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BUP49 transistor - Max frequency?

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Patrick

Sat Apr 16 2011, 08:46PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ash Small wrote ...

But the Mazilli circuit, to me, looks more like a push-pull circuit (centre tapped primary, two transistors....) Does it operate in flyback mode or push-pull?

Doesnt it just push pull, hence the inherently low voltage compared to pulsed mode? I have only a few attempts at the mazilli as they dont seem to fit my needs. So I could be wrong.

Ash Small

Sat Apr 16 2011, 08:51PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Patrick wrote ...

.Doesnt it just push pull, hence the inherently low voltage compared to pulsed mode? .

I agree Patrick, but it's referred to as a ZVS flyback driver.......confusing.....

Should it be called a Mazilli push-pull driver?

(Or am I just being confrontational

)

Patrick

Sat Apr 16 2011, 08:55PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ash Small wrote ...

Patrick wrote ...

.Doesnt it just push pull, hence the inherently low voltage compared to pulsed mode? .

I agree Patrick, but it's referred to as a ZVS flyback driver.......confusing.....

Should it be called a Mazilli push-pull driver?

(Or am I just being confrontational

)

As i said previously, there are two different meanings, the flyback topology, and then the flyback transformer. the topology doesnt need an air gap, the transformer type definately does.

I believe it should be a "mazilli push-pull flyback driver".

Ash Small

Sat Apr 16 2011, 09:09PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'm going to have to disagree here, flybacks only need a gap if they are saturating. 'flyback' and 'push-pull' are different topologies.

(I'll attempt to demonstrate this with these cores)

Patrick

Sat Apr 16 2011, 09:16PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ash Small wrote ...

'flyback' and 'push-pull' are different topologies.

Yeah, DUH, of course they are different.

What im saying is, that flyback topolgy and a flyback transformer i think are different, ive seen ATX power supplies that use the flyback topology yet not a true flyback transformer, im still pondering this thought though.

Patrick wrote ...

I believe it should be a "mazilli push-pull flyback driver".

when I said this , I meant that the mazilli is really a push-pull driver for a flyback transformer, with the flyback transformer not really being in flyback mode

Ash Small

Sat Apr 16 2011, 09:45PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Patrick wrote ...

.when I said this , I meant that the mazilli is really a push-pull driver for a flyback transformer, with the flyback transformer not really being in flyback mode

I was hoping to post this before you replied Patrick.

'Mazilli LOPT push-pull driver'.

line output transformers are commonly called in the US by the name of 'flyback transformers'. There is a common myth that these are called 'flybacks' because the electron beam 'flies back' to the beginning of the screen......this is incorrect....they are called 'flybacks' due to the 'sawtooth' shape of the driving current......it 'flies back' to zero current, but gradually increases to peak current....hence the 'sawtooth shape' (I think I'm using the correct terminology, current not voltage....but maybe someone can clarify)

Wikipedia is incorrect on this point.

Hence my suggestion that it should be called a 'Mazilli LOPT push-pull driver'......saves a lot of confusion.

EDIT: I think it should read 'voltage' instead of 'current'.

Patrick

Sat Apr 16 2011, 11:22PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ash Small wrote ...

I was hoping to post this before you replied Patrick.

Ive been in this predicament too.

yeah like i said ive read articles and books, that seem to use the word "flyback" (meaning the topology, and not the transformer) when i think they mean "forward" converter as in both use passive reset and a single switch.

I almost have the inclanation to believe there are regional differences in what things are called, like Europe or the US, and past nomenclature like the 70's-80's and now. That may also contribute to the confusion.

Ash Small wrote ...

Hence my suggestion that it should be called a 'Mazilli LOPT push-pull driver'......saves a lot of confusion.

It took a lot of bread crumbs , but im glad i presauded you.

Ash Small

Sat Apr 16 2011, 11:31PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Whatever.....

Patrick

Sat Apr 16 2011, 11:34PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Steve Conner

Sun Apr 17 2011, 07:13PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Sorry for the snark, I was in an evil mood this morning. >-)

My point is, why make life harder by using BJTs. They really suck for switched mode. These BUP49 type devices are probably meant for a 1970s design chopper in a forklift or golf cart, operating at a few kHz.

I would ask Semelab to tell you the charge storage time and/or Ft. If they won't and you're still curious, I guess you'll just have to buy one and try it.

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