PWM TO DC LC filter inductor considerations? saturation vs rating

[SArepairman]

So I would like to do a relatively high voltage high current LC filter connected to a IGBT.


Inductors are pretty mysterious to me, it looks like I need 2 inductors in the 0.3mH range to make a 3rd order LC filter. to filter ~10KHz switching frequency PWMed to DC.

I wanted these supplies to put out like up to ~4 amps @ rectified mains voltage (~170v)

When I look at digikey I see current rating and current saturation, should both of these values be chosen to be greater then four amps?


http://www.digikey.com/product-detail/en/AIRD-03-331K/535-11337-ND/2660627

Will this work? Do I need to consider core material in my application? Are there any traps for young players here?

[Harvs]

In a round about manner it sounds like you're building a Buck converter.  Would that be the case?

Tt would be worth also considering mosfets, 170V isn't actually that high, and most commercial PSUs at twice that voltage are still using mosfets. What's the input voltage?

Sizing up parts for a buck converter is pretty straight forward given a set of requirements, and there's plenty of app notes out there (and many many books).

But to answer your questions about inductor ratings.  The current rating is the DC current at which the device will reach max operating temperature given a specific ambient temp (e.g. usually 25c) due to the copper resistance.  The Saturation current is the peak current where the core material moves out of the relatively linear region on the BH curve.  In short, your RMS current can not be higher than the current rating (in fact you need to de-rate that for ambient temp and add margin,) and the peak current should be kept well below the saturation current.

[SArepairman]

In a round about manner it sounds like you're building a Buck converter.  Would that be the case?

Tt would be worth also considering mosfets, 170V isn't actually that high, and most commercial PSUs at twice that voltage are still using mosfets. What's the input voltage?

Sizing up parts for a buck converter is pretty straight forward given a set of requirements, and there's plenty of app notes out there (and many many books).

But to answer your questions about inductor ratings.  The current rating is the DC current at which the device will reach max operating temperature given a specific ambient temp (e.g. usually 25c) due to the copper resistance.  The Saturation current is the peak current where the core material moves out of the relatively linear region on the BH curve.  In short, your RMS current can not be higher than the current rating (in fact you need to de-rate that for ambient temp and add margin,) and the peak current should be kept well below the saturation current.

Yea I guess I am just designing a ghetto buck converter with no real feedback that can do up to rectified mains voltage, the idea is to have it run off mains with no transformer or anything. I am using a IGBT because I have IGBT and driver handy. This fits my design goal perfectly, I have no need for anything more advanced.

[johansen]

you need more like 5 mH, for 20% current ripple.

plug your own numbers in here: http://www.daycounter.com/Calculators/Switching-Converter-Calculator.phtml