I got the formula from a degree thesis written about DC-DC in the
300W class. What I'm trying to determine is the proper parameters for
the transformer magnetics in a flyback converter. Not how to build the
transformer magnetics. So parameters like L [Henries], N [Ratio], Ipk
[Ampere] etc.. are the one's I'm seeking.
I found the energy principle lately a good way to analyze this lately.
Could you please quote the Author's name, the thesis title and year,
and the institution holding it on record?
There are increasingly severe restrictions affecting the simple
flyback topology at higher power levels, although I have used it with
some modifications, and seen similar work, above 3KW.
A study of higher power flyback applications that does not include a
physical iteration of the magnetic structure runs the risk of not
being taken seriously.
Minimization of core and copper losses, with rationalization of the
resulting stress affects on the surrounding components, would need to
consider, at least in passing, the physical turns count of the winding
and the flux densities anticipated in the core.
Another puzzle is how to analyze the input filter choke, there's a
inductor with 10uH in series and then a 26,7 uF capacitor (48V). I
calculate I need only about 1uF. So is the inductor choke there to
handle the transient surge that the capacitor can't handle due
ESR ..?, because there's simple not enough energy in the inductor to
take the load of charging the transformer primary.
If the self-resonant frequency of the filter components or parasitics
is anywhere near the operating frequency of the converter, there will
be undamped resonances that can interfere with normal or efficient
operation. Input filter inductors are not normally configured to enter
into the conversion process itself, in the flyback topology.
At 48V, a 300W flyback will be drawing large pulsating currents that a
1uF supply decoupling component might have difficulty handling, hence
a larger value.
The fact that the component is specified with 3 significant figures of
accuracy in capacitance is an indication that it's value does not
originate in a practical situation. Power electronic components are
seldom available in tolerances better than 5% at room temperature.
Theseseses often make interesting reading. Their value is often not in
the actual practical results recorded - in fact the best may describe
a complete experimental disaster and point to important errors in
innitial assumptions or quoted references.
