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londark

Homework / Study Help Thread

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Long story short

 

On Xmas break right now, will be back at uni on monday, with an exam (damn right). Professor is on break too and won't respond to our mails...So i'll be seeking some help here as well.

 

Subject is System and Control Theory. 

Here are some question i'm stuck on.

 

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Will add other problems later if someone can help. 

 

For other feel free to ask for help on whatever you are studying

Edited by londark

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you need 1 special wall 2 pshycal walls and at least one wall breaker! for mor details to this DM me.

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21 hours ago, londark said:

(quite easily) done with that. 

 

Next one will be about Electromagnetic Compatibility 

first fix your sig, noob

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Never used either sorry; but if it's not a software-specific question I might be able to help.

-

On related news, I was in Italy last week and met a few guys from polimi.

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Nice, if you ever come near Venice tell me. 

 

I think I got the solution actually, was just a simulation setting problem. 

I have to make a dc/dc flyback converter from scratch and was having problems with the transformer model used by the software

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Yeah, usually the trick is in configuring the parts. Not sure about these software, but other simulators provide manufacturer-defined models as well as template parts which you can customize to obtain something closer to your application. Have you ever used Spice?

--

I spent two weeks in Trieste a couple years ago and got to visit a few of the northern cities, might return there some time.

In fact I'll be moving to Spain this year, plan to spend a few months there.

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Yeah, used PSpice, and Simetrix is quite similar actually. My problem was that the ideal DC transformer doesn't have a Primary Inductance value, that I need to define some target values for the converter. I added an inductor to simulate the primary inductance and apparently it didn't work out, but I had just to change some settings on the simulation details. 

 

Anyway, I'm in Udine if you ever get back here. Trieste isn't far away as well 

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On 9/11/2019 at 9:49 PM, londark said:

Yeah, used PSpice, and Simetrix is quite similar actually. My problem was that the ideal DC transformer doesn't have a Primary Inductance value, that I need to define some target values for the converter. I added an inductor to simulate the primary inductance and apparently it didn't work out, but I had just to change some settings on the simulation details. 

 

Anyway, I'm in Udine if you ever get back here. Trieste isn't far away as well 

get back on steam so we can play dead by daylight and rust

 

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@axx

 

So, i'm almost done with everything, i just need to design a regulator. 

I went for a type 2 scheme with an Opamp and a feedback with 2 capacitors and 1 resistor.

 

These are the specs:

Vin = 9-36V

Vout = 5V

Iout = 0-4A

f = 100KHz

 

I got a Rout of 1.25, an Lm of 23u and a Cout of 40u ( it's big but i had required ripple of less than 0.5V peak). 

To design the compensator i usually set the cutting frequency at around f/10, and i choose the components so that the compensator zero is equal to the flyback pole and viceversa the compensator pole is equal to the flyback pole. 

 

I don't know why this time i'm getting weird numbers, could it be because this time i'm having a step down type converter and so the gain is less than 1?

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wtf it took me longer to get in than the actual question

 

assuming you are using tantalum capacitors for reasons

 

flc = 1 / (2 x pi x sqrt(0.00000023 x 0.00008) = 37103 hz (1)
fesr = 1 / (2 x pi x 2 x 0.00004) = 1989 hz (2)
f0 = fs/10 = 10000 hz (3)

flc < fesr < f0 < fs/2 (4)

37khz < 2khz < 10 khz < 50 khz

 

you need to check those capacitors

if (4) does not hold, the type II will go haywire

 

or you can cheat and say lm = 140u

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6gqqvmUr.jpg

 

Hope like this It's easier to understand

 

I increased a little the cut off frequency to 33K, the rest should be correct. The ESR is 170m.

 

 

EDIT: I also did a fast stability check on the regulator and it's stable using those values. The poles and zero frequencies are also really close to the chosen ones, and it should be pretty cool.

Using simplis to simulate the regulator and PWM on a Buck converter using the flyback values it works decently enough. 

 

I also don't really need a perfect regulator, but i just needed to do some math on it, the actual feedback control on the circuit is done by the  LT3758

 

 

Edited by londark

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Not sure I understand what you mean honestly. The output current is already at 4A (5/1.25), used the max output current cause during lessons I was told to always use the minimum possible Rout when making this kind of regulator. 

 

Unless you mean to use a Norton load with a current generator of 4A

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was just implying that you should now build the protorype, thats the fun part

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