Smps FeedBack type selection

[tictac]

feedback type

Hi
I konw there is some type of isolation feedback for smps .
1- with TL431 and one optocoupler
2- with auxiliary winding
3- current feedback

I design one smps with this output 2500 v-DC and 20 mA
can you suggest me to best type of feedback with some descriptions, please??

by regards,

 

[tictac]

smps feedback

is there anybody to help me out?

 

[FvM]

schematic smps high side tl494

There's on obvious point, only voltage sense at the secondary (optocoupler variant) can achieve accurate voltage regulation.

 

[tictac]

tl431 optocoupler

Thanks for reply
I think because of large resistor devider it was slow for feedback or may be because of snubber circuit. can you describe your idea in details and with schematic ,please?

 

[Dmitron]

is optocoupler used in smps

1) you need isolated power source for tL431.
2) buffer the devider signal with op amp
3) put capacitance in parallel with resistor in deviders - and you'll get quick response.
If you have difficultyes with you smps, you can contact me there:

 

[dick_freebird]

types of smps

There are architectures which put the controller on the
output side, and feed back only the gate drive signal
to the primary. This eliminates all concerns with the
speed & quality of feedback besause you only throw
the dirtiest signal across the isolation barrier. But you
do need a "kicker" of some sort to get startup. Gate
drive by pulse transformer from the secondary side is
what I'm talking about, with some sort of primary side
startup circuit that will be stepped on once the secondary
gets out of undervoltage.

 

[tictac]

smps feedback circuits

There are architectures which put the controller on the
output side, and feed back only the gate drive signal
to the primary.

do you mean to use tl431 and 4n136 for example at output side ?
can you describe your idea a little,please?

 

[Dmitron]

isolation type in smps

he means to put UC3843/tl494 or enother on the second side.

 

[FvM]

smps high voltage low current design

I think because of large resistor devider it was slow for feedback or may be because of snubber circuit.

You did neither report any results nor described your existing design. So I don't know, where the "slow feedback" comment refers to.

Generally, an auxilary supply for the optocoupler can save you some output power. In case of a DC/DC converter with cascade rectifier, this would be easy without an auxilary winding.

I suggest to start with a basic design (that's the TL431/optocoupler topology used in perhaps 100 millions of small of-mains SMPS) and consider advanced techniques (e.g. secondary controller) if you experience principal limitations.

 

[eem2am]

type of smps

well you must be doing radar with that high voltage and low current.

you do supply for TWTA ?

-but anyway, maybe where you work they very secretive and not show you how to do.

but yes, you will get problems with the immense divider ratio, as that divider ratio goes in the transfer function.

do yuo know how to make transfer function for your smps?.....if not then take no fear, as 99.9% of engineers also aint got no clue.

but you can use gain phase analyzer to investigate that loop of yours then you see gain and phase margin.

you could use the beautiful UC3909 high frequency pulse transformer driver to give you a nice piece of isolated feedback.

and i recommend that to you too.

but hey?.....howcome you need isolation???

after all, your highest voltage is on the output........

and also, for military equipment, do they really care about domestic standards?

Anyway, happy wave tubing..........