Re: DC power supply again

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Sunday, August 24, 1997 11:45 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: DC power supply again

Re my plans for the flyback supply:
                                     I was overly pessimistic 
regarding transformer core losses:

> > I designed the transformer several weeks ago and am looking at core 
> > losses of around 90W, hoping to achieve the same or better in the 
> > windings (difficult given the winding window I will have to live with)
> >and hopefully switch losses of the same order.

In fact: those are the *peak* losses. The average loss will be 
considerably lower given that the duty cycle is 50% at full power and
the peak loss is based on peak core flux. The true picture then is:
Core loss: 90W/(2 x 2)  = maybe 25W average.
Same sort of scenario for copper losses given I^2 x R 
And the switches, although none of this takes diode loss into account 
(50 output Vd's = about 0.25% loss in output voltage-wise).
    The core consists of 16 C-core halves (8 complete "flyback" 
cores), gapped to a total of 3.2mm around the flux path.