Seth wrote:
>
> Lee-
>
> Thanks for the comments, they are always appreciated.
>
> First, I am not sure of the topology myself, I was going on memory from
> the last time I read anything about switching power supplies. The
> transformer is a high frequency type formerly used as a step up stage
> after rectification of the 60Hz AC line and it was placed after the
> rectified AC was switched. I believe it was switched between 10 and
> 20kHz. Not audible at least. (If I remember correctly). It actually came
> out of a early 90's vintage 1kW switcher but it no longer works.
>
> I will try my hand at a bit of ascii
>
> Is this what I should have for a flyback? I didn't put in gate drive,
> Isense, Vsense (if required) or pwm generation circuits.
>
> ___________ cap diode
> AC----| |-------|------------)||(--|>----|--------|
> | bridge | --- )||( --- 48V
> | rectifier| --- )||( --- Battery
> GND---| | | / )||( | (52-60V)
> | |----------/ -------)||(-----------------|
> ------------ xfmer cap
> 10kHz 17:11
> IGBT
>
>
>
>
> borrowed from: http://www.web-ee.com/primers/files/AN120.pdf
>
> I can probably afford a different transformer but would like to use the
> IGBTs unless there is a good reason not to. I am not sure about margin
> on voltage for the 200 or 250V IGBTs. I suspect it will be fine, but I
> doubt I will be good at protecting the IGBT from spikes, at least for
> the first (few) builds. But the price is right for those parts, like you said.
>
> Seth
Seth, Lee is correct in the Ig selection. Use 600 volters!!! Since you
are giving Smalley a toasted motor drive, I can get you a hand full of
1200 volt 150 amp IGbt modules. Some I can actually garentte work.
The old 250volts were Most likley Powerex trench gates "5Fs"that I
blew up severly in the mid 90s.
They have the lowest Vsat, and the smallest package for the amps of any
Igbt that I have found. They were so easy to break the they were gone
before I knew it. What lived, ran cool, really nice. Also forget 20 Khz,
use 10Khz. The switching losses are kinda obsene in these old Igs.
I am using Powerex "12Fs" in the PFC50s. 600 volt, and they are being
driven in "2 trasnistor Boost-buck" mode. Main PWM control chip is the
TI UCC 3854. I have one client that wants 500+ volts of output... that
will require 1200v parts.
--
Rich Rudman
Manzanita Micro
www.manzanitamicro.com
1-360-297-7383,Cell 1-360-620-6266
