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-   -   UC 3846 current mode control IC help (http://www.diyaudio.com/forums/power-supplies/125106-uc-3846-current-mode-control-ic-help.html)

jegandren 19th June 2008 03:57 PM

UC 3846 current mode control IC help
 
hi,

im just studying on using UC 3846 as my SMPS control ic... i have tried conecting an open loop test circuit....but the it looks like there is no output pulse given to drive the switch of the trasistor...is there anyway to test the UC3846 current control IC. newbie here please help!!!

(any replies regarding this would be appreciated)

ifrythings 21st June 2008 06:18 PM

check out this http://focus.ti.com/docs/prod/folders/print/uc3846.html

go close to the bottom and there is a section called application notes, go through those and see if that helps you.

jtkraj 24th June 2008 01:57 PM

These devices are Current controlled. you have to provide a Current sense resistor and fead back circuit.

Each cycle have to be controlled through these signals.

check you have configured the comp signal properly.

switchmodepower 1st July 2008 04:41 PM

Make sure that the comp pin is high, shutdown is low, make sure CL pin is set. You can also add a slope comp circuit to get some sort of ramp on the curr feedback pin- (this also helps with noise immunity)

App note..
http://www.ti.com/litv/pdf/slua075


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