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Re: flyback transistor choice
Original poster: Hypatia's =?iso-8859-1?Q?Prot=E9g=E9?= <hypatia@xxxxxxxxxxxxxxxxxxx>
Greetings, Scott! :)
If you insist on BJTs you'll be far better served by a push-pull arrangement
employing a marched pair...
An MP of 2N3773s is a better choice from both HFE & VCE standpoints -- Barring
this, a pair of well matched 2N3055s should be fine so long as you
observe their
relatively low VCE.
I've taken the liberty of transmitting a schematic & discussion of an example
circuit to your personal e-mail Addy.
////
FWIW the circuits (i.e. that described in your post and the markedly improved
design [i.e. push-pull arrangement] suggested here) are 'power oscillators'.
The noted frequency 'pulling' attendant to load/PS (i.e. impedance) alteration
is a natural and (RE: the application at hand) highly desirable characteristic
of such arrangements inasmuch as driver & load impedance are thus automatically
matched. (technically, as regards said circuits, no quantitative distinction
exists between driver and load -- hence the effect)
Hope to have been of assistance.
Best regards
Dan Sarandon
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, March 25, 2007 10:35 PM
Subject: flyback transistor choice
Original poster: "Scott Bogard" <teslas-intern@xxxxxxxxxxx>
Hi All,
I'm not sure if this is the right place to ask this, but I'm
sure sombody out there will be able to help me. I built a few of
those simple flyback drivers with the single 2N3055 transistor and I
have experienced a few problems. They are a bit too weak to drive my
12in argon filled plasma globe, unless I parallel 4 transistors, and
that blows out my step down transformer (it pulls like 6 Amps, the
transformer is rated for 2, and a single transistor pulls about 1.8
A). Is there a better transistor I can use? or will I be forced to
get a huge step down transformer. Any input would be appreciated,
and if this is the wrong list for this, I can go elsewhere, it is no
problem! (but I'm sure sombody out there knows what to do).
Scott Bogard
P.S. the frequency shifts all over the place with just one, making
consistant plasma impossible at low pressures, but this goes away
with 3 or more transistors. Also, I need a transistor that won't
make an audible scream, as my sister will kill me whenever I come
home (she hates the noise with a passion, I'm not too fond of it
eithor, which is why I like the 3055, it is reasonably quiet). Thanks.