Output active filter .

[vimalkhanna]

Hi Guys ,
My circuit for DC converter is 2400watts delivery at 48VDC
design operation is for -30*C ambients where capacitors malfunction.
The tantallums/multilayers ceramic are unable to withstand ripples .
Suggest Active ripple filters at 1.5MHz flyback switchings to give smooth output with >40dB atten
Analog opamp design is useful with chebychev slope ..

 

[FvM]

It's absurd to implement an active filter for this purpose. You'll find however a lot of capacitors that can work at -30 degree C.

Most foil capacitors as well as X5R/X7R ceramics are specified down to -55 °C.

 

[vimalkhanna]

That is right for the -30*C operation.
However , Zo being very low and fundamental freq . suppression is 1.5MHz ,the foil are inoperative .
The ceramics X5R punctures and loses value after 30mins operation.
The tantallum caps burst .as they cannot withstand large ripple contents

 

[tony_lth]

There are plastic film capacitors that can stand very low temperature, you can search in Panasonic.

 

[FvM]

However , Zo being very low and fundamental freq . suppression is 1.5MHz ,the foil are inoperative .

There are rather different form factors with different inductance values. But of course, one need to know the filter parameters to determine if it's feasible

The ceramics X5R punctures and loses value after 30mins operation.

So you are operating the capacitors beyond their specification? Did you measure or at least calculate the ripple currents?

The tantallum caps burst .as they cannot withstand large ripple contents

Yes, sounds plausible.