Frequency inverter power supply topology

[stoyanoff]

Greetings! Can I have your opinion on three phase 400V frequency inverter power supply design? In my design I am using a simple transformer(230V/50hz to 4x15V+1x9V) and LVRs(LM317 and LM337) to drive the half-bridges. This schematic is quite cheap, but I am concern about the quality, durability an so on. I`ve notice all frequency inverters on the market are using some modification of flyback converter.
Do you think there is a specific reason for this choice? My power supply is quite bigger, but I don`t have problems with generated parasitic frequencies and so on. If I switch to flyback converter it will be smaller but proper transformer is hard to find. My product is designed for specific purpose and I don`t expect high qualities. But it must be as reliable as possible.
So which design is better for this app? Which one do you prefer?

[capt bullshot]

You'd better use a 400V primary transformer, as the neutral (to provide 230V L-N) usually isn't available in the typical environment.
Other things to consider:
For the gate drivers, you'll have quite steep dU/dt (ballpark values 1 ... 10kV / us) on the switching node. If this is tied to a "normal" transformer, it's insulation might break over time. Your transformer (as well as a DC/DC module that one might want to use) must have explicit rating for this high dU / dt, and appropriate insulation ratings to meet CE / UL / whatever.
Usually the flyback (or similar) transformers used for gate driver supply are custom made to these requirements. IIRC, TI have some examples of appropriate supplies in their application circuits collection. Maybe Würth (or some other manufacturer) sells transformers that are suitable for these examples.

[David Hess]

Flyback converters are popular when multiple outputs are needed at lower power levels because of their low cost.  At higher power levels, other topologies are more cost effective.

[stoyanoff]

capt bullshot, these are good suggestions! I ca easily change the input voltage and ask for isolation level up to 10kV. The transformer is custom made.
david hess, I am not well familiar with all topologies, so I used flyback as an example.
Thanks!

PP: By the way, I found a few pulse transformer winding tutorials and I think I can do it! So may be I can try half bridge and see what`s gonna happen.