output of the 13.5v buck converter to provide vcc. My reason for doing this is to limit the power dissipation by the linear regulator since it will only be on for a very short time. I am not sure if this is what is causing the soft start not to work. Let me send you a snap shot of the circuit I am simulating.

Regards,

Danilo

  • 0
    TI__Guru 73175 points

    Hi,

    Your snapshot of the circuit resolution is not enough for read. So I am not able to review your circuit.

    I think you can trace down where the high startup/inrush current comes from. For example, you can arbitrarily pull-down your soft start capacitor during power on, so UC3843 won't start until you manually release the pull-down. With this, if you still see the high startup current, then you would know the current not from the UC3843. Then you can trace down the other circuit to see where the high current is from.