Building Your Own Flyback Transformer

Thanks for the goggle reminder. (I wear glasses, so, for years, I was exempt from the goggle requirement in the undergrad chem labs. No contact lenses in the chem labs... no no no... the solvents would dissolve your contacts while on your eye...)

I think I'll try an IRF530 then, since my TIP31A won't do. (Or I could try paralleling 4 2N2222s...) For a mosfet, that means I have to increase the gate drive voltage to 10V or so, right? Scary. For safety's sake I think I'll use a "safety resistor" in series with my primary coil and the mosfet. A 12V lamp should do...

And you're right, it's more fun to adopt a "deserted islander mentality" and do this on the cheap, which is partly why I opted to go discrete for the multivibrator instead of using a 555. On the other extreme, I could just BUY 6 lead acid batteries and connect them in series to get my big voltages... but what's the fun in that...

Michael

GREAT idea! Flyback Converters for Dummies

I never would have guessed... just like I wouldn't ever expect "Nonlinear Partial Differential Equations for Dummies" either...

Michael

Yabbut ! Many of those materials are made intentionally very lossy.

Graham

Would be damn handy if there was.

Especially if it's one colour on one side with another one the other. White and yellow are very popular. Damn, which company is that ? Big American one.

Graham

Less than you might think. I've sent quite a bit of energy across sub-penny class ferrite beads and none ever got hot.

and yellow are very

Nope, it's Adidas:

But seriously, yellow and white is usually a hydrogen reduced EMI ferrite for low frequency stuff. MicroMetals uses the colors but so do others.

Excellent tutorial. I'd save many miles on the freeway if everyone would be familiar with the scope plot in figure six. When you see that shark fin it's time for duck and cover.

A few days ago I saw a book "The Bible for Dummies". At first it shocked me a bit but hey, whatever it takes.

Anyhow your IRF530 is a lot better than the TIP31 but keep in mind that whatever is driving it needs to wallop the 700pF gate capacitance around and it needs to push it up to 10V. And fast.

The prices you design to never fail to amaze me.

Graham

and > yellow are very popular. Damn, which company is that ? Big American

Micrometals were indeed the ones I had in mind.

Graham

Not always. What I am designing right now is more the "whatever it takes" kind. But even there one must keep later mass production in mind, it would not help anyone if I came up with a Princess on the Pea solution.

As for hand-wound stuff the world changes as well. Labor rates in Asia are picking up.

It is useful to pull a MacGuiver once in a while. A few years ago I was on a troubleshooting job at NSA and I found that a glitch in a logic circuit was causing it to malfunction, and it was preventing the use of a $50,000 piece of equipment used for critical circuit breaker calibration. I figured that a small capacitor would fix it, but we didn't bring an assortment of parts, and their cal lab didn't have that sort of thing either. It would have been very difficult to go back out through security and go somewhere to get some parts and then come back in, and we really needed to get this test set up and running. Luckily, someone had a broken multimeter that we were able to cannibalize and get a capacitor that fixed the problem. So they were able to get their testing done, and national security (or at least my job security) was once again assured.

There should be a techie version of "Survivor" that require the participants to use electronic junk to cobble together some sort of circuit that allows them to get out of situations.

Paul

Wow, that would make a great show!

Michael

On Aug 29, 4:05 pm, Joerg wrote: ...

Figure 16 has pretty much what I was trying to do, but better - brilliant use of the 555 feedback pin! But... No protection diode for the mosfet, though? And no capacitor to block the DC?

Shark fin... well, at least it guarantees income, right? :)

Can my 555's output pin 3 handle it? Should I use a resistor in series with the gate, or don't bother...?

Thanks,

Michael

It sounds promising. An electronic 'Scrapyard Challenge' kind of.

Graham

sounds like junkyard wars, but with added politics.

Bye. Jasen

What diode, and why block DC? Big MOSFETs carry a staunch parasitic body diode that can often handle around the same current the MOSFET itself can take. DC flux: That's why you must use a gapped core here. A non-gapped core will run away within tens of usec ... kablouie.

Yeah, except some of the proto boards I get fill the lab with such a burn stench that I have to keep the windows open even in winter.

I rarely use gate resistors. But if the trace/wire length is more than

:-)

I once went around and asked whether someone had an older portable transistor radio. "What for?" ... "Well, I need the little audio transformer in there and I'll pay $20" ... "Twenty bucks? Deal! Here!"

BTW, next time that happens ask if there is a RadioShack nearby. One that hasn't mutated into a cell phone shop like ours did. They have little Smorgasbord-kits for a few Dollars, containing a nice mix or ceramic through-hole capacitors. I have been known to do Viking-style raids on RadioShacks near clients. Once we had a pile of a dozen clamp-on ferrites and it still wasn't enough. "Oh, I'll just hop over to RadioShack" ... "Ahm, that's where these came from, I cleaned out all four stores around here yesterday evening".

...

If I build a Boost converter instead of a transformer, does my inductor still need an air gap?

(figure 3):

Thanks,

Michael

Yes. It makes no difference whether the boost (flyback) converter has an isolated output winding or gets the output off the primary winding. Both versions alternately store input energy in a magnetic field, then dump that energy to the output. Solid ferrite does not store very much energy before saturating, but the air gap in the flux path stores lots more energy per volume than the ferrite core material does.