isolated feedback signal - help needed

[darla1]

isolated feedback

dear all

i need help on isolated feedback signal.

for a dc/dc isolated converter need to take output voltage feedback with isolation..i need this isolated voltage same as output.....can any boy tell....how can we do this

thanks
darla

 

[eem2am]

isolated feedback

yes there is a chip which does what you want....is it uc1909...no its something like that though....its a kind of 2MHz oscillator which feeds back the actual voltage using Amplitude modulation of the oscillation.

uc3900 ?...no

i cant remeber

but its called an isolated feedback something...


voila...

https://focus.ti.com/lit/ds/symlink/uc2901.pdf

please tell us how it goes...sounds like fun!

 

[darla1]

Re: isolated feedback

hi ee2am thanks for reply

i dont want use ic, i want to use any cmponents,....

 

[oscar_pdx]

Re: isolated feedback

use simple LTV817 with resistor limitter for led. (ex: 470k feedback from 300V)
for transistor use 4k7 fixed + trimmer 47k for pull-up to 5V.

 

[darla1]

Re: isolated feedback

hi oscar

thanks for reply and suggestion

can you please give rough schematics of this to get lenear voltge

thanks
darla

 

[oscar_pdx]

Re: isolated feedback

Sample for feedback:

 

[darla1]

Re: isolated feedback

dear Oscar

thank you very much for your post.....

by observing the schematic the output is 4.75 when you give +5.4V and 4.75 becomes 0.15 when u give 100V. I am i right here..

i need the circuit like this

when you give 5v input i need 5v output
when you give 2v input i need 2v output

these things i need with isolation....

thanks
darla

 

[oscar_pdx]

Re: isolated feedback

another sample

 

[oscar_pdx]

Re: isolated feedback

sorry