Some Tutorials and Articles

[wally7856]

http://nptel.iitm.ac.in/courses/Web... Electronics/PDF/L-23(DP)(PE) ((EE)NPTEL).pdf

Middle of page 12.

In case the inductor current becomes discontinuous
the linearity between switch duty ratio and output voltage is lost and the output-voltage controller
circuit, which is often designed using linear control theory, is not able to maintain the desired
quality of output voltage. Hence filter inductor should be chosen to be sufficiently large such that
under expected range of load current variation, the inductor current remains continuous. In many
cases the minimum value of load current may not be specified or may be too low. If the load
connected to the output is very light or if there is no load, the inductor current will not remain
continuous. Hence, as a thumb rule, the filter inductor size may be chosen such that the inductor
current remains continuous for more than 10% of the rated load current. At 10% of the load, the
inductor current may be assumed to be just continuous. This gives a basis for choosing the
inductor value as detailed below:

 

[wally7856]

Tahmid, here is something to think about. Think back on all the SMPS schematics you have seen in the forums were people have said they work ok. Many of those SMPS have no output inductor at all. From my research it seems that with no output inductor to regulate the current, bigger slugs of current have to come from the transformer.

 

[wally7856]

Tahmid, i looked over your calculation for number of turns for an inductor.
“ Let’s say we’ll use an inductance of 450µH. Let’s say that we’ve selected a toroid core with an AL value of 64nH per turn squared.

The required inductance is 316µH which is equal to 316000nH.”

Turns = square root of (316000nH / 64nH per turn) = 70.3 turns.

Now that i see nH over nH in an example it makes perfect sense, The nH cancels out and you have turns left. It did not dawn on me you should just convert uH to nH for the equation.

In the past i needed to calculate turns for mH and i looked a long time to find a formula that had a constant in it so i could use mH for the inductor and nH for AL. After reading your post i converted my .1mH to 100,000nH and divided by my AL of 405nH per turn and got the same 15.71 turns i got with the other equation i found. Once again good work, you are very good at explaining things in simple terms that anyone can understand.

 

[Tahmid]

Thanks Wally.

I would appreciate it if you mention on my blog comment space what you've mentioned here. If you narrate your experience, others will find it beneficial and can learn from that as well.

I'm looking into Imin and I'll talk about that soon.

Any suggestions for further tutorials/articles?

 

[smps_fan]

Hi Tahmid,
I would be interested in RC compensation networks with an error amp, even if it´s just a quick set up by measurement with oscillocope and pictures.
Thank you and kind regards
smps_fan