Re: Flyback power supply design

On Sat, 28 Jul 2007 00:06:21 +0100, "Marcin Osiniak"
<marc_kropka_o@xxxxx> wrote:

LVMarc wrote:
Most of te semiconductor houses now have online or downloadable
circuit cimulators and tools. For switch mode power supplies Linear
technology is a well known suplier and they have a LT switcher tool.
so may as well start there.

The key to all switchmode is sizing the inductor for correct value at
full current load (current de-magnetizes the coil, saturation effets)
and then sizing the capacitors to limit ripple. The rest is finese. You
wil also nee a good supply of schottky diodes tha also handle
peakswitch mode currents.

If you need help for a commmecial product let me now and our group
will put together a professinal supply and source the materials you
neeed along with manufatring acument.

IN any event have fun and good luck

Marc

Firs of all, thanks for quick answer...

Power supply will be the part of biger student project so I don't want to
use a specialistic chip in design. I was thinking about simple PWM generator
with comparator (like UC3842).

I posted an inverting switcher, essentially a flyback, schematic to
a.b.s.e. a week or so ago. I like this design because it is sort of
discrete. Something similar could be done with all transistors, no
IC's at all, without much difficulty. The IC I'm using is just a gate
driver with hysteresis, not intentionally a switching controller.

The really interesting issue is control loop stability at various
inputs and loads, especially in continuous mode. My struggle with
capacitor esr and such has been a running thing here.

John





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