Design of SMPS

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#23
As i understand ( and please correct me if i'm wrong ) the 7W unit is a flyback and it powers from the solar pannels, well at souch low power flyback is great for good efficiency if everything is well designed for this purpose, low current means low losses, that combined with components that assures the lowest losses possible means that you can espect an efficiency of up to 90% or more.
 
#24
Flyback converters run in current mode are very efficient 80% + over at least 2 decades load variation, check out the photoflash chargers in mobile phones. Where they give ground to other designs is at moderate to high load.

On the original topic designing an SMPS from scratch requires a good grounding in electrical theory and a bit of control theory doesn't hurt, fortunately the makers of power electronic devices have published many example designs which are good enough and if used without too much modification are unlikely to have an unstable control loop. An understanding of electronics is still required to use these designs effectively if the PCB artwork is not published, stray capacitance and stray inductance can play havoc with high dV/dt and high dI/dt circuits.
 
#25
The problem arises from the fact that my solar power system in negative earthed, and the pone I have (panasonic) has it logic referenced to one of the telco line, so a short circuit across telephone line occurs. Then my converter needs to be isolated, although regulation is made in the primary side without photocoupler. If would not be the case, a simple buck would do the job more efficiently.
 
#28
ISTPYRO said:
Hi there guys,

First of all, forgive me if my English isn't so fluent. 😛

I had 2 courses in the field of Power Electronics. One of the class was "Power Electronics" and the other was "Switching Power Systems". However I didn't had the part of the converter control theory as I'd like to.

Even with not much free time, I want to start build a SMPS to feel the problems that can arise from the practical point of view.

I have read a couple of books/papers/thesis and have read lot's of post in 2 or 3 forums. The sensation that I have is that there is lot of people that are building their SMPS without knowing well enough about the SMPS and switching power systems theory. Ok, they can read the Pressman's book or Marty's book and some applications note and with that they can build their SMPS. But I wonder if they do know the theory behind that. The idea that I have is that those guys doesn't even have an university degree. So I ask, do they know how to project a feedback loop, a controller project if they understand what is the steady-state equivalent circuit model, the AC equivalent circuit modelling, state-space averaging model, canonical model of the converter? Or just grab the book from Marty Brown or other one and build them the circuit. Grab some application note, follow the recipe and it's done?

The same goes for those who says that build their commercial SMPS.

I really don't know if that is relevant and important to build a SMPS. Of course that I can grab the app. note and the Marty's book and build the SMPS, but building a SMPS isn't a great responsibility to the point that maybe following the recipe it is not a negligent position?

My greatest problem is trying to understand and the model of the feedback loop design; get the transfer functions, see the phase margin, gain margin, etc.

On the other hand, I don't know at which point is important to know deeply how those things work in order to design a SMPS. We have several IC's that do the control part. We can just grab the datasheet and an app. note (as I told before) and understanding that we can design the feedback loop.

There anyone that works in this industry and could share his point of view and what think about what I said?

Thanks for reading. I'll wait for your answers
Click to expand...

Good motivation! Here are some links, below. The first one seems really good, to me. But they are all very good, in some ways.

http://www.onsemi.com/pub_link/Collateral/TND352-D.PDF

http://www.intersil.com/content/dam/Intersil/documents/tb41/tb417.pdf

http://www.ee.bgu.ac.il/~pel/presentation/PET06/PET06.pdf

http://www.ti.com/lit/an/slva301/slva301.pdf

http://www.irf.com/technical-info/appnotes/an-1162.pdf

http://www.cpdee.ufmg.br/~porfirio/...izing dynamic response for buck converter.pdf

https://ps-ssl.de/regiamea.de/ablage/dn-62.pdf

http://web.cecs.pdx.edu/~tymerski/chap1.pdf

http://www.cirrus.com/cn/pubs/training/apex_tech_sem/TechSemV12.pdf

Cheers,

Tom
 
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