I'm mainly interested in what these designs look like in the inside so I
can get an idea of how they get them so small. Our current rugedized
constructed power supply module is 10X bigger. I'd like to see if there
are any tricks they are using beside pushing components to the ragged
edge to make the supply smaller. even at 5X this size it would be a
substantial improvement in our present one.
Rolling your own is a decision that has to be justified, in the first
place. If you can't beat them, the alternative is to use their
product. High reliability situations may even preclude the use of a
single converter. Like I said - define ruggedness.
Can you stick to telecom bus dc inputs? Safety agencies recognize
these as being isolated, so that only basic isolation is required for
SELV at the system output. This may not be important for printed
transformer winding use, but that use is a decision that needn't be
predetermined.
Second consideration is topology selection for magnetics and silicon
utilization, over the functional operating range. Unless you have
bright ideas, you're going to be using two magnetic components, with
the isolation transformer operating under reversing flux levels. You
may be able to get away with murder at lower power levels, but the
closer you get to competitive power densities, the less room there is
for the 'big semi - small heatsink' solution.
The single transformer employment in your OP showed an attempt at
resonant transfer, judging from the output ripple waveforms. This may
have worked fine for higher output voltages and lower turns ratios,
but you could see the results of trying to stretch it to low output
voltages and higher output currents.
Switched snubbing and synchronous rectification are the most common
methods of reducing size of the parts used, even for single-magnetics
type flybacks, in spite of their potential complexity. These can be
stretched and massaged for the application. There's a plethora of
literature out there covering component selection for those circuits.
RL
