Some Tutorials and Articles

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Tahmid

New member
I have found the different projects on this forum quite interesting. I have designed quite a lot of SMPS circuits, yet none based on the IR2153. The forum projects and discussions on SMPS circuits based on IR2153 were very interesting. While most discussions are related to projects and circuits, I would like to share with the forum members a few tutorials and articles I have written on some topics pertaining to SMPS.

Using the SG3525 PWM Controller - Explanation and Example: Circuit Diagram / Schematic of Push-Pull Converter:
http://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html

Ferrite Transformer Turns Calculation for High-Frequency/SMPS Inverter:
http://tahmidmc.blogspot.com/2012/12/ferrite-transformer-turns-calculation.html

Low-Side MOSFET Drive Circuits and Techniques - 7 Practical Circuits:
http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html

Research on transformerless AC-AC (sine wave) conversion- Part 1: AC-AC Buck:
http://tahmidmc.blogspot.com/2012/11/research-on-transformerless-ac-ac.html

I hope that members find these tutorials helpful!
 
T

Tahmid

New member
You're welcome! I hope you found them useful and helpful. I will soon write another article on high-side MOSFET drive and isolated MOSFET drive. I have a plan of writing one on the UC384X as well. I would love suggestions on topics and what you think would benefit or help you and/or other members.
 
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wally7856

New member
The first thing that comes to mind is a URL with an index of your blogs. Now you have to go through all the blog posts to see what is available.

I would like to know more about calculating output inductors. From my initial study it appears that different topologies require different calculations for the inductor. If this is true i would like to know how to calculate the output inductors for the popular topologies.
 
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Tahmid

New member
wally7856 said:
The first thing that comes to mind is a URL with an index of your blogs. Now you have to go through all the blog posts to see what is available.
Click to expand...

Added. Thanks for the suggestion. You can now see it here: http://tahmidmc.blogspot.com/p/blog-page.html
To go there from within any other page, there's a link at the top that says "Index - View All Posts".

I would like to know more about calculating output inductors. From my initial study it appears that different topologies require different calculations for the inductor. If this is true i would like to know how to calculate the output inductors for the popular topologies.
Click to expand...
That would make an interesting article. I shall do that soon.
 
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wally7856

New member
The new index page is very helpful, thank you.

I have looked at your blog on calculating transformer turns. I like the way you used the maximum duty cycle to give a more accurate turns calculation.

I tried to follow your example on calculating turns for an auxiliary winding, but had trouble with the 111 number.

Naux = Nsec / NA = 111 / 19 = 5.84

Was 111 supposed to be the 96.3 turns you calculated earlier in the blog?
 
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Tahmid

New member
Yes. That was a mistake. Fixed. I used a different voltage setting now. But I fixed it.

111 was a figure from a previous design and while updating/correcting to 96, 111 got left back there. Thanks for pointing it out!
 
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wally7856

New member
“Did you go through the article? Did you try out for any other specifications? “

Yes i did go through it and there were some minor errors but i was not going to say anything. But as long as you asked.

You started out with “Vd = 0.5V” and later used .3V instead.

“Vaux = 19.375V – 0.3V = 19.1V (rounded off)”

This would change the 19.1 to 18.875V

So in the next few sentences you should change the 19V there also.
 
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wally7856

New member
I see you fixed it all up. Good work. It was very helpful to have all of the information for calculating the auxiliary secondary winding all in one place, laid out with so much detail. I did not relies it could be calculated so closely.
 
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michelle

New member
Hi Tahmid
greetings do you have any ocp schematic which can be added to IR2153 smps i have made which i have made and its working good
warm regards
michelle
 
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Tahmid

New member
michelle said:
Hi Tahmid
greetings do you have any ocp schematic which can be added to IR2153 smps i have made which i have made and its working good
warm regards
michelle
Click to expand...

Hi michelle,

I assume ocp means over current protection. I'm afraid I do not have any such circuit ready. For over current protection, you can use current sensing in the primary or secondary. Secondary sensing will be more accurate.

For short-circuit protection, you need someting quick. So you can not use a shunt for a half-bridge converter. Use a hall-effect sensor or a current transformer.

For over current protection, your current sensor may be a shunt. However, since you'll be implementing a short-circuit protection circuit (I hope you're not omitting or ignoring this), just use that for over current protection (crude). For more accurate/precise protection, use secondary sensing.

Hope this helps.
Tahmid.
 
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smps_fan

New member
Nice Tahmid I love your blog it´s so much information there ! The information about the compensation of the error amp isn´t spread so much on the internet. Could you say something about the compensating network ? Could it be calculated ? Or is it faster to measure it out ?

Greatings smps_fan
 
T

Tahmid

New member
wally7856 said:
The first thing that comes to mind is a URL with an index of your blogs. Now you have to go through all the blog posts to see what is available.

I would like to know more about calculating output inductors. From my initial study it appears that different topologies require different calculations for the inductor. If this is true i would like to know how to calculate the output inductors for the popular topologies.
Click to expand...

Hi,
All forward-mode converters have the same formula / methodology for calculating the output inductor. This includes the forward, push-pull, half-bridge and full-bridge topologies. Flyback converters don't essentially need an inductor, although it does help to use one for filtering. Buck and boost converters have different methods of calculating the output inductor.

Is this what you were talking about?

Regards,
Tahmid.
 
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wally7856

New member
Tahmid said:
Hi,
All forward-mode converters have the same formula / methodology for calculating the output inductor. This includes the forward, push-pull, half-bridge and full-bridge topologies. Flyback converters don't essentially need an inductor, although it does help to use one for filtering. Buck and boost converters have different methods of calculating the output inductor.

Is this what you were talking about?

Regards,
Tahmid.
Click to expand...

Yes, that is a big help. Thank you.
 
W

wally7856

New member
Tahmid, That was a very good write up on inductor design for forward converters. It has more information than i have seen anyware.

I slowly worked thru your method for calculating inductance and then i re-read all my literature on calculating inductors. Most methods were based on your formula with slight variations. Your comprehensive write up helped me understand the other variations of the formula.

One of the differences in the formulas is what to use for I min. G Chryssis says .25Imax, M Brown does not say but used 10% in one example. Schmidt-walter says "L is chosen so that ΔIL=0,4 x Iout for >Vin_max". Pressman derivation of his formula says he uses 10% of I max.

If I use 10% Imax in your formula “1.78A” (250W / 14vdc = 17.8A) then i get a L of 44.4uH.

I used your numbers for the half bridge converter you designed and entered them in the other formulas.

http://schmidt-walter.eit.h-da.de/smps_e/hgw_smps_e.html

gave an inductance of 9.32uH.

G Chryssis book said 16uH at .25Imax. But at 10% was 39uH

Tahmid method at 10% says 44.4uH

Pressman’s book said 47uH. Based on 10%

M Brown book said 57uH. Based on 10%

If we throw out schmidt-walter, you ended up approximately in the middle of the other calculations, so i would say your write up has to be correct. M Brown’s value is a little high because he does something strange. He says that “Toff(est)” means “ON time” so that explains why his value is unexpectedly high.

One last thing on Imin for these calculations. Imin does not mean that the power supply must not go below that current. It only means that the output goes into discontinuous mode after Imin and you loose the benefit of the inductor. If you have a regulated supply it will stay regulated. So you do not need to place a load resistor on the output to make Imin.

Next, i will continue on your write up to calculate the number of turns to make the inductor. I will let you know how that turns out.

Thanks again.
 
T

Tahmid

New member
wally7856 said:
Tahmid, That was a very good write up on inductor design for forward converters. It has more information than i have seen anyware.
Click to expand...

Thanks!

One last thing on Imin for these calculations. Imin does not mean that the power supply must not go below that current. It only means that the output goes into discontinuous mode after Imin and you loose the benefit of the inductor. If you have a regulated supply it will stay regulated. So you do not need to place a load resistor on the output to make Imin.
Click to expand...

Thanks for pointing it out. This requires further research on my part then.
 
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