By practical switching frequencies i mean switching losses on the same order as conduction losses.
i'm using 100 volt 14mOhm fets, so that's really hard to do, considering the current sense resistors are dumping 3 times the conduction losses, but no switching losses. the inductors are essentially copper loss only, given the very large air gap and the 24 turns of 15 awg wire. --about 3.1 mills per foot, figure 3 feet that is 9m ohms, double it for skin effect.
i'll have to dip the board in lacquer, run the input up to 30-60 vdc un filtered, and let the ouput climb to 90vdc and see what frequencies and losses it runs at with reasonable loads.
--because i didn't know what to expect from the l6562, i chose .02 ohm resistors, and the total current sense resistance is 45 m ohms, i can change this as needed.
i might be able to use 10mohm sense resistors and still get acceptable results.
another limitation is the parasitic inductance of the boost diode.
honestly i think for a 48 volt battery bank you are safe to use 60 volt surface mounted no heatsink mosfets, set the output for 56 vdc maximum running a tight control loop, and you would be fine. use 80 volt fets if you put the boost converter on the tower, to account for line losses
Its possible to run surface traces only and then glue the circuit board to an aluminum plate for cooling, but its a higher inductance path to do that. another option is just heatsink the fets.
i think the way to do it is have multiple switches and inductors per phase, and then you can surface mount everything and avoid heatsinks completely.