Re: Flyback output diode peak curent vs average current

On Jul 3, 12:12=A0pm, "Mook Johnson" <m...@[EMAIL PROTECTED]
> wrote:
> In a DCM flyback with its high peak to average current ratio. =A0When
siz=
ing a
> diode do you rate thediode for the maximum peak current. =A0I have a 2A
> average current with 12A peaks at the start of the flyback. =A0Repeats
ev=
ery
> 5uS.
>
> Which current rating should I look for in the diode? =A03A? 6A? 15A?
=A0A=
ll of
> this makes a difference in the size of the diode package which I'm
trying=
 to
> minimize. =A0The diode datasheets don't have a repetative peak current
ra=
ting
> on the nonrepeataive rating.
>
> thanks

Put the smallest diode in and see how hot it gets.  If you can hold
your finger on it it's probably good enough.  Some may tell you it
should sizzle when you spit on it.  This is the backyard engineering
way to do it.  To do this correctly you would want to calculate losses
and determine junction temperature in hottest environent and so
forth.  To calculate losses you need to know instantaneous current and
voltage and then integrate that over a switching cycle.  stand by for
a bunch of alternate ways of doing.  many ways to skin this cat.

regards,
Bob
N9NEO
just say NEO!