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Overshoot after current limit!!!

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pswatw

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hi:
I designed a current mode boost converter!
But there is overshoot in vout when current limit release !
It is not easy to slove this problem use traditional soft start!
How to solve this problem!!??
THANKS!!

PSWATW
 

leo_o2

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A good way for it is to design a soft start circuit for reference voltage. If ref voltage starts up very slowly and smoothly, there is no overshoot on output voltage.

Added after 54 seconds:

Torex (a Japanese IC company) has some ICs to suppress overshoot in this way.
 

pswatw

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hi: leo_o2

Thanks for your answer!!
But when the current limit occur, the vref is 1.23v!
the vref will not "starts up"

How to solve this problem!!??
 

pswatw

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HELP!! TELL ME HOW TO SOLVE THIS PROBLEM, PLEASE
 

leo_o2

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If you make the reference voltage starting up very slowly (>1mS), you don't need to do any change for current limit. You can just design a normal current limit (same current limit level for both before start-up and after start-up). For boost, you need to avoid the fast charging for output cap if you can't turn off the PMOS path (for synchronous boost).
 

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