On Jun 29, 2:27 pm, "Bob Eld" <nsmontas...@[EMAIL PROTECTED]
> wrote:
> <mrdarr...@[EMAIL PROTECTED]
> wrote in message
>
>
news:bb341062-6a8f-4d0e-b4f9-7ee805e78362@[EMAIL PROTECTED]
>
>
>
> > I've got a toroidal core, and I'm planning on winding it with pulsed
> > 12VDC on the primary, and want to get out 50V on the secondary, center
> > tapped so I can get +/- 25V.
>
> > The 12VDC will be provided from a 555 switching a power MOSFET at 10
> > kHz, 50% duty cycle.
>
> > I'm hoping to get a maximum of 100W out of the secondary, so the
> > secondary will be carrying 2 amps, and the primary will be carrying
> > about 8 amps. I'll be using 22 gauge wire. (A little thin, I know,
> > but it'll do at least for small scale tests at around 50W.)
>
> > 12V / sqrt(2) = 8.5 V RMS. (Does this apply for pulsed square waves?)
>
> > 50V / 8.5 = 5.9, so if the primary is of length X, the center-tapped
> > secondary should be of length 5.9X, right?
>
> > How many turns of primary are necessary for the transformer to work?
> > In theory, only one turn of wire would be necessary (and then I'd need
> > 6 turns on the CT secondary), but I know this is hogwash. How do I
> > know how many turns I will need on the primary?
>
> > Thanks,
>
> > Michael
>
> What's with the RMS? Your primary drive is 12 Volts peak to peak. Your
> secondary is 100 Volts peak to peak. The turns ratio is 12:100. It's not
a
> matter of length but rather number of turns.
secondary should be 50V p-p... or am I missing something here? +/-
25V after a bridge rectifier... as shown under "Power supply circuit
diagram" here: http://www.redcircuits.com/Page100.htm,
to the right
of the transformer
> Be sure to drive the transformer through a capacitor to keep ALL DC out
of
> it.
ok will do. But how do these guys get away without the cap?
http://www.repairfaq.org/sam/smpsbd.gif
from http://www.repairfaq.org/sam/smpsfaq.htm
>
> The number of turns depends on the area of the core and the maximum flux
> density, Bm for the particular core. The core material must not have too
> much loss at 10kHz.
>
> You need to know something about the core, it's size and material.
What kind of cores are commonly found in pc power supplies? that's
where I got it...
thanks
Michael
|
