Getting started with Switcher design

Why would you want to do that? A receiver isn't going to draw much current, yet to use a switching supply means you have to deal with all the noise that such supplies generate, not a good thing when building a receiver.

The effort in making the power supply as noise free as possible might be a useful learning process, if there was an actual need for higher current, but it's not.

As for the rest, define what you want to do. Do away with transformers? Provide regulation without a lot of loss?

The best place to start would seem to be a hybrid, start with a 60Hz stepdown transformer, rectifiers and a filter capacitor, and then build a switching regulator. Learn from that, don't get lost in extra stages, and then later you can go to a full switching supply.

Michael

Perhaps for his stated purpose -- to learn? Building quiet switchers used to be real voodoo, but there's a lot of interest in them and hence a lot of knowledge floating around out there. The biggest "trick" that I'm aware of is controlled slew rates on the gate drives, to slow down the edges on the FET outputs. You trade switching loss for EMI, which is a nice way to guarantee employment.

Your "low current" may be my "high current", though.

Amen.

From what power source? The wall? A battery? What voltage battery? What constraints do you want to place on yourself? What don't you care about?

If you're going to go off the wall, search on "off-line switchers" for information.

AFAIK flyback topologies are generally most useful when you're going up in voltage.

A flyback is useful for more then just boosting voltages. Its simple to derive multiple output voltages either negative or positive polarity. It provides galvanic isolation from the rectified line voltage.Its one of the least complex lowest part counts converters for offline power conversion.

Almost every consumer and or industrial electronic device under a

The OP should go and browse ONsemis and Fairchilds site for offline controllers for tons of info includeing examples and sources for small quantity magnetic's.

I don't know why you would use anything other then a flyback for 100W or less for a line powered converter when primary to secondary isolation is a must. They are even the prefered topology for TELCO power conversions all kinds of examples for 48Vdc conversion useing a flyback are avaliable on google.

True.

Right now, the main purpose is to learn about these beasts.

in them and hence

It's the "floating around" bit, I'd like to deal with. That is, where do I find some of this knowledge.

I suggested application notes myself but unless one has some prior knowledge each and every one of them seems to be the latest and the greatest. Some pointers would be helpful.

Chris

Fair comment.

I suggested this because, (a) I need one, (b) I thought it a not too extreme goal. A good point about the noise, though.

:-(

Again, even if I, following your advice, should do this particular project with a linear power supply, learning about switchers is still interesting.

Getting rid of heat and heatsinks is definitely a priority. My question about flyback was motivated by the notion that they include transformers and provide galvanic isolation.

Excellent idea. I have a small (too small for the above project) potted mains transformer in my junk box that could get me going.

Chris

Good point about small quantity magnetics.

ONsemi's tutorial page has 24 documents alone! I'll have a look.

Thanks

Chris

This,

this,

this,

these,

and this?

Jon

Wow, even the first one will keep me occupied for a while.

Thanks, Jon.

Chris

Wow, even the first one will keep me occupied for a while.

Thanks, Jon.

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Here is an oldie (1987) but goodie from Linear Technology (Switching Regulators For Poets):

Also, you can easily simulate these and other circuits using LTSpice or SwitcherCAD which is available free on the website:

Paul

C Egernet wrote in news:d17ba18f- snipped-for-privacy@i28g2000yqa.googlegroups.com:

occasionally here.

choice of

the principle of

get going. (I

the question.)

supply for a

topology

Have there to start