Small DC DC Conveter (SMPS) Design Help

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Adam Horden" <adamhorden-at-acidtech-dot-net> 

Hi All,

I took on the headache of building a full bridge and gate driver for a 
CM600HA igbt brick full bridge. The bricks are the same the ones on Steve 
Conners OLTC.

I have done the design of the gate drivers and everything works very nicely 
just awaiting the pcbs from the pcb house now.

I need 4 isolated supplies (small step-down transformer and no good here 
due to the winding inter capacitance and using 4  transformers 4 lots of 
fuses 4 regulator stages seems a bit long winded)

So I came up with this idea.

40V supply (LV transformer full wave rectified and smoothed) > pwm osc 
40Khz > mosfet driver stage > full bridge IRFP460 > transformer > 4 x 
secondary 45V 1A

Everything up to the transformer is pretty standard.

There is a block diagram here http://www.acidtech-dot-net/ah-dmdrv-isolated.html

The problem is the design for the transformer. I know the turns ratio 
formula and used it for standard mains transformers I have wound in the 
past but can I apply this standard set of formulas here?

Would any one talk me through the design stage of the transformer or know a 
book / website that can help?

Would I need an air gap to store the core saturating?

Thanks,

Adam