My two bobs worth. Please DONT re-do the 10KW EMW charger. Its a pretty poor design. Microcontrollers are good supervisors, but poor SMPS controllers.

This (inverted buck) topology was what I used in my original 2Kw charger design (which ate mosfets due to the poorly sized inductor saturating and becoming a power resistor instead) - and another (working version) is available online -

http://ludens.cl/Electron/latsup/latsup.html. I scaled this one out to 2.5Kw. Took one big bugger of an inductor to avoid saturation.

Current mode is the simplest way to do this, and keeping below 50% duty cycle eliminates the need for loop compensation.

Inductors - Toroid, or massive bar inductors. EE-core need to be ridiculously sized (that 70mm one, even double-stacked, is going to need quite an airgap (3-5mm) to avoid saturation, and then you need to take into account the localised heating of the windings over the gap due to flux concentration) Bar inductors are the easiest to wind, although they are not a closed magnetic path, interference is very likely (as is a gapped EE).

If you want to know the maths behind this - N87 saturates at 0.350T, but you really shouldn't go over 0.3T in practice.

Flux density in an inductor is determined by the following:

B = (AL * N * I) /Ae

Where B is flux in mT

AL is in nH per turn squared

N is the number of turns

I is the current in amps

Ae is the effective area in mm2

Run some numbers through that and you will be surprised at just how large the flux density is in some scenarios.

I needed a 1.5mH inductor capable of 20A before saturation. I tried a 2mm gapped ETD59 (pretty big core) - a 2mm Gapped ETD59 N87 core has an AL of 311nh.

This equates to 70 turns of wire.

Running these numbers against my 2mm gapped ETD59 core

B = (311 * 70 * 16) / 368

B = 946mT - 0.95T (!!!!) Obviously undersized!

Rummaging around in my junk box - I found a massive bar core (25mm*50mm*100mm), with 25 turns of litz wire around it, measuring at 90uH. This works out to 0.144uh/turn squared. The core itself weighs 350g, and makes an ETD59 look like a toy.

Plugging the numbers in, need 83 turns to get 1000uh (1mh - needed for 20A, may as well go big).

B = (144 X 83 X 20) / 1250

B = 191mt = 0.191T - Plenty of headroom.

Running this coil at 30A (not going to happen but anyways)

B = (144 X 83 X 30) /1250

B = 286mT = 0.286T - yep still possible.

Its very interesting how large a core you need for a buck inductor due to its DC content - what would be fine for a half/full bridge is useless for high powered buck or flyback.

In energy storage topology (as you figured) lower frequencies mean larger inductors. But they also mean you can get away with poor routing, not need to use copper foil or litz wire to reduce skin affect, and the input filters for common mode noise reduction are far simpler to model. It also means you can use things like IGBT's with much better SOAR ratios than mosfets of the same capabilities.

If you want maximum energy out of your powerpoint - you need good power factor. I would be looking at buck PFC topology. Its a single inductor, single switch topology using a controller UCC29910A.

I've designed some big buck SMPS'es before - the maths is reasonably straightforward.

GNG offroad build on Craftworks DHR with 12S2P lipo. Light, balanced, powerful, able to climb a tree.

Project Vectrii (2) - status - Finished. Nope. 38S Leaf cells are next. Now have 2 of them - Averages 50Wh/Klm