wanting to get into smps designing and building

[demogorgon]

No doubt you will be leaving the ice behind! Befor you leave, try looking at this website at OnSemi:

http://www.onsemi.com/pub/Collateral/SG3525A-D.PDF

Bon Voyage,

Steve

I'm not nesecarily very sorry to be leaving, but it'l be good to get some time off from school. no ice down south last year at this time for shure

I'l take at look at the site. thanks.
at the time i'm busy goint through the smps tutorial here:
http://www.smpstech.com/tutorial/t00con.htm

 

[Curmudgeon]

I'm surprised not to see this:Linear Technology App Notes or this LT Design Aids; Some of the LT app notes are classics. And although it's been a while since I used the tools, they worked very well.

 

[demogorgon]

hey guys.

just letting you who helped me getting started know that i'm on track and i'm starting to play around with practical designs today. pretty basic stuff, but i'm aiming low for now, and then i'l see what comes later. i'l even bring you a pic or two

-Marius

 

[N-Channel]

eagerly waiting...........

 

[demogorgon]

hehe, dont hold your breath

i'm testing out a smps in it's simplest form, using an external signal generator and a low voltage source. just to get the feel for it.

i'd like to ask someone of the knowledgeble here the following:

what is the deffinition of a halfbridge and fullbridge smps?

and when using an IC for switching controll, how about voltage suply?
is a dropdown resistor used? are there high voltage IC's available?
so many questions...

thanks
-Marius

 

[richie00boy]

Half bridge is like a single ended audio amp, full bridge is like a bridged audio amp.

 

[demogorgon]

Half bridge is like a single ended audio amp, full bridge is like a bridged audio amp.

ok, i suppose i get it.
halfbridged it is then.

 

[demogorgon]

and wheres the protoboard when you need it?

nowhere to be found.

well, at least i got the oscilloscope and signal generator in house.
and i'l se what can be done on protoboards tomorrow.

-Marius

 

[demogorgon]

got the demoboard, the oscilloscope set up, the sig-gen wired up and the time on my hands to play around a litle.

thinking i'm gonna go for the simplest possible first, anything you see thats terribly wrong with this simplest of circuts?

thanks
marius

 

[richie00boy]

You would usually use an n-channel device and connect the load to the drain and 0V to source.

 

[demogorgon]

hehe, thanks richie, i'm gonna do that.

i'm using 2sk1217 for switching, but i'm uncertain as to if it's a depletion or enhancement piece. gonna try it out tomorrow, se if it runs. had to go to an extra meeting at work, just home to eat and shower, then i'm back again.

-Marius

 

[richie00boy]

If it's a TO220 case power device (which is at least what you should be using in an SMPS) it will be depletion. Usually only JFETs are enhancement.

Are you using a 12 volt supply for everything?

 

[Onra]

Enhancement, not Depletion Type

Hi,
@richie00boy:
It´s the other way around:
2SK1217 is an enhancement type MOSFET and most JFET are depleteion types

 

[Eva]

Marius, I'm sorry to say that but your circuit is not likely to work. Rethink it. What are you expecting to get in the output? What waveforms are you expecting to see in each node?

 

[demogorgon]

small updated schematic, this time, with a rectifier bridge.

i reccon thats what you reacted on eva?

if not, then i'm at loss as to what's missing or wrong

Eva, Richie00boy and Onra, thanks for helping me out
appreciate it.

-Marius

 

[richie00boy]

That is better, I don't know how I missed you had no recitifer before!

That kind of circuit can work (I used something very similar for my first design) but it is very crude.

 

[Eva]

Your secondary side looks right now, however the transformer will saturate because the secondary side inductor will short it through the diodes during the off-time, thus preventing it from resetting.

Try to find a way to drive the primary in a symmetrical way, for example in push-pull.

 

[richie00boy]

When I built that kind of thing I didn't use an inductor on the secondary, I guess that would help against the saturation problem. It is a crude way though and a centre tapped primary would be better.

 

[demogorgon]

ok, the circut is up and powered, though only wierd resoults have arisen so far, and no squarewave is yet connected. gonna troubleshoot a bit.
i altso have taken a few pics for your viewing pleasure

the switching frequency is 25kHz, Vp2p is 2v, the load resistor is 1k.
anything anyone would like to add to this?

i'l keep you posted.
-Marius

 

[demogorgon]

ok, connected the source and drain wrong, nothing more.

now, i altso connected the squarewave, and more wierd resoults emerged. never the less, here another picture